FIELD OF INVENTION
The present invention relates to a mechanism of discrete contact breaking in a brake
switch. More particularly, the present invention relates to a brake switch having a
mechanism of discrete contact breaking (‘NC’ to ‘NO’) at discrete position.
BACKGROUND AND PRIOR ART OF INVENTION
Generally vehicles are provided with Brake Switch. The brake switch is connected to
the brake lamps / stop lamps and is actuated when the brake pedal is pushed
downward to apply brakes. Thus the brake switch operates to send an electric signal
to the brake lamp and it glows warning others of the stopping vehicle.
In existing mechanism (ref. fig. 1), during operation from “NC” (Normally Closed) to
“NO” (Normally Open) condition, when force is applied on the plunger (1), the whole
plunger assembly moves downwards. The force from the plunger is transferred to a
cup washer (2) which in turn is connected to the diaphragm (3). This downward force
is opposed by the moving contact spring (5) to which the diaphragm (3) is connected
by means of the carrier (6). When the stiffness of the plunger spring (4) becomes
equal to the stiffness of the moving contact spring (5), the moving contact (7)
gradually begins to move downward on further application of force. At this point,
contact breaking between the moving contact (7) and bimetallic rivet (8) takes place.
The bimetallic rivet (8) is connected to the terminals (9).
Thus, the switch is said to have reached the “NO” condition. However, the existing
switch has certain demerits such as gradual contact breaking which increases the
probability of contact burning or arcing.
In other words, the researchers are constantly working to develop a user friendly and
technically advanced brake switch. More specifically, a brake switch whereby the
contact breaking is discrete and problems of contact burning and arcing are less
existent.
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SUMMARY OF THE INVENTION
The present invention relates to the Switching Operation for Discrete Contact making
and breaking in Brake Switch. More specifically, the invention relates to the
mechanism of construction and operation of a contact type brake switch wherein
discrete contact breaking is achieved by means of a third spring. Accordingly, the
present invention provides a brake switch for discrete contact making and breaking,
comprising a casing having a first end and a second end, opposite to one another. A
plunger assembly is disposed resiliently in the interior of the said casing by means of
a retainer spring. The plunger assembly comprises a plunger, a plunger spring, a
washer and a plunger medium coupled with the plunger spring. The plunger further
comprises a first cylindrical section and a second cylindrical section, the second
cylindrical section being adapted to be resiliently loaded by means of a retainer spring
and a collar section disposed in between the first cylindrical section and the second
cylindrical section. The said collar section extends radially outwards from the first
and second cylindrical section. The said brake switch also comprises a base assembly
secured to the second end of the casing. The base assembly has a base and a plurality
of fixed contacts. A carrier is disposed in the base and is movable in the longitudinal
direction. The carrier is resiliently supported on the base by means of a moving
contact spring. Also, a moving contact, secured to the carrier, is movable along with
the carrier in the longitudinal direction.
BRIEF DESCRIPTION OF FIGURES
Further aspects and advantages of the present invention will be readily understood
from the following detailed description with reference to the accompanying
figures. The figures together with a detailed description below, are incorporated in
and form part of the specification, and serve to further illustrate the embodiments
and explain various principles and advantages, but not limiting the scope of the
invention. In the accompanying drawings,
Figure 1 shows a sectional view of existing brake switch.
Figure 2 shows the exploded views of the invention; the various sub-parts and subassemblies
that are contained in the brake switch. It depicts the following essential
parts of the present invention in accordance with an embodiment:
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101- Casing
102- O-Ring
103- Retainer spring
104- Plunger Assembly
105- Support Plate
106- Diaphragm
107- Carrier
108- Base Assembly
109- Bellow
110- Metal Cap
Figure 3 shows an exploded view of the plunger assembly. It depicts the following
essential parts of the present invention in accordance with an embodiment:
104 a- Plunger
104 b- Plunger spring
104 c- Circular washer
104 d- Plunger medium
Figure 4 shows an exploded view of the base assembly. It depicts the following
essential parts of the present invention in accordance with another embodiment:
108 a- Base
108 b- Moving Contact Spring
108 c- Moving Contact
108 d1- Bimetallic Rivets
108 d2- Terminals
108 e- Rectangular washer
Figure 5 depicts the sectional view of a brake switch according to an embodiment of
the present invention.
