US2257623A - Portable hammer - Google Patents

Description

R- E. SKOGLUND Sept. 30, 1941.

` PORTABLE HAMMER Filed June 7, 1940 3 Sheets-Sheet l Sept 30, 1941. R E, SKQGLUND 2,257,623

PORTABLE HAMMER 3 Sheets-Sheet 5 l kllz,

Sept. 30, l941- R. E. sKoGLUND PORTABLE HAMMER Filed June '7, 1940 Patented Sept. 30, 1941 UNITED` STATES PATENTv OFFICE 2,257,623 PORTABLE HAMMER i Ragnar E. Skoglund, Chicago, Ill.

Application June 7, 1940, Serial No. 339,351 `(o1. 153-48) Claims.

This invention relates to hammers andmore particularly to portable mechanical hammers having a reciprocable hammer element and adapted to be operated from an electrical motor or other suitable power source by means of a flexible shaft. The invention is particularly adapted for straightening sheet metal, such as automobile bodies and fenders, or for riveting, calking, chiseling, and the like. It may be successfully used as a stone cutting tool or for any other purpose where a high speed short stroke hammer is required. It is an object of the invention to provide a power-operated hammer of the character described which may be hand-controlled and provided with a suitable anvil and support therefor, and in which the anvil support is adjustable and removable from the hammer unit so that the device may be usable for operation on work which would otherwise be inaccessible. For instance, the device including the hammer unit and removable anvil support are so constructed that the hammer and anvil may be positioned for operation on irregularly shaped sheet metal such as automobile fenders and the like, and the anvil may be adjusted relative to the hammer sothat the elements properly may co-operate to straighten the material by removing otherwise inaccessible dents or doing any other work for which the device is adapted.

Another object is to provide a hand-controlled portable hammer and anvil and support therefor in which the anvil and its support may readily be separated from the hammer unit, so that the hammer may be used for various types of work in which an anvil may not be required, and in which the separation may be accomplished merely by an angular movement of the hammer handle.

Another object is the provision of a portable power operated hammer which may be operated at high speed and the operation of which may at all times be under the control of the operator. In fact, in the embodiment illustrated, the power is continuously supplied to the hammer from any suitable power source through a flexible shaft, and the operation of the hammer element per se may be controlled by the same hand of the operator which is holding the hammer in position for work.

Another object is the provision of a hammer operated by means of a continuously rotating shaft in which the energy for operating each working stroke of the hammer element is stored while the hammer element is stationary at the work end of its stroke and the element is then raised and the stored energy released to perform a Working stroke of the hammer element. In other words, the energy is stored with the hammer element` at the bottom of its stroke and is released with the hammer element at the4 top of its stroke.

Another object is the provision of a new and novel energy storing and hammer tripping transmission between the ilexible shaft and the hammer element which will alternately store energy and raise and trip the hammer element to release the stored energy andin which the storing and tripping mechanism is normally ineffective and may be made effective by an easily controlled trigger arrangement under the control of the operator.

A further object is the provision of a hammer of the character described which will be of comparatively small size, of few parts, easy to assemble and disassemble, and which will not easily get out of order in use.

Further objects will be apparent from the speciiication and the appended claims.

In the drawings:

Fig. 1 is a side elevation of one embodiment of i Fig. 1 and is taken on a line substantially corresponding to line 4-4 of Fig. 3.

Fig. 5 is a fragmentary sectional view taken` on a line substantially corresponding to line 5--5 of Fig. 4.

Fig. 6 is a perspective view of the spring loading yoke which is slidably supported in the hammer element.

Fig. 7 is a perspective View of the hammer trip control block which is supported on the yoke illustrated in Fig, 6 and which is adapted to be moved by the trigger to control the operation of the hammer.

Fig. `8 is a vertical sectional View oi the as-` sembled floating pivot elements shown in Figs. v 6 and 'l and is taken on line 8-8 of Fig. 6.

