Forced opening device for electromagnetic safety valve

Abstract

To inhibit a translation cam and a pressing rod from swiftly moving to a return direction due to energizing force of a return spring 6 when an operation part turns beyond a cam part top portion 8241, in a forced valve opening device for a solenoid safety valve that presses and moves a valve element 22 from a valve closing position to a valve opening position where an adsorption piece 24 abuts on an electromagnet 25 and in which a cam mechanism 8 for converting rotating motion of a motor into a linear motion of the pressing rod 5 abutting on the valve element is constituted by a rotation cam 81 rotated and driven by the motor and the translation cam 82 abutting on the pressing rod and a cam part 824 swollen to form a mountain shape on the rotation cam central side relative to a turning trajectory S of the eccentric operation part 812 provided in the rotation cam is provided in the translation cam.SOLUTION: Step parts 8243a-c are provided in a cam part inclined surface portion 8243 on which the operation part 812 abuts when turning beyond the cam part top portion 8241, and the abutment of the step parts 8243a-c to the operation part 812 suppresses rapid movement of the translation cam 82 to a return direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a forced opening device for an electromagnetic safety valve, which includes a valve body that can be seated on a valve seat, an attraction piece that is connected to the valve body via a valve stem that extends in the opposite direction from the valve seat, an electromagnet that faces the attraction piece, and a valve spring that biases the valve body to a valve-closed position where it is seated on the valve seat. [Background technology]

[0002] A known forced valve-opening device of this type includes a pressure rod that can contact the valve disc from one axial direction toward the valve seat, a return spring that urges the pressure rod toward one axial stroke end position, a motor, and a cam mechanism that converts the rotational motion of the motor into linear axial motion of the pressure rod, and by moving the pressure rod in the other axial direction, the other axial end of the pressure rod contacts the valve disc, thereby pressing the valve disc from a valve-closed position to a valve-open position where the attraction piece contacts the electromagnet. Here, the conventional cam mechanism is composed of a cam body that is rotated by the motor, and a radial protrusion formed on the outer peripheral surface of the cam body contacts one axial end of the pressure rod, thereby pressing the pressure rod in the other axial direction (see, for example, Patent Document 1).

[0003] However, in this type of device, because the protrusion abuts against one axial end of the pressure rod from one radial direction (a direction perpendicular to the axial direction), a pressing force acts on that end in the other radial direction, causing the pressure rod to tilt radially by the amount of sliding clearance, and the valve stem may also tilt slightly radially via the valve disc.When the pressure on the valve disc by the pressure rod is released after the valve disc is attracted and held in the open position, a radial pushing force acts on the attracting piece as the biasing force of the valve spring corrects the radial tilt of the valve stem, which may cause the attracting piece to peel off from the electromagnet or accelerate wear on the attracting surfaces between the attracting piece and the electromagnet.

[0004] Therefore, in Japanese Patent Application No. 2020-185243, the present applicant previously proposed a cam mechanism comprising a rotating cam driven by a motor and a linear cam with a rod abutment portion that moves axially along the pressure rod and abuts one axial end of the pressure rod. In this mechanism, the rotating cam is provided with an operating portion eccentric to the center of rotation of the rotating cam, and the linear cam has a cam portion that protrudes in a mountain-like shape toward the center of the rotating cam relative to the rotational trajectory of the operating portion. As the operating portion rotates in one direction in that direction, the operating portion abuts against a sloped portion on one side of the cam portion that gradually approaches the center of the rotating cam toward the apex of the cam portion that protrudes most toward the center of the rotating cam, thereby pushing the linear cam in the other axial direction. In this way, the pressure rod is pushed in the other axial direction via the rod abutment portion, so no force acts on the pressure rod to tilt it radially. Therefore, the valve stem does not tilt radially due to radial tilt of the pressure rod. As a result, when the pressure on the valve body by the pressure rod is released, no radial gouging force acts on the attractive piece, and the above-mentioned problems such as the attractive piece peeling off from the electromagnet due to this gouging force or accelerated wear on the attractive surfaces between the attractive piece and the electromagnet do not occur.

