CARRIER AND SUPPORTING MECHANISM FOR WORKPIECES

The present invention relates to containers and supports for carrying, containing and/or supporting a work piece or work pieces, including containing and/or supporting a work piece or work pieces during a work piece treatment process and during shipment to and from a treatment process site.

Radiation processing is a widely used method of commercial sterilization. In particular, gamma and electron beam radiation are widely used. Both methods are prominent within the industry for the sterilization of health care products, while electron beam processing holds a large size of the market for raw materials and products such as commercial polymers and gem stones.

Gamma radiation has long been recognized as a safe, cost competitive method for the sterilization of health care products, components and packaging. Gamma radiation, a form of pure energy which is generally characterized by deep penetration of low dose rates, effectively kills micro-organisms throughout a subject product and its packaging with very little temperature effect. Some advantages of gamma radiation are precision dosing, rapid processing, uniform dose distribution, system flexibility and immediate availability of product after processing through dosimetric release. Gamma radiation is a penetrating sterilant. No area of the product, or its components, is left with uncertain sterility after treatment. Packaging remains intact with gamma processing because there is no requirement for pressure and vacuum seals are not stressed. In addition, gamma radiation eliminates the need for permeable packaging materials.

Electron beam (e-beam) radiation is a form of ionizing radiation that can be an effective means of destroying microorganisms. E-beam irradiation, generally characterized by low penetration and high dose rates, is a process by which products are exposed to a concentrated, high current stream of electrons generated by accelerators that produce a beam that is either pulsed or continuous. A work piece or subject material absorbs energy from the electrons as it passes beneath or in front of the electron beam. E-beam irradiation is mostly used in the health care products market for processing of high volume, low value products such as syringes, and for low volume, high value products such as cardio-thoracic devices.

The energy absorbed per unit mass of material processed by radiation is referred to as the absorbed dose and is identified as either a kilo Gray (kGy) or Megarad (Mrad) unit of measure. This absorption alters various chemical and biological bonds, and it is this absorption of energy or dose delivery that destroys the reproductive cells of microorganisms. Commercial e-beam accelerators range in energies from 3MeV to 12MeV (million electron volts) and usually operate at a single energy. Typically, high energy electron beams are needed for sterilization of health care products to achieve penetration of product and packaging. Product density, size and orientation of packaging must be considered when evaluating e-beam sterilization. In general, e-beam irradiation performs best when used on low density, uniform and uniformly packaged products. E-beam sterilization requires the simultaneous control of the beam's current, scan width and energy, as well as the speed and/or time of exposure, e.g., control of the speed of a conveyor transporting a product through a beam. Speed of the conveyor may be regulated with feed back circuitry from the beam current. If the beam current changes during processing, the conveyor speed correspondingly changes to insure that the delivered dose is held constant.

There are problems, however, currently associated with radiation processing regardless of the type of radiation. First, radiation treatment of work pieces in containers of materials different than that of the work piece may cause the work pieces to have a greater absorbed dose variation. A dissimilar support plate or packaging material can reduce the energy of the penetrating electrons by varying amounts and create a non-uniform dose absorption over the surface area or throughout the thickness of the work piece. In addition, out-gassing from dissimilar support plates and packaging materials causes contamination of the work piece. Finally, work pieces are often manually placed onto and removed from conveyor systems. Handling work pieces in this manner can cause contamination or damage to the work piece.

Accordingly, it would be advantageous to provide a device for use in carrying and/or supporting work pieces to be subjected to e-beam radiation, or other treatments, before, during and after the treatments, wherein the device improves or at least does not adversely impact the efficacy of the e-beam or other treatment.

Document US-A-5,174,453 discloses a surgical tray system being a U-shaped instrument rack removably positioned within an enclosure base and capable of suspending a complete set of surgical operating instruments. Several additional trays may be stacked above or below each other.

It is mentioned that the surgical tray may be made of any commercially available material, but preferably of anodized aluminium. The operative surgical instruments, such as general, gynaecological and thoracic or endoscopic instruments are suspended by their shafts in a flat rectangular tray through several slots or apertures, which are provided in said tray. A sterilisation of the tray system and of the instruments can be performed using an autoclave.

