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(11) | EP 0 072 693 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Electrical brushes Elektrische Bürsten Balais électriques |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] This invention relates to an electrical brush having a brush wear sensor in the form of a loop of insulated electrical conductor within the brush body and also relates to a method of anchoring a brush wear sensor in an electrical brush body.
[0002] United States Patent Specification No. 3153164 (R.M. JOPP) discloses a method of anchoring a flexible conductor in an electrical brush body. The specific method being the use of a button 21 to secure a loop 17 of a shunt or pigtail 16 in a recess 13, the shunt or pigtail loop being passed down a single passage 15 (see column 2 lines 17 to 28 of the specification).
[0003] However, in contradistinction to the electrical continuity necessary between conductor and brush, a wear sensor lead has to be insulated from the conductive brush body. In the high temperature conditions experienced by heavy duty or heavy current brushes, difficulty is experienced in anchoring the necessary high temperature insulators which are based on materials such as polymers of fluoroethylene. These high temperature insulators have a smooth, generally inert surface that cannot be simply bonded in the brush body to anchor the sensor.
[0004] It is an object of the present invention to overcome the aforesaid difficulty of anchoring sensor leads in a brush body.
[0005] According to the present invention an electrical brush has a brush wear sensor in the form of a loop of insulated electrical conductor provided in a bore in the brush body leading from an upper surface thereof to a depth equivalent to the point at which brush wear is to be sensed, whereby a pair of fine bores lead from the brush upper surface to meet a transverse hole in a side face of said brush body at said wear depth, and a respective arm of said wear sensor loop lies in a respective one of said fine bores with the inner end of said sensor looping from one of said fine bores to the other of said fine bores via said transverse hole. The transverse hole may be filled with an epoxy resin cement or the like.
[0006] The invention is also directed to a method of anchoring a brush wear sensor in an electrical brush comprising the steps of:-
i) forming a transverse hole in a side face of the brush body at a depth (d) equivalent to the point at which brush wear is to be sensed;
ii) drilling an upper surface of said brush body to form a pair of said fine bores that meet said transverse hole;
iii) inserting the free ends of the arms of a loop of insulated electrical conductor into said transverse hole and passing each of said free ends through a respective one of said fine bores;
[0007] whereby a brush wear sensor is formed by the loop that is anchored in the brush body by virtue of its looping from one fine bore to the other via the transverse hole.
[0008] The invention is illustrated by way of example in the drawings, wherein:-
Fig. 1 is a side elevation of a brush in accordance with the invention, and
Fig. 2 is a front elevation of the brush of Fig. 1.
[0009] As shown, a brush 1 has a pair of silastomer sleeved flexible current shunts 2 and 3 located by tamped copper powder connections in the top 4 of the brush.
[0010] Two fine bores 5 and 6 are drilled from the brush top 4, close to the side 7, and angled towards one another to converge at a short hole 8 drilled transversely from the side 7. Transverse hole 8 is drilled at a depth dfrom the brush top 4 at which it is desired to sense brush wear.
[0011] A brush wear sensor 9 in the form of a lead or conductor insulated with TEFLON (Trade Mark) is made into a loop of which the two arms 10 and 11 are each fed into one of the bores 5 and 6 via the transverse hole 8. The sensor arms are twisted together above the brush and the free ends are connected to a terminal 12. This construction has the advantage of ease of assembly as the lead ends are simple to insert through the transverse hole 8 into the bores 5 and 6. Also the wear depth d can be set accurately, as it is a combination of the siting of hole 8 and the protrusion into the hole of the loop end 13.
i) forming a transverse hole (8) in a side face (7) of the brush body (1) at a depth (d) equivalent to the point at which brush wear is to be sensed;
ii) drilling an upper surface (4) of said brush body to form a pair of said fine bores (5, 6) that meet said transverse hole;
iii) inserting the free ends (10, 11) of the arms of a loop of insulated electrical conductor into said transverse hole and passing each of said free ends through a respective one of said fine bores;
whereby a brush wear sensor (9) is formed by the loop (13) that is anchored in the brush body by virtue of its looping from one fine bore to the other via the transverse hole.
i) twisting said sensor loop arms (10, 11) together above said brush body upper surface (4); and
ii) connecting said sensor loop free ends to a terminal (12).
i) on ménage un canal transversal (8) dans une face latérale (7) du corps de balai (1), à une profondeur (d) équivalant au point où l'usure du balai doit être détectée,
ii) on fore dans une surface supérieure (4) du corps de balai pour former deux fines forures (5, 6) qui débouchent dans le canal transversal,
iii) on introduit les extrémités libres (10, 11) des branches d'une boucle de conducteur électrique isolé dans le canal transversal et on fait passer chaque extrémité libre par une des fines forures qui y correspond,
étant entendu qu'un détecteur d'usure de balai (9) est formé par la boucle (13) qui est ancrée dans le corps de balai grâce à son passage en boucle d'une fine forure à l'autre par l'intermédiaire du canal transversal.
i) on commet les branches (10, 11) de la boucle de détecteur au-dessus de la surface supérieure (4) du corps de balai, et
ii) on connecte les extrémités libres de la boucle de détecteur à une borne (12).
(i) ein Querloch (8) in einer Seitenfläche (7) des Bürstenkörpers (1) in einer Tiefe (d) ausgebildet wird, welche dem Punkt entspricht, an welchem ein Bürstenverschleiss zu erfassen ist, dass
(ii) in einer oberen Fläche (4) des Bürstenkörpers gebohrt wird, um ein Paar enger Bohrungen (5, 6) auszubilden, die auf das Querloch treffen, und dass
(iii) die freien Enden (10, 11) der Arme einer Schlaufe eines isolierten elektrischen Leiters in das Querloch eingesetzt werden und die beiden freien Enden durch je eine der engen Bohrungen geführt werden, so dass ein Bürstenverschleisssensor (9) durch die Schlaufe (11) gebildet wird, welche im Bürstenkörper aufgrund ihres Verlaufes von einer engen Bohrung zur anderen über das Querloch verankert ist.
(i) die Sensorschlaufenarme (10, 11) oberhalb der oberen Fläche (4) des Bürstenkörpers zusammengedreht werden und dass
(ii) die freien Enden der Sensorschlaufe mit einem Anschluss (12) verbunden werden.