[0005] However, the prior art application was found to have the following drawback. Specifically, when the operating portion of the rotating cam further rotates in one direction beyond the apex of the cam and abuts against the slope on the opposite side of the cam, which slopes from the apex of the cam toward the apex toward the rotating cam, a force assisting the operating portion in rotating in one direction acts as a component of the abutment force, which is the biasing force in one axial direction of the return spring acting on the linear cam via the pressure rod. Therefore, when the operating portion further rotates in one direction beyond the apex of the cam, the rotation speed of the operating portion in one direction increases, and the speed of movement of the linear cam and pressure rod in one axial direction due to the biasing force of the return spring also increases. The pressure rod then reaches the stroke end position in one axial direction with great force, generating an impact. The vibrations caused by this impact can cause the attracting piece to detach from the electromagnet. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-333234 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above, an object of the present invention is to provide an improved forced valve opening device for the electromagnetic safety valve of the above-mentioned prior application, which is capable of mitigating the impact when the pressing rod reaches one of the stroke end positions in the axial direction, thereby preventing the attraction piece from peeling off from the electromagnet. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a forced opening device for an electromagnetic safety valve, which includes a valve element that can be seated on a valve seat, an attraction piece that is connected to the valve element via a valve stem that extends in the opposite direction from the valve seat, an electromagnet that faces the attraction piece, and a valve spring that urges the valve element to a valve closed position where it sits on the valve seat, and which includes a pressing rod that can abut against the valve element from one axial direction that is the valve seat side, a return spring that urges the pressing rod to a stroke end position in one axial direction, a motor, and a cam mechanism that converts the rotational movement of the motor into linear axial movement of the pressing rod, and by moving the pressing rod in the other axial direction against the urging force of the return spring, the other axial end of the pressing rod abuts against the valve element, and the valve element is pushed from the valve closed position to a valve open position where the attraction piece abuts against the electromagnet, and the cam mechanism includes a rotating cam that is rotationally driven by the motor, and a linear cam that is movable in the axial direction of the pressing rod and has a rod abutment portion that abuts against one axial end of the pressing rod, and and an operating part that is eccentric with respect to the center of rotation of the rotating cam is provided, and the linear cam has a cam part that protrudes in a mountain shape toward the center of the rotating cam with respect to the rotational trajectory of the operating part, and as the operating part rotates in one direction as the rotating cam rotates in that direction, the operating part abuts against a sloped part on one side of the cam part that is inclined so as to gradually approach the center of the rotating cam toward the apex part of the cam part that is most protruding toward the center of the rotating cam, and the linear cam is pushed and moved in the other axial direction, and at least one step part is provided in the middle of the sloped part on the other side of the cam part that is inclined so as to gradually move away from the center of the rotating cam from the apex part of the cam part in the one direction, and is parallel to the tangent to the rotational trajectory of the operating part or has an angle difference with the tangent line smaller than other parts, and when the operating part passes the apex part of the cam part and further rotates in the one direction, the sudden movement of the linear cam in one axial direction via the pressing rod due to the biasing force of the return spring is suppressed by the step part abutting against the operating part.

[0009] According to the present invention, when the operating part further pivots in one direction beyond the apex of the cam part, even if the speed of movement of the linear cam in one axial direction temporarily increases due to an increase in the pivoting speed of the operating part in one direction, the step provided midway along the sloped portion on the opposite side of the cam part abuts against the operating part, suppressing the sudden movement of the linear cam in one axial direction, thereby mitigating the impact when the pressure rod reaches one axial stroke end position. As a result, vibrations generated by the impact when the pressure rod reaches one axial stroke end are also mitigated, making it possible to prevent the attraction piece from peeling off from the electromagnet due to such vibrations.

[0010] In the present invention, it is also preferable that the step have a portion that is inclined in the one direction relative to a tangent to the pivotal path of the actuating part so as to approach the center of the rotating cam. In this way, when this inclined portion of the step abuts against the actuating part, a component of force acts on the actuating part to pivot it in the direction opposite to the one direction, braking the pivoting of the actuating part in the one direction and more effectively preventing sudden axial movement of the linear cam in one direction.

