JP2002107213A - Electronic force balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the stiffness of a Roberval mechanism and to easily change a spring constant. SOLUTION: A lever housing part 2b is opened from one end 2a side on the inside of the Roberval mechanism 2 and houses and fixes a lever 4 to miniaturize the whole. Since a free end 4b of the lever 4 locates on the outside of the Roberval mechanism 2, an equilibrium driving means 6 for moving the lever 4 in a balanced condition can be installed in the outside position of the Roberval mechanism 2, and assembling and maintenance checking are made easy. A step 22d is installed in the lever housing part 2b in the length direction of the Roberval mechanism 2, and comes in contact with one side of the lever 4. Therefore, in the assembly of the lever 4, the lever 4 is guided, no fitting error is produced, and the assembly is made correct.

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 that can be easily assembled and maintained and can be reduced in size.

[0002]

FIG. 9 is a front sectional view showing a first electronic balance (disclosed in Japanese Patent Publication No. 6-29761), and FIG. 10 is a perspective view of the same. The electronic balance 80 is configured such that the movable portion 81b provided with the mounting plate 90 is movable with respect to the fixed portion 81a, the lever 83 interlocked with the movement of the movable portion 81b, and the lever 83 is in an equilibrium state. An electromagnetic coil 85 for movement control, a position detection sensor (not shown) for detecting the equilibrium state of the lever 83, and a control unit (not shown) for controlling the energization of the electromagnetic coil 85 and calculating and outputting the mass of the object to be weighed. It is roughly configured.

As shown in the figure, the roberval mechanism 81 has a pair of upper and lower parallel roberval portions 86 formed by cutting aluminum or the like in the shape of a rectangular parallelepiped from the side. A total of four thin spring portions 87 are formed in the roberval portion 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 receiving this load. Then, the movable portion 81b moves downward while maintaining the horizontal state.

In conjunction with this, the free end 83b of the lever 83 is displaced upward from the equilibrium position. 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.

FIG. 11 is an exploded perspective view showing a second conventional electronic balance (disclosed in JP-A-11-51756). In the electronic balance 90, a roberval mechanism 91 and a lever 92 are formed separately. The lever 92 is provided so as to connect both sides of the roberval mechanism 91, and the lever 92 is held by a fulcrum member 93 and a suspension member 94.

[0006]

Since the lever 83 in the configuration of the first electronic balance is formed integrally with the roberval mechanism 81, the electromagnetic coil 85 is provided inside the roberval mechanism 81, Coil 85
It is difficult to assemble and maintain. Further, the roberval mechanism 81 has to be designed in consideration of the storage of the electromagnetic coil 85, and the length of the lever 83 is restricted. The longer the lever 83 is, the longer the movable portion 81 of the roberval mechanism 81 is.
The load applied to b can be attenuated, and the displacement (displacement) of the free end 83a of the lever 83 can be increased to improve the measurement accuracy. However, the length of the lever 83 is restricted.

Further, in the second electronic balance 90, since the roberval mechanism 91 and the lever 92 are formed separately, the overall size, particularly the width W, is equal to the width of the roberval mechanism 91 and the width of the lever 92. The width was increased by the amount of the size and the size was increased.
For example, when trying to measure a heavier mass than before, the width W of the roberval mechanism 91 is increased, but the entire width is always wider by the addition of the lever 92, and the size cannot be reduced. Further, since the holding of the lever 92 on the base end portion 92b side is held by the plurality of fulcrum members 93 and the suspension bands 94, assembly and adjustment of this portion cannot be performed easily.

The present invention has been made in view of the above problems, and has as its object to provide an electronic balance that can be easily assembled and maintained and that can be reduced in size.

[0009]

In order to achieve the above object, an electronic balance according to the present invention comprises a movable portion which moves under the load of an object to be weighed, and a movable portion which moves between a fixed portion and the movable portion. A roberval mechanism 18 having a predetermined length and provided in a pair and moving the movable section 14 in a horizontal state, and a lever formed inward from one end 2a in the longitudinal direction of the roberval mechanism 2 The base portion movable portion 32a is accommodated in the housing portion 2b and the lever housing portion 2b and is fixedly connected to the movable portion 14 of the roberval mechanism 2 so as to interlock with the movement of the movable portion 14 of the roberval mechanism 2. A lever 4 whose free end 4b is displaced by a predetermined amount from the equilibrium state, and a lever 4 which is located outside the lever accommodating portion 2b of the roberval mechanism 2 and is provided at the free end 4b of the lever 4 so that the lever 4 is Characterized in that a balancing drive means 6 for moving controlled to be.

