US3620312A

US3620312A - Rock drill

Info

Publication number: US3620312A
Application number: US826923A
Authority: US
Inventors: Eugene L Krasnoff
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1969-05-22
Filing date: 1969-05-22
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16
Also published as: ZA702286B; CA922208A; SE363474B; JPS4932401B1; DE2022490C3; FR2048623A5; DE2022490B2; GB1302759A; DE2022490A1

Abstract

A hydraulically powered impact tool particularly useful for rock drilling. The percussive tool is valveless with the hammer controlling the inflow and exhaust of motive liquid. The drill is powered by liquid under pressure from an outside source and from energy stored in storage chambers. Tanks positioned in the inlet and exhaust lines of the tool reduce pressure surges in the inlet and exhaust lines of the tool.

Description

United States Patent Inventor Eugene L. Krasnofl Princeton, NJ. App]. No. 826,923 Filed May 22, 1969 Patented Nov. 16, 1971 Assignee lngersoll-Rand Company New York, N.Y. Continuation-impart of application Ser. No. 728,854, May 13, 1968, now abandoned which is a continuation of Ser. No. 629,561, Apr. 10, 1967 abandoned. This application May 22, 1969, Ser. No. 826,923

ROCK DRILL 15 Claims, 5 Drawing Figs.

U.S. Cl 173/138, 91/5, 173/105 1nt.Cl E21c 3/20, E21c 3/30 Field oiSearch 173/134-138,

[56] References Cited UNITED STATES PATENTS 3,468,222 9/1969 Cordes et al 173/134 X 1,703,840 2/1929 Maxson 91/5 2,743,741 5/1956 0rd 60/51 UX 3,183,668 5/1965 Johnson et a1. 60/51 3,192,717 7/1965 Lee 60/51 X 3,408,897 11/1968 Hoen et a1. 60/51 X FOREIGN PATENTS 1,033,739 6/1966 Great Britain 91/5 Primary ExaminerErnest R. Purser AtromeysCarl R. Horten, David W. Tibbott and Frank H.

Thomson ABSTRACT: A hydraulically powered impact tool particularly useful for rock drilling. The percussive tool is valveless with the hammer controlling the inflow and exhaust of motive liquid. The drill is powered by liquid under pressure from an outside source and from energy stored in storage chambers. Tanks positioned in the inlet and exhaust lines of the tool reduce pressure surges in the inlet and exhaust lines of the tool.

PATENTEUunv 1s

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3, 6 20 3 1 2 sum 1, or 2 INVENTOR EUGENE L. KRASNOFF ATTORNEY PATENTEDuuv 16 1971 3.620.312

sum 2 OF 2 INVENTOR EUGENE L. KRASNOFF ATTORNEY ROCK DRILL BACKGROUND OF THE INVENTION This application is a continuation-in-part of my copending application Ser. No. 728,854, filed May 13, 1968, now abandoned, which was a continuation of my then copending application Ser. No. 629,561, filed Apr. 10, 1967, now abandoned.

This invention relates to a liquid pressure powered reciprocating machine and more particularly to a liquid pressure actuated rock drill. The use of liquid as a motive fluid has, heretofore, created problems in reciprocating devices. Conventional liquid actuated drills and impact tools use a separate valve such as a spool valve to direct high-pressure liquid to produce the reciprocating motion in the hammer. Too, the use of such valving tends to result in a rather complex machine. The valving is likely to lead to pressure waves in the inlet and exhaust lines. This can result in poor and unstable valve and hammer motion, loss of energy and cavitation in both the inlet and exhaust lines and in the working cylinder. These problems are usually attributed to the low compressibility of the working fluid.

Attempts have been made to employ the compressibility of liquid to provide the motive force in drilling apparatus. Such a device often employs some means for moving with the piston or hammer into a liquid filled closed chamber which motion pressurizes the liquid in the chamber. The hammer is then released and is driven forward by the stored energy in the chamber. Arrangements such as these have not, however, been altogether satisfactory.

SUMMARY It is, therefore, the principle object of this invention to provide a novel liquid actuated reciprocating device which is capable of more efficient operation than prior such tools.

It is another object of this invention to provide a hydraulic fluid powered impact tool which eliminates the use of complex valving of the hydraulic fluid.

It is another object of this invention to provide a fluid actuated impact tool which uses two separate but related means for driving the piston of the tool.

