GB2313436A - Portable refrigeration device - Google Patents

Abstract

A portable refrigerator for storing medicines comprises an insulated storage compartment 3, an evaporator 6 comprising a coiled tube, and a cylinder containing liquid refrigerant connected to the evaporator via a one-way valve for releasing refrigerant into the evaporator. A pressure relief valve 9 is able to release evaporated refrigerant to atmosphere. In a second arrangement, the compartment 3 contains an evaporator 6 and an expansion chamber 10 forming part of a closed refrigerant circuit including a condenser 14 located externally of the storage compartment 3 and a manually-operated compressor 12 for priming the circuit. The expansion chamber 10 surrounds the evaporator 3 and provides a reservoir for refrigerant between the evaporator 3 and compressor 12 which increases the period of time the device can operate to maintain a required storage temperature without operating the compressor 12.

Description

PORTABLE REFRIGERATION DEVICE This invention relates to a portable refrigeration device and to a manually operable compressor particularly, but not exclusively, for use in such device.

The portable storage device of this invention has particular application for the storage of medicines used for treating or relieving an illness, injury or other condition of a patient and. as used herein, the term medicine includes any medicament such as antibiotics, drugs or other pharmaceuticals or like substances.

Many medicines deteriorate at ambient or higher temperatures and are therefore kept at lower temperatures usually by storing in a refrigerator or the like.

This can present the patient with serious problems where medicines have to be taken at regular intervals over a prolonged period of time, for example insulin used by diabetics. In particular, when travelling long distances from home, especially overseas business trips or foreign holidays, a refrigerator may not be available or may be inadequate to maintain the required storage temperature particularly at the higher ambient temperatures commonly encountered. As a result, the medicine may become ineffective with potentially serious consequences for the patient.

It is an object of the present invention therefore to provide a portable refrigeration device which can be used for storing medicines at the required temperature so that a patient can keep a supply of the medicine to hand at all times.

It is a further object of the present invention to provide a manually operable compressor suitable for use in such portable refrigeration device.

According to a first aspect of the present invention there is provided a portable refrigeration device comprising an insulated storage compartment and means for absorbing heat from within the storage compartment by evaporation of a refrigerant.

In the invented portable refrigeration device, the heart apscrptio means may be adapted to provide any desired storage temperature and is preferably operable to provide a storage temperature lower than the external ambient temperature.

Preferably, the heat absorption means comprises aflevaporator arranged within the storage compartment and connected top supply of refrigerant such that heat is absorbed by evaporation of the refrigerant within the evaporator.

In one preferred embodiment, the refrigerant is supplied to the evaporator from a cylinder and the evaporator has a non-return valve for discharging vaporised refrigerant to atmosphere externally of the storage compartment when the pressure of the refrigerant within the evaporator exceeds a predetermined minimum.

Conveniently, the cylinder is detachable facilitating replacement of an empty cylinder by a full cylinder for continued operation of the device.

Empty cylinders may be re-filled for re-use.

Preferably, means is provided to give a visual and/or audio indication when a cylinder requires replacement, for example by monitoring the refrigerant level in the cylinder and/or the temperature in the storage compartment.

In another preferred embodiment, the evaporator forms part of a closed refrigerant circuit including a compressor and a condenser for recycling the refrigerant.

Advantageously, the compressor is manually operable for priming the circuit and an expansion chamber is provided between the evaporator and the compressor. The expansion chamber acts as a reservoir for vaporised refrigerant so as to relieve the pressure in the evaporator in the manner of the pressure relief valve of the first embodiment and is preferably connected to the evaporator by flow control means such as a capillary tube.

Alternatively or additionally, the expansion chamber could receive liquid refrigerant from the evaporator.

In this way, the expansion chamber provides for continued operation of the device before re-priming is necessary and, by appropriate selection of the capacity of the expansion chamber and the characteristics of the refrigerant an operating period of up to 24 hours may be achieved between successive priming operations.

Advantageously, the expansion chamber is also arranged around the evaporator within the storage compartment so as to provide a secondary degree of insulation around the evaporator. Where liquid refrigerant is ejected into the expansion chamber some vaporisation will occur with resultant temperature drop. In this way, the expansion chamber can provide a further heat sink for absorption of internal heat and additionalty acts to isolate the evaporator from external ambient temperatures.

Preferably, the condenser is air cooled and is arranged externally of the storage compartment for giving up the heat from the vaporised refrigerant to atmosphere and condensing the refrigerant.

Conveniently, the condensed refrigerant from the condenser is collected in a receiver and refrigerant from the receiver is delivered to the evaporator through an expansion valve.