[0011] Furthermore, in the present invention, it is desirable that the pivot angle range in which the operating portion abuts against the sloped portion on one side of the cam portion is greater than the pivot angle range in which the operating portion abuts against the sloped portion on the opposite side of the cam portion. In this way, even if the rotating cam is rotated at a constant speed in one direction, the average movement speed when moving the linear cam in one axial direction is slower than the movement speed when pushing the linear cam in the other axial direction. Therefore, sudden movement of the linear cam in one axial direction can be more reliably prevented. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a valve unit incorporating a forced valve opening device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional side view of the valve unit taken along line II-II in FIG. 1. [Figure 3] 3(a) is a cross-sectional plan view showing the forced valve-opening device according to the embodiment of the present invention taken along line III-III in FIG. 2, and FIG. 3(b) is a cross-sectional plan view showing the operating state of the forced valve-opening device. [Figure 4] 3 is a perspective view of a rotary cam provided in the forced valve-opening device of the embodiment, viewed from diagonally below. FIG. [Figure 5] 3 is a perspective view of a direct acting cam and a pressure rod in an exploded state, which are provided in the forced valve opening device of the embodiment, as viewed obliquely from above; FIG. [Figure 6] FIG. 3 is an enlarged plan view of a cam portion of a direct acting cam provided in the forced valve opening device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 and 2 show a valve unit installed in a gas supply path to a burner. This valve unit is equipped with an upstream electromagnetic safety valve 2 and a downstream flame power control valve 3, both of which are incorporated in a valve casing 1 having a gas inlet 11 and a gas outlet 12 connected to the burner.

[0014] The electromagnetic safety valve 2 comprises a valve element 22 in the valve chamber 13 that can be seated on a valve seat 21 located at the downstream end of the valve chamber 13 in the valve casing 1 that communicates with the gas inlet 11, an attracting piece 24 that is connected to the valve element 22 via a valve stem 23 that extends in the opposite direction to the valve seat 21, an electromagnet 25 that faces the attracting piece 24, and a valve spring 26 that urges the valve element 22 to a valve-closed position where it seats on the valve seat 21. A valve seat member 21a that forms the valve seat 21 is mounted inside the valve casing 1.

[0015] The heat control valve 3 includes a fixed plate 31 fixed within the valve casing 1 so as to cover the upper surface of the gas chamber 14 located downstream of the electromagnetic safety valve 2 within the valve casing 1, and a disc-shaped valve plate 32 that rotates while in contact with the underside of the fixed plate 31. The fixed plate 31 is in contact with the underside of the upper cover 15 of the valve casing 1, which defines the gas outlet 12, via a packing 33. The valve plate 32 is connected to a rotating shaft 72 that is connected to an output shaft 71 of a motor 7, such as a stepping motor, mounted on the underside of the valve casing 1, and is further biased upward by a spring 34. The fixed plate 31 has a passage hole 31a that communicates with the gas outlet 12, and the valve plate 32 has a valve hole (not shown). When the valve plate 32 is rotated by the motor 4, the overlapping opening of the valve hole relative to the passage hole 31a changes, thereby adjusting the heat.

[0016] When an ignition operation is performed, the electromagnetic safety valve 2 is forcibly opened by a forced valve-opening device 4 according to an embodiment of the present invention. Referring also to Fig. 3, the forced valve-opening device 4 includes a pressure rod 5 that can come into contact with the valve element 22 from one axial direction (the left side in Figs. 2 and 3) on the valve seat 21 side, a return spring 6 that urges the pressure rod 5 in one axial direction, the motor 7, and a cam mechanism 8 that converts the rotational motion of the motor 7 into linear axial motion of the pressure rod 5. The end of the other axial direction (the right side in Figs. 2 and 3) of the pressure rod 5 comes into contact with the valve element 22, pushing the valve element 22 from the valve-closed position to the valve-opened position where the attraction piece 24 comes into contact with the electromagnet 25. In this state, the electromagnet 25 is energized to attract and hold the valve element 22 in the valve-opened position.

[0017] The cam mechanism 8 is made up of a rotating cam 81 and a linear cam 82 that is movable in the axial direction of the pressing rod 5 and has a rod abutment portion 821 that abuts against one axial end of the pressing rod 5. Referring also to Figure 4, a non-circular fitting hole 811 into which the non-circular cross-sectional portion of the rotating shaft 72 is fitted is formed at the rotation center of the rotating cam 81, and the rotating cam 81 is rotationally driven by the motor 7. In addition, the rotating cam 81 is provided with an operating portion 812 that is eccentric to the rotation center.

