US1972328A - Power hacksaw - Google Patents

Description

G. J. BLUM POWER HAcKsAw sept. 4, 1934.

Filed June 22. 1931 3 Sheets-Sheet l Sept. 4, 1934. G. J. BLUM 1,972,328

POWER HACKSAW Filed Jpme 22. 1931 5 Sheets-Sheet 2 Y O 101 23 95 l 100 95 95 97 2 109 Q 98 l; l 05 I f G. J. BLUM POWER HAcxsAw Sept. 4, 1934.

Filed June 22. 1931 5 Sheets-Sheet 5 lill ll'llllllllll lOl Patented Sept. 4, 1934 UNITED STATES PATENT OFFICE strong-Blum Mfg. Co., Chicago, Ill., a corporation of Illinois Application June 22, 1931, Serial No. 545.949 i 20 Claims.

The invention relates to power hacksaws for sawing bars of metal or other material into desired lengths, the machine being entirely automatic so that it is only necessary to place a bar of material in the machine, make the proper adjustments, and start the operation.

One of the principal objects of the present invention is to provide a means for automatically throwing out the feeding mechanism, in

0 a machine of this character, should the downward feeding movement be obstructed at any point, so that none of the parts of the machine will be broken.

A further object is to provide a new and irnproved construction by which the blade is raised from the stock. during the back stroke of the blade and depressed during the cutting stroke, and which is coupled with the means for throwing out the feeding mechanism.

Another object is to provide a construction by which the blade is raised from the stock during the back stroke of the blade and depressed during the cutting stroke, and which is yieldable to avoid damage to the machine should any obstruction occur.

Another object is to provide means for positively throwing out the feeding mechanism at the top of its stroke, should the reversing mechanism fail to act.

Still another object is to provide an improved construction of the feeding mechanism.

Further objects reside in an improved construction of the device for stopping the machine automatically at the end of a single cut, in an improved counterbalance for the head, and in improvements in the means for drawing the stock forwardly for a new cut.

Other objects and advantages will become apparent from the following description taken in connection 'with the accompanying drawings, in which:

Figure 1 is a perspective view of a machine embodying the features of the invention.

Fig. 2 is an enlarged fragmentary elevational view of the device for stopping the machine after a single cut.

Fig. 3 is a front elevation, partially in section, of the machine.

0 Fig. 4 is a fragmentary sectional view taken on the line 4-4 of Fig. 3.

Fig. 5 is an elevation, partially in section, of a portion of the feeding mechanism.

Fig. 6 is a fragmentary view taken substan- 55 tially on the line 6-6 of Fig. 5.

(c1. zii- 73) Fig. '1 is a sectional view taken substantially on the line 7-7 of Fig. 5.

Fig. 8 is a fragmentary sectional view taken substantially on the line 8-8 of Fig. 5.

The machine in general this upright is a horizontally extending bracket 22 providing a support for a horizontally reciprocable frame 23 carrying a saw blade 24. Vertical movement is imparted to the bracket 22, and thereby to the frame 23, through the medium of a feed screw 25 arranged to be actuated in opposite directions by a pawl and ratchet echanism generally designated by the numer- Reciprocatory motion is imparted to the saw frame 23 by means of a crank arm 30 (Fig. 3) oscillated in the rotation of a shaft 31 and connected to the frame 23 by means of a pitman 32. Also, actuation of the pawl and ratchet feed mechanism 26 is effected from said shaft 31 by means of a lever 33 fulcrumed between its ends and connected at one end to the crank arm 30 by means of a link 34. The other end of the lever 33 has a pivotal connection with a rack bar 35, the latter constituting the driver for the pawl and ratchet mechanism 26. Since this actuating mechanism is generally of the same characteras that shown in my said copending application, a detailed description thereof is deemed unnecessary.

