Machines have been proposed for washing textiles using ultrasonic energy.

There are several advantages to washing textiles using ultrasonic energy such as improved cleaning action, generally faster washing, typically less energy is used and more thorough and more gentle washing. However, although a number of machines have been proposed, there is currently no successful commercially available machine for washing textiles using ultrasonic energy.

Most of the existing ultrasonic washing machines suffer from the disadvantage that a significant proportion of the ultrasonic energy does not reach the textiles being washed, as the ultrasonic transducers are mounted outside a perforated metallic drum containing the textile articles being washed and the ultrasonic energy does not pass through the wall of the perforated drum efficiently.

In accordance with a first aspect of the present invention, a method of washing a textile article comprises immersing the textile article in a liquid and generating ultrasonic energy in the liquid, the ultrasonic energy generated having a frequency in the region of substantially 20kHz to 80kHz.

In accordance with a second aspect of the present invention, apparatus for washing a textile article comprises a liquid holding container, and an ultrasonic

energy generating device, the ultrasonic energy generating device being adapted to generate ultrasonic waves in a liquid within the container, in use, and the ultrasonic generation device generating ultrasonic waves with a frequency in the region of substantially 20kHz to 80 kHz.

Preferably, the ultrasonic waves generated have a frequency in the region of 25kHz to 40 kHz.

Preferably, the apparatus further includes a heating device adapted to heat the liquid within the container. Typically, the liquid in which the textile article is immersed has a temperature in the region of 15°C to 50°C, preferably 15°C to 35°C and most preferably approximately 20°C to 30°C.

In one example of the invention, the ultrasonic energy generation device may be located adjacent a bottom wall of the container. However, in an alternative embodiment of the invention, the ultrasonic energy generation device may be located adjacent a side wall of the container. The ultrasonic energy generation device may be mounted within the container or on an outside wall of the container.

Typically, the input power to the ultrasonic energy generation device may be in the region of 20W to 70W per liter of liquid within the container, in use.

Preferably, the power input to the ultrasonic energy generation device is in the region of 25W per liter to 50W per liter and most preferably, is in the region of 30W per liter to 40W per liter. An advantage of the invention is that by using a

relatively low frequency of ultrasonic energy, it is possible to generate more intense cavitation and therefore, produce a better washing action on a textile article than at higher frequencies.

A textile article to be washed may be supported in the container on a frame or hanger. Alternatively, a textile article may simply be placed in the container.

In one example of the invention, it is possible that the method may further comprise generating movement of the textile article during generation of the ultrasonic energy, and typically, the apparatus may include means to generate movement of the textile article in the container.

Examples of a method of and apparatus for washing a textile article. in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of a first example of an ultrasonic washing machine with ultrasonic transducers mounted on a side wall ; Figure 2 is a cross-sectional view of the ultrasonic washing machine shown in Figure 1 in use; Figure 3 is a plan view of a second example of an ultrasonic washing machine with ultrasonic transducers mounted on a bottom wall ; Figure 4 is a cross-sectional view of the ultrasonic washing machine shown in Figure 3 in use;

Figure 5 is a plan view of a third example of an ultrasonic washing machine; Figure 6 is a cross-sectional view of the ultrasonic washing machine shown in Figure 5, in use; Figure 7 is a plan view of a fourth example of an ultrasonic washing machine; Figure 8 is a cross-sectional view of the ultrasonic washing machine shown in Figure 7 in use; Figure 9 is a plan view of fifth example of an ultrasonic washing machine; Figure 10 is a cross-sectional view of the ultrasonic washing machine shown in Figure 9 in use; Figure 11 is a plan view of a sixth example of an ultrasonic washing machine; and Figure 12 is a cross-sectional view of the ultrasonic washing machine shown in Figure 11 in use.

Figures 1 and 2 show a first example of an ultrasonic washing machine 1 which comprises a tank 2, two ultrasonic transducers 3, two heaters 4 and a thermocouple 5. The tank 2 is mounted on feet 20. The ultrasonic transducers 3 are mounted on a side wall 5 within the tank 2 and the heaters 4 are mounted in a side wall 6 adjacent to a bottom wall 7 of the tank 2. A metal grill 8 is located immediately above the heaters 4, as shown in Figure 2. It should be noted that for the purposes of clarity, the metal grill 8 has been omitted in Figure 1. The ultrasonic transducers 3 are supported on the side wall 5 by support rods 10,11.

The thermocouple 5 is coupled to a temperature controller (not shown) which switches the heaters 4 on and off in response to the temperature sensed by the thermocouple 5. This enables liquid 9 in the tank 2 to be maintained at a substantially constant temperature.

The ultrasonic transducers 3 generate ultrasonic energy at a frequency of 28 kHz and the distance, L, from the ultrasonic transducers 3 to an opposite side wall 12 of the tank 2 is chosen such that L = NS/2 where N is an integer and X is the wavelength of the ultrasonic energy generated in the tank 2.

In use, the tank 2 is filled with a liquid 9, such as water, which may contain a cleaning agent such as a surfactant and/or a detergent. Textile articles 15 are immersed in the liquid 9 in the tank 2, as shown in Figure 2 and are prevented from contacting the heaters 4 by the metal grill 8. The heaters 4 are used to heat the liquid 9 in the tank 2 to a desired temperature. Typically, the liquid 9 will be heated to a temperature in the region of 15°C to 50°C, preferably 15°C to 35°C, more preferably 20°C to 30°C and most preferably, approximately 25°C.

When the liquid 9 in the tank 2 reaches the desired temperature, the transducers 3 are switched on to generate ultrasonic energy within the tank 2.

