JPS5833432B2 - Safety device for linear actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device for overload prevention added to one end of a linear actuator such as an electric thruster. The setting values can be changed.

When a linear actuator is used to convey an article in the vertical direction by moving the actuating rod back and forth, the load applied to the actuating rod is generally different when the actuating rod is extended and when it is retracted.

For example, in a linear actuator for a lift, a larger load is applied to the actuator during upward movement in the anti-gravity direction than during downward movement.

In an actuator for bowing conveyed objects, a heavy load is applied only when the actuating rod is contracted, and a light load is applied when the actuating rod is extended.

Therefore, in order to cut off the drive source of the actuating rod in order to prevent overload of the linear actuator, it is necessary to set different cut-off values when the actuating rod is extended and when it is retracted.

This is because the cutoff setting value should be a value that is plus or minus the respective load values normally used when the operating rod is extended and retracted.

However, the safety devices of conventional linear actuators have only one internal spring, or the springs that are compressed by overload when the operating rod is extended and retracted are each installed separately, so the safety tolerance is low. The set value must be determined by adjusting the amount of compression of the spring when the operating rod is extended and retracted, which is not only inconvenient, but also has the disadvantage that the longitudinal dimension of the spring becomes large.

The present invention therefore provides a method that eliminates the drawbacks of the conventional devices as described above.

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. In the linear actuator 4 that moves forward and backward (corresponding to the left and right direction), a casing 5 is attached to the rear end in the longitudinal direction of the actuator 4, and a rod 6 (not shown) installed inside the casing 5 so as to be movable in the forward and backward directions is attached. The front and rear stoppers 8, 9 and the front and rear drive source cutoff IJ switches io and ii are pivotally connected to the frame I so as to be able to support the reaction force from the workpiece, and are spaced apart from each other in the advance and retreat directions in the casing 5. In addition to installing
A striker 1 for operating the limit switch is attached to the rod 6.
2 and the front and rear protruding flanges 13, 14 are attached, and a fixed spring receiver 16 and a first movable spring receiver 17 with the first spring 15 sandwiched between the front and rear stoppers 8, 90 are provided, and the first spring The first movable spring receiver 17 and the second movable spring receiver 19 sandwiching the second spring 18 parallel to the spring 15 are connected to the front and rear protruding collars 1.
3.14, and is configured such that at least one of the first spring 15 and the second spring 18 is compressed during operation.

In this embodiment, the first spring 15 and the second spring 18 are arranged concentrically, the spring constant of the first spring 15 is smaller than that of the second spring 18, and each spring is The interior is compressed.

Further, in FIG. 2, which is the first embodiment of the present invention, the protrusion 19a of the second movable spring receiver 19 engages with the fixed spring receiver 16, so that the movable spring receiver 19 can only move to the left in the figure. It has become.

The tip of the operating rod 3 is pivotally connected to a link such as a lift (not shown).

Next, the operation of the present invention will be explained.

(1) Figures 1 and 2 show a safety device for a linear actuator mainly used for pushing. The actuating rod 3 moves to the right, and the actuating rod 3 extends to move a conveyor, etc. (not shown).

At this time, the reaction force from the carrier is applied to the casing 5 of this device.
The stopper 9 fixed to the casing acts to compress the first spring 15 and the second spring 18 via the spring receivers 16 and 19.

However, since the husband's spring 15.18 is compressed in advance and inserted into the spring receiver, and is pressed against the spring receiver 16.19, as long as the elastic force is greater than the reaction force, the spring 1
5.18 is not compressed and the operating rod 3 continues to extend.

(2) Next, when an overload is applied to the tip fitting 20 when the operating rod 3 is extended, the casing 5 moves to the left and the springs 15, 18
is compressed, and the limit switch 11 installed in the casing 5 is pressed by the striker 12 and activated, cutting off the driving force of the driving source 2.

The extension of the operating rod 3 is thus stopped, thereby preventing an increase in overload.

(3) Next, when the actuating rod 3 of the linear actuator of the above embodiment is contracted and returned, the actuating rod 3 moves to the left.

At this time, if the end fitting 20 of the operating rod 3 is obstructed from contracting by an obstacle or the like, a force in the opposite direction to the contraction direction is applied to the operating rod 3, and this force moves the casing 5 to the right and the second
Only the spring 18 is compressed.

And a limit switch 1 installed in the casing 5
0 to stop the drive source.

When the operating rod 3 is contracted, the operating rod 3 is stopped by a load that is enough to compress only the second spring 18, and its tip fitting 20 does not move any further, preventing the above-mentioned obstacles from being damaged by the tip fitting. prevent such things from happening.

Next, FIGS. 3 and 4 show a second embodiment of the present invention, which is a safety device attached to the tip of an operating rod of a linear operating machine 4. In FIG.

