US3010431A - Percussion tools - Google Patents

Description

Nov. 28, 1961 J. K. HOLDO PERCUSSION TOOLS 5 Sheets-Sheet 2 Filed Jan. 5, 1960 IIIIIIII/l/Y/IIIIIIII i la Nov. 28, 1961 JQK. HOLDO PERCUSSION TOOLS Filed Jan. 5, 196 0 5 Sheets-Sheet 3 ATTORNEY NOV. 28, 1961 J, K, HQLDO 3,010,431

pERcussion TOOLS Filed Jan. 5, 1960 5 Sheets-Sheet 4 Fig. 5

9 9lcu INVENT BY a ATTORNEY Nov. 28, 1961 J. K. HOLDO PERCUSSION TOOLS 5 Sheets-Sheet 5 Fig. 6

Filed Jan. 5, 1960 ":IVEN m W ,Z/LATTQRNEY United States Patent Ofitice 3,010,431 Patented Nov. 28, 1961 3,010,431 PERCUSSION TOOLS Jan Kristian Holdo, Stockholm, Sweden, assignor to Atlas Copco Aktiebolag, Nacka, Sweden, a corporation of Sweden Filed Jan. 5, 1960, Ser. No. 550 10 Claims. (Cl. 121-36) This invention relates to improvements in percussion tools having a housing, a working cylinder formed in said housing, and a hammer piston reciprocable in said working cylinder under the action of a pressure fluid. The invention is particularly directed to portable percussion tools such as paving breakers, hammers, riveters, rock drills and the like but the invention may also be used in pile drivers, sheeting drivers or the like. piston in tools according to the invention may be operated pneumatically or hydraulically or by other pressure fluids as the case may be. A disadvantage of percussion tools is the vibrations or shocks transmitted to the handles or other members serving to feed or to carry the tool towards a work piece during operation of the tool. One object of the invention is to minimize or eliminate said shock and vibration transmission. A further object of the invention is to provide a simple, economical and efiicient percussion tool in which the transmission of vibrations or shocks from the tool to the handle or handles or other feeding means is materially reduced. A still further object of the invention is to provide a tool in which mechanical springs for cushioning of shocks or vibrations are avoided. Another object of the invention is a tool in which transmission of vibrations and shocks to a handle or other member in which vibrations are undesirable is eliminated or minimized irrespective of the force with which the operator presses the tool towards a work piece, such as a street pavement. For the above and other purposes I provide pneumatic means for forming a force transmitting connection between a handle or other member in which vibration is undesirable and a percussion tool having a housing, a working cylinder in said housing, and a hammer piston reciprocable in said working cylinder under the action of a pressure fluid,

I provide in a tool of the type described servo motor:

means carried by the tool for operating pressure fluid supply control means on the tool and manually operated means at the handle or other member for actuating said servo motor means to operate the fluid supply control means.

Further features of the invention will be apparent from the following specification and drawings which illustrate by way of example one embodiment, and a modification thereof, of a percussion tool according to the invention.

The hammer However, other modifications of the invention may nat- I urally be made within the scope of the appended claims. The hammer piston of the tool may, for instance, be driven hydraulically in one or both directions. The-hammer piston may also be steam driven.

The illustrated tool is a portable pneumatic concrete;

is a longitudinal section through the cylinder axis of the breaker according to FIG. 1 on a plane perpendicular to the section plane of FIG. 2. FIG. 3 is a longitudinal section through the cylinder axis of the same tool on a plane at 45 to the section planes of FIGS. 1 and 2. FIG. 4 is a transverse section on line IVIV of FIG. 3. FIG. 4 also illustrates the planes II, IIII and IIIIII on which the longitudinal sections of FIGS. 1 to 3, respectively, are taken. FIGS. 5 and 6 are longitudinal sec tions of a modification of the tool in FIGS. 1-4. FIG. 7 is a cross section on line VIIVH of FIG. 6.

The tool illustrated in FIGS. 1 to 4 has a housing comprising a cylinder casing 1, a front casing 2, and a cylinder-head 3 which are bolted together by means of longitudinal bolts 4, 4 and nuts 5, 5. The cylinder casing 1 has a cylindrical bore 6 in which a hammer piston 7 is reciprocable and defines a rear chamber 8 and a front chamber 9. The front end of the bore of the cylinder casing 1 accommodates a guide member 10 'for an anvil block 11 which transmits hammer blows to a steel shank 12. The shank 12 is guided in a bushing 13 fixed in the front casing 2 and retained in the tool by a steel retainer 14 of conventional design which cooperates with a collar 15 on a steel '16, such as a spike for breaking concrete or asphalt pavement or the like. The steel retainer 14 permits removal of the steel 16 and is in all respects constructed in conventional manner and is therefore not described in detail. The anvil block 11 has the usual collar 17 for limiting axial movement of the anvil block.

