US2812745A

US2812745A - Hammer pistons and tools provided therewith

Info

Publication number: US2812745A
Application number: US272475A
Authority: US
Inventors: Pyk Herman Theodor
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1951-02-20
Filing date: 1952-02-19
Publication date: 1957-11-12
Anticipated expiration: 1974-11-12
Also published as: DE1030780B

Description

Nova. 12, 1957 H, T, PYK 2,812,745

HAMMER PISTONS AND TOOLS PROVIDED THEREWITH Filed Feb. 19, 1952 4 Sheets-Sheet 1.

gunman) Nov. 12, 1957 H. r. PYK 2,812,745

HAMMER PISTONS AND TOOLS PROVIDED THEREWITH Filed Feb. 19, 1952 4 Sheets-Sheet 2 D Nub vii, 1 957 I TDPYK 2,812 745 HAMMER PISTONS AND TOOLS PROVIDED THEREWITH I Filed Feb. 19. 1952 4 Sheets-Sheet 3 Fig.3

Nqv. 12, 1957 H. 'r. PYK 2,812,745

I HAMMER PISTONS AND TOOLS PROVIDED THEREWITH Filed Feb. 19. 1952 I 4 Sheets -Sheet 4 Fig.5

HAMMER PISTONS AND TOOLS PROVIDED THEREWITH Herman Theodor Pyk, Saltsjo-Duvnas, Sweden, assignor to Atlas Copco Aktiebolag, a corporation of Sweden Application February 19, 1952, Serial No. 272,475

Claims priority, application SwedenFebmary 20, 1951 11 Claims. (Cl. 121-31) This invention relates to freely reciprocable hammer pistons for percussion tools driven by an elastic pressure fluid and to percussion tools provided with such hammer pistons. One object of the invention is to provide an improved hammer piston forsuch tools which permits the transmission of a greater quantity of energy at each blow to a working implement, such as a rock drill rod, a chisel, a riveting tool, or the like, than in hammer pistons of conventional design without increasing the maximum stresses in the working implement. This may be obtained by the provision of a hammer piston which without increasing the amplitude of the percussion wave produced in the impact receiving member increases the length of the wave or the duration of the maximum amplitude of the wave. A further object of the invention is to provide hammer pistons for rock drills which may be made to suit various kinds of rock and to produce various shapes of the percussion wave to suit the different kinds of rock for producing the most favourable drilling result. A still further object of the invention is to provide a hammer piston the elastic properties of which are adjustable. The expression elastic flexing used in the following specification and. claims is intended to indicate such a flexing in a body or a material which does not produce a permanent change of the shape of the body or the material. For the above and other purposes I provide a freely reciprocablehammer piston for percussion tools driven by an elastic pressure fluid and having a piston head and an impact portion so constructed that a substantial portion of the mass of the piston head will flex elastically in the direction of the blows relative to the rest of the piston in such a manner that upon delivery of a blow to a member by the impact portion an elastic flexing of the above mentioned substantial portion of the mass of the piston head in the direction of the blow is obtained which is materially greater than the elastic flexing of a solid cylindrical steel piston with the same weight and length as the hammer piston upon an equivalent impact but which does not exceed the flexing of a solid cylindrical steel piston with the same weight and ten times the length of the hammer piston upon an equivalent impact. Preferably the main portion of the mass of the piston head is designed to-flex elastically in the direction of the blows. Such a head may comprise a plurality of superimposed elastic elements capable of flexing in the direction of the blow relative to the impact delivering portion of the piston. The invention also includes percussion tools provided with hammer pistons according to the invention and with means for imparting a reciprocating motion to the hammer piston withthe aid of an elastic pressure fluid, such as compressed air pressure gas, or the like.

In the accompanying drawings some embodiments of hammer pistons andhammer tools according to the invention are illustrated by way of example. Fig. 1. is a side elevation and partial section of a compressed air driven hammer rock drill according to the invention and proyided with a differential hammer piston. Fig. 2 is a side nited States Patent 9 i 2,812,745 Patented Nov. 12, 1957 elevation and partial section of a compressed air driven concrete breaker provided with a hammer piston according to the invention. Figs. 3 and 4 illustrate on a larger scale and partially in section the hammer pistons of the percusson tools according to Figs. 1 and 2, respectively. Figs. 5 and 6 illustrate hammer pistons according to two further embodiments of theinvention.

The compressed air driven hammer rock drill illustrated in Fig. 1 consists of a cylinder 1, a back head 2, a valve casing 3, a front head 4, and an intermediate casing 5. The back head 2 andthe 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 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 obviously not confined to the. use .of such a valve and a drill according to the invention may, for instance, be provided with tubular valves, disc valves, piston valves, double valves, or other conventional valve designs suitable for controlling the distribution of compressed air to the working cylinder and in some case the exhaust of the air from the working cylinder of the drill.

The front head 4 of the drill and the intermediate casing 5 enclose 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 formed on a drill chuck 11 in which a drill rod 12 is fitted. 13 is the main admission 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 at the back head of the drill. 15 indicates a connection for supplying flushing water to the drill.

The cylinder 1 contains a reciprocable hammer piston which is illustrated in detail in Fig. 3 and which consists of a steel portion 16 designed for delivering impacts directly to a drilling implement and of cylindrical shape of reduced diameter and a piston head of larger diameter comprising a plurality of elastically flexing steel discs 17. The impact portion 16 is provided with a duct 18 for accommodating a water flushing tube 19 and is movable and guided nad forms a seal in a member 29 forming the lower head of the working chamber of the cylinder 1. The portion 16 has a further reduced extension 21 which extends through the piston head and on which the discs 17 arefitted and secured in position by a nut 22. The discs 1'7 together in effect form a stiff spring the tension of which may be adjusted by tightening or loosening the nut 22. The adjustment of the tension or the flexing ability of the discs is made possible by the discs having one surface convex, as indicated at 23, and the opposite surface provided with a peripheral ridge 24. The discs 17 are superimposed in such a manner that they contact each other alternately at the two convex faces 23 and the two ridges 24, as clearly shown in Fig. 3.

Upon suitable tightening of the nut 22 the discs contact each other at the ridges 24 and along circles having a diameter larger than the diameter of the extension 21. The total flexing in the direction of a blow of such a piston of a suitable material usch as flexible steel and of suitable thickness of the discs and with a length L is materially larger than the elastic flexing in the direction of a blow of a solid cylindrical steel piston 25 of circular cross section and the same Weight and length L as the hammer piston described above. Preferably the elastic flexing may be over 20% larger than that of the solid steel piston 25. This means, for instance, that if the cylindrical solid piston 25 is subjected to a load P and a reduction of the length resulting therefrom is AL then the compression of the

piston

16, 17 according to theinvention r 3 when the upper disc is subjected to the same load P would be more than 1.2 AL.

If the nut 22 is tightened less a piston is obtained in which the total flexing in the direction of the blow is larger than above described. This means that if such a piston is subjected to a load P this load would produce a compression, for instance of the order of 1.5AL. This means that the discs 17 apart from contacting each other along the ridges 24 contact each other along circles with a diameter closer to the diameter 21 than in the first case.

By making the discs 17 of less thickness or of larger diameter than illustrated in Fig. 3 the piston head may be made still weaker so that the flexing at a certain load P is for instance more than 2AL, i. c. more than 160% larger than the elastic compression of the comparable solid piston 25 subjected to the same load.

During the operation of the above described hammer piston in a percussion tool it may be assumed that the piston acts as if the piston head was made of a solid material having a lower modulus of elasticity than the steel in the comparable solid steel piston 25.

However, the elasticity of the hammer piston according to the invention should not be too great and under no circumstances should the hammer piston be so weak that upon an impact it will flex more than a cylindrical solid steel piston with the same weight as the hammer piston and ten times its length. Preferably the hammer piston should not flex more than a cylindrical solid steel piston of the same Weight as the hammer piston and with the same diameter as the working implement to which the hammer piston is designed to deliver impacts.

The concrete breaker illustrated in Fig. 2 consists of a cylinder 26, a back head 27 provided with a handle and an admission valve, a front head 23 carrying a retainer 29 for a tool 3%, and an intermediate portion 31 forming the front head of the working cylinder. An anvil block 32 is mounted in the intermediate portion 31 and serves to transmit percussion energy from the hammer piston to the tool 30 and to provide a seal in the front head of the working cylinder.

The hammer piston cf the concrete breaker in Pig. 2 which is illustrated on a larger scale in Fig. 4 consists of a central rod forming an impact portion 33 and carrying a plurality of flexible steel discs 34 fitted on the rod and maintained thereon by a nut 35. The discs 34 are provided at their outer periphery with a peripheral ridge 36 and at their inner periphery with a peripheral ridge 37. The discs contact each other alternately at the

ridges

36 and 37 so that a very stiff bellows type spring is formed by the discs. A hammer piston according to this embodiment has a flexibility in the direction of the blows which is substantially greater than the flexibility of a solid cylindrical steel piston of circular cross section and of the same weight and length as the hammer piston but should such flexibility, according to the invention, not be greater than the flexibility of a solid cylindrical steel piston of circular cross section and of the same weight and ten times the length of the hammer piston. A weak flexible piston of this type produces a rather elongated percussion wave.

Fig. illustrates a hammer piston of a rock drill which is a modification of Figs. 1 and 3. The impact portion 38 according to Fig. 5 is provided with straight and oblique grooves 39, 4t) in order to rovide means for obtain ing the drill bit by virtue of power taken from the piston in a conventional manner (not illustrated). The piston head consists of a cylindrical sleeve 41. in which a stiff bellows type spring forming the main part of the mass of the piston head is disposed between the base 42 of the sleeve and a disc-shaped flange 43 at the upper end of the impact portion 38. The spring may be compressed by means of a disc 44 screw-threaded into the open end of the sleeve 41 and enclosing the disc-shaped flange 43. The spring consists of annular bellows elements 5 comprising two steel discs connected at their inner peripheral edges so as to form integral elements provided with outer peripheral ridges 46 by means of which the elements contact each other, the base 42 of the sleeve and the flange 43 so as to form a stiff bellows type spring. This structure is fitted and guided on a central extension 52 of the impact portion 38.

