US1743625A - Impact machine - Google Patents

Description

14, 1930. E. H; sHAFF IMPACT MACHINE Filed July '7, 1925 2 Sheets-Sheet l mw lh..

Jan. 1.4, 1930. E. H. sHAFF 1,743,625

IMPACT MACHINE Filed July 7'.. 1925 2 Sheets-Sheet 2 a6 a4. 63a/ a7 lll Inven o 21 E/es .Safj

Patented Jan. 1.4, 1930 oNrrEn STATES PATENT 'rines ERNEST H. SHAPE, oF GRAND HAVEN, MICHIGAN, AssIGNor. To' WILLIAM KELLER INC., or GRAND HAVEN', MICHIGAN, A CORPORATION or MICHIGAN MPACT MACHINE n Application filed July 7,

This application is a continuation in part of my prior application Serial No. 606,378,- iled December 12,1922. A A

My invention relates to apparatus for converting the energy of pressure fluid into me-l chanical work and is particularly concerned with impact tools.

Among the objects of my invention is to seA cure economy in construction and efiiciency in operation. The invention will be best understood from the following description when read in .light of the accompanying drawings of several specific embodiments thereof selected for illustrative purposes, while the scope of the invention will be particularly pointed out in the appended claims.

In the drawings Y Fig. 1 shows a riveting hammer, constructv ed according to the invention, in longitudinal section with parts broken away Fig. 2 is a section similar to Fig. 1 but showing the parts in aI diiferent position;

Fig. 3 is a modiiied form of the hammer shown by Fig. 1; y

Fig. 4 is a section on the line 4 4 of Fig. 2 g" and Fig'. 5 is a section 0n the line 5-5 of Fig. 4.

Referring particularly to Figs. 1 and 2 of the drawings, I have shown a riveting hammer which constitutes one specific embodiment of my invention selected forlillustrating its application to an impact tool. I have indicated the cylinder of the riveting hammer at 1, which cylinder at its forward end slidably carries a removable rivet set 3, and, at its rearward end, a grasping handle a portion of which is indicated at 5. p l

In the cylinder 1 is a hammer piston 7, which piston is caused to reciprocate for impacting the shank of the rivet set at the forward end of the piston stroke. d

Herein, the rearward end of the cylinder member 1 is recessed at 9 to receive the'forward section 11 of a. valve block, while` at the rear end of the section 11 is mounted the section 13 of the valve block. Thehandle 5 is provided with an internally screw threaded sleeve 15 which engages the rearward screw threaded portion of the cylinder. The bottom wall 17 of the socket formedl by the sleeve 1925. serial 110.41382.

15 abuts'with the rearward face vof the valve section 13. In this manner the parts are held In assembled relation.

As shown, the forward portion of the valve block 11 is bored out to form a continuation of the piston chamber afforded by the cylinder 1, while the rearward portion of the valve block 11 and the valve block 13 are bored to receive the shell valve 19 the interior of which latter forms a further continuationV of the piston chamber.

As illustrated, the valve 19 is provided at ward position, saidgroove is uncovered by the rearward end of said valve, and, when the valve is in its rearward position, said groove is in communication with the valve groove 25. Adjacent the forward end of the valve, the valve block 11 is formed with an internal annular groove 29 so located as to be covered by the valve, when-the later is in its forward position, and uncovered by the forward end of the valve when the latter is in its rearward position. i

From the groove 29 leads one or more passages 31 formed in the valve block, and with each passage 31 communicates a series of coaXia-lly arranged communicating passages 33, 34 and 35, relativelyof'increasing cross-sectional area and placing said'passage 31 in communication with thel atmosphere.,V Opening into each/passage 31, is a passage 37 of rel'- atively small cross-sectional area, which passage is arranged coaXially of the passages 33, 34 and 35 and communicates at its rearward end with a passage 39 of larger cross-sectional area. The passages 39 at their rearward ends communicate with the internal bore of the'valveblock 13, at such points, that when the valve is in its rearward position, said passages are placed in communication with the groove 27 by means of the valve groove 25. Each passage 37 forms the nozzle of an ejecciated passage 3l.

Leading from the chamber behind the flange 21 and connecting said chamber with the passage 31 is a passage 41, while leading from the chamber in front of said flange 2l is a passage 43 which opens into an intermediate portion of the cylinder through a 'port 45 at such position that it is overrun by the piston in each direction of its travel. The passage 43 has in communication therewith a passage 46 which opens into an annular groove 47 formed in the valve block section 11 about the forward outer edge of the valve.

