Title: Wear indicator
Abstract: The present invention relates to a wear indicator for a motor carbon brush which includes a housing, carbon brushes, an elastic element, a circuit board with an alarm indicator light and an electric probe disposed on the circuit board. The electric probe is connected to the alarm indicator light and the carbon brush has a contact portion on its outer surface which when the brush is worn and need to be changed is electrically connected to the alarm indicator light through the electrical probe to turn the alarm indicator light on. The present invention is simple to manufacture and gives a indication of wear.
Patent Number: 6,933,650 Issued on 08/23/2005 to Wang
| Inventors:
|
Wang; Yongfeng (Suzhou, CN)
|
| Assignee:
|
Positec Power Tools (Suzhou) Co., Ltd. (Suzhou, CN)
|
| Appl. No.:
|
754274 |
| Filed:
|
January 9, 2004 |
Foreign Application Priority Data
| Jan 14, 2003[CN] | 03112700 A |
| Current U.S. Class: |
310/245; 310/68; 310/239; 310/242 |
| Intern'l Class: |
H01R 039/58 |
| Field of Search: |
310/238-239,242-249,251,68.B
|
References Cited [Referenced By]
U.S. Patent Documents
| 3924147 | Dec., 1975 | Tarnow et al.
| |
| 4024525 | May., 1977 | Baumgartner et al.
| |
| 4344009 | Aug., 1982 | Reynolds.
| |
| 5509625 | Apr., 1996 | Oullette et al.
| |
| Foreign Patent Documents |
| 58009552 | Jan., 1983 | JP.
| |
| 61142943 | Jun., 1986 | JP.
| |
| 10257735 | Sep., 1998 | JP.
| |
Primary Examiner: Mullins; Burton
Attorney, Agent or Firm: Nydegger; Workman
Claims
1. A wear indicator for a motor carbon brush that is used in association with
a commutator having a surface comprising:
a housing;
a carbon brush slidably mounted within the housing in a sliding direction, wherein
the front end of the carbon brush touches the surface of the commutator and the
surface of the carbon brush has a contact portion, the contact portion comprising
a protrusion protruding from the surface of the carbon brush;
a guiding slot in the housing which extends co-directionally with the sliding
direction, the protrusion protruding through the guiding slot,
an elastic element positioned on the housing which bears against the rear end
of the carbon brush;
a circuit board which is equipped with an alarm indicator light and is fixed
to the housing; and
an electric probe disposed on the circuit board which is electrically connected
to the alarm indicator light, the electric probe comprising a substantially columnar
projection projecting from the circuit board,
wherein in use when the carbon brush is in a first operational state, a surface
of the electric probe is disconnected from the contact portion of the carbon brush
and when the carbon brush is in a second operational state, the surface of the
electric probe touches the contact portion of the carbon brush.
2. A wear indicator according to claim 1, wherein the circuit board is a substantially
planar body and wherein the substantially columnar projection and the contact portion
are capable of relative movement from the first operational state to the second
operational state.
3. A wear indicator according to claim 2, further comprising an elongate truncated
slot disposed on the surface of the carbon brush which extends co-directionally
with the sliding direction, wherein the contact portion is an end portion of the
elongate truncated slot and the electric probe has an end inserted freely into
the elongate truncated slot.
4. A wear indicator according to claim 3, wherein the end portion of the elongate
truncated slot is arced.
5. A wear indicator according to claim 1, further comprising: an elongate truncated
slot disposed on the surface of the carbon brush wherein the contact portion is
disposed at the end of the elongate truncated slot.
6. A wear indicator according to claim 1, wherein the substantially columnar
projection has an arced surface opposing a contact surface of the protrusion wherein
in use when the carbon brush is in the second operational state, the arced surface
contacts the contact surface of the protrusion.
7. A wear indicator according to claim 6, wherein the contact surface of the
protrusion is arced.
8. A wear indicator according to claim 1, wherein the contact portion is an electrically
conductive protrusion protruding from the surface of the carbon brush whose root
is embedded in the carbon brush.
9. A wear indicator according to claim 8, wherein the substantially columnar
projection has an arced surface opposing a contact surface of the electrically
conductive protrusion wherein in use when the carbon brush is in the second operational
state, the arced surface contacts the contact surface of the electrically conductive protrusion.
10. A wear indicator according to claim 9, wherein the contact surface of the
electrically conductive protrusion is arced.
11. A wear indicator as claimed in claim 1, wherein the contact portion is continuously exposed.
12. A wear indicator as claimed in claim 1, wherein the contact portion and/or
the surface of the electric probe is arced.
