GB2103719A

GB2103719A - Distributing liquid flow to a plurality of actuators

Info

Publication number: GB2103719A
Application number: GB08220467A
Authority: GB
Inventors: Rauno Rajala; Aimo Sainio
Original assignee: Tampella Oy AB
Current assignee: Tampella Oy AB
Priority date: 1981-08-17
Filing date: 1982-07-14
Publication date: 1983-02-23
Also published as: CA1193515A; AU8719982A; DE3226181A1; FR2511446B1; SE8204687L; IT1152499B; SE8204687D0; ZA825410B; FI812541L; FR2511446A1; FI64440C; FI64440B; IT8222859A0; NO822778L; GB2103719B; JPS5837305A

Abstract

A method of and a hydraulic circuit for distributing a liquid flow (Q) produced by a pump (2) uniformly to a plurality of hydraulic actuating means (9). The liquid flow from the pump is divided by means of a rotating multiblock distributor (4) into partial flows (Q1) which are each conducted to respective actuating means. Between each block (5) of the distributor and the associated actuating means is mounted a pressure control valve (7) by means of which the pressure (p1) of the partial flows (Q1) are adjusted to the same value which is higher than the working pressure (p2) of any actuating means (9) in order to maintain the pressure difference (ps-p1) constant over the individual blocks of the distributor irrespective of any variations in the working pressures of the actuating means. <IMAGE>

Description

SPECIFICATION A method of and a hydraulic circuit for distributing a flow of liquid produced by a pump to a plurality of actuating means The present invention relates to a method of distributing a flow of liquid produced by a pump uniformly to a plurality of hydraulic actuating means, according to which method the liquid flow of the pump is by means of a rotating distributor divided into partial flows which are each conducted to respective actuating means.

In practice, it is often necessary to operate simultaneously a plurality of hydraulic actuating means to which pressurized liquid is supplied by means of a common pump. In order to prevent the liquid flow produced by the pump from being primarily directed to the actuator or actuators subjected to the lowest load and, instead, to ensure a uniform distribution of the flow among all actuating means in order to produce a simultaneous operation of all actuators, it is previously known to control the distribution of the liquid flow produced by the pump by various means, including the following: 1. Flow regulating valves provided for each actuating means. This solution suffers from the disadvantages of a difficult and inaccurate control and a high loss of power, especially if the pump output varies.

2. Slide-type flow distribution valves. This solution suffers from the disadvantages of a distribution in two partial flows only and a difficult and inexact control which varies according to the load.

3. A rotating distributor. This solution has the disadvantage that the control varies according to the load.

4. Actuating means connected in series. This solution has the disadvantage of a multiplication of an error and a high feed pressure or big actuating means.

5. A feedback synchronization. This solution suffers from the disadvantages of being expensive, complicated and unreliable in operation under difficult ambient conditions.

6. Individual control valves for each actuating means, each of said valves having a control element of their own. The disadvantage is the difficulty of the operator to control several actuating means simultaneously.

The object of the present invention is to provide a method which avoids the above-mentioned disadvantages and permits a uniform distribution of the liquid flow produced by the pump to the individual actuating means in spite of any differences in the loads acting on said actuating means. This object is achieved by means of the method according to the invention which is characterized in that, the pressures of the partial flows from the distributor are by throttling said partial flows adjusted higher than the working pressure required by any actuating means.

In the method according to the invention, a rotating distributor is in a manner known per se used for distributing the pump output. Said distributor has for each actuating means one flow distributing block, and it divides the volumetric flow from the pump into partial flows corresponding to the number of blocks. However, the same load is provided for all blocks of the distributor by throttling the partial flows leaving the distributor. The invention is based on the idea that by arranging the loads for the individual blocks of the distributor to remain constant irrespective of any load variations in the actuating means, also the distribution ratio of the distributor remains constant.By throttling the partial flows so that the pressures of the partial flows in the distributor are higher than the working pressure required by any actuating means, the pressure differences over the individual blocks of the distributor remain unchanged and, accordingly, also the distribution ratio of the distributor remains unchanged, even if the pressures of the partial flows would vary after the throttling point due to variations in the working pressures of the actuating means. The distribution ratio of the rotating distributor is easily meintained if the pressure difference over the individual blocks remains unchanged. However, if the pressure difference varies, also the distribution ratio changes because the volumetric efficiency of the blocks, i.e. the outflow is very much dependent on the pressure difference.By means of the method according to the invention, the pump output will be reliably distributed among the individual actuating means irrespective of any load variations therein.

