US2260172A - Portable power hammer - Google Patents

Description

Oct. 21, 1941. A. G. DECKER, JR

PORTABLE POWER HAMMER 4 Sheets-Sheet 1 4 Sheets-Sheet 2 A. G. DECKER, JR

PORTABLE POWER HAMMER Filed, July 21, 1939 Oct. 21, 1941.

Oct. 21, 1941.

A. G. DECKER, JR PORTABLE POWER HAMMER Filed July 21, 1939 4 Sheets-Sneet 3 1941- A. G. DECKER, JR 2,260,172

' PORTABLE POWER HAMMER- Filed Jui 21, 1959 4 Sheets-Sheet 4 Patented Oct. 21, 1941 UNITED STATES PORTABLE POWER HAMMER Alonzo G. Decker, Jr., Towson,. Md., assignor to The Black and Decker Manufacturing Company, a corporation of Maryland Application July 21, 1939, Serial No. 285,681

16 Claims.

The present invention relates to a hand directed, supported and controlled power hammer of the general type shown in Baker Patent No. 2,013,296. This is operated by an electric motor enclosed within the tool casing, but various features of the invention are capable of application to portable hammers operated from other sources of power. While the ram in this type of hammer is operated by a crank and connecting rod, it is dependent for the storage of energy at each stroke upon a spring which is either a coiledspring or a pneumatic spring or a combination of coil and pneumatic spring, to increase at the proper instance, the impact incident to the normal reciprocation by means of crank and con-- necting rod.

The improvement of the present invention relates particularly to the means for storing and delivering this excess impact avoiding certain defects which have come to be recognized as of importance.

In accordance with previous development in this art, the spring was concentrically loaded and for this purpose was provided with closed coils at each end and there was sufficient clear ance between the outer surface of the piston body and the active coils which intervene between the closed coils at the ends to eliminate wear. Outstanding defects of this design were found to be that the spring would break due to wear adjacent-the ends of the closed coils and due to concentration of stress at these points and a further defect was due to the fact that the unsupported end or ends of this spring wereof sufficient weight to cause surging or vibration due to the inertia of these parts of the spring made eifective by the rapid reciprocation. Surging results in excess stresses which also cause spring failure, also there was a tendency to break at the point between the closed coils where the springs were rigidly supported and the free portions where they were not so supported.

The present invention provides a new spring arrangement and a new spring in which the 45 closed coils at the end or ends have been elimi-' f nated resulting in a spring which must be loaded eccentrically and which to avoid lateral bending is supported throughout its entire length,, thissupport is also of great benefit in that itprovides a dampening. action which not. only eliminates the effect of the weight and the inertia of. the spring during reciprocation but by its dampening action it reduces or eliminates surging above referred to and it also has the effect of reducing 5 the tendency to concentrate the stress adjacent the ends where the closed coils occurred.

The invention also provides means for connecting the ram to the cross head comprising a hollow ram which serves as a cylinder which receives the shank of a steel piston which'is made hollow and of an'enlarged diameter to provide a frictional support for the spring throughout its length. This construction is economical to manufacture and increases the life of the piston on account of the feasibility of constructing it of steel and permits a large diameter piston shank for a given diameter of spring which in turn 1ncreases the available size of the compression chamber which connects the ram tothe cross head thus improving the hammer action. gOther telescoping members may be substituted for the cylinder and piston.

In accordance with an alternative construction which has considerable advantages, a steel sleeve is pressed on to an aluminum or similar light metal piston, which sleeve serves as a support for the spring andthesteel ram is trepanned providing for the compression of the spring withoutcausing the supporting sleeve to strike the ram. I

In these constructions it-has been found that due partly to the increase in the size of the piston shank and consequently the size of the com pression chamber, the ram tends to continue its motion and to strike blows on the nose of the hammer when the drill bit has beenremoved. To overcome this tendency means has been'provided to catch the ram and hold'it long enough to throw it out of synchronism with the cross head thereby reducing or preventing the 'recoilof the ram and thus stopping the hammer action. Two forms of ram checking means are shown.

In the accompanying drawings; I have illustrated so much-of a portable power'driven-hammer aszis necessary toa full comprehension of the invention in its various forms and of the manner of constructing, applying; operating and using the same.

