Trailer mounted power washer

The present invention relates to a trailer mounted power washer, and particularly to a trailer mounted power washer for supplying pressurised hot water.

It is well known to provide a high pressure power washer mounted on a trailer. A typical trailer mounted power washer may be powered by a petrol or diesel engine and be capable of delivering water supplied from a water tank through a hand held gun at a pressure of between 120 and 250 Bar, and at a flow rate of between 12 and 18 litres per minute. Generally, the water supplied is cold, for example between 2 and 10 degrees centigrade.

However, hot water is sometimes required. For example, hot water is used on building sites for defrosting metal reinforcing prior to concreting and for cleaning tasks. Hot water is also required by the military, for example, for showering of soldiers in remote locations and for decontamination. There is therefore a need to provide a high pressure power washer capable of delivering hot water.

One known method of providing hot water on location is to fill the water tank of an existing trailer mounted power washer with hot water. However, this is generally inconvenient, because there may be no adequate source of hot water available, and the hot water, once in the tank of the power washer may cool before use, particularly if the hot water source is some distance from the location where the hot water is required.

Furthermore, the seals in the washer are typically not designed to cope with hot water, for example, in excess of 50 degrees centigrade, and leaks may occur.

Alternatively, it is known to provide a machine providing high pressure hot water by passing a high pressure cold flow directly through a heated coil. However, machines of this type are typically large and heavy and are not particularly suitable for trailer mounting. They also require regular servicing and have a relatively short life expectancy.

According to the present invention there is provided a trailer mounted power washer comprising a water supply system including a tank, a pump, a pressure regulator, a

heat exchanger, and a water circuit enabling water to be drawn from the water tank, through the heat exchanger and the pressure regulator, and expelled through an outlet by means of the pump, and a heating system including an oil fired heater, a circulation pump, a fluid reservoir, and a fluid circuit enabling fluid from the reservoir to be circulated through the heater and the heat exchanger and returned to the fluid reservoir.

It is an advantage of the invention that when the heating system is operative, water from the tank passes through the heat exchanger and is heated on demand. Furthermore, if the heating system is not running, the water from the tank is pumped cold, ie at ambient temperature.

Preferably the heat exchanger is positioned on the low-pressure side of the pump in the water circuit. This means that the heat exchanger is not subjected to the high pressure of the water after it passes through the pump, and is therefore less likely to fail.

Preferably the heat exchanger is a counter-flow plate heat exchanger.

Preferably the heating system and heat exchanger are mounted on a sub-frame. This enables the heating system and heat exchanger to be easily removed and replaced for servicing.

Preferably a thermostat is provided for controlling the temperature of fluid in the fluid circuit.

Preferably the oil fired heater has a power output of between 20 and 36 kilowatts.

Preferably, the oil fired heater has a power output of 30 kilowatts.

Preferably the heating system is adapted to increase the temperature of water drawn from the water tank by between 40 and 65 degrees centigrade at a flowrate of 12 litres per minute.

Preferably the heating system is adapted to increase the temperature of water drawn from the water tank by between 40 and 65 degrees centigrade at a flowrate of up to 16 litres per minute.

Preferably the pump and pressure regulator are adapted to provide a water pressure at the outlet of between 120 and 250 bar.

Preferably the pump and pressure regulator are adapted to provide a water pressure at the outlet of 207 bar.

Preferably the outlet is controlled by a gun, and a bypass loop is connected between the pressure regulator and the pump.

Preferably a cooler is provided in the bypass loop.

This has the advantage that if the gun is not operated for a period of time when the pump and heating system are operating, then the water in the bypass loop does not overheat due to friction. Over heating of the water in the bypass loop can cause the seals in the pump to fail, and by providing the cooler in the bypass loop, this risk is mitigated.

Preferably an alternator is driven from a power take-off from the pump.

Preferably the alternator provides a 24V DC electrical supply to a battery pack and the oil fired heater.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying single figure of the drawings, which shows a schematic diagram of a trailer mounted power washer in accordance with the invention.