Document US-A-5, 922, 067 discloses a cassette for holding instruments, such as medical or dental instruments, through cleaning, sterilization, comprising a tray member to which the instruments are positioned. Said instruments are fixed through clamping members, which are releasably securable to said tray. Said tray member is made of stainless steel. In order to fix or to clamp the instruments, clamping members comprising a pad or cushion of silicone rubber or of other flexible compressible heat resistant material are provided. A sterilisation of the cassette and of the instruments can be performed using an ultrasonic cleaner and then an autoclave.

The present invention is a carrying and support device that will not adversely affect work pieces when subjected to e-beam radiation or other treatments, Specifically, the present invention will reduce or eliminate the amount of out-gassing from dissimilar materials and minimize the absorbed dose variation within the work pieces. The present invention relates to an apparatus for minimizing the amount of out-gassing and absorbed dose variation, as well as a method for sterilizing or otherwise treating a work piece wherein there is little or no out-gassing and a minimum amount of absorbed dose variation.

More specifically, the carrying and support device of the present invention comprises at least one plate which has at least one relieved region for holding a work piece. The plate has a density the same as or very similar to the density of the work piece, so that the plate and work piece together have a substantially uniform density. In addition, in some embodiments the plate can be used for packaging. The plate can be sent to a manufacturer, where the work piece is placed on or into the carrying and support device, without any additional packaging. The manufacturer would then send the entire unit to the treatment site where it is subjected to treatment. The entire unit, now containing a sterilized or otherwise treated work piece, is then sent back to the manufacturer.

As a first aspect, the present invention is related to a use of a device in carrying and/or supporting at least one work piece being a silicon wafer, said device comprising as elements at least one plate, said plate having edge portions adapted for possible stacking with other plates by engagement of said edge portions with complementary edge portions located on said other plates, said plate having further at least one relieved region located on the top surface of the plate, said relieved region having a shape adapted to receive the work piece, characterised in that said device is made of aluminium.

Preferably, the relieved region of the plate has a lip to support the work piece.

Preferably, the relieved region has an inner surface and said inner surface, the top surface of the plate, and the lip are permanently attached to one another and form a whole.

Preferably, the lip is a separate piece fastened to the inner surface of the relieved region.

Preferably, the lip is one unit and runs continuously along the inner surface of the relieved region.

Preferably, the lip occupies only small sections along the inner surface of the relieved region.

Preferably, the lip is positioned deep enough into the relieved region so that the entire work piece (30) may lie within the relieved region.

Preferably, the relieved region has an inner surface which is angled in to create a funnel so that it may support the work pieces.

Preferably, the plate has several relieved regions having a selected shape adapted to receive work pieces of various complementary shapes.

Preferably, it further comprises additional relieved regions or holes conceived to reduce the weight of the plate or in operating conditions to shape or modify the transmission of the radiation beam in the radiation treatment process.

Preferably, several plates made of aluminium are forming a stack with the receiving plate, said other plates including a bottom plate and a top plate.

Preferably, the top plate and the bottom plate have substantially continuous surface.

Preferably, it further comprises attachment members or fastening means, preferably screws, to connect the plates of the stack, said attachment members or fastening means having a density which is the same or similar density as the density of the work pieces to be held thereon.

Preferably, the radiation treatment process is a radiation sterilisation process.

Preferably, the radiation treatment process is an electron beam radiation treatment process or a gamma radiation treatment process.

According to a second aspect, the present invention relates to a device carrying and/or supporting at least one work piece being a silicon wafer for use in a radiation treatment process, said device comprising as elements at least one plate, said plate having edge portions adapted for possible stacking with other plates by engagement of said edge portions with complementary edge portions located on said other plates,said plate having further at least one relieved region located on the top surface of the plate said relieved region having a shape adapted to receive the work piece, characterised in that said device is made of aluminium.

Preferably, the relieved region of the plate has a lip to support the work piece.

