Safety switch

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

.

At this time, any attempt to rotate the drive cam

1

with an operating plate (such as a screwdriver or the like) other than the dedicated actuator

102

is disabled by the control plates

2

,

3

.

When a pressure plate D is inserted through a central portion of the slot

101

a

(or

10

b

) to be pressed against the recess

1

a

(or

1

b

) of the drive cam

1

, as shown in

FIG. 25A

, the drive cam is rotated a little as shown in FIG.

25

B. However, when the pressure plate D approaches the control plates

2

,

3

, the notches

2

b,

3

b

of the control plates control the forward movement of the cam follower pin

6

while the guide grooves

7

a,

7

a

of the pin guides

7

hold the cam follower pin

6

, controlling the movement thereof in the rotation direction. Thus, the cam follower pin

6

cannot move forward nor in the rotation direction, disabling the rotation of the drive cam

1

.

Even if both or either of the control plates

2

,

3

is rotated using the pressure plate D, the drive cam

1

never rotates. In the initial state of the drive cam

1

and control plates

2

,

3

as shown in

FIG. 26A

, the cam follower pin

6

is positioned out of interference with the notches

2

b,

3

b

of the control plates

2

,

3

. Therefore, as shown in

FIG. 26B

, the attempt to rotate the control plates

2

,

3

by pushing them with the pressure plate D only results in the rotation of the control plates

2

,

3

alone while the drive cam

1

stands still with no force applied thereto.

In the safety switch assembly, the drive cam

1

is adapted to rotate to switch the connection contact of the contact block

9

incorporated in the switch section

112

only when the depressed pressure face

121

a

and projected pressure faces

121

b,

121

b

of the actuator

102

substantially simultaneously press the drive cam

1

and the control plates

2

,

3

on the opposite sides thereof. Hence, even if an attempt to rotate the drive cam

1

is made by inserting a tool with a flat tip, such as a screwdriver, into the operation section

111

, the rotation of the drive cam

1

is prevented for inhibition of the operation of the operation section

111

.

However, a problem exists with the arrangement wherein the ingress of the actuator into the operation section

111

enables the drive of the machine in the room but the egress of the actuator

102

from the operation section

111

at the opening of the door

103

returns the operation section

111

to its initial state to shut off the power to the machine whereby the operator is allowed to enter the room. That is, the arrangement involves fear that if a third person unaware of the presence of the operator in the room inadvertently closes the door

103

, the actuator

102

is re-inserted in the operation section

111

to enable the drive of the machine in the room in which the operator is locked.

The conventional safety switch assembly mentioned above involves the possibility of occurrence of such an event because the ON/OFF control of the power supply to the industrial machine in the room depends upon whether the actuator

102

is inserted in the operation section

111

or not.

The invention contemplates the solution to the above problem and is directed to prevent the inadvertent closure of the door or the like from enabling the power supply to the industrial machine in the presence of the operator in the dangerous zone and to prevent the operator from being locked in the dangerous zone.

DISCLOSURE OF THE INVENTION

According to the invention for achieving the above object, a safety switch assembly for providing ON/OFF control of a main circuit via a connection contact switched by an operative rod of a switch section moved by an actuator inserted in an operation section of a switch body is characterized in that the operation section includes a drive cam formed with a lock step in its periphery and rotated according to ingress or egress of the actuator; that a main lock mechanism is juxtaposed with the switch body and comprises a switchable portion selectively switched between Lock position and Unlock position, an operation piece removably mounted to the switchable portion for switching operation of the switchable portion and becoming removable at transfer of the switchable portion to Unlock position, and a lock body which, during the ingress of the actuator, is locked to the lock step as interlocked with the switchable portion switched to Lock position thereby disabling the rotation of the drive cam for inhibition of the egress of the actuator and is released from the lock step as interlocked with the switchable portion switched to Unlock position thereby enabling the rotation of the drive cam for permission of the egress of the actuator; that an auxiliary lock mechanism is juxtaposed with the switch body and comprises a drive portion operated by a trigger externally applied when the switchable portion is at Lock position, an auxiliary contact connected in series with the main circuit jointly with the connection contact, and an operative portion which, during a non-operative state of the drive portion, maintains the switchable portion at Lock position for keeping the auxiliary contact closed and which, during an operative state of the drive portion, permits transfer of the switchable portion to Unlock position for opening the auxiliary contact; and that the main circuit is closed on condition that the drive portion of the auxiliary lock mechanism is non-operative, the switchable portion of the main lock mechanism is at Lock position and the actuator is inserted.

In this arrangement, even if the door is open with the actuator uninserted and then is inadvertently closed to insert the actuator despite the presence of the operator in the room as the dangerous zone wherein the industrial machine is installed, the main circuit stays open disabling the power supply to the industrial machine unless the drive portion of the auxiliary lock mechanism is switched to the non-operative state thereby to switch the switchable portion of the main lock mechanism to Lock position.