The lever accommodating portion 2b abuts on one side of the lever 4 along the length of the roberval mechanism 2 to guide the position of the lever 4 accommodated in the lever accommodating portion 2b. May be formed.

According to the above configuration, the lever accommodating portion 2b is formed inside the roberval mechanism 2 from the one end 2a side. The lever 4 is accommodated and fixed in the lever accommodating portion 2b, and has a width smaller than the opening diameter and a free end 4b extending outward. Thereby, the equilibrium drive means 6 is connected to the roberval mechanism 2.
Can be provided at an external position, and assembly and maintenance can be easily performed. The lever accommodating portion 2b is formed with a step portion 22d that abuts on one side of the lever 4 along the length direction of the roberval mechanism 2 and guides the lever 4 when accommodating it, thereby eliminating mounting errors and facilitating assembly. I do.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an electronic balance according to the present invention will be described. 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 in an equilibrium state, a position detecting unit 42, and a control unit (not shown). .

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 2.
3 is a plan view of the same, and FIG. 4 is a sectional side view of the same. The roberval mechanism 2 has a fixed part 12 and a movable part 14 that moves vertically with respect to the fixed part 12. The upper surface of the movable part 14
It is formed slightly higher than the fixing portion 12. The roberval mechanism 2 is formed by hollowing out a rectangular parallelepiped aluminum lump having a length L and a width W1 from the front side and penetrating a hollow portion 16 therein. In addition, the roberval mechanism 2 may form the hollow portion 16 by extrusion or the like. At this time, a pair of parallel roberval portions 18 having a predetermined thickness are provided above and below. The pair of roberval portions 18 have the same length in the length direction L, and have thin spring portions 2 at both ends.
0 is formed. The spring portions 20 are provided at two locations on the upper and lower surfaces, for a total of four locations. Each of the spring portions 20 has an arc shape when viewed from the upper and lower surfaces, and is formed in a linear shape that is continuous in the width W1 direction.

At a position directly below the upper roberval portion 18,
A lever fixing portion 22 for fixing the lever 4 is formed in parallel with the roberval portion 18. The lever fixing part 22 is composed of the fixing part 12 of the roberval part 18 and the movable part 14.
Has a cutting portion 22s in the middle of the length L direction corresponding to
There is a gap that does not hinder the movement of the movable part 14 with respect to the fixed part 12. By this cutting, the lever fixing part 22
It has a fixed side 22a and a movable side 22b.

A protruding piece 24 of a predetermined length is formed on the upper end of one end 2a of the roberval mechanism 2 in the longitudinal direction L, and the balance driving means 6 is mounted on the lower surface.
An approximately rectangular parallelepiped lever housing 2b is formed by opening from the center of one side surface of the roberval mechanism 2 located at the one end 2a toward the inside of the roberval mechanism 2. The lever accommodating portion 2b is
2, and is hollowed out to a position on the side of the movable portion 14 as viewed from the front side in FIG. 2 (until it reaches a position beyond the spring portion 20 of the roberval portion 18).

FIG. 5 is a front view of the lever 4, FIG. 6 is a plan view thereof, and FIG. 7 is a side view thereof. The lever 4 has a width W2 smaller than the width W1 of the roberval mechanism 2 and is reduced in size and weight. On the base end portion 4a side, the fixed portions 3 fixed to the fixed portion 12 and the movable portion 14 of the roberval portion 18 respectively.
0, a movable portion 32a is formed. The other end is a free end 4b. The free end 4b extends to a position outside the roberval mechanism 2 after the lever is fixed, and is located immediately below the protruding piece 24.

The movable portion 32a 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 has two fulcrums A and B
And a function of attenuating the mass (load load) of the object to be weighed applied to the movable portion 14 by a predetermined amount by the two fulcrums A and B, and shortening the length L2 of the lever 4. I have.