It is a further object of this invention to provide a fluid actuated impact tool which has reduced pressure fluctuations in the input and exhaust lines.

In general, these objects are carried out by providing an impact tool which comprises a casing defining a cylinder; a hammer disposed for reciprocal movement within the cylinder and adapted to deliver an impact to a workpiece. The hammer defines with the casing at least one chamber. There is means for reciprocating the hammer including means for periodically pressurizing said chamber. There is energy storage means containing hydraulic fluid and communicating with said chamber through a port separate from said means for pressurizing said chamber for alternately receiving energy from said chamber and releasing energy to said chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned and other objects of this invention will become apparent when the following description is considered with the annexed drawings wherein:

FIG. I is a perspective view of a rock-drilling apparatus employing one embodiment ofthe present invention;

F IG. 2 is a longitudinal sectional view of a portion of a rock drilling embodying the present invention with the hammer shown in the impacting position;

FIG. 3 is a sectional view on an enlarged scale taken on the line 33 of FIG. 2 showing the hammer of the rock drill of the present invention at the beginning of the working stroke;

FIG. 4 is a sectional view taken on the line 44 of FIG. 3 looking in the direction of the arrows; and

FIG. 5 is a fragmentary detail showing a modification of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 shows a rock drill of a drifter type and is generally indicated at I. The drill is suitably mounted on a supportingapparatus 2 of any desired type.

The drill 1 includes a casing 4 having a central portion 5 having a longitudinal passage 6 therethrough. A sleeve 7 is mounted within the passage 6 and together with the casing 4 defines a cylinder 8. A hammer or piston 10 is mounted for reciprocal movement within the cylinder 8. The hammer 10 includes an enlarged diameter portion 11 which divides the cylinder 8 into a pair of chambers 8a and 8b. A backhead 9 closes one end of the cylinder 8 and a fronthead 12 is mounted on the forward end of the drill. A spacer 13 is positioned between the fronthead 12 and casing 4. The backhead 9 and fronthead 12 are held on the casing 4 by means of bolts 14.

A drill steel 15 having a drill bit 16 secured to one end is mounted in the fronthead 12 and extends into the forward end of the cylinder 8 where it is adapted to be struck by the hammer 10 as the hammer reciprocates. A centralizer I7 is mounted on the supporting structure 2 for guiding the drill steel 15.

Suitable apparatus for rotating the drill steel 15 has been provided. Such apparatus includes a rotary motor 20 mounted on the drill 1. The drive shaft 21 of the motor 20 rotates a spur gear 22 suitably mounted by means of bearings in the fronthead 12 of the drill. The spur gear 22 meshes with spur gear 23 which drives a spur gear 24. The gear 24 meshes with gear teeth 25 on a chuck 27. The chuck 27 is drivingly connected to a chuck jaw 29 which is provided with internal splines which mesh with splines 30 on the drill steel 15. As the chuck 27 and jaw 29 are rotated, the drill steel 15 is rotated. A retainer 32 holds the chuck jaw 29 and drill steel 15 in the fronthead of the machine. A cap 33 is threadedly secured to the fronthead 12 to hold the retainer 32 in position.

Air passages have been provided in the fronthead of the machine for supplying air under pressure to the bottom of the hole being drilled for blowing cuttings out of the hole. Air under pressure is supplied from a conduit 35 to a passage 36 in the fronthead of the machine. The passage 36 leads to an annular space 38 in the fronthead of the machine. A plurality of radial passages 39 are provided in the retainer 32 and lead to an annular passage 40 surrounding the drill steel 15. The drill steel 15 is provided with a longitudinal passage 41 and a radial passage 42 for receiving air from the annular passage 40 and conducting it to the bottom of the hole being drilled.

The central portion 5 of the casing 4 is provided with a plurality of annular passages. These passages have been designated by the numerals 50, SI, 52, 53, 54 and 55 proceeding from the back of the machine toward the front of the machine. The sleeve 7 is provided with radial passages which communicate with the annular passages in the casing 6. These passages have been designated 70, 71, 72, 73, 74 and 75 proceeding from the back of the machine toward the front of the machine.