Referring to Figure 1, a trailer mounted power washer is indicated generally at 10. A cold water tank 12 capable of holding 1 ,000 litres of water is connected to a counter flow heat exchanger 14. An output of the heat exchanger is connected to a high pressure pump 16, capable of producing a pressure increase of between 120 and 250

bar. The output of the high pressure pump is connected to a pressure regulator 18 and to a hand-held gun 20. A bypass cooler 22 is connected between the pressure regulator 18 and the high pressure pump 16 in a bypass loop 24. The cold water tank 12, high pressure pump 16, pressure regulator 18 and bypass cooler 22 are mounted on a trailer 26.

A heating system, indicated generally at 28, is mounted together with the heat exchanger 14 on a sub-frame 30, which is also mounted on the trailer 26. The heating system comprises a 20 litre header tank 32 connected to a 24V DC circulating pump, and an oil fired heater 36. An output from the heater 36 is connected to the counter flow heat exchanger 14 and a return pipe 38 from the heat exchanger 14 is connected to the header tank 32. The trailer mounted power washer 10 also includes an engine (not shown) for driving the high pressure pump 16, a 24V battery pack (not shown) and an alternator (not shown) connected to a power take-off from the high pressure pump 16.

The heater 36 is an oil fired heater, and is preferably a Webasto diesel fired DBW 300 heater capable of producing a 30 kilowatts power output. Alternative heaters with outputs in the range between 20 and 36 kilowatts may also be suitable. The heater 36 requires a 24V DC power supply, which is provided by the alternator. The alternator should be capable of generating around 55 amps. The heat exchanger 14 is preferably a FlatPlate™ heat exchanger manufactured in the USA by FlatPlate, Inc. These heat exchangers are small in size, typically around 0.3 x 0.12 x 0.10 m, and are lightweight. The working fluid of the heating system 28 is a 50:50 glycohwater mixture, which is pumped continuously through the heater 36 and heat exchanger 14 and back to the header tank 32 when the heating system 28 is in operation. The temperature of the working fluid is controlled by an adjustable electronic thermostat.

When the heating system 28 is not in operation, the washer 10 may be used as a cold water washer. Water is pumped from the cold water tank 12, through the heat exchanger 14 (which is cold), through the pump 16 and pressure regulator 18 and to the hand-held gun 20. When the gun is not in operation, the water circulates from the pressure regulator 18 back to the high pressure pump 16 through the bypass loop 24.

When high pressure hot water is required, the heating system 28 is operative, and the cold water from the tank 12 is heated as it passes through the heat exchanger 14,

immediately prior to entering the high pressure pump. The water passing from the gun 20 is typically at around 65 ⁰ C and at a pressure of 3,000 psi (207 bar). The flow rate is typically 15 litres per min. However, different arrangements may provide a pressure of between 120 and 200 bar and flow rates of between 12 and 18 litres per min depending on the size of the engine, and output of the pump. When the gun 20 is not in operation, the hot water passes from the pressure regulator 18 through the bypass loop 24 back to the high pressure pump 16, and passes through the 12V DC bypass cooler. The cooler is thermostatically controlled and is an oil cooler with a 12V DC fan. The fan operates to dissipate heat from the water in the bypass loop 24, which otherwise would increase in temperature due to friction. This cooling is important, because if the temperature in the bypass loop increases undesirably, then the seals in the high pressure pump can fail.

The trailer mounted power washer is advantageous over existing units, because it is compact and lightweight in design, can provide hot and cold pressurised water for washing, and can be towed by a Sports Utility Vehicle (SUV) or the like. As previously explained, the heating system 28 and heat exchanger 14 are mounted on a sub-frame 30 in a modular design, which can be easily removed from the trailer 28 for servicing. The system can either be refitted after servicing, or a replacement system can be fitted in order to reduce the amount of down-time on site.

The electrical systems of the trailer 26 are operated by the 24V DC battery pack charged via the alternator, thus providing a fully mobile and safe system.

The Webasto oil fired heater is typically used for heating systems on buses, and is approved for vehicle use in the United Kingdom.