At the rear end of the tool a handle member 18 is pro vided which carries two handles 19, 19 and forms a cap which fits the outside of the cylinder casing 1 with a sliding fit. The handle member 18 has secured thereto piston rods 20 which are rigidly secured to the handle member by nuts 21 and which are slidably guided in bushngs 22 in the casing v1 and carry pistons 23 reciprocable 1n bores 24 in the cylinder casing 1. The pistons are sealed in the bores by means of sealing rings 25. The two pistons 23 are movable in the bores 24 a limited distance and provide a force connection between the handle member 18 and the tool which permits axial longitudinal relative movement of the tool and the handle member 18 within certain limits.

The cylinder casing 1 carries a distributing valve casing 26 accommodating a tubular air distributing valve 27 moveable longitudinally of the tool in valve guides 28, 29 and illustrated inFIG. 3 in a position in which compressed air admission to the rear chamber 8 is closed and said chamber is connected to the atmosphere. Compressed air is supplied to the tool through a hose 30, a mam valve casing 31, a passage 32 in the main valve casing, a passage 33 in the distributing valve casing and in open position of the distributing valve 27 through a passage 34 to the rear working chamber 8 in the cylinder casing 1. Compressed air is also supplied from the passage 32 through a conduit 35 and a passage 36 in the casing 1 over a pressure reduction valve 37, actuated by a spring 38 through a passage 39 to a chamber 40 in the front casing 2. The spring 38 is so dimensioned that the pressure in the chamber 40'may be kept. at a low value, for instance at a few hec-tograms per square centimeter. The comparatively large chamber 40 communicates through a passage 41 with the front chamber 9 in the working cylinder. Instead of the pressure reduction valve 37 a constant pressure valve of conventional design may naturally be provided.

The main valve casing 31 accommodates a servo motor operated valve member 42 which is provided with a piston portion 43 reciprocable in a bore 44 in the main valve casing 31'. The bore 44 is closed by a cover 45 to form a working chamber 57 for the piston portion 43. The annular space 58 at the lower side of the piston portion 43 is vented to the atmosphere through closes. the valve 42.

a'passage 46. A hose 47 is secured. to a nipple 48 formed by the cover 45 and leads to a valve chamber 49 formed in the handle member 18. The chamber 49 accommodates a small poppet valve 50 which is normally kept closed by a spring 51 provided between the valve head and a plug 52. The plug 52 has a bore 53 forming a communication between the chamber 49 and the atmosphere in open position of the valve member 50. The handle member carries a trigger 54, which is journaled on a pin 55, and cooperates with the stem 56 of the poppet valve 50 so that thepoppet valve may be opened against the pressure of the spring 51 by pressing the trigger 54 towards the handle 19. The valve 42 has a fine passage 82 through which compressed air in inoperative position of the tool is admitted to the chamber 57. When the tool is at rest air pressure in the chamber 57 keeps the valve 42 closed since the annular chamber 58 is vented to the atmosphere through passage 46. When the trigger 54'is pressed the pressure air is vented from the chamber 57 and the air pressure in the supply hose 30 then opens the valve 42 to admit compressed air to the passages 32, 33, 34. As soon as the pressure on the trigger 54 is released the poppet valve 50 closes the vent passage from the chamber 49 so. that air pressure again builds 1 up in the chamber 57 and Compressed air admitted to the passages 32, 33 flows in the illustrated position of the distributing valve 27 through a passage 60 to an annular space 61 in which it acts on the shoulder 62 of the distributing valve 27. The air pressure which builds up in the chamber 40'as soon as the trigger 54 has been pressed down lifts the piston 7 to the top of the bore 6 causing compression of the air in the rear portion of the working chamber 8. Compressed air from the rear portion of the chamber 8 is conducted through a passage 63 to an annular space 64 in which it acts on a flange 65 'on the distributing valve 27 so that said valve is moved to the lower position in which it admits air to the rear working chamber 8 in the cylinder afterthe rebound of the piston against the air cushion at the upper end of the'chamber '8. The compressed air admitted to the chamber 8 drives the piston 7 downwardly against the anvil-block '11 and when the piston on its working stroke has uncovered a passage 66 in the wall of the cylinder 1 compressed air from the chamber 8 is con ducted through the passage 66 to an annular chamber 69 in which it actuates the distributing valve member 27 upwardly in FIG. 3-so that the admission of compressed air to the chamber 8 is closed'and an exhaust passage from the chamber 8 is opened through the passage 34 and the interior 70 of the valve member and further through a passage 71 to the atmosphere. Two chambers 72 with several times as great volume as chamhere 73 confined in the bores 24 by the two pistons 23 are provided in the casing 1. Preferably the volumes of the chambers 72 and bores 24 may be between ZOand 30 times the volumes displaced by thepistons 23 during 7 7 operation of the tool so that displacements of the pistons 23 in the bores 24' do not materially change the pressurein the chambers 72 which are interconnected by a 'large passage 74 and connected to the bores 24 by large 7 The annular chambers on the rear side of passages 75. V the pistons 23 are vented to theratmo'sphere through passages 80. As soon as the tool is connected to a compressed air s'upply source through the hose 300cmpressed air is conducted through a hose or conduit 76 a to the chambers 72 at 77 in FIGS. '3 and 4. The passage into the chamber 72 goes through a fine bore 78 and the chambers 73 'are provided-with openings leading to the atmosphere and controlled by the pistons 23, said openings being considerably larger than the bore 78 so that low air'pressure only, tor instance about one kilogramme per square centimeter above atmospheric pressure, can be built up in the working chambers 73 when the openings 79 are uncovered by the pistons 23.