Motive fluid is supplied the machine through a passage 49 in communication with an annular space 51 surrounding the rearward end of the valve block and communicating with the groove 27 thereof by means of one or more radial passages 53.

At the forward end of the cylinder bore is shown an annular enlargement in the form of a groove 54 with which communicates one or more passages 55 formed radially through the wall of the cylinder. For closing the passages 55 when desired, I provide for each a removable screw threaded plug 56.

The operation of the pneumatic hammer with the parts sol far described and with the plug or plugs 56 removed is as follows:

IVith the valve in the position shown by Fig. 1 and the piston at the rear end of the cylinder, motive fluid will enter the cylinder bore through the passage 49,the annular space 51, the radial passages 53 and the groove 27, and, as the forward end of the cylinder with the valve in thisposition is connected to the atmosphere, the motive fluid at the rear of the cylinder bore will drive the piston forwardly to cause it to strike the shank of the rivet set. Vhen the piston in its forward traveluncovers the vport 45, motive-fluid will pass from the cylinder bore through said portand the passage 43 to the passage 46 and the groove 47 and to Vthe chamber in front ofthe flange 21, thereby exerting a rearward pressure on the extreme forward end of the valve and on the flange 21 sufcient to overcome the forwardly acting pressure of the live air on the eXtreme rear end of the valve, and in consequence the valve moves rearwardly into the .position shown by Fig. 2.

With the valve in the position shown by Fig. 2, the motive fluid admitted on the forward stroke of the piston exhausts through the groove 29, passages 31 and sets of passages 33, 34 and 35. The motive fluid enters the passages 39 by way of the passage 49, the annular space 51, the radial passages 53, groove 27, and groove 25. This supplies air to the ejector nozzles 37, which air is .projected in the form of jets into the combining tubes afforded by the sets of passages 3334 and 35,

and by friction effect, the jets cause air to be sucked from the rearward end of the cylinder through the groove 29 and the passages 31. In consequence of this, the pressure of the air at the rear of the piston is reduced and the piston is returned towards the rear of the cylinder due tothe preponderant atmospheric pressure at the forward end of the cylinder.

Then the piston in its rearward travel closes the groove 29, communication between the cylinder and the atmosphere is interrupted. `In consequence of this, the piston by its momentum traps and compresses air in the rearward end of the cylinder, which air acting on the extreme rearward end of the valve causes it to be forced forwardly aided by the effectl of suction induced by the ejector on the extreme forward end of the valve.

It will be noted according to the foregoing cycle of operation that when the valve moves rearwardly from the position shown by Fig. 1 to the position shown by Fig. 2, the groove 23 is moved out of communication with the passage 43 and that this traps air in the chamber in front of the flange 21. This trapped air will act to lock the valve in its rearward position, but to insure against the valve moving, due to leakage from the space in front of the flange or from other causes, I have Yshown additional locking means comprising the passage 41 which leads from the chamber behind the flange 21 to the passage 31 of the ejector to vent such leakage and to subject the rearward side of the flange to suction.

I have found that the speed of the hammer may be increased materially (about thirty per cent) by operatingthe machine with the passage or passages 55 plugged or said passages omitted. For improving the operation of the machine under these conditions, I have herein provided a passage or passages 57 which communicatel with the groove 54, and extend rearward through the wall of the cylinder to the counter-bore 9, the valve block,` as shown by Fig. 5, blanking the rearward end of the passages. With the machine so arranged, it will be observed thatthe forward end of the cylinder is closed from communication with the atmosphere, and, when the piston on its rearward stroke reaches theposition shown by Fig. 2, the passages 43 and 46 will connect bothends of the cylinder, in consequence of which the chamber formed by the forward end of the cylinder and passage 57 will be partially exhausted by the ejector. This exhausting, aided materially by the expansion of the chamber due .to the rapid rearward movement of the piston, causes the pressure in the cylinder bore forwardly of the piston to be materially below that of the atmosphere when the piston starts on its forward stroke, the effect of which is to increase the force tending to move the piston forwardly. As the piston moves forwardly, it compresses the air in front of it, the rapidity of compression raising the temperature of the air so that its pressure, when the piston is at the forward Vend of its stroke, is sufficientelfectively to initiate the return of the piston. T he presence of the chambers formed by the passage or passages 57 increases the volume of the forward end of the cylinder bore sufficiently to afford a suflicientamount of working fluid for securing the results just mentioned, and the passages 43 and 46, acting as described, take care of intentional or unintentional leakage from the rearward cylinder chamber, and ensure that the low pressure conditions on the forward end of the cylinder will be initiated and maintained. By properly proportioning the parts, the pressure in the forward end of the cylinder bore, when the return stroke is initiated, can be varied within considerable limits, and preferably vthis pressure will be above atmospheric pressure.

