JP2003014532A - Overload preventing device for balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overload preventing mechanism in which the protection of a load detecting sensor from an overload is constituted in such a way as to receive a load by a casing or a base by the deformation of an elastic body without providing a mechanical stopper. SOLUTION: A load transmitting shaft 8 is inserted in a through hole 6 bored in the load detecting sensor 5, and the load transmitting shaft 8 is fastened to the load detecting sensor 5 by the elastic body 9 provided between the load detecting sensor 5 and the through hole 6. Therefore, when an inadmissible load is added to the load transmitting shaft 8, the elastic body 9 is deformed to release the load transmitting shaft 8 and the load detecting sensor 5 from fastened relation and move the load transmitting shaft 8 downward into contact with the casing 10 or the base 11. The load is thereby received by the casing 10 or the base 11 to protect the load detecting sensor 5 from the overload.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision balance and, more particularly, to an overload preventing device therefor.

[0002]

2. Description of the Related Art Generally, in a precision balance, the load of a measurement object placed on a weighing pan is detected by a load of a balanced electromagnetic force generator or a load cell via a load transmission shaft or a load receiver. It is transmitted to the sensor and the magnitude of the load is measured. However, since the load detection sensor is vulnerable to overload and impact load, it is usually necessary to protect the load detection sensor from these overload and impact load. For this reason, in conventional precision balances, in order to protect the load detection sensor, various mechanical stoppers are provided to prevent the load exceeding the allowable load from acting to prevent displacement and deformation of the load receiver and load detection sensor. ing. For example, in an electronic balance using a double beam type load cell, in general,
One end of the load cell is fixed to the base of the balance via a support frame, etc., and the load receiving part is attached with the other end as the free end, but on the bottom of the free end (movable column) of the load cell, A stopper is placed to regulate the displacement of the load cell below the allowable level. In addition, the moving parts of the balance
The method of fixing to the fixed part of the balance is adopted, such as the method of screwing to the fixed part or the method of applying a pressing force to the load transmission shaft or load receiving part that engages the weighing pan by using a spring etc. and fixing it to the fixed part of the balance. .

[0003]

However, the conventional method of limiting the displacement and deformation of the load detection sensor with a mechanical stopper is as follows: when a larger load or impact load is applied to the load detection sensor, There is a risk of displacement and deformation, including mechanical stoppers, and it is insufficient as an overload protection mechanism. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an overload prevention device for a balance, which protects the load detection sensor from a load larger than an allowable load.

[0004]

In order to achieve the above-mentioned object, the balance of the present invention is provided with a guide mechanism capable of relatively displacing the load transmission shaft in the load detection sensor, and the load transmission shaft in the guide mechanism. Between the load detection sensor,
The locking mechanism that locks the load transmission shaft with the load detection sensor only when the measured load is within the range of the measurement allowable load of the load detection sensor is provided. Therefore, the locking mechanism loses the locking function when an overload is applied, the load transmission shaft penetrates the load detection sensor, and the load detection sensor is not overloaded.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. The locking mechanism characterized by the present invention utilizes an elastic spring body and a rubber body as constituent elements, and the property of deforming them when overloaded. The present invention will be described below with reference to some examples. FIG. 1 shows an overall outline of an embodiment of the present invention, in which a through hole 6 is provided at a free end of a load detecting sensor 5 and a load transmission shaft 8 is inserted into the through hole 6 to detect the load detecting sensor. An elastic body 9 made of a rubber material or the like is mounted around the through hole 6 at the bottom of the unit 5. The details of the operation when a load more than the permissible load is applied to the load transmission shaft 8 is shown in FIG. That is, in FIG. 2, when the elastic body 9 is deformed, the load transmission shaft 8 moves downward along the through hole 6, and the weighing pan 7 is pressed against the casing 10, so that the casing 10 receives the load and the load detection sensor. 5 shows a state where 5 is protected.

