Hammer piston for percussion apparatuses and percussion apparatus provided therewith

April 9, 1957 g. l. b. wahlsten 2,787,984

HAMMER PISTON FOR,PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 1

<img file="US2787984A_D0001.tif" />

April 9, 1957 g. l. b. wahlsten 2,787,984

HAMMER PISTON FOR, PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 2

Fig. 2

<img file="US2787984A_D0002.tif" />

April 9, 1957 g. l. b. wahlsten 2,787,984

HAMMER PISTON FOR, PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 3

<img file="US2787984A_D0003.tif" />

Αρη! 9, 1957 g. _l. _b wahlsten 2,787,984

HAMMER PISTON FOR, PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 4

Fig. 4

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<img file="US2787984A_D0005.tif" />

April 9, 1957 g. l. b. wahlsten 2,787,984

HAMMER PISTON FOR, PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 5

<img file="US2787984A_D0006.tif" />

April 9, 1957 g. l. b. wahlsten 2,787,984

HAMMER PISTON FOR, PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 6

63

<img file="US2787984A_D0007.tif" />

<img file="US2787984A_D0008.tif" />

April 9, 1957 g. _l b. wahlsten 2,787,984

HAMMER PISTON FOR,PERCUSSION APPARATUSES AND PERCUSSION

APPARATUS PROVIDED THEREWITH

Filed June 17, 1952 7 Sheets-Sheet 7

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<img file="US2787984A_D0010.tif" />

United States Patent Office

2,787,984

Patented Apr. 9, 1957

2,787,984

HAMMER PISTON FOR PERCUSSION APPARATUSES AND PERCUSSION APPARATUS PROVIDED THEREWITH

Gosta Ludvig Bertii Wahlsten, Stockholm, Sweden, assignor io Atlas Copco Akiiebolag, Nacka, Sweden, a corporation of Sweden

Application fere 17, 1952, Serial No. 294,102

Claims priority, application Sweden June 18,1951 «aims. (CL 121—31)

This invention relates to hammer pistons for pressure fluid driven percussion machines and tools particularly but not exclusively of the type having a free flying hammer piston driven by a pressure fluid, such as compressed air, pressure gas, or the like. The invention also relates to machines and tools provided with such hammer pistons, such as rock drills, concrete breakers, riveting hammers, or the like. One object of the invention is to provide a hammer piston or percussion tool, respectively, which permits the supply of an increased quantity of energy to a working implement, such as a rock drill bit, a drill rod, a concrete breaking tool, a riveting tool, a chisel, or the like, without increasing the maximum stresses in said working implement. This may be achieved by providing a hammer piston which without increasing the amplitude of the percussion wave produced in the working implement increases the length of the percussion wave or the duration of the maximum amplitude Of the percussion wave. It has previously been suggested to improve the transmission of energy to a working implement of the type indicated hereinabove by provision of a hammer piston which has great length relative to the diameter of the portion of the hammer piston designed for delivering blows. However, such a long hammer piston has the disadvantage that the machine dr tool in which the piston is provided becomes rather long. Said disadvantage may be avoided according to the invention by the provision of a hammer piston which replaces the long hammer piston and which may be considered as a folded long hammer piston in which the various portions between the folds form a continuous percussion wave path which in similar way as in the long piston has great length in the direction of the blows. The hammer piston according to the invention is substantially characterized by this that it comprises two or more concentric portions which are so arranged relative to each other that they deliver the blows or impacts in commoil and then form a continuous percussion wave path at one end of which a portion designed for delivering impacts is formed and which path has materially greater length than the hammer piston.

.Tn the accompanying drawings some embodiments Of rock drills and a concrete breaker according to the invention are illustrated by way of example together with pistons for such tools. Fig. 1 is a side view and partial section of a compressed air driven rock drill according to the invention with a differential hammer piston. Fig. 2 is an axial section of the hammer piston for the rock drill according to Fig. 1 on a larger scale. Fig. 3 is a side view and partial section of another compressed air driven rock drill according to the invention provided with a differential hammer piston of a different type. Fig. 4 is an- axial section of the hammer piston of the drill according to Fig. 3 On a larger scale. Fig. 5 is a sec2 tion on line V—V in Fig. 4. Fig. 6 is a side view and jpartial section of a concrete breaker according to the invention. Fig. 7 illustrates in longitudinal section a hammer piston for such a concrete breaker on a larger 5 scale. Fig. 8 is a hammer piston for a concrete breaker, a riveting hammer or similar tool of a still further modified design.

The compressed air driven rock drill illustrated in Fig. 1 consists of a cylinder 1, a back head 2, a valve casing 3, 10 a front head 4, and an intermediate casing 5. The . back head 2 and the valve casing 3 form together a valve chamber 6 in which a valve member controlling the distribution of compressed, air for producing the working stroke and the return stroke, respectively, of the hammer piston 15 is arranged in conventional manner. In the embodiment illustrated in Fig. 1 the valve member comprises an oscillating disc valve 7, but the invention is naturally not confined to the use of such a valve and the drill may be provided with a tubular valve, a flat disc valve, a piston 20 valve, double valves, or Other known valve designs fit for controlling the supply of compressed air to the working chambers of the drill and sometimes also for controlling the exhaust of the air therefrom.

The front head 4 of the drill and the intermediate cas25 ing 5 encloses a drill turning mechanism which may be Of any conventional design and which in the illustrated embodiment consists of a motor 8 which drives a shaft 9 carrying a screw which engages a worm wheel 10 on a drill chuck 11 for a drill rod 12. 13 is the main ad30 mission valve of the drill which controls the supply Of compressed air to the Valve chamber 6 and the turning motor 8, and 14 is a handle secured to the . back head 2 of the drill. 15 indicates a supply conduit for flushing Water or other flushing fluid.

The cylinder 1 Contains a reciprocable differential hammer piston which is of a design illustrated in detail in Fig. 2. The piston has a portion 16 designed, for delivering blows directly to a drill rod 12, a large diameter cylindrical piston head 17 which forms , a seal and is 40 guided in a cylindrical portion of large diaihetef of the cylinder 1, and a smaller diameter cylindrical piston shank 18 forming a seal and guided in the intermediate casing 5 and connected to the piston head 17 by means of a substantially frusto-comcal intermediate portion 19. The 45 diameter of the piston head 17 is materially larger than the diameter of the piston shank and in the illustrated embodiment the diameter of the piston head is about two times the diameter of the piston shank. The portion 16 for delivering blows is provided at the end of 50 a centrally disposed substantially cylindrical body 20. A substantially cylindrical sleeve 21 encloses the body 20 with a sliding fit and has a bottom 22 resting On the top end of the body 20 opposite the blow delivering portion. The body 20 has a flange 23 forming an abutment 55 24 on which a tubular ring 25 rests with one end face.

The opposite end face of the ring 25 is rolled into a recess 26 in the sleeve 21, said recess forming an abutment between which and the abutment 2'4 the ring 25 is press fitted so that the sleeve 21 is pressed steadily with the ⁶⁰ bottom 22 against the top end of the body 20 opposite the impact delivering portion 16. A sleeve 27 is fitted around the sleeve 21 with a sliding fit and forms the guide and sealing surfaces 17, 18 of the piston as well _6g as the intermediate portion 19. The sleeve 27 rests oh an abutment 28 provided on the sleeve 21 and is pressed against said abutment by a-tubular ring 29 inserted with a press fit between an abutment 30 on the sleeve 27 and

2,787,984 an annular abutment 31 formed in the bottom 22 into which the ring 29 is rolled.

Due to the illustrated design of the hammer piston and upon fitting of the rings 25, 29 with suitable pressure the piston portions 20, 21 and 27 are pressed towards each other at 22 and 28 so that a continuous percussion wave path is formed (from the impact delivering portion 16 through the body 20, the bottom 22, the envelope portion of the sleeve 21, over the abutment 28, the portion 18, the intermediate portion 19, and the piston head portion 17). The abutment surfaces between the upper end of body 20 and the bottom 22 of sleeve 21 and the abutment surfaces provided by the abutment 28 engaging the sleeve part 18 provide the percussion wave transition means by virtue of which the percussion wave is transmitted through a path including the length of the part 20, the length of the sleeve 21 and the length of the outer member including the sleeve part 18, which is substantially three times the length of the overall length of the hammer piston. Said percussion wave path is almost three times as long as the total length of the piston illustrated in Fig. 2.

The various piston portions 20, 21 and 27 are made of steel and carried out in such a manner that the cross sectional area in various parts of the piston is almost the same along the whole length of the piston and the weight of each unit length of the piston is consequently substantially constant along the whole of the length of the piston.

The piston illustrated in Fig. 2 has a recess 32 in the piston head 17 and the intermediate portion 19 and the drill has a displacement body 33 which corresponds to said recess 32. 34 indicates a tube for flushing medium which in conventional manner extends through a central bore 35 in the piston.

The rock drill illustrated in Fig. 3 is of substantially the same design as the rock drill illustrated in Fig. 1 and described hereinabove. Consequently, all parts of the rock drill illustrated in Fig. 3 which correspond to equivalent parts in Fig. 1 are designated with the same reference numerals and are not described again. The only difference consists in the design of the hammer piston and the valve casing 3. The differential hammer piston of the rock drill according to Fig. 3 which is illustrated on a larger scale in Figs. 4 and 5 consists of two separate piston portions having shanks 36 and 37, respectively, and head portions 38 and 39, respectively. The shank 36 ends with a portion 40 designed for delivering blows to the drill rod 12. The head portion 38 is connected with the shank 36 by means of a substantially frustoconical intermediate portion 41, and the head portion 38 forms the large diameter sliding surface 42 of the piston. The shank 37 is disposed concentrically in the shank 36 and fits in the shank 36 with a sliding fit. The head portion 39 forms a cover for the big end of the piston and has a rim 43 which rests on an end face 44 of the head portion 38. Small recesses 45 or bores in the head portion 39 form a restricted passage from the cylinder chamber 88 above the head portion 39 to a space 46 defined between the head portions 38, 39 and 41, and further passages are formed between the piston shanks 36 and 37. For this purpose the shank 37 has two flat portions 47 extending along the whole length of the shank as obvious from Fig. 5. A bore 48 for accommodating the flushing fluid tube 34 is provided in the shank 37 and a somewhat larger bore 49 is provided in the impact delivering portion 40 so that a passage is formed around the tube 34 in said portion. It is obvious that pressure fluid prevailing in the chamber 88 on top of the piston head 39 will enter through the recesses 45 into the space 46 and pass through the passages formed between the flat portions 47 and the inner walls of the piston shank 36 through the space between the walls of the bore 49 and the flushing fluid tube 34 to the space 91 in the drill chuck which is vented to the atmosphere through special vent openings 89 or through leakage around the drill steel shank. Consequently, lubricating oil carried by the working fluid is deposited on the sliding surfaces between the piston shanks 36 and 37. It is also obvious that the space 46 will be in continuous communication with a 5 vented space in the rock drill, and the area of the passages defined by the flat portions 47 and the bore 49 should be so much larger than the area of the passages or recesses 45 that the building up of pressure in the space 46 is avoided. Consequently, the pressure exerted by the 10 working fluid of the drill on the head 39 or the portion 41 forces the piston head 39 and the piston head 38 against one another so that said piston portions are kept together and deliver a unitary blow. At least at the moment when said blow is delivered the piston portions 15 provide a continuous pressure wave path from the face 40 through the shank 36, the intermediate portion 41, the piston head 38, the head 39 and the shank 37 to the end of said shank, which is free to move in the shank 36.

The concrete breaker illustrated in Fig. 6 consists of 20 a cylinder 50, a back head 51 provided with a handle 52 and an admission valve manipulated with a handle 53, a front head 54 with a tool retainer 55 for a working tool 56, and an intermediate casing 57 which forms a cover for the lower end of the working cylinder and in 25 which an anvil block 58 is slidable and forms a seal.

A substantially cylindrical hammer piston is reciprocable in the cylinder 50 said hammer piston being illustrated on a larger scale in Fig. 7. Said hammer piston consists of a central cylindrical body 60 which is de30 signed for delivering blows by means of an impact delivering end portion 61. A substantially cylindrical sleeve 62 encloses with a sliding fit the body 60 and has a bottom portion 63 which rests on an end face 59 of the body 60. A cylindrical sleeve 64 is fitted on the sleeve 62 with a 35 sliding fit and the sleeves 64 and 62 and the body 60 form together a continuous percussion wave path which begins at the portion 61. The sleeve 62 is connected to the central body 60 by means of a ring 65 resting on an abutment 66 on the body 60 which for this purpose has 40 a flange 67. The ring is rolled into a recess 68 forming an abutment on the sleeve 62. The sleeve 64 is fitted between an abutment 69 on the sleeve 62 and a ring 70 which is rolled into an annular recess 71 in the bottom portion 63. The piston according to Fig. 6 forms a continuous percussion wave path from the end portion 61 ⁴⁵ through the body 60, the bottom portion 63, the sleeve 62, and the sleeve 64, said percussion wave path being substantially, three times as long as the piston. The cross sectional area of the piston portions 60, 62 and 64 is substantially constant along the whole length of the ⁵⁰ piston.

Fig. 8 illustrates a further embodiment of a hammer piston according to the invention, said hammer piston being intended for a concrete breaker, a chisel hammer, or the like. The hammer piston according to Fig. 8 com⁰ prises a portion 75 designed for delivering blows to a working implement or an anvil block and is provided with a reduced extension 76 carrying a screw threaded portion 77. A ring shaped portion 78 rests on an abutment 79 formed by the portion 75. A sleeve 80 which ⁰⁰ surrounds the portion 78 with a sliding fit has an internal flange 82 forming an abutment 83 which rests on the rear end of the sleeve 78. A second sleeve 84 is arranged concentrically to the sleeves 80 and 78 and fits on the sleeve 80 with a sliding fit. The sleeve 80 forms an external flange 85 providing an abutment 86 on which the end face of the sleeve 84 rests. The sleeve 84 has .an internal flange 87 which forms a seat for a nut 90 secured on the screw threads 77 of the extension 76. It γθ is obvious that the piston illustrated in Fig. 8 provides a continuous percussion wave path which starts at the impact delivering portion 75 and extends through the body 78, the sleeve 80, and the sleeve 84. Said percussion wave path is about three times the length of the pis75 ton illustrated in Fig. 8.

2,787

..

The operation of the above described hammer pistons is substantially the same as if the piston material had been extended to a distance of two and three times, respectively, of the length of the illustrated pistons, or as if the piston material had had a modulus of elasticity which had 5 been two and three times, respectively, the modulus of elasticity of steel.

The embodiments of the invention above described and illustrated in the drawings should only be considered as examples and the invention may be modified in var- 10 ious different ways within the scope of the claims. Pistons according to the invention may, for instance, be employed in other percussion tools than those described hereinabove. The various portions of the pistons may be of different material. The connection of the piston por- 15 tions in order to form a continuous percussion wave path may be other than those illustrated in the drawings and described hereinabove, and, for instance, the various piston portions may be welded together or soldered together. The number of piston portions which are arranged con- 20 centrically may naturally be larger or smaller than those illustrated in the drawings.