In the drawings:

Fig. 1 is a longitudinal section on a plane of Fig. 1, the internal construction being shown in broken lines.

Fig. 6 is a section showing a modified construction, the View being'a section on a plane of the barrel axis, corresponding to Fig. 1.

Fig. 7 is a section on the line in Fig. 6.

Fig. 8 is an external elevation of a hammer of this type shown on a reduced scale.

Fig. 9-

a fragmentary section on a plane of the barrel axis showing a modified form of friction ring for checking the motion of the ram to throw it out of synchronization.

Fig. 10 is a section on the line le -w in Fig. 9.

Fig. 11 is a view corresponding. ta Fig. 1 taken on the barrel axis, showing a, slightly modified form of nose and spring expansion ring. for checking the ram and throwing it out of synchronization.

Fig. 12 is a section on the line |2- |2 ea are partsioftheouter casing which also includes field casing l, andbrush housing or casing 5-. The: gear casing and the: field casing are shown as detachable and the brush housing-inthe form shown'is'integral with the field casing. The illustration-also includes a handle or grip 6 attached tothe crarikcase and to' thefield casing;

the handleor grip inthe form; shown being provided with a switch operating trigger I and a cord protector 8 enclosing the inner end{ of i the cable 9i a In the form illustrated iii-Fig; 5. an electric motor I isenclosed within the field casing. The motor i I0 isprovid'ed with a coolingfan- H and-connected by -geaiis |2,' to and with a crank l-fl 'a-nd crank I pin I152 which operates a connecting-rod l6 which reciprocates a cross head'- H, to which" it is connected bywrist pin N3, the crosshead havinga suitable guide 1 9 which in the form shown 'i'n Fig. 1 is integral with the ram guide andsomewhat' larger in cross section.- The term erossghead is, however, i not strictly limited 'to a" crank operatedmember similar reciprocation being other-wise obtainable. The arrangement above defined is: known practice capable-of wide variation and not essential tattle-invention;

=Referring-particularlyto Figs; 1 "and; 2; the barrel I is jprovided 'With a nose 24 at its lower end which in theform shownis-threaded into thelower end' 'of the barrel and provided with a bit socket or guide 22 which is aligned with the axis of the bar'rel The 'ramfgu'ide Zil'WhiCh: is a meter tube iii an cord. with the existing practice istlrireadjed or otherwise secured at its ends at 2-4 and-fZ-S Within the barrfiel "which provides a jacket 23 or cool-.

ing space aboutfthefguide 'and said jacket'is ventilated 'at 2-1 The rain- 1s connected; to the cross head H by 'meansof a cylinder and pistons." In t'he "construction shown in- Fig; 1,

fit in the genius and provide for ventingthespace beneath the ram, 'and' the crcsshead' is similarly vented at to avoid impounding air within the barrel.

The operation of the parts thus described is more fully explained in the above cited patent.

The cross head I! has formed integral therewith a piston 36 which controls a suitable compression space 32 within the cylinder 3| and a spring 38 is compressed between the cylinder 3| and the. cross head ll, whereby energy is stored in the spring and by compression beneath the piston 36 to be released in synchronism with the normal reciprocation of the cross head as in the above cited'patent. The action of the cylinder and piston. providing alternate compression and vacuum at 32. combined with the action of spring 3;; provides aresilient means between the cross head and ram whereby motion is transmitted tothe cross head from the ram and the ram is vibrated relatively to the cross head as the latter reciprocates. The spring 38 as shown is secured at its upper end in groove 33- formed inan enlarged portion 41 at the-upper end or the piston. The spring 38 which is of l ielic-al form t'ermi nates in a helically arranged end porti'orififl which bears against the lower surface of the cross head- H- and has! its operative portion M frictionally engaged with the: enlarged bar-rel 36"" of piston 36 which is hollow at 3:1 to provide ire-- duc ed weight with sufficientdiameter tdengage the spring-whereby the spring is permitted} tocontract and expand but" is: frictionally engaged for purposes of dampening. The lower end 'of this spring 38 at 43. is 'helically'arranged and atits extreme end 43" bears against the-top: sur

which is grooved at 39 to engage the spring and the lower end of the spring at 43", and the fricti'onallyengaged portion 42 moves along" the piston as. the spring contracts and expands and the cylinder and piston move one relatively to the other.