13. A commutator motor comprising one or more wear indicators as defined in claim 1.
14. A wear indicator for a motor carbon brush that is used in association with
a commutator having a surface comprising:
a housing;
a carbon brush slidably mounted within the housing in a sliding direction, the
carbon brush having a front end touching the surface of the commutator;
a contact portion comprising an electrically conductive protrusion protruding
from a surface of the carbon brush, the contact portion having a root embedded
in the carbon brush;
a guiding slot in the housing which extends co-directionally with the sliding
direction, the electrically conductive protrusion protruding through the guiding
slot;
an elastic element positioned on the housing which bears against the rear end
of the carbon brush;
a circuit board which is equipped with an alarm indicator light and is fixed
to the housing; and
an electric probe disposed on the circuit board which is electrically connected
to the alarm indicator light, the electric probe comprising a substantially columnar
projection projecting from the circuit board,
wherein in use when the carbon brush is in a first operational state, a surface
of the electric probe is disconnected from the contact portion projecting from
the carbon brush and when the carbon brush is in a second operational state, the
surface of the electric probe touches the contact portion projecting from the carbon
brush.
15. A wear indicator according to claim 14, wherein the circuit board is a substantially
planar body and wherein the substantially columnar projection and the contact portion
are capable of relative movement from the first operational state to the second
operational state.
16. A wear indicator according to claim 14, further comprising an elongate truncated
slot disposed on the surface of the carbon brush wherein the contact portion is
disposed at the end of the elongate truncated slot.
17. A wear indicator according to claim 16, further comprising an elongate truncated
slot disposed on the surface of the carbon brush which extends co-directionally
with the sliding direction, wherein the contact portion is an end portion of the
elongate truncated slot and the electric probe has an end inserted freely into
the elongate truncated slot.
18. A wear indicator according to claim 17, wherein the end portion of the elongate
truncated slot is arced.
19. A wear indicator according to claim 14, wherein the substantially columnar
projection has an arced surface opposing a contact surface of the electrically
conductive protrusion wherein in use when the carbon brush is in the second operational
state, the arced surface contacts the contact surface of the electrically conductive protrusion.
20. A wear indicator according to claim 19, wherein the contact surface of the
electrically conductive protrusion is arced.
21. A wear indicator as claimed in claim 14, wherein the contact portion is continuously exposed.
22. A wear indicator as claimed in claim 14, wherein the contact portion and/or
the surface of the electric probe is arced.
23. A commutator motor comprising one or more wear indicators as defined in claim 14.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to China Patent Application No. 03112700.2
filed on Jan. 14, 2003 which is incorporated herein by specific reference.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to a wear indicator for a motor carbon brush and
to a commutator motor comprising one or more of the wear indicators.
2. The Relevant Technology
A conventional commutator motor includes a housing, a carbon brush which is slidably
mounted within the housing and at least one alarm indicator light. An end of the
carbon brush bears against an elastic element and the other end contacts the round
surface of the commutator. The carbon brush is biased against the commutator by
means of the elastic element. A wire is embedded in the carbon brush in order to
detect the wear degree to ensure that the carbon brush is timely replaced. When
the carbon brush is worn and slides to a predetermined position, the wire is exposed
and turns the alarm indicator light on. Generally such a carbon brush with an embedded
wire is complicated to manufacture.
Another conventional arrangement incorporates an opening at a predetermined
position of the carbon brush. A lighting element is disposed on one side of the
carbon brush and a receiving element on the other side. When the carbon brush is
worn and slides to a predetermined position, the receiving element receives through
the opening the light emitted by the lighting element and turns the alarm indicator
light on. A disadvantage of this arrangement is that the opening may become blocked
(e.g., by dust) which interrupts the light making the alarm ineffective.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple and reliable wear
indicator for a motor carbon brush
Thus viewed from one aspect the present invention provides a wear indicator
for a motor carbon brush including:
- a housing;
- a carbon brush slidably mounted within the housing, wherein the front
end of the carbon brush touches the surface of the commutator and the surface of
the carbon brush has a contact portion;
- an elastic element positioned on the housing which bears against the
rear end of the carbon brush;
- a circuit board which is equipped with an alarm indicator light and
is fixed to the housing;
- an electric probe disposed on the circuit board which is electrically
connected to the alarm indicator light,
- wherein in use when the carbon brush is in a first operational state,
a surface of the electric probe is disconnected from the contact portion of the
carbon brush and when the carbon brush is in a second operational state, the surface
of the electric probe touches the contact portion of the carbon brush.
