CA1121779A - Thermal element - Google Patents
Thermal elementInfo
- Publication number
- CA1121779A CA1121779A CA000363012A CA363012A CA1121779A CA 1121779 A CA1121779 A CA 1121779A CA 000363012 A CA000363012 A CA 000363012A CA 363012 A CA363012 A CA 363012A CA 1121779 A CA1121779 A CA 1121779A
- Authority
- CA
- Canada
- Prior art keywords
- casing
- washer
- pin
- thermal element
- tubular casing
- 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
Landscapes
- Valve Housings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A thermal element having a tubular casing with an open end, a volume of heat-responsive expandable wax positioned in said casing at a distance from the open end thereof, a spherical resilient seal member compres-sively positioned in the casing adjacent said wax, a motion-transmitting pin extended between the seal member and the open end of the casing and having a relatively soft washer affixed thereto for engagement against the seal member and with at least one peripheral notch in the washer permitting flow of liquid thereacross.
1.
A thermal element having a tubular casing with an open end, a volume of heat-responsive expandable wax positioned in said casing at a distance from the open end thereof, a spherical resilient seal member compres-sively positioned in the casing adjacent said wax, a motion-transmitting pin extended between the seal member and the open end of the casing and having a relatively soft washer affixed thereto for engagement against the seal member and with at least one peripheral notch in the washer permitting flow of liquid thereacross.
1.
Description
THERM~L ELEME NT
. .
B~CK~,ROUND OF THE INVENTIO'.`1 ....
l'his invention pertains ~o hea-t-responsive thermal elements usable for actuation of devices such as fluid control valves which are responsive to temper-ature of the fluid.
For many years, various types of control de-vices which are temperature-responslve have been operated by a thermal element. The thermal element has a casing 1~ carrying a charge or volume of material expandable in response to heatiny thereof with such material typically being a wax material~ The thermal element also has motion-transmitting means for transmitting the foxce created by the heat-expandable wax to a member to be operated, such .
as the valve member of a fluid valve such as a reliéf valve and also structure to form an interface between the , wax material and the motion-transmitting means. Such in-terfaces have typically utilized either O-rings or other forms of hollow cylindrical seals. Such prior devices have required some structural part to impart a radially outwardly force to form a seal with the casing of the thermal elernent.
Some of the prior art thermal elernents have atternpted to prevent flow of a part of the controlled ~luid to a location bet~7een the motion-transmitting struc-ture and the sealing structure which imposes additional design requirements for the thermal element.
SUMMARY OF T~IE INVENTION
A primary feature of the invention disclosed 3q herein is to provide a thermal element of new and improved
. .
B~CK~,ROUND OF THE INVENTIO'.`1 ....
l'his invention pertains ~o hea-t-responsive thermal elements usable for actuation of devices such as fluid control valves which are responsive to temper-ature of the fluid.
For many years, various types of control de-vices which are temperature-responslve have been operated by a thermal element. The thermal element has a casing 1~ carrying a charge or volume of material expandable in response to heatiny thereof with such material typically being a wax material~ The thermal element also has motion-transmitting means for transmitting the foxce created by the heat-expandable wax to a member to be operated, such .
as the valve member of a fluid valve such as a reliéf valve and also structure to form an interface between the , wax material and the motion-transmitting means. Such in-terfaces have typically utilized either O-rings or other forms of hollow cylindrical seals. Such prior devices have required some structural part to impart a radially outwardly force to form a seal with the casing of the thermal elernent.
Some of the prior art thermal elernents have atternpted to prevent flow of a part of the controlled ~luid to a location bet~7een the motion-transmitting struc-ture and the sealing structure which imposes additional design requirements for the thermal element.
SUMMARY OF T~IE INVENTION
A primary feature of the invention disclosed 3q herein is to provide a thermal element of new and improved
2.
_..
7'7~
constructlon having a minimal number of components in a pencil-thin, relatively short package, which develops more load and which is designecl for fully automatic assembly.
