US2314847A - Fastener driving machine - Google Patents

Description

March 23,1943. I POLZER I 2,314,847

FA'STENER DRIVING MACHINE Filed Dec. 20, 1940 4 Sheets-Sheet 1 INVENTOR ATToRNE'Ys March 23, 9.43.

'- F. POLZER FASTENER DRIVING MACHINE Filed Dec. 20, 1940 v 4 Sheets-Sheet 2 ATTORN EY5 March 23, 1943. F. POLZER FASTENER DRIVING MACHINE Filed Dec. 20, 1940 4 Sheets-Sheet 3 ATTORNEYS.

arch 23, 1943'. POLZEfi FASTENER DRIVING MACHINE Filed Dec. 20, 1340 4 sheets sheet 4 ATTORNEYS Patented Mar. 23, 1943 FASTENER DRIVING IVIACHINE Fridolin Polzer, Norwalk, Conn., assignor to The E. H. Hotchkiss Company, Norwalk, Conn, a corporation of Connecticut I Application December 20, 1940, SerialNo. 371,011

12 Claims.

This invention relates to a fastener driving machine of the type in which a spring is used for driving the plunger to set the fastener, and has for an object to provide a construction in which if it is desired to change the driving power, as for example to increase the driving power, the spring may be easily and quickly changed with a simple operation to either provide a heavier or lighter spring as desired.

It is also an object to provide a construction in which as the operating handle is depressed there is no increase in pressure required on this handle as it moves toward the end of its movement, but a substantially uniform pressure will operate the handle throughout this entire movement, or the pressure required may even be lighter at the end than at the beginning of its movement as contrasted with old types of machines where the pressure required to operate the handle and compress the spring increases as the spring is compressed.

It is another object to provide a construction in which substantially all of the parts maybe stamped and formed from sheet metal.

It is a further object of the invention to pro- C vide a device in which the same mechanism may be used to drive various types of fasteners such for example as two-pronged staples, tacks, nails and the like, it being necessary for the different types of fasteners to merely change the shape and size of the fastener guiding and feeding means and the driving plunger to suit the type and size of fastener used.

With the foregoing and other objects in view I have devised a construction as illustrated in the accompanying drawings forming a part of this specification. It is however to be understood that I am not confined to the specific construction and arrangement shown but may employ various changes and modifications within the scope of the invention. In these drawings:

Fig. l is a side elevation of my improved fastener driving machine with parts broken away to more clearly show the construction;

Fig. 2 is a front elevation thereof with parts broken away to more clearly show the construction;

Fig. 3 is a bottom plan view of the device;

Fig. 4 is a transverse vertical section substantially on line 44 of Fig. 1;

Fig. 5 is a vertical longitudinal section showing the parts in their normal positions;

Fig. 6 is a front elevation showing the securing means for the yoke released to permit exchange of the driving spring;

Figs. 7, 8 and 9 are detailed sections substantially on lines 1-1, 8--8 and 9-9 respectivelyof Fig. 5;

Fig, 10 is a partial side elevation and partial vertical longitudinal section showing the operating handle depressed and the elements in the positions they occupy just prior to the release of the plunger for the fastener driving operation;

Fig. 11 is a detailed section substantially on line ll-l! of Fig. 10 with the side plates of the outer housing omitted;

Fig. 12 is a side elevation, with parts broken away to more clearly show the construction of the operating unit for raising the plunger to compress the driving spring prior to the fastener driving operation;

Fig. 13 is a front elevation thereof looking as indicated by line I3l3 of Fig. 12 v Fig. 14 is a rear elevation and section looking as indicated by line I4I4 of Fig. 12;

Figs. 15, 16 and 17 are a bottom plan view, front elevation and side elevation respectively of the plunger for carrying and operating the driver for the fastener, parts of Fig. 16 being broken away to more clearly show the construction;

Fig. 18 is a side elevation looking toward'the inner side of one of the side plates of thebody housing; 7

Figs. 19, 20, 21 and 22 are detail sections substantially on lines I 9l9, 28-20, 2|-2| and 22 22 respectively of Fig. 18;

Fig. 23 is a top plan View of the support for staple fasteners and carrying them to driving position;

Fig. 24 is a side elevationthereof;

Fig. 25 is a front end view of the fastener support of Figs. 23 and 24;

Fig, 26 is a transverse section substantially on line 26-26 of Fig. 24.;

Figs. 2'7 and 28 are a front and side elevation respectively of the front portion of a strip of staple fasteners which may be used in this machine;

Fig. 29 is a top plan view of a horizontal dividing and spacing wall between the side plates of the housing and forming a cover over the staple guiding support; and

Fig. 30 is a side elevation of one end portion thereof.

