Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-10-06
2002-11-05
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S060000, C228S173400, C228S212000
Reexamination Certificate
active
06474535
ABSTRACT:
The present invention relates to a welding method and apparatus, and more particularly to a method and apparatus for automated welding of tubes for use in brachytherapy.
In the treatment of various cancers, and in particular prostate cancer, a process called brachytherapy has proved effective. In brachytherapy, small capsules containing radioactive material are implanted in or near to the tumour.
One known form of capsule or canister, commonly used to treat prostate cancer and referred to as a “seed”, is shown in FIG.
7
. The capsule
100
comprises a silver rod
102
, coated with a radioactive isotope of iodine such as I-125, inside a hollow titanium tube
104
. The ends of the tube are welded closed. Resin balls coated with radioactive iodine can be used instead of the silver rod
102
. The completed capsule has a width of approximately 1.0 mm and a length of approximately 4.5 mm. The capsules or seeds can be implanted into a patient individually; alternatively, the capsules can be inserted into medical stitching material or suture, which is then inserted into the prostate and left there.
The number of capsules implanted into each patient obviously varies in accordance with the regime of treatment required, but is commonly in the region of
50
to
100
. The capsules are normally made by hand, with the welding process used to close the ends of the tube being carried out manually. It will be appreciated that making such a large number of capsules for each patient by hand takes considerable time and expense.
According to a first aspect of the invention, there is provided an automated method of welding closed one end of each of a multiplicity of open-ended tubes suitable for use in the manufacture of brachytherapy capsules, which comprises repeating the steps of loading each tube into a holder, bringing the tube in the holder to a welding station, welding closed one end of the tube, and releasing the welded tube from the holder.
With such a method, a large number of tubes can be processed relatively quickly.
Preferably, the step of loading each tube into a holder comprises the steps of orientating the tubes into a particular orientation in a feeder, and feeding each tube from the feeder to a holder. Once orientated in the feeder, the tubes can be fed to the holder in a desired orientation. Manual picking up and orientation of the tubes is avoided.
As the tubes are for use in making brachytherapy seeds, they will be of a suitable size for brachytherapy implantation, for example, a few millimetres long by about one millimetre wide. The tubes are typically a little longer than the product brachytherapy seed, since it is usual for some of the tube material to be used to form the weld closure.
The welding of one end of the tube closed is preferably effected by melting the material of the tube such that the melted material forms the end closure. Preferably, no additional material is required.
Closure of the remaining open end of the tube will be effected after the active substance for brachytherapy has been inserted.
In general, the tubes to be welded will be formed by being cut from a long length of tubing, and having been so cut they will be randomly orientated. According to the method of the invention, the tubes are orientated in the feeder, so that each tube is ready to be fed to a holder. A preferred method comprises agitating the tubes in order to orientate them in the feeder.
Various ways may be used to control feeding of each tube to a holder. For example each tube may be individually picked up by a robot arm and placed in the holder. Preferably, the method comprises arranging the tubes end to end one above another in the feeder, urging a restraining member against a side of the lowermost-but-one tube to prevent it from downward movement, and releasing the lowermost tube from the feeder individually to the holder. The restraining member thus engages the lowermost-but-one tube and in so doing all the tubes above are held in position, allowing the lowermost tube to be individually released. After release, a blocking member is preferably moved into a blocking position below the tubes and the restraining member is retracted to allow the tubes to drop down, the then lowermost tube being stopped by the blocking member. The restraining member can then be advanced against the now lowermost-but-one tube and the feeding cycle is then repeated.
In a preferred method, the holder receives a tube, conveys the tube to the welding station, and releases the tube, said holder moving in a closed loop.
The provision of a holder which moves in a closed loop facilitates the automation of the welding process. The tube to be welded is supplied to the holder in a particular orientation. The tube is then carried to the welding station where it is welded. The welded tube is released, preferably at an ejection station to which it is carried from the welding station. Since the holder moves in a closed loop, it comes back to its original position, and the procedure can then be repeated.
It is possible to use one holder, although the rate of production of such an apparatus is low, as it can only operate on a single tube at a time. Accordingly, it is preferred that a plurality of said holders are provided. This allows greater productivity.
The welding of the end of each tube obviously requires high temperatures in order to melt the metal of the tube. It is possible for these high temperatures to cause damage to whatever is holding the tube during the welding operation, particularly if repeated welding operations are carried out. Some form of cooling can be provided to reduce the risk of damage. However, in a preferred method, the holders move through said welding station sequentially, each of the plurality of holders cooling between successive welding operations while the other holders move through the welding station. This ensures that after each of the holders holds a tube while it is being welded, it cools down before it next holds a tube being welded. This reduces the risk of heat damage to the holders.
Many possible methods of moving the or each holder through the welding station can be employed. For example, each could be individually driven along a track. However, in a preferred method, the or each holder is mounted at the periphery of a rotatable member. Receiving, welding and releasing stations may conveniently be provided at successive points along the rotational path of the holder. Where a plurality of holders are provided they can all be mounted by the rotatable member, with the advantage of simplicity, as it is then only necessary to provide a single drive means.
The holder may for example be a cavity into which the tube can be dropped by the feeder and which restricts movement of the tube adequately during welding. Preferably, however, the holder adopts an open condition when receiving and releasing a tube and a closed condition to grip the tube firmly at least during welding of the tube. This arrangement assists the receiving and releasing steps, whilst properly holding the tube during welding.
The holder may be in the closed condition at all times except when receiving and releasing a tube. However, the method preferably comprises causing the holder to move from the open condition to the closed condition when the holder is at the welding station. Thus, means can be provided at the welding station for causing the closing action, rather than such means being provided as part of the holder itself. This can advantageously simplify the design of the holder, which is particularly advantageous where the holder is conveyed from one processing station to another, e.g. by a rotatable member.
Viewed from another aspect the invention provides an automated method of welding closed one end of each of a multiplicity of open-ended tubes suitable for use as brachytherapy capsules, comprising repeating the steps of feeding each individual tube to a holder in an open condition, conveying the holder in the open condition to a welding station, causing the holder to close and grip the tube firmly by means of a
Hallgren Robert
Helle Kevin
Krewer John
Shanks Charles
Chisholm Robert F.
Elve M. Alexandra
Nycomed Imaging AS
Pittman Zidia
Ronning, Jr. Royal N.
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