Passages

72, 73, 74 and 75 each terminate in an

annulus

60, 61, 62 and 63. respectively. A second sleeve 78 is positioned within the sleeve 7 towards the back of the machine and is dimensioned to receive a portion of the hammer 10. The sleeve 7 is provided with an enlarged portion 79 at its forward end dimensioned to receive the forward portion of the hammer 10. The sleeve 78 is provided with radial passages 80 which terminate in an annulus 82 and radial passages 81 which terminate in an annulus 83. The

passages

80 and 81 communicate with the

radial passages

70 and 71 in the sleeve 7 and annular passages 50 and SI in the casing 5.

As can best be seen from FIG. 3, the casing 4 includes a pair of outboard energy storage chambers and 91. These energy storage chambers are closed at their ends by plugs and 96. Energy storage chamber 90 communicates with cylinder 8 through a port 94, annular passage 54 and radial passage 74. Energy storage chamber 91 communicates with the cylinder 8 through a port 92, annular passage 52 and radial passage 72.

At various points along its length, the hammer is provided with rows of circumferentially spaced longitudinal slots. These rows of slots have generally been indicated 64, 65, 66, 67 and 68 proceeding from the back of the hammer 10 toward the front. Although slots have been shown, the slots may be replaced by reduced diameter portions extending around the complete circumference of the hammer. The selection of slots as shown or a reduced diameter portion depends upon the particular machine and the fluid flow desired.

The drilling machine is further provided with pressure

wave filtering tanks

100 and 101. One of these tanks 100 is clearly shown in FIG. 2. The second tank 101 is a duplicate of the tank 100 in size and, shape and is positioned next to the tank 100, as can be seen from FIG. 1. The inlet tank 100 is provided with a conduit 103 for conducting hydraulic fluid under pressure from a suitable source'such as a reservoir and pump (not shown) to the interior of the tank 100. A pair of conduits 110 and 111 are positioned in the tank 100 for conducting fluid from the tank 100 to opposite sides of the enlarged portion 11 of the hammer 10. A conduit 121 is positioned in the tank 101 for exhausting fluid from both chambers formed on opposite sides of the enlarged portion 11 of the hammer 10. The outlet tank 101 is provided with a conduit 104 for conducting the hydraulic fluid back to the reservoir.

OPERATION Motive power for driving the hammer 10 forward to deliver an impact to the drill steel is supplied from energy stored in the chamber 91 and from the flow of hydraulic fluid through the inlet 103, filter wave tank 100 and inlet conduit 110. Motive power for raising the hammer is supplied from energy stored in the chamber 90 and from the flow of fluid through inlet 103, filter wave tank 100 and inlet conduit 1 1 1.

ln describing the operation, it will be assumed that, at start, the hammer 10 is in the position of FIG. 2 where it is delivering an impact to the drill steel 15. Hydraulic fluid such as oil under pressure is supplied from the line 103 to the tank 100. The oil under pressure flows through the conduit 111 in the tank 100 and through a port 1 15 in the casing portion 6 to the annular passage 55. From the annular passage 55, the fluid under pressure passes through the radial ports 75 and annulus 63 in the sleeve 7 to the row of slots 68. Fluid passes through the slots 68 to the chamber 80 formed on the forward side of enlarged portion 11 and acts on a shoulder 11a defined by the enlarged diameter portion 11 to move the hammer 10 rearwardly; i.e., toward the backhead 9. Since energy storage chamber 90 is always in communication with chamber 8a through port 94 and

passages

54, 74, and 62, fluid flows into the energy storage chamber 90 to pressurize it and thereby store energy.

At this time, the inlet passage defined by conduit 110, port 116, and

passages

51, 71, 81 and 83 is blocked by the upper portion of the hammer l0 and exhaust tank 101 is in commu-' nication with chamber 8b through

passages

122, 53 and 73 and slots 66. As the hammer moves upwardly, the shoulder 11b defined by the enlarged diameter portion 11 of the hammer 10 first exhausts fluid from the chamber 8b through the row .of slots 66 to annulus 61 and