4 In order to adjust the pressure in the chambers 72 adjusting screws 81 are provided.

The described tool operates in the following manner: It will be understood that as soon as the operator holding the tool by means of the handles 19 presses the trigger 54 air pressure on the servomotor piston 43 in the chamber 57 is reduced so that air pressure in the hose 30 opens the main valve 42. Compressed air is then admitted to the valve casing 26 and the chamber 40. The only force acting in longitudinal direction of the tool on the handles 19 is then the air pressure in the chambers 73 which tends to lift the pistons 23 in the bores 24. The rear side or the pistons 23 being continuously vented to the atmosphere through the passages in the piston rods 20. When the operator presses harder on the handles 19, pressure in the chambers 73 is gradually increased but during operation with the operator pressing the handles with the same force the pressure in the chambers 73 will remain substantially constant and said pressure will remain constant irrespective of the vibrations in'axial direction set up in thetool during the hammer reciprocation. It will be observed that a movement of the cylinder casing 1 towards the handles 19 causes the pistons 23 to. momentarily close the openings 79 but due to the small size of the passage 78 and the size of the displacement volume of the pistons 23 relative to the cylinder chambers 72 and 73 no ap preciable increase in pressure in the chambers 73 occurs during such intervals so that no shock will be transmitted to the handles 19. The same applies if the casing 1 from the position illustrated in FIG. 1 moves downwardly away from the handles in which case the ports 79 are uncovered so that part of the air in the chambers 72 may escape. The area of the openings 79 is so small that air losses during these intervals of normal oscillation of the housing relative to the handle member are comparatively small and in the present tool the extra air consumption for vibration dampening purposes is therefore small. The air losses are naturally compensated by the air supply through the small passage 78 so that an equilibrium is maintained. It has been found that the area of openings 79 may be 10 to 20 times the area of passage 78. The arrangement works to minimize transmission of vibrations from the tool to the handles on idle running of the tool as well as when the operator presses the handles and the tool more or less towards the ground or the like and the handle member takes a mean position relative'to'the housing which moves only a small distance under various forces applied by the operator. V

The tool above described should be considered only as an example and may be modified in various ways within the scope of the claims. In cases, for instance, where it is not necessary to be able to turn the tool on the cylinder axis by means of the handle or handles a single piston and cylinder concentric with the Working cylinder may replace the pistons 23 and cylinders 24.

