CA1231748A - Electric heater employing semiconductor heating elements - Google Patents
Electric heater employing semiconductor heating elementsInfo
- Publication number
- CA1231748A CA1231748A CA000474040A CA474040A CA1231748A CA 1231748 A CA1231748 A CA 1231748A CA 000474040 A CA000474040 A CA 000474040A CA 474040 A CA474040 A CA 474040A CA 1231748 A CA1231748 A CA 1231748A
- Authority
- CA
- Canada
- Prior art keywords
- holder
- heating element
- core
- members
- air
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
- H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H3/00—Air heaters
- F24H3/02—Air heaters with forced circulation
- F24H3/04—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element
- F24H3/0405—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between
- F24H3/0411—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between for domestic or space-heating systems
- F24H3/0417—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between for domestic or space-heating systems portable or mobile
Abstract
INVENTION: IMPROVED ELECTRIC HEATER
EMPLOYING SEMICONDUCTOR
HEATING ELEMENTS
INVENTOR: KOSTA PELONIS
ABSTRACT OF THE DISCLOSURE
An electric heater is described which employs plate-shaped heating elements, each consisting of a core of semiconductor material whose opposing faces are coated with conductive material and having a multiplicity of apertures to permit passage of air. The heater includes a housing with a rear air inlet and a forward air outlet. A fan having a fan venturi causes air flows forwardly through the housing. A two-piece, ceramic holder maintains a number of the plate-shaped heating elements in generally coplanar, spaced-apart relationship,in front of a forward venturi opening. The holder has a large recess positioned over the forward venturi opening which receives substantially all air flow from the venturi, and a number passages, one associated with each heating element, which direct air from the recess through the cores towards the forward air outlet. Each of the passages flares radially outwardly and rearwardly from the rear face of the associated heating element, and opens into the recess,and the recess flares radially outwardly and rearwardly from about the passage openings to the forward venturi opening. The arrangement results in improved heat transfer and much quieter operation then would otherwise be achieved. To accomodate thermal expansion and contraction of the heating elements, the two pieces of the holder are clamped together by spring-loaded bolts which permit the spacing between the holder members to vary, while still securing the heating elements.
EMPLOYING SEMICONDUCTOR
HEATING ELEMENTS
INVENTOR: KOSTA PELONIS
ABSTRACT OF THE DISCLOSURE
An electric heater is described which employs plate-shaped heating elements, each consisting of a core of semiconductor material whose opposing faces are coated with conductive material and having a multiplicity of apertures to permit passage of air. The heater includes a housing with a rear air inlet and a forward air outlet. A fan having a fan venturi causes air flows forwardly through the housing. A two-piece, ceramic holder maintains a number of the plate-shaped heating elements in generally coplanar, spaced-apart relationship,in front of a forward venturi opening. The holder has a large recess positioned over the forward venturi opening which receives substantially all air flow from the venturi, and a number passages, one associated with each heating element, which direct air from the recess through the cores towards the forward air outlet. Each of the passages flares radially outwardly and rearwardly from the rear face of the associated heating element, and opens into the recess,and the recess flares radially outwardly and rearwardly from about the passage openings to the forward venturi opening. The arrangement results in improved heat transfer and much quieter operation then would otherwise be achieved. To accomodate thermal expansion and contraction of the heating elements, the two pieces of the holder are clamped together by spring-loaded bolts which permit the spacing between the holder members to vary, while still securing the heating elements.
Description
~23~
F IELD OF THE IN~ENTI ON
The inYention relates to forced-air electric heaters, and more particularly to improvements in the construction of electric heaters incorporating semiconductor heating elements.
CACK~ROUND OF THE I N~ENT I ON
Electric heaters employing semiconductor heating alements represent a msrked improYement over prior resistance-wire type heaters. These new heaters include heating elements which consists of a planar core of semiconductor material 10 formed with a multiplicity of apertures that permit passage of air to draw heat from the core. Opposing faces of the core are coated with electrically conductiYe coatings that produce a fairly eYen distribution of current flow in the core when a Yoltage difference is applied to the coatings. These heaters tend to be more durable than 15 prior resistance-wire type heaters, tend to be more compact for a giYen heat requirement, and haYe the additional adYantage that Yery hot air flows can be produced while the temperature of the associated heating element remains below about 200 degrees centigrade, thereby reducing the risk of fire, particularly where 20 thsre sre flammable materials in the heated environment. Such a heater was proposed by me in my Canadian patent No. 1,190,579 i ssued on Jul y 1 6,1 9C5.
Heaters incorporating semiconductor heating elements of the type described above are still relatively novel, and a number of 25 problems have arisen in the construction of such heaters. In particular, a conYenient, inexpensiYe mechanism is required to hold '" ;~`
~LZ3~
the heating elements. The ex~xct m~nner in which the heating elements are held tends to be more critic~l in the new type he~ters than in the old resistance-wire type~ as the heating elements tend to ~e ~maller, ~nd sir flows from ~n ~ssoci~ted f,3n must S consequently be more ti~htly constr~ined to achie~e the full ~enefit of employlng SllCil he~ting elements. As well~ ~eoi3use of the size ~nd nature of the heatin~ elements~ considerable care must be taken to ensure ~imultoneous electric31 an~ therm~l isolation of the he~ting elements frorn ~ny assoc:ia~ed housing/ ~n~ proper electrical 10 contact with a supply of line ~olt3ge. Moero~er~ it is ~esir~ble to impro~e ttle he3t transfer e~iciency of suctl a heater, and to pro~id~
~uieter oper~tion~ operation tending to be noi~y beoause of the extent to whioh ~ir flows ~re ~ffected ~y the limited cross-seotion~l sre~ of the new heoting elements.
Accordin~ly! it i~ one o~ject of the present in~,~ention to pro~ide ~ he~ter oonstruction employin~q semioonduotor he~tin~q elements of the type described ~bo~e which results in impro~ed he~t tr~nsfer ond quiet oper3tion.
It is another o~ject o~ the in~ention to pro~ide ~
~0 GonYenient~ inexpensi~e meoh~nism tor holdin~ ~nd eleotric~lly cont~oting semiconductor he~tin~ elements of the type descri~ed 3bo~e.
eRIEF SUMMAR'f OF TH IN~ENTION
The inYention provides ~n electric he~ter which includes ~5 ~ housin~ h~ing ~ rear ~ir inlet ~nd ~ ~orw~rd ~ir olltlet. A f~n is mounted inside the housin~ intermedi3te of the reor ~ir inlet ~nd the ~23~
forward air inlet to produoe an air flow through the housing. The fan is of a type whioh inoludes ~ fan Yenturi that. ~ireot.s air flows generated ~y the fan frorll a re.ar Yenturi openin~ ~whioh i~ plaoed in oommunioation with the rear air inlet of t.he hou~ing~ to a for,ward 5 ~enturi opening.
The fan air flows are heated ~y a multiplicity of disk-shape~ heatin~ elements. Each heating element inolu~es a ~enerally planar eore with a pair of opposin~ forward and resr core faoesl aleotrioally conduotiYe ooatin~s oo~ering eaoh of the 10 opposin~ faoesl and a multiplioity of apertures whioh permit air flnw throu~h the oore. The oores are formed of a ~emioonduotor materi~l with preferrably a positi~e re~i~tanoe-temperat~re ooeffioientl the ~i~nifio~noe of whioh will ~e discussed ~elow in oonneo~ion with a preferred em~odiment of ~he in~ention.
A heatin~ element holder formed of an electric~lly insulatin~ and heat-insulating materi~l is mounted in the hou~in~
intermediate of the forw~rd f~n Yenturi openin~ and the forward air outlet of the housin~. The holder includes holdin~ means whic.h m~intoin the heating elements in ~ener~lly coplanar, spaced-apart 20 relationship relative to one ~nother. When the holder iSr in an operati~e positionl the heating elements are oriented ~enerally perpendicul~r to the longitudinal ~xis of the f3n venturi and spaced forwardly therefroml ~,4fith each rear core fac.e facin~ ~ow~rds the ~orw~rd venturi openin~.
~5 The holder is adapted to direct air flows esGapin~ from the forw~rd fan venturi opening through the cores. Aocordinglyr the ., ~lVfl 3~Lt7~3 holder comprises ~ir flow reoei~in~ me~ns inoludinç~ a reoess formed in 3 rear f~oe of the holder ~nd pnsitioned ~t. the fnrw~rd f~n Yenturi openin~r whioh reoei~e su~st~ntislly ~11 air flow from the forward ~enturi openin~ in t.he reoe~s. A niultiplioity of p~ss3ges in S the holder ~ui~e air reoei-~ed in the reoess through the he~tin~
elements. E~oh pass~e extends ~etween ~ forw~rd f~oe ~nd the re~r f~oe of the holderr ~nd e~oh p~ssage has ~ forw~rd openin~ in the forward faoe of the holder ~nd ~ renr openin~ in the reoessl ~p~oed forwardly of the forw~rd f~n ~enturi openin~. E30h p~ssn~e is ~ssooi~ted with ~ different one of the he~ting elements! the assooi~ted he~tin~ element bein~ positioned intermedi3te of the forw~rd ~nd re3r p~ss~e openillgsr ~nd positioned so th~t ~11 sir flow in the pass~qe is oonstr~ined to flow throu~h the oore.
The p~s~r~e 3nd the recess ~re sh~ped or dimensioned to proYide ~ smooth ~ir flow through the cores. In p~rticular, each of ~he p~ss~ges h~s ~ minimum cross-section~l area which corresponds su~s~anti~lly to the cross-~ection~l area of the ~ooi~ted he~tin~ element. E~ch p~ss~ge is flared re~rw~rdly ~nd r~di~lly outw~rdly from the rear faoe of the ~ssoci~ted heatin~
~0 element t.o gwide ~ir flow~ smoothly towards the he~ing element.
The recess is simil~rly fl~red~ radi~lly outwardly ~nd rearw~rdly, from ~bbut the re~r p~s~ge openin~s to the re~r f~ce of the holder.
The fl~ring which may ~e either conYex or concaYe result in less tur~ulent ~ir flows and cnnsequently quieter oper3tion.
Electric~l connection me~ns are proYided which extend into the holder ~or placing the co3tin~qs of e~c:h he~tin~ element in ~3~7~8 oont3c.t with the source of electric. power/ ~nd also ser~e to pl~ce the fan in contact with the so~lroe of power.