As L = Nu/2, a standing wave is set up within the tank 2. This has the advantage of increasing the power of the ultrasonic waves in the tank 2.

In this example, the ultrasonic transducers 3 generate waves with a frequency of 28 kHz. However, the ultrasonic transducers may generate ultrasonic waves with a frequency in the region of 20 kHz to 80 kHz, more preferably 25 to 40 kHz, preferably 25 to 30 kHz and most preferably approximately 28 kHz.

Figures 3 and 4 show a second example of a washing machine 30 that includes the tank 2, the transducers 3, the heaters 4 and the thermocouple 5. The washing machine 30 is similar to the washing machine 1, except the transducers 3 are mounted adjacent the bottom wall 7 of the tank 2. In this example, it is important that a distance, D, from the transducers 3 to a surface 31 of the liquid 9 is chosen such that D = Nu/2, where N and X are as defined above. This is because the ultrasonic energy generated by the transducers 3 is emitted by the transducers 3 towards the surface 31 of the liquid 9 within the tank 11 and is reflected from the surface 31. Therefore, the liquid surface 31 acts in a similar manner to the opposite side wall 12 in the washing machine 1 shown in Figure 1, by reflecting the ultrasonic energy back towards the transducers 3. Hence, if the distance D of the liquid in the tank 2 is chosen such that D = Nus/2, standing wave is established within the liquid 9 in the tank 2.

In the washing machine 30, a metal grid 32 is positioned in the tank 2 immediately above the transducers 3 to separate the transducers 3 from textile articles 15 within the tank 2. In addition, the transducers 3 are supported in the tank 2 by support rods 33,34.

Figures 5 and 6 show a third example of a washing machine 40 which includes an outer housing 41 in which a tank 42 is mounted. The housing 41 is mounted on feet 43 and a number of ultrasonic transducers 44 mounted on a bottom wall 45 of the tank 42. As the transducers 44 are mounted on the bottom wall 45, the ultrasonic energy generated by the transducers 44 is emitted by the transducers 44 through the bottom wall 45 into liquid 9 within the tank 42. The washing machine 40 operates in a similar manner to the washing machine 30 shown in Figures 3 and 4 and the distance, D, is chosen such that D = Nk/2, where D, N and X are all as defined above for the washing machine 30. An advantage of the washing machine 40 is that the transducers 44 do not have to be waterproof as they are mounted on the outside of the tank 42 which contains the liquid 9.

Figures 7 and 8 show a fourth example of a washing machine 50 which is similar to the washing machine 40 and includes the same housing 41 within which is mounted the tank 42. However, the transducers 44 are mounted on the outside of a side wall 51, instead of the outside of the bottom wall 45.

Therefore, the washing machine 50 operates in a similar manner to the washing machine 1 shown in Figures 1 and 2 and the distance, L, is chosen such that L = N ? J2 where L, N and X are as defined above for the washing machine 1.

Figures 9 and 10 show a fifth example of a washing machine 60 which comprises a housing 61 on which is mounted a tank 62. Housing 61 is mounted on feet 63 and a cylindrical ultrasonic transducer 64 is mounted in a lower

recess 65 formed in the bottom of the tank 62. The washing machine 60 operates in a similar manner to the washing machine 30 shown in Figures 3 and 4 and the distance, D, is chosen such that D = NA/2 where N, X and D are all as defined above for the washing machine 30.

Figures 11 and 12 show a sixth example of a washing machine 70 which is similar to the washing machine 60 and has the same housing 61 mounted on feet 63. However, the washing machine 70 has a tank 71 which does not have the recess 65. Instead, the washing machine 70 has an ultrasonic transducer 72 which is mounted centrally within the tank 71, as shown in Figures 11 and 12.

In the washing machine 70, the transducers 72 emit ultrasonic energy into the liquid 9 radially in all directions around the transducer 72 towards the inner wall of the tanks 71.

In the washing machine 70, the distance, L, from the external surface of the transducers 72 to the inner surface of the tank 71 is chosen such that L = NA/2 where N and X are as defined above.

In the washing machines 40,50,60,70, water heaters 4 and thermocouples 5 are not shown. However, it is possible that water heaters 4 and thermocouples 5 could be incorporated into any of the washing machines 40,50,60,70 in order to control the temperature of the liquid 9 within the washing machines 40,

50,60,70. Similarly, it is possible that the washing machines 1,30 may have the water heaters 4 and the thermocouple 5 omitted.

In addition, in the washing machines 60,70, the tanks 62,71 respectively can be rotatable so that rotation of the tank agitates textile articles 15 within the tanks 61,71 during the washing cycle.

In all the washing machines 1,30,40,50,60,70 the combined power supplied to the respective transducers 3,44,64,72 is typically in the region of 20W to 70W per liter of liquid contained within the respective tanks 2,11. Preferably, the combined power supplied to the transducers 3,44,64,72 is in the region of 25W per liter to 50W per liter and more preferably in the region of 30W per liter to 40W per liter and most preferably approximately 35W per liter.

In the invention, as the ultrasonic energy generated by the transducers 3,44, 64,72 has a relatively low frequency, this produces more intense cavitation within the respective tanks 2,41,62,72 which produces a better washing action within the tanks 2,62,72 for textile articles in the tanks 2,62,72 than at higher frequencies greater than 80 kHz.

In addition, it is possible that the washing machines 1,30,40,50 may generate movement of the textile articles immersed in the tanks 2,11 to enhance the washing action of the ultrasonic waves. For example, the movement may be generated by an agitation device located in the tanks 2,41. As shown in Figures 2,4,6,8,10 and 12 textile articles 15 are placed in the liquid 9. However, it is possible that the textile articles 15 could be supported in the liquid 9 on suitable supports or hangers.