Emergency stop switch and controller provided therewith

Abstract

The present invention improves stability at the time of contact and separation of a contact of an emergency stop switch. The emergency stop switch 1 includes a plurality of opening-biasing springs 14, 14' that bias a plurality of contacts C1, C2, in an opening direction, disposed at a radial distance R from the switch center O. The respective opening-biasing springs 14, 14' are disposed radially outwardly from the respective contacts C1, C2. When the contact circle CC passing the respective contacts C1, C2 is drawn around the switch center O, the respective opening-biasing springs 14, 14' are disposed outside the contact circle CC.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to an emergency stop switch and more particularly to an improvement of its structure for improving stability at the time of contact and separation of contacts.BACKGROUND ART

[0002] Japanese patent publication No. 3899281 discloses a push button switch for emergency stop. As shown in paragraph

[0053] and figures 1, 2, the push button switch (1) includes first and second contacts (17, 21) that are contactable with and separatable from each other, and a spring (31) as an opening biasing means that bias the second contact (21) in an opening direction in which the second contact (21) is non-contact with the first contact (17).

[0003] According to such a push button switch (1), by providing the spring (31) as the opening biasing means, the first and second contacts (17, 21) in contact with each other are biased in an opening direction in which they are out of contact. The biasing force of the spring (31) after the pressing operation of the push button is smaller than that of the spring (31) prior to the press operation of the push button. Thereby, even in the case that either of parts of the push button switch (1) is damaged, the first and second contacts (17, 21) can be prevented from returning to the contact state (see paragraphs

[0071] to

[0072] ).

[0004] Japanese patent publication No. 5059594 discloses a push button switch. As shown in paragraph

[0028] and figures 5 to 10, the push button switch includes a stress transmitting shaft (62) that moves by the operation of the operation handle (11). The contacts are adapted to come into contact with and separate from each other in conjunction with the movement of the stress transmitting shaft (62).

[0005] Japanese patent publication No. 7042136 discloses an emergency-stop push button switch. As shown in figures 1, 5(A) and 5(B), the emergency-stop push button switch (1) includes a button (101) and a housing (301) that holds the button (101). In figure 5(B), the button (101) includes an outer circular ring portion (101) disposed on the outer circumferential side and an inner circumferential ring portion disposed radially inward side of the outer circular ring portion (101) at a predetermined distance. The inner circumferential ring portion is unsigned, but it is hatched in the same direction (i.e. diagonally downward right direction) as the outer circular ring portion (101) . The inner circumferential ring portion is formed with a plurality of outer peripheral protrusions that protrude radially outwardly.

[0006] In figure 5(B), the housing (301) is unsigned, but it is a circular ring member disposed between the outside circular ring portion (101) and the inside circular ring portion of the button (101) and hatched in the diagonally upward right direction. The housing (301) is formed with a plurality of inner peripheral protrusions that protrude radially inwardly. The inner peripheral protrusions are disposed between the adjacent respective outer peripheral protrusions of the button (101). The outer peripheral protrusion of the button (101) is in circumferentially contact with the corresponding inner peripheral protrusion of the housing (301), such that thereby anti-rotation measures are taken so as not to excessively rotate the button (101)PRIOR ART REFERENCES Patent Documents

[0007] Patent Document 1: Japanese patent publication No. 3899281 (see paragraphs

[0053] ,

[0071] to

[0072] , and figures 1, 2); Patent Document 2: Japanese patent publication No. 5059594 (see paragraph

[0028] , and figures 5 to 10); and Patent Document 3: Japanese patent publication No. 7042136 (see figures 1, 5(A), 5(B)). SUMMARY OF THE INVENTION Objects to be Achieved by the Invention

[0008] In the push button switch described in the above-mentioned Japanese patent publication No. 3899281, as shown in figures 1, 2, a single spring (31) as an opening biasing means is provided and disposed below (beneath) the first and second contacts (17, 21) on one side across the switch central axis. The spring (31) and the first and second contacts (17, 21) are disposed at an equal distance (i.e. at the same radial position) from the switch central axis.

[0009] In this way, in the above-mentioned push button switch (1), since the spring (31) is provided only on one side across the switch central axis, especially, in a layout such as the first and second contacts (17, 21) are disposed at positions apart from the switch central axis, it cannot be denied that there is no possibility that the biasing force of spring (31) disposed on one side across the switch central axis is not fully applied to the first and second contacts (17, 21) disposed on the other side across the switch central axis. If such a situation happens, stability of the contacts especially at the time of opening is hindered.

[0010] In the push button switch described in the above-mentioned Japanese patent publication No. 5059594, as shown in figures 5, 6 and 7 (cross-sectional views of figure 1 taken along lines A-A', B-B', C-C', respectively), the stress transmitting shaft (62) is just supported by the locking nails (64, 66) from the outer peripheral side. Therefore, support from the outer peripheral side is not necessarily adequate. It cannot be denied that there is not possibility that rattling of the stress transmitting shaft (62) occurs in the radial direction during operation.

[0011] In the push button switch described in the above-mentioned Japanese patent publication No. 7042136, as shown in figure 5(B), both the side surface of the outer peripheral protrusion of the button (101) and the side surface of the inner peripheral protrusion of the housing (301) that comes into contact with the side surface of the outer peripheral protrusion of the button (101) extend radially (toward the switch center) . When an excessive rotational force is imparted to the button (101), an excessive pressing force is applied from the side surface of the inner peripheral protrusion of the housing (301) to the distal end of the side surface of the outer peripheral protrusion of the button (101), and also an excessive pressing force is applied from the side surface of the outer peripheral protrusion of the button (101) to the distal end of the side surface of the inner peripheral protrusion of the housing (301). Due to the action of such excessive pressing forces, twisting strength of the button (101) is likely to be decreased and anti-rotation of the button (101) is likely to become non-functional.

