阅读说明：本技术 部件减少和可靠性改善的中性位置限位开关头设计 (Neutral position limit switch head design with reduced components and improved reliability ) 是由 S·S·凯萨卡 A·E·德维利斯 于 2019-07-25 设计创作，主要内容包括：本发明题为“部件减少和可靠性改善的中性位置限位开关头设计”。本发明涉及限位开关操作头,其包括能够沿顺时针方向和逆时针方向旋转的轴；被支撑在轴上并且能够响应于轴的旋转而沿顺时针方向和逆时针方向旋转的凸轮构件；以及响应于凸轮构件的旋转而由凸轮构件致动的从动件,其中从动件包括枢轴销,能够围绕枢轴销枢转的杠杆部分,以及安装到杠杆部分并与凸轮构件接触的滚动销。致动器构件接触杠杆部分并且响应于杠杆部分的枢转而沿第一方向或第二方向线性平移。滚动销在凸轮构件旋转时沿凸轮构件的轮廓运动,以便使杠杆部分枢转,其中致动器构件响应于杠杆部分的枢转而沿第一方向或第二方向线性平移。(The invention provides a neutral position limit switch head design with reduced components and improved reliability. The invention relates to a limit switch operating head, which comprises a shaft capable of rotating in a clockwise direction and a counterclockwise direction; a cam member supported on the shaft and rotatable in a clockwise direction and a counterclockwise direction in response to rotation of the shaft; and a follower actuated by the cam member in response to rotation of the cam member, wherein the follower includes a pivot pin, a lever portion pivotable about the pivot pin, and a roll pin mounted to the lever portion and in contact with the cam member. The actuator member contacts the lever portion and linearly translates in the first direction or the second direction in response to pivoting of the lever portion. The roll pin moves along a profile of the cam member as the cam member rotates to pivot the lever portion, wherein the actuator member linearly translates in the first direction or the second direction in response to pivoting of the lever portion.)

1. An operating head for providing actuation in a limit switch, the operating head comprising:

a housing;

a shaft rotatable in a clockwise direction and a counterclockwise direction;

a cam member supported on the shaft and rotatable in the clockwise and counterclockwise directions in response to rotation of the shaft;

a follower actuated by the cam member in response to rotation of the cam member in the clockwise and counterclockwise directions, the follower comprising:

a pivot pin secured to the housing;

a lever portion positioned on the pivot pin and pivotable in opposite directions about the pivot pin; and

a roll pin mounted to the lever portion and in contact with the cam member; and

an actuator member in contact with the lever portion and linearly translating in a first direction or a second direction in response to pivoting of the lever portion;

wherein the roll pin moves along a profile of the cam member when the cam member is rotated in the clockwise or counterclockwise direction to pivot the lever portion, wherein the actuator member linearly translates in the first or second direction in response to pivoting of the lever portion.

2. The operating head of claim 1, wherein the cam profile of the cam member includes a protrusion that slopes from a cam surface of decreasing diameter to a cam surface of increasing diameter, and wherein the rolling pin floats at a half-point on the sloping protrusion when the operating head is in a vertical operating position.

3. The operating head of claim 2, wherein when the cam member rotates in the clockwise direction, the rolling pin moves down the inclined protrusion to the reduced diameter cam surface, pivoting the lever portion toward the cam member and the actuator member linearly translates in the first direction.

4. The operating head of claim 2, wherein when the cam member rotates in the counterclockwise direction, the rolling pin moves up the inclined protrusion to the increased diameter cam surface, pivoting the lever portion away from the cam member and the actuator member linearly translates in the second direction.

5. The operating head of claim 2, wherein the rolling pin moves from the half-point on the inclined protrusion to the reduced diameter cam surface or the increased diameter cam surface upon 5 ° of pre-stroke rotation of the shaft in the clockwise or counterclockwise direction in order to move the actuator member to a first position or a second position.

