GB1566773A

GB1566773A - Brush holder for electric machines

Info

Publication number: GB1566773A
Application number: GB38978/77A
Authority: GB
Original assignee: Lucien Ferraz et Cie SA
Current assignee: Lucien Ferraz et Cie SA
Priority date: 1976-09-17
Filing date: 1977-09-19
Publication date: 1980-05-08
Also published as: JPS5344807A; FR2365226A1; DE2741875C2; FR2365226B1; DE2741875A1; SE7710396L; IT1084748B; SE431044B; CH616535A5

Description

(54) A BRUSH HOLDER FOR ELECTRIC MACHINES (71) We, LUCIEN FERRAZ & CIE, a French Sociétë Anonyme, of 28, rue Saint Philippe, 69003 Lyon, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to brush holders in which the pressure spring is composed of a resilient band tending to wind about itself (self-winding spring), the wound portion bearing against the brush, while the outer end is fixed to an easily removable part of the cage of the brush holder in question.

In certain known constructions the removable part carrying the self-winding spring is folded over in the form of a resilient clip in such a manner as to clip into an inner longitudinal groove of the cage of the brush holder but to be able to be released there from and bent over laterally. An arrange ment of this kind is entirely satisfactory to the user, but it considerably complicates the formation of the cage and therefore entails a high cost price. Furthermore, the clip in question is held by a transverse pin and therefore can be replaced only by removing this pin. An arrangement has also been pro posed in which the brush holder part is in the form of a bipod engaging in the cage.

An arrangement of this kind hides the brush and hinders the inspection and replacement of the latter. In addition, it is cumbersome.

Finally a brush holder part is sometimes used which comprises a single branch engag into in the corresponding cage through the reaction of the spring itself. This arrange neat is simple; it entails no complication of the shape of the cage or of the dimensions of the brush holder; the part in ques bon is easily removable and interchangeable.

These indisputable advantages are neverthew less offset by the unacceptable disadvantage thit the part is held in position moldy by the reaction of the spring, so that if the latter break or lose its resilience tbe part will simply fall into the electric ohine, ich obviotidy gives rise to serious danger.

The invention seeks to permit the construction of a brush holder in which the movable part carrying the self-winding pressure spring is held engaged in the corresponding cage of the brush holder independently of the reaction of the pressure spring, so that in the event of the complete failure of the spring the part in question will remain in position and there will be no danger of its falling accidentally into the machine.

The invention further seeks to make this part with a single branch so that it can be produced at a particularly low cost price from a band or strip of metal by simply cutting out, punching, and drawing.

In connection with a spring holder part of the kind in question one embodiment of the invention further seeks to form the elementary cage and/or the entire brush holder itself from an extruded section which is symmetrical on two axes, so as to provide the user with a large selection of possible arrangements of the case or brush holder in relation to their support.

As an alternative, the invention also seeks to make it possible to form a brush holder by the simple shaping of a metal band, in contrast to known arrangements of the kind in question which are generally produced by casting with or without injection pressure.

According to the present invention, there is provided a brush holder for electric machines, the holder comprising a cage and a detachable clip, the cage being arranged to slidably accommodate a brush and having a longitudinal groove provided in one of the inner walls thereof, the clip having a central leg, a self-winding band spring being fixed at its outer end to the central leg, the wound portion of the spring being adapted to bias, in operation, the associated brush, the central leg being engaged slidably in said groove; the clip including engaging means for retaining the clip in the longitudinal direction against the reaction of the spring and two side legs arranged to bear resiliently against the outer face of the cage on each side of the groove.

The central leg is preferably made substantially more rigid than the side legs, so as to lie very flat against the bottom of the corresponding depression. For this purpose it may be provided with side edges raised at right angles.

The means adapted to secure the brush holder part after it has been completely driven into the cage may consist of a raised tongue incompletely cut out of the central leg of the part and a corresponding opening provided in the bottom of the aforesaid depression.

According to another optional feature of the invention a brush holder cage adapted to receive a brush holder part of the kind described above is simply cut out from a hollow cross-shaped section of which at least one arm forms the depression receiving the central leg of the part, the side legs of the latter projecting on each side of the said arm and bearing resiliently against the side walls of the two adjacent arms. This section preferably has two axes of symmetry so that the brush holder part can be engaged in either of two oppositely situated depressions.

The bottoms of these depressions are then cut out to form an aperture serving at will either to receive the securing tongue of the spring holder part or to permit the passage of a bolt or rivet for fastening the cage to a support. The section selected may obviously be entirely symmetrical so as to form four identical depressions adapted to receive the spring holder part.

