Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Patent
1997-06-18
2000-02-08
Browne, Lynne H.
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
277944, 277921, 525 88, F16J 1510
Patent
active
060220287
DESCRIPTION:
BRIEF SUMMARY
Magnetic gaskets for refrigerators and amagnetic gaskets for chest freezers are known, formed from extrusions cut into 45.degree.-ended pieces which are joined to form a frame structure by welding then together at their corners.
As an example of the state of the art the following patents may be cited: U.S. Pat. Nos. 67709, 2,958,912, 3,119,158, 3,132,386, 4,700,509, 4,017,759, GB patent 894,249 and Italian patent 1,223,221.
These are generally gaskets comprising a foot for their fixing to the refrigerator door, an extendable bellows chamber and a seat for a bar of magnetized material, or a balloon-type structure for sealing by compression.
PVC has been shown to be a material satisfying the main requirements for the satisfactory manufacture of such gaskets. One such requirement is weldability, ie the ability to resist the welding process when performed on the small thicknesses typical of this type of gasket.
A further requirement is good compromise between rigidity of the extrusion and its ability to recover elastically so as to ensure the elastic movement required for the gasket to seal.
A final requirement is its ability to be extruded into such small thicknesses.
As stated, PVC has proved to be an ideal material for satisfying these basic requirements in gasket manufacture. However in recent times PVC has been questioned from the ecological viewpoint in relation in particular to its disposal, for example by incineration, and waste recycling.
There is therefore an increasing requirement in this sector for a material which can ultimately be proposed as an alternative to PVC in gasket manufacture.
For gasket manufacture, the PVC formulation must include additives, mainly plasticizers, which do not demonstrate migration, in particular towards the anti-impact polystyrene of the refrigerator door liner, or result in staining of the surface finish of the refrigerator cabinet.
For this reason gasket PVC must be formulated with particular plasticizers having minimum migration (as required by DIN 53405). In addition such plasticizers must not be volatile and must provide a permanent plasticizing effect.
It can therefore be seen that the requirements to be satisfied in seeking a replacement material relate to various parameters and factors which are decisive for the technical success of a gasket.
For example vulcanized rubber, in use before the advent of PVC, would not be suitable because traditional vulcanized rubber cannot be extruded to the small thicknesses required for modern gaskets without considerable difficulty, and there are also problems in welding the corners when the gasket pieces are assembled into a frame shape for mounting on the refrigerator.
The basic object of the present invention is to provide a PVC replacement material satisfying all the necessary requirements for manufacturing a gasket of the aforesaid type.
This object together with considerable additional advantages are attained extremely effectively by a material in accordance with claim 1.
According to a preferred embodiment of the invention said mixture comprises a first .alpha.-olefin copolymer chosen from polyolefinic thermoplastic rubbers, and a second .alpha.-olefin copolymer chosen from thermoplastic block rubbers of the styrene-ethylene-butylene-styrene (SEBS) type.
Said polyolefinic thermoplastic rubber is preferably an ethylene-propylene copolymer.
According to the invention, the constituent mixture of the polymeric material comprises other suitable components such as fillers, oil and other usual components suitable for forming the mixture.
For example the mixture suitable for the purposes of the invention can be prepared by mixing together said .alpha.-olefin copolymers in compound form, ie containing the various additives required for its formulation.
The characteristics and advantages of the invention will be more apparent from the following non-limiting practical examples.
EXAMPLE 1
A mixture according to the invention is prepared in the following manner.
Compounded granules of the commercial product Adflex.RTM. 7036 XCT (
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Buzzoni Giancarlo
Cittadini Paolo
Bochna David E.
Browne Lynne H.
Industrie Ilpea S.p.A.
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