In short, the main circuit is closed only when the drive portion of the auxiliary lock mechanism is non-operative, the switchable portion of the main lock mechanism is at Lock position and the actuator is inserted. This obviates the event that the power supply to the industrial machine is started by the inadvertent closure of the door when the operator is present in the dangerous zone or that the operator is locked in the dangerous zone.

According to the invention, the safety switch assembly is further characterized in that constraining means is provided for constraining the lock body for inhibition of the transfer of the switchable portion from Unlock position to Lock position when the actuator is not inserted.

In this arrangement, unless the door is closed to insert the actuator, for example, the constraining means constrains the lock body thereby to inhibit the transfer of the switchable portion to Lock position. Therefore, the safety of the operator is ensured even if, for example, the operator is present in the room as the dangerous zone and the door is inadvertently closed to insert the actuator. This is because the operation piece is incapable of transferring the switchable portion from Unlock position to Lock position as long as it is separate from the switchable portion and because the ingress of the actuator does not immediately effect the closure of the main circuit.

According to the invention, the safety switch assembly is further characterized in that the operation piece comprises a key; and that the switchable portion comprises a key-insertion portion for receiving the key, an operation cam rotated by turning the key inserted in the key-insertion portion, a cam groove defined in the operation cam, an insert pin inserted in the cam groove, and a move body which is urged by urging means in an egress direction of the actuator but is moved from Lock position to Unlock position against the urging means as interlocked with the insert pin moved by the rotation of the operation cam.

In this arrangement, the operation piece comprised of the key is easy to use while the move body of the switchable portion may readily be switched by mere turning of the key inserted in the key-insertion portion of the switchable portion. If keys are individually formed in different shapes for incompatibility, access to the dangerous zone may be limited to the operator having a key of a specific shape. Hence, the dedicated operator to the services and the prevention of misoperation of the machine contribute enhanced security.

According to the invention, the safety switch assembly is further characterized in that the drive portion of the auxiliary lock mechanism comprises a solenoid excited by the trigger; that the operative portion of the auxiliary lock mechanism comprises a plunger attractively moved by the excited solenoid and urged back to its initial place by the urging means when the solenoid is deexcited; that the operation cam is formed with a recess for removably receiving a distal end of the plunger; that the plunger has its distal end received by the recess thereby inhibiting the rotation of the operation cam for maintaining the move body at Unlock position; and that the plunger is attractively moved to disengage its distal end from the recess thereby permitting the rotation of the operation cam.

In this arrangement, the distal end of the plunger is inserted in the recess to disable the rotation of the operation cam so that the move body is maintained in Unlock position. Therefore, if in this state, the operation piece in the form of the key is inserted in the switchable portion of the main lock mechanism, the operation piece cannot be turned, thus disabled from switching the move body to Lock position. Accordingly, even if the door is inadvertently closed to insert the actuator, the move body cannot be transferred to Lock position unless the excited solenoid attractively moves the plunger for disengaging the distal end thereof from the recess. Thus, the ingress of the actuator does not immediately effect the closure of the main circuit.

According to the invention, the safety switch assembly is further characterized in that the operation piece includes one that is also used for the drive of a system besides the main circuit.

This arrangement provides for such procedures that after removing the operation piece from the switchable portion of the main lock mechanism, the operator enters a room, as the dangerous zone where an additional system as well as the main circuit are installed, and uses the operation piece to drive the additional system. Thus, the operator can safely perform the maintenance services on the additional system in the dangerous zone.

According to the invention, the safety switch assembly is further characterized in that the trigger is applied by a manual operation or a control unit on condition that an electrical equipment connected to the main circuit is shut down.

In this arrangement, unless the electrical equipment is shut down, the drive portion of the auxiliary lock mechanism cannot be actuated to transfer the switchable portion of the main lock mechanism to Unlock position where the lock body of the main lock mechanism permits the egress of the actuator (for example, permit the door to be opened). Hence, the operator is prevented from entering the dangerous zone when the electrical equipment is in operation.

According to the invention, the safety switch assembly is further characterized in that the switch body is secured to place near a doorway formed in a partitioning wall defining a specific area in a building; that the actuator is secured to a door disposed at the doorway; and that when the actuator is removed from the operation section by opening the door, the operation piece becomes removable from the switchable portion to be brought by an operator with him into the specific area.

