NZ622343A - Drive coupling for pump - Google Patents

Abstract

A pumping apparatus (30) for the supply of high-pressure water. The pumping apparatus including an engine (12); a pump (14); and an outlet jet (20) having a trigger mechanism (21). Operation of the trigger mechanism determines a load on the engine. The engine has an output drive shaft (22) and the pump has an input drive shaft (32), the engine drive shaft and the pump drive shaft being releasably coupled. Preferably, the engine drive shaft and the pump drive shaft are releasably coupled by a centrifugal clutch.

Description

“DRIVE COUPLING FOR PUMP” Field of the Invention The present invention relates to a connection between an engine, such as a diesel engine, and a pump used in generating a high-pressure water spray.

Background to the Invention Portable high-pressure water spray or jetting units generally consist of two main elements: an engine and a pump. A typical engine for this purpose may be diesel powered, and is often in the order of 15hp in power output. A commonly used engine for this purpose is made by the Honda Motor Company under the brand name ‘Honda iGX’.

The engine has a drive shaft, which is connected to the pump, typically a positive displacement pump. The connection may be a direct connection, where the pump is operated at the output speed of the engine (typically 3200- —3600rpm), or may be through a gear box which generally has a 2:1 ratio, dropping the pump speed to about 1450rpm.

The pump acts to pressurise water which is supplied to a trigger operated spray jet. When the trigger is depressed, water can be sprayed from the spray jet under pressure at a constant rate.

Problems can occur when the engine is running, but the trigger is not depressed. In a traditional arrangement, the pump continues to operate at the engine speed (adjusted by any gear ratio) while the trigger is closed. The continuing operation of the pump in these conditions leads to a significant increase in the temperature of water in the head of the high-pressure pump.

Two factors in particular lead to this: the transfer of heat along the drive shaft from the engine to the pump; and the conversion into heat of energy supplied by the pump to the water.

Observations have demonstrated that if the pump is left running for several minutes, without the trigger being depressed, water temperatures can increase beyond 60°C. This can be extremely deleterious to the system, with the potential in particular for plastic components to degrade.

In an attempt to alleviate these problems, the Honda iGX engine includes a switching mechanism to move, based on the load required, between full engine output and an engine idle condition. When the trigger on the spray is released, the engine senses the immediate reduction in required load on the pump. The engine then scales down to an idle speed (about 2000rpm) until the trigger on the spray is depressed. Trigger depression causes an increase in required load on the pump and a return of the engine to full speed (about 3400rpm).

The present invention seeks to provide a more effective method of alleviating the problems caused by heat transfer into the water in the head of the pump.

Summary of the Invention According to one aspect of the present invention there is provided a pumping apparatus for the supply of high-pressure water; the pumping apparatus including an engine; a pump; and an outlet jet having a trigger mechanism, wherein the engine has an output drive shaft and the pump has an input drive shaft, and wherein the engine drive shaft and the pump drive shaft are releasably coupled.

The engine drive shaft and the pump drive shaft may be arranged to be coupled or decoupled according to a rotational speed of the output drive shaft.

Preferably the engine drive shaft and the pump drive shaft are coupled by a clutch. This may be a centrifugal clutch.

According to a second aspect of the present invention there is provided a pumping apparatus for the supply of high pressure water; the pumping apparatus including an engine; a pump; and an outlet jet having a trigger mechanism, wherein the engine has an output drive shaft and the pump has an input drive shaft, and wherein the engine drive shaft and the pump drive shaft are coupled by means of a centrifugal clutch, such that when the engine drive shaft is rotating at a first speed the pump drive shaft is coupled to the engine drive shaft and rotates, and when the engine drive shaft is rotating at a second speed the pump drive shaft is decoupled from the engine drive shaft and does not rotate.

The first speed may represent a full load running speed of the engine, and the second speed may represent an engine idle speed.

It is preferable for a signalling means to be provided to cause the engine to move between the first and second speeds according to demand.

In one embodiment of the invention the signalling means may be connected to a water flow switch associated with the pump, whereby when water is flowing in a water flow line between a pump inlet and a pump outlet a signal is provided to the engine to cause the engine to operate at the first speed, and when water ceases to flow in the water flow line (for instance, when the trigger is released) a signal is provided to the engine to cause the engine to operate at the second speed.

In an alternative embodiment of the invention the signalling means may be connected to a pressure switch associated with the pump outlet, whereby a change in static water pressure on the outlet side of the pump (for instance, as caused by the engagement or release of the trigger) causes an appropriate signal to be provided to the engine.

It will be appreciated that by this arrangement the pump becomes stationary and decoupled from the engine during periods when water flow is not required. When water flow is required, (for instance as indicated by the engagement of the trigger) this can be quickly re-established by coupling of the pump drive shaft to the engine drive shaft.

Brief Description of the Drawings It will be convenient to further describe the invention with reference to preferred embodiments of the present invention. Other embodiments are possible, and consequently the particularity of the following discussion is not to be understood as superseding the generality of the preceding description of the invention. In the drawings: Figure 1 is a schematic diagram representing a pumping apparatus of the prior art; Figure 2 is a schematic diagram representing a pumping apparatus in accordance with a first embodiment of the present invention; Figure 3 is a photograph of the pumping apparatus of Figure 2; Figure 4 is a photograph of a portion of the pumping apparatus of Figure 2; and Figure 5 is a schematic diagram representing a pumping apparatus in accordance with a second embodiment of the present invention.