[0012] The present invention has been made in view of these circumstances and its object is to provide an emergency stop switch that can improve stability at the time of contact and separation of contacts. Also, the present invention is directed to further improving stability at the time of contact and separation of contacts in an emergency stop switch by decreasing rattling of a shaft portion. Moreover, the present invention is directed to increasing a twisting strength of a push button in such an emergency stop switch.Means of Achieving the Objects

[0013] An emergency stop switch according to the present invention includes a plurality of opening-biasing springs that bias a plurality of contacts in an opening direction, which are disposed at a radial distance from a switch center, and the respective opening-biasing springs are disposed radially outwardly from the respective contacts.

[0014] According to the present invention, since a plurality of opening-biasing springs are provided, a biasing force in the opening direction by the opening-biasing springs can be fully applied to a plurality of contacts, stability at the time of contact and separation of the respective contacts can be improved, a load necessary for safety potential ®< in which a force is applied in the opening-biasing direction that the contacts become contactless can be separated at a plurality of positions around the switch center, and duplexing (or multiplexing) effect of the force in the opening-biasing direction can be given. Moreover, according to the present invention, since the opening-biasing springs are disposed radially outwardly from the respective contacts disposed at a radial distance from the switch center, stability at the time of contact and separation of the respective contacts can be further improved, and the length of the emergency stop switch can be shortened thus achieving a short emergency stop switch.

[0015] When a contact circle passing the respective contacts is drawn with its center located at the switch center, the respective opening-biasing springs may be disposed outside the contact circle.

[0016] The respective opening-biasing springs may be disposed circumferentially at a substantially equal distance.

[0017] The respective contacts may be formed of a plurality of fixed contacts and a plurality of movable contacts that respectively correspond to the fixed contacts. The respective opening-biasing springs may bias the respective movable contacts in an opening direction to be separated from the corresponding respective fixed contacts.

[0018] The emergency stop switch may further comprise a push button and a shaft portion movable by an operation of the push button. Around the shaft portion, a pair of first hold members for holding the push button at a position prior to press-operation may be disposed opposite each other across the shaft portion, and a pair of second hold members for holding the shaft portion from an outer peripheral side in a direction intersecting an array direction of the respective first hold members may be disposed opposite each other across the shaft portion.

[0019] According to the present invention, since the shaft portion is held from the outer peripheral side by the first and second hold members in the direction intersecting each other, the shaft portion can be securely held from the outer peripheral side and rattling in the radial direction can be prevented from occurring at the shaft portion during operation. Thereby, stability of the respective contacts at the time of contact and separation can be further improved.

[0020] The first support member may comprise an engaging member that has an engaging surface releasably engageable with an engaged surface at an outer circumference of the shaft portion and a biasing member that biases the engaging member toward the shaft portion.

[0021] The second support member may include an inner circumferential surface that extends circumferentially along an outer circumference of the shaft portion.

[0022] The emergency stop switch may further comprise a push button and a body portion that holds the push button rotatably. The body portion may include a rotation stopper having a regulatory surface that regulates a rotation of the push button and the push button may include a contact portion having a contact surface that comes into contact with the regulatory surface of the rotation stopper. The rotation stopper may protrude radially inwardly and the regulatory surface may include a tapered surface that tapers toward an outer peripheral side, and the contact portion may protrude radially outwardly and the contact surface may include a tapered surface that tapers toward an inner circumferential side. Alternatively, the rotation stopper may protrude radially outwardly and the regulatory surface may include a tapered surface that tapers toward an inner circumferential side, and the contact portion may protrude radially inwardly and the contact surface may include a tapered surface that tapers toward an outer circumferential side.

[0023] According to the present invention, when an excessive rotational force is applied to the push button, an excessive pressing force from the contact portion of the push button is applied to the regulatory surface of the rotation stopper of the body portion, and also an excessive pressing force from the rotation stopper of the body portion is applied to the contact surface of the contact portion of the push button. At this juncture, radial components of these pressing forces act in such a direction that the contact portion of the push button and the rotation stopper of the body portion come into a firmer engagement with each other, thereby increasing the twist strength of the push button.

[0024] The regulatory surface may be disposed at both side surfaces of the rotation stopper, which may be double-tapered, and the contact surface may be disposed at both side surfaces of the contact portion, which may be double-tapered.

[0025] A controller according to the present invention incorporates the above-mentioned emergency stop switch.

[0026] The rotation stopper may be circumferentially disposed in a plurality, and the contact portion may be circumferentially disposed in a plurality among the respective rotation stoppers that are disposed circumferentially adjacent to one another.Effects of the Invention

