Safety switch

Details Safety switch Safety switch

2000-09-05

2001-10-30

Bradley, Paula (Department: 2832)

Electricity: circuit makers and breakers

Switch activation inhibitor

Actuator locking device

C200S061620

Reexamination Certificate

active

06310305

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a safety switch assembly mounted at place on a wall such as near a doorway to a room with an industrial machine installed therein and operative to shut off the power to the industrial machine when a door at the doorway is opened.
BACKGROUND ART
In dangerous zones such as rooms or plants with the industrial machines installed therein, the provision of a lock system is required for locking the machine drive at incomplete closure of the door to the dangerous zone in order that trouble of injury of an operator getting caught in the machine is obviated.
As such a lock system, there has been proposed to the art a safety switch assembly of an arrangement shown in
FIGS. 16
to
26
.
The safety switch assembly is electrically connected to an industrial machine installed in a room and consists of a switch body
101
and an actuator
102
, as shown in
FIGS. 16
to
18
. The switch body
101
is secured to a wall surface near a doorway to the room, whereas the actuator
102
is secured to a door
103
. The actuator is positioned in corresponding relation to a slot
101
a
of the switch body
101
so as to enter an operation section
111
of the switch body
101
when the door
103
is closed.
The ingress of the actuator
102
closes a connection contact of a contact block
9
incorporated in a switch section
112
, thereby providing power supply to the machine in the room for machine drive. When, on the other hand, the door
103
is opened to remove the actuator
102
from the operation section
111
, the operation section
111
returns to its initial state with the open connection contact of the contact block
9
, thereby shutting off the power to the machine.
As shown in
FIG. 16
, the actuator
102
consists of a pressure piece
121
and a pair of support pieces
122
,
123
supporting the pressure piece. The pressure piece
121
is formed with projected pressure faces
121
b,
121
b
at opposite ends thereof and a depressed pressure face
121
a
interposed therebetween.
Next, description will be made on the arrangement of the operation section
111
. As shown in
FIGS. 19
to
23
, the operation section
111
includes a drive cam
1
in the center thereof, which is rotatably carried by a support frame
11
via a cam shaft
4
for moving an operative rod
8
of the switch section
112
.
The drive cam
1
is formed with rectangular recesses
1
a,
1
b
in its outer periphery for receiving the pressure piece
121
of the actuator
102
, the recesses adapted to correspond to a slot
101
a
or
101
b.
The drive cam
1
is also formed with a cam groove
1
c
on the opposite side from the recesses
1
a,
1
b
with respect to the cam shaft
4
. A cam follower pin
6
is inserted through the cam groove
1
c.
Opposite ends of the cam follower pin
6
reach the proximity of the support frame
11
and are supported by guide grooves
7
a,
7
b
of pin guides
7
, respectively. The guide grooves
7
a,
7
b
serve to limit the movement of the cam follower pin
6
in one direction and are formed along straight lines each extending through the center of the cam shaft
4
and parallel to the movement of the operative rod
8
.
The cam follower pin
6
is coupled to an end of the operative rod
8
so that the movement of the cam follower pin
6
causes the operative rod
8
to move forward or backward to switch the connection contact of the switch section
112
between a closed position and an open position.
The actuator is provided with control plates
2
,
3
on lateral sides thereof. The pair of control plates
2
,
3
are disposed in corresponding relation to the projected pressure faces
121
b,
121
b
of the actuator
102
and are rotatably carried by the cam shaft
4
. Torsion coil springs
5
,
5
are mounted to respective places between the control plates
2
,
3
and the support frame
11
(shown in
FIGS. 19 and 20
) for returning the control plates
2
,
3
to their respective initial positions. The torsion coil spring
5
,
5
has one end thereof fixed to the support frame
1
and the other to the control plate
2
,
3
.
The control plates
2
,
3
are each formed with a relief hole
2
a,
3
a,
an edge of which is defined with a notch
2
b,
3
b
for restricting the movement of the cam follower pin
6
.
The notch
2
b,
3
b
is cut into a semi-circular shape to receive the cam follower pin
6
, as shown in FIG.
23
. When the control plate
2
,
3
is in the initial state (shown in FIGS.
20
and
21
), the notch is positioned ahead of the cam follower pin
6
with respect of the movement thereof, as shown in FIG.
24
A.
In the above arrangement, the drive cam
1
and the control plates
2
,
3
in the initial state shown in
FIGS. 20 and 21
are located in such a positional relation as to produce a rotational phase difference corresponding to a level difference between the depressed pressure face
121
a
and the projected pressure faces
121
b,
121
b
of the actuator
102
.
Now referring to
FIGS. 24A
,
24
B and
24
C, the operations will be described. Incidentally, although
FIGS. 24A
to
24
C omits the reference character
3
for the unillustrated control plate on the left side as viewed from the slot
101
a
of the operation section
111
, the control plate will be represented as “
2
,
3
” herein because the pair of control plates operate in the same manner in this embodiment.
When the actuator
102
enters an interior of the operation section
111
through the slot
101
a,
the depressed pressure face
121
a
and projected pressure faces
121
b,
121
b
at a distal end thereof first come into contact with the drive cam
1
and the control plates
2
,
3
, respectively (see
FIGS. 24
a
). At this point of time, the cam follower pin
6
is not moved, staying at a cam-shaft-side end of the cam groove
1
c
of the drive cam
1
.
Further ingress of the actuator
102
brings the drive cam
1
and control plates
2
,
3
into rotation to advance the cam follower pin
6
along the cam groove
1
c
and to displace the notches
2
b,
3
b
of the control plates
2
,
3
out of the travel path of the follower pin
6
(see FIG.
24
B). Subsequently, when the actuator
102
is further advanced to an insertion end, the connection contact of the switch section
112
is closed while the pressure piece
121
of the actuator
102
is fit in the recess
1
a
of the drive cam
1
, as shown in FIG.
24
C.
When the control plates
2
,
3
are rotated in the above operations, the torsion coil springs
5
,
5
are twisted in the direction of rotation so that the control plates
2
,
3
are subject to a torque in the opposite direction to the rotation (returning force) resulting from the resilient force of the springs.
In removal of the actuator
102
from the position shown in
FIG. 24C
, the pressure piece thereof
121
pushes an inside surface of the recess
1
a
thereby bringing the drive cam
1
into the reverse rotation of that during the ingress of the actuator. This permits the operative rod
8
to retreat, returning the connection contact to its initial position (open) while the recess
1
a
of the drive cam
1
returns to its initial position shown in FIG.
24
A. On the other hand, the control plates
2
,
3
are urged back to their initial positions by the torsion coil springs
5
,
5
, thus replacing the pin-lock notches
2
b,
3
b
on the travel path for the cam follower pin
6
.
Although the operations of the operation section are described by way of example where the actuator
102
is inserted in the slot
101
a
on a front side of the operation section
111
, which include the two slots
101
a
and
101
b.
However, when the actuator
102
is inserted in the slot
101
b
on a top side of the operation section
111
, the same operations as shown in
FIGS. 24A
to
24
C take place. That is, the drive cam
1
and control plates
2
,
3
are rotated to advance the operative rod
8
thereby switching the connection contact while the pressure piece
121
of the actuator
102
is fitted in the recess
1
b
of the drive cam
1
.
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