Figure 6 depicts a 3-dimensional view of the present invention with respect to the
working mechanism of the plunger assembly of the present invention.
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Figures 7 (a) and (b) are 3-dimensional view of the base assembly of the brake
switch in accordance with an embodiment of the present invention.
Figures 8 (a) and (b) depict 3-dimensional isometric views of the carrier in
accordance with one other embodiment of the present invention.
Skilled artisans will appreciate that elements in the drawings are illustrated for
simplicity and have not necessarily been drawn to scale. For example, the dimensions
of some of the elements in the drawings may be exaggerated relative to other elements
to help to improve understanding of embodiments of the present invention.
DETAILED DESCRIPTION OF INVENTION
While the invention is subject to various modifications and alternative forms, specific
embodiment thereof has been shown by way of example in the figures and will be
described below. It should be understood, however that it is not intended to limit the
invention to the particular forms disclosed, but on the contrary, the invention is to
cover all modifications, equivalents, and alternative falling within the spirit and scope
of the invention as defined by the appended claims.
Before describing in detail the various embodiments of the present invention it may
be observed that the novelty and inventive step that are in accordance with the present
invention resides in the construction of brake switch. It is to be noted that a person
skilled in the art can be motivated from the present invention and can perform various
modifications. However, such modifications should be construed within the scope of
the invention.
Accordingly, the drawings are showing only those specific details that are pertinent to
understanding the embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of ordinary skill in the art
having benefit of the description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to
cover a non-exclusive inclusion, such that an assembly, setup, system, device
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that comprises a list of components does not include only those components but
may include other components not expressly listed or inherent to such system or
device or setup. In other words, one or more elements in the system or apparatus or
device proceeded by “comprises a” does not, without more constraints, preclude the
existence of other elements or additional elements in the assembly or system or
apparatus. The following paragraphs explain present invention. The invention in
respect of the same may be deduced accordingly.
Accordingly, the present invention provides a brake switch for discrete contact
making and breaking; the brake switch comprising;
a casing; the casing having a first end and a second end; the two ends
being located opposite to one another in longitudinal direction;
a plunger assembly disposed resiliently in the interior of the said casing by
means of a retainer spring; the plunger assembly comprising
a plunger;
a plunger spring;
a circular washer; and
a plunger medium coupled with the plunger spring; wherein
the plunger comprises
a first cylindrical section; and
a second cylindrical section; the second
cylindrical section being adapted to be resiliently loaded
by means of a retainer spring; and
a collar section disposed in between the first
cylindrical section and the second cylindrical section;
the collar section extending radially outwardly from the
first and second cylindrical section;
a base assembly secured to the second end of the casing; the base
assembly having a base and a plurality of fixed contacts;
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a carrier being disposed in the base and movable in the longitudinal
direction;
the carrier being resiliently supported on the base by means of a
moving contact spring; and
a moving contact secured to the carrier and movable along with
the carrier in the longitudinal direction.
In an embodiment of the present invention, the plunger has a cylindrical channel
defining an open end and a closed end.
In another embodiment of the present invention, the plunger spring is accommodated
in the interior of the said cylindrical channel.
In yet another embodiment of the present invention, the plunger spring is supported
by a circular washer from the open end.
In an embodiment of the present invention, a plunger medium is received in the
channel from the open end such that it is under a force of the plunger spring.
In one more embodiment of the present invention, the plunger medium is provided
with a flanged portion extending radially outwardly; the flanged portion being
supported on the circular washer; the circular washer being adapted to be locked by a
corresponding inward flange/caulking on the plunger.
In one other embodiment of the present invention, the support plate has an upper face
and a lower face; and comprising a through hole in the centre to allow the passage of
the plunger medium there-through during actuation of the plunger.
In yet another embodiment of the present invention, the plunger assembly is
supported on the supported plate by means of the retainer spring; the retainer spring
being supported on the upper face of the support plate.