The device is illustrated as adapted for driving substantially U-shaped or two-pronged staples or staple fasteners, but as above indicated the same mechanism may be employed for driving other types of fasteners, such for example as other types of staples, tacks and nails, it being necessary merely to change the shape or form and size of the fastener support and guiding means and the driver for the fastener to correspond with the type and size of fastener used. Also the device is shown for driving the staple fastener directly into the article to be fastened without clinching and is therefore what is known as a tacker, but it may be used with a base carrying an anvil in alignment with the staple driver for bending over and clinching the staple prongs as in the type of machine known as a stapler, such base and anvil not being shown however in the drawings as they may be of a conventional type.

The device comprises a body including two spaced side plates l and 2 forming a main or outer housing. These plates are preferably stamped and formed from sheet metal of proper gauge and are made substantially the same except that they are right and left hand, or each is reversed with'respect to the other, the right hand plate 2 being shown in detail in Figs. 18 to 22. The main body of each of these plates is provided with an elongated opening 3, and when the plates are assembled in upright parallel spaced relation these openings are in alignment for passage of the fingers of the operator and form the lower part of the grip on the machine. The front part of the plate is offset as indicated at 4 to provide one-half of a guide for a vertically movable plunger carrying the staple driver 6. The other plate I is similarly offset in the opposite direction as indicated at 1 to complete the other half of the vertical guide for the plunger. The rear edges of each of these offsets may have an ear 8, the two being side by side and may be secured together by any suitable means such as a screwor rivet 8a or by welding.

The plunger ;5 which is guided for vertical movement in the guideway formed by the offsets 4 and I has a substantially rectangular head portion 9 and a stem In providing a shoulder 9a. The head portion is recessed on its lower front face as indicated at -l I to receive the upper end of the driver B, and in the wall of this recess is another recess I2 to receive a lug l3 cut and bent backwardly from the driver to connect the driver to the plunger sothat the driver will be carried upwardly with upward movement of the plunger. The shoulder l4 at the top of the recess ll engages the upper end of the driver so as to force the driver downwardly to drive the fastener as the plunger is driven downwardly under action of a spring l5 as will later be described. This spring embraces the stem l9 and rests at its lower end on the shoulder 9a. At its upper end it engages the under side of the top wall I6 of a yoke IT. This yoke may also be stamped and formed from sheet metal and has side arms I 8 extending downwardly from the top wall 16 on opposite sides of the plunger guide portions 4 and 1 of the body. On the outer walls of each of these guide portions 4 and 7 there is a downwardly extending hook or lug l9 cut from the walls of the guide and forced outwardly therefrom so as to pass through opening 28 formed in the corresponding arm [8 of the yoke, and by engaging over the lower edge of this opening as shown in Figs. 1 and 2 retaining the yoke in position on the body. The yoke may be easily removed by forcing it downwardly against the action of the spring l5, which can be done by pressure of the hand on top of the yoke, until the walls of the arms l8 under the hooks 19 are released therefrom permitting the arms to spring outwardly as indicated in Fig. 6. This releases the arms, and the yoke may then be readily lifted from the body.

