DE1039329B - Pressure relief valve for hydraulic systems, especially for power lifts on vehicles - Google Patents

Description

GERMAN

The invention relates to a pressure relief valve for hydraulic systems, in particular for power lifts Vehicles, with a piston-type, spring-loaded closing element, which is connected by a piston a small face compared to the cross section of the closing member is controlled.

One for this task, but for gaseous media certain pressure relief valve is known in which the controlling pressure acts on a piston that is connected to the closing member, has a smaller diameter than this and of the overflow point away. This has the advantage that the pressure drop that occurs during the overflow is the controlling one Pressure not affected. The passages of this valve are relatively short in the stroke direction. Particularly at higher overflow pressures and with liquid media, vibrations of the occur as a result Closing link and annoying and harmful chatter.

It is also known, in the case of a valve, the control piston of which has radial openings with its edges up to run these overflow openings as bores that run along a spiral on the circumference of the Piston guide are distributed. These holes are the same size and overlap very far; the The overflowing liquid therefore increases evenly with the piston stroke and the force of a closing spring to. As a result, the control pressure fluctuates as a function of the amount of the overflowing agent in turn causes the closing element to vibrate, so that noises and disturbances occur, and that furthermore the pressure in the connected pipe system is not kept at the same level can.

These disadvantages are avoided according to the invention in that the adjacent to the control piston, space under the working pressure of the system from the flow cross-section so far is removed so that pressure changes resulting from the overflow do not act on the control piston and that the flow cross-section consists of a plurality of radial bores, which at least in the stroke direction are offset from one another and are dimensioned so that the diameter of the larger stroke is free holes are larger than the holes opened in front of them.

The simultaneous use of these features, which should be protected alone, allows the to keep the closing member controlling the opening pressure away from the flow area, so that the pressure drop at this cross-section does not affect the control pressure and due to the increasing diameter the holes clear correlations between the opening movement of the closing member and the free

Pressure relief valve for hydraulic systems, in particular for power lifts on vehicles

Applicant:

Robert Bosch GMBH,
Stuttgart-W, Breitscheidstr. 4th

Werner Dieter, Stuttgart,

Eberhard Korkowski, Stuttgart-Feuerbach,

and Dipl.-Ing. Werner Zeuch, Fellbach (Württ.),

have been named as inventors

to produce the cross-section. These features together therefore surely avoid the occurrence of undesirable ones Vibrations of the closing link.

An embodiment according to the invention is shown in the drawing, namely shows

Fig. 1 is a diagram of an entire system,
2 shows a section through the overflow valve.
From a storage container 1, 2 oil is withdrawn by a pump. E & is passed through a pipe 3 into an overflow valve 4 and from there through a line 5 to a control valve 6 of a type known per se. Depending on the setting of this valve with a handle 7, the pressure oil is fed to one of the working lines 8 or 9. It flows into a working cylinder 10 and moves a working piston 11 sliding therein down or up. The oil flowing back in the other line returns through the control valve 6, a line 12, the overflow valve 4 and a pipe 13 back into the reservoir 1.

The overflow valve 4 has the task when the pressure in the line 5 and thus also in the pipe 3 increases too much to return the oil directly via the pipe 13. It is constructed in the following way:

In a housing 14 there are openings 15, 16, 17 and 18 for the pipes or lines 3, 5, 12 and 13 appropriate. They lead to a bore 19 made transversely to them. An inner housing is in this 20 inserted; it is with its wider portion 21 of a screw 22 against a Shoulder 23 of the housing 14 pressed. Sealing cords 24 inserted in bevels of the housing and 25 ensure a tight seal.