The lever 4 is also formed by hollowing out an aluminum lump or the like. In particular, the cutting portion 28 (28a, 28b, 28c) is formed in a substantially U-shape when viewed from the front. The fixed portion 30 is provided at the substantially central portion by the cut portion 28,
The movable portions 32 (32
a, 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 located at fulcrums A and B. The spring part 34 is formed in substantially the same shape as the spring part 20 of the roberval mechanism 2, and the description is omitted.

The load applied to the proximal end 4a is efficiently transmitted to the free end 4b via the fulcrums A and B of the spring 34 on the movable portion 32 side. In order to maintain the strength, a plurality of spring parts 3
6 is formed similarly to the spring portion 34.

On the free end 4b side of the lever 4, a weight mounting piece 3
8 is formed so as to protrude downward, and a substantially horizontal screw hole 38b is formed.
The balance weight 40 is attached to the part so as to be slidable in the horizontal direction. As will be described later, the balancing weight 40 is provided to balance the lever 4 by adjusting the balancing weight 40 when a heavy load such as a load receiving member is applied to the movable portion 14 of the roberval mechanism 2. A position detection sensor 42 is disposed at the free end 4 b of the lever 4. Position detection sensor 42
Is composed of a detection plate 42a fixed to the free end 4b side of the lever 4 with a predetermined height vertically and a light emitting / receiving sensor 42b fixed to the lower surface of the protruding piece 24 of the roberval mechanism 2. A detection hole is opened in the detection plate 42a,
The light emitting / receiving sensor 42b detects the vertical movement of the detection hole of the detection plate 42a, detects the equilibrium state of the lever 4 and the amount of vertical displacement based on the equilibrium state, and outputs the same to the control unit.

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. This balance driving means 6
Receives the 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.

FIG. 8 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. In the roberval mechanism 2, the fixing part 12 is fixed on the base plate 10 with screws 11. Lever housing 2
The lever 4 is inserted into “b”, and the proximal end 4 a is fixed to the lever fixing portion 22 with the screw 25. As shown in FIG. 4, a step portion 2 that guides one side surface of the lever 4 along the length direction L is provided on a lower surface of the lever fixing portion 22 that forms the lever housing portion 2b.
2d is formed. This eliminates mounting errors when the lever 4 is inserted, allows accurate positioning, and facilitates assembly.

The fixed part 30 of the lever 4 is fixed to the fixed side 22a of the lever fixed part 22, and the movable part 32 of the lever 4 is fixed to the movable side 22b of the lever fixed part 22.
In this fixed state, the free end 4 b of the lever 4 protrudes from the one end 2 a of the roberval mechanism 2 and is located immediately below the protruding piece 24. Thus, since the balance driving means (electromagnetic coil) 6 can be provided outside the roberval mechanism 2, maintenance such as assembly at the time of manufacturing, adjustment after assembly, replacement, and the like can be easily performed. Further, the lever 4 is provided from the inside to the outside of the roberval mechanism 2 so that the lever 4
The electronic balance 1
The overall width can be determined by the width of the roberval mechanism 2, and both the width and the length of the electronic balance 1 can be reduced in size.

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 moving and adjusting the balance weight 40 in the horizontal direction, the lever 4 can be adjusted to balance the load receiving portion (including the conveyor weight) in a heavy load state. The equilibrium state of this lever is determined by the position detection sensor 4
2 detected.

Next, the objects to be weighed are placed on the conveyor and conveyed on the conveyor. In the roberval mechanism 2, the movable portion 14 descends in the Z1 direction in FIG. At this time, the roberval portion 18 has a total of four spring portions 2.
By the deformation of 0, the movable part 14 is lowered while maintaining the horizontal state.

In conjunction with the lowering of the movable section 14, the movable section 32 of the lever 4 also moves down. When the movable part 32a moves down, the movable part 32b moves in the Z2 direction around the spring part 34 (fulcrum A), and the free end 4b of the lever 4 (the movable part 32) moves.
c) rises in the Z3 direction around the spring portion 34 (fulcrum B).