At the lower end of each of the arms 18 is an inwardly extending lug 2! each passing through an opening 22in the outer side wall of the offset guide portions 4 and I. These extend into the guideway for the plunger over the top of a resilient; cushioning bumper 23 under the plunger to arrest downward movement of the plunger and cushion the blow. This bumper may be of various constructions but that shown comprises a central rubber plug 24 embraced by a heavy spring 25. This bumper is supported on a transverse wall 26 mounted in the lower part of the guideway. In the present construction this wall is a block having lugs 21 extending into and seated in openings 28 formed in the walls 4 and 1 whereby the block 26 is supported. It has a notch or recess 2% (Fig. 7) in its front .edge for passage of the driver 6. The lugs 2| by extending inwardly over the bumper prevent the bumper from moving upwardly in the plunger guideway so that it is retained in proper position on the wall 25. The head 9 of the plunger is provided with grooves 29 to form clearance for the lugs 2| and permit the plunger to move downwardly by these lugs. The top wall N5 of the yoke extends downwardly on the front and rear sides of the plunger guideway as shown at 30 to help retain the yoke in position.

Between the side plates 1 and 2 and at the lower portions thereof is a staple support and guide 3|. This may be a solid bar but is preferably formed of sheet metal and substantially U- shaped in cross section as shown in Figs. 4, 8 and 275.. The staples 32, preferably in a connected strip 33, are supported on this support and guided thereby to the staple driving position, the staple strip being inserted on the sup port through the right hand or rear end of the housing as viewed in Figs. 1 and 5. This support is the general shape of the inner part of the staple and as the staple 32 shown is tapered, that is the prongs are inclined inwardly so that the free ends of the prongs are closer together at the bottom of the staple than at the connected portion at the top as shown in Fig. 2'7, the side walls of the support 3| are also inclined to correspond. This retains the staples on the support and prevents their falling or rising off the top thereof. This support and guide will of course be of a size and shape to correspond with the staple or other fastener for which the machine is designed to be operated.

These staples are fed along this support by means of a follower 34 of substantially inverted U-sha-pe to slide along the top of the support 3| with its side wall embracing this support as shown in Fig. 8. At its forward end the follower may have a downwardly extending lip 34a between the sides of support 3| to engage the top or cross member of the staples and insure these staples do not ride onto the top of the follower. This follower is provided with a loop 35 embracing and slidable on a rod 35 located between the sides of the support 31 and on which is a coil spring 31 tending to shift the follower 34 forwardly along the support 3! to feed the fasteners forwardly to the driving position. The end of the rod may be flattened at 36a to make it wider to prevent the loop 35 sliding off the end of the rod. At the rear end the rod 36 is bent upwardly and forwardly as shown at 38 to provide a hook 39 adapted to hook into an opening 40 at the rear end of the member 4| forming a top wall or cover over the support 3I and extending transversely between the plates I and 2. It forms a spacing element between the plates and helps to them in proper relation. At its edges this member 4| has lugs 42 extending into openings 43 in the plates I and 2 to position the plates I and 2 and member 4! in proper relation to each other and also support the member M. This member 4I also has downwardly extending flanges Mo on the opposite side edges to rest on the lower edges 44 of the openings 3 in the plates I and 2 and to extend downwardly on the outer sides of these plates as shown in Figs. 1 and to hold the plates against separation and also to form a finish at the lower sides of the openings. By lifting the hook 39 from the opening the follower 34 may be withdrawn from the rear end of the support 3I to permit insertion of a strip of staples onto this support. Then the follower may be replaced and the hook 39 inserted in the opening 48.

The staple support and guide 3! is mounted on the lower member 45 which is substantially channel or U-shape, and the member 31 is secured at its lower wall on the bottom wall of this member by any suitable means such as rivets 46, spot welding, or the like. The outer side flanges 4'! embrace the lower edges of the side plates I and 2 and the bottom wall 45 has elongated openings 48 therein to receive lugs or projections 49 projecting downwardly from the lower edges of the plates I and 2 to properly position the member 45 and support BI with relation to the side plates I and 2 and the other elements of the device.

These lugs 49 or the plates I and 2 near them are secured to the side flanges 41 of the bottom member 45 by suitable means such as rivets or welding 49a.

