JP2013250196A - Metering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metering device capable of protecting a load cell against overloading when an abnormal load is placed on a load receiving part or connection member.SOLUTION: A metering device 100 includes a first overloading protection mechanism and a second overloading protection mechanism. The first overloading protection mechanism comprises a first support part 121a provided to a fixed member 12 and a first part 131a provided to a connection member 14. The second overloading protection mechanism comprises a second support part 122b provided to the fixed member 12 and a second part 132b provided to the connection member 14. When a first load is placed on a metering hopper 28, the first support part 121a supports the first part 131a from below. When a second load larger than the first load is placed on the metering hopper 28, the first support part 121a supports the first part 131a and the second support part 122b supports the second part 132b from above simultaneously.

Description

  The present invention relates to a weighing device using a load cell, and more particularly to a weighing device provided with a load cell overload protection mechanism.

  Conventionally, as a means for protecting the load cell of the weighing device from overload, a method of restricting the movement of the load cell on the free end side within a predetermined range has been adopted. For example, a load cell stopper mechanism disclosed in Patent Document 1 (Japanese Utility Model Laid-Open No. 5-28937) includes a boss (connecting member) attached to the free end side of the load cell, and a protruding portion protruding in the horizontal direction from the boss. A load receiving portion fixed to the boss and a restricting portion provided with a gap in the vertical direction with respect to the protruding portion, and when the load is applied to the load receiving portion, the protruding portion is provided on the restricting portion. Excessive movement is regulated by abutting.

  However, since the stopper mechanism as described above corresponds to an overload that can occur in normal operation, for example, an excessive force is applied when removing the load receiving portion, or an operator mistakenly removes the load receiving portion. When an abnormal load is applied to the load receiving portion such as when riding on the load, a force in the direction opposite to the load direction is generated at the free end of the load cell with the restricting portion serving as a fulcrum, and the load cell may be damaged.

  The subject of this invention is providing the measuring device which can protect a load cell from an overload, even when an abnormal load acts on a load receiving part or a connection member.

  A weighing device according to a first aspect of the present invention is a weighing device using a load cell, and includes a fixing member, a weighing hopper, a connecting member, and an overload protection mechanism. The fixing member fixes one end of the load cell. The weighing hopper places an object to be weighed. The connecting member connects the weighing hopper and the free end of the load cell. The overload protection mechanism protects the load cell from overload. The overload protection mechanism has a first support part and a second support part provided on the fixing member. When the first load is applied to the load cell, the first support portion supports the first portion set to either the load cell or the connecting member directly from below or via a predetermined member. When a second load greater than the first load is applied to the load cell, the first support portion supports the first portion, and at the same time, the second support portion is connected to the weighing hopper on the opposite side of the first support portion. The second part set on either the member or the load cell is supported from above.

  In this weighing device, when an abnormal load is applied to the weighing hopper or the connecting member, the first support portion supports the first portion of the connecting member from below, so that the free end of the load cell is displaced below the limit. That is limited. Further, when a second load greater than the first load is applied, the first support portion serves as a fulcrum, a bending moment is generated in the connecting member, and the connecting member is deformed upward, but the second support portion is connected to the connecting member or Since the second portion set on one of the load cells is supported from above, it is limited that the free end of the load cell is displaced upward beyond the limit.

  The weighing device according to a second aspect of the present invention is the weighing device according to the first aspect, and the second support portion is provided at a position farther from the first support portion than the free end of the load cell.

  In this weighing device, the second support portion may in principle be positioned above the free end of the load cell. However, the connecting member is connected to the free end of the load cell, so that the second support portion can be freely arranged. The degree is limited. However, if the position is farther from the first support portion than the free end of the load cell, it is possible to avoid interference with the surrounding structure and arrange the structure without increasing the size.

  A weighing device according to a third aspect of the present invention is the weighing device according to the first aspect, in which the second support portion is provided at a position farther from the first support portion than the fixed end of the load cell.

  In this weighing device, the gap between the second portion and the second support portion becomes smaller as it is closer to the first support portion due to the principle of leverage, and fine adjustment becomes difficult. However, the second support portion is more difficult than the fixed end of the load cell. In addition, by being provided at a position away from the first support portion, the clearance between the second portion and the second support portion can be easily adjusted.

  A weighing device according to a fourth aspect of the present invention is the weighing device according to the first aspect, wherein the overload protection mechanism is located above the coupling member and faces the first support portion with the coupling member interposed therebetween. It further has a support part.

  In this weighing device, when an operator mistakenly handles the weighing hopper or the connecting member upward, the upper opposed support part supports the connecting member from above, so that the free end of the load cell exceeds the limit and moves upward. Displacement is limited.

