Patent Description:
Cassettes for storage, organization and presentation of medical instruments represent well-known systems in the art. Most of these cassettes comprise at least one tray with holding means in which the medical instruments are accommodated and a cover to close the tray.

Such a cassette is disclosed for instance in <CIT>. The surgical tool container described therein comprises an outer case having a separable lid and base portion and a tool-holding tray removably inserted within the base portion. Elastomeric grommets and resilient finger brackets are secured on the tool-holding tray for accommodating shanks of the surgical tools, such that the latter are removably held by these elastic elements due to frictional engagement therewith.

A further cassette including an instrument tray and a cover for storage, transport and sterilization of medical instruments is disclosed in <CIT>. Interchangeably disposed along the surface of the tray and cover are a plurality of support members, whereby each support member includes variously dimensioned, notched receptacles for receiving a respective medical instrument. The support members are made of resilient material which is capable of replaceably accommodating medical instruments.

Further examples of cassettes for storage of medical instruments are described, e.g. in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

<CIT> discloses a fastener cartridge that can be formed from a single piece of sheet metal and allows for retaining a fastener within a housing of the fastener cartridge. The fastener cartridge further includes a retaining member and the fastener includes a head that is supported on a seat. The retaining member engages the fastener head, thereby securing the latter between the seat and the retaining member.

<CIT> discloses a device for releasably holding a medical instrument in an instrument mounting station. The mounting station includes a holding portion for releasably holding the proximal end of a surgical or medical instrument while allowing access to the proximal end for grasping and removal of the instrument from the device by a user. The device has a recessed area for receiving the distal end of the instrument to facilitate preventing of inadvertent contact of the distal end by the user while the instrument is held by the device.

<CIT> discloses a packaging for a dental implant having a rigid enclosure and an implant holder situated therein. The implant holder has a recess, e.g. a slit, which tapers inwardly for accommodating the implant. The enclosure is able to stand on two different planes and has a receptacle for the implant holder as well as an opening for access to the implant holder and/or an implant held therein.

<CIT> discloses a support having a receiving recess for receiving a portion of an instrument. The recess has a tongue-shaped tab forming a lateral slot and a housing with a support zone situated opposite to the tab. The tab is movable between a withdrawal position permitting introduction of the portion of the instrument in the housing and a wedging position permitting maintenance of the portion in the housing.

<CIT> discloses a cassette for housing one or more medical instruments, the cassette including a tray having at least one passage. The tray has a rigid structure and a resilient holding means for retaining the medical instrument within the passage. Thereby, an uppermost section of the passage is formed by the rigid structure and at least a portion of a lower section of the passage is formed by the resilient holding means.

In the cassettes of the prior art, the holding means usually comprise elastomeric material and are usually fixed on the tray, e.g. by form fit, molding, welding or gluing. Although such elastomeric materials provide a good hold on the medical instruments, these materials can also have severe disadvantages.

One problem is that these materials are sensitive and prone to environmental pollution. For instance, they can easily get contaminated with blood or soft tissue when the instruments are grabbed by the surgeon with contaminated surgical gloves.

Rising hygiene standards require the instruments to be cleaned and sterilized within the cassette. Thus, the instruments and the cassette should not be cleaned separately any more but in the assembled state by Automated Cleaning and Disinfection (ACD) machines. However, problems arise if elastomeric components are included in the cassettes. Firstly, the method of connection between the elastomeric holding means and cassette often results in undercuts and other small spaces in which dirt can collect and which are difficult to clean. Additionally the cleaning agents used in the ACD machines can affect the properties of the elastomeric material, e.g. by removing the softener. This affects the ability of the holding means to reliably grip the instrument and increases the adhesion of dirt particles to the holding means. Further, when a cassette comprises two or more different types of material these will have different heating and cooling rates, as well as different rates of thermal expansion. This can lead to stresses within the cassette as well as condensation problems. As the cassette should be completely free of water prior to sterilisation, condensation formation on the holding means can be problematic.

Therefore, the problem to be solved by the present invention is to provide a cassette for one or a plurality of medical instruments which allows safe holding, storing, cleaning and sterilization of the medical instrument(s) within and which can be cleaned in an ACD machine without damage to the cassette.

According to one aspect therefore the present invention provides a cassette for storage of medical instruments, the cassette comprising at least one spring sheet, the spring sheet comprising at least one holding means for retaining a medical instrument therein, the holding means comprising an aperture forming a passage through the spring sheet for receiving the medical instrument and at least one spring element provided adjacent to the passage for exerting a biasing spring force to retain the medical instrument within the passage, wherein the spring sheet further includes, in addition and separately to the at least one holding means, at least one secondary holding means, the at least one secondary holding means comprising a through-hole and a cylindrical extension piece, said extension piece having a through-bore comprising an undercut, which undercut allows formation of a snap-fit connection to a complementary protrusion provided on the surface of a further medical instrument, the extension piece being welded or otherwise connected to the spring sheet such that it forms an extension of the spring sheet, and wherein the spring sheet, including the at least one holding means and the at least one secondary holding means, is made of a metal or a metal alloy.

The term "sheet" as used in the context of the present invention relates to a, preferably planar, structure whose thickness is smaller than its length and width and by the term "a passage" therethrough it is meant that the passage extends through the thickness of the spring sheet.

Thus, the present invention provides a holding means which can be formed entirely of metal or metal alloy and hence prevents the problems associated with the use of elastomeric grommets. This is achieved by removably holding the at least one medical instrument, such as a drill, insertion tool, wrench, punch, tap etc., within a passage in the spring sheet by means of at least one spring element positioned adjacent to the passage and configured to releasably retain the medical instrument therein. The retentive force is thus provided by a metal or metal alloy component and not an elastomeric material.

In order to retain the medical instrument within the holding means, the cross-section of the passage is restricted by the at least one adjacent spring element to an extent that the medical instrument can only be inserted into the holding means under deformation of the spring element(s). Thus, in general, the cross-section or diameter of the passage, which is in part defined by the adjacent spring element(s), is at least slightly smaller than the diameter of the medical instrument when the at least one spring element is in its resting position. It goes without saying that by the "instrument diameter" and "instrument cross-section" it is hereby referred to the cross-section and the diameter of that part of the instrument which is to be accommodated within the holding means.

When inserting the medical instrument into the holding means, the outer surface of the medical instrument comes into contact with the at least one spring element, whereupon the spring element is compressed and/or deflected in a direction in the plane of the spring sheet. This compression and/or deflection of the spring element (and the fact that the spring element aims to return to its resting position) results in the generation of a biasing spring force, by means of which the medical instrument is retained within the passage. Thus, the provision of the at least one spring element enables a releasable retention of the medical instrument within the holding means of the spring sheet by creating a friction fit connection. The retentive force of the friction connection is preferably limited to a degree which allows a relatively easy retrieval of the medical instrument from the holding means, e.g. by simply pulling the medical instrument along its longitudinal axis out of the holding means. Nevertheless, the retentive force allows the holding means to safely hold the medical instrument within the spring sheet during the course of various events such as cleaning, sterilisation, packing, transportation and storage, such that accidental dislocation of the medical instrument is prevented.

The cassette of the present invention therefore enables organization, protection and thorough cleaning and sterilization of at least one medical instrument stored within the cassette. The spring sheet allows for holding the medical instrument in a secure manner, yet also permits the instrument to be readily removed from the cassette for use.

The cross-section of the passage, in the plane of the spring sheet, can be any shape suitable for housing a particular medical instrument, e.g. circular, oval, polygonal etc..

Preferably the cross-section of the passage comprises two or more areas of contact surface for contacting the medical instrument, one of said contact surfaces being formed by a surface of the at least one spring element and said contact surfaces being spaced apart from one another about the circumference of the passage. This results in areas of non-contact being formed around the cross-section of the passage. These areas create channels that allow a flow of cleaning fluid through the passage even when a medical instrument is held therein. The areas of contact between the holding means and medical instrument should be kept to a minimum while at the same time ensuring adequate support to the instrument. Preferably the cross-section of the passage is provided with three areas of contact surface interposed by recesses. In one embodiment the areas of contact surface are concave arcs for contacting a circular cylindrical shaft of a medical instrument, and the recesses are formed by indents located between these arcs. In an alternative embodiment the areas of contact can be provided by convex nubs that protrude into the passage.

The diameter of the passage through the spring sheet can remain constant, decrease or increase at various stages along its length. This means that it is also possible for the diameter of the passage to undergo a step change. Preferably however the diameter and cross-section of the passage remains constant along its length.

The at least one spring element of the holding means can be a separate component which is inserted, clamped, welded or otherwise attached to the spring sheet. For example, the spring element may be inserted in to a groove or cavity within or beside the aperture and held in place by a positive (form) or non-positive (friction) fit.

