US3509723A - Gas-powered impact hammer - Google Patents

Description

May 5, 1970 R. J. DORN GAS-POWERED IMPACT HAMMER 4 Sheets-Sheet 1 Filed Aug. 5, 1968 INVENTOR. Russell John Darn ATTORNEY May 5, 1970 R. J. DORN GAS-POWERED IMPACT HAMMER 4 Sheets-Sheet 2 Filed Aug. 5, 1968 wavy wm ok p omb vfl QM V i INVENTOR. Russell John Dorn BY a 1. @w

ATTORNEY May 5, .1970 R. J. DORN GAS-POWERED IMPACT HAMMER 4 Sheets-Sheet 5 Filed Aug. 5, 1968 INVENTOR. Russell John Dorn ATTORNE Y y 5, 1970 R. J. DORN 3,509,723

GAS-POWERED IMPACT HAMMER Filed Aug. 5, 1968 4 Sheets-Sheet 4 59 92 99 2O 8 5 y r50 g if g Q INVENTOR.

Russell John Dorn ATTORNEY 3,509,723 GAS-POWERED IMPACT HAMMER Russell John Dorn, Aurora, Colo., assignor to Arrow Manufacturing Company, Denver, Colo., a corporation of Colorado Filed Aug. 5, 1968, Ser. No. 750,303 Int. Cl. F011) 31/00 C]. 60-57 9 Claims ABSTRACT OF THE DISCLOSURE A compressible-fluid-powered impact hammer is mounted on a dirigible automotive vehicle. The hammer includes a cylindrical jacket slidably and telescopingly mounting a tool carrying impact ram. An internal plunger mounted within the jacket is received within an axial cavity in the inserted end of the ram to define an internal gas chamber. Hydraulic pressure fluid is used to retract the ram into the jacket and thereby compress the cowtained gas in the chamber. A valve mechanism releases the hydraulic fluid pressure and the compressed gas expands to drive the ram to an impact point.

BACKGROUND OF THE INVENTION The present invention relates to a compressible-fluidpowered impact hammer mechanism. More particularly, the invention resides in a nitrogen gas-powered impact hammer finding particular, but not necessarily exclusive, use as a vehicle mounted percussion tool for the tamping of fills, the cutting and breaking of pavements, the driving of posts and pilings, the demolition of structures and like operations.

The use of a compressed gas to power an impact hammer, is an old and Well known expedient. Difliculties have been encountered, however, in obtaining satisfactory sliding seals, and in providing efiicient means for retracting the ram to load or cock the hammer. Additional problems have also been encountered in connection with throttling of the pressure fluid utilized to compress the gas when the ram is actuated or fired. The throttling action results in a substantial heat rise and degradation of the pressure fluid, as well as in a loss of efi'iciency in that the compressed gas must not only drive the ram, but must also act against the pressure created by throttling the fluid.

OBJECTS OF THE INVENTION The principal object of the present invention is to provide a novel gas-powered impact hammer which is rugged in construction, susceptible of severe use in a wide variety of construction and demolition operations, is simple in operation, requires a minimum of maintenance, and is suitable for mounting on a dirigible automotive vehicle.

Another object of the present invention is to provide an efiicient powerful gas-powered impact hammer in which the ram is retracted and the gas is compressed by means of an improved hydraulic fluid circuit and in which throttling of the fluid is minimized and the hydraulic fluid pressure can be quickly reduced to eliminate back pressure as the ram is driven by the expanding gas.

SUMMARY The foregoing objects are accomplished by a vehicle mounted, pressure-fiuid-controlled-gas-powered impact hammer as described herein. The vehicle includes a wheeled chassis with a frame rotatably mounted thereon and carrying the power elements and an angular boom. The hammer is mounted on the end of the boom and is positioned by hydraulic means controlled by an operator at the control station on the vehicle. The hammer embody- United States Patent O 3,509,723 Patented May 5, 1970 ice ing the invention is made up of a ram slidably mounted in a jacket. The inner end of the ram is tubular and receives a fixed compressor rod. A gas chamber is defined between the tubular end of the ram and the compressor rod in which gas is compressed to act as motive power for the ram. Substantially coextensive annular chambers are defined within the jacket. The ram is received in one of the annular chambers while the other acts as an annular exhaust passage. The hammer is controlled by a pressure fluid operated solenoid valve mechanism which in turn actuates a spool valve which controls the operation of the ram. This is accomplished by the selective opening or closing of the ports communicating between the pressure side and the exhaust side of the ram. The ram is cocked or loaded by means of pressure fluid which acts against the ram to retract it and compress the gas. To fire the ram the fluid pressure is reduced to zero by shifting the solenoid 'valve. to open both annular chambers to exhaust.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a vehicle mounting an impact hammer embodying the present invention.