passages

73 and 53 to passage 122 and conduit 121 into tank 101. Fluid then flows out of tank 101 back to the reservoir through line 104. After the hammer, 10 has moved a predetermined distance, the inlet port 75 and communication between slots 66 and annulus 61 are blocked. Energy previously stored in energy storage chamber 90 is released to chamber 80 to act on hammer 10 to continue the rearward movement of the hammer. Further rearward movement of the hammer will tend to compress liquid in the chamber 81;. Since the chamber is in communication with energy storage chamber 91 through port 92, annular passage 52, port 72 and annulus 60, the hydraulic fluid which fills chamber 91 will be compressed. Thus, as the hammer continues to move rearwardly, energy is stored in the chamber 91. As the hammer continues to move upward toward the top dead center position shown in FIG. 3, the slots 65 come into alignment with the annulus 83 which opens inlet port 71. At the same time, slots 67 become aligned with annulus 61 to permit chamber to communicate with exhaust port 73. Inertia keeps the hammer moving rearwardly toward the top dead center position shown in FIG. 3. Inlet port 71 and exhaust port 73 are opened before the top dead center position is reached because chamber 8b is not instantaneously pressurized when the inlet is opened and chamber 80 is not instantaneously exhausted when the exhaust port opens. The hammer requires a certain period of time to reverse its direction of movement. The opening of the inlet and exhaust ports before top dead center is reached insures efficient and stable operation of the system.

Fluid under pressure now flows from tank through conduit 110, port 116, annular passage 51, passages 71, annulus 83 and through slots 65 to act on shoulder 11b. The hammer 10 reverses its direction of movement and is driven forward by pressure in chamber 8b to deliver an impact to the drill steel 15. Because energy storage chamber 91 is always in communication with chamber 8b, the fluid under pressure from the inlet tank 100 also serves to further increase the pressure in energy storage chamber 91 and hence further increase the energy stored in the chamber 91. At this time, chamber 80 is exhausted through slots 67, annulus 61, port 73 and passage 53 to outlet port 122 which leads to conduit 121 positioned in outlet filter wave tank 101. The motive fluid is then exhausted from tank 101 through conduit 104.

As the hammer 10 moves forward, inlet port 71 and the exhaust of chamber 8a through port 73 are blocked. Since the energy storage chamber 91 is always in communication with chamber 9b, the energy previously stored in the chamber 91 is applied to the hammer 10 to thereby increase the force at which the hammer delivers an impact to the drill steel.

Continued forward movement of hammer 10 results in the opening of the inlet port 75 and the exhaust port for chamber 8b and the delivering of an impact to the drill steel. The inlet port 75 for chamber 80 and exhaust port for chamber 8b both open before the impact point for the same reasons that the inlet 71 for chamber 8b and exhaust port for chamber 80 both open before top dead center; i.e., to provide efficient and stable operation.

The cycle is repeated in rapid succession to deliver repeated impact blows to the workpiece.

The positioning and length of the rows of

slots

64, 65, 66, 67 and 68 and the positioning and size of the

ports

70, 71, 72, 73 and 75 with respect to each other is important. Communication between chamber 8open and inlet port 71 through slots 65 and communication between chamber 80 and outlet port 73 through slots 67 must occur at almost exactly the same time. Communication between chamber 80 and inlet port 75 through slots 68 and communication between chamber 81; and outlet port 73 through slots 66 must also occur at almost the same time. Communication between chamber 8a and outlet 73 will be blocked before inlet 75 is opened so that energy may be stored in the energy storage chamber 90 and communication between chamber 8b and outlet 73 will be blocked before inlet 71 is open so that energy will be stored in accumulator 91.

In order to further increase the impacting force of the hammer, a portion 131 of the cylinder 8 above the hammer may be filled with air or a hydraulic fluid. A passage for supplying fluid to chamber 131 is opened upon delivering an impact to the workpiece so that a charge of whatever fluid fills chamber 131 will make up for any leakage which may occur. As the hammer moves rearwardly, the passage 130 is closed. Continued rearward movement of the hammer 10 causes the fluid in the chamber 130 to be compressed. When the hammer starts its forward movement, the energy stored in chamber 131 is transferred to the hammer to increase the impacting force at which the hammer strikes the workpiece.

In general, overtravel of the hammer is prevented by the fact that the hammer reciprocates on a hydraulic cushion. As

an added safety feature to prevent the hammer from contacting important surfaces such as

shoulders

133 and 134 after it delivers an impact, an overtravel safety apparatus has been provided. Such apparatus includes means for conducting fluid from the working side of the hammer to the accumulator 91 to thereby reduce the pressure on the working side of the hammer below that in the return side of the hammer. If overtravel occurs, the slots 64 will provide communication between inlet port 81 and port 80. Fluid under pressure will travel through radial port 70 and annular passage 50 to passage 135 which leads to the accumulator 91. The length and diameter of the passage 135 are important to the operation of the overtravel safety apparatus to insure that pressure fluctuations and cavitation do not occur.

As an alternative embodiment, rather than using

energy storage chambers

90 and 91, an intensifier such as that shown in FIG. 5 may be used. In this arrangement, a chamber 150 is filled with hydraulic fluid. An intensifier piston 151 has a first diameter portion 152 and a second enlarged diameter portion 153. The enlarged diameter portion communicates with the cylinderB through a passage 154. If the passage 154 is in communication with annular passage 54, when the hammer moves forward, fluid under pressure acts on piston portion 153 causing the piston 151 to move downward and pressurize the chamber 150. The stored energy in chamber 150 is released to the cylinder 3 by acting on reduced diameter end 152 to move the piston 151 up. A charging port 155 may be provided to replace liquid which may leak from the chamber 150.

From the foregoing it is apparent that the objects of this invention have been carried out. A novel impact delivering tool has been provided which can be operated exclusively on hydraulic fluid. The compressibility of hydraulic fluid is used to increase the efficiency of the rock drill. Motive power is provided by both fluid flow from an outside source such as a pump and stored energy from the

energy storage chamber

90 and 9!. The length of inlet conduits 110 and 111 connecting filter tank 100 to the working cylinder 8 and the outlet conduit 121 connecting the working cylinder 8 to the outlet tank 101 must be coordinated to the size of the drill and the

tanks

100 and 101 and the pressure at which the drill is operating. Pressure fluctuations and cavitation are eliminated by using large pressure

wave filtering tanks

100 and 101.

lclaim:

l. A hydraulically powered actuator comprising:

a casing defining a cylinder;

a piston mounted for reciprocal movement within the cylinder and having a pressure surface thereon;

supply means for supplying hydraulic fluid under pressure into the cylinder to act on such surface to move the piston in one direction and exhaust means for exhausting the hydraulic fluid from the cylinder;

hydraulic fluid energy storage means having constant com munication with a surface on said piston such that the pressure of hydraulic fluid therein continuously urges the piston in said direction and having communication with said supply means;

valve means operatively associated with said supply means and exhaust means and actuated so that hydraulic fluid is supplied into the cylinder to move the piston in said one direction and to pressurize the hydraulic fluid energy storage means during a first part of the piston travel from an initial position, then cuts off the supply of hydraulic fluid to the cylinder and the hydraulic fluid energy storage means during a second part of its travel from the initial position so that thereafter only the hydraulic fluid energy stored in the energy storage means moves the piston, and then during the last part of its travel, hydraulic fluid is exhausted from the hydraulic fluid energy storage means; and

compression means adapted to be compressed by the piston as the piston travels in said one direction to its final positron.

2. A hydraulically powered actuator in accordance with claim 1 wherein the compression means in the cylinder adapted to be compressed by the piston is a chamber containing a fluid.

3. A hydraulically powered actuator in accordance with claim 1 wherein the piston has a shoulder defining said pressure surface and said surface is continuously exposed to the pressure of hydraulic fluid in the energy storage means and said piston is provided with rows of circumferentially spaced slots and dimensioned to serve as the valve means so that the hydraulic fluid fed into the cylinder flows through one row of circumferentially spaced slots and against said shoulder surface during the first part of the travel of the piston from an initial position and hydraulic fluid is exhausted through another row of circumferentially spaced slots during the last part of the travel of the piston.

4. A hydraulically powered actuator in accordance with claim 1 in which said valve means is actuated when the piston is moved in the opposite direction to first continue the exhaust of hydraulic fluid, then close such exhaust so that hydraulic fluid in the energy storage means is pressurized by movement of the piston, and thereafter opens the supply means to further pressurize the hydraulic fluid in the energy storage means.

5. A hydraulically powered actuator in accordance with claim I in which the valve means is actuated to open the supply means in the event the piston during the last part of its travel is said one direction moves beyond a predetermined position.

