US1984974A - Broaching machine - Google Patents

Description

Dec. 18, 1934. F. J. LAPOINTE 1,984,974

BROACHING MACHINE Filed Dec. 16, 1952 5 Sheng-sheet 1` Dec. 18, 1934. F.,J. LAPOINTE 1,984,974 I BROACHING MACHINE Filed Deo. 1e, -1952 5 sheets-shea 2 Dec. 18, 1934. F. .1. LAPOINTE BROACHING MACHINE Filed'Deo. 16, 1952 5 Sheets-Sheet 3 Dec. 18, 1934. F. .1, LAPOINTE BHOACHING MACHINE .Filed DSC. 16, 1932 5 Sheets-Sheet 4 ne@ 1s, 1934.

F. J. LAPOINTE BROACHING MACHINE Filed Dec. 16; 1952 5 sheets-sheet 5 I, I l I l Patented Dec. 18, 1934 UNITED STATES PATENTA OFFICE i v l 1,934,974

BROACHING MACHINE Francis J. Lapointe, Ann Arbor, Mich. Application December 16, 1932, Serial No. 647,633

`10 Claims.

My invention has for its object to provide an eiiicient means for automatically momentarily releasing or cushioning the pressure transmitted from a driving means to a member actuated thereby with the object of preventing a pressure upon the actuated device beyond that normally sustainable thereby. The invention is particularly applicable to machines wherein the ele-f ments used to form articles are of a character that for efficient operation should be actuated'at a pressure or by a force that is belowa certain maximum` when performing the function for which the elements are designed, or to prevent their operation under a pressure in excess to that which they can normally stand Without risk of injury. The invention thus provides an efficienty means for the maintenance of the operation' of the elements, such as cutting operations, and prevent breakage where, by reason of their peculiar construction, one or more of their sections are of such `a character as to'have a relatively '1 small safety factor.

The invention provides a means for limiting* the pressure exerted on the machining element to apoint below a predetermined maximum and thus operates to automatically protect the lelement from injury. :y

The invention also provides an indicator for indicating continuously the changes in pressure required to move the machining element and thereby indicate the change in the condition of element While in use and the condition of the material being operated upon. Thus, by my invention1 the condition of a tool, such as a cutting tool, is automatically indicated or an unusual hardness of the material is indicated, as is often found in connection with work on any particular product formed of a plurality of like articles. Indication will be given as to whether the Work on the particular article shall progress further or whether the tool should be replaced or resharpenedor reformed, or a new tool should be inserted in place of the one that'givesY indicationy containing the invention may partake of different forms and may be varied in their details and still embody the invention. To illustrate a practical application of the invention, I'have selecteda broaching .machine embodying the inventionas an example ofthe various structures and the details of such structures that contain the invention and shall describe the selected structure hereinafter, it being understood that variations may be kmade and that certain features of my invention may be used to advantage without a corresponding use of other features of the invention,j and without departing from the spirit of the invention. 'I'he particular structure selected is shown in the accompanying drawings.

Fig. 1 illustrates a vertical section of the broaching machineselected as an example of the embodiment of: the invention. Fig. 2 illustrates a control lever and a side view of fa tool elevator for `manipulating the broaching tool to enable replacement vof the work. Fig. 3 illustrates a front view of the machine. Fig. 4 illustrates a viewof a',k section of the machine showing a rack and pinion that'foperates the guide plate and the drawhead of the broaching machine. Fig. 5 illustrates a View of a section taken on the plane of the line 5-5 indicated in Fig. 1. Fig. 6 illustrates a view of a section taken on the plane of. the line'6-6 indicated in Fig. 5. trates' a view of a section taken on the plane of the line .7-7 indicated in Fig. V5 and particularly illustrates valves for controlling the flow of a iluid to and from the drawhead of the broaching machine. part of the machine and particularly illustrates switches that are controlled raccording to the Fig. 7 illus-v Figfillustrates a broken view of a i extent ofmovement of the broaching tool. Fig. 9

illustrates a side'view of a cam block used for manipulating the switches.

Y In the particular form of construction shown in the drawings, a drawhead 1 is connectedto a'guide plate 2 thatis vertically reciprocably mounted in aframe 3 having suitable ways 4 for guiding the plate 2. v The plate 2 is reciprocated by means of a rack 5 connected to the plate 2 and a pinion 6 driven by a suitable electric motor 7, through' reducing gear, such as the gear Wheel 8, `the worm 9, a worm wheel 10 which is connected to the shaft 11 to which is keyed, or on which is formed, the pinion 6. 'I'hese parts are suitably r mounted in the frame 3. The worm 9 and worm o movements of the breach head as guided by the plate 2 and the frame 3 of the machine.

