JP2002296101A - Electronic balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a fine balance adjustment easily. SOLUTION: A weight member 42 becomes capable of moving forward and backward in the direction of the length of a lever 4 with an adjusting rod 44 screwed to a free end 4b side of the lever 4. Movement of the weight member 42 is restricted by subjecting a moved tip of a fixed rod 46, which is penetrated into and screwed to the weight member 42, to abut on the lever 4 side. The weight member 42 can thereby be moved finely, enabling to easily perform a fine balance of the lever.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic balance for measuring the mass of an object to be weighed, and more particularly to an electronic balance having a balance adjusting mechanism for maintaining a balance of a lever.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a conventional electronic balance.
FIG.
The electronic balance 80 shown in FIG. 8 includes a movable section 81b provided with a mounting plate 90 on which an object to be weighed is mounted, and a base frame 92.
A roberval mechanism 81 movable with respect to a fixed portion 81a fixed to the support 92a of the first and second members, a lever 83 linked with the movement of the movable portion 81b, an electromagnetic coil 85 for controlling movement of the lever 83 so as to be in an equilibrium state, It mainly comprises a position detection sensor (not shown) for detecting the equilibrium state of the object, and a control unit (not shown) for controlling the energization of the electromagnetic coil 85 to calculate and output the mass of the object to be weighed.

The roberval mechanism 81 has a pair of upper and lower parallel roberval portions 86 formed by cutting aluminum or the like in a rectangular parallelepiped shape from the side. 4 in total for Roberval section 86
When an object to be weighed is placed on the placing plate 90 of the movable portion 81b, the spring portion 87 is deformed by this load, and the movable portion 81b is in a horizontal state. Move downward while maintaining.

[0004] The lever 83 is integrally formed with the roberval mechanism 81 and is hollowed out, and is disposed in the roberval section 86. A proximal end 83a of the lever 83 has a movable portion 8 formed by a connecting portion 88 having narrowed portions 88a and 88b formed at both ends.
1b side. This lever 83 has a proximal end 83
A portion closer to the free end 83b than a is supported by a constricted portion 83c that serves as a fulcrum continuously on the fixed portion 81a side. An electromagnetic coil 85 is provided at the free end 83b of the lever 83.

The free end 83b of the lever 83 is displaced upward from the equilibrium position in conjunction with the downward movement of the movable portion 81b of the roberval mechanism 81 under load. The control unit controls the energization of the electromagnetic coil 85 based on the output of the position detection sensor so that the lever 83 is in an equilibrium state, and calculates the mass of the object to be weighed based on the current value to the electromagnetic coil 85 when the lever 83 is in equilibrium. Calculation output.

In the electronic balance having the above-described configuration, the free end of the lever 83 is raised by the weight of the placing plate 90 even when the object to be weighed is not placed on the placing plate 90. The current always flows to maintain the equilibrium state of the lever 83. It is sufficient that the placing plate 90 is lightweight. However, when a weighing conveyor for measuring and transporting an object to be weighed is provided in the movable portion 81b, the electromagnetic coil 85 is used to maintain the weight and balance of the weighing conveyor. A large current needs to flow. For this reason, the amount of heat generated by the electromagnetic coil 85 increases, and high-precision measurement cannot be performed.

Also, a large weight such as a weighing conveyor,
When the balance is established by the force generated by the current flowing through the electromagnetic coil 85, mass imbalance occurs between the weighing conveyor and the lever 83. As a result, high-precision measurement cannot be performed due to the influence of external vibrations of the floor and the equipment.

The above problem is solved by providing a weight on the free end 83b side of the lever 83. The balance of the weight needs to be adjusted according to the mass of a weighing conveyor mounted on the electronic balance. Conventionally, this balance adjustment involves a weight adding method and a weight moving method.

[0009] As shown in FIG.
A support rod 91 is extended from a free end 83b of the lever 83, and a plurality of types of weights 92 are added to or replaced with the support rod 91. In the weight moving method, as shown in FIG. 9B, a male screw type support rod 91 is extended from a free end 83b of a lever 83, and two female screw type weights 9 are attached to the support rod.
2 and 92 are movably screwed into each weight 9 at a desired position.
2 and 92 are abutted and fixed, and are configured as a so-called lock nut.
The weights 92, 92 are moved in the length direction of the lever 83 toward the center.

[0010]

However, the above-mentioned conventional electronic balance provided with a weight has the following problems. In the case of the weight adding method, a plurality of types of weights 92 (including a difference in outer shape, a difference in thickness, a difference in material, etc.) are required at the time of balance adjustment, and all of the weights 92 must be prepared. In addition, in the weight addition method, fine adjustment is difficult because the weight of each weight 92 is within the adjustment range of balance.

