GB2128808A - Apparatus for the controlled cooling of a product - Google Patents

Abstract

Cooling apparatus for modifying the cooling rate of a sample which is at least partially of liquid form, especially for the preservation of biological materials, comprises one or more Peltier- effect modules (44) providing a surface at which heat is absorbed, and one or more sample holders (30) arranged to carry one or more samples (28), wherein the modules (44) and the samples (28) are mounted to provide relative movement between contact and out-of- contact positions. The Peltier-effect modules (44) are preferably mounted for pivotal movement. An optical detector (70) adjacent to the sample (28) detects the presence or absence of particles in the sample. <IMAGE>

Description

SPECIFICATION Apparatus for the controlled cooling of a product This invention relates to apparatus for the controlled cooling of a product. The invention is particularly concerned with the controlled cooling of specimens or samples which are at least partially in liquid form.

One particular application of the invention is to the freezing, e.g. for preservation, of biological materials.

Our published U.K. patent application Serial No.

2096827A describes methods of and apparatus for modifying the cooling rate of a specimen which is at least partially in the liquid phase, in a controlled manner. In the aforesaid patent application there is described a method of cooling a specimen which is at least partially of liquid form, which comprises the steps of: a) cooling a specimen in toto to a temperature level which is close to a given critical temperature, and b) at said temperature level subjecting the specimen to supplementary cooling by passing an electric current through Peltier effect means in thermal contact with the specimen.

There is also described in the aforesaid patent application a cooling device for cooling a specimen which is at least partially of liquid form, comprising cooling means arranged to be connected to an electric power source and to function in accordance with the Peltier effect to provide a surface at which heat is absorbed thereby to cool said surface, a container for the specimen in thermal contact with said surface, and control means operative to initiate energisation of said cooling means at a temperature which is close to a given critical temperature for said specimen.

The present invention is particularly concerned with practical embodiments of apparatus for car rying out the aforesaid method. By carrying out the cooling in a controlled manner one can for example induce crystallisation of the body of liquid at a particular location, or induce precipitation or sedimentation of material from the liquid, or absorb the heat of an exothermic reaction occurring during a cooling process, even if no crystallisation, precipitation or sedimentation occurs at that point in the cooling process.

In general, the present invention, as well as being applicable to automatic seeding, can also be used in other applications where a boost in the rate of cooling of biological material may be required.

In accordance with one aspect of the present invention there is provided cooling apparatus for modifying the cooling rate of a sample which is at least partially of liquid form, comprising cooling means arranged to be connected to an electric power source and to function in accordance with the Peltier effect to provide a surface at which heat is absorbed thereby to cool said surface, and a sample holder arranged to carry a sample, wherein the cooling means and the sample holder are relatively movable to bring said surface into thermal contact with the sample.

Preferably, there is provided displacement means to displace said cooling means between a first position in which said surface is in thermal contact with the sample and a second position in which said surface is remote from the sample.

In one arrangement a movement of the sample into a position for cooling initiates the displacement of the cooling means from its said second position to its said first position. For example, the initiation of the displacement of the cooling means towards its said first position can be effected by the sample holder striking against a portion of the cooling means.

Alternatively, the displacement means may comprise a movable striker mechanism, movement of which initiates the displacement of the cooling means to its said first position.

In a preferred arrangement the cooling means is pivotable about pivot means for displacement between its said first and second positions.

Preferably, the cooling means comprises a Peltier effect module mounted on a cantilevered support whereby the module automatically moves out of contact with the sample when no external force is exerted on the module.

The cooling means may comprise a Peltier effect module and a heat-conductive element in contact with the module and defining said surface.

In a preferred embodiment the sample holder comprises an elongate rod with sample carrier means adjustably movable along the rod to permit adjustment of the sample relative to the sample holder.

Optical detector means may be used to detect the presence or absence of particles within the sample, preferably an infra-red detector device.