A suitable chuck 16 is connected to the drawhead 1. The chuck 16 is of the type illustrated and described in the Lapointe application No. 517,336, filed February 21, 1931, it being provided with means for engaging the breach when pressure a spring pressed collar i7 is released. Disengagement with the breach is produced by the descent of the drawhead 1 so as to press the collar 17 .of Athe chuck 1.6 against the work plate or some part connected therewith. The breach 18 is provided with a breach head 1.9- that is connected to the body of the breach by means of a neck 20 that is engaged by suitable dogs as described in the said Lapointe applicatien and illustrated, particularly, in Fig. 5.

The drawhead 1 is located above 'the' work plate 2l and, te enable insertion of work below the werk plate, the upper end of the breach is position-ed well below the work plate. To connect the breach 18 with the drawhead, the breach is raised and insertedk through the Work and the work plate and into the chuck 16 and held against the drawhead and, when the drawheadl is raised so as to relieve the pressure of the werk plate against the collarl'?, the breach head is engaged in the chuck. Whereupon the breach is pulled through the work by the operation of the pinion 6 that meshes with the rack 5 that is connected to the guide plate 2.

As is well known in connection with mechanical-l a number of articles of like character there will,

often be a great variation in the hardness, or elasticity, of portions of the articles. There will be seme that will be exceedingly hard wherev others will be relatively soft and also parts of any one article may be much softer than other parts, hence kthe breaching tool will bel subject'to varying cutting resistance in connection with any particular breaching operation. Where uniform movement of the breach is produced, notwithstanding variatien in cutting resistance, breaches will be broken or teeth of the breach will be chipped or nicked, or where the hardness differsv in; the articles of like character being breached, the teeth will dull at varying rates, increasing the cutting resistance at varying rates. Also, where large holes are being cut and large teeth are required to withstand the cutting strain, requiring considerable clearance for chips and consequently requiring increased distances between the cutting edges of consecutive teeth, there is produced a large variation in the tool resistance as the number of teeth in contact with the surface of the article being cut is Varied. Where the teeth are large the cutting resistance may vary as much as 20%, as'where four teethare in contact with the article and a fifth engages, subsequently one of the teeth leaves the article, followed by a tooth entering into or engaging withan article. Also, as is well known in connection with breaching operations, breaches partake of different forms in their cross sections as for cutting slots or square holes or hexes or oblong holes or chane nels, or undercutting sides of holes or slots, etc. In order to form such slots er openings intel-their characteristic shapes, breaches must necessarily be so constructed as to provide teeth having cerresponding shapes and provision must be made f er clearance and for gathering of the chips within the article from each teeth as it progresses in the article, which results in varying shapes of the shanks or bodies of the breach, particularly the portions located intermediate the teeth. Frequently the cross sectional area of the body of the breach is very slender and of such cross sections as is necessitated by the configuration of the cutting edge and the necessity of provision of clearance and spaces between the teeth for gathering the chips. This frequently necessitates designing breaches within a narrow margin of safety, er with a small safety factor, and while the mechanicallyoperated breach machines are desirable because of their pesitiveness and uniformity of movement and their speed control, yet for the same reason they fracture breaches because of lack of give er resiliency. Also the practical irresisting forward drive of the breach frequently causes fracture of the heavier breaches by reason of the fact that the spring lof the metal of the breaches, when subject to high pressure, causes fracture in the whip back and back lash as the consecutive teeth enter and leave the material. The advantageous features of mechanically driven breaches are retained and the disadvantages eliminated, in my invention, by providing a regulatable cushioning yielding means between the breach and the breach actuating element.

The breach being light in weight, or small'in mass, it is exactly responsive in its tensiente the variation in cutting resistance and when yieldingly connected, as. distinct from elastically connected, te the pressure head of thcmachine, it changes in movement in response to resistance tomovement. While the mechanically operated driving member moves at a uniform speed, irrcspective tothe tool resistance, the invention-provides for cushioning the breach in its movement relative tothe driving. member. This eliminates breaking ofthe teeth, er fracture of the body of thezbroach, caused by jarring, or bumping of the teeth produced by subjecting one or more of the teeth, within an exceedingly short time, to a pressure that exceeds their elastic limit. |The invention provides a means that enables the breach to adjust itself by a momentary diminution of the pressure when it reaches er approximates what may be considered an excess, although the drawhead moves steadily forward regardless of such changes in pressure.