At the forward end of the support 3% there is mounted an L -shaped member having an upright wall 50 between the sides of the member 3| and forming the rear wall of a guideway or raceway 5I for passage of the staples under the action of the driver 6. This member is mounted by means of its lower wall 52 seating on the bottom wall 3Ia of the member 3| and secured thereto by any suitable means such as rivets 53 or by welding. The wall 50 may be supported against backward movement by means of lugs 50a1anced from the side walls of support 3! and bent inwardly to engage the rear side of wall 50 and support it as shown in Figs. 5, 23 and 24. The front wall of the raceway 5I is formed by a removable plate 54. This plate has its opposite vertical side edges bent backwardly and inwardly to form flanges 55 (Fig. 9) embracing outwardly extending flanges 56 on the forward edges of the side plates I and 2 and below the offset plunger guide portions 4. Spacing plates 51 may be secured to member 54 and placed between the plate 54 and the flanges 6 at opposite sides of the driver 56 to give a proper spacing of the front wall of the member 58 from the guide wall 59 to form the raceway 5! for passage of the staples and the driver 5. The member 54 is placed in position by merely sliding it upwardly on the flanges 55 from the lower ends thereof, and it is held in position by any suitable means such as a spring plate or finger 58 secured to the front wall of the offsets 4 by any suitable means such as rivets 59 and overlapping the member 54. A lug 65 cut and bent backwardly from the spring plate 58 may seat in a recess in the front wall of the member 54 to form a catch to retain the member 54 in position. By merely lifting the lower end of spring 58 outwardly, this catch may be released and the member 54 slid downwardly out of position to give access to the front end of the staple support and the lower portion of the driver 6, and also to permit removal of any staple which may become jammed in the raceway. The forward end of the bottom wall 45 may be beveled as shown at 45a (Figs. 23, 24 and 25) to prevent backwardly inclined staple prongs from jamming on this wall and. for guiding such prongs into the raceway 5 I.

The means for lifting the plunger against the action of the spring I5 to compress this spring and also to raise the driver 6 to permit a fastener to be fed into the raceway under this driver in position to be driven thereby is mounted and assembled as a separate unit, which unit is shown in Figs. 12, 13 and 14 removedfrom the machine, but is shown in assembled relation in the machine in Figsr5 and 10. This unit assembly comprises an inner housing BI of general U-shape having side walls 62 and a bottom wall 63 connecting the lower edges to the side walls. This may also be formed of sheet metal of suitable gauge or thickness and bent to shape. Pivoted between the sides of this housing adjacent the upper edges thereof and on the pivot pin 64 is an operating handle 65. This handle is also formed from sheet metal and is of generally channel or inverted U-shape in cross section, and the side walls at the forward end thereof are extended downwardly from the pivot I54 to for a lever arm 66. At the lower end of this arm and mounted between the side walls thereof is a roller 6! mounted on a suitable cross pin 58. The two sides of the lever .arm 66 extend on the opposite sides of and embrace a cam lever 69 pivoted between the sides 52 of the housing on the pivot '10 rearwardly of the .pivot 64, and the lower edge 'II of this cam lever is shaped to form a suitable cam surface contacting and cooperating with the roller 61.

Embracing the forward end of this cam lever; 69 is a pawl I2. This pawl is of general channel shape in cross section with its side walls 13 embracing the front end of the lever 59 and pivoted thereto adjacent its lower end by means of the pivot pin 14. This pawl 52 is located between the side walls 62 of the inner housing. The top end of its front wall I5 may engage under a downwardly facing shoulder 15 formed on the rear wall of the plunger 9 to lift the plunger when the pawl is lifted, as will presently be described. A spring 11 mounted in a recess in the forward end of the cam lever and embracing a stud IE on the pawl tends to shift the upper end of the pawl, outwardly or forwardly about the pivot 14. The upper edges of the side walls 13 are inclined to form a cam 18 to engage a cross pin 19 mounted in and extending between the side walls 52 of the inner housing to shift the upper end of the pawl 12 backwardly when it approaches the end of its upward movement and thus to withdraw the upper end of the wall 15 from under the shoulder 15 on the plunger to release the plunger to permit it and the driver 6 to be forced downwardly is provided projecting beyond the sides 13 of the pawl into slots 8| in the side walls 62 of the inner.

housing, and by engaging the front or forward edges of these slots limit the forward movement of the pawl.