In the weight moving method, the two weights 92, 92 are moved with respect to the support rod and fixed by abutting the weights. Therefore, when the weights 92, 92 are fixed, the weights 92, 92 must be slightly moved. No. For this reason, the balance adjusted by moving the weights 92, 92 and the balance after fixing the weights 92, 92 are slightly different, and it is difficult to obtain a desired balance.

In view of the above, an object of the present invention is to provide an electronic balance capable of easily performing fine balance adjustment in order to solve the above-mentioned problems.

[0013]

In order to achieve the above object, an electronic balance 1 according to the present invention comprises a pair of roberval portions 18 provided between a fixed portion 12 and a movable portion 14 with a spring portion 20 interposed therebetween. A roberval mechanism 2 for moving the movable portion 14 receiving the load of the object in a horizontal state, and a free end 4b having a base end 4a connected to the movable portion 14 and held via fulcrums A and B. None, a lever 4 whose free end 4b is displaced by a predetermined amount in conjunction with the movement of the movable portion 14, and a balance adjustment mechanism attached to the free end 4b side of the lever 4 to maintain the balance of the equilibrium state of the lever 4. 40, wherein the balance adjusting mechanism 40 comprises:
A weight member 42, an adjusting rod 44 integrally extended with the weight member 42 and capable of moving forward and backward along the length direction of the lever 4 and screwed to the free end 4 b side of the lever 4; A fixed rod 46 that is movable in an axial direction parallel to the axis of the adjusting rod 44 and is threaded through the weight member 42, and the moved tip abuts on the lever 4 side to restrict movement by the adjusting rod 44; , Consisting of

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of the electronic balance. The electronic balance 1 includes a roberval mechanism 2, a lever 4, an equilibrium driving unit 6 including an electromagnetic coil for controlling the lever 4 to be in an equilibrium state, a position detection unit (not shown), and a control unit (not shown). Do it.

A load receiving member (not shown) is fixed on the movable portion 14 of the roberval mechanism 2, and a dynamic balance having a conveyor mounted on the load receiving member can be constructed. Then, the mass of the object is measured while the object is conveyed by the conveyor. In addition, it is also possible to provide a placing plate on the movable portion 14 and use the object to be weighed on the placing plate as a static balance for measuring the mass.

FIG. 2 is a front view showing the roberval mechanism, and FIG.
Is a side view of the same. The roberval mechanism 2 includes a fixing unit 12
And a movable portion 14 that is movable in the vertical direction with respect to the fixed portion 12. The upper surface of the movable part 14 is formed slightly higher than the fixed part 12. The Roberval mechanism 2 has a length L
1. A block of a single material such as an aluminum block, which is a rectangular parallelepiped hard material having a width W1, is cut out from the front side, and a hollow portion 16 is formed inside the block. In addition, this Roberval mechanism 2
The hollow portion 16 may be formed by extrusion molding or the like. At this time, a pair of parallel roberval portions 1 having predetermined thicknesses at the top and bottom
8 are provided. The pair of roberval portions 18 have the same length in the length direction L1, and thin spring portions 20 are formed at both ends. The spring portions 20 are provided at two locations on the upper and lower surfaces, for a total of four locations.

A lever fixing part 22 is formed in the hollow part 16 and directly below the upper roberval part 18. The lever fixing portion 22 is connected to the roberval portion 18.
The fixed portion 12a and the movable portion 14 are formed continuously so as to connect the fixed portion 12 and the movable portion 14 in the length L1 direction, and then are linearly cut in the width W1 direction through the interval portion 22s. 22b.

As described above, the fixed side 22a and the movable side 2a
The lever 4 is fixed to the lever fixing part 22 divided into 2b. That is, a fixed portion 30 of the lever 4 described below is fixed to the fixed side 22a, and a movable portion 32 of the lever 4 described later is fixed to the movable side 22b. Also, lever fixing part 2
2 is parallel to the roberval portion 18 and fixes the lever 4 parallel to the roberval portion 18.

A protruding piece 24 having a predetermined length is formed on one end 2a of the roberval mechanism 2 in the longitudinal direction L1. The balance driving means 6 is attached to the lower surface of the protruding piece 24. On one side surface of the roberval mechanism 2 located below the protruding piece 24, a lever accommodating portion 2b formed in the length L1 direction and communicating with the hollow portion 16 is formed with an opening.