In this arrangement, if a need arises, for example, for the operator to enter the specific area containing the industrial machine equipped with the main circuit in order to perform the maintenance services on the industrial machine, the main circuit is never closed to supply the power to the industrial machine under service as long as the operator brings the operation piece with him in the specific area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view showing a first embodiment of the invention;

FIG. 2

is a perspective view showing the first embodiment hereof in another state;

FIG. 3

is a perspective view showing the first embodiment hereof in yet another state;

FIG. 4

is a plan view showing the first embodiment hereof;

FIG. 5

is a plan view showing the first embodiment hereof without a cover;

FIG. 6

is a perspective view showing a lock body according to the first embodiment hereof;

FIG. 7

is a plan view showing a lock mechanism body without a cover according to the first embodiment hereof;

FIG. 8

is a plan view showing the lock mechanism body according to the first embodiment hereof;

FIG. 9

is a bottom view showing the cover of the lock mechanism body according to the first embodiment hereof;

FIG. 10

is a plan view showing the lock mechanism body without the cover according to the first embodiment hereof;

FIG. 11

is a plan view showing a state of the lock mechanism body without the cover according to the first embodiment hereof;

FIG. 12

is a plan view showing another state of the lock mechanism body without the cover according to the first embodiment hereof;

FIG. 13

is a plan view showing yet another state of the lock mechanism body without the cover according to the first embodiment hereof;

FIG. 14

is a plan view showing a lock mechanism body without a cover according to a second embodiment hereof;

FIG. 15

is a plan view showing a lock mechanism body without a cover according to a third embodiment hereof;

FIG. 16

is a perspective view showing a state of a background art example of the invention;

FIG. 17

is a plan view showing the background art example hereof without a cover;

FIG. 18

is a side view showing the background art example hereof with the cover broken away;

FIG. 19

is a plan view showing a part of the background art example hereof with the cover broken away;

FIG. 20

is a side view showing a part of the background art example hereof with the cover broken away;

FIG. 21

is a vertical section taken along the line on the center of a part of the background art example hereof;

FIGS. 22A

, and

22

B are a group of diagrams explanatory of the operations of another part of the background art example hereof;

FIG. 23

is a side view showing yet another part of the background art example hereof;

FIGS. 24A

to

24

C are a group of diagrams explanatory of operations of the background art example art hereof;

FIGS. 25A

to

25

C are a group of diagrams explanatory of the operations of the background art example hereof;

FIGS. 26A

, and

26

B are a group of diagrams explanatory of the operations of the background art example hereof; and

FIG. 27

shows the main circuit, the connection contact and the auxiliary contact.

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment)

Now, a first embodiment of the invention will be described with reference to

FIGS. 1

to

13

.

FIGS. 1

to

3

are perspective views each showing a different state of the first embodiment;

FIG. 4

a plan view thereof;

FIG. 5

a plan view thereof with a cover removed;

FIG. 6

a perspective view of a lock body;

FIG. 7

a plan view of a lock mechanism body with the cover removed;

FIG. 8

a plan view of the lock mechanism body;

FIG. 9

a bottom view of the cover of the lock mechanism body;

FIGS. 10

to

13

plan views each showing a different state of the lock mechanism body with the cover removed.

Generally likewise to the conventional safety switch assembly mentioned supra, a safety switch assembly according to the first embodiment is electrically connected to an industrial machine installed in a room as a dangerous zone. The safety switch assembly comprises a switch body

200

; a main lock mechanism body

210

juxtaposed with the switch body

200

and including a main lock mechanism

211

and an auxiliary lock mechanism

212

; and an actuator

220

.

Likewise to the conventional example, the switch body

200

and the lock mechanism body

210

are secured to a wall of the room near its doorway whereas the actuator

220

is secured to a door

230

. The actuator

220

is positioned in corresponding relation to one

201

a

of slots

201

a,

201

b

of the switch body

200

so as to enter an operation section

202

of the switch body

200

when the door

230

is closed.

If, at the ingress of the actuator

220

, a drive portion (described later) of the auxiliary lock mechanism

212

is non-operative while the main lock mechanism

211

is in Lock position, a connection contact of a contact block

9

incorporated in a switch section

203

of the switch body

200

is closed. This closes a main circuit to energize the machine in the room so that the machine becomes drivable. On the other hand, the main circuit is opened to shut off the power to the machine in any of the cases where the drive portion of the auxiliary lock mechanism

212

is in operative state, where the main lock mechanism

211

is in Unlock position, and where the actuator

220

is removed from the operation section

202

by opening the door

230

.

Likewise to the conventional example, the actuator

220

has an insertion portion into the operation section

202

, which comprises a pressure piece

221

at a distal end thereof and a pair of support pieces

222

,

223

supporting the pressure piece, as shown in FIG.

3

. The pressure piece

221

is formed with projected pressure faces

221

b,

221

b

at opposite ends thereof and a depressed pressure face

221

a

interposed therebetween.

The operation section

202

and switch section

203

of the switch body

200

is essentially of the same arrangement as the conventional example. The operation section

202

comprises the drive cam

1

; control plates

2

,

3

disposed on lateral sides of the drive cam; the cam shaft

4

for rotatably bearing these; the torsion coil springs

5

for urging the control plates

2

,

3

; the cam follower pin

6

and the like. The rotation of the drive cam

1

causes the cam follower pin

6

to move. This causes the operative rod

8

of the switch section

203

to advance or retreat, thereby switching the connection contact of the contact block

9

of the switch section

203

between the closed position and the open position. The drive cam

1

is rotated only when the drive cam

1

and the control plates

2

,

3

are substantially simultaneously pressed by the actuator

220

inserted in the operation section

202

.

