Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-01-05
1997-04-08
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523205, 523206, 523208, 523210, 524 13, 524 14, 524 31, 524 32, 524 33, 524 35, C08K 900
Patent
active
056188587
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a polymer material for manufacturing arcing chambers for low-voltage switchgear, as well as to a method for manufacturing the same.
In low-voltage switchgear, such as low-voltage power circuit-breakers, the switch-off arc is supposed to migrate from the point of origin, i.e., from the separating contacts, quickly into the quenching device, i.e., into the arc splitter plates. The properties of the material of the arc-quenching or arcing chamber have a considerable effect on this arcing movement, particularly in the case of short-circuit breaking. It happens, namely, during arcing movement that gaseous products are released from the chamber material because of the briefly occurring high arc temperature. These gases are needed to quickly extinguish the arc if they have the necessary chemical composition and when they are formed--per switching operation--in a quantity that is suited for avoiding too high a pressure inside the switch.
Under the state of the art, one has generally used molded materials based on cellulose-fiber-filled melamine-formaldehyde resins to fabricate arcing chambers (see, e.g.: Hansj urgen Saechtling "Kunststoff-Taschenbuch" [Plastics Manual], 24th edition, Carl Hanser Publishers, Munich 1989, p. 452). However, these are thermosetting materials, and--due to the long mold occupation time and the required postcure--it is, therefore, complicated and expensive to manufacture the chambers, even though this is done analogously to injection molding.
The object of the invention is to specify a polymer material that will make it possible to substantially shorten the cycle times required in the manufacturing of arcing chambers for low-voltage switchgear.
SUMMARY OF THE INVENTION
This is achieved in accordance with the invention by a material having a thermoplastic polymer matrix of polyamide or polyolefin which contains a cellulose material sheathed by cured melamine-formaldehyde resin.
DETAILED DESCRIPTION OF THE INVENTION
The polymer material according to the invention is a thermoplastic material, i.e., a thermoplastic compound. The advantages of this compound--in comparison to thermosetting compounds--lie in an improved processibility. While, namely, a 75 s cycle must be observed when working with the injection molding of thermosetting material, cycle times as low as 3 s can be attained with the thermoplastic compound according to the invention. It is thus possible, then, to have a substantially more economical manufacturing. Moreover, from an electrical standpoint, the thermoplastic material is at least equal to the thermosetting material; the mechanical properties are even better--due to a greater flexibility.
The chamber material produced from the thermoplastic compound exhibits better arc quenching properties than the material used in known methods heretofore. It is also superior with regard to the switching capacity, since the compressive load is substantially lower (reduction in the maximum pressure by up to 50%).
In the case of the thermoplastic compound according to the invention., the polymer matrix consists of polyamide or polyolefin; preference is given to polyamide. For cellulose material, which is advantageously used in the form of fibers, one can use in particular, pure cellulose, wood dust, paper or rayon staple fiber; cellulose is preferred in this case.
The individual components of the thermoplastic compound are preferably available in the following ratio: polymer, i.e., polyamide or polyolefin, to melamine-formaldehyde resin/cellulose material: 6:1 to 1:1, preferably 2:1; melamine-formaldehyde resin to cellulose material: 3:2 to 1:2, preferably 1:1.
The polymer material is produced in accordance with the invention in that cellulose material sheathed by melamine-formaldehyde resin and polymer are mixed together homogeneously at temperatures above 150.degree. C. The temperature is dependent in this case upon the processing temperature of the polymer used. When working with polyamide, it can lie between about 190.degree.
REFERENCES:
patent: 3755220 (1973-08-01), Freimark et al.
patent: 3943079 (1976-03-01), Hamed
Saechtling, H., "Kunststoff Taschenbuch," 24.Ausgabe, Carl Hanser Verlag, M unchen 1989, pp. 452-453.
Haas Wilfried
Hacker Heinz
Hauschildt Hans-Georg
Cain Edward J.
Siemens Aktiengesellschaft
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