FIG. 2 is a longitudinal, detailed, section view of an impact hammer embodying the present invention with the impact ram retracted.

FIG. 3 is an enlarged, fragmentary, section view showing one end portion of the hammer shown in FIG. 2, and illustrating particularly the servo-valve control mechanism.

FIG. 4 is a section view taken substantially in the plane of line 4-4 on FIG. 3.

FIG. 5 is a section view taken substantially in the plane of line 5-5 on FIG. 3.

FIG. 6 is a section view, similar to that shown in FIG. 2, but in a generally schematic form.

FIG. 7 is a schematic view similar to FIG. 6, but showing the ram in a partially extended position.

FIG. 8 is a schematic view similar to FIG. 6, but showing the ram in a fully extended position.

FIG. 9 is a schematic view similar to FIG. 6, but showing the ram in a partially retracted position.

DESCRIPTION OF THE PREFERRED EMBODIMENT In general There is shown in the drawings, with particular reference to FIG. 1, a pressure fluid controlled, gas powered impact hammer, indicated generally at 20', mounted at the outboard end of a boom, indicated generally at 21, carried on a dirigible, wheeled, automotive vehicle, indicated generally at 22. The vehicle may be either a conventional piece of roadworking equipment, or may be a specially constructed unit for carrying the boom 21 and hammer 20. For purposes of illustration, the vehicle shown in FIG. 1 comprises a chassis 24 provided, in the present instance, with wheels 25, although crawler tracks may be utilized to advantage for some applications. The wheels 25 are individually mounted and journaled on the chassis 24, and are each powered by a pressure fluid driven motor (not shown). Appropriate steering gear and linkage (not shown), also pressure fluid powered, are provided as is conventional in the art.

For carrying and mounting the various components of the assembly, including a power source 28, operator and control stations, and the boom 21, a frame 26 is supported on the chassis by a rotatable mounting structure 27, so that the frame 26 may be swungor rotated about a vertical axis. The frame 26 carries an internal combustion engine driven power unit 28 which includes a pressure fluid or hydraulic pump for supplying pressure fluid to the various components of the vehicle, boom and hammer. For controlling the vehicle and its adjuncts, an operator control station, including a seat 29, steering gear 30 and controls 31, is mounted on the frame 26. The vehicle is driven and all controls are actuated from the operators station 29. The unit is thus suitable for one man operation and is a completely self-contained, self-powered apparatus. Hydraulic fluid is supplied to the various components through appropriate conduit and the rotatable mounting structure 27 includes means making provision for the application of pressure fluid from the power source 28 to the various hydraulic motors carried on the chassis 24 for driving the wheels 25 and steering mechanism.

For carrying the impact hammer 20 embodying the present invention, a generally angular boom 21 is mounted on the frame 26 for swinging movement in a generally vertical plane, so that the position of the hammer may be raised or lowered. The boom can be moved up and down in a vertical plane and, by rotating the frame 26 about a vertical axis with respect to the chassis, the boom can be swung from side to side, thereby enabling the operator to position it throughout a complete 360 area relative to the chassis. For raising the boom 21, a hydraulic ram 35 is fixed between the frame 26 and the boom at approximately the apex of the angle therein. This hydraulic ram 35 is actuated by controls located at the control station 31, and receives its pressure fluid from the power unit 28 on the vehicle.

As shown in FIG. 1, the hammer 20 is mounted on the outer end of the boom 21. The necessary hydraulic fluid conduits for operating the hammer and for positioning the same are secured on and carried by the boom. In order to support the hammer on the boom, a yoke 38 is pivotally mounted on the outer end of the boom. To this end, the boom is formed with a pair of outwardly directed cars 39 carrying a pin 40 journaled between them for rotation about a horizontal axis. The yoke 38 is carried on the pin 40 intermediate the cars 39. For rotating the pin and thereby swinging the yoke in a vertical plane, a lever 41 is afiixed to one end of the pin 40 outwardly of the adjacent boom ear 39. The free end of the lever is secured to a hydraulic ram 42 mounted on the boom 21. Actuation of the ram thus serves to rotate the pin about a horizontal axis thereby to swing the yoke and the structures mounted thereon in a vertical plane. The yoke in turn mounts a cylinder (not shown) for receiving a trunnion (not shown) to which is secured a hammer mounting bracket and shock absorber 45. Hydraulically actuated rams 46 are mounted on the yoke 38 for rotating the trunnion thereby to swing the mounting structure and the hammer 20 carried thereby about a generally horizontal axis so that the hammer 20 can be swung from side to side.