6. The operating head of claim 5, wherein after a 5 ° pre-stroke rotation of the shaft moving the roller pin to the reduced diameter cam surface or the increased diameter cam surface, the roller pin moves along the reduced diameter cam surface or the increased diameter cam surface to cause the shaft to make another 85 ° to 90 ° post-stroke rotation in the same direction.

7. The operating head of claim 1, wherein the actuator member is positioned so as to be out of alignment with an axis about which the follower member rotates.

8. The operating head of claim 1, wherein the shaft includes a notch formed therein, and wherein the operating head further comprises:

a stop positioned in the notch so as to contact the shaft; and

a coil spring abutting the stop on one end and the housing on an opposite end;

wherein the coil spring is operative to bias the stop and shaft into a vertical operating position when no rotational force is applied to the shaft.

9. The operating head of claim 1, wherein the rolling pin rolls along the profile of the cam member when moving along the profile so as to reduce friction between the follower and the cam member.

10. An electrical limit switch comprising:

a switch subassembly, the switch subassembly comprising:

a plurality of fixed electrical terminals; and

a contact carrier including electrical contacts thereon, the contact carrier being movable between a plurality of different switch positions to selectively transfer the positions of the electrical contacts to different electrical terminals to make and break different electrical circuits in the switch sub-assembly; and

an operating head subassembly, the operating head subassembly comprising:

a shaft rotatable in a clockwise direction and a counterclockwise direction;

a cam member supported on the shaft and rotatable in the clockwise and counterclockwise directions in response to rotation of the shaft;

an actuator member configured to move linearly in a first direction or a second direction in response to rotation of the cam member in the clockwise direction or the counterclockwise direction, wherein movement of the actuator member causes corresponding movement of the contact carrier; and

a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in the clockwise or counterclockwise direction into linear motion of the actuator member in the first or second direction, wherein the follower directly actuates the actuator member.

11. The electrical limit switch of claim 10, wherein the follower comprises:

a pivot pin secured to a housing of the operating head subassembly;

a lever portion positioned on the pivot pin and pivotable about the pivot pin in opposite directions, the lever portion in contact with the actuator member so as to allow movement thereof; and

a roll pin mounted to the lever portion and in contact with the cam member;

wherein the roll pin moves along a profile of the cam member when the cam member is rotated in the clockwise or counterclockwise direction to pivot the lever portion, wherein the actuator member linearly translates in the first or second direction in response to pivoting of the lever portion.

12. The electrical limit switch of claim 11 wherein the cam profile of the cam member comprises a protrusion that slopes from a cam surface of decreasing diameter to a cam surface of increasing diameter, and wherein the rolling pin floats at a half-point on the sloping protrusion when the operating head is in a vertical operating position.

13. The electrical limit switch according to claim 12, wherein when the cam member is rotated in the clockwise direction, the roll pin moves down the inclined projection to the reduced diameter cam surface, pivoting the lever portion toward the cam member and the actuator member linearly translates in the first direction.

14. The electrical limit switch according to claim 12, wherein when the cam member is rotated in the counterclockwise direction, the roll pin moves up the inclined projection to the increased diameter cam surface, thereby pivoting the lever portion away from the cam member and the actuator member linearly translates in the second direction.

15. The electrical limit switch according to claim 12, wherein upon a 5 ° pre-stroke rotation of the shaft in the clockwise or counterclockwise direction, the rolling pin moves from the half-point on the inclined protrusion to the reduced diameter cam surface or the increased diameter cam surface to enable movement of the contact carrier to one of the plurality of different switching positions.

16. The electrical limit switch according to claim 11, wherein the actuator member is positioned so as to be adjacent an end of the lever portion and offset from a center of a central force axis about which the follower rotates.

17. The electrical limit switch of claim 10 wherein the switch subassembly further comprises a plunger aligned with the actuator member and configured to move linearly in response to a force applied thereto by the actuator member, the plunger abutting the contact carrier to cause movement thereof.