It will be observed that under the conditions just described, during the first part of the Vforward stroke of the piston, a partial vacuum exists in the bore of the cylinder forwardly of the piston, and that the piston receives its initial rearward movement by air above atmospheric pressure, the remainder of the rearward movement being caused by the partial vacuum in the rearward end of the vcylinder bore created bv the ejector after the motive fluid used to drive the piston forwardly is exhausted. Tests have shown, that with this arrangement, the driving power of the tool is increased about ten per cent with no increase of push back7 on the hand of the operator.

F or increasing the ease in which the operation of the piston maybe initiated, I preferably provide a restricted passage 58 which places the passage 5T in communication with the atmosphere and allows a small amount of air to leak into the forward end of the cylinder bore. This passage, which may be a drill hole of diameter in the order of lth inch, owing to its small size and the rapidity of reciprocation of the hammer (about 1250 blows per minute), does not cause a material reduction in the partial vacuum in either end of the cylinder bore, which occurrence I explain happens by reason of the fact, that with the use of the passage 58, the speed of the hammer is slightly increased with the effect of sufficiently wire drawing the air passing through the passage to compensate for the increased amount of air handled by the ejector. At the same time, the passage 58 will insure, that when the opera-tion of the hammer is initiated, atmospheric pressure will exist in the forward end of the cylinder bore, and that the pressure in this end, when the return stroke is initiated, will be above atmospheric pressure, because the size of the passage 58 is so small compared to the speed ber.

of the piston that it cannot vent the passage 57 to'any material degree.

If it is desired to provide for a still higher pressure for initiating the return stroke of the piston, I may provide a restricted passage 53a (in practice a gth inch drill hole) connecting the bore of the cylinder to the passage 57. The effect of this construction is to admit live air to the forward end of the cylinder bore when the piston on its forward stroke uncovers the passage. Under these conditions the action is as hereinbefore described, except that the pressure initiating the rearward stroke is increased, Vthe resultant rapid movement of the piston rapidly expanding the forward piston chamber on the rearward stroke, so that after the passages 43 and 46 act on the forward piston chamber and the piston initiates itsforward stroke, a partial vacuum will exist in the front piston cham- In the embodiment of my invention illustrated by Fig. 3, the parts are constructed and arranged as heretofore described, except that the valve is locked in its rearward position in a different manner. Specifically, I provide a restricted passage 59 in communication with one of the passages 39, which passage 59 opens into the chamber receiving the flange 2l of the valve in such position as to be closed by the flange when the valve is in its forward position. Leading from the extreme rear of the chamber receiving the flange 2l, I provide a passage 5l, into which opens a restricted passage 63 in communication with said chamber in the same plane as the passage 59. l/Vhen the valve is moved to the position shown by Fig. 3, the passage 59 is open and this admits motive fluid to the space in front of the flange 2l. The passage 6l takes care of leakage to the rearward side of the flange 2l, while the passage 63 which is of smaller effective cross-sectional area than the passage 59 prevents the pressure in front of the flange from building up to too high a degree.

It will be understood that I have provided an expansible chamber motor in which the piston 7 is the movable wall and the spaces at each side of said piston are expansible chambers.

It will be understood that the arrangement of ports and passages in Figs. l, 2 and 3 is somewhat diagrammatic, the passages being moved as far as possible into the same plane for convenience of illustration.

Although I have described forV purposes of illustration several specific embodiments of my invention, it is to be understood that within the scope of my invention wide deviations may be made from these embodiments without departing from the spirit 0f my invention.