Fig. 9 is a vertical sectional View taken on a line substantially corresponding to line 9 9 of Fig. 4 with the hammer operating mechanism shown in full lines.

Fig. 9A is a somewhat diagrammatic perspective view of the hammer and operating mechanism, a portion of the casing and other elements being shown in section.

Fig. 10 is a diagrammatic View illustrating the movement of the spring loading and hammer operating trip when it is retained in hammer operating position by means of-the manually controlled trigger.

Fig. 11 is a diagrammatic view similar to Fig. 10, but illustrates the normal position and operation of the loading and trip member when the.

controlling trigger is not depressed and 'the hammer is not in operation. g j

Fig. 12 is a top view of the hammer elemen and upper bearing assembly.

Fig. 13 is a detail sectional view taken on line I3-I3 of Fig. V12. l

Referring to` the drawings in detail, the embodimentril-ljustrated comprises an elongated vertical hammer housing or casing I which includes, preferably integrally therewith,a laterally extending handle 2 by which the entire device may be supported and positioned by one hand of the operatorv and controlled for operation in a manner whichwill later -be described. VA. flexible shaft casing 3 is connected to thehandle 2 and a exible shaft .li of any suitable type is supported within the casing in the usual manner,`

and` this flexible shaft is adapted to be connected to .any suitablev power source such as an electric motor, not shown. v

An anvil supporting yoke is removably connected to the casing I and comprises )an upper yoke arm 5 and an anvil supporting arm 6 adjustably connected thereto in the manner illustrated in Fig...2.v The arm 6 is preferably shaped somewhat as shown in order that the yoke may accommodate therein various sheet metal shapes to which the hammer may be applied, and this arm 6 is provided at its outer end with acupshaped portion 'I having an anvil 8 supported therein by means of a compression spring 9 (Fig. 4). This provides a somewhat resilient anvil which is in axial alignment with the casing I and the hammer element supported therein. The anvil 8 is provided with retaining pins 8a whereby the anvil may be inserted in the cup by means of clearance slots 8b and then turned 90 degrees as shown.

As shown in Fig. 2, the anvil may be adjusted relative to the hammer by raising or lowering the `arm 6 Vby means of an ornamental knurled hand wheel I having a hollow stem II mounted in the upper arm Band rotatably secured therein by means of a lock screw I2 extending into an annular groove I3 in the hollow stem. A post I4 is secured in the lowerv arm by means of a pin I5 or other means, and extends upwardly into the hollow stem I I. The stem I I is provided with a cam slot I6 into which a pin I'I secured in the post Il!Y extends. The cam slotmay '-be of any suitable shape so that, by rotation of the hand wheel I0, the lower arm 6 may be raised or lowered to position 'the anvil as desired relative to the hammer..

An arm aligning post i3 is rigidly secured in the lower arm 5 in any suitable manner and extends into a suitable bore in the upper arm 5 as shown.' 'The post I8 is provided with an annular lilange I'8a, and a spring I9 tends to urge the the anvil supporting yoke.

instances, the material is of such shape thatV it is diiiicult to insert the material between the anvil and hammer and in position between the arms of The anvil supporting yoke and the hammer unit are, therefore, adapted connecting elements illustrated in Figs. l, 4, and

`r5. These `elements comprise an upwardly ex- 23a in a suitable bearing in the lower end of the tending pivot pin 2l which is rigidly secured in the arm 5 preferably by means of a pin 22. The housing I is pivotal-ly mounted on the pivot pin ZI, as shown in Fig. 4, and lis normally retained thereon by meansV of a taper pin 23 in the housing and extending into a groove 2li in the pivot pin. The slot 243 is limited in extent as shown in Fig. .5

and. terminates in a cut-away at side 25 of the pivot 2i, so that, when the casing is turned .90 degrees, as illustrated by dotted lines in Fig. .3, the elements may easily be separated. Y Y

The yoke arm 5 is provided with an .upwardly extending horizontally arcuate dovetail portion 27 which is adapted to engage in a 4complementary dovetail slot 28 in the underside of the handle 2, whereby, when the partsfare assembled and the hammer unit moved to the full line lposition shown in Figs. 1 and 3, the housing and yoke are lockedv together by means of the pivot pin vand the dovetail arrangement.

