GB2291276A

GB2291276A - Connections to brush holders/brush wear and thermal monitoring

Info

Publication number: GB2291276A
Application number: GB9513892A
Authority: GB
Inventors: Wolfgang Dietrich
Original assignee: DIETRICH G GmbH
Current assignee: DIETRICH G GmbH
Priority date: 1994-07-07
Filing date: 1995-07-07
Publication date: 1996-01-17
Anticipated expiration: 2015-07-07
Also published as: GB2291276B; GB9513892D0; DE9410881U1; DE19521702B4; CZ281646B6; CZ176295A3; CZ3414U1; DE19521702A1

Abstract

A ready-wired bridge rocker has brush wear indication and thermal monitoring, the brush ring 1 consisting of a thermosetting, heat-resistant moulded material to which the brush holders are riveted, conductors 4 formed of solid copper billets being connected to the brush holders 2 by upsetting. Brush wear indicators may comprise micro switches Fig 5 or spring contacts Fig 1, 4 having connecting lugs 18 extending into a covered groove (21 Fig 3) on the rear of the ring. The groove also carries connections to the thermal sensor 22 located in a recess below the brush holders (Fig 2). The connections terminate at a plug connector 23, 24 Fig 1. <IMAGE>

Description

BRUSH ROCKER FOR D.C. MACHINES The invention relates to a brush rocker for low voltage d.c. machines, comprising: a brush ring having brush holders; a potential-free brush wear indicator; a thermal circuit breaker for monitoring brush temperature; and electric connections of the brush holders.

It is known to use brush rings of the kind specified made from thermosetting moulding material and having riveted-on or screwed brush holders of cast brass or brass plate. The electric connections of the brush holders, the brush wear device and the device for temperature monitoring, if any, were hitherto assembled integrated in the engine production assembly line. The pole connections between the pairs of brush holders are made via flexible insulated copper wires screwed via cable brackets to the brush holders.

The cables and the cable brackets are spacewasting, the result being shortage of space and increased cost of incorporation in the confined conditions of the engine bearing plate. The indicating device and thermal controller wires, which are of substantially smaller cross-section, are normally attached to the connections of the brush holders by means of cable binders. The brush wear and temperature monitoring devices of the brush rockers are connected to an evaluating apparatus via individual commercially available plug-in connections.

In indicating devices for indicating the wear on carbon brushes, it is possible to use a rammed-in indicating contact (so-called indicating brushes). However, each time the brushes are interchanged the expensive contact is lost, costs being increased correspondingly.

In the case of potential-carrying indicating devices current flowing via the brushes is used as an indicating current. Contact is made via the brush compression springs with resilient contacts attached to the brush ring. The connections between two pairs of contact springs equipped with plug-in tongues are made by means of wires having plug-in receptacles.

In industrial d.c. machines the indicating contact is effected by microswitches. Conventional microswitches are unreliable and were due to the heavy accumulation of dirt and humidity in special applications such as, for example, workshop floor conveying vehicles. The dirt penetrating to the switches renders the sensitive mechanism inoperative. For this reason encapsulated switches can be used, although these should be avoided as far as possible, for reasons of cost.

It is an object of the invention to provide a cheap robust brush rocker completely wired ready for incorporation and having a potential-free brush wear indicator and thermal brush temperature monitor, wherein the monitoring apparatus must be capable of connecting brush wear and temperature monitoring without risk of confusion. The indicating device must be protected against the heavy accumulation of dirt taking place during operation, due to dust and coal dust, as a result of wear on the brushes and humidity. Heat resistance must correspond to insulating material class F=155 C. The connecting wires for the brush holders should extend in a space-saving manner and be advantageously connected to the brush holders, while at the same time ensuring that the carbon brushes can be connected independently.

To solve this problem according to the invention the brush ring consists of a thermosetting, heatresistant moulded material to which the brush holders are riveted, while for the pole connection use is made of conductors of solid copper billets which are connected to the brush holders by upsetting.

Advantageously, contact elements mounted directly in recesses in the brush ring are used as the indicating device for wear indication. The indicating wires for wear indication can be disposed in grooves and in wider recesses, connected via the grooves on the rear side of the brush ring. According to a further feature of the invention the recesses and grooves for receiving the wires of the indicating devices are closed by a one-part cover ring of heat-resistant plastics.

Preferably the indicating wires are connected to the contact elements by folding or crimping.

An indicating device for wear indicating is particularly simple, due to the feature that contact elements are provided which are mounted directly in recesses in the brush ring. The contact elements can be actuated either directly by the brush compression spring via an insulated end, or a two-armed lever mounted on a spindle is provided for the actuation of the contact elements.