[0027] As mentioned above, according to the present invention, an emergency stop switch can be achieved that can improve stability at the time of contact and separation of contacts.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a general perspective view of an emergency stop switch according to an embodiment of the present invention; FIG. 2 is a bottom plan view showing the internal structure of the emergency stop switch of FIG. 1; FIG. 2A is a schematic explaining a positional relation of the respective contacts and the respective opening biasing springs of FIG. 2; FIG. 2B is a schematic illustrating an alternative embodiment of FIG. 2A; FIG. 3 is a perspective view of the emergency stop switch of FIG. 2 as viewed from a diagonally downward left; FIG. 4 is a perspective view of the emergency stop switch of FIG. 2 as viewed from diagonally downward right; FIG. 5 shows the emergency stop switch of FIG. 3 with the distal end of the fixed terminal upward; FIG. 6 shows the emergency stop switch of FIG. 4 with the distal end of the fixed terminal upward; FIG. 7 shows the emergency stop switch of FIG. 5 with the push button attached; FIG. 8 is a top plan view of the cross section of the emergency stop switch of FIG. 1 as viewed from above, showing the support structure of the shaft portion; FIG. 9 is a perspective view of the emergency stop switch of FIG. 8 as viewed diagonally above; FIG. 10 is an internal structure diagram of the emergency stop switch of FIG. 1 as viewed from the front with the push button, the body portion, the support block and the like detached, explaining the support structure of FIG. 8; FIG. 11 is an upside-down view of FIG. 10, omitting the shaft portion; FIG. 12 is a top plan view of FIG. 10 as viewed from above; FIG. 13 is a top plan view as viewed from the top of the head of the push button, explaining the rotation stopper of the push button of the emergency stop switch of FIG. 1; FIG. 14 is a perspective view of the push button of FIG. 13 as viewed from the back, showing the contact portion provided at the push button; FIG. 15 is a back view of the push button of FIG. 15; FIG. 16 is a perspective view of the body portion supporting the push button of FIG. 13 as viewed from diagonally above, showing the rotation stopper provided at the body portion; FIG. 17 is a top plan view of the body portion of FIG. 16; FIG. 18 illustrates an example of the state in which the contact portion (FIG. 14) of the push button (FIG. 13) is engaged with the rotation stopper of the body portion (FIG. 16); FIG. 19 is a partially enlarged view of FIG. 18, showing a pressing force that acts on the regulatory surface of the rotation stopper in the state of engagement of FIG. 18; FIG. 20 is a schematic illustrating the pressing force of FIG. 19 decomposed in the direction toward the switch center (i.e. radial direction) and the perpendicular direction (i.e. circumferential direction); FIG. 21 is a partially enlarged view of FIG. 18, showing a pressing force that acts on the contact surface of the contact portion in the state of engagement of FIG. 18; FIG. 22 is a schematic illustrating the pressing force of FIG. 21 decomposed in the direction toward the switch center (i.e. radial direction) and the perpendicular direction (i.e. circumferential direction); FIG. 23 shows a rotation stopper of the prior-art push button, corresponding to FIG. 19 of the present embodiment and illustrating the pressing force acting on the regulatory surface of the rotation stopper in the engagement state of the contact portion of the push button with the rotation stopper; FIG. 24 is a schematic illustrating the pressing force of FIG. 23 decomposed in the direction toward the switch center (i.e. radial direction) and the perpendicular direction (i.e. circumferential direction); FIG. 25 illustrates the pressing force acting on the contact surface of the contact portion in the engagement state of FIG. 23, corresponding to FIG. 21; FIG. 26 is a schematic illustrating the pressing force of FIG. 25 decomposed in the direction toward the switch center (i.e. radial direction) and the perpendicular direction (i.e. circumferential direction); FIG. 27 schematically shows the disposition of the contact portion of FIG. 15 of the push button of FIG. 13; FIG. 28 schematically shows the disposition of the rotation stopper of the body portion of FIG. 17; FIG. 29 shows an alternative embodiment of FIG. 27; and FIG. 30 shows an alternative embodiment of FIG. 28. BEST MODE FOR CARRYING OUT THE INVENTION

[0029] Embodiments of the present invention will be described below in reference to the accompanying drawings.

[0030] FIGS. 1 to 7 show an emergency stop switch according to an embodiment of the present invention. FIG. 1 is an external view of the emergency stop switch and FIGS. 2 to 7 are internal structure views of the emergency stop switch.

[0031] As shown in FIG. 1, Emergency stop switch 1 includes a push button 2, a body portion 3 that holds the push button 2 axially (i.e. up-down direction in FIG. 1) movable and circumferentially rotatable, a lock nut 4 that is screwed into a male screw formed at an end portion 30 of the body portion 3, a plurality of fixed terminals 5 extending downwardly from the lower surface of the end portion 30 of the body portion 3, and a plurality of movable terminals (described later) that respectively correspond to the respective fixed terminals 5.

[0032] The push button 2 is provided press-operatable manually by an operator in a pressing direction (i.e. downwardly in FIG. 1) and return-operatable in a puling direction (i.e. upwardly in in FIG. 1) and a circumferential direction. The lock nut 4 is a member for the purpose of fitting the emergency stop switch 1 to a panel of a machine, control equipment and the like.

[0033] FIG. 2 is a bottom plan view showing the internal structure of the emergency stop switch of FIG. 1, omitting the push button 2, the body portion 3 and the lock nut 4, etc. As shown in FIG. 2, the emergency stop switch 1 includes a generally cylindrical hold block 10 (see FIGS. 5 to 7) fitted to the body portion 3 (FIG. 1), and the hold block 10 has a through hole 10a at the center thereof. A point on a central axis of the hold block 10 is referred to as a switch center O. An end of a shaft portion 11 extending axially (i.e. in the direction perpendicular to the page of FIG. 2) is inserted into the through hole 10a of the hold block 10 and the other end of the shaft portion 11 extends into the page of FIG. 2 and is disposed inside the push button 2 (FIGS. 5 to 7). The shaft portion 11 is movable axially (i.e. a press-operation direction and an opposite return-operation direction) through the operation of the push button 2.

[0034] On an outer peripheral side of the hold block 10, a pair of first hold members 12, 13 are provided (see FIGS. 3 to 7). These first hold members 12, 13 are disposed opposite each other across the shaft portion 11 and circumferentially spaced substantially 180 degrees apart from each other. The first hold members 12, 13 are designed for the purpose of holding the push button 2 at a position prior to the pressing operation by acting on the shaft portion 11 from the outer peripheral side prior to the pressing operation of the push button 2.

[0035] The first hold member 12 includes an engaging member 12A that has an engaging surface (described later) that is releasably engageable with an engaged surface (described later) formed at an outer circumference of the shaft portion 11 and a spring 12B as a biasing member that biases the engaging member 12A toward the shaft portion 11. Similarly, the first hold member 13 includes an engaging member 13A that has an engaging surface (described later) that is engageable with an engaged surface (described later) formed at an outer circumference of the shaft portion 11 and a spring 13B as a biasing member that biases the engaging member 13A toward the shaft portion 11.

