WO1991000486A1

WO1991000486A1 - Apparatus for and method of drying articles

Info

Publication number: WO1991000486A1
Application number: PCT/GB1990/001041
Authority: WO
Inventors: Gordon Edwin Littleford; Richard Andrew Cushing
Original assignee: Kerry Ultrasonics Limited
Priority date: 1989-07-05
Filing date: 1990-07-05
Publication date: 1991-01-10
Also published as: GB9104222D0; GB2242968A; GB8915439D0

Abstract

In a drying cabinet (10), using hot air, the inflowing air is directed downwards at an oblique angle from the periphery of the cabinet through inlets (18) and air is withdrawn through outlets (26) in the bottom (20) of the cabinet. This creates a circulatory air flow (32, 34) with low leakage.

Description

APPARATUS FOR AND METHOD OF DRYING ARTICLES

This invention relates to apparatus for and a method of drying articles, and is particularly concerned with the use of hot air for that purpose.

The apparatus and method of the present invention are particularly suitable for incorporation into liquid process systems, as exemplified by ultrasonic cleaning systems where articles are cleaned, rinsed and then dried.

It has been customary to dry articles in ultrasonic cleaning systems using solvents. However, the realisation that some solvents may be environmentally harmful has caused a return to the use of hot air for drying purposes. Known hot air drying systems simply involve directing hot air at the articles to be dried, i.e. with the hot air travelling in a substantially linear path.

It is an object of the present invention to provide apparatus for and a method of drying articles, using hot air, which uses the hot air more effectively and/or efficiently.

In accordance with the present invention this is achieved by apparatus for drying articles, comprising a container within which articles to be dried are positioned, means to supply heated air to the interior of the container, and means to create a flow of air within the container to dry the articles therein, characterised in that the container has air inlet means through which the heated air is directed downwards into the container, and air outlet means at or adjacent to the bottom of the container through which air is drawn down from the interior of the container. Also in accordance with the invention there is provided a method of drying articles in a container in which articles to be dried are positioned, which comprises directing heated air downwards into the container, and withdrawing air through outlet means at or adjacent to the bottom of the container, thereby to create a circulatory air flow path within the container.

Preferably, the inflowing air is directed downwards at an oblique angle from the periphery of the container*.

Although the air flow path has a degree of turbulence, the path is a defined path, not a random path.

With the arrangement of the present invention the hot air is used to greater effect for the drying of the articles and, in addition, because of the nature of the air flow path the hot air is more readily able to get into crevices and holes within articles to be dried, as compared with a system in which hot air travels linearly over and past the articles to be dried.

Also, with the arrangement according to the invention one can substantially reduce the leakage of air from the container. In order that the invention may be more fully understood, one presently preferred embodiment of apparatus in accordance with the invention will now be described by way of example and with reference to the accompanying drawing which is a schematic view of the apparatus.

Referring to the drawing, there is shown a drying cabinet or process tank 10 within which articles to be dried are arranged to be suspended or positioned. In the case of small articles these would be suspended in baskets (not shown) positioned within the cabinet. Although not shown, the cabinet is preferably fitted at the top with a cover, for example a counterbalanced pivotable cover.

Mounted on the outside of the cabinet 10 is a blower unit 12. The blower unit 12 is arranged to direct air over a heater 14. Ducting 16 around the outside of the cabinet directs the heated air upwards to inlet slots 18. The inlet slots 18 are preferably positioned equidistantly around the periphery of the tank 10. The number and position of the slots 18 will depend upon the shape and dimensions of the tank. Two slots 18, positioned opposite each other, may be sufficient, although generally a greater number of slots will be more advantageous. In the extreme case, a single continuous inlet slot 18 around the periphery of the tank may be provided.

As can be seen from the drawing, the inlet slot or slots 18 are shaped so that they direct the air flowing through them in a downward direction towards the base 20 of the cabinet. The slot or slots 18 is/are split by a divider or dividers 22. The base 20 of the cabinet is a sloping wall which is provided with a drain hole 24 for water removed from the articles being dried. The base 20 also is provided with an air outlet or outlets 26. The outlet 26 may consist of a continuous hole in the base 20, connected to an outlet duct 28, or alternatively may comprise a plurality of holes in the base, suitably connected to the outlet duct 28. In each case the outlet hole or holes 26 are positioned around a central portion 30 of the base of the cabinet, preferably about midway between the centre and periphery of the cabinet. The central portion 30 acts as a surface which deflects air coming from the inlets. The position, shaping, dimensions and alignment of the air inlets and outlets causes a circulatory movement of the hot air within the volume of the cabinet, generally as indicated by the arrows 32 in the drawing. Air which is initially directed downwards rises up in the centre of the cabinet and, when it reaches the cover, will at least in part be forced downwards again. As indicated by arrows 34, air is drawn down to the outlets 26 from the outer portion of the cabinet volume. Preferably, one is not generating random turbulence within the cabinet but a controlled circulatory air flow path which will more efficiently dry the articles suspended within the cabinet.