In a modified embodiment the cage in question is made by folding a metal band, which can moreover thus form a plurality of successive cages of cross-shaped profile having one or two axes of symmetry as the case may be, the ends of this band being fixed by welding or otherwise to a base plate adapted to be fixed in turn by screws, bolts, or the like inside the machine concerned.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a side view of a brush holder cage to which the present invention is applied, Figure 2 is a longitudinal section thereof, Figure 3 is a plan view of the cage shown separately, Figure 4 shows in perspective the spring holder part or clip, Figure 5 illustrates how cages according to Figures 1 to 3 can be mounted between two longitudinal members in order to form a multiple rigid brush holder, Figure 6 is . a plan view ofa modified construction of a brush holder according to the irivention, and Figure 7 is a cross-section of a modification -of the arrangement shown in Figure 5.

The embodiment shown in Figures 1 to 4 comprises a cage I having a hollow cross shaped transverse profile (see Figure 3) which is symmetrical with respect to two planes A-A and B-B which are perpendicular to one another. The arms la, lb, ic and id of this profile form four internal rectangular depressions, namely a pair of identical depressions, le, Ig and a pair of identical depressions If, Ih. Elongated windows li, Ij are cut out of the bottoms of two opposite depressions le and Ig. In addition, the outer face of the bottom of the depression ig is provided with transverse grooves lk.

The two opposite depressions 1k and Id delimit the ends of a rectangular space in which a brush 2 is slidable, the brush being intended to bear against a rotating element 3, such as for example a commutator. Pressure is applied to this brush by a self-winding band type spring 4 the loop 4a which acts on the head of the brush, which is suitably shaped for the purpose. In the example illustrated the head of the brush has a depression 2a formed in it for the purpose of centering the loop 4a, but the head could also be in the form of an inclined plane in known manner.

The free end of the spring 4 is fixed bv a rivet 5 (Figure 2) to the end of the central leg 6a of a spring holder part or clip 6. This leg 6a is provided with raised side edges 6b giving it great rigidity. It is engaged in the depression le, the aforesaid edges 6b bearing against the bottom of the depression.

thus forming the space necessary to receive the head of the fastening rivet 5. A tongue 6c is also cut out incompletely by punching from this leg 6a, this tongue 6c being directed obliquely and forming a tooth engaging against the opposite end of the window li to that where the rotating element 3 is disposed.

The leg 6a (Figure 4) is surrounded with suitable clearance by two side legs 6d which bear resiliently against the outer side faces of the arms lb and Id adjacent the arm la which delimits the depression le receiving the rigid central leg 6a. It will be understood that in these circumstances the part 6 thus forms a kind of three-branched clip which clips against the bottom of the depression le independently of the reaction of the spring 4 acting on it.

The part 6 is exfended above the legs 6a 6d by a portion 6e which forms a common base for the said legs, and then by a narrower lug 6f which is curved above the loop 4a (the latter being assumed to be in its highest position).

The part 6 is thus held in place reliably even if the spring 4 should break or for any reason cease to apply the intended reaction to the part 6. Consequently, it cannot in any circumstances be accidentally released from the cage. -It - is placed in position almost instantaneously: it is sufficient to engage the central leg 6a in the depression le, taking care to leave the other two legs outside the cage. Similarly, when it is desired to remove it, it is sufficient to push the lug 6f towards the right in Figures 1 and 2 so as to release the tongue 6c. The second window lj can be used for the passage of a bolt 7 or the like making it possible to fix the cage against a support having a knurled surface, such as that indicated at 8.

The depressions le and ig are interchangeable as regards the fastening of the part or clip 6, which means that if it is desired to dispense with any grooved or knurled bearing surface it is possible to place this clip on the right in Figures 1 and 2, the cage being fastened on the left.

It is important to note that the cage 1 has a very simple cross-sectional profile which is continuous from one end to the other. It can therefore be produced by cutting out from a hollow section of great length, or even continuously extruded, the grooving and the cutting-out of the windows being effected during the cutting. It is thus possible to achieve extremely low cost prices which are considerably lower than those of the cages at present produced by moulding.

The device according to Figures 1 and 2 permits the construction of brush holders having one or more cages. It is in particular possible to use an arrangement according to which complete cages, that is to say cages containing their brush and the system applying pressure to the latter, are mounted in the style of braces between two longitudinal members so as to form, together with the latter, a light but very rigid compound beam.