In the second embodiment, only the second spring 18 is compressed in response to an overload acting in the push-in direction, and only the first spring 15 is compressed in response to an overload acting in the tension direction. Determine the allowable thrust of

In addition, the spring receiver 16°17.19,19' protruding collar 13,1
Various allowable thrusts can be determined by changing the shape and position of 4, so an appropriate design can be made depending on the application and specifications.

For example, (a) in FIG. 4, the protrusion 1 of the fixed spring holder 16
When 6a is lengthened so that it engages with the protrusion 19a of the second movable spring receiver 19, only the second spring 18 is compressed in the pushing direction, and the first spring 15 and the second spring 18 are compressed in the pulling direction.

(b) In addition, in FIG. 4, only 19' of the two second movable spring receivers is turned in the opposite direction, and the protrusion 16 of the fixed spring receiver 16 is
a, the first spring 1 is engaged in the pushing direction.
5 and the second spring 18 are compressed together, and in the tension direction,
Only the first spring 15 is compressed.

(/→ Also, in Fig. 4, the protrusion 16 of the fixed spring holder 16
a is made longer so that it engages with the protrusion 19a of the second movable spring receiver 19, and at the same time one of the two second movable spring receivers
Turn only 9′ in the opposite direction and insert the protrusion 16a of the fixed spring holder 16.
When the first spring and the second spring are engaged with each other, the first spring and the second spring are compressed in both the pushing direction and the pulling force direction.

2) Furthermore, in the casing 5, the first movable spring receiver 1
7, second movable spring receiver 19, 19' and fixed spring receiver 1
By reversing the arrangement of 6, the set loads in the pushing direction and the pulling direction can be reversed.

The present invention has the above configuration and has the following effects.

Since the present invention has double springs and three or four spring holders as described above, when the normal load applied to the operating rod of the linear actuator is different between when it is extended and when it is retracted, Optimal pushing and pulling forces can be applied to the workpiece.

In response to a constant load, the operating rod is stopped to prevent damage to the workpiece and the linear operating machine.

Furthermore, since this device has a double spring structure in which the springs 15 and 18 are arranged concentrically in parallel, the length in the longitudinal direction of this device can be shortened, and this device can be installed in a small space. Is possible.

Further, the sum of the constants of each of the two springs can be used as the overall constant.

Furthermore, by changing the position and shape of the spring receiver and the protruding flange, various allowable thrust forces can be obtained, and the actuator for retraction can be changed to one for pushing, or the like.

Since the thrust of the actuating rod can be set according to the load, wear and damage to the actuator can be prevented and its life can be extended.

Furthermore, the present invention can be used extremely effectively not only as a simple overload prevention but also in all applications in which a stop is applied to a stop (the load increases rapidly during the stop, resulting in an overload condition, and the operating rod stops at that position).

). It should be noted that the present invention is of course not limited to the above-mentioned embodiments, and can be modified without departing from the technical idea of the present invention.For example, if the space for installing a limit switch is small, it may be possible to extend the limit switch with a single switch. In order to prevent overload during contraction, one switch is connected to a striker of 12.
The switch may be attached to the distal end surface of the switch in a pressed state, so that the switch can be shifted from the pressed state to the open state in response to an overload in either direction of expansion or contraction.

Furthermore, even if the positions of the limit switches 10, 11 and the striker 12 of this embodiment are exchanged, their relative movements and functions remain the same, so such an invention also falls within the technical scope of the present invention.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of the main part of FIG. 1. 3 to 4 show the second embodiment, and FIG. 4 is a vertical sectional view of the main part of FIG. 3. 1... Safety device, 2... Drive source, 3.
...Operating rod, 4...Linear actuator, 5...
...Casing, 6...Rod, 7...
...Frame, 8,9...Stopper 10.
11... Limit switch, 12...
Striker, 13, 14...Protruding tsuba, 15...
...First spring, 16...Fixed spring holder, 16
a... Fixed spring receiving protrusion, 17... First
Movable spring holder, 18...Second spring, 19...
...Second movable spring receiver, 19'...Second movable spring receiver, 19a...The second movable spring receiver is a projection.

Claims (1)

[Claims] 1. In a direct actuator that is connected to a drive source and whose actuating rod moves back and forth, either a casing or a rod installed in the casing so as to be movable in the forward and backward directions is attached to one end in the longitudinal direction of the actuator. At the same time, the other side is arranged so as to be able to support the reaction force from the workpiece, and front and rear stoppers and a limit switch for cutting off the drive source are installed on the casing at a distance from each other in the advance and retreat directions, and the rod The limit switch striker and the front and rear protruding flanges are attached, and a fixed spring holder and a first movable spring holder each having a first spring sandwiched between the front and rear stoppers are provided, and the first movable spring holder
A safety device for a linear actuator, characterized in that the first movable spring receiver and the second movable spring receiver, in which a second spring parallel to the spring is sandwiched, are provided between the front and rear protruding flanges.