Preferably, the relieved region has an inner surface and said inner surface, the top surface of the plate, and the lip are permanently attached to one another and form a whole.

Preferably, the lip is a separate piece fastened to the inner surface of the relieved region.

Preferably, the lip is one unit and runs continuously along the inner surface of the relieved region.

Preferably, the lip occupies only small sections along the inner surface of the relieved region.

Preferably, the lip is positioned deep enough into the relieved region so that the entire work piece may lie within the relieved region.

Preferably, the relieved region has an inner surface which is angled in to create a funnel so that it may support the work piece.

Preferably, the plate has several relieved regions having a selected shape adapted to receive work pieces.

Preferably, it comprises additional relieved regions or holes conceived to reduce the weight of the plate or in operating conditions to shape or modify the transmission of the radiation beam in the radiation treatment process.

Preferably, several other plates made of aluminium are forming a stack with the receiving plates, said other plates including a bottom plate and a top plate.

Preferably, the other plates of the stack comprise a top plate and a bottom plate, the receiving plate and the top and bottom plates preferably comprising threaded bores extending through each of the plates.

Preferably, the top plate and the bottom plate have substantially continuous surface, and preferably have substantially the same shape as the receiving plate.

Preferably, it further comprises attachment members or fastening means (26), preferably screws, to connect the plates (6,28) of the stack, said attachment members or fastening means (26) having a density which is the same or similar density as the density of the work pieces (30) to be held thereon.

As a third aspect, the present invention relates to a method of commercial sterilization by radiation treatment, comprising the steps of:

• providing work pieces to be sterilised;
• providing the device according to any one of claims 16 to 29;
• carrying and/or supporting the work pieces with said device;

Preferably, the sterilisation uses electron beam radiations or gamma radiations.

These and other features, aspects, and advantages of the present invention will become better understood with regard to the hollowing description, appended claims, and accompanying drawings.

• Figure 1 is a top perspective view or one embodiment of the present invention;
• Figure 2 is a cross-sectional view of one embodiment of the present invention, wherein an embodiment of the support device of the present invention may be combined or stacked for use in a method of treating work pieces;
• Figures 3a and 3b are cross-sectional views of embodiments of the present invention; and
• Figure 4 depicts further details of the embodiment depicted in Figure 2.

The present invention relates generally to a support and carrying device for work pieces. Specifically, the present invention can be used to support and carry work pieces to be subjected to radiation treatment, before, during and after treatment.

Any reference to front and back, right and left, top and bottom and upper and lower are intended for convenience of description, not to limit the present invention or its components to any one positional or spacial orientation.

One embodiment of the present invention is a single plate 6, as shown in Figure 1. The receiving plate 6 of this embodiment is generally rectangular; however, the overall shape of the receiving plate 6 can be adapted to the particular needs of the work piece manufacturer. The receiving plate 6 has a selected number of relieved regions 8 for receiving work pieces. While the depicted relieved regions 8 are circular holes, it should be appreciated that the relieved regions 8 may have a selected shape adapted to receive work pieces of various complementary shapes. The relieved regions 8 have a lip 16 to support a work piece.

The receiving plate 6 has a top surface 10 and a bottom surface 20. Except for the relieved regions 8, the top surface 10 may be substantially continuous or, in other embodiments, may have additional relieved regions or holes for reducing the weight of the plate 6, or for shaping or modifying the transmission of the treatment of the selected treatment process. The top surface 10 may be adapted to have regions that are transparent, partially transparent and/or non-transparent to various forms of radiation techniques. The receiving plate 6 has side surfaces 12. The width 14 of the side surfaces 12 will vary depending on the work piece and the treatment process.

In some embodiments, the top surface 10 has engagement elements 18 adapted to engage or contact other plates or plate edges for improving the plate-to-plate connection when the plates 6 are stacked or otherwise connected, as shown in Figure 2. The bottom surface 20 has receiving elements 22 adapted to receive engagement elements 18. In alternative embodiments, the engagement elements could be located on the bottom surface 20, and the receiving elements could accordingly be located on the top surface 10. As shown, the engagement elements and receiving elements are located on the corners of receiving plate 6. Other embodiments are possible where receiving plates 6 have no corners, or where the engagement elements 18 and receiving elements 22 are located elsewhere on the receiving plates 6.