In a further embodiment of the present invention, a diaphragm is interposed between
the lower face of support plate and the proximal end of the base.
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In an embodiment of the present invention, the carrier has an upper face and lower
face; the upper face being adapted to abut the diaphragm co-axially.
In yet other embodiment of the present invention, a cylindrical protrusion is extending
perpendicularly away from the lower face of the carrier.
In an embodiment of the present invention, a plurality of guiding slots is formed
oppositely on the sides of the carrier in the longitudinal direction.
In another embodiment of the present invention, the moving contact is secured to a
cylindrical protrusion of the carrier.
In one other embodiment of the present invention, a plurality of guiding pins is
formed oppositely on the sides of the base in the longitudinal direction.
In an embodiment of the present invention, the base is provided with mounting slots
to accommodate the fixed contacts.
In one more embodiment of the present invention, the fixed contacts comprising
terminals and bimetallic rivets.
In one other embodiment of the present invention, the moving contact is maintained in
contact with the fixed contacts under normal/non-actuated condition of the brake
switch.
In a further embodiment of the present invention, the guiding slots are adapted to
receive the guiding pins of the base.
In a still further embodiment of the present invention, the plunger spring has stiffness
greater than the stiffness of the moving contact spring.
In one other embodiment of the present invention, caulking has been done to secure
the base assembly to the second end of the casing.
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The following paragraphs describe the present invention with reference to Figures 2 to
8 according to an embodiment of the present invention.
Referring to Figures 2 to 8 of the present disclosure, the brake switch comprises a
casing (101), an O-Ring (102), a retainer spring (103), a plunger assembly (104), a
support plate (105), a diaphragm (106), a carrier (107), a base assembly (108), a
bellow (109) and a metal cap (110).
As shown in Figures 2 and 3, the brake switch comprises a cylindrical casing (101).
The casing (101) is a generally cylindrical structure having a first end (101a) and a
second end (101b) disposed opposite to one another. The interior of the casing (101)
is hollow and is adapted to accommodate a plunger assembly (104). It is to be noted
that the shape and configuration of the casing (101) is not limited to the present
disclosure and may vary as per the suitability of the manufacturer or other external
factors. Disposed resiliently in the interior of the casing (101) is the plunger assembly
(104). The plunger assembly (104) comprises a plunger (104a); the plunger having a
first cylindrical section (A) and second cylindrical section (C). Located in between the
first cylindrical section (A) and second cylindrical section (C) is a collar section (B).
The collar section (B) protrudes radially outwardly from the circumference of the first
cylindrical section (A) and second cylindrical section (C). The plunger (104a) has a
cylindrical channel (104e) extending partially in the longitudinal direction from the
second cylindrical section (C) towards the first cylindrical section (A); thereby
defining an open end (W) and a closed end (W’). The term ‘longitudinal direction’
herein refers to a direction along axis Y-Y as shown in figure 5. Disposed in the
interior of the said cylindrical channel (104e) is a plunger spring (104b). Circular
washer (104c) is used to support the plunger spring (104b) at open end (W) of the
cylindrical channel (104e). In the mounted condition, a plunger medium (104d) is
received in the channel (104e) from the open end (W) such that it is under a force of
the plunger spring (104b). The plunger medium (104d) is provided with a flanged
portion (104d1) extending radially outwardly. The flanged portion of the plunger
medium (104d), in the mounted condition in the cylindrical channel (104e), is
supported on the circular washer (104c). The said circular washer can thus be locked
by a corresponding inward flange/caulking on face X of the plunger (104a), as shown
in figure 6.
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As shown in figures 2, 4 and 5, the base assembly (108) comprises a hollow region
defined by an outer shell formed by base (108a) of the base assembly. The base
(108a) has a proximal end and distal end. The term ‘proximal end’ herein refers to an
open end of the base (108a) which is located near the second end (101b) of the casing
(101) in the mounted condition. The term ‘distal end’ herein refers to a closed end of
the base (108a) which is located away from second end (101b) of the casing (101) in
the mounted condition. In the mounted condition of the said brake switch the base
assembly is secured to the casing so as to form an encapsulation. A plurality of fixed
contacts (108d) comprising terminals (108d2) and bimetallic rivets (108d1) are
disposed in the hollow region of the base (108a). The plurality of fixed contacts
(108d) is mounted in the longitudinal direction in the base (108a) by means of a pair
of rectangular washers (108e). A moving contact (108c) is accommodated resiliently
in the hollow region of the base (108a) by means of a moving contact spring (108b)
such that the moving contact (108c) is maintained in contact with the plurality fixed
contacts (108d) under normal/non-actuated condition of the brake switch.