18. An operating head for providing actuation in a limit switch, the operating head comprising:

a shaft rotatable in a clockwise direction and a counterclockwise direction;

a cam member supported on the shaft and rotatable in the clockwise and counterclockwise directions in response to rotation of the shaft;

an actuator member that moves linearly in a first direction or a second direction from a vertical position in response to rotation of the cam member in the clockwise direction or the counterclockwise direction, the actuator member being movable between a first actuated position and a second actuated position; and

a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in the clockwise or counterclockwise direction into linear motion of the actuator member in the first or second direction;

wherein the shaft has a pre-stroke rotation of about 5 ° to move the actuator member to the first and second actuated positions.

19. The operating head of claim 18, wherein the follower comprises:

a pivot pin fixed to a housing of the operating head;

a lever portion positioned on the pivot pin and pivotable in opposite directions about the pivot pin; and

a roll pin mounted to the lever portion and in contact with the cam member;

wherein the roll pin moves along a profile of the cam member when the cam member is rotated in the clockwise or counterclockwise direction to pivot the lever portion, wherein the actuator member linearly translates in the first or second direction in response to pivoting of the lever portion.

20. The operating head of claim 18, wherein the actuator member is positioned so as to be out of alignment with an axis about which the follower member rotates.

Background

The present invention relates generally to limit switches and, more particularly, to a neutral position limit switch that includes a simplified head assembly design with fewer moving parts.

Electrical limit switches comprise a widely adopted class of switching devices for selectively making and/or breaking one or more electrical connections depending on the position of a displaceable switch sensing member. Many electrical limit switches include a head assembly that incorporates a rotary actuator that converts rotary motion into linear motion to actuate the limit switch. A typical head assembly has a crank or other lever for rotating the actuator shaft, and an output member driven by the actuator shaft, the output member having a linear output motion. The output member engages and drives elements of the displaceable switch sensing member for selectively completing and/or interrupting one or more electrical connections. In some embodiments, the electrical limit switch may be configured as a neutral position switch, wherein the actuator shaft of the head assembly is rotatable in both a clockwise direction and a counterclockwise direction to effect movement of the output member and corresponding translation of the displaceable switch sensing member from the neutral position to two different positions in different modes.

It should be appreciated, however, that the above-designed head assemblies presently constructed have certain drawbacks with regard to their operational characteristics and construction of interest. For example, a neutral position limit switch in which the actuator shaft of the head assembly is capable of rotation in both a clockwise and counterclockwise direction typically requires a large degree of pre-stroked rotation of the actuator shaft (e.g., approximately 15 ° -20 °) before rotation is converted into linear motion of the output member, which results in increased switching/tripping time of the limit switch. While this large degree of pre-stroke rotation can be reduced, the head assembly is often made more complex by having more complex moving parts for the head assembly, such as by having separate cam members and providing for mounting these cam members in different orientations relative to the actuator shaft and output member to achieve the desired operation. Accordingly, it should be appreciated that a head assembly having such a configuration includes a large number of moving parts, which increases the cost and complexity of the head assembly and may lead to reliability issues in the field.

Accordingly, it is desirable to provide a head assembly for a neutral position limit switch that requires a small degree of pre-stroking rotation of the actuator shaft (e.g., approximately 5 °) before rotation is converted into linear motion of the output member in order to provide faster switching/trip times for the limit switch. It is also desirable that the head assembly achieve this reduced degree of pre-stroke rotation through a simplified head assembly design having a reduced number of moving parts which will require less time and cost to assemble them and will enhance the reliability of the limit switch due to the reduction of moving parts therein.

Disclosure of Invention

According to one aspect of the present invention, an operating head for providing actuation in a limit switch includes a housing, a shaft rotatable in clockwise and counterclockwise directions, a cam member supported on the shaft and rotatable in clockwise and counterclockwise directions in response to rotation of the shaft, and a follower actuated by the cam member in response to rotation of the cam member in clockwise and counterclockwise directions, wherein the follower further includes a pivot pin fixed to the housing, a lever portion positioned on the pivot pin and pivotable in opposite directions about the pivot pin, and a roll pin mounted to the lever portion and in contact with the cam member. The operating head also includes an actuator member in contact with the lever portion and linearly translating in the first direction or the second direction in response to pivoting of the lever portion. When the cam member is rotated in either a clockwise or counterclockwise direction, the roll pin follows a profile of the cam member to pivot the lever portion, wherein the actuator member linearly translates in either the first or second direction in response to pivoting of the lever portion.