[0036] A pair of movable terminals 6, 6' are disposed at opposed positions across the switch center O. The respective movable terminals 6 are thin plate members extending longitudinally and disposed parallel to each other in this example. On opposite sides of the movable terminal 6, a movable contact C 1 is provided and likewise, on opposite sides of the movable terminal 6', a movable contact C 2 is provided. Fixed contact 5c (see FIGS. 5 to 7) of the fixed terminals 5 are correspondingly disposed opposite the respective movable contacts C 1 , C 2 . The fixed contacts 5 are fixed to the body portion 3 (FIG. 1). The respective movable terminals 6, 6' are biased toward the fixed terminals 5 through the biasing force of the coil springs 7, 7' (see FIGS. 5, 6). The respective movable contacts C 1 , C 2 of the movable terminals 6, 6' are in elastic contact with the respective fixed contacts 5c of the opposing fixed terminal 5 and impart a predetermined contact pressure to the respective fixed contacts 5c.

[0037] The respective movable terminals 6, 6' and the respective coil springs 7, 7' are unitized as a movable terminal unit 15 (see FIGS. 5 to 7). The movable terminal unit 15 is movable axially (i.e. in the direction perpendicular to the page of FIG. 2) along with the movement of the shaft portion 11 by the operation of the push button 2. At the time of press operation of the push button 2, due to the movement of the movable terminal unit 15, the respective movable terminals 6, 6' move away from the fixed terminals 5, such that thereby the respective movable contacts C 1 , C 2 of the movable terminals 6, 6' are separated from the respective fixed contacts 5c of the fixed terminals 5. At the time of return operation of the push button 2 in the pulling direction, due to the movement of the movable terminal unit 15, the respective movable terminals 6, 6' move toward the fixed terminals 5, such that thereby the respective movable contacts C 1 , C 2 of the movable terminals 6, 6' come into contact with the respective fixed contacts 5c of the fixed terminals 5. In such a way, the respective movable contacts C 1 , C 2 are contactable with and separatable from the respective fixed contacts 5c.

[0038] In FIG. 2, the respective fixed contacts of a pair of fixed terminals 5m (see FIGS. 3 to 7) disposed between the respective movable terminals 6 and 6' and the respective movable contacts of a pair of movable terminals 6m (see FIGS. 5 to 7) disposed opposite the respective fixed contacts form a monitor contact for monitoring the operating state of the emergency stop switch. At the time of press operation of the push button 2, due to the movement of the movable terminal unit 15, the movable contact of the movable terminal 6m comes into contact with the fixed contact of the fixed terminal 5m. At the time of return operation of the push button 2, due to the movement of the movable terminal unit 15, the movable contact of the movable terminal 6m separates from the fixed contact of the fixed terminal 5m.

[0039] As shown in FIG. 2A, the respective movable contacts C 1 , C 2 of the movable terminals 6, 6' are disposed at positions with a radial distance R from the switch center O. When drawing a circle CC (hereinafter referred to as "contact circle") of radius R with its center located at the switch center O, the respective movable contacts C 1 , C 2 are disposed on the contact circle CC. The respective movable contacts C 1 , C 2 maybe located at substantially equal intervals on the circumference of the contact circle CC. At opposing positions across the switch center O, opening biasing springs 14, 14' are provided. The respective opening biasing springs 14, 14' are disposed at positions with a radial distance R' (>R) from the switch center O. When drawing a circle CC' of radius R' with its center located at the switch center O, the respective centers O 1 , O 2 of the opening biasing springs 14, 14' are disposed on the circle CC'. That is, the opening biasing springs 14, 14' are disposed outside the contact circle CC and radially outside of the contacts C 1 , C 2 . In FIG. 2, positions of the respective opening biasing springs 14, 14' are shown by the centers O 1 , O 2 .

[0040] The respective opening biasing springs 14, 14' are designed for the purpose of biasing the respective movable contacts C 1 , C 2 of the movable terminals 6, 6' in such a separation direction that the movable contacts C 1 , C 2 separate from the respective fixed contacts 5c of the fixed terminal 5. The opening biasing springs 14, 14' are fitted to the movable terminal unit 15. The opening biasing spring 14 is disposed in the vicinity of the respective movable contacts C 1 , preferably at a substantially equal distance from the movable contacts C 1 . Similarly, the opening biasing spring 14' is disposed in the vicinity of the respective movable contacts C 2 , preferably at a substantially equal distance from the movable contacts C 2 . The opening biasing spring 14 is designed mainly for the purpose of opening the respective movable contacts C 1 and the opening biasing spring 14' is designed mainly for the purpose of opening the respective movable contacts C 2 .

[0041] In the example shown in FIG. 2, as a contact structure of the emergency stop switch 1, a duplex-contact type (excluding a monitor contact) formed of the movable contacts C 1 , C 2 (and respectively corresponding fixed contacts 5c) was shown, but the application of the present invention is not restricted to such an example. A triple-contact type may be used. Alternatively, a multiple-contact (including more than three contacts) type may be used.

[0042] FIG. 2B shows an example of a triple-contact type. In the example of FIG. 2A, the movable terminal is formed of two movable terminals 6, 6' disposed in parallel. In the example of FIG. 2B, the movable terminal is formed of three movable terminals 6, 6', 6". The adjacent respective movable terminals 6 and 6'; 6' and 6"; 6" and 6 intersect each other at an acute angle. The respective movable terminals 6, 6', 6" are arranged in a generally triangle.

[0043] The movable contact C 1 is provided at both ends of the movable terminal 6, the movable contact C 2 is provided at both ends of the movable terminal 6', and the movable contact C 3 is provided at both ends of the movable terminal 6". Fixed contacts (not shown) of the fixed terminals respectively corresponding to the movable contacts C 1 , C 2 , C 3 are disposed opposite the movable contacts C 1 , C 2 , C 3 . The respective movable contacts C 1 , C 2 , C 3 of the movable terminals 6, 6', 6" are in elastic contact with the respective fixed contacts of the oppositely disposed fixed terminals and impart a predetermined contact pressure to the respective fixed contacts.

