GB2240386A - Drying washed articles - Google Patents

Abstract

A drying unit 13 for use in cleaning apparatus 11 in which heated air is circulated around articles which are to be dried. Water on the articles either drips from the articles or evaporates. The drying unit 13 includes a drying tank 15 for receiving articles to be dried, means 19 for creating a flow of air, means 27 for heating the air and ducting and deflection means 29 for directing the air towards the articles. <IMAGE>

Description

CLEANING APPARATUS This invention relates to a drying unit for use, inter alia, in cleaning apparatus of the kind used, for example, in hospitals for cleaning surgical instruments.

A known drying unit for use in a cleaning apparatus makes use of a high output centrifugal fan to provide a blast of warmed air directed at the washed articles to be dried. The belief is that the forceful blast of air assists the drying process by forcing moisture from the surfaces of the articles. The articles to be dried are carried in baskets moved one at a time into the drying unit from a previous treatment station. The centrifugal fan and its associated ducting is positioned, in the direction in which articles are transported to the drying unit, either in front of, or behind the basket of articles to be dried, and so is a significant factor in the overall length of the drying unit, and therefore the overall length of the cleaning apparatus.Moveover, the use of a centrifugal fan providing a forceful air blast has additional disadvantages in that it is relatively noisy, and in that the blast of air can give rise to at least localised high pressure regions within the drying unit, in turn resulting in leakage of heated air around, for example, the inlet doors of the drying unit. Such leakage of air is of course detrimental to the overall energy efficiency of the unit. Furthermore, since the centrifugal fan is positioned at one end of the unit (in relation to the direction in which articles are transported) the output of the fan is directed into the unit at that end. This is disadvantageous particularly where the end in question is the front end and the unit can accommodate two batches of articles since moisture will then be blown from wetter articles to drier ones.

The batch transportation system utilized in a known cleaning apparatus requires top doors of the drying unit to be hinged about axes parallel to the direction in which batches are transported and thus parallel to the direction of the air blast entering the unit from the centrifugal fan. This can give rise to increased leakage of air from the unit and since the air leaking from the unit is likely to be moisture laden then the effect on the surroundings is of an undesirable nature.

It is an object of the present invention to provide a drying unit wherein the aforementioned disadvantages are minimised.

In accordance with the present invention there is provided a drying unit comprising a rectangular drying tank for receiving, batches of articles to be dried, fan means for generating a flow of air, said fan means including an elongate, generally cylindrical, rotatable impellor disposed parallel to a wall of the tank, an inlet through which air is drawn by rotation of said impellor said inlet being elongate in a direction parallel to the direction of elongation of the impellor, and a similarly elongate outlet through which an air flow issues from said impellor, the drying unit further including an air flow duct, the width and depth of which are not significantly less than the width and depth of the fan outlet, the duct conducting the air flow from the fan outlet and directing the air flow into the drying tank, and, heater means for heating the air of the air flow generated by the fan means.

Desirably the fan means is disposed below, or adjacent the level of the base of the drying tank, the duct extends vertically along one side of the drying tank, and is provided, at its end remote from the fan means, with deflection means for directing the air flow downwardly and across the tank.

Desirably the inlet of the fan means communicates with the drying tank below the articles to be dried and the drying unit includes air extraction means whereby a proportion of the air circulated through the drying tank by the fan means is extracted and discharged.

Desirably the heater means is disposed within the duct so that the air issuing from the outlet of the fan is heated during its passage through the duct.

Preferably the deflector means at the outlet end of the duct is smoothly curved.

Preferably the deflection means includes first and second deflectors each of which deflects a respective portion of the flow of air through a respective predetermined angle.

Desirably the first and second deflectors extend parallel to the direction of elongation of the fan impellor and are concentrically curved.

Conveniently the tank has an open top closed in use by a pair of hinged doors, the hinge axes being transverse to the flow of air from said duct into the tank.

Preferably the tank is arranged to accommodate first and second batches of articles, the two batches being positioned in line parallel to the direction of elongation of the fan impellor.

One example of the invention is illustrated in the accompanying drawings wherein: Figure 1 is a diagrammatic sectional view of a drying unit, Figure 2 is an enlargement of part of Figure 1, and Figure 3 is a diagrammatic, front elevational view, to a reduced scale, of the drying unit.