Claims:

l. In an impact tool, a cylinder, a piston therein, a source of motive fluid supply, an

ejector, means for admitting motive fluid to the rearward end of said cylinder for driving the piston forwardly, means for cutting off said fluid and permitting its escape from the rearward end of said cylinder, means for supplying said ejector with motive fluid and for connecting its suction intake to the rearward end of said cylinder for causing the piston to return, and means for connecting the forward end of said cylinder to the suction intake of said ejector after said piston has acquired momentum on its rearward stroke.

2. In a pneumatic impact tool, a cylinder, a piston in sai d cylinder, means for admitting motive fluid to the rear of said cylinder for driving said piston forwardly, means for subjecting the rear of said cylinder to suction to return said piston, means for subjecting the forward end of said cylinder to suction during a portion of the rearward stroke, and for Vdiscontinuing theI subjection of the rear of said cylinder to suction while continuing the subjection of the front to suction.

3. In a pneumatic tool, a cvlinder, a piston in said cylinder, means for admitting motive fluid to said cylinder for driving said piston forwardly, and means for subjecting the rearward end to suction during the first part of the return stroke and the forward end to suction during the last part of the return stroke.

t. In a pneumatic impact tool, a cylinder', a piston in said cylinder, a Valve having opposed pressure areas, an ejector, a source of motive fluid supply, ports and passages for causing said valve alternately to supply the rear end of said cylinder with motive fluid from said source and interrupt said supply, and means for causing said `valve when it interrupts said supply to supply the ejector with motive fluid from said source and to connect the suction intake of said ejector to the rearward end of said cylinder, means for intermittently admitting fluid to one of said areas for shifting said valve, and means for subjecting the other of said areas to the suction effect of said ejector for locking said valve when shifted.

5. In a pneumatic hammer, a cylinder, a piston for said cylinder, a controlling valve having opposed areas, means for intermittently admitting fluid to one of said areas to shift said valve, and means for creating a suction on the other of said areas for holding said valve when shifted.

6. In a pneumatic hammer, a cylinder, a piston for said cylinder, a controlling valve having opposed areas, a passage communicating with said cylinder through a Dort adapted to beoverrun by said piston and for subjecting one of said areasto pressure fluid from said cylinder to cause said valve to shift, and means for subjecting the other of said areas to suction for holding saidvalve when shifted.

7 In a pneumatic hammer, a cylinder, a piston for said cylinder, a controlling valve having opposed areas, a passage communieating with said cylinder through a port adapted to be overrun by said piston in each direction of its travel and for subjecting one of said areas to pressure fluid from said cylinder to cause said valve to shift, and means for subjecting the other of said areas to suction for holding said valve when shifted.

8. In an impact tool, a cylinder, a piston in said cylinder, a hollow valve in said cylinder and forming part of the piston chamber, an ejector, means including ports and passages controlled by said valve to cause the rear endof said cylinder alternately to be supplied with motive fluid and to be eX- hausted by said ejector, and means for causing the pressure in the forward end of said cylinder to be reduced by said ejector to below atmospheric.

9. In an impact tool, a piston, a cylinder having a chamber for said piston, the portion of said chamber in front of the piston being substantially sealed, means for reducing to below atmospheric the pressure in such portion of said chamber, and means for alternately connecting the rearward end of the said chamber to live pressure fiuid and to a place of pressure lower than that in the portion of said chamber in front of said piston.

10. In an impact tool, a piston, a cylinder having a chamber for said piston and in which said piston is mounted for reciprocation, means for admitting live pressure fluid to the rear of said chamber to drive said piston forwardly, means for subjecting the rear of said chamber to suction to cause Said piston to return, and a by-pass controlled by motion of said piston for placing the ends of said chamber in communication during the return stroke.

11. In an impact tool, a reciprocatory piston, a cylinder'having a piston chamber the lfront end of which is substantially sealed against the escape of air on the forward piston stroke, an expansion chamber for the forward end of the piston chamber, means for admitting live pressure fluid to the rearward end of the piston chambertodrive the piston forwardly, and means for subjecting both ends of said iston chamber to suction.

12. In a pneumatic tool, a cylinder, a piston in said cylinder, means for admitting motive fluid to said cylinder for driving said piston forwardly, means for causing said piston to make a return stroke, means forming an ejector Carried by said cylinder, and means controlled in response to motion of said piston for causing said ejector to subject the forward end of said cylinder to suction prior to the next successive forward stroke.

13. In an impact tool, a reciprocatory piston, a cylinder having a piston chamber, an expansion chamber for the forward end of the piston chamber, means for admitting live l tion before live pressure fluid is again ad-v mitted to the rearward end thereof.