  In the weighing device according to the present invention, when an abnormal load is applied to the weighing hopper or the connecting member, the first support portion supports the first portion of the connecting member from below, so that the free end of the load cell is lower than the limit. Displacement is limited. Further, when a second load greater than the first load is applied, the first support portion serves as a fulcrum, a bending moment is generated in the connecting member, and the connecting member is deformed upward, but the second support portion is connected to the connecting member or Since the second portion set on one of the load cells is supported from above, it is limited that the free end of the load cell is displaced upward beyond the limit.

The front view of the combination weighing machine provided with the weighing | measuring apparatus which concerns on 1st Embodiment of this invention. The perspective view of the weighing | measuring device which concerns on 1st Embodiment except a control part. The block diagram of the measuring device modeled simply according to the lever principle. A graph showing the relationship between the load applied to the weighing hopper and the maximum strain on the gauge surface of the load cell. The front view of the said load cell and connecting member which shows the shape of the load cell when not applying force to the measurement hopper, and a connecting member. The front view of the said load cell and connection member which shows the shape of a load cell when a force of 10 kg is made to act on a weighing hopper, and a connection member. The front view of the said load cell and connection member which shows the shape of a load cell and a connection member when 50 kg of force is made to act on a measurement hopper. The front view of the said load cell and connecting member which shows the shape of a load cell when connecting 160 kg of force to a measurement hopper, and a connecting member. The front view of the said load cell and connection member which shows the shape of a load cell when a force of 160 kg is made to act on a weighing hopper in the conventional type which is not equipped with the 2nd overload protection mechanism. The block diagram of the weighing device made into the simple model which concerns on a 1st modification. The block diagram of the weighing device made into the simple model which concerns on a 2nd modification. The block diagram of the weighing device made into the simple model which concerns on a 3rd modification. The block diagram of the weighing device made into the simple model which concerns on a 4th modification. The perspective view of the weighing | measuring device which concerns on 2nd Embodiment except a control part. The block diagram of the weighing | measuring apparatus which concerns on 2nd Embodiment made into the simple model. The graph showing the relationship between the load applied to the weighing hopper and the output of the load cell. The block diagram of the simplified model of the weighing device provided with the overload protection mechanism that functions when operation is stopped. The block diagram of the simplified model of the weighing device provided with another overload protection mechanism that functions when operation is stopped.

  Embodiments of the present invention will be described below with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.

<First Embodiment>
(1) Configuration of Combination Weighing Machine 150 Provided with Weighing Device FIG. 1 is a front view of a combination weighing machine 150 provided with a weighing device according to the first embodiment of the present invention. In FIG. 1, a combination weighing machine 150 includes a supply conveyor 21, a supply chute 22, a dispersion feeder 24, a vibration feeder 25, a pool hopper 26, a weighing hopper 28, a collecting chute 31, a control unit 50, a weighing unit 60, and a frame F. I have.

  The supply conveyor 21 sends the article M to the supply chute 22. The article M that has passed through the supply chute 22 is put on a vibrating dispersion feeder 24. In the vicinity of the outer periphery of the dispersion feeder 24, a plurality of vibration feeders 25 are arranged radially in a plan view. The vibration feeder 25 receives the article M dispersed around by the vibration of the dispersion feeder 24. Further, the vibration feeder 25 can carry out the article M in the radial direction by vibrating with a predetermined amplitude and number of vibrations.

  The pool hopper 26 is disposed below the outer end of the vibration feeder 25. A weighing hopper 28 is arranged below the pool hopper 26. The article M is sent to the pool hopper 26 by the vibration of the vibration feeder 25 and temporarily pooled there in accordance with the weighing operation. Then, the article M is put into the weighing hopper 28 when the discharge gate of the pool hopper 26 is opened.

  The weighing unit 60 measures the weight of the article M put into the weighing hopper 28 with the built-in load cell 10 and outputs a weight signal to the control unit 50. The control unit 50 performs a combination calculation based on the weight signal, selects the weighing hopper 28 having a combination weight within an allowable range set based on the target weight, opens the discharge gate of the weighing hopper 28, and M is collected by the collecting chute 31 and discharged from the timing gate 32. The discharged article M is packaged by a lower packaging machine (not shown) to become a bag-packed product having a weight within an allowable range.

  The frame F supports the dispersion feeder 24, the vibration feeder 25, and the pool hopper 26. The frame F supports the measuring unit 60 inside. The weighing hopper 28 is supported by the weighing unit 60.

(2) Configuration of Weighing Device 100 In this embodiment, the weighing device 100 includes the weighing hopper 28, the control unit 50, and the weighing unit 60.

