KR20110106668A - Linear electric actuator - Google Patents

Abstract

The present invention relates to a vertically actuated electric driver capable of miniaturizing a portion for detecting the number of revolutions of the vertically actuated electric driver when the vertical actuated electric driver is operated, and controlling the valve manually in case of emergency.
The vertically actuated electric actuator according to the present invention is screwed to the operating shaft 21 rotatably provided with a valve driving unit 20 for opening and closing the valve while sliding when the operating shaft 21 rotates, and a driving motor ( The first worm wheel 34 engaged with the first worm gear 32 coupled to 31 is fastened, and the second worm gear 36 engaged with the second worm wheel 37 provided on the operating shaft 21 is engaged. It includes an electric drive unit 30 for driving the valve driving unit 20 by the drive shaft 33, the upper and lower installed in the pipe to control the flow of the fluid or to control the flow rate of the fluid transferred through the inside of the pipe In the actuated electric actuator, the rotary shaft 51 is fastened to the operating shaft 21 and provided to rotate together with the operating shaft 21 and is formed along the longitudinal direction at the rear end so that the slit 51a is formed to divide the rear end. And the outside of the rotary shaft 51 A worm shaft 52 which is integrally rotated with the front shaft 51, an interlocking pin 53 fixed to the worm shaft 52 and provided through the slit 51a formed on the rotating shaft 51, and the worm shaft ( An encoder 55 is provided coaxially with the pinion 54 meshed with 52 to output a signal according to rotation.

Description

Vertical actuating electric actuator {LINEAR ELECTRIC ACTUATOR}

The present invention relates to a vertically actuated electric driver for opening and closing a valve, and more particularly, it is possible to miniaturize a portion for detecting the rotational speed of the vertically actuated electric driver when the vertical actuated electric driver is operated, and in case of emergency, the valve can be manually operated. It relates to a vertically operated electric drive that can control the.

Pipes used to transfer various fluids are connected to valves for the purpose of controlling the flow of internal fluids or regulating the flow rate.

Although these valves can be opened and closed manually, recently, a vertical actuation that controls the flow of fluid by operating in a direction perpendicular to the flow direction of the fluid to each valve for the purpose of quickly and automatically controlling a plurality of valves at a long distance. An electric actuator is attached, and the vertical actuating electric actuator operates a valve to regulate the flow of fluid in the pipe or regulate the flow rate.

The vertically actuated electric actuator controls the opening and closing of the valve by precisely moving the valve shaft by measuring and feeding back an operation signal for moving the valve shaft as much as desired and the actual amount of movement of the valve shaft.

However, according to the conventional vertical actuated electric actuator as described above, an encoder or the like is attached directly to the valve shaft to measure the movement amount of the operating shaft, which complicates the configuration of the operating shaft, and installs the encoder as much as the moving shaft moves. There is a problem that takes up a lot of space of the vertical actuator electric drive.

In addition, when an abnormality occurs in the drive unit of the vertical actuated electric actuator, it is configured to operate manually. Even in the normal case, if the handle is operated manually, the operating shaft moves to prevent the smooth opening and closing of the valve. There is a problem. That is, the manual operation should not be possible unless an abnormality occurs in the driving unit, and should be selectively operated so as to enable manual operation by switching modes only when an abnormality occurs.

The present invention has been invented to solve the above problems, and an object of the present invention is to provide a vertically operated electric actuator having a small size for detecting a moving distance of an operating shaft.

Another object of the present invention is to provide a vertically operated electric actuator capable of automatically controlling the valve by operating automatically using a drive motor in normal times and manually switching in an emergency.

Vertical actuated electric actuator according to the present invention for achieving the above object is coupled to the drive shaft and the driving motor for opening and closing the valve while sliding when the operating shaft is rotated is screwed to the operating shaft is rotatably provided; A first worm wheel engaged with the first worm gear, and an electric drive unit for driving the valve driving unit by a drive shaft in which a second worm gear engaged with the second worm wheel provided in the operating shaft is engaged. And a vertical actuating electric actuator used to control the fluid conveyed through the inside of the pipe or to adjust the flow rate of the fluid, which is fastened to the working shaft and provided to rotate together with the working shaft and is formed along the longitudinal direction at the rear end thereof. And a rotary shaft in which a slit is formed so that a rear end is divided, and is fitted to an outer side of the rotary shaft and integrally with the rotary shaft. The charge is characterized in that it is provided with a worm shaft, an interlocking pin which is fixed to the worm shaft and penetrates a slit formed on the rotating shaft, and an encoder that is coaxial with a pinion engaged with the worm shaft and outputs a signal according to rotation. .