Feeding mechanism The pawl and ratchet mechanism 26 for ac- 95 tuating the feed screw 25 includes, as in the case of the case of the machine shown in my copending application, a ratchet wheel 40 (see Figs. 5, '7 and 8) secured to .the feed screw 25 and constituting, together with an actuating pawl 41, an actuator for effecting an upward movement of the bracket 22. The mechanism also includes a pair of ratchet wheels 42 and 43, with driving pawls 44 and 45 therefor, for effecting a downward feeding movement of the feed screw 25. The ratchet wheel 43 is connected to the ratchet wheel 40 for rotation therewith, thus being capable of imparting a positive feeding movement to the feed screw, while the ratchet wheel 42 is interposed between and has frictional contact with the other two wheels to impart to the feed screw a non-positive movement of an extent depending upon the resistance offered to the downward feeding movement of the saw. The ratchet wheel 42 is capable of acting throughout the entire cutting stroke of the saw, while the ratchet wheel 43 is limited in its action only to the latter part of the cutting stroke by means of an adjustable guard ring 46 (Fig. 8) surrounding the ratchet wheel 43 and having a slot 47 cut therein. During the major portion of the cutting stroke, the pawl slides on the periphery of the guard ring 46, but toward the end of the stroke, the pawl moves through the slot in the guard ring and into engagement with the ratchet wheel 43.

The ratchet wheel 43, as in my copending application, is adjustable axially of the feed screw 25 to vary the frictional engagement of the ratchet wheel 42 with the other two wheels. Thus, a spring 50 is coiled about the upper end of the feed screw 25 and bears between the ratchet Wheel 43 and an adjustable nut 51 threaded on the feed screw.

The present invention provides means (Fig. 5) eliminating any tendency of the nut 51 to rotate out of a set position, and yet permit it to be readily adjusted when so desired. To this end, a washer 52 is interposed between the spring 50 and the nut 51 and is retained against rotation relative to the feed screw as by a tongue 53 extending into a longitudinal groove 54 cut in the feed screw. The abutting end faces of the nut 51 and washer 52 are correspondingly serrated, as indicated at 55, to prevent relative rotation when the spring 50 holds said faces together. 'I'he serrations 55 are rounded off so that, when itis desired to turn the nut 51, the nut and washer may be readily cammed apart suiciently to permit the serrations to pass each other.

The driving pawls 41, 44 and 45, as in the machine shown in my prior application, are mounted in a shiftable carrier which is oscillated in the reciprocation of the rack bar 35. This carrier is pivotally mounted on a crank arm 56 rigid with a gear segment 57 (Fig. 7) which meshes with the rack bar 35. The pawl carrier is in the form of a U-shaped member 60 (Fig. 5) having its ends mounted to turn on a pin 61 mounted vertically on the free end of the crank arm 56, the latter being constructed to provide a rigid frame member 62 (Fig. 6) in which the upper and lower ends of the pin 61 are mounted. The driving pawls 4l, 44 and 45 are pivotally mounted on the pin 6l, and the carrier 60 is shiftable from a neutral position to one side of such neutral position to place the pawl 41 in an operative position, or to the other side of such neutral position to place the pawls 44 and 45 in operative positions, the carrier being held in any of such positions by means of a spring detent 63.

The pawls 41 and 44, since they are used alternately, are formed integrally on a block 64 which is normally held in a neutral position by a spring detent. According to the present invention, the spring detent is of a simplified construction, is inexpensive to manufacture, and efficiently holds the pawls in operative position when the carrier 60 is so shifted. To this end, a plate 65 (see Figs. 5, 6, 7 and 8) is pivotally mounted on the outer face of the carrier by means of an inwardly turned fiange 66 on the plate 65 resting on the upper edge of the carrier and held in such position by a coiled spring 67 bearing on the outer face of the plate 65 and against an abutment on a pin 68 extending from the carrier. The lower end of the plate 65 is punched to form two pins 69 extending at right angles to the plate and through a pair of holes in the carrier 60 to bear against the block 64 on opposite sides of the pivot pin 61.

In the operation of the pawl and ratchet device, when either the pawl 41 or the pawl 44 is thrown into an operative position by shifting the carrier 60 from neutral to one side `or the other, either pawl, in passing over the teeth of its ratchet, is cammed aside so that the block 64 is turned on the pin 61. The pins 69 on the plate 65 are swung outwardly against the action of the spring 67 until the pawl passes over the ratchet tooth, when the pressure of the spring turns the block 64 back to bring the pawl in an engaging position. Thus, each pawl acts on its ratchet in the usual manner but the construction is simplified by the use of a single spring acting on both of the pawls.

