GB2082690A - Dump actuated by pass control for multi operator use - Google Patents

Abstract

In a high pressure fluid jetting system to control the flow from a single pump 1 to two or more jetting nozzles 14A/B, a novel dump actuated by pass valve 6A/B is provided, in each supply line, with a return line 7A/B to the header tank 3 and an existing type of dump control valve 9A/B fitted on the outlet. A check valve is also fitted between each dump control valve and the nozzle. In the by-pass condition each bypass valve 6A/B presents a restriction to flow substantially equivalent to the nozzle 14A/B in use, and pilot flow is arranged to pass to the corresponding dump control valve 9A/B. Manual operation of any of the dump control valves, actuates the by pass valve to divert the main flow to the nozzle 14A/B, and the load on the pump remains substantially unchanged. <IMAGE>

Description

SPECIFICATION Damp actuated by pass control for multi operator use The invention constitutes an improved method for controlling the constant flow output of a positive displacement pump such as is generally used for high pressure water jetting purposes when it is required that two or more nozzles shall be operated simuitaneously from the same pump output without one affecting or being affected by any of the others.

High Pressure Water Jetting is the term generally applied to the process whereby the constant flow output of a positive displacement water pump normally in the range 10-30 GPM is applied via a delivery hose at high pressure normally in the range 5,000-1 5,000 PSI to a nozzle hole, or holes of relatively small diameter from which it then emerges at relatively high velocity and is applied to carry out a wide range of tasks. One method of operation is to supply the total output flow to one control point from which the flow to the nozzle or nozzles may be interrupted, without the output of flow from the pump having to be stopped and re-started.In other applications the output of one pump may be suppiied to a number of control points, each of which must be capable of controlling the flow to a nozzle independently of the others and without affecting any of the others, so that each, any combination, or all, of the nozzles may be brought into or out of use at any time. Known existing devices which permit this method of operation to be employed are subject to either or both of the following limitations. Namely, that the supply line to each operator control remains pressurised when the supply to the nozzle on that line is interrupted and that the flow in use on a line continues to discharge at the operators control gun or valve, even though it is diverted from the working nozzle, and the pressure dissipated elsewhere.

The invention provides for the addition into each operator supply line of a novel by pass valve, each of which will divert flow back to the supply tank when the nozzle which it controls is not in use, without affecting or being affected by the operation of any other by pass valve on the system. The advantages of the modified method of operation are prevention of the waste of water, normally associated with dump control systems, together with general improvement of safety conditions in the operating area arising from elimination of pressurised lines and flow being by passed at the pump, rather than dumped at the operator's control point.

A typical system would be as shown in Fig. 1.

Positive displacement pump 1 is driven by prime mover 2, drawing water from header tank 3 via inlet line 4 and discharging via high pressure lines 5A and 5B to the by pass valves 6A and 6B. Under non jetting conditions each by pass valve is arranged to direct most of the input flow back to header tank 3 via return lines 7A and 7B, although full working pressure is maintained on the pump output, in lines 5A and 5B. This pressure also causes a small amount of flow to pass through supply lines 8A and 8B, from each valve, to dump guns 9A and 9B, discharging through dump barrels 1 2A and 12B.Operation of trigger 10 on either or both dump guns 9A or 9B causes the corresponding by pass valve 6A or 6B to actuate, diverting pump flow from the by pass line 7A or 7B, to the outlet nozzle 1 4A or 14B. Either or both diversions cause no significant change in load on the pump 1. Release of either or both triggers reverses the process, re-directing pump output to by pass with a small proportion of the flow continuing to discharge through dump control valve 9A or 9B.

The novel features by means of which the above process takes place are shown in Fig. 2, representing either of the by-pass valve, dump gun, check valve combinations shown in Fig. 1.

Under normal non-jetting conditions flow from the pump 1 enters the by pass valve at port 15. The piston 22, under the influence of spring 28 is positioned at the far left of its travel, thus leaving a water flow path to chamber 26, where pressure is developed in order to maintain flow through the restriction 19, created by the position of valve stem 20 relative to valve seat 18, which may be either fixed or variable, thus allowing water to flow through to port 21 and back to header tank 3 at return line pressure. Restriction 1 9 is arranged to provide substantially the same restriction to flow as the working nozzle jet 38.The pressure thus developed in chamber 26 also applies to orifice 1 6 in the valve body, which is of a relatively small size, so that the flow which then also passes through this orifice is a minor proportion of the flow entering the by pass valve. This flow passes into chamber 23 and thence to outlet port 1 7 and to the dump control valve 9. The dump control valve, or dump gun, 9 is a well known type of equipment, of which a typical example is shown here to illustrate the method of operation. In the non jetting condition the pilot flow through dump gun 9 is allowed to discharge freely through port 31.