The invention in one broad aspect pertains to a heat-responsive thermal element comprising four parts including a tubular casing having an open end, a volume of heat-responsive expandable material positioned in the casing at a distance from the open end thereof, a motion-transmitting pin within the casing and having a portion thereof extending through the open end of the casing, and a generally spherical resilient seal member compressively positioned with random orientation in the casing between the material and the pin and free of connection to the pin for freedom of positioning and orienta-tion to maintain a seal with the tubular casing. The seal member defines in each adjusted position an annular zone of maximum sealing force engagement with the casing substantially about the center of the seal member.
An additional aspect of the invention is to provide a thermal element as defined in the preceding paragraph wherein the pin is loosely fitted within the tubular casing and has a washer of relatively soft material attached to an end thereof for engagement against the seal member to prevent extrusion of the seal member in the space between the pin and the tubular casing and snugly fit the interior of the casing and hold the pin against inadvertent movement.
Still ano-ther aspect of the invention is to provide a thermal element as defined in the prececling paragraphs wherein the washer is an annular member ~itted on a reduced diameter section of the pin and secured by an integral part of the pin and with the washer having means, preferably in -the form of at least one notch on the periphery thereof, to prevent entrapment between the washer and the seal member.
_..
7'7~
constructlon having a minimal number of components in a pencil-thin, relatively short package, which develops more load and which is designecl for fully automatic assembly.
The invention in one broad aspect pertains to a heat-responsive thermal element comprising four parts including a tubular casing having an open end, a volume of heat-responsive expandable material positioned in the casing at a distance from the open end thereof, a motion-transmitting pin within the casing and having a portion thereof extending through the open end of the casing, and a generally spherical resilient seal member compressively positioned with random orientation in the casing between the material and the pin and free of connection to the pin for freedom of positioning and orienta-tion to maintain a seal with the tubular casing. The seal member defines in each adjusted position an annular zone of maximum sealing force engagement with the casing substantially about the center of the seal member.
An additional aspect of the invention is to provide a thermal element as defined in the preceding paragraph wherein the pin is loosely fitted within the tubular casing and has a washer of relatively soft material attached to an end thereof for engagement against the seal member to prevent extrusion of the seal member in the space between the pin and the tubular casing and snugly fit the interior of the casing and hold the pin against inadvertent movement.
Still ano-ther aspect of the invention is to provide a thermal element as defined in the prececling paragraphs wherein the washer is an annular member ~itted on a reduced diameter section of the pin and secured by an integral part of the pin and with the washer having means, preferably in -the form of at least one notch on the periphery thereof, to prevent entrapment between the washer and the seal member.
3.
! 7~ .
Still another aspect of the invention is to provide a thermal element as defined in the preceding para-graphs wherein the spherical resilient sealed member is formed as a ball of soft material, such as silicone rubber or the like, and having a diameter greater than the internal diameter of the tubular casing for compressive deformation to seal against the interior of the casing while being movable axially thereof as the heat-expandable material expands and contracts.
Still another aspect of the invention is to pro-vide a thermal element having the structure as set ~orth in the preceding paragraphs which is capable oE simple assembly, wherein the tubular casing is formed of stainless steel that may be formed to the desired dimensions and the motion-transmitting pin is suitably formed of metal or plastic with a reciuced diameter end to receive the annular washer thereon with the pin end burnished over the washer to retain it in association with the pin and at the same time the washer is notched at the periphery to provide for said flow of lic~uid therepast in operation. The washer has a snug fit with the tubular casing whereby once the pin and washer are assemhled into the casing the parts may be easily transported and positioned in different ways without any separation of the parts and with the pin being f~ee of contact of the tubular casing whereby no close tolerances between the pin and interior of the tubular casing are required.
. .