[0044] The respective movable contacts C 1 , C 2 , C 3 of the movable terminals 6, 6', 6" are disposed at positions with a radial distance R from the switch center O. When drawing a circle (i.e. contact circle) CC of radius R with its center located at the switch center O, the respective movable contacts C 1 , C 2 , C 3 are disposed on the contact circle CC. The respective movable contacts C 1 , C 2 , C 3 may be located at substantially equal intervals on the circumference of the contact circle CC. When drawing a circle CC' of radius R' (>R) with its center located at the switch center O, the opening biasing springs 14, 14', 14" are disposed on the circle CC' . The respective opening biasing springs 14, 14', 14" are disposed at positions with a radial distance R' from the switch center O. Therefore, the respective opening biasing springs 14, 14', 14" are disposed outside the contact circle CC and radially outside of the contacts C 1 , C 2 , C 3 . In this example, the respective opening biasing springs 14, 14', 14" are disposed circumferentially at an equal distance on the circle CC'.

[0045] In FIG. 2B, an example is shown in which the opening biasing spring 14 is disposed between the respective ends of the movable terminals 6 and 6', the opening biasing spring 14' is disposed between the respective ends of the movable terminals 6' and 6", and the opening biasing spring 14" is disposed between the respective ends of the movable terminals 6" and 6, but the arrangement of the respective opening biasing springs 14, 14', 14" is not restricted to such an example.

[0046] The respective opening biasing springs 14, 14' , 14" may be disposed opposite the respective central portions of the movable terminals 6, 6', 6" on the circle CC'. That is, the opening biasing spring 14 may be disposed at an intermediate position between the respective movable contacts C 1 of the movable terminal 6 on the circle CC', the opening biasing spring 14' may be disposed at an intermediate position between the respective movable contacts C 2 of the movable terminal 6' on the circle CC', and the opening biasing spring 14" maybe disposed at an intermediate position between the respective movable contacts C 3 of the movable terminal 6" on the circle CC'.

[0047] In such a manner, according to the present embodiment, since a plurality of opening-biasing springs are provided as an opening-biasing spring, a biasing force in the opening direction by the opening-biasing springs can be fully applied to a plurality of contacts, thus improving stability at the time of contact and separation of the respective contacts. Moreover, according to the present embodiment, a load necessary for safety potential ®< in which a force is applied in such an opening-biasing direction as the contacts become contactless can be separated at a plurality of positions around the switch center. Thereby, duplexing (or multiplexing) effect of the force in the opening-biasing direction can be achieved.

[0048] Also, according to the present embodiment, since the opening-biasing springs are disposed radially outwardly from the respective contacts disposed at a radial distance from the switch center, stability at the time of contact and separation of the respective contacts can be further improved, and the length of the emergency stop switch can be shortened thus achieving a short emergency stop switch.

[0049] Then, the support structure of the shaft portion 11 of the emergency stop switch 1 will be explained in reference to FIGS. 8 to 12.

[0050] FIG. 8 is a top plan view of a cross section of the emergency stop switch of FIG. 1 as viewed from above (i.e. from the push button side), and FIG. 9 is a perspective view of FIG. 8.

[0051] As shown in FIG. 8, a pair of second hold members 31, 32 are disposed in the direction D2 intersecting (e.g. at right angles) the arrangement direction D1 of a pair of first hold members 12, 13. The second hold members 31, 32 are formed integrally with the body portion 3 inside the body portion 3, disposed opposite each other across the shaft portion 11, and designed for the purpose of holding the shaft portion 11 from the outer peripheral side. The second hold members 31, 32 arewall-shapedmembers (see FIG. 9) that extend circumferentially in an arc-shape and extend axially (in the up-down direction in FIG. 8). The second hold members 31, 32 have an inner circumferential surface 31a, 32a respectively that extend in an arc-shape along the outer perimeter of the shaft portion 11. The inner circumferential surface 31a is disposed oppositely to the outer circumferential surface 11C 1 of the shaft portion 11 and the inner circumferential surface 32a is disposed oppositely to the outer circumferential surface 11C 2 of the shaft portion 11.

[0052] FIG. 10 is an internal structure diagram of the emergency stop switch of FIG. 1 as viewed from the front with the push button, the body portion, the hold block and the like detached. FIG. 11 is a view omitting the shaft portion of FIG. 10. FIG. 12 is a top plan view of FIG. 10 as viewed from above.

[0053] As shown in FIG. 10, a pair of flange portions 11A, 11B protruding radially outwardly are provided at the outer circumferential surface of the shaft portion 11. The respective flange portions 11A, 11B are positioned against each other across the axial line and have a chevron-shaped longitudinal section respectively. The flange portion 11A includes an inclined surface (engaged surface) 11a 1 located below and an inclined surface 11a 2 located above. Similarly, the flange portion 11B includes an inclined surface (engaged surface) 11b 1 located below and an inclined surface 11b 2 located above.

[0054] On the other hand, the distal end portions of the respective engagement members 12A, 13A of the first hold members 12, 13 have a generally chevron-shaped longitudinal section respectively as viewed from the front. The distal end portion of the flange member 12A includes an inclined surface 12a 1 located above and an inclined surface 12a 2 located below. Similarly, the distal end portion of the engagement member 12B includes an inclined surface 13a 1 located above and an inclined surface 13a 2 located below (see FIGS. 11, 12).

[0055] In the state prior to press operation of the push button 2, as shown in FIG. 10, the inclined surface 12a 1 at the distal end portion of the engaging member 12A of the first hold member 12 is in contact and engagement with the inclined surface 11a 1 of the flange portion 11A of the shaft portion 11. Likewise, the inclined surface 13a 1 at the distal end portion of the engagement member 13A of the first hold member 13 is in contact and engagement with the inclined surface 11b 1 of the flange portion 11B of the shaft portion 11. Thereby, the shaft portion 11 is held at the position prior to the press operation by the first hold members 12, 13.

[0056] In such a way, according to the present embodiment, since the shaft portion 11 is held from the outer peripheral side by the first hold members 12, 13 and the second hold members 31, 32 from the intersecting direction, the shaft portion 11 can be securely held from the outer peripheral side, rattling of the shaft portion can be decreased, thus preventing a radial rattling from occurring at the shaft portion 11 during operation. Thereby, stability of the respective contacts at the time of contact and separation can be still further improved.

