DE2039743A1 - Brush for electrical machines - Google Patents

Description

Patent attorneys

^{Dr.- T} iij. VXi helmet rich oil

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!!, TLRNATIONAL RESEARCH & DEVELOPMENT COMPANY LIMITED Fossway, Newcastle upon Tyne 6, England

Brush for electrical machines

Addition to the main patent ...... (patent application P 19 10 906.9)

The invention relates to a brush for electrical machines with several elements made of a metal jacket and a non-metallic core according to the main patent ..... (patent application P 19 10 906.9).

; .erkoHir;. common carbon, graphite or metal wire brushes are For extraordinarily high current densities in the order of magnitude of

1GGO A / 6, y cm is not suitable for a high relative speed of the brush in relation to the current transfer surface. In particular, the wear resistance of such brushes is too low.

:: It is known from US Pat. No. 3,382,367 to use a Burst © C ^ s to manufacture individual resilient wires, each of which including a tubular metal jacket and one of the metal jacket or the core enclosed by the metal shell consists of graphite or some other lubricant. The lubricant lies in powdered form and is used to weld the wires to the slip ring or another power transmission surface to prevent and to reduce the friction between the moving parts. At the same time, the lubricant ensures for good electrical contact. The tubular metal jacket, dor A0% or an even greater percentage of the transverse

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Makes up the cut surface of the wire, ensures on the one hand the electrical conductivity and on the other hand for the mechanical strength of the wire. Because of the large overall diameter and because of the strength of the metal jacket, such a wire is relatively rigid and stiff and therefore requires a high contact pressure, which results in high wear on the brush wires and the current transmission surface. Furthermore, since a brush is formed by a relatively small number of wires, a noticeable irregularity in the brush current transmission capacity occurs in the absence of a sufficiently good contact between only one or two wires and the current transmission surface.

According to the main patent (patent application P 19 10 906.9) graphite or carbon fiber brushes have already been proposed in which each individual fiber has a metallic coating to increase wear resistance. Contrary to expectations it has been shown that the majority of the current through the metal coating and only a small proportion of the current through the Carbon threads flow when the metallic coating is the entire length every fiber covered. Instead of carbon or graphite threads, you can therefore support the metallic coating use other fibers or threads without noticeably impairing the high current transmission capacity and the good wear resistance the brushing decreases.

The brush described at the beginning is therefore characterized according to the invention in that the non-metallic core has a heat-resistant, fiber is not made of carbon or graphite and that the metal cladding is a on the surface of the fiber deposited metal film is.

With such a brush constructed according to the invention the mechanical properties of the individual brush elements are determined by the non-metallic fibers or threads, which have a high Have strength and flexibility and also very little Have diameter. The contact pressure required is therefore very high

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low, so there is wear and tear on the brushes and the current transmission surface is decreased. Furthermore, the inventive Brush have a larger number of brush elements in a given area, so that despite changes in the contact of the individual elements with the current transmission surface the overall power transmission capability is not impaired becomes, so remains the same.

A preferred embodiment of the invention is based on Figures described.

Fig. 1 is a cross section through one formed in accordance with the invention Brush that on. dragging a moving ladder. ■ · -

Fig. 2 shows an individual element of the brush shown in Fig. 1,

The brush 1 shown in Fig. 1 grinds for the purpose of power transmission on the surface 2 of an electrical conductor 3. In the Conductor 3 can be, for example, a slip ring or the commutator of a dynamo machine. The head 3 can but also an «uninterrupted power rail for an electrically powered vehicle *

The brush 1 contains several brush elements 4, which are essentially touch along their entire length and are held together by a metal housing 5. One from electrically · .conductive Material made braid 6 connects the brush to a terminal or winding of the machine. How it looks Fig. 2 shows, each of the brush elements 4 consists of a non-metallic heat-resistant fiber 7, which is a metallic Has coating 8. The diameter of each fiber is less than 12 x 10 l, and the thickness of the metallic coating is important preferably 0.75 * 10 "" m, but generally never more than a tenth of the diameter of the fiber »

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The fibers or filaments can be made of boron nitride or a heat-resistant one Oxide be made, for example from aluminum oxide or clay. From these materials can, interrelated Threads or fibers of high strength are formed. For this one can apply methods that the method for producing of graphite or carbon filaments and which are described in an article in "The Engineer", Volume 221, Page 815, dated May 27, 1966, entitled "High strength, high modulus, carbon fibers", by W. West, L.N. Philips and V /. Johnston and British Patent 1,110,791. Glass fibers can also be used for the invention Purposes.

The thin metal film can be applied by electroplating or vacuum deposition. The film can be any Consist of metal with good electrical conductivity, for example silver or an alloy with a noble metal, for example silver with another metal, for example copper.

The brushes constructed according to the invention can be used for current densities on the order of 1000 A / 6.5 cm, with the relative movement between the brush and the current transfer surface 5400m / min. The

»Brush wear only 1 cm with a brush grinding distance of 12
10 centimeters. The wear of the current transmission surface moves in the same order of magnitude and is less than

10 1 mm with a relative movement of 3 * 10 cm between the Brush and the power transmission surface.

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Claims (1)

Claim Brush for electrical machines with multiple elements a metal jacket and a non-metallic core according to the Main patent (patent application P 19 10 906.9), characterized in that the non-metallic core is a heat-resistant one Carbon or graphite made fiber and that the Metal jacket is a metal film deposited on the surface of the fiber. BATH 100B 10 / 152S Blank page