The invention also relates to a hydraulic circuit utilizing the method described above, and this circuit is characterized in that in the liquid flow connection between the distributor and each actuating means is mounted a throttling element which adjusts the pressure of each partial flow from the distributor to a higher value than the working pressure required by any actuating means. By means of the throttling element, it is possible to adjust the pressures of the partial flows from the distributor to a value which, in use, remains constant due to the fact that it always is higher than the highest working pressure of the actuating means. In this way, the same constant load is obtained for the individual blocks of the distributor which ensures a constant distribution ratio for the distributor irrespective of any variations in the working pressures of the actuating means.

The invention may be applied, for example, to the lifting of hydraulic-cylinder operated ground supports of a drilling platform. In particular, the invention is suitable for apparatuses provided with telescopic legs in which case the lowermost ground supports are each provided with a control lever and the remaining supports are lifted by means of the same lever. In addition, the invention is generally applicable to the synchronization of hydraulic actuating means, such as cylinders or motors if an absolute precision is not required.

In the following, the invention will be described in more detail with reference to the accompanying drawing which shows schematically a hydraulic circuit in which the method according to the invention is applied.

In the drawing, a pump 2 driven by a motor 1 is connected by a conduit 3 to a rotating distributor 4 which, in this embodiment, comprises four individual blocks 5. Distributors of this type provided with 2, 3 and 4 blocks are commercially available.

Each block of the distributor is connected by a conduit 6 to a pressure control valve 7 which, in turn, is connected by a conduit 8 to a hydraulic actuating means 9.

The opening pressures p, for the pressure control valves 7 are adjusted to the same value which is higher than the working pressure p2 required by any actuating means 9 but lower than the feed pressure Ps of the pump 2. The tank pressure of the actuating means is denoted by Pt The pump procedures at the feed pressure p5 a liquid flow 0 which is divided by the individual blocks 5 of the distributor into four partial flows Q, the pressures of which in the conduits 6 are equal to the opening pressures p, of the valves. Because all valves have the same opening pressure, also the pressure differences p5 - p1 over the blocks of the distributor are equal due to which the partial flows Q, will continuously be of the same size. The partial flows pass through the valves 7 into the conduits 8 and further to the actuating means 9 in order to actuate said means.

It will be noted that all other pressures except the working pressures p2 of the actuating means are the same for all blocks of the distributor. In a state of continuity, each pressure control valve throttles the liquid flow from the block so that p, remains constant, even if the pressure loss p1 - p2 changes as the working pressure p2 of the actuating means varies.

The drawing and the related description are only intended to illustrate the idea of the invention. In details the method and hydraulic circuit according to the invention may vary within the scope of the claims.

Claims

1. A method of distributing a flow of liquid produced by a pump uniformly to a plurality of hydraulic actuating means, according to which method the liquid flow (0) of the pump (2) is by means of a rotating distributor (4) divided into partial flows (Q1) which are each conducted to respective actuating means (9), characterized in that, the pressures (p,) of the partial flows (0,) from the distributor (4) are by throttling said partial flows adjusted higher than the working pressure (p2) required by any actuating means (9).

2. A method according to claim 1, characterized in that the difference between the feed pressure (p5) of the liquid flow (Q) produced by the pump (2) and the pressure (p,) of each partial flow (0,) from the distributor (4) is adjusted to the same value.

3. A method according to claim 1 or 2, characterized in that each partial flow (Q,) is throttled by means of a pressure control valve (7).

4. A hydraulic circuit for supplying actuating means with pressurized liquid, comprising a pump (2), a rotating distributor (4) receiving a liquid flow (Q) produced by the pump and dividing said flow into partial flows (Q,), and a plurality of actuating means (9) each receiving one of said partial flows through a respective flow connection (6, 8), characterized in that in the flow connection (6, 8) between the distributor (4) and each actuating means (9) is mounted a throttling means (7) which adjusts the pressure (p,) of each partial flow (Q1) from the distributor higher than the working pressure (p2) required by any actuating means (9).

5. A hydraulic circuit according to claim 4, characterized in that said throttling means (7) comprise pressure control valves, having the opening pressures (p,) of said valves being adjusted to the same value which is higher than the working pressure (p2) required by any actuating means (9) so that the pressure difference (p5 - p1) over the individual blocks (5) of the distributor are equal.