As illustrated in figures 5 and 6, in the assembled condition of the brake switch, the
plunger assembly (104) is disposed in the interior of the casing (101) such that the
first cylindrical section (A) of the plunger (104a) is located towards the first end
(101a) of the casing (101) and the second cylindrical section (C) of the plunger (104a)
is located towards the second end (101b) of the casing (101). Under this condition, the
second cylindrical section (C) of the plunger assembly (104a) is received co-axially in
the retainer spring (103) such that an end of the retainer spring abuts with the collar
section (B) of the plunger (104a). The other end of the retainer spring (103) is
supported on a circular support plate (105) such that the plunger (4a) is co-axial with
the support plate (105). Thus, the plunger assembly (104) is supported on the
supported plate (105) by means of the retainer spring (103). The retainer spring (103)
is a compression spring and compression of the retainer spring (103) takes place along
a longitudinal axis. The support plate (105) is a circular disc having an upper face and
a lower face; and comprising a through hole in the centre adapted to allow the passage
of the plunger medium (104d) there-through during actuation of the plunger (104). In
the mounted condition, the upper face of the support plate (105) is secured with the
second end (101b) of the casing (101) and the lower face of the support plate (105) is
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secured to the proximal end of the base (108a). Interposed between the lower face of
support plate (105) and the proximal end of the base (108a) is a rubber diaphragm
(106). The carrier (107) having an upper face and a lower face is secured to the rubber
diaphragm (106) such that its upper face abuts with the diaphragm (106) co-axially. A
cylindrical protrusion, extending longitudinally towards the distal end of the base
(108a) is formed on the lower face of the carrier (107). The moving contact (108c) is
secured to a cylindrical protrusion of the carrier (107). The protrusion of the carrier
(107), to which the moving contact (108c) is attached, is kept lifted from the distal
end of the base (108a) by the moving contact spring (108b) under normal/nonactuated
condition of the brake switch.
Referring to figure 6, plunger (104a) has face X, corresponding to face X of the
plunger the support plate (105) has a face Y on the upper side. During actuation of the
said brake switch, the face X of the plunger (104a) abuts with a corresponding face Y
on the support plate (105) during downward movement of plunger (104a), thereby
restricting the further movement of plunger (104a). To ensure tight contact, caulking
(CK1) has been done to secure the base assembly (108) to the casing (101). This
further prevents entry of dust, water and other contaminants into the brake switch,
thereby enhancing work lifecycle of the said brake switch.
Figures 7(a) and (b) depict the base assembly (108) according to an embodiment of
the present invention. As shown in figure 7 (a), formed oppositely in the longitudinal
direction, in the interior of the base (108a), is a pair of guiding pins (108f). Mounting
slots (M) are provided oppositely in the base (108a) to accommodate the fixed
contacts (108d). The mounting slots (M) extend longitudinally from the proximal end
to the distal end of the base (108a). A plurality of holes, corresponding to the
mounting slots (M), is provided in the distal end of the base (108a). The terminals
(108d2) of the fixed contact (108d) are have an L-shape geometry comprising a short
arm (S) and a long arm (T). In the mounted condition of the fixed terminals in the
base (108a), as shown in figure 7(b), the long arm (T) of the terminal (108d2) is
received in the mounting slots (M) of the base (108a) such that an end of the long arm
(T) emerges externally from the hole in the distal end of the base (108a). The short
arm (S) of terminal (108d2), in the mounted condition, rests on flat portions (F)
formed in the base (108a). Rectangular washer (108e) is used to secure the terminal at
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the distal end of the base. Caulking (CK2) is done on long arm (T) of the terminal
(108d2) at the interface of rectangular washer (108e). Thus, the terminals are held
firmly in the base (108a) and entry of contaminants is prevented.
