Low-temperature storage device with cassette handler

The storage device is adapted to store a plurality of objects, such as sample tube holders, at low temperatures, e.g. at −80° C. It comprises a storage chamber with a plurality of storage cassettes arranged in its bottom section. A cassette lift in its top section can be used to lift individual storage cassettes up and to move them to an access opening, where the contents of the storage cassette can be accessed.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the priority of Swiss patent application 1429/14, filed Sep. 22, 2014, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to a low-temperature storage device for storing a plurality of objects at a temperature of less than 0° C., in particular below −20° C., typically at approximately −80° C.

BACKGROUND ART

Storage devices of this type are e.g. used to store a large number of biological samples at low temperatures. Such samples are e.g. stored in tubes, which in turn are arranged in tube holders. Such tube holders can e.g. be held in storage cassettes.

A device of this type is described in US 2003/0233842. It comprises a storage chamber having a bottom section and a top section. The bottom section forms a cassette store having a plurality of cassette locations. Each such location holds one storage cassette.

A cassette handler with a cassette lift is located in the top section of the storage chamber. The cassette lift is adapted to lift individual cassettes from their cassette location to an elevated position, where a spatula removes or inserts one object (e.g. tube holder) from/into the storage cassette. After this operation, the cassette is lowered back into its cassette location.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a low-temperature storage device of the type above that that allows to efficiently handle the objects in the storage cassettes.

Accordingly, the device comprises:A storage chamber having a bottom section and a top section. This is the chamber where the objects are stored.A refrigerator device adapted and structured to cool said storage chamber to a storage temperature below 0° C., in particular below −20° C. This device is used to cool the objects to their storage temperature.Vertical, insulating walls enclosing said storage chamber. The storage chamber is insulated, and this insulation comprises said vertical walls.A transfer location arranged outside said storage chamber. This is the location that at least temporarily holds the objects that are to be moved into the storage chamber or that have been removed from the storage chamber.An access opening arranged in at least one of said insulating walls between said storage chamber and said transfer location. The objects pass this access opening on their way between the storage chamber and the transfer location.A cassette store arranged in said bottom section of said storage chamber and forming a plurality of cassette locations. This is the location where the storage cassettes are stored.A plurality of storage cassettes arranged beside each other in said cassette locations. Each storage cassette comprises a plurality of storage locations arranged vertically above each other, and each such storage location is structured and adapted to receive at least one of said objects. In other words, the objects are stored in locations above each other in said cassettes, such that a plurality of objects can be handled simultaneously in a single cassette.A cassette handler located in said storage chamber comprising

a) a cassette lift to move an individual storage cassette between its cassette location and said top section and

b) a cassette holder adapted and structured to hold a cassette raised by the cassette lift in a raised position in said top section,

c) a transport mechanism to horizontally displace said cassette holder with a raised cassette, between a position where said raised cassette is vertically above its cassette location to an access position where said raised cassette is adjacent to said access opening.

The cassette handler is therefore able to lift individual storage cassettes from their cassette locations and to lower them back to the cassette locations. Raised cassettes can be held in the upper section by means of the cassette holder, which can form part of the cassette lift or be a device separate from the cassette lift. Further, the transport mechanism allows to horizontally move a cassette held by the cassette holder from a position above its cassette location to a position where the cassette is located adjacent to the opening in the vertical insulating wall. And the transport mechanism can also move the cassette back from the position adjacent to said opening to the position above its cassette location, from where it can be lowered back into the cassette location.

When a cassette is at the position adjacent to the opening in the insulating wall, the objects therein can be accessed quickly and efficiently, and this at a higher temperature than the storage temperature.

Advantageously, the cassette handler further comprises a cassette housing horizontally enclosing a cassette space for receiving at least part of a cassette raised by said lift. This cassette housing comprises an open section at one vertical side of the cassette space. The open section faces the access opening in the access position of the cassette holder. Hence, in the access position, the cassette space is shielded towards the storage chamber by the cassette housing, while the cassette is accessible through the access opening and the open section.

In another advantageous embodiment, the storage device comprises a plurality of signal lights arranged vertically along the access opening. These lights can be used for highlighting the vertical location to be accessed in a cassette held by the lift when said cassette holder is in said access position.