[0057] Next, the rotation preventive structure of the push button 2 of the emergency stop switch 1 will be explained in reference to FIGS. 13 to 30.

[0058] As shown in FIGS. 13 to 15, the push button 2 includes an outer cylindrical portion 20 that has a cylindrical surface to form an outer circumferential surface of the push button 2 and that is open to the bottom (i.e. into the page of FIG. 13), and an inner cylindrical portion 21 that is disposed radially inwardly from and concentrically with the outer cylindrical portion 20 at a predetermined distance and that is similarly open to the bottom. A pair of contact portions 22, 23 protruding radially outwardly are provided at and integrally formed with the outer circumferential surface of the inner cylindrical portion 21. The respective contact portions 22, 23 are disposed oppositely to each other on the outer circumferential surface (that is, spaced equally around the outer circumference) of the inner cylindrical portion 21. Left and right sides of the contact portion 22 form contact surfaces 22a, 22b contactable with a rotation stopper (described later) of the body portion 3. Likewise, left and right sides of the contact portion 23 form contact surfaces 23a, 23b contactable with a rotation stopper (described later) of the body portion 3.

[0059] As shown in FIGS. 16 and 17, the body portion 3 that holds the pushbutton2 rotatably includes a cylindrical portion 3A that forms an outer circumferential surface of the body portion 3. At the inner circumferential surface of the cylindrical portion 3A, a pair of rotation stoppers 33, 34 protruding radially inwardly are formed integrally with the inner circumferential surface. The respective rotation stoppers 33, 34 are disposed opposite each other on the inner circumferential surface (that is, spaced equally around the inner circumference) of the cylindrical portion 3A. Left and right sides of the rotation stoppers 33, 34 form regulatory surfaces 33a, 33b, 34a, 34b that either of the contact surfaces 22a, 22b, 23a, 23b of the contact portions 22, 23 of the push button 2 contacts to regulate the rotation of the push button 2.

[0060] When the push button 2 is incorporated into the body portion 3, the cylindrical portion 3A of the body portion 3 is disposed at an inner space between the outer cylindrical portion 20 and the inner cylindrical portion 21 (FIGS. 14, 15) of the push button 2. At this time, the respective contact portions 22, 23 of the push button 2 are disposed between the respective rotation stoppers 33 and 34 of the body portion 3. For example, when the contact portion 22 is disposed at an inner space above the body portion 3 in FIG. 17 and the contact portion 23 is disposed at an inner space below the body portion 3 in FIG. 17, as the push button 2 is rotated counterclockwise in FIG. 13, the contact surface 22a of the contact portion 22 comes into contact with the regulatory surface 33a of the rotation stopper 33 of the body portion 3 and the contact surface 23a of the contact portion 23 comes into contact with the regulatory surface 34a of the rotation stopper 34 of the body portion 3. On the contrary, as the push button 2 is rotated clockwise in FIG. 13, the contact surface 22b of the contact portion 22 comes into contact with the regulatory surface 34a of the rotation stopper 34 of the body portion 3 and the contact surface 23b of the contact portion 23 comes into contact with the regulatory surface 33b of the rotation stopper 33 of the body portion 3.

[0061] Now, assuming that the contact surface 22a of the contact portion 22 is in contact and engagement with the regulatory surface 33a of the rotation stopper 33 of the body portion 3 (see FIG. 18), at this time, we will consider a force applied to the contact surface 22a and the regulatory surface 33a in reference to FIGS. 19 and 21 (and FIGS. 20 and 22).

[0062] As shown in FIG. 19, a partially enlarged view of FIG. 18, the rotation stopper 33 has a generally trapezoidal shape and the outer-circumferential-side length (i.e. top base) Lo is shorter than the inner-circumferential-side length (i.e. bottom base) Li. The regulatory surfaces 33a, 33b of the rotation stopper 33 have a tapered surface that tapers toward the outer peripheral side (i.e. downwardly in FIG. 19). On the other hand, the contact portion 22 has a generally trapezoidal shape that is up-side down relative to the rotation stopper 33 and the inner-circumferential-side length (i.e. top base) Li' is shorter than the outer-circumferential-side length (i.e. bottom base) Lo'. The contact surfaces 22a, 22b of the contact portion 22 have a tapered surface that tapers toward the inner peripheral side (i.e. upwardly in FIG. 19). Also, in this example, angle α between the bottom base and the inclined surface of the rotation stopper 33 is an acute angle. Similarly, angle β between the bottom base and the inclined surface of the contact portion 22 is an acute angle.

[0063] In FIG. 19, a pressing force F acts on the regulatory surface 33a of the rotation stopper 33 from the contact surface 22a of the contact portion 22. The pressing force F is perpendicular to the contact surface 22a. Here, as shown in FIG. 20, when the pressing force F is resolved into the radial direction toward the switch center (i.e. up-down direction in FIG. 20) and the circumferential direction (i.e. left to right direction in FIG. 20) perpendicular to the radial direction, the radial component Fr is directed radially inwardly. The radial component Fr acts in such a direction that the engagement state of the regulatory surface 33a with the contact surface 22a can be further strengthened.

[0064] In FIG. 21, a pressing force F' acts on the contact surface 22a of the contact portion 22 from the regulatory surface 33a of the rotation stopper 33. The pressing force F' is equal to the pressing force F at the same point of application of force as the pressing force F, but here, for illustration purposes and explanatory convenience, we focus on the force acting on a different point of application of force from the pressing force F. The pressing force F' is perpendicular to the regulatory surface 33a. Here, as shown in FIG. 22, when the pressing force F' is resolved into the radial direction toward the switch center (i.e. up-down direction in FIG. 22) and the circumferential direction (i.e. left to right direction in FIG. 22) perpendicular to the radial direction, the radial component F'r is directed radially outwardly. The radial component F'r acts in such a direction that the engagement state of the contact surface 22a with the regulatory surface 33a can be further strengthened.