In order that the invention may be fully understood, various embodiments of cooling apparatus in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a partial side view, with parts broken away, of a preferred embodiment of cooling apparatus in accordance with the present invention; Figure 2 is a view, on an enlarged scale, illustrating the movement of the Peltier module relative to a sample; Figure 3 shows the sample holder of Figures 1 and 2; Figure 4 is a more detailed view of the striker mechanism by which the relative movement between the Peltier module and the sample is controlled; Figure 5 is a view, on an enlarged scale, of a plurality of samples in the form of straws positioned for optical sensing by an optical detector device; and, Figures 6A and 6B are side views of an alternative embodiment of cooling apparatus, Figure 6A showing the situation where a sample in the form of an ampoule is about to be lowered into a working chamber which contains the Peltier module, and Figure 6B showing the relative positions of the components after the ampoule has been lowered into the housing into thermal contact with the Peitier module.

The cooling apparatus which is shown in Figures 1 to 5 comprises a plurality of individual cooling devices arranged at stations arranged in a circular array around a central core. The individual cooling devices are mounted in or are supported from a top plate 10 which is provided with a pair of lifting handles 12. A plurality of supporting members 14 extend down below the top plate 10 and carry a hollow cylindrical cage 16. The lower half of the cage 16 is provided with a plurality of apertures 18 in the form of windows around its circumference and equal in number to the number of cooling devices. Around the bottom of the cage 16 is secured an annular strip 20. The underside of the strip 20 is provided with a shaped bracket 22 at each cooling station and these brackets 22 support an annular ring 24 which is provided with an aperture therethrough at each cooling station.

At each cooling station, i.e. associated with each cooling device, there is provided a sample holder, indicated generally at 26 in Figure 1 and shown more clearly in Figure 3. The cooling apparatus is designed particularly for use with samples either in the form of ampoules or thin straws, as indicated at 28 in Figures 2 and 5. In the drawings the sample or samples are shown as straws. These may be for example 2 mm or 3 mm in diameter.

Each sample holder 26 comprises a rod 30 which is provided at its upper end with a plug 32 which fits into a correspondingly sized hole in the top plate 10.

The bottom end of the rod 30 is provided with an enlarged foot 34 which locates within the hole in the bottommost support ring 24. The rod 30 also carries a sample clamp 36 which is held in place on the rod by upper and lower retaining rings 38. Between the sample clamp 36 and the foot of the rod there is mounted a sample retainer 40 which is displaceable upwards and downwards on the rod. The sample retainer 40 comprises a generally C-shaped bracket which has a hole 42 in the upper web. With this arrangement, a sample in the form of a straw, straws or an ampoule is held in position relative to the sample holder 26 by having the bottom end of the sample resting on the lower web of the retainer 40 and having the clamp 36 in contact with a midportion of the sample.By raising or lowering the sample retainer 40 the position of the sample relative to the sample holder can be altered so that a particular section of the sample can be aligned with the cooling module.

The Peltier module 44 is mounted on a cranked support arm 46 which has its lower end resting within a shaped seat provided in the top of the support ring 20. A fixing screw 48 retains the cranked arm 46 in position within the seat. The "cold" face of the Peltier module 44 has a yoke 50 attached to it, for example by soldering. The yoke 50 is of a material which is an extremely good conductor of heat, and is preferably of copper. The yoke 50 is shaped so that it has a reducing cross-sectional area in the direction away from the face of the Peltier module and the face of the yoke adjacent to the sample is suitably shaped so that it can make intimate contact with the sample. For example, this face of the yoke may be generally smoothly concave, or have a profile adapted to the type and size of sample used, whether this be a straw, an ampoule or some other container.The rear face of the Peltier module 44 is provided with cooling fins or a heat sink 52. As shown in Figure 2 in particular, each Peltier module is pivotable between a contact position in which the cranked arm 46 is generally upright and the yoke 50 is in direct contact with the sample, and a second position in which contact is broken and the cantilev exaction of the cranked arm 46 tilts the module backwards through the window 18 in the cylindrical cage 16 to the position indicated by chain-dotted lines in Figure 2 where the lower end of the cranked arm 46 abuts the bottom edge of the window 18.