The invention also provides a means for indicating the cutting resistance to which the breach is subjected whereby increasing dullness, although at varying rates, may be readily noted, Also` exceedingly hard articles in any particular product may be quickly noted and the machine stopped, or the characteristic hardness of the articles may be investigated and the articles may be assorted as to their hardness and another breach used for cutting the harder articles or a slower speed used. Thus my invention enables operation of breaching machines at a maximum speed .and `results in a great saving in cest of operation. By reason of the indicated tool resistance, it enables a very greatly increased breaching rate since it enables speeding up of breaching machines to the maximum safe rate.

ln order te obtain these advantageous results in the particular form of construction selected as an example of an embodiment. of my invention, the breach 1,8 is directly connected te a fluid fi i) pressed piston 26 by means of the chuck 16 and portions v,of the fluid are allowed to escape when the pulling pressure exceeds a safe maximum, the cylinder 27 in which the piston is located forming a reservoir of the fluid in an amount suiiicient to meet exigencies of cutting resistance variations for which fthe machine is designed. The escape of the fluid eliminates the reactions of elasticity.v

and the whip-like action caused thereby.

The piston rod 25, the piston 26 and the cylinder 27 form a part of the drawhead 1. The cylinder 27 is charged with oil under pressure by means of the pump 28 that is operated by the electric motor 29. The pump 28 is located in the reservoir 30 that operatesto force the oil under pressure through the pipes 32 and 33, the passageway 35 formed in the plate 2 and the drawhead l to the cylinder 27.v The passageway 35 opens into the lower end of the cylinder 27 and beneath the piston 26 and operates to press the piston 26 towards the upper end of the cylinder 27. A suitable engaging screw or stop 36 may be provided in the upper end of the cylinder 27 to adjustably limit the upward movement of the piston 26 and thus limit the o-il content of the cylinder and thus limit the slack between the stroke of the broach head and the broach.

When the drawhead 1 is raised by the opera` tion of the pinion 6, the oil located below the piston 26 is subjected to a pressure depending upon the cutting resistance to which the broach 18 is subjected and consequently the piston 26 will give according to the flow of the oil from the cylinder.` The piston, however, being subject at A all times to a pressure at least equal to that producible by the pump 28 is returned to the upper end of the cylinder and the cylinder charged with a fresh supply of oil upon completion of the working stroke of the broach. The pressure during the working stroke rises well above the pressure that may be'prcduced vby the pump 28 by reason of the fact that the oil that passes through the passageway 35 is trapped bymeans of the oneway spring pressedvalve 40. The valve 40 allows substantially free movement of the oil from the pipe 34 into the passageway 35 but operates to prevent anyreturn of oil into the pipe 34 and consequently any counter pressure on the pump 28. Thus by a relative small pump the advantages of my invention may be produced.

The oil may escape from the cylinder only when it reaches a predetermined pressure as determined by an adjustable spring pressed needle valve 43 located in an opening 44 having a small port and formed in a sleeve 45. The sleeve 45 is located in the drawhead 1. The needle valve 43 is provided with a head 46 that is spring pressed by means of the spring 47. The tension of the spring 47 may be adjusted by means of the screw 48 having the knurled head 49. If desired, a nut 50 may be provided for frictionally securing the screw 48 in its adjusted position. The bore 44 is exceedingly small, ap-

proximating capillaric size and communicates with the passageway 35 that leads to the lower end of the cylinder 27 and the end of the needle 43 is located in proximity to a passageway 51 extending at right angles to the opening 44. The passageway 51 communicates with the passageway 44 when the end of the needle is removed from the passageway 44 and thus allows a very ne stream of oil to escape from the passageway 35 and consequently from the cylinder 27. The opening 44 being practically capillaric in size, the amount of escape of oil is very minute upon each application of excess pressure, that is, pressure in excess of that determined by the pressure of the spring 47. The pressure immediately lowers by reason of the release of this minute quantity o oil which gives opportunity for the broaching tool to adjust itself to the cutting resistance produced by any onev of the various circumstances or conditions as to change in number of teeth engaging the article or momentary change in' cutting resistance due to local characteristic change in a minute part of they material or due to a fracture of the tooth near the cutting edge or due to momentaryfailure of delivery of chips from the cutting edges. In other words, it affords a yieldingv means directly connected to the broachto enable the broach to readily change its speed and yieldingly over-` come the resistance to its movement without being subject to any resiliency of the fluid or air in the oil and allow the tool to gradually adjust itself to its own elasticity.