Pressure-fluid controlled gas-powered impact hammer The impact hammer 20 embodying the present invention is illustrated in detail in the drawings, and particularly in FIGS. 2 and 3, and comprises an outer cylindrical jacket '50 having a bore 51 in which is telescopingly and slidingly received an impact ram 52. A tool or guide mounting flange 54 is provided on the lower end of the jacket 50, and the impact end 55 of the ram 51 is shaped to receive a hammer tool or like instrument 53. At the lower or impact end of the jacket from which the ram projects, the jacket cylinder is recessed to define a counter bore 56 in which is mounted cylindrical bearing-supporting inner and outer inserts 58, 59, one of which inserts 58 includes an internally tapered bore 60 extending part way through the insert and tapering from a larger diameter at its innermost end 61 to a relatively smaller diameter. The insert 58 seats against a shoulder 62 defined in the jacket 50 by the counter bore '56. At its end opposite from the tapered bore, the insert 58 is provided with a bore 64 in which is mounted a ram guiding and supporting bearing ring 65, the inner surface of which is provided with seals 66. The outer insert 59 is positioned in the jacket bore 56 and seats against the inner insert 58 and a shoulder '68 defined by a counter bore 69 in the outermost end of the jacket 50. The insert 59 supports a bearing ring 70 which is provided with a dust seal 71 adapted to engage the surface of the ram 52.

For supplying pressure fluid to the interior of the jacket, a pressure fluid input port 74 is provided in the jacket 50. This port '74 communicates with an input channel 75 in the insert 58 and a plurality of input passages 76 therethrough opening into the tapered bore 60 surrounding the ram 52. Pressure fluid is supplied from a pressure fluid source on the vehicle through appropriate conduits (not shown) secured to the boom 21. A check valve (not shown) may be provided in the pressure fluid input line so that unidirectional flow is achieved.

The inner end portion 78 of the ram 52 is telescoped within the jacket 50, and is generally tubular to define a gas receiving cavity 79. For supplying a compressible gas to the cavity, the ram is provided, adjacent its impact or tool end 55, with a fill bore or passage 87, and a gas valve fill stem 81. To support the inner end 78 of the ram 50 for sliding movement, the jacket is provided, at its end opposite from the mounting flange 54, with an end member 80 seated in the jacket and supported against an internal shoulder 82 defined by a counter bore 83 within the end of the jacket. An end cap 84, threadably and sealingly engaged within the jacket 50, securely holds the end member 80 within the jacket and against the seat 82. The end member 80 is provided at one end with a central axially extending valve spool recess 85, and at its other end the member 80 supports a plunger or compressor rod 86 which extends axially within the jacket 50 and is telescopingly received within the tubular end 78 of the ram 52. The end member 80 also supports an internal cylinder or sleeve 88 co-extensively surrounding the plunger or compressor rod 86 and positioned in the space defined between the outer surface of the rod 86 and the inner surface 51 of the jacket 50. The inner surface 89 of the cylinder or sleeve 88 defines, with the outer surface of the plunger or compressor rod 86, a first annular chamber 90 within which the tubular end 78 of the ram 52 is received. The outer surface 91 of the cylinder or sleeve 88 defines, with the inner surface 51 of the jacket '50, a second annular chamber 92, which is generally co-extensive with the first annular chamber 90. To further define a compressible-gas chamber, the free end of the compressor rod 86 embodies a generally axial recess or chamber 94.

The tubular end of the ram is enlarged to define an internal shoulder '95, and at its free end mounts an annular bearing member 96 which carries appropriate seals 98, 99 for engaging the walls of the internal sleeve 88 and the compressor rod 86 respectively. With the foregoing sleeve and seal arrangement, it can be observed that the gas chamber defined by the chambers 79 and 94 is completely sealed so that, when charged with a compressible gas, the gas may either be compressed or allowed to expand without substantial leakage. The valve stem 81 is, of course, provided for use in replenishing the gas supply to make up for the small amount of leakage which will inevitably occur.