To bring the working nozzle 14 onto load trigger 10 of the dump gun 9 is operated. This causes piston 39 to be pushed inwards, thus closing off port 31. The pilot flow is now contained in the supply line 8, against piston 34, acting in conjunction with valve seat 33, in check valve 13. Since the line is being supplied from the higher pressure present in chamber 26, via orifice 16, the pressure in the line will continue to rise until it approaches this higher level.At some predetermined point this pressure, acting on the area of piston 22 sealing on valve seat 24 will overcome the force exerted by spring 28 and the piston will move to the right, it will continue to move to the right under the influence of the pressure in chamber 26, now acting on the piston formed by sealing diameter 27, until piston 22 contacts seat 25, thus closing off the flow path through chamber 26 and port 21 and causing the full flow on this line to divert to chamber 23 and thence to outlet port 17. The effect of this flow diversion is to cause piston 34 to lift from its seat 33 in check valve 13, allowing full flow to pass to orifice 38 in nozzle 14. The nozzle is now in a jetting condition and full load pressure applied on piston 34 via sealing diameter 36 prevents any leakage through clearance diameter 37.

To interrupt jetting the trigger 10 on dump gun 9 is released, whereupon piston 39 moves outwards under pressure, allowing port 31 to open and flow to pass freely to dump. At the same time pressure at port 32 in check valve 13 drops to zero, allowing piston 34 to close back onto seat 33; also pressure at port 17 in by pass valve 6 drops to a level sufficient only to aliow line flow to be maintained through dump gun 9, discharging through port 31 to dump barrel 12, as a transient condition. The by pass valve is arranged in such a way that this pressure at port 17, acting on piston 22 against seat 25 results in a force which is unable to continue to overcome the influence of spring 28 and the piston 22 now moves to the left, thus reopening the path to chamber 26 and by pass port 21. The movement continues until the piston is back on seat 24 thus closing off the main flow path to port 17. The line is now again in a non-jetting condition, with the main flow being directed to restriction 1 9 in order to simulate the jetting nozzle restriction, before being by passed back to the header tank, whilst the pilot flow passes through orifice 16 and then via outlet port 17 to discharge freely through dump gun 9.

The process as described is applicable to either of the two operator systems shown in Fig. 1, or to any number of operator systems which may be added, within the capacity of the single pump unit providing the output flow.

Claims (5)

1. In a high pressure fluid pump system where the medium is normally but not exclusively water and where means are to be provided to control the flow of fluid from a single pump output to two or more nozzles in such a way that the flow to each nozzle may be controlled without affecting or being affected by any of the others, operated in any combination, whilst delivery of the pump is maintained at a substantially constant rate, the provision of a by pass control means in the line to each nozzle, allowing the major part of the flow to each nozzle to be diverted back to the supply tank, whilst maintaining full load pressure on the pump output but with no pressure being developed in the line connecting each by pass control means to the corresponding nozzle; further, by using secondary means to cause pressure to increase in any of the lines connecting a by pass means to a nozzle to cause the by pass means to cease by passing and divert an equal flow into the line connected to the nozzle. Conversely by using secondary means to cause pressure to decrease in the line connecting any by pass means to a nozzle to cause the by pass means to open and divert the line flow back to the supply tank.

2. In a system such as in Claim 1 each by pass means being situated between the pump output and the corresponding secondary control means and remote from the secondary control means so that when in the by pass mode line flow is not passing through the secondary control means.

3. In a system such as in Claim 1 the provision of a check valve means to prevent premature leakage of fluid from the line connecting each by pass valve to the corresponding nozzle, through the nozzle, until such time as the pressure in the line has reached a level sufficient to cause the by pass means to close, diverting full line flow to the nozzle.

4. In a system such as in Claim 1 each by pass means to include in the by pass line a restrictor, either fixed or variable, to ensure that the restriction to flow entering the by pass means remains substantially constant whether in the by pass or the jetting mode.

5. In a system such as in Claim 1 each by pass means to include an orifice which meters flow from that region of the valve which remains at full load pressure when by passing takes place, into the line connecting the by pass means to the secondary control means, and thence to the nozzle, to provide the means of pilot control.