Switching mechanism and electric switch using the same

Details Switching mechanism and electric switch using the same Switching mechanism and electric switch using the same

2002-11-19

2003-12-16

Enad, Elvin (Department: 2832)

Electricity: circuit makers and breakers

Snap

Double snap

C200S332200

Reexamination Certificate

active

06664490

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switching mechanism and an electric switch, and more particularly to a switching mechanism for a spring-reversal type of electric switch appropriate for use in electric power tools.
2. Related Arts
Spring-reversal type of electric switches are used in electric power tools for closing and opening their circuits in which heavy current flows. Such spring-reversal type of electric switches give a pleasing click feeling to users at the time of turning on and off, and the quick “on” and “off” switching action is appropriate for closing and opening circuits in which heavy currents flow. Also, spring-reversal type of electric switches can be used commonly for AC and DC.
Spring-reversal type of electric switches, however are liable to allow their contacts to bounce at the time of turning on and off. Particularly at the time of turning “on” a rush current flows, thereby making it easy for arcs to appear across confronting contacts as a result of bouncing. Thus, the contacts will be badly worn or deformed and accordingly the life of the electric switches will be shortened.
A conventional contact-making mechanism comprises a spring reversal mechanism, a push spring for producing a given strength of pressure and associated movable contacts. The contact-making mechanism, however, is liable to reduce drastically its contact pressure just prior to the reversing action, which is caused by the push spring. If the electric switch should be shaken at the instant of the contact pressure being reduced, arks are liable to appear with the result that the contacts are badly worn or deformed.
With a view to solve these problems of spring-reversal type of electric switches, DE19930558A1 proposes an improved contact-making mechanism, which is described below by referring to
FIGS. 18
to
25
.
The improved spring-reversal type of electric switch
1
comprises a housing
2
, a base
3
, a cover
4
, stationary contacts
5
and associated terminals
6
, a slide
7
and associated movable contacts
8
(see FIG.
19
), an operating lever
9
for switching operation, a first spring
10
and associated contact detents
11
a
and
11
b
(see FIG.
21
), a second spring
12
, a slider
13
and compression springs
28
(see FIG.
19
).
As seen from
FIG. 18
, the housing
2
has four stationary contacts
5
and associated terminals
6
fastened to its bottom, and electric wires are connected to the terminals
6
.
The slide
7
has four movable contacts
8
and two compression springs
28
on its lower surface as seen from FIG.
19
. As seen from
FIG. 20
, the slide
7
is put in the housing
2
with the movable contacts
8
confronting the stationary contacts
5
.
A carrier
16
has openings
17
on its opposite end walls (see FIG.
18
). The carrier
16
contains the second spring
12
, and is movable on the slide
7
. Two stoppers
19
a
and
19
b
and a guide
14
are fastened to the upper surface of the slide
7
. The guide
14
takes the role of guiding the projections
15
a
and
15
b
of the slider
13
for engaging with the second spring
12
.
The slide
7
along with the slider
13
can move between the switching “off” position in which the movable contacts
8
are apart from the stationary contacts
5
and the switching “on” position in which the movable contacts
8
are in contact with the stationary contacts
5
.
The second spring
12
is a compression spring, which can produce a counter force opposite to the direction in which the slide
7
moves on the way to the switching point, and can produce a force in the direction in which the slide
7
moves when the switching point has been traversed.
The first U-shaped spring
10
is a kind of compression spring, and the U-shaped spring
10
has two legs
20
a
and
20
b
, each having a ramp
21
projecting outward. The spring constant of the first spring
10
is so determined that the force produced at the switching point of the first spring
10
may be equal to the sum of the two compression springs
28
positioned behind the movable contacts
8
.
The contact detents
11
a
and
11
b
are given in the form of ramps
22
projecting inward from the opposite longitudinal sides of the housing
2
. Each ramp
22
is shaped asymmetric.
The first spring
10
works in cooperation with the detents
11
a
and
11
b
as follows: when the operating lever
9
is pushed and rotated about its pivot to drive the slide
7
for the switching-on position, the spring
10
is responsive to movement of the slide
7
for storing its resilient energy as a counter reaction until the point of critical compression (switching point) has been reached, at which point of critical compression the resistance to movement of the slide
7
is maximized. Then, the stored energy is suddenly released to jerk the slide
7
to the switching-on position.
The slider
13
is operatively connected to the operating lever
9
so that depression of the operating lever
9
may make the slider
13
withdraw, and that release of the operating lever
9
may make the slider
13
advance. The slider
13
has a third spring
24
contained in its chamber
27
, and it has stoppers
18
a
,
18
b
and
25
formed on its front and rear sides respectively. The stoppers
18
a
,
18
b
are formed on the projections
15
a
and
15
b.
The projections
15
a
and
15
b
act on the opposite ends of the second spring
12
via the guides
14
of the slide
7
, as seen from FIG.
20
.
There is play left between the stoppers
18
a
,
18
b
of the slider
13
and the stoppers
19
a
,
19
b
of the slide
7
, so that the slider
13
when pushed forward may travel the short distance of play before engaging with the second spring
12
.
The electric switch
1
turns on and off as follows: first, the electric switch
1
is put in the switching “off”-position as shown in
FIG. 22
, and then, the operating lever
9
is depressed so that the slider
13
may act on the left end of the second spring
12
via the projection
15
a
to stretch the spring
12
. After reducing the play the stopper
18
mates with the stopper
19
a
with the result that the slide
7
is displaced rightward for the switching “on”-position.
The slow displacement continues until the switching point has been reached while overcoming the counter force of the first spring
10
with its opposite legs abutting the detents
11
a
,
11
b
. After traversing the switching point the energy stored in the first spring
10
and the second spring
12
are released instantly, thereby jerking the slide
7
rightward to the switching “on” position as shown in FIG.
23
. The movable contacts
8
mate with the stationary contacts
5
, and then, the compression spring
28
is compressed (see FIG.
20
).
If it is desired that the electric switch
1
turn off, the operating lever
9
is released to reset the slider
13
by the third spring
24
(see FIG.
20
). In resetting the slider
13
the projection
15
b
acts on the right end of the second spring
12
, stretching the second spring
12
after reducing the play. For the while the slide
7
remains still, keeping the movable contacts
8
and stationary contacts
5
mating together.
Thereafter the slide
7
moves a very short distance leftward by the force of the first spring
10
abutting the steep inclinations
29
b
of the ramps
22
. The movable contacts
8
, however, are kept still abutting on the stationary contacts
5
as the compression spring
28
is loosened. This position continues until the switching point has been reached (see FIG.
25
).
After the switching point is traversed, the total energy stored in the first spring
10
and the second spring
12
is released to jerk the slide
7
leftward instantly, allowing the movable contacts
8
to leave the stationary contacts
5
. Thus, the electric switch
1
turns “off”, as shown in FIG.
22
.
The electric switch
1
uses the compression spring (first spring
10
) to suppress the bouncing of the movable contacts off the stationary contacts. Specifically the movable contacts are so

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