EP0624937A1 - Carbon brush and process for fixing and mounting a conducting cord thread therein - Google Patents

Abstract

The invention relates to a carbon brush (10) having an indicating braid (26, 28) for indicating a specific amount of wear of the carbon brush. The indicating braid is rammed into a blind hole (30) and is arranged at a distance from the base (32) of the blind hole. In order that unambiguous indication of the amount of carbon brush wear is ensured, the base of the blind hole is covered with a layer (40) consisting of insulating material. <IMAGE>

Description

The invention relates to a carbon brush with a signal wire for indicating a certain consumption of carbon brushes, the signal wire being stamped into a recess, preferably running in the longitudinal direction of the carbon brush, such as a blind bore and spaced apart from the bottom of the recess, insulating material being on the floor.

The invention further relates to a method for arranging and fastening a section of a signaling wire in a carbon brush.

In particular for machines intended for commercial purposes, it is necessary to indicate when the carbon brush is worn to an extent, that a commutator or slip ring of a motor will soon be lifted off by means of a shut-off nipple embedded in the carbon brush. The display is made via a signal wire that comes into conductive contact with the commutator or slip ring.

In order to attempt to cause a signal to appear only when there is a certain amount of wear, a large number of measures are known, but these do not fundamentally ensure that a signal is not triggered via the signaling wire until a predetermined wear is reached.

According to FR-A 2 223 858, it is provided to arrange a signaling wire in a sleeve made of insulating material, which extends at least in regions within a correspondingly adapted recess of the carbon brush. Since the signal wire itself is surrounded by an insulating material, problems can arise when it is clearly arranged in the sleeve.

According to EP 0 232 209 A1, optical conductors are used to detect carbon brush wear, via which light signals are transmitted or received.

A carbon brush for collector motors is known from DE 28 04 547 A1, in which a signaling wire surrounded by an insulating jacket is arranged in a longitudinal bore. In order to position the signaling wire uniquely, suitable adhesive materials must be used. However, especially in the case of jerky bumps, it is not ensured that the signaling wire is not moved.

To avoid these disadvantages, a prefabricated plastic sleeve is provided according to G 84 33 023 U1, which can be inserted into a bore in a carbon brush. The signal wire is then inserted into the plastic part itself. So that the signaling wire remains in the sleeve, it is slotted so that the signaling wire is clamped between the longitudinal halves of the sleeve which can be moved relative to one another when it is introduced into the carbon brush. High accuracy of fit is required to ensure that the sleeve clamps the signal wire. Regardless of this, the sleeve can melt at the high temperatures occurring in carbon brushes, so that an uncontrolled displacement of the signaling wire takes place.

To remedy this, EP 0 512 234 A2 provides that the signaling wire is received by a sleeve made of metal and squeezed with it. This results in a clear position fixing of the signaling wire in the sleeve, which in turn can be clearly fixed in position with a circumferential flange-like edge in a correspondingly adapted bore of the carbon brush. The free end of the signal wire protrudes above the sleeve. The free end of the signal wire is spaced from the bottom of the bore receiving the sleeve in the carbon brush. As a result of this, however, a signal can be triggered prematurely if coal dust reaches the signaling wire when the soil is rubbed off.

Carbon brushes of the type mentioned are also e.g. can be found in DE 41 11 206 A1 or DE-OS 21 32 053. In order to electrically separate the signaling wires from the carbon brush, the former are surrounded at least on the inside or outside by sleeves made of insulating material.

In order to isolate a signaling wire from a carbon brush, it is proposed according to US Pat. No. 4,536,670 that the signaling wire is covered with Teflon. Since Teflon is difficult to glue, the signal wire must be twisted into the blind hole.

In order to fix a signal wire in a carbon brush, one end of the signal wire is inserted into a mini carbon brush according to US Pat. No. 4,636,778, which in turn is surrounded together with the signal wire by an insulating sleeve which is glued into a blind hole in a carbon brush.

The present invention is based on the problem of developing a carbon brush of the type mentioned at the outset in such a way that a signal is only triggered via the signaling wire if wear and tear has occurred to an unacceptable extent, that is to say that an early signal cannot be given. In addition, manufacturing simplifications should be given, but at the same time allow a check, whether the signal wire is properly arranged in the carbon brush.

