Safety switch

Abstract: Reduction of size is achieved by using one piece of plate cam 1 which rotates and moves the operating rod 6 of the contact of the switch portion as the operating portion 111 of the actuator 102 enters, and the lock plates 2, 3 are arranged on the side of the plate cam 1 to form a lock mechanism for restricting the rotation of the plate cam 1 so that the lock mechanism of the plate cam 1 by lock plates 2, 3 is released and the plate cam 1 is rotated only when the actuator 102 enters, thereby preventing the operating portion from being operated by any tool other than the special-purpose actuator.

Description: BACKGROUND OF THE INVENTION The present invention relates to a safety switch according to the preamble of claim 1. Typically, such a safety switch is mounted on the wall surface of a doorway of a room in which, for example, industrial machinery is installed, and which is capable for stopping the power supply to the industrial machinery, etc. when the door of the doorway is opened. In a hazardous zone during driving established for rooms in which industrial machinery is installed, plants, or industrial machinery, respectively, troubles in which workers are caught in and injured frequently occur. Consequently, in order to prevent these dangers, a so-called lock system has been required to be installed, in which driving of the machine is stopped when the door of the doorway in the room or a danger zone is not completely closed. For such lock system, conventionally, a system 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 has been adopted. However, because with this kind of lock system, operation of the machine inside the room is enabled by operating an actuator (section) of the limit switch, there is a defect for a safety countermeasure. To solve this kind of defect, there proposed is a safety switch which has a construction for preventing this kind of maloperation (Japanese Non-examined Patent Publication No. Hei 6-76674). The safety switch of 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 (mobile piece) of the contact block is changed over, and 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 safety switch stated in the Japanese Non-examined Patent No. Hei 6-76674, but recently, as applications of safety switch of this kind are diversified, demands of a small-size safety switch which requires small installation space have increased. From DE 39 43 376 C a safety switch according to the preamble of claim 1 is known. In this prior art safety switch, lock plates are provided to be shifted along an axis of their shafts which axis intersects the actuator inserting direction and which is parallel to an axis of a plate cam. - When the actuator is fixed to a heavy door and the door is closed with excessive force, the actuator enters the operation portion including the cam plate and the lock plates which he hits with considerable force. As the lock plates cannot give way easily and safely, that force can impose an undue overstress on the lock plates and surrounding mechanisms and even cause failure of the device. SUMMARY OF THE INVENTION Under these circumstances, it is the main object of this invention to provide a safety switch which has functions and safety equivalent to or better than those of conventional ones and is small-size. In order to achieve this object, the invention provides a safety switch according to claim 1. In the particular mounting of the invention, the first lock plate which is located on the side of the first plate cam is adapted to rotate around an axis intersecting the actuator inserting direction and is in addition configured as indicated below. - Hence, when the actuator enters into the operating portion of the switch proper, the tip-end protrusion of the supporting piece of the actuator comes in contact with the first inclined surface of the first lock plate and causes it to safely open outwards with the axis as a center, thereby releasing the lock of the first plate cam achieved by the first engaging pawl, and at the same time the first plate cam is rotated by the pressurizing piece and the pressurizing piece fits into the recess formed on the outer circumferential surface of the first plate cam. By configuring as above, the invention can prevent the operation of the operating portion even if any operating plate other than the special-purpose actuator is inserted in an insertion of the operating portion hole. That is, in the construction according to the invention, since the rotation of the first plate cam is enabled only when the lock plate is opened outwards to release the lock, even if any tool with a flat tip end such as a screwdriver, etc. is inserted into the operating portion to rotate the first plate cam, the first engaging pawl latches the lock groove of the first plate cam and prevents rotation of the first plate cam. Since in the construction of the