  FIG. 2 is a perspective view of the weighing device 100 according to the first embodiment excluding the control unit 50. In FIG. 2, the measuring unit 60 includes a load cell 10, a fixing member 12, and a connecting member 14. The fixing member 12 fixes one end of the load cell 10 at a predetermined portion. Hereinafter, of the both ends of the load cell 10, one end fixed to the fixing member 12 is called a fixed end, and the other end not fixed to the fixing member 12 is called a free end. The connecting member 14 is a member that connects the weighing hopper 28 and the free end of the load cell 10.

(3) Detailed configuration (3-1) Fixing member 12
The fixing member 12 is roughly divided into a first region 12a and a second region 12b. The first region 12 a is provided so as to cover the upper side of the connecting member 14. The second region 12b is provided so as to cover the fixed end side of the load cell 10.

  In addition, the fixing member 12 has a plurality of support portions corresponding to each predetermined portion in order to support a plurality of predetermined portions set in advance on the connecting member 14. Specifically, the plurality of support parts include a first support part 121a and a second support part 122b.

  The 1st support part 121a is set to the lower end of the opening 121 formed in the position close | similar to the connection member 14 among the 1st area | regions 12a. The 2nd support part 122b is set to the upper end of the slit 122 formed in the position close | similar to the fixed end of the load cell 10 among the 2nd area | regions 12b.

  As shown in FIG. 2, the second support portion 122 b is provided at a position farther from the first support portion 121 a than the free end of the load cell 10. This is because the connecting member 14 is connected to the free end of the load cell 10 to limit the degree of freedom of the arrangement of the second support portion 122b. The second support portion 122b is more than the free end of the load cell 10. Further, by being provided at a position away from the first support portion 121a, interference with the surrounding structure and an increase in the size of the structure are suppressed.

(3-2) Connecting member 14
The connecting member 14 includes a main body block 140, a first block 141, and a second block 142. The main body block 140 connects the free end of the load cell 10 and the weighing hopper 28.

  The first block 141 protrudes from the main body block 140 so as to penetrate the opening 121. The first block 141 has a screw hole 141 e that penetrates from the upper end side to the lower end side of the opening 121. The first bolt 131 is screwed into the screw hole 141e. The clearance between the upper surface of the head of the first bolt 131 and the upper end of the opening and the clearance between the tip of the first bolt 131 and the lower end of the opening are both set to predetermined dimensions.

  The second block 142 extends from the main body block 140 so that a tip end portion thereof enters the slit 122. The distal end portion of the second block 142 has a screw hole 142e penetrating from the upper end side of the slit 122 toward the lower end side. The position of the second block 142 is adjusted so that the screw hole 142e faces the upper end of the slit 122, and the second bolt 132 is inserted from below the screw hole 142e.

  For convenience of explanation, the front end surface of the first bolt 131 facing the first support portion 121a is referred to as a first portion 131a, and the upper end surface of the second bolt 132 facing the second support portion 122b is referred to as a second portion 132b. Call it.

(3-3) Overload Protection Mechanism In the weighing device 100, the mechanism for protecting the load cell 10 from overload is configured by the first support portion 121a and the second support portion 122b described above, and the first support portion 121a is A mechanism for supporting the first portion 131a functions as a first overload protection mechanism, and a mechanism for the second support portion 122b supporting the second portion 132b functions as a second overload protection mechanism.

  In the first overload protection mechanism, the first support portion 121a prevents the first portion 131a from being displaced beyond a predetermined value. In the second overload protection mechanism, the second support portion 122b prevents the second portion 132b from being displaced beyond a predetermined value. The mechanism of each overload protection mechanism is included in the following operation description.

(4) Operation FIG. 3 is a configuration diagram of the weighing device 100 that is simply modeled according to the lever principle. FIG. 4 is a graph showing the relationship between the load applied to the weighing hopper 28 and the maximum strain on the gauge surface of the load cell 10.

(4-1) Mechanism of First Overload Protection Mechanism First, in FIG. 3, when a downward force is applied to the weighing hopper 28, the connecting member 14 is bent downward, and the first portion 131a is the first support portion 121a. Get closer to. Here, when a force acting on the weighing hopper 28 when the first portion 131a abuts on the first support portion 121a is a first force, when a force larger than the first force is applied to the weighing hopper 28, The first support part 121a supports the first part 131a from below and prevents the first part 131a from being displaced downward.

  As shown in FIG. 4, the maximum strain on the gauge surface in this operation increases in the positive direction after a force is applied to the weighing hopper 28 until the force reaches the first force. When the force is applied beyond the first force, the strain of the load cell 10 is once reduced, and thereafter, the load cell 10 starts to increase in the opposite direction (positive direction). This is because when the first portion 131a contacts the first support portion 121a, the downward displacement of the free end of the load cell 10 is prevented, and at the same time, a bending moment is generated in the connecting member 14 with the first support portion 121a as a fulcrum. This is because a force is applied to lift the free end of the load cell 10 upward.

