JPH04138632A - Limit switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention automatically measures the length of a tool attached to a manning center, NC drilling machine, etc. to check the progress of wear and determine the need for tool replacement. This relates to a high-precision limit switch used when determining whether or not the

(Prior Art) A conventional limit switch used for the above applications is shown in FIG.

This limit switch is constructed by attaching an operating head 24 equipped with a carbide tip 23 for abutting the tip of a tool such as a trill to the tip of an operating shaft 22 supported on a case 20 via a bushing 21 so as to be able to slide freely in a straight line. The switch 27 is built into the case 20, and is biased to protrude by a return spring 25 built into the operating shaft 22, and is pressed and operated by an operating piece 26 attached to the operating shaft 22.

This limit switch is used as follows.

The limit switch is fixed at a predetermined position on the machine tool so that the tip of the tool attached to the machine tool can be received by the upper surface of the operating head 24 of the operating shaft 22, and the newly installed tool is advanced to the operating shaft. 22 is pressed and displaced. The position of the tool at the time when the internal switch 27 is switched (for example, from ON to OFF) by the displacement of the operating shaft 22 is measured and stored, and the corresponding set tool length is preset.

After using the tool for a suitable period of time, the tool is advanced again and the operation shaft 22 is brought into contact with the tool.The position of the tool at the time when the internal switch 27 is switched is measured, and compared with the previous preset value, the tool position is measured. The wear amount of the tool is determined, and it is determined whether or not the tool needs to be replaced.

(Problem to be Solved by the Invention) However, in the conventional limit switch, the displacement of the operation shaft 22 directly becomes the operation amount of the internal switch 27, and the operation amount cannot be obtained sufficiently, so the detection accuracy of the switch 27 is There was a basic problem: low yield.

In order to increase this detection accuracy, it would be possible to use a highly precisely constructed high-precision switch, but in reality it is difficult to obtain such a high-precision switch, and it is also expensive. there were.

In particular, in the past, the operation amount fluctuated due to the tilt of the operation shaft 22 due to a slight rearance in the sliding portion of the operation shaft 22, resulting in low detection accuracy.

The limit switch detection error is the sum of the position error of the tool contact surface of the operation shaft 22 and the operation error of the internal switch 27, and as described above, the inclination of the operation shaft 22 causes the tool contact surface to An increase in the position error immediately increases the detection error of the entire limit switch.

For example, in order to improve the positional accuracy of the tool contact surface of the operating shaft 22, the clearance on the sliding surface of the operating shaft 22 should be reduced, and the bearing of the operating shaft 22 should have a larger span to reduce the inclination of the operating shaft 22. However, considering the sliding resistance of the operating shaft 22, there is a limit to how much the sliding surface clearance can be reduced, and if the span of the bearing is increased, the entire limit switch will become larger. However, there were practical limits.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to improve the detection accuracy of a limit switch.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes an operating shaft that is supported by a case so as to be linearly slidable, and a case that is supported by a case so as to be swung along with the displacement of the operating shaft. It is equipped with a built-in lever and a switch built into the case so that it is suppressed and operated by the free end of the lever. The configuration was such that the distance was set larger than the distance to the fulcrum.

(Function) According to the configuration of the present invention, the displacement of the operating shaft is magnified by the lever and becomes the operating amount of the internal switch.

(Embodiment) An embodiment of a limit switch according to the present invention is shown in FIGS. 1 to 3.

This limit switch consists of a case 11 operating shaft 2,
Switch 3 for displacement detection, lever 4 for switch operation,
It consists of a safety switch 5, etc.

The operating shaft 2 is supported by the case l via a pair of upper and lower bearing bushes 6 so as to be slidable up and down, and is urged upwardly by a return spring 7 provided at its lower end.
A carbide tip 8 is attached to the upper end of the operating shaft 2 for abutting and supporting the tip of the tool.

The switch 3 switches an internal contact by pressing an operating section 3a provided on the top surface of the switch 3, and is configured to be turned on in normal conditions and turned off when the operating section 3a is pushed a set amount. is used.

The lever 4 has a fulcrum pin 9 screwed into the case 1.
A contact member 10 screwed to the notch surface 2a of the operating shaft 2 is in point contact with the lower surface of one end of the balance, and the lever The lever 4 is configured to press and operate the operation part 3a of the switch 3 with the lower surface of the other end of the lever 4, and the lever 4 is slightly swung in the direction of contacting the contact member IO by a spring 11 provided on the upper surface of the switch 3. Forced.

Further, the distance between the swinging fulcrum P of the lever 4 and the switch operating portion 3a is set to be two to three times the distance between the swinging fulcrum P and the lever contact point of the contact member IO.

The safety switch 5 is installed to be pressed and operated by the abutting member IO when the operation shaft 2 is pushed and displaced excessively by a tool, and the tool advancement operation is stopped when the safety switch 5 is activated. It is connected to the machine drive control section of the machine tool.

In addition, the reference numeral 12 in the figure is a seal ring attached to the sliding protrusion of the operating shaft 2, 13 is a cover plate formed on the front surface of the case l to close the opening for assembly, and 14 is the case l and the cover case. 13. This is a rubber seal in the shape of a knot that is pressed between the

In the above configuration, when the operating shaft 2 is pressed by a tool, the switch operating part 3a of the lever 4 is displaced upward by an amount 2 to 3 times the amount of displacement by the pressing, and when the amount of displacement exceeds a preset value. The switch 3 is turned off, and it is determined that the amount of wear is large, and the tool is replaced.

Furthermore, if the operating amount error due to the inclination of the operating shaft 2 is δ, and the operating error of the switch 3 itself is δ, then the lever ratio is 2.
．． When set to 0, the apparent operating error of switch 3 is 1
/2δ, and the operating error δ of the limit switch as a whole is δ=δ, +1/2δ.

Therefore, the accuracy is higher (
(lower operating error).

(Effects of the Invention) As explained above, according to the present invention, the displacement of the operating shaft is expanded by the lever, and the amount of operation of the internal switch can be increased, thereby improving the apparent accuracy of the internal detection switch. As a result, the accuracy of the limit switch has been improved.

In addition, it is possible to improve the accuracy of the entire limit switch without particularly reducing the operating amount error caused by the tilt of the operating shaft, that is, without increasing the span of the bearing and increasing the size of the switch. did it.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a vertical front view, FIG. 2 is a vertical side view, and FIG. 3 is a perspective view of the main parts. Moreover, FIG. 4 is a longitudinal sectional front view of the conventional example. ■...Case, 2...Operation shaft, 3...Switch, 3a...Operation section, 4...Lever

Claims (1)

[Claims] (1) An operating shaft (2) supported by the case (1) so as to be able to slide freely in a straight line, and a lever (4) built into the case (1) so as to be swung as the operating shaft (2) is displaced. and a switch (3) built into the case (1) so as to be pressed and operated by the free end of the lever (4). A limit switch that is set larger than the distance from the lever operation position to the swing fulcrum using the shaft (2).