DE1728188A1 - Hydraulic coupling hammer - Google Patents

Description

Applicant in; Company Langenstein% Sone-mann Aktiengesellschaft

Title:

Hydraulic coupling hammer

B e s c h r e i b ti η g

P 17 23 188.8

"The invention relates to a hammer with hydraulic coupling, in which a drivable bear can be moved back and forth on a stand compared to an opposing bear, in which the drivable bear is connected to a driving piston that is subjected to a blow with driving fluid and can be moved back hydraulically after the blow, in which at least one passage having a valve device closed for the impact leads to the outside from a hydraulic coupling engaging the drivable bear, in which the drive piston is driven back against the pressure of the fluid against the pressure of the fluid after the impact by means of a pressure fluid feed into a cylinder piston device and in which from d for the pressure fluid infeed p: it delivers the fluid which flows off via a blow valve that is open for the blow. '

l'Jiri by di (. _; German patent specification 'No. 1 116 510 better known

209853/0135

Documents (Art 7 § l para. 2 no. 3 l set dae Änderunosee ". V. 4. 9. VJ

BAD ORIQiNAt

Hammer of this type is designed as a counter-blow hammer, which has an upper and a lower bear. In this known counter-blow hammer, the driving piston is with the upper one. Bears rigidly connected. By feeds the drive piston _va ■ Impact acting Treibfluidum wird'ein blowing cylinder chamber. The lower head is connected to the drive piston via a hydraulic coupling designed as a counter-coupling. Because of the rigid connection of the upper ram with the drive piston and because of the counter-coupling, the cylinder piston device also serves as the retraction hydraulics of the two rams.

In this hammer, the charge with propellant fluid for interrupted a retreat of the bears. However, it is also possible to stop the charging of propellant fluid during the withdrawal to maintain or the bears against the pressure of the propellant fluid move back. This is the pail for a through the German Auslegeschrift No. 1 249 637 known hammer, in which the propellant fluid is trapped in a pressure chamber encompassing a propulsion cylinder chamber during impact Gas is ..

The valve device provided on the counter-coupling in the known hammer of the type mentioned at the beginning serves to fill the counter-coupling with liquid and to adequately fill it. keep filling. The ZyIj the nderkolbeiieinrich environment zugefutH'te pressure fluid drives the driven ^B: i: reindeer and Treibkol-

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OR / GfNAL

ben back against the pressure of the propellant fluid. At one stroke the pressure fluid feed already flows into the cylinder piston device pressure fluid supplied via the open impact valve, which has a sufficiently large cross-section for this possesses, almost unhindered.

In the case of a hammer of the type mentioned above, there are bouncing blows undesirable. A bounce occurs when a bear immediately jumps back from the workpiece after hitting a workpiece, however, after jumping back, falls again on the workpiece, i.e. dances. For the purpose of "avoiding bouncing blows is in the case of the German Auslegeschrift No. 1 249 known counter-blow hammer provided that the pressure fluid feed Constantly delivered pressure fluid in the event of an impact by closing the impact valve in the cylinder piston device so.f ort takes effect in the sense of a backward movement of the bears.

It can be seen that when the pressure of the propellant fluid, against which the drive piston is driven back, in order to increase the impact energy is increased by the German Auslegeschrift No. 1 249 ^ 32 known counter-blow hammer Bouncing blows are not avoided to a sufficient extent. The aim of the invention is to provide a new way of reducing the hammer of the type mentioned at the beginning To create bouncing blows. It is also a disadvantage of known ones Counter-blow hammers so that they cannot be used as a press

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are cash. The invention therefore aims to create a hammer of the type mentioned at the beginning, which can also be used for pressing is, - The invention finally aims a hammer of To create the type mentioned at the beginning, whose drivable bear can be moved back and forth easily and without great effort and which has a low overall height.

For this purpose, the invention provides a hammer of the type mentioned at the beginning, which is characterized in that the drive piston is designed as a free piston, the cylinder piston device engages the free piston, a retraction hydraulics for the drivable Bear is provided, and a relief valve in the passage between the drivable bear with the free piston connecting hydraulic coupling and a liquid low Pressure containing accumulator is arranged, the relief valve at the standstill of the moving for the blow Bear is opened. The opening of the relief valve takes about 40 msec in practice with automatic control after the start of the standstill.

In the hammer according to the invention, the free piston is not rigid with either of the two bears but by means of the coupling with the drivable bear connected. For one stroke the coupling is completely filled with liquid from the reservoir and due to of the closed relief valve is effective. During or immediately after the impact, the relief valve is opened, so that the pressure of the pressurized fluid no longer acts on the drivable bear and this is displaced by liquid

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can jump back from the coupling almost unhindered. The sabot is moved back after the impact by means of the cylinder piston device independently of the drivable bear.

During the hydraulic return movement of the drivable ram and the return movement of the free piston, which take place as usual, i.e., the "cocking" of the hammer, is the relief valve open and the coupling fills up from memory. The hammer according to the invention has the advantage that the drivable bear or both bears can be moved as far apart as you want without changing the pressure acting on the retracted free piston. This allows an exact energy dosage of the field.

The hammer according to the invention can be used as a press if it additionally has a press cylinder space above a plunger surface engaging the drivable bear, into which pressure fluid can be brought via a pressure line having a valve battery, the relief valve both when the drivable bear M is moved back and forth is open. The operation of such a hammer during pressing takes place in a manner known per se and with devices known per se. When pressing, the impact valve is closed and the drive piston is at rest. The relief valve is open so that liquid can always flow back and forth between the coupling and the reservoir.

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With regard to the reduction of bouncing blows, the Advantageously develop hammer according to the invention in that the pressure of the pressurized fluid supplied by the pressurized fluid infeed in the cylinder piston device acting on the free cylinder is greater than the pressure of the fluid in the hydraulic one Coupling on impact and the pressure of the fluid in the hydraulic coupling on impact is greater than the pressure of the propellant fluid acting on the free piston. With this hammer, the pressure in the coupling of the free piston and the drivable bear is lower than with the pressure fluid supplied by the pressure fluid infeed. Lower pressure but allows faster acceleration of Liquid and thus easier drainage of the liquid to the coupling through the relief valve.

The hammer according to the invention is to be operated as a single haramer, whereby only the drivable bear and not the counter bar is moved for one stroke. However, the hammer of the present invention is preferably designed as a counter blow hammer, wherein

»The drivable bear and the opposing bear in a manner known per se by means of a hydraulic counter-coupling with one another are connected. The negative coupling is expediently designed in such a way that it only allows bouncing blows to a small extent. Here, small amounts of liquid are used in the negative feedback respected. If the hammer according to the invention is designed as a counter-blow hammer, the negative coupling to the Pressing preferably turned off.

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In the hammer according to the invention "the free piston does not need to be moved during idle strokes of the drivable bear, so that a power-consuming displacement of the free piston against the pressure of the driving fluid is avoided. During idle strokes, the free piston rests either in the lowered position or in the retracted position with the flap valve closed. It is preferably provided here that a pressure chamber filled with compressed gas as the drive fluid is connected to a drive cylinder space which is delimited by the free piston and which is shut off for impact.

Preferred embodiments are shown below with reference to the drawing of the hammer according to the invention described. In the Drawing shows

Fig. 1 in section designed as a counter blow hammer Hammer and

Fig. 2 in section the upper part of a single hammer working hammer.

The two hammers shown work vertically and respectively each have a base plate 21 lying on a foundation, not shown, on which a stand 18 stands. One upper drivable bear 1 with an upper die 22 opposite a lower bear 16 is arranged. The Gegenbär 16 carries a lower die 23. On top of the stand is a memory 24 provided. - 8th -

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BATH ORIGINAL

The embodiment according to Fig. 2 is designed as a single hammer, but dhre. Devices for striking and pressing can also be used with a counter-blow hammer. the The embodiment according to FIG. 1 is designed as a counter-blow hammer, the counter-bear 16 with the drivable bear 1 is connected by a hydraulic counter-coupling 63.

The negative coupling 63 has two coupling branches 64 which Attack sideways on the drivable bear 1 and on the opposing bear 16. Each coupling branch 64 has one at one end drivable bear 1 attached coupling rod 12, the other end merges into a movable plunger 13. Of the. movable Plunger 13 protrudes into a coupling space 14 which is immovable with respect to opposing bear 16 and which is filled with liquid, e.g. Oil, is filled. The coupling space 14 is delimited at the top by a piston surface 15 connected to the opposing bear 16 and is at the bottom completed by a plunger 17 resting opposite the base plate 21. Der.ruhende plunger 17 points upwards a hole 19 open to the coupling space 14 into which the ■ movable plunger 13 can be inserted. The coupling spaces 14 of all coupling branches 64 are through compensating lines 20 connected to one another, which pass through the stationary plunger 17.

Each coupling branch 64 is designed in such a way that the coupling space 14 extends through an extension of the coupling rod 12 with the opposing bear 15 extends piece rigidly connected. The ■

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BAO ORIG / NAL

The coupling space 14 is opposite to the movable plunger 13 End closed by the resting plunger 17, which is axially in the bore 19 provided in the mentioned piece is movable and is attached at one end to the stand 18 and at its other end that formed by the piece Piston surface 15 is arranged opposite.

In the hammer according to FIG. 1, a splash 65 is also provided on each of the four sides of the opposing ram 16, which when the opposing ram is lowered against a hydraulic buffer 66. Λ , which is provided in the base plate 21, presses. A hydraulically actuated ejector device 67, which is known per se, is provided on the base plate 21 below the opposing ram 16. -

Each hammer has a retraction hydraulics 3 to which a Piston 25 belongs to the one with the drivable bear 1 Piston rod 31 rigidly connected and centrally to the drivable Bear is arranged. This piston 25 limits one in:

. . '■■■ .. m

Storage 24 arranged retraction cylinder space 26 above. In the ™ Retraction cylinder space 26 opens into a line 11. In the embodiment According to FIG. 2, this line 11 runs to a pressure accumulator, not shown. The pressure accumulator, not shown ict is a well-known facility that is continually Lind constantly pushes liquid under relatively low pressure into the pipe 11 and acts like a spring. In the embodiment according to FIG. 1, the line 11 runs via a Y-valve 39 to a main pump 38

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BAO ORIGINAL

With the line 11 leading to the retraction hydraulics 3 lying valve 39, the line 11 can be shut off by lowering the valve body of the valve. A solenoid valve is used for this 69 open, which lies in a control line 68. The solenoid valve 69 is connected via an electrical line 70 to an electrical switch 71, which is known per se Way is attached to the stand 18 movable up and down. The electrical switch 71 is one of the drivable Bear 1 attached cam 72 can be actuated.

A pressure chamber 27, which merges into a drive cylinder chamber 28, is provided laterally next to the retraction cylinder space 26 and partially protruding into the reservoir 2A. In the drive cylinder space, a piston can be moved up and down, which is called free piston 2 in the following, because it is not rigidly connected to either the drivable ram or to the opposing ram 16. It is therefore provided that the movement path of the free piston 2 runs laterally next to the movement path of the piston 25 of the I-pulling hydraulic system 3, which is rigidly connected to the drivable B ^ reri 1. The pressure chamber 27 is blocked for striking.

The 'free piston 2 belongs to a hydraulic coupling.G, which connects the drivable bear 1 with the free piston. This coupling € v / eis a fluid-filled coupling space 29, to which a below the free piston ? located cylindrical space and a space connected to this above a rigidly connected to the drivable bear 1

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which piston surface 30 belongs to. A plunger 32 rigidly connected to the stator 18 protrudes through the piston 25 into the piston rod 31. In the embodiment according to Pig the maintenance of the rush, ο Ib ens 2 located cylindrical space through the plunger 32 into the space above the piston surface 30. In the embodiment according to ^;; ß "Pj f .. 2, the space above the piston surface 30 is partially Λον piston rod 31 and partially arranged above the piston 25. Bas in the piston rod 31 protruding plunger tuck 3-2 is at a distance from the piston rod.

In both embodiments, soir.it is provided that the Piston rod 31 to which the drivable bear 1 is attached on the one hand is, on the other hand-the second piston 25 of the hydraulic Coupling 6 carries. The plunger 32 rigidly connected to the stator IS protrudes through the piston 25 into the piston rod 31. The coupling space 29 of the coupling 6 extends along the plunger 32 to below its free end in the Piston rod 31.

A relief valve 5 is connected to the coupling 6 by a passage 33 from the coupling space 29 into the reservoir 24 leads and can be shut off by lifting a movable valve body 34 of the relief valve 5. The moving valve body 34 of the relief valve 5 is integral with the loaded

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BAD ORiGINAL

movable valve body 35 of an impact valve 8. The impact valve 8 has a large cross section and is located in a line of large cross-section, which connects the cylinder of a cylinder piston device 4 with the memory 24.

A piston 3-6 of the cylinder piston device 4 is located below the free col- umn, acted upon by propellant fluid at the top. bens 2, is rigidly connected to this and protrudes like a rod through part of the coupling roughness 29. The free piston 2 is

™ also borders the coupling space 29 of the coupling 6. Into the cylinder The cylinder piston device 4 is supplied with a pressure fluid feed 7 with a valve 37, which comes from the main pump 38. The pressurized fluid feed 7 is connected to the line 11 leading to the retraction hydraulics 3 via a pressure relief valve 40 tied together. The main pump 38 is in the embodiment according to FIG. 1 in the memory 24 and in the embodiment according to FIG 2 in a manner not shown, e below next to the opposing bear 16 arranged, wherein they liquid over from the memory 24

fc a line 41 sucks. The impact valve 8 is in the memory 24 arranged near the cylinder space of the cylinder piston device 4. A control line 42 in which an electrically operated Solenoid valve 43 is located, leads from a control pump 44 to the impact valve 8. The control pump 44 pushes liquid out of the Memory 24 through the control line 42 to the impact valve 8. Dor The movable valve body 35 of the impact valve 8 is used to close the impact valve by means of a weak spring 45 pressed down. The impact valve 8 is known per se

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Way designed so that after it has been opened by lifting its valve body 35, Von from the cylinder space the cylinder piston device 4 is kept open flowing fluid. Bs closes by itself when there is no more fluid flowing through it. Since the valve body 34, 35 of the Impact valve 8 and the relief valve 5 rigid with one another are connected, the impact valve 8 is connected to the relief valve 5 coupled in opposite directions. The relief valve is also 5 because of its connection with the impact valve 8 by means of the from the cylinder piston device 4 when striking the drivable Bear 1 displaced fluid controllable-designed.

The coupling 6, ie its coupling space 29, can be connected via a passage 73 with a compartment suction valve 9 to the reservoir 24 in which the coupling is arranged. In the embodiment according to FIG. 1, the compartment suction valve 9 can be opened and closed from the outside via an electrical line 46 and in the embodiment according to FIG. 2 with an auxiliary hydraulic system 47. In any case, it is provided that the externally actuated compartment suction valve 9 is additionally provided in the passage 73 between the coupling 6 and the liquid supply present in the reservoir 24. It also follows from the foregoing that the free piston 2, the cylinder piston device 4 and the coupling 6 are arranged in the accumulator 24 and the passage 73 with the compartment suction valve 9 leads into the accumulator.

The two hammers each have a press hydraulic 10,

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to which a press cylinder space 48 arranged above the drivable bear 1 belongs. The press cylinder space 48 is after at the bottom of a plunger surface 49 which acts on the drivable bear 1 and which can be moved up and down in the press cylinder space Piston limited. In the embodiment according to FIG. 1, the piston rigidly connected to the drivable bear 1 has 25 this plunger surface 49 and encloses the press cylinder space 48 the plunger 32. In the embodiment According to FIG. 2, the press cylinder space 48 is in the plunger 32 is provided and a plunger 50 resting at the bottom of the piston rod 31 protrudes upward into the press cylinder space 48 and carries there the plunger surface 49.

Pressure fluid can be brought into the press cylinder chamber 48 via a press line 51. In the embodiment of FIG. 2, a press pump 52 feeds this pressurized fluid via a Jen tilbatterie 53 with a solenoid valve in the press line 51. The valve battery 53 can be adjusted from the outside via an electrical line 54 so that once pressurized fluid flows into the press cylinder chamber 48 and the other liquid can flow back into the reservoir 24 from the press cylinder space.

In the embodiment according to FIG. 1, the pressure line runs 51 to a valve cluster 55 "presses", which in turn with the main pump 38 is connected. The main pump 38 is with the pressure fluid feed 7 and the line 11 via a valve cluster 56 "withdrawal" connected. The entirety of ven-

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The valve battery 55 "press" and valve battery 56 "retraction" can be actuated from outside the memory 24 and in the press known manner not shown in detail.

In the embodiment according to FIG. 1, the conveying direction of the main pump 38 can be reversed by means of a lever mechanism 57 attached to the wall of the accumulator 24 and a control hydraulic system 58. The conveying direction of the main pump 38 is once adjusted so that the main pump operates in the valve bank 55 "presses", and the other adjustable as A bar that the main pump operates in the valve bank 56 "retreat."

In the embodiment according to Pig. 1 run from the press cylinder space 48 outlets 59 into the memory 24, below which a poppet valve 60 is located. The poppet valve 60 is rigidly connected to an auxiliary piston 61, which by means of spring force is pushed up. Above the auxiliary piston 61 opens a control line 62, which can be fed at the other end by the main pump 38 when this is fed to the Yentilbatterie 56 ™ "Retreat" works.

In the reservoir 24 there is liquid, for example oil, under low pressure. The low pressure is, for example, 0.1 or 0.2 atm. and is in any case less than the pressure with which the propellant fluid acts on the free piston 2 after an impact. The propellant fluid is when the free piston 2 is back

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"moves and the hammer is ready to strike, under one lower pressure, e.g. 40 atm. amounts to. This low pressure is also after a when the free piston is advanced Blow, even greater than the low pressure of the liquid in the reservoir.

The propellant fluid is a gas, e.g., nitrogen, that is trapped and compressed in the pressure chamber 27. The lower one The pressure of the gas changes only slightly as a result of the movement of the free piston, e.g. by 5 atm.

The coupling 6 or its coupling space 29 can be filled with liquid, e.g. oil. As long as the coupling 6 is open, so with is connected to the liquid supply of the reservoir 24, the pressure of the liquid supply prevails in the coupling space 29, that is to say the low pressure mentioned above. As soon as the coupling 6 is closed and the impact valve 8 is opened, there is in the Coupling space 29 a mean pressure which is greater than the lower pressure and e.g. 100 atm. amounts to.

That for driving back the free piston 2 of the cylinder piston device 4 is preferably a liquid such as oil under a high pressure. The high, pressure is on greater than the mean pressure and is e.g. 200 ^ atm.

With regard to the pressure conditions described, is at

two embodiments provided that the propellant fluid

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effectively acted upon piston area 74 is larger than that of the Pressurized fluid to effectively acted upon piston surface 75 of the cylinder piston device 4. The effective piston surface 76 of the coupling 6 connected to the free piston 2 is on the one hand smaller, than the piston area 74 effectively acted upon by the propellant fluid and, on the other hand, larger than that of the pressurized fluid effectively acted upon piston surface 75 · Finally, the with the drivable bear 1 connected piston surface 30 of Coupling 6 can be selected to be smaller than that with the free piston " 2 connected effective piston area 76. This leads to the fact that the stroke of the piston 2 can be kept shorter than that of the drivable bear 1.

In order to hammer with the hammer according to FIG. 1 or FIG. 2, ie to carry out one or a plurality of blows, the pressure chamber 27 is filled with compressed gas and shut off via auxiliary devices not shown, which are known per se. The pressure of the gas on the free piston 2 is constantly on the free piston. The main pump 38 constantly supplies pressure fluid through the pressure fluid feed 7. In the embodiment according to FIG. 1 , no pressure fluid is conveyed through the pressure line 51. In the embodiment according to FIG. 2, the press pump 52 is switched off. The pressure fluid supplied by the main pump 38 holds the free piston 2 in its upper position against the pressure of the gas in the pressure chamber 27. In the embodiment according to FIG.

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BAO ORiGINAU

hydraulics 3 also the drivba;: en bear 1 in its upper retracted position. In the embodiment according to FIG. 2 becomes the drivable bear 1 through the pressure accumulator, not shown via line 11 in its retracted position held.

The solenoid valve 43 is actuated briefly for one impact, whereby the impact valve 8 counteracts via the control line 42 the pressure of the spring 45 is raised and opened. When the impact valve 8 is open, the cylinder space is the cylinder piston device 4 connected to the memory 24. In the embodiment according to FIG. 1, by opening the impact valve 8, the cylinder space of the hydraulic retraction system 3 is connected to the accumulator 24. By actuating the solenoid valve 43 the relief valve 5 is also closed. Because the anti-cavitation valve 9 is closed for a stroke anyway, the coupling 6 is now a closed system.

When the impact valve 8 is open and the coupling 6 is closed, the gas in the pressure chamber 27 drives the free piston 2 and over the coupling 6 the drivable bear 1 downwards. At the same time, the piston 3 connected to the free piston 2 pushes the cylinder piston device 4 liquid through the impact valve 8 into the memory 24. The movable valve body 35 of the impact valve 8 rests on the flowing through the impact valve Liquid flow. It falls off as soon as the drivable bear 1 stops its downward movement when striking and the liquid

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2 0 9 8 5 3/01 35 bad original

cessation of electricity. By falling off of the valve body 35 of the impact valve 8, the relief valve 5 is opened and the coupling space 29 of the coupling 6 is connected to the memory 24.

The drivable bear 1 that springs back after the blow is relieved of the pressure of the gas and can spring back freely and with full effectiveness into the cylinder of the retraction hydraulics 3 flowing liquid are moved back. At the same time, what is delivered by the main pump 38 arrives again Pressure fluid in the cylinder piston device 4 and drives return the Freikolbeii 2.

For pressing purposes , the free piston 2 preferably remains in its retracted position and is held there with the impact valve 8 closed and because of the one-way valve 37. The hammer is then operated like a customary press, the relief valve 5 being opened because of the closed impact valve 8 and the coupling space 29 being connected to the accumulator 24. In the embodiment according to Mg. 1, the main pump 38 is alternately set for a forward run of the drivable bear 1 to conveying into the press cylinder room 48 via the valve battery "presses" 55 ⁿ V & for a return of the drivable bear to conveying into the cylinder space of the retraction hydraulics 3 . In the embodiment according to FIG. 2, on the other hand, the main pump is switched off and conveyed with the press pump 52 for a 'advance of the drivable bear' in the press cylinder space 4.8 *

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_, - ■ - Ir

BAO ORIGINAL

This funding is for a return of the drivable bear 1 interrupted, so that this bear moves back again because of the pressure accumulator, not shown.

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Claims (1)