The frictional. supporting f-uncti'on prevents lateral bending of the spring, i. e;, the bending of the spring toone side asthe load is applied and also prevents surging of the spring giving What may be termed adampening'acti'on eliminating: the. effect ofweight of the spring particularly the closed coil formerly employed This method also avoids: the concentration. of

stress due to-having the ends of't-hese springs in v closed coils for loading purposes. -It willalso be noted that the shank of the piston 36 is'hollowed out toreduce its weightpermitting it to bemade of sufiicient size-to support the spring frie tionally. This method of construction provides for economical manufacture and increases: the

lifefof the piston and permits it: to be maderofs hard; metal as steel instead ofthe; lighter metals: and. that it increasesthesize of the compres-.-

sion chamber which improvesthe action ofthe;

ram.

It has been. found, due to. the. increasedsize of the piston orpi'ston shank and the. conse- I quent increased size of the compression chamben.

the ram has a tendency to continue. to strike blows on the nose 2i of' the hammer. after the drill bit has been removed. To overcome this tendency means has been providedinthe pathof.

theram beyond its normal. stroke butwithin the the strokewhich is' performed in the absence of a bit, said means beingadapted to check or prevent the recoil of the'ram as it passes beyond its normalstroke. By m'erely'checking the recoil of the ram, it is thrown out'of'synchronization with'the vibrations of the spring and the motion of the cross head, the hammering action of the rain, in idling, being thus either prevented or so reduced that it becomes harmless.

For this'purpose, inthe form of the invention now being discussed an expanding sleeve 48 has been provided as shown in Figs. 1, 3 and 4, and this sleeve 48'which is also referred to as a ring, is divided into six segments 49 by six slots 49' which as shown are parallel to the axis and extend downwardly from the top edge 49" to a portion 50 at the lower end which is thickened and threaded internally and externally at 50 and. 50" respectively, the internal threads 50' in theform shown engage the nose and the external thread engages the inside of the ram guide near the end whereby the ring is turned down against suitable packing at provided on a peripheral upturned shoulder 52 on the nose 2|, the nose in turn having a threaded engagement at 53 with the inner surface of the lower end of the barrel I.

The-sleeve or ring 48 is shown as int'ernallytapered at its upper end at 54 being thus adapted to engage the lower end of the ram 30 which is correspondingly tapered at 55, the internal diameter of the sleeve or ring 48 being slightly less than the external diameter of the ram, thus when the bit or star drill is removed the ram moves forward or downwardly it is forced into the expanding sleeve or ring 48 and held by the sleeve long enough to throw the ram out of synchronism with the piston and cross head I! thus checking the tendency of the ram to build up hammer action due to the combined synchronized action of the spring and vacuum in the chamber 31 with the cross head'motion whichsynchronized action is explained in the prior patent above cited.

Figs. 6 and 7 illustrate a modified form of the construction in which the ram Ell-is formed with an upwardly extending piston 6| which fits in a cylinder 62 formed in a cylinder casting 65 carried by and attached to the cross head 63, being in this instance formed integrally with the cross .head which fits and slides in the ram guide 59.

In this case a steel sleeve 64 is pressed onto and outside of the outer surface of the cylinder casting- 65 which for lightness is of aluminum and thehead of the rank trepanned or grooved circumferentially about the base of the piston at 66; providing for the entrance of the end of the sleeve 64. into this groove so that the spring 61 can'be' compressed between the ram and the cross head without causing the sleeve to strike the head of the, ram, said head being indicated by reference character 68. Thegroove 66 which extends cir-' cumferentiallyaround the base of'the piston 6| is-parallel to the axis extending downwardly in a direction away from the cross head 63.

The sleeve 64 serves as a guide and as a dampener for the spring 6! which corresponds to the spring 38 in Fig. 1. The outer surface of sleeve 64' serving the purpose of the outer surface of the piston 36 in Fig. 2, i. e., as a guide for an eccentrically loaded spring and as a dampener to prevent surging. I

It'will'be noted'that the cylinder 621s provided with vents 69 and to limit the pressure and vacuum and-itheram head 68 1s grooved at 1| to cent the point of impact;

prevent accumulation of back pressure beneath the ram.

