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(11) | EP 0 075 618 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Fluid pressure circuit control arrangement |
| (57) A fluid pressure circuit control arrangement is provided in which a control circuit
(4) shown including control valve means (40) supplies fluid under pressure to a distributor
valve (5) for distributing the fluid to cylinders (2) containing operating pistons
(3) inter-connected with operated pistons (13) in cylinders (12) of a piston pump
such as a fluid pressure transformer (1) of the differential piston kind. The transformer
(1) in turn supplies fluid to one or more output circuits (8), e.g. at high pressure
compared with low pressure supply by the circuit (4),the arrangement being such that
the supply of fluid to the output circuit or circuits (8) is controlled by the valve
means (40). The fluid in the output circuit or circuits is separate from and can be
different to, that of the control circuit (4). Provision for piston return operation
and sealing details as well as double acting arrangements are also described. |
[0001] This invention relates to the control of one or more fluid pressure (e.g. hydraulic) circuits especially a high pressure circuit or circuits where the latter is or are operated by at least one low pressure circuit (or vice versa) via a pump such as a fluid pressure transformer, e.g. of the differential piston kind.
[0002] The object of the invention is to provide an improved circuit control arrangement whereby control of fluid at high pressure and/or of a difficult nature tp handle can be readily effected. Practical advantages of the invention in this and other respects will be apparent from the following disclosure.
[0003] Basically according to the invention a fluid pressure circuit control arrangement comprises an input control circuit operable for controlling the supply of fluid under pressure to distributor valve means for distributing said fluid to cylinders containing operating pistons of a piston pump (such as a fluid pressure transformer of the differential piston kind) whereby one or more fluid output circuits supplied by the pump or transformer can be controlled by said input control circuit.
[0004] Practical examples of circuit control arrangements and other details are shown in the accompanying drawings in which:-
FIGURE 1 is a hydraulic circuit diagram of one arrangement,
FIGURES 2 and 3 are detail views of modified piston return means,
FIGURE 4 is a hyaraulic circuit diagram of a double acting arrangement,
FIGURE 5 is a hydraulic circuit diagram of a further double acting arrangement, and
FIGURE 6 shows an alternative control circuit.
[0005] Like parts are referred to by the same or similar reference designation in the drawings. Referring to FIGURE 1, the general circuit arrangement comprises a low pressure input control circuit 4 for supplying fluid at low pressure to the differential piston and cylinder units 22 of a pump or fluid pressure transformer 1 via a distributor valve 5 controlling the supply of fluid to the cylinders 2 of the units 22 so as to act upon the large diameter operating pistons 3 of the latter in an appropriate sequence of operation. Each piston 3 is shown connected in a compound manner by a piston rod 11 to a corresponding small diameter operated piston 13 in a cylinder 12 of each unit 22.
[0006] The distributor valve 5 is shown having a rotary action in which a rotatable valve member 50 operates in relation to ports 52 in the valve chamber 51, each port 52 being communicated with a corresponding cylinder 2. That part of the valve chamber 51 about the valve member 50 is supplied at 53 with fluid from the low pressure output of the control circuit 4, the hollow interior 500 of the valve member 50 being in constant exhaust communication with a reservoir 45 via the outlet port 54. The direction of rotation of the valve member 50 is indicated for the sequence of piston operation shown but rotation in the opposite direction is possible with a corresponding sequence of operation (see FIGURE 4).
[0007] For a continuous pumping action with little or no pulsation preferably not less than three sets of inter-connected pistons 3, 13 and respective cylinders 2, 12 are employed and may be of any practical number above three.
[0008] The cylinder 12 of each unit 22 containing a small diameter operated piston 13 is communicated through non-return valve means 7 with a high pressure output circuit 8 for circulation of fluid at high pressure for any required purpose. Each unit 22 is shown connected in a common high pressure circuit 8 but they may be connected to individual output circuits or in any desired grouped arrangement.
[0009] The low pressure input circuit 4 includes a pump 44 which may be of variable speed and/or variable capacity for supplying fluid to the distributor valve 5, the circuit 4 also including the reservoir 45.