Other ~speets 3nd ~ nt~ges of the present inYention, particlllarly a no~el heating element holderJ will be apparent from 5 the description below of a preferred em~odiment.
~OF THE ~RAWIN~S
The inltention will ~e better ~Inderstood with reference to dr~wings illustr~tin~ a preferred embodimentr in which:
fi~. 1 is ~ perspecti~e ~iew of ~n eleotric he~ter 10 embodyin~ the in~ention;
fig. 2 is ~n explo~ed perspecti~e ~ieYY of the he3ter;
fig. 3 is ~ perspeeti~e ~iew of ~ he~tin~ elemen~ h~lder inc.orpor~ted in the heater;
fi~. 4 is ~ cross-seotion~l ~iew alon~ the lines 4-4 of 15 f i ~ nd~
fi~. 5 is a schematic drawing 4f the electric;al control oirouitry assooiated with the heater.
DE50RIPT ~N OF PREFERRED Et~BODIMENT
Fig. 1 illustrates the major components ~exo~ptin~
~O wirin~ of ~n electrio he~ter 10 embodyin~ the in~ention. The heater 10 incll~des a housin~ constrwcte~ of sheet. metal. The housin~ inGllldes 3 m~in housing member 1~ whose front face h~s a forward air outlet 1~ ciroumscribed by abuttment flanges 1~ ~only one spe~ifically indio~te~ in fig. ~. The housin~ ~lso includes ~
~5 re~r housin~ insert 1~ which fits ti~htly into the ~ack of the m3in housin~ mernber 1~ and which is att30hed to the main ~-,ousing 3L23~7~
B
member 12 by mean~ of s~rews ~not illustr~ted~ thre~ded through hole~ ~only one hole ~0 specifically indicated~ proYided in the sidewalls of the main housing membe.r 17. The re~r housing insert 1 ~ has a rear ai r i nl et ~7 whi ch i ~ normal 1 y oo~ered by a remo~abl e 5 sheet ~4 of ~ppropriate air filterin~ material, retained by means of br~ckets ~ ~two such ~r~ckets being illustrated in the oross-sectional view of fi~. 4~. The construetion, tfunctiorl and ~s~em~ly of many of the oomponents will ~e readily apparent~ and oonsequently only det~ils ot the Yariou~ components relating 10 specifio~lly to aspectC. of the inYention will be proYide~ in order to better highlight the in~ention.
The ~e~ting function of the electric heater 10 i~ pro~ided by four disk-shaped heating elements 2~.~ 30~ 4. The he~ting elements are sub~t~ntially identical~ ~ncl c.onsequently only the 15 heating element ~8 will be desoribe~ in detail~ with particular referenoe to tig. 5 where components of the he~ting element 2~
~etter illustrated. The heatin~ element ~ inelu~es ~ planar eore 40 of semioonduotor m~terial h~Y~ng 3 forYYard f~ee 4~, an opposing rear f~e 44 ~nd ~ ~enerally eireul3r peripheral ed~e 4~. The 20 thiokness of the oore 40 is ~bout 1~4 ineh) ~nd the diameter ot the peripheral ed~e 4~ i~ a~Gl~t 1 ~n~ 15~1~ inehe~. ~ondueti4~e sil~er ooatings 4~, 50 are deposited on the forward ~nd rear eore f~oes 42, 44, and ser~e to produoe a distributed o~rrent flo~Y between the opposing oore f~ces 4~, 44 ~YYhen a Yoltage differenoe is applied to ~5 the ooatin~s 4~, 50. A multiplioity of apertures ~not specifioally indioated~ extending between the forw~rd and rear oore faoes 4~, 44 ~LZ3~L7~8 permit ~ir flow throu~h the oore ~0 to dr~w heat from the oore 40 durin~ oper~tion. The rel~tiS~e orient~tion of the oore~; is th~t illustr~teci in fig. ~, n~mely) ~ ~enerally copl~n~r~ sp~oe~ p~rt rel~tionship.
The semioon~uotor m3teri~1 of the cores is preferr~ly mixture of le~d titanate ~nd barillm tit~nate~ ~lthou~h ~ St~riety of o~ler semioonduotor m~teri~ls may be used. The semioorlciuctor m~teri~l has ~ relatiStely high resistsnGe-temper~ture coeffioient~
whioh is norm~lly ~bout 7.65 ohms~ciegrees oenti~r~e ~3S mes~ured ~etween the opposin~ faoes of ~11 oores ~nd oon~i~erin~ the oores ~s p~r~llel resist~noe~s~. The rasistanoe as me~swred between tha opposin~ f~oes of the cores ~onoe ag~in considerin~ the oores to ~e resistanoes oonneoted in p~rallel~ tot~ls about ~ ohms ~t 1~5 ~eQrees oenti~racie and about 161 ohms at 1~5 degrees oenti~rade.
With a line ~tolt~e of l 10 st. RMS ~pplied to the npposing faces of the cores~ the cores will ha~e a nominal power oonsumption of about 1~500 W ~t ~n oper~tin~ temper~ture of 1~ degrees oenti~r~de~ ~nd 3 nomin~l power consump~ion of ~5 W at ~n operstin~ temper~ture of 1~5 de~ree~ centigrade. It will ~e re3dily ~pp~rent th~t the ~0 power oonsumption of the cores drops m~rkedly 3s the oper~tin,q temper~ture of the oores rises. Aooordin~lyJ in most eircumst~noes, with no sir flow throu~h the oores to draw hest, the cores m~y ~e expeoted to re~oh ~n equilibrium temper3ture below ~bout 200 de~rees centi~r~de.
F IELD OF THE IN~ENTI ON
The inYention relates to forced-air electric heaters, and more particularly to improvements in the construction of electric heaters incorporating semiconductor heating elements.
CACK~ROUND OF THE I N~ENT I ON
Electric heaters employing semiconductor heating alements represent a msrked improYement over prior resistance-wire type heaters. These new heaters include heating elements which consists of a planar core of semiconductor material 10 formed with a multiplicity of apertures that permit passage of air to draw heat from the core. Opposing faces of the core are coated with electrically conductiYe coatings that produce a fairly eYen distribution of current flow in the core when a Yoltage difference is applied to the coatings. These heaters tend to be more durable than 15 prior resistance-wire type heaters, tend to be more compact for a giYen heat requirement, and haYe the additional adYantage that Yery hot air flows can be produced while the temperature of the associated heating element remains below about 200 degrees centigrade, thereby reducing the risk of fire, particularly where 20 thsre sre flammable materials in the heated environment. Such a heater was proposed by me in my Canadian patent No. 1,190,579 i ssued on Jul y 1 6,1 9C5.
Heaters incorporating semiconductor heating elements of the type described above are still relatively novel, and a number of 25 problems have arisen in the construction of such heaters. In particular, a conYenient, inexpensiYe mechanism is required to hold '" ;~`
~LZ3~
the heating elements. The ex~xct m~nner in which the heating elements are held tends to be more critic~l in the new type he~ters than in the old resistance-wire type~ as the heating elements tend to ~e ~maller, ~nd sir flows from ~n ~ssoci~ted f,3n must S consequently be more ti~htly constr~ined to achie~e the full ~enefit of employlng SllCil he~ting elements. As well~ ~eoi3use of the size ~nd nature of the heatin~ elements~ considerable care must be taken to ensure ~imultoneous electric31 an~ therm~l isolation of the he~ting elements frorn ~ny assoc:ia~ed housing/ ~n~ proper electrical 10 contact with a supply of line ~olt3ge. Moero~er~ it is ~esir~ble to impro~e ttle he3t transfer e~iciency of suctl a heater, and to pro~id~
~uieter oper~tion~ operation tending to be noi~y beoause of the extent to whioh ~ir flows ~re ~ffected ~y the limited cross-seotion~l sre~ of the new heoting elements.
Accordin~ly! it i~ one o~ject of the present in~,~ention to pro~ide ~ he~ter oonstruction employin~q semioonduotor he~tin~q elements of the type described ~bo~e which results in impro~ed he~t tr~nsfer ond quiet oper3tion.
It is another o~ject o~ the in~ention to pro~ide ~
~0 GonYenient~ inexpensi~e meoh~nism tor holdin~ ~nd eleotric~lly cont~oting semiconductor he~tin~ elements of the type descri~ed 3bo~e.
eRIEF SUMMAR'f OF TH IN~ENTION
The inYention provides ~n electric he~ter which includes ~5 ~ housin~ h~ing ~ rear ~ir inlet ~nd ~ ~orw~rd ~ir olltlet. A f~n is mounted inside the housin~ intermedi3te of the reor ~ir inlet ~nd the ~23~
forward air inlet to produoe an air flow through the housing. The fan is of a type whioh inoludes ~ fan Yenturi that. ~ireot.s air flows generated ~y the fan frorll a re.ar Yenturi openin~ ~whioh i~ plaoed in oommunioation with the rear air inlet of t.he hou~ing~ to a for,ward 5 ~enturi opening.
The fan air flows are heated ~y a multiplicity of disk-shape~ heatin~ elements. Each heating element inolu~es a ~enerally planar eore with a pair of opposin~ forward and resr core faoesl aleotrioally conduotiYe ooatin~s oo~ering eaoh of the 10 opposin~ faoesl and a multiplioity of apertures whioh permit air flnw throu~h the oore. The oores are formed of a ~emioonduotor materi~l with preferrably a positi~e re~i~tanoe-temperat~re ooeffioientl the ~i~nifio~noe of whioh will ~e discussed ~elow in oonneo~ion with a preferred em~odiment of ~he in~ention.
A heatin~ element holder formed of an electric~lly insulatin~ and heat-insulating materi~l is mounted in the hou~in~
intermediate of the forw~rd f~n Yenturi openin~ and the forward air outlet of the housin~. The holder includes holdin~ means whic.h m~intoin the heating elements in ~ener~lly coplanar, spaced-apart 20 relationship relative to one ~nother. When the holder iSr in an operati~e positionl the heating elements are oriented ~enerally perpendicul~r to the longitudinal ~xis of the f3n venturi and spaced forwardly therefroml ~,4fith each rear core fac.e facin~ ~ow~rds the ~orw~rd venturi openin~.
