GB1585340A

GB1585340A - Electrical brush apparatus

Info

Publication number: GB1585340A
Application number: GB21314/78A
Authority: GB
Original assignee: Towmotor Corp
Current assignee: Caterpillar Industrial Inc
Priority date: 1977-10-26
Filing date: 1978-05-23
Publication date: 1981-02-25
Also published as: FR2407584B1; ES474555A1; CA1109514A; SE7810405L; FR2407584A1; DE2846082A1; DE2846082C2

Description

(54) ELECTRICAL BRUSH APPARATUS (71) We, TOWMOTOR CORPORA TION, a corporation organized and existing under the laws of the State of Ohio, United States of America, of 7111 Tyler Boulevard, Mentor, Ohio 44060, United States of America, 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: Electrical machinery, such as direct current motors for example, use brushes for transferring power between an electric circuit and commutator. The brushes are in contact with the rotating commutator and, during use, wear and erode from such contact. The brushes must be replaced when sufficiently worn to prevent damage to the commutator and ensure efficient power transfer. Current devices can signal when the brushes are sufficiently worn to need replacing but usually interfere with the movement or useability of the brush.

It is desirable to have a device which signals when the brushes have been substantially come pletely worn away and does not interfere with the movement of the brush. By so utilizing substantially the entire brush there is an avoidance of waste.

According to the present invention, an electrical apparatus comprises a brush having first and second ends which approach one another, in use, in response to wear at the second end of the brush; first and second electrical contactors movable one relative to the other between an open position and a closed position, the contactors being moved relatively from one of the open and closed positions toward the other of the open and closed positions in response to wear of the second brush end under the control of biasing means which urges the brush in a direction from the first end towards the second end and allows a resilient contactor mounting to cause movement of a selected one of the first and second contactors in response to wear of the brush, the biasing means being in contact with one of the first and second contactors and in contact with the first end of the brush, and the brush being substantially free for longitudinal movement independently of the position of the contactors and biasing means in response to wear.

Two examples of apparatus constructed in accordance with the invention are illustrated in the accompanying drawings, in which: FIG. 1 is a diagrammatic, longitudinal cross section of one apparatus; FIG. 2 is a diagrammatic view similar to FIG. 1; FIG. 3 is partial front view of the FIG. 1 apparatus; FIG. 4 is an isometric view of another apparatus; FIG. 5 is schematic illustration of an electrical circuit associated with the apparatus; and, FIG. 6 is a simplified top view taken on the line VI-VI in FIG. 1.

Referring to FIG. 1, an electric machine, such as a direct current motor 10 for example, has a rotatable commutator 12 and a brush 14. The brush 14 transfers power between the commutator 12 and a power source or electric circuit 16.

The brush 14 has a first end 20 adjacent the power source 16 and a second end 18 adjacent the commutator 12. The first end 20 is movable in response to wearing away of the brush from a first position at which the first and second ends 20, 18 are spaced a preselected distance one from the other to a second position at which the first end 20 is displaced toward the second end 18. The brush 14 is preferably of a uniform composition throughout, such as graphite, for example. The ends 18, 20 are preferably sub stantially coincident at the second position and are limited in movement between the first and second positions only by connection of the first end 20 to the power source 16.

The brush 14 interacts with first and second contactors 22, 24 which are movable one relative to the other between an open position and a closed position. The contactors 22, 24 controllably move from one of the open and closed positions toward the other of the open and closed positions in response to wear and resultant movement of the first end 20 of the brush 14.

The first and second contactors 22, 24 form a path for current flow which is interrupted when the contactors 22, 24 move toward the open position.

Referring to Figure 5, an indicating apparatus 28, such as a lamp for example, is connected to the first and second contactors 22, 24 and forms an electric circuit 30. The lamp 28 preferably lights when the contactors 22, 24 are in the closed position to indicate a predetermined amount of wear of the brush 14. A thyristor 31 or similar device can be connected to the lamp 28 and contactors 22, 24 to achieve greater control of the circuit 30.

