JPH0143618Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an overload protection device used in a load measuring device.

[Conventional technology]

Conventional load measuring instruments have a fixed measurable rated value and are configured to measure loads that do not significantly exceed the rated value.

[The problem that the idea attempts to solve]

Therefore, it has been extremely difficult to continuously measure loads that constantly fluctuate greatly using conventional load measuring instruments. Furthermore, when the load exceeds the rated value, it is difficult to control it without affecting the measuring mechanism, so there is a problem that the measuring instrument is susceptible to damage.

In view of the above-mentioned problems, this device can continuously measure loads that fluctuate widely, prevent damage to the measuring device even when the load exceeds the rated value, and is easy to operate. The purpose is to provide an overload protection device.

[Means to solve the problem]

In order to solve the above problem, the overload protection device of this invention includes a hollow housing, a stopper attached to one end of the housing, and a plate having a proximal end attached to the other end of the housing and equipped with a strain gauge. a spring, a spindle that is inserted into an axial hole formed in the leaf spring and whose distal end approaches the stopper and receives a load at its proximal end; The spring has one end hooked to the spindle for biasing, a pressure adjusting screw hooking the other end of the spring, and a connecting fitting connecting the pressure adjusting screw to the leaf spring.

[Effect]

According to this invention, by first moving the pressure adjustment screw spirally, the other end of the spring hooked to the pressure adjustment screw is expanded and contracted, and the compression reaction force of the spring is balanced with the rated load of the measuring instrument. Set it like this. When a fluid load exceeding the rated value is applied to the spindle, the spindle moves in the direction of the load, but since the spring constant of the spring is smaller than that of the leaf spring, the spring starts to move from the moment the rated load is exceeded. will be compressed toward the pressure adjustment screw. Then, the tip of the spindle hits the stopper, preventing movement of the spindle, thereby preventing damage to the leaf spring or strain gauge.

〔Example〕

An embodiment of this invention will be described below with reference to the accompanying drawings. Figure 1 is a vertical side view showing the overload protection device according to this invention, Figure 2 is a front view showing the inside of the overload protection device, and Figure 3 is a load measurement device equipped with this overload protection device. It is a graph showing the relationship between load and strain output.

First, the configuration of the device of this invention will be explained.

Reference numeral 2 denotes a hollow housing, which has a disk surface at the base of a cylindrical body, and a shaft hole 2a formed in the center of the disk surface.

A base end portion of a rectangular plate spring 3 is attached to the lower part of the disk surface in the housing 2 with a bolt 13 so as to be movable back and forth. Further, the leaf spring 3 has a shaft hole 3a formed concentrically with the shaft hole 2a of the housing 2. Further, at the bottom of the leaf spring 3, there is a known strain gauge 4, which is made up of a plurality of strain gauges, in order to convert the amount of strain movement into the amount of variation in electrical resistance value, and display this as a strain output on a meter (not shown). attached.

Further, a connecting fitting 5 is attached to the front end side of the leaf spring 3 with a bolt 14. A recess 5a with a shaft hole is provided inside the lower part of the connecting fitting 5.

The spindle 1 is inserted through the shaft hole 2a of the housing 1, the leaf spring 3a, and the recess 5a of the connecting fitting 5. In the recess 5a of the connecting fitting 5, a push fitting 6 having a large-diameter stepped portion at the proximal portion of the cylindrical body is integrally fitted to the spindle 1 with a screw 15. Also, a spring 1 is attached to the step part of the pusher 6.
One end of the spring 7 is hooked in order to urge it in a direction opposite to the load received by the spring 7. The spring constant of the spring 7 is set lower than that of the leaf spring 3.

In addition, the pressure adjusting screw 8, which is a cylindrical body with a female thread on the inner diameter surface of the recess 5a of the connecting fitting 5 and a male thread on the outer circumferential surface, is loosely fitted into the pusher fitting 6, and the male thread part spirals. It is inserted so that the amount of movement forward and backward can be adjusted. and spring 7
The other end is hooked to the pressure adjusting screw 8. The female threaded portion of the connecting fitting 5 and the male threaded portion of the pressure adjustment screw 8 maintain their shape when the compression reaction force of the spring 7 is balanced with the rated load applied to the spindle 1 by the spiral of the pressure adjustment screw 8. A screw 16 is screwed in for this purpose.

Further, a disk-like lid 11 having the same diameter is attached to the front opening of the housing 2 with a female thread 17. A male threaded stopper 9 is inserted into a female threaded portion formed at the center of the lid 11 so as to be able to move back and forth in a spiral manner. The stopper 9 is arranged concentrically with the spindle 1, and is screwed into the spindle 1 by the lock nut 10.
It has become possible to maintain distance between

Next, the operation of the device of this invention will be explained.

When using a measuring instrument equipped with this overload protection device to measure the load of a fluid, for example, the measuring instrument is attached to a part of the machine to be measured, and the spindle 1 is secured by a bolt 18 as shown in FIG. Install with horizontal axis. After connecting the outer base end of the spindle 1 to the output side of the fluid load,
The spiral pressure adjustment screw 8 is used to set the compression reaction force of the spring 7 to be balanced with the rated load of the measuring device.