~5 The holder is adapted to direct air flows esGapin~ from the forw~rd fan venturi opening through the cores. Aocordinglyr the ., ~lVfl 3~Lt7~3 holder comprises ~ir flow reoei~in~ me~ns inoludinç~ a reoess formed in 3 rear f~oe of the holder ~nd pnsitioned ~t. the fnrw~rd f~n Yenturi openin~r whioh reoei~e su~st~ntislly ~11 air flow from the forward ~enturi openin~ in t.he reoe~s. A niultiplioity of p~ss3ges in S the holder ~ui~e air reoei-~ed in the reoess through the he~tin~
elements. E~oh pass~e extends ~etween ~ forw~rd f~oe ~nd the re~r f~oe of the holderr ~nd e~oh p~ssage has ~ forw~rd openin~ in the forward faoe of the holder ~nd ~ renr openin~ in the reoessl ~p~oed forwardly of the forw~rd f~n ~enturi openin~. E30h p~ssn~e is ~ssooi~ted with ~ different one of the he~ting elements! the assooi~ted he~tin~ element bein~ positioned intermedi3te of the forw~rd ~nd re3r p~ss~e openillgsr ~nd positioned so th~t ~11 sir flow in the pass~qe is oonstr~ined to flow throu~h the oore.
The p~s~r~e 3nd the recess ~re sh~ped or dimensioned to proYide ~ smooth ~ir flow through the cores. In p~rticular, each of ~he p~ss~ges h~s ~ minimum cross-section~l area which corresponds su~s~anti~lly to the cross-~ection~l area of the ~ooi~ted he~tin~ element. E~ch p~ss~ge is flared re~rw~rdly ~nd r~di~lly outw~rdly from the rear faoe of the ~ssoci~ted heatin~
~0 element t.o gwide ~ir flow~ smoothly towards the he~ing element.
The recess is simil~rly fl~red~ radi~lly outwardly ~nd rearw~rdly, from ~bbut the re~r p~s~ge openin~s to the re~r f~ce of the holder.
The fl~ring which may ~e either conYex or concaYe result in less tur~ulent ~ir flows and cnnsequently quieter oper3tion.
Electric~l connection me~ns are proYided which extend into the holder ~or placing the co3tin~qs of e~c:h he~tin~ element in ~3~7~8 oont3c.t with the source of electric. power/ ~nd also ser~e to pl~ce the fan in contact with the so~lroe of power.
Other ~speets 3nd ~ nt~ges of the present inYention, particlllarly a no~el heating element holderJ will be apparent from 5 the description below of a preferred em~odiment.
~OF THE ~RAWIN~S
The inltention will ~e better ~Inderstood with reference to dr~wings illustr~tin~ a preferred embodimentr in which:
fi~. 1 is ~ perspecti~e ~iew of ~n eleotric he~ter 10 embodyin~ the in~ention;
fig. 2 is ~n explo~ed perspecti~e ~ieYY of the he3ter;
fig. 3 is ~ perspeeti~e ~iew of ~ he~tin~ elemen~ h~lder inc.orpor~ted in the heater;
fi~. 4 is ~ cross-seotion~l ~iew alon~ the lines 4-4 of 15 f i ~ nd~
fi~. 5 is a schematic drawing 4f the electric;al control oirouitry assooiated with the heater.
DE50RIPT ~N OF PREFERRED Et~BODIMENT
Fig. 1 illustrates the major components ~exo~ptin~
~O wirin~ of ~n electrio he~ter 10 embodyin~ the in~ention. The heater 10 incll~des a housin~ constrwcte~ of sheet. metal. The housin~ inGllldes 3 m~in housing member 1~ whose front face h~s a forward air outlet 1~ ciroumscribed by abuttment flanges 1~ ~only one spe~ifically indio~te~ in fig. ~. The housin~ ~lso includes ~
~5 re~r housin~ insert 1~ which fits ti~htly into the ~ack of the m3in housin~ mernber 1~ and which is att30hed to the main ~-,ousing 3L23~7~
B
member 12 by mean~ of s~rews ~not illustr~ted~ thre~ded through hole~ ~only one hole ~0 specifically indicated~ proYided in the sidewalls of the main housing membe.r 17. The re~r housing insert 1 ~ has a rear ai r i nl et ~7 whi ch i ~ normal 1 y oo~ered by a remo~abl e 5 sheet ~4 of ~ppropriate air filterin~ material, retained by means of br~ckets ~ ~two such ~r~ckets being illustrated in the oross-sectional view of fi~. 4~. The construetion, tfunctiorl and ~s~em~ly of many of the oomponents will ~e readily apparent~ and oonsequently only det~ils ot the Yariou~ components relating 10 specifio~lly to aspectC. of the inYention will be proYide~ in order to better highlight the in~ention.
The ~e~ting function of the electric heater 10 i~ pro~ided by four disk-shaped heating elements 2~.~ 30~ 4. The he~ting elements are sub~t~ntially identical~ ~ncl c.onsequently only the 15 heating element ~8 will be desoribe~ in detail~ with particular referenoe to tig. 5 where components of the he~ting element 2~
~etter illustrated. The heatin~ element ~ inelu~es ~ planar eore 40 of semioonduotor m~terial h~Y~ng 3 forYYard f~ee 4~, an opposing rear f~e 44 ~nd ~ ~enerally eireul3r peripheral ed~e 4~. The 20 thiokness of the oore 40 is ~bout 1~4 ineh) ~nd the diameter ot the peripheral ed~e 4~ i~ a~Gl~t 1 ~n~ 15~1~ inehe~. ~ondueti4~e sil~er ooatings 4~, 50 are deposited on the forward ~nd rear eore f~oes 42, 44, and ser~e to produoe a distributed o~rrent flo~Y between the opposing oore f~ces 4~, 44 ~YYhen a Yoltage differenoe is applied to ~5 the ooatin~s 4~, 50. A multiplioity of apertures ~not specifioally indioated~ extending between the forw~rd and rear oore faoes 4~, 44 ~LZ3~L7~8 permit ~ir flow throu~h the oore ~0 to dr~w heat from the oore 40 durin~ oper~tion. The rel~tiS~e orient~tion of the oore~; is th~t illustr~teci in fig. ~, n~mely) ~ ~enerally copl~n~r~ sp~oe~ p~rt rel~tionship.
The semioon~uotor m3teri~1 of the cores is preferr~ly mixture of le~d titanate ~nd barillm tit~nate~ ~lthou~h ~ St~riety of o~ler semioonduotor m~teri~ls may be used. The semioorlciuctor m~teri~l has ~ relatiStely high resistsnGe-temper~ture coeffioient~
whioh is norm~lly ~bout 7.65 ohms~ciegrees oenti~r~e ~3S mes~ured ~etween the opposin~ faoes of ~11 oores ~nd oon~i~erin~ the oores ~s p~r~llel resist~noe~s~. The rasistanoe as me~swred between tha opposin~ f~oes of the cores ~onoe ag~in considerin~ the oores to ~e resistanoes oonneoted in p~rallel~ tot~ls about ~ ohms ~t 1~5 ~eQrees oenti~racie and about 161 ohms at 1~5 degrees oenti~rade.
With a line ~tolt~e of l 10 st. RMS ~pplied to the npposing faces of the cores~ the cores will ha~e a nominal power oonsumption of about 1~500 W ~t ~n oper~tin~ temper~ture of 1~ degrees oenti~r~de~ ~nd 3 nomin~l power consump~ion of ~5 W at ~n operstin~ temper~ture of 1~5 de~ree~ centigrade. It will ~e re3dily ~pp~rent th~t the ~0 power oonsumption of the cores drops m~rkedly 3s the oper~tin,q temper~ture of the oores rises. Aooordin~lyJ in most eircumst~noes, with no sir flow throu~h the oores to draw hest, the cores m~y ~e expeoted to re~oh ~n equilibrium temper3ture below ~bout 200 de~rees centi~r~de.
2~ A fan 5~ is mounted inside the m~in housin~ member 1 intermediate of the rear ~ir inlet 1~ ~nd the forw~rd air outlet 14.
3~ 8 1~
The f~n 5~ has ~ fan rasin~ 54 whioh define~ ~ f~n ~enturi 56. The f~n ~enturi 5~ h~s ~ forw~rd ~enturi opening 5~, ~ re~r ~enturi opening ~0 Jnd ~ rentr~l longitlIdin~l ~xis 6~. The f~n 5~ h~s 3 rentr31 hub 64 mounted in the f~n ~enturi 5~ in gener~l ~lignment S with the ~enturi ~xis 6~ ~y me~ns of ~ spider 6~ whioh h~s four 1Q9S
68 ~only one sperific~lly indio~ted~ oonneoting the hu~ ~4 to the f~n casing 54. The hu~ 64 oontains ~n electrio motor ~not illustrsted~
~nd a f~n ~13de ~ssem~ly 70 whioh c~n ~e rot~ted oy the motor to produoe ~n air flow forw~rdly throu~h the f~n ~enturi S~. Power to 10 oper~te the motor is oondurted through one of the legs of the ~pider in ~ manner whioh will not ~e de~rri~ed. A suitable f~n is sold ~y Rotron Inc. of Woodstook~ llew ~ork, U.S.A. under the tr~de m~rk 11UFFIll.
The he~ter 10 ~lso includes ~ heating element holder whir.h holds the heating elements 2~/ ~0. 3~1 ~4 in the generally copl~nsr, spsred-spsrt rel~tionship referred to ~bove. The hestin~
element holder ~lso orients the cores of the he~ting elements generally perpendicular to the longitudin~l ~xis ~2 of the lan nturi 5~, spaced s~out 1 inch forw~rdly of the forw~r~ Yenturi ~0 openin~ 5~ with esch rear oore f~oe f~cin~ towards the forward Yenturi opening 5~. The hol~er has ~ two-pieee sep~r~ble construction in~ol~ing ~ forward holder member- 7~ ~nd 9 re3r holder mem~er 74/ each of which is formed of 3 cersmic msteri~l. The term "ceramic m~teri~l" ss used in this specific~tion is intended to 25 denote a clay-like m~terisl such ss fired ~reenware, porcel~in or ~ny other material that c~n ~e mol~ed in ~n initi~l condition ~nd ~L23~8 then fired to produoe a hard dur~le produot ~nd that is both therm~lly ond electriG~lly insul3ting ~uch oer~mic m~teri~ls ~re ~ner~lly inexpensi~ ~nd e~sily mol~e~ into the e.h3pes required. It will ~e ~ppreoi3ted~ howe~er, '~h~t the resùl'~nt produot tends to be 5 ~ry ~rittle.