Here, the operation handle is provided on the upper end of the drive shaft, the conversion lever rotatably provided on the drive shaft and rotated by a handle, and is provided rotatably on the conversion lever, the lower end pressurizing the upper surface of the first worm wheel It is preferable to further include a manual driving unit including a stopper provided to the stopper, and a stopper spring elastically supported so that the stopper pressurizes the first worm wheel.

A groove is formed radially on an upper surface of the first worm wheel, and a lower end of the stopper is located inside the groove.

In addition, the first worm wheel is preferably elastically supported toward the upper surface by a disk spring fitted to the drive shaft, and is selectively engaged with the first worm gear by the stopper.

On the other hand, in order to detect the upper limit and the lower limit of the operating rod may further include a limit switch operated by the pinion engaged with the worm shaft.

According to the vertical actuated electric actuator according to the present invention having the configuration as described above, by downsizing the size of the valve opening detection unit for detecting the position of the operating rod to move forward or backward to control the valve, the entire vertical actuated electric actuator There is an advantage that can be miniaturized. The number of revolutions of the working shaft even if the working rod moves forward or backward by providing an worm shaft that rotates forward and backward of the working rod with the working shaft that is screwed into the working rod and rotates together with the rotating shaft. Since the encoder that does not move does not move, the size of the portion that detects the opening of the valve can be miniaturized.

In addition, when the electric motor cannot be operated, such as when power cannot be applied to the driving motor, the valve may be opened and closed manually.

1 is a perspective view of a vertical actuated electric actuator according to the present invention.
Figure 2 is a perspective view showing a state in which the housing, the shaft support and the rubber boot removed from the perspective view of FIG.
Figure 3 is an exploded perspective view of the vertical actuating electric drive of Figure 2;
Figure 4 is an exploded perspective view showing the connection between the rotating shaft, the worm shaft and the interlocking pin of Figure 3;
Figure 5 is a cross-sectional view of the vertical actuated electric actuator according to the present invention.
Figure 6 is an exploded perspective view showing a state viewed from another angle the vertical actuated electric actuator of the present invention.
FIG. 7 is an exploded perspective view of the vertically operated electric drive of FIG. 6; FIG.
8 and 9 are side views illustrating the principle of the manual driving unit in the vertical actuated electric actuator according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the vertically operated electric actuator according to the present invention.

3 and 6, the vertical actuated electric actuator 1 according to the present invention is provided on one side of the housing 11, the valve driving unit 20 and the valve driving unit 20 to directly control the valve ) Is driven by the driving force generated by the driving motor 31, the electric drive unit 30, the manual drive unit 40 and selectively actuated with the electric drive unit 30, the valve drive unit 20 is operated when the valve It includes a valve opening detecting unit 50 for detecting the position.

The housing 11 drives the valve therein and accommodates the electric drive unit 30, the manual driving unit 40, and the valve opening detecting unit 50 for measuring the opening degree of the valve (not shown), and the housing 11. To be driven inside the.

In particular, one side of the housing 11 is provided with a shaft support portion 12 to close the one side of the housing 11 and to support the rotatable operating shaft 21, the drive shaft 33 to rotate. In charge of.

In addition, an indicator 60 is provided on one side of the housing 11 to check the opening degree of the valve.

The guide 13 is provided at one side of the housing 11 or the shaft support 12, and the housing 11 is connected to the pipe side where the valve is installed. That is, one end of the guide 13 is connected to a valve or a pipe in which the valve is installed, and the other end is connected to the housing 11, so that the vertically operated electric actuator 1 according to the present invention can be installed in the valve. .

In addition, the guide 13 serves to guide the movement of the slider 23 to be described later.