This provides a limit stop to the tilting movement.

The position of each Peltier module relative to the associated sample, i.e. whether contact is made or broken, is controlled by a separate mechanism positioned radially inwardly of the Peltier modules.

One central striker mechanism is provided to provide displacement movement, as desired, for each of the invididual Peltier modules. Figure 4 shows the striker mechanism, and Figure 2 shows how it functions in conjunction with the Peltier modules.

The striker mechanism comprises a shaft 54 which is provided at its upper end with a knob 56. The knob 56 also carries an index pin 58 as a locatorforthe striker mechanism in the top support plate 10. This index pin 58 fits into a hole formed in the top plate 10. The shaft 54 is provided with a spindle coupling 60 and with a guide bar 62 which, as can be seen from Figure 2, slides within the screening cage 16.

The lower end of the shaft 54 is provided with a boss 64 which is provided with a number of peripheral holes 66 equal in number to the number of cooling stations. At each of these holes 66 one can fasten a spring member 68. In the preferred embodiment of the invention, ten such springs 68 are provided around the boss 64. As will be seen from the drawings, each of the springs 68 extends upwardly and outwardly and has a curved outer end.

As is shown in Figure 2, when the striker mechanism is raised, the Peltier modules tilt backwards out of contact with the samples. As the striker mechanism is lowered into the cage 16 the individual springs 68 will first strike against the rearward upper corner of the cooling fins or heat sink 52 of the Peltier modules. As the striker mechanism continues to move downwards into the cage 16 so the spring will exert a force on the Peltier modules to pivot them outwards to make contact with the samples. In the lowermost position of the striker mechanism the curved upper end of each spring is positioned part way down the rear face of the cooling fins or heat sink 52 so as to exert a positive force against the Peltier modules and to ensure good thermal contact between the yoke 50 and the sample.

The cooling apparatus of the present invention is preferably provided with an optical detector to detect the presence of particles within the sample 28.

This can be the precipitation or sedimentation of material from the liquid, or the appearance of crystals, etc. This optical detector is shown most clearly in Figures 1,2 and 5. An infra-red solid-state source 70 is mounted in optical alignment with a phototransistor 72 which is sensitive to the infra-red radiation emitted by the source. The source and detector are positioned one on each side of the sample or samples 28 so as to detect the presence of particles within the sample 28. The source 70 and detector 72 are mounted on arms 74 carried by support brackets 76 which are attached to the cranked arm 46. As the sample or samples are cooled by the Peltier module to the condition where crystals or particles appear within the sample, so the inra-red beam from the source 70 will be scattered and there will be a loss of signal from the detector 72.This can be used to isolate the electrical supply to the Peltier module to control the cooling action which it produces. As will be seen from Figure 5, this optical detector can be used with a series of for example five straws 28 arranged side-by-side between the source 70 and the detector 72.

With the components in the positions shown in solid lines in Figure 2, where there is contact between the Peltier modules and the samples, one can then commence the cooling process, for example as described in our published UK patent application Serial No. 2096827A.

Although in the embodiment illustrated in Figures 1 to 5, the displacement of the modules is effected by the downward movement of the central striker mechanism, one could alternatively arrange for the modules to be tilted forwards by an upward movement of a central striker mechanism. Again, a semi-flexible strip or strips are used which come into contact with the backs of the Peltier modules as the striker mechanism is raised.

Again, instead of having a plurality of individual springs 68 positioned around the striker mechanism, one could have a continuous wiper element extending around the periphery of the boss 64 and effective on all the modules simultaneously. However, the advantage of using individual springs 68 is that individual ones can be removed as desired if a particular cooling station or stations are not in operation.

Reference is now made to Figures 6A and 6B which show a modified embodiment of cooling device in accordance with the invention. In this embodiment the Peltier module is not moved by a separate striker mechanism, but is movable in response to the presence or absence of the sample itself. By the insertion of a sample into the cooling device the Peltier module is automatically brought into the correct position for intimate contact with the sample at the correct point in order to facilitate the desired supplementary cooling.