The forw3r~ holder mem~er 72 defines 3 forward f~oe 7 of the holder ~nd h~s ~n opposing inner f~oe ~. The re~r holder mem~er 74 defines ~ re~r f~oe ~0 of the holder ~n~ h~s ~n opposing inner f~Ge ~2 which is positione~ ~dj~oent the inner f~oe 7~ when 10 the he~ting element hol~er is fully ~s~em~led.
The inner hnlder mem~er f~ces 7~ re oontoure~ to define pooket~ ~two speoifio~lly indio~ted ~y referenoe numer~ls ~, 8& in the eross-see~ion~l ~iew of ~ig. 4~ in whioh the he3ting elements arQ ret~ined. The oontourillg in this inst~nee oonsists of 15 ~ener~lly tri~n~ul~r projections ~only two projeotions 8~, 90 speoifio~lly indio~ted in fig. ~ where the oontouring is ~est shown~
and oentr~l oiroul~r projections 92, ~4, hest illustrated in the ~iew of fi~. 3 where the holder mem~ers 7~, 76 ~re shown sep~r~ted.
When the holder is ~ssem~led, as in fi~. 4, the pookets oloe.ely reoeive the he~ting elements, gripping the oppo~ing faoes of e~oh hester el ement oore. Al thou~h ~he pookets ~ef i ned ~re rel ati ~el y loose ~in r~di~l direGtions~, the ~rr3ngement has pro~en suffioient for the purposes of the invention.
The heating element holder 31so has four p~ss~es, one assooi sted wi th 3 di f f erent one of the f our hea~i n~ el ements, whi oh direot ~ir flows through the heating elements. Eaoh p~ss~g~ extends ~231~
1~
between the forw3rd ~nd re3r holder faces 76/ ~0, ~nd h~s a forward p~ss3ge openin~ ~not spec;ifioally irldioated~ in the forward holder faoe ~6 and ~ re~r pass~e openin~ ~not speoific311y indioated~ in the re~r holder f~ke ~0/ more speoifioally, in 3 reoess formed in the . 5 rear holder f~oe ~0 and desoribed more fully below. Two suoh pass3~es 96, Y~ are speoifioally indio3ted in the oross-seotion31 ~iew of fig. 4. It will be apparent from fi~. 4 th3t eaoh of the p3ss3ges g~, 9~ intersects the poeket in whioh the ~ssooiated heating element ~ or ~, respeoti~ely, is oont~ined, and that eaoh of the p~ssages 96; g~ h~s ~ minimum oross-seotion31 area perpendioular to the ~enturi axis 6~ whioh is subst~nti~lly the s~me as the oross-seotional 3rea of the assooiated heatin~ element, there~y ensuring retention of the assooi~ted heatin~ elsment without si~nifio3ntly impedin~ 3ir tlow throu~h the assooi~ted heatin~ element. The he~tin~ elements ~re of oourse so positioned in the ~ssooiate~ pass~ges th3t substanti~lly 911 ~ir flow in the passa~es is constrained to flow throu~h the eores of the h~ating elements.
The holdei- is also ~dapted t~ reoei~e su~stantially all air flow from the forw~rd ~enturi openin~ 5~. In p3rtioular, the re3r holder mem~er 74 h~s a reotan~ulsr oiroumf~renti~l lip 100 dimensioned to fit 3~cut ~ oorrespondin~ lip 10~ of the f~n cssin~
54. Air flow from the forward ~enturi opening 5~ is conse~w~ntly directed ~inst the re~r holder f~ce ~0, 3nd ~ 13r~e r~cess 104 is formed in the resr holder faoe ~0 ~djaoent to ~nd in ~ener31 3xisl ~lignment with the forward ~enturi openin~ 5~ to recei~e t.he 3ir , ~Z3~7~8 flows. E~ch of the passa~es ~suGh as the pass3ges ~, 98~ in whioh the heatin~ elements are positioned has its re~r p~s~e opening looated within the recess 104/ spaced forw3rdly of the forward ~enturi opening 5~. As will ~e app~ren~ in fig Clr where the 5 orosg-seotional shape of the passages g6r g~ is shown, the passages g~ flare radially outwardly an~ re~rwardly from the re~r faoe of each assooiated heating element 2~ ~2 respeoti~ely to the ~ssoci3ted rear p~ss3~e opening. Simislrly/ the reoess 104 flares radially outwar~ly and rearwardly from a~out the re3r pass~ge 10 openings to the re~r holder face B0. Aocordin~ly~ su~stantially all ~ir escaping from the forward venturi openin~ 5B is deli~ered in relati~ely smooth fashion to the heatin~ elements.
The forw~rd holder member 7~ is identical to the rear holder member ~ and is effeoti~ely the re~r holder mem~er 76 15 rot.~ted through 1~0 degrees a~ou~ a ~ertio31 axis. ~coordingly~ the forw~r~ hol~er mem~er 72 defines a large recess 10~ in the forward older face 76 into whioh eaoh of the forw~rd passage openin~qs opens. Aocordin~qly, eaoh of the hol~er pass3~e~ ~UCh as ~he pass~es g6, ~ whioh are exemplar~ and illustrated in fi~. 43 fl~res ~0 r~di~lly outw~r~ly and forw3rdly from the front faoes of e~ch assooiated he~ting elernent~ ~nd the recess 106 fl~res radi~lly outwardly and forwardly from a~out the forward passage openings to the forw~rd holder f~ee 76. This arr~ngemsnt produoes ~
smoothin~q of the heated air flows escapin~ from the forward air ~5 outlet 14~ but is not striotl~ essential to o~t~ining improl/ed he~t transfer effioienoy and quieter operation. The ~rrangement does~
~-~3~ 48 1~
howevet-, eliminste the need for ~n ~ditional distinot oomponent in the hester 10.
Forw~rd and rear oon~uotive metal plates 10~, 110 proYide eleetrical oontaot with the forward sn~ rear faoes of the he~tin~ element oores inside the holder. It will ~e ~pparerIt from the view of fig. ~ th3t the forw~rd conduotive plate lOB seats in reoess defined by the tri~n~ul~r projeetions on the inner f~ee 7B, and h~s a een~ral ~perture 112 whioh permits olearanoe of the oentr~l projeotion ~2. The plate 10~ oYerlsys the forward fsoe~ of the he~ting element oores to proYide the required eleotrical cont~ot.
Four apertures 114 lonly one specifioslly indioated~ with ~ oiroular periphery ~re forme~ in the pl~te 10~ ~n~ ~re po~itioned olY~er the forwsrd fsee~ of the hester element cores to permit pas~e of ~ir.
The di~meter of the spertures on the pl~te 1 14 is m~rginally sm~ller thsn th~t of the he~tin~ elements to ensure eleetrie~l eontaot. A metal terminal strip 11~ is spot welded to the pl~te 10~, ~nd extends to points external of the he~ter element holder, when assembled, to permit line ~olta~e to ~e convenientl~ applied to the pl~te lQa To ~Gcommod~te the terminal strip 11~, 3 ~roove 2~ is formed in the inner faoe 7~ of the forward holder member 76, ~n~ is dimensioned to recei~te the terminal strip 11~ loosely. The conducti~e pllte 110 provides electriosl contaot with the re~r faces of the heating element Gores, ~nd seats sg3inst the inner f~ce ~ of the resr holder member, in ~ msnner ~nalo~ous to the sestin~ of the plate 10~. The struotllre and function of the two pl2tes 10~, 110 is su~stantially i~entio~ nd consequently no further detail will ~e ~ 23~L~7 pro~ided reg3rdin~ the plate 110.
The hol~ler members 72, 74 ~re dr~wn to~ether ~o oont~in the he~tin~ elements in the pockets ~y means of four fasteners.
~inee the fasteners are identie31, only one`f~tener 1~0 h~s ~een speGifiGally illustrated 3nd indiosted, in fi~. ~. The fastener 1~0 oonsists ~sicslly of ~ ~olt 1~ nd ooil spring 124 ~nd a nut 12~.
The heatin~ element holder is first loosely assem~led, for ex~mple, by seatin~ the plate 110 a~3inst the inner faoe ~ of the re~r holder member 74, positienin~ the he3ter element~ ~ppr~pri3tely o~er the lQ ~pertures in the pl~te 110, se~tin~ the pl~te lQ~ 3~inst the inner f~oe 7~ of the forward holder mem~er 72, and then carefully ~ringing the hol~er mem~er 72, 7~ to~ether in ~n operatiS,~e orientation. The holder mem~ers 72, 74 then h~e four p~irs of 31igned ~pertures, only the ~pertures 1~ 130 ~ein~ speoifio~lly indioated, whioh extend fully ~etween the forward and re3r holder faees J~, ~0. The ooil spring 124 is loo~ted a~out the ~h~ft 1~2 of the ~olt 12~, 3nd the sh~ft extended fully throu~h the aligned 3pertures 12~, 13Q. The nut 1~6 i~ then threaded onto the re3r sh3f~ en~ portion 1~4 until the nut 1~ abuts the rear holder faoe ~0. The ooil ~prin~ 124, which h3s a 13rger diameter than the ~pertures 1~ 0, locs~es in the process ~out ~ forward shaft end portion 1~, and acts betY~een the bolt he3d and the forw~rd holder face 76 to draw the holder mem~ers 7~, 74 together. To ensure po~iti~e seatin~ of the coil spring 124 3g~in~t the for~3rd ~5 holder memher 7~, 3 ~hallow well 140 i~ located 3~0ut the ~per~ure 12~ in the forward holder face 7~ and dimensioned to recei~e a ~2~17~3 portion of the coil spring 124. In the preferred embod.iment illustrated, a metal grill 141 is interposed between the bolt head of each fastener and the associated coil spring to fasten the grill directly to the forward holder member 72, but the grill 141 could equally well be attached to the abutment flanges 1~ of the main housing member 12.
The four fasteners being spring-loaded permit separation of the holder members 72, 74 in response to thermal expansion of the heating elements. This arrangement is critical, as the ceramic holder members 72, 74 are very brittle, and could otherwise be easily cracked during operation of the heater 10.
The heating element holder and grill 141 when assembled together are then attached to the fan casing 54.