Preferably however, the at least one spring element is integrally formed in one piece with the spring sheet. In this way, there is no join between the spring element and the spring sheet into which bacteria, fluids, dirt etc. could enter, which allows a better cleaning. In addition, the provision of an integrally formed spring element in the spring sheet facilitates the production of the latter and greatly increases the stability of the spring element itself. As a result, the production costs of the spring sheet can be lowered and the overall lifetime increased.

In such embodiments the at least one spring element and the spring sheet form a monolithic structure. A spring element that is integrally formed in one piece with the spring sheet can be prepared for instance by cutting the spring sheet, preferably by means of a water stream or laser cutting procedure, or by injection moulding or machining. When the at least one spring element is integrally formed with the spring sheet in most instances the spring element will extend the length of the passage, or in other words the thickness of the spring sheet, and hence will supply a biasing force to the instrument along the length of the passage.

The at least one spring element can have any shape which enables it to be deflected and/or compressed in the plane of the spring sheet such that it exerts a biasing force into the adjacent passage. In some embodiments the spring element may also in addition be compressed and/or deflected in a direction perpendicular to the plane of the spring sheet.

In a preferred embodiment the at least one spring element comprises a tongue having an attachment end connected to the spring sheet, preferably integrally formed therewith in one piece, and a free end arranged at the opposing end of the tongue, the tongue having a contact surface, preferably in the area of the free end, which is designed to abut against the medical instrument for retaining the latter within the passage.

The contact surface of the tongue may be centred about the central longitudinal axis of the tongue. In such embodiments the tongue will usually extend non-linearly along said axis, e.g. the tongue may have a "zig-zag" or "kinked" shape. However, the location of the contact surface of the tongue is preferably such that its normal axis, i.e. the axis running perpendicular to the plane of the contact surface, is oriented at an angle to the longitudinal axis of the tongue, preferably at an angle of <NUM>° to <NUM>°, more preferably at an angle of approximately <NUM>°. When the medical instrument is inserted into the passage and brought into contact with the contact surface, this angle enables the spring element to be deflected in the plane of the spring sheet relative to the attachment end, thus creating the biasing force.

When the medical instrument is inserted into the passage, the contact surface of the tongue engages with the outer surface of the instrument and the tongue is thereby deflected from its resting position laterally in the plane of the spring sheet, such that the diameter of the passage is widened to allow insertion of the instrument. The biasing force applied by the contact surface to the instrument as the spring element attempts to return to its resting position retains the instrument within the holding means.

The spring characteristics, in particular the bending properties of the tongue can be adjusted by altering the length, width and/or the thickness of the tongue. In addition, the tongue can be provided with one or more slots which allow for an increased bending capacity of the tongue.

According to an alternative preferred embodiment, the at least one spring element is formed by a spring bridge having at either end an attachment end attached to the spring sheet, preferably integrally formed therewith in one piece, such that the spring bridge protrudes into the passage. In this way the spring bridge forms a "C" or "<IMG>" shape. In this embodiment, the contact surface is provided on the outer surface of the spring bridge. Thus, upon insertion of the medical instrument into the passage, the contact surface abuts against the outer surface of the medical instrument and the spring bridge is thereby compressed and/or deflected radially away from the longitudinal axis of the medical instrument in the direction of the plane of the spring sheet.

It is possible for the holding means of the present invention to comprise a plurality of spring elements. For example, the holding means could comprise two spring elements on opposing sides of the passage. Upon insertion of a medical tool into the passage the spring elements would be deflected and/or compressed in opposite directions and each would then supply a biasing force to the instrument which presses it towards the contact surface of the opposing spring element. In this way the medical instrument would be retained between the spring elements.

Preferably however the at least one holding means of the present invention comprises a single spring element. This simplifies the design and manufacture of the spring sheet. In such embodiments the single spring element of the holding means exerts a biasing spring force to press the medical instrument against the interior wall of the passage.

Therefore at least one area of contact surface is formed on the interior wall of the passage, preferably at least two areas circumferentially spaced from each other in order to allow fluid to pass through the passage when an instrument is retained therein. Thus, the effective diameter of the passage is limited by the contact surfaces on the interior wall of the passage and on the spring element, which can be elastically pushed back to provide sufficient space for the medical instrument to fit within the passage.

In one embodiment the aperture of the at least one holding means is open to a lateral edge of the spring sheet, thereby forming a laterally open passage for allowing insertion of the medical instrument. In this preferred embodiment it is preferable that the spring sheet is positioned vertically within the cassette. That is to say, the spring sheet extends substantially perpendicular to the horizontal plane of the cassette.

According to an alternative preferred embodiment the aperture of the at least one holding means has a closed cross-section such that the medical instrument is inserted into the aperture along an axis coaxial to the passage. In this preferred embodiment it is preferable that the spring sheet is oriented essentially parallel to the horizontal plane of the cassette such that the passage extends through the sheet from the upper to lower surface.

All references to horizontal and vertical orientations refer to the orientation of the components when the cassette is positioned on a flat surface in its correct orientation, i.e. with its lower surface facing the flat surface.

Preferably the cassette comprises a base tray and a cover part forming an outer housing, the at least one spring sheet being located within said outer housing. Preferably said base tray and cover part are made of metal or metal alloy. This prevents the aforementioned problems that can arise when the cassette comprises materials having different heating and cooling rates.

In such preferred embodiments, when the aperture of the holding means is open to a lateral edge of the spring sheet, it is preferable that one edge of the spring sheet is fixed to the base tray such that it protrudes therefrom in a direction substantially perpendicular to the base tray and thus is positioned vertically within the cassette. In this embodiment it is particularly preferred that the aperture is open to a top edge of the spring sheet, namely that edge facing away from the base tray, such that the medical instrument can be inserted laterally into the aperture, whereby the longitudinal axis of the instrument is oriented more or less perpendicular to the plane of the spring sheet and parallel to the plane of the base tray.

In this embodiment it is further preferred that the at least one holding means in the spring sheet is provided with a shape which can provide the user with physical feedback once the medical instrument is securely fastened within the holding means. Such a physical feedback can be achieved, for instance, by providing a protruding detent or nub on the interior wall of the passage, past which nub the maximum diameter of the instrument must be pushed in order to correctly seat the instrument within the passage. In this way, the medical instrument can be laterally pressed into the aperture and as the maximum diameter of the medical instrument overcomes the nub, the user is provided with a physical sensation, e.g. a jolt, snap or reduction in resistance, that informs them that the medical instrument is correctly seated and is latched into the aperture under deformation of the spring element.

In a further embodiment, when the aperture of the holding means is open to a lateral edge of the spring sheet, the cassette further comprises at least one secondary sheet, whereby the spring sheet and secondary sheet are fixed to the base tray such that they protrude therefrom in a direction substantially perpendicular to the base tray and are spaced apart by a certain distance. Preferably, the spring sheet and secondary sheet protrude vertically from the base tray and are either arranged essentially parallel or at a predefined angle to each other. The secondary sheet comprises at least one aperture open to a lateral edge of the sheet within which the medical instrument can be received. The size and shape of the aperture can be adjusted in accordance with the size and shape of the medical instrument to be received therein. The use of one or more secondary sheets ensures that the medical instrument is supported along its length and prevents the instrument from tilting along its longitudinal axis, which could result in it detaching from the holding means or interfering with other instruments housed within the cassette. The medical instrument is retained by the holding means in the spring sheet of the present invention. The at least one secondary sheet may comprise an aperture with no spring element or other retention means, such that the aperture provides only support to the instrument. In such instances the at least one secondary sheet is referred to as a support sheet. Alternatively the at least one secondary sheet can comprise additional holding means for retaining the medical instrument. In such instances the at least one secondary sheet is preferably a spring sheet according to the present invention, such that the medical instrument is retained within the holding means of two or more spring sheets.

In a further embodiment, when the aperture of the holding means is open to a lateral edge of the spring sheet, a plurality of spring sheets are fixed to the base tray such that they protrude therefrom in a direction substantially perpendicular to the base tray and are spaced apart by a certain distance. Each spring sheet comprises at least one holding means in accordance with the present invention and at least one additional aperture open to a lateral edge of the spring sheet which has no retentive function. The spring sheets are arranged such that the holding means of one spring sheet is aligned with a non-retentive aperture of a second spring sheet. In this way a plurality of spring sheets can be used to support a plurality of medical instruments, the longitudinal axes of which are oriented more or less perpendicular to the planes of the spring sheets. Each instrument is housed within a plurality of spring sheets but is only retained by the holding means of one or a limited number of these spring sheets.

As well as fixing the above discussed vertically orientated sheet(s) to the base tray it is also possible for such sheets to be fixed to other components of the cassette. For example, the one or more spring sheets and optionally one or more support sheets can be fixed to the underside of the cover part. Alternatively or additionally the cassette may comprise an additional sheet held within the cassette parallel to the base tray. The above described vertical spring sheet(s) and support sheet(s) could also be attached to such an additional sheet.

In other embodiments the spring sheet is preferably located essentially parallel to the base tray, i.e. it is horizontally orientated within the cassette. In such embodiments the aperture of the at least one holding means preferably has a closed cross-section. The horizontal spring sheet is preferably removeably attached to the cassette such that the spring sheet can be removed to allow access to the base tray.