The pawl carrier 60 may be automatically shifted from one operative position through neutrai and to the other operative position, to cause the feed mechanism to move the bracket up or down, as in the case of the machine shown in my copending application. The pawl carrier 60 may also be shifted to and locked in its neutral position by means of a slide 70 having a projection 7l movable into engagement with a pair of spaced lugs 72 formed on the under side of the pawl carrier 60 on opposite sides of the pivot pin 61, the projection 71 turning the carrier about the pin 61 until the projection 71 bears against both lugs 72.

Safety features of the feed mechanism One of the chief features of the present invention is a means for automatically throwing out the feed mechanism 26, should the downward feeding movement be obstructed at any point. in order to avoid breakage of any parts of the machine. This is coupled with a new and improved means for raising the saw blade during the back stroke, the last-mentioned means being yieldable in character and adapted to actuate the means for throwing out the feed mechanism on yielding.

The means for raising the saw blade from the work during the back stroke and depressing the blade during the cutting stroke operates, in the present embodiment (see Figs. 3 and 5) on the feed screw 25 which is threaded in a nut 80 formed on the bracket 22. The feed screw is free to be moved longitudinally up and down to an extent which is sufficient to raise the saw slightly out of cutting contact with the work. Such longitudinal movement of the feed screw is limited in a downward direction by a thrust bearing 81 positioned in a ledge 82 formed within the column 21, and in an upward direction by a collar 83 secured to the screw and adapted to abut against a second ledge 84 formed within the column 21 and spaced from the first ledge 82.

The means for raising the feed screw comprises a spring 85 bearing against the ledge 84 and against a collar 86 secured to the feed screw. Opposing the tendency of the spring 85 to raise the screw is a means for depressing the screw comprising, in the present embodiment, a lever 90 having a fork 91 at one end embracing the feed screw and bearing downwardly on the collai` 86, a thrust bearing 92 being interposed therebetween to prevent the screw from binding when depressed. The lever 90 is mounted on a fixed pivot such as a pin 93 extending from a lug 94 formed on the side of the column 21.

To swing the lever 90, a second or auxiliary lever 95 is pivotally supported between its ends on the other end of lever as by a pin 96. The second lever carries a roller 97 at one end which bears on the peripheral surface of a cam 98 carried on the main shaft 31.

The second lever 95 is adapted to be yieldably held in such position relative to the flrst lever 90 that the two levers move normally as a unit. To this end, an overhanging lug 100 is formed on the first lever adjacent the end of the second lever opposite to the end carrying the roller 97, and a rod 101 is adjustably secured in said lug and extends through the adjacent end of the second lever. A compression spring 102 is coiled around the rod 101 and bears against the second lever to hold it yieldably in abutment with the overhanging lug 100. Thus, on rotation of the main shaft 31, the cam 98 will raise the roller 97, and the two levers swinging as a unit will depress the feed screw 25, while the spring 85 will raise the feed screw and swing the levers back when the high point of the cam has passed the roller. Since both the cam 98 and the crank 30, through which the saw is reciprocated, are driven by the main -shaft 31, the relation between the cutting and back stroke of the saw and the raising and depressing thereof may be properly timed.

In the operation of the hacksaw, if there should be an obstruction preventing the depression of the saw by the lever 90, the second lever 95, being pivoted on the first lever and being yieldably held in abutment with the lug 101, may turn relative to the first lever and compress the spring 102. Thus, the cam 98 will move the second lever alone while the first lever remains stationary.

As mentioned above, when such an obstruction occurs as to cause the second lever 95 to yield relative to the first lever, means automatically throws out the feed mechanism. To this end, said means is provided for connecting the second lever 95 with slide 70 of the feeding mechanism whereby the slide is moved to the position in which the pawl carrier 60 is shifted and locked in its neutral position, when the second lever 95 yields relative to the first lever 90.