According to another aspect of the invention, an electrical limit switch includes a switch sub-assembly having a plurality of fixed electrical terminals and a contact carrier including electrical contacts thereon, the contact carrier being movable between a plurality of different switch positions to selectively transfer positions of the electrical contacts to different electrical terminals to make and break different electrical circuits in the switch sub-assembly. The electrical limit switch further includes an operating head subassembly having a shaft rotatable in a clockwise direction and a counterclockwise direction; a cam member supported on the shaft and rotatable in a clockwise direction and a counterclockwise direction in response to rotation of the shaft; an actuator member configured to move linearly in a first direction or a second direction in response to rotation of the cam member in a clockwise direction or a counterclockwise direction to cause corresponding movement of the contact carrier; and a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in a clockwise or counterclockwise direction into linear motion of the actuator member in a first or second direction, wherein the follower directly actuates the actuator member.

According to yet another aspect of the invention, an operating head for providing actuation in a limit switch includes a shaft rotatable in a clockwise direction and a counterclockwise direction; a cam member supported on the shaft and rotatable in a clockwise direction and a counterclockwise direction in response to rotation of the shaft; and an actuator member that moves linearly in a first direction or a second direction from a vertical position in response to rotation of the cam member in a clockwise direction or a counterclockwise direction, the actuator member being movable between a first actuated position and a second actuated position. The operating head also includes a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in a clockwise or counterclockwise direction into linear motion of the actuator member in the first or second direction. In operation of the operating head, the shaft has a pre-stroke rotation of about 5 ° to move the actuator member to the first and second actuating positions.

Various other features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

Drawings

The drawings illustrate preferred embodiments presently contemplated for carrying out the invention.

In the drawings:

fig. 1 is a perspective view of a neutral position limit switch according to an embodiment of the present invention.

Fig. 2 is a perspective view, shown in phantom, of an operating head of the neutral position limit switch of fig. 1, according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the operating head taken along line 3-3 of FIG. 2.

FIG. 4 is a schematic view of the operating head of FIG. 2 showing the operating head in a vertical position or position.

FIG. 5 is a schematic view of the operating head of FIG. 2 showing the operating head as its rotatable shaft rotates in a clockwise direction.

FIG. 6 is a schematic view of the operating head of FIG. 2 showing the operating head as its rotatable shaft rotates in a counterclockwise direction.

Detailed Description

Embodiments of the present invention provide a neutral position limit switch having a simplified head assembly with a reduced number of moving parts and improved reliability. The head assembly is configured with an actuator shaft that, as it rotates, causes rotation of a single cam and corresponding pivoting of a follower based on an interface between the cam and a roll pin of the follower. Only a small degree of pre-stroke rotation of the actuator shaft (e.g., approximately 5 °) is required before the cam is rotated sufficiently to interact with the roll pin and translate the rotation into linear motion of the output member, resulting in actuation of the limit switch.

Referring to fig. 1, a neutral position limit switch 10 is shown according to an embodiment of the present invention. The neutral position limit switch 10 includes an operating head subassembly 12 and a switch subassembly 14. The operating head 12 is held on the switch sub-assembly by four screws (not shown), one at each corner, and may be separated therefrom by removing such screws. In operation, the limit switch 10 may selectively control making and/or breaking one or more electrical connections depending on the position of a displaceable switch sensing member in the switch subassembly 14, as will be explained in greater detail below.