An arrangement of this kind intended for two cages is shown by way of example in Figure 5, but extrapolation would obviously be possible in the case of three or more cages. At 9 can be seen the two flat longitudinal members with their ends 9a folded over at right angles to constitute a fastening lug. The two cages 1 are connected to the members 9 by means of rivets 10 whose heads are of slight height so as not to obstruct the positioning of the central leg of the spring holder part or clip (not shown).

Pins 11 permit the fastening of the usual braids associated with the brushes. The transverse walls of the two cages 1 which are in contact may optionally be welded to one another in order to improve rigidity.

In order to permit the engagement of the retaining tongue 6c of each clip it is sufficient to provide a hole such as 9b in one of the longitudinal members 9 and in the adjacent wall of each cage.

Figure 6 shows a modified embodiment in which one or more cages intended to receive spring holder parts according to the invention are formed by folding from the same metal strip 12 so as to constitute two successive projections 12a, 12b with corresponding internal depressions 12c, 12d adapted to receive a part or clip of the kind given the reference 6 in Figures 1 to 3. The strip is then folded over twice at 90" so as to form a generally U-shaped profile, the free ends of the branches of this U being folded over at 900 to form fastening lugs 12e. Another piece of strip 13, folded over to form a narrower and much shorter U, closes the outlet of the other U-shaped profile, the ends of its branches being folded over at 13a to coincide with the lugs 12e. The bottoms of the depressions 12c, 12d are perforated at 12f, 12g in order to enable the spring carrier clip to be clipped in position.

In the arrangement shown in Figure 6 the two brushes, which have been shown in section at 2a and 2b are in contact with one another, because there is no separating partition.

The brush holder shown in Figure 6 could obviously contain only a single brush, or on the contrary be arranged to receive more than two brushes, if desired.

It will be noted that in the arrangement shown in Figure 6 the double cage is not symmetrical in relation to its longitudinal axis, so that the clips can be mounted only on one of its sides. However, it will be readily be understood that symmetry could be respected if so desired.

Figure 7 shows in section a modified detail of the arrangement shown in Figure 5. Here again are seen the two longitudinal members 9 with their fastening lugs 9a, a cage 1, and its rivets 10 for fastening it to the longitudinal members 9. Here, however, holes 11 and 9e, facing one another, are provided in the longitudinal members and in the cages in order to receive bolts 14 which are fastened in position by nuts 15, their ends projecting on the outside serving the purpose of the pins 11, which are here not provided. The user can thus place the connecting braids on the side which seems to him more convient, and in addition the operation of welding the pins 11, which is always a little difficult, is avoided.

WHAT WE CLAIM IS:- 1. A brush holder for electric machines, the holder comprising a cage and a detachable clip, the cage being arranged to slidably accommodate a brush and having a longitudinal groove provided in one of the inner walls thereof, the clip having a central leg, a self-winding band spring being fixed at its outer end to the central leg, the wound portion of the spring being adapted to bias, in operation, the associated brush, the central leg being engaged slidably in said groove, the clip including engaging means for retaining the clip in the longitudinal direction against the reaction of the spring and two side legs arranged to bear resiliently against the outer