For instance, the spring sheet is preferably provided with at least one support leg which protrudes from the bottom surface of the spring sheet at an essentially right angle and which is intended to be positioned on the base tray. Supported by the at least one support leg, the spring sheet is thereby arranged essentially parallel to but at a distance to the base tray.

This has the advantage that the base tray can be used to store additional instruments.

For providing a stable support, preferably at least three support legs are provided. In a particularly preferred embodiment, four support legs are provided, each of the support legs being attached to a respective corner of the spring sheet.

Additionally or alternatively the spring sheet can be placed directly on an upper rim of the base tray. In such embodiments the base tray comprises a planar base surface and four walls extending substantially vertically therefrom. The upper surface of these walls can provide a ledge on which the spring sheet can be supported essentially parallel to the base surface of the base tray.

In each of the above described preferred embodiments, it is further preferable that a stop surface is provided essentially parallel to and at a distance to the spring sheet for providing a physical stop to the medical instrument inserted through the holding means. This ensures correct positioning of the medical instrument within the holding means and helps to stabilise long instruments and prevent any tilting during transport and storage.

According to one embodiment the stop surface is formed by a part of the base tray. Preferably however it is formed by a separate metal or metal alloy stop sheet provided at a fixed distance with respect to the spring sheet. Therefore, the cassette preferably further comprises a metal or metal alloy stop sheet, which is provided essentially parallel to and at a distance to the spring sheet.

It is preferable that the stop sheet has the same footprint as the spring sheet, such that the stop sheet can provide a stop surface for holding means positioned at any location on the spring sheet.

The stop sheet may be a continuous surface or may also have at least one through-hole which is coaxially aligned with the passage to allow a portion of the medical instrument to be accommodated within the through-hole. Thus, if the medical instrument is provided with two adjoining portions of different cross-sections, in particular a first portion with a larger cross-section adjoined by a second portion with a smaller cross-section, an intermediate shoulder is formed on the medical instrument. This intermediate shoulder can then be used as a bearing surface that bears against the stop surface if the through-hole in the stop sheet has a larger diameter than the diameter of the second portion but a smaller diameter than the diameter of the first portion.

Additionally or alternatively a stop surface may also be provided in form of a pin or a post. A stop surface is then provided by the surface of the individual pin or post, which is aligned with and oriented essentially parallel to the cross-section of the passage. This design of stop surface has the advantage that the distance of the stop surface to the holding means can be varied, depending on the height of the pin or post. For instance, if the spring sheet comprises at least two holding means for holding at least two different medical instruments, the surface of a first pin or post can provide a first stop surface, which is aligned with the first holding means and positioned essentially parallel and at a first distance thereto, and the surface of a second pin or post can provide a second stop surface, which is aligned with the second holding means and positioned essentially parallel at a second distance thereto, wherein the first and the second distances are different from each other.

Such a stop pin or post can be attached to any suitable surface of the cassette, e.g. a base tray or cover part.

However, it is preferable that the stop pin is located on a stop sheet. In this way both the surface of the stop sheet and the stop pin form stop surfaces for different medical instruments.

The stop sheet according to the present invention therefore is preferably a planar metal or metal alloy sheet comprising at least one pin, wherein the surface of the stop sheet and the surface of the pin facing the spring sheet form stop surfaces.

The stop sheet could be a metal or metal alloy sheet attached to the base tray or cover and extending essentially perpendicular thereto. Such a stop sheet can be used in combination with spring sheets orientated vertically within the cassette.

The use of a stop surface however is most beneficial in combination with a spring sheet orientated horizontally within the cassette, as it ensures that the instrument is not inserted too far through the holding means. This could result in the instrument touching or damaging any further instruments stored under the spring sheet, e.g. on a base tray.

In a preferred embodiment the cassette further comprises an intermediate sheet, comprising at least one guide hole which is coaxially aligned with the holding means and which is positioned essentially parallel and at a distance to the spring sheet, between the spring sheet and the stop sheet. Such intermediate sheets are of most benefit when the aperture of the at least one holding means of the spring sheet has a closed cross-section. The cross-section of the guide hole is adapted to be slightly larger than the cross-section of the medical instrument to be held within the holding means such that when correctly orientated the instrument can pass through the guide hole without contacting the intermediate sheet. Thereby the guide hole in the intermediate sheet provides axial guidance to the medical instrument during its insertion into the cassette. The medical instrument will pass through the guide hole in the intermediate sheet and come to rest on a stop surface of the stop sheet, e.g. the upper surface of the stop sheet or a pin or post fixed to this surface. By being held within the passage in the spring sheet and within the guide hole in the intermediate sheet, the medical instrument is securely held within the cassette at a predefined orientation. Thus, even if the cassette is shaken or tilted, the medical instrument does not easily become disengaged from the holding means and cannot assume a skewed position which may impede removal of the medical instrument.

In a preferred embodiment the at least one guide hole has polygonal cross-section, most preferably a triangular cross-section. When a circular cylindrical shaft of a medical instrument is inserted through such a hole, only points of surface contact can occur. In this way, even if the instrument contacts the guide hole for any reason, e.g. misalignment caused by shaking during transport, this contact is minimal and does not interfere with circulation of cleaning fluid past the instrument.

In a particularly preferred embodiment a spring sheet and stop sheet are connected together to form a sandwich unit which can be positioned and removed from the cassette as a single unit. A single cassette may contain one or more such sandwich units, each sandwich unit comprising the same or alternative configurations of spring and stop sheets, and optionally including one or more intermediate sheet, in accordance with the present invention. Preferably the components of the sandwich unit are permanently fixed together, for example by welding.

In a particularly preferred embodiment the sandwich unit comprises a spring sheet, intermediate sheet and stop sheet.

Such sandwich units can be removed from the cassette and positioned independently on a surface, while maintaining the order and sterility of the instrument(s) contained therein.

Preferably the sheets, i.e. spring, stop and optional intermediate sheet, of the sandwich unit are orientated horizontally within the cassette. In such embodiments the spring sheet preferably comprises one or more holding means comprising a closed aperture.

Preferably the sandwich unit comprises one or more support leg, each support leg preferably comprising two or more step changes in diameter, thus forming two or more intermediate shoulders on which the spring sheet, stop sheet and optional intermediate sheet(s) can be positioned at a fixed distance to one another. Preferably the sheets are welded to the intermediate shoulders of the one or more support legs. Support columns can optionally be provided between the sheets of the sandwich unit in order to provide additional support. Preferably four support legs are provided, one at each corner of the sandwich unit.

The support legs can be arranged to contact the base tray when the sandwich unit is housed within the cassette. Preferably the support legs are at least partially hollow in order to enable a complementary support post protruding from the base tray to be inserted. This ensures an accurate placement of the sandwich unit within the tray and prevents any sliding of the sandwich unit within the cassette.

The spring sheet of the present invention preferably includes a plurality of holding means according to the present invention, each suitable for retaining a medical instrument. The holding means can be identical in shape or be provided in a variety of shapes depending on designer choice and needs. The at least one spring element of each of the plurality of holding means can have different forms. For example a number of holding means can comprise tongue springs and a further number of holding means can comprise bridge springs. The tongue and bridge springs of different holding means may also have different shapes to one another. It is preferred that holding means designed to hold different instruments have different shapes. This assists the user in identifying the correct holding means for each instrument. Alternatively or in addition, the spring sheet can be provided with different colours or distinctive markings, such as letters, pictograms or numerals to identify each holding means. The clear distinction between different holding means allows fast and accurate assembly of the instruments within the cassette.

In addition, user information is preferably provided on the base tray and/or the spring sheet to assist in identifying the medical instruments and/or a correct sequence of medical instruments in a medical procedure. This reduces the time required to identify, clean, sort, count, and group medical instruments before, during or after a medical procedure.

When a plurality of holding means are provided in a spring sheet for retaining instruments of differing lengths, the intermediate sheet described above can also function as a secondary stop sheet. The surface of the intermediate sheet facing the spring sheet can form a stop surface and may alternatively or additionally comprise stop pins of the type described above. Further, the intermediate sheet can comprise through-holes for accommodating a part of the medical instrument having a smaller diameter than an adjacent portion, such that an abutment surface of the instrument rests against the intermediate sheet.

In addition to the holding means of the present invention it is also possible for the cassette to comprise additional holding means for a retaining a medical instrument.

As initially mentioned, the cassette further comprises one or more secondary holding means comprising a through-hole provided with an undercut, which undercut allows formation of a snap-fit connection to a complementary protrusion provided on the surface of the medical instrument. The undercut can be formed by an annular groove in the through hole or an annular protrusion, the undercut being created by the far side of the protrusion. In such embodiments the medical instrument comprises a complementary protrusion. At least the protrusion of the instrument (or, where present, the protrusion of the through hole) is resilient such that this can be deflected and/or compressed to allow the instrument to be inserted into the through hole until the undercut of the through hole and protrusion of the instrument are brought into alignment, whereupon the protrusion springs back to, or towards, its original shape. This provides the user with physical feedback that the instrument has been correctly inserted and the snap fit connection provides an axial retention between the holding means and the instrument.