This attachment is effected by passing the rear shaft portions of the various fasteners through apertures in the fan casing 54 and attaching additional nuts to the rear shaft end portions. For example, with the fastener 120 illustrated, an aperture 142 in the fan casing 54 is aligned 20 with the previously aligned holder member apertures 128, 130 and the rear shaft end portion 134 passed through the aperture 142. A nut 144 is then threaded onto the rear shaft end portion 134 to complete connection to the fan casing 54. The fan casing is in turn attached to the rear 2.5 housing insert 18 by means of four screws ~not illustrated) which are threaded through aligned aperatures (only one pair ~..,~
17~31~74~3 1 16(a) oE aligned apertures 146, 148 speciEically indicated) in the fan casing 54 and rear housing insert 18. A strip of insulating material 150 (fragmented) is wrapped around the periphery of the heating ~3~8 element holder, and the entire assembly so forme~ ls inserted lnto the mairl housing mem~er 1~ until th~ grill 14~ engages the a~.utment flanges 1~. ~.eGurem0nt is completed ~.y threading screws throu~h the holes ~0 in the main howsin~ mem~er 12 to secure the 5 rear hnusing insert t~ to the main housing mem~er t~, as mentioned a~ove.
The electric31 wiring and control circwitry associ3ted with the he3ter 10 is schematic~lly illustrated in fi~. 5. Line power is deli~ered ~ia a power cord 5~ tthe two lines of the power cord 10 bein~ indicsted with the same reference numeral 5~,~ to the conduotive plates 1O~J t 10. The electricsl connection so formed is direct, invol~in~ no switchin~ GirGuitry to control the amount of power delivered, except for a simple dou~le pole sinp,le throw switGh t 54 which serves to turn the power to the heater 10 off and 15 on. The power consumed ~y the heating elements, 3nd the heat conse~uently delivered is controlled entirely ~y varyino, fan speed with a fan control 15~. The fan control 15~ includes ~s 3 primary switching element a ~i~irection~l siliccn controlled rsctifier which permits su~stantially continuous variation of fan speed. ~
~0 inereasing fan speed the temperatllre of the heatin~ elements drops, ~.ut the resultsnt incre~se in conductivity of the hestin~
element Gores resul~s in ~ marked increase in power consumpti4n.
Thus, without effectively upw3rdly or downwardly scalinp, the line volta~e applied to the heatino, element cores, the quantitu, ~If heat ~5 delivered c~n ~e varied. The re~uired control circuitry and switGhes can ~e conveniently mounted to the rear housinp insert 18 with ~L23~7~8 1~
appropriate wirin~, as sohem~tio~lly illwstrated/ oonduct.ing power to the fan 52 and heating element~. These matters will be readily app~ren~ to one s~illed in the art.
A tesl: was performed to determine whether ~ he~ter 5 substanti~lly identioal to the preferred embodiment 10 exhibited improYed he~t transfer effioiency and quieter operation. The test inYol~e~l a oomparison with ~ prototype de~ioe that h~d an identio~l housin~qJ identio~l heating elementsJ sn identioal f~nJ ~nd identioal oontrol cirouitry. The prinoipal differenoe tletween the prelimin~ry 10 prototype ~nd the preferre~ Yersion of the heater resided in the he~tin~ element holder. The four hestin~ elements were oontained between t34o metal platesJ bolted to~etherJ e~ch of whioh was apertured to permit pass~e of air throu~h the he~tin~ elements in manner simil~r to that of the oonduotiYe pl3tes 108r 110. The 15 ~ssem~ly SQ formed was ~olted to the ~ssooi~ted fsn with the - heatin~ elements positioned at a~out 1 inoh ~rom the forwsrd f3n Yenturi opening. Power oorlsumption of the oores w~s monitore~ b~
mean~ of a watt nneter. With the protot~p~ ~ersi~n eoupled to a 1 lO
. ~MS lin~ souroeJ an am~iant temperature of ~out ~5 ~egrees ~O centigrade~ ~nd the fan operatin~ at full spee~J the heatin~ e.lements h~d a to~al power oon~umption of about 1J~OO W h noti~le le~k~ge of air baoksoattered throu~h the rear fan ~enturi openin~
was also noted. The preferred ~ersion substantially identical to the preferred embodiment 10 wa~ operated under simil~r oonditionsJ
25 and a hea~ing element power consumption of a~out 1J3~0 ~ Wa~
noted with no apparent leakage of air throu~h the rear fan ~enturi ~23~L'7~8 1~
openin~. This represents about a 1S% impro~ement in energy transf~r to f~n ~ir flows. Addition~lly~ on a purely qualit3ti~e basis~ it w~s noted th~t the preferrsd ~ersion was oonsidera~ly quiet~r in operation.
1~ will ~e appreoi~ted th~t a preferred embodimsnt of the in~en~ion has ~een dssori~ed and that modifications may ~e macle therein without dep3rting from the spirit of the in~ention and the soope of the ~ppended ol~ims.
The f~n 5~ has ~ fan rasin~ 54 whioh define~ ~ f~n ~enturi 56. The f~n ~enturi 5~ h~s ~ forw~rd ~enturi opening 5~, ~ re~r ~enturi opening ~0 Jnd ~ rentr~l longitlIdin~l ~xis 6~. The f~n 5~ h~s 3 rentr31 hub 64 mounted in the f~n ~enturi 5~ in gener~l ~lignment S with the ~enturi ~xis 6~ ~y me~ns of ~ spider 6~ whioh h~s four 1Q9S
68 ~only one sperific~lly indio~ted~ oonneoting the hu~ ~4 to the f~n casing 54. The hu~ 64 oontains ~n electrio motor ~not illustrsted~
~nd a f~n ~13de ~ssem~ly 70 whioh c~n ~e rot~ted oy the motor to produoe ~n air flow forw~rdly throu~h the f~n ~enturi S~. Power to 10 oper~te the motor is oondurted through one of the legs of the ~pider in ~ manner whioh will not ~e de~rri~ed. A suitable f~n is sold ~y Rotron Inc. of Woodstook~ llew ~ork, U.S.A. under the tr~de m~rk 11UFFIll.
The he~ter 10 ~lso includes ~ heating element holder whir.h holds the heating elements 2~/ ~0. 3~1 ~4 in the generally copl~nsr, spsred-spsrt rel~tionship referred to ~bove. The hestin~
element holder ~lso orients the cores of the he~ting elements generally perpendicular to the longitudin~l ~xis ~2 of the lan nturi 5~, spaced s~out 1 inch forw~rdly of the forw~r~ Yenturi ~0 openin~ 5~ with esch rear oore f~oe f~cin~ towards the forward Yenturi opening 5~. The hol~er has ~ two-pieee sep~r~ble construction in~ol~ing ~ forward holder member- 7~ ~nd 9 re3r holder mem~er 74/ each of which is formed of 3 cersmic msteri~l. The term "ceramic m~teri~l" ss used in this specific~tion is intended to 25 denote a clay-like m~terisl such ss fired ~reenware, porcel~in or ~ny other material that c~n ~e mol~ed in ~n initi~l condition ~nd ~L23~8 then fired to produoe a hard dur~le produot ~nd that is both therm~lly ond electriG~lly insul3ting ~uch oer~mic m~teri~ls ~re ~ner~lly inexpensi~ ~nd e~sily mol~e~ into the e.h3pes required. It will ~e ~ppreoi3ted~ howe~er, '~h~t the resùl'~nt produot tends to be 5 ~ry ~rittle.
The forw3r~ holder mem~er 72 defines 3 forward f~oe 7 of the holder ~nd h~s ~n opposing inner f~oe ~. The re~r holder mem~er 74 defines ~ re~r f~oe ~0 of the holder ~n~ h~s ~n opposing inner f~Ge ~2 which is positione~ ~dj~oent the inner f~oe 7~ when 10 the he~ting element hol~er is fully ~s~em~led.
The inner hnlder mem~er f~ces 7~ re oontoure~ to define pooket~ ~two speoifio~lly indio~ted ~y referenoe numer~ls ~, 8& in the eross-see~ion~l ~iew of ~ig. 4~ in whioh the he3ting elements arQ ret~ined. The oontourillg in this inst~nee oonsists of 15 ~ener~lly tri~n~ul~r projections ~only two projeotions 8~, 90 speoifio~lly indio~ted in fig. ~ where the oontouring is ~est shown~
and oentr~l oiroul~r projections 92, ~4, hest illustrated in the ~iew of fi~. 3 where the holder mem~ers 7~, 76 ~re shown sep~r~ted.
When the holder is ~ssem~led, as in fi~. 4, the pookets oloe.ely reoeive the he~ting elements, gripping the oppo~ing faoes of e~oh hester el ement oore. Al thou~h ~he pookets ~ef i ned ~re rel ati ~el y loose ~in r~di~l direGtions~, the ~rr3ngement has pro~en suffioient for the purposes of the invention.
The heating element holder 31so has four p~ss~es, one assooi sted wi th 3 di f f erent one of the f our hea~i n~ el ements, whi oh direot ~ir flows through the heating elements. Eaoh p~ss~g~ extends ~231~
1~
between the forw3rd ~nd re3r holder faces 76/ ~0, ~nd h~s a forward p~ss3ge openin~ ~not spec;ifioally irldioated~ in the forward holder faoe ~6 and ~ re~r pass~e openin~ ~not speoific311y indioated~ in the re~r holder f~ke ~0/ more speoifioally, in 3 reoess formed in the . 5 rear holder f~oe ~0 and desoribed more fully below. Two suoh pass3~es 96, Y~ are speoifioally indio3ted in the oross-seotion31 ~iew of fig. 4. It will be apparent from fi~. 4 th3t eaoh of the p3ss3ges g~, 9~ intersects the poeket in whioh the ~ssooiated heating element ~ or ~, respeoti~ely, is oont~ined, and that eaoh of the p~ssages 96; g~ h~s ~ minimum oross-seotion31 area perpendioular to the ~enturi axis 6~ whioh is subst~nti~lly the s~me as the oross-seotional 3rea of the assooiated heatin~ element, there~y ensuring retention of the assooi~ted heatin~ elsment without si~nifio3ntly impedin~ 3ir tlow throu~h the assooi~ted heatin~ element. The he~tin~ elements ~re of oourse so positioned in the ~ssooiate~ pass~ges th3t substanti~lly 911 ~ir flow in the passa~es is constrained to flow throu~h the eores of the h~ating elements.