This is a highly satisfactory construction as to the details described, though the construction first described is preferred as capable of production on a large scale at a relatively small cost. 1 Figs. 9 and 10 illustrate a modified form of friction or expansion ring correspondingto the ring 48 in Figs. 1, 3 and 4. These figures show a ram head 15 of the hollow type in a ram guide 13', which is grooved internally at 16, the groove l6 being substantially parallel to a plane at right angles to the axis of the tool, this groove contains a spring wire hexagonal ring 11 which is of an internal diameter a little less than the external diameter of the ram head 15, so that theram head mayexpand the ring, as to' the centers of its hexagonal sides 19 as it advances towardthe'nose' 8| when the bit is displaced. The spring ring is to prevent hammering of the ram on the nosezwhen the bit is removed and consequent injury to the tool.

It will be noted that the ram head 15 is shown ascircumferentially grooved as to its outer surface at which provides a seat and grip for the ring 76 as the groove 80 passes said ring,'u sually engagin on the up stroke. a

As previously'noted in connection with the member 48 in Figs. 1, 3 and 4 thepurpose of this construction is to check the recoilof the ram due to the spring and/or vacuum-andpressure in the cylinder, etc., and to either holdit in depressed position or to throw itout of synchronization with the 'reciprocationsof' thef'cross' head thus reducing in 'the absence of a bit in operative engagement-with thework, the energy imparted to the ram on its descent. At other times the ram is stopped by'th'e bit near the position shown in Fig. 1 so that the friction expanding sleeve or ring 48* or 16 is non-essential under such circumstances; i.' e. when the bit is in place and pressed against the work, and has no effect. When the bit is removed, however, the ram advances to or" approaches the position shown in Fig. 9, groove BIJ passing ring 16 and on its return stroke the frictionor expansion ring 16 becomes-effective to throw the vibrations of the. ram due to the spring 61' or 38 and/or the cylinder and piston: action'out of' synchronization with the recipro'cations' due to the action 'of the crank andcross head reducing the stroke of the ram andthe power of the same so that it does not"'advance into'contactwith-thenose 8|.

Figs. 6, 9 and 10"show vents 82near: the lower end of the ib'a'rrel, providing afpassage for theventilating air to"co6l'the guide and ram adja- Referrin'gnow-to Figs. 11, 12 and 13; Fig. 11 resembles'Figi' -1' except as to the type of friction expansion sleeve orr'ing 48in Fig. 1, for checking the recoil of the ram.

Figs. 11, 12 and 13 show the ram guide 20 grooved circumferentially at" 83 near its lower end, the groove being parallel to a plane atright angles to-the tool axis.v The barrel is indicated by reference character I and the ram guide by reference character 20} 1 I The groove 83 receivesthev spring expansion ring 84 which 'inthis instance is in the form of three relatively flat arcs 85' meeting at their ends at continuou's corner porticn s 85 these corners 85' are'deeply seated in the groove 83, the middle portion of-th'e arcs-85 projecting from' the groove into the guidespaceto be engaged'by the head 86' of the ra'm as" it approaches tlie-nose 81 on ,rnaliy on retunm strokm. eff-eel: bein thatthe delivery; on the energy; stonedi by: compression in the spring and/or inz the; is

out/of. synchronization with: the normal reqinnocaztion ofi the cross headi reducing". the: strekefandl anoidingf hammering: aetinm off the ram head: on; the. nose: 81;: which would; otherwisetaliern aeerwhenthe bitiis withdrawm The term cross head as used? hereina inchides neeiproeating; member: op ratin hezramr hnql ehi and: her, way of: a2 resilient. element and he erm nrma inelndesianmesilient meainssserw in a simila-r purpose.

t The improved operatiom amdrthe-advantagessre suiting-iron); the;v new constructifine a bnae dislosed; av be n fully described amt dismissed the, preambleandiingconneetiemwith: the: details of he rawmss;

The: preferred; and, severak. medifledE formsz of theginnentiqn and the manner oi 'oon'stnucting;

, applying operating amt'usingrthe: same injcone nation. with: a p w r: driyem hammer whereby thesesadvatages. aoerue' having been thus: de scribed; specifically and; 1m detail; in; order that r h mannerat censtrutti ei app yin nenatin V ande 115m inyention' manbe. fill-1132s linden.

stood; thezspeeifie. terms; are: used: desexiptivel-y r her than in at limi ing sense the: eonstruation shown bein e p b r oi wide'variation within the, spiritofi the: invention. v