  In FIG. 4, the principle that the characteristic curve of the maximum strain changes from ascending to descending at the point where the force acting on the weighing hopper 28 becomes the first force, and the force acting on the weighing hopper 28 is the first force. The principle of having an inflection point at which the maximum strain characteristic curve changes from descending to ascending while increasing from the force to the second force will be described from the viewpoint of the strain gauge of the load cell 10.

  First, in a state where no force is applied to the weighing hopper 28, the strain gauge is deformed by a certain amount due to the tare weight such as the weight of the weighing hopper 28 itself. Here, when the first force acts on the weighing hopper 28, the free end of the load cell 10 is displaced downward until the first portion 131a contacts the first support portion 121a. Becomes larger, and the characteristic curve of the maximum strain in FIG. 4 rises.

  However, once the first portion 131a comes into contact with the first support portion 121a, a bending moment is generated in the connecting member 14 with the first support portion 121a as a fulcrum, so that the free end of the load cell 10 that has been displaced downward is Displaces upward. At this time, as the free end of the load cell 10 is displaced upward, the absolute value of the deformation amount of the strain gauge changes in a decreasing direction, so that the maximum strain characteristic curve is lowered.

  Then, once the deformation amount of the strain gauge is eliminated, the descending of the maximum strain characteristic curve in FIG. 4 stops. However, when a larger force is applied to the weighing hopper 28, the free end of the load cell 10 is further displaced upward. Therefore, again, the absolute value of the deformation amount of the strain gauge changes in the increasing direction, and the maximum strain characteristic curve in FIG. 4 starts to rise.

  As described above, even when an abnormal force is applied to the weighing hopper 28 or the connecting member 14, the first support portion 121 a supports the first portion 131 a from below, so that the free end of the load cell 10 exceeds the limit and moves downward. Displacement is limited.

(4-2) Mechanism of the second overload protection mechanism When the force acting on the weighing hopper 28 is further increased, the connecting portion between the free end of the load cell 10 and the connecting member 14 is displaced upward. It approaches the second support part 122b. Here, if the force acting on the weighing hopper 28 that causes a bending moment to act on the connecting member 14 until the second portion 132b comes into contact with the second support portion 122b is the second force, When a force larger than the force is applied, the second support portion 122b supports the second portion 132b from above and prevents the second portion 132b from being displaced upward.

  As shown in FIG. 4, the maximum strain of the gauge surface in this operation once decreases after a force greater than the first force is applied to the weighing hopper 28, and then the opposite direction (forward direction). ) At a substantially constant rate, but when the force acts beyond the second force, it begins to increase at a different rate than before. This is because upward displacement of the second portion 132b is prevented by the second portion 132b coming into contact with the second support portion 122b.

  For reference, in FIG. 4, the maximum strain on the gauge surface when the second support portion 122 b is not provided is indicated by a dotted line. In the absence of the second support portion 122b, when the force acting on the weighing hopper 28 further increases beyond the second force, the maximum strain on the gauge surface increases abruptly and reaches a limit value (horizontal two-dot chain line in FIG. 4). ).

  However, when the second support portion 122b is provided, even when the force further increases beyond the second force, the increase rate of the maximum strain on the gauge surface is moderate as compared with the case where the second support portion 122b is not provided. Yes, the load load allowed until the limit value (horizontal two-dot chain line in FIG. 4) is reached is twice or more that when the second support portion 122b is not provided.

  Therefore, when a second force larger than the first force is applied, the first support portion 121a serves as a fulcrum, a bending moment is generated in the connecting member 14 and the connecting member 14 tends to deform upward. Since the 2 support part 122b supports the 2nd part 132b from upper direction, it is restrict | limited that the free end of the load cell 10 displaces an upper direction exceeding a limit.

(4-3) Behavior of Load Cell 10 and Connecting Member 14 FIGS. 5A to 5D show shapes of the load cell 10 and the connecting member 14 when forces of 0, 10 kg, 50 kg, and 160 kg are applied to the weighing hopper 28, respectively. 3 is a front view of the load cell 10 and a connecting member 14. FIG. 5A to 5D are diagrams in which the actual deformation amount is enlarged 50 times.

  5E shows the load cell 10 and the connecting member when a force of 160 kg is applied to the weighing hopper 28 in the conventional type in which the second support portion 122b does not include the second overload protection mechanism for supporting the second portion 132b. 14 is a front view of the load cell 10 and the connecting member 14 showing the shape of FIG. FIG. 5E is a diagram in which the actual deformation amount is enlarged by 50 times.