The drawings show just a single Peltier module.

However, a plurality of such modules could be used, mounted in rows, lines or in a circular array within a working chamber, as illustrated in Figure 1. In Figures 6A and 6B the same or corresponding components to those shown in Figures 1 to 5 are indicated by the same reference numbers. The sample 28 is here shown as an ampoule. It is carried in a bucket 80 secured to or integral with a sample holder in the form of an elongate rod 30 having a curved lower end 82. The upper end of the sample holder is provided with a cylindrical plug 32 sized to fit into a hole 84 through the top wall 10 of a working chamber.

The Peltier module 44 is again provided with cooling fins 52 and is mounted on a cranked support arm 46. The support arm 46 is pivotally mounted by a hinged -member indicated at 86 and has a bottom surface 88 which, in the attitude shown in Figure 6B, approaches a stationary stop 90. A further stop 92 is provided against which the cranked arm 46 rests when the assembly is in the position shown in Figure 6A. A rod 94 which is secured to or is integral with the cranked arm 46 projects forwardly from the support member and is arranged to extend horizontally when the assembly is in the position shown in Figure 6B.

Below the Peltier module assembly there is mounted a stationary receptor 96 which has an upwardly directed hole or slot arranged to receive the sample holder 30 as it is lowered into the working chamber. The receptor 96 is positioned in relation to the sample holder 30 so that as the curved lower end 82 of the sample holder strikes the edge of the hole or slot in the receptor 96 the sample holder 30 will be "steered" so that the bucket 80 on the sample holder moves laterally towards the Peltier module assembly as the holder is lowered into the working chamber. A backing support 98 in the form of a rod is provided on the sample holder 30 at a position where it lies behind the ampoule 28.

In use, when the ampoule holder 30 is not present, or is in its raised position as shown in Figure 6A, then the Peltier module tilts backwards about the pivot 86, into contact with the stop 92, because of the cantilever effect. When the sample holder 30, with an ampoule 28 having its base seated in the bucket 80, is lowered down through the hole 84 in the top of the working chamber, the curved lower portion 82 of the ampoule holder first strikes against the edge of the slot in the receptor 96, and the sample holder is thereafter displaced so that the base of the bucket 80 strikes against the projecting rod 94 and tilts the Peltier module assembly into an upright position, as shown in Figure 6B.In this position the yoke 50 presses against the ampoule 28 at the desired position towards the upper end of the ampoule, and exerts a pressure against the ampoule against the restraining effect of the support rod 98.

In a modified form of the apparatus shown in Figures 6A and 6B, instead of using an ampoule holder 30 having a curved lower end, one could use a straight rod and provide a stationary inclined surface instead of the receptor 96, whereby the lower end of the rod, in striking against the sloping surface and sliding down it, will again be displaced towards the Peltier module in order that the bucket 80 will strike against the projecting rod 94.

It will be appreciated that the cooling apparatus of the present invention is particularly attractive when one is considering semi-automation of the cooling of large numbers of samples. The ampoules or straws or other containers can be loaded into the sample holders outside the working chamber and the Peltier modules can then be brought accurately and reliably into contact with the appropriate part of the samples without manual adjustment.

A further advantage of the cooling apparatus of the present invention is that the sample, whether it be an ampoule, a straw or whatever, is reliably held in the correct position so that the right part of the sample is presented for contact by the Peltier module. In the preferred embodiment shown in Figures 1 to 5, the particular portion of the sample which is to be contacted by the Peltier module can be chosen as desired simply by moving the sample retainer 40 up or down on the rod 30.

Although in the embodiments described above a direct mechanical engagement is used to initiate movement of the Peltier modules, one could alternatively use an electro-mechanical system where the insertion of the sample into the working chamber actuates a switch which triggers a motor to drive the Peltier module from its out-of-contact position to its operational position.