809 638/245

Claims (3)

The inner housing 20 contains a longitudinal bore 26 with a part 27 designed as a cylinder guide and a narrower extension 28, furthermore in its wider section 21 a wide transverse bore 29 and an annular groove 30. This provides the direct connection between the openings 17 and 18, i. H. between the line 12 and the pipe 13. The part 27 receives a closing member 31 designed as a hollow cylinder. A compression spring 32 rests with one end in a bore 33 of the locking screw 22, with the other on the open end face of the closing element 31. This is thereby pressed with its end face against a collar 35 of a piston 36. This piston slides sealingly in the bore extension 28. It has transverse grooves 37 which make it difficult for liquid to penetrate into this extension. The collar 35 contains a transverse groove 38. the end face 34 has a small bore 39. The otherwise closed space in front of the end face 34 is thus connected to the interior of the closing element 31. An annular groove 40 is screwed into the outside of this closing element; bores 41 lead from this into the interior of the closing element. In the housing 20, opposite radial openings 42 with a small diameter and, axially offset in contrast, further openings 43 and 44 are drilled. During normal operation of the system, pressurized oil comes through the pipe 3 and the opening 15 into the bore 19, fills this around the thinner part of the housing 20 and flows on through the opening 16 to the line 5. The oil flowing back through the line 12 goes back through the opening 17, the annular groove 30, the transverse bore 29 and the opening 18 to the pipe 13 and to the storage container 1. The piston 36 and the closing element are in the position shown: the openings 42 are closed. If the pressure in the line 5 and thus also in the bore 19 rises above a certain level, the force acting on the exposed end of the piston 36 overcomes the pressure of the spring 32 and pushes the piston and with it the closing element 20 To the right. The compression spring 32 is chosen so that this process occurs at the limit of the permissible pressure. If the closing member 31 is displaced, its annular groove 40 comes into the area of the openings 42, and pressure oil flows off through the bores 41. If the pressure increases even further, the annular groove 40 controls the larger openings 43 and 44, so that finally the entire amount of oil supplied by the pump can flow off in this way. The pressure at the openings 42 changes depending on the amount or speed of the oil flowing through; it decreases with increasing speed. However, the end face of the piston 36 is not influenced by this: it is constantly under the pressure in the pipe 3 and the line 5. This ensures that this pressure never exceeds the set pressure and always remains the same during the overflow, regardless of its extent. Because the liquid in the space can only flow in or out from the end face 34 via the bore 39, the movement of the closing member 31 is damped. The relatively large stroke, which is necessary for full opening up to the opening 44, also prevents the closing element from swinging back and forth. In order to suppress the swinging or creaking of the closing element, one of these two measures alone is sufficient in many cases. Because the overflowing liquid enters the closing element radially, the closing element is prevented from being influenced by back pressure on its side or bottom surfaces. The flow cross-section for the liquid on its way through the bores 41, the interior of the closing member 31, the longitudinal bore 26 and the transverse bore 29 widens in each case so that the liquid can flow off to the pipe 13 without congestion. This measure also prevents the closing element 31 from being influenced by the outflowing liquid. The overflow valve can also be assembled with the control valve 6 in a housing, so that the lines 5 and 12 run within this housing. Pä TEXT REQUIREMENTS: 1. Pressure relief valve for hydraulic systems, especially for power lifts on vehicles, with a closing member, which corresponds to the one opposite to the cross section of the closing member small area, the liquid pressure acts against a spring force like a radial slide Flow cross-section on controls, characterized in that the adjacent to the control piston ,,, The space under the working pressure of the system is so far away from the flow cross-section that pressure changes resulting from the overflow do not act on the control piston, and that the flow cross section consists of a plurality of radial bores which are at least in Stroke direction offset from each other and are dimensioned so that the diameter of the larger stroke free holes is larger than the holes opened in front of them. 2. Pressure relief valve according to claim 2, characterized in that in front of the closed end face the closing member is a closed, only through a narrow hole with the interior of the Closing member connected cavity is. 3. Pressure relief valve according to one of claims 1 to 3 with a hollow cylinder as the closing body, which is open at one end and connected to a return line, on its circumference with after provided openings leading inside and exposed to the inlet pressure on its closed end face is, characterized in that the openings on the outside of the hollow cylinder with an annular groove are connected, the openings of the closing body containing the opening which form the flow cross-section during the stroke of the closing member Housing meets. Printed publications considered: German Patent Nos. 172 373, 378 953, 139, 847 388, 886 990; U.S. Patent No. 2,305,519. 1 sheet of drawings © 809 638/245 9.