In terms of the device, the object is essentially achieved in that the insulating material is an inherently rigid insulating layer covering the bottom of the recess. The insulating layer, such as insulating plate or insulating plate, can be fiber material or hard paper, as is e.g. is known from transformer technology and is marketed under the name Pertinax®.

In order to ensure a clear positioning of the signaling wire within the recess, the free end of the signaling wire should touch the insulating layer like the insulating plate, that is to say preferably stand on it.

In order to also ensure that a conductive connection between the signal wire and carbon brush dust originating from the side wall of the recess does not lead to premature signal triggering, according to a further embodiment of the invention it is provided that the signal wire is surrounded laterally by an insulating material as ramming powder, that is to say stamped in by it is. This can be a thermoset or a mixture of thermosets, e.g. are sold under the name Minolite®.

According to a further embodiment of the invention, the signaling wire, namely its core, is arranged within the recess in such a way that there is an equal circumferential distance between the core and the side wall or the bottom of the recess.

In order to ensure defined conditions, the bottom of the recess should run perpendicularly or essentially perpendicularly to its inner wall. In other words, the recess should be a blind hole with a flat bottom surface.

For carbon brushes with larger dimensions (cross-sectional area preferably larger than 10x8 mm²), the signaling wires should be z. B. made of metal sleeves such Crimp sleeves must be enclosed. These can be preassembled on the signaling wires on automatic assembly machines, so that there are no disadvantages in terms of production technology.

The sleeves result in a good fit of the signaling wire in the hole on the one hand and on the other hand a higher mechanical strength is achieved (increase the pull-out strength).

However, the sleeve should end at a distance from the free end of the signal wire. The upper end should advantageously run below the plane spanned by the surface of the carbon brush. However, this is not a mandatory feature.

In order to provide additional protection against uncontrolled loosening of the signaling wire in the recess, according to a further development of the invention, a stripping coating covering the ramming powder is present between the signaling wire and the carbon brush surface.

• Bohren eines Sackloches mit planem oder im wesentlichen planem Boden,
• Einbringen einer den Boden des Sacklochs abdeckenden eigensteifen Isolierschicht wie Isolierplatte,
• gegebenenfalls Vormantage einer die Meldelitze umgebenden Hülse,
• Einführen des Abschnitts der Meldelitze in das Sackloch bis deren Ende die Isolierplatte berührt,
• Einstampfen der Meldelitze mit Isoliermaterial und gegebenenfalls
• Ablacken von Stampfpulver.

A method for arranging and fastening a section of a signaling wire in a carbon brush is characterized by the method steps:

• Drilling a blind hole with a flat or essentially flat bottom,
• Introduction of an inherently rigid insulating layer, such as an insulating plate, covering the bottom of the blind hole,
• if applicable, pre-mount of a sleeve surrounding the signal wire,
• Inserting the section of the signal wire into the blind hole until its end touches the insulating plate,
• Stamping the signal wire with insulating material and if necessary
• Stripping of ramming powder.

In order to adapt the dimensions of the inherently rigid insulating layer, such as insulating plate or insulating plate, to the cross section of the blind bore and on in a simple manner To lay the ground, it is provided that a flat insulating material to be unwound from a roll is passed through the bore and punched out of these insulating plates with a punching tool, the insulating plate or the insulating plate being introduced into the blind hole by means of the punching tool or a stamp . In addition, a matrix can optionally be present between the carbon brush and the insulating material band in order to facilitate the punching out of the insulating plate or the insulating plate.

According to a proposal with its own inventive content, it is also provided that the signaling wire is cut to length by means of a cutting tool such as cable shears, a voltage being applied between the cutting tool and the carbon brush to check the insulated arrangement of the signaling wire section in the blind hole.

These measures can be used to determine whether the signal wire is cut to length, whether it is electrically insulated from the carbon brush or, e.g. there is an electrically conductive connection due to material or assembly errors, which leads to the corresponding carbon brush becoming unusable.

Further details, advantages and features of the invention result not only from the claims, the features to be extracted from them - individually and / or in combination - but also from the following description of a preferred exemplary embodiment which can be seen from the drawing.