It is emphasised that in its broadest aspect the present invention is concerned with affecting or modifying the rate of cooling of a specimen or sample. The method and apparatus of the present invention are therefore appropriate also for the absorption of the heat of an exothermic reaction occurring during a cooling process, even if no crystallisation, precipitation or sedimentation occurs at that point in the cooling process.

Although in the embodiments described above the Peltier modules are mounted for pivotal movement, it should be understood that the present invention is not to be regarded as limited to that particular arrangement. Other ways of achieving relative movement between the cooling modules and the samples are within the scope of the invention. For example, one could have a fixed cooling assembly with a movable sample, or alternatively have both the cooling assembly and the sample separately movable between contact and out-of-contact positions.

Claims (18)

1. Cooling apparatus for modifying the cooling rate of a sample which is at least partially of liquid form, comprising cooling means arranged to be connected to an electric power source and to function in accordance with the Peltier effect to provide a surface at which heat is absorbed thereby to cool said surface, and a sample holder arranged to carry a sample, wherein the cooling means and the sample holder are relatively movable to bring said surface into thermal contact with the sample.

2. Cooling apparatus according to claim 1, which includes displacement means to displace said cool ing means between a first position in which said surface is in thermal contact with the sample and a second position in which said surface is remote from the sample.

3. Cooling apparatus according to claim 2, in which a movement of the sample into a position for cooling initiates the displacement of the cooling means from its said second position to its said first position.

4. Cooling apparatus according to claim 3, in which the initiation of the displacement of the cooling means towards its said first position is effected by the sample holder striking against a portion of the cooling means.

5. Cooling apparatus according to claim 2, in which said displacement means comprises a movable striker mechanism, movement of which initiates the displacement of the cooling means from its said second position to its said first position.

6. Cooling apparatus according to claim 5, in which the striker mechanism comprises a resilient contact member which makes and breaks contact with the cooling means and which exerts a biasing force against the cooling means in its said first position urging the cooling means towards the sample.

7. Cooling apparatus according to any of claims 2 to 6, in which the cooling means is pivotable about pivot means for displacement between its said first and second positions.

8. Cooling apparatus according to any preceding claim, wherein the cooling means comprises a Peltier effect module mounted on a cantilevered support whereby the module automatically moves out of contact with the sample when no external force is exerted on the module.

9. Cooling apparatus according to any preceding claim, in which the cooling means comprises a Peltier effect module and a heat-conductive element in contact with the module and defining said surface.

10. Cooling apparatus according to any preceding claim, in which the sample holder comprises an elongate rod with sample carrier means adjustably movable along the rod to permit adjustment of the sample relative to the sample holder.

11. Cooling apparatus according to any of claims 1 to 9, in which the sample holder comprises an elongate rod with carrier means to support and locate the sample, said carrier means being engageable with a projecting portion of said cooling means to initiate displacement of the latter.

12. Cooling apparatus according to claim 11, in which the elongate rod has a curved portion which is slidingly engageable with stationary abutment means to steer the sample holder into a path in which it strikes the cooling means to initiate displacement of the latter.

13. Cooling apparatus according to any preceding claim, which includes optical detector means adjacent to the sample to detect the presence or absence of particles in the sample.

14. Cooling apparatus according to claim 13, in which the optical detector means comprises a source of infra-red radiation and a photo-transistor responsive to said radiation.

15. Cooling apparatus according to claim 13 or 14, in which the optical detector means is arranged to trigger disconnection of the electrical supply to the cooling means upon detection of the presence of particles in the sample.

16. Cooling apparatus to any preceding claim, which comprises a plurality of cooling stations arranged in a circular array and each comprising individual cooling means and sample holder, with a displaceable striker mechanism arranged by its movement to initiate joint movement of all said cooling means and/or sample holders.

17. Cooling apparatus according to claim 16, wherein the stricker mechanism is positioned centrally within the cooling stations and is movable vertically.

18. Cooling apparatus substantially as hereinbefore described with reference to Figures 1 to 5 or Figures 6A and 6B of the accompanying drawings.