The holdei- is also ~dapted t~ reoei~e su~stantially all air flow from the forw~rd ~enturi openin~ 5~. In p3rtioular, the re3r holder mem~er 74 h~s a reotan~ulsr oiroumf~renti~l lip 100 dimensioned to fit 3~cut ~ oorrespondin~ lip 10~ of the f~n cssin~
54. Air flow from the forward ~enturi opening 5~ is conse~w~ntly directed ~inst the re~r holder f~ce ~0, 3nd ~ 13r~e r~cess 104 is formed in the resr holder faoe ~0 ~djaoent to ~nd in ~ener31 3xisl ~lignment with the forward ~enturi openin~ 5~ to recei~e t.he 3ir , ~Z3~7~8 flows. E~ch of the passa~es ~suGh as the pass3ges ~, 98~ in whioh the heatin~ elements are positioned has its re~r p~s~e opening looated within the recess 104/ spaced forw3rdly of the forward ~enturi opening 5~. As will ~e app~ren~ in fig Clr where the 5 orosg-seotional shape of the passages g6r g~ is shown, the passages g~ flare radially outwardly an~ re~rwardly from the re~r faoe of each assooiated heating element 2~ ~2 respeoti~ely to the ~ssoci3ted rear p~ss3~e opening. Simislrly/ the reoess 104 flares radially outwar~ly and rearwardly from a~out the re3r pass~ge 10 openings to the re~r holder face B0. Aocordin~ly~ su~stantially all ~ir escaping from the forward venturi openin~ 5B is deli~ered in relati~ely smooth fashion to the heatin~ elements.
The forw~rd holder member 7~ is identical to the rear holder member ~ and is effeoti~ely the re~r holder mem~er 76 15 rot.~ted through 1~0 degrees a~ou~ a ~ertio31 axis. ~coordingly~ the forw~r~ hol~er mem~er 72 defines a large recess 10~ in the forward older face 76 into whioh eaoh of the forw~rd passage openin~qs opens. Aocordin~qly, eaoh of the hol~er pass3~e~ ~UCh as ~he pass~es g6, ~ whioh are exemplar~ and illustrated in fi~. 43 fl~res ~0 r~di~lly outw~r~ly and forw3rdly from the front faoes of e~ch assooiated he~ting elernent~ ~nd the recess 106 fl~res radi~lly outwardly and forwardly from a~out the forward passage openings to the forw~rd holder f~ee 76. This arr~ngemsnt produoes ~
smoothin~q of the heated air flows escapin~ from the forward air ~5 outlet 14~ but is not striotl~ essential to o~t~ining improl/ed he~t transfer effioienoy and quieter operation. The ~rrangement does~
~-~3~ 48 1~
howevet-, eliminste the need for ~n ~ditional distinot oomponent in the hester 10.
Forw~rd and rear oon~uotive metal plates 10~, 110 proYide eleetrical oontaot with the forward sn~ rear faoes of the he~tin~ element oores inside the holder. It will ~e ~pparerIt from the view of fig. ~ th3t the forw~rd conduotive plate lOB seats in reoess defined by the tri~n~ul~r projeetions on the inner f~ee 7B, and h~s a een~ral ~perture 112 whioh permits olearanoe of the oentr~l projeotion ~2. The plate 10~ oYerlsys the forward fsoe~ of the he~ting element oores to proYide the required eleotrical cont~ot.
Four apertures 114 lonly one specifioslly indioated~ with ~ oiroular periphery ~re forme~ in the pl~te 10~ ~n~ ~re po~itioned olY~er the forwsrd fsee~ of the hester element cores to permit pas~e of ~ir.
The di~meter of the spertures on the pl~te 1 14 is m~rginally sm~ller thsn th~t of the he~tin~ elements to ensure eleetrie~l eontaot. A metal terminal strip 11~ is spot welded to the pl~te 10~, ~nd extends to points external of the he~ter element holder, when assembled, to permit line ~olta~e to ~e convenientl~ applied to the pl~te lQa To ~Gcommod~te the terminal strip 11~, 3 ~roove 2~ is formed in the inner faoe 7~ of the forward holder member 76, ~n~ is dimensioned to recei~te the terminal strip 11~ loosely. The conducti~e pllte 110 provides electriosl contaot with the re~r faces of the heating element Gores, ~nd seats sg3inst the inner f~ce ~ of the resr holder member, in ~ msnner ~nalo~ous to the sestin~ of the plate 10~. The struotllre and function of the two pl2tes 10~, 110 is su~stantially i~entio~ nd consequently no further detail will ~e ~ 23~L~7 pro~ided reg3rdin~ the plate 110.
The hol~ler members 72, 74 ~re dr~wn to~ether ~o oont~in the he~tin~ elements in the pockets ~y means of four fasteners.
~inee the fasteners are identie31, only one`f~tener 1~0 h~s ~een speGifiGally illustrated 3nd indiosted, in fi~. ~. The fastener 1~0 oonsists ~sicslly of ~ ~olt 1~ nd ooil spring 124 ~nd a nut 12~.
The heatin~ element holder is first loosely assem~led, for ex~mple, by seatin~ the plate 110 a~3inst the inner faoe ~ of the re~r holder member 74, positienin~ the he3ter element~ ~ppr~pri3tely o~er the lQ ~pertures in the pl~te 110, se~tin~ the pl~te lQ~ 3~inst the inner f~oe 7~ of the forward holder mem~er 72, and then carefully ~ringing the hol~er mem~er 72, 7~ to~ether in ~n operatiS,~e orientation. The holder mem~ers 72, 74 then h~e four p~irs of 31igned ~pertures, only the ~pertures 1~ 130 ~ein~ speoifio~lly indioated, whioh extend fully ~etween the forward and re3r holder faees J~, ~0. The ooil spring 124 is loo~ted a~out the ~h~ft 1~2 of the ~olt 12~, 3nd the sh~ft extended fully throu~h the aligned 3pertures 12~, 13Q. The nut 1~6 i~ then threaded onto the re3r sh3f~ en~ portion 1~4 until the nut 1~ abuts the rear holder faoe ~0. The ooil ~prin~ 124, which h3s a 13rger diameter than the ~pertures 1~ 0, locs~es in the process ~out ~ forward shaft end portion 1~, and acts betY~een the bolt he3d and the forw~rd holder face 76 to draw the holder mem~ers 7~, 74 together. To ensure po~iti~e seatin~ of the coil spring 124 3g~in~t the for~3rd ~5 holder memher 7~, 3 ~hallow well 140 i~ located 3~0ut the ~per~ure 12~ in the forward holder face 7~ and dimensioned to recei~e a ~2~17~3 portion of the coil spring 124. In the preferred embod.iment illustrated, a metal grill 141 is interposed between the bolt head of each fastener and the associated coil spring to fasten the grill directly to the forward holder member 72, but the grill 141 could equally well be attached to the abutment flanges 1~ of the main housing member 12.
The four fasteners being spring-loaded permit separation of the holder members 72, 74 in response to thermal expansion of the heating elements. This arrangement is critical, as the ceramic holder members 72, 74 are very brittle, and could otherwise be easily cracked during operation of the heater 10.
The heating element holder and grill 141 when assembled together are then attached to the fan casing 54.
This attachment is effected by passing the rear shaft portions of the various fasteners through apertures in the fan casing 54 and attaching additional nuts to the rear shaft end portions. For example, with the fastener 120 illustrated, an aperture 142 in the fan casing 54 is aligned 20 with the previously aligned holder member apertures 128, 130 and the rear shaft end portion 134 passed through the aperture 142. A nut 144 is then threaded onto the rear shaft end portion 134 to complete connection to the fan casing 54. The fan casing is in turn attached to the rear 2.5 housing insert 18 by means of four screws ~not illustrated) which are threaded through aligned aperatures (only one pair ~..,~
17~31~74~3 1 16(a) oE aligned apertures 146, 148 speciEically indicated) in the fan casing 54 and rear housing insert 18. A strip of insulating material 150 (fragmented) is wrapped around the periphery of the heating ~3~8 element holder, and the entire assembly so forme~ ls inserted lnto the mairl housing mem~er 1~ until th~ grill 14~ engages the a~.utment flanges 1~. ~.eGurem0nt is completed ~.y threading screws throu~h the holes ~0 in the main howsin~ mem~er 12 to secure the 5 rear hnusing insert t~ to the main housing mem~er t~, as mentioned a~ove.
The electric31 wiring and control circwitry associ3ted with the he3ter 10 is schematic~lly illustrated in fi~. 5. Line power is deli~ered ~ia a power cord 5~ tthe two lines of the power cord 10 bein~ indicsted with the same reference numeral 5~,~ to the conduotive plates 1O~J t 10. The electricsl connection so formed is direct, invol~in~ no switchin~ GirGuitry to control the amount of power delivered, except for a simple dou~le pole sinp,le throw switGh t 54 which serves to turn the power to the heater 10 off and 15 on. The power consumed ~y the heating elements, 3nd the heat conse~uently delivered is controlled entirely ~y varyino, fan speed with a fan control 15~. The fan control 15~ includes ~s 3 primary switching element a ~i~irection~l siliccn controlled rsctifier which permits su~stantially continuous variation of fan speed. ~
~0 inereasing fan speed the temperatllre of the heatin~ elements drops, ~.ut the resultsnt incre~se in conductivity of the hestin~
element Gores resul~s in ~ marked increase in power consumpti4n.
Thus, without effectively upw3rdly or downwardly scalinp, the line volta~e applied to the heatino, element cores, the quantitu, ~If heat ~5 delivered c~n ~e varied. The re~uired control circuitry and switGhes can ~e conveniently mounted to the rear housinp insert 18 with ~L23~7~8 1~
appropriate wirin~, as sohem~tio~lly illwstrated/ oonduct.ing power to the fan 52 and heating element~. These matters will be readily app~ren~ to one s~illed in the art.