As shown in figures 8(a) and (b), the carrier (107) has an upper face (107a) and lower
face (107b). A cylindrical protrusion (107c) is formed co-axially on the lower face
(107b) of the carrier; the protrusion (107c) extending perpendicularly from the lower
face (107b) of the carrier (107). A plurality of guiding slots (107d) is formed
oppositely on the sides of the carrier in the longitudinal direction. In the mounted
condition, the guiding slots (107d) receive the guiding pins (108f) of the base (108a)
so as to support the longitudinal movement of the carrier (107), thereby restricting
tangential/rotational movement of the carrier about the longitudinal axis.
Referring to figures 5 and 6, under normal/non-actuated condition, the said brake
switch is in “NC” (Normally Closed) position. In the NC position the face DD of the
carrier (107), to which the moving contact (108c) is attached, is kept lifted from the
distal end of the base (108a) by the loaded moving contact spring (108b) such that the
moving contact (108c) is in contact with the plurality of fixed contacts (108d). Also, a
gap (120) is maintained between diaphragm (106) and plunger assembly (104) by the
pre-loaded retainer spring (103).
When an actuating force is applied on the first cylindrical section (A) of the plunger
(104a) in the longitudinal direction, the retainer spring (103), gets compressed. The
plunger assembly (104) thus moves longitudinally downwards and the plunger
medium (104d) passes through the support plate (105). Upon overcoming the gap
(120) the plunger medium (104d) hits the diaphragm (106). The stiffness (Ka) of
plunger spring (104b) is greater than the stiffness (Kb) of the moving contact spring
(108b), thus the actuating force gets transmitted to the carrier (107) through
diaphragm (106). This results in the immediate compression of the moving contact
spring (108b) causing discrete contact breaking between moving contact (108c) and
the plurality of fixed contacts (108d). The moving contact spring (108b) gets fully
compressed when face G of the carrier (107) abuts face F of the base (108a). At this
position, the switch is said to have reached the actuated / “NO” (Normally Open)
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position. On further application of the actuating force on the plunger (104a), the
plunger spring (104b) starts getting compressed absorbing the over-travel of the brake
pedal. Plunger (104a) travels downwards, till stopper face X of the plunger hits upper
face Y of the support plate (105) thereby restricting further movement of the plunger
in the longitudinal direction.
On releasing the actuating force from plunger (104a), retainer spring (103), the
moving contact spring (108b) and the plunger spring (104b) (if in a compressed state)
get uncompressed respectively to bring the said switch back to “NC” position.
ADVANTAGES OF INVENTION
The primary advantage of the present invention is that there is discrete contact
breaking between the moving contacts and the terminals. Thus problems like contact
burning or arcing are eliminated increasing the life cycle of the said switch.
Another advantage of the present invention is that there is less voltage drop at
specified current due butt contact between the fixed contact and moving contact.
Yet another advantage of the present invention is that over travel of the plunger is
compensated by the plunger spring and excessive force of the plunger is absorbed.
This results in significant increase in the work lifecycle of the mechanical components
in the switch.
One other advantage of the present invention is that the resting face of the terminal on
the body of the base has been made flat. This ensures no variation in height of both
the terminals, hence results in no premature failures and proper contact pressure is
maintained.

We claim
1. A brake switch for discrete contact making and breaking, the brake switch
comprising;
a casing (101); the casing having a first end (101a) and a second end
(101b); the two ends (101a, 101b) being located opposite to one another in
longitudinal direction;
a plunger assembly (104) disposed resiliently in the interior of the said
casing (101) by means of a retainer spring (103); the plunger assembly
comprising
a plunger (104a);
a plunger spring (104b);
a circular washer (104c) and
a plunger medium (104d) coupled with the plunger spring
(104b); wherein
the plunger (104a) comprises
a first cylindrical section (A); and
a second cylindrical section (C); the second
cylindrical section being adapted to be resiliently loaded
by means of a retainer spring; and
a collar section (C) disposed in between the first
cylindrical section (A) and the second cylindrical
section (C); the collar section (B) extending radially
outwardly from the first and second cylindrical section
(A, C);
a base assembly (108) secured to the second end (101b) of the casing
(101); the base assembly (108) having a base (108a) and a plurality of fixed
contacts (108d);
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a carrier (107) being disposed in the base (108a) and movable in the
longitudinal direction;
the carrier being resiliently supported on the base (108) by
means of a moving contact spring (108b); and
a moving contact (108c) secured to the carrier (107) and
movable along with the carrier in the longitudinal direction.
