Note: Descriptions are shown in the official language in which they were submitted.
S~
E]ectrical machinery, such as direct current motors for example7
use brushes for transferring power between an electric circuit and a
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 preven~ damage to the commutator and insure
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
whell the brushes have been subs~antially completely worn away and does not
interfere with the movement of the brush. sy so utilizing substantially the
entire brush there is an avoidance of waste.
According to one aspect of the present invention, there is provided
an apparatus comprising: a brush having first and second ends, said first
end being movable between a first position at which said first and second
ends ara spaced a preselected distance one from the other and a second
position at which said first end is placed toward the second end, said
first end moving from the first position toward the second position in
response to wear of said brush; first and second contactors movable one
relative to the other between an open position and a closed positioll, said
contactors controllably moving from one of the open and closed positions
in response to wear of said brush; and biasing means for urging said brush
in a preselected direction and controllably moving a selected one of said
~;rst and second contactors in response to wear of said brush, said biasing
means being in contact with the selected one of said first and second con-
tactors and in contact with said first end of said brushJ said brush being
; substantially free for movement in the preselected direction independently
of the position of the contactors and biasing means in response to wear,
said biasing means being a roll spring.
According to another aspect oE the invention, there is provided an
electrical apparaeus comprising: a brush having first and second ends which
C ~ '
_ .
. : . .. : .
s~ ~
approach one another, in use, in response to wear of the second end of
the brush; biasing means for urging the brush in a direction from the first
end towards the second end in response to wear of the second brush end;
and first and second electrical contactors movable one relatïve to the
other between an open position and a closed position, a selected one of
the contactors being moved from one of the open and closed positions toward
the other of the open and closed positions under the resil;ence of the
respective contactor mounting in response to wear of the second brush end
and under the control of the biasing means, the biasing means being in
contact with the selected one of the first and second contactors and with
the first end of the brush, and the brush being substantially free for
longitudinal movement independently of the posi~ion of the contactors and
biasing means in response to wear, said biasing means being a roll spring.
Two examples of apparatus constructed in accordance with the
invention are illustrated in the accompanying drawings, in which:
,:
~ - 2a -
$~
FIG. 1 is a diagrammatic, longitudinal cross section
of one apparatus;
FIG. 2 is a diagrammatic view similar to FIG. l;
FIG. 3 is partial front view of the FIG. 1 apparatus;
S FIG. 4 is an isometric view of another apparatus;
FIG. S is schematic illustration of an electric cir-
cuit 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 commuta-
tor 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 to-
ward the second end 18. The brush 1~ is preferably of a uni-
form composition throughout, such as graphite, for example.
The ends 18, 20 are preferably substantially 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 be~ween 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
or current flow which is interrupted when the contactors
22, 24 move toward the open positionO
Referring to FIG. 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 ~hyristor 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 biasing means 32, prefer-
ably a roll spring. The spring 32 urges the brush 14 in a
preselected direction, preferably toward the commutator 12.
The s~ring 32 controllably moves a selected one of the first
and second contactors 22, 24, preferably the first con~actor
22, in response to wear of the brush 14. The spring 32 is
preferabl~ in contact wikh the first contackor 22 and prefer-
ably only the irst end 20 of the brush 14. The brush 14 is
substantially free of restrictive contact with the spring 32
and contactors 22, 24 durinq movement of the brush 14 between
the first and second positions. The brush 14 is substantially
free for movement in the preselected~direction independently
o the contactors 22, 24 and biasing means 32 in response to
wear.
.. . . . ..
- - . . ,
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 con-
tactors 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 3~ which engages the
box 34. Each brush box 34 may hold more ~han 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 bia~. 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.
-5-
J~ ~
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.
Other aspects, objects and advantages will become
apparent from a study of the specification, drawings and
appended claims.
- . . .