Figure 2 shows an embodiment of the present invention in which a plurality of the receiving plates 6 are stacked. In this embodiment, a top plate 28 and a bottom plate 28 are provided. The top and bottom plates have substantially continuous surfaces and are substantially the same shape as the receiving plates 6. The top and bottom plates 28 may or may not be transparent, opaque, or neutral to the treatment process. The top and bottom plates 28 and receiving plates 6 may have a plurality of threaded bores 24 (shown in phantom) extending through each of the plates. Suitable attachment members, e.g., screws 26 or the like, may be used to connect the plates 28 to form the stack.

Preferably, the top and bottom plates 28 and the receiving plates 6 are made of a material having the same or similar density as the work pieces. According to the invention as shown in Figure 2, the work pieces 30 are silicon wafers. Accordingly, the top and bottom plates 28 and the receiving plates 6 are aluminum. It is also preferred that fastening means, in this embodiment screws, are made of a material having the same or similar density as the work pieces. The combination of the device of the present invention with the work pieces, as shown in Figure 2, when placed in an irradiator, thus presents itself in a manner such that it is of uniform or near uniform density. This minimizes the variation in dose distribution throughout the combination.

Figure 3a shows top surface 10 having a relieved region 8. The relieved region 8 has an inner surface 32. As shown in Figure 3, the inner surfaces are substantially perpendicular to each other, and the distance between them is slightly larger than the length of the work piece 30. Relieved region 8 has a lip 16 for supporting the work piece 30. Preferably, the lip 16, inner surface 32, and top surface 10 are permanently attached to one another, i.e., they are all one unit. Alternatively, the lip 16 could be a separate piece fastened to the inner surface 32 by any suitable means. In the preferred embodiment, the lip 16 is one unit and runs continuously along the inner surface 32. Alternatively, the lip 16 could occupy only small sections along the inner surface 32, so long as there is enough lip to support the work piece 30. Preferably, the lip 16 is positioned deep enough into the relieved region 8 so that the entire work piece 30 lies within the relieved region 8.

Figure 3b shows an alternative embodiment of the relieved region of the present invention. The relieved region of this embodiment has no lip 16. The inner surface 32 is angled in to create a funnel shape such that the inner surface 32 performs the function of the lip 16 of the preferred embodiment and supports the work piece 30.

Figure 4 shows an exemplary plate-to-plate connection of one embodiment of the present invention. Engagement element 18 is a raised portion along the outer edge of the top surface 10. Preferably, engagement element 18 is one piece with the rest of the receiving plate 6 and is made of the same material as the receiving plate 6. In this preferred embodiment, receiving element 22 is an open area the same shape and size as the engagement element and located on the bottom surface 20. The engagement element 18 is inserted into the receiving element 20 in an interlocking fashion. This interlocking connection prevents the plates from moving or sliding relative to each other.

In this embodiment, the engagement elements 18 are located along the corner of top surface 10. In alternative embodiments, the engagement elements 18 may be located anywhere on the top surface 10, so long as the complementary receiving elements 22 are located accordingly. In yet another embodiment, the engagement elements 18 are located on the bottom surface 20 while the receiving elements 22 are located on the top surface 10. The size of the engagement elements 18, and thus the receiving elements 22, is not important except that the engagement elements 18 should not be taller than the width 14 of the side surface 12.

Preferably, the entire device of the present invention, including all fastening means, is made of a material having the same or similar density as the work piece or pieces to be treated. This minimizes the amount of out-gassing and thus minimizes the contamination of the work piece. In addition, use of a support and carrying device having the same or similar density as the work piece minimizes the variation in dose distribution throughout a material or product to be treated. Optimally, the work piece plus device is subjected to double-sided irradiation. This further reduces the variation in dose distribution throughout a material or product to be treated.

Although the present invention has been described with reference to depicted exemplary embodiments, other versions are possible.