SELF-HOLDING TYPE KEY SWITCH DEVICE

Abstract: A key switch is equipped with a rotatable member or cylinder (3) adapted to be rotated by means of a key (4), a cam (5) adapted to rotate integrally with the rotatable cylinder (3), and a switch (2) adapted to be turned on or off by engagement with the peripheral side surface (5a) of the cam (5). In order to prevent the turned-on switch (2) from being rapidly returned to the turned-off condition owing to erroneous operation by an operator and to keep the switch (2) reliably in the turned-on condition, a pawl (6) is urged to be swivelled against the peripheral side surface (5a) of the cam (5) and engages with a tooth (7) formed on the pheripheral side surface (5a) of the cam (5) when the switch (2) is turned on by rotation of the cam in normal direction, so that reverse rotation of the cam (5) is prevented and the switch (2) is kept turned on until the cam (5) is rotated in the normal direction by about 360°.

Description: SPECIFICATION TITLE OF THE INVENTION: SELF-HOLDING TYPE KEY SWITCH DEVICE BACKGROUND OF THE INVENTION This invention relates to a key switch device comprising a combination of a switch and a lock for controlling the ON and OFF operation of the switch. In a key switch device of the prior art such as one disclosed in Japanese Utility Model Laid-Open No. 1341/1981, a rotor of a lock main body is rotated by a key which is inserted into the rotor, and a microswitch fitted to the rear of the lock main body is turned on and off by a cam which rotates integrally with the rotor. Since the rotor and the cam are freely rotatable in both normal and reverse directions by use of a key, it is not possible to reliably hold the switch in the ON state for a predetermined period of time, depending upon the manipulation of an operator. For, when the key is rotated in the normal direction to turn on the switch and is then rotated immediately in the reverse direction without rotating the key up to 3600 in the normal direction, for example, the switch returns to the OFF state within an extremely short period of time. SUMMARY OF THE INVENTION It is therefore on object of the present invention to provide a self-holding type key switch device which prevents a switch from returning quickly to the OFF state due to the erroneous operation of an operator, and which can keep reliably the switch in the ON state for a predetermined period of time necessary for equipment for which the key switch device is used. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate one preferred embodiment of the invention, in which: Figure 1 is a front view of a key switch device; Figure 2 is a right-hand side view showing a part of the key switch device in a longitudinal section; Figure 3 is a rear view with a rear seat plate being omitted; and Figure 4 is a transverse sectional view of a cam used for the key switch device. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, one preferred embodiment of the invention will be described with reference to the accompanying drawings. Briefly stated, the gist of the invention resides in that a pawl 6 is disposed sideways of a switch operating cam 5, and is urged to rotate towards the peripheral side surface Sa of the cam 5, and a tooth 7 for meshing with the tip of the pawl 6 is disposed on the peripheral side surface 5a of the cam so that reverse rotation of the cam 5 is prevented by the engagement of the pawl 6 with the tooth 7. In the embodiment shown in the drawing, a fitting base plate 8 is fixedly mounted to the rear of a lock main body 1 by a screw 9, and a microswitch type switch 2 is fixed to the fitting base plate 8 by a rear seat plate 10 in cooperation with a nut 11. The front end portion of an interlocking plate 13 is slidably inserted into the rear end portion of a key groove 12 formed on a rotor 3 in its axial direction, and the rear end portion of this interlocking plate 13 is fitted into a split groove 14 of the cylindrical cam 5 that extends in the radial direction of the cam. The rear end portion of the interlocking plate 13 is fixed to the cam 5 by a spring pin 15. A compression spring 17 and a small ball 18 are stored in a center through-hole 16 of the cam 5. The forward end portion of the compression spring is brought into pressure contact with the interlocking plate 13, and the small ball 18 is brought into pressure contact with a receiving hole 19 that is disposed on the rear seat plate 10. Accordingly, the cam 5 is urged to slide towards the rear surface of the lock main body 1. Is formed on the peripheral side surface 5a of the cam 5 a step portion 21 into which an actuator 20 of the switch 2 fits. When the actuator 20 is positioned at the innermost portion of the bottom surface 21a of the step portion 21, the switch 2 is kept OFF. The tooth 7 described above is formed at a portion of the peripheral side surface 5a of the cam 5 with which the actuator 20 does not come into sliding contact, that is, at the forward end portion of the peripheral side surface 5a of the cam 5. The base end portion of the pawl 6 is rotatably fitted to a bolt 22 which is interposed between the fitting base plate 8 and the rear seat plate 10. One of the ends of the pawl 6 is anchored to the fitting base plate 8 with the other being urged to rotate towards the peripheral side surface 5a of the cam 5 by a twist coil spring 23 which is brought into contact with the side surface at the tip of the pawl 6. A spacer cylinder 24 is fitted into the bolt portion 22 between the pawl 6 and the rear seat plate 10. Lock of the rotor 3 to the lock main body 1 is effected by use of a heretofore known disc tumbler mechanism, pin tumbler mechanism, or the like. This embodiment employs the pin tumbler mechanism. A follower pin 27 and a driving pin 28 that are stored in pin receiving holes 25, 26 in the radial direction of the rotor 3 and the lock main body 1, respectively, are urged to slide by a compression spring 29 in the axial direction of the rotor 3. Next, the operation of the present device will be described. When the key 4 is inserted into the key groove 12 of the rotor 5 in a predetermined length, the contact surface of the follower and driving pins 27, 28 coincides with the outer peripheral surface of the rotor 5, so that lock of the rotor 5 to the lock main body 1 is released. When the key 4 is pushed in the axial direction of the rotor 5, the interlocking plate 13 and the cam 5, that have been placed at the positions represented by dash line in Figure 2, are pushed by the tip 4a of the key, and move backwards to the position represented by solid line in Figure 2. Next, when the rotor 5 is rotated clockwise in the normal direction by the key 4 as shown in Figure 1, the interlocking plate 13 and the cam 5 follow the rotation of the rotor 5 are rotate in the same direction, so that the tip of the pawl 6 sequentially comes into sliding contact with slope surfaces 7a, 7b, 7c of the tooth 7 and then with the peripheral side surface 5a of the cam 5. During the period in which the pawl 6 passes through the portion of the tooth 7 in this manner, the actuator 20 is pushed by the bottom surface 21a of the step portion at the position P1 in Figure 1, so that the switch 2 is turned on. The switch is kept turned on until the actuator 20 comes into sliding contact with the peripheral side surface 5a of the cam 5. ;hen the cam 5 .thus rotates to the position P2 in Figure 1, the actuator 20 drops into the step portion 21, so that the switch 2 is turned off. When normal rotation is further continued until the position PO in Figure 1, the pin receiving holes 25 and 26 are aligned on the same line, so that the key 4 can be removed from the rotor 3. As described above, in the key switch device of the present invention, the pawl 6 is disposed sideways of the switch operating cam 5, and is urged to rotate towards the peripheral side surface 5a of the cam, and the tooth 7 for meshing with the tip of the pawl 6 is disposed on the peripheral side surface 5a of the cam. According to this arrangement, after the switch 2 is turned on at the position P1 in Figure 1, even if an attempt is made to rotate the key 4 counter-clockwise in Figure 1 and then to rotate the cam 5 in the reverse direction, the cam 5 can not be rotated reversely to the OFF range between the positions PO and P1 in Figure 1, because the pawl 6 meshes with the tooth 7 before the actuator 20 drops into the step portion 21 and engages with its restricting slope surface 7b. For this reason, the operator can not but rotate again the key in the normal direction in order to remove the key 4 at the position P1 in Figure 1. As described above, the present invention guides or forces the operator to fully rotate the cam 5 to 3600 by a ratchet mechanism consisting of the pawl 6 and the tooth 7. Thus, the switch 2 is reliably kept in the ON state from the position P1 to the position P2 in Figure 1 for a predetermined period of time required for equipment to which the key switch device is adapted.

Claims: Patent Claims: I. A self-holding type key switch which is equipped with a rotatable member or cylinder (3) adapted to be rotated by means of a key (4) inserted into the rotatable cylinder (3), a cam (5) adapted to rotate integrally with the rotatable cylinder (3), and a switch (2) adapted to be turned on and off by engagement with the suitably formed peripheral side surface (5a) of the cam (5), characterized in that a pawl (6) is disposed at the side of the cam (5) and is urged to be swivelled against the peripheral side surface (5a) of the cam (5), and a tooth (7), adapted to engage with the pawl (6) when the switch (2) is turned on by rotation of the cam (5) in normal direction, is formed on the peripheral side surface (5a) of the cam (5) in such manner that a reverse rotation of the cam (5) is prevented by the engagement of the pawl (6) with the tooth (7), so that the switch (2) is kept turned on until the cam (5) has been rotated in the o normal direction by about 360 2. A key switch according to claim 1, characterized in that the switch (2) is kept turned on until the rotatable cylinder (3) and the cam (5) have been rotated in the normal direction almost to a position of the rotatable cylinder (3) in which the key (4) may be withdrawn from the rotatable cylinder (2).

Inventors: TAKAHASHI, TETSUO
Applicants: TAKIGEN SEIZOU CO., LTD.
Application year: 1984
Main classification: H01H27
IPC codes: H01H27, H01H19