Electricity: circuit makers and breakers – Switch activation inhibitor – Removable actuator
Reexamination Certificate
1999-09-15
2001-02-27
Gellner, Michael L. (Department: 2832)
Electricity: circuit makers and breakers
Switch activation inhibitor
Removable actuator
C200S061620
Reexamination Certificate
active
06194674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a safety switch which is mounted on the wall surface of a doorway of a room in which, for example, industrial machinery is installed, and which stops the power supply to the industrial machinery, etc. when the door of the doorway is opened.
2. Description of the Related Art
In a hazardous zone of the rooms or plants in which industrial machinery is installed, or industrial machinery itself, a system for locking the drive of the machine is required to be installed when the door of the doorway in the room or a danger zone is not completely closed, in order to prevent troubles in which workers are caught in by the machine and injured.
For such a lock system, conventionally, a system has been adopted to install limit switches at the sliding portions of the door and to supply power to the industrial machinery installed in the room only when the door closed condition is detected by the limit switches.
However, according to this kind of system, operating the actuator of the limit switch without closing the door enables the operation of the machines in the room, and it cannot be said to be a perfect safety measure.
Therefore, the inventor has already proposed a safety switch which has a construction for preventing this kind of misoperation (Japanese Non-examined Patent Publication No. Hei 6-76674).
The safety switch of the this proposal is a switch which has a construction in which the special-purpose of actuator fixed to the door enters the operating portion of the switch proper mounted to the wall surface in the circumference of the doorway of the room when the door of the doorway is closed, and with this action, the mobile contact of the contact block is changed over, and with this kind of change-over operation, the circuit connection is changed over to the main circuit side (power supply circuit to industrial machinery), causing the machines inside the room to be ready for operation.
Now, there is no special problem in functions, safety, etc. with the existing safety switch, etc. stated in the Japanese Non-examined Patent No. Hei 6-76674, but according to the proposed safety switch, because a driving cam and restricted cam (both are plate cams) with groove cams formed, respectively, are arranged at the operating portion, the rotating phase difference is provided between the driving cam and the restricted cam, and all the cams are rotated to change over the connection contacts of the switch portion only when the special-purpose actuator enters the operating portion, it is inevitable that the profile, processing, etc. of each cam be complicated, and if there is any deviation in positional relationship of groove cams between the driving cam and the restricted cam, there is a fear of causing maloperation, and it is essential to process the groove cam of each cam at high accuracy.
SUMMARY OF THE INVENTION
It is the an object of this invention to provide a safety switch which has a simple construction, is low-cost, and at the same time achieves safety equivalent to that of conventional ones.
In order to achieve this object, the safety switch of this invention is a switch constructed to change over a connection contacts by the actuator entering the operating portion of the switch proper and moving the operating rod of the switch portion correspondingly, wherein the actuator has the inserting portion to the operating portion comprising a pressurizing piece at the tip end and a supporting piece for supporting the pressurizing piece, and to the pressurizing piece, protruded portion pressurizing surfaces are located on both ends and a recessed portion pressurizing surface located in-between.
To this operating portion, a driving cam is installed that rotates as the actuator advances and retracts and restricting plates are located on both sides of the driving cam and are able to rotate around the rotation center of the driving cam, respectively, and a cam follower pin is connected to the end portion of the operating rod, whose both ends extend to the side of the driving cam. To the driving cam, a groove cam is formed for providing the cam follower pin with displacement in the moving direction of the operating rod, and to each of the restricting plates, a pin engaging portion is located on the moving passage of the cam follower pin under the initial condition where the actuator is not inserted and intended to restrict the move of the follower pin, and an elastic member is included for returning the restricting plates to the initial condition, respectively.
When only the driving cam is intended to rotate under an inital condition, the movement of the cam follower pin is stopped by the restricting plate, and the rotation of the driving cam is restricted, and when the actuator is inserted, the recessed portion pressurizing surface at the tip end presses the driving cam, and the protruded portion pressurizing surfaces press the restricting plates, and both the driving cam and the restricting plates rotate together to move the operating rod.
In the safety switch of this invention of the above-mentioned construction, the motion at the operating portion can be prevented even if something other than the special-purpose actuator (for example, a screwdriver, etc.) is inserted into the insertion hole. That is, in the safety switch of this invention, because the driving cam rotates only when the driving cam and the restricting plates on both sides are pressed nearly simultaneously with the recessed portion pressurizing surface and the protruded portion pressurizing surfaces of the actuator, even if something with a flat tip end such as a screwdriver, etc. is inserted to the operating portion to rotate the driving cam, the movement of the cam follower pin is restricted by the pin engaging portion of the restricting plates when the driving cam slightly rotates, and thereby the rotation of the driving cam is prevented. In addition, because to the restricting plates, no groove cams, etc. for providing displacement to the cam follower pins are processed, even if they are rotated individually, they only idle and do not cause the operating rod to move.
Now, in the safety switch of this invention, it may be configured to have the pin guide member equipped with a guide groove for restricting the moving direction of the cam follower pin to one direction on both ends of the cam follower pin.
The driving cam and restricting plates equipped on both sides of it are desirable to be rotatably supported on the same shaft independently, respectively. The driving cam and the restricting plates are desirable to be arranged at locations that may generate, between the driving cam and the restricting plates under the initial condition, the rotating phase difference that corresponds to the level difference between the protruded pressurizing surfaces and the recessed pressurizing surface of the actuator.
In addition, it may be constructed in such a manner that the driving cam includes a hollowed-out portion extending in a specified width from the circumferential surface towards the rotation center of the driving cam formed on the portion corresponding to the groove cam formed portion, and the operating rod end portion is intended to be inserted, into the hollowed-outportion and to the rod end, portion, the cam follower pin is connected.
It may also be constructed in such a manner that a recessed portion to which the pressurizing piece of the actuator is fitted is formed on the circumferential surface of the driving cam, and when the driving cam rotates as the actuator advances into the operating portion, the pressurizing piece of the actuator fits into the recessed portion of the driving cam circumferential surface. It is desirable that the recessed portion be formed at two places on the circumferential surface of the driving cam, and in correspondence to these recessed portions, an inserting hole of the actuator be provided at two places of the operating portion.
One specific example of the pin engaging portion to be equipped to the restrictin
Armstrong, Westerman Hattori, McLeland & Naughton
Gellner Michael L.
IDEC Izumi Corporation
Nguyen Nhung
LandOfFree
Safety switch does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Safety switch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Safety switch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581377