A reciprocable hammer element 29 is mounted in the casing I and provided with a hammer head casing. VThe hammer stroke is comparatively short, preferably only about one-eighth of an inch, and the hammer head `29a projectsbelow the lower `edge of the housing I approximately one-half of the length of the stroke, that is, about one-sixteenth of an inch. It has been found that this provides the best operating relationship of the hammer for the reason that, when thisfrelationship is maintained, the casing performs a function somewhat similar to that of a stripper when the hammer is in operation on sheet metal inserted between the anvil andv the hammer. That is, the metal tends to follow the hammer upwardly, and, if the hammer extends materially below the casing, extreme vibration of the material worked on tends to reduce the efficiency of the hammer in so far as accurate straightening of the material is concerned. It is, therefore, an important feature of the present invention to providea relationship wherein the hammer, particularly when used for sheet metal work, never vextends below the bottom of the casing more than a comparatively small portion of the stroke. t

The hammerV head '25a may be secured to the body of the hammer element 4by means of a taper pin 3l] and the hammer head may be removed and replaced 'by a similar head 0r Va head of any desired type by removing the screws 3| (Fig. 9) and then removing the taper pin 311 throughone of the openings provided by removal ofthe screws. The hammer element 29 is in the form of a yoke, as shown in Figs. 9 and 9A, and provided with an opening 32 therethrough to receive the drive shaft and operating mechanism. The hammer element is also yprovided on each side with a vertical slot 33 for guiding a loading yoke 34 which is slidably mounted therein and which Will be described later. A

The upper end of the hammer element 29 is provided with a reduced portion 35 which is slidably mounted in a suitable bearing 36 which latter may be secured in the casing by means of a press lit or otherwise, as desired, and may be secured against rotation by a setscrew 36a (Fig. 13). A feather key 31 is mounted in the shaft and engages in the bearing `36 to prevent rotation of the hammer and maintain it in proper alignment with the other operating elements. An adjustable plate 38 is slidably mounted on adjustable studs 39 threaded into the bearing .38, and springs 40 are positioned on the studs and between the plate 38 and the bearing 35 so that the plate 38 may be adjusted by means of the studs 39 to provide any desired compression of the springs 49. A cap nut 4| is threaded on the `,upper end of the hammer element, as shown,

and normally rests on the spring-supported plate 38 when the hammer is in its normal lowered position. The screws 39 are locked against rotation by means of an octagonal washer 39a (Fig. l2) which engages the flat side of `each screw head. Pins 38a may be provided in the plate 38 and serve as stops to limit the downward movement of the hammer element if the springs 40 become weakened;

A transverse shaft 42 extends through the opening 32 in the hammer element and` is supported in suitable bearing bushings 43 and 44, as shown in Fig. 4, and the terminal of the flexible shaft 4 may be connected thereto by any suitable means, for instance, such as the threaded coupling 45. The shaft 42 will, therefore, -be continuously driven and is provided with an eccentric 45, preferably integral therewith. This eccentric is in alignment with the hammer element, asillustrated, and an eccentric strapforming a trip member 41 is mounted on the eccentric and provided with an upwardly extending trip lug or pawl 48. The pawl portion 48 is adapted, during operation of the eccentric, to co-operate with a downwardly extending lug 49 which is preferably a hardened steel insert in the hammer element 29.

