GB2129978A

GB2129978A - Control of hydraulic distributor via relay valve

Info

Publication number: GB2129978A
Application number: GB08328148A
Authority: GB
Inventors: Maurice Tardy
Original assignee: Bennes Marrel SA
Current assignee: Bennes Marrel SA
Priority date: 1982-10-21
Filing date: 1983-10-21
Publication date: 1984-05-23
Also published as: IT1169591B; SE8305755L; GB2129978B; DE3338291A1; IT8323366A0; JPS59170507A; GB8328148D0; SE8305755D0; FR2534984A1; FR2534984B1

Abstract

An hydraulic distributor 8 is controlled from a supply located at a distance. Pressure reduction valves 11, 12 operate as relays between the control 1, 2 and the slide valve of the distributor. In the very long pipes there circulate only pressure impulses of very low output. Input to either valve moves a slide to communicate an output chamber 9 or 10 with a pressure supply 13 until the slide is balanced by equal forces in the input and output chambers. <IMAGE>

Description

SPECIFICATION A remote control device for a hydraulic circuit The present invention relates to an improved remote control device for a hydraulic circuit of the kind that is found on machines, vehicles, civil engineering equipment, barges, ships and the like.

It-is known that in a hydraulic circuit the control switching is carried out by one or more distributors, generally of the type using a slide valve. The operator manipulates the lever of a starting or supply component, which hydraulic connections of greater or lesser length connect to the corresponding distributor. In certain cases therefore a great length of hydraulic piping exists between the supply and the distributor.

In known systems of remote control, the volume of oil necessary for the displacement of the distributor slide valve passes from the supply and circulates in the pipes connecting the supply to the distributor.

Because of this, during the circulation of the fluid, load-losses appear which in consequence increase response time of the control. In order to minimise these losses, the diameter of the piping is increased, but it will be realised that this increases the volume of oil to be compressed.

The compressibility loss of the line therefore increases, which further penalises the response time. It is therefore necessary to find a compromise between load-loss and compressibility loss, to obtain the best response to the control. The choice of this compromise is rarely satisfactory on systems known until now.

The present invention has the aim of avoiding these disadvantages by achieving an amplified remote control in which the volume of oil circulating in the pipes is very low for each impulse released from the supply.

A device according to the invention comprises a hydraulic supply connected by two pipes, one to each of the pilot chambers situated at the two ends of a hydraulic distributor, and it is characterised in that in each pipe between the supply and the pilot chamber of the corresponding end of the distributor there is interposed a pressure reduction valve, fed at a nominal pressure that a throttle and switching slide, moving according to the impulses coming from the supply, can modulate to instigate the desired movement of the distributor slide valve.

Owing to this arrangement, the long length of piping connecting the supply to each pressure reducing valve has to transmit only an impulse of pressure, which corresponds to an extremely low volume of oil displaced. Each pressure reducing valve acts as a relay operating on the corresponding end of the distributor slide valve.

The attached drawing, given by way of nonlimiting example, will allow the characteristics of the invention to be better understood.

Figure 1 shows diagrammatically a controlled hydraulic circuit of known type.

Figure 2 is a similar view of a hydraulic circuit according to the invention.

Figure 3 is a large-scale view showing the details of one ofthe pressure reduction valves according to the invention in axial section.

In a circuit with the known type of control illustrated in Figure 1, the operator moves the control lever 1 of a hydraulic supply 2. This supply receives the oil under pressure from a pipe 3 and it is connected by a pipe 4 to a return reservoir 5.

The outlet of the supply 2 comprises two pipes 6 and 7 which are connected to the two ends of the slide valve of a distributor 8. The pipe 6 is connected to the corresponding pilot chamber 9 at the left end of the slide valve of the distributor 8.

The pipe 7 is connected to the corresponding pilot chamber 10 at the right end.

It will be understood that in the case of remote control, that is to say if the supply 2 is far removed from the distributor 8, the length of the pipes 6 and 7 becomes considerable, as does the volume of oil to be moved through these pipes 6 and 7 for each control of the distributor 8.

According to the present invention (Figure 2), a pressure reduction valve 11 is interposed in the pipe 6 between the supply 2 and the pilot chamber 9. Similarly, a pressure reduction valve 12, similar to the valve 11, is interposed in the pipe 7 between the supply 2 and the pilot chamber 10. Each of the pressure reduction valves 11 and 12 also has a side feed of oil under pressure 13 and a return 14 to a reservoir 1 5.