In order to readilycontrol the transmissible pressure between the pressure head and the broach, a pressure indicator 54, of any suitable type, may be connected to the lower end of the cylinder, such as through the passageway 55. The indicator 54 is mounted on the drawhead 1 and indicates the pressure of thev oil in the cyl-V inder 27 and consequently the resistance to movement met by the broaching tool. breaching operation on the product or in vusing a new broach, the cutting resistance will be noted^and the pressure within the cylinder r27 may be promptly varied accordingly by the adjustmentxof the tension of the spring 47. When f a large broach is used the tension oi the spring is raised and the variations in the cutting resistance, as the teeth pass over the work, is noted and adjustments made to afford the desired lgive in the pressure, according to the changes in resistance to movement of the tool, and thus produce the desired protective yield. As the broaching operation progresses,` increased dullness of one or more of its teeth is indicated. by a gradual increased pressure. Quite sudden though uniform rate of change will vindicate increased dullness anddecrease in chip delivery from the edges or burnishing of the work at the edges of one or more of its teeth. There will be variations of movement of the indicator by reason of the teeth entering and leaving the work which is noted and allowed for and bumping prevented. Marked rise in the indicator will indicate either local hardness of portions of the article being broached or fracture yof broach edges which may be immediately determined by,k

examination of the broach and which will require variation either to raise the pressure transmissible to the broach o1' to allow for decrease of pressure by allowing the escape of oil in slightly increased, though still minute, quantities to increase the give or cushioning effect of the oil.

When these conditions are revealed through the indicator, suitable alterations may be made.

The oil that is allowed to escape from the-cylinder is returned to the'reservoir 30 through the passageway 52 and pipes 53, 56 and 57. The cylinder 27 andthe drawhead'l are provided with a passageway for the discharge of any oil that may accumulate in the upper end of the cylinder to the passageway 52 which is con--` nected to the reservoir. This prevents blocking of the piston when the cylinder is filled. The drawhead is also provided with apassageway l61 In starting the l Cir which will draw off the oil that passes the pack`- ing of the piston rod 25.k

The pipes 34 and 53 telescope within the pipes 33 and 56 respectively. Suitable packing glands being provided in the xture 64 located at the upper ends of the pipes 33 and 56 prevent the escape of oil from the pipes at the telescopic connections. The pipes 34 and 53 are connected te the guide plate 2 and move vertically within the pipes 33 and 56 respectively to maintain the tric current and for making the disconnection with the source and for reversing the motor. The switches and circuit controlling devices will vary according to the character of the motor as to whether a direct current motor or an alter' nating current is used and, if alternating, the switching devices and electric system will vary according to the phases of the current. These features form no part of my invention and provide merely the means for connecting and disconnecting the motor or for reversing the motor. In order that the motor may be disconnected er may be reversed, I have provided switches contained in switch boxes 66 and 67 having arms 68 and 69 that carry rollers 70 and 71. The arms 68 and 69 are connected to suitable switch arms that operate the movable contacts of the switches and when operated they either open or reverse the meter current. The switch contained in the bex 66 is operatedto open the circuit of the meter by an adjustable cam 73 connected to ablock 74, While the switch contained in the box 67 operates to reverse the motor by means of the cam 75 connected to the block 76. The cam 75 operates to raise the roller 71 and swing the arm 69 te reverse the current when the drawhead is raised suiiiciently to complete the movement of f the teeth of the breach 18 through the work but leaving in the work the pilot 77 to guide it en the return stroke of the drawhead.

The blocks 74 and 76 are adjustably secured in the frame 3 of the machine and particularly in a slet 78 by' means of suitable bolts 79 that extend through the slot and clamp the blocks in desired positions to cause reversal of the motor at the desired point in the operation of the breach and to open the circuit of the meterA upon completion of the return of the drawhead 1. The switch boxes 66 and 67 are supported on the guide plate 2 and in position te be operated by the cams 73 and 75 located on the frame 3.