FIG. 4 is a front view showing the lever, and FIG. 5 is a side view of the same. The lever 4 has a substantially rectangular parallelepiped shape having a length L2 and a width W2. A fixed portion 30 fixed to the fixed portion 12 (fixed side 22a) of the roberval portion 18 and a fixed portion 30 fixed to the movable portion 14 (movable side 22b) are provided on the base end 4a side, which is one end side in the length L2 direction of the lever 4, respectively. The part 32 (32a) is formed. The other end of the lever 4 in the length L2 direction is a free end 4b.

The movable portion 32 of the lever 4 moves in conjunction with the movement of the movable portion 14 of the roberval mechanism 2, and the free end 4b moves up and down. The lever 4 in the present embodiment has two fulcrums A and B, and the mass (load load) of the object to be weighed applied to the movable part 14 is attenuated by a predetermined amount by the two fulcrums A and B. The function of the lever 4 and the length L2 of the lever 4 are reduced.

A specific configuration of the lever 4 will be described. The lever 4 is formed by cutting out a lump of a single material such as an aluminum lump like the roberval mechanism 2. At this time, as shown in FIG. 4, the cutting portion 28 (2
8a, 28b, 28c) are formed through. A fixed portion 30 is formed substantially at the center by the cutting portion 28, and a plurality of movable portions 32 (3
2a, 32b, 32c) are formed.

The fixed portion 30 and the movable portion 32 of the lever 4 are connected to each other by two thin spring portions 34 forming fulcrums A and B by forming the cutting portion 28. At the fulcrum A, a spring portion 34 formed between the cutting portions 28a and 28b
Thereby, the fixed part 30 and the movable part 32b are connected. At the fulcrum B, the fixed part 30 and the movable part 32c are connected by a spring part 34 formed between the cutting parts 28b and 28c. The spring portion 34 is formed in substantially the same shape as the spring portion 20 of the roberval mechanism 2, and the description is omitted.

The movable part 32 of the lever 4 efficiently transmits the load applied to the base end 4a to the free end 4b through the fulcrums A and B of the spring part 34, and the strength of the spring 34 Are formed in a plurality of stages (three stages in the present embodiment) via a spring portion 36 in order to maintain the height. First stage movable part 32a
Constitutes the base end 4a side of the lever 4,
Is fixed to the movable portion 14 (the movable side 22b). The second-stage movable portion 32b is connected to the first-stage movable portion 32a via two spring portions 36. Third stage movable part 32c
Constitutes the free end 4b side of the lever 4, and is connected to the second-stage movable portion 32b via the spring portion 36. The spring portion 36 is formed in substantially the same shape as the spring portion 20 of the roberval mechanism 2, and the description is omitted.

FIG. 6 is a partially cut front view showing an assembled state of the electronic balance. In this drawing, for convenience, the lever 4 is not cut, and only the robarbal mechanism 2 is cut.

The electronic balance 1 is configured by inserting and fixing a lever 4 inside the roberval mechanism 2. Roberval mechanism 2
The fixing portion 12 is fixed on the base plate 10 with the screw 11. Then, the lever 4 is inserted into the lever accommodating portion 2b of the roberval mechanism 1 fixed to the base plate 10 from the base end 4a.

The lever 4 is configured such that the fixing portion 30 is
2 is fixed to the fixed side 22a with the screw 25. In the lever 4, the movable part 32 (32 a) is fixed to the movable side 22 b of the lever fixing part 22 with a screw 25. In this fixed state,
The free end 4 b (movable portion 32 c) of the lever 4 projects from the one end 2 a of the roberval mechanism 2 and is located immediately below the projecting piece 24. As described above, the lever 4 is provided inside the roberval mechanism 2.
Is provided, the overall size can be reduced.

The lower surface of the lever fixing portion 22 forming the lever accommodating portion 2b is provided on the lower surface of the lever 4 along the length direction L1.
A step portion 22d for guiding one side surface is formed. This facilitates positioning when inserting the lever 4 and facilitates assembly.

On the free end 4b side of the lever 4, a weight mounting piece 3
8 protrudes downward. This weight mounting piece 3
8 is provided with a balance adjusting mechanism 40 for maintaining the balance of the equilibrium state of the lever 4.

FIG. 7 is a perspective view showing a balance adjusting mechanism. As shown in FIG. 6 and FIG.
Numeral 0 has a weight member 42, an adjusting rod 44, and a fixed rod 46.

The weight member 42 is for balancing the lever 4 when a heavy load such as a load receiving member or the like is applied to the movable portion 14 of the roberval mechanism 2 assembled as described above. Therefore, the weight member 42 has a desired weight for balancing the lever 4. The weight member 42 is
In the present embodiment, it is formed in a disk shape.