If a lever is used, the lever is preferably twoarmed, the load side lever arm being longer than the force side arm. The bearing of the lever on a spindle converts the motion of the unstable flat spiral spring of the carbon brush into a clearly-defined motion for the precision triggering of the indicating contact. The contacts are separated almost abruptly by the lever on geometry, any possible contact flutter being reduced to a minimum.

The brush rocker according to the invention is a compact, handleable construction having an integrated monitoring sensor system, which can be rapidly connected without risk of confusion via a multi-contact plug, and also rigid space-saving brush holder connecting wires without interfering flexible cables or stranded wires.

Another advantage of ready handleability and rapid ready assembly in the bearing plate, the machine manufacturer is relieved of the previous expense of wiring the individual elements. The number of constructional members is reduced, thus enabling warehousing costs to be lowered.

An embodiment of the invention will now be described with reference to the drawings, which show: Fig. 1. The brush ring with brush holders attached thereto, Fig. 2. A cross-section through the brush ring, Fig. 3. The rear side of the brush ring, Fig. 4. An alternative for the brush indicating device having a resilient contact arm actuable by the brush compression spring, in operational positions a and b, and Fig. 5. Further alternatives for the brush indicating device with a microswitch, in operational positions a and b.

Brush holders 2 preferably of brass plate, is disposed on a brush ring 1 of a thermosetting plastic, heat resistant moulded material and riveted to the ring.

By its free end 3a a brush spring 3 produces the necessary contact pressure and thrust force of carbon brushes 30 against commutator 31 of a d.c. machine. Rigid pole connecting wires 4 of bent round copper are provided and covered with an insulating sheath 5 or coated with some other suitable insulating material. The pole connecting wires are connected to the brush holders at positions 6 by upsetting. The rigid round copper wires attached by riveting to the brush holders are clearly-defined in their position, thereby ensuring an adequate insulating distance 7, to form an air gap. An additional insulation 5 acts as a safety device. Wires, disposed freely in the air flow, ensure a satisfactory heat dissipation to the cooling air flowing through the engine.The space-saving construction is suitable for the confined conditions of incorporation in the bearing plate of the d.c. machine, more particularly in the case of engines of workshop floor conveying vehicles, while at the same time facilitating assembly.

A wear indicating device having a two-armed actuating lever 8, a fixed contact 9 and a movable contact spring 10 having a sliding member 11 attached thereto are provided for each carbon brush. In each case a wear indicating device of a pair of brushes is shown in the indicating position with the carbon brush worn, the opposite indicating device being shown in the starting position with the carbon brush renewed. The actuating lever 8 pivotably mounted on the brush holder 2 absorbs via its bearing on a spindle 12 the motion of the unstable flat spiral spring 3 and opens the contact via sliding member 11 when the indicating point is reached.

The lever geometry is so designed that the contacts are separated as rapidly as possible, reduce their flutter to a minimum. This purpose is achieved by a lever load arm which is longer than its force side arm loadable by the brush compression spring. The fixed contact 9 and the resilient contact 10 are inserted and locked directly in slot-shaped recesses 13 (Fig. 3) of the brush ring. This makes it superfluous to produce switches separately which would have to be attached to the brush rocker.

In another embodiment of the indicating device a movable contact spring 14 (Figs. 4a and 4b) having an insulated end member 15 can be provided, the actuating lever being eliminated. The brush compression spring 3 bears directly against the insulated end of the contact spring and opens the contact as soon as the carbon brush 30, due to its wear at the contact end has been pushed to a corresponding distance into the brush holder. Fig.

4 shows re-equipment with the opened brush compression spring.

In the variant illustrated in Figs. 5a and 5b an advantageously encapsulated microswitch 16 is used. In this embodiment actuation is again performed via an actuating lever 8.

The contacts 9 and 10 have projections 17 beneath which connecting lugs 18 of indicating wires 19 engage, being electrically conductively connected thereto in one operation by folding or crimping. The indicating wires 19 are placed in grooves 21 in the rear side of the brush ring. The connecting lugs 18 extend through the corresponding slot-shaped recesses 13 in the brush ring 1 to the lugs 17 of the contacts 9 and 10. The individual input and output wires 19 of the indicating device and the thermal monitor 22 have commercially available round plugs 23 and are accommodated in a common plug casing 24. This technique of plug-in connection ensures a rapid and reliable connection of the entire monitoring sensor system of the engine to the monitoring apparatus by means of the multipole commercially available plug-in connections. The grooves 21 in the rear side of the brush rocker and also further recesses 25 for accessibility to the contacts 9 and 10 and the plug casing 24 are closed with a plastics cover ring 26.

Claims

1. A brush assembly for use in a d.c. machine, which brush assembly comprises a brush ring, at least one brush holder, and a conductor connected to said brush holder, wherein said conductor comprises a solid member which is connected to said brush holder by upsetting.

