JPS622503Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a load cell scale.

Conventional load cell scales have a beam to which a strain gauge is attached and a Roberval mechanism, each of which is installed separately, and the Roberval mechanism corrects the load of the item placed on the load tray into a load that acts in the vertical direction even if it is an unbalanced load. It is of the type that transmits the signal to the beam. Although there are types in which the beam and the roberval mechanism are provided independently and those in which they are provided integrally, the structure and shape are still complicated, and the number of assembly and adjustment work increases. In addition, strict dimensional control is required for the portions of the beam to which each strain gauge is attached in order to achieve uniform bending action.

This idea was developed in view of the above points, and the beam itself to which the strain gauge is attached has a roberval function, reducing the number of parts and simplifying the structural shape.Furthermore, the flexible part is shaved to increase the wall thickness. The object of the present invention is to provide a load cell weigher that can adjust the bending characteristics of each flexible portion to make them uniform.

This invention consists of a fixing part fixed to a base, an arm having one end connected to the fixing part and facing parallel to each other in the vertical direction, and the other end of the arm facing parallel to the fixing part and suspended in the air. A beam having a predetermined thickness in the left and right direction is provided, and each arm has a flexible part that bends in the vertical direction while holding a strain gauge. A printed circuit board is formed by positioning each piece at a corner of a parallelogram when viewed from the side, and a printed circuit board that extends to the side of the arm and connects the strain gauge is fixed to the side surface of the fixed part. The present invention is characterized in that an opening part for opening the flexible part is formed on the substrate. In other words, the beam is deformed by transmitting the load to the pressure receiving part,
The amount of deformation is converted into an electrical signal by a strain gauge and measured.The beam is integrally formed with a fixed part, a movable part, and an arm to form a parallelogram, and the arm is attached to the corner of the parallelogram. By forming a flexible part in a position where
Accurate measurements can be made, the number of parts can be reduced, the structural shape can be simplified, assembly work can be facilitated, and even when a printed circuit board is attached to the side of the beam, the flexible part can be removed from the open part. The structure is such that the wall thickness can be adjusted, thereby making it easy to make adjustments to make the bending characteristics of each flexible part uniform.

An embodiment of this invention will be explained based on the drawings.
Reference numeral 1 shown in FIG. 1 is a base, and a mounting base portion 2 is formed protruding from a part of the upper surface of the base 1. As shown in FIG. Next, a beam 3 made of a rectangular aluminum material having a predetermined thickness is provided. This beam 3 has a fixed part 4 and a movable part 5 facing each other on the left and right sides, connected by arms 6 and 7 facing each other on the upper and lower sides, and is integrally formed to form a parallelogram. Furthermore, a mounting hole 8 is formed in the fixed part 4 to be screwed to the mounting base part 2 of the base 1, and a mounting hole 10 is formed in the upper surface of the movable part 5 to be connected to the load receiving plate 9. A hard receiving plate 12, such as a piece of iron, is fixedly attached to the lower surface of the movable part 5, and a stopper 11 formed on the base 1 by means of an adjustment screw is fixedly mounted thereon. An opening 13 is formed. Further, a protrusion 14 that protrudes toward the movable part 5 in a cantilevered state is connected to the fixed part 4, and this protrusion 14
Attachment holes 15 are formed in the distal end portion of the fixing portion 4 and the fixing portion 4 . This protruding portion may be formed from a separate member and attached to the fixing portion 4. Furthermore, two thin flexible parts 18 are formed on each of the arms 6 and 7 by forming flat recesses 16 on the upper and lower surfaces in the center of the beam 3 and forming irregularly shaped openings 17 penetrating the sides. has been done. Irregular opening 17
The shape is an H-shape in which two vertically elongated ellipses are spaced apart and the intermediate portions of the two are connected through a horizontal hole, assuming that the protrusion 14 does not exist.
Therefore, the inner surface of the flexible portion 18 is a semicircular curved surface, and the position of the flexible portion 18 is determined to be a corner of a parallelogram when viewed from the side. However,
Strain gauges 19 and 2 are attached to the outer surface of each flexible portion 18.
0, 21, and 22 are attached. These strain gauges 19 to 22 and the flexible portion 18 are sealed all around with a thin rubber layer 23 such as silicone rubber or butyl rubber (see FIG. 8).