The through hole may comprise a rib, which protrudes radially inwards into the space of the through-hole thus forming an undercut which is intended to engage to a protrusion, for instance a nub, rim or clamping ring, provided on the surface of the medical instrument, thereby creating a snap fit between the medical instrument and the through hole.

Alternatively, a groove may be provided on the interior wall of the through-hole to provide a snap fit connection to a medical instrument which has a protrusion, e.g. a nub, rim or clamping ring, on the outer surface of the instrument and protruding therefrom. The diameters of the through-hole and the medical instrument, as well as the dimensions of the undercut and the protrusion, are such that the instrument is held in place within the holding means when the protrusion of the instrument snaps into the undercut of the through hole.

The described snap fit construction allows a safe retention of the medical instrument in the through-hole, although only a small surface area of the medical instrument needs to be in contact with the contact surface.

In line with the claimed invention, the one or more secondary holding means is formed on the spring sheet, in addition and separately to the at least one holding means. Preferably the one or more secondary holding means comprises a cylindrical extension piece having a through-bore comprising the undercut, which is welded or otherwise connected to the spring sheet such that it forms an extension of the spring sheet. This ensures a suitable thickness for forming the snap fit connection without unnecessarily thickening the entire spring sheet. Alternatively or additionally one or more secondary holding means can be positioned on the stop or intermediate plate.

In a similar manner to the spring element, such snap fit through-holes enable the cassette to hold one or more medical instruments without recourse to elastomeric components. Instead the holding means can be formed entirely of metal or metal alloy.

As mentioned, the present invention provides a cassette for storage of at least one medical instrument, the cassette comprising at least one holding means, the holding means comprising a through-hole provided with an undercut, which undercut allows formation of a snap-fit connection to a complementary protrusion provided on the surface of a medical instrument and wherein the holding means is made of a metal or a metal alloy.

Preferably the cassette further comprises a spring sheet as described above. Further preferred embodiments of this aspect are the same as those described above and below in relation to the first aspect.

In a further alternative, the holding means of the present invention can be adapted to retain a locking element of the cassette rather than a medical instrument. In this way the spring sheet provides an indirect retention to one or more medical instruments.

Such alternative holding means are particularly advantageous in cassettes in which the medical instruments are held within vertical spring sheets and/or vertical support sheets of the type described above, such that the instruments lie parallel to the horizontal plane of the cassette. In such embodiments the cassette preferably comprises one or more support sheet comprising one or more aperture shaped to accommodate a medical instrument and open to a lateral side of the support sheet, said sheet being orientated vertically within the cassette, the cassette further comprising a locking element which is moveable relative to the at least one support sheet which can be moved from a first position, in which it prevents the medical instrument from being removed from the at least one aperture, to a second position in which the medical instrument can be removed from the at least one aperture, the cassette further comprising retention means comprising an aperture defining a passage therethrough for holding a part of the locking element and a spring element positioned adjacent to said aperture for exerting a biasing spring force to retain the part of the locking element within the passage when the locking element is in the first position, thus preventing movement of the locking element into the second position.

In such embodiments the medical instruments are supported in apertures that do not comprise spring elements, such that the retentive force is provided by the locking element, which is retained by a spring element of the retention means. The retention means is preferably formed on the at least one support sheet, although it can be provided on another component of the cassette.

The locking element can be moved from the first to second position by, e.g. sliding the element relative to the cassette. Preferably however the locking element is connected to the cassette by a hinge, thus enabling the locking element to move from first to second position by rotation about the axis of the hinge.

In some embodiments at least one vertical spring sheet provides additional retention directly to one or more of the instruments. However, preferably the sole retention is provided by the locking element.

In order to assist with the cleaning process, it is preferable that the upper surface of the spring sheet and where present the stop sheet, the intermediate sheet, the base tray and/or the cover part is/are planar. A planar surface is easier to clean than one comprising grooves and protrusions, where dust and fluid can gather and which are difficult to clean effectively.

In a preferred embodiment the spring sheet comprises multiple additional holes to allow circulation of a cleaning medium. Preferably the spring sheet and, where present, the base tray, the cover part, the stop sheet and intermediate sheet and locking element are perforated such that a cleaning fluid, e.g. liquid or gaseous, can flow through the cassette, even in a closed state. Essentially it is preferred that all components of the cassette are perforated by fluid circulation holes. These fluid circulation holes allow the cassette with the at least one medical instrument stored therein to be cleaned, e.g. in an ACD machine, and then sterilized, e.g. in an autoclave.

Preferably the fluid circulation holes in adjacent sheets are offset from one another but provide a "line of sight" through the cassette.

In a particularly preferred embodiment a spring sheet is positioned essentially parallel to the base tray and a support sheet comprising a retention means, hereafter referred to as a retention sheet, is fixed to the base tray such that it protrudes therefrom in a direction towards the cover part. The at least one retention sheet may be fastened to the base tray, e.g. by welding, preferably such it protrudes therefrom at an essentially right angle, and the spring sheet is positioned above the at least one retention sheet. In particular, the distance of the spring sheet to the base tray is generally greater than the height of the retention sheet protruding from the base tray. Preferably the base tray comprises a plurality of support sheets attached thereto, the retention and support sheets forming vertical ribs extending from the base tray and the cassette further comprising at least one locking element. The spring sheet is preferably part of a removable sandwich unit comprising the spring sheet, an intermediate sheet and a stop sheet, or alternatively only the spring sheet and a stop sheet, which are welded or otherwise fixedly connected together such that these can be inserted and removed from the cassette as a single unit. Preferably the aperture of the at least one holding means has a closed cross-section. The sandwich unit may be positioned on at least one support leg, preferably at least three support legs, which is/are placed on one or more protruding support posts of the base tray to thereby hold the sandwich unit at a distance above the base tray.

The support leg(s) may be of the type described above comprising intermediate shoulders. Alternatively the support legs can be formed in one piece from the spring sheet, base tray or stop sheet. In a further alternative embodiment the sandwich unit is designed to rest on top of vertical walls of the base tray.

According to a particularly preferred embodiment, the cassette is a metal-only cassette, which means that all components of the cassette are made of metal or a metal alloy. Most preferably, the metal is stainless steel, aluminium or titanium as these metals have particularly suitable characteristics, such as durability, rigidity, stain-resistance, bacteria-resistant, chemical inertness and oxidation resistance. Preferably the one or more spring sheets of the cassette are formed of spring steel, in particular spring stainless steel, e.g. <NUM>.

The cassette preferably comprises at least one medical instrument held within the holding means of the spring sheet, preferably at least one dental surgical tool for use in the placement of a dental implant. The dental surgical tool could be, for example, a drill, tap, insertion tool, mucosa punch etc. Preferably a plurality of such instruments are held within a plurality of holding means within the spring sheet.

Particularly preferred embodiments of the present invention are described below, by way of example only, and illustrated in the drawings in which purely schematically:.

<FIG> shows an embodiment of the cassette <NUM> according to the present invention, wherein the cassette <NUM> comprises a metal cover part <NUM>, a metal base tray <NUM> and a metal sandwich unit <NUM> that is enclosed between the former two parts. The cover part <NUM> and the base tray <NUM> form a box-like, essentially rectangular outer housing within which the sandwich unit <NUM> is housed.

For purposes of description herein, the terms "upper," "lower," "right," "left," "rear, " "front," "vertical," "horizontal," and derivatives thereof shall relate to the cassette <NUM> as oriented in <FIG>.

The sandwich unit <NUM> is removably insertable into the cassette <NUM> and includes a spring sheet <NUM> forming the horizontal top surface of the sandwich unit <NUM> and comprising numerous holding means <NUM>, which are each intended to retain a medical instrument therein, as will be described in more detail below.

In the shown embodiment, the cover part <NUM> and base tray <NUM> are both boat-shaped and each includes a horizontally oriented, essentially rectangular planar surface as well as four side walls <NUM>, <NUM>, which project vertically downwardly and upwardly, respectively.

The cover part <NUM> and the base tray <NUM> are designed such that the cover part <NUM> can be releasably connected to the latter, enclosing the sandwich unit <NUM> with the medical instruments (not shown) for cleaning, sterilization, transport and storage. For securing the cover part <NUM> on the base tray <NUM>, the former comprises closure elements <NUM>, which are configured to couple with the base tray <NUM>. More specifically, the cover part <NUM> comprises two closure elements <NUM> on each broadside, each comprising a larger C-shaped flap <NUM> and a smaller S-shaped spring latch <NUM>. Each flap <NUM> is guided through a cutout <NUM> in the broadside of the spring sheet <NUM>. The spring latches <NUM> have kinked free end portions <NUM> that are configured to snap into place underneath a bracket structure <NUM> formed on both broadside walls <NUM> of the base tray <NUM>. Thereby, the cover part <NUM> can be clamped in position with respect to the base tray <NUM> and thereby securely hold the sandwich unit <NUM> there-between (see <FIG>). It is to be noted that the closure element <NUM> can be any closure device or feature suitable to secure the cover part <NUM> to the base tray <NUM> and/or the sandwich unit <NUM> of the cassette <NUM>.