Also to assist in preventing catching of the plunger on the pawl the lower rear edge of this plunger may be inclined or chamfered as shown at 82. A spring 83 is coiled about the pivot 64 and has one end 84 pressing on the under side of the lever 65 and its other end 85 resting in a groove 86 on top of the cam lever 69. This spring therefore tends to raise the hand lever 65 upwardly about the pivot 64 and to swing the cam lever 69 downwardly about its pivot 10.

When the lever 65 is depressed the roller 61 is forced to the left as viewed in Fig. and runs along the cam surface II. This raises the free end of the cam lever 69 about its pivot and thus raises the pawl 72. this pawl is engaged under the shoulder 16 on the plunger 9 it raises this plunger and with it the driver 6 and compresses the spring l5. The cam H is so shaped that as the roller 61 runs along this cam when the hand lever 65 is depressed this roller moves away from the pivot 10 of the cam lever. Therefore the greater the lever 65 is depressed the farther the roller 61 and its point of engagement with the cam surface becomes spaced from the pivot 19. It will thus be seen that as the lever is depressed its leverage on the cam lever 69 through the roller 67 increases or becomes greater as the spring I5 is compressed. Thus the farther the lever 65 is depressed the greater will be the leverage on the cam lever 69 and therefore the cam H can be designed to cause this increase in leverage to compensate for the increase in the resistance of the spring I5 as this spring is compressed. The cam H can be made so that as the operating lever 65 is depressed there is no increase in pressure required as it approaches the lower extreme of its movement. In fact the cam H can be so designed if desired, that the pressure required to operate the lever may decrease as the lever is operated. The shape of this cam also determines the travel or throw of the plunger and the cam can therefore be designed to give a greater or less movement to the plunger in relation to the movement of the operating handle as desired. It will also give a relatively long throw to the plunger with a short stroke of the operating handle.

To give a more comfortable grip, a resilient or soft rubber pad 81 may be mounted on the top of the lever 85 and secured thereto by any suitable means such as rivets 83. Another soft rubber pad 89 may be mounted between the side plates l and 2 of the body at the upper part of the openings 3 and secured in position by any suitable means such as pins or rivets 90.

The removable unit assembly including the inner housing 6| may be mounted in the outer housing between the body plates I and 2 as shown in Figs. 5 and 10 and secured therein by any suitable means such as the screws or rivets 9! extending transversely through the side members of the two housings. By removing these securing means 9| this operating assembly as shown in Figs. 12, 13 and 14-. may be removed as a unit from the body or outer housing as shown in dotted lines Fig. 1.

In operation the operator grips the device by passing his fingers through the openings 3 under and engaging the grip pad 89 and with the palm of the hand resting on top of the operating lever 55. Then after setting the lower edge of the de- As the upper edge of vice on the article to be fastened the lever may be depressed to the position shown in Fig. 10. This operation through the action of the roller 6! on the cam H raises the forward end of the cam lever 69 about the pivot 19. This raises the pawl 12 and as the forward upper edge of this pawl engages the shoulder on the plunger 9, it also lifts this plunger against the action of the spring l5, thus compressing the spring and' storing energy in it. Upward movement of the plunger also carries with it the driver 6, and as the lower end of this drives passes above the top of the staple support 3| and the strip of staplesthereon, this strip is fed forwardly by the follower 34 to carry the forward staple 3211 (Fig. 10) into the driving position in the raceway 5| and under the lower end of the driver 6. As the lever 65 is further depressed from the position of Fig. 10 the pin l9 acting on the cam 18 on the pawl '12 moves the upper end of this pawl to the right or rearwardly withdrawing the upper edge of this pawl from the shoulder 16 on the plunger. This releases the plunger whereupon the spring l5 forces it downwardly with a quick action carrying with it the driver 6. This driver forces downwardly the forward staple 32a and drives it into the work to be fastened. The downward movement of the plunger is arrested by its lower end striking the top of the bumper 23 as shown in Fig. 5. This being a resilient bumper also cushions the force of the blow preventing objectionable blows or hammer action on the other elements of the mechanism. After the fastener is driven release of pressure on the handle 65 permits it to be raised under the action of the spring 83 returning the parts to the position of Fig. 5. This permits the cam lever 58 and the pawl l2 carried thereby to be moved downwardly by their own weight and action of the spring arm 85 and cause the forward upper edge of the pawl to pass below and engage under the shoulder 16 on the plunger in position for again lifting the plunger on depression of the operating lever 65 for setting another fastener.