The brush 14 is biased by the biasing means 32, which in this example is a roll spring.

The spring 32 urges the brush 14 in a direc tion toward the commutator 12, and causes movement of a selected one of the first and second contactors 22, 24, in this case the first contactor 22, in response to wear of the brush 14, by reduction of the bias against a leaf spring on which the selected one of the contactors is mounted. The spring 32 is preferably in contact with the first contactor 22, and it also contacts the first end 20 of the brush 14. The brush 14 is substantially free of restricted contact with the spring 32 and contactors 22, 24 during movement of the end 20 of the brush 14 between the first and the second positions. The brush 14 is sub stantially free for movement in a direction towards the commutator 12 independently of the contactors 22, 24 and the biasing means 32, in response to wear of the second end 18.

Referring to FIGS 1-3 the brush 14 is positioned in a brush box or holder 34 which preferably holds a single brush 14. The brush 14 is slidably movable in the box 34. The second contactor 24 is preferably connected to the box 34 and electrically isolated from the box 34. The box 34 has a construction sufficient for holding the brush 14, spring 32 and first contactor 22. The spring 32 and first contactor 22 preferably form a unit 35 which is insertable in and removable from the box 34. The spring 32 and contactors 22, 24 can form a unitary structure 36 which is removably positioned in a preselected location relative to the brush 14 (FIG. 4). The unit 35 and unitary structure 36 are held in the box 34 by a protrusion 38 which engages the box 34. Each brush box 34 may hold more than one brush 14 or unit 35.

A plug-in connector 40 preferably connects the indicating apparatus 28 to a terminal 42 of the second contactor 24 (FIG. 6). The brush box 34 and terminal 42 are preferably connected to an insulator 44. The spring and first contactor unit 35 is preferably removable from the brush box 34 without removing the plug-in connector 40 from the terminal 42.

The spring 32 biases the first contactor 22 toward one of the open and closed positions.

The first contactor 22 moves toward the other of the open and closed positions in response to reduction of the bias. The bias is reduced in response to wear of the brush 14.

In operation, an unworn brush 14 is positioned in the box 34 and the spring 32 holds the first and second contactors 22, 24 in the open position. As the brush 14 wears, the contactors 22, 24 move toward the closed position. When the brush 14 is sufficiently worn, the contactors 22, 24 close and energize the indicating apparatus 28. The brush 14 continues to wear until replaced.

WHAT WE CLAIM IS: 1. An electrical apparatus comprising a brush having first and second ends which approach one another, in use, in response to wear at the second end of the brush; first and second electrical contactors movable one relative to the other between an open position and a dosed position, the contactors being moved relatively from one of the open and closed positions toward the other of the open and closed positions in response to wear of the second brush end under the control of biasing means which urges the brush in a direction from the first end towards the second end and allows a resilient contactor mounting to cause movement of a selected one of the first and second contactors in response to wear of the brush, the biasing means being in contact with one of the first and second contactors and in contact with the first end of the brush, and the brush being substantially free for longitudinal movement independently of the position of the contactors and biasing means in response to wear.

2. An apparatus according to claim 1, including a box which holds the brush whereby the brush is slidably movable in the box, the second contactor being connected to the box and electrically isolated therefrom.

3. An apparatus according to claim 1, including a box which holds the brush, biasing means and first contactor, the biasing means and first contactor forming a unit.

4. An apparatus according to claim 3, wherein an electric circuit is connected to the second contactor and the unit is removable from the box while the second contactor is connected to the electric circuit.

5. An apparatus according to claim 1, wherein the biasing means and the first and second contactors are connected and form a unitary structure removably positioned in a preselected location relative to the brush.