'Ihe lower side of the eccentric strap 41 is providedwith a spiral or angular gear tooth slot 50 which is in mesh with an upwardly extending complementary tooth such as an involute or epicycloid gear tooth on a `trip control block 52. This tooth 5| provides a pivot on which the strap` 41 oscillates during rotation of the eccentric. The upwardly extending tooth 5| is an integral portion of a laterally movable trip control block 52 (Fig. 7), which latter is provided with transverse holes 53, whereby the block may be slidably mounted in the opening 34a of the previously mentioned loading yoke 34, as shown in Figs. 6 and 7, the pins being riveted over at their ends after assembly to limit the sliding movement of pivot block 52 as shown in Fig. 8. Coil springs 55 are mounted on the pins 54 between the trip control block 52 and the loading yoke 34 to normally hold these blocks separated so that the angular pivot `tooth 5| is normally in the position shown in Fig. 11, whereby the hammer element is inoperative during rotation of the eccentric as the pawl 48 will not engage the hammer lug 49. The block 52 is provided with a bearing portion 56 (Fig. 7) which extends ining 51 in the loading yoke.

The loading yoke 34 is`provided with downwardly extending -legs 58 which are slidably mounted in the slots 33 in the hammer element, as shown in Fig. 9A. The lower ends of these legs 58 are secured to a ring 59 by means of pins or screws 59a, as shown in Fig. 4. The ring 59 is slidably mounted on the hammer element 29 and a comparatively heavy compression spring 60 is mounted between the ring and the hammer head 29a, whereby the loading yoke 34 and the laterally movable pivot tooth 5| slidably mounted thereon are normally urged upwardly against the eccentric ring to retain the teeth in mesh, as shown. Therefore, with each rotation of the eccentric, the teeth will be retained in mesh to oscillate the eccentric pawl, and the block 52, loading yoke 34, and ring 59 will be moved downwardly to compress the spring` El).`

As previously stated, `the trip control block is normally held by means of the springs 55 in its outward position shown in Figs. 4 and 8, and in this position, due to the angular relationship of the tooth slot 50 and pivot tooth 5|, the eccentric strap and lug 48 thereon will operate in the position shown in Fig. 11 relative to the lug 49 on the hammer element. With the tooth 5| in this position, the point or tripping edge 5| of the tripping lug 48 will, with each revolution of the eccentric, travel in the substantially elliptical path shown by the dotted line B2 and in the direction of the arrowheads and will, therefore, not engage the hammer lug 49, and the hammer will not be operated although the eccentric is continuously rotated.

In order to provide a manual control to push the trip control block 52 inwardly so that the angular pivot tooth 5| will position the eccentric strap as shown in Figs. 9A and l0 to thereby operate the hammer element, a `sliding pin or rod 63 (Figs. 4 and 9A) is slidably mounted in albushing 64 in the casing l and with its forward end resting against the `trip control block 52. A trigger 65 is pivoted at 65 and provided with a hardened steel portion 61 bearing against the opposite end of the sliding pin 63. This trigger 65 is normally urged downwardly to the position shown in Fig. 4 by means of a spring 58. The curved forward end of the yoke arm 5 is releasably connected to the hammer unit and forms a trigger guard to prevent accidental operation of the trigger 65 as shown in Figs. l and 4.

As previously stated, with the parts in the position illustrated in Figs. 4 and 11, the eccentric maybe continuously rotated Without operating the hammer element. When it is desired to operate the hammer element, the trigger 55 is pressed upwardly by the hand of the opera- *tor and the lsliding pin 63 will force the trip control block and the angular pivot tooth thereon inwardly so `that the eccentric strap and trip pawl 48 thereon are positioned as shown diagrammatically in Fig. 10. This rotary positioning of the cam strap is due to the angular or spiral relationship of the gear teeth, whereby lateral movement of the teeth will rotarially position the eccentric strap. In this position shown in Figs. 9 and 10, the edge or point 6| of the tripping pawl will move in the substantially elliptical path 69 in the direction of the arrowheads, and, therefore, with each revolution of the eccentric, the pawl 48 will engage under lthe hammerlug and raise -the hammer and then release it for Ya working stroke.