In the embodiment of the cassette <NUM> shown in <FIG>, the top surface of the sandwich unit <NUM> and the upper surface <NUM> of base tray <NUM> have an essentially rectangular shape and are essentially of the same size. In an alternative embodiment however the sandwich unit <NUM> may have a smaller footprint and be fully enclosed by the base tray <NUM> and cover unit <NUM> when the cassette is in the closed state.

The cover part <NUM> and the base tray <NUM> are both perforated, which means that they include a plurality of fluid circulation holes <NUM>. The various components of the sandwich unit <NUM> also comprise fluid circulation holes <NUM>. These permit circulation of a gaseous or liquid cleaning medium within and through the cassette <NUM> in the closed state. In particular, the fluid circulation holes <NUM> allow that the cassette <NUM> with the at least one medical instrument stored therein can be cleaned, e.g. in an ACD machine, and then sterilized, e.g. in an autoclave. The fluid circulation holes <NUM> in the cover part <NUM>, sandwich unit <NUM> and the base tray <NUM> have various shapes and sizes, although the majority of the holes <NUM> are circular.

The sandwich unit <NUM> forms a removable tray comprising the horizontal spring sheet <NUM>, an intermediate sheet <NUM> and a stop sheet <NUM> (see <FIG>) which are welded or otherwise fixedly connected together such that these can be inserted and removed from the cassette <NUM> as a single unit. The spring sheet <NUM> comprises four side walls <NUM>, which extend downwards from the edges of the horizontal spring sheet <NUM> in a skirt-like manner, such that the opposing side walls <NUM> are arranged parallel to one another. In the assembled state of the cassette <NUM> (shown in <FIG>), the downwardly extending sidewalls <NUM> of the cover part <NUM> are aligned with the downwardly extending side walls <NUM> of the spring sheet <NUM> and with the upwardly extending side walls <NUM> of the base tray <NUM>. In particular, the lower edges of the front and rear side walls <NUM> of the cover part <NUM> are provided with tab-like vertical protrusions <NUM>, which are intended to fittingly extend into corresponding cut-outs <NUM> provided the spring sheet <NUM>. In this way, the side walls <NUM> of the cover part <NUM> and the side walls <NUM> of the sandwich unit <NUM> are secured and aligned with respect to each other in a simple manner. As discussed above, the left and right side walls <NUM> of the spring sheet <NUM> also comprise cut outs <NUM> to enable the C-shaped flaps <NUM> of the cover part <NUM> to extend through the sandwich unit <NUM> and contact the base tray <NUM>.

For placing the sandwich unit <NUM> on the base tray <NUM>, the sandwich unit <NUM> comprises four support legs <NUM>, each of which being attached to a respective corner of the spring sheet <NUM> and protruding therefrom at an essentially right angle towards the base tray <NUM>. The support legs <NUM> are configured to be positioned on the top of support posts <NUM> provided in each of the four corners of the base tray <NUM>. By placing the support legs <NUM> on top of the support posts <NUM>, the sandwich unit <NUM> can be removably positioned on the base tray <NUM> and aligned therewith, such that the side walls <NUM>, <NUM> are aligned flush one above the other. As a result, the sandwich unit <NUM> is arranged essentially parallel to the base tray <NUM> and positioned at a vertical distance thereto. The base tray <NUM> can thus be used to store additional instruments. For this purpose, the base tray comprises a number of support sheets <NUM> and retention sheets <NUM>, which will be discussed in detail in relation to <FIG>.

<FIG> shows the cassette <NUM> of <FIG> in the closed state, wherein the base tray <NUM> and the cover part <NUM> form a rigid, generally box-like outer housing defining a generally rectangular interior space in which the medical instruments are stored.

In the shown embodiment, the downwardly extending side walls <NUM> of the cover part <NUM> and the upwardly extending side walls <NUM> of the base tray <NUM> align with top edges and bottom edges respectively of the sandwich unit side walls <NUM>.

As mentioned above, the cover part <NUM> comprises a pair of C-shaped flaps <NUM> and a pair of S-shaped spring latches <NUM>, which are attached to the cover part <NUM>. The spring latches <NUM> are pivotally mounted on the cover part <NUM> such they can pivot between a locking and non-locking position, in known manner. In the locking position, the spring latches <NUM> engage underneath the bracket structure <NUM> formed on both broad side walls <NUM> of the base tray <NUM>.

Cover part <NUM> comprises four D-shaped cut-outs <NUM> in its planar top surface. These cut-outs <NUM> enable a user's fingers to be inserted therein to lift the cassette <NUM>, e.g. out of a sterilisation container or transportation package. Thanks to the D-shaped cut-outs <NUM>, no handle is required, which avoids areas of overlapping material and therefore facilitates cleaning and sterilization of the cassette <NUM>.

<FIG> shows the sandwich unit <NUM> in an exploded view. The sandwich unit <NUM> is comprised of three sheets, namely spring sheet <NUM>, intermediate sheet <NUM> and stop sheet <NUM>. These three sheets <NUM>, <NUM>, <NUM> are all made of metal or a metal alloy and are welded or otherwise fixedly connected together such that the assembled sandwich unit <NUM> can be inserted and removed from the cassette <NUM> as a single unit. The spring sheet <NUM>, intermediate sheet <NUM> and stop sheet <NUM> are held at a vertical distance to one another by means of the support legs <NUM> provided in each of the four corners of the sandwich unit <NUM>. Additionally, support columns <NUM> are positioned between the intermediate sheet <NUM> and the stop sheet <NUM> to further strengthen the sandwich unit <NUM> and maintain the distance between the intermediate sheet <NUM> and stop sheet <NUM>. The support columns <NUM> have an upper end <NUM> that is fixed, e.g. by welding, to the intermediate sheet <NUM> and further have a lower end <NUM> that is fixed, e.g. by welding, to the stop sheet <NUM>.

<FIG> shows a top view of the spring sheet <NUM> in isolation. From this view, it is clearly visible that the spring sheet <NUM> comprises a plurality of holding means <NUM> for retaining medical instruments. In addition the spring sheet <NUM> comprises numerous fluid circulation holes <NUM> as well as through-holes <NUM>, the purpose of which will be discussed below in relation to <FIG>. The top surface of the spring sheet <NUM> forms the upper surface of the sandwich unit <NUM> and is marked to assist the surgeon with identification of the instruments and the order or sequence of use of the medical instruments accommodated within the spring sheet <NUM>. Pictograms <NUM> are provided to ensure the correct pairing of medical instrument and holding means <NUM> and lines <NUM> indicate the order of use of the instruments. The pictograms <NUM> and lines <NUM> can be provided on the spring sheet <NUM> by, e.g. silk printing.

As best seen in <FIG>, the holding means <NUM>, which are intended to accommodate and retain respective medical instruments therein, each comprise an aperture <NUM>, <NUM>', <NUM>'' with a closed cross-section forming a passage <NUM>, <NUM>', <NUM>'' and a spring element <NUM>, <NUM>', <NUM>''. The passages <NUM>, <NUM>', <NUM>'' in the spring sheet <NUM> are essentially circular, however in other embodiments they may have various other cross-sections, i.e. oval, rectangular, polygonal, etc..

In the shown embodiments, the spring elements <NUM>, <NUM>', <NUM>'' comprise a resilient metal tongue <NUM>, <NUM>', <NUM>''. More specifically, the tongues <NUM>, <NUM>', <NUM>'' of the spring elements <NUM>, <NUM>', <NUM>'' have an attachment end <NUM>, <NUM>', <NUM>'' and a free end <NUM>, <NUM>', <NUM>'' that is arranged at the opposing end of the tongue <NUM>, <NUM>', <NUM>''.

In order to retain an instrument within the holding means <NUM>, the cross-section of the passage <NUM>, <NUM>', <NUM>'', in the plane of the spring sheet <NUM>, is restricted by the adjacent respective spring element <NUM>, <NUM>', <NUM>'' to an extent that the medical instrument can only be inserted into the passage <NUM>, <NUM>', <NUM>'' under deformation of the associated spring element <NUM>, <NUM>', <NUM>''. Thus, the cross-section or diameter of the passage <NUM>, <NUM>', <NUM>'' is at least slightly smaller than the diameter of the medical instrument when the spring element <NUM>, <NUM>', <NUM>'' is in its resting position.

In the present embodiment, the spring elements <NUM>, <NUM>', <NUM>'' are integrally formed in one piece with the spring sheet <NUM>. In this way, there is no join between the spring elements <NUM>, <NUM>', <NUM>'' and the spring sheet <NUM> into which bacteria, fluids, dirt etc. could enter, which allows a better cleaning. The spring element <NUM>, <NUM>', <NUM>'' can be prepared by cutting the spring sheet <NUM>, e.g. by means of a water stream or laser cutting procedure.