The valve driver 20 is connected to the valve through the valve shaft 14 to control the valve mounted on the pipe. The valve driving unit 20 has an operating shaft 21 that rotates by a driving force supplied from the outside, and an operating rod 22 that is screwed with the operating shaft 21 to slide in accordance with the rotation of the operating shaft 21. And, the slider 23 to prevent the rotation of the operating rod 22 to convert the rotational movement of the operating shaft 21 to a linear movement of the operating rod 22, and the operating shaft 21 and the operating rod A sleeve 24 that protects the outside of the connection of 22;

The actuating shaft 21 is provided to penetrate the housing 11 and the shaft support 12, and allows the valve to open or close the inside of the pipe by the rotation of the actuating shaft 21. A screw thread is formed on the outer circumferential surface of the working shaft 21 to be screwed with the working rod 22.

The actuating rod 22 has a hollow inside along the axial direction, and a thread is formed along the inner circumferential surface to be screwed with the thread formed on the actuating shaft 21. The actuating rod 22 is screwed into the actuating shaft 21 and the actuating rod 22 while the front end portion of the actuating shaft 21 is inserted through the rear end. Both sides are fastened to a slider 23 provided at both ends of the actuating rod 22 so as to be slidable to the guide. When the actuating shaft 21 rotates, the actuating rod screwed with the actuating shaft 21. 22 is comprised in the said slider 23, and it does not rotate but moves forward or backward along the guide 13. As shown in FIG.

The sleeve 24 is formed in the hollow in the axial direction, one end is fastened to one side of the housing 11, the operating shaft 21 and the operating rod 22 is screwed inside the sleeve 24 In combination, the rotational movement of the operating shaft 21 is converted into a linear movement of the operating rod 22.

On the other hand, the rear end of the sleeve 24 is provided with a disk spring 25 to support the operating shaft 21, the operating rod 22 and the sleeve 24. By supporting the rear end of the sled 24 using a plurality of disc springs 25, when excessive force is applied to the operating shaft 21 and the operating rod 22, the operating shaft 21 and the operating rod 22 ) Can be deformed, allowing the disk spring 25 to absorb it. In addition, in the process of closing the valve by the elastic force of the disk spring 25 advances the operating shaft 21, the operating rod 22 to one minute so that the valve is completely closed.

In addition, a rubber boot 26 is provided between the slider 23 and the end of the sleeve 24 to prevent the inflow of foreign matters and prevent the operation rod 22 from being exposed to the outside even when the slider 23 is moved. .

As shown in detail in FIGS. 2 and 3, the electric drive unit 30 connects the drive motor 31 provided in the housing 11, the output shaft of the drive motor 31, and the operation shaft 21. And a drive shaft 33 to generate power to operate the valve.

The drive motor 31 is provided inside the housing 11 to generate power for opening and closing the valve. At this time, it is preferable that the drive motor 31 can precisely control the valve to a desired position by precisely controlling the rotation amount of the drive motor using the step motor.

The drive shaft 33 is provided to be rotatable by the drive motor, and rotates the operation shaft 21. The drive shaft 33 is connected to the drive motor 31 through a power transmission means in a state rotatably provided in the housing 11 or the shaft support 12. The power transmission means provided by the drive motor 31 to rotate the drive shaft 33 includes a first worm gear 32 coupled to the rotation shaft of the drive motor 31 and the first worm gear 32. The first worm wheel 34 to be coupled to the drive shaft 33 so as to be. The worm gear-worm wheel can obtain a large reduction ratio so that the drive shaft 33 can be rotated even with a small power, and since the worm wheel can not reversely drive the worm gear, even if a small drive motor 31 is used, The valve can be opened and closed inside a pipe through which a high pressure and a large amount of fluid are transferred.

Meanwhile, the driving shaft 33 rotates the operating shaft 21 again, and the second worm gear 36 and the second worm wheel 37 are engaged with each other in the driving shaft 33 and the operating shaft 21, respectively. The rotational force is transmitted to the working shaft 21 only at (33).

Therefore, when the drive motor 31 is rotated, the drive shaft 33 and the operating shaft 21 can be rotated to open and close the valve.

In this case, when the drive shaft 33 is installed in the housing 11 or the shaft support 12, the first worm wheel 34 is elastically supported by elastic means, for example, a disk spring 35. That is, the first worm wheel 34 is fitted to the drive shaft 33 to be engaged with the first worm gear 32, the disk spring 35 is the first worm wheel 34 of the first worm gear 32 By elastically supporting in the direction of releasing the engagement, it is possible to manually rotate the drive shaft 33 when necessary.