The expansion valve may be constituted by a capillary tube connecting the receiver and evaporator and which also controls the flow rate.

Alternatively, or in addition, a small pellet of porous ceramic or other sintered material with a high pressure drop characteristic to provide a balanced flow may be provided between the receiver and evaporator.

According to a second aspect of the invention, there is provided a compressor having a fluid inlet, a fluid outlet, a piston/cylinder unit for compressing fluid by axial displacement of the piston relative to the cylinder, first means biasing the cylinder in a direction to isolate the inlet, and second means biasing the piston in the opposed direction, said first means being weaker than said second means such that the cylinder is displaced by the piston under the biasing of the second means to connect the inlet and, when the piston is depressed against the biasing of the second means, the cylinder is displaced by the first means to isolate the inlet.

Preferably, the piston/cylinder unit is mounted in a tubular body having a manually operable actuator at one end for displacing the piston against the biasing of the second means.

Conveniently, the cylinder is slidably mounted in a sleeve member arranged at the other end of the body with the first means acting between the sleeve member and the cylinder.

Preferably, one end portion of the piston is slidably received in the cylinder and the other end portion projects from the cylinder for engagement by the actuator with the second means acting between the sleeve member and said other end portion.

Advantageously, the first means comprises a helical spring encircling the cylinder and the second means comprises a hollow convoluted cylindrical flexible bellows surrounding the piston/cylinder unit.

Alternatively, the second means may comprise a compression spring encircling the piston/cylinder unit or any other means for resiliently biasing the piston, for example a resiliently expandable foam or like material.

Preferably, the sleeve member carries a coupling member having an exhaust port closed by a one-way valve to isolate the outlet, said one-way valve being opened to connect the outlet when the piston is depressed to compress the fluid.

Advantageously, the sleeve member has at least one transfer port that is closed by the cylinder to isolate the inlet when the piston is depressed to compress the fluid.

According to a third aspect of the invention there is provided a refrigeration system comprising a compressor having an inlet side and an outlet side, an evaporator on the inlet side, a condenser on the outlet side, and an expansion chamber on the inlet side between the evaporator and the compressor.

The provision of the expansion chamber may result in an improvement in energy efficiency and potential savings in operating costs by reducing the operation of the compressor required to maintain a desired temperature.

As will be appreciated, this has application both for the portable storage device of the first aspect of the invention and for other types of refrigeration apparatus including domestic, commercial and industrial fridges, freezers, coolers and the like.

Embodiments of the various aspects of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein: FIGURE 1 is a longitudinal section of a first embodiment of a portable refrigeration device; FIGURE 2 is a longitudinal section of a second embodiment of a portable refrigeration device; and FIGURE 3 is a longitudinal section of a manually operable compressor suitable for use in the device shown in Figure 2.

The embodiments of portable refrigeration device 1 shown in Figures 1 and 2 of the accompanying drawings comprise an insulated container 2 providing a storage compartment 3 for storing a medicine at or below a predetermined temperature, for example for storing phials of insulin used by diabetics at a temperature of 5-80C.

The container 2 comprises an open-topped body 4 closed by a removable lid 5. The body 4 and lid 5 are made of thermal insulation material.

It will be understood that the required insulation properties may be obtained by any suitable materials and/or construction of the container 2, for example the body 4 and/or lid 5 may have a double-wall with the cavity between the walls evacuated to create a vacuum.

The container 2 may be of any suitable size and shape which can be easily carried and stored, for example as hand luggage when travelling. A cylindrical shape approximately 3" in diameter and 4" long is found to be suitable but other sizes and shapes may be equally convenient.

Attached to the body 4 is an adjustable length strap (not shown) for carrying over the shoulder or by hand. Alternatively, or in addition to such strap, a handle or grip may be provided for carrying the device.

The container 2 may also include one or more external pockets (not shown) for storing materials and/or equipment used in administering the stored medicine, for example syringes, needles, cotton wool and sterilising fluid for injecting insulin.

Alternatively, such additional storage pockets may be provided in a bag or case in which the container 2 is received with such bag or case being provided with a strap and/or handle or grip as above-described.

Referring now to Figure 1, there is shown located within the storage compartment 3, an evaporator 6 comprising a coiled tube having one end connected to a centre mounting block 7 on the base of the body 4 and the other end connected to a pressure relief valve 8 opening to atmosphere on the side of the body 4 below the lid 5.

A cylinder 9 containing a liquid refrigerant is screwed or otherwise detachably secured to the mounting block 7 so as to open a one-way valve (not shown) for releasing the refrigerant into the evaporator 6.