It will thus be seen that the device can be made principally of parts stamped and formed from sheet metal, decreasing the weight of the device and increasing its strength for the amount of metal used. Also that it will not be as fatiguing to operate as older types of fastener driving machines where the pressure required to operate the operating lever increases with movement of this lever, but that in this device the pressure required to operate the lever does not increase and may even decrease toward the end of its movement. If more driving power is desired all that is necessary is to remove the yoke I1, remove the old spring and insert a new and stronger spring, or any other spring of the desired power.

Having thus set forth the nature of my invention, what I claim is:

1. A fastener driving machine comprising an outer housing including spaced side plates, a guideway at the front of the housing, a vertically reciprocable driver and support in said guideway, a spring for forcing the driver downwardly to drive a fastener, means for feeding fasteners to a driving position under the driver, and means for lifting the driver against the action of the spring preparatory to the driving operation comprising a unit assembly mounted between the side plates including an inner housing, an operating lever pivoted in the inner housing and having a depending arm, a cam lever pivoted in said latter housing and having a cam on its lower edge,

'means on the-depending arm to run on said cam 'to lift the cam lever, and means on the cam lever ;to engage the driver support to lift the driver.

2. Afastener driving machine comprising an 'outer housing including spaced side plates, a

guideway at the front of the housing, a vertically reciprocable driver and support in said guideway, a spring for forcing the driver downwardly -to drive a fastener, means for feeding fasteners to a driving position under the driver, a unit assembly comprising an inner housing, an operating lever and a cam lever mounted in said latter housing, said cam lever having a cam on one edge, means carried by the operating lever .running on said cam to lift the cam lever, a pawl carried by the cam lever, and means for mounting the unit assembly in the first housing with the pawl in position to engage the driver support to lift said driver against the action of the way, a spring for forcing the driver downwardly to drive a fastener, means for feeding fasteners to a driving position under the driver, a unit assembly comprising an inner housing, a hand lever and a cam lever mounted in said latter housing, said cam lever having a cam on the lower edge thereof, said hand lever having a depending arm carrying a roller to run on said cam to life the cam lever, a pawl pivoted at the free end of the cam lever, spring means tending to return the two levers to normal position, and means for mounting the unit assembly in the first housing with the pawl in position to engage the driver support to lift said driver against the action of the first spring.

4. A fastener driving machine comprising a housing having an upright guideway, a driver and its support in said guideway, said support having a downwardly facing shoulder, a spring for forcing the driver downwardly for driving a fastener, means for feeding fasteners to the driving position under the driver, a hand lever pivoted in the housing, a second lever, cooperating means on the hand lever and second lever for lifting the latter lever on depression of the hand lever, a pawl substantially U-shape in cross section embracing the free end portion of the second lever, means for pivoting theside walls of the pawl to the lever, the upper end of said pawl being adapted to engage said shoulder to lift the driver, a cam on the pawl, and cooperating means to engage said cam to shift the pawl from said shoulder as the hand lever approaches its lower limit of movement.

5. A fastener driving machine comprising a housing having an upright guideway, a driver and its support in said guideway, said support having a downwardly facing shoulder, a spring for forcing the driver downwardly for driving a fastener, means for feeding fasteners to the driving position under the driver, a unit assembly including an inner housing, a hand lever pivoted in the latter housing, a second lever pivoted in said housing, cooperating means on said levers for raising the second lever on depression of the first lever, a pawl pivoted on said second lever and adapted to engage said shoulder to raise the driver, a spring tending to swing the pawl outwardly into alignment with said shoulder, said inner housing having a slot in a side wall thereof, a projection on the pawl extending into said slot "and adapted to engage an edge thereof to limit outward movement of the pawl, and cooperating means on the pawl and housing to remove the pawl from said shoulder as the hand lever ap proaches the limit of its downward movement.