[0010] Provided in the low pressure input circuit 4 for the purpose of this invention is control valve means 40 shown consisting of a shut-off valve 41 and a variable flow or relief valve 42 connected across the output and return flow lines of the low pressure circuit 4. These valves 41,42 are shown by way of typical example only and one or more valves may be employed according to requirements. Thus, if desired, the shut-off and variable relief valves 41, 42 may be incorporated in one valve unit or provided by a single valve.
[0011] As will be appreciated control of low pressure fluid flow by the control valve means 40 to the transformer 1 via the distributor valve 5 in turn effects fluid flow in the high pressure circuit 8 (or circuits). Thus if the shut-off valve 41 is opened then the distributor valve 5 is by-passed and so becomes inoperative so that no fluid flow occurs in the high pressure circuit 8. Similarly, setting of the variable relief valve 42 results in corresponding operation of the transformer 1 and likewise corresponding fluid flow in the high pressure circuit 8.
[0012] It is thus possible to employ one or more control valves of simple and inexpensive construction at 40 in the low pressure circuit 4 for effecting control of fluid flow in the separate high pressure circuit 8 (or circuits) where otherwise valves of specialised and expensive construction would be necessary in the latter. Furthermore, the remote control afforded in this way also has advantage where fluid in the circuit 8 (or circuits) is of a difficult nature to handle, (e.g. an acid or other corrosive or dangerous liquid or gas) which again would otherwise entail highly specialised control valve means.
[0013] Return or suction stroke movement of the inter-connected pistons 3, 13 may be assisted by return springs 21 and/or by fluid pressure operation which is also shown in FIGURE 1. For the latter purpose the volumetric space 23 in the cylinder bores 2, 12 between the large and small diameter pistons 3, 13 and about the piston rod 11 is communicated at 26 with a corresponding space 23 of a next or second cylinder unit 22 and which in turn is communicated in a similar manner with the space 23 of the third cylinder unit 22.
[0014] The space 23 of one of the cylinder units 22 such as the third unit shown in FIGURE 1, is arranged to be supplied via a non-return inlet valve 24 with hydraulic fluid whereby all three spaces 23 are filled with a required quantity of fluid for the purpose and at a suitable pressure determined by a relief valve 25 also shown communicated with the space 23 of the third cylinder unit 22.
[0015] As the pistons 3, 13 perform power and return stroke movements, the volumes 23 are varied with displacement of fluid from one to the other and for effecting appropriate piston return movement. Thus the volume of the associated space or spaces 23 of whatever pistons 3, 13 are performing a power stroke movement must equal the space volume at 23 of whatever pistons 3, 13 are performing a return stroke. In this way the volumes of the spaces 23 corresponds to piston movement and maintains a substantially constant total volume.
[0016] Such fluid pressure operated return of the pistons 3, 13 may obviate the need for return springs 21 although such springs can be provided as auxiliary means of piston return.
[0017] Since it is preferable to employ hydraulic fluid in the communicated spaces 23, instances may arise where the fluid employed at the low pressure side and/or the high pressure side is of a different nature so that sealing means additional to that provided by the pistons 3, 13 themselves is preferably provided between the pistons and is shown in the form of a tubular member 60 (FIGURE 2) about the connecting rod 11 and having outwardly directed flanges 63,613 at each end of appropriate diameter to the adjacent piston 3, 13 and provided with sealing rings 64 co-operating with respective cylinder bores 2, 12.
[0018] A suitable volumetric space 230 entrapped between the flanges 63, 613 receives hydraulic or other suitable fluid and these spaces 230 which are variable in volume are communicated with one another at 26 in the manner already described so as to effect piston return also as described.
[0019] In FIGURE 3 a similar arrangement is shown but where the large diameter piston 3 is operated by the small diameter piston 13 of each cylinder unit 22 from a distributor valve. In such case it is desirable to provide a large diameter area for effecting return movement of the small diameter piston 13 by displacement of fluid from another similar or identical cylinder unit 22 via the communicating passage 26.