A cap 10 is threadedA on the topof the casing i, as shown in Fig. 4, and forms a part thereof. The cap may easily be vremoved to provide access to Ithe `adjustable screws 39 and tol enable convenient assembly Yof the mechanism. The casing fl is intended-tobe iilledwith lubricant and is properly sealed by means of va packing ring 'H around the hammer head and suitable gaskets are used wherever needed. 'A steel bushing 12 is 'threaded into the handle 2 and the flexible shaft casing is secured'therein by a coupling 13. The Ybushing 12 retains bearing bushings in assembled relation at all times.

'A desirable 'feature of the'present invention is the fact that the hammerelement 29 is not `at any vtime raised against the compression of a spring. Instead, energy for operating thehammer element is storedl-in the springt!) only when thel hammer element is Vstationary at Jthebottom limit of its working stroke. .Duringthe loading movement of the eccentric and iassociatediparts, the bearing pressure is onlyon `the .upper side of the shaft '42. Afterthe spring is loaded, the

pawl lug 48 passes under the hammer lug 49 and raises the spring loaded hammer. Therefore, during the upwardlmovement of .the eccentric, the load on .the .bearings is .substantiallyequalized. :In other words, the hammer Velement is raised without any spring pressure `applied to the shaft r bearings.

An important featureof 'the inventionV is the method of assembly. A.'Ilh'eha'mmer element and loading elements provideasuh-fassembly which is rst inserted in the casing;.and;properly supin portedy therein by. means of the springs 49. and associated elements, including the nut 4i. The shaft 42 and assembled Vbushings are then inserted through the handle 2 `andrlocked in place by means 'of thesteel bushing '12. There is no lateral pressurevon the shaft 42 and associated drivenelements. The hammer may be directly connected to a motor if desired. A satisfactory motor speedfis approximately 3600 R. P. M.

.It is intended, of course, that the invention should not beflimited tothe specific embodiment or embodiments disclosedv herein, since many modicationsmay be made, and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the truespirit andscope of thisinvention.

Having thus .described this invention, what is claimed and desired to be secured by Letters Patent is: t

1,. In a portable hammer having a reciprocable hammer element,- a continuously rotating power driven means, energy storing means comprising a spring between said rotating means and said hammer, means movable on said hammer element and operable'by said power means to compress said spring, said elements being constructed and related to cause hammer operating energy to -be stored in said spring when said hammer element is at the limit of its working stroke, and means controlled by said rotating means simultaneously to Vraise said hammer element and said energy loaded spring and release said energy at the limit of the nonworking stroke of saidhammer. element to cause a working stroke.

42. A .portable hammer ,comprising accontinuously `rotating power driven means, a reciprocable hammerV element, lenergy. storing means between said rotating means and said hammerelement and normally tending to `move saidyham.-

'spagaat merelement to one limit'of its stroke, means to causeenergy-to be stored in vsaidfstoringlmeans Whens'aid hammer element Yisv at said one limit of its stroke, and means controlled by said rotatingv means to cause free movement of said hammer element to the limit of its 'nonworking stroke and then quickly release said `stored Yenergy to perform an unrestricted working stroke.

- f3'. lA'hammer of the character described comprising a reciprocable hammer element, a power shaft, -a compression spring on said hammer element and 4bodily movable therewith, means for 'compressing said spring with each revolution of said power shaft, normally ineifective pawl means operable by and during each rotation of said power `shaftfand manually operable means to Amake said pawl means effective during each rotation .of said `Vpower shaft to engage said hammer element and -move said element and said compression spring to the limit ofthe nonworking stroke and quickly release said hammer element to enable said spring to vcause a working stroke thereof. Y t

`4. In avpovrtable power hammer of the char-Y acter described, a continuously rotatable eccentric associated with a reciprocable hammer element, an eccentric strap on said eccentric and having .a pivot slot angular to the axisthereof, a cross headV on saidhammer element and movable longitudinally of said hammer element and having a movable pivot in said pivot slot, a compressionspring between said cross head and said hammer` elementl a pawl lug on said eccentric and normally movable Vtherewith in a path out of the 'patlroi saidhammer element, and manually operablemeans for moving said pivot in said slot to change the relationship of said eccentricV strap to .said eccentric so that said pawl lug intermittently moves `in theY path of said hammer element to move and release said hammer element and .spring fora working stroke.