The manual driving unit 40 plays a role of manually opening and closing the valve when the electric driving unit 30 fails or cannot operate the driving motor 31 due to a power failure. As shown in detail in FIGS. 6 and 7, the manual driving unit 40 is rotatable to the operation shaft 41 and the driving shaft 33 connected to the end of the driving shaft 33 so that the user can apply the operating force. And a stopper 44 to allow the first worm wheel 34 to be selectively engaged with the first worm gear 32 according to the rotation of the conversion lever 42. And a stopper spring 45 elastically supporting the stopper 44.

The operation handle 41 is provided at the end of the drive shaft 33 to allow the user to rotate the drive shaft 33 by using the operation handle 41.

The conversion lever 42 is operated so that the first worm wheel 34 and the first worm gear 32 are engaged with each other or the engagement of the first worm wheel 34 and the first worm gear 32 is selected to release. It is provided to. In particular, the conversion lever 42 is engaged with the handle 43 exposed to the outside of the housing 11 or the shaft support 12, by rotating the handle 43 from the outside the conversion lever 42 is Let it work

The stopper 44 has a lower end fixed to the conversion lever 42 so as to be rotatable by the conversion lever 42, and an upper end thereof is elastically supported on the conversion lever 42 side using an elastic member.

In addition, a lower end of the stopper 44 presses an upper surface of the first worm wheel 34. In this case, a groove is radially formed on an upper surface of the first worm wheel 34 so that the first worm wheel 34 may rotate even when the stopper 44 holds the first worm wheel 34. The lower end of the stopper 44 is convex, so that the lower end of the stopper 44 is located in the groove so that the first worm wheel 34 is pressed even when the stopper 44 presses the first worm wheel 34. Make this rotatable.

On the other hand, the first worm wheel 34 and the second worm gear 36 is configured to be selectively engaged. Steps are formed in the drive shaft 33 to which the second worm gears 36 are coupled, and the second worm gears 36 are positioned at the part where the steps are formed. In addition, the elastic means is compressed by using the conversion lever 42 and the stopper 44 in a state in which the drive shaft 33 is elastically supported toward the operation handle 41 by providing the elastic means on the drive shaft 33. When the first worm gear 32 and the first worm wheel 34 are engaged with each other, and the force pressed by the conversion lever 42 and the stopper 44 is removed, the elastic means is the first worm wheel 34 ) So as not to be engaged by being separated from the first worm gear 32, the rotational force of the drive motor 31 is no longer transmitted to the drive shaft 33.

As described above, by selecting the engagement of the first worm gear 32 and the first worm wheel 34 according to the operation of the conversion lever 42, the valve is controlled by the rotational force of the drive motor 31, or the operation handle The valve is controlled by the operating force of (41).

The valve opening detecting unit 50 detects the number of rotations of the driving shaft 33 and calculates the amount of movement of the operating rod 22. The valve opening detecting unit 50 has a rotating shaft 51 which rotates together with the operating shaft 21, a worm shaft 52 coupled to the outside of the rotating shaft 51, and a pinion 54 engaged with the worm shaft 52. It is provided coaxially with the encoder 55 for detecting the rotational speed of the rotary shaft (51).

The rotary shaft 51 is coupled to the working shaft 21 by the tip, and rotates at the same angular speed as the working shaft 21. For example, as shown in FIG. 5, the front end of the rotating shaft 51 is fitted to the rear end of the operating shaft 21 so that the rotating shaft 51 rotates at the same angular speed as the operating shaft 21. At the rear end of the wing rotary shaft 51, a slit 51a is formed to divide the rear end of the rotary shaft 51 along the longitudinal direction in the longitudinal direction.

The worm shaft 52 is provided outside the rotation shaft 51. A tooth of a worm gear is formed outside the worm shaft 52 and provided to rotate so as to have the same angular velocity as the rotating shaft 51.