In the shown embodiments, the cross-section of the passage <NUM>, <NUM>', <NUM>'' comprises at least three areas of contact surface for contacting the medical instrument. Said areas of contact surface are spaced apart from one another about the circumference of the passage <NUM>, <NUM>'. A first area of contact surface <NUM>, <NUM>', <NUM>'' is formed by a surface of the free end <NUM>, <NUM>', <NUM>'' of the tongue <NUM>, <NUM>', <NUM>'' and at least two further areas of contact surface <NUM>, <NUM>', <NUM>'' are provided on the interior wall of the passage <NUM>, <NUM>', <NUM>''. The areas of contact surface <NUM>, <NUM>', <NUM>'' provided by the interior wall of the passage are concave arcs for contacting a circular cylindrical shaft of a medical instrument (not shown) and are interposed by recesses <NUM>, <NUM>', <NUM>'' which have a greater radius than the areas of contact surface <NUM>, <NUM>', <NUM>''. The recesses <NUM>, <NUM>', <NUM>'' provide areas about the passage <NUM>, <NUM>', <NUM>'' which in use do not contact the medical instrument, and hence create channels that allow a flow of cleaning fluid through the passage <NUM>, <NUM>', <NUM>'' even when a medical instrument is held therein. The area of contact surface <NUM> provided by the tongue <NUM> of <FIG> is also concave, however the contact surfaces <NUM>', <NUM>'' of the tongues <NUM>', <NUM>" of <FIG> are convex.

The area of contact surface <NUM>, <NUM>', <NUM>'' that is provided at the free end <NUM>, <NUM>', <NUM>" of the tongue <NUM>, <NUM>', <NUM>'' of the spring elements <NUM>, <NUM>', <NUM>'' is angularly offset from the central longitudinal axis T, T', T'' of the tongue <NUM>, <NUM>', <NUM>''. More specifically, the location of the first area of contact surface <NUM>, <NUM>', <NUM>'' is such that its normal axis, i.e. the axis running perpendicular to the plane of the contact surface, is oriented at an angle of approximately <NUM>° in relation to the longitudinal axis T, T', T'' of the tongue <NUM>, <NUM>', <NUM>''. When the medical instrument is inserted into the passage <NUM>, <NUM>', <NUM>'' and brought into contact with, inter alia, the first contact surface <NUM>, <NUM>', <NUM>'', this angle enables the spring elements <NUM>, <NUM>', <NUM>'' to be deflected in the plane of the spring sheet <NUM> relative to the attachment end <NUM>, <NUM>', <NUM>''. This deflection of the spring element <NUM>, <NUM>', <NUM>" (and the fact that the spring element aims to return to its resting position) results in the generation of the biasing spring force, by means of which the medical instrument is releasably retained within the passage <NUM>, <NUM>', <NUM>'' by friction fit. Said biasing spring force is such that it allows for securely yet releasably retaining the medical instrument within the aperture <NUM>, <NUM>', <NUM>''.

The different embodiments shown in <FIG> illustrate that the shape and dimensions of the areas of contact surface <NUM>, <NUM>', <NUM>'' and <NUM>, <NUM>', <NUM>'' as well as of the areas of non-contact surface <NUM>, <NUM>', <NUM>'', can be adjusted to the shape and dimension of the medical instrument to be retained within the respective passage <NUM>, <NUM>', <NUM>''. The same applies for the shape and size of the tongue <NUM>, <NUM>', <NUM>''. In particular, the spring characteristics, in particular the bending properties of the tongue <NUM>, <NUM>', <NUM>'' can be adjusted by altering the length, width and/or the thickness of the tongue <NUM>, <NUM>', <NUM>''.

<FIG> shows the intermediate sheet <NUM> in isolation. The intermediate sheet <NUM> is positioned essentially parallel and at a distance to the spring sheet <NUM>, between the spring sheet <NUM> and the stop sheet <NUM>. The main purpose of the intermediate sheet <NUM> is to provide axial guidance to the medical instruments held in the holding means <NUM> of the spring sheet <NUM>. The intermediate sheet <NUM> comprises multiple guide holes <NUM> coaxially aligned with the holding means <NUM> of the spring sheet <NUM>. The cross-section of the guide holes <NUM> is adapted to be slightly larger than the cross-section of the medical instrument to be held within the associated passage <NUM> formed in the spring sheet <NUM>. Thereby the guide holes <NUM> in the intermediate sheet <NUM> provide axial guidance to the medical instruments during their insertion into the sandwich unit <NUM>. In the present embodiment the guide holes <NUM> have a triangular cross-section. Intermediate sheet <NUM> further comprises fluid circulation holes <NUM>. These holes have varying cross-sections, e.g. circular, square, irregular etc. in order to enable maximum flow of fluid, particularly in the vicinity of the instruments within the guide holes <NUM>, while still maintaining a suitable strength of the plate.

<FIG> shows stop sheet <NUM> in isolation. The main purpose of the stop sheet <NUM> is to provide a stop surface <NUM>, i.e. a physical stop, which is intended to bear against an end face of the medical instrument inserted through one of the holding means <NUM> in the spring sheet <NUM>. The stop surface <NUM> thereby ensures that the instrument is not inserted too far through the holding means <NUM>, which could result in the instrument touching or damaging any further instruments stored under the spring sheet <NUM>, e.g. on the base tray <NUM>. In the shown embodiment, the stop sheet <NUM> has the same footprint as the spring sheet <NUM>.

The stop surfaces <NUM> provided underneath the holding means <NUM> in the spring sheet <NUM> are mostly formed by the top surface <NUM> of the stop sheet <NUM>.

Some stop surfaces <NUM> are however also provided by pins <NUM> located on the stop sheet <NUM> (see <FIG>). More specifically, these stop surfaces <NUM> are provided by a top surface <NUM> of the individual pin <NUM>, which is aligned with and oriented essentially parallel to the cross-section of the associated passage <NUM>. Thus, the top surface <NUM> of the stop sheet <NUM> and the top surfaces <NUM> of the stop pins <NUM> form stop surfaces <NUM> for different medical instruments. This has the advantage that the distances of the stop surfaces <NUM> to the holding means <NUM> in the spring sheet <NUM> can be varied, depending on the height of the pin <NUM>. The stop pins <NUM> are welded to the stop sheet <NUM> at welding points <NUM>. Further welding points <NUM> are provided on both the stop sheet <NUM> and intermediate sheet <NUM> for the attachment of the support columns <NUM> (see <FIG>).

Stop sheet <NUM> also comprises numerous fluid circulation holes <NUM>. As with the intermediate sheet <NUM>, some of the holes have an irregular shape. These irregular holes <NUM> are positioned in order to allow maximum flow around the stop surfaces <NUM> and hence the medical instruments held there.

In use, the medical instrument will pass through the holding means <NUM> in the spring sheet <NUM>, through an associated guide hole <NUM> in the intermediate sheet <NUM> and come to rest on an associated stop surface <NUM> of the stop sheet <NUM>, e.g. the top surface <NUM> of the stop sheet <NUM> or the top surface <NUM> of a pin <NUM> fixed to this surface <NUM>. In this way, the medical instrument is securely held within the cassette <NUM> at a predefined orientation (see <FIG>). Thus, even if the cassette <NUM> is shaken or tilted, the medical instrument does not easily get disengaged from the holding means <NUM> and cannot assume a skewed position which may impede removal of the medical instrument.

In this particular embodiment of the present invention the intermediate sheet <NUM> also functions as a secondary stop sheet. This will be described in more detail in connection with <FIG>.

In the embodiment shown, the sandwich unit <NUM> not only comprises holding means <NUM> as described above but further comprises additional holding means for holding a medical instrument. More specifically, the spring sheet <NUM> comprises a number of through-holes <NUM> - in addition and separately to the apertures <NUM> with the associated spring elements <NUM>. Each through-hole <NUM> is aligned with a cylindrical extension piece <NUM> having a through-bore <NUM> and which is welded or otherwise connected to the underside of the spring sheet <NUM>.

As shown in more detail in <FIG>, extension piece <NUM> has through bore <NUM> provided with an annular protrusion <NUM> in an upper end area. Said protrusion <NUM> creates an undercut <NUM> that allows for the formation of a snap-fit connection to a respective protrusion, for example a clamping ring, provided on the outer surface of a medical instrument.