Referring to the drawings, the drying unit is intended to form part of a cleaning apparatus and may share a common cabinet or housing with other parts of the cleaning apparatus. For example, the cleaning apparatus may include a washing station, a rinsing station, and a drying station and all three may be disposed in longitudinally spaced relationship within a single cabinet. In the arrangement illustrated in the accompanying drawings the cabinet 11 houses a rinsing unit 12 and a drying unit 13, the washing unit being in a cabinet positioned, in use, end to end with the cabinet 11 and in advance of the rinsing unit 12.Articles to be cleaned are arranged in batches, in baskets, and there is a transportation mechanism for transporting baskets from a storage location into the washing station, from the washing station into the rinsing station, from the rinsing station into the drying station, and from the drying station to a clean article storage station. The transportation mechanism forms no part of the present invention, and it is sufficient to recognise that generally the transportation mechanism will operate to transport baskets of articles along a rectilinear path containing the washing, rinsing, and drying stations and will be controlled to ensure that batches of articles remain within the appropriate stations for appropriate treatment times.

The part of the cabinet 11 housing the drying station 13 has hinged doors 14 constituting the majority of its upper surface, the doors 14 being spring loaded, or counterbalanced, so as to have a rest position in which they close the upper surface of the cabinet. However, the lowering of a basket of articles to be dried onto the doors 14 will cause the doors 14 to swing open thus providing access to the interior of the drying station or drying unit 13. Within the cabinet 11 the drying unit 13 includes a rectangular drying tank 15 the base 16 of which has a perforated region 16a. The tank 15 is notionally divided into first and second drying regions 15a, 15b each of which can receive, above the base region 16a, a basket of articles to be dried.However, there is no internal dividing wall, and although the intention is that a basket first subjected to drying within the region 15a of the tank 15 will then be transferred to the region 15b, while the basket dried in the region 15b will be moved to the clean article storage station, it is to be understood that there is in fact no real distinction between the regions 15a, 15b and the remaining description applies to the tank 15 as a whole.

Beneath the base 16 of the tank 15 is a drainage/fan compartment 17, the lower wall 18 of which is inclined so as to slope downwardly from its rear edge to its front edge. The compartment 17 extends completely beneath the tank 15 and the front edge of the compartment 17 is defined in part by the housing 21 of a fan unit 19.

Articles to be dried are lifted in their baskets from the rinsing station 12 and are then moved in a rectilinear direction to be positioned above the tank 15 before being lowered into the tank 15. The rectilinear direction can, for convenience, be considered as the length direction of the apparatus. The housing 21 of the fan unit 19 extends through the full length of the compartment 17, and thus the full length of the tank 15. The inlet 22 of the fan unit 19 communicates with the interior of the compartment 17, and the outlet 23 of the fan unit communicates with a duct 24 extending vertically up the front face of the tank 15.

The fan unit 19 is of the kind sometimes known as a "tangential" fan and also sometimes known as an "crossflow" fan having an elongate enclosure 21 within which is rotatable an elongate, generally cylindrical, impellor 20. The impellor is rotatable about its longitudinal axis by means of an electric motor disposed on the exterior of one end wall of the housing 21. The impellor has a plurality of curved, axially extending blades and as the impellor rotates it draws air from the inlet 22 and expels it from the outlet 23. Both the inlet 22 and the outlet 23 extend the whole length of the impellor 20 which in turn extends substantially the whole length of the housing 21. Thus the axial length of the impellor is substantially equal to the length of the tank 15. Such fan units are available from "Airwheel Limited".In a particular practical embodiment the length of the tank 15 and therefore the length of the compartment 17, is 835 mm and the fan unit 19 has an impellor 830 mm long, and 100 mm in diameter.

The walls of the tank 15 are formed from galvanised mild steel sheet, or stainless steel sheet and the duct 24 extends upwardly on the front wall 25 of the tank 15, between the wall 25 and the wall of the cabinet. The wall 25 defines one wall of the duct 24, the duct 24 being rectangular in transverse cross-section, the other three walls of the duct being formed from the same material as the wall 25. The width dimension of the duct (the dimension parallel to the length of the tank 15) is equal to the length of the tank, and thus is equal to the length of the outlet 23 of the housing of the fan unit 19. The depth (measured in the front to back direction of the unit) is indicated in Figure 2 as dimension "A" and is equal to the equivalent dimension of the outlet 23 of the fan housing.Thus the cross-section of the duct 24 matches the outlet 23 and there is no flow restriction imposed on the output of the fan unit 19 by the duct.

The duct 24 communicates with the interior of the tank 15 by way of a rectangular aperture 26 in the wall 25. The aperture 26 extends for the full width dimension of the duct (the length of the tank) and the height of the aperture 26 is, as shown in Figure 2, "A", that is to say equal to the depth dimension of the duct. The air flow from the fan unit 19 passes up the duct 24 to the aperture 26, and in so doing passes through a heater unit 27 within the duct. The heater unit 27 does not significantly restrict the flow of air through the duct, but serves to heat the air as it passes along the duct.