At this time, it is preferable that the interlocking pins 53 are provided to restrain the rotary shaft 51 and the worm shaft 52 so that the rotary shaft 51 and the worm shaft 52 rotate at the same angular velocity. As shown in FIG. 4, the interlocking pin 53 penetrates the rotation shaft 51 and the worm shaft 52, which are located inside and outside each other, is fixed to the worm shaft 52 and slides about the rotation shaft 51. It is provided to enable. The interlocking pin 53 is fixed to the worm shaft 52, but is coupled to the rotation shaft 51 so as to pass through the slit 51a of the rotation shaft 51. Therefore, when the rotating shaft 51 rotates, the rotating shaft 51 rotates the interlocking pin 53 so that the worm shaft 52 also rotates. In addition, although the rotating shaft 51 is a slight amount in the axial direction of the rotating shaft 51 in accordance with the opening and closing of the valve at the same time as the rotation, but moving forward or backward in accordance with the linear movement of the operating shaft 21, the operating rod 22, the interlocking pin Since 53 is slidable within the slit 51a of the rotary shaft 51, the rotary shaft 51 performs linear and rotary motions, but only rotates the worm shaft 52 and does not perform linear motion.

The encoder 55 is installed on the same shaft as the pinion 54 provided to be engaged with the worm shaft 52, and the encoder 55 outputs a signal proportional to the rotational speed of the worm shaft 52.

On the other hand, one side of the worm shaft 52 is connected to the pinion in which the worm shaft 52 is engaged, and if the worm shaft 52 is excessively rotated, that is, exceeds the predetermined upper limit and lower limit, the limit switch 55 operates By cutting off the power supply of the drive motor 31, it operates only within a predetermined range and blocks operation outside a predetermined area. Advancing or retracting the operating rod 22 out of a predetermined range means that the operating shaft 21 and the rotating shaft 51 are excessively rotated, and the limit switch 56 is connected to the worm shaft 52. By sensing through), the operating rod 22 is operated only within a predetermined range.

In addition, by operating the limit switch 57 operated by the disk 58 fixed to both ends of the spring fitted to the rotary shaft 51 on the outer side of the rotary shaft 51 so that the rotary shaft 57 operates only within a predetermined range. do.

The operation of the vertically actuated electric driver according to the present invention having the configuration as described above will be described.

The vertically actuated electric actuator 1 according to the present invention typically operates by electric control to control the valve, and operates manually by using the manual driving unit 40 only when the electric driving unit 30 does not operate.

In the case of operating the vertically operated electric actuator 1 by using the electric drive unit 30, the valve is controlled by applying power to the drive motor 31 to rotate the drive motor 31. The drive motor 31 starts to rotate. When the drive motor 31 starts to rotate, the operating shaft 21 also rotates via the drive shaft 33. The drive motor 31 and the drive shaft 33 are connected by the first worm gear 32 and the first worm wheel 34, the drive shaft 33 and the operating shaft 21 is the second worm gear 36 and the first It is connected by two worm wheels 37, when the drive motor 31 starts to rotate, the working shaft 21 also rotates.

The working shaft 21 rotates and slides the working rod 22 connected to the valve. As the operating shaft 21 rotates, the slider 23, which is screwed to the operating shaft 21 and slidably provided on the guide 13, performs a slide motion of moving forward or backward along the guide 13, The valve is opened or closed through the operating rod 22 fastened to 23. For example, when the actuating rod 22 is advanced, the valve is closed and when it is reversed, the valve is opened.

The drive motor 31 determines the rotation direction according to the opening or closing of the valve, and controls the valve while the operation rod 22 moves forward or backward according to the rotation direction of the drive motor 31.

At this time, the first worm gear 32 is coupled to the output shaft of the drive motor 31 by maintaining the state where the first worm gear 32 and the first worm wheel 34 are engaged by the conversion lever 42. It is possible to rotate the first worm wheel (34).

On the other hand, when the electric drive unit 30 as described above can not be operated by using the manual drive unit 40 to open and close the valve.

First, the conversion lever 42 is operated to release the engagement between the first worm gear 32 and the first worm wheel 34. When the conversion lever 42 is rotated from the state shown in FIG. 8 to the state shown in FIG. 9 by using the handle 43, the stopper 44 holding the first worm wheel 34 is also converted to the conversion lever 42. While rotating together with the spaced apart from the upper surface of the first worm wheel (34). When the stopper 44 is spaced apart from the surface of the first worm wheel 34, the elastic means 35 provided on the drive shaft 33 pushes the first worm wheel 34 to allow the first worm gear 32 and the first worm wheel ( 34) is released.

When the engagement of the first worm gear 32 and the first worm wheel 34 is released, the operation shaft 41 may be rotated to rotate the drive shaft 33. When the drive shaft 33 rotates, the operation rod as described above. 22 may control the valve by moving forward or backward.

As described above, the degree of opening of the valve is measured by sensing the rotational speed of the operating shaft 21 while controlling the valve by electric or manual operation. That is, as the operating rod 22 controls the valve while the operating shaft 22 moves forward or backward according to the rotation of the operating shaft 21, the opening degree of the valve may be measured by sensing the amount of rotation of the operating shaft 21. .

When the working shaft 21 rotates, the rotating shaft 51 together with the working shaft 21 also rotates along with the working shaft 21. Since the said operating shaft 21 and the rotating shaft 51 are fastened and rotate by the same number, the rotation speed of the operating shaft 21 can also be measured by measuring the rotation speed of the rotating shaft 51.

When the rotating shaft 51 rotates, the encoder 55 is rotated while the worm shaft 52 fitted to the outside of the rotating shaft 51 also rotates like the rotating shaft 51.

As the encoder 55 rotates, it outputs a signal proportional to the rotational speed of the operating shaft 21, and calculates this to determine the opening degree of the valve by measuring the forward or backward distance of the operating rod 22. .

At this time, the interlocking pin 53 provided through the rotating shaft 51 and the worm shaft 52 rotates the rotating shaft 51 and the worm shaft 52, but the linear motion of the worm shaft 52 together with the rotating shaft 51 is Although not, the linear movement amount of the rotation shaft 51 is grasped through the rotation amount of the worm shaft 52, and the opening and closing degree of the valve is sensed.

1: Vertical Actuator 11: Motor Housing
12: shaft support 13: guide
14: valve shaft 20: valve driving unit
21: working shaft 22: working rod
23: slider 24: sleeve
25: disc spring 26: rubber boot
30: electric drive unit 31: drive motor
32: first worm gear 33: drive shaft
34: first worm wheel 35: disk spring
36: second worm gear 37: second worm wheel
40: manual drive unit 41: operation handle
42: conversion lever 43: handle
44: stopper 45: stopper spring
50: valve open detection unit 51: rotary shaft
52: worm shaft 53: interlocking pin
54: pinion 55: encoder
56: limit switch 57: limit switch
58: disc 60: indicator

Claims (5)

It is screwed to the rotatable operating shaft (21) is rotated when the operating shaft 21 rotates the valve drive unit 20 for opening the valve while sliding, and the first worm gear (32) coupled to the old motor (31) Is coupled to the first worm wheel 34 by the drive shaft 33 which is engaged with the second worm gear 36 engaged with the second worm wheel 37 provided on the operating shaft 21. In the up and down actuated electric actuator including an electric drive unit 30 for driving the 20, used to control the flow of the fluid or to control the fluid flow through the inside of the pipe,
A rotating shaft 51 fastened to the working shaft 21 and provided to rotate together with the working shaft 21 and formed along the longitudinal direction at a rear end thereof so that a slit 51a is formed to divide the rear end;
A worm shaft 52 which is fitted to the outside of the rotary shaft 51 and rotates integrally with the rotary shaft 51;
An interlocking pin (53) fixed to the worm shaft (52) and provided to pass through the slit (51a) formed on the rotating shaft (51);
The worm shaft (52) is engaged with the pinion (54) is coaxially provided with an encoder (55) for outputting a signal in accordance with the rotation is provided with a vertical drive electric drive. The method of claim 1,
An operation handle 41 provided at an upper end of the drive shaft 33;
A conversion lever 42 rotatably provided on the drive shaft 33 and rotated by a handle 43;
A stopper 44 rotatably provided at the conversion lever 42 and provided at a lower end to press the upper surface of the first worm wheel 34;
The stopper 44 further includes a manual drive unit 40 including a stopper spring 45 which is elastically supported to press the first worm wheel 34. The method of claim 2,
Grooves are radially formed on an upper surface of the first worm wheel (34), and a lower end of the stopper (44) is located inside the grooves. The method of claim 2,
The first worm wheel 34 is elastically supported toward the upper surface by a disk spring 35 fitted to the drive shaft 33,
Up and down actuated electric drive, characterized in that the gear is selectively engaged with the first worm gear (32) by the stopper (44). The method of claim 1,
And a limit switch 56 which is operated by a pinion engaged with the worm shaft 52 in order to detect the upper limit and the lower limit of the actuating rod 22.

Images