The free end 4b of the lever 4 is displaced (elevated) by a predetermined amount with respect to the equilibrium state.
2 is detected. 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 to obtain the current value to the electromagnetic coil 6b when the position detection sensor 42 detects that the lever 4 has rebalanced. Then, the mass of the object to be weighed is calculated and output based on the current value.

As described above, the fulcrum of the lever 4 is set at two points A,
By providing B, the mass (load load) of the object to be weighed applied to the movable portion 32 can be attenuated and transmitted to the free end 4b side, and at the same time, the displacement of the free end 4b side with respect to the movement amount of the movable portion 32 side It can be obtained in increasing amounts. This allows
The weighing accuracy can be improved. In addition, the length L2 of the lever 4 can be reduced and the configuration having a predetermined amount of attenuation can be achieved. By reducing the size and weight of the lever 4, 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 can be braked with a small force at the free end 4b. Become like

The electronic balance 1 can withstand use as a dynamic balance in which a heavy object such as a conveyor is provided on a load receiving portion. This rigidity is obtained because the roberval mechanism 2 has a relatively wide width W1. Due to the improvement of the rigidity, the electronic balance 1 can withstand an impact or the like when the object to be weighed is placed on the conveyor. As described above, even when the width W1 of the roberval mechanism 2 is increased, since the lever 4 is provided inside the roberval mechanism 2, the width of the electronic balance 1 is reduced.
And the overall size can be reduced.

[0031]

According to the electronic balance of the present invention, the lever accommodating portion has an opening formed from the one end side inside the roberval mechanism, and the lever is accommodated and fixed in the lever accommodating portion. Can be located outside. As a result, the equilibrium drive means can be provided at a position outside the roberval mechanism, and assembly and maintenance and inspection can be easily performed. Further, the lever is configured to be accommodated in the lever accommodating portion, so that the overall size can be reduced. Also, if a step is provided in the lever housing along the length direction of the robarbal mechanism and it comes into contact with one side of the lever, it can be guided when assembling the lever, eliminating mounting errors and accurate assembly Can be easily performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an electronic balance of the present invention.

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

FIG. 3 is a plan view of a roberval mechanism.

FIG. 4 is a side sectional view of the roberval mechanism.

FIG. 5 is a front view showing a lever.

FIG. 6 is a plan view of a lever.

FIG. 7 is a side view of a lever.

FIG. 8 is a cutaway front view showing a state in which a lever is incorporated in the roberval mechanism.

FIG. 9 is a front sectional view showing a conventional electronic balance.

FIG. 10 is a perspective view of the conventional electronic balance.

FIG. 11 is an exploded perspective view showing another conventional electronic balance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic balance, 2 ... Robarbal mechanism, 2b ... Lever accommodation part, 4 ... Lever, 4a ... Base end part, 4b ... Free end, 6 ... Balance drive means (electromagnetic coil), 12 ... Fixed part, 14 ... Movable part , 18 ... Robarbal part, 20 ... Spring part, 22 ... Lever fixing part, 22d ... Step part, 22s ... Cutting part, 30 ... Fixing part, 32 (32a, 32b, 32c) ... Movable part, 34 ...
Spring parts (fulcrums A and B), 40: balance weight, 42: position detection sensor.

Claims (2)

[Claims] 1. A movable part (14) which moves under a load of an object to be weighed, and a pair having a predetermined length provided between a fixed part (12) and the movable part, and the movable part is placed in a horizontal state. A roberval mechanism (2) comprising: a roberval portion (18) to be moved as it is; a lever accommodating portion (2b) formed inward from one end (2a) in the longitudinal direction of the roberval mechanism; The movable end (32a) on the base end side is fixedly connected to the movable part of the roberval mechanism, and the free end (4b) is displaced by a predetermined amount from the equilibrium state by interlocking with the movement of the movable part of the roberval mechanism. A lever (4), and equilibrium driving means (6), which is provided outside the lever accommodating portion of the roberval mechanism and is provided at a free end portion of the lever, and controls movement of the lever so as to be in an equilibrium state. Specially Electronic balance to be a sign. 2. The lever accommodating portion (2b) abuts one side of the lever along the length direction of the roberval mechanism (2) to guide the accommodating position of the lever in the lever accommodating portion. The electronic balance according to claim 1, wherein a step portion (22d) is formed.