A tesl: was performed to determine whether ~ he~ter 5 substanti~lly identioal to the preferred embodiment 10 exhibited improYed he~t transfer effioiency and quieter operation. The test inYol~e~l a oomparison with ~ prototype de~ioe that h~d an identio~l housin~qJ identio~l heating elementsJ sn identioal f~nJ ~nd identioal oontrol cirouitry. The prinoipal differenoe tletween the prelimin~ry 10 prototype ~nd the preferre~ Yersion of the heater resided in the he~tin~ element holder. The four hestin~ elements were oontained between t34o metal platesJ bolted to~etherJ e~ch of whioh was apertured to permit pass~e of air throu~h the he~tin~ elements in manner simil~r to that of the oonduotiYe pl3tes 108r 110. The 15 ~ssem~ly SQ formed was ~olted to the ~ssooi~ted fsn with the - heatin~ elements positioned at a~out 1 inoh ~rom the forwsrd f3n Yenturi opening. Power oorlsumption of the oores w~s monitore~ b~
mean~ of a watt nneter. With the protot~p~ ~ersi~n eoupled to a 1 lO
. ~MS lin~ souroeJ an am~iant temperature of ~out ~5 ~egrees ~O centigrade~ ~nd the fan operatin~ at full spee~J the heatin~ e.lements h~d a to~al power oon~umption of about 1J~OO W h noti~le le~k~ge of air baoksoattered throu~h the rear fan ~enturi openin~
was also noted. The preferred ~ersion substantially identical to the preferred embodiment 10 wa~ operated under simil~r oonditionsJ
25 and a hea~ing element power consumption of a~out 1J3~0 ~ Wa~
noted with no apparent leakage of air throu~h the rear fan ~enturi ~23~L'7~8 1~
openin~. This represents about a 1S% impro~ement in energy transf~r to f~n ~ir flows. Addition~lly~ on a purely qualit3ti~e basis~ it w~s noted th~t the preferrsd ~ersion was oonsidera~ly quiet~r in operation.
1~ will ~e appreoi~ted th~t a preferred embodimsnt of the in~en~ion has ~een dssori~ed and that modifications may ~e macle therein without dep3rting from the spirit of the in~ention and the soope of the ~ppended ol~ims.
Claims (26)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electric heating unit, comprising:
a plate-shaped heating element having a core of semiconductor material with a positive resistance-temperature coefficient, the core having a pair of opposing core faces including a first core face and a second core face and a multiplicity of apertures extending between the first. and second core faces whereby air can flow through the core, the heating element having a first conductive coating over the first core face and a second conductive coating over the second core face;
a heating element holder formed of an electrically and thermally insulating material, the heating element holder including first and second separable holder members, the first holder member overlaying the first core face and the second holder member overlaying the second core face, the first and second holder members being apertured adjacent the first and second core faces respectively to define a passage through the heating element holder permitting air flow through the core;
electrical contact means for electrically contacting the heating element, including coating contact means between the first and second holder members for separately contacting each of the first and second conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the costing contact means for defining a first terminal electrically connected to the first conductive coating and a second terminal electrically connected to the second conductive coating and electrically isolated from the first terminal; and, attachment means for drawing together the first and second holder members, the attachment means including biasing means for urging the first and second holder members towards one another in elastically displaceable relative relationship so that the heating element is secured between the holder members in contact with the contact means.
a plate-shaped heating element having a core of semiconductor material with a positive resistance-temperature coefficient, the core having a pair of opposing core faces including a first core face and a second core face and a multiplicity of apertures extending between the first. and second core faces whereby air can flow through the core, the heating element having a first conductive coating over the first core face and a second conductive coating over the second core face;
a heating element holder formed of an electrically and thermally insulating material, the heating element holder including first and second separable holder members, the first holder member overlaying the first core face and the second holder member overlaying the second core face, the first and second holder members being apertured adjacent the first and second core faces respectively to define a passage through the heating element holder permitting air flow through the core;
electrical contact means for electrically contacting the heating element, including coating contact means between the first and second holder members for separately contacting each of the first and second conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the costing contact means for defining a first terminal electrically connected to the first conductive coating and a second terminal electrically connected to the second conductive coating and electrically isolated from the first terminal; and, attachment means for drawing together the first and second holder members, the attachment means including biasing means for urging the first and second holder members towards one another in elastically displaceable relative relationship so that the heating element is secured between the holder members in contact with the contact means.
2. An electric heating unit as claimed in claim 1 in which:
the first holder member has a first holder face internal to the heating element holder;
the second holder member has a second holder face internal to the heating element holder;
the first and second holder faces are contoured together to define a pocket containing the heating element.
the first holder member has a first holder face internal to the heating element holder;
the second holder member has a second holder face internal to the heating element holder;
the first and second holder faces are contoured together to define a pocket containing the heating element.
3. An electric heater unit as claimed in claim 2 in which the coating contact means comprise a pair of conductive metal plates located between the first and second holder faces and shaped to seat against the first and second holder faces, the pair of conductive metal plates including a first metal plate overlaying the first conductive coating and a second metal plate overlaying the second conductive coating, the first and second metal plates being apertured to permit passage of air through the apertures of the core of the heating element.
4. An electric heating unit as claimed in claim 3 in which the first and second holder members are formed of a ceramic material.
5. An electric heating unit as claimed in claim 1 in which the first and second holder members have a multiplicity of pairs of aligned apertures, one aperture of each a pair of aligned apertures being formed in the first holder member and the other aperture of each pair of aligned apertures being formed in the second holder member, and in which the attachment means comprise:
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a first shaft end portion extending externally of the first holder member and a second shaft end portion extending externally of the second holder member, a first abuttment member attached to the first shaft end portion, a second abuttment member attached to the second shaft end portion and bearing against the second holder member, and coil spring means acting between the first abuttment member and the first holder member for urging the first holder member against the second holder member.
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a first shaft end portion extending externally of the first holder member and a second shaft end portion extending externally of the second holder member, a first abuttment member attached to the first shaft end portion, a second abuttment member attached to the second shaft end portion and bearing against the second holder member, and coil spring means acting between the first abuttment member and the first holder member for urging the first holder member against the second holder member.
6. An electric heating unit as claimed in claim 5 in which the first and second holder members are formed of a ceramic material.
7. An electric heating unit, comprising:
a multiplicity of plate-shaped heating elements in generally coplanar spaced-apart relationship, each heating element having a core of semiconductor material with a positive resistance-temperature coefficient, the core having a pair of opposing core faces including a first core face and a second core face and a multiplicity of apertures extending between the first and second core faces whereby air can flow through the core, each heating element having a first conductive coating over the respective first core face and a second conductive coating over the respective second core face;
a heating element holder formed of an electrically and thermally insulating material, the heating element holder including first and second separable holder members, the first holder member overlaying the first core faces of the heating elements and the second holder member overlaying the second core faces of the heating elements, the first and second holder members being apertured adjacent the first and second core faces to define passages through the heating element holder permitting air flow through the cores;
electrical contact means for electrically contacting the heating elements, including coating contact means between the first and the second holder members for separately contacting the first conductive coatings and the second conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the coating contact means for defining a first terminal electrically connected to the first conductive coatings and a second terminal electrically connected to the second conductive coatings and electrically isolated from the first terminal; and attachment means for drawing together the first and second holder members, the attachment means including biasing means for urging the first and second holder members towards one another in elastically displaceable relative relationship so that the heating elements are secured between the holder members in contact with the contact means.
a multiplicity of plate-shaped heating elements in generally coplanar spaced-apart relationship, each heating element having a core of semiconductor material with a positive resistance-temperature coefficient, the core having a pair of opposing core faces including a first core face and a second core face and a multiplicity of apertures extending between the first and second core faces whereby air can flow through the core, each heating element having a first conductive coating over the respective first core face and a second conductive coating over the respective second core face;
a heating element holder formed of an electrically and thermally insulating material, the heating element holder including first and second separable holder members, the first holder member overlaying the first core faces of the heating elements and the second holder member overlaying the second core faces of the heating elements, the first and second holder members being apertured adjacent the first and second core faces to define passages through the heating element holder permitting air flow through the cores;
electrical contact means for electrically contacting the heating elements, including coating contact means between the first and the second holder members for separately contacting the first conductive coatings and the second conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the coating contact means for defining a first terminal electrically connected to the first conductive coatings and a second terminal electrically connected to the second conductive coatings and electrically isolated from the first terminal; and attachment means for drawing together the first and second holder members, the attachment means including biasing means for urging the first and second holder members towards one another in elastically displaceable relative relationship so that the heating elements are secured between the holder members in contact with the contact means.
8. An electric heating unit as claimed in claim 7 in which:
the first holder member has a first holder face internal to the heating element holder;
the second holder member has a second holder face internal to the heating element holder;
the first and second holder faces are contoured together to define a multiplicity of pockets each containing one of the heating elements.
the first holder member has a first holder face internal to the heating element holder;
the second holder member has a second holder face internal to the heating element holder;
the first and second holder faces are contoured together to define a multiplicity of pockets each containing one of the heating elements.
9. An electric heater unit as claimed in claim 8 in which the coating contact means comprise a pair of conductive metal plates located between the first and second holder faces and shaped to seat against the first and second holder faces, the pair of conductive metal plates including a first metal plate overlaying the first conductive coatings and a second metal plate overlaying the second conductive coatings, the first and second metal plates being apertured to permit passage of air through the apertures of the cores of the heating elements.
10. An electric heating unit as claimed in claim 9 in which the first and second holder members are formed of a ceramic material.
11. An electric heating unit as claimed in claim 7 in which the first and second holder members have a multiplicity of pairs of aligned apertures, one aperture of each a pair of aligned apertures being formed in the first holder member and the other aperture of each pair of aligned apertures being formed in the second holder member, and in which the attachment means comprise:
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a first shaft end portion extending externally of the first holder member and a second shaft end portion extending externally of the second holder member, a first abuttment member attached to the first shaft end portion, a second abuttment member attached to the second shaft end portion and bearing against the second holder member, and coil spring means acting between the first abuttment member and the first holder member for urging the first holder member against the second holder member.
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a first shaft end portion extending externally of the first holder member and a second shaft end portion extending externally of the second holder member, a first abuttment member attached to the first shaft end portion, a second abuttment member attached to the second shaft end portion and bearing against the second holder member, and coil spring means acting between the first abuttment member and the first holder member for urging the first holder member against the second holder member.
12. An electric heating unit as claimed in claim 11 in which the first and second holder members are formed of a ceramic material.