[0018] The direct-acting cam 82 is axially movably accommodated in the gas chamber 14 within the valve casing 1. That is, guide surfaces 141 parallel to the axial direction are formed on the side walls of the gas chamber 14 located on both sides in the axial direction and the direction orthogonal thereto, and side surfaces 822 on both sides of the direct-acting cam 82 in the axial direction and the direction orthogonal thereto are formed as surfaces parallel to the axial direction, such that the direct-acting cam 82 is guided by the guide surfaces 141 and moves axially.

[0019] Also, referring to FIG. 5 as well, on the direct-acting cam 82, a standing wall 823 is erected at the edge on the other side in the axial direction. And at the center of the surface of the standing wall 823 facing the other side in the axial direction, a rod contact portion 821 is provided, which is formed in an arc shape convex in the other direction in the axial direction (accurately, an arc shape that is substantially concentric with the rotation center of the rotary cam 81 when the direct-acting cam 82 moves to a position where it pushes the pressing rod 5 to the stroke end position on the other side in the axial direction described later). By forming the rod contact portion 821 in such an arc shape, even if the direct-acting cam 82 tilts by the sliding clearance, the pushing stroke of the pressing rod 5 can be kept constant.

[0020] On the surface of the standing wall 823 facing one side in the axial direction, a cam portion 824 is provided, which is raised in a mountain shape toward the center side of the rotary cam 81 with respect to the turning locus S of the operating portion 812 of the rotary cam 81. When the rotary cam 81 is rotated in the clockwise direction in FIG. 3 from the position shown in FIG. 3(a), with the clockwise turning of the operating portion 812 accompanying this rotation, the operating portion 812 abuts against one inclined surface portion 8242 of the cam portion 824, which is inclined so as to gradually approach the center side of the rotary cam 81 toward the apex portion 82, which is the most raised portion on the center side of the rotary cam 81 of the cam portion 824. As a result, the direct-acting cam 82 is pushed axially in the other direction, and the pressing rod 5 is pushed axially in the other direction against the biasing force of the return spring 6. And when the operating portion 812 reaches the apex portion 8241 of the cam portion 824 as shown in FIG. 3(b), the pressing rod 5 is pushed to the stroke end position on the other side in the axial direction, and the valve body 22 of the electromagnetic safety valve 2 reaches the valve opening position slightly before this stroke end position.

[0021] In this state, the valve element 22 of the electromagnetic safety valve 2 is attracted and held in the valve open position by energizing the electromagnet 25, and the rotating cam 81 is further rotated clockwise. As a result, the operating portion 812 abuts against a sloped portion 8243 on the opposite side of the cam portion 824, which is inclined clockwise from the apex portion 8241 of the cam portion 824 so as to gradually move away from the center of the rotating cam 81, and the linear cam 82 and the pressing rod 5 move in one axial direction by the biasing force of the return spring 6, and the pressing rod 5 moves away from the valve element 22, which is attracted and held in the valve open position. When the pressing rod 5 reaches one axial stroke end position, the other axial end of the pressing rod 5 is positioned to one axial side of the valve seat 21 so as not to prevent the valve element 22 from returning to the valve closed position in which it seats on the valve seat 21 when the energization of the electromagnet 25 is stopped.

[0022] Here, when the operating portion 812 rotates further in the clockwise direction beyond the apex portion 8241 of the cam portion 824 and abuts against a portion of the inclined surface portion 8243 on the opposite side of the cam portion 824 that is inclined in the clockwise direction away from the center of the rotating cam 81, a force assisting the operating portion 812 in rotating in the clockwise direction acts on the operating portion 812 as a component of the abutment force that is the biasing force in one axial direction by the return spring 6 that acts on the linear cam 82 via the pressing rod 5. Therefore, if the inclined surface portion 8243 on the opposite side of the cam portion 824 is inclined over its entirety as described above, when the operating portion 812 rotates further in the clockwise direction beyond the apex portion 8241 of the cam portion 824, the rotation speed of the operating portion 812 in the clockwise direction increases, and the moving speed in one axial direction of the linear cam 82 and the pressing rod 5 due to the biasing force of the return spring 6 also increases. Then, the pressure rod 5 reaches one of the stroke end positions in the axial direction with force, causing an impact (an impact caused by the collision of the stopper portion 511 of the pressure rod 5 with the step portion 161 described later), and the vibration caused by this impact may cause the attraction piece 24 to peel off from the electromagnet 25, making it impossible to attract and hold the valve body 22 in the open position.