Next, as shown in FIGS. 2 and 3, a printed circuit board 2 is installed to connect each strain gauge 19 to 22 to an external circuit via a cord 24 and a connector 25.
6 is provided. This printed circuit board 26 is T-shaped, consisting of a horizontal part 27 along the protruding part 14 and a vertical part 28 extending from its tip toward the middle of the arms 6 and 7, and is separated from the beam 3 by a spacer 29. It is attached with a screw 30 that is screwed into the attachment hole 15 in this state. The printed circuit board 26 extends to the middle part of the irregularly shaped opening 17, and because it is T-shaped, an open part 31 is formed to open the inner surface of the flexible part 18 (see FIGS. 2 and 9). The strain gauges 19 to 22 are connected to form a bridge circuit 32 as shown in FIG. 6, and a resistor 33 called a span resistor made of nickel foil is connected to the input side of the bridge circuit 32. There is a correction resistor 3 between 22
4, 35, 36, and 37 are connected. resistance 3
3 compensates for the temperature coefficient of the Young's modulus of the beam 3. The correction resistors 34 to 37 are for correcting the bridge circuit 32, and the zero balance correction resistance uses a manganin wire, and the zero balance temperature coefficient correction resistance uses a copper wire. A wiring pattern 38 that satisfies the wiring described above is formed on the surface of the printed circuit board 26 using copper foil. In this wiring pattern 38, the wiring pattern 38
A pattern 39 is also formed to prevent electrical interference such as electrostatic induction between the two. Further, connection portions a and b for connecting the correction resistors 34 to 37 are formed in a part of the wiring pattern 38, respectively. Furthermore, as shown in FIG. 5, on the back surface of the printed circuit board 26, a shield pattern 40 that is grounded to the beam 3 is formed by forming copper foil over the entire surface or arranging it in a mesh pattern. . Therefore, as shown in FIG. 7, a capacitor 41 can be configured by the wiring pattern 38 and the shield pattern 40 to form an equivalent circuit.

In such a configuration, when an object to be measured is placed on the load receiving tray 9, the movable portion 5 descends while bending the flexible portion 18. The strain gauges 19 to 22 are the flexible part 1
A signal is emitted depending on the degree of bending of 8, and the weight is measured electrically. The movable part 5 faces the fixed part 4 in parallel with a vertical axis, and is supported by arms 6 and 7 extending in parallel from the fixed part 4, and the flexible part 18 forms a corner of a parallelogram. Due to its position, the beam 3 itself has a roberval function. That is, even if an unbalanced load is applied to the load receiver 9, the load is corrected as a load that acts acutely and is applied to the beam 3. This ensures accurate measurements. In addition, since no separate Roberval mechanism is required, the number of parts is reduced.
The structural shape can be simplified and made compact. Assembly and adjustment work is also easy. Moreover, since each of the strain gauges 19 to 22 is located in the recess 16 and retracted inward from the upper and lower surfaces of the beam 3 and both side surfaces, it can be protected from mechanical damage.

By being supported by the stopper 11, the beam 3 can prevent abnormal deformation of the flexible portion 18 when an overload is applied. In this case, the beam 3 is made of aluminum, but the stopper 1
Since the receiving plate 12 is fixed to the surface opposite to the receiving plate 1, it will not wear out or leave impressions. Also, beam 3
By forming the opening 13 in the movable part 5, the mass can be reduced and the impact during transportation or dropping can be reduced. Thereby, abnormal deformation of the flexible portion 18 can be prevented. The opening 13 may have any shape such as circular, elliptical, or polygonal, but if it is a hole, it can have a predetermined thickness on the upper, lower, and side surfaces. As a result, although the beam 3 is supported by the stopper 11 and is made of soft aluminum, it has sufficient strength.

Furthermore, the strain gauges 19 to 22 are attached to the flexible portion 1.
By sealing the entire circumference with the rubber layer 23 together with 8, the flexible part 18 and the strain gauges 19 to 22 are protected from harmful outside air and moisture, and in particular, the sensitive flexible part 18 is prevented from being adversely affected by corrosion. do not have.