13. An electric heater comprising:
a housing having a rear air inlet and a forward air outlet:
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis;
a multiplicity of plate-shaped heating elements each having a core of semiconductor material with a positive resistance-temperature coefficient, each core having a pair of opposing core faces including a forward core face and a rear core face and a multiplicity of apertures extending between the forward and rear core faces whereby air can flow through the cores, each heating element having a forward conductive coating over its forward core face and a rear conductive coating over its rear core face:
a heating element holder mounted in the housing intermediate of the forward venturi opening and the forward air outlet and having forward and rear holder faces, the heating element holder including holding means for holding the heating elements in generally coplanar, spaced-apart relationship and for orienting each of the cores generally perpendicular to the longitudinal venturi axis and spaced forwardly of the forward venturi opening, the rear holder face having a recess positioned over the forward venturi opening to the holder having a multiplicity of passages each having a forward passage opening in the front face of the heating element holder and a rear passage opening in the recess spaced forwardly of the forward venturi opening, each passage having an associated one of the heating elements positioned intermediate of its forward and rear passage through the associated heating element, each passage flaring radially outwardly and rearwardly from the rear core face of the associated heating element to its rear passage opening, the recess flaring radially outwardly and rearwardly from about the rear passage openings to the rear face of the heating element holder; and, electrical contact means extending into the heater element holder for use in placing the forward and rear conductive coatings of the heating element cores and the fan in contact with a source of electric power.
a housing having a rear air inlet and a forward air outlet:
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis;
a multiplicity of plate-shaped heating elements each having a core of semiconductor material with a positive resistance-temperature coefficient, each core having a pair of opposing core faces including a forward core face and a rear core face and a multiplicity of apertures extending between the forward and rear core faces whereby air can flow through the cores, each heating element having a forward conductive coating over its forward core face and a rear conductive coating over its rear core face:
a heating element holder mounted in the housing intermediate of the forward venturi opening and the forward air outlet and having forward and rear holder faces, the heating element holder including holding means for holding the heating elements in generally coplanar, spaced-apart relationship and for orienting each of the cores generally perpendicular to the longitudinal venturi axis and spaced forwardly of the forward venturi opening, the rear holder face having a recess positioned over the forward venturi opening to the holder having a multiplicity of passages each having a forward passage opening in the front face of the heating element holder and a rear passage opening in the recess spaced forwardly of the forward venturi opening, each passage having an associated one of the heating elements positioned intermediate of its forward and rear passage through the associated heating element, each passage flaring radially outwardly and rearwardly from the rear core face of the associated heating element to its rear passage opening, the recess flaring radially outwardly and rearwardly from about the rear passage openings to the rear face of the heating element holder; and, electrical contact means extending into the heater element holder for use in placing the forward and rear conductive coatings of the heating element cores and the fan in contact with a source of electric power.
14. An electric heater as claimed in claim 13 in which:
the heating element holder includes forward and rear separable holder members, the forward holder member overlaying the forward core faces and the rear holder member overlaying the rear core faces;
the electrical contact means include coating contact means between the forward and rear holder members for separately contacting each of the forward and rear conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the coating contact means for defining a first terminal electrically connected to the forward conductive coatings and a second terminal electrically connected to the rear conductive coatings and electrically isolated from the first terminal; and, attachment means for drawing the forward and rear holder members together in elastically displaceable relative relationship whereby the heating elements are secured in the heating element holder and the forward and rear holder members are separable with expansion of the heating elements.
the heating element holder includes forward and rear separable holder members, the forward holder member overlaying the forward core faces and the rear holder member overlaying the rear core faces;
the electrical contact means include coating contact means between the forward and rear holder members for separately contacting each of the forward and rear conductive coatings, and including terminal means accessible externally of the heating element holder and connected to the coating contact means for defining a first terminal electrically connected to the forward conductive coatings and a second terminal electrically connected to the rear conductive coatings and electrically isolated from the first terminal; and, attachment means for drawing the forward and rear holder members together in elastically displaceable relative relationship whereby the heating elements are secured in the heating element holder and the forward and rear holder members are separable with expansion of the heating elements.
15. An electric heater as claimed in claim 14 in which:
the forward holder member has a face internal to the heating element holder;
the rear holder member has a face internal to the heating element holder;
the internal faces of the holder members are contoured together to define a multiplicity of pockets, each pocket containing one of the heating elements.
the forward holder member has a face internal to the heating element holder;
the rear holder member has a face internal to the heating element holder;
the internal faces of the holder members are contoured together to define a multiplicity of pockets, each pocket containing one of the heating elements.
16. An electric heater as claimed in claim 15 in which the coating contact means comprise a pair of conductive metal plates located between the forward and rear holder members and shaped to seat against the internal faces of the forward and rear holder members, the pair of conductive metal plates including a forward metal plate overlaying the forward conductive coatings and a rear metal plate overlaying the rear conductive coatings the forward and rear metal plates being apertured to permit passage of air through the apertures of the cores of the heating elements.
17. An electric heater as claimed in claim 16 in which the forward and rear holder members have a multiplicity of pairs of aligned apertures, one aperture of each pair of aligned apertures being formed in the forward holder member and the other aperture of each pair of aligned apertures being formed in the rear holder member, and in which the attachment means comprise:
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a forward shaft end portion extending externally of the forward holder member and a rear shaft end portion extending externally of the rear holder member, a forward abuttment member attached to the forward shaft end portion, a rear abuttment member attached to the rear shaft end portion, and coil spring means acting between one of the forward and rear abuttment members and a corresponding one of the forward and rear holder members for urging the holder member together.
a multiplicity of fasteners, one fastener associated with each of the pairs of aligned apertures;
each fastener having a shaft extending through the associated pair of aligned apertures with a forward shaft end portion extending externally of the forward holder member and a rear shaft end portion extending externally of the rear holder member, a forward abuttment member attached to the forward shaft end portion, a rear abuttment member attached to the rear shaft end portion, and coil spring means acting between one of the forward and rear abuttment members and a corresponding one of the forward and rear holder members for urging the holder member together.
18. An electric heater as claimed in claim 17 in which the forward and rear holder members are formed of a ceramic material.
19. The electric heating unit of claim 1, 2 or 3 including means for moving air through the core.
20. The electric heating unit of claim 4, 5 or 6 including means for moving air through the core.
21. The electric heating unit of claim 7, 8 or 9 including means for moving air through the cores.
22. The electric heating unit of claim 10, 11 or 12 including means for moving air through the cores.
23. The electric heating unit of claim 13 in which:
the heating element holder includes forward and rear separable holder members; and attachment means for drawing the forward and rear holder members together in elastically displaceable relative relationship whereby the heating elements are secured in the heating element holder and the forward and rear holder members are separable with expansion of the heating elements.
the heating element holder includes forward and rear separable holder members; and attachment means for drawing the forward and rear holder members together in elastically displaceable relative relationship whereby the heating elements are secured in the heating element holder and the forward and rear holder members are separable with expansion of the heating elements.
24. The electric heating unit of claim 1, 2 or 3 including:
a housing having a rear air inlet and a forward air outlet;
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis; and fan speed control means permitting substantially continuous variation of fan speed and whereby the heat consequently delivered is controlled entirely by varying the fan speed.
a housing having a rear air inlet and a forward air outlet;
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis; and fan speed control means permitting substantially continuous variation of fan speed and whereby the heat consequently delivered is controlled entirely by varying the fan speed.
25. The electric heating unit of claim 7, 8 or 9 including:
a housing having a rear air inlet and a forward air outlet;
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis; and fan speed control means permitting substantially continuous variation of fan speed and whereby the heat consequently delivered is controlled entirely by varying the fan speed.
a housing having a rear air inlet and a forward air outlet;
a fan mounted inside the housing for producing an air flow forwardly from the rear air inlet to the forward air outlet, the fan having a fan venturi for directing the air flow including a forward venturi opening, a rear venturi opening and a longitudinal venturi axis; and fan speed control means permitting substantially continuous variation of fan speed and whereby the heat consequently delivered is controlled entirely by varying the fan speed.
26. The electric heating unit of claim 13, 14 or 15 including fan speed control means permitting substantially continuous variation of fan speed and whereby the heat consequently delivered is controlled entirely by varying the fan speed.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000474040A CA1231748A (en) | 1985-02-11 | 1985-02-11 | Electric heater employing semiconductor heating elements |
| DE1986300809 DE204393T1 (en) | 1985-02-11 | 1986-02-06 | ELECTRIC HEATING UNIT. |
| EP86300809A EP0204393A3 (en) | 1985-02-11 | 1986-02-06 | An electric heater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000474040A CA1231748A (en) | 1985-02-11 | 1985-02-11 | Electric heater employing semiconductor heating elements |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1231748A true CA1231748A (en) | 1988-01-19 |
Family
ID=4129812
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000474040A Expired CA1231748A (en) | 1985-02-11 | 1985-02-11 | Electric heater employing semiconductor heating elements |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0204393A3 (en) |
| CA (1) | CA1231748A (en) |
| DE (1) | DE204393T1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4104521C2 (en) * | 1991-02-14 | 1995-07-06 | Chang Chung Tai | PTC heating element |
| FR2690112B1 (en) * | 1992-04-21 | 1995-06-23 | Valeo Thermique Habitacle | DEVICE FOR HEATING-VENTILATION OF THE INTERIOR OF A MOTOR VEHICLE POWERED BY A LOW-THERMAL EMISSION ENGINE. |
| FR2701757B1 (en) * | 1993-02-18 | 1995-04-21 | Valeo Thermique Habitacle | Electric heating radiator, in particular for the passenger compartment of a motor vehicle. |
| CN109595788A (en) * | 2019-02-13 | 2019-04-09 | 深圳热鑫能源科技有限公司 | A kind of Household hot water dispenser |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5148815B2 (en) * | 1973-03-09 | 1976-12-23 | ||
| JPS53110133A (en) * | 1977-03-07 | 1978-09-26 | Tdk Electronics Co Ltd | Porcelain heating element made from positive characteristic semiconductor |
| DE2744639B2 (en) * | 1977-10-04 | 1980-11-06 | Petz Electro, Schmitten (Schweiz) | Wall fan heater |
| GB2061075B (en) * | 1979-10-11 | 1983-08-10 | Tdk Electronics Co Ltd | Ptc heating apparatus |
-
1985
- 1985-02-11 CA CA000474040A patent/CA1231748A/en not_active Expired
-
1986
- 1986-02-06 DE DE1986300809 patent/DE204393T1/en active Pending
- 1986-02-06 EP EP86300809A patent/EP0204393A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE204393T1 (en) | 1987-06-11 |
| EP0204393A2 (en) | 1986-12-10 |
| EP0204393A3 (en) | 1987-08-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |