US3404603A

US3404603A - Hydraulically operated tools

Info

Publication number: US3404603A
Application number: US544598A
Authority: US
Inventors: Addison Edward; Jackson John Peter
Original assignee: Vickers Ltd
Current assignee: Vickers Ltd
Priority date: 1965-04-23
Filing date: 1966-04-22
Publication date: 1968-10-08
Anticipated expiration: 1985-10-08
Also published as: GB1125755A; DE1503222A1; CH455675A

Description

AIDDISQN ETAL HYDHAULI CALLY OPERATED TOOLS 3 heets-Sheet 1 Filed April 22, 1966 Q NR K W% Oct. 8, 1968 E. ADDISON ETAL HYDRAULICALLY OPERATED TOOLS 3 heets-$heet 2 Filed April 22, 1966 Oct. 8, 1968 E. ADDiSON ETAL. 3,404,603

HYDRAULICALLY OPERATED TOOLS Filed April 22, 1966 3 Sheets-Sheet 3 United g States Patent 3,404,603 HYDRAULICALLY OPERATED TOOLS Edward Addison and John Peter Jackson, Weymouth, Dorset, England, assignors to Vickers Limited, London,

England, .a British company 1 Filed Apr. 22, 1966, Ser. No. 544,598 Claims priority, application Great Britain, Apr. 23, 1965, p 17,350/ 65 Claims. (Cl. 91-5) .A hydraulically operated reciprocating tool whose fluid supply is external. A double acting piston imparts repeated blows on a tool head and each forward stroke is assisted by. a hydraulic spring fitted on the tool, while the fluid forced from the exhaust side of the piston during this stroke is ducted through the tool to reduce back pressure effects onthe piston rod. The return stroke is slower since the hydraulic spring is then being energized by the returning piston. The valve means for directing the fluid supply preferably consists of a ported cylinder, also reciprocable, in which the piston slides.

i This invention relates to hydraulically operated tools.

According to the present invention there is provided a hydraulically operated tool comprising a body; a double acting piston and cylinder assembly in the body; means for imparting, when the piston and cylinder are relatively reciprocated, motion to a tool head for engaging the work on which the tool is to operate; an inlet for connection to a source of fluid under pressure, there being ducting in the body from said inlet to the piston and cylinder assembly; valve means co-operating with the ducting operable alternately to connect, in use of the tool, the inlet with one and the other of the variable volume chambers of the piston and cylinder assembly to produce a forward stroke and a return stroke respectively of the piston; and a hydraulic spring which operates on the same liquid as that used, fpr actuating the piston, such liquid in the spring being slightly compressed by a member, which co-operates with said piston, upon the return stroke of the latter, thereby storing energy which is subsequently imparted by said members to said piston to assist its forward stroke.

For a better understanding of the present invention and to show how the same may be carried into efl'ect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIGURE 1 is an axial section of a hydraulic hammer with its middle portion shown in outline,

I FIGURE 1A is an axial section, to a larger scale, of the middle portion of the hammer of FIGURE 1,

FIGURE 2 is a partly sectioned side view of a tool holder forming part of the hammer of FIGURE 1, and

FIGURE 3 is a section of a hydraulic fluid accumulator incorporated in the hammer of FIGURE 1.

In the following description the right hand end of the hammer as shown in FIGURE 1 will be referred to as the lower end and the left hand end as the upper end of the hammer.

The hammer of FIGURES 1 and 1A has a cylindrical body or casing 1 having an axial bore 1a in which a sleeve 2 is slidably mounted. The sleeve 2 has an outer surface of uniform radius but its inner surface is of a smaller radius at the central portion 2a of the sleeve than at the lower end portion 2b and the upper end portion 2c of the sleeve. The sleeve 2 therefore has a lower shoulder 2d and an upper shoulder 2e at the junction of the portions 2a and 2b, and 2a and 2c. The ends of the sleeve. are bevelled. A double piston 3 is a close sliding fit within the central portion 2a of the sleeve 2 and is in 3,404,603 Patented Oct. 8, 1968 the form of a cylindrical block with a shallowannular recess 4 around the central portion of the block. From the lower end of the piston 3 a rod 5 extends beyond the body 1 and is a close sliding fit in the spigot 6a of a closure cap 6. The spigot 6a fits within the lower end portion 2b of the sleeve 2 and an O-ring 7 in an annular groove in the cap 6 provides a seal between the latter and the body 1. A cover plate 8 in the for-m of a disc with athickened central portion apertured to receive the rod 5 covers the lower end of the body 1 and retains the cap 6 in position against the body 1. A gland 8a surrounding the rod 5 is fitted in a recess in the lower end of the cap 6 and the thickened central portion of the cover plate 8 is entered in this recess to retain the gland therein. A chamber 9 is formed around the rod 5 between the lower end face of the piston 3, the end face of the spigot 6a and the inner surface of the sleeve 2.

From the upper end face of the piston 3 extends a rod 10 of greater cross-sectional area than the rod 5, this rod 10 being a close sliding fit within a spigot 11a of a cap 11 covering the upper end of the body 1. The spigot 11a fits within the upper end portion 20 of the sleeve 2. A chamber 12 is formed around the rod 10 between the upper end face of the piston 3, the end face of the spigot 11a and the inner surface of the sleeve 2.

A dome 13 covers the cap 11 and has handles 13a thereon. The dome 13, the cap 11 and the body 1 are secured together by bolts 14 and a block 15 is clamped by its annular flange 15a between the body 1 and the cap 11, the flange 15a fitting closely within a cylindrical recess in the cap 11. A seal 16 is provided between the lower face of the flange 15a and the cap 11 and a seal 17 between the upper face of the flange 15a and the base of the dome 13. The rod 10 enters freely Within a recess in the block 15 forming a cylindrical chamber 15b, and a hydraulic spring piston 18 having a cap 18a on its upper end extends from the upper end of the rod 10 through an axial bore in the block 15, which acts as a guide for the piston 18, into the chamber 19 formed between the dome 13 and the block 15. The chamber 19 is filled with fluid at high pressure. A block 20 on the lower end of the rod 18 is trapped by a T-slot formed in the upper end of the rod 10, this slot giving a lost motion connection between the piston 18 and the rod 10. There is clearance between the piston 18 and the stem of the T-slot 21 and clearance between the block 20 and the ends of the transverse part of the T-slot 21. The slot 21 is connected via an axial passage 22 in the rod 10 and radial passages 23 in the piston 3 wit-h the annular recess 4. The piston 18 has radial passages 24 at a point intermediate its length which meet in an axial passage 25 which extends to the upper end of the piston 18 through the cap 18a to open into the chamber 19. At the summit of the dome opposite the upper end of the rod 18 there is provided a vent plug 26. An inclined pasage 27 in the base of the dome leads from the chamber 19 to a non-return valve 28 housed in the flange 15a of the block 15. The valve 28 is biased by a spring 29 to seat against the upper end of an aperture 30 through the flange 15a, the lower end of the aperture 30 opening into a radially extending recess in the base of the block 15.

A socket 31 for a pressure supply line (not shown) is provided on the lower end of the body 1. At the base of this socket is a chamber 32 in which is disposed a valve poppet 33 urged by a spring 34 against a valve seat 35. A rod 36 for shifting the puppet 33 is guided in a bore, parallel to the axis of the hammer, formed through the body 1, the cap 11, the flange 15a and the base of the dome 13, and is operable by means of a lever 37 pivoted on one of thehandles 13a. The valve seat 35 is at the lower end of a cylindrical chamber 38 Whose axis is parallel to the axis of the hammer. The lower end of the rod 36 passes through this chamber 38, which has a closed upper end. Co-axially arranged within this chamber 38 is a perforated tube 39 spaced from the cylindrical wall of the chamber 38. The tube 39 is located by a recesss 40 formed in the body 1 at the upper end of the chamber 38. A cylindrical gauze filter 41 lines the inner surface of the tube 39, the gauze extending over the perforations in that tube.

A duct 42 leads from the upper end of the chamber 38 to an annular groove 43 formed in the bore 1a of the body 1 which receives the sleeve 2. A duct 44 leads from near the bottom of the chamber 38 to another annular groove 45 formed in the bore 1a. Between the

grooves

43 and 45 two

further grooves

46 and 47 are formed in the bore 1a. These grooves are shallower than the

grooves

43 and 45, the groove 46 being connected by a duct 48 with an annular chamber 49 between the lower end of the body 1 and the cap 6, and the groove 47 being connected by a duct 50 with an annular chamber 51 formed between the upper end of the body 1 and the cap 11. The chamber 49 can receive the lower end portion 2b of the sleeve 2 and the chamber 51 can receive the upper end portion 20 of the sleeve 2. An annular groove 52 of similar size to the

grooves

43 and 45 is formed in the bore 1a between the groove 45 and the chamber 49. A similar groove 53 is formed between the groove 43 and the chamber 51. Both grooves 52 and 53 are connected to an exhaust duct 54 extending parallel to the axis of the hammer and open at its upper end to the recess c and via that recess to the chamber 15b. The grooves formed in the bore 1a of the body 1 are symmetrically arranged either side of the plane midway between the

grooves

46 and 47. An exhaust or return line socket 55 in the exterior of the body 1 communicates with the duct 54 and a passage 56 through the body 1 and the cap 6 places an annular groove 6b in the inner cylindrical surface of the cap -6 in communication with the exhaust duct 54 and thus the exhaust line socket 55.

A tube 57 having a flange 57a is secured to the underside of the plate 8 by bolts 58 passed through the flange 57a and through the plate 8 to engage in the body 1. This tube 57 houses a hammer head 59 attached to the lower end of the piston rod 5. The lower end of the rod 5 is formed with an annular notch 60 around which is engaged a split collar 61. A cylindrical collar 62 retains the collar 61 on the rod end and a retainer ring 63 is screwed into a recess in th upper end of the hammer head with clearance between the ring and the rod 5 and between the ring and the curved outer surface of the collar 62. The ring 63 is locked to the hammer head 59 by a grub screw 63a. This arrangement permits slight freedom of radial movement between the hammer head 59 and the rod 5 whilst securing the head 59 against any axial movement relative to the rod 5.

A cover 64 is welded over the lower end of the tube 57 and a tool head holder or guide 65 is resiliently mounted below the cover 64. A tool head 66 is permitted limited axial mvement within this holder 65, the upper end of the tool head extending through the cover 64 and through a buffer plate 67 mounted on a rubber ring on the upper side of the cover 64. Studs 69 extending downwardly from the cover 64 through a flange at the upper end of the holder 65 each have a disc 70 retained by a nut 71 on the lower end thereof. Springs 72 acting between each flange and associated disc urge the holder against the cover 64. The holder 65 has lugs 73 between which is pivoted a safety catch 74. The catch 74 is in the form of a bell-crank lever mounted on a pivot pin 75. The longer armof the lever normally extends upwardly along the side of the holder 65 and the shorter arm extends inwardly to engage the tool head 66 at a location below a collar 664: formed thereon. It is the collar 66a engaging the holder 65 and the catch 74 that limits the movement of the tool head relative to the body 1. A cylindrical recess 76 is provided in the holder '65 and a plunger 77 entered in the recess 76 is urged by a spring 78 against the base I w J j: of the shorter arm of the catch 74 to maintain the catch engaged with the tool head 66. The catch 74 can be turned in an anti-clockwise direction (FIGURE 2) against the action of the spring 78 to release the tool head 66.

The sleeve 2 has porting for co-operating with the grooves in the bore 1a of the valve body 1. At the upper end of the portion 2a of the sleeve 2, adjacent the shoulder 2e, ports 79, through the sleeve are spaced around the sleeve 2, each port 79 having a width, measured. in the axial direction of the sleeve, that is half the width of the grooves 43 or 53'. At the lower end of the portion 2a, adjacent the shoulder 2d, there is another similar set of ports 80 which have a widthhalf that of the grooves 45 or 52. The lands between the grooves 43 and 53 and between the grooves 45 and 52 each have an axial extent equal to the width measured in the axial direction of the sleeve of the ports 79 and 80. Between the ports 79 and 80 on the outer surface of the portion 2a are formed annular grooves 81 and 82, these grooves having the same width as the

grooves

46 and 47. Ports 83 at the lower end of the groove 81 place that groove in communication with the inside of the sleeve 2. Ports 84 at the upper end of the groove 82 place that groove also in communication with the inside of the sleeve 2. The grooves 81 and 82 are spaced apart by an amount equal to the spacing between the

grooves

46 and 47 and the ports 79 and 80 are symmetrically disposed either side of the grooves 81 and 82, the centre to centre spacing between corresponding ports 79 and 80 being equal to the centre of centre axial spacing of the grooves 43 and 52 and that between the grooves 53 and 45.

The accumulator shown in FIGURE 3 is for attenuating pressure pulses in the supply line of hydraulic fluid to the hammer. This accumulator is arranged between the chamber 38, which in use of the hammer has high pressure fluid therein, and the exhaust duct 54. A passage 85 leads from the chamber 38 and has at its end remote from the chamber 38 a wider portion in which a piston 86 is a close sliding fit. Between the passage 85 and the exhaust duct 54 is a cylindrical chamber 87 in which the piston rod 88 of the piston 86 is co-axially arranged, its end remote from the piston 86 being slidably entered in a recess in a plug 89 which closes the chamber 87. A pile of spring dished washers 90 surrounding the rod 88 are arranged with adjacent washers convex in opposite directions to form a spring assembly which acts between the piston 86 and the plug 89, urging the piston 86 into the wider portion of the passage 85. The chamber 87 opens into the exhaust duct 54 through a port 91. Any excess pressure in the chamber 38 is absorbed by movement of the piston 86 against the resistance of the pile of spring washers 90.

For use of the hammer, a tool head 66 for engaging the work on which the hammer is to operate is mounted in the holder 65 and held there by the safety catch 74. A pressure supply line is connected to the socket 31 by (for example) a self-sealing coupling and an exhaust return line is connected to the socket 55.

There will now be described a complete cycle of the hammer starting from the position shown in FIGURE 1. It will be assumed that the valve poppet 33 has been shifted away from the valve seat 35 by the lever 37. The sleeve 2 is at the limit of its downstroke and the piston 3 is at the limit of its upsroke. Fluid in the groove 51 is at exhaust pressure, the groove 51 being in communication with exhaust through the duct 50, the groove 47, the ports 84, the chamber 9 and the ports 80. The chamber 12 is filled with high pressure fluid which has entered the chamber 12 via the duct 42, the annular groove 43 and the ports 79. The chamber 19 is also filled with fluid at high pressure and the piston 20 is therefore assisting in urging the rod 10 downwards. In practice the principal force on the piston 3 will be from the piston 20 rather from the fluid in the chamber 12. The grooves 45 and 53 are blanked ofl? by the ut surf of the sleeve 2,.the lower end. of the piston 3 blocks the ports 83, and-fluid in the chamber 49 is at exhaust p'ressure, the chamber 49 having just been cut off from exha'ust viathe recess 4, thezpassages 23 and 22, the'T-slot ZLtheachamber 15b and the recess15c by the piston 3 blocking the ports 83. The high pressure fluid in the chamber 12 acting on the shoulder 2e maintains the sleeve 2 against the'cap6.

With high pressure fluid in the chamber 12 and the piston 18 urging therod downwards, the downstroke begins. The ports 79 are immediately completely opened by the piston 3 moving downwards, fluid is expelled from the chamber 9, and the recess 4 in the piston 3 comes into registry with the ports 83. Some fluid from the chamber 9 escapes to the exhaust return line, but most of the fluid from the chamber 9 passes along the duct 54 and the recess c and into the chamber 15b which is being vacated by the rod 10. At the same time the ports 84 are sealed off by the piston 3 but will later also come into registry with the recess 4 as the ports 83 are about to be cut-off again by the piston 3. No change takes place in the position of the sleeve 2 since fluid at high pressure still acts on the shoulder 2e.

Further downward movement of the piston 3 forces more fluid from the chamber 9 into the recess 15c and thence into the chamber 15b, and uncovers the ports 83 again. Fluid at inlet pressure is therefore admitted via the duct 48 to the chamber 49, and this high pressure fluid, by virtue of the bevelled edge of the end of the sleeve portion 2b exerts an upward pressure on the sleeve 2 greater than the downward force on the shoulder 2e. The sleeve 2 therefore starts to move in an upward direction, opposite to that of the piston 3. Oil from the chamber 51 escapes via the duct 50 and the ports 84 into the recess 4 and thence into the passages 23 and 22.

As the piston 3 reaches the bottom of its downstroke, the sleeve 2 moves up to abut the cap 11, the ports 79 being moved away from the groove 43 and coming into registry with the groove 53 so that the chamber 12 is open to exhaust via the port 79, the groove 53 and the duct 54. The groove 43 is blocked by the outer surface of the sleeve 2 but the groove 45 is in communication via the ports 80 with the chamber 9 and therefore high pressure fluid acts on the bottom end face of the piston 3 and on the shoulder 2d at the bottom of the middle portion 2a of the sleeve 2. The sleeve 2 is therefore urged against the cap 11 and the piston 3 is started on its return or upstroke. At the bottom of its stroke the hammer head 59 delivers a blow on the tool head 66. Should it overrun beyond a certain limit the head 59 is arrested by the buffer plate 67 which offers a resilient resistance by virtue of its mounting on the rubber ring 68. The cover 64 offers a final stop to the buffer plate 67. Also at the bottom of the stroke, the rod 10 moves so that the block is left at the top of the transverse part of the T-slot 21 since the cap 18a on the upper end of the piston 18 arrests the piston 18 before the piston 3 bottoms.

The pressure of fluid in the chamber 9 pushes the piston 3 upwards and exhaust fluid from the chamber 12 is expelled through the ports 79, via the groove 53 to the exhaust duct 54. The sleeve 2 remains in its uppermost position. The bottom of the transverse part of the T-slot 21 re-engages the bottom end face of the block 20 and forces the piston 18 up into the chamber 19, compressing the fluid in that chamber and storing up energy for the downstroke. The sequence of events during the return stroke corresponds to similar ones on the downstroke and the change-over of the sleeve at the end of the stroke is similar to what has already been described.

It will be understood that the downstroke is faster than the upstroke. This is because the downstroke is assisted by the pressure of fluid in the chamber 19 acting through the piston 20, and the freer exhaust created by the chamber 9 partly diverted to the expanding chamber 15B rather than wholly via the passage 55. andythejfull resistance of the exhaust line. Also, on the return stroke, the piston 3 has to work against the action of the fluid under pressure in the chamber 19,.andthepiston-rod 10 has to do work in expelling fluid from the recess 15b. The duct 54 has the effect of evening out the flowrpulses in the exhaust line.

Should the pressure difference between the fluid in the exhaust-duct 54 and in the chamber19fall'below a certain value, the non-return valve 28 will open 'the aperture 30 so that any loss. of oil from the chamber 19 is made up. Fluid-that might leak from the chamber 19 along the rod 5 between the latter and the.spigot .6u of the cap 6 will be vented via the groove 6b and the passage 56 to exhaust. Any fluid that passes beyond the groove 61: is prevented from escaping by the gland8a.