[0020] For this purpose and also to enable a displacing fluid to be isolated from that acting on the pistons 3, 13, a tubular member 70 about the connecting rod 11 is provided having outwardly directed flanges 73, 713 provided with sealing rings 74 co-operating with corresponding bores 27, 217 therefor of the cylinder unit 22 whereby a volumetric space 237 is entrapped between the flanges 73, 713.
[0021] Displacement of fluid into the volumetric space 237 acts between the shoulder 227 between the bores 27 and 217 and the flange 713 to effect return movement of the small diameter piston 13 (and the large diameter piston 3 therewith) and vice versa. Passageways 80, 81 vent variable air spaces 280, 281 to atmosphere.
[0022] In the arrangement shown in FIGURE 4 each inter-connected pair of pistons 3, 13 is connected by a further connecting or piston rod 33 to a corresponding pair of inter-connected pistons 3', 13' in a complementary or opposed manner so as to provide a balanced double acting arrangement. Thus each opposed pair of larger pistons 3, 3' are connected by the central piston rod 33.
[0023] For the purpose of obtaining sequential operation of the pistons, the cylinders 2, 2' containing the large diameter operating pistons 3, 3' are supplied by fluid under pressure from the distributor valve 5 of which each port 52 is communicated with a corresponding cylinder 2 or 2' of the units 22, 22'.
[0024] As a pair of inter-connected pistons 3,13 perform a power stroke, the corresponding pair of pistpns 3', 13' perform a return or suction stroke and vice versa. Thus piston return movement is positively obtained without the need for return springs or other provision such as special fluid pressure operation for return purposes. Furthermore the operating capacity of the pump or transformer is increased,(e.g. doubled) yet can still remain a compact arrangement.
[0025] In a similar manner to the cylinders 12, the cylinders 12' are shown communicated via non-return valves 7' with a high pressure output circuit 8'. The circuits 8, 8' may be separate or communicated with a common output or again the cylinders 12, 12' may be communicated with individual output or circuitslin any desired grouped arrangement.
[0026] The double acting arrangement shown in FIGURE 4 is controlled by the low pressure circuit 4 via the distributor valve 5 in the same manner as that already described with reference to FIGURE 1 and with the same practical advantages.
[0027] The relative diameter of the pistons 3,13 or 3', 13' may be varied according to fluid pressure transformation requirements or, in some cases, with the advantages referred to above, may be of the same diameter.
[0028] Referring to FIGURE 5 a modified form of transformer 1 is shown in which a differential piston action is obtained due to the difference in effective surface area bf opposite sides of a piston 30, 30' in each cylinder 20, 20'.
[0029] In the double acting arrangement shown the pistons 30, 30' are connected by a connecting or piston rod 33 so that as one piston performs a power stroke the other performs a return or suction stroke or vice versa and low pressure fluid is admitted at the appropriate time into each cylinder 20, 20' from the distributor valve 5 which in turn is supplied by the control circuit 4 in the manner already described.
[0030] In a power stroke the low pressure fluid acts on the unrestricted face or head 303 of a piston 30 or 30' so that the other face 313 of reduced effective area (i.e. less the cross-sectional area of the piston rod 33) expels fluid at increased pressure from the cylinder 20 or 20' to the output circuits8 or 8' via the appropriate non-return valve 7 or 7'.
[0031] As will be apparent from tne arrangement shown in FIGURE 5 a simplified and compact double acting form of the transformer 1 is provided.
[0032] In FIGURE 6 an alternative form of control circuit 4 is shown in which the control valve means 40, viz: the shut-off valve 41 and variable relief valve 42 (or a single valve providing such functions) act directly in line with the distributor valve inlet 53 and the pump 44 for controlling the operation of the distributor valve 5 and hence the output from the circuit 8 or circuits 8, 8'. On shut-off of the valve 41 or restricting operation of the valve 42 excess output from the pump 44 is returned to the reservoir via the relief valve 46.
1. A fluid pressure circuit control arrangement characterised by a control circuit
(4) operable for controlling the supply of fluid under pressure to distributor valve
means (5) for distributing said fluid to cylinders (2 or 20) containing operating
pistons (3 or 30) of a piston pump (such as a fluid pressure transformer 1 of the
differential piston kind) whereby one or more fluid output circuits (8) supplied by
the pump or transformer (1) can be controlled by said control circuit (4).