BRIEF DESCRIPTION OF ~HE DRAWING
F'ig. l is a central vertical section of the thermal element;
Fig. 2 is a fraymentary vertical section, on an enlarged scale and taken along the lines 2-2 in Fig. l;
Fig. 3 is a fragmentary exploded view showing several components of the thermal element; and Fig. 4 is a sec-tional view taken along line 4-4 of Fig l.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
The thermal element is shown in assembled rela-tion in Fig. l and identi~ied generally at 10. The thermal element has four primary parts including a tubular casing indicated generally at ll, a motion-transmitting pin indi-cated generally at 12, a resilient seal member indicated generally at 15, and heat~expandable material 16, preferably in the form of a commercially available wax.
The tubular casing ll is formed from metal, such as copper or thin wall stainless steel, with the lat-ter being pre-ferred, and has a closed end 20 and an open end 21. The stain-less steel has relatively high strength ~nd, tllerefore, the tubular casing can be made of a thinner wall than copper to provide for a larc,Jer internal diameter in khe same si~e thermal element to provide for a greater cross section of -the heat-expandabLe material 16. 'rhj,s can provide'greater axial Éorces and loads with the same pressure oE the heat-expandable wax 16. With the greater force or load pro-vided with this construction, the thermal element is some-what less load sensi'tive when used in a structure, SUCil asa relief valve and which has to overcome a preset closing 5.
' pressure on the valve member tha-t is to be opened by the thermal element upon e~pansion of -the heat-expandable ma terial. Although stainless steel is considered difficult to form because it work hardens, a two-step roll-orming method is usecl to very effectlvely close the end,20 of the tubular casing with the final sealing of it by use of Tungsten Inert Gas welding.
The heat-expandable material 16 is preferably in the form of a commercially available wax and has a working range of 195-~17F., i.e., a transition point at 195F. At this temperature it starts to turn from a hard and brittle solid to a plastic-like substance and expansion begins. At 217F., it starts turning to a li~uid and expansion is con-siderably slowed.
After forming of the tubular casincJ 11, as described above, the next step lS to fill the tubular caslng with liquid wax at some temperature between 230F. and 260F. followed by -~ a~xamming at 190F. The ramming is reqiiired to remove solid wax from the wall of the ~ubular casing and to create a uniform wax length within the tube.
The r~silient seal member 15 is a spherical or ball-shaped member of relatively soft silicone rubber selected to provide optimum performance at temperatures encountered. For exarnpl~, the tempexatures encount~red in a valve application could be ].~0F, to 180F. with higher test temperatures, The rubher ball lS has a diameter greater than the int~rnal dia eter of the tubular casincJ 11, as shown in Fig. 3, and is positioned by squeeziny into the bore oE the tubular casiny.
I-ts shape permits considerable stored eneryy or memory and the ball does not have to be oriented for assembly or for proper function inside the element. In addition, the ball provides more latitude in dimensional control, -~1. d~ L 7 7 9 without losing sealing capability or creating excessive sidewall pressure. Additionally, it has been found that the ball seals very ~ell over an internal weld seam in the tubular casing if the tubular casing is made with a raised weld seam.
After placing of the wax within the tubular casing, as described above, the tube is evacuated by apply-lng a vacuum and the seal member 15 is lnserted within the casing against the upper level of the wax 16.
The motion-transmitting pin 12 is a cylindrical member and of a diameter less than the internal diameter of the tubular casing 11 in order that the major part 25 of the pin has a loose fit therein. This enables free movement of the pin relative to the tubular casing.
The pin has an upper end 26 of reduced diameter extending beyond the open end 21 of the casing for engagement wlth a structure, such as the structure associated with the valve member causing opening thereof as the pin 12 moves up-wardly, as viewed in Fig. 1.
An annular washer 30 of relatively soft materlal is fitted on a reduced diameter lower end 31 of the pin 12 and held thereto by a flattened sec-tion 32 of the pin formed as by burnishing whereby the washer 30 moves with the pin. This washer has a snug fit within the tubular casing 11 to prevent inadvertent fall-out of the pin from the casi.ng if the casing is inverted and also to prevent extrusion of the seal member 15 into the space between the pin section 2S and the interior of the tubular casing.