The spring sheet <NUM>, intermediate sheet <NUM> and stop sheet <NUM> are connected together by support legs <NUM>. <FIG> shows a cross-sectional view of one of the support legs <NUM>. As mentioned above in connection with <FIG>, the support legs <NUM> are configured to be positioned on the top of support posts <NUM> provided in each of the four corners of the base tray <NUM>. As can be seen from <FIG>, the support legs <NUM> have a hollow space <NUM> in the bottom end <NUM>. This enables the tip of the support posts <NUM> of the base tray <NUM> to be inserted into the support legs to fix the sandwich unit <NUM> to the base tray <NUM>. The support legs <NUM> have a telescopic shape, i.e. a basic cylindrical shape, the diameter of which is reduced from a bottom end <NUM> towards a top end <NUM> in a step-like manner. With each reduction of the diameter of the support leg <NUM>, a respective intermediate shoulder is formed. In the shown embodiment, the support leg <NUM> has three step changes, thereby forming a first shoulder <NUM> that is located in proximity to the bottom end <NUM>, an second intermediate shoulder <NUM> and a third shoulder <NUM> that is located in proximity to the top end <NUM> of the support leg <NUM>.

As shown in <FIG>, <FIG>, each of the stop sheet <NUM>, intermediate sheet <NUM> and spring sheet <NUM> comprise circular openings <NUM>, <NUM>, <NUM> in each of their corners. In analogy to the shape of the support legs <NUM>, the size of the openings <NUM> in the stop sheet <NUM> are larger than the size of the openings <NUM> in the intermediate sheet <NUM> and the latter are again larger than the openings <NUM> in the spring sheet <NUM>. In particular, the openings <NUM> in the corners of the stop sheet <NUM> are smaller than the diameter of the support leg <NUM> in the area of the bottom end <NUM> but larger than the diameter of the support leg <NUM> in the area of the second shoulder <NUM>. As such, the openings <NUM> in the stop sheet <NUM> can be partly passed over the support legs <NUM> until the sheet rests on first shoulder <NUM>. Similarly, the sizes of the openings <NUM> in the intermediate sheet <NUM> and the openings <NUM> in the spring sheet <NUM> are such that in the assembled state of the sandwich unit <NUM>, the intermediate sheet <NUM> rests on the second intermediate shoulder <NUM> of the support legs and the spring sheet <NUM> rests on the third shoulder <NUM> of the support legs. The support legs <NUM> are welded in place to create the sandwich unit <NUM>.

<FIG> shows a plan view of the assembled sandwich unit <NUM> and <FIG> shows a vertical cross-section through the sandwich unit <NUM> along line A-A of <FIG>. Here, the positioning of the intermediate sheet <NUM> that is sandwiched in between the horizontal spring sheet <NUM> and the stop sheet <NUM> can be clearly seen. Thus, the intermediate sheet <NUM> is arranged essentially parallel and at a distance to both of the spring sheet <NUM> and the stop sheet <NUM>. One of the support legs <NUM> is also shown, illustrating that the stop sheet <NUM> rests on the first shoulder <NUM> of the support leg, the intermediate sheet <NUM> rest on the second intermediate shoulder <NUM> of the support leg and the spring sheet <NUM> rests on the third shoulder <NUM> of the support leg <NUM>.

Support columns <NUM> can also be seen between the intermediate sheet <NUM> and stop sheet <NUM>. In addition, stop pin <NUM> and extension piece <NUM> are visible. In the assembled state, the side walls <NUM> of the spring sheet <NUM> enclose the intermediate sheet <NUM> and end in approximate alignment with the stop sheet <NUM>.

In cross-section it can clearly be seen that the passages <NUM> of the holding means <NUM> align with the guide holes <NUM> in the intermediate sheet <NUM> and stop surfaces <NUM> of the stop sheet <NUM>, as is shown further below.

<FIG> shows the cross-section of <FIG> wherein medical instruments <NUM> are accommodated within the sandwich unit <NUM>. Starting from the left, a first instrument 100a is held the holding means 19a and passes through a guide hole <NUM> in the intermediate sheet <NUM>. With its front face, the medical instrument 100a rests on the top surface <NUM> of the stop pin <NUM>. A second medical instrument 100b is held within the holding means 19b and rests with its front face on the top surface of the intermediate sheet <NUM>. Thus in this embodiment the intermediate sheet <NUM> acts as secondary stop sheet. A third medical instrument 100c is held in snap fitting engagement with the extension piece <NUM>. The further four medical instruments 100d-g shown in <FIG> are retained within holding means <NUM> in the spring sheet <NUM> and pass through guide holes <NUM> in the intermediate sheet <NUM> to rest with their front faces on the top surface <NUM> of the stop sheet <NUM>.

<FIG> shows the base tray <NUM> of the cassette <NUM> in isolation. The base tray <NUM> comprises a plurality of support sheets <NUM> that are fastened to the base tray <NUM>, e.g. by welding, such that they protrude therefrom in a direction substantially perpendicular to the base tray <NUM> and are spaced apart by a certain distance. The support sheets <NUM> therefore form vertical ribs extending from the base tray <NUM>. Each support sheet <NUM> is provided with a plurality of apertures <NUM> which are open to a top edge <NUM> of the support sheet <NUM>, namely that edge facing away from the base tray <NUM>, such that a medical instrument <NUM> can be inserted laterally into the aperture <NUM>, whereby the longitudinal axis of the instrument is oriented more or less perpendicular to the plane of the support sheet (see <FIG>).

In addition, two retention sheets <NUM> are provided that are fastened to the base tray <NUM>, e.g. by welding, such that they protrude therefrom in a direction substantially perpendicular to the base tray <NUM> and are spaced apart by a certain distance. The retention sheets <NUM> comprise further apertures <NUM>, for holding the medical instruments and in addition a retention means <NUM> (see <FIG>). The support and retention sheets <NUM>, <NUM> are arranged on the base tray <NUM> such that at least some of the apertures <NUM> of one sheet <NUM>, <NUM> are aligned with apertures <NUM> of a neighbouring sheet <NUM>, <NUM>. In this way, more than one sheet <NUM>, <NUM> can be used to support one instrument - the longitudinal axes of which is oriented more or less perpendicular to the planes of the sheets <NUM>, <NUM>. This prevents the instrument from tilting along its longitudinal axis. With respect to the apertures <NUM> it is to be noted that these apertures <NUM> do not necessarily have to be identical in size and shape but can be adjusted independently from one another in accordance with the size and shape of the medical instrument to be received therein.

To securely hold the instruments within the apertures <NUM>, locking elements <NUM> are provided. The locking elements <NUM> are moveable relative to the base tray <NUM> and sheets <NUM>, <NUM> and are connected to the cassette <NUM> by a hinges <NUM>, thus enabling the locking element <NUM> to move from a first to a second position by rotation about the axis of the hinge <NUM>. In the first position, shown in <FIG>, the locking element <NUM> is in contact with or positioned just above the medical instruments held within the apertures <NUM>, and thus prevents the medical instrument(s) from being removed from the apertures <NUM> in the sheets <NUM>, <NUM>. In the second position the locking element <NUM> is rotated about the hinge <NUM> such that it is remote from the medical instruments <NUM>, which can then be removed from the apertures <NUM>.

In the first position, a latch <NUM> of the locking element <NUM> is retained within retention means <NUM> of the retention sheet <NUM>, which is shown in more detail in <FIG>.

In <FIG>, the retention sheet <NUM> is shown in isolation in a side view. Said retention sheet <NUM> comprises apertures <NUM> for supporting a plurality of instruments and additionally a retention means <NUM>. The retention means comprises an aperture <NUM>, forming a passage <NUM> for receiving the latch <NUM> of the locking element <NUM> and spring element <NUM>. Spring element <NUM> is positioned adjacent to the passage <NUM> and restricts its diameter to an extent that the latch <NUM> can only be inserted into the passage <NUM> upon deflection and/or compression of the spring element <NUM> in the plane of the retention sheet <NUM>. This results in the spring element <NUM> applying a biasing force to the latch <NUM>, thus retaining it within the passage <NUM>. Retention means <NUM> is designed to retain the latch <NUM> of the locking element <NUM> within the aperture <NUM> when the locking element <NUM> is in the first position - in which removal of the medical instruments is prevented.

Spring element <NUM> is in the form of a tongue having an attachment end <NUM> integrally formed with the retention sheet <NUM> and an opposing free end <NUM>. A contact surface <NUM> is formed on a lateral side of the tongue for contacting the latch <NUM>. Spring element <NUM> further comprises a longitudinal slot <NUM> to increase the bending capacity of the element.

In addition nubs <NUM> are formed on the passage wall in order to provide contact surfaces for the latch <NUM>. This creates areas of non-contact <NUM>, which enable fluid to flow through the passage <NUM> even when latch <NUM> is retained therein.

As mentioned previously, base tray <NUM> is perforated by fluid circulation holes <NUM> in order to allow a good circulation of cleaning fluid. While the majority of these holes <NUM> are circular, the base tray <NUM> also comprises large cut-outs <NUM> in the shape of the instruments to be retained in the base tray <NUM>. These function both as fluid circulation holes and a visual guide to the user showing the correct position for each instrument.

In an alternative embodiment the base tray <NUM> can comprise vertical spring sheets <NUM> having holding means <NUM> according to the present invention. An example of such a vertical spring sheet and holding means is shown in <FIG>.