[0065] According to the present embodiment, when an excessive rotational force is applied to the push button 2, an excessive pressing force acts on the respective regulatory surfaces 33a, 33b, 34a, 34b of the rotational stoppers 33, 34 of the body portion 3 from the contact portions 22, 23 of the push button 2, and an excessive pressing force acts on the respective contact surfaces 22a, 22b, 23a, 23b of the contact portions 22, 23 of the push button 2 from the rotation stoppers 33, 34 of the body portion 3. At this juncture, the radial components of these pressing forces act in such a direction that the contact portions 22, 23 of the push button 2 and the rotation stoppers 33, 34 of the body portion 3 are made engaged more firmly, thereby increasing a twisting strength of the push button 2.

[0066] Here, for reference, in the case of a prior-art push button, we will consider an acting force at the time of engagement of a contact portion of a push button with a rotation stopper of a body portion in reference to FIGS. 23 to 26. FIGS. 23 to 26 respectively correspond to FIGS. 19 to 22 of the resent embodiment.

[0067] As shown in FIG. 23, the rotation stopper 33' has a generally trapezoidal shape and the inner-circumferential-side length (i.e. top base) li is shorter than the outer-circumferential-side length (i.e. bottom base) lo. The regulatory surfaces 33'a, 33'b of the rotation stopper 33' have a tapered surface that tapers toward the inner peripheral side (i.e. upwardly in FIG. 23). On the other hand, the contact portion 22' has a generally trapezoidal shape that is up-side down relative to the rotation stopper 33' and the outer-circumferential-side length (i.e. top base) lo' is shorter than the inner-circumferential-side length (i.e. bottom base) li'. The contact surfaces 22'a, 22'b of the contact portion 22' have a tapered surface that tapers toward the outer peripheral side (i.e. downwardly in FIG. 23). Also, in this example, angle α' between the top base and the inclined surface of the rotation stopper 33' is an obtuse angle. Similarly, angle β' between the top base and the inclined surface of the contact portion 22' is an obtuse angle.

[0068] In FIG. 23, a pressing force f acts on the regulatory surface 33'a of the rotation stopper 33' from the contact surface 22'a of the contact portion 22'. The pressing force f is perpendicular to the contact surface 22'a. Here, as shown in FIG. 24, when the pressing force f is resolved into the radial direction toward the switch center (i.e. up-down direction in FIG. 24) and the circumferential direction (i.e. left to right direction in FIG. 24) perpendicular to the radial direction, the radial component fr is directed radially inwardly. The radial component fr acts in such a direction that the engagement of the regulatory surface 33'a with the contact surface 22'a is released.

[0069] In FIG. 25, a pressing force f' acts on the contact surface 22'a of the contact portion 22' from the regulatory surface 33'a of the rotation stopper 33'. The pressing force f' is perpendicular to the regulatory surface 33'a. Here, as shown in FIG. 26, when the pressing force f' is resolved into the radial direction toward the switch center (i.e. up-down direction in FIG. 26) and the circumferential direction (i.e. left to right direction in FIG. 26) perpendicular to the radial direction, the radial component f'r is directed radially inwardly. The radial component f'r acts in such a direction that the engagement of the contact surface 22'a with the regulatory surface 33'a is released.

[0070] FIGS. 27 and 28 schematically show the respective arrangement of the contact portions 22, 23 of the push button 2 of the above-mentioned embodiment and the rotation stoppers 33, 34 of the body portion 3, respectively corresponding to FIGS. 15 and 17. In FIGS. 27 and 28, like reference numbers indicate identical or functionally similar elements.

[0071] In the above-mentioned embodiment, an example was shown in which the rotation stoppers 33; 34 of the body portion 3 protrude readily inwardly (see FIGS. 28, 17), the regulatory surfaces 33a, 33b; 34a, 34b have a tapered surface that tapers toward the outer peripheral side (see FIG. 28), the contact portions 22, 23 of the push button 2 protrude radially outwardly (see FIGS. 27, 15), and the contact surfaces 22a, 22b; 23a, 23b have a tapered surface that tapers toward the inner peripheral side (see FIG. 27), but the application of the present invention is not restricted to such an example.

[0072] FIGS. 29 and 30 show an alternative embodiment of the present embodiment. FIG. 29 corresponds to FIG. 27 and FIG. 30 corresponds to FIG. 28. In FIGS. 29 and 30, like reference numbers indicate identical or functionally similar elements.

[0073] As shown in FIG. 29, contact portions 22 1 ; 23 1 of the push button 2 protrude radially inwardly from the inner circumferential surface of the outer cylindrical portion 20. The respective contact surfaces 22 1 a, 22 1 b; 23 1 a, 23 1 b have a tapered surface that tapers toward the outer peripheral side. As shown in FIG. 30, the rotation stoppers 33 1 ; 34 1 of the body portion 3 protrude radially outwardly from the outer circumferential surface of the inner cylindrical portion 3B disposed radially inwardly from the cylindrical portion 3A. The respective regulatory surfaces 33 1 a, 33 1 b; 34 1 a, 34 1 b have a tapered surface that tapers toward the inner peripheral side.

[0074] In such an alternative embodiment as well, similar to the above-mentioned embodiment, when an excessive rotational force is applied to the push button 2, an excessive pressing force acts on the respective regulatory surfaces 33 1 a, 33 1 b; 34 1 a, 34 1 b of the rotational stoppers 33 1 ; 34 1 of the body portion 3 from the contact portions 22 1 , 23 1 of the push button 2, and an excessive pressing force acts on the respective contact surfaces 22 1 a, 22 1 b; 23 1 a, 23 1 b of the contact portions 22 1 , 23 1 of the push button 2 from the rotation stoppers 33 1 , 34 1 of the body portion 3. At this juncture, the radial components of these pressing forces act in such a direction that the contact portions 22 1 , 23 1 of the push button 2 and the rotation stoppers 33 1 , 34 1 of the body portion 3 are made engaged more firmly, thereby increasing a twisting strength of the push button 2.