The first annular chamber 90 defined between the compressor rod 86 and the sleeve 88, is generally considered to be an exhaust chamber, and passages or ports 100 are provided connecting this chamber with the valve recess 85. The recess 85 further communicates, through appropriate passages 101, with an exhaust port 102 and associated pressure fluid conduit (not shown) which leads to a pressure fluid supply or sump on the vehicle. Again, a one way check valve may be provided in the exhaust line so that fluid flow through the exhaust port is unidirectional.

The second annular chamber 92 defined between the sleeve 88 and the jacket 50 communicates with the first annular chamber 90 through radially extending passages 104 in the end member 80. For purposes of selectively opening or closing these passages to control the communication between the first and second annular chambers, there is provided a sliding valve spool 105 mounted in the recess 85 in the end member 80. The spool 105 is provided with generally axially extending passages 106 to insure open communication between the exhaust port 102, the end member passages 100, and the first annular chamber 90. The spool 105 is selectively positioned by a servo valve stem 108 which is secured to the spool 105 and extends outwardly through the end cap 84 where it is engaged with a servo valve control mechanism 109. The servo valve mechanism 109 includes a cylinder 110 surrounding a piston 111 aflixed to the servo valve stem 108. Pressure fluid ports 112, 113 are provided for applying pressure fluid from the pressure fluid source on the vehicle to a selected side of the piston 111. Appropriate seals and sealing rings are provided as is conventional practice in the art. Further, a bushing 114 is desirably provided in the recess 85 in the end member 80 for slidably receiving the valve spool 105.

Operation of the impact ram In the operation of the impact ram 20 herein described, the operator of the ram carrying vehicle 22 positions the ram 20 with the impact tool 53 operatively adjacent a work surface. The solenoid operated servo control valve 109 is actuated, by applying pressure fluid to port 112, to position the valve spool 105 to close the radial passages 104 communicating between the end member recess 85 and the second or outer annular chamber 92 in the jacket 50. Referring to FIG. 6, the valve spool 105 is moved to the right by the application of pressure fluid to solenoid valve port 112. It will be observed that the first or inner annular chamber 90 containing the telescoping tubular end 78 of the ram 52 is at all times open to the pressure fluid exhaust line through port 102, the axial passages 100 in the end member 80 and the axial passages 106 in the valve spool 105. Thus the inner annular chamber 90 is effectively at zero pressure. Pressure fluid is then supplied to the pressure fluid port 74 in the jacket 50 by the actuation of appropriate controls at the operator controlled station 31. Because the second or outer annular chamber 92 is closed to exhaust by the valve spool 105, fluid pressure will build up in the annular chamber. The diflerential across the inserted end 78 of the ram 52 results in a force being exerted on shoulder 95 on the ram. This force moves the ram inwardly of the jacket, as shown in FIG. 9, and effects a telescoping movement between the ram and the compressor rod or plunger 86. In this manner, the contained gas in chamber 79 is compressed to a pressure substantially equal to that of the pressure fluid. For example, hydraulic oil pressure at 2000 lbs. per square inch in the construction shown, will compress the nitrogen gas confined within the gas chamber 79 to a pressure of 2000 lbs. per square inch. As the ram is withdrawn into the jacket to the position shown in FIG. 6, the pressure fluid filling the first annular space behind the ram will be exhausted through the exhaust port 102 to the supply source of the pressure fluid. This fluid flows from the inner annular chamber 90 through the generally axial passages 100 in the end member 80, thence through the axially directed pasages 106 in the spool 105 and out through the radial passages 101 in the end member 80 to the exhaust port 102. When the ram has been fully retracted within the jacket, as shown in FIG. 6, the contained compressed nitrogen gas in chambers 79*, 94 is at maximum pressure and the ram is cocked ready for hammer operation. A check valve in the fluid pressure supply line prevents pressure fluid from flowing out of the inlet port 74 so that the ram remains in a fully cocked or loaded position until it is fired.