Furthermore, the printed circuit board 26 has one end of the fixed part 4 held therein, the other end held by the protruding part 14 extending from the fixed part 4 to the center of the arms 6 and 7, and has a vertical part 28 that projects in the vertical direction. By doing so, the length of the lead wires to the strain gauges 19 to 22 can be shortened, and the lead wires do not come into contact with each other, making it easy to organize them. Since the tip of the printed circuit board 26 is also fixed by the mounting hole 15 at the tip of the protrusion 14 and the screw 30, it will not warp and the lead wires to the strain gauges 19 to 22 will not break. Further, the printed circuit board 26 is connected to the arm 6,
7, but is separated from the arms 6, 7 which are bent up and down by the spacer 29, so there is no room for friction to occur that would inhibit the bending action of the arms 6, 7. This allows accurate measurements to be made.

Furthermore, the printed circuit board 26 is connected to the bridge circuit 3.
A wiring pattern 38 forming a beam 2 is formed on the surface thereof, and a shield pattern 40 is grounded to the beam 3.
is formed on the back surface, and a capacitor 41 can be formed by both. As a result, a bypass circuit is formed that allows high-frequency induced noise to escape, and the mechanical load can be accurately extracted as an electrical signal. A part of the wiring pattern 38 is provided with connection parts a and b for connecting correction resistors 34 to 37 that correct the zero balance of the bridge circuit 32 and correct the temperature coefficient of the zero balance. And adjustment work of resistance value is easily performed. For example, to connect the correction resistors 34 and 36 for zero balance correction, as shown in FIG. Cut the copper foil part of the wiring pattern between connection parts a and b. The resistance value is corrected by changing the amount of solder and substantially changing the length of the correction resistor 34.

Further, although the printed circuit board 26 extends to the center of the arms 6 and 7, the inner surface of the flexible portion 18 is opened by an open portion 31. Therefore, it is possible to easily adjust the roberval mechanism by cutting the inner surface of the flexible portion 18 with a hand grinder or the like and adjusting the thickness thereof. As shown in FIG. 10, when a square printed circuit board 42 is used,
For example, the open portion 43 that opens the inner surface of the flexible portion 18 may be formed by a D-shaped hole or a hole or notch in another shape.

Since this device is constructed as described above, it is possible to form a beam while forming a parallelogram with the fixed part, movable part, and arm, and also to place the flexible part in the arm at the corner position of the parallelogram. By positioning and forming the beam, it is possible to give the beam itself a roberval function and perform accurate measurements.This reduces the number of parts, simplifies and downsizes the structure, and facilitates assembly work. Furthermore, even when a printed circuit board is attached to the side of the beam, it is possible to easily adjust the bending characteristics of each flexible part by cutting the flexible part from the open part and adjusting the wall thickness. It is something that you have.

[Brief explanation of the drawing]

The drawing shows one embodiment of this invention.
The figure is a front view of a single beam, the second figure is a perspective view, and the third figure is a perspective view.
The figure is a plan view, Figure 4 is an enlarged front view of the front side of the printed circuit board, Figure 5 is an enlarged rear view of the back side of the printed circuit board, Figure 6 is a bridge circuit diagram, and Figure 7 is an equivalent diagram. Circuit diagram, Figure 8 is a partially enlarged front view,
FIG. 9 is a front view, and FIG. 10 is a front view showing a modification. 1...Base, 3...Beam, 4...Fixed part,
5... Movable part, 6-7... Arm, 9... Load receiver, 18... Flexible part, 19-22... Strain gauge, 26... Printed circuit board, 31... Open part,
42...Printed circuit board, 43...Open section.

Claims (1)

[Scope of utility model registration request] a fixed part fixed to the base; an arm connected to the fixed part at one end and facing parallel in the vertical direction; and an arm connected to the other end of the arm in a suspended state, facing parallel to the fixed part A beam having a predetermined thickness in the left-right direction and a movable part connected to a load receiving tray is provided, and each arm has two flexible parts on each side that can bend in the vertical direction while holding a strain gauge. A printed circuit board is positioned and formed at a corner of a parallelogram when viewed from above, and a printed circuit board that extends to the side of the arm and connects the strain gauge is fixed to the side surface of the fixed section, and the A load cell scale characterized by forming an open part that opens a flexible part.