The present invention relates to a wear indicator for a motor carbon brush comprising:
a housing and a carbon brush which is slidably mounted within the housing. An elastic
element is positioned on the housing and is biased against the rear end of the
carbon brush. A circuit board with an alarm indicator light is fixed to the housing.
A front end portion of the carbon brush contacts the round surface of the commutator.
The circuit board is equipped with an electric probe which is electrically connected
to the alarm indicator light. The carbon brush surface has a contact portion such
that when the carbon brush is in the first operational state, the surface (e.g.,
end) of the electric probe is disconnected from the contact portion on the carbon
brush and the circuit which is made up of the carbon brush, electric probe and
alarm indicator light in series is incomplete so that the alarm indicator light
is switched off. When the carbon brush is in the second operational state, the
surface (e.g., end) of the electric probe contacts the contact portion on the carbon
brush and the circuit which is made up of the carbon brush, electric probe and
alarm indicator light in series is complete so that the alarm indicator light is
turned on.
The present invention exploits the conductive character of the carbon brush by
providing a continuously exposed contact portion on the carbon brush to which the
alarm indicator light may be electrically connected through an electric probe.
When the brush is worn and needs to be changed, the electrical connection is made
and the alarm indicator light is turned on. The present invention is reliable and
simple to manufacture.
Preferably the contact portion (and/or the surface of the electric probe
which it contacts) is arced.
Preferably the contact portion is continuously exposed.
Preferably the circuit board is a substantially planar body and the electric
probe takes the form of a substantially columnar or angular projection from the
planar body, wherein the substantially columnar or angular projection and the contact
portion are capable of relative movement from the first operational state to the
second operational state. Typically the substantially columnar or angular projection
is static and the carbon brush moves between the first and second operational state
as it wears. The position of the carbon brush in the second operational state can
be predetermined to coincide with a position in which the carbon brush is worn
to a degree which requires its replacement.
In a preferred embodiment, the wear indicator further comprises: an elongate
truncated
slot disposed on the surface of the carbon brush, wherein the contact portion is
disposed at the end of the elongate truncated slot (e.g., the end wall).
In a preferred embodiment, the carbon brush is slidably mounted within the housing
in a sliding direction and the wear indicator further comprises: an elongate truncated
slot disposed on the surface of the carbon brush which extends co-directionally
with the sliding direction, wherein the contact portion is an end portion of the
elongate truncated slot (e.g., the end wall) and the electric probe takes the form
of an angular projection from the planar body whose end is inserted freely into
the elongate truncated slot.
Particularly preferably the angular projection has an arced end surface
opposing the end portion, wherein in use when the carbon brush is in the second
operational state, the arced end surface contacts the end portion of the elongate
truncated slot.
Particularly preferably the end portion of the elongate truncated slot
is arced.
The angular projection may take any suitable form. For example, the angular projection
may be comprise a main body from which is angularly dependent an arm which extends
into the elongate truncated slot. The main body may project from the planar body
be twin legs.
The housing will typically have an elongate slot coincident with the elongate
truncated slot in the carbon brush.
Alternatively preferably the contact portion is a protrusion protruding
from the surface of the carbon brush.
Particularly preferably the carbon brush is slidably mounted within
the housing in a sliding direction and the wear indicator further comprises: a
guiding slot in the housing which extends co-directionally with the sliding direction,
wherein the protrusion protrudes through the guiding slot and wherein the electric
probe takes the form of a substantially columnar projection from the planar body.
Particularly preferably the substantially columnar projection has an
arced surface opposing a contact surface of the protrusion wherein in use when
the carbon brush is in the second operational state, the arced surface contacts
the contact surface of the protrusion.
Particularly preferably the contact surface of the protrusion is arced.
Alternatively preferably the contact portion is an electrically conductive
protrusion protruding from the surface of the carbon brush whose root is embedded
in the carbon brush.
Particularly preferably the carbon brush is slidably mounted within
the housing in a sliding direction and the wear indicator further comprises: a
guiding slot in the housing which extends co-directionally with the sliding direction,
wherein the electrically conductive protrusion protrudes through the guiding slot
and wherein the electric probe takes the form of a substantially columnar projection
from the planar body.
Particularly preferably the substantially columnar projection has an
arced surface opposing a contact surface of the electrically conductive protrusion
wherein in use when the carbon brush is in the second operational state, the arced
surface contacts the contact surface of the electrically conductive protrusion.