A specific configuration will be described below with reference to FIGS. 1 and 2. First, the overall configuration of the electronic balance of the present invention will be described with reference to FIG. 1. The electronic balance 1 is installed on the installation table 3 via the legs 2. A support frame 4 is arranged in the electronic balance 1, and a load detection sensor 5 is supported by the support frame 4 in a cantilever manner. This load detection sensor 5
A through hole 6 is formed on the free end side of the load transmission shaft 8, and a load transmission shaft 8 having a weighing pan 7 arranged at the upper end is inserted into the through hole 6. An elastic body 9 made of a rubber material or the like is installed at the lower end of the through hole 6, that is, around the through hole 6 below the load detection sensor 5, and the load inserted into the through hole 6 by the elastic body 9 is installed. The transmission shaft 8 is locked to the load detection sensor 5 and is in an integrated state for measurement. In addition, strain cage 1
2 detects the weight of the object to be weighed on the weighing pan 7, and the indicator drive circuit 13 receives the detection signal from the strain gauge 12 to display the indicator 1
The weight is displayed at 4.

By the way, in the electronic balance having such a structure, when an object to be measured having an allowable load or more is placed thereon or an overload or impact load is applied due to vibration or the like, the load detection sensor 5 is operated to Needs to be protected from overload. In this case, FIG. 2 shows a state in which the casing 10 receives an overload applied to the balance. That is, when a load more than an allowable value is applied to the weighing pan 7, the elastic body 9 is deformed, the joint between the load transmission shaft 8 and the load detection sensor 5 is released, and the load transmission shaft 8 is penetrated by the load detection sensor 5. It moves downward along the through hole 6. Then, when the weighing pan 7 comes into contact with the casing 10, the movement of the load transmission shaft 8 is blocked, and the casing 10 receives the load. In this way, it is possible to prevent the load detection sensor 5 from being applied with an unacceptable load. The withstand load until the elastic body 9 is deformed is set to the allowable load.

FIG. 3 shows a state in which an overload is received by the base 11, and when a load more than an allowable load is applied to the weighing pan 7, FIG.
Similarly, the deformation of the elastic body 9 releases the joint between the load transmission shaft 8 and the load detection sensor 5, and the load transmission shaft 8 is inserted into the through hole 6
By moving the inside downward and coming into contact with the base 11, the movement of the load transmission shaft 8 is prevented, and the load is prevented from being applied to the load detection sensor 5 by the base 11 receiving the load. 2 shows a structure in which the casing 10 receives the overload as in FIG. 1, but FIG. 3 shows the structure in which the base 11 receives the overload, and the base 11 can reliably handle a considerably large overload. You will receive it.

FIG. 4 is an enlarged view of a portion of a locking mechanism mainly composed of the elastic body 9. The lower end portion of the load transmission shaft 8 inserted into the through hole 6 formed in the load detection sensor 5, that is,
A return taper 8a is formed at a portion joined to the elastic body 9. By providing the return taper 8a on the load transmission shaft 8, the return to the measurement state is facilitated when the load transmission shaft 8 moved downward due to overload is pulled up.

In the embodiment of the present invention, as shown in FIG. 1, a through hole 6 is bored in the load detecting sensor 5, and the through hole 6 is used as a guide mechanism in which the load transmitting shaft 8 is provided. Although the structure for insertion is adopted, it is also possible to attach a guide mechanism including a guide frame for guiding the load transmission shaft to the free end side of the load detection sensor 5 and insert the load transmission shaft in the guide frame. . Also at that time, the elastic body is deformed only when the load transmission shaft is overloaded, and the locking relation between the load receiving portion and the load detection sensor via the guide mechanism of the load transmission shaft is released, and the load detection sensor is released. Is configured to protect against overload.

5 and 6 show a modification of the locking mechanism of the present invention. FIG. 5 shows a first modification of the locking mechanism of the present invention, which shows a locking mechanism using a reciprocating stopper. In this reciprocating stopper, a spool 16 having a roller 15 arranged at the tip is installed on the load detection sensor 5 via a compression spring 17, and the measured load is the load detection sensor 5.
When it is within the range of the measurement allowable load of
The roller 15 is pressed against the load transmission shaft 8 vertically by the elastic force of, and the load transmission shaft 8 is locked to the load detection sensor 5. When the load transmission shaft 8 is overloaded, the downward force of the load transmission shaft 8 acts on the spool 16 via the roller 15 and loses the elastic force of the compression spring 17, so that each spool 16 moves in the left-right direction. Pressed. As a result, the load transmission shaft 8
The lock function of the load detection sensor 5 with respect to is released, and the load detection sensor 5 is protected from overload.