  In FIG. 5A, when no force is applied to the weighing hopper 28, the load cell 10 and the connecting member 14 are naturally not deformed. 5B, when a force of 10 kg is applied to the weighing hopper 28, that is, when a force corresponding to the first force shown in FIG. 4 is applied, the free end of the load cell 10 is displaced downward.

  5C, when a force of 50 kg is applied to the weighing hopper 28, that is, when a force corresponding to the second force shown in FIG. 4 is applied, the first portion 131a is the first support portion 121a (FIG. 2). Therefore, a bending moment acts on the connecting member 14 with the first support portion 121a as a fulcrum, and the free end of the load cell 10 is displaced upward. At this time, since the second portion 132b is supported by the second support portion 122b (see FIG. 2), the upward displacement of the free end of the load cell 10 is limited thereafter.

  In FIG. 5D, when a force of 160 kg is applied to the weighing hopper 28, the upward displacement of the free end of the load cell is seen even though the second portion 132b is supported by the second support portion 122b. This is because the connecting member 14 and the fixing member 12 themselves are deformed.

  Still, compared with the change in shape of the load cell 10 and the connecting member 14 in the conventional type that does not include the second overload protection mechanism shown in FIG. 5E, the deformation amount is remarkably small, and the second support portion 122b replaces the second portion 132b. The effect of the 2nd overload protection mechanism to support is remarkable.

(5) Features (5-1)
The weighing device 100 includes a first overload protection mechanism and a second overload protection mechanism. The first overload protection mechanism includes a first support part 121 a provided on the fixing member 12 and a first part 131 a provided on the connecting member 14. The second overload protection mechanism includes a second support part 122 b provided on the fixing member 12 and a second part 132 b provided on the connecting member 14. When the first force is applied to the weighing hopper 28, the first support portion 121a supports the first portion 131a from below. When a second force larger than the first force is applied to the weighing hopper 28, the first support portion 121a supports the first portion 131a, and at the same time, the second support portion 122b pushes the second portion 132b from above. To support.

  As a result, when the first force is applied to the weighing hopper 28, the first support portion 121a supports the first portion 131a from below, so that the free end of the load cell 10 is restricted from being displaced below the limit. Is done. When a second force greater than the first force is applied, the first support portion 121a acts as a fulcrum, a bending moment is generated in the connecting member 14 and the connecting member 14 is deformed upward. Since the portion 122b supports the second portion 132b from above, it is limited that the free end of the load cell 10 is displaced upward beyond the limit.

(5-2)
In the weighing device 100, the second support portion 122 b is provided at a position farther from the first support portion 121 a than the free end of the load cell 10. If the position is farther from the first support portion 121a than the free end of the load cell 10, the second support portion 122b can be disposed without avoiding interference with the surrounding structure and without increasing the size of the structure.

(6) Modification (6-1) First Modification In the first embodiment, the second support part 122b is provided at a position farther from the first support part 121a than the free end of the load cell 10. It is not limited to. For example, FIG. 6 is a configuration diagram of the weighing device 100 that is simplified and modeled according to the first modification. In FIG. 6, the second support portion 122 b is farther from the first support portion 121 a than the fixed end of the load cell 10. It is provided at the position.

  The gap between the second portion 132b and the second support portion 122b becomes smaller as it is closer to the first support portion 121a due to the lever principle, and fine adjustment is difficult. However, according to the weighing device 100 according to this modified example, the second support portion 122b is provided at a position farther from the first support portion 121a than the fixed end of the load cell 10, whereby the second portion 132b and the second support portion are supported. The gap with the part 122b becomes large, and the adjustment becomes easy.

(6-2) Second Modification In the first embodiment, the first portion 131a is set to the connecting member 14, but the present invention is not limited to this. For example, FIG. 7 is a configuration diagram of the weighing device 100 that is simplified and modeled according to the second modification. In FIG. 7, the first portion 131 a is provided near the free end of the lower surface of the load cell 10 and faces it. Thus, the first support portion 121a is arranged.

  Originally, the first support portion 121a and the first portion 131a limit the displacement of the free end of the load cell 10 beyond the limit, so the configuration of the second modification is reasonable.

(6-3) Third Modification However, it is difficult to provide the first portion 131a near the free end of the lower surface of the load cell 10 due to the configuration of the fixing member 12 when implementing the configuration as in the second modification. This is also the case. Therefore, it is also possible to dispose an inclusion between the first support part 121a and the first part 131a so that the first support part 121a indirectly supports the first part 131a.