Other advantageous embodiments are listed in the dependent claims as well as in the description below.

MODES FOR CARRYING OUT THE INVENTION

Definitions

A “low-temperature storage device” is a storage device adapted to store objects at temperatures below 0° C., in particular below −20° C., advantageously between −90° C. and −60° C.

A “plate spring” is a spring having a sheet-like, elastic body that is designed to be bent to varying curvatures against an elastic force. In most embodiments, the elastic body is, in a relaxed position, arranged in a plane, i.e. flat.

An embodiment of a storage device is shown inFIGS. 1-3. It comprises a storage chamber1enclosed by vertical insulating side walls2a, an insulating ceiling2band an insulating floor2c.

A transfer chamber3(FIG. 1) is located adjacent to storage chamber1and shares at least one of the insulating side walls2awith storage chamber1. In the embodiment ofFIG. 1, transfer chamber3is divided into two sub-chambers3a,3bwith a separating wall4having a lock door5arranged between them, but transfer chamber3can also be a single chamber.

A door6provides user access to transfer chamber3. In the embodiment ofFIG. 1, stairs7lead up to door6because transfer chamber3is above the level of bottom wall2cof the device. For the same reason, transfer chamber3is supported by struts8at its bottom side.

A refrigerator device10is provided to cool storage chamber1to a storage temperature below 0° C., in particular below −20° C. Typically, the storage temperature is in the range of −90° C. to −60° C. Refrigerator device10also cools transfer chamber3to a transfer temperature below 0° C., in particular at approximately −20° C.

The storage chamber1shown here is of cuboid shape. As best seen inFIG. 2, it is divided into a bottom section11and a top section12. For reasons that will become apparent, top section12comprises typically 50-70% of the volume of storage chamber1, and bottom section11the rest.

Bottom section11holds a cassette store14formed by a gridding15located at the top of bottom section11. Gridding15forms an array of rectangular apertures16. Each rectangular aperture16forms a cassette location for receiving a storage cassette. One such storage cassette17is shown in dotted lines inFIG. 2.

The gridding of cassette store14is mounted at a fixed height, e.g. by means of a central arrangement of struts18as well as by suitable lateral supports along its periphery (not shown).

An example of a storage cassette17is shown inFIG. 7. It comprises two vertical sidewalls20, with ledges21formed thereon. The ledges form storage locations22for receiving the objects to be stored. At its top end, the storage cassette17comprises an insulating head section23. The head sections of all storage cassettes17inserted into cassette store14form an insulating wall between bottom section11and top section12of storage chamber1, thereby helping to maintain a more constant temperature in bottom section11where most of the objects are stored.

A metal plate24or a coupling24′ (shown in dotted lines) is located at the top of each storage cassette17, whose purpose will be described below.

The individual cassette locations or apertures16in cassette store14have a size fitting the footprint of the storage cassettes17to be received. As best seen inFIG. 3, the embodiment of the device shown inFIGS. 1-3has a cassette store14adapted to receive storage cassettes17of rectangular footprint, e.g. of 134×86 mm, such that the storage cassettes can be dimensioned to receive objects having the standardized SBS dimensions of 127.75×85.48 mm.

In another advantageous embodiment, cassette store14is designed to receive at least two types of storage cassettes having different footprints.FIG. 6shows an example for such a cassette store14as seen from above, albeit a store for being mounted in a larger storage chamber than the one shown inFIGS. 2 and 3. This cassette store forms a plurality of first cassette locations16aand of second cassette locations16b, wherein the two types of cassette locations have different footprint. For example, the first type of cassette locations16ahas a rectangular footprint in the SBS format of 134×86 mm, while the second type of cassette locations16bhas a “cryobox” square footprint of 137×137 mm.

As mentioned, and as best seen inFIG. 2, a cassette handler25is located in top section12of storage chamber1. It comprises a cassette lift26adapted to move an individual storage cassette17between its cassette location16in cassette store15and top section12. Further, cassette handler25comprises a cassette holder, which is advantageously formed by cassette lift26, for holding a raised cassette in top section12of storage chamber1.