Embodiments of the present invention relate particularly to the mechanisms housed within the operating head 12, and thus figures 2 and 3 show a more detailed view of the operating head 12. As shown therein, the operating head 12 is generally configured to include an outer housing 16, a top cover 18, a rotatable shaft 20, an actuator member 22, a cam member 24, a follower 26, a stop 28, and a return mechanism (e.g., a coil spring) 30. The shaft 20 extends from the exterior of the housing 16 and through a sleeve bearing 32 into the interior of the housing 16, with the shaft 20 extending through an opening 34 in the cam member 24 and being pivotably seated in a mount or sleeve bearing 36 formed in the housing 16 opposite the sleeve bearing 32. Although not shown in fig. 2 and 3, it is recognized that the neutral position limit switch 10 will include an operating arm mounted on the shaft 20 at an angle and fixed thereto (e.g., by tightening a screw) to provide rotation of the shaft 20, as is known in the art. The operating arm may include a roller for engagement by a moving machine component or the like, which causes rotation of the operating arm and corresponding rotation of the shaft 20.

The shaft 20 is configured as a generally circular cylindrical member and has a semi-circular portion, with the shaft 20 having a flat drive surface 38 in the area that is disposed within the cam member 24, such that rotation of the shaft 20 imparts rotation to the cam member 24. The shaft 20 also includes a notch 40 formed therein to receive the stop 28, wherein the stop 28 is seated on a flat surface in the notch 40 such that the stop 28 may be oriented/arranged flush with the shaft 20. The stop 28 is centered on the shaft 20 and is mounted relative to the shaft by a pair of guide pins 41. The stops 28 are aligned on the guide pins 41 via openings included in the stops 28 on opposite ends thereof, with the stops 28 translating linearly along the guide pins 41 in response to rotation of the shaft 20. A coil spring 30 is positioned adjacent the stop 28 and within the recess 40, the coil spring having one end of the coil spring 30 mounted to the inner surface of the housing 16 and an opposite end of the coil spring 30 in contact with the stop 28. The coil spring 30 serves to bias the stop 28 and the shaft 20 to a neutral position when no rotational force/torque is applied to the shaft 20, as will be explained in more detail below.

As best shown in fig. 3, the follower 26 is generally formed of a lever portion 42, a pivot pin 44 and a roll pin 46. Pivot pin 44 is attached to housing 16 and mates with an opening 47 formed in lever portion 42 to provide rotation of lever portion 42 about pivot pin 44. The lever portion 42 extends outwardly from the location of the pivot pin 44 and is aligned so as to be positioned adjacent to and between the cam member 24 and the actuator member 22. The first surface 48 of the lever portion 42 abuts the actuator member 22 and is formed as a generally flat surface, with the surface 48 interacting with the actuator member 22 to cause movement thereof upon rotation of the lever portion 42. The roll pin 46 is secured to the lever portion 42 generally adjacent a second surface 50 thereof opposite the first surface 48. The roll pin 46 is inserted into an opening 52 formed in the lever portion 42, wherein the opening 52 is formed in the lever portion 42 at a location that is longitudinally located between the location of the pivot pin 44 and the location where the actuator member 22 abuts the lever portion 42. The lever portion 42 is thicker in this position so as to form an opening 52 therein and to receive the roll pin 46 within the opening 52. The roll pin 46 extends outwardly from an opening 52 in the lever portion 42 to abut the cam member 24 and allow interaction between the follower 26 and the cam member 24.

As also best shown in fig. 3, the cam member 24 comprises a disc cam or a plate cam and has a cam profile shaped to include a protrusion 54 that slopes from a cam surface 56 of decreasing diameter to a cam surface 58 of increasing diameter. The shaft 20 is positioned within the opening 34 of the cam member 24 in a manner (e.g., a friction fit) such that the cam member 24 is secured to the shaft 20 at a desired location. The cam member 24 is positioned relative to the follower 26 such that the roll pin 46 of the follower 26 floats at a half-point on the inclined projection 54 of the cam member 24, which half-point corresponds to the neutral position of the operating head 12 and limit switch 10. Thus, rotation of the cam member 24 in a clockwise direction causes the roller pin 46 to move down the inclined projection 54 of the cam member 24 to the reduced diameter cam surface 56, while rotation of the cam member 24 in a counterclockwise direction causes the roller pin 46 to move up the inclined projection 54 of the cam member 24 to the increased diameter cam surface 58. Thus, movement of the lever portion 42 of the follower 26 in an upward or downward manner is achieved as the cam member 24 rotates.