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cage. Similarly, when it is desired to remove it, it is sufficient to push the lug 6f towards the right in Figures 1 and 2 so as to release the tongue 6c. The second window lj can be used for the passage of a bolt 7 or the like making it possible to fix the cage against a support having a knurled surface, such as that indicated at 8. The depressions le and ig are interchangeable as regards the fastening of the part or clip 6, which means that if it is desired to dispense with any grooved or knurled bearing surface it is possible to place this clip on the right in Figures 1 and 2, the cage being fastened on the left. It is important to note that the cage 1 has a very simple cross-sectional profile which is continuous from one end to the other. It can therefore be produced by cutting out from a hollow section of great length, or even continuously extruded, the grooving and the cutting-out of the windows being effected during the cutting. It is thus possible to achieve extremely low cost prices which are considerably lower than those of the cages at present produced by moulding. The device according to Figures 1 and 2 permits the construction of brush holders having one or more cages. It is in particular possible to use an arrangement according to which complete cages, that is to say cages containing their brush and the system applying pressure to the latter, are mounted in the style of braces between two longitudinal members so as to form, together with the latter, a light but very rigid compound beam. An arrangement of this kind intended for two cages is shown by way of example in Figure 5, but extrapolation would obviously be possible in the case of three or more cages. At 9 can be seen the two flat longitudinal members with their ends 9a folded over at right angles to constitute a fastening lug. The two cages 1 are connected to the members 9 by means of rivets 10 whose heads are of slight height so as not to obstruct the positioning of the central leg of the spring holder part or clip (not shown). Pins 11 permit the fastening of the usual braids associated with the brushes. The transverse walls of the two cages 1 which are in contact may optionally be welded to one another in order to improve rigidity. In order to permit the engagement of the retaining tongue 6c of each clip it is sufficient to provide a hole such as 9b in one of the longitudinal members 9 and in the adjacent wall of each cage. Figure 6 shows a modified embodiment in which one or more cages intended to receive spring holder parts according to the invention are formed by folding from the same metal strip 12 so as to constitute two successive projections 12a, 12b with corresponding internal depressions 12c, 12d adapted to receive a part or clip of the kind given the reference 6 in Figures 1 to 3. The strip is then folded over twice at 90" so as to form a generally U-shaped profile, the free ends of the branches of this U being folded over at 900 to form fastening lugs 12e. Another piece of strip 13, folded over to form a narrower and much shorter U, closes the outlet of the other U-shaped profile, the ends of its branches being folded over at 13a to coincide with the lugs 12e. The bottoms of the depressions 12c, 12d are perforated at 12f, 12g in order to enable the spring carrier clip to be clipped in position. In the arrangement shown in Figure 6 the two brushes, which have been shown in section at 2a and 2b are in contact with one another, because there is no separating partition. The brush holder shown in Figure 6 could obviously contain only a single brush, or on the contrary be arranged to receive more than two brushes, if desired. It will be noted that in the arrangement shown in Figure 6 the double cage is not symmetrical in relation to its longitudinal axis, so that the clips can be mounted only on one of its sides. However, it will be readily be understood that symmetry could be respected if so desired. Figure 7 shows in section a modified detail of the arrangement shown in Figure 5. Here again are seen the two longitudinal members 9 with their fastening lugs 9a, a cage 1, and its rivets 10 for fastening it to the longitudinal members 9. Here, however, holes 11 and 9e, facing one another, are provided in the longitudinal members and in the cages in order to receive bolts 14 which are fastened in position by nuts 15, their ends projecting on the outside serving the purpose of the pins 11, which are here not provided. The user can thus place the connecting braids on the side which seems to him more convient, and in addition the operation of welding the pins 11, which is always a little difficult, is avoided. WHAT WE CLAIM IS:-

1. A brush holder for electric machines, the holder comprising a cage and a detachable clip, the cage being arranged to slidably accommodate a brush and having a longitudinal groove provided in one of the inner walls thereof, the clip having a central leg, a self-winding band spring being fixed at its outer end to the central leg, the wound portion of the spring being adapted to bias, in operation, the associated brush, the central leg being engaged slidably in said groove, the clip including engaging means for retaining the clip in the longitudinal direction against the reaction of the spring and two side legs arranged to bear resiliently against the outer

face of the cage on each side of the groove.

2. A brush holder according to Claim 1, wherein the central leg is substantially more rigid than the two side legs.

3. A brush holder according to Claim 2, wherein the central leg has side edges raised at right angles.

4. A brush holder according to Claim 3, wherein the raised edges are directed towards the bottom of the groove.

5. A brush holder according to any of the preceding claims, wherein the engagement means for securing the central leg comprise a tongue raised by incomplete cutting out from the leg and engageable in an aperture provided in the bottom of the groove.

6. A brush holder according to any of the preceding claims, comprising at least one cage with a hollow cross-shaped section having four arms at least one of which forms the longitudinal groove which has the form of a depression adapted to receive the central leg of the clip, the side legs of the clip projecting on each side of the arm so as to bear resiliently against the side walls of the two adjacent side arms.

7. A brush holder according to Claim 6, wherein the cross-shaped section of the cage is symmetrical with respect to two planes of symmetry perpendicular to one another, in such a manner that the clip can be engaged as desired in either of two longitudinal grooves facing one another, the bottoms of both the grooves being perforated so as to receive respectively the engagement means of the clip or a suitable fastening member.

8. A brush holder according to any of the preceding claims wherein, the or each cage is formed with thin metal walls whose profile in a plane transverse to the displacement of the brush or brushes at least partly surrounds the latter and has at least one groove adapted to receive a spring holder clip and, wherein the or each cage comprises a first portion having a U-shaped transverse profile, in the side branches of which the depressions are formed, the ends of the said branches being folded over to form fastening lugs, and a second portion likewise having a U-shaped transverse profile and closing the outlet of the first portion so as to form a member retaining the brush or brushes, the second portion also having ends folded over in the form of fastening lugs and superimposed on the folded-over end of the first portion.

9. A brush holder for electric machines substantially as herein described with reference to and as shown in Figures 1 to 4, Figure 5, Figure 6 or Figure 7 of the accompanying drawings.