6. A hydraulically powered actuator comprising:

a casing defining a cylinder;

a piston mounted for reciprocal movement within the cylinder;

means for supplying hydraulic fluid under pressure into the cylinder to reciprocate the piston and means for exhausting the hydraulic fluid from the cylinder; first and second hydraulic fluid energy storage means located so that a first surface and a second surface of the piston are continuously exposed to hydraulic fluid in the first and second hydraulic fluid energy storage means, respectively; said piston being shaped so that hydraulic fluid fed into the cylinder to move the piston in one direction pressurizes the hydraulic fluid energy storage means during a first part of its travel from an initial position, then directly cuts off the flow of hydraulic fluid to the hydraulic fluid energy storage means during a second part of its travel from the initial position so that thereafter only the hydraulic fluid energy stored in the first energy storage means and acting against said first piston surface moves the piston, and after the beginning of said second part of its travel, permits hydraulic fluid to be fed into the cylinder to later move the piston in the other direction. 7. A hydraulically powered actuator in accordance with claim 6 wherein the surfaces of the piston continuously exposed to hydraulic fluid in the hydraulic fluid energy storage means are shoulders and said piston is provided with rows of circumferentially spaced slots located on the piston and dimensioned so that the hydraulic fluid fed into the cylinder flows through a row of circumferentially spaced slots and against a shoulder during the first part of the travel of the piston from an initial position.

8. Apparatus for delivering an impact to a workpiece comprising:

a casing defining a cylinder; a hammer disposed for reciprocal movement within the cylinder and adapted to deliver an impact to a workpiece;

said hammer defining with said cylinder a pair of chambers with one of said chambers containing hydraulic fluid to move the hammer in one direction and said casing having a port extending from the other of said chambers;

energy storage means connected to said port;

means for supplying hydraulic fluid under pressure to said other chamber to move said hammer in the other direction and means for exhausting hydraulic fluid from said other chamber;

said hammer being shaped to directly control the supply of hydraulic fluid into said other chamber to thereby pressurize said other chamber and the energy storage means during a first part of its travel from an initial position and then to directly cut off the flow of hydraulic fluid to said other chamber so that energy stored in the energy storage means is applied against the hammer and is the only force moving the hammer during a second part of its travel from the initial position and to exhaust said other chamber during the last part of its travel in said other direction.

9. An apparatus in accordance with claim 8 wherein the hammer is provided with slots located on the hammer and dimensioned so that hydraulic fluid fed into the cylinder flows through said slots and into said other chamber during the first part of the travel of the hammer from an initial position.

10. An apparatus in accordance with claim 9 wherein compression means are provided in the cylinder and adapted to be compressed by the hammer as the hammer travels from its initial position to its final position.

11. An apparatus in accordance with claim 10 wherein the compression means in the cylinder adapted to be compressed by the hammer is a chamber containing a fluid.

12. Apparatus for delivering an impact to a workpiece comprising:

a casing defining a cylinder;

a hammer disposed for reciprocal movement within the cylinder and adapted to deliver an impact to a workpiece;

said hammer defining with said cylinder a pair of chambers and said casing having a port extending from each chamber;

an energy storage means connected to each port; and

means for supplying hydraulic fluid under pressure altern'ately to each chamber to reciprocate said hammer and means for exhausting the hydraulic fluid from the cylinder;

said hammer being shaped to directly control the feeding of hydraulic fluid into each chamber to thereby pressurize said chamber and its associated energy storage means during a first part of its travel from an initial position and then to directly cut off the flow of hydraulic fluid to said chamber so that energy stored said energy storage means is applied against the hammer during a second part of its travel from the initial position.

13. An apparatus in accordance with claim 12 wherein the hammer is provided with rows of circumferentially spaced slots located on the hammer and dimensioned so that the hydraulic fluid fed into the cylinder flows through a row of slots and into its associated chamber during the first part of the travel of the hammer from an initial position.

14. An apparatus in accordance with claim 13 wherein the cylinder is provided with compresion means adapted to be compressed by the hammer as the hammer moves away from the workpiece.

15. An apparatus in accordance with claim 14 wherein the compression means is a chamber containing a fluid.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 620,3l2 Dated November 16, 1971 Inventor(s) Eugene L. Krasnoff It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the drawings, Fig. 2, delete the passageway, the leading line, and identifying numeral 135. Fig. 3, add a passageway through casing 4 connecting annulus 50 and energy storage chamber 91 giving it a leading line, and identifying numeral 135. Also in Fig. 3, correct the leading line from numeral 81 to the next port leftward. Column 4, line 33, "chamber 9b" should read chamber 8b Signed and sealed this 12th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 3M PO-lOSO (YO-69} v u 5 GOVERNMENT Pwwrmo orrrcs sass o 'sasaun