Cassette lift26, or at least the cassette holder, is arranged on a transport mechanism27a,27b, which is adapted to horizontally displace the cassette holder with a raised cassette, between a position where the raised cassette is vertically above its cassette location16to an access position where the raised cassette is adjacent to an access opening30(seeFIGS. 3 and 4) of storage chamber1.

In order to provide enough room for an upright storage cassette17as well as the overhead required by cassette handler25, top section12of storage chamber1is advantageously somewhat higher than bottom section11.

Transport mechanism27a,27bcomprises a horizontal beam27aspanning storage chamber1and being held at opposite ends by rails27b. Beam27ais located at the top of upper section12. Cassette lift26is suspended from beam27a. A displacement drive31is provided for horizontally displacing beam27aalong the rails27b, and also for horizontally displacing cassette lift26along beam27a.

Cassette lift26is shown in more detail inFIG. 5. It comprises the already mentioned cassette holder33, which is, in the embodiment ofFIG. 5, a magnetic cassette holder adapted to hold a storage cassette by its metal plate24(cf.FIG. 7).

An advantageous embodiment of a magnetic cassette holder33is shown inFIG. 8. It comprises a permanent magnet34in combination with an electromagnet35, with electromagnet35oriented to cancel, or at least reduce, the magnetic field of permanent magnet34. In this manner, cassette holder33will firmly hold a storage cassette in the absence of a current through electromagnet35, while a current is required to release the cassette. This design prevents an accidental release of the cassette in a power failure.

Turning back toFIG. 5, cassette lift26comprises a lift drive adapted to move cassette holder33along a vertical guide rail34. This lift drive comprises a chain36attached at a first end to cassette holder33. It extends upwards from cassette holder33to a first guide wheel37located at the top of cassette lift26. At first guide wheel37, chain36is redirected into a slight downward direction to a second guide wheel38, and from there it is redirected into a slight upward direction to a sprocket39driven by a lift motor40. At sprocket39, chain36is redirected into a substantially vertical downward direction to a fourth guide wheel41and from there backwards up to be moored at its second end in the top of cassette lift26.

A damped chain tightener is adapted to elastically pull second guide wheel38down and thereby to elastically urge it against chain36.

A spring member43is adapted to pull third guide wheel41downwards, thereby keeping the section of chain36between sprocket39and its second end taught.

In operation, lift motor40drives sprocket39, which in turn causes cassette holder33to be lifted or lowered. If a cassette lifted by cassette holder33gets temporarily stuck, e.g. on an ice formation, chain tightener42yields, thereby avoiding the generation of excessive forces in chain36.

As shown inFIGS. 5 and 13, lift26comprises a cassette housing50, which is located at a fixed vertical position and encloses a cassette space51which is intended to receive at least part, typically all, of a raised storage cassette. Cassette housing50comprises an open section52at one of its vertical sides. This open section52faces access opening30when cassette lift26and cassette holder33are in their access position. This will be described in more detail below.

At the bottom of cassette lift26, a bottom wall54eis provided (FIG. 5), which closes the bottom of cassette space51, except for a lift opening55, whose size matches the footprint of the storage cassette to be handled by cassette lift26. When the cassette is in its raised position, i.e. in cassette space51, lift opening55is blocked by the cassette, thereby reducing an exchange of air at that location.

As can further be seen fromFIG. 5, cassette lift26comprises a guiding device57for laterally guiding a storage cassette while it is being raised or lowered by cassette lift26. Guiding device57is arranged at the bottom end of cassette lift26, advantageously around lift opening57.

In the embodiment ofFIG. 5, guiding device57comprises a first pair of rollers58a,58bas well as a second pair of rollers59a,59b. Each pair of rollers comprises two rollers that can be rotated around respective horizontal roller axes. The roller axes of each pair extend parallel to each other and are spaced apart, by a distance exceeding a horizontal dimension of the cassette, so that the two rollers can run along opposite vertical sides of the cassette. The axes of the first pair of rollers58a,58bare perpendicular to the axes of the second pair of rollers (59a,59b) such that the rollers can engage the cassettes from all four sides.