Particularly preferably the contact surface of the electrically conductive
protrusion is arced.
Viewed from a further aspect the present invention provides a commutator motor
comprising one or more wear indicators as defined hereinbefore.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the present invention will now be discussed with reference
to the appended drawings. It is appreciated that these drawings depict only typical
embodiments of the invention and are therefore not to be considered limiting of
its scope.
FIG. 1 shows a sectional view of a first embodiment of the invention with the
carbon brush in the first operational state;
FIG. 2 shows a sectional view of the carbon brush in the second operational state;
FIG. 3 shows an enlarged sectional view of A in FIG. 2;
FIG. 4 is the alarm indicator circuit diagram;
FIG. 5 shows an exploded view of the embodiment;
FIG. 6 shows a perspective view of the first embodiment from a first angle;
FIG. 7 shows a perspective view of the first embodiment from a second angle;
FIG. 8 shows a sectional view of a second embodiment of the present invention
with the carbon brush in the first operational state; and
FIG. 9 shows a sectional view of a third embodiment of the present invention
with the carbon brush in the first operational state
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1-9 illustrate a wear indicator for a carbon brush including a housing
3 and a carbon brush
4 which is slidably mounted within the housing
3. A torsion spring
1 is positioned on the housing
3 and bears
against the rear end of the carbon brush
4. The front end of the carbon
brush
4 touches the round surface of a commutator
7 and the surface
of the carbon brush
4 has a contact portion. A planar circuit board
13
which is equipped with an alarm indicator light
2 is fixed to the housing
3. On the circuit board
13 is disposed an electric probe
5
which is electrically connected to the alarm indicator light
2. When the
carbon brush
4 is in a first operational state, an end surface of the electric
probe
5 is disconnected from the contact portion. When the carbon brush
4 is in a second operational state, the end surface of the electric probe
5 touches the contact portion of the carbon brush
4. Embodiments
having three different contact portions are described below.
In the first embodiment (FIGS.
1-
7), an elongate truncated slot
6 is disposed on the surface of the carbon brush
4 which extends
in the sliding direction of the carbon brush
4. The electric probe
5
takes the form of an angular projection freely insertable into the elongate truncated
slot
6. The contact portion is an end wall
9 of the elongate truncated
slot
6 which is arced (see FIG.
3). The electric probe
5 has
an arced end surface
8 opposing the arced end wall
9 (i.e., an end
surface
8 arced in a direction opposite to the direction of travel of the
carbon brush). When the carbon brush
4 is in the first operational state,
the arced end surface
8 slides freely in the slot and the alarm indicator
remains unlit. When the carbon brush
4 is in the second operational state,
the arced end surface
8 touches the arced end wall
9 of the carbon
brush
4 (see FIG. 3) and the alarm indicator light
2 is switched on.
As illustrated most clearly in FIG. 5, the slot
6 is truncated (i.e.,
the
end of the carbon brush
4 is remote from the arced end wall
9 of
the slot
6) by a predetermined distance. When the arced end wall
9
of the carbon brush
4 touches the electric probe
5, the carbon brush
4 need not be displaced immediately and in fact may be used continually
for a short period of time (e.g., an hour) without burning the motor.
In the second embodiment of the present invention (FIG.
8), the contact
portion of the carbon brush
4 is an electrically conductive protrusion
10
made from an electrically conductive material such as a metal which protrudes from
the surface of the carbon brush
4 and the housing
3. The root of
the electrically conductive protrusion
10 is embedded in the carbon brush
4. The electrically conductive protrusion
10 follows the movement
of the carbon brush
4 along a guiding slot
11. An electric probe
5 protrudes from the circuit board
13. The electrically conductive
protrusion
10 contacts the electric probe
5 when the carbon brush
4 has moved a predetermined distance. The end face of the electrically conductive
protrusion
10 and the surface of the electric probe
5 which contact
each other are arced.
In the third embodiment of the present invention (FIG.
9), the contact
portion of the carbon brush
4 is a protrusion
12 integrally formed
on the carbon brush
4 which protrudes from the surface of the carbon brush
4 and the housing
3. The protrusion
12 follows the movement
of the carbon brush
4 along a guiding slot
11. An electric probe
5 protrudes from the circuit board
13. The protrusion
12 contacts
the electric probe
5 when the carbon brush
4 has moved a predetermined
distance. The end face of the protrusion
12 and the surface of the electric
probe
5 which contact each other are arced.
*