6. A fastener driving machine comprising a housing having an upright guideway open at the tending resilient arms on opposite sides of the guideway, means for detachably connecting said yoke to the housing comprising downwardly opening hooks on the outer walls of the guideway and openings in the arms to receive said hooks, operating means for raising the driver against action of said spring preparatory to driving a fastener, and means for feeding fasteners to the driving position under the driver.

'7. A fastener driving machine comprising a housing having an upright guideway open at the top, a driver and its support mounted in the guideway for reciprocating movement, a spring for moving the driver downwardly for driving a fastener, a removable yoke having a wall over the open top of the guideway and forming an abutment for said spring, said yoke having downwardly extending arms embracing opposite sides of the guideway, downwardly opening hooks on the outer walls of the guideway, said arms having openings to receive the hooks and engage under them under action of the spring to retain the yoke on the housing, means for raising the driver preparatory to driving a fastener, and means for feeding fasteners to driving position.

8. A fastener driving machine comprising a housing having an upright guideway open at the top, a driver and its support mounted in the guideway for reciprocating movement, a spring for moving the driver downwardly for driving a fastener, a removable yoke having a wall over the open top of the guideway and forming an abutment for said spring, said yoke having downwardly extending arms embracing the opposite sides of the guideway, means for detachably securing said arms to the housing, a supporting wall at the lower part of the guideway, a resilient bumper supported on said wall to receive the blow of said support and limit its downward movement, said arms having lugs extending inwardly through walls of the guideway to a position over the bumper to limit upward movement of the bumper, means for raising the driver preparatory to driving afastener, and means for feeding fasteners to the driving position.

9. A fastener driving machine comprising a housing having an upright guideway open at the top, a driver and its support mounted in the guideway for reciprocating movement, a spring for moving the driver downwardly for driving a fastener, a removable yoke having a wall over the open top of the guideway and forming an abutment for said spring, said yoke having downwardly extending arms embracing opposite sides of the guideway, downwardly opening hooks on the outer walls of the guideway, said arms having openings to receive the hooks and retain the yoke on the housing, a supporting wall at the lower part of the guideway, a resilient bumper supported on said wall to receive the blow of said support and limit its downward movement, said arms having lugs extending inwardly through walls of the guideway to a position over said bumper, means for raising the driver preparatory to driving a fastener, and means for feeding fasteners to the driving position.

10. A fastener driving machine comprising a housing having a guideway, a driver and its support reciprocable in said guideway, a spring for shifting the driver to set a fastener, a supporting wall in the guideway, a resilient bumper on said wall to receive the blow of the support and limit its movement and comprising a resilient rubber core surrounded by a coiled spring, means for retracting the driver against action of the first spring preparatory to a driving operation, and means for feeding fasteners to driving position in front of the driver.

11. A fastener driving machine comprising a housing having an upright guideway open at the top, a driver and its support mounted in the guideway for reciprocating movement, a spring for moving the driver downwardly for driving a fastener and removable through the top of the guideway, a removable yoke including a wall over said open top of the guideway forming an abutment for said spring and downwardly extending arms at the opposite sides of the guideway, means for detachably securing the yoke to the housing comprising downwardly opening hooks on the walls of the guideway and openings in said arms to receive said hooks and engage at their lower edges under the hooks under action of the spring to retain the yoke in place, and said yoke being shiftable downwardly against action of the spring to release the arms.

12. A fastener driving machine comprising a housing having an upright guideway open at the top, a driver and its support mounted in the guideway for reciprocating movement, a spring for moving the driver downwardly for driving a fastener and removable through the top of the guideway, a removable yoke including a wall over said open top of the guideway forming an abutment for said spring and downwardly extending resilient arms at the opposite sides of the guideway, downwardly opening hooks on the walls of the guideway, said arms having openings to receive said hooks and engage at their edges under the hooks under action of the spring to retain the yoke in place, said yoke being shiftabledownwardly against action of the spring, and said arms tending to spring outwardly so that when the yoke is thus shifted downwardly the arms will move outwardly away from the hooks to release the yoke.

FRIDOLIN POLZER.

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