The heater unit can be electrically powered, in that the air passes over a plurality of electrical heating elements, or alternatively can be in the form of a plurality of pipes extending transverse to the air flow, and carrying within them a flow of steam.

The baskets of articles to be dried do not fill the whole of the tank 15, and as can be seen diagrammatically in Figure 1 a basket 28 may be supported on supports and guides (not shown) which centralize the basket 28 in relation to the front and rear walls of the tank, and support the basket spaced above the perforated base 16.

A basket occupying the region 15a will be adjacent one end wall of the tank while a basket occupying the region 15b of the tank will be adjacent the opposite end wall of the tank. In order to direct the air flow efficiently from the duct 24 onto the articles carried by the baskets 28 in the regions 15a and 15b of the tank respectively the end of the duct 24 adjacent the aperture 26 has a pair of curved deflectors. Both deflectors extend the full length of the aperture 26, and both are formed from the same sheet metal as the walls of the tank 25 and the walls of the duct 24. The first deflector 29 abuts the uppermost horizontal edge of the aperture 26 and tangentially abuts the wall of the duct 24 opposite of the wall 25.The deflector 29 is of cylindrical form, being part circular in cross-section, the radius of curvature of the deflector 29 being such that the axis thereof is coincident with the lower horizontal edge of the aperture 26. The arcuate extent of the deflector 29 exceeds 90 , such that the deflector 29 includes a portion 31 projecting rearwardly and downwardly from the upper edge of the aperture 26, within the tank 15. The extent of the projecting portion 31, measured horizontally, is indicated as dimension "B" in Figure 2, and the effect of the deflector 29 is to smoothly deflect the air flow through an angle in excess of 90 , to direct the air flow rearwardly and downwardly into the baskets 28.

Within the aperture 26 is a second deflector 32 which also extends the full length of the aperture 26. The deflector 32 is, with the exception of one edge, arcuate, defining a part cylindrical surface coaxial with the deflector 29. At its opposite ends the deflector 32 includes integral tabs 33 whereby it is welded to the opposite end walls of the duct 24. The positioning of the deflector 32 in relation to the deflector 29 is such that the gap between them is equal to the dimension "B" mentioned above. The curved part of the deflector 32 o o extends through 135 , and thus there is an arc of 45 projecting rearwardly and downwardly within the tank 15.

However, the deflector 32 does not terminate at the end o of the 45 projection and includes an integral, straight (as opposed to arcuate) portion 34 the width of which is indicated by the dimension "C" in Figure 2. It will be recognised that the deflector 32 will turn part of the flow of air along the duct 24 through a slightly greater angle than that guided by the deflector 29 so ensuring that part of the flow enters the front edge of the basket 28. Thus the combined effect of the deflectors 29 and 32 is to smoothly, and therefore efficiently, deflect the air flow from the duct 24 downwardly into substantially of the whole of the open top area of the baskets 28.

In an arrangement in which the tank has a length of 835 mm, a front to back dimension of 710 mm and the top edge of the aperture 26 is 390 mm above the level of the bottom of the baskets 28 and 265 mm above the open top edge of the basket, and the fan is as specified previously, then dimension "A" is 85 mm, dimension "B" is 50 mm, and dimension "C" is 5 mm.

Articles from the rinsing station 12 enter the drying station and are placed in region 15a of tank 15 after a basket of articles previously subjected to a drying operation in region 15a of tank 15 has been moved to region 15b. The transporting mechanism is withdrawn, and the doors 14 close automatically. The fan unit 19 is operated and air driven along the duct 24 by the fan and heated by the heating unit 27 flows into the tank 15, being directed rearwardly and downwardly within the tank 15 to impinge primarily upon the baskets 28, and thus the articles therein. Most loose water will have drained from the baskets 28 as they are lifted from the rinsing station 12, but any loose water dripping from the bottom of the basket or baskets 28 will pass through the perforated base 16 and will be collected as it runs down the inclined wall 18 of the compartment 17 by a water extraction arrangement (not shown). The warm air blown onto the articles in the baskets 28 is drawn through the baskets, and thus flows around the articles ultimately to pass downwardly through the perforated base 16 and back into the fan unit inlet 22 for recirculation. The flow of heated air warms the articles and thus causes evaporation of the water from the surfaces of the articles. As the fan unit 19 is operated an extraction fan (not shown) is also operating to withdraw air from the upper region of the tank 15 through rows of apertures 35 in the rear wall of the tank.An extraction duct 36 on the exterior of the rear wall of the tank 15 establishes communication between the extractor fan and the apertures 35, and the arrangement is such that as warm air is circulatedthrough the tank 15 by the fan unit 19, a proportion of the air, which of course is moisture laden, is extracted through the apertures 35 and discharged to atmosphere. The extraction of air from the tank 15 of course fractionally reduces the pressure within the tank 15, and thus since the doors 14 are not sealed, drier, ambient air can be drawn into the tank 15, and then forms part of the air being warmed, and circulated, and subsequently extracted.