In order to simplify explanation, the structure and operation of the valve 11 (Figure 3) will now be described, it being understood that the valve 12 is similarly constructed and is fixed symmetrically.

The fixed body 1 6 of the valve 11 has two interior grooves 1 7 and 18 into which the high pressure inlet 13 and the return to the tank 14 open respectively. Between these two grooves 17 and 18 there is an annular land 19 in which a cylindrical slide valve 20 is able to slide while forming a seal. In the latter, there is a peripheral central groove 21 with its bottom communicating through radial channels 22 with a blind axial drilling 23.

At each of the two ends of the slide valve 20 there is formed in the body 16 on the one hand the above-mentioned pilot chamber 9 and on the other hand a control chamber 24 connected through the pipe 6 to the supply 2.

Interior annular lands 25 and 26 of the same inside diameter as the land 1 9 ensure sealing on the periphery of the slide valve 20, this isolating the grooves i 7 and 18 from the chamber 9 and 24.

Finally, the axial width 27 of the groove 21 is less than or at most equal to the axial length 28 of the land 19.

Finally, the groove 21 permanently communicates with the pilot chamber 9 through the channels 22 and the blind drilling 23.

The operation is as follows: When the operator, moving the lever 1 of the supply 2, sends a pressure impulse into the pipe 6, this pressure is immediately estabiished in chamber 24. It repels the slide valve 20 (towards the right in Figure 3), which puts in communication the grooves 17 and 21. The high feed pressure 13 therefore, passes through the channels 22 and through the blind drilling 23 to be established in chamber 9. The distributor slide valve 8 is then impelled as indicated by the arrow 29.

As soon as the pressure in the pilot chamber 9 becomes equal to that in the chamber 24, the slide valve 20 is in balance. If the pressure in the pilot chamber 9 tends to increase, then the slide valve 20 returns towards the left and produces a cut-off between the corresponding edge of the land 19 and the groove 21.

If the pressure increases further in the pilot chamber 9, the slide valve 20 of the pressure reduction valve moves further to the left and puts chamber 9 into connection with the return pipe 14, by means of the grooves 21 and 18 then placed in communication.

It will be understood that the device according to the invention mainly presents the advantage of considerably reducing the volume of oil to be circulated in the pipe 6 to cause the displacement of the slide valve of the distributor 8. There is practically no loss of load between the supply 2 and the valve 11, so that the response time of the installation becomes very favourable.

Similarly, this low volume allows the bore of the connection pipes 6 and 7 between the supply 2 and the pressure reduction valves 11 and 12 to be reduced. Thus the volume of oil under pressure is reduced, therefore the compressibility loss and in consequence the response time of the installation are also reduced.

It will be recalled that the pressure arriving through the pipe 13 may be of any value provided it is above the maximum value necessary to obtain the full travel of the slide valve 20.

Claims

1. A remote control device for a hydraulic circuit comprising a hydraulic supply connected by two pipes, one to each of the pilot chambers located at the two ends of the slide valve of a hydraulic distributor, characterised in that in each of the pipes between the supply and the pilot chamber of the corresponding end of the distributor, there is interposed a pressure reduction valve, fed at a nominal pressure by a supply pipe, the cut-off and switching slide of the pressure reduction valve movable according to the impulses coming from the supply, modulates the nominal pressure to send it as modified to the corresponding pilot chamber which acts on the slide valve of the distributor.

2. A remote control device according to Claim 1, characterised in that the long length of pipe connecting the supply to each pressure reduction valve transmits only pressure impulse, which corresponds to a very low volume of oil displaced, very much lower than that which is necessary in the pilot chamber for complete travel of the slide valve of the distributor.

3. A remote control device according to any one of the preceding claims, characterised in that each pressure reduction valve comprises in its fixed body: - a control chamber connected to the corresponding control pipe; - a pilot chamber connected to the corresponding end of the slide valve of the distributor; - between the pilot chamber and the control chamber three annular interior lands are provided forming between them first and second annular grooves; - a slide valve sliding freely between the lands while ensuring a seal with them; - an inlet for nominal pressure into the first groove; - a connection between the second groove and a return reservoir.

4. A remote control device according to Claim 3, characterised in that the slide valve includes a central blind drilling opening into the pilot chamber, and communicating through a radial channel with the bottom of a groove around the periphery of the slide valve.

5. A remote control device according to Claims 3 and 4, characterised in that the width of the groove in the slide valve is smaller or at the most equal to the width of the central one of the three lands.

6. A remote control device constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.