Following rotation of the cam member 24 in either the clockwise or counterclockwise direction and corresponding upward or downward movement of the lever portion 42 of the follower 26, the actuator member 22 in contact with the lever portion 42 is also caused to move from the vertical or unbiased position. That is, the actuator member 22 can slide inwardly or outwardly along a linear path based on the movement of the follower 26, wherein the actuator member 22 is movable between a fully actuated position, commonly referred to as a first actuated position, and a second actuated position, each of which causes tripping of the limit switch 10. According to an exemplary embodiment, the actuator member 22 is positioned so as to be adjacent to the end of the lever portion 42 and so as to be out of alignment with the axis about which the follower member 26 rotates (i.e., off the central axis of force rotation of the shaft 20). This positioning of the actuator member 22 away from the central axis of force rotation reduces the level of torque required to be applied to the rotating shaft 20 and reduces the force transmitted between the cam member 24 and the roll pin 46.

As the actuator member 22 is moved by the follower 26, the actuator member 22 slides along/within the opening 60 in the top cover 18 to provide linear actuation to the components of the switch subassembly 14, with the top cover 18 providing a guide for the actuator member 22. As shown in fig. 4, the actuator member 22 extends into the switch housing 62 of the switch subassembly 14 (via a bushing 64 formed in the switch housing 62) and causes relative movement thereof in contact with the carrier 66. More specifically, according to one exemplary embodiment, the actuator member 22 abuts the plunger 68 in the switch subassembly 14 aligned therewith to cause linear movement of the plunger 68, which in turn results in relative movement of the contact carrier 66. The contact carrier 66 shifts the position of the contacts 70 in the switch sub-assembly 14 to different terminals 72 to make or break different circuits in the switch sub-assembly 14. That is, the contact carrier 66 shifts the position of the contact 70 to a different terminal 72 based on the inward or outward movement of the actuator member 22 to the first and second actuating positions to make or break a different circuit in the two-step switch of the switch subassembly 14. A compression spring 74 is disposed between the bottom side of the switch housing 62 and the bottom of the plunger 68 to urge the plunger 68 and the actuator member 22 and return to the vertical/neutral position.

Referring still to fig. 4 and now also to fig. 5 and 6, a schematic representation of the function of the operating head 12 in the vertical/neutral position and as the shaft 20 rotates in the clockwise and counterclockwise directions and the interaction of the operating head 12 with the switch subassembly 14, respectively, is shown in accordance with one embodiment of the present invention. As shown first in fig. 4, the operating head 12 is in a vertical/neutral position in which the cam member 24 is in a non-rotating position such that the roll pin 46 of the follower 26 floats at half a point on the inclined projection 54 of the cam member 24. Thus, the follower 26 (i.e., the lever portion 42 thereof) is also in the vertical/neutral position, and the actuator member 22 is also at rest in the vertical/neutral position. Thus, the contact carrier 66 of the switch subassembly is in the unbiased position with the contacts 70 thereon correspondingly positioned to make/break the circuit associated with the unbiased position.