~.~l2~'7~7~
The washer 30 has an annular groove formed, as by machining for example, to provide a relatively thin flexible section 33 for contact with the tubular casing. This reduction in contact width of the washer enables flexing thereof and greater tolerances for the washer and tubular casing without undue sliding friction therebetween.
As shown particularly in Fig. 2, the washer section 33 has a pair of notches 35 and 36 at the periphery thereof to prevent the washer frorn forming a fluid seal with the tube.
With the notches 35 and 36 in the washer, a leak path for flow of liquid across the washer in both directions is pro-vided to avoid trapping of liquid, rather than trying to pre-vent leakage past the washerO Without the notches, it would ~be possible for a condition to exist where the pin 12 would extend out from the casing 11 a distance sufficient to space the washer 30 from the seal member 15. Over an extended period of time, water under pressure could seep into said space. When the wax 16 expands rapidly, this water would be trapped and act as a solid fill.
In design of the motion-transmitting pin 12, the pin must be of sufficient strength to withstand some small amount of bending and the tensile loads developed by loads i.n the valve, such as a spring load which resists opening - of the valve mcmber. Preferably, this pin is oE brass, al-though stainless steel and certain plastics could be used.
In forming of the pin, the pin i.s machined to the configura-tion shown and the washer 30 is installed with the flat-tened end being formed by burnishing in the machine which machines the pins and at the same time the notches 35 and 36 are formed '7~ .
in the washer. The washer is also machined to form the flexible sec-tion 33. The assembled pin is then placed within the tubulax casiny and is retained in position during additional handling of the thermal element by the snug fit between the annular washer 30 and the tubular casing.
Use of plastics for the pin 12 would enable - the pin and washer to be a one-piece molded or machined part.
lQ The thermal element disclosed herein results in an extremely simple structure having the four primary elements and without requiring springs and plugs and extra plastic spacers. The disclosed thermal element results in .
reduced assemhly time and costs. The use of the spherical seal member 15 avoids the requirement for some additional part of the unit to impart radially outward forces on an ; 0-ring for example in order to impart a siae wall squeeze against the tubular casing. The notched washer 3~ permits leakage therepast with no adverse effects on operation of the unit since the leakage fluid can flow across the washer.
Alternatively, the washer can be formed of a hexagonal or octagonal shape to provide the same functional results as the annular, notched washer.
! 7~ .
Still another aspect of the invention is to provide a thermal element as defined in the preceding para-graphs wherein the spherical resilient sealed member is formed as a ball of soft material, such as silicone rubber or the like, and having a diameter greater than the internal diameter of the tubular casing for compressive deformation to seal against the interior of the casing while being movable axially thereof as the heat-expandable material expands and contracts.
Still another aspect of the invention is to pro-vide a thermal element having the structure as set ~orth in the preceding paragraphs which is capable oE simple assembly, wherein the tubular casing is formed of stainless steel that may be formed to the desired dimensions and the motion-transmitting pin is suitably formed of metal or plastic with a reciuced diameter end to receive the annular washer thereon with the pin end burnished over the washer to retain it in association with the pin and at the same time the washer is notched at the periphery to provide for said flow of lic~uid therepast in operation. The washer has a snug fit with the tubular casing whereby once the pin and washer are assemhled into the casing the parts may be easily transported and positioned in different ways without any separation of the parts and with the pin being f~ee of contact of the tubular casing whereby no close tolerances between the pin and interior of the tubular casing are required.
. .
BRIEF DESCRIPTION OF ~HE DRAWING
F'ig. l is a central vertical section of the thermal element;
Fig. 2 is a fraymentary vertical section, on an enlarged scale and taken along the lines 2-2 in Fig. l;
Fig. 3 is a fragmentary exploded view showing several components of the thermal element; and Fig. 4 is a sec-tional view taken along line 4-4 of Fig l.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
The thermal element is shown in assembled rela-tion in Fig. l and identi~ied generally at 10. The thermal element has four primary parts including a tubular casing indicated generally at ll, a motion-transmitting pin indi-cated generally at 12, a resilient seal member indicated generally at 15, and heat~expandable material 16, preferably in the form of a commercially available wax.