2. A brake switch as claimed in claim 1, wherein the plunger (104a) has a
cylindrical channel defining an open end (W) and a closed end (W’).
3. A brake switch as claimed in claims 1 and 2, wherein the plunger spring
(104b) is accommodated in the interior of the said cylindrical channel.
4. A brake switch as claimed in claims 1, 2 and 3, wherein the plunger spring
(104b) is supported by a circular washer (104c) from the open end (W).
5. A brake switch as claimed in claim 1, wherein a plunger medium (104d) is
received in the channel (104e) from the open end (W) such that it is under
a force of the plunger spring (104b).
6. A brake switch as claimed in claims 1 and 5, wherein the plunger medium
(104d) is provided with a flanged portion (104d1) extending radially
outwardly; the flanged portion (104d1) being supported on the circular
washer (104c); the circular washer (104c) being adapted to be locked by a
corresponding inward flange/caulking on the plunger (104a).
7. A brake switch as claimed in claim 1, wherein the support plate (105) has
an upper face and a lower face; and comprising a through hole in the
centre to allow the passage of the plunger medium (104d) there-through
during actuation of the plunger (104).
8. A brake switch as claimed in claims 1 and 5, wherein the plunger assembly
(104) is supported on the supported plate (105) by means of the retainer
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spring (103); the retainer spring (103) being supported on the upper face of
the support plate (105).
9. A brake switch as claimed in claim 1, wherein a diaphragm (106) is
interposed between the lower face of support plate (105) and the proximal
end of the base (108a).
10. A brake switch as claimed in claim 1, wherein the carrier (107) has an
upper face (107a) and lower face (107b); the upper face being adapted to
abut the diaphragm (106) co-axially.
11. A brake switch as claimed in claims 1 and 10, wherein a cylindrical
protrusion (107c) is extending perpendicularly away from the lower face
(107b) of the carrier.
12. A brake switch as claimed in claims 1 and 10, wherein a plurality of
guiding slots (107d) is formed oppositely on the sides of the carrier in the
longitudinal direction.
13. A brake switch as claimed in claims 1 and 12, wherein the moving contact
(108c) is secured to a cylindrical protrusion of the carrier (107).
14. A brake switch as claimed in claim 1, wherein a plurality of guiding pins
(108f) is formed oppositely on the sides of the base (108a) in the
longitudinal direction.
15. A brake switch as claimed in claim 1, wherein the base (108a) is provided
with mounting slots (M) to accommodate the fixed contacts (108d).
16. A brake switch as claimed in claim 1, wherein the fixed contacts (108d)
comprising terminals (108d2) and bimetallic rivets (108d1).
17. A brake switch as claimed in claims 1, 13 and 15, wherein the moving
contact (108c) is maintained in contact with the fixed contacts (108d)
under normal/non-actuated condition of the brake switch.
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18. A brake switch as claimed in claims 1 and 15, wherein the terminals
(108d2) have a short arm (S) and a long arm (T).
19. A brake switch as claimed in claims 1, 6 and 7, wherein Caulking (CK2) is
done on long arm (T) of the terminal (108d2) at the interface of
rectangular washer (108e).
20. A brake switch as claimed in claims 1, 12 and 14, wherein the guiding
slots (107d) are adapted to receive the guiding pins (108f) of the base
(108a).
21. A brake switch as claimed in claim 1, wherein the plunger spring has a
stiffness (Ka) greater than the stiffness (Kb) of the moving contact spring.
22. A brake switch as claimed in claim 1, wherein caulking (CK1) has been
done to secure the base assembly (108) to the second end (101b) of the
casing (101).