I :elairm and; desire to secure: bwl'eettens Batentiis Q f a; n a. h nd con r lled? and: supn r edx pow r. opera-ted of; the: type? described: having a r ciproca r s head: and a: ram and oo-' one t na eyi nd nranapiston membere conn ct-- mg the cross head: and: the: pistoni being? hollow, anda spning coiled; aboutandzhavinga suppontithezspringragainstlateraliyielding i fir-iotionah engagementiwithr one: qiisaidt members 7 for; a snbstantia'lz portion ofiits lengthgsaid spring being; in pressure transmitting; relation. atT-one' end with; the: cross head: and at the other enct with the ram said frictional enga ement,- serving to dampen the action of. theaspfii giandpiievent. sur in an iram hecking: means be1ow' he:nor

'endl against the erase head -and atethe othen end.

against the; ram? and; tending, to 'advanee'the namgsaid spring bein s,eccen ri yfloadedr a trictional;eneaeementservinete damneni the; ace 7.5.

3; In a, handd'controlledi and supportedypowen operated hammer 0t the type-2. described; haying a reciprocating cross; head". and; a ram with telescoping: members between. the; cross: head. and ram, a substantially helical. spring; encircling: one of said! members: and having: frictional engage-=- menti therewith;v and: adapted: to, apply; pressure at one end against the cross head; amt at'the otlien end against: the rain: "and; tendin'gf to; advance: the;- ram, saidi frictional: engagement ex; tending: substantially throughout: ther'lengthoi? theespring betweem itsxbe-aringi on the oross1- head and the: bearing: om the: ram; and; serving; ta

dampen: the action "of-.7 the spring and: prevent slinging; the; spring being: eccentripally; loaded? and. said: frictional contact also: serving toypreei ventlaterazhyieldingrofi theespring'. "r

4'. A power operaterhhammenoff theereciprodate i'ng type having a. reciprocating; cross: headfiand a. ram; teleseopingfmembers; and: resilient means: connecting the crosso heath itoz'tl'ietram to vibrate; the; ram: relatively to the: cross-z head: and: by synchronization to. aecentuatel thea blows diie: to thee reciprocation .ofi the: cross heazdi eheckin'g meanssinz the path of thezram operating beyond the end of the normal stroke of theram: to? checlc the: reooit off the whenz thertooli'is iiil ing'in the: absence ofiaibit'whereby; har'mfuli v hammering: in. idling is prevented: by stopping the ram: or: throwing: it out of synchronization with the; spningand crosse-headi I 5:. 'A-L powen' operated: hammer of? the re'ciproiel eating type having: a: reciprocating; crosshead: and amam: and" telesceping members and; aspi ing cooperating; therewith: to transmit pressur'ez'fromi the: crosshea'ot to the ram to: vibrate the; rami relatively to: the I cross head: and by-"synchrbniaaa tion to. accentuate the blows due to the: reeipr o cation. of? the cross head, friction: rneans in the path of the ram: located beyond the end of the normal stroke of the ram tocheck the rehound of the ram when thetool" is idling, said friction means being rigidly: engaged with a statio'nary portionofthe-hammer. Y

eating type having a reciprocating prose head the blows due to the reciprocation of thecross hea d, friction means in the path of] therainif l operating beyond-"the end of the normalstroke of the ram to throw" the vibrations of they due-to the'spri'ng action ont'of synehronizat n; with: the reeiprooation'sof the cross head when' the ram is idling; said frietion means being iii the.v form of ending in the path off'the ram and? rig-idly: engaged with a stationary portion'of the hammer; the upper portion ofsaid ring beingtapered and the ring being of slightly-less inff i ternal: diameter than the external 'diameterio'f the ram and havingslots extending downwardly from: its: upper edge to provide for yieldingto permit theentrance offtheram int'o-the ring. A power operated hammer of- 'the reeipr-ol eating type having a positivelyopera-ted oi oss i head! and. a ram and telescopingi'memb'ers 'and a: spring; cooperating: therewith: to corinect'th cross head to the ram to vibrate-the; Tami-relate i'velfy, torthe crosst head anct by"synchroni'zati6n ti)- acoentuate the: blows due toithe recipnooatiom" Q i the r m fri-Q nngmeans the: path 6i power operatedliaznrner" of the re -mm: V

ram located beyond the end of the normal stroke of the ram to throw the vibrations of the ram due to the spring action out of synchronization with the reciprocations of the cross head when the ram is idling, said friction means being in the form of a spring ring of less internal diameter than the outside diameter of the ram near its lower end said ring encircling the path of the ram beyond its normal path and being seated in a stationary portion of the tool.