  For example, FIG. 8 is a configuration diagram of the weighing device 100 that is simplified and modeled according to the third modification. In FIG. 8, the first portion 131 a provided near the free end of the lower surface of the load cell 10 has a bracket 135. One end (fixed end) is fixed. The other end (free end) of the bracket 135 extends in a direction away from the free end of the load cell 10. And the 1st support part 121a is arrange | positioned so that the predetermined location from the fixed end of the bracket 135 to a free end may be opposed.

  As a result, even if the first support portion 121a and the first portion 131a cannot be structurally opposed to each other, the first support portion 121a supports the first portion 131a by interposing the bracket 135. Can be secured.

(6-4) Fourth Modification Although the first embodiment has been described on the assumption that the force acting on the weighing hopper 28 is in the downward direction, the upward movement of the weighing hopper 28 due to incorrect handling by the operator is described. A force may act.

  The problem of the fourth modified example is that, in addition to the problem already described in the first embodiment, even when an upward force is applied to the weighing hopper 28, the free end of the load cell 10 is displaced above the limit. It is an object of the present invention to provide a weighing device that can limit the above.

  FIG. 9 is a configuration diagram of the weighing device 100 that is a simplified model according to the fourth modification. In FIG. 9, the fourth support portion 121d is disposed above the connecting member 14, and faces the first support portion 121a with the connecting member 14 interposed therebetween. And the 4th part 131d is set to the connection member 14 in the position which opposes the 4th support part 121d.

  Specific configurations of the fourth support portion 121d and the fourth portion 131d will be described with reference to FIG. In FIG. 2, the fourth support portion 121 d is set on the upper end surface of the opening 121, and the fourth portion 131 d is set on the head upper end surface of the first bolt 131.

  The gap between the fourth support portion 121d and the fourth portion 131d is changed by adjusting the screwing amount of the first bolt 131. At this time, the gap between the first support portion 121a and the first portion 131a is also simultaneously. Change. Therefore, the gap between the fourth support portion 121d and the fourth portion 131d is set while adjusting the gap between the first support portion 121a and the first portion 131a.

  In the weighing device according to the fourth modified example, even when the operator mistakenly handles the weighing hopper 28 or the connecting member 14 so as to push it upward, the fourth support portion 121d is set to the connecting member 14. Since the portion 131d is supported from above, it is limited that the free end of the load cell 10 is displaced upward beyond the limit.

Second Embodiment
(1) Configuration of Weighing Device 200 FIG. 10 is a perspective view of the weighing device 200 according to the second embodiment excluding the control unit 50. In FIG. 10, the weighing unit 60 of the weighing device 200 includes the load cell 10, the fixing member 12, and the connecting member 34. In addition, since the connection member 34 of the weighing device 200 has a configuration in which the connection member 14 of the weighing device 100 according to the first embodiment is changed, only the connection member 34 will be described in detail here, and the others are the first. The detailed description is omitted as it is the same as the embodiment.

(2) Detailed configuration (2-1) Connecting member 34
The connecting member 34 has a main body block 340, a first block 341, and a second block 342. The main body block 340 connects the free end of the load cell 10 and the weighing hopper 28.

  The first block 341 protrudes from the main body block 340 so as to penetrate the opening 121. The first block 341 has a screw hole 341 e that penetrates from the upper end side to the lower end side of the opening 121. The first bolt 131 is screwed into the screw hole 341e. The clearance between the upper surface of the head of the first bolt 131 and the upper end of the opening and the clearance between the tip of the first bolt 131 and the lower end of the opening are both set to predetermined dimensions.

  The second block 342 extends from the main body block 340 so that the tip portion thereof enters the slit 122. The distal end portion of the second block 342 has a screw hole 342e penetrating from the upper end side of the slit 122 toward the lower end side. The position of the second block 342 is adjusted so that the screw hole 342e and the upper end of the slit 122 face each other, and the second bolt 132 is inserted from above the screw hole 342e.

  In addition, the 1st part 131a is set in the front end surface of the 1st volt | bolt 131, and the 1st part 131a opposes the 1st support part 121a. A second portion 132b is set on the top surface of the head of the second bolt 132, and the second portion 132b faces the second support portion 122b. Further, a third portion 132 c is set on the front end surface of the second bolt 132, and the third portion 132 c faces the third support portion 122 c that is the lower surface of the slit 122.

(2-2) Overload protection mechanism In the weighing device 200, the mechanism for protecting the load cell 10 from overload is configured by the first support portion 121a, the second support portion 122b, and the third support portion 122c described above. A mechanism in which the first support portion 121a supports the first portion 131a functions as a first overload protection mechanism, and a mechanism in which the second support portion 122b supports the second portion 132b functions as a second overload protection mechanism.