invention, the plate cam is one piece, the size can be reduced as compared to conventional ones. That is, in the conventional safety switches as in the case of those presented in the Japanese Non-examined Patent Publication No. Hei 6076674 previously presented, since three pieces of plate cam are used and all these plate cams are designed to be rotated with the pressurizing piece of the actuator, the geometry of the actuator is large and the operating portion and switch portion must be increased accordingly, while in the first invention, only one piece of plate cam is required, and the length of the pressurizing piece of the actuator can be shortened, and the switch can be made compact as much. Now, in the safety switch of the invention, the desired object can be achieved by mounting the first lock plate to either right or left first plate cam, but the first lock plate may be mounted on both sides of the first plate cam. It is preferable to mount the first lock plate on both right and left sides of the plate cam because double lock is applied to the first plate cam and still higher safety can be secured. In addition, the safety switches with these constructions is configured in such a manner that the first lock plate is rotatable around two axes intersecting each other, and to the operating portion, two actuator insertion holes are provided, whose actuator inserting directions intersect each other, and inserting the actuator into either one of the two insertion holes can release restrictions to rotation of the first plate cam by the first engaging pawl. When the safety switch is configured in this way, the actuator can be inserted in two directions, and the degree of freedom at the time of mounting increases. In this case, providing an insertion hole of the actuator on the front side of the switch proper can bring the actuator inserting direction and outgoing direction of wiring on the same straight line, contributing to space saving. The invention can prevent the operation of the operating portion even if any operating plate other than the special-purpose actuator is inserted in the insertion hole. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an external view in perspective of the embodiment according to the invention; Fig. 2 shows the application condition of the embodiment according to the invention; Fig. 3 is a center longitudinal sectional view , showing the construction of the operating portion 111 of the embodiment of the invention; Fig. 4 is a front elevation showing the construction of the operating portion 111 with a cover partly broken away of the embodiment according to the invention; Fig. 5 is a cross-sectional view taken on the lines x-x of Fig. 3 ; Fig. 6 is a view on arrow Y of Fig. 3; Fig. 7 illustrates the operation of the embodiment according to the invention; Fig. 8 illustrates the operation of the embodiment according to the invention ; Fig. 9 illustrates the operation of the embodiment according to the invention; Fig. 10 illustrates the operation of the embodiment according to the invention; Fig. 11 illustrates the operation of the embodiment according to the invention; Fig. 12 illustrates the operation of the embodiment according to the invention; Fig. 13 illustrates the operation of the embodiment according to the invention; Fig. 14 illustrates the operation of the embodiment according to the invention; Fig. 15 (A) and Fig. 15 (B) schematically show a configuration example of the contact block of the switch portion 112 of the embodiment according to the invention; Fig. 16 is an external view in perspective of the other embodiment of the invention; Fig. 17 is an external view in perspective an alternate embodiment ; Fig. 18 shows the application condition of the alternate embodiment; Fig. 19 is a side view showing the construction of the operating portion 511 with a cover partly broken away of the alternate embodiment; Fig. 20 is a front elevation showing the construction of the operating portion 511 with a cover partly broken away of the alternate embodiment; Fig. 21 is a cross-sectional view taken on the lines X-X of Fig. 19 ; Fig. 22 is an enlarged view showing the lock piece extracted; Fig. 23 illustrates the operation of the alternate embodiment; Fig. 24 illustrates the operation of the alternate embodiment; Fig. 25 illustrates the operation of the alternate embodiment; Fig. 26 (A) and Fig. 26 (B) schematically show a configuration example of the contact block of the switch portion 512 of the alternate embodiment; Fig. 27 is a perspective view of the operating portion 111 of the alternate embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, preferred embodiments according to the invention will be described in detail hereinafter. Fig. 1 is an external view in perspective of the embodiment according to the invention, and Fig. 2 shows the application condition of the embodiment according to the invention. First of all, referring to Fig. 1 and Fig. 2, the construction of the safety switch according to this embodiment is briefly described. The safety switch of this example is a switch electrically connected to the industrial machinery installed in a room, and primarily comprises a switch proper 101 and an actuator 102. The switch proper 101 is secured at the wall surface in the periphery of the doorway of the room and the actuator 102 is secured at a door 103. The actuator 102 is located at the position opposite to the insertion hole 101a of the switch proper and enters the operating portion 111 of the switch proper 101 when the door 103 is closed. The entry of the actuator 102 changes over the contact of the contact block (see Fig. 15) built in the switch portion 112, and the machinery inside the room is ready for operation. On the other hand, when the actuator 102 is removed from the operating portion 111 by the opening of the door 103, the contact for power supply is changed over and the power supply to the machine is turned off. The actuator 102 has the insertion portion to the operating portion 111 composed of a pressurizing piece 121 at the top end portion and a pair of supporting pieces 122, 123 for supporting both ends. The top end portion of the pair of supporting pieces 122, 123 protrude ahead from the pressurizing piece 121, and to the top end surface of the actuator 102, two pressurizing surfaces 121a and 121b, one in recess and the other in protrusion, are formed. To the switch proper 101, in addition to the insertion hole 101a on the front side, an insertion hole 101b is provided on the lower surface side of the switch proper 101, so that either insertion hole 101a or 101b can be chosen in accord with the condition of the location. Referring now to Fig. 3 through Fig. 6, and Fig. 27, the mechanism of the operating portion of this embodiment will be described in detail hereinafter. Fig. 3 is a center longitudinal cross-sectional view, while Fig. 4 is a front elevation with the cover broken away. Fig. 5 and Fig. 6 are a view taken on the line X-X and view on the arrow Y of Fig. 3, respectively, and Fig. 27 is a perspective view of the operating portion 111. To the operating portion 111, a plate cam 1 is mounted. This plate cam 1 serves to provide displacement to the operating rod 6 of the contact block of the switch portion 112 shown in Fig. 15, and is ratably supported to the support frame 11 via a cam shaft 4. Around the outer circumferential surface of the plate cam 1, rectangular recesses 1a, 1b are formed in correspondence with the insertion holes 101a and 101b of the actuator, and in addition, between the two recesses 1a and 1b, lock grooves 1c, 1d are formed. On the other hand, on both right and left sides of the plate cam 1, lock plates 2, 3 are arranged, respectively. To this pair of right and left lock plates 2, 3, inclined surfaces 2a, 3a and 2b, 3b are formed at the position opposite to the insertion holes 101a and 101b. At the top end portion on the front side, engaging pawls 2c, 3c for fitting into the lock grooves 1c, 1d of the plate cam 1 are formed. The inclined surfaces 2a, 3a and 2b, 3b of each lock plate 2, 3 are surfaces tilted 45° with respect to inserting direction of the actuator, respectively, and are processed in a shape expanding outwards as they come closer to the insertion holes 101a, 101b, respectively. The inclined surfaces 2a, 3a and 2b, 3b are formed at positions corresponding to the pressurizing surface 121b of the protruded portion of the actuator 102. Each of lock plates 2, 3 is rotatably supported to the support frame 11 via the spherical fulcrums 2d, 3d formed integrally to the bottom end of the rear side (switch portion 112 side) of the operating portion 111, and in addition, the posture shown in Fig. 3 through Fig. 5 is maintained by compression coil springs 5, 5 fitted into the clearance with the support frame 11, and by the support with these members, each of the lock plates 2, 3 passes the center of each fulcrums 2d, 3d, and can rotate around two axes intersecting the rotation center of the plate cam 1, that is, around two axes parallel to the actuator inserting direction. Next, referring to Fig. 7 through Fig. 10, the operation of the embodiment according to the invention will be described. Fig. 7 through Fig. 10 show the cases when the actuator 102 in inserted in the insertion hole 101a located on the front side, of the two insertion holes installed to the operating portion 111. Fig. 9 shows a view on the arrow Y of Fig. 3 as is the case of Fig. 6, and Fig. 10 is a view as seen from the actuator inserting direction (front elevation), showing the condition in which the actuator is inserted to the insertion end. When the actuator 102 enters the inside of the operating portion 111 through the insertion hole 101a, first of all, the pressurizing surface 121b of the protruded portion at the top end comes in contact with the inclined surfaces 2a, 3a of lock plates 2, 3 (Fig. 9). At this point, the pressurizing surface 121a of the recess of the actuator does not come in contact with the plate cam 1. When the actuator 102 advances from this condition, the inclined surfaces 2a, 3a of lock plates 2, 3 are pressed in response to this advancement, and after the lock plates 2, 3 instantaneously open outwards with the fulcrums 2d, 3d as a center (axis intersecting the actuator inserting direction), lock plates 2, 3 are held to parallel position by the elastic force of compression coil springs 5, 5, and when the actuator 102 further advances, lock plates 2, 3 open outwards this time with the axis which passes the center of fulcrums 2d, 3d and is parallel to the actuator inserting direction as shown in Fig. 10, and with this action, engaging pawls 2c, 3c come off from lock grooves 1c, 1d of the plate cam 1, respectively and the plate cam 1 is unlocked, and at the same time, the pressurizing surface 121a of the recess of the actuator 102 comes in contact with the plate cam 1 as shown in Fig 7 to rotate the plate cam 1. In response to this rotation of the plate cam 1, the operating rod 6 of the switch portion 112 advances, and the contact changes over when the actuator 102 advances to the insertion end and at the same time the pressurizing piece 121 of the actuator fits into the recess 1a of the plate cam 1. In the foregoing operation, when lock plates 2, 3 open outwards, compression coil springs 5, 5 are held compressed between lock plates 2, 3 and the support frame 11. Then, when the actuator 102 is removed from the condition of Fig. 8 and Fig. 10, reversing motion of the actuator 102 causes the plate cam 1 to rotate reversibly from the previous condition, and in response to this, the operating rod 6 reverses and the contact is changed over, and the lock grooves 1c, 1d of the plate cam 1 returns to the original position, that is, the position shown in Fig. 7 and Fig. 9, and lock plates 2, 3 returns to the original position (lock position) by the elastic force of compression coil spring 5, and the rotation of the plate cam 1 is restricted by fitting of engaging pawls 2c, 3c of lock plates into lock grooves 1c, 1d, respectively. Fig. 11 through Fig. 14 illustrate operations when the actuator 102 is inserted into the other insertion hole 101b. Fig. 13 corresponds to the front elevation of Fig. 4, and Fig. 14 is a view as seen from the inserting direction of the actuator (bottom plan view) showing the condition in which the actuator is inserted to the insertion end. In this case, same as before, when the actuator 102 enters the inside of the operating portion 111 through the insertion hole 101b, first of all, the top end of the actuator 102 comes in contact with the inclined surfaces 2b, 3b of lock plates 2, 3 (Fig. 13), then, the lock plates 2, 3 open outwards with the fulcrums 2d, 3d set as a center (axis parallel to the actuator inserting direction) (Fig. 14), and engaging pawls 2c, 3c, come off from lock grooves 1 c, 1d of the plate cam 1, respectively, and the plate cam 1 is unlocked. In response to this, the pressurizing surface 121a of the recess of the actuator 102 comes in contact with the plate cam 1 to rotate the plate cam 1 as shown in Fig. 11, and in accord with the rotation of this plate cam 1, the operating rod 6 of the switch portion 112 advances to change over the contact, and at the same time, the pressurizing piece 121 of the actuator 102 fits into the recess 1b of the plate cam 1. The operation when the actuator 102 is pulled out is the same as that described before and the description will be omitted. Now, because in the foregoing embodiments, lock plates 2, 3 are designed to be rotatable around two axes which intersect each other, suitably varying the position and the quantity of the recess and lock groove formed on the outer circumferential surface of the plate cam 1 can change the inserting direction of the actuator 102, and for example, as shown in Fig. 16, actuator insertion holes 20 1a and 20 1b can be provided at corners 0 f the front and top surfaces of the operating portion 211. Next discussion will be made on the alternate embodiment. Fig. 17 is an external view in perspective of an alternate embodiment, and Fig. 18 shows the application condition of this embodiment. First of all, referring to Fig. 17 and Fig. 18, the construction of the safety switch according to this embodiment is briefly described. The safety switch of this example is a switch electrically connected to the industrial machinery installed in a room, and primarily comprises a switch proper 501 and an actuator 102. The switch proper 501 is secured at the wall surface in the circumference of the doorway of the room and the actuator 102 is secured at a door 103. The actuator 102 is located at the position opposite to the insertion hole 501a of the switch proper and enters the operating portion 511 of the switch proper 501 when the door 103 is closed. And the entry of the actuator 102 changes over the contact of the contact block (see Fig. 26) built in the switch portion 512, and the machinery inside the room is ready for operation. On the other hand, when the actuator 102 is removed from the operating portion 511 by the opening of the door 103, the contact for power supply is changed over and the power supply to the machine is turned off. The actuator 102 same as that used for the embodiment described before is used and the description is omitted here. Referring now to Fig. 19 through Fig. 22 the mechanism of the operating portion of this embodiment will be described in detail hereinafter. Fig. 19 and Fig. 20 are a side view and front elevation view with the cover broken away, respectively. Fig. 21 is a view taken on the line x-x and Fig. 22 is an enlarged view with the lock piece extracted. To the center of the operating portion 511, a plate cam 51 is mounted. This plate cam 51 serves to provide displacement to the operating rod 7 of the contact block shown in Fig. 26, and is rotatably supported to the support frame 11 via a cam shaft 54. Around the periphery of the plate cam 51, rectangular recesses 51a to which a pressurizing piece 121 of the actuator 102 fits in is formed toward the direction of the cam shaft 54, and in addition, lock stepped portion 51b is formed at the position about 80° rotated from the recess 51a. On both right and left sides of the plate cam 51, lock pieces 52, 53 are arranged, respectively. On both right and left sides of the plate cam 51, lock pieces 52, 53 are arranged, respectively. This pair of right and left lock pieces 52, 53 are mounted to the corner portion of the operating portion 511 and rotatably supported to the shaft 55 parallel to the rotation center (cam shaft 54) of the plate cam 51, and to each top end portion, engaging pawls 52b, 53b for latching the lock stepped portion 51b of the plate cam 51 are integrally formed. On each of the lock pieces 52, 53, inclined surfaces 52a, 53a are formed at the position opposite to the insertion hole 501a. These inclined surfaces 52a, 53a are surfaces tilted to the inserting direction of the actuator 102, and is formed at the position corresponding to the pressurizing surface 121b of the protruded portion of the actuator 102. In addition, to each of lock pieces 52, 53, spring holders 52c, 53c are mounted, and by the compression coil spring 56 (see Fig. 22) fitted into the spring holders 52c, 53c, the engaging pawls 52b, 53b of the lock pieces 52, 53 are pressurized against the outer circumferential surface of the plate cam 51. Under the foregoing construction, when the actuator 102 is not inserted in the operating portion 511, as shown in Fig. 19, the recess 51a of the plate cam is located at the position opposite to the insertion hole 501a of the actuator, and engaging pawls 52b, 53b of lock pieces 52, 53 come in contact with the forward side of the lock stepped portion 51b, and the engaging pawls 52b, 53b oppose the lock stepped portion 51b, and even if the plate cam 51 only is attempted to rotate under this condition, engaging pawls 52b, 53b latch the lock stepped portion 51b and their rotation is prevented. Next, referring to Fig. 23 through Fig. 25, the operation of the embodiment according to this invention will be described. When the actuator 102 enters the inside of the operating portion 511 through the insertion hole 501a, first of all, the pressurizing surface 121b of the protruded portion at the top end comes in contact with the inclined surfaces 52a, 53a of lock pieces 52, 53 (Fig. 23). At this point, the pressurizing surface 121a of the recess of the actuator 102 does not enter the inside of the recess 51a of the plate cam 51 and is located at the rear side of the recess 51a. When the actuator 102 further advances, the inclined surfaces 52a, 53a of lock pieces 52, 53 are pressed in response to this advancement, and as shown in Fig. 24, lock pieces 52, 53 rotate around the shaft 55, and by this action, engaging pawls 52b, 53b come off from the plate cam 51, move to the position free from interference with the lock stepped portion 51b and the plate cam 51 is unlocked, and at the same time, the pressurizing piece 121 of the actuator 102 fits into the recess 51a of the plate cam 51, and pressing of the pressurizing surface 121a against the inner surface of the recess 51a causes the plate cam 51 to rotate (Fig. 25). In response to the rotation of this plate cam 51, the operating rod 7 of the contact block advances, and when the actuator 102 advances to the insertion end, the contact of the contact block (Fig. 26) is changed over. With the actuator 102 advancing to the insertion end, the pressurizing piece 121 is located on the forward side of the recess 51a of the plate cam 51. Then, when the actuator 102 is removed from the condition of Fig. 25, reversing motion of the actuator 102 causes the pressurizing piece 121 to fit in the recess 51a of the plate cam 51 to press the recess inner surface; then, the plate cam 51 begins to rotate reversibly from the previous condition, and in response to this, the operating rod 7 reverses and the contact recovers the original condition, and at the same time, the lock stepped portion 51b of the plate cam 51 returns to the original position, that is, the position shown in Fig. 19, and lock pieces 52, 53 return to the original position (lock position) by the elastic force of compression coil spring 56, and the rotation of the plate cam 51 is restricted. In the foregoing embodiment, the insertion hole 501a of the actuator is provided on the top surface side of the operating portion 511, but the position of the insertion hole 501a may be brought to the front side of the operating portion 511 by suitably changing the position of the recess and lock stepped portion formed on the outer circumferential surface of the plate cam 51. Under the foregoing two embodiments, by the elastic force of spring not shown, the operating rods 6, 7 are constantly pressurized against the outer circumferential surface of the plate cams 1, 51, respectively. In addition, in the foregoing embodiments, the plate cams 1, 51 serve to provide displacement to the operating rods 6, 7, directly, but medium members may be arranged between the operating rod 6 and the plate cam 1, or between the operating rod 7 and the plate cam 51, respectively. In the construction according to this, the operating rods 6, 7 may serve to provide displacement, indirectly.

Claims: A safety switch comprising an actuator (102) adapted to be fixed to a door (103) and a switch proper (101) wherein said actuator (102) enters an operating portion (111) of the switch proper and an operating rod (6) of said switch proper (101) moves in response to said entering, and a contact is changed over, wherein said actuator (102) has an inserting portion (121, 122, 123) comprising a pressurizing piece (121) as well as a supporting piece (122, 123) which supports both ends of this pressurizing piece and whose top end protrudes ahead of the pressurizing piece, wherein the operating portion (111) comprises a first plate cam (1) which rotates in response to the entry of the actuator (102) to displace the operating rod (6) and has a recess (1a, 1b) and a lock groove (1c, 1d) formed on the outer circumferential surface of the first plate cam (1), wherein the operating portion (111) further comprises a support frame (11) adapted to support both ends of the cam shaft (4) rotatably supporting said-first plate cam (1), a first lock plate (2), which is located on a side of the first plate cam (1) and at the same time has a first inclined surface (2a) tilted in the actuator inserting direction and a first engaging pawl (2c) fitted into the lock groove (1c) of the first plate cam (1) and a first spring (5) fitted between the first lock plate (2) and the support frame (11), wherein when the actuator (102) is not inserted in the operating portion (111), the first lock plate (102) is held to the position locked by the first spring (5) and the first engaging pawl (2c) is fitted into the lock groove (1c) of the first plate cam (2) to restrict rotation of the first plate cam (1), when the actuator (102) enters into the operating portion (111) a tip-end protrusion of the supporting piece (122, 123) comes in contact with the first inclined surface (2a) to cause the first lock plate (2) to open outwards thereby releasing the lock of the first plate cam (1) by the first engaging pawl (2c), and at the same time the first plate cam (1) is rotated by the pressurizing piece (121) and the pressurizing piece (121) fits into the recess (1a) formed on the outer circumferential surface of the first plate cam (2), characterized in that the first lock plate (2) is adapted to rotate around an axis intersecting the actuator inserting direction and the first lock plate (2) is configured to be rotatable around two axes intersecting each other, and two actuator insertion holes (101a, 101b) are provided in the operating portion (111), wherein actuator inserting directions intersect each other, and inserting the actuator into either one of the two insertion holes releases restrictions to rotation of the first plate cam (2) by the first engaging pawl (2c). A safety switch according to claim 1 wherein the first lock plate (2, 3) is provided on both sides of the first plate cam (1).

Inventors: FUKUI TAKAO, SASAKI NARUHITO, FUKUI, TAKAO, SASAKI,NARUHITO, Fukui, Takao, c/o IDEC IZUMI CORP., Sasaki,Naruhito, c/o IDEC IZUMI CORP.
Applicants: IDEC IZUMI CORP, IDEC IZUMI CORPORATION
Application year: 1998
Main classification: H01H27
IPC codes: H01H27