Fig. 6 illustrates a piston in which the main part of the mass of the piston head is made of a material having other elastic properties than steel. The piston consists of an impact portion 47 carried at the end of a rod 48 provided with a flange 49 and a nut 56 between which and the flange a tubular cylindrical body 51 is secured. This body may be made of bronze or other material with at least a 30% lower modulus of elasticity than steel so that said body is capable of flexing in the direction of the blows substantially more than a steel piston of the same length and weight. In order that this body shall not be too light the material of the body 51 should preferably have a specific gravity of more than 4 kilogrammes pc cubic decimetre.

The above described embodiments of the invention should be considered only as examples and the invention may be modified in several different ways within the scope of the claims. The piston or the piston head may, for instance, be made as an integral bellows type spring in which case the

discs

17, 34 or elements 45 are connected at their inner and outer edges. The

central rod

21, 33, 46, 48 may be dispensed with if the flexible piston head itself 'is constructed to form an impact portion. Preferably, a piston according to the invention may be designed to deliver blows with an impact velocity of more than 5 metres per second.

What I claim is:

l. A free motion hammer piston for percussion tools driven by an elastic pressure fluid comprising a piston head acted on by the pressure fluid to reciprocate the piston, a portion designed for delivering impacts to a member, a plurality of elements forming the major portion of the mass of said head and having a specific gravity greater than 4 and arranged in such a manner that they are in part axially spaced to permit the spaced parts to flex axially in the direction of the blows upon an impact of said impact portion on said member.

2. A hammer piston according to claim 1 in which the flexible elements comprise flexible discs superimposed in the direction of the blows with the spaced parts of the discs arranged to permit flexing of the discs in the direction of the blows relative to the rest of the piston.

3. A free motion hammer piston for percussion tools comprising a piston head, a portion designed for delivering impacts, a plurality of flexible discs formed as separate elements contacting each other alternately at inner and outer edges so as to form a flexible bellows structure forming the major portion of the mass of said head, and means for holding said discs and said impact portion together.

4. A hammer piston according to claim 3 in which at least certain of the flexible discs provide confronting surfaces of revolution contacting each other along circles the radius of which is variable in accordance with the pressure exerted on said discs.

5. A hammer piston according to claim 3 in which said means is adjustable to produce an initial stress in the flexible portion of said piston head.

6. A free motion hammer piston for percussion tools comprising a piston head, a portion designed for delivering impacts, and an integral flexible bellows capable of flexing elastically in the direction of blows and forming the major portion of the mass of said head.

7. A free motion hammer piston for percussion tools comprising a piston head, a portion designed for delivering impacts, a plurality of flexible bellows elements, each element comprising at least two discs connected to each other to'form integral bodies, and means for holding said bellows elements and said impact portion together.

8. A hammer piston according to claim 7 in which said means is adjustable to produce an initial stress in the flex ible portion of said piston head.

9. A hammer piston for percussion tools in which said hammer piston is reciprocated by means of an elastic pressure fluid and comprising an impact delivering piston portion, and a piston head the major portion of the mass of which comprises a plurality of elastic elements with a specific gravity greater than 4 in superimposed arrangement and in part axially spaced so as to permit the spaced parts of said elements to flex elastically in the direction of movement of the piston relative to said impact delivering portion when the impact delivering portion is arrested at the end of a working stroke of the piston.

10. A hammer piston for percussion tools in which said hammer piston is reciprocated by means of an elastic pressure fluid and comprising an impact delivering piston portion, a metallic piston head the major mass of which forms a spring, and means for adjustably compressing said spring in the direction of movement of said piston.

11. In a percussion tool having a working cylinder, a hammer piston reciprocable in said cylinder, means for supplying elastic pressure fluid to said cylinder to reciprocate said piston, said piston comprising a first portion adapted to deliver impact blows directly to a blowreceiving member and a second portion forming a piston head the major portion of the mass of which comprises a plurality of elastic elements with a specific gravity greater than 4 in superimposed arrangement and in part axially spaced so as to permit the spaced parts of said elements to flex elastically in the direction of movement of the impact delivering portion of the piston in said impact delivering direction when said first portion of the piston is arrested at the end of a working stroke of the piston.

References Cited in the file of this patent UNITED STATES PATENTS 618,324 Blum Jan. 24, 1899 1,105,876 Briegel Aug. 4, 1914 1,884,969 Carpenter Oct. 25, 1932 2,025,288 Johnson Dec. 24, 1935 FOREIGN PATENTS 283,849 Great Britain July 12, 1928 322,515 Great Britain Dec. 5, 1929 536,880 Germany 1931 984,182 France 1951