Fluid in the chamber 19 is compressed slowly on the upstroke of the piston 18 as compared with the decompression that takes place when the piston 18 is on the downstroke. Oil on the piston 18 in the close clearance fit in the block 15 leaks or is wiped off at dilferent rates and this might cause a possible pumping action in which oil would be injected from the chamber 15b into the chamber 19, building up the pressure of fluid in that chamber. This would have the undesirable effect of making the spring effect of the piston 18 stiffer. The

passages

25 and 24 allow excess pressure fluid in the chamber 19 to escape into the chamber 15b at the bottom of the hammer stroke.

The fluid used in the above described hammers will have a certain compressibility to permit movement of the piston 18. A normal mineral oil having a compressibility such that the volume change is /2 per 1,000 p.s.i. has been found suitable. For example with a W in. diam eter piston (.249 in. area) having a 2 in. stroke in a 25 cubic inch chamber 19, the .498 in. compression gives a peak pressure of 3,990 psi. and a stiffness of 496 lbs./ inch.

The porting in the sleeve 2 has been described as symmetrical. In order to assist the difference in speed in downward and return stroke the porting could be modified to make the arrangement asymmetrical or the piston 3 could have its upper end face cut back so that on the down stroke the ports 83 would be uncovered earlier to cause an earlier shift of the sleeve 2.

What is claimed is:

1. A hydraulically operated tool comprising (a) a body with ducting therein for hydraulic fluid and with an inlet and outlet for connection to an external fluid supply.

(b) a double acting piston and cylinder assembly in the body and having a first variable volume chamber for pressure fluid supplied thereto to cause a forward stroke and a second variable volume chamber for pressure fluid supplied thereto to cause a return stroke.

(c) a tool head for engaging the work on which the tool is to operate,

(d) means for imparting motion to the tool head when the piston and cylinder are relatively reciprocated,

(e) valve means co-operating with said ducting for alternately connecting said first and second chambers to said inlet via said ducting,

(f) a hydraulic spring mounted on said body and operative on said hydraulic fluid,

(g) a member connecting said spring with the piston of said assembly to urge the latter in the direction of said forward stroke and to store energy by compressing the fluid in said spring on said return stroke,

(h) a third chamber is said body between said first chamber and said hydraulic spring into which said connecting member extends and into which a piston rod of the piston and cylinder assembly extends, the connecting member and said piston rod being coupled in said third chamber, and

(i) further ducting in said body between said third chamber and said second chamber and connected to said outlet, closed by said valve means on the return stroke for fluid in said third chamber to escape to said outlet and opened by said valve means on the forward stroke to pass fluid from said second to said third chamber.

2. A tool according to claim 1, wherein the means for coupling said connecting member and said piston rod in said third chamber is a lost motion connection.

-3. A tool according to claim 1, including a one-Way valve in said body between said further ducting and said hydraulic spring for passage of fluid from said further ducting to said hydraulic spring at and below a predetermined pressure differential therebetween.

4. A tool according to claim 1, wherein said connecting member has a passage therethrough, one end opening into the fluid chamber of said hydraulic spring and the other opening into said third chamber at the end of said forward stroke, said passage being otherwiseclosed by said body.

5. A tool according to claim 1, wherein the cylinder of the piston and cylinder'assembly. is a sleeve reciprocably mounted in a tool body with porting therein forming said valve means. I a 1 References Cited UNITED STATES PATENTS 3,088,440 5/1963 Wilmer 91 -5 3,150,488 9/1964 Haley 60-51 3,183,668 5/1965 Johnson 6051 3,186,169 6/1965 Hauser 91 5 3,213,615 10/1965 Bjornberg 60-51 MARTIN P. SCHWADRON, Primary Examiner.

B. L. ADAMS, Assistant Examiner.