Fig. 1

eine erfindungsgemäß ausgebildete Kohlebürste im Schnitt und im Ausschnitt,

Fig. 2

einen Ausschnitt aus der Kohlebürste nach Fig. 1,

Fig. 3

eine Prinzipdarstellung eines Verfahrensschritts zum Anordnen einer Isolierplatte in einem Sackloch und

Fig,. 4

einen Ausschnitt einer weiteren Ausführungsform einer erfindungsgemäß ausgebildeten Kohlebürste.

Show it:

Fig. 1

a carbon brush designed according to the invention in section and cutout,

Fig. 2

1 shows a section of the carbon brush according to FIG. 1,

Fig. 3

a schematic diagram of a method step for arranging an insulating plate in a blind hole and

Fig. 4th

a section of a further embodiment of a carbon brush designed according to the invention.

In the figures, in which the same elements are provided with the same reference numerals, a section of a carbon brush (10) is shown, in which a current-carrying wire (12) and a shut-off nipple (14) are arranged. The shut-off nipple (14) consists of insulating material and is spring-biased in the direction of the longitudinal axis (16) of the carbon brush (12), preferably by means of a helical spring (18).

Both the stranded wire (12) and the shut-off nipple (14) are stamped into powdered-in metal powder (20) or (22). An insulating plate (24), on which the helical spring (18) is supported, can additionally be arranged between the ramming powder (22) covering the shut-off nipple (14) and the end face facing it.

A section (26) of a signaling wire (28) also runs inside the carbon brush (10), via which a signal is then triggered when the carbon brush (10) interacting with a commutator or slip ring (not shown) is worn to the extent that a Renewing is necessary, that is, before the carbon brush (10) is consumed to such an extent that the shut-off nipple (14) lifts the carbon brush (10) off the slip ring or the commutator.

The signaling wire (28) is arranged in a blind hole (30) running essentially parallel to the longitudinal axis (16), the bottom surface (32) of which is flat, that is to say perpendicular or essentially perpendicular to the inner wall (34) of the blind hole (30). runs.

In order on the one hand to ensure that the section (26) of the signaling wire (28) is clearly fixed in position and on the other hand to exclude that when the commutator or slip ring rubs off the base (32), coal dust creates a conductive connection between the carbon brush (10) and the signaling wire ( 28), d. H. for its conductive core (36), which is surrounded by an insulating jacket (38), the bottom surface (32) is covered with an insulating plate or plate (40), which e.g. can consist of fiber material or hard paper. The free end (42) of the core (36) stands on the insulating plate (40).

The insulation jacket (38) surrounding the core (36) can extend to the surface of the insulating plate or be stripped at a distance from it, as is illustrated in principle with reference to FIG. 1.

The circumference of the section (26) is stamped in, namely by an insulating stamped powder, which is or may contain a thermoset. A material sold under the name Minolite® can preferably be used.

2, the cross section of the blind hole (30) is matched to the cross section of the core (36) of the section (26) of the signaling wire (28) surrounding the insulation jacket (38) and the thickness ( b) the insulating plate (40) chosen so that these and the distance (a) between the core (36) and the inner surface of the blind hole (30) are the same.

After the section (26) is stamped into the blind hole (30), the stamped powder (34) is covered on the outside with a coating (44) which extends from the surface of the carbon brush (10) to the outside of the insulation jacket (38).

In order to match the insulating plate (40) to the cross-section of the bottom (32) of the blind hole (30) in a simple manner and to lay it thereon, an insulation tape which is to be unwound from a roll is placed over the blind hole opening as shown in FIG. 3 in principle (46) moved in order to be punched out directly above the blind hole (30) by means of a punching tool (48) and to be pushed into the blind hole with the punching tool (48). A support (50) can be provided between the carbon brush (10) and the insulating tape material (46) for support.

The signal wire (28) itself is also unwound from a roll and cut to the desired length. This takes place after the section (26) has been stamped into the blind hole (30). During the cutting, a voltage of z. B. 500 V, which is measured against the carbon brush (10). If the section (26) is insulated in the blind hole (30), no conductive connection between the cutting tool (48) and the carbon brush (10) may be determined. This measure results in a quality control which takes place simultaneously with the assembly of the carbon brush (10) with the signaling wire (28).