5. A `power .operated portablehammer comprising a casing .having a laterally extending handle, a reciprocating hammer'element in said casing, a power shaft extending through said handle in-perpendicular axial alignment with the axis of said hammer element, an eccentric on said Ypower shaft in alignment with said hammer element, a slidable cross head on said hammer element, a pivot for said eccentric strap on said cross head, axcompression spring between said cross head and said hammer element, a pawl on said eccentric strap and normally out of operativeyengagementwith said hammer element, a triggerv adjacent said handle and operable to move-said pivot to change the relationship of said pivoted 'eccentric strap to said eccentric whereby, during'each revolution of said eccentric, said vpawl will vengage and move said hammer element to the limit of its nonworking stroke and release.

6. A portablel power hammer comprising a casing, a hammer element mounted for limited reciprocation in'said casing and havinga working head Vextending therefrom only a restricted portion of its stroke so that the work is prevented by said casing from following'said'hammer head, a. power driven, continuously rotatable eccentric, a compression spring between said eccentric and said yhammer lhead and arranged to be compressed duringlalternate; half cycles of said eccentric with saidfhammer element at rest,'and pawl means on said eccentric and adapted'to bodily move said hammerelementfand compressed-spring to nonworking position en tirely within said casing` and quickly release said hammer element for a working stroke.

'1. A portable power hammer comprising a casing, a hammer element mounted for limited reciprocation in said casing and having a working head extending therefrom only a restricted portion of its strokeso` that the work is prevented by said casing fromfollowing said hammer head, a power driven, continuously rotatable eccentric, a compression spring between said eccentric and said hammer head and arranged to be compressed during alternate half cycles of said eccentric with said hammer element at rest, pawl means on said eccentric and adapted to bodily move said hammer `element and compressed spring to nonworking position entirely within said casing and quickly release said hammer element for a working stroke, said pawl being normally inelective to cause operation of said hammer,V and means controllable by an operator for making said pawl effective or ineffective at will.

8. A portable power hammer comprising a casing, a hammer element mounted for limited reciprocation in` said casing and extending therefrom only a restricted portion of its stroke so that the work is prevented by said casing from following the hammer element, a pawl mounted on a floating pivot for lateral movement relative to said hammer element, said pivot being movable relative to said hammer element, a spring normally urging relative movement of said pivot and said hammer element, a trip lug on said hammer element for engagement by said pawl, and continuously operable means to alternately move said pivot to store energy in said spring with said hammer element. at the limit of its working stroke and to cause said pawl to move said hammer element to the opposite limit of its stroke and quickly release said energy loaded spring and said hammer element for a working stroke.

9. A hammer of the character described `comprising a comparatively small diameter elongated casing having a laterally extending handle, a reciprocating hammer element in said casing and having a bearing adjacent each end thereof, ad-

justable resilient means adjacent the upper end of said casing to cushion and limit the working stroke of said hammer element, a power shaft extending through said handle and through an opening in said hammer element, an eccentric on said shaft in alignment with said hammer element, an eccentric strap on said eccentric, a cross head on said hammer element between said eccentric strap and the working end of said hammer element, a compression spring between said cross head and the working end of said hammer element, said cross head having an element movable parallel with the axis of said eccentric strap and having an angular tooth thereon in mesh with complementary angular teeth on said eccentric strap to form a pivot for `said strap, a pawl lug` on said eccentric strap and normally ineffective to engage said hammer element, and trigger means associated with said handle to move said toothed cross-head element to position said eccentric so that said pawl lug will engage and move said hammer element to the limit of its nonworking stroke and release said element during each revolution of said eccentric.