2. A brush assembly as claimed in Claim 1, wherein a first part of said conductor lies parallel to a portion of said brush holder, a second part of said conductor passes through said portion of said brush holder, and a third part of said conductor is upset so that said brush holder is firmly held between said first and third parts of said conductor.

3. A brush assembly as claimed in Claim 1 or 2, wherein said conductor comprises copper.

4. A brush assembly as claimed in Claim 1, 2 or 3, wherein said brush ring comprises a thermo-setting, heat resistant moulded material.

5. A brush assembly as claimed in any preceding Claim, wherein said brush holder is riveted to said brush ring.

6. A brush assembly as claimed in any preceding Claim, including a thermally actuable circuit breaker.

7. A brush assembly as claimed in any preceding Claim, including a wear sensor which, when a brush is placed in said brush holder and said brush assembly is in use provides an indication when said brush needs replacement.

8. A brush assembly as claimed in Claim 7, wherein said wear sensor comprises at least one contact element which is disposed in a recess in the brush ring.

9. A brush assembly as claimed in Claim 7 or 8, wherein said wear sensor is associated with at least one wire which is disposed in a groove in said brush ring.

10. A brush assembly as claimed in Claim 8 or 9, wherein said wire is provided with a connecting lug and said contact element is provided with a projection for receiving said connecting lug.

11. A brush assembly as claimed in Claim 10, wherein said lug is crimped to said connecting lug.

12. A brush assembly as claimed in Claim 10 or 11, wherein said brush ring is provided with a recess shaped and positioned to facilitate engagement of said connecting lug on said projection.

13. A brush assembly as claimed in any of Claims 9 to 12, including a cover ring of heat-resistant plastic material overlying said groove.

14. A brush assembly as claimed in any of Claims 8 to 13, wherein said wear sensor comprises a lever which has two arms and which is mounted on a pivot.

15. A brush assembly as claimed in Claim 14, wherein the input arm of the lever is shorter than the output arm.

16. A brush assembly as claimed in any of Claims 9 to 15, including a brush in said brush holder, a brush spring for biasing said brush towards a commutator, and a second spring housing an insulated end and which, in use, is displaced by said brush spring when said brush has worn by a certain amount.

17. A brush assembly as claimed in any one of Claims 8 to 16, including a micro switch.

18. A brush rocker for low voltage d.c. machines, comprising: a brush ring having brush holders; a potential free brush wear indicator; a thermal circuit-breaker for monitoring brush temperature; and an electric connection of the brush holders to one another, characterized in that the brush ring (1) consists of a thermosetting, heat-resistant moulded material to which the brush holders are riveted, while for the pole connection use is made of conductors (4) of solid copper billets which are connected to the brush holders (2) by upset ting.

19. A brush rocker according to Claim 18, characterized in that contact elements (9,10) inserted directly into recesses (13) in the brush ring and locked are provided as the indicating device for wear indication.

20. A brush rocker according to Claim 18 or 19, characterized in that indicating wires (19) for wear indication are disposed in grooves (21) and in recesses (25) connected via the grooves on the rear side of the brush ring.

21. A brush rocker according to one of Claims 18 to 20, characterized in that the contact elements (9,10) have projections (17) for receiving connecting lugs (18) of the indicating wires (19).

22. A brush rocker according to Claim 21, characterized in that the projections (17) are connected to the connecting lugs (18) by folding or crimping.

23. A brush rocker according to Claim 21 or 22, characterized in that the connecting lugs (18) are guided to the projections (17) of the contacts (9,10) by slotshaped recesses (13) in the brush ring (1).

24. A brush ring (sic) according to Claim 19 or 20, characterized in that the recesses (25) and grooves (21) for receiving the wires of the indicating devices are closed by a one-part cover ring (26) of heat-resistant plastics.

25. A brush rocker according to one of Claims 18 to 24, characterized in that the indicating device has for the actuation of the contact elements a two-armed lever (8) mounted on a pivot (12).

26. A brush rocker according to Claim 25, characterized in that the load side arm is longer than the force side arm of the lever (8).

27. A brush rocker according to one of Claims 18 to 26, characterized in that one of the contact elements is a spring (14) having an insulated end (15) which can be actuated directly by the brush compression spring (3).

28. A brush rocker according to one of Claims 18 to 27, characterized in that the lever (8) is operatively connected to a microswitch (16) for the indicating device.

29. A brush rocker according to one of Claims 18 to 28, characterized in that the input and output wires (19) of the indicating device and the thermal controller (22) are equipped with commercially available round plugs (23) accommodated in a common plug casing (24) which is screwed to the brush ring.