In the present embodiment, said connecting means comprises a rod 103 extending through a fork 104 formed on the end of the second lever 95 and yieldably secured so as to be moved thereby, by means of a pair of springs 105 coiled about the rod on opposite sides of the fork 104. The upper end of the rod 103 is secured to one end of a bell crank 106 pivoted on the column 21. The other end of the bell crank 106 extends adjacent a lug 107 (Fig. 5) formed on the slide 70. A handle 108 is also formed on the end of the bell crank to which the rod 103 is attached to permit the crank to be operated manually.

In the normal operation of the levers 90 and 95, that is, when they move as a unit, the movement of the fork 104 is substantially transverse to the rod 103 so that the rod is not moved. However, when an obstruction occurs preventing movement of the rst lever 90, the second lever 95 moves relatively thereto, causing the fork 104 to move longitudinally of the rod and thus drawing the rod with it. Such movement of the rod swings the bell crank 106 and moves the slide 70 to a position in which the projection 71 engages the lugs 72 on the pawl carrier 60 and locks the latter in a neutral position. Thus, the

feeding mechanism is rendered inoperative when any obstruction or excessive resistance occurs which prevents depression of the saw on the cutting stroke.

vAnother safety feature of the present invention is a means for throwing out the feed mechanism at the top of the stroke of the bracket 22 in case the reversing mechanism fails to act. In the present embodiment, this means acts through the slide 70 to lock the pawl carrier 60 in a neutral position, and comprises alever 110 (see Figs. 5 and 7) mounted on a xed pivot 111 with one end extending up through an aperture 112 formed in the slide 70. The other end of the lever 110 extends downwardly into the path of the bracket 22. On upward movement of the latter, should the means for reversing the feed mechanism fail to act before the bracket strikes the end of the lever 110. the bracket will cause the lever to swing, thus moving the slide 70 to shift and lock the pawl carrier 60 in its neutral position to render the feed mechanism inoperative.

Counter-balancing device The present invention includes a new and improved device for counter-balancing the weight of the bracket 22 and saw frame 23 in order to render the feed mechanism more responsive to the conditions of cutting. The embodiment shown in the drawings comprises a means adapted to be rotated in one direction by downward movement of the bracket 22, and means resisting such rotation by tending to rotate said firstmentioned means in the opposite direction. To this end, a rod (see Figs. 3 and 4) is mounted for vertical sliding movement through the top of the base 20 and abuts against the underside of the bracket 22 adjacent the column 21. Within the base is a sheave 121, the groove of which guides the lower end of the rod 120. The sheave 121 is rotatably mounted on a horizontal shaft 122 mounted within the base and held against rotation relative thereto. To cause the sheave to rotate on downward movement of the rod, a

chain 123 or other flexible means is secured at l one end to the lower end of the rod and is wrapped around the sheave in the groove thereof with its other end attached to the sheave.

The means tending to rotate the sheave in the opposite direction comprises, in the present instance, a torsion spring 124 coiled about the shaft 122 and secured thereto at one end with its other end secured to the sheave. Thus, when the sheave is rotated by the rod moving downwardly, the spring is wound to exert a torsional force on the sheave. 'Ihe spring is made of such strength that it normally balances the weight of the bracket, etc., acting through the rod to turn the sheave. The sheave is held against any tendency of the spring to slide it longitudinally along the shaft as by means of a washer 125 and a cotter pin 126.

The shaft 122 is held against rotation by means of a bolt 127 extending through the shaft and through a boss 128 formed on the outer face of the base 20. If it is desired to adjust the torsional force exerted by the spring, the bolt 127 may be removed and the shaft rotated in the desired direction as by a tool inserted in a hole 129 in the outer end of the shaft.

Single cut control The present invention includes, as in the case of the machine shown in my copending application, a construction permitting the machine to lin? GTI

be set to effect a single cut through a piece of stock and then stop automatically. To this end, I provide a dog 130 (see Figs. 1 and 2) mounted to move with the bracket 22 in a path adjacent a control rod 131 which on rotation is adapted to operate a, switch 132 controlling the electric driving motor of the machine. As shown in the drawings, the dog 130 is conveniently mountedon a feed reversing dog 133 carried by the bracket. 'I'he dog 130 comprises a bell crank pivoted on a pin 134 and having one arm extending into the path of a finger 135 secured to the control rod 131. The other arm of the bell crank is weighted and tends to hold the first arm in said path.