[0023] 6, first to third steps 8243a, 8243b, and 8243c are provided on the sloped surface 8243 on the opposite side of the cam portion 824. The steps 8243a are parallel to the tangent TL of the rotational locus of the operating portion 812 or have smaller angles of inclination with respect to the tangent TL than other parts of the sloped surface 8243. The first step 8243a is substantially parallel to the tangent TL of the rotational locus of the operating portion 812, and the second and third steps 8243b and 8243c have portions that are inclined by a predetermined angle θ with respect to the tangent TL of the rotational locus of the operating portion 812 in the clockwise direction so as to approach the center of the rotating cam 81.

[0024] By providing the steps 8243a-c on the slope portion 8243 on the opposite side of the cam portion 824 in this manner, sudden movement of the linear cam 82 in one axial direction via the pressing rod 5 due to the biasing force of the return spring 6 when the operating portion 812 passes the apex portion 8241 of the cam portion 824 and further rotates clockwise is suppressed by the steps 8243a-c abutting against the operating portion 812. This reduces the impact when the pressing rod 5 reaches one axial stroke end position. As a result, vibrations generated by the impact when the pressing rod 5 reaches one axial stroke end position are also reduced, making it possible to prevent the attraction piece 24 from peeling off from the electromagnet 25 due to this vibration. Furthermore, when the second and third steps 8243b and 8243c, which have portions inclined clockwise relative to the tangent line TL of the rotation trajectory of the operating part 812 so as to approach the center of the rotating cam 81, come into contact with the operating part 812, a component force acts on the operating part 812 to rotate it in the direction opposite to the clockwise direction. This component force then brakes the clockwise rotation of the operating part 812, making it possible to more effectively prevent sudden movement of the linear cam 82 in one axial direction.

[0025] 3, in this embodiment, the cam portion 824 is formed so that the pivot angle range θ2 in which the operating portion 812 abuts against the slope portion 8243 on the opposite side of the cam portion 824 is larger than the pivot angle range θ1 in which the operating portion 812 abuts against the slope portion 8242 on one side of the cam portion 824. As a result, even if the rotating cam 81 is rotated clockwise at a constant speed, the average movement speed when the translation cam 82 is moved in one axial direction is slower than the movement speed when the translation cam 82 is pushed and moved in the other axial direction. This makes it possible to more reliably prevent the translation cam 82 from suddenly moving in one axial direction.

[0026] As shown in FIG. 5 , the pressure rod 5 is composed of a first rod portion 51 against which the rod abutment portion 821 of the linear cam 82 can abut, a second rod portion 52 against the valve element 22, and a cushion spring 53 interposed between the first and second rod portions 51, 52. The first rod portion 51 has three stopper portions 511 circumferentially located and capable of abutting from the other axial direction against a stepped portion 161 formed in a passage 16 in the valve casing 1 connecting the electromagnetic safety valve 2 and the gas chamber 14, and three claw receiving portions 512 circumferentially located near the stopper portions 511. A return spring 6 interposed between the first rod portion 51 and the valve seat member 21a biases the first rod portion 51 toward one axial stroke end position where the stopper portions 511 abut against the stepped portion 161. The second rod portion 52 is provided with three claw pieces 521 circumferentially located and extending in one axial direction. The second rod portion 52 is biased and held by the biasing force of the cushion spring 53 in a state in which the claw portion at the tip of the claw piece 521 engages with the claw receiving portion 512 of the first rod portion 51.