8. A power operated hammer .of the reciprocating type having a cross head and a ram, a ram guide and cylinder and piston members connecting the cross head to the ram the piston being hollow, a spring coiled about one of said members to vibrate the ram relatively to the cross head in synchronization with the motion of the cross head and accentuate the blows due to the reciprocation of the cross head the spring being in frictional engagement with said member substantially throughout its length said member being of the largest diameter which the guide will admit and a ram checking device operating on the ram when it moves beyond its normal stroke, said checking device serving to check the recoil of the ram when the hammer is idling in the absence of a bit.

9. A power operated hammer having a cross head, .a ram and telescoping members and a spring connecting the ram to the cross head and tending to advance the ram, the spring being coiled about one of said members in frictional sliding engagement therewith substantially throughout its length and secured thereto at one end and having its other end open and inclined and bearing against the other said member at its extremity only.

10. In a power hammer of the type described having a cross head, a ram and cylinder and piston members and a spring connecting the cross head and ram to set up vibration of the ram relatively to the cross head, one of said members being provided with a jacket overlapping the other said member, the spring being coiled about said jacket and frictionally engaged therewith intermediately of and for a substantial proportion of the length of the spring.

11. In a power hammer of the type described having a cross head, a ram and cylinder and piston members and a spring connecting the cross head and ram to set up vibration of the ram relatively to the cross head, one of said members being of light metal provided with a hard metal jacket overlapping the other said member, the spring being coiled about said jacket and frictionally engaged therewith intermediately of and for a substantial proportion of the length of the spring one of said members being grooved in line with the jacket to admit the end of the jacket when the spring is approaching full compression.

12. In a power hammer of the type described having a cross head and a ram and cylinder and piston members and a spring connecting the cross head and ram to set up vibration of the ram relatively to the cross head, one of said members being of light metal with a hard metal jacket, the spring being coiled about said jacket and frictionally engaged therewith intermediately of and for a substantial proportion of the length of the spring.

13. In a hand controlled and supported, power operated hammer having two reciprocating members comprising a cross head and a ram and a coiled spring in pressure transmitting relation at one end with the cross head and at the other end with the ram and tending to advance the ram, and means having telescoping engagement with one of said members and having frictional engagement with the coils of the spring substantially throughout the length of the spring, said frictional engagement serving to dampen the action of the spring and prevent surging.

14. In a hand controlled and supported power operated hammer having a reciprocating cross head and a ram with telescoping guiding means therefor, a substantially helical spring transmitting pressure from the cross head to the ram and tending to advance the ram with the cross head, said spring having a frictional engagement with one of said telescoping members throughout its length serving to dampen the action of the spring and prevent surging, the spring being eccentrically loaded and said frictional contact also serving to guide and prevent lateral yielding of the spring.

15. In a hand controlled and supported power operated hammer, having a positively operated reciprocating cross head, a ram with resilient means between the ram and the cross head and ram checking means in the path of the ram, said resilient means transmitting the motion from the cross head to the ram and permitting vibration of the ram relatively to the cross head, said checking means being inoperative within the normal stroke of the ram, but engaging the ram when it moves beyond its normal working stroke as in idling in the absence of a bit.

16. A power operated hammer of the reciprocating type having a positively operated cross head and a ram, and resilientmeans between the cross-head and the ram to reciprocate the ram and permit vibration of the ram relatively to the cross head as the latter reciprocates and to accentuate the blows due to the reciprocation of the cross head, means in the path of the ram located beyond the end of the normal stroke of the ram, said latter means being in the form of a spring ring of less internal diameter than the outside diameter of the ram near its lower end, said ring encircling the path of the ramnear the lower end of its stroke and means securing the ring in a stationary portion of the tool, said ring being adapted to be entered by the lower end of the ram and to grip the ram when it passes beyond its normal stroke.

ALONZO G. DECKER, JR.

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