Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Patent
1989-11-22
1991-08-27
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
264225, B29C 4514
Patent
active
050431269
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the production of a plastic stopcock consisting of a plug and a housing which is used in connection with medical devices, for example in connection with infusion devices.
Known stopcocks having this purpose are made of plastic, however, housing and plug are injected in separate moldings. These parts are assembled after lubricating the neighboring sliding surfaces with silicon oil. Therefore, both parts must be formed such way that they allow an assembly as easy as possible. The undercuts which keep the plug tight after it has been inserted into the housing, therefore cannot undercut the plug very much, since otherwise the insertion of the plug into the housing would be hampered considerably. But the smaller such undercuts are the more probably the problem arises that the stopcocks are not leakproof enough or, however, if the stopcock is connected into a conduit in which liquid or gas is being carried under relatively high pressure, the plug could be pushed out of the housing. Such accidents can be dangerous for the patient's life.
The document EP-A-0 147 571 discloses a method where an injection molding part consists of several single parts. The injection molding part in this method is produced by injecting a first part into a first injection mold which part is then removed from the injection mold and then is put into a second injection mold where a second part is injected to the first part. Corresponding to the number of parts this procedure is continued and thus the injected substance is every time removed from the injection mold and inserted into the next injection mold. This method has a substantial disadvantage with the medical devices as discussed herein, namely that by changing the injection mold the risk of contamination is quite high. Since, however, medical devices and therefore also its parts are subjected to underly rigid hygienic regulations this method is not to be applied for the production of these devices.
FR-A-2 316 060 discloses a method where an object consisting of two parts is produced in an injection mold by injecting first one part of it and afterwards the other part of it. This method however, aims to achieve that the connection of the two parts has a big enough clearance, so that the one part is easily movable relative to the other part. In the case of a plug arranged within the housing of a stopcock it is demanded in first instance that the stopcock inside the housing is arranged that way that the medium flowing inside the stopcock cannot escape therefrom.
The object of the invention is to increase the operational security of stopcocks.
This object is solved in the present invention in that stopcock and housing are no longer mounted together right after their production but that first one of the parts is injected and then the other part is injected into or around the afore-in-jected part. Preferably this method can be carried out in one single injection molding form, thus, at first one of the parts can be injected and then without removing this part from the form the second part can be injected into this form in or around the initially injected part.
Thus, it is possible to form the bordering face between both parts such way that the plug cannot be removed from the housing not even under high pressure, and that for example if the bordering face between both parts is shaped labyrinth-like the stopcock is leakproof even under high gas or liquid pressure. Finally also the later assembly of housing and plug becomes unnecessary, so that the surfaces of the stopcock which get into connection with the infusion liquid are sterile.
Indeed it was already known to produce a toy animal in only one injection molding form in two injection procedures by using two differently dyed plastic masses, for example a monkey whose body is made of brown dyed PVC and whose face consists of beige dyed PVC, however, these are not parts which have to be movable relative to each other and nevertheless must be sufficiently sealing at the bordering face between the two plas
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patent: 4197876 (1980-04-01), Lobdrell
patent: 4414170 (1983-11-01), Sano
Patent Abstracts of Japan, vol. 8, No. 73, (M-287) (1510), Apr. 4, 1984, & JP, A, 58219031 (Sony), Dec. 20, 1983.
Frank Plastic GmbH
Hackler Walter A.
Jones Brian
Silbaugh Jan H.
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