The diameter of the blind hole (30) can e.g. 2.5 mm at a height of 5.3 mm. Typical dimensions for the cross section of the signaling wire (28) including the insulation jacket (38) are approximately 1.1 mm, the insulation jacket (38) having a thickness in the range between 0.125 and 0.25 mm. The thickness (b) of the insulation plate (40) and thus the distance (a) between the core (36) of the signaling wire (28) and the inner wall (34) of the blind hole (30) can be in the range of approximately 0.7 mm .

Regarding the insulation jacket (38), it should be noted that this should consist of, for example, a polyester elastomer, Teflon or another temperature-resistant insulation. The paint finish (44) should be a two-component adhesive based on epoxy resin.

4 shows an embodiment of the teaching according to the invention to the extent that the signaling strand section (26) within the blind hole (30) is surrounded by a sleeve (50), preferably made of metal, such as a crimp sleeve.

The crimp sleeve (50) ends at a distance from the free end (42) of the section (26) of the signaling wire (28). The outside of the sleeve should also be completely surrounded by ramming powder. This means that the upper edge (52) is covered by ramming powder, that is to say runs below the plane spanned by the surface of the carbon brush (10).

The sleeve results on the one hand in a good fit of the signaling wire (28) in the blind hole (30) and on the other hand a higher mechanical strength is achieved, i. H. the pull-out strength is increased.

Surrounding the signaling strand section (26) with the sleeve (50) should be of larger dimensions, particularly in the case of carbon brushes. These are those which have cross-sectional areas of preferably 10x8 mm² or more.

Claims (12)

Carbon brush (10) with a signaling wire (26, 28) for indicating a certain consumption of carbon brushes, the signaling wire being stamped into a recess (30), preferably in the longitudinal direction (16) of the carbon brush, like a blind hole and spaced apart from the bottom (32) of the recess ,
with insulating material on the floor
characterized,
that the insulating material is a self-rigid insulating layer (40) covering the bottom (32) of the recess (30). Carbon brush according to claim 1,
characterized,
that the insulating layer such as insulating plate (40) or insulating plate made of fiber material or hard paper. Carbon brush according to claim 1 or 2,
characterized,
that the signal wire (26, 28) with its free end (42) touches the insulating layer (40) or stands on it. Carbon brush according to at least one of the preceding claims,
characterized,
that the signal wire (26, 28) is stamped into the insulating material on the side as ramming powder. Carbon brush according to at least one of the preceding claims,
characterized,
that the thickness (b) of the insulating layer (40) is equal to the distance (a) between the outside of the core (36) of the signaling wire (26, 28) and the inner wall of the recess (30). Carbon brush according to at least one of the preceding claims,
characterized,
that the ramming powder and the material of the insulating layer (40) have the same or almost the same specific resistances. Carbon brush according to at least one of the preceding claims,
characterized,
that between the signal wire (28) and the carbon brush surface there is a stripping (44) covering the powder. Carbon brush according to at least one of the preceding claims,
characterized,
that the section (26) of the signaling wire (28) is surrounded by a sleeve (50), preferably made of metal, such as a crimp sleeve, the sleeve being preferably completely surrounded on the outside and on the edge by ramming powder. A method for arranging and fastening a section of a signal wire in a carbon brush comprising the method steps - drilling a blind hole with a flat or essentially flat bottom, Introduction of an insulating layer covering the bottom of the blind hole, Inserting the section of the signal wire into the blind hole until its end touches the insulating plate, - Stamp the signal wire with insulating material and, if necessary - Destruction of the ramming powder of the signal wire. Method according to claim 9,
characterized,
that the signal wire is at least partially surrounded in its section to be inserted into the blind hole by a sleeve before insertion into the blind hole. Method according to claim 9,
characterized,
that a flat insulating material to be unwound from a roll is guided over the blind hole and the insulating plate is punched out directly above the blind hole with a punching tool in such a way that the insulating plate is subsequently introduced into the blind hole by means of the punching tool or a part thereof. Method according to at least one of the preceding claims,
characterized,
that the signaling wire is cut to length by means of a cutting tool, a voltage being applied between this and the carbon brush to check the insulated arrangement of the signaling wire section in the blind hole.

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