Each roller is held by at least one spring member60, which is structured to elastically yield in horizontal direction, thereby keeping the rollers in contact with the surfaces of the cassette. In the embodiment ofFIG. 5, each spring member is formed by a plate spring (flat spring) mounted to bottom wall54e.

In the embodiment ofFIG. 5, two pairs of such rollers are provided. If the cassette requires guidance primarily along one direction only, a single pair of rollers can be used.

Guiding device57is located at a fixed vertical position within storage chamber1.

Alternative Cassette Holder:

In the embodiment ofFIG. 8, a magnetic cassette holder33has been shown.FIGS. 9-12show a mechanical embodiment of such a holder. This holder is suspended, alternatively to the magnetic holder, on the same trolley60(FIG. 5) of cassette lift26. For this purpose, a cover plate61(only shown inFIG. 10) is provided with a suitable adaptor stub62at its top side.

The cassette holder of this second embodiment comprises a rigid frame63. It further comprises two engaging mechanisms64a,64bthat are of identical design and arranged symmetrically around a center of the holder.

Each engaging mechanism64a,65bcomprises a first pair of parallel plate springs65a,65barranged at a distance from each other, with the sheet-like bodies of the springs aligned vertically (i.e. parallel to the longitudinal axis of the storage cassette17to be picked up). The first ends of the plate springs65a,65bare mounted to frame63, while the second ends are mounted to a link body66. Due to its suspension by the plate springs65a,65b, link body66can substantially move along one horizontal line only.

The first ends of a second pair of parallel plate springs67a,67bare mounted to link body66. The sheet-like bodies of the second pair of plate springs67a,67bare aligned horizontally. The second ends of these springs are attached to a gripper body68. Hence, gripper body68is displaceable along one vertical line in respect to link body66, and along a vertical plane in respect to frame63.

A magnetic actuator70is arranged in frame63. It comprises a pusher71, which is in a retracted position when no current is applied to actuator70(as shown inFIG. 12), and in an extended position (FIG. 11) when a current is applied. Upon applying a current, pusher71pushes link body62against the force of the first pair of plate springs65a,65bfrom the position ofFIG. 12into the position ofFIG. 11, thereby moving gripper body68along arrow A ofFIG. 11.

By operating both actuators70of the engaging mechanisms64a,64bat the same time, both gripper bodies68are moved from their positions inFIG. 12to their positions inFIG. 11.

As best seen inFIG. 10, frame63comprises an opening75at its bottom side, which has a diameter sufficient to receive coupling24′ of a storage cassette17(cf.FIG. 7, where coupling24′ is shown in dotted lines). Coupling24′ projects over the top side of storage cassette17and comprises a neck76and a head77at the top of neck76, with head77projecting laterally beyond head76.

When coupling24′ is inserted in opening75, the gripper bodies68can engage the coupling24′ below head77from both sides when they are in their closed position77as shown inFIG. 12, while they release head77when moved to their opened position as shown inFIG. 11.

When the gripper bodies68have engaged head77of coupling24′ and the cassette is lifted by vertically moving the whole cassette holder, the weight of the cassette will pull the gripper bodies68downwards (against the resilient forces of the second pairs of plate springs67a), until the gripper bodies68come to rest against a bottom support63aof frame63, such that the weight can be transferred directly to frame63and does not have to be carried by the mechanically more sensitive parts of the engaging mechanisms64a,64b.

As in the first embodiment, the second embodiment of the cassette holder33is designed such that it safely engages the storage cassette in the absence of electrical power, and electrical power is required for releasing the storage cassette, which again avoid accidents in case of a power failure.

Hence, in more general terms, the cassette holder33of this second embodiment comprises:A frame63forming a support63a;At least two gripper bodies68arranged above the support63aand mounted to be resiliently displaced, advantageously by at least 2 mm, in vertical direction in respect to the frame63; andAt least one engaging mechanism64a,64badapted and structured for displacing the gripper bodies68against the coupling24′ of one of the storage cassettes inserted into the frame63, thereby engaging this coupling (24′).

The cassette holder33is adapted and structured such that the weight of the storage cassette17, whose coupling24′ is engaged by the gripper bodies68, pulls the gripper bodies68down to rest against the support63a.