The tubular casing ll is formed from metal, such as copper or thin wall stainless steel, with the lat-ter being pre-ferred, and has a closed end 20 and an open end 21. The stain-less steel has relatively high strength ~nd, tllerefore, the tubular casing can be made of a thinner wall than copper to provide for a larc,Jer internal diameter in khe same si~e thermal element to provide for a greater cross section of -the heat-expandabLe material 16. 'rhj,s can provide'greater axial Éorces and loads with the same pressure oE the heat-expandable wax 16. With the greater force or load pro-vided with this construction, the thermal element is some-what less load sensi'tive when used in a structure, SUCil asa relief valve and which has to overcome a preset closing 5.
' pressure on the valve member tha-t is to be opened by the thermal element upon e~pansion of -the heat-expandable ma terial. Although stainless steel is considered difficult to form because it work hardens, a two-step roll-orming method is usecl to very effectlvely close the end,20 of the tubular casing with the final sealing of it by use of Tungsten Inert Gas welding.
The heat-expandable material 16 is preferably in the form of a commercially available wax and has a working range of 195-~17F., i.e., a transition point at 195F. At this temperature it starts to turn from a hard and brittle solid to a plastic-like substance and expansion begins. At 217F., it starts turning to a li~uid and expansion is con-siderably slowed.
After forming of the tubular casincJ 11, as described above, the next step lS to fill the tubular caslng with liquid wax at some temperature between 230F. and 260F. followed by -~ a~xamming at 190F. The ramming is reqiiired to remove solid wax from the wall of the ~ubular casing and to create a uniform wax length within the tube.
The r~silient seal member 15 is a spherical or ball-shaped member of relatively soft silicone rubber selected to provide optimum performance at temperatures encountered. For exarnpl~, the tempexatures encount~red in a valve application could be ].~0F, to 180F. with higher test temperatures, The rubher ball lS has a diameter greater than the int~rnal dia eter of the tubular casincJ 11, as shown in Fig. 3, and is positioned by squeeziny into the bore oE the tubular casiny.
I-ts shape permits considerable stored eneryy or memory and the ball does not have to be oriented for assembly or for proper function inside the element. In addition, the ball provides more latitude in dimensional control, -~1. d~ L 7 7 9 without losing sealing capability or creating excessive sidewall pressure. Additionally, it has been found that the ball seals very ~ell over an internal weld seam in the tubular casing if the tubular casing is made with a raised weld seam.
After placing of the wax within the tubular casing, as described above, the tube is evacuated by apply-lng a vacuum and the seal member 15 is lnserted within the casing against the upper level of the wax 16.
The motion-transmitting pin 12 is a cylindrical member and of a diameter less than the internal diameter of the tubular casing 11 in order that the major part 25 of the pin has a loose fit therein. This enables free movement of the pin relative to the tubular casing.
The pin has an upper end 26 of reduced diameter extending beyond the open end 21 of the casing for engagement wlth a structure, such as the structure associated with the valve member causing opening thereof as the pin 12 moves up-wardly, as viewed in Fig. 1.
An annular washer 30 of relatively soft materlal is fitted on a reduced diameter lower end 31 of the pin 12 and held thereto by a flattened sec-tion 32 of the pin formed as by burnishing whereby the washer 30 moves with the pin. This washer has a snug fit within the tubular casing 11 to prevent inadvertent fall-out of the pin from the casi.ng if the casing is inverted and also to prevent extrusion of the seal member 15 into the space between the pin section 2S and the interior of the tubular casing.
~.~l2~'7~7~
The washer 30 has an annular groove formed, as by machining for example, to provide a relatively thin flexible section 33 for contact with the tubular casing. This reduction in contact width of the washer enables flexing thereof and greater tolerances for the washer and tubular casing without undue sliding friction therebetween.
As shown particularly in Fig. 2, the washer section 33 has a pair of notches 35 and 36 at the periphery thereof to prevent the washer frorn forming a fluid seal with the tube.