6. An apparatus according to any one of the preceding claims, wherein the biasing means is a roll spring.

7. An apparatus according to any one of the preceding claims, wherein the first and second contactors form a path for current

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the open and closed positions in response to wear and resultant movement of the first end 20 of the brush 14. The first and second contactors 22, 24 form a path for current flow which is interrupted when the contactors 22, 24 move toward the open position. Referring to Figure 5, an indicating apparatus 28, such as a lamp for example, is connected to the first and second contactors 22, 24 and forms an electric circuit 30. The lamp 28 preferably lights when the contactors 22, 24 are in the closed position to indicate a predetermined amount of wear of the brush 14. A thyristor 31 or similar device can be connected to the lamp 28 and contactors 22, 24 to achieve greater control of the circuit 30. The brush 14 is biased by the biasing means 32, which in this example is a roll spring. The spring 32 urges the brush 14 in a direc tion toward the commutator 12, and causes movement of a selected one of the first and second contactors 22, 24, in this case the first contactor 22, in response to wear of the brush 14, by reduction of the bias against a leaf spring on which the selected one of the contactors is mounted. The spring 32 is preferably in contact with the first contactor 22, and it also contacts the first end 20 of the brush 14. The brush 14 is substantially free of restricted contact with the spring 32 and contactors 22, 24 during movement of the end 20 of the brush 14 between the first and the second positions. The brush 14 is sub stantially free for movement in a direction towards the commutator 12 independently of the contactors 22, 24 and the biasing means 32, in response to wear of the second end 18. Referring to FIGS 1-3 the brush 14 is positioned in a brush box or holder 34 which preferably holds a single brush 14. The brush 14 is slidably movable in the box 34. The second contactor 24 is preferably connected to the box 34 and electrically isolated from the box 34. The box 34 has a construction sufficient for holding the brush 14, spring 32 and first contactor 22. The spring 32 and first contactor 22 preferably form a unit 35 which is insertable in and removable from the box 34. The spring 32 and contactors 22, 24 can form a unitary structure 36 which is removably positioned in a preselected location relative to the brush 14 (FIG. 4). The unit 35 and unitary structure 36 are held in the box 34 by a protrusion 38 which engages the box 34. Each brush box 34 may hold more than one brush 14 or unit 35. A plug-in connector 40 preferably connects the indicating apparatus 28 to a terminal 42 of the second contactor 24 (FIG. 6). The brush box 34 and terminal 42 are preferably connected to an insulator 44. The spring and first contactor unit 35 is preferably removable from the brush box 34 without removing the plug-in connector 40 from the terminal 42. The spring 32 biases the first contactor 22 toward one of the open and closed positions. The first contactor 22 moves toward the other of the open and closed positions in response to reduction of the bias. The bias is reduced in response to wear of the brush 14. In operation, an unworn brush 14 is positioned in the box 34 and the spring 32 holds the first and second contactors 22, 24 in the open position. As the brush 14 wears, the contactors 22, 24 move toward the closed position. When the brush 14 is sufficiently worn, the contactors 22, 24 close and energize the indicating apparatus 28. The brush 14 continues to wear until replaced. WHAT WE CLAIM IS:

1. An electrical apparatus comprising a brush having first and second ends which approach one another, in use, in response to wear at the second end of the brush; first and second electrical contactors movable one relative to the other between an open position and a dosed position, the contactors being moved relatively from one of the open and closed positions toward the other of the open and closed positions in response to wear of the second brush end under the control of biasing means which urges the brush in a direction from the first end towards the second end and allows a resilient contactor mounting to cause movement of a selected one of the first and second contactors in response to wear of the brush, the biasing means being in contact with one of the first and second contactors and in contact with the first end of the brush, and the brush being substantially free for longitudinal movement independently of the position of the contactors and biasing means in response to wear.

flow, the current flow path being interrupted in response to the contactors moving towards the open position.

8. An apparatus according to any one of the preceding claims, including an indicating apparatus connected to the second contactor and forming an electric circuit with the first and second contactors.

9. An apparatus according to claim 1, sub stantially as described with reference to either of the examples illustrated in the accompanying drawings.