  Furthermore, the mechanism in which the third support portion 122c supports the third portion 132c functions as an auxiliary mechanism for the first overload protection mechanism and the second overload protection mechanism.

  In the first overload protection mechanism, the first support portion 121a prevents the first portion 131a from being displaced beyond a predetermined value. In the second overload protection mechanism, the second support portion 122b prevents the second portion 132b from being displaced beyond a predetermined value. Further, the auxiliary mechanism suppresses an increase in the amount of displacement of the load cell 10 until the first portion 131a comes into contact with the first support portion 121a. The mechanism of each overload protection mechanism is included in the description of the operation.

(3) Operation FIG. 11 is a configuration diagram of the weighing device 200 according to the second embodiment that is simplified according to the lever principle. FIG. 12 is a graph showing the relationship between the load applied to the weighing hopper 28 and the output of the load cell 10.

(4-1) Mechanism of First Overload Protection Mechanism First, in FIG. 11, when a downward force is applied to the weighing hopper 28, the connecting member 34 is bent downward, and the first portion 131a is the first support portion 121a. Get closer to. However, the third portion 132c contacts the third support portion 122c (the auxiliary mechanism operates) before the first portion 131a contacts the first support portion 121a (the first overload protection mechanism operates). As described above, a gap between the third portion 132c and the third support portion 122c is set.

  Therefore, as shown in FIG. 12, the output from the load cell 10 increases rapidly until the point A where the third portion 132c abuts on the third support portion 122c, but the first portion 131a passes the point A. It rises relatively gently up to point B that contacts the first support portion 121a.

  After the first portion 131a and the first support portion 121a come into contact with each other, a bending moment is generated in the connecting member 34 with the first support portion 121a as a fulcrum, and the force that lifts the free end of the load cell 10 upward. Work.

  Therefore, as shown in FIG. 12, the output from the load cell 10 drops after passing the point B (because a force works in the opposite direction). Therefore, even when an abnormal force is applied to the weighing hopper 28 or the connecting member 34, the first support portion 121a supports the first portion 131a from below, so that the free end of the load cell 10 is displaced downward beyond the limit. That is limited.

(4-2) Mechanism of the second overload protection mechanism When the force acting on the weighing hopper 28 is further increased, the connecting portion between the free end of the load cell 10 and the connecting member 34 is displaced upward, so the second portion 132b is also It approaches the second support part 122b. Here, when a force that causes a bending moment to act on the coupling member 34 until the second portion 132b contacts the second support portion 122b, the second support portion 122b supports the second portion 132b from above, The upward displacement of the second portion 132b is prevented. That is, the second overload protection mechanism acts.

  Therefore, as shown in FIG. 12, the output from the load cell 10 is almost after the point C at which the second portion 132b abuts on the second support portion 122b (the second overload protection mechanism operates). It becomes constant.

  For reference, in FIG. 12, the output of the load cell 10 without the third portion 132c and the third support portion 122c is indicated by a dotted line. In FIG. 12, when there is no third portion 132c and the third support portion 122c, it rises to the point G on the extension line of the point A and almost the same output level as the point B, and descends after passing the point G. (Because the force works in the opposite direction)

  When there is the third portion 132c and the third support portion 122c, the output from the load cell 10 until the first portion 131a contacts the first support portion 121a after the third portion 132c contacts the third support portion 122c. However, it rises more slowly than when there is no. Therefore, the load load with which the first portion 131a contacts the first support portion 121a can be made larger than when there is no load. That is, it is possible to set a large gap between the first portion 131a and the first support portion 121a.

  The mechanism is that when a certain load (a load exceeding the weighing range of the weighing device) acts on the load cell 10, the third support portion 122c first hits the third portion 132c, and the connecting member 34 rotates with the third portion 132c as a fulcrum. Then, the first portion 131a hits the first support portion 121a, the connecting member 34 rotates with the first portion 131a as a fulcrum, the third support portion 122c is separated from the third portion 132c, and finally the second portion The principle is that 132b hits the second support portion 122b.

(5) Features For example, adjustment of the gap between the first portion 131a and the first support portion 121a requires adjustment with a very small distance and high accuracy. This is because it is necessary to adjust the clearance so that the first portion 131a does not contact the first support portion 121a and contacts before the displacement of the load cell 10 exceeds the limit when the load is within the measurement range. Because.

  However, because of the structure (waterproof structure or the like), the first portion 131a and the first support portion 121a may not be accessible or may be difficult to access due to the gap adjustment between the first portion 131a and the first support portion 121a. It is not easy to adjust the gap with the high accuracy.

  On the other hand, by providing the third part 132c and the third support part 122c at a position where the gap adjustment is easy, the gap adjustment between the first part 131a and the first support part 121a can be simplified or not adjusted. it can.

