DE8811775U1 - Metal brush holder for a multi-layer brush - Google Patents

Description

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^ ' 1 Siemens AG

Metal brush holder for a multi-layer brush 5

The innovation relates to a metal brush holder for a multi-layer brush according to the generic term of protection claim Ij. Such a metal brush holder is known from Richter: "Electrical Machines", 1950, Volume 5, pages 83-86.

In order to avoid the damaging effect of the so-called rest EMF on the commutation of AC universal motors, it is known to use layered brushes in the form of so-called multi-layer brushes to increase the resistance in the short-circuit circuit. To ensure that this effect is not at least partially cancelled out by a conductive bridging of the individual layers of the multi-layer brush that are insulated from one another by the brush guide walls of the metal brush holder, it is also known to insulate the guide walls from the multi-layer brushes that touch them.

A particularly reliable operation, which remains fully effective even with long service life and, in combination with this, particularly favorable friction conditions in the sense of the smallest possible difference between the static and sliding friction values with a low friction value in terms of the absolute value, is achieved by means of a polytetrafluoroethylene insulation layer.

Surprisingly, it has been shown that a polytetrafluoroethylene coating represents an optimal combination with regard to all parameters relevant to commutation and brush service life.

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Due to the resulting high elasticity and high adhesive strength of the polytetrafluoroethylene insulation layer according to the innovation, one embodiment of the innovation provides that the brush holder is punched or formed from a metal plate provided with the polytetrafluoroethylene insulation layer. In terms of manufacturing technology, this provides a significant advantage over the subsequent coating of the guide walls on the already formed brush holder.

The innovation and other advantageous embodiments of the innovation are explained in more detail below using a schematically illustrated exemplary embodiment in the drawing, which shows:

FIG 1 a commutator-side top view of a metal brush holder with insulation layer and multiple brush in the direction of view I-I according to FIG 2, FIG 2 a radial section according to section line II-II

through the metal brush holder as shown in FIG 1. 20

A multi-layer brush is guided in a metal brush holder 2 and is pressed with its lower grinding surface against lamellae 11 of a rotary encoder 1 by means of a bow spring 5 that extends through a slotted opening into the interior of the brush holder 2 and rests on the radial surface of the brush 3. A brush connection wire 4 that is in contact with the upper radial end of the multi-layer brush 3 serves to supply current.

The multi-layer brush 3 consists in a manner known per se of at least two layers 31, 32 with at least one insulating intermediate layer 33, such that in the rest position when two adjacent lamellae make contact no direct short-circuit cross currents can flow in the area of the guide walls of the multi-layer brush 3.

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According to the innovation, a polyethylene fluoroethylene isolating layer is applied as an insulating layer between the multilayer brush 3 and the lateral guide walls of the brush holder 2 on the guide surfaces facing the multilayer brush 3,

2 Protection claims 2 Figures

Claims (2)

·! &igr;!! ;*·..'% .;;..··. 8863 388OE Protection claims I ₄ Metal brush holder for a multi-layer brush with an insulating layer applied to the brush guide walls, characterized in that a polytetrafluoroethylene insulating layer (22) is applied to the brush guide walls of the brush holder (2). 2. Metal brush holder according to claim 1, characterized in that the brush holder (2) is made of a material coated with a polytetrafluoroethylene ------- (22/ Accidental punched or formed 1st.