The present invention relates to chillers and more particularly but not exclusively to chillers for use in shoe manufacture.

It is traditional in shoe manufacture to chill shoes at the end of the production stages. For example, it may be necessary to chill shoes held about a shoe last after a heat treating operation to cure adhesive cement between insole board and uppers.

Traditionally such chillers have comprised a refrigeration system arranged to produce chilled air within a tunnel arrangement. A conveyor upon which the shoes are conveyed is arranged to pass through the chilled tunnel. Thus, a time period for the shoe within the tunnel can be accurately set by virtue of the conveyor belt speed. Typically, the air is partially re-circulated in order to conserve energy and so within the tunnel there are cool air jet orifices and a vent through which cool air is drawn back towards the evaporator elements using a centrifugal fan.

It will be appreciated, to maintain efficiency there are benefits in periodically defrosting the evaporator of the refrigeration system in the chiller. In a shoe production environment such defrosting is in effect downtime for the production line. Typically, a defrosting cycle will take 5 minutes and so it is possible that 75 minutes of production time may be lost in a single day. This is costly and may require additional production capacity to achieve targets. Furthermore, it will be understood that the time period between defrost cycles is dependent upon environmental humidity thus an interval of only 30 minutes between cycles would not be unusual.

It is an objective of the present invention to provide a chiller suitable for shoe manufacture that substantially improves upon the performance of previous apparatus.

In accordance with the present invention there is provided a shoe chiller comprising transport means to convey a

plurality of shoes or articles in an appropriate orientat through a chiller housing arranged to direct chilled air fl toward said articles, said chiller housing including refrigeration system and means for propelling chilled toward said articles, said refrigeration system including least two separate evaporators and a switch valve mechan coupled to respective inlets and outlets of each evaporator allow selective operation of each evaporator and so al evaporators not in use to be defrosted characterised in t each evaporator when being defrosted is substantially isola from said air flow through the chiller by shuttering eleme to limit defrosted liquid being drawn from that evapora into the evaporator which is operational in its duty cycle chill said air flow through said chiller. Preferably, a condenser of the refrigeration system arranged to direct its heat energy to defrost the evapora not in use.

Preferably, selective operation between evaporators controlled by a control unit in accordance with predetermined time period regime which may be varied accord to humidity or dependent upon detection of ice build-up on evaporator in use.

Preferably, the chiller includes a drainage tray channel to remove defrosted liquid from the chiller. Preferably, a control unit arranges that the duty cyc of each evaporator overlap to a limited extent to ens consistent chilling of air flows.

Preferably, the chiller includes air flow direct means, such as baffle paddles, to direct air flow to e evaporator when in use, the air flow direction means be configured to have a relatively quick change in operat between evaporators.

Preferably, the transport means is a conveyor b mechanism through the chiller to carry the articles to cooled such as partially fabricated shoes.

An embodiment of the present invention will now described by way of example only with reference to accompanying drawings in which:-

Fig. 1 is a schematic cross-section of a chiller suitable for chilling shoe preforms;

Fig. 2 is a schematic diagram of the refrigeration system of the chiller; and, Fig. 3 is a schematic plan cross-sectional view of the chiller.

Firstly referring to Fig. 1 which schematically shows a chiller 1 in accordance with the present invention. Within the chiller 1 an evaporator of a refrigeration system 2 is located such that air can be drawn through the evaporator where it is cooled and subsequently pushed through the chiller 1 to impinge from the channel side orifices or jets upon an article 3 which may be a shoe held upon a shoe last. In principle, the chiller air flow system is a closed loop, however, it is normal, as illustrated in Fig. 1, to provide an open tunnel-type passage for the article 3 to pass through upon a conveyor 4. Thus, a certain amount of cooled air escapes through the 'opening in the tunnel 5. It will be appreciated that both the speed of the conveyor through the tunnel 5 and possibly the temperature and the flow rate of air generated by a fan 6 may be varied in accordance with desired chilling operations. There are a wide variety of chilled air projection arrangements and return vent configurations which again will alter the chilling function. Furthermore, it is possible to add dehumidifying elements to the chiller air flow path but even with such dehumidifiers, the evaporator of the refrigeration system 2 eventually becomes clogged with ice about its surface.

It will be understood that ice is a poor conductor of heat energy, so the thicker the ice upon an evaporator becomes the less efficient that evaporator is with regard to chilling air flow.

Fig. 2 is a schematic illustration of a refrigeration system for use in the chiller 1. The refrigeration system 2 is conventional in that a compressor 21 feeds refrigerant to a condenser 22 and liquid refrigerant is collected in a receiver 23. The liquid refrigerant is pushed from the receiver 23 through a refrigerant dryer 24 and into a first evaporator 25

through a controlled expansion valve 26. The liqu refrigerant is vaporised and results in low temperatu refrigerant gas passing through the evaporator providing cooling function in the chiller 1. Either side of the first evaporator 25 at its inlet a outlet junctions there are valve switches 27,28. The inl valve switch 27 is just after a non-return valve 29. Thu with these valve switches 27,28 as illustrated in Fig. 2 conventional refrigeration system is provided including t first evaporator 25. The area marked out with a broken li is the active air chilling segment of the refrigeration syst 2 in the configuration illustrated.

A second evaporator 30 with associate control valve 31 effectively an equivalent system to evaporator 25 and val 26. However, this evaporator 30 in the configuration shown Fig. 2 is not connected into the refrigeration system and exposed to ambient air and preferably to any heat ener emanating from the condenser 22 due to compression of t regrigeration gas by the compressor 21 of the refrigerati system 2.

When the evaporator 25 requires defrosting the swit valves 27,28 are operated to couple the second evaporator into the refrigeration system and exclude the first evaporat 25. Thus, the first evaporator 25 is now exposed to ambie air temperature and preferably any heat energy emanating fr the condenser 22 due to compression of the refrigeration g and so ice deposited upon the first evaporator 25 is melte The melted ice is collected in a drip tray or channel (n shown) to be piped or pumped away. i will be appreciated that when the second evaporator requires defrost then the switch valves 27,28 are reversed a a similar melting operation is performed. Typically, defrost cycle will take 5 minutes. However, the time peri is very much dependent upon ambient air temperature, he generated from the condenser 22 and air flow in addition the amount of ice deposited upon the evaporator 25,30. T fan 6 is generally the same fan that stimulates air fl through the whole chiller 1.

It will be appreciated that evaporators 25, 30 cannot be instantaneously brought to cooling efficiency, i.e. brought down to temperature. Thus, it is usual to arrange that the valve switches 27,28 allow a time period in switch-over from the first evaporator 25 to the second evaporator 30 and vice- versa during which both evaporators 25,30 are operational to ensure consistent air chilling. Typically this change-over period may be 5 minutes.

Fig. 3 is a schematic plan of a chiller including the refrigeration system as illustrated in Fig. 2. The evaporators 25,30 are located centrally within the chiller 1 with the fan 6, compressor 21 and receiver 23 located to one side whilst on the other side of the evaporators 25,30 there is located an air flow direction area 32 and associate activation device 33.

The air flow direction area 32 includes in the embodiment illustrated two baffle paddles 34, 35 which are part of shuttering elements for the chiller evaporator path sealing arrangement and air flow routing. These paddles 34,35 effectively provide alternative paths through the chiller 1. In the position shown in Fig. 3 the first evaporator 25 is arranged to chill the air flow whilst the second evaporator 30 is exposed to ambient air temperature and thus is defrosted. The paddles 34,35 can be moved by any appropriate means including manually from position AA as depicted to position BB whereby the second evaporator 30 chills the air flow and the first evaporator 25 is defrosted.

It will be understood from Figure 3 that the air flow path of each evaporator 25, 30 is isolated from the other evaporator 25, 30 in use thus, as depicted, air flows through evaporator 25 and is chilled whilst the evaporator 30 is isolated by positioning of paddles 34, 35 and a slidable shutter 37. With the evaporator 30 effectively isolated by the paddles 34, 35 and shutter 37, defrosted liquid from evaporator 30 can be removed without possibility of pick-up by the air flow through evaporator 25. The shutter 37 is slidable between sealing evaporators 25, 30 under control of activator means (not shown). Typically, shutter 37 will be a

simple sheet of material in appropriate rails. With low flow rates shutter 37 may be removed as the possibility defrosted liquid pick-up is diminished.

It will be understood that a heater element could provided within the chiller in order to expedite the defr cycle. However, for a normal operation such a heater wo not be necessary.

From the drawings and description, it will be underst that the operation of the refrigeration system from start as controlled by a controller device such as a microproces is as follows:

(1) Check defrost liquid has been removed from chil after previous operation, if not pump this liquid a and then proceed, (2) Activate the refrigeration system 2 by stimulat of refrigerant flow through evaporator 25 and monitor evaporator 25 using the controller device in order determine that >it has reached an appropriate operat temperature e.g. -20"C. This monitoring operation co use an expansion valve dependent upon refriger pressure, a thermocouple or simply by setting a start- time for the chiller. Once evaporator temperature achieved then proceed,

(3) Propel air flow through the evaporator 25 towards the articles to be chilled in the chiller whil monitoring air flow. Once air flow has diminished due ice build-up on the evaporator 25 another evaporator should be activated. Air flow decrease in the chill can be detected using a pressure gauge or simply setting a duty cycle time period for each evaporator 2

30 at the end of which, irrespective of the degree of build-up that evaporator 25, 30 is de-activated. In event, prior to the end of the present evaporator 25 d cycle, the next evaporator 30 is activated. (4) he temperature of next evaporator 30 is monito by the controller device as at start-up with regard evaporator 25 in order to determine when it has b brought down to temperature e.g. -20"C. Once evapora

30 has reached temperature the air flow is diverted by paddles 34, 35 and shutter 37 through that evaporator 30 rather than through evaporator 25 in order that the air flow is now cooled by evaporator 30. The paddles 34, 35 direct air flow and the shutter 37 prevents defrosted water being drawn up to the air flow by a venturi effect.

(5) Once isolated from the air flow evaporator 25 is at least exposed to ambient temperature or preferably hot gases from the condenser of the refrigeration system and/ or a heater in order to defrost the evaporator 25. Defrosted liquid is collected and removed.

(6) It will be appreciated whilst evaporator 25 is being defrosted, evaporator 30 is accumulating ice and the air flow is again monitored by the controller device to determine when air flow should again be returned to evaporator 25 for chiller efficiency and evaporator 30 then defrosted as with regard to evaporator 25 as described at (5) above.

(7) In accordance with the above, alternative duty cycle and defrost operations are performed with respect to evaporators 25, 30 in order to ensure chilled air flow is always presented in the chiller without "down-time".

As indicated previously, it is expected that the duty cycles of evaporators 25, 30 will overlap by about 5 minutes as this is a normal period of time for an evaporator to reach its optimum duty cycle temperature.