2. A fluid pressure circuit control arrangement according to claim 1 wherein the pump
or transformer (1) comprises at least three cylinders (2 or 20) containing operating
pistons (3 or 30) and arranged to receive fluid under pressure in turn from the distributor
valve means (5) for operation of the operating pistons (3 or 30) in said cylinders
(2 or 20) in a sequential manner.
3. A fluid pressure circuit control arrangement according to either of the preceding
claims wherein the distributor valve means (5) is not controlled by movement or position
of any of the pistons (3, 13 or 30) of the pump or transformer (1).
4. A fluid pressure circuit control arrangement according to claim 1, 2 or 3 wherein
the distributor valve means (5) contains a rotary valve member (50) for effecting
admission of fluid under pressure and exhaust of fluid to or from the cylinders (2
or 20) of the pump or transformer (1) containing the operating pistons (3 or 30) for
the operation of the latter in a sequential manner.
5. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein control valve means (40) of the control circuit (4) provides shut-off
control (41) and/or variable relief control (42) in input communication with the distributor
valve means (5).
6. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein the control circuit (4) is provided in input communication with the
distributor valve means (5) for low pressure distribution of fluid by the latter to
the pump or transformer (1) for corresponding control by the control circuit (4) of
one or more high pressure output circuits (8) supplied by*the pump or transformer (1).
7. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein the control valve means (40) of the control circuit (4) is arranged
to bypass fluid pressure input supply to the distributor valve means (5).
8. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein a variable speed or variable capacity pump (44) of the control circuit
(4) controls supply of fluid under pressure to the distributor valve means (5) by
variable operation of the pump (44).
9. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein the pistons of the pump or transformer (1) consist of inter-connected
pairs of operating and operated pistons (3, 13) in respective cylinders (2, 12), a
volumetric space (23) being disposed between each pair of operating and operated pistons
(3, 13) in the cylinders (2, 12), the volumetric spaces (23) so provided being communicated
(at 26) with one another for flow of fluid from one volumetric space (23) to another
whereby operative movement of at least one of said inter-connected pairs of operating
and operated pistons (3, 13) causes displacement of fluid between said volumetric
spaces (23) for effecting return or suction movement of one or more other inter-connected
pairs of operating and operated pistons (3, 13) dependent on their relative positions
at a particular instant of their operation.
10. A fluid pressure circuit control arrangement according to claim 9 wherein at least
one of the volumetric spaces (23) is arranged to be communicated (at 24) with a source
of supply of fluid for maintaining the communicated volumetric spaces (23) filled
with the required quantity of fluid.
11. A fluid pressure circuit control arrangement according to claim 9 or 10 wherein
at least one of the volumetric spaces (23) is provided with a relief valve (25) for
determining the pressure of fluid in the communicated volumetric spaces (23).
12. A fluid pressure circuit control arrangement according to any of claims 9 to 11
wherein the volumetric space (23) between the pistons (3, 13) of each inter-connected
pair thereof is contained or isolated between end flanges (63, 613 or 73, 713) of
a tubular member (60 or 70) about the inter-connection (11) between the pistons (3,
13) which flanges (63, 613 or 73, 713) have a piston-like sealing co-operation with
respective cylinder bores (2, 12 or 27, 217).
13. A fluid pressure circuit control arrangement according to claim 12 wherein one
of the flanges (713) provides a relatively large diameter piston-like area and operates
in a cylinder bore (217) for facilitating return movement of the small diameter piston
(13) of an associated inter-connected pair of pistons (3, 13) under the action of
fluid movement between the communicated volumetric spaces (237).
14. A fluid pressure circuit control arrangement according to any of the preceding
claims wherein at least the operating pistons (3 or 30) in the cylinders (2 or 20)
are connected to corresponding further operating pistons (3' or 30') in cylinders
(2' or 20') in a complementary or opposed manner whereby power operation of the first
mentioned operating pistons (3 or 30) effect return or suction operation of the corresponding
operating pistons (3' or 30') and vice versa in a double acting arrangement.