14. In a pneumatic impact tool, a cylinder, a piston therein, a piston-controlled, fluid-actuated, reciprocatory valve for controlling movement of said piston, and means including passages controlled by said valve for causing, when said valve is at one end of its travel, admission of motive iiuid to said cylinder for driving said piston forward, and, when said valve is at the other end of its travel, subjection of both said piston and valve to suction for returning the former and locking the latter'against movement.

'15. In apneumatic impact tool, a cylinder, a piston therein, a reciprocatory controlling valve for said piston, means including passages jointly controlled by said valve ,and piston for causing the valve when at one end of its travel to admitl motive fluid to the cylinder for .driving the piston forward and the valve to be moved to the opposite end of its travelin consequence of suchkforward movement, said valve when at the last mentioned end of its travel causing, by its edect on said passages, subjection of both itself and said piston to suction for returning the piston and locking the valve against movement. 16, In a pneumatic impact tool, a cylinder, a piston in said cylinder, a valve; means including an injector, and pressure surfaces on said valve and passages controlled by said valve for admitting motive fluid to drive said piston forwardly and to return it by suction; and means including pressure surfaces on said valve and coordinated ports and passages for causing said piston to trap and compress part of the contents of said cylinder at the end portion of the return stroke and -utilize t-he same to effect movement of said valve in-one direction and for causing suction induced by said ejector to act on said valve for locking it` against such movement during other portions of said return stroke.

17. In an impact tool, a reciprocatorypis'-,

ton, a cylinder having a piston chamber, an

expansion chamber forthe forward end of said piston chamber, means for admitting live pressure to the rearward end of said` piston chamber to drive said piston forwardly, means for permittingV escape of such ,livev fluid from said chamber when said piston has moved forwardly and for subjecting said rearward end to suction for causing said pisfton to return, and means for placing the ends of Ysaid piston chamber in communication after said piston has made a portion Vo f` its return stroke. j

18. In an impact tool, a reciprocatory piston, a cylinder having a piston chamber, 'an expansion chamber for the forward end of said piston chamber, means for admittinglive pressure to the rearward end of said pistion chamber to drivel said piston forwardly, means for permitting escape of such live fluid from said chamber when said piston has moved forwardly and for subjecting-,said rearward end to suction for causing said piston to: return, and a by-pass controlled by said piston and operative to place the ends of said piston'chamber in communication on the return stroke. v.

19. In a pneumatic impact tool, al cylinder having a piston chamber, a hammer piston in said chamber, a passage connecting the yrearward end of said chamber to the atmosphere, a nozzle opening into said passage for creating. suction therein, a valve .for controlling said passage, said valve being arranged to close said passage and to interrupt the supply of motive fluid for said nozzle in one position and to simultaneously supply motive fluid to the rear end of said chamber, and when in its other position to open said passage and supply motive fluid to said nozzle and simultaneously interrupt the supply of motive fluid to the rear end of said chamber, a second passagecontrolled by said valve and for connecting the rearward and forward ends of saidchamber when the piston is at an intermediate portion of its rearward stroke, and saidsecond passage being opened and closed by said valve at the same times as the first passage. Y' y f 20. In a pneumatic impact machine, a cylinder having a piston chamber, a hammer piston in said chamber, an admission passage for the rearward end of said chamber, an eX- haust passage connecting the rearward end of said chambervto the atmosphere', ,a nozzle for said exhaust passage, a valve controlling said passages and said nozzle, and a by-pass passage for connecting said exhaust passage to an intermediate portion of said cylinder through a port controlled by said piston.

21. A pneumatic hammer having, in combination, a cylinder having therein a reciprocatory hammer piston provided with opposed pressure surfaces, means forming an ejector carried by said cylinder; means controlled injresponseto motionof said piston for ad- 22. Ina pneumatic impact! machine, a cyl-l inder having a piston chamber, Va hammer piston` inwsard chamber, an admission passage for Vthe rearward end of said chamber,

an exhaust passage connecting the rearward end of said chamber to :the atmosphere, a nozzle for said ex'haustpassage, a valve conpressure upon the other-.of

llO

Vmitting motive Huid to said cylinder to act trolling said passages and said nozzle, and a by-pass passage controlled by said valve and for connecting said exhaust passage to an intermediate portion of said cylinder through a port controlled by said piston.