When the drawhead returns and presses the collar 17 against the work plate 31, the chuck 16 releases the breach head and delivers the breach te a means for lewerincr the breach to a peint well below the work plate to enable insertion of the work intermediate the head oi the breach and the work plate. When the Work has been placed in position, the breach is then raised to insert its head into the chuck and the motor 7 is started by the operation of a suitable switch which raises the drawhead l, allows the chuck to engage the kbreach head and draw the breach through the A iixed piston 82 having a hollow stem 83 is cennec-ted by means of a pipe 84 te the pipe 32, the valve 85 and the pipe 86. When the valve 85 is operated the cylinder 88 is emptied through the hollow piston' red 83, the pipe 84, the valve 85 and the pipe 87 which is connected to thepipe 5'7 that leads to the reservoir. The valve 85 may be operated by a suitable pedal lever 89. When, therefore, the breach 18 is to be raised, the lever 89 is depressed and the valve is shifted to connect the pipe 84 withl the pump 28 through the pipe 32. This directs the eil under pressure to the upper end of the cylinder through the hollow piston rod 83 and raises the breach 18 te locate the breach head 19 within the chuck of the draw'- head. A switch is operated for closing the circuit of the motor and the d'rawplate and drawhead are raised by the operation of the pinion 6, the pressure in the cylinder 88 causing the breach to follow up the drawhea'd until the breach is locked in the chuck. The drawhead continues to move up until the werking is completed. The motor is then reversed and the drawhead then descends, the cylinder 88 being held up bythe pressure of the oil that is inserted in the upper end of the cylinder, While the lever 89 is held down by the operator. When the drawhead reachces the lower peint in its travel the chuck is opened and the breach is released and the motor circuit is opened, the operator then releases the lever 89 and allows the escape of oil te the reservoir through the valve 85k and the cylinder 38 together with the breach 18 descends by the weight of the cylinder. If desired, the lever 89 may be released upon locking the breach in the chuck. This permits the immediate return of the cylinder 88, the chuck operating to drop the breach, the lower end entering the socket 91, upon the completion of the return movement of the drawhead. l

I claim: a

l. ln a machine, a drawhead, means for reciprocating the drawhead, a reciprocable machine member, a cylinder and piston for connecting the reciprecable member to the drawhead, means for introducing `a iiuid inte the cylinder and an indicating means for indicating the resistance to movement of the reciprocable machine member, means for maintaining a supply of fluid in the cylinder and means for varying the pressure of the iiuid in the cylinder.

2. In a breaching machine, va drawhead, a means for reciprocating the drawhead, a breaching tool, a vcylinder and piston for connecting the breaching tool to the drawhead, a source ofy supply of iiuid under pressure, means for connecting the said source of supply with the said cylinder, means for indicating the pressure transmitted through the fluid by the movement of the drawheaol when actuating the breaching tool and means for releasing the pressure of the fluid in the cylinder.

3. In a breaching machine, a guide plate, a rack connected to the guide plate, a drawhead connected to the guide plate, a breaching tool, a cylinder and piston for connecting the breachtool to the drawhead, a source of supply of iiuid under pressure, means for connecting the said source of supply with the cylinder, adjustable means for varying the resistance te the return new of fluid in the cylinder to the source oi means ier indicating the pressure of the fluid in the cylinder.

4. ln a breaching machine, a guide plate, a rack connected to the guide plate, a pinionv for raising and .lowering the rack, a frame, a werk plate connected to the frame, a drawhead connected te the guide plate and located above .the vwerk-plate, a breach tool, anautomatic chuck for engaging the breaching tool fer releasing the breaching tool when `pressed against the werk plate, a cylinder and piston` for connecting the chuck `te the drawhead, a source of supply ef fluid under pressure means for connecting the said source of supply with the cylinder, and means for varying the pressure transmissible through the fluid in the cylinder te the chuck.

5. In a breaching machine, a guide plate, a rack connected te the guide plate, a pinion for raising and lowering the rack, a frame, a werk plate connected te the frame, a drawhead connected te the guide plate and located above the work plate, a breaching tool, an automatic chuck for engaging the breaching tool for releasing the breaching tool when pressed against the werk plate, a cylinder and piston for connecting the chuck to the drawhead, a source of supply of fluid under pressure, means for connecting the said source of supply with the cylinder, means for varying the pressure transmissible through the iluid in the cylinder to the chuck, and a cylinder and piston for lowering and raising the breaching tool from the chuck when the chuck engages the werk plate, and means for connecting the last named cylinder with the source of supply under pressure.