<Other embodiments>
(1) Overload protection mechanism that functions when operation is stopped FIG. 13 is a simplified configuration diagram of a weighing device 300 that includes an overload protection mechanism that functions when operation is stopped. In FIG. 13, the weighing device 300 is the same type of weighing device as the weighing device 100 according to the first embodiment, but the weighing device 100 according to the first embodiment is provided with a lock mechanism 125 that sandwiches the connecting member 14. And different.

  The lock mechanism 125 includes an upper lock member 125a positioned above the connecting member 14, a lower lock member 125b positioned below the connecting member 14, and a drive unit that retracts the upper lock member 125a and the lower lock member 125b during operation. (Not shown). The drive unit is appropriately selected from a motor, a solenoid, an air cylinder, and the like.

  The upper lock member 125a and the lower lock member 125b are always urged in the direction of the connection member 14 by a spring (not shown) so that the upper lock member 125a and the lower lock member 125b can move to a position where the connection member 14 is sandwiched. When the operation is stopped and the drive unit releases the retraction of the upper lock member 125a and the lower lock member 125b, the upper lock member 125a and the lower lock member 125b protrude to the lock position of the connecting member 14 by the spring.

  When the operation is stopped, for example, when an operator accidentally applies excessive force to the weighing hopper 28 or the connecting member 14 during maintenance, the upper lock member 125a and the lower lock member 125b restrain the operation of the connecting member 14. Therefore, a situation that damages the load cell 10 can be avoided.

(2) Other overload protection mechanism that functions when operation is stopped FIG. 14 is a simplified configuration diagram of a weighing device 400 that includes another overload protection mechanism that functions when operation is stopped. In FIG. 14, a weighing device 400 is the same type of weighing device as the weighing device 100 according to the first embodiment. However, the weighing device 400 according to the first embodiment is provided with a lock mechanism 127 that restrains the connecting member 14. 100.

  The lock mechanism 127 includes a through hole 127a that penetrates the connecting member 14, a lock member 127b into which the through hole 127a is inserted, and a drive unit (not shown) that retracts the lock member 127b from the through hole 127a during operation. . The drive unit is appropriately selected from a motor, a solenoid, an air cylinder, and the like.

  The lock member 127b is always urged in the direction of the connecting member 14 by a spring (not shown) so that the lock member 127b can move to a position where it enters the through hole 127a of the connecting member 14. When the operation is stopped and the drive unit releases the retraction of the lock member 127b, the lock member 127b enters the through hole 127a of the connecting member 14 by the spring and restrains the connecting member 14.

  When the operation is stopped, for example, when an operator mistakenly applies too much load to the weighing hopper 28 or the connecting member 14 during maintenance, the lock member 127b restrains the operation of the connecting member 14, so that the load cell 10 is It is possible to avoid a situation that causes damage.

  As described above, according to the present invention, the load cell of the weighing device can be protected from overload. Therefore, the present invention is useful not only for measuring devices but also for protecting devices that use the load cell.

DESCRIPTION OF SYMBOLS 10 Load cell 12 Fixing member 14 Connection member 28 Weighing hopper 100 Weighing apparatus 121a 1st support part (overload protection mechanism)
122b Second support (overload protection mechanism)
122c 3rd support part (overload protection mechanism)
121d 4th support part (upper opposed support part, overload protection mechanism)
131a 1st part (overload protection mechanism)
132b Second part (overload protection mechanism)
132c 3rd part (overload protection mechanism)
131d Fourth part (overload protection mechanism)
135 Bracket (predetermined member)

Japanese Utility Model Publication No. 5-28937

Claims (4)

A weighing device using a load cell,
A fixing member for fixing one end of the load cell;
A weighing hopper for placing an object to be weighed;
A connecting member that connects the weighing hopper and the free end of the load cell;
An overload protection mechanism for protecting the load cell from overload;
With
The overload protection mechanism has a first support part and a second support part provided on the fixing member,
When a first load is applied to the load cell, the first support portion supports the first portion set in either the load cell or the connecting member directly from below or via a predetermined member,
When a second load greater than the first load is applied to the load cell, the first support portion supports the first portion, and at the same time, the second support portion sandwiches the first support portion and the measurement On the side opposite to the hopper, the second part set on either the connecting member or the load cell is supported from above.
Weighing device. The second support portion is provided at a position farther from the first support portion than the free end of the load cell.
The weighing device according to claim 1. The second support part is provided at a position farther from the first support part than the fixed end of the load cell.
The weighing device according to claim 1. The overload protection mechanism further includes an upper opposing support portion that is located above the connection member and faces the first support portion with the connection member interposed therebetween.
The weighing device according to claim 1.

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