The adjusting rod 44 extends integrally with the weight member 42. The adjusting rod 44 has an external thread and the lever 4
Of the lever 4 is screwed into a screw hole 38a provided along the length L2 direction of the lever 4 at the free end 4b. The adjusting rod 44 can be advanced and retracted in its own axial direction, which is the length direction of the lever 4, by a tightening and loosening operation screwed into the screw hole 38a. Accordingly, the weight member 42 moves forward and backward in the length L2 direction of the lever 4 in accordance with the tightening and loosening operation of the adjusting rod 44.

The fixed rod 46 has a male thread, and the adjusting rod 44
And is screwed through the weight member 42 so as to be parallel to the axis of. That is, the fixed rod 46 is movable in an axial direction parallel to the axis of the adjustment rod 44 by the tightening and loosening operation of the weight member 42 screwed. Further, the fixed rod 46 has its moved tip abutted on the surface around the screw hole 38a of the weight mounting piece 38 to which the adjusting rod 44 is screwed by the tightening operation. As a result, the adjusting rod 44 cannot be tightened or loosened, and the movement of the adjusting rod 44 (weight member 42) is restricted.

As shown in FIG. 7, at the rear end of the weight member 42 and the fixed rod 46 extending along the axis of the adjusting rod 44, a tightening operation of the adjusting rod 44 and the fixed rod 46 is performed by using a tool (a screwdriver, a hexagon wrench, etc.). ) So that the tool fitting portion 42
a, 46a may be provided. In this way, lever 4
Can be easily adjusted.

As described above, the balance adjusting mechanism 40
Moves the weight member 42 to the lever 4
Is moved in the direction of the length L2 to change the load of the weight member 42 applied to the free end 4b of the lever 4 to maintain the balance of the equilibrium state of the lever 4. In addition, the balance adjustment mechanism 40
After the balance adjustment of the equilibrium state of the lever 4, the movement of the weight member 42 is regulated by the tightening operation of the fixed rod 46, and the position of the weight member 42 in which the balance is maintained is maintained.

Note that the equilibrium state of the lever 4 is detected by a slit provided at the free end 4b of the lever 4 and a position detection sensor (not shown) fixed to the protruding piece 24 side. Is to be detected.

The electromagnetic coils constituting the balance driving means 6 are as follows:
An annular magnet 6a is fixed to the lower surface of the protruding piece 24, and a wound coil 6b is fixed to the inside of the ring of the magnet 6a on the upper surface of the free end 4b of the lever 4. As described above, since the electromagnetic coil can be provided outside the roberval mechanism 2, assembly and maintenance during manufacturing can be easily performed. The equilibrium drive unit 6 receives current control of the control unit when measuring the object to be weighed, changes the magnetic force between the magnet 6a and the current supplied to the coil 6b, and returns the lever 4 to the equilibrium state.

Next, the operation of measuring the mass of an object to be weighed by the electronic balance 1 having the above configuration will be described. By adjusting the balance adjusting mechanism 40, the lever 4 is balanced in the weight-loaded state of the load receiving member (including the conveyor weight). The equilibrium state of the lever 4 is detected by a position detection sensor.

Next, the object to be weighed is placed on a conveyor placed on a load receiving member as a dynamic balance, and is conveyed and moved on this conveyor. In the roberval mechanism 2, the movable portion 14 moves down in the Z1 direction in FIG. At this time, the roberval section 18 lowers the movable section 14 while maintaining the horizontal state by deformation of the spring sections 20 at a total of four places.

In conjunction with the lowering of the movable section 14, the movable section 32a of the lever 4 similarly moves down. When the movable portion 32a descends, the movable portion 32b is moved around the spring portion 34 (fulcrum A).
Moves in the Z2 direction in FIG. With the movement of the movable portion 32b, the free end 4b (the movable portion 32c) of the lever 4 rises in the Z3 direction in FIG. 6 around the spring portion 34 (the fulcrum B).

The free end 4b of the lever 4 is displaced (raised) by a predetermined amount with respect to the equilibrium state, and this displacement is detected by a position detecting sensor. The control section controls the energization of the electromagnetic coil of the balancing means 6 so that the lever 4 returns to the balanced state again. At this time, the current direction of the electromagnetic coil to the coil 6b and the amount of current to be supplied are controlled, and the lever 4 is detected by the position detection sensor.
Obtains a current value to the electromagnetic coil 6b when it is detected that the balance has reached the equilibrium state again, and calculates and outputs the mass of the object to be weighed based on this current value.