[0075] In the above-mentioned embodiment, an example was shown in which the both side surfaces of the rotation stoppers 33, 34 are respectively tapered (both-tapered), but only one side surface of the rotation stopper 33 may be tapered and the other side surface of the rotation stoper 33 may extend radially toward the switch center O. Likewise, only one side surface of the rotation stopper 34 may be tapered and the other side surface of the rotation stoper 34 may extend radially toward the switch center O. In these cases, the respective side surfaces of the rotation stoppers 33, 34 are single-tapered.

[0076] Similarly, in the above-embodiment, an example was shown in which the both side surfaces of the contact portions 23, 23 are respectively tapered (both-tapered), but only one side surface of the contact portion 22 may be tapered and the other side surface of the contact portion 22 may extend radially toward the switch center O. Likewise, only one side surface of the contact portion 23 may be tapered and the other side surface of the contact portion 23 may extend radially toward the switch center O. In these cases, the side surface of the respective contact portions 22, 23 are single-tapered.

[0077] In the above-mentioned embodiment, an example was shown in which two of the rotation stoppers 33, 34 are provided in the circumferential direction and two of the contact portions 22, 23 are provided in circumferential direction between the circumferentially adjacent rotation stoppers 33 and 34, but the number of the rotation stoppers and the contact portions is not restricted to two and three or more is fine.

[0078] Also, the emergency stop switch employing the present invention is provided at mechanical equipment in a factory or its control equipment and various controllers such as a teaching device connected to the control equipment. During operation of the emergency stop switch, it makes an emergency-stop the mechanical equipment.<Other Embodiments and Alternative Embodiments>

[0079] The above-mentioned embodiment should be considered in all respects only as illustrative and not restrictive. Those skilled in the art to which the invention pertains may make various modifications and other embodiments employing the principles of the present invention without departing from its spirit or essential characteristics particularly upon considering the foregoing teachings, even if there are no explicit explanations in the description.INDUSTRIAL APPLICABILITY

[0080] The present invention is of use to an emergency stop switch and suitable especially to a structure for improving stability at the time of contact and separation of contacts.DESCRIPTION OF REFERENCE NUMERALS

[0081] 1: emergency stop switch 2: push button 22, 23: contact portion 22a, 22b, 23a, 23b: contact surface 3: body portion 33, 34: rotation stopper 33a, 33b, 34a, 34b: regulatory surface 5c: fixed contact (contact) 11: shaft portion 11a 1 , 11b 1 : engaged surface 12, 13: first hold member 12A, 13A: engaging member 12a 1 , 13a 1 : engaging surface 12B, 13B: spring (biasing member) 14, 14', 14": opening biasing spring 31, 32: second hold member 31a, 32a: inner circumferential surface C 1 -C 3 : movable contact (contact) O: switch center R: radial distance CC: contact circle

Claims

1. An emergency stop switch, wherein said emergency stop switch includes a plurality of opening-biasing springs that bias a plurality of contacts in an opening direction, which are disposed at a radial distance from a switch center, and wherein said respective opening-biasing springs are disposed radially outwardly from said respective contacts.

2. The emergency stop switch according to claim 1, wherein when a contact circle with its center located at said switch center is drawn passing the respective contacts said respective opening-biasing springs are disposed outside said contact circle.

3. The emergency stop switch according to claim 1, wherein said respective opening-biasing springs are disposed circumferentially at a substantially equal distance.

4. The emergency stop switch according to claim 1, wherein said respective contacts are formed of a plurality of fixed contacts and a plurality of movable contacts that correspond to said plurality of fixed contacts, and wherein said respective opening-biasing springs bias said respective movable contacts in an opening direction to be separated from said corresponding respective fixed contacts.

5. The emergency stop switch according to claim 1, said emergency stop switch further comprising a push button and a shaft portion movable by an operation of said push button, wherein around said shaft portion, a pair of first hold members for holding said push button at a position prior to press-operation are disposed opposite each other across said shaft portion and a pair of second hold members for holding said shaft portion from an outer peripheral side in a direction intersecting an array direction of said respective first hold members are disposed opposite each other across said shaft portion.

6. The emergency stop switch according to claim 5, said first hold member comprises: an engaging member that has an engaging surface releasably engageable with an engaged surface formed at an outer circumference of said shaft portion; and a biasing member that biases said engaging member toward said shaft portion.

7. The emergency stop switch according to claim 5, wherein said second hold member includes an inner circumferential surface that extends circumferentially along an outer circumference of said shaft portion.

8. The emergency stop switch according to claim 1, said emergency stop switch further comprising a push button and a body portion that holds said push button rotatably, said body portion including a rotation stopper having a regulatory surface that regulates a rotation of said push button, and said push button including a contact portion having a contact surface that is contactable with said regulatory surface of said rotation stopper, wherein said rotation stopper protrudes radially inwardly and said regulatory surface has a tapered surface that tapers toward an outer peripheral side of said regulatory surface, and said contact portion protrudes radially outwardly and said contact surface has a tapered surface that tapers toward an inner peripheral side of said contact surface, alternatively, wherein said rotation stopper protrudes radially outwardly and said regulatory surface has a tapered surface that tapers toward an inner peripheral side of the regulatory surface, and said contact portion protrudes radially inwardly and said contact surface has a tapered surface that tapers toward an outer peripheral side of said contact surface.

9. The emergency stop switch according to claim 8, wherein said regulatory surface is disposed at both side surfaces of said rotation stopper, which are double-tapered, and wherein said contact surface is disposed at both side surfaces of said contact portion, which are double-tapered.

10. The emergency stop switch according to claim 8, wherein said rotation stopper is circumferentially disposed in a plurality, and said contact portion is disposed in a plurality in the circumferential direction among said respective rotation stoppers that are disposed circumferentially adjacent to one another.

11. A controller that incorporates said emergency stop switch according to claim 1.

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