The hot air within the cabinet 10 is preferably maintained at a temperature of between 100°C and 120°C, although possibly up to as high as 140°C. Maintenance of the desired temperature is achieved by the provision of a thermocouple 36 within the cabinet, connected to appropriate control circuitry linked to the heater 14. At the top of the cabinet, above the ducting

16, is provided a further duct 38 incorporating lip vents and a fan 40.

Within the outlet duct 28 is positioned a butterfly valve 42 which is operated by a solenoid. An air inlet duct 44 connects with the outlet duct 28 between valve 42 and the blower unit 12, and is fitted with a butterfly valve 46 which is also operated by a solenoid.

In use, for the drying of articles suspended in the cabinet, air is circulated through the cabinet as indicated by the arrows in the drawing. The valves 42 and 46 are fully or partially open as required to produce a balanced state. During the drying process, hot air will recirculate through the system, with some of the air being vented off, together with extraneous moisture, via the lip vents at the top of the cabinet. Make-up air will be drawn in through the supply duct 44 past the valve 46. A balanced system can thus be achieved. The temperature within the cabinet is measured by the thermocouple 36 and control of the heater 14, the cycle times and the valve functions is effected by a suitable control unit (not shown) . This control unit can also control preceding wash and rinse, stages in a cleaning process. The main feature is that the cabinet has an air inlet or inlets through which air is directed downwards into the container and an air outlet or outlets through which air is drawn down from the container, preferably from the upper portion and/or the peripheral portion of the container. At the end of the drying cycle it may be desirable that the articles should be cooled. This can readily be achieved by the apparatus of the present invention by fully opening valve 46 and closing valve 42. This will cause ambient air to be drawn into the system through the air inlet duct 44 continuously and to be vented through the lip vents. During this cycle the heater 14 is switched off.

Although the invention has been described above in relation to a static cabinet with articles suspended or positioned therein, the principle of generating a non-linear circulatory hot air flow could also be applied to a system in which articles are moving through a process tank and are dried as they pass through the tank. Furthermore, although in the illustrated embodiment the base 20 of the cabinet is used as a deflector for the incoming hot air, one could alternatively provide an internal baffle or baffles within the cabinet to trigger the circulatory movement of the air.

Claims

CLAIMS :

1. Apparatus for drying articles, comprising a container within which articles to be dried are positioned, means to supply heated air to the interior of the container, and means to create a flow of air within the container to dry the articles therein, characterised in that the container has air inlet means through which the heated air is directed downwards into the container, and air outlet means at or adjacent to the bottom of the container through which air is drawn down from the interior of the container.

2. Apparatus according to claim 1, in which air is drawn down from the upper portion of the interior of the container to said air outlet means.

3. Apparatus according to claim 1 or 2, in which air is drawn down from the peripheral portion of the interior of the container to said air outlet means.

4. Apparatus according to claim 1, 2 or 3, in which the inflowing air is directed downwards at an oblique angle from the periphery of the container.

5. Apparatus according to any preceding claim, in which there is a circulatory flow path for the air within the container, the air rising at the centre of the container and moving downwards outside the central column.

6. Apparatus according to any preceding claim, in which the container is provided with a duct around the upper edge thereof, said duct incorporating lip vents and extractor fan means.

7. Apparatus according to any preceding claim, which includes an air circulation duct from the air outlet means to a blower which is in communication with the air inlet means, an air make-up duct arranged to provide a supply of air to the blower, and valve means in the air circulation duct and in the air make-up duct.

8. Apparatus according to any preceding claim, in which the interior of the container has a sloping bottom surface.

9. Apparatus according to any preceding claim, in which the air inlet means is located adjacent to the top of the container, and the air outlet means comprises a hole or holes located in the bottom of the container approximately midway between the centre and the periphery thereof.

10. A method of drying articles in a container in which articles to be dried are positioned, which comprises directing heated air downwards into the container, and withdrawing air through outlet means at or adjacent to the bottom of the container, thereby to create a circulatory air flow path within the container.

11. A method according to claim 10, which comprises directing the air downwards at an oblique angle into the container from the periphery thereof, and withdrawing air through the bottom of the container.