In use, when the air temperature within the storage compartment rises above the predetermined storage temperature, heat is absorbed by evaporation of the liquid refrigerant within the evaporator 6 so as to reduce the air temperature.

As a result of such evaporation, the pressure within the evaporator 6 increases and the pressure relief valve 9 is operable at a pre-set pressure to open so as to release the evaporated refrigerant to atmosphere thereby reducing excess pressure for maintaining the pre-set pressure in the evaporator 6.

The above operation occurs automatically so that refrigerant is gradually released from the cylinder 9 into the evaporator 6 to maintain the required storage temperature in the storage compartment 3 and, when the cylinder 9 is empty, it can be replaced by a full cylinder 9 and the empty cylinder 9 re-charged for later use thereby ensuring continuous operation of the device 1.

As will be understood, the cooling requirement will vary in use due to a number of factors such as the external ambient temperature, the efficiency of the insulation, the frequency with which the container is opened and the characteristics of the refrigerant employed.

As a result, the effective operating period of the device will not be constant and it is preferred to provide means for monitoring the refrigerant level and giving an audio and/or visual indication when a cylinder requires replacement.

Alternatively, or in addition, means may be provided for monitoring the temperature within the storage compartment and giving an audio and/or visual indication when the temperature exceeds the required storage temperature by more than a pre-set amount thereby warning the user that the device 1 is malfunctioning, for example requiring replacement of the cylinder.

Referring now to Figure 2, there is shown located concentrically within the storage compartment 3, an evaporator 6 and an expansion chamber 10 each of hollow U-shape.

The evaporator 6 and expansion chamber 10 form part of a closed refrigerant circuit containing a liquid refrigerant.

A capillary tube 11 leads from the bottom of the evaporator 6 and opens into the bottom of the expansion chamber 10 for controlling the flow of refrigerant from the evaporator 6 to the expansion chamber 10.

Alternatively, the capillary tube 11 can lead from the top of the evaporator 6b and open into the top of the expansion chamber 10 as shown in broken lines in Figure 2.

The expansion chamber 10 is connected at the top to the inlet side of a compressor 12 located externally of the storage compartment 3.

The compressor 12 is manually operable by means of an actuator cap 13 accessible to the user for priming the refrigeration circuit as described later and is connected on the outlet side to an air cooled condenser 14 also positioned externally of the storage compartment 3.

The condenser 14 comprises a coiled or looped tube to provide a large surface area for air cooling and may optionally be finned or otherwise adapted for extending the surface area to facilitate heat dissipation.

Downstream of the condenser 14 there is a receiver 15 for collecting the refrigerant that has been cooled and condensed in the condenser 14.

The receiver 15 is connected to the evaporator 6 by a small bore capillary tube 16 which functions as an expansion valve opening into the bottom of the evaporator 6 for controlling the flow of refrigerant from the receiver 15 to the evaporator 6.

After manufacture or a period of non-use, the refrigerant circuit is in a totally saturated state, that is with an appropriate volume of both liquid and vapour refrigerant.

In this state, the circuit is in equilibrium with liquid settled at the bottom of the evaporator 6, possibly the expansion chamber 10 and capillary tube 11 as well as in the condenser 14, receiver 15 and capillary tube 16.

The remaining volume is filled by vapour in which the basic pressure is generally governed by the ambient air temperature surrounding the circuit, externally and internally, as well as the characteristics of the refrigerant.

From this state, the circuit is primed by manually operating the compressor 12 which reduces the pressure in the expansion chamber 10 on the suction stroke causing the liquid refrigerant, if any, therein to vaporise.

Vaporised refrigerant is drawn into the compressor 12 and liquid/vapour refrigerant flows from the evaporator 6 to the expansion chamber 10 controlled by the capillary tube 11 or any other device.

On the compression stroke, the vaporised refrigerant is compressed thereby increasing the pressure and temperature and is discharged into the condenser 14 where it is condensed by air cooling and collected in the receiver 15.

Simultaneously, liquid refrigerant flows from the receiver 15 to the evaporator 6 controlled by the capillary tube 16 and is vaporised on re introduction into the evaporator 6 with absorption of heat from the storage compartment 3.

In this way, the temperature within the storage compartment 3 is reduced by absorption of heat through vaporisation of the refrigerant so as to control the temperature within the storage compartment.

The amount of heat removed from the storage compartment 3 is influenced by the external ambient temperature and the ability of the insulation to keep the external sources of heat input to a minimum.