23. A pneumatic hammer having, in combination, a cylinder having therein a reciprocatory hammer piston provided with opposed pressure surfaces, means forming an ejector cariied by said cylinder; means controlled in response to motion of said piston for admitting motive fluid to said cylinder to act uponone of said surfaces for driving said piston in one direction, and likejmeans for causing said ejector to act toreduce tobelow atmospheric the pressure upon both of said surfaces.

24. A pneumatic hammer having, in combination, a cylinder having therein a reciprocatory hammer piston provided with opposed pressure surfaces, means forming an ejector carried by said cylinder; means controlled in response to motion of said piston for admitting motive fluid to said cylinder to act upon one of said surfaces for driving said piston in one direction, and lilre means for intermittently operating said ejector and causing it to act to reduce to below atmospliericy the pressure upon both of said surfaces.

25. A pneumatic hammer having, in combination, a., cylinder having therein a reciprocatory hammer piston provided with opposedpressure surfaces, means forming an ejector carried by said cylinder; means controlled in response to motion of said piston for admitting motive fluid to said cylinder to act upon one ofv said surfaces for driving said piston in one direction, and'like means for causing said ejector to act and alternately to connect said ejector to opposite end portions of said cylinder for reducing to below atmospheric the pressure upon said surfaces.

Q16. A pneumatic hammer having, in combination, a cylinder having therein a recipi'ocatory hammer piston provided with opposed pressure surfaces, means Vforming an ej ector carried bysaid cylinder; means controlled in response to motion of said piston for admit-- ting motive fluid to said cylinder to act upon one of said surfaces for driving said piston in one direction, and like meansfor causing said ejector to act intermittently and alter-V nately to connect said ejector to opposite end*V portions of said cylinder for reducing to below atmospheric the pressure upon said'surfaces.

27. In a pneumatic impact machine, a cylinder having a piston chamber, a hammer piston in said chamber, an admission passage for the rearward end of said chamber, an exhaust passage connecting the rearward end of said chamber to the atmosphere, a nozzle forsaid exhaust passage, a valve controlling said passages and said nozzle, a by-pass paschamber, a piston reciprocating in said cham-V bers,'a passage controlled by said valve for admitting fluid to the rearward end of said aligned chambers, a passage controlled by the front end of said valve for exhausting the rearward end of said aligned chambers, a nozzle opening into the last named passage, a forwardly directed surface for said valve, a passage for directing fluid against said surface and opening into an intermediate portion of the chamber of said cylinder through a port controlled by said piston, an internal groove in said cylinder controlled by the front end of 'said valve, and said groove connecting said last named passage and said passage for exhausting the rear end of said cylinder.

29. In a pneumatic impact machine, a cylinder, a piston therein, an exhaust passage, a valve having a forwardly directed surface, a passage for directing pressure fluid against said surface and opening into an intermediate portion of said cylinder through ya port controlled `by said piston, means for closing said passage after the valve has shifted, said valve when so shifted opening said exhaust passage, a nozzle for said exhaust passage and arranged to be supplied with motive fluidV when so shifted-opening said exhaust passage, afnozzle for said exhaust passage and ar` ranged to be supplied with motive fluid when said valve is so shifted, a connection between said nozzle and the space in front of said surface, and a leak passage from said space to the atmosphere.

31. An impact tool having in combination,

a cylinder, a piston, a controlling valve, an

ejector, ports and passages controlled by said valve foradmitting high pressure actuating fluid to the rearward piston chamber for driv-y ing said piston on its forward stroke, ports' and passages controlled by said valve forv connectingV the suction intake of said ejector tothe rearward piston chamber for creating suction for returning the piston, conduit means for causing the forward piston chamber to be connected to said ejector during the rearward stroke of said piston, and conduit means for admitting a restricted amount suction for returning the piston, conduit means for causing the forward piston chamber to be connected to said ejector during the rearward stroke of said piston, and conduit means for admitting a restricted amount of actuating fluid from the atmosphere to said forward piston chamber.