Referring to fig. 5, the shaft 20 of the operating head 12 rotates in a clockwise direction. As the shaft 20 rotates, the cam member 24 rotates and begins to interact with the roll pin 46, causing the pivoting of the follower 26 and the translation of the actuator member 22 such that the rotation of the shaft 20 reaches or exceeds a minimum amount of rotation, such as a pre-stroke of greater than about 5 ° (i.e., 5 ° of pre-stroke +/-2 °), thereby rotating the cam member 24 an amount to linearly move the actuator member 22 to the first actuated position to trip the limit switch 10. Thus, when the shaft 20 rotates in the clockwise direction beyond this minimum amount of rotation, the cam member 24 is rotated such that the roll pin 46 of the follower 26 moves the angled protrusion 54 of the cam member 24 fully downward to the reduced diameter cam surface. This causes the lever portion 42 of the follower 26 to move/rotate rearwardly toward the cam member 24 and the actuator member 22 to correspondingly retract back a predetermined linear distance into the housing 16 of the operating head 12, i.e., to a first actuated position. Retracting the actuator member 22 to the first actuated position causes the plunger 68 of the switch sub-assembly to move the contact carrier 66 to the first biased position, wherein the contacts 70 thereon are correspondingly positioned to make/break the electrical circuit associated with the first biased position.

Referring to fig. 6, the shaft 20 of the operating head 12 rotates in a counterclockwise direction. As the shaft 20 rotates, the cam member 24 rotates and begins to interact with the roll pin 46, causing the pivoting of the follower 26 and the translation of the actuator member 22 such that the rotation of the shaft 20 reaches or exceeds a minimum amount of rotation (e.g., exceeds a pre-stroke of about 5 °), such that the amount of rotation of the cam member 24 causes the actuator member 22 to move linearly to the second actuated position to trip the limit switch 10. Thus, when the shaft 20 rotates in the counterclockwise direction beyond the minimum amount of rotation, the cam member 24 rotates such that the roll pin 46 of the follower 26 moves the angled protrusion 54 of the cam member 24 fully upward to the increased diameter cam surface. This causes the lever portion 42 of the follower 26 to move/rotate outwardly and away from the cam member 24 and the actuator member 22 to correspondingly extend further outwardly from the housing 16 of the operating head 12 a predetermined linear distance, i.e., to the second actuating position. Extension of the actuator member 22 to the second actuated position causes the plunger 68 of the switch sub-assembly to move the contact carrier 66 to the second biased position, wherein the contacts 70 thereon are correspondingly positioned to make/break the electrical circuit associated with the second biased position.

With respect to the movement of the actuator member 22 caused by the follower 26 when the rotation of the cam member 24 exceeds a prescribed amount of pre-stroke, the positioning of the actuator member 22 will remain in its actuated position for another 85-90 of the post-stroke of the cam member 24 in the same direction, or until the torque/rotational force on the shaft 20 and cam member 24 is terminated and the cam member 24 and follower 26 return to their vertical/neutral positions. To return the cam member 24 and follower 26 to their vertical/neutral positions, the helical spring 30 of the operating head 12 exerts a force on the stop 28 and causes the stop 28 to slide on the guide pin 41 and exert a force on the shaft 20, which in turn pushes the shaft 20 back to its vertical non-rotated position — so that the cam member 24 and follower 26 also return to their vertical/neutral positions as a result. Thus, the return of the cam member 24 and follower 26 to their vertical/neutral positions also returns the actuator member 22 to its resting, vertical/neutral position such that the contact carrier 66 of the switch subassembly 14 is in its unbiased position. This completes the operating cycle of the limit switch 10.

The configuration of the operating head 12 and the arrangement of the components therein provides a number of benefits in the design of the present invention. First, positioning the roll pin 46 at half point on the angled protrusion 54 of the cam member 24 in the neutral position provides the limit switch 10 with only a small amount of pre-stroke rotation of the actuator shaft 20 (e.g., about 5 °) under the interaction of the cam member 24 with the roll pin 46 of the follower 26 (and the linear movement of the actuator member 22) over this pre-stroke range (i.e., 0 ° -5 °) before the cam member 24 rotates sufficiently to cause the limit switch 10 to trip. This small amount of required pre-travel allows the switch subassembly 14 to more quickly toggle/trip in the limit switch 10. In addition, the use of the roll pin 46 in the follower 26-and its interaction with the cam member 24-reduces the friction between the follower 26 and the cam member 24 as the cam member 24 rotates. This reduction in friction, generally along with the shape and pivoting nature of follower 26, allows for a large oscillation within the range of cam pressure angles (e.g., between 30 ° and 45 °) acceptable for interaction between follower 26 and cam member 24. In addition, the positioning of the actuator member 22 so that it is misaligned with the axis about which the follower member 26 rotates (i.e., disengages the central axis of force rotation) reduces the level of torque required to be applied to the rotating shaft 20 and reduces the force transmitted between the cam member 24 and the roll pin 46. A reduction in the level of torque required to rotate cam member 24 is desirable to reduce the force in operating head 12 and increase the life of operating head 12.

Advantageously, embodiments of the present invention thus provide a neutral position limit switch having an operating head subassembly with a simplified design in which the number of moving parts is reduced, which requires less time and cost to assemble them, and which enhances the reliability of the limit switch due to the reduction of moving parts therein. The operating head subassembly requires only a small degree of pre-stroke rotation of the actuator shaft (e.g., approximately 5 °) before the rotation is sufficient to linearly translate the output member to the fully actuated position in order to provide faster switching/tripping times for the limit switch. In addition, the construction of the operating head subassembly provides its desired functionality in a limited small space (i.e., a compact operating head subassembly). Thus, the benefits of a simplified design with a reduced number of moving parts are achieved which enhances the reliability of the limit switch without having to increase the outer boundary/size of the operating head subassembly.

Thus, according to one embodiment of the present invention, an operating head for providing actuation in a limit switch includes a housing, a shaft rotatable in a clockwise direction and a counterclockwise direction, a cam member supported on the shaft and rotatable in the clockwise direction and the counterclockwise direction in response to rotation of the shaft, and a follower actuated by the cam member in response to rotation of the cam member in the clockwise direction and the counterclockwise direction, wherein the follower further includes a pivot pin fixed to the housing, a lever portion positioned on the pivot pin and pivotable in opposite directions about the pivot pin, and a roll pin mounted to the lever portion and in contact with the cam member. The operating head also includes an actuator member in contact with the lever portion and linearly translating in the first direction or the second direction in response to pivoting of the lever portion. When the cam member is rotated in either a clockwise or counterclockwise direction, the roll pin follows a profile of the cam member to pivot the lever portion, wherein the actuator member linearly translates in either the first or second direction in response to pivoting of the lever portion.

According to another embodiment of the invention, an electrical limit switch includes a switch sub-assembly having a plurality of fixed electrical terminals and a contact carrier including electrical contacts thereon, the contact carrier being movable between a plurality of different switch positions to selectively transfer positions of the electrical contacts to different electrical terminals to make and break different electrical circuits in the switch sub-assembly. The electrical limit switch also includes an operating head subassembly having a shaft that is rotatable in a clockwise direction and a counterclockwise direction. A cam member supported on the shaft and rotatable in a clockwise direction and a counterclockwise direction in response to rotation of the shaft; an actuator member configured to move linearly in a first direction or a second direction in response to rotation of the cam member in a clockwise direction or a counterclockwise direction to cause corresponding movement of the contact carrier; and a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in a clockwise or counterclockwise direction into linear motion of the actuator member in a first or second direction, wherein the follower directly actuates the actuator member.

According to another embodiment of the present invention, an operating head for providing actuation in a limit switch includes a shaft capable of rotating in a clockwise direction and a counterclockwise direction; a cam member supported on the shaft and rotatable in a clockwise direction and a counterclockwise direction in response to rotation of the shaft; and an actuator member that moves linearly in a first direction or a second direction from a vertical position in response to rotation of the cam member in a clockwise direction or a counterclockwise direction, the actuator member being movable between a first actuated position and a second actuated position. The operating head also includes a follower in contact with each of the cam member and the actuator member to convert rotation of the cam member in a clockwise or counterclockwise direction into linear motion of the actuator member in the first or second direction. In operation of the operating head, the shaft has a pre-stroke rotation of about 5 ° to move the actuator member to the first and second actuating positions.

The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.