The spring sheet of <FIG> comprises a plurality of apertures <NUM>, <NUM> which open onto the upper side of the sheet <NUM>. Some of these apertures <NUM> provide no axial retention and so simply provide support to the instruments positioned therein. A number of apertures <NUM> however form part of a holding means <NUM>. These apertures <NUM> form a number of passages <NUM> through the sheet. Adjacent to the passages <NUM> are spring elements <NUM>. These take the form of bridge springs which have an attachment end <NUM> at either end and protrude into the passage <NUM>, thus restricting its cross-section. When an instrument <NUM> is inserted into the passage <NUM> the spring element <NUM> is deflected and/or compressed in the lateral direction of the sheet and thus provides a biasing force to retain the instrument within the holding means <NUM>.

The spring sheet <NUM> of <FIG> can be welded to the base tray <NUM> in a similar manner to the support sheets <NUM> and retention sheets <NUM> of the main embodiment and provide direct retention to the instruments held therein. In an alternative embodiment the bridge spring of <FIG> could be adapted to cooperate with the latch <NUM> of locking element <NUM>.

In an alternative embodiment, cassette <NUM> can comprise a sandwich unit comprising only a spring sheet and stop sheet, with no intermediate sheet. Such an alternative sandwich unit <NUM>' is shown in <FIG>.

Sandwich unit <NUM>' comprises a spring sheet <NUM>' and stop sheet <NUM>' with no intermediate sheet. The spring sheet <NUM>' is identical to that described above and therefore the same reference numerals have been used to indicate the features of the spring sheet <NUM>' which have previously been described in relation to spring sheet <NUM>. In particular, spring sheet <NUM>' comprises the holding means <NUM> previously described particularly in relation to <FIG> and through holes <NUM> to which the cylindrical extension pieces <NUM> are welded or otherwise connected, as described in particularly relation to <FIG>.

Stop sheet <NUM>' is similar to that shown in <FIG>. Stop surfaces <NUM>' are provided underneath the holding means <NUM> in the spring sheet <NUM>'. These are mostly formed by the top surface <NUM>' of the stop sheet <NUM>'. Some stop surfaces <NUM>' are however also provided by pins <NUM>', <NUM>, <NUM> located on the stop sheet <NUM>'. More specifically, these stop surfaces <NUM>' are provided by a top surface <NUM>' of the individual pin <NUM>', <NUM>, <NUM>, which is aligned with and orientated essentially parallel to the cross-section of the associated passage. Thus, the top surface <NUM>' of the stop sheet <NUM>' and the top surfaces <NUM>' of the stop pins <NUM>', <NUM>, <NUM> form stop surfaces <NUM>' for different medical instruments. This has the advantage that the distances of the stop surfaces <NUM>' to the holding means <NUM> in the spring sheet <NUM>' can be varied, depending on the height of the pins <NUM>', <NUM>, <NUM>.

In comparison to the stop sheet <NUM> of <FIG> the stop sheet <NUM>' of <FIG> comprises a greater number and variety of stop pins. These additional stop pins <NUM>, <NUM> have a greater length than stop pins <NUM>', and provide a stop surface for tools that in other embodiments may be supported by the intermediate sheet. <FIG> more clearly show the different heights of the stop pins <NUM>', <NUM>, <NUM> and how these enable different lengths of instrument to be supported. Each stop pin <NUM>', <NUM>, <NUM> is located under a holding means <NUM>. The extension pieces <NUM> are not aligned with the stop pins as the extension pieces <NUM> provide an inbuilt axial stop in the form of the snap connection discussed above.

The stop pins <NUM>', <NUM>, <NUM> are welded to the stop sheet <NUM>' at welding points <NUM>'. A further welding point <NUM>' is provided on the stop sheet <NUM>' for the attachment of a support column <NUM>', which will be discussed below.

Stop sheet <NUM>' also comprises numerous fluid circulation holes <NUM>', some of which have an irregular shape. These irregular holes <NUM>' are positioned in order to allow maximum flow around the stop surfaces <NUM>' and hence the medical instruments held there. Further, stop sheet <NUM>' comprises additional fluid circulation holes <NUM> at the centre of each stop surface <NUM>' formed on the top surface <NUM>' of the sheet. These enable sterilisation fluid to contact the end of the medical instrument abutting the surrounding stop surface <NUM>'. In some embodiments the instruments may enter the fluid circulation holes <NUM> for better centring and stability. The fluid circulation holes <NUM>' of the stop sheet <NUM>' and <NUM> of the spring sheet <NUM>' are offset from one another but provide multiple lines of sight through the sandwich unit <NUM>', as can be seen in <FIG>.

In a similar manner to sandwich unit <NUM>, alternative sandwich unit <NUM>' also comprises a support column <NUM>', however in this embodiment only a single column is provided which extends between the spring sheet <NUM>' and stop sheet <NUM>'. Welding point <NUM> is provided on the stop sheet <NUM>' for attachment of the lower end <NUM>' of this column <NUM>' while the support column <NUM>' is welded at its upper end <NUM>' to the spring sheet <NUM>' using one of the fluid circulation holes 22A, see <FIG>. The support column <NUM>' helps to maintain the correct distance between the stop and spring sheets.

With the removal of the intermediate sheet the design of the support legs <NUM>' is simplified. The support legs <NUM>' of the alternative embodiment are shown in detail in <FIG> and comprise only two shoulders, for welded attachment of the spring sheet <NUM>' and stop sheet <NUM>'.

In an analogous manner to the first embodiment, the support legs <NUM>' are configured to be positioned on the top of support posts <NUM> provided in each of the four corners of the base tray <NUM>. As can be seen from <FIG>, the support legs <NUM>' have a hollow space <NUM>' in the bottom end <NUM>'. This enables the tip of the support posts <NUM> of the base tray <NUM> to be inserted into the support legs to fix the sandwich unit <NUM>' to the base tray <NUM>. In contrast to the support legs <NUM> of the last embodiment, hollow space <NUM>' is tapered to assist in the centering of the legs <NUM>' over the support posts <NUM> to ease correct positioning of the sandwich unit <NUM>' within the cassette <NUM>. The support legs <NUM>' have a telescopic shape, i.e. a basic cylindrical shape, the diameter of which is reduced from a bottom end <NUM>' towards a top end <NUM>' in a step-like manner. With each reduction of the diameter of the support leg <NUM>', a respective intermediate shoulder is formed. In this embodiment, the support leg <NUM>' has two step changes, thereby forming a first shoulder <NUM>' that is located in proximity to the bottom end <NUM>', and a second shoulder <NUM>' that is located in proximity to the top end <NUM>' of the support leg <NUM>'.

As shown in <FIG> and <FIG> respectively, the stop sheet <NUM>' and spring sheet <NUM>' comprise circular openings <NUM>', <NUM> in each of their corners. In analogy to the shape of the support legs <NUM>', the size of the openings <NUM>' in the stop sheet <NUM>' are larger than the size of the openings <NUM> in the spring sheet <NUM>'. In particular, the openings <NUM>' in the corners of the stop sheet <NUM>' are smaller than the diameter of the support leg <NUM>' in the area of the bottom end <NUM>' but larger than the diameter of the support leg <NUM>' in the area of the second shoulder <NUM>'. As such, the openings <NUM>' in the stop sheet <NUM>' can be partly passed over the support legs <NUM>' until the sheet rests on first shoulder <NUM>'. Similarly, the size of the openings <NUM> in the spring sheet <NUM>' are such that in the assembled state of the sandwich unit <NUM>' the spring sheet <NUM>' rests on the second shoulder <NUM>' of the support legs as can be seen in <FIG>. The support legs <NUM>' are welded in place to create the sandwich unit <NUM>'.

Claim 1:
A cassette for storage of medical instruments (<NUM>), the cassette comprising
at least one spring sheet (<NUM>) including
at least one holding means (<NUM>) for retaining a medical instrument therein, the holding means (<NUM>) comprising an aperture (<NUM>) forming a passage (<NUM>) through the spring sheet (<NUM>) for receiving the medical instrument and at least one spring element (<NUM>) provided adjacent to the passage (<NUM>) for exerting a biasing spring force to retain the medical instrument within the passage (<NUM>),
wherein the spring sheet (<NUM>), including the at least one holding means (<NUM>), is made of a metal or a metal alloy,
characterized in that the spring sheet (<NUM>) further includes, in addition and separately to the at least one holding means (<NUM>), at least one secondary holding means,
the at least one secondary holding means being made of a metal or a metal alloy and comprising a through-hole (<NUM>) and a cylindrical extension piece (<NUM>),
said extension piece (<NUM>) having a through-bore (<NUM>) comprising an undercut (<NUM>), which undercut allows formation of a snap-fit connection to a complementary protrusion provided on the surface of a further medical instrument (100c), the extension piece (<NUM>) being welded or otherwise connected to the spring sheet (<NUM>) such that it forms an extension of the spring sheet (<NUM>).