On the upward travel of the bracket 22, the dog 130 is shaped so that the finger 135 cams the dog aside permitting it to pass. When the feed mechanism is reversed and the bracket starts down, the dog engages the lnger 135 causing it to turn the rod 131 and shut off the motor. However, the bracket is moved up and down a short distance respectively on the back stroke and cutting stroke by the saw relieving mechanism while the feeding mechanism is still moving the bracket upwardly. It might occur that the dog 130 just passed the finger 135 on the upward movement caused by the saw relieving mechanism, so that on the succeeding depression of the saw by said relieving mechanism, the dog 130 would engage the finger 135 and stop the machine while the feeding mechanism is still set for upward movement. To prevent such occurrence, before the dog turns the rod 131, it is adapted to move slightly upwardly, as permitted by an elongated hole in which the pivot pin 134 is mounted. as shown at 136, in order to have the reversal of the feed mechanism fully completed before the machine is stopped.

To render the dog inoperative when it is desired to make more than a single cut, a stop member 137 is pivotally mounted on the feed reversing dog 133 and is adapted to be swung in a counter-clockwise direction (Fig. 2) into a position abutting a nose 138 on the dog 130 to hold the lower end of the latter out of the way of the finger 135.

It will be apparent that, when it is desired to make a single cut, the stop member 137 is swung to release the dog 130 before the bracket moves up. The dog then becomes effective on the start of the next succeeding down stroke and stops the machine, leaving the machine in down feeding position for the next cut.

Work feeding device As in my prior Patent No. 1,201,244, dated October 17, 1916, the machine is capable of automatically feeding the work forward to a proper position for a new cut at the completion of each cut. To this end, a work vise 140 (see Fig. 1) is slidably mounted on a pair of bars 141 and is adapted to be pulled forwardly thereon by means of a cable 142 wound on a drum rotated by a pulley 143 adapted to be driven by a belt from the main shaft. The pulley and drum are carried on a lever 144 which normally is held in such position that the belt slips freely on the pulley. On upward movement of the bracket 22 after the completion of a cut, the lever 144 is swung to tighten the belt and cause the pulley and drum to be driven.

In my prior machine, the means for moving the lever 144 moved with bracket 22. Such a means proved to be satisfactory in smaller maa pair of levers pivoted to yLeraars chines but in larger machines where the length of travel o f the bracket is great, space is not available to permit said means to travel such a length.

The present invention includes as a feature, means for-swinging the-lever 144, which operates only during the upper-part of the travel of the bracket and is provided with a lost motion device permitting said means to remain stationary during the other part of the travel of the bracket. To this end, a bored-out stop member 150 is secured to a suitable part of the bracket, such as the reversing dog 133 (see Fig. 2), and a rod 151 slidably extends through the bore of the member 150. The lower end of the rod 151 extends through the free end of the lever 144 which is yieldably supported on the rod by a collar 152 and spring 153. On the upper end of the rod, a nut 154 is threaded which is adapted to be engaged by the upper end of the stop member 150 on upward movement of the bracket so as to lift the rod with the bracket. v'I'he nut 154 also constitutes a means whereby the point at which the rod is prevent the nut 154 from jarring out of adjustment, the upper part of the rod is flattened on one side, as at 155, and a spring plunger 156 is mounted within the nut to bear against said flattened side of the rod. The rod is also prevented from turning within the bore of the stop member 150 by a screw 157 which extends across the flattened side 155, said screw also serving to secure the stop member 150 to the feed re versing dog 133.

When the bracket 22 is in its top position, the rod 151 hangs from the dog 133 with the nut 154 bearing on the top of the stop member 15'0. On downward movement of the bracket, the rod moves therewith until its lower end strikes the base 20 and it can be lowered no farther. I'he stop member 150 then slides down along the rod. When the bracket starts its upward movement, the stop member slides up along the rod until coming in contact with the nut 154. Continued upward movement of the bracket carries the rod with it, and near the upper end of the travel of the bracket, when the saw is clear of the work, the collar 152 on the lower end of the rod acts through the spring 153 to lift the free end of the lever 144. The swinging of the lever 144 causes the belt driving pulley 143 to be tightened, and the drum winds up the cable 142 to draw the vise 140 and the work forwardly to the position for a new cut.

