IL31282A - Fluid pressure operable pumping apparatus - Google Patents

Description

PRESSURE OPERABLE PUMPING This invention relates to fluid pressure operable pumping devices of the kind comprising a double acting piston to opposite sides of which fluid pressure is applied in turn to produce reciprocatory motion The object of the invention is to provide such a device in a simple and convenient According to the invention a device of the kind specified comprises in a load sensitive fluidic bistable device for switching a source of pressure fluid alternately between a pair of conduits communicating respectively with the opposite ends of the cylinder containing the a of non return valves located in said conduits respectively and positioned to allow fluid from the source to the ends of the a pair of control each valve having a control element which is actuated by a force developed by fluid pressure applied to an inlet to prevent flow through a flow path of the the flow path being opened by a predominating acting on the control element as a result of fluid pressure in the flow the inlets of the valves being connected respectively to said conduits upstream of said non return valves and the flow paths being connected respectively between the downstream sides of the non return valves and an the flowpath of each valve being connected to the conduit with which its inlet is In the accompanying drawings Figure 1 is a fluid circuit of one example of a pumping device in accordance with the invention and Figure 2 is a fluid circuit of part of the circuit extending from its opposite ends The free piston 10 is located within a cylinder 12 whilst the subsidiary pistons 11 are located within extensions 13 respectively of the cylinder The combination so far described constitutes a proportioning pump and during the downward movement of the piston as indicated fluid will be discharged from the lower end of the cylinder 12 and also from the lower cylinder The quantities of fluid discharged are in a constant Connected to the opposite ends the cylinder 12 are a pair of conduits 14 and 15 respectively and which communicate through a device 16 with an inlet 17 which is connected to a source of fluid under In the present instance this fluid is water and for controlling the pressure a constant pressure valve 18 is Intermediate the device 16 and the ends of the cylinder the conduits 14 and 15 are provided with non return valves 19 and 20 These valves are arranged to permit the flow of water in the direction towards the cylinder but to prevent the return flow of In the particular example the non return valves 19 and 20 are free foil on the downstream side of the non return valve 19 and 20 are positioned restrictors 21 Also provided are a pair of control valves 22 and Each control valve includes a valve member to one side of which fluid pressure can be applied from an Movement of the valve member under the influence of this fluid pressure causes closure of a flow path but fluid pressure in the flow path can develop a force on the valve member to The flow path the control valve 23 is connected between the conduit 14 at a position downstream of the restrictor 21 and the outlet in the outlet there is provided a further restrictor In the particular example the control valves 22 and 23 include free foil The device 16 comprises a sensitive fluidic device through which flow of water from the inlet 17 is switched alternately between the conduits 14 and Such devices are well known and an outline of the fluid paths of the device is seen in Figure From Figure 2 it will be seen that the device has an inlet 17ai which is connected to the inlet 17 and a pair of outlets and which are connected to the conduits 14 and 15 In addition the device is provided with four further fluid connections but these are for use when forced switching is required between the In the present example these connections are carried to a drain so that switching between the outlets occurs as a result of blocking of the flow of liquid through one outlet when the piston reaches its extreme In operation water entering the device 16 flows to one or other of the conduits 14 and 15 and as shown in the drawing it is flowing to conduit Valve 19 is opened to permit the flow of water to the upper end of the cylinder 12 and the free piston 10 is forced towards the opposite end of the Water discharged from this end of the cylinder flows by way of the control valve 22 to the outlet the non return valve 20 being The pressure of fluid control valve 23 to prevent flow through its flow the pressure drop across the restrictor 21 in the conduit 14 ensuring that the flow path of the control valve 23 remains the piston 10 reaches the lower end of the cylinder 12 the device 16 responds to the increased pressure in the conduit 14 and switches over so that the water is diverted along the conduit In doing this the non return valve 20 is opened and water is admitted to the lower end of the cylinder 12 to move the free piston The foils of the control valves 22 and 23 are moved to their alternative positions and the non return valve 19 is In this manner as long as water under pressure is applied at the inlet the piston will reciprocate within its The restrictor 25 in the outlet is provided to restrict the rate of travel of the free piston and to maintain the pressure within the flow paths of the control valves to ensure efficient operation One use for such a proportioning valve is in an artificial kidney machine where it is required to dilute concentrated dialysate with water before it is used in the dialysis The dialysate is contained in a tank 26 and flows to the cylinders 13 in turn by way of valves 27 respectively and flows the cylinders 13 to a mixing tank 28 by way of valves 29 The mixing tank 28 receives the water from the outlet insufficientOCRQuality

Claims (3)

Claims :«

1. A fluid pressure operable pumping device of the kind comprising a double acting piston mounted within a cylinder and comprising in combination, a load sensitive fluidic bistable device for switching a source of pressure fluid alternately between a pair of conduits communicating respectively with the opposite ends of the cylinder containing the piston, a pair of non return valves located in said conduits respec t ive ly . and positioned to allow fluid flow from the source to .the ends of the cylinder, a pair of control valves, each valve having a control element which is .actuated by a force developed by fluid pressure applied to an inlet to prevent flow through a flow path of the valve., the flow path being opened by a predominating force acting on the control element as a result of fluid pressure in- the flow path, the inlets of the valves being connected respectively to said conduits upstream of said non return valves and the flow paths being connected respectively between the downstream sides of the non return valves and an outlet, the flow path of each valve being connected to. the conduit with which its inlet i s connec t ed ■ .

2. A device as claimed in claim 1 including restrictions respectively disposed in said conduits intermediate the non return valves and the ends of the cy 1 inder . -

3. A device as claimed in claim 2 including a restriction disposed in said outlet to control the rate of movement of the piston.