Y 6. In a breaching machine, a draw head means for reciprocating the draw head, the cylinder mounted on the draw head, a piston located in the cylinder, a breaching tool connected te the piston, a source of supply of iiuid under pressure connected to the cylinder at a peint located en the side of the piston on which the breaching tool is located for transmitting pressure from the draw head te the breaching tool during the working stroke, a pressure indicating means cennected to the cylinder en the breach side of the piston, the machine having a passageway cennected te the source ef supply and te the cylinder en the breach side of the piston, and an adjustable valve, located in the passageway for varying the pressure transmitted from the draw head te the breaching teel.

7. In a breaching machine a pressure head, means for reciprocating the pressure head, a cylinder, mounted on the pressure head, a piston located in the cylinder, a breaching tool connected te the piston, arseurce of supply of fluid, a pressure means for subjecting the fluid to pressure, the machine having a passageway for cenducting the fluid under pressure te the cylinder at a peint located on one side of the piston, a one way Valve located in the passageway for preventing return ilew of the fluid tothe pressure means, the machine having a return passageway connected rte the cylinder en the said one side of the piston and to the source of iluid supply, and a pressure control valve located in the said return passageway and opened by the pressure of the fluid in the said return passageway, a spring for counteracting the fluid pressure on the pressure control valve and normally operating to maintain the control valve closed against the pressure of uid in the cylinder, and means for adjusting the pressure of the spring te adjust the maximum pressure transmissible from the cylinder te the piston te limit the actuating pressure exerted by the pressure head en the tool during their working strokes.

f. 8.`In,a breaching machine .a pressure head, means forfreciprecating Athe pressure head, a cylindery mounted onthe pressure head, a piston .located in the'cylinder, a breaching tool cennected tothe piston, a source of supply of fluid,

a pressure means for subjecting the fluid te pressure, the machine having a passageway for cenducting the lluid under pressure to the cylinder at a peint located en one side of the piston, a one way valve located in the passageway for preventing return flew of the fluid te the pressure means, the machine having a return pas'- sageway connected te the cylinder en the said ene side of the piston and to the source of fluid supply, and a pressure control Valve located in the said return passageway and opened by they pressure of the fluid in the said return passageway, a spring for counteracting the fluid pressure on the pressure control Valve and normally operating te maintain the control valve closed against the pressure ef uid in the cylinder, means for adjusting the spring, for varying the limit of pressure transmissible from the cylinder to the piston, andan adjustable step located within the cylinder for limiting the movement of the piston relative to' the cylinder in a direction away from the said one side of the piston for limiting the slack between the pressure head stroke and the breach movement `produced by fluid escapement te the said source of supply of iluid.

9. I n a breaching machine, a draw head, means for reciprocating the draw head, a cylinder mounted en the draw head, a piston located in the cylinder, a breaching teel connected to the piston, a source of supply of iluid, a pressure means for subjecting the fluid to pressure, a passageway for conducting the fluid under pressure to the cylinder at a peint located on the side of the piston en which the breaching tool is located, a one way valve located in the passageway for preventing return ilow of the iluid. to the pressure means, the machine having a return passageway connected to the cylinder on the breaching side of the piston and to the source of iiuid supply, and a pressure control valve'lecated in the said return passageway, a spring for counteracting the iluid pressure en the cent1-ol valve and normally operating to maintain 'the j control valve closed against the pressure of fluid in the cylinder, and means fer adjusting the pressure ef the spring for adjusting the pressure transmissible from the draw head te the breach- .ing tool and limiting the draft pressure on the tool and easing the movement of the teel relative to the draw head.

10. InV a breaching machine, a draw head, means for reciprocating the draw head, a cylinder mounted on the draw head, a piston located in the cylinder, a breaching tool connected te the piston, a source of supply of fluid, a pressure means for subjecting the iluid to pressure, a passageway for conducting the iluid under pressure to the cylinder at a point located en the side of the piston en which the breaching tool is located, a one way valve located in the passageway forpreventing return flow of the fluid to the pressure means, the machine having a return passageway connected to the cylinder on the breaching side of the piston and to the source of iiuid supply and a pressure control valve located in the said return passageway, a spring for ceunteracting the fluid pressure on the control valve and normally operating to maintain the control Valve closed against the pressure of fluid in the cylinder, means for adjusting the pressure ,in which the broaching tool is drawn by the of the spring for adjusting the maximum presdraw head for vlimiting the slack between the sure transmissible from the drawhead to the draw head stroke and the broach movement pro.- broaehing tool, and an adjustablestop located duced by fluid escapement through the said re- 5 within the cylinder for limiting the movement turn passageway.

of the piston relative tothe cylinder in a direction FRANCIS J. LAPOINTE.

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