I claim as my invention:

1. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support downwardly including a screw shaft, means tending to raise said shaft, means for intermittently depressing said shaft including a connection adapted 'to yield when resistance to downward movement of said support becomes excessive, and means associated with said connection and actuated by the yielding thereof for rendering said feeding mechanism inoperative.

2. In a hacksaw, the combination of a reciprocable saw, a-vertically movable support for said saw, mechanism for feeding said support vertically including a screw shaft threaded in said support, means tending to raise said shaft, means for intermittently depressing said shaft including each other, said levers normally moving in unison but being adapted to move relatively to each other, means for renderlraised may be adjusted. Tol

1- tively, said means ing said feeding mechanism inoperative, and means connecting said last-mentioned means and one of said levers and adapted to be actuated when said one lever moves relatively to the other.

3. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a screw shaft threaded in said support, means tending to raise said shaft, a first lever for depressing said shaft, a second lever pivoted on said rst lever, means for intermittently actuating said second lever, means connecting said levers normally causing them to move in unison but adapted to yield to permit said secf 0nd lever alone to move, and means associated with said connection and actuated as an incident to the yielding thereof for rendering said feeding mechanism inoperative.

4. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a screw shaft threaded in said support, means tending to raise said shaft, a rst lever for depressing said shaft, a second lever pivoted on said first lever, means for intermittently actuating said second lever, means normally preventing pivotal movement of said second lever on said first lever but adapted to yield to permit such movement, and means actuated by the pivotal movement of said second lever on said first lever for rendering said feeding mechanism inoperative.

5. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically comprising a screw shaft threaded in said support, and a pawl and ratchet device for turning said screw shaft, means for moving said pawl to an inoperative position, means tending to raise said shaft, means for depressing said shaft on the cutting stroke of said saw including a member adapted to yield to permit said shaft to remain in its raised position, and spring means connect-ed to said pawl-moving means and said member and adapted to operate said pawl-moving means when said member yields.

6. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a screw shaft threaded in said support, means tending to raise said shaft, means for depressing said shaft on the cutting stroke of the saw including a member normally movable in one predetermined path but capable of movement in another predetermined path when said shaft is prevented from being depressed, and means associated with said member and actuated as an incident to the movement of said member in said other path for throwing out the feeding mechanism.

7. In a hacksaw, the combination of a reciprocable saw, mechanism for feeding said saw vertically, means for raising and depressing the saw on the back stroke and the cutting stroke respecbeing yieldable to permit the saw to remain in its raised position, and means connected with said yieldable means and actuated as an incident to the yielding thereof for rendering said feeding mechanism inoperative.

8. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a pair of pawl and ratchet devices for feeding said tively, and means support up and down respecfor moving said pawls to an inoperative position, said means being actuated by said support on reaching the upper end of its stroke.

9. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a pair of pawl and ratchet devices, one for moving said support up and the other for moving said support down, and a carrier for said pawls adapted to be shifted to bring the respective pawls in operative relation to the ratchets, and means for shifting said carrier to a neutral position in which both pawls are inoperative, said means bcing actuated by said support on reaching the upper end of its stroke.

10. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically comprising a plurality of pawl and ratchet devices, a carrier for said pawls adapted to be shifted for moving the pawls from an operative position to an inoperative position, means for shifting said carrier to a position where said pawls are simultaneously inoperative, and a lever for moving said means, said lever being actuated by said support when the latter reaches the upper end of its stroke.

11. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a pair of pawl and ratchet devices, one for moving said support up and the other for moving said support down, automatic means for moving said pawls to an inoperative position at any point in the downward travel of said support on excessive resistance to such travel, and means operated by said support for moving said pawls to an inoperative position when said support reaches the upper end of its travel.

12. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support vertically including a pair of pawl and ratchet devices, one for moving said support up and the other for moving said support down, means for moving said pawls simultaneously to an inoperative position, a pair of levers for independently actuating said means, means movable in a predetermined manner on excessive resistance to the downward travel of said support, and means actuated by movement of said last-mentioned means and operable at any point in the downward travel of said support for moving one of said levers, the other of said levers being movable by said support on reaching the upper end of its travel.

13. In a power hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, means for feeding the stock forwardly for a new cut including a control lever, and means for automatically movingsaid lever at the completion of a cut comprising a rod secured to said support and having a limited sliding movement relative thereto but adapted to move therewith during the latter part of the upward movement of said support, means for adjusting the movement of said rod, and a resilient abutment on said rod for moving said lever.

14. In a power hacksaw, the combination of a vertically movable saw support, mechanism for feeding said support vertically, and counter-balancing means for said support comprising a rod movable with said support, a rotatable sheave positioned to support the rod in its groove, a flexible member secured to the end of the rod and extending around said sheave to rotate the latter jusv on movement of the rod, and a torsion spring tending to rotate said sheave in a direction to raise said rod and said support.

15. In a power hacksaw comprising a frame and a saw support mounted for vertical movement on said frame, means for counter-balancing said support comprising, in combination, a vertical rod bearing against said support and guided in said frame, a sheave mounted for rotation on a horizontal axis and guiding the lower end of said rod, a chain attached to the lower end o1' said rod and to said sheave and extending around said sheave to rotate it on downward movement of the rod, and a torsion spring fixed at one end and secured to said sheave at the other end and tending to rotate said sheave in a direction to raise said rod.

16. In a hacksaw, a feeding mechanism comprising, in combination, a screw shaft, a pair of ratchets for rotating said shaft respectively in opposite directions, one of said ratchets being axially movable relatively to the other, a. third ratchet interposed between said pair of ratchets and having frictional driving contact therewith, a spring coiled aroundsaid shaft and bearing at one end against said axially movable ratchet, a Washer keyed to said shaft but movable longi tudinally thereof and bearing against the other end of said spring, and a nut threaded on said shaft and abutting against said washer to permit adjustment of said spring, the abutting faces of said nut and washer being correspondingly serrated normally preventing rotation therebe tween but adapted to permit relative rotation when the nut is manually turned.

17. In a hacksaw, the combination of a source of power, a rod having a finger mounted thereon and adapted on rotation to shut off said source, a vertically movable bracket, a dog pivotally mounted on said bracket and adapted to swing by gravity into position to strike said finger, said dog being adapted to actuate said flnger on downward movement ot said bracket but adapted to be swung aside by said finger on upward movement of said bracket, and a stop member pivotally mounted on said bracket and adapted to be' swung into engagement with said dog to hold the latter in an inoperative position.

18. In a hacksaw, the combination oi' a source of power, means for controlling said source of power, a reciprocable saw blade, a vertically movable bracket supporting said bladeffeeding mechanism for said bracket, means for raising said vbracket on the back stroke of the blade and for depressing said bracket on the cutting stroke, and a dog carried by said bracket for operating said control means on downward movement of said bracket, said dog having limited movement relative to said bracket to prevent operation of said control means by depression of said bracket on the cutting stroke.

19. In a power hacksaw comprising a hollow base frame having a top wall and a saw support mounted for vertical movement on said frame, means for counterbalancing said support comprising, in combination, a rod bearing against the underside of said support and slidably guided intermediate its ends in the top wall of said frame, a sheave rotatably mounted within the frame and positioned tangentially to said rod with the lower end of the latter guided in the groove of said sheave, a flexible member wound around said sheave with one end extending tangentially therefrom and attached to the lower end of said rod, and resilient means tending to resist rotation of said sheave in the direction caused by downward movement of said support.

20. In a hacksaw, the combination of a reciprocable saw, a vertically movable support for said saw, mechanism for feeding said support downwardly including a member carrying said support, means tending to raise said member, means for intermittently depressing said member, said depressing means being yieldable on a predetermined resistance to downward movement of said support, and means connected to said depressing means and actuated as an incident to the yielding thereof for rendering said feeding mechanism inoperative.

GEORGE J. BLUM.

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