To fire the ram to achieve a hammer blow of the tool 53 on a work surface, the servo valve 109 is reversed to withdraw the valve spool 105, a left hand direction as shown in FIG. 7, and open the radial ports 104. Communication is thereby opened between the two annular chambers and 92 through the axial ports 100 in the end member 80. Because the annular chambers 90 and 92 are also open to the exhaust port 102 and are thus effectively at zero pressure, the force on the loading shoulder is reduced to substantially zero. There being no pressure fluid restraint on the ram 52, the confined compressed nitrogen gas rapidly expands and drives the ram outwardly of the jacket as shown in FIG. 7, to an impact position. Pressure fluid contained in the first annular chamber 90 between the inner sleeve 88 and the plunger or compressor rod 86 flows through the outer annular chamber 92 and the radial ports 104 into the end member recess 85. The pressure fluid will then be drawn into chamber 90 in back of the tubular end of the ram 78 as the ram moves out of chamber 90, that is, toward the right as shown in FIG. 7. Because of this flow of fluid into the inner chamber 90, it will be appreciated that there is little or no throttling effect and the hydraulic fluid remains at essentially zero pressure or even under a slight vacuum.

As the ram approaches its outer limit of travel, as shown in FIG. 8, the shoulder 95 on the end 78 of the ram is received in the tapered bore 60 of the sleeve insert 58 which is mounted within the end of the jacket 50. This has the effect of gradually compressing pressure fluid in the space defined between the outer surface of the ram, the inner surface of the bore in the insert 58, and the shoulder 95. Inasmuch as the bore 60 of the insert 58 is tapered, the pressure increases rapidly as the ram moves forward. In

this manner, fluid trapped in the insert bore acts as a cushion and retarding element to slow and stop the movement of the ram before the shoulder 95 comes into contact with the end of the insert 59. Under most circumstances however, the tool will impact against a work surface prior to or just as the shoulder 95 enters the tapered bore 60. The shock of the impact is transmitted through the ram and jacket to the shock absorber mounting 45 on the end of the boom 21. This mounting absorbs the shock and vibration from the impact so that severe stresses are not transmitted through the boom to the vehicle.

The hammer mechanism described above is position independent and will operate equally well in any position, whether vertical, horizontal or any position in between. The hammer may be directed upwardly, sidewise or downwardly thereby making the unit admirably suited not only for road work but for building demolition, mine work and the like.

I claim as my invention:

1. A gas powered impact ram comprising, in combination, a jacket, a ram slidably and telescopingly mounted in said jacket, said ram having an impact end extending outwardly from said jacket and a tubular end inserted within said jacket, a compressor rod fixedly mounted in said jacket and telescopingly received within the tubular end of said ram, said compressor rod and tubular end of said ram defining a gas chamber, a compressible gas contained within said chamber, pressure fluid means for retracting said ram into said jacket thereby to compress the compressible gas between said ram and said rod, and means for releasing said pressure fluid retracting means, whereby said compressed gas drives said ram with impact force outwardly of said jacket.

2. A pressure fluid controlled, gas powered impact hammer comprising, in combination, a generally cylindrical jacket, a compressor rod fixedly mounted on said jacket at one end thereof and extending axially within the jacket, an internal sleeve mounted on said jacket and extending axially into said jacket in substantially coextensively surrounding relation with said compressor rod, said sleeve defining with said rod a first internal annular chamber and defining with said jacket a second internal annular chamber, means for controlling the flow of pressure fluid between said annular chambers, means defining a pressure fluid exhaust passage through said jacket, in open communication with said first annular chamber, a ram slidably mounted in telescoping relation in said jacket, said ram having an impact end extending outwardly of said jacket and a tubular end inserted into the first annular space and telescopingly receiving said compressor rod, to define therewith a chamber internally of said ram for confining a charge of gas, said tubular end of the ram defining an annular shoulder adjacent the innermost end thereof, sealing means on said tubular end slidably engaging the opposed walls of said first annular chamber, means defining a pressure fluid port opening through the jacket adjacent the impact end of the ram and communicating with said first and second annular chambers, means slidably and sealingly supporting the impact end of said ram with said jacket, and servo valve control means on said jacket for selectively actuating said controlling means to obstruct the flow of pressure fluid between said annular chambers so that the application of fluid pressure within said annular chambers exerts a retracting force on said shoulder to telescope the ram inwardly of the jacket and thereby to compress said charge of gas contained in the chamber defined between said compressor rod and said impact ram, and for selectively actuating said controlling means to release the flow of pressure fluid between said annular chambers so that pressure fiuid contained in said second annular chamber is released to flow to said first annular chamber and to said exhaust port whereby the retracting force on said ram is released so that said compressed gas rapidly expands to drive said ram forcibly outwardly of the jacket.