With the notches 35 and 36 in the washer, a leak path for flow of liquid across the washer in both directions is pro-vided to avoid trapping of liquid, rather than trying to pre-vent leakage past the washerO Without the notches, it would ~be possible for a condition to exist where the pin 12 would extend out from the casing 11 a distance sufficient to space the washer 30 from the seal member 15. Over an extended period of time, water under pressure could seep into said space. When the wax 16 expands rapidly, this water would be trapped and act as a solid fill.
In design of the motion-transmitting pin 12, the pin must be of sufficient strength to withstand some small amount of bending and the tensile loads developed by loads i.n the valve, such as a spring load which resists opening - of the valve mcmber. Preferably, this pin is oE brass, al-though stainless steel and certain plastics could be used.
In forming of the pin, the pin i.s machined to the configura-tion shown and the washer 30 is installed with the flat-tened end being formed by burnishing in the machine which machines the pins and at the same time the notches 35 and 36 are formed '7~ .
in the washer. The washer is also machined to form the flexible sec-tion 33. The assembled pin is then placed within the tubulax casiny and is retained in position during additional handling of the thermal element by the snug fit between the annular washer 30 and the tubular casing.
Use of plastics for the pin 12 would enable - the pin and washer to be a one-piece molded or machined part.
lQ The thermal element disclosed herein results in an extremely simple structure having the four primary elements and without requiring springs and plugs and extra plastic spacers. The disclosed thermal element results in .
reduced assemhly time and costs. The use of the spherical seal member 15 avoids the requirement for some additional part of the unit to impart radially outward forces on an ; 0-ring for example in order to impart a siae wall squeeze against the tubular casing. The notched washer 3~ permits leakage therepast with no adverse effects on operation of the unit since the leakage fluid can flow across the washer.
Alternatively, the washer can be formed of a hexagonal or octagonal shape to provide the same functional results as the annular, notched washer.
Claims (6)
1. A heat-responsive thermal element comprising four parts including a tubular casing having an open end, a volume of heat-responsive expandable material positioned in said casing at a distance from the open end thereof, a motion-transmitting pin within the casing and having a portion thereof extending through the open end of the casing, and a generally spherical resilient seal member compressively positioned with random orientation in said casing between said material and said pin and free of connection to said pin for freedom of positioning and orientation to maintain a seal with said tubular casing, said seal member defining in each adjusted position an annular zone of maximum sealing force engagement with said casing substantially about the center of the seal member.
2. A heat-responsive thermal element according to claim 1, including a washer secured to an end of the pin adjacent said seal member and having provision for flow of liquid therepast.
3. A thermal element as defined in claim 2 wherein said pin has a loose fit in said tubular casing and said washer is of a relatively soft material and has a flexible section providing a snug fit in said tubular casing.
4. A thermal element as defined in claim 2 wherein said washer has at least one notch at the periphery thereof to provide for said flow of liquid therepast.
5. A thermal element as defined in claim 2 wherein said washer is an annular member of relatively soft material, said pin has a reduced diameter lower end for mounting of said washer and said lower end is flattened to provide a retaining flange for said washer.
6. A thermal element as defined in claim 1, 2 or 3 wherein said resilient seal member is a ball of soft material such as silicone rubber or the like and has a diameter greater than the internal diameter of the tubular casing for compressive deformation to seal against the interior of the tubular casing while being movable axially in the tubular casing as said ball of soft material expands and contracts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000363012A CA1121779A (en) | 1980-10-22 | 1980-10-22 | Thermal element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000363012A CA1121779A (en) | 1980-10-22 | 1980-10-22 | Thermal element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1121779A true CA1121779A (en) | 1982-04-13 |
Family
ID=4118219
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363012A Expired CA1121779A (en) | 1980-10-22 | 1980-10-22 | Thermal element |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1121779A (en) |
-
1980
- 1980-10-22 CA CA000363012A patent/CA1121779A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |