DE8324442U1 - Double-acting piston-cylinder unit - Google Patents

Description

BOEHMERT & BOEHMERT LAW FIRM

fWhmcrt & boihmcn. Pmtfath/P O Bo« !07127. D 2800 Brtmen

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To the

German Patent Office Zweibrückenstr. 12

8OOO Munich 2 PATENT ATTORNEY DR -ING KARL BOEHMERT (1933-1973&igr; PATENT ATTORNEY DIPL.-ING. ALBERT BOEHMERT. BKF MEN ATTORNEY WILHELM J H STAHLBERG. BPEMEN PATENT ATTORNEY DR-ING.WALTERHOORMANN.BREMEN PATENT ATTORNEY DlPU-PHYS DR HEINZ GODDAR BREMEN PATENT ATTORNEY DIPL -ING EDMUND F EITNER MUNICH ATTORNEY WOLF-DIETER KUNTZE. BREMEN ATTORNEY DIPL-INC. JAN G. TÖNNIES. BREMEN PATENT ATTORNEY DIPL -CHEM DR C NEID». STIPPLER ML'NCH)

Your reference Your ref.

New registration

Your letter of

Our sign Our rtf. BX 1799 Bremen, Hollerallee 32 25 August

1983

J. and H. Büter Maschinenfabrik GmbH, Neue Industriestraße 2, 4472 Hären, Ems

Double-acting piston-cylinder unit

The invention relates to a double-acting piston-cylinder unit, whose cylinder-guided,
a piston rod attached to its
(first) end face is to be pressurized with a pressure medium, in particular hydraulic oil, which is to be guided into the cylinder in a controlled manner via a first connection piece arranged at an end section of the cylinder _; and on its opposite other (second) end face is to be pressurized with pressure medium which is in a
a middle section of the piston rod and the inner wall of the cylinder, the second end face

512

Office Bremen / Bremen Office.

P.O. Box 107127 Hullcrallee 32, D-2800 Bremen I Telephone: (0421) «34 9071 Telecop./Telecop.: (04 21) '34 9071 CCITT 2 Telegr.' Cables: Diagramm Bremen «"

Telex: 244 958 bopatd ,"

Accounts /Accounts. Bremer Bank, Bremen (bank code 29080010) 100144900 Deutsche Bank. Bremen (bank code 29070050) Ul 2002 <»&Rgr;?"·* / ür,G emeinwirtscha{t, M ünrhen

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of the piston and a cylinder end piece and is connected to a pressure medium reservoir which is connected to the ring chamber via a second connection piece arranged at the other end section of the cylinder.

Such generic piston-cylinder units are generally operated hydraulically and are therefore - in accordance with the terminology commonly used in practice - also referred to below as hydraulic cylinders.

Double-acting hydraulic cylinders used to have two connection ports for pressure medium, usually hydraulic oil, arranged at each end of the cylinder, between which there was a connecting line with a corresponding reversing valve, which could be used to act on either the first or second piston face depending on the desired piston rod position. However, the control valve of the connection line to the second connection port, etc., are components which are already quite expensive for such hydraulic cylinders and lead to a not inconsiderable reduction in price if they can be dispensed with. In addition, a second pressure medium connection for a second pressure medium line is often not desired for assembly reasons, space reasons, etc., and in particular not for devices to be equipped with such double-acting hydraulic cylinders, which also have to be extremely inexpensive in order to be competitive.

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For this reason, a piston-cylinder unit was developed without a second connection piece (and of course without a corresponding connecting line, without a correspondingly complicated control valve, etc.) and the return of the piston rod was effected by means of an external spring. In the design discussed above, this spring is put under tension when the piston is pressurized. If the pressurization is then switched off and the connecting line is released for return flow, the spring in this type of hydraulic cylinder, which is then under the corresponding tension in this extended position, ensures that the piston rod moves back to its original position.

However, such external tension springs are extremely undesirable in many applications. Not only are they viewed as dangerous by professionals (and therefore often require a certain degree of encapsulation or similar, which increases the cost even further), but they are also very popular with users, apart from the fact that such a design makes a rather makeshift impression and is also exposed to a wide variety of interference.

For this reason, hydraulic cylinders with so-called hydro accumulators have been developed, i.e. the second connection piece has been provided - just as in the known design described at the beginning - but this is not connected to a pressure medium connection line, but rather to a so-called hydraulic accumulator. This is a pressure accumulator, which is described in more detail below using the example.

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accumulator with a substantially closed housing in which a membrane is arranged, on one side of which, which forms a closed chamber with the corresponding housing section, a pressurized gas (generally nitrogen) is arranged, while the opposite side of the membrane is connected to the connection port of the cylinder with the remaining part of the housing with the connection port. If the hydraulic accumulator is pressurized with the hydraulic cylinder's pressure medium via its connection port, the pressure medium compresses the gas in its chamber, deforming the membrane, and builds up a corresponding pressure, which, depending on the pressure conditions prevailing at the connection port of the hydraulic accumulator, can then be released back out - i.e. here into the annular chambers of the hydraulic cylinder.

Such generic hydraulic cylinders with hydraulic accumulators have proven themselves to be very effective, especially since hydraulic accumulators are now manufactured in such large numbers that the unit price is relatively low. However, they still have considerable disadvantages, which are in particular that the ring chamber and the hydraulic accumulator must first be filled with pressure medium Sr= when they are put into operation, and above all that the constant leakage (of hydraulic fluid) on the piston rod and/or on the piston side results in a drop in pressure in the ring chamber/hydraulic accumulator system, which inevitably leads to the failure of the piston-cylinder unit after a certain period of operation.

The aim of the present invention is to improve the piston-cylinder unit of the type described at the beginning, while avoiding the aforementioned and other components, so that despite the basically unavoidable leakage losses, no pressure reduction occurs and the piston-cylinder unit therefore remains operational despite the inevitable leakage losses. In this case, a separate filling process for the annular chamber and the hydraulic accumulator with pressure medium under the appropriate pressure should also be dispensed with. Furthermore, the aim is that in the event of operational faults, the piston-cylinder unit or the hydraulic accumulator can be repaired or replaced easily by laypersons without this posing any danger to the person concerned. Finally, the inventive designs should make it possible to achieve further savings or reductions in cost compared to the previously known generic design in that the piston-cylinder unit according to the invention allows the use of normal standard seals (in contrast to special seals in the generic previously known prior art) and, moreover, does not place such high demands on the surface quality of the cylinder inner wall as is the case with the prior art.

The solution to this problem is characterized according to the invention in that a connecting line is provided between the first connection piece and the second connection piece of the piston-cylinder unit, via which a pressure equalization can take place when the piston is pressurized at its first end face by the pressure medium

is pressurized, and that the connecting line is interrupted when the piston is not pressurized by the pressure medium on its first end face, i.e. the inlet and outlet lines connected to the first connection piece are "open", i.e. without pressure and the pressure medium, i.e. generally the hydraulic oil, flows back in a known and usual manner / whereby only a simple ball valve or similar needs to be present as a control or shut-off device in the line leading to the first connection piece of the piston-cylinder unit.

The connecting line is preferably arranged inside the cylinder and, according to a preferred embodiment of the invention, it extends through the piston and a section of the piston rod, whereby a check valve can be arranged in the connecting line to implement the blocking measure described above.

&Sgr;&eegr; a particularly simple» robust and therefore reliable and also extremely inexpensive design, the connecting line is designed as a (double) rotary bore, which extends from the first end face of the piston to a peripheral section of the piston rod, which is always connected to the ring chamber«

The check valve preferably consists of a ball and a compression spring, which is supported at one end on the piston rod and at the other end on the ball and pushes it towards the first end face

the ball presses against a ball seat, whereby the preload of the spring can preferably be changed - if necessary by replacing it - in order to be able to easily realize different counterpressure conditions.

To ensure that when pressure medium is applied

In order to ensure that pressure equalization towards the annular chamber and thus towards the hydraulic accumulator can always occur when the first end face of the piston is acted upon, as is described in more detail below, while this pressure equalization is interrupted in the other operating state, it is preferably provided that when pressure is applied by the pressure medium on the first end face of the piston, the ball rests against a second ball seat with elastic deformation of the spring, wherein a flow path is present on the second ball seat through which pressure medium can flow through the connecting line when the ball rests against the second ball seat, wherein this flow path can be designed in an embodiment of the present invention as at least one slot-shaped recess on the second ball seat, which always connects the sections of the connecting line lying adjacent to the second ball seat on both sides.

Preferred embodiments of the present invention are described in the subclaims.

The invention is explained further below using an embodiment with reference to a drawing.

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The drawing shows a double-acting piston-cylinder unit 1 according to the invention with a pressure medium accumulator 2 for hydraulic actuation, thus a hydraulic cylinder with a hydraulic accumulator, the piston 6 of which is guided in the cylinder 3 and fastened to a piston rod 4 and is to be pressurized with hydraulic oil on its one end face 7, referred to above and below as the "first" end face, which is to be guided into the cylinder 3 in a controlled manner via a connection piece 8 arranged on an end section of the cylinder 3.

It can be seen that the cylinder 3 consists essentially of a pipe section ³¹ , at the ends of which a cylinder end piece 9 or 10 is arranged. The cylinder end piece 9, which has a pivoting attachment 13 provided with a bore 12, which is welded to the cylinder piece 9, is in turn welded to the pipe section 3*, the connecting piece 8 being located at the end of the piston-cylinder unit 1 described above.

At the opposite end, the pipe section 3' is not permanently connected to the cylinder end piece 10 located there in order to be able to assemble and, if necessary, disassemble the piston rod 4 of the piston 6. Rather, the bush-shaped cylinder end piece 10 is provided with an external thread 14 and is screwed into a corresponding internal thread, which is located at this end of the pipe section 3*. To achieve the required tightness, a seal 16 is arranged between the cylinder end piece 9 and the inside of the pipe section 3 ¹ of the cylinder 3.

net, which is a normal standard seal.

Two further seals 17 are arranged at this end of the piston-cylinder unit 1 between the piston rod 4 and the inner side of the cylinder end piece 10, which has a circular cross-section.

At this end of the piston-cylinder unit 1 there is a second connection piece 18 for the hydraulic accumulator 2, which is screwed into the connection piece 18 with a connection provided with a corresponding external thread.

The end of the piston rod located at this end has - just like the articulation projection 13 - a bore 21 and, as cannot be seen in the side view shown in the drawing, is provided with a slot in the middle which extends from its free outer end over a section in the direction of the other end of the piston rod 4, as is known per se.

The piston 6, which also has a seal 22 to the inner wall 23 of the piston 3, is also provided with a guide band 24 on its peripheral surface and has a design on its radially extending loading side 7, referred to above and below as the "first end face", which prevents the first end face 7 from being able to fully abut the inside of the cylinder end piece 9 without leaving a space 26. Rather, as can be seen from the drawing, such a

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Chamber 26 is present so that when pressurized pressure medium is supplied via the connecting line (not shown in the drawing) to the first connection piece 8 in the direction of arrow 27, pressure can build up in chamber 26 (the pressure medium can flow from the connection piece 8 through a bore 28 in the cylinder 3 into chamber 26).

If the piston rod 4 is to be moved from the end position set in the drawing in the direction of the arrow to the left in order to operate any device, device or component (not shown in the drawing), the operator in question opens a ball valve arranged in the line connected to the first connection piece 8 and hydraulic oil flows in the direction of the arrow 27 into the chamber 26, whereby a force is then exerted on the piston 6 which corresponds to the product of the pressure built up (of 180 bar, for example) multiplied by the projection area of the first end face 7 on a plane running at right angles to the central axis 31 and this pressure causes the piston rod 4 to move in the direction of the arrow 29.

Without going into detail at this point how pressure medium gets into the annular chamber 32 and how pressure is built up in it, this is assumed at this point - i.e. in accordance with the usual operating state - so that it can be determined that the piston C with its annular second end face 33 forms a

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Pressure is exerted on the hydraulic fluid in the annular chamber 32, so that when the piston rod 4 and the piston 6 move in the direction of the arrow 29 to the left, the fluid escapes via the second connection piece 16 into the hydraulic accumulator and presses there on the membrane described above , so that the gas filling (phytochemical) present on the other side of the membrane in a closed chamber is compressed accordingly.

It should also be noted that the area of the wide end face 33 of the piston 6 is smaller than its first end face, so that in the annular chamber 32 in the normal operating state when the chamber 26 is pressurized with pressure medium a smaller pressure prevails than in the chamber 26.

If, after a corresponding actuation of the device to be operated with the piston-cylinder unit 1 or the like, a return movement is to take place against the arrow 29, the operator therefore actuates the ball valve (not shown in the drawing) so that no more pressurized pressure medium is supplied to the connection nozzle 8 and thus to the chamber 26. Rather, the line connected to the first connection nozzle 8 is then "open" and free to flow back hydraulic fluid without excess pressure. The pressure required for this is exerted by the hydraulic accumulator, which keeps the hydraulic fluid in the ring valve 32 under the appropriate pressure and only has to cause a pushing out without significant counterpressure during the return movement.

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Now, as explained above, during operation certain leakages inevitably occur at the seals 16, 17, which would ultimately lead to failure of the piston-cylinder unit 1 if the leakages are not compensated (under appropriate pressure).

In the embodiment according to the invention described above and below, this takes place automatically, just like the initial filling of the annular chamber 32 or the pressure medium reservoir 2, in that a connection has been created between the first connection nozzle 8 and the wide connection nozzle 18, via which a pressure equalization can always take place when the piston 6 is pressurized by the pressure medium on its first end face 7, while the connection is interrupted when the piston 6 is not pressurized by pressurized pressure medium on its first end face 7, but the inflow line is open and the hydraulic 31 flows back. This connecting line is, as can be seen from the drawing, arranged within the cylinder 3 and extends through the piston 6 and a section of the piston rod 4. Both are provided with a bore 34 or 36 located on the central axis 31, whereby the axially extending bore 36 is connected to a radially extending bore 37 which leads to the ring can 32 and is connected to it in every piston position.

As can also be seen from the drawing, the bore 34 provided in the piston 6 widens at the end of the piston facing the piston rod 4

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and forms a seat 38 for a ball 39, which can lie in the widened section 34' of the bore 34 _; thus has a diameter that is smaller than the length of the widened section 34'. The bore 36 also has an widened section 36'. A pre-stressed compression spring 41 is arranged in this, which is supported at one end on the shoulder 42, which is formed due to the widening of the bore 36, and at its other end on the ball 39, so that it initially holds the ball in contact with the ball seat 38.

If the chamber 26 is pressurized by supplying pressure medium according to arrow 27 and the piston 6 is therefore moved to the left in the direction of arrow 29, pressure medium can also flow into the bore 34 of the piston and press the ball 39 against the effect of the compression spring 41, whereby the ball 39 comes to rest on the free end of the extension section 36*. There, however, it does not seal the extension section 36* and thus the bore 36, but rather slots 43 are provided on this "second" ball seat, through which pressure medium under pressure can always flow from the bore 34 - past the ball 39 - into the bore 36.

This process then takes place first of all during the operating period, i.e. in addition to the space 26 and the holes 34/36, the annular chamber 32 is also filled with hydraulic fluid and thus, via the second connection piece 18, the corresponding part of the pressure medium accumulator 2, until a state of equilibrium is reached due to the geometric conditions.

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occurs when the piston rod 4 has moved completely to the left in the direction of arrow 29.

If in this position the pressure in the inflow line and thus at the first connection piece 8 is removed by operating the ball valve (not shown), this results in the pressure prevailing in the hydraulic accumulator 2 and the annular chamber 32 not only acting on the second end face 33 of the piston 6, but also on the ball 39 via the bores 37, 36 and 36*, so that the latter is pressed into the position shown, in which it therefore rests lightly on the ball seat 38, so that the pressure medium liquid located beyond the ball 39 can flow out in the opposite direction to the arrow 2?, but pressure medium (under the corresponding pressure) nevertheless remains in the annular chamber 32 and in the hydraulic accumulator.

It is evident that any leakage losses are automatically compensated for in the same way as the initial filling, and that accordingly there is no pressure reduction during operation, which would require laborious refilling under corresponding pressure, etc.

For the same reasons, it is obvious that the piston-cylinder unit according to the invention can be made with standard seals and not particularly high-quality surfaces, since the size of the leakage (naturally within reasonable limits) is completely uncritical in contrast to the state of the art described above.

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However, this also results in a longer service life, since seals with low leakage losses require greater contact pressure on the sealing surfaces, which in turn leads to correspondingly higher wear in the case of a corresponding relative movement.

The piston-cylinder unit according to the invention therefore fulfils all tasks in accordance with the requirements placed on it in an almost optimal manner, whereby the measures taken for this purpose, namely the formation of the bores 34, 36 and the arrangement of the compression spring 41 and the ball 39, can be implemented with extremely little effort, since the piston rod is already clamped for machining purposes and therefore no additional alignment work is required to create the bores. The assembly of the spring and the ball is obviously extremely simple, and what is more, these additional costs are at least partially compensated by the fact that the inner wall 23 of the cylinder 3 does not have particularly high smoothness requirements and, furthermore, the seals used are significantly less expensive due to their standard designs than the special seals that must be provided in the comparable state of the art in order to make the leakage losses and the associated pressure drop as small as possible.

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BSZUG3Z2ICHENLI3T.S (LIST O? HSFSRSNCS ITJK2RAL3)

Piston-cylinder unit (=hydraulic cylinder)

2 pressure medium accumulators (= hydraulic accumulators) p 3 cylinders (of 1) 4 piston rods (from 1* 5 - 5 6 pistons (of 1) 6 7 first front side (from f>\ 7 8 first connection piece (on 3) 8th 9 Cylinder end piece (of 3) q 10 Cylinder end piece (of 3) 10 11 11 12 holes (of 13) 12 13 Articulation approach 1, 14 threads (of 10) 14 Vy - 15 16 Seal 16 17 seals 17 18 second connection piece 18 19 Connection q 20 - 20 21 Bore 21 22 Seal (of 6) , 22 23 interior walls (of 3) 23 24 Guide band 24 25 - 25 Pp ₁ room 2S 27 Arrow 27 28 Hole (in 3) 28 29 Arrow 29 50 r 30

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}i central axis (of 1) 31 32 Annular chamber 32 33 second front side (of 6) 33 3^ Bohruno (in 6) 34' extension section (of 34) 35 - ac 3&euro; fiohruna (in 4) 36* JSJ^fflfcecunßßftJ^cjiJ^nJ,^ (from 36) 37 Bohruna (in 4) 37 38 Kuaelflitz (door 391 38 39 Kueei 39 40 - 40 41 Pressure faders 41 42 öohulter 42 4^ ^ffilhi^i.tee 43 44 44 45 45 46 46 47 47 48 48 49 49 50 50 51 51 52 52 53 53 54 54 55 &bull; 55 56 56 d7 57 58 5^ 59 59 60 60 61 . 61 62 62 63 63 64 64 65 65

Claims (9)

&bull;&bull;&bull;&bull;4&diams; ··· ·* · BX 1799 claims ssaasseaacsassass 1. Double-acting piston-cylinder unit, the piston of which is guided in the cylinder and attached to a piston rod and is to be pressurized on its (first) end face with a pressure medium, in particular hydraulic oil, which is to be guided into the cylinder in a controlled manner via a first connection piece arranged on one end section of the cylinder and is to be pressurized on its opposite other («wide») end face with pressure medium which is located in an annular chamber formed by a middle section of the piston rod and the inner wall of the cylinder, the second end face of the piston and the iron cylinder end piece and is connected to a pressure medium reservoir which is connected to the annular chamber via a second connection piece arranged on the other end section of the cylinder, characterized in that a pressure connection line (34/ 36, 37} is present, via which a pressure** equalization can take place when the piston (6) is pressurized by the pressure medium on its first end face (7); And that the connection (34, 36, 37) is interrupted when the piston (6) is not pressurized by the pressure medium on its first end face (7). · &bull;# · is applied. 2. Piston-cylinder unit according to claim 1, characterized in that the connecting line (34, 36, 37) is arranged inside the cylinder (3). 3. Piston-cylinder unit according to claim 2, characterized in that the connecting line (34, 36, 37) extends through the piston (6) from a section of the piston rod (4). 4. Piston-cylinder unit according to claim 3, characterized in that the connecting line (34, 36, 37) is designed as a through-bore which extends from the first end face (7) of the piston (6) to a circumferential bore of the piston rod (4), which is always connected to the annular collar (32). 5. Piston-cylinder unit according to one or more of the preceding claims, characterized in that a check valve (38, ₃₉ , 4t) is arranged in the connecting line (34, 36, 37). 6. Piston-cylinder unit according to claim § and one of several of claims 2 to 4, characterized in that the check valve (38, 39, 41) consists of a ball (39) and a compression spring (41) which is supported at one end on the piston rod (4) and at the other end on the ball (39) and presses the latter against a ball seat (38) in the direction of the first end face (7) of the piston (6). I t ItII lit 7. Piston-cylinder unit according to claim 6, characterized in that the preload of the spring (41) is variable. β. Piston-cylinder unit according to claim 7, characterized in that the ball (39) rests against a second ball seat when pressure is applied by the pressure medium on the first end face (7) of the piston (6) with elastic deformation of the spring (39), a flow path (43) being present on the second ball seat through which pressure medium can flow through the connecting line (34, 36, 37) when the ball (39) rests against the second ball seat. 9. Piston-cylinder unit according to claim 8, characterized in that the flow path is designed as at least one slot-shaped recess (43) on the second ball seat, which always connects the sections (34*, 36') of the connecting line (34, 36, 37) lying adjacent to the second ball seat on both sides. e«, c· ·