[0027] Here, the biasing force of the cushion spring 53 is greater than the resultant force of the biasing forces of the return spring 6 and the valve spring 26. Therefore, when the first rod portion 51 is pushed in the other axial direction via the rod abutment portion 821 due to movement of the linear cam 82 in the other axial direction, the second rod portion 52 also moves in the other axial direction together with the first rod portion 51. Then, when the valve body 22 reaches the valve open position and the second rod portion 52 can no longer move in the other axial direction, further movement of the linear cam 82 in the other axial direction causes the first rod portion 51 to be pushed to the stroke end position in the other axial direction while compressing the cushion spring 53, as shown in FIG.

[0028] Furthermore, after the operating part 812 is rotated to the end of the sloped part 8243 on the opposite side of the cam part 824 and the pressing rod 5 is returned to one stroke end position in the axial direction, the flame power is adjusted by rotating the valve plate 32 due to the rotation of the motor 7 outside the rotation angle range in which the operating part 812 abuts against the cam part 824. When extinguishing the fire, the operating part 812 is rotated clockwise to the position shown in Figure 3(a) and waits until the next ignition.

[0029] Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to this. For example, in the above embodiment, three steps 8243a-c are provided on the sloped surface 8243 on the opposite side of the cam portion 824, but the number of steps may be one, two, or four or more. Also, in the above embodiment, the pressing rod 5 is equipped with a cushioning mechanism having the cushion spring 53, but it is also possible to obtain the cushioning function in a separate structure and make the pressing rod 5 an integrated structure. [Explanation of symbols]

[0030] 2...electromagnetic safety valve, 21...valve seat, 22...valve body, 23...valve stem, 24...adsorption piece, 25...electromagnet, 26...valve spring, 4...forced valve opening device, 5...pressure rod, 6...return spring, 7...motor, 8...cam mechanism, 81...rotating cam, 812...actuating part, 82...linear cam, 821...rod contact part, 824...cam part, 8241...vertex part, 8242...slope part on one side, 8243...slope part on the opposite side, 8243a-c...step part, S...rotation trajectory of the actuating part, TL...tangent to the rotation trajectory, θ1...rotation angle range in which the actuating part contacts the slope part on one side of the cam part, θ2...rotation angle range in which the actuating part contacts the slope part on the opposite side of the cam part.

Claims

1. A forced valve opening device for an electromagnetic safety valve comprising: a valve body that can be seated on a valve seat; an attraction piece that is connected to the valve body via a valve stem that extends in the opposite direction to the valve seat; an electromagnet that faces the attraction piece; and a valve spring that biases the valve body to a valve-closed position where it is seated on the valve seat, the valve element is provided with a pressure rod that can come into contact with the valve element from one axial direction that is the valve seat side, a return spring that urges the pressure rod to a stroke end position in one axial direction, a motor, and a cam mechanism that converts the rotational motion of the motor into linear axial motion of the pressure rod, and by moving the pressure rod in the other axial direction against the urging force of the return spring, the other axial end of the pressure rod comes into contact with the valve element, and the valve element is pushed from the valve closed position to the valve open position where the attraction piece abuts against the electromagnet; The cam mechanism is composed of a rotating cam that is driven to rotate by a motor, and a linear cam that is movable in the axial direction of the pressing rod and has a rod abutment portion that abuts against one axial end of the pressing rod, and the rotating cam is provided with an operating portion that is eccentric with respect to the center of rotation of the rotating cam, and the linear cam has a cam portion that protrudes in a mountain shape toward the center of the rotating cam with respect to the rotation locus of the operating portion, and as the operating portion rotates in one direction as the rotating cam rotates in that direction, the operating portion abuts against a sloped portion on one side of the cam portion that is inclined so as to gradually approach the center of the rotating cam toward the apex portion that protrudes most toward the center of the rotating cam, and the linear cam is pushed and moved in the other axial direction, 1. A forced opening device for an electromagnetic safety valve, comprising: a cam section having a cam apex, a cam shaft, a spring ...

2. 2. The forced opening device for an electromagnetic safety valve according to claim 1, wherein the step has a portion that is inclined in the one direction relative to the tangent line so as to approach the center of the rotary cam.

3. 3. The forced opening device for an electromagnetic safety valve according to claim 1, wherein the rotation angle range in which the operating part abuts on the sloped portion on one side of the cam part is larger than the rotation angle range in which the operating part abuts on the sloped portion on the opposite side of the cam part.

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