Whereas in a conventional refrigeration system, the compressor is connected directly to the evaporator on the suction side, the provision of the expansion chamber 10 and capillary tube 11 to control flow from the evaporator 6 in the above-described embodiment effectively eliminates excessive initial reduction of pressure and vaporisation of refrigerant in the evaporator 6. This acts as an aid to a more controlled and balanced flow, thereby prolonging the time before saturation of the system occurs requiring re-priming of the system.

As a result, a significant operating period, for example 24 hours, may be achieved during which the required temperature within the storage compartment 3 is maintained before re-priming is required.

In a modification (not shown), more than one,expansion chamber may be provided between the evaporator 6 and compressor 12.

In another modification, a temperature responsive valve 17, shown in broken lines in Figure 2, may be provided to control the flow of refrigerant through capillary tube 16 from the receiver 15 to the evaporator 6 using any suitable mechanical or electronic means with appropriate circuitry and sensors operable by a small battery (not shown) to control the valve 17.

In a further modification (not shown), means powered by a small micro-cell battery or other suitable power source may be provided to give a visual and/or audio indication of the ideal start conditions. For example, a digital LCD of temperature and/or pressure may be provided.

In yet a further modification (not shown), supplemental cooling of the storage compartment may be achieved by the provision within the storage compartment of a freezable fluid such as water that is frozen during normal operation and acts as a heat sink to absorb heat for maintaining the required temperature in the storage compartment during night-time hours or other long periods when re-priming of the system may be impractical. The fluid may be contained in a separate pack or bag which can be removed from the storage compartment, for example to allow the fluid to be pre-frozen prior to adding to the storage compartment. Alternatively, a suitable reservoir for the fluid may be built-into the storage compartment as an integral part of the device.

Referring now to Figure 3, there is shown a manually operable compressor 20 such as may be used in the refrigerant circuit of the second embodiment above-described.

The compressor 20 comprises a tubular body 21 having a manually operable actuator cap 22 slidably mounted at one end and a sleeve member 23 mounted at the other end.

The sleeve member 23 has external axially spaced land portions 24,24' provided with annular grooves 25,25' respectively in which sealing rings (not shown) are received for sealing the sleeve member 23 relative to the internal surface of the body 21.

Between the land portions 24,24', the sleeve member 23 defines with the body 21 an annular chamber 26 having a lateral inlet 27 in the sidewall of the body 21 for connection to a fluid supply line and a plurality of circumferentially spaced transfer ports 28 (one only shown) in the sleeve member 23 between the land portions 24,24'.

The outer end of the sleeve member 23 carries a tubular coupling member 29 having a valve seating 30 defining an exhaust port 31 at the inner end and an axial outlet 32 at the other end for connection to' a fluid delivery line. Located within the coupling member 29 is a non-return valve 33 comprising a valve member 34 biased by a return spring 35 to close the exhaust port 31.

The inner end of the sleeve member 23 slidably mounts a cylinder 36 of a piston/cylinder unit 37. The cylinder 36 has an inlet port 38 at the front end aligned with the exhaust port 31 in the coupling member 29.

The front end of the cylinder 36 is encircled by a helical coil spring 39 that acts between the cylinder 36 and the sleeve member 23 to bias resiliently the cylinder 36 towards the coupling member 29 to connect the inlet port 38 and the exhaust port 31.

A piston rod 40 of the piston/cylinder unit 37 is slidably mounted in the cylinder 36 and sealed at the front end relative to the inner surface of the cylinder 36 by a cup-shaped seal member 41.

The piston rod 40 extends through an aperture 42 in the rear end of the cylinder 36 and is connected at the rear end to one end of a hollow convoluted cylindrical bellows 43 surrounding the piston/cylinder unit 37.

The other end of the bellows 43 is connected to the inner end of the sleeve member 23.

The bellows 43 biases the piston rod 40 to the back stroke position shown in Figure 3 in which the front end of the cylinder 36 is raised above the transfer ports 28 against the weaker biasing of the coil spring 39 by engagement of the front end of the piston rod 40 with the rear end of the cylinder 36.

As a result, the cylinder 36 is connected to the inlet 27 through the open transfer ports 28 and is isolated from the outlet 32 by the valve member 34 closing the exhaust port 31.

If the actuator cap 22 is depressed from the back stroke position, the bellows 43 is axially compressed causing axial displacement of the piston rod 40 so that the cylinder 36 is no longer held in the back stroke position by the piston rod 40 and moves with the piston rod 40 under the biasing of the coil spring 39 to seat against the coupling member 29 with the valve seating 30 engaged by an annular washer 44. As a result, the transfer ports 28 are closed to isolate the inlet 27 from the cylinder 36.