Claims

1. A hydraulically powered actuator comprising: a casing defining a cylinder; a piston mounted for reciprocal movement within the cylinder and having a pressure surface thereon; supply means for supplying hydraulic fluid under pressure into the cylinder to act on such surface to move the piston in one direction and exhaust means for exhausting the hydraulic fluid from the cylinder; hydraulic fluid energy storage means having constant communication with a surface on said piston such that the pressure of hydraulic fluid therein continuously urges the piston in said direction and having communication with said supply means; valve means operatively associated with said supply means and exhaust means and actuated so that hydraulic fluid is supplied into the cylinder to move the piston in said one direction and to pressurize the hydraulic fluid energy storage means during a first part of the piston travel from an initial position, then cuts off the supply of hydraulic fluid to the cylinder and the hydraulic fluid energy storage means during a second part of its travel from the initial position so that thereafter only the hydraulic fluid energy stored in the energy storage means moves the piston, and then during the last part of its travel, hydraulic fluid is exhausted from the hydraulic fluid energy storage means; and compression means adapted to be compressed by the piston as the piston travels in said one direction to its final position.

5. A hydraulically powered actuator in accordance with claim 1 in which the valve means is actuated to open the supply means in the event the piston during the last part of its travel in said one direction moves beyond a predetermined position.

6. A hydraulically powered actuator comprising: a casing defining a cylinder; a piston mounted for reciprocal movement within the cylinder; means for supplying hydraulic fluid under pressure into the cylinder to reciprocate the piston and means for exhausting the hydraulic fluid from the cylinder; first and second hydraulic fluid energy storage means located so that a first surface and a second surface of the piston are continuously exposed to hydraulic fluid in the first and second hydraulic fluid energy storage means, respectively; said piston being shaped so that hydraulic fluid fed into the cylinder to move the piston in one direction pressurizes the hydraulic fluid energy storage means during a first part of its travel from an initial position, then directly cuts off the Flow of hydraulic fluid to the hydraulic fluid energy storage means during a second part of its travel from the initial position so that thereafter only the hydraulic fluid energy stored in the first energy storage means and acting against said first piston surface moves the piston, and after the beginning of said second part of its travel, permits hydraulic fluid to be fed into the cylinder to later move the piston in the other direction.

7. A hydraulically powered actuator in accordance with claim 6 wherein the surfaces of the piston continuously exposed to hydraulic fluid in the hydraulic fluid energy storage means are shoulders and said piston is provided with rows of circumferentially spaced slots located on the piston and dimensioned so that the hydraulic fluid fed into the cylinder flows through a row of circumferentially spaced slots and against a shoulder during the first part of the travel of the piston from an initial position.

8. Apparatus for delivering an impact to a workpiece comprising: a casing defining a cylinder; a hammer disposed for reciprocal movement within the cylinder and adapted to deliver an impact to a workpiece; said hammer defining with said cylinder a pair of chambers with one of said chambers containing hydraulic fluid to move the hammer in one direction and said casing having a port extending from the other of said chambers; energy storage means connected to said port; means for supplying hydraulic fluid under pressure to said other chamber to move said hammer in the other direction and means for exhausting hydraulic fluid from said other chamber; said hammer being shaped to directly control the supply of hydraulic fluid into said other chamber to thereby pressurize said other chamber and the energy storage means during a first part of its travel from an initial position and then to directly cut off the flow of hydraulic fluid to said other chamber so that energy stored in the energy storage means is applied against the hammer and is the only force moving the hammer during a second part of its travel from the initial position and to exhaust said other chamber during the last part of its travel in said other direction.

12. Apparatus for delivering an impact to a workpiece comprising: a casing defining a cylinder; a hammer disposed for reciprocal movement within the cylinder and adapted to deliver an impact to a workpiece; said hammer defining with said cylinder a pair of chambers and said casing having a port extending from each chamber; an energy storage means connected to each port; and means for supplying hydraulic fluid under pressure alternately to each chamber to reciprocate said hammer and means for exhausting the hydraulic fluid from the cylinder; said hammer being shaped to directly control the feeding of hydraulic fluid into each chamber to thereby pressurize said chamber and its associated energy storage means during a first part of its travel from an initial position and then to directly cut off the flow of hydraulic fluid to said chamber so that energy stored in said energy storage means is applied against the hammer during a second part of its travel from the initial position.

14. An apparatus in accordance with claim 13 wherein the cylinder is provided with compression means adapted to be compressed by the hammer as the hammer moves away from the workpiece.