It is found that the arrangement described above exhibits significant benefits over the known arrangement. The known arrangement operates on the principle of providing a high air flow rate, to the extent of providing a blast of air, in the belief that this leads to efficient drying. It is found however that while the air blast does move surface water from some articles, it simply deposits the water on other articles, and may deposit the water on articles which previously were drier than those articles from which the water has been removed. In the apparatus described above there is no air blast effect, and instead there is a continuous, gentle circulation of heated air which, coupled with continuous extraction of a proportion of the circulating air, leads to a more efficient drying.The increase in efficiency leads to the facility to utilise a fan of lower power consumption, and more particularly a fan arrangement which generates far less noise than the air blast arrangement. Moreover, the air blast arrangement, utilising a centrifugal fan, had the fan positioned between the rinsing station 12 and the drying station 13 and so contributed significantly to the overall length of the apparatus. By comparison the elongate "tangential" fan extends parallel to the length of the tank 15 and so does not contribute significantly to the length of the apparatus.

The ancillary control apparatus will of course determine the period of time during which the fan unit 19 and the extractor unit operate, and also the temperature to which the air passing along the duct 24 is raised.

It will be recognised that in the absence of the deflectors 29 and 32 the air flow would not be efficiently distributed within the tank, and furthermore a vortex would be generated adjacent the closed end of the duct so reducing the overall efficiency.

Although a single impellor fan is disclosed above, the arrangement could embody a fan having two axially aligned, spaced impellors driven by a motor disposed between them. Such an arrangement could have individual inlets and outlets for each impellor and individual ducts, or the inlet, outlet, and duct could be common to both impellors. Individual ducts could merge adjacent the deflectors or could have respective apertures 26 with respective sets of deflectors.

It should be recognised that a dryer similar to that disclosed above can be provided for use as a "standalone" device rather than being part of a cleaning apparatus.

Claims (10)

1 A drying unit comprising a rectangular drying tank for receiving, batches of articles to be dried, fan means for generating a flow of air, said fan means including an elongate, generally cylindrical, rotatable impellor disposed parallel to a wall of the tank, an inlet through which air is drawn by rotation of said impellor said inlet being elongate in a direction parallel to the direction of elongation of the impellor, and a similarly elongate outlet through which an air flow issues from said impellor, the drying unit further including an air flow duct, the width and depth of which are not significantly less than the width and depth of the fan outlet, the duct conducting the air flow from the fan outlet and directing the air flow into the drying tank, and, heater means for heating the air of the air flow generated by the fan means.

2 A drying unit as claimed in Claim 1 wherein the fan means is disposed below, or adjacent the level of the base of the drying tank, the duct extends vertically along one side of the drying tank, and is provided, at its end remote from the fan means, with deflection means for directing the air flow downwardly and across the tank.

3 A drying unit as claimed in Claim 1 or 2 wherein the inlet of the fan means communicates with the drying tank below the articles to be dried and the drying unit includes air extraction means whereby a proportion of the air circulated through the drying tank by the fan means is extracted and discharged.

4 A drying unit as claimed in any one of Claims 1 to 3 wherein the heater means is disposed within the duct so that the air issuing from the outlet of the fan is heated during its passage through the duct.

5 A drying unit as claimed in any one of Claims 2 to 4 wherein the deflection means at the outlet end of the duct is smoothly curved.

6 A drying unit as claimed in any one of Claims 2 to 5 wherein the deflection means includes first and second deflectors each of which deflects a respective portion of the flow of air through a respective predetermined angle.

7 A drying unit as claimed in Claim 6 wherein the first and second deflectors extend parallel to the direction of elongation of the fan impellor and are concentrically curved.

8 A drying unit as claimed in any one of the preceding claims wherein the tank has an open top closed in use by a pair of hinged doors, the hinge axes being transverse to the flow of air from said duct into the tank.

9 A drying unit as claimed in any one of the preceding claims wherein the tank is arranged to accommodate first and second batches of articles, the two batches being positioned in line parallel to the direction of elongation of the fan impellor.

10 A drying unit substantially as hereinbefore described with reference to the accompanying drawings.