As a result, if a fluid load not exceeding the rated value is applied to the spindle 1, the spindle 1 moves in the direction of the arrow in proportion to the load. At this time, since the compression reaction force of the spring 7 is set to be balanced with the rated value, the above fluid load is transmitted to the leaf spring 3 as it is via the pressure adjustment screw 9 and the connecting fitting 5 without attenuation. . Therefore, the leaf spring 3, which is connected to the connecting fitting 5 at its upper end, moves in the moving direction of the spindle 1 with the fixed base as a fulcrum, causing distortion. Since a strain gauge 4 is attached to the strain position of the leaf spring 3, the load is accurately transmitted to the strain gauge 4. This amount of distortion is then converted into an amount of variation in electrical resistance value and displayed as a distortion output on a meter (not shown). This allows this load to be recognized numerically.

Also, when a fluid load exceeding the rated value is applied to the spindle 1, the spindle 1 moves in the direction of the arrow as described above, but at this time, the spring constant of the spring 7 is smaller than that of the leaf spring 3. ,
As soon as the load exceeds the rated value, the spring 7 is compressed toward the pressure adjusting screw 8. Then, the tip of the spindle 1 quickly hits the stopper 9, and the back and forth movement of the spindle 1 is prevented, so that damage to the leaf spring 3 and strain gauge 4 can be prevented.

Furthermore, when the load applied to the spindle 1 returns to the rated value range again, the spring 7 can again exert the specified compression reaction force, so the load is transferred to the plate spring through the pressure adjustment screw 8 and the connecting fitting 5 in the same way as described above. 3, and the normal measurement mode can be restored.

The above measurement mode is explained in Fig. 3.
If the rated value of the load W applied to the spindle 1 is 5 kg, by setting the compression reaction force of the spring 7 to be balanced with the rated value of the load W by helical operation of the pressure adjustment screw 8, it is possible to temporarily When the load W is increased in increments of 1 kg until reaching the rated value, a strain output P proportional to the load W value is obtained linearly as shown in the figure.

However, the load W on spindle 1 exceeds the rated value.
Even if the standard increase of 1 kg is applied regularly as described above, the spring 7 contracts from the point when the rated value is exceeded and the tip of the spindle 1 hits the stopper 9, so the strain output P remains almost flat. As a result, almost no signal is transmitted to the leaf spring 3 side. This clearly shows that the overload prevention effect is working.

The reason why the strain output P under overload is not completely flat and extends slightly upward is because even if the spindle 1 contacts the stopper 9, the load applied to the spindle 1 does not reach the stopper 9 until it completely contacts the stopper 9. This is because the leaf spring 3 moves somewhat.

According to this invention, when an overload is applied, the internal spring 7 is compressed, and the spindle 1 is quickly applied to the stopper 9, so that the plate spring 3 is not overloaded. The load can be measured continuously, and even if the load exceeds the rated value, damage to the measuring device can be prevented. Moreover, by spirally moving the pressure adjustment screw 8, the other end of the spring 7 hooked to the pressure adjustment screw 8 is expanded and contracted, and the compression reaction force of the spring 7 is simply balanced with the rated load of the measuring instrument. Since protection against overload can be easily achieved, troublesome work such as accurately adjusting the distance between the tip of the spindle 1 and the stopper 9 is unnecessary.

[Effect of idea]

According to this invention, excellent effects as described below are exhibited.

When an overload is applied, the built-in spring contracts and the spindle quickly hits the stopper, which prevents overload from being applied to the leaf spring, making it possible to continuously measure widely fluctuating loads. Moreover, even when the load exceeds the rated value, damage to the measuring instrument can be prevented.

By spirally moving the pressure adjustment screw, the other end of the spring hooked to the pressure adjustment screw is expanded and contracted, and the compression reaction force of the spring is set to balance with the rated load of the measuring device. Since protection against loads can be easily achieved, troublesome work such as accurately adjusting the distance between the tip of the spindle and the stopper is unnecessary.

[Brief explanation of drawings]

Figure 1 is a vertical side view showing the overload protection device according to this invention, Figure 2 is a front view showing the inside of the overload protection device, and Figure 3 is the load measurement device equipped with this overload protection device. It is a graph showing the relationship between load and strain output. 1...Spindle, 2...Housing, 3...
Leaf spring, 4... Strain gauge, 5... Connection fitting, 6... Push metal fitting, 7... Spring, 8...
Pressure adjustment screw, 9...stopper, P...strain output, W...load.

Claims (1)

[Scope of utility model registration request] A hollow housing 2, a stopper 9 attached to one end of the housing 2, a leaf spring 3 having a proximal end attached to the other end of the housing 2 and equipped with a strain gauge 4, and a shaft hole formed in the leaf spring 3. 3a, the distal end thereof is brought close to the stopper 9, and the base end receives a load; and the spindle 1 has a spring constant smaller than that of the leaf spring 3.
a spring 7 whose one end is hooked to the spindle 1 in order to bias it in a direction opposite to the load received by the spring 7; a pressure adjusting screw 8 which hooks the other end of the spring 7;
An overload protection device characterized by comprising a connecting fitting 5 that connects the pressure adjusting screw 8 to the plate spring 3.