As mentioned, and as can be seen inFIGS. 3 and 4, an access opening30is arranged in one of the vertical insulating walls2aof storage chamber1. Access opening30is located between storage chamber1and a transfer location90outside storage chamber1.

FIG. 13shows the situation when cassette handler25brings cassette holder33holding a storage cassette17to its access position. In this position, storage cassette17if adjacent to access opening30, such that the storage locations22in storage cassette17can be accessed through access opening30.

As can be seen, cassette housing50with its walls54a,54b,54cis, in this position, located such that its open section52faces access opening30, and housing50comes into contact with a frame91of access opening30. Thereby, a sealed connection is formed between access opening30and cassette space51. In this context, the term “sealed connection” does not necessarily imply that the connection is truly gas tight. However, the gap between cassette housing50and docking section91should be no more than 20 mm, in particular no more than 1 mm.

The height of access opening30advantageously corresponds to at least the combined height of all storage locations22of one storage cassette17. Further, in the access position, all storage locations22of storage cassette17held by cassette holder33are accessible through access opening30. In this way, every object in the storage cassette can be accessed easily and quickly.

The width of access opening30should be larger, but advantageously not more than 20% larger, than the width of the storage locations22and/or than the width of the objects stored therein.

In the embodiment ofFIG. 13, frame91of access opening30is formed by a bay92extending from insulating wall2ainto storage chamber1.

As can be seen fromFIG. 4, a vertical line of signal lights93is located along an edge of access opening30. As mentioned, these signal lights93can be used for highlighting the vertical location to be accessed in a storage cassette17held in the lift when cassette holder33is in said access position. They can e.g. be controlled by a control unit that keeps track of the objects stored within storage chamber1.

In the embodiment ofFIG. 4, a light barrier99comprising a laser light source100and a light receiver101extends vertically over access opening30. It is used for detecting objects that are not completely inserted into their respective object location22in storage cassettes17and issue a warning if this is the case.

Also as best seen fromFIG. 4, an access door94can be provided for closing access opening30when it is not in use. By closing this door, an air exchange (and in particular the entry of unwanted humidity into storage chamber1) can be prevented, which is of particular advantage when cassette lift26moves away from access opening30.

Even though transfer location90can be located completely outside the storage device, it is advantageously positioned in a transfer chamber3(seeFIG. 1). In order to further reduce heat transfer and the entry of humidity into storage chamber1, transfer chamber3can be cooled by means of refrigerator device10. The temperature within transfer chamber3is advantageously below 0° C. but above the storage temperature in storage chamber1. Typically, the temperature in transfer chamber3is around −20° C.

As shown inFIG. 1and as already disclosed, transfer chamber3can be divided into two sub-chambers3a,3bwith a separating wall4having a lock door5arranged between them. This allows to form an airlock that further improves the insulation of storage chamber1.

As also can be seen fromFIG. 1, various equipment for working on the samples or objects stored in storage chamber1can be located in transfer chamber3. Placing such equipment there allows to operate it at only moderately low temperatures, thereby improving equipment reliability and user accessibility.

As one particularly advantageous example, such equipment can comprise an item picker96, which can be used when the stored objects are containers containing individual items, such as tube holders holding sample tubes. Item picker96is adapted and structured to remove and/or insert individual items from/into the objects, e.g. for sorting, assembling, individually removing or individually adding them. Such an item picker, which is of a generally known design, typically comprises an item picker location97for receiving at least one of the objects to be stored in the storage cassettes, as well as a picker device98with a gripper or similar structure that can handle the items in the object. In particular, picker device98can be structured and adapted for removing an individual item from a plurality of items in an object at picker location97and/or for adding an individual item to a plurality of items in the object at said picker location97.

As can be seen fromFIG. 2, storage chamber1forms advantageously a single, horizontally undivided space, which makes it easy to cool it by means of cooling aggregates arranged e.g. along the insulating walls. However, storage chamber1may also have vertical dividing walls arranged therein.

For handling different types of storage cassettes17, in particular types that have different footprint as mentioned above in reference toFIG. 6, at least two separate cassette lifts26can be used, each one tailored to one type of storage cassettes. Alternatively, a single cassette lift can be used if guiding device57is adjustable in size.