Since the operation section

202

and the switch section

203

generally operate the same way as the conventional example, the following description on the operation section

202

, the switch section

203

and other portions of the embodiment principally focuses on differences from the conventional example, dispensing with the redundancies.

As shown in

FIG. 5

, the operation section

202

is provided with a lock body

240

constituting a part of the main lock mechanism

211

. The lock body

240

disables the rotation of the drive cam

1

thereby inhibiting the egress of the actuator

220

(unremovable). On the other hand, the lock body permits the rotation of the drive cam

1

as interlocked with a switchable portion

250

of the main lock mechanism

211

switched to Unlock position, thereby permitting the egress of the actuator

220

(removable).

The lock body

240

is disposed at place above the drive cam

1

and the control plates

2

,

3

and comprises a support piece

241

, engagement pieces

242

,

242

formed by downward bending of opposite ends of the support piece

241

, and a locking piece

243

formed integrally with the support piece

241

and having a U-shaped form as viewed in plan. One of the engagement pieces

242

of the support piece

241

is disposed in a recess

11

a

defined in the support frame

11

of the operation section

202

and is engaged with a part of a move body of the main lock mechanism

211

to be described later.

Next, description is made on the arrangement of the main lock mechanism

211

and auxiliary lock mechanism

212

of the lock mechanism body

210

. First, the main lock mechanism

211

comprises the switchable portion

250

selectively switched between Lock position and Unlock position; an operation piece

260

removably mounted to the switchable portion

250

for switching operation of the switchable portion

250

and becoming removable at transfer of the switchable portion

250

to Unlock position; and the lock body

240

.

The auxiliary lock mechanism

212

comprises a drive portion

270

actuated by a trigger externally applied upon transfer of the switchable portion

250

to Lock position; an auxiliary contact

280

jointly forming a series circuit with the connection contact

217

of the contact block

9

of the switch section

203

to be connected in series with the main circuit

215

and switched between the closed position and the open position depending upon whether the drive portion

270

is in the non-operative state or in the operative state; and an operative portion

290

operative to maintain the switchable portion

250

at Lock position for keeping the auxiliary contact

280

closed during the non-operative state of the drive portion

270

or to switch the switchable portion

250

to Unlock position when the drive portion

270

is operative (see also FIG.

27

).

More specifically, the operation piece

260

of the main lock mechanism

211

comprises a key to be turned in a locking direction or an unlocking direction as distinctly depicted in

FIGS. 2 and 3

. As shown in

FIGS. 7

to

9

, the switchable portion

250

comprises a key-insertion portion

251

disposed at a cover

211

a

of the lock mechanism body

210

for receiving the key (operation piece)

260

; an operation cam including a first cam

252

a

and a second cam

252

b

and brought into rotation by turning the key (operation piece)

260

in the key-insertion portion

251

in the locking direction or the unlocking direction; a cam groove

253

defined in the second cam

252

b

of the operation cam; an insert pin

254

inserted in the cam groove

253

; and a move body

256

urged by a spring

255

, as urging means, in the egress direction of the actuator

220

and moved (advanced) against the spring

255

from Lock position to Unlock position as interlocked with the insert pin

254

moved by the rotation of the second cam

252

b

of the operation cam.

As shown in

FIG. 7

, the spring

255

is mounted in a minor chamber

210

c

in encompassing relation to a rod

256

a

of the move body

256

and has its opposite ends locked to a partitioning wall

210

d

and an operative body

256

b

thereby urging the operative body

256

b

and the rod

256

a

toward Unlock position (in the egress direction of the actuator

220

).

As shown in

FIG. 9

, the first cam

252

a

of the operation cam is mounted on a back side of a cover

211

a

of the key-insertion portion

251

so as to rotate as interlocked with the rotation of the key (operation piece)

260

. The first cam

252

a

is formed with a concave

252

c

in its lower surface. The second cam

252

b,

as shown in

FIG. 7

, is formed with a convex

252

d

in its upper surface to fit in the concave

252

c

such that the engagement between the concave

252

c

and the convex

252

d

establishes interlock between the first cam

252

a

and the second cam

252

b

for rotation.

The cam groove

253

is defined in the upper surface of the second cam

252

b

and includes a pin locking portion

253

a

defined at one end thereof, as shown in FIG.

7

. When the move body

256

is at Unlock position, the insert pin

254

is locked in the pin locking portion

253

a.

Further referring to

FIG. 7

, the move body

256

comprises the rod

256

a,

the operative body

256

b

orthogonally mounted to the rod

256

a,

and a U-body

256

c

to be described later. The rod

256

a

extends through the partitioning wall

210

d

to be disposed in the minor chamber

210

c,

the partitioning wall dividing the interior of the lock mechanism body

210

into a major chamber

210

b and the minor chamber

210

c.

The rod

256

a

is longitudinally movably carried on opposite ends thereof so as to alternate between Lock position and Unlock position. The insert pin

254

is attached to one end of the rod

254

a

extended into the major chamber

210

b

whereas the operative body

256

b

is attached to the other end of the rod

256

a

in the minor chamber

210

c.

The operative body

256

b

is integrally formed with the U-body

256

c,

as constraining means, at one end thereof. The U-body

256

c

extends through a wall of the lock mechanism body

210

into the switch body

200

, receiving a lower end of one of the engagement pieces

242

of the lock body

240

. Thus, when the actuator

220

is not present in the operation section, the lock body

240

is constrained thereby to inhibit the transfer (retreat) of the move body

256

from Lock position to Unlock position.

When the move body

256

is moved (retreated) to Lock position, the U-body

256

c

urges the lower end of one of the engagement pieces

242

of the lock body

240

in the retreat direction thereby bringing the lock body

240

into rotation about the support piece

241

in a direction to present the locking piece

243

thereof to the drive cam

1

and control plates

2

,

3

. Accordingly, the locking piece

243

is locked in lock steps

1

d

and

2

c,

3

c

which are formed on respective peripheries of small radius portions of the drive cam

1

and control plates

2

,

3

(see FIGS.

22

B and

23

). This inhibits the rotation of the drive cam

1

and control plates

2

,

3

for inhibition of the egress of the actuator

220

.

When the move body

256

of the main lock mechanism

211

is moved (advanced) to Unlock position, the U-body

256

c

urges the lower end of the one engagement piece

242

of the lock body

240

in the opposite direction to the above thereby bringing the lock body

240

into rotation about the support piece

241

in a direction to bring the locking piece

243

away from the drive cam

1

and control plates

2

,

3

. Accordingly, the locking piece

243

is disengaged from the lock steps

1

d

and

2

c,

3

c

of the drive cam

1

and control plates

2

,

3

. Thus, the drive cam

1

and control plates

2

,

3

are allowed to rotate thereby permitting the egress of the actuator

220

.

The engagement between the one engagement piece

242

of the lock body

240

and the U-body

256

c

provides the following operation in a case where the actuator

220

is not inserted in the operation section

202

while the key (operation piece)

260

is removed. When the key (operation piece)

260

is inserted and turned in the locking direction to transfer (retreat) the move body

256

from Unlock position to Lock position, the U-body

256

urges the lower end of the one engagement piece

242

of the lock body

240

in the retreating direction. This causes the locking piece

243

to pivot about the support piece

241

toward the drive cam

1

and the control plates

2

,

3

and to abut against peripheries of great radius portions of the drive cam

1

and control plates

2

,

3

. Thus, further rotation of the lock body

240

is disabled. The lock body

240

is constrained so that the move body

256

is inhibited from transferring from Unlock position to Lock position. That is, a state is established wherein the key (operation piece)

260

cannot be turned.

The drive portion

270

of the auxiliary lock mechanism

212

comprises a solenoid excited by an external trigger. The operative portion

290

of the auxiliary lock mechanism

212

comprises a plunger which is attracted by the excited solenoid (drive portion)

270

to move (advance) against a spring

291

, as urging means, but is urged back (retreat) to its initial position by the spring

291

when the solenoid (drive portion)

270

is deexcited. It is noted that the spring

291

urges the plunger (operative portion)

290

in the same direction that a distal end of the plunger approaches the first cam

252

a

of the operation cam (retreat direction). The auxiliary contact

280

in series with the main circuit is opened or closed corresponding to the excitation (operative state) or deexcitation (non-operative state) of the solenoid (drive portion)

270

.

When the solenoid (drive portion)

270

is deexcited, the spring

291

is allowed to urge the plunger (operative portion)

290

back to its retreat position, the distal end of the plunger (operative portion)

290

slidably moving from a great radius portion to a small radius portion of the first cam

252

a

rotated by the key (operation piece)

260

turned in the locking direction.

The external trigger for exciting the solenoid (drive portion)

270

may be applied as an electrical signal through manual operation of the operator or based on sequence of an unillustrated control unit. The application of the trigger is at least conditional on the shutoff of the power to the industrial machine connected to the main circuit.

The plunger (operative portion)

290

is formed with a projection

292

at its distal end which removably engages a protrusion

252

e

formed at the first cam

252

a

of the operation cam (see FIG.

9

).

When the key (operation piece)

260

inserted in the key-insertion portion

251

is turned in the locking direction, the distal end of the plunger (operative portion)

290

slidably moves on the periphery of the first cam

252

a

of the operation cam to establish the engagement between the projection

292

and the protrusion

252

e.

The engagement inhibits the rotation of the first cam

252

a

thereby to disable the key (operation piece)

260

from turning in the unlocking direction. Thus, the move body

256

is maintained at Lock position. The move body

256

may be released from Lock position by exciting the solenoid (drive portion)

270

for attraction of the plunger (operative portion)

290

whereby the projection

292

at the distal end of the plunger (operative portion)

290

is disengaged from the protrusion

252

e.

Next, description will be made on the operations of the embodiment. If the actuator

220

enters the operation section

202

of the switch body

200

at closure of the door

230

and the key (operation piece)

260

is inserted in the key-insertion portion

251

to be turned in the locking direction, the ingress of the actuator

220

causes the rotation of the drive cam

1

and control plates

2

,

3

to advance the operative rod

8

which closes the connection contact of the contact block

9

of the switch section

203

. If, at this time, the solenoid (drive portion)

279

is deexcited (non-operative state), the auxiliary contact

280

is closed so that the main circuit is closed to supply the power to the industrial machine connected thereto, bringing the industrial machine into operation. The operative state of the machine will hereinafter be referred to as “State 1”.

In State 1, the move body

256

of the main lock mechanism

211

is moved to Lock position (retreated) as shown in FIG.

10

. Therefore, the U-body

256

c

urges the lower end of the one engagement piece

242

of the lock body

240

in the retreat direction thereby bringing the lock body

240

into rotation about the support piece

241

in the direction to present its locking piece

243

to the drive cam

1

and control plates

2

,

3

. Thus, the locking piece

243

is locked in the lock steps

1

d,

2

c

and

3

c

of the drive cam

1

and control plates

2

,

3

.

Hence, an attempt to draw out the actuator

220

is reacted by the inhibited rotation of the drive cam

1

and control plates

2

,

3

due to the lock between the locking piece

243

and the lock steps

1

d,

2

c

and

3

c

of the drive cam

1

and control plates

2

,

3

. As a result, the actuator

220

cannot be removed.

In State 1, the projection

292

at the distal end of the plunger (operative portion)

290

is engaged with the protrusion

252

e

and hence, the rotation of the first cam

252

a

of the operation cam is inhibited thereby disabling the key (operation piece)

260

from turning in the unlocking direction. Thus, the move body

256

is maintained at Lock position.

When the solenoid (drive portion)

270

is excited in State 1, the plunger (operative portion)

290

is attracted to advance against the spring

291

, as shown in

FIG. 11

, thereby disengaging the projection

292

at its distal end from the protrusion

252

e.

As advanced by the excited solenoid (drive portion)

270

, the plunger (operative portion)

290

opens the auxiliary contact

280

. The excited state of the solenoid (drive portion)

270

will hereinafter be referred to as “State 2”.

In State 2, the turning of the key (operation piece)

260

in the unlocking direction brings the first and second cams

252

a,

252

b

of the operation cam into rotation which causes the insert pin

254

to move along the cam groove

253

, as shown in FIG.

12

. This causes the move body

256

to advance against the spring

255

and then, the insert pin

254

is locked in the pin locking portion

253

a.

The state of the key (operation piece)

260

turned in the unlocking direction will hereinafter be referred to as “State 3”.

The advancement of the move body

256

causes the U-body

256

c

to urge the lower end of the one engagement piece

242

of the lock body

240

in the advance direction so that the lock body

240

rotates about the support piece

241

in the direction to bring the locking piece

243

away from the drive cam

1

and control plates

2

,

3

. This releases the locking piece from the lock steps

1

d,

2

c

and

3

c

of the drive cam

1

and control plates

2

,

3

thereby permitting the rotation of the drive cam

1

and control plates

2

,

3

. Accordingly, the actuator

220

can be drawn out of place by opening the door

230

. The state of the actuator

220

thus removed will hereinafter be referred to as “State 4”.

In State 4, the actuator

220

is not inserted and therefore, an attempt to turn the inserted key (operation piece)

260

in the locking direction is reacted as follows. While the turning of the key (operation piece)

260

tends to retreat the move body

256

to Lock position, the U-body

256

c

urges the lower end of the one engagement piece

242

of the lock body

240

in the retreat direction, bringing the lock body

240

into rotation about the support piece

241

to present its locking piece to the drive cam

1

and control plates

2

,

3

. Thus, the locking piece

243

abuts against the peripheries of the great radius portions of the drive cam

1

and control plates

2

,

3

thereby disabling the further rotation of the lock body

240

. The lock body

240

so constrained inhibits the move body

256

from retreating to Lock position. As a result, the key (operation piece)

260

cannot be turned.

When the solenoid (drive portion)

270

is deexcited in State 4, the plunger (operative portion)

290

tends to move in the retreat direction as urged by the spring

291

. However, the distal end of the plunger abuts against the periphery of the first cam

252

a

of the operation cam, as shown in FIG.

13

. Accordingly, the plunger (operative portion)

290

is inhibited from retreating thereby maintaining the auxiliary contact

280

at the open position. The state where the auxiliary contact

280

is kept open by the inhibition of the retreat of the plunger (operative portion)

290

will hereinafter be referred to as “State 5”.

In State 5, when the door

230

is closed to insert the actuator

220

into the operation section

202

, the drive cam

1

and control plates

2

,

3

rotate to advance the operative rod

8

thereby closing the connection contact of the contact block

9

. On the other hand, the rotation of the drive cam

1

and control plates

2

,

3

locates the locking piece

243

of the lock body

240

on the peripheries of the small radius portions of the drive cam

1

and control plates

2

,

3

and hence, the lock body

240

is allowed to rotate. The state of the lock body

240

allowed to rotate will hereinafter be referred to as “State 6”.

In State 6, when the key (operation piece)

206

is inserted in the key-insertion portion

251

and turned in the locking direction, the spring

291

is allowed by the deexcited solenoid (drive portion)

270

to urge the plunger (operative portion)

290

back to its retreat position, the distal end of the plunger (operative portion)

290

slidably moving from the great radius portion to the small radius portion of the first cam

252

a

rotated by the key (operation piece)

260

in the locking direction. Thus, the auxiliary contact

280

is closed thereby to close the main circuit so that the power is supplied to the industrial machine connected to the main circuit. Then, the operations return to State 1.

The safety switch assembly is adapted to close the main circuit only when the solenoid (drive portion)

270

of the auxiliary lock mechanism

212

is deexcited (non-operative), the switchable portion

250

of the main lock mechanism

211

is at Lock position, and the actuator

220

is inserted.

Accordingly, even if the door

230

is open with the actuator

220

uninserted and then is accidentally closed to insert the actuator

220

despite the presence of the operator in the room, the key (operation piece)

260

removed from the main lock mechanism

211

positively prevents the industrial machine from being energized via the closure of the main circuit, unless the steps are taken which include re-inserting the key (operation piece)

260

in the key-insertion portion

251

, deexciting the solenoid (drive portion)

270

of the auxiliary lock mechanism

212

, and turning the key (operation piece)

260

in the locking direction.

When the key (operation piece)

260

is removed, the door is unlocked so that the lock body

240

is unlocked (with the drive cam

1

and control plates

2

,

3

rotated). Therefore, the closure of the door

230

does not result in the locked state (the door

230

disabled from opening) even if it is closed. The door

230

can be opened again so that the operator is protected from being locked in the room.

In addition, it is ensured that the operator removes the key (operation piece)

260

and then enters the room bringing the key

260

with him. As long as the operator brings the key (operation piece)

260

with him when entering the room for maintenance services of the industrial machine, it never occurs that the main circuit is closed to energize the industrial machine being inspected. Hence, the operator can carry out the maintenance services with safety.

According to the first embodiment, the main circuit is closed only when the solenoid (drive portion)

270

of the auxiliary lock mechanism

212

is deexcited (non-operative), the switchable portion

250

is at Lock position, and the door

230

is closed to insert the actuator

220

. This ensures the prevention of the event that the door

230

is inadvertently closed to energize the industrial machine in the presence of the operator in the room (dangerous zone) or that the operator is locked in the room (dangerous zone).

Unless the door

230

is closed to insert the actuator

22

, the switchable portion

250

is disallowed to transfer to Lock position, resulting in the inhibition of the turning of the key (operation piece)

260

. Hence, the main circuit is kept open even if the door

230

is inadvertently closed to insert the actuator

220

despite the presence of the operator in the room (dangerous zone). In this case, the key (operation piece)

260

is allowed to turn in the locking direction only after the actuator

220

is inserted by closing the door

230

. This uniquely defines the operation procedure for closing the main circuit such that the main circuit cannot be closed unless the given procedure is followed. This contributes to further enhanced safety.

(Second Embodiment)

According to a second embodiment of the invention, the first cam

252

a

of the operation cam may be formed with a recess

252

f

in the periphery thereof for disengageably receiving the projection

292

at the distal end of the plunger (operative portion)

290

, as shown in FIG.

14

.

In this arrangement, the engagement between the projection

292

and the recess

252

f inhibits the rotation of the operation cam or the turning of the key (operation piece)

260

thereby maintaining the move body

256

at Unlock position. On the other hand, the excited solenoid (drive portion)

270

attractively moves the plunger (operative portion)

290

, thereby disengaging the projection

292

at the distal end of the plunger (operative portion)

290

from the recess

252

f.

Thus, the rotation of the operation cam or the turning of the key (operation piece)

260

is permitted.

According to the arrangement of

FIG. 14

, the turning of the key (operation piece)

260

is not permitted unless the solenoid (drive portion)

270

is excited. That is, the safety of the operator is further enhanced because the key (operation piece)

260

cannot be turned in the locking direction.

(Third Embodiment)

According to a third embodiment of the invention, the key (operation piece)

260

of the second embodiment may be used not only for the On/OFF control of the main circuit for power supply to the industrial machine in the room but also for the drive of other systems.

In a case where another system is installed in the room as the dangerous zone, the operator may enter the room after removing the key (operation piece)

260

from the main lock system

211

and perform the maintenance services on another system with safety.

The constraining means for constraining the lock body

240

for the inhibition of transfer of the move body from Unlock position to Lock position is not necessarily limited to the U-body

256

c

illustrated in the first and second embodiments which is formed integrally with the operative body

256

. An alternative arrangement may be made, as shown in

FIG. 15

, wherein one end of the operative body

256

b

is extended into the recess

11

a

of the switch body

200

to engage the lower end of the one engagement piece

242

of the lock body

256

b,

thereby urging the lower end of the engagement piece in the advance direction (advance) only when the move body

256

transfers from Lock position to Unlock position.

As shown in

FIG. 15

, the drive cam

1

may be configured to dispense with the extension, shown in

FIG. 12

, at the great radius portion thereof so that the locking piece

243

of the lock body

240

may not abut against the periphery of the great radius portion of the drive cam

1

. This permits the key (operation piece)

260

to be turned in both the locking direction and the unlocking direction regardless of the ingress or egress of the actuator

220

. This excludes the unique definition of the operation procedure for closing the main circuit.

If the drive cam

1

of

FIG. 12

is configured to dispense with the extension at the great radius portion thereof as shown in

FIG. 15

, then the locking piece

243

of the lock body

240

does not abut against the periphery of the great radius portion of the drive cam

1

. Hence, the key (operation piece)

260

can be turned in both the locking direction and the unlocking direction regardless of the ingress or egress of the actuator

220

.

According to the description of the foregoing embodiments, the drive cam

1

is provided with the control plates

2

,

3

on the opposite sides thereof so that the operative rod

8

may be advanced only by the substantially simultaneous depression of the drive cam

1

and the control plates. However, the control plates

2

,

3

are not always required. It is apparent that the invention can be implemented the same way when the operation section

202

of the switch body

200

is provided with the drive cam

1

alone.

According to the description of the foregoing embodiments, the operation piece

260

of the main lock mechanism

211

is implemented in the key whereas the switchable portion

250

is implemented in the combination of the key-insertion portion

251

, the operation cam including the first and second cams

252

a,

252

b,

the cam groove

253

defined in the second cam

252

b,

the insert pin

254

and the move body

256

urged by the spring

255

. However, the arrangement should not be limited to the above but the switchable portion may be arranged in any way as long as it is at least selectively switchable between Lock position and Unlock position. On the other hand, the operation piece may be arranged in any way as long as the operation piece is removably mounted to the switchable portion for selective switching of the switchable portion and becomes removable at the transfer of the switchable portion to Unlock position.

According to the description of the foregoing embodiments, the drive portion

270

of the auxiliary lock mechanism

212

is implemented in the solenoid whereas the operative portion

290

is implemented in the plunger attracted by the excited solenoid. As a matter of course, the drive portion

270

and operative portion

290

should not be limited to the solenoid and plunger, respectively. In short, the drive portion may be implemented in anything that is operated by the trigger externally applied when the switchable portion of the main lock mechanism is switched to Lock position. The operation piece may be implemented in anything that maintains the switchable portion at Lock position for keeping the auxiliary contact closed when the drive portion is non-operative and that permits the transfer of the switchable portion to Unlock position when the drive portion is operative.

The dangerous zone is not limited to the specific room mentioned supra, but an equivalent effect to the foregoing embodiments may be attained by applying the invention to any space that is defined by a partitioning element with an open/close element, such as a door, and permits the installation of the electric equipment such as the industrial machine.

According to the description of the foregoing embodiments, the constraining means is implemented in the U-body

256

c

formed integrally with the operative body

256

b

of the move body

256

. However, the constraining means should not be limited to the U-body

256

c

but may be of any arrangement that is at least capable of constraining the lock body for inhibiting the transfer of the switchable portion from Unlock position to Lock position when the actuator is not inserted. Specifically, the constraining means may be implemented in an arrangement wherein a part of the operative body

256

b

is inserted in a hole defined in one of the engagement pieces

242

of the lock body

240

.

As mentioned supra, the safety switch assembly of the invention permits the main circuit to be closed only when the drive portion of the auxiliary lock mechanism is non-operative, the switchable portion of the main lock mechanism is at Lock position, and the actuator is inserted. This is effective to prevent the occurrence of an event that the industrial machine is energized by the inadvertent closure of the door in the presence of the operator in the dangerous zone or that the operator is locked in the dangerous zone. Hence, the safety of the operator working in the dangerous zone is further improved.

Number	Name	Date	Kind
5464954	Kimura et al.	Nov 1995
6118087	Fukui	Sep 2000

Number	Date	Country
0869524	Oct 1998	EP
7-134924	May 1995	JP
8-111145	Apr 1996	JP
8-148062	Jun 1996	JP
8-159388	Jun 1996	JP
8-167350	Jun 1996	JP
9-245584	Sep 1997	JP
11-25810	Jan 1999	JP

Safety switch

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (2)

Foreign Referenced Citations (8)