The illustrated distributing valve 27 may be replaced by a conventional valve which controls the pressure fluid supply to the rear chamber 8 and the front chamber 9, and such avalve may also control the exhaust from said chambers.- The illustrated servo control of the main valve 42 may be replaced by electric control or me chanical linkage which do not transmit vibrations from the tool to the handle member. in the modification illustrated in FIGS. 5, 6 and 7 parts corresponding to equivalent parts in FIGS. 1 to 4 are designated .with the same reference numerals and are not described again. The main difference between the tools illustrated in FIGS. 5-7 and the above described tool is as follows:

The damper pistons 23in FIGS. 5 and 6 are provided on piston rods 83 which are not connected to the handle member 18 but 'are only pressed against the inside of said 'member'with their rear ends which in order to avoid metallic contact are provided with rubber caps 83a. The

air pressure in the chambers 73 keeps the rods 83 pressed towards the handle member 18 as soon as the tool is connected to a compressed air source. The guiding function of the piston rods 20 in FIG. 1 is performed by separate guide rods 84, secured to the handle member 18 by means of nuts 85 and guided in bushings 87 and provided with heads 88 at their front ends. The tube 47 from the trigger control valve 50 has been replaced by a passage 89 and a telescopic tube 90 secured to the handle member 18 and movable in a bore 91 in the casing 1 and providing a communication, via port passage 91a and an external annular groove in the plug 91b, with the chamber 57 at the large end of the main valve 43. The tube 90 communicates with the bore 91 through openings 92 which are so positioned that when the tool is lifted by means of the handle member 18 the openings 92 are closed by a bushing 93 causing the hammer piston to stop its reciprocation.

The distribution valve 27 of the tool in FIGS. and 6 is of a type which controls the air supply to the rear chamber 8 as well as to the front chamber 9 of the tool and also auxiliary exhaust passages from the front and rear chambers. The valve 27 is a piston valve which is moved axially by compressed air admitted to the rear and front ends of the valve, when the hammer piston uncovers a passage 94 or a passage 95, respectively.

Compressed air from the main valve is supplied to the annular chamber 96 and in the upper position of the piston valve 27 through a number of openings 97 to the rear chamber 8 and in the lower position of the piston valve 27 through the annular recess 98 and the passage 99 to the front chamber 9. 100 is a vent passage, which in the lower position of the piston valve 27 permits the air from a part of the air cushion in the chamber 8 to escape slowly to the atmosphere during the return stroke of the hammer piston 7 so that a reduced or non-cushioning efl'ect is obtained in the chamber 8 on the return stroke of the hammer piston 7. 101 is a vent passage which in similar manner brings the chamber 9 in communication with the atmosphere in the upper position of the piston valve 27 so that the air compression in the chamber 9 is reduced or avoided until the hammer piston has delivered the blow. The final exhaust of the air in the chambers 8 and 9 is controlled in conventional manner by the hammer piston 7 which on the working stroke uncovers a groove 102 and on the return stroke a groove 103 which grooves are connected with conventional exhaust ports (not shown). The chamber 9 is connected through a passage 104 to a space 165 forming an air magazine communicating with the chamber 9.

The reduction or elimination of vibrations transmitted from the housing of the tool in FIGS. 5-7 operates in the same way as in the embodiment of the invention disclosed in FIGS. 1-4'and is consequently not described again.

What I claim is: I

1. In combination with a percussion tool having a housing, a working cylinder formed in said housing, and a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, a member in which vibration is undesirable, pneumatic means for transmitting force between said member and said housing, and means operative to effect pneumatic control of said first mentioned means for automatically adjusting the value of said force to maintain said member relative to said housing in a substantially predetermined means position and for maintaining such adjusted value relatively constant over a considerable number of successive reciprocations of said hammer piston.

2. In combination with a percussion tool having a housing, a working cylinder formed in said housing, and a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, a member in which vibration is undesirable, pneumatic piston and cylinder means for transmitting force between said memberand said housing, one of said means being carried by the member and the other means by the housing, means for guiding said member relative to said housing for motion in the direction of the axis of the working cylinder, and means operative to effect pneumatic control of said first mentioned means for automatically adjusting the value of said force to maintain said member relative to said housing in a substantially predetermined mean position and for maintaining such adjusted value relatively constant over a considerable number of successive reciprocations of said hammer piston.

3. In combination with a percussion tool having a housing, a working cylinder formed in said housing, and a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, a member in which vibration is undesirable, pneumatic piston and cylinder means for transmitting force between said member and said housing, one of said means being carried by the member and the other means by the housing, means for guiding said member relative to said housing for motion in the direction of the axis of the working cylinder, a damper working chamber in said cylinder means having a compressed air inlet opening and a compressed air outlet opening, said outlet opening having greater area than said inlet opening, and said piston means cooperating with said outlet opening to control and maintain in said damper chamber a substantially constant pressure during successive hammer piston reciprocations.

4. A percussion tool according to claim 3, in which said damper chamber continuously communicates with an air magazine chamber.

5. In combination with a percussion tool, having a housing, a working cylinder formed in said housing, a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, means in the housing for supplying pressure fluid to the working cylinder, means in the housing for leading fluid away from the working cylinder, and means associated with the housing for controlling the supply ofpressure fluid to the working cylinder, a member in which vibration is undesirable, means for forming a connection between said member and said tool providing limited relative sliding motion in the direction of the axis of the working cylinder between said member and said tool, cooperating damper cylinder and piston means for transmitting force in the direction of said axis from said member to said tool, a damper working chamber in said damper cylinder means having a compressed air inlet opening and a compressed air outlet opening, said outlet opening having greater area than said inlet opening.

6. In combination with a percussion tool, having a cylinder housing, a working cylinder formed in said housing, a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, means in the housing for supplying pressure fluid to the working cylinder, means in the housing for leading working fluid away from the working cylinder, means carried by the housing for controlling the supply of pressure fluid to the working cylinder, a handle member for holding and directing said tool, means for forming a connection between said handle member and said tool providing limited relative sliding motion in the direction of the axis of the working cylinder between said handle member and said tool, servomotor means carried by the housing for operating said supply control means, and manually operable means at said handle member for actuating said servomotor means to open the supply control means.

7. In combination with a percussion tool, having a housing, a working cylinder formed in said housing, a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, means in the housing 7 for supplying pressure fluid to the working cylinder, means in the housing for leading working fluid away from the workingcylinder, and means carried by the housing for controlling the supply of pressure fluid to the working cylinder, a handle member for holding and directing said tool, means for transmitting force between said handle member and said housing, means for autornatically adjusting the value of said force to maintain said handle member relative to said housing in a substantially predetermined mean position and for maintainin-g such adjusted value relatively constant over a considerable number of successive reciprocations of said hammer piston, servomotortmeans carried by the housing for operating said supply control means and manually operable means at said handle member for actuating said servomotor means to open the supply control means.

8. In combination with a percussion tool having a housing, a working cylinder formed in said housing, a

, hammer piston reciprocable in said working cylinder member and said housing, means operative to effect pneumatic control of said first mentioned means for automatically adjusting the value of said force to maintain said member relative to said housing in a substantially predetermined mean position -and for maintaining such adjusted value relatively constant over a considerable number of successive reciprocations of said hammer piston, means in the housing for supplying pressure fluid to the working cylinder, distributing valve means in the housing controlling pressure fluid supply to working chambers in the working cylinder for producing a rapid working stroke and a relatively slow return stroke and including a distributing valve member, passages in said distributing valve means for venting the main portion of the compressed air cushions produced by the hammer piston during the working stroke and the return stroke, respec: tively, and further passages in the distributing valve means for supplying pressure fluid for moving said distributing valve member to positions for admitting pressure fluid to said working chambers, respectively.

9. In combination with a percussion tool, having a housing, a working cylinder formed in said housing, a hammer piston reciprocable in said working cylinder under the action of a pressure fluid, a handle member slidable in the direction of the axis of the working cylinder a limited distance relative to said housing and nonrotatable relative to the housing, two damper cylinders in the housing parallel with the working cylinder, damper pistons and piston rods movable in said damper cylinders and engaging said handle member to move the handle member away from the housing under the action of compressed air supplied to the damper cylinders, guide rods connected to said handle member and guided in the housing to allow the handle member to move a limited distance along the axis of the working cylinder relative to the housing, auxiliary compressed air chambers in the 7 housing communicating with damper chambers in said damper cylinders, a compressed air inlet opening ineach damper chamber, a compressed air outlet opening in each damper chamber having greater area than said inlet'opening and controlled by said damper piston, respectively, means in the housing for supplying pressure fluid to the working cylinder, and servomotor means controlled from the handle member for controlling the pressure fluid supply means.

10. A percussion tool according to claim 9 in which servo motor means includes a telescopic connection between the handle member and the housing operable to interrupt pressure fluid supply to the working cylinder when the tool is lifted by means of the handle member.

References Cited in the file of this patent UNITED STATES PATENTS Altschuler June 5, 1956

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