Continued axial displacement of the piston rod 40 by the actuator cap 22 compresses the fluid within the cylinder 36 and, when the pressure of the fluid exceeds the biasing of the return spring 35, the valve member 34 is displaced so as to open the exhaust port 31 and the fluid is expelled from the cylinder 36 into the coupling member 29 and discharged through the outlet 32 to the delivery line.

If the actuator cap 22 is then released, the piston rod 40 is raised by expansion of the bellows 43 and, when the biasing of the return spring 35 overcomes the reduced pressure in the cylinder 36, the exhaust port 31 is closed by the valve member 34 to isolate the outlet 32.

At the end of the return stroke of the piston rod 40, the cylinder 36 is lifted away from the coupling member 29 against the biasing of the coil spring 39 opening the transfer ports 28 to connect the inlet 27 for refilling the cylinder 36 for the next compression stroke.

As will now be appreciated, for priming the refrigeration device 1 shown in Figure 2, the lateral inlet 27 of the compressor 20 would be connected to the expansion chamber 10 and the axial outlet 32 would be connected to the condenser 14 by any suitable means.

The system pressure can vary according to the type of refrigerant employed and, to assist priming at higher pressure, a rotatable winder (not shown) operatively connected to the compressor piston by any suitable means such as a crank may be used to provide a mechanical advantage when actuating the compressor. The winder may incorporate a handle which can be folded to a compact stored position when not in use. Alternatively or additionally, the winder may be driven by a motor powered by any suitable means such as rechargeable batteries.

It will be understood that the invention in each of its aspects is not limited to the embodiments above-described and is capable of alternative applications and uses. For example, the portable refrigeration device has wider application for storing other products requiring a temperature controlled environment and is not limited to the storage of medicines. The compressor also has wider application for compressing a fluid in other systems and is not limited to the portable refrigeration device.

Claims (17)

Claims:

1. A portable refrigeration device comprising an insulated storage compartment and means for absorbing heat from within the storage compartment by evaporation of a refrigerant.

2. A portable refrigeration device according to Claim 1 wherein the heat absorption means comprises an evaporator arranged within the storage compartment and connected to a supply of refrigerant such that heat is absorbed by evaporation of the refrigerant within the evaporator.

3. A portable refrigeration device according to Claim 2 wherein the refrigerant is supplied to the evaporator from a cylinder and the evaporator has a non-return valve for discharging vaporised refrigerant to atmosphere externally of the storage compartment when the pressure of the refrigerant within the evaporator exceeds a predetermined minimum.

4. A portable refrigeration device according to Claim 3 wherein the cylinder is detachable allowing replacement of an empty cylinder for continued operation of the device.

5. A portable refrigeration device according to Claim 3 or Claim 4 wherein means is provided to give a visual and/or audio indication when a cylinder requires replacement.

6. A portable refrigeration device according to Claim 5 wherein the indicator means is arrangedto monitor the refrigerant level in the cylinder and/or the temperature in the storage compartment.

7. A portable refrigeration device according to Claim 2 wherein the evaporator forms part of a closed refrigerant circuit including a compressor and a condenser for re-cycling the refrigerant.

8. A portable refrigeration device according to Claim 7 wherein the compressor is manually operable for priming the circuit.

9. A portable refrigeration device according to Claim 7 or Claim 8 wherein an expansion chamber is provided between the evaporator and the compressor.

10. A portable refrigeration device according to Claim 9 wherein the expansion chamber is arranged around the evaporator within the storage compartment so as to provide a secondary degree of insulation around the evaporator.

11. A portable refrigeration device according to any one of Claims 7 to 10 wherein the condenser is air cooled and is arranged externally of the storage compartment for giving up the heat from the vaporised refrigerant to atmosphere and condensing the refrigerant.

12. A portable refrigeration device according to Claim 11 wherein condensed refrigerant from the condenser is collected in a receiver for delivery to the evaporator through an expansion valve.

13. A portable refrigeration device according to Claim 12 wherein the expansion valve is provided by a capillary tube which connects the receiver and evaporator and controls the flow rate.

14. A portable refrigeration device according to Claim 12 wherein a porous ceramic or other sintered material with a high pressure drop characteristic is arranged to provide a balanced flow between the receiver and evaporator.

15. A self-contained portable refrigeration device for storing substances such as medicaments comprises an insulated storage compartment, a closed refrigerant circuit including an evaporator for absorbing heat from within the storage compartment and a condenser for dissipating absorbed heat externally of the storage compartment, and a manually operable compressor for priming the circuit, the arrangement being such that in use the temperature within the storage compartment can be controlled.

16. A portable refrigeration device substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

17. A portable refrigeration device substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.