Detailed Description of Preferred Embodiments Referring to Figure 1, there can be seen a schematic arrangement of a prior art pumping apparatus 10 for high-pressure water. The pumping apparatus 10 includes an engine 12, which may be a 13HP Honda iGX 390 engine, and a positive displacement pump 14. The pump 14 has a water inlet 16 and a water outlet 18. The water outlet 18 is connected to a high-pressure spray jet 20 having a trigger 21.

The engine 12 has an output drive shaft 22, which is connected to the pump 14.

In use, the engine 12 runs the output drive shaft 22 at either a full speed (about 3400rpm) or an idle speed (about 2000rpm). The pump 14 runs at the same speed.

When the trigger 21 is depressed water flows from the water inlet 16, through the pump 14 and the water outlet 18 to the spray jet 20. The engine 12 senses the load on the output drive shaft 22, and runs at full speed.

When the trigger 21 is released, the flow of water ceases. The engine 12 senses the drop in load, and runs at idle speed. Pressure and temperature in the water outlet 18 increase, but not to the extent which would occur were the engine to remain at full speed.

Referring to Figure 2, there can be seen a schematic arrangement of a pumping apparatus 30 for high-pressure water in accordance with a first embodiment of the present invention. Like numerals refer to like features.

In the embodiment of Figure 2, the engine output drive shaft 22 does not extend to the pump 14. Rather, the pump 14 has its own input drive shaft 32, which is releasably coupled to the engine output drive shaft 22 at a centrifugal clutch 34.

The arrangement is such that the centrifugal clutch 34 engages the pump input drive shaft 32 when the engine output drive shaft 22 is operating at full speed, thus coupling the two shafts together. The centrifugal clutch 34 disengages the pump input drive shaft 32, thus decoupling the two shafts, when the engine output drive shaft 22 is operating at idle speed.

It will be appreciated that this arrangement prevents the transfer of heat and energy into the pump 14 and the water when it is not required. It will also be appreciated, however, that the engine 12 can sense a reduction in required load to idle, but once the clutch 34 has decoupled the drive shafts 22, 32 the engine 12 cannot sense an increase in required load.

In order to overcome this problem, the pumping apparatus 30 includes a water flow switch 36. In the embodiment shown the water flow switch is placed in the water inlet 16, although it will be appreciated that the water flow switch 36 could be placed elsewhere in the water flow line. The water flow switch 36 is arranged to send an electrical signal to the engine 12 by means of a signal transmitting wire 38 when water begins to flow in the water inlet 16; that is, when the trigger 21 is depressed on the spray jet 20. The engine 12 is arranged to accept that signal as an indication of load required, and will accelerate to full speed. This acceleration of the output drive shaft causes a coupling of this shaft with the pump input drive shaft 32, by operation of the centrifugal clutch 34. The pump 14 will thus begin to operate.

Referring to Figure 5, there is shown a schematic arrangement of a pumping apparatus 40 for high-pressure water in accordance with a second embodiment of the present invention. The pumping apparatus 40 is similar to the pumping apparatus 30 of the first embodiment, with the difference being in the way that the engine 12 is signalled to accelerate to full speed.

In the embodiment of Figure 5 a pressure switch 42 is located along the water outlet 18. The pressure switch 42 is arranged to sense a change in static water pressure within the water outlet 18; for instance, a drop in static pressure caused by the depressing of the trigger in the spray jet 20; and to send an appropriate signal to the engine 12 in response by means of the signal transmitting wire 38.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims (9)

Claims 1.

1. A pumping apparatus for the supply of high-pressure water; the pumping apparatus including an engine; a pump; and an outlet jet having a trigger mechanism, whereby operation of the trigger mechanism determines a load on the engine, and wherein the engine has an output drive shaft and the pump has an input drive shaft, the engine drive shaft and the pump drive shaft being releasably coupled.

2. A pumping apparatus as claimed in claim 1, wherein the engine drive shaft and the pump drive shaft are arranged to be coupled or decoupled according to a rotational speed of the output drive shaft.

3. A pumping apparatus as claimed in claim 2, wherein the engine drive shaft and the pump drive shaft are coupled by a clutch.

4. A pumping apparatus as claimed in claim 3, wherein the clutch is a centrifugal clutch.

5. A pumping apparatus for the supply of high pressure water as claimed in claim 4, wherein when the engine drive shaft is rotating at a first speed the pump drive shaft is coupled to the engine drive shaft and rotates, and when the engine drive shaft is rotating at a second speed the pump drive shaft is decoupled from the engine drive shaft and does not rotate.

6. A pumping apparatus as claimed in claim 5, wherein the first speed represents a full load running speed of the engine, and the second speed represents an engine idle speed.

7. A pumping apparatus as claimed in claim 5 or claim 6, wherein a signalling means is provided to cause the engine to move between the first and second speeds according to demand.

8. A pumping apparatus as claimed in claim 7, wherein the signalling means is connected to a water flow switch associated with the pump, whereby when water is flowing in a water flow line between a pump inlet and a pump outlet a signal is provided to the engine to cause the engine to operate at the first speed, and when water ceases to flow in the water flow line a signal is provided to the engine to cause the engine to operate at the second speed.

9. A pumping apparatus as claimed in claim 7, wherein the signalling means is connected to a pressure switch associated with the pump outlet, whereby a change in static water pressure on the outlet side of the pump causes an appropriate signal to be provided to the engine. PUMPS AUSTRALIA PTY LTD By its Patent Attorneys ARMOUR IP P2086NZ00