33. An impact tool having in combination, a cylinder, a piston, a controlling valve, an ejector, ports and passages controlled by said valve for admitting high pressure actuating fluid to the rearward piston chamber for driving said piston on its forward stroke, ports and passages controlled by said valve for connecting the suction intake of said ejector to the rearward piston chamber for ycreating suction for returning the piston, conduit means for causing the forward piston chamber to be connected to said ejector during the rearward stroke of said piston, and conduit means for admitting a restricted amount of high pressure actuating fluid to said forward piston chamber. Y

34. An impact tool having in combination,

a cylinder, a piston, a cont-rolling valve, an

35. An impact tool having in combination,

a. cylinder, a piston, a controlling valve, an ejector, ports and passages controlledby said valve for admitting high pressure actua-ting fluid to the rearward piston chamber for driving said piston on its forward stroke, ports and passages controlled by said valve for connecting the suction intake of said ejector to the rearward piston chamber for creating suction for returning the piston, conduit means for causing the forward piston chamber to be connected to said ejector during the rearward stroke of said piston, means controlled by said piston for admitting-,high pressure actuating fluid to the forward piston chamber during the forward stroke, and a permanently open restricted connection between said forward piston chamber and the atmosphere. Y

36. An impact tool having in combination, a cylinder, a piston, a controlling valve, an ejector, ports and passages controlled by said valve and by said piston for causing said piston and valve to reciprocate, said valve inone position admitting high pressure actuating fluid to the rearward piston chamber for driving said piston forwardly and in its opposite position connecting said rearward pistonchamber to the atmosphere and the suction intake of said ejector, means for maintaining a sufficient amount of actuating fluid in the forward piston chamber tocause the rearward stroke of said pist-on to be initiated by and compressed by said piston vto above atmospheric pressure, and a conduit means controlled by said piston for connect-V ing the forward piston chamber to the suction intake of said ejector for causing the pressure in said forward piston chamber to be below atmospheric pressure when the forwardstroke is initiated.

37. 'An impact tool having in combination, a cylinder, a pistonv` a controlling valve, an ejector, a source of high pressure actuating fluid, ports and passages-.cooperating with said piston,` said valve andsaid ejector and controlledbysaid piston and valve for admitting high pressure actuating fluid to the rear piston `chamber during the forward stroke Vof the piston and for causing said piston to compress in the forward piston chain-` ber actuating fluid to abovel atmospheric pressure for initiating the return stroke of the piston, and said ports and passages causing said ejector to created a partial vacuum in the rearward piston chamber for completing` the return stroke of the piston, and a partial vacuum in the forward piston chamber during the return stroke.

38. In an impact tool, a piston, Aa cylinder having a chamber in whichjsaid piston is mounted for reciprocation, means for admitting live pressure fluid to said chamber at the rear of said pistonto drive saidy piston forwardly, means for subject-ing said chamber atthe rear of said piston to suction to cause said piston to return, and means for subjecting said chamber forwardly of said piston to suction while said piston is returning and before live pressure fluid is again admitted to said chamber at the rear of said piston for again driving` said .piston for` wardly.

39. In a pneumatc hammer, a cylinder, a

soi

piston for said cylinder, a controlling valve having opposed areas, means comprisingV a port opened and closed by said piston for admitting motive fluid against one of said areas for causing said valve to shift, means controlled by said valve for trapping such motive iuid, and means controlled by said valve for subjecting the other of said areas to suction after the valve has shifted.

40. In a pneumatic hammer, a piston, a cylinder having a chamber for said piston. means including a controlling valve and ejector for alternately admitting motive fluid to the rearward end of said Chamberland subjecting said end to suction, the forward end of said chamber being substantially sealed against the escape of air therefrom on the forward stroke of said piston.

41. In a pneumatic hammer, a piston, a cylinder having a chamber for said piston. means including a controlling valve and ejector for alternately admitting motive fluid to the rearward end of said chamber and subjecting said end to suction, the forward end of said chamber being substantially sealed against the escape of air therefrom on the forward stroke of said piston, and means for causing said ejector to reduce the pressure in the forward end of said chamber to below atmospheric when said piston is at the rearward end of said chamber.

42. In a pneumatic hammer, a piston, a cylinder having a chamber for said piston, means' including a controlling valve and ejector for alternately admitting motive fluid to the rearward end of said chamber and subjecting said end to suction, and means includingl said ejector for causing the forward end of said chamber to be below atmospheric pressure when the piston is at the rearward end of its stroke and said piston to compress the contents of said chamber to above atmospheric pressure during the forward piston stroke.

In testimony whereof, I have signed my name to this specification.

' ERNEST H. SI-IAFF.

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