Claims 1. Hammer with hydraulic coupling, "in which a drivable bear can be moved back and forth with respect to an opposing bear on a stand, in which the drivable bear is connected to a driving piston acted upon for a blow with driving fluid and is hydraulically movable back after the blow, in which from a hydraulic coupling engaging at one end of the drivable bear at least one passage having a valve device closed for the impact leads to the outside, in which the drive piston is driven back against the pressure of the drive fluid after the impact by means of a pressure fluid feed into a cylinder piston device against the pressure of the drive fluid! Fluid supplied by the pressurized fluid feed flows off via an impact valve opened for impact, characterized in that the drive piston is designed as a free piston (2), the cylinder piston device (4) engages the free piston, a retraction hydraulics (3) for the drivable bear en (1) is provided and a relief valve (5) in the passage (33) between the hydraulic coupling (6) connecting the drivable bear with the free piston and a reservoir (24) containing low pressure did, the relief valve when the for the beat moving bear (1) is opened. - 22 - 209853/0135 (Art 7, Paragraph 1, Paragraph 2 f Jr. 1 Salt 3, d «3 Amendwxmgage ·. V. 4. 9- t'J. 2. Hammer according to claim 1, characterized in that it additionally has a press cylinder space (48) above a press piston surface (49) engaging the drivable ram (1), into which a press line ( 51) Druckfluidum can be brought, wherein the relief valve (5) is open both when moving back and forth of the drivable bear. 3. Hammer according to claim 1 or 2, characterized in that the impact valve (8) is coupled in opposite directions to the relief valve (5). 4. Hammer according to claim 1, characterized in that the pressure dea from the pressure fluid feed (7) supplied pressure fluid in the cylinder piston device (4) acting on the free piston (2) is greater than the pressure of the liquid in the hydraulic coupling (6) at the stroke and the pressure of the fluid in the hydraulic coupling during impact is greater than the pressure of the propellant fluid which acts on the precharge piston. 5. Haauner according to one of the preceding claims t to 4 » characterized in that the relief valve (5) in ■ ■ ■ -. ' _Λ in a manner known per se by means of the cylinder-piston device (4) when hitting the drivable bear (1) displaced pressure fluid is designed to be controllable. - 23 - 209853/0135 6. Hammer according to one of the preceding claims 1 to 5, characterized in that in the line (11) leading to the hydraulic retraction system (3) there is a valve (39) which can be actuated by means of a solenoid valve (69) located in a control line (68) which can be actuated via an electrical line (70) by an electrical switch (71) attached to the stand (18) so that it can be adjusted up and down, which in turn can be actuated by a nook (72) attached to the drivable bear (1) » 7. Hammer according to one of the preceding claims 1 to 6, characterized in that an externally operable suction valve (9) is provided in a passage (73) between the hydraulic coupling (6) and a liquid supply. ο Hammer according to one of the preceding claims 2 to 7, characterized in that the pre-piston (2), the cylinder piston device (4) and the hydraulic coupling (6) are arranged in the accumulator (24) and the passage (73) with the suction valve (9) leads to memory. 9. Hammer according to one of the preceding claims 1 to 8, characterized in that the movement path of the free piston (2) runs laterally next to the movement path of the piston (25) of the retraction hydraulics (3) rigidly connected to the drivable bear (1). - 24 209853/0135 10. Hammer according to one of the preceding claims 1 to 9, characterized in that the free piston (2), which on the one hand is acted upon by the propellant fluid, on the other hand delimits the coupling space (29) of the hydraulic coupling (6) and has a piston (36) the cylinder piston device (4) is rigidly connected, which runs like a rod through the coupling space 11. Hammer according to one of the preceding claims 1 to 10, characterized in that in the case of a piston rod (31) on which on the one hand the drivable bear (1) is attached and which on the other hand carries the second piston (25) of the hydraulic coupling (6) , a plunger piece (32) rigidly connected to the stator (18) protrudes through the piston (25) into the piston rod (31) and the coupling space (29) of the hydraulic coupling extends along the plunger piece to below its free end in the piston rod. 12. Hammer according to one of the preceding claims 1 to 11, characterized in that the drivable bear (1) and the opposing bear (16) are connected to one another by means of a hydraulic counter-coupling (63) in that the one bear (1) has a coupling rod (12 ), which dips with a movable plunger (13) into a fluid-filled coupling space (H) which is delimited by a piston surface (15) on the other bear (16) which can be reciprocated on the stand (18). ■ ■ ': - ■', * ²⁵ · - 209853/0135 13. Hammer according to claim 12, characterized in that the coupling space (14) extends as an extension of the coupling rod (12) through a piece rigidly connected to the counterbearer (16) and at the end opposite the "movable plunger (13)" from one end resting plunger (17) on which the mentioned piece with a bore (19) is axially movable and which is attached with one end to the stator (18) and with its other end opposite the piston surface (I5) formed by the piece, is arranged. 14. Hammer according to claim 13, characterized in that the stationary plunger (-17) has a bore (19) which is open to the coupling space (14) and into which the movable plunger (I3) can be pushed. 209853/0135