FIG. 6 shows a second modified example of the locking mechanism of the present invention, which shows a locking mechanism using a swingable stopper 18. The swing-type stopper 18 is rotatably suspended from the load detection sensor 5 about a fulcrum 19, and a compression spring 20 is press-fitted between the swing stopper 18 and the load detection sensor 5 as shown in the figure. The load transmission shaft 8 is locked to the load detection sensor 5 by the elasticity of the compression spring 20. When the load transmission shaft 8 is overloaded, the end of the swingable stopper 18 is pushed downward around the fulcrum 19 by the downward force of the load transmission shaft 8, and the other end of the swingable stopper 18 moves the fulcrum 19 to the fulcrum 19. As the center, it swings upward against the elastic force of the compression spring 20. As a result, the locking relationship between the load transmission shaft 8 and the load detection sensor 5 is released, and the load detection sensor 5 is protected from overload.

Further, if a stopper is provided on the base portion so that the dish receiving shaft can be fixed, it is possible to protect the load detection sensor from an impact during transportation of the balance.

[0014]

As described above, according to the present invention, a rubber material, a spring material or the like which receives a load when a load more than an allowable load is applied to the load receiving portion without providing a mechanical stopper. The locking mechanism consisting of the elastic body of the actuation operates, the load transmission shaft and the load detection sensor become completely free, and the casing or base is configured to be overloaded, so when a larger load is applied, the load It is possible to prevent the detection sensor from being deformed or displaced including the mechanical stopper. Further, by providing a mechanism for fixing the load receiving portion, it becomes possible to protect the load detection sensor during transportation.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an electronic balance according to an embodiment of the present invention.

FIG. 2 is a view showing the operation of the locking mechanism of the embodiment of the present invention, and is a view showing a state in which the casing receives a load.

FIG. 3 is a view showing the operation of the locking mechanism of the embodiment of the present invention, showing a state in which a load is received by the base.

FIG. 4 is an enlarged view of a main part of the locking mechanism according to the embodiment of the present invention.

FIG. 5 is a diagram showing a first modified example of the locking mechanism in the present invention.

FIG. 6 is a diagram showing a second modified example of the locking mechanism in the present invention.

[Explanation of symbols]

1 ... Electronic balance 2 ... legs 3 ... Installation stand 4 ... Support frame 5… Load detection sensor 6 ... through hole 7 ... Scale plate 8 ... Load transmission shaft 8a ... Return taper 9 ... Elastic body 10 ... Casing 11 ... Base 12 ... Strain gauge 13 ... Display driving circuit 14 ... Indicator 15 ... Laura 16 ... spool 17 ... Compression spring 18 ... Oscillating stopper 19 ... fulcrum 20 ... Compression spring

Claims (4)

[Claims] 1. A balance in which a load placed on a weighing pan is transmitted to a load detection sensor via a load transmission shaft having a weighing pan capped at the upper end, and the load is detected by the load detection sensor. A guide mechanism that allows the load transmission shaft to be displaced relatively is provided, and the load is transmitted only between the load transmission shaft and the load detection sensor in this guide mechanism when the measured load is within the range of the measurement allowable load of the load detection sensor. An overload prevention device for a balance, comprising a locking mechanism for locking the shaft to a load detection sensor. 2. An elastic body, wherein the locking mechanism is installed on a load detecting sensor so as to lock a lower end of a load transmitting shaft, and transmits the load to the load detecting sensor only when the load is within an allowable load range. The balance overload preventing device according to claim 1, wherein the overload preventing device is configured as follows. 3. A spool, wherein the locking mechanism is installed in a load detection sensor, is movable in a direction perpendicular to the load transmission shaft, and is locked at a lower end of the load transmission shaft when the load transmission sensor advances, and the spool is connected to the load transmission shaft. 2. A spring for urging to the side, wherein when an overload is applied, the spool retracts against the elastic force of the spring and the load transmission shaft is unlocked. Balance overload prevention device. 4. A swing-type stopper, which is swingably installed on a load detection sensor and has its tip abutting against a lower end of a load transmission shaft to lock the load transmission shaft, and the swing mechanism. The tip of the shaped stopper is composed of a spring that urges it to contact the lower end of the load transmission shaft. When an overload is applied, the oscillating stopper retracts against the elastic force of the spring and locks the load transmission shaft. The overload prevention device for a balance according to claim 1, wherein