3. A pressure fluid controlled, gas powered impact hammer comprising, in combination, a generally cylindrical jacket, internal bearing means mounted in said jacket adjacent one end thereof, an end member mounted in said jacket adjacent the other end thereof, a compressor rod fixedly mounted on said end member and extending axially within the jacket, an internal sleeve mounted on said end member and extending axially into said jacket in substantially coextensively surrounding relation with said compressor rod, said sleeve defining with said rod a first internal annular chamber and defining with said jacket a second internal annular chamber, said end member having an axially extending recess defined therein, means defining generally axially extending passages through said end member opening into said recess and said first annular chamber, means defining generally radially extending passages through said end member opening into said recess and said second annular chamber, means defining a pressure fluid exhaust passage through said end member and jacket, a valve spool slidably mounted in said recess for selectively opening and closing said radial passages, said spool having passages extending in an axial direction therethrough and providing open communication between said axial passages in said end member and said pressure fluid exhaust port, servo control means mounted on said jacket for selectively positioning said spool for opening or closing said radial passages, a ram slidably mounted in telescoping relation in said jacket, said ram having an impact end extending outwardly of said jacket and a tubular end inserted into the first annular space and telescopingly receiving said compressor rod, said compressor rod having a recess defined in the free end thereof for confining a charge of gas within said tubular end of the ram, said tubular end of the ram defining an annular shoulder adjacent the innermost end thereof, sealing means on said tubular end slidably engaging the opposed walls of said first annular chamber, means defining a pressure fiuid port opening through the jacket adjacent the impact end of the ram and communicating with said first and second annular chambers, the impact end of said ram being slidably and sealingly supported by said internal bearing means, and servo valve control means on said jacket for positioning said valve spool to close said radial passages, so that the application of fluid pressure within said annular chambers exerts a retracting force on said shoulder to telescope the ram inwardly of the jacket and thereby to compress said charge of gas contained in the chamber defined between said compressor rod and said impact ram, and for positioning said valve spool to open said radial passages so that pressure fluid contained in said second annular chamber is released to flow to said first annular chamber and to said exhaust port thereby releasing the retracting force on said ram so that said compressed gas rapidly expands to drive said ram forcibly outwardly of the jacket.

4. A gas powered impact ram as defined in claim 1 including means within said jacket for retarding movement of said ram and stopping the same at the outer limit of travel thereof.

5. A gas'powered impact ram as defined in claim 2 including a second internal sleeve coaxially mounted within said jacket axially spacedly adjacent said compressor rod, said sleeve having a bore therein tapered from a larger diameter at its end adjacent said compressor rod to a smaller diameter at its opposite end, said sleeve being adapted to closely receive said annular shoulder on said ram in progressively more confining releationship Whereby as said shoulder enters said tapered bore pressure fluid is confined and compressed between said shoulder and said tapered bore to retard the movement of said ram and stop the same at the outer limit of travel thereof.

6. A gas powered impact ram as defined in claim 2 wherein said means slidably and sealingly supporting the impact end of said ram within said jacket comprise a bearing support sleeve mounted within said jacket in coaxial surrounding relation with said ram and a pair of spaced apart bearing members supported Within said sleeve for sealingly and slidingly supporting said ram.

7. A gas powered impact ram as defined in claim 3 wherein said end member comprises a generally cupshaped member, said compressor rod being fixedly mounted on the base of said cup-shaped member, and a peripheral shoulder defined on said cup-shaped member adapted to seat against an internal shoulder defined in a the inner wall of said jacket.

8. A gas powered impact ram as defined in claim 7 including an end cap threadably engaged within said jacket for holding said cup-shaped member therein, said end cap mounting said servo valve control means and having an axially extending aperture therethrough for receiving said valve stem.

9. A gas powered impact ram as defined in claim 7 wherein said cup-shaped member includes an internal sleeve bushing slidably supporting said valve spool.

References Cited UNITED STATES PATENTS 2,731,892 1/1956 Simmonds. 2,787,123 4/1957 Delvaux 6057 2,827,764 3/ 1958 Simmonds 605 1 FOREIGN PATENTS 485,617 5/ 193 8 Great Britain. 729,941 5/ 1955 Great Britain.

EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R.

Images