10. A portable hammer comprising a casing having a laterally extending handle, a longitudinal reciprocable hammer element in said casing, an eccentric in said casing, a transmission extendingthrough said handle rfor continuous operation of said eccentric and adapted foroperative `connection to a powersource, an eccentric strap on said eccentric, a iloatingpivot for said eccentric strap to causeoscillation of said strap and vertical reciprocation of `said pivot during each revolution of said eccentricL aspring between said pivot and saidV hammer element continuously urging relative` movement (thereof whereby energy is stored in said spring during partialrotation ofsaid eccentric, and a pawl lug on said eccentric, said lug being adapted during further movement of said eccentric to engage and move said hammer element in one direction and during 'further movement to release said hammer element to enable said stored energy to cause a working stroke of said hammer. Y

` l1. A portable power hammer comprising a casing` having a laterally extending handle, a hammer element mounted for limited reciprocation in said casing and having ahammer head, a power shaft extending through said handle and having an eccentric thereon in alignment with said hammer element, a cross head slidable on said hammer element between saidl eccentric and said hammer head, a compression spring between said cross head and said hammer head, an eccentric strap on said eccentric and provided with a pair of angularly positioned gear teeth, said cross head including a transversely movable element having an angular gear tooth meshing with the teeth on said eccentric strap and forming a pivot therefor whereby said spring is compressed with each revolution of said eccentric, a pawl lug on said eccentric and adapted to enter beneath a shoulder on said hammer element and raise and release said hammer element with each pivotal movement of said eccentric strap, said pivot tooth element normally being positioned to prevent hammer operation by said pawl lug, a manually operable trigger adjacent said handle, and means between said trigger and said pivot element to move said pivot element by operation of said trigger so that the angular relationship of said pivot teeth will position said eccentric to cause intermittent hammer engagement by said pawl lug.

12. An anvil supporting, substantially U- shaped yoke for a portable hammer unit comprising an anvil supporting arm, a hammer supporting arm, means connecting said arms for relative movement, adjustable means to enable adjustment of said arms to and from each other while retaining the same relative angular relationship, said connecting means comprising telescopic means for retaining said arms inv alignment, said adjustable means comprising a manually operable cam for moving saidarms toward each other and spring means tending to separate said arms.

13. A portable hammer of the character described comprising a casing having a laterally extending handle, a power shaft extending through said handle, a hammer element in said casing and operable by said power shaft, a substantially U-shaped yoke pivotally connected with said casing and having a portion in interlocking engagement with a complementary portion of said handle when said handle is in alignment with said yoke, said pivotal connection and said portions being constructed to enable removal of said yoke by rotary movement of said casing and handle on said pivotal connection tc separate saro. portions and an anvil supported on the free arm of!said.yoke in alignment Withsaid. hammer element.; y I

14` A` hammer. of thecharacter dscribedcomprisingza1 vertical? casing, a;y hammer element. assembly longitudinally recprocablein said casing andl Y having a bearing ,at` each end thereof," said hammer el'ementbeing` insertablev longitudinally in"saidcasingand'having a compression spring thereon adapted when compressed and released to operate` said hammer,ret'aining means adjacent one ,bearing and adapted to secure said hammer assembly in said casing forlimited'movement, 'spring'meansbetwe'en saidretaining means and said` casingj to' limit the Working stroke of saidY hammer assembly, a laterally extendingjhollow' handle ons'aidcasing', .a drivelshaft" assembly in said handle having an eccentric` thereon positionable in the axial plane ofsaid hammer element. and' having" bushing -bearings'positionable in saidica'singg, a` bushing adapted to-v be threaded. in saidhandle andia'dapted to retain: saidv shaft assembly; andmeanson said eccentri'cilf'or' com'- porting yoke extending'under said handle and having a vertical' pivotal connection With said hammer. unit adjacent the inner end. of said handle, said pivotal connection having interlocking portions releasable by a'partial rotation of said hammer unit,a releasable" interlocking connectionbetween said yoke and the outer end of said handle, and' a hammer controlling trigger positioned' under said handle, said yoke being formed between said` interlockingv connections toV provide a trigger'g'uard.

RAGNAR` E. SKOGLUND.

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