As described above, the lever 4 is connected to the movable section 3 having a plurality of stages.
By providing a plurality of (two) fulcrums A and B as 2a, 32b and 32c, the mass (load load) of the object to be weighed applied to the movable part 32a side can be reduced by the free end 4b (the movable part 32).
The transmission can be attenuated to the side c), and at the same time, it can be obtained by increasing the amount of displacement on the free end 4b (movable part 32c) side with respect to the amount of movement on the movable part 32a side. Thereby, the measurement accuracy can be improved. Further, the length of the lever 4 in the direction of the length L2 can be shortened, and a configuration having a predetermined amount of attenuation can be achieved. Further, since the lever 4 is reduced in size and weight, the response of the movement to the load can be made more sensitive, and the measurement accuracy can be improved. If a force is applied from the free end 4b of the lever 4, the force can be increased and transmitted to the movable portion 32 (the movable portion 14 of the roberval mechanism 2), so that the lever 4 is braked with a small force at the free end 4b. become able to.

Therefore, in the electronic balance 1 configured as described above, the weight member 42 that moves by the tightening and loosening operation of the adjusting rod 44 in the direction of the length L2 of the lever 4 with respect to the free end side of the lever 4.
Was provided. Thereby, the weight member 42 can be slightly moved,
The adjustment of the balance balance of the lever 4 can be finely adjusted.

A fixed rod 46 is provided for the weight member 42 to be moved by tightening and loosening in the same direction as the moving direction of the weight member 42, and the tip of the fixed rod 46 contacts the free end side of the lever 4. The movement of the weight member 42 is regulated. Thus, the weight member 42 can be fixed at a position where the weight member 42 is slightly moved.

Further, since the adjustment operation by the balance adjustment mechanism 40 can be performed by tightening and loosening the adjustment rod 44 and the fixed rod 46, the balance can be easily adjusted.

[0046]

As described above, in the electronic balance according to the present invention, as the balance adjusting mechanism for maintaining the balance of the balance of the lever, the weight member is extended by the adjusting rod screwed to the free end side of the lever. The moving end of the fixed rod screwed through the weight member is brought into contact with the lever side to regulate the movement of the weight member. Thus, the weight member can be finely moved, and the adjustment of the balance of the lever can be finely adjusted. Further, since the distal end of the fixed rod abuts on the free end side of the lever to regulate the movement of the weight member, the weight member can be fixed at a position where the weight member is slightly moved. Further, since the adjustment can be performed by tightening and loosening the adjusting rod and the fixed rod, the balance can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an electronic balance.

FIG. 2 is a front view showing a roberval mechanism.

FIG. 3 is a side view showing the Roberval mechanism.

FIG. 4 is a front view showing a lever.

FIG. 5 is a side view showing a lever.

FIG. 6 is a partially cut front view showing an assembled state of the electronic balance.

FIG. 7 is a perspective view showing a balance adjustment mechanism.

FIG. 8 is a front sectional view showing an example of a conventional electronic balance.

FIGS. 9A and 9B are schematic diagrams showing a structure of a conventional balance adjustment.

[Explanation of symbols]

1. Electronic balance, 2. Robarbal mechanism, 4. Lever, 4a
... base end, 4b ... free end, 12 ... fixed part, 14 ... moving part,
18 Roberval part, 20 Spring part, 40 Balance adjustment mechanism, 42 Weight member, 44 Adjusting rod, 46 Fixed rod,
A, B ... fulcrum.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Sakai 5-10-27 Minamiazabu, Minato-ku, Tokyo Anritsu Corporation

Claims (1)

[Claims] 1. A pair of roberval portions (18) via a spring portion (20) between a fixed portion (12) and a movable portion (14).
And a roberval mechanism (2) for moving the movable part receiving the load of the object to be weighed in a horizontal state, and a base end (4a) connected to the movable part (14). B) form a free end (4b) held through
A lever (4) whose free end is displaced by a predetermined amount in conjunction with the movement of the movable portion; and a balance adjusting mechanism (40) attached to the free end side of the lever to maintain the balance of the balance of the lever. An electronic balance comprising: a weight member (42); a weight member (42); and a free end of the lever that is integrally extended with the weight member and is capable of moving forward and backward along a length direction of the lever. An adjusting rod (44) screwed on the side of the adjusting rod; an adjusting rod (44) that is movable in an axial direction parallel to the axis of the adjusting rod and is threaded through the weight member; Fixed rod (4
6) An electronic balance, comprising: