JPS6322529B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a weight measuring device, and in particular, when there is a difference in the weight of two objects to be measured applied to both ends of a balance,
The present invention relates to a weight measuring device that can measure the weight of one object to be measured when a balance becomes unbalanced. For example, powder and granules such as cement, sugar, and salt;
A liquid such as oil or drinking water is first supplied to one of two containers arranged side by side, and when the weight of one container reaches a certain value, the cement, etc. is supplied to the other container. Then, when the weight of the other container reaches a certain value, the empty container is replaced with the container that reached a certain weight during feeding to the other container. A weight suitable for use in a metering and feeding device, etc. that continuously supplies cement, etc. to a large number of containers, such as bags, without stopping the flow by repeating the same operation as re-supplying the cement, etc. It is an object of the present invention to provide a weight measuring device that is highly sensitive and highly accurate. Conventionally, powder and granular materials such as cement have been supplied to a container using a supply device as shown in FIG. This feeding device consists of two scales 1A and 1B.
are arranged adjacently on one base 2 so that the weights W _A and W _B of the two containers 3A and 3B can be measured at the same time, and a discharge pipe 4 for discharging cement etc. without interruption is installed. It is provided with a switching mechanism 5 that reciprocates the discharge end in the horizontal direction to switch the supply destination of cement or the like. This switching mechanism 5 includes a drive section 7 which operates to pull the discharge end of the discharge pipe 4 toward the container 3B side by a plunger 6 in response to an output from a control circuit (not shown), and a drive section 7 which operates to pull the discharge end of the discharge pipe 4 toward the container 3B side by means of a plunger 6. The drive unit 7 and the spring 8 are arranged opposite to each other with the discharge pipe 4 in between. Reference numeral 9 denotes a wire connected between the tip of the plunger 6 of the drive unit 7 and the tip of the spring 8, and a fitting ring portion 10 into which the discharge end of the discharge pipe 4 is fitted is provided in the middle of the wire. There is. This wire 9 transmits the force from the drive part 7 and the spring 8 to the discharge end of the discharge pipe 4. Reference numeral 11 denotes a guide device which receives cement etc. discharged from the discharge pipe 4 at the upper socket 12 and guides the cement etc. to containers 3A and 3B through bifurcated branch guide pipes 13A and 13B. be. The supply of cement or the like to the container by this supply device is carried out as follows. That is, this supply device is configured such that the drive unit 7 does not pull the end of the discharge pipe 4 when the weight W _A of the container 3A does not reach a predetermined value W _S ; The end of the container 4 is positioned closer to the container 3A by the contraction force of the spring 8. As a result, the cement etc. discharged from the discharge pipe 4 are supplied into the container 3A through the branch guide pipe 13A of the guide tool 11.
Then, when the weight _WA of the container 3A reaches a predetermined value W _S , a signal is transmitted from the weight scale 1A to the control circuit, and the drive section 7 is operated by the control circuit. Then, the end of the discharge pipe 4 is connected to the spring 8
is moved to the container 3B side against the contraction force of
Cement and the like discharged from the discharge pipe 4 are supplied into the container 3B via the branch guide pipe 13B. At this time, the container 3A is removed from the weighing scale 1A and the empty container 3A is placed on the weighing scale 1A. And weight scale 1
When the weight W _B of the container 3B on B reaches a predetermined value W _S , a signal is transmitted from the weight scale 1 B, and as a result, the control circuit stops outputting the signal that was operating the drive unit 7 . is in a state where the end of the discharge pipe 4 is not pulled. Therefore, the end of the discharge pipe 4 is moved toward the container 3A by the contracting force of the spring 8, returning to the state shown in FIG. After that, this kind of thing is repeated. In this manner, the supply device shown in FIG. 1 allows a constant weight of cement, etc. to be supplied to the container without stopping the flow. However, such a dispensing device requires two scales to measure the weight of the two containers. Therefore, there was a problem that the structure of the device became complicated and the cost of the device became extremely high. The present invention was made in view of the above-mentioned problems.
For example, it is ideal for a feeding device that performs a continuous feeding operation, such as feeding powder, granular material, liquid, etc. into one of two containers and then feeding it into the other container when it reaches a predetermined weight. It is an object of the present invention to provide a weight measuring device which has a simple structure, is inexpensive, has high sensitivity, and can significantly improve weight measurement accuracy without deteriorating accuracy. The present invention will be described in detail below with reference to embodiments shown in the accompanying drawings. FIG. 2 is a front view schematically showing the structure of a feeding device using an embodiment of the present invention as a weight measuring device. The cross-sectional shape of the balance is, for example, rectangular (the cross-sectional shape of the balance does not necessarily have to be rectangular, but may be any cross-sectional shape that allows strain to occur due to a bending moment). 14
A and 14B are hook-shaped engagement pieces formed on the lower side surfaces of both ends of the balance 14. Reference numeral 15 denotes a rotating shaft at the center of the balance 14, and the balance 14 is supported so as to be rotatable about the rotating shaft 15 as a fulcrum. 1
Stoppers 6A and 16B are respectively provided at right and left positions appropriately spaced upward from both ends of the balance 14 when it is oriented in the horizontal direction. Therefore, when the balance 14 is tilted from the horizontal direction in a certain rotating direction due to an unbalance of the gravity applied to both ends, the upper surface of the end of the balance 14 to which the smaller gravity is applied is pressed against the corresponding stopper 16A or 16B. The stopper 16A or 16B prevents the balance 14 from tilting any further. A bending moment M acts on the balance 14 due to the larger gravity, and this bending moment causes strain. SGa to SGd are four strain gauges that measure the strain generated in the balance 14. SGa and SGb form a pair, and SGa is attached to the upper surface of the balance 14 at a distance _l0 from the rotating shaft 15 to one end side (for example, the left side in FIG. 2), and SGb
is the position A corresponding to SGa on the bottom surface of the balance 14, i.e.
It is attached on the same vertical line as SGa. Also,
SGc and SGd form a pair, and the rotation axis 15 of the balance 14
to the other end side (for example, the right side in Figure 2)
It is attached to the upper and lower surfaces of position B on the same vertical line, which is spaced apart from the above distance _l0 . Furthermore, l ₁ is the balance 14
The distance between the position A where the strain gauges SGa and SGb of the balance 14 are attached and the position of the hook-like engagement piece 14A where gravity is applied, which will be described later, is the distance l ₂ is the distance between the position B where the strain gauges SGc and SGd of the balance 14 are attached. piece, 1
This is the distance from 4B to the position where gravity is applied, which will be described later. For example, a bridge circuit as shown in FIG. 3 is formed by the resistors Ra to Rd made up of the four strain gauges SGa to SGd. Ep is the bridge power supply applied to the bridge circuit, and e ₀ is the output voltage of the bridge circuit. 4 is a discharge pipe for discharging cement, etc.; 5 is a switching mechanism that reciprocates the discharge end of the discharge pipe 4 to switch the supply destination of cement, etc.; It consists of a wire 9 having a fitting end 10 into which the discharge end of the tube 4 is fitted. 11 receives the cement etc. discharged from the discharge pipe 4 at the socket 12 and transfers it to the container 3A or 3 through the branch guide pipes 13A and 13B.
This is a guide to guide you to B. The functions of the switching mechanism 5 and the guide tool 11 are the same as those used in the feeding device shown in FIG. 1, so a description thereof will be omitted. Reference numerals 17 and 17 are small-diameter suspension shafts, the upper ends of which are bent into a U-shape, and the U-shaped portions 17a, 17a.
The upper end is bent downward so that it can come into contact with the upper surfaces of the engaging pieces 14A, 14B at both ends of the balance 14. Containers 3A and 3B are suspended from the lower ends of the suspension shafts 17 and 17, respectively. 18, 18 are spring supports fixed to the measuring device body; 19;
19 is a coil spring supported on the upper surface of the spring supports 18, 18; 20, 20 are connecting plates fixed to the upper ends of the coil springs 19, 19; 17 intermediate parts are connected. Therefore, from the weights W _A and W _B of containers 3A and 3B, spring 19
The weights W _A ′ and W _B ′ (that is, W _A −T,
and W _B −T) will act on both ends of the balance 14. The principle of the weight measuring device shown in FIG. 2 will be explained below. When the weights W _A and W _B of the containers 3A and 3B are both smaller than the reaction force T of the springs 19, 19, gravity naturally does not act on both ends of the balance 14. However, the weight of containers 3A and 3B
One or both of W _A and W _B is spring 1
9 and 19, and for example, if the weight W _A of the container 3A is the weight W _B of the container 3B.
If the force of the spring 19 is heavier than that of the spring 19 and acts in a direction opposed to gravity, the left end of the balance 14 in FIG. 2 will naturally fall.
The right end is tilted upward, and the right end comes into contact with the stopper 16B. Then, the balance 14 is prevented from tilting further by the stopper 16B. As a result, a bending moment M is generated in the balance 14 due to the weight W _{A ' which} is reduced by the spring force of the spring 19 from the weight W A of the heavier container 3A. Strain is generated by this bending moment M, and the strain is detected by four strain gauges SGa to SGd.
The bridge circuit shown in Fig. 3 produces an output voltage e ₀ whose magnitude is proportional to the magnitude of its bending moment M.
is obtained. Therefore, strain gauge SGa~
Using SGd, the weight W _{A '} of the heavier container 3A can be measured by subtracting the reaction force T from the weight W _A of the heavier container 3A.
To explain the relationship between the weight W _A ' and the bending moment M in more detail, the bending moment M generated in the balance 14 is the bending moment M _A at point A and B
It is the sum of the bending moment M _B at the point, and the bending moments M _A and M _B are each expressed by the following formulas. M _A = W _A ′・l ₁ M _B = M _A ′・l ₂ +l ₀ /l ₁ +l ₀・l _2And since l ₁ and l ₂ +l ₀ /l ₁ +l ₀・l ₂ are constant values, , M, that is, M _A + M _B is proportional to the weight W _A ′, and
Since M _A + M _B and the output voltage e ₀ of the bridge circuit are proportional to each other, the weight W _A ′ and the output voltage of the bridge circuit are
It is proportional to e ₀ and the weight W _A ′ can be extended to measure the true weight W _A of the container 3A. Also, conversely, the weight W _B of container 3B is greater than that of container 3A.
If the weight W is larger than _A , the output voltage _e of the bridge circuit and the container 3B are determined by the same principle as described above.
Since the weight W _B of the container 3B is proportional to the weight W B of the container 3B, the weight W _B of the container 3B can be measured. In the embodiment shown in FIG. 2, each pair of strain gauges SGa, SGb and SGc, SGd is provided at a position spaced apart from the rotating shaft 15 at the center of the balance 14 toward the end. As shown in FIG. 5, which is a plan view of the apparatus, the distance l ₀ between the strain gauges SGa, SGb, SGc, and SGd and the rotating shaft 15 may be set to 0. Furthermore, in order to obtain a large strain output, four of these strain gauges are attached to the surface of the balance to form a bridge, but for example, it is also possible to attach only two strain gauges to the top of the balance, or even to the center of the balance. Just one piece may be attached to either the upper surface or the lower surface. FIG. 4 is a control circuit diagram for controlling the drive section 7 of the supply device shown in FIG. 2. In the same figure,
AMP is the output voltage of the bridge circuit shown in Figure 3.
The amplifier that amplifies e ₀ , COM, is a comparator that compares the output voltage V _AMP of the amplifier AMP with a reference voltage V _S of a magnitude corresponding to the reference weight W _S applied from the reference voltage generation circuit E _S. The output voltage V _COM of this comparator COM is "L" (low level) when the output voltage V _AMP of the amplifier AMP is smaller than the reference voltage V _S.
Then, when the voltage V _AMP exceeds the reference voltage _VS , it becomes "H" (high level). NAND1 to NAND4 are NAND circuits,
NAND1 and 2 constitute a gate circuit,
NANDs 3 and 4 constitute a flip-flop FF. The output Q of the flip-flop FF is used to control the drive section 7, and when the output Q is "H", the plunger 6 is moved to the right in FIG. 2 by electromagnetic force. LSA and LSB are limit switches for detecting the inclination of the balance 14, respectively, and LSA is a limit switch for detecting the inclination of the balance 14, and the end of the balance 14 to which the weight W _B ' due to the container 3B is applied, that is, the right end in FIG. 2, rises and contacts the stopper 16B. On the other hand, the LSB is turned on when the end of the balance 14 on which the container 3A is suspended, that is, the left end in FIG. 2, rises and comes into contact with the stopper 16A. Then, the “H” level voltage is applied to the input terminal of the NAND circuit NAND1 through the limit switch LSA, and the “H” level voltage is applied to the input terminal of the NAND circuit NAND1 through the limit switch LSB.
level voltage is applied to one input terminal of the NAND circuit NAND2, and the output voltage of the comparator COM is applied to the other input terminal of the NAND circuits NAND1 and 2.
V _COM is applied. The output voltage V _NAND1 of this NAND circuit NAND1 is connected to the set terminal SS of the flip-flop FF, and the output voltage V NAND1 of the NAND circuit NAND2 is connected to the set terminal SS of the flip-flop FF.
V _NAND2 is the flip-flop FF reset terminal R
and when the output voltage V _NAND1 or V _NAND2 is “L”, the flip-flop FF
is set or reset. FIG. 6 is a time chart of this control circuit, and the operation of the control circuit will be explained below with reference to this diagram. The initial state of the control circuit flip-flop FF is set to a reset state. Therefore, the output Q of the flip-flop FF is at the initial point
At _t0 , the state is "L", the drive unit 7 is in a non-operating state, and the end of the discharge pipe 4 is positioned on the container 3A side by the contraction force of the spring 8. As a result, cement and the like are first supplied to the container 3A, and its weight W _A gradually increases, and therefore W _A ' also increases, and accordingly, the output V _AMP of the amplifier AMP gradually increases. By the way, since only W _A ′ becomes heavier, an imbalance occurs between the weight W _A ′ and the weight W _B ′, and the balance 14 tilts accordingly, causing the right end of the balance 14 in FIG. 2 to stop. 16B
comes into contact with. Limit switch LSA at that time t ₁
turns on, and one input of the NAND circuit NAND1 becomes "H". After that, the weight W _A ′ continues to increase, and the output voltage V _AMP of the amplifier AMP also continues to increase accordingly. Then, when the weight W _A reaches the set reference value W _S and as a result, W _A ′ reaches the reference value W _S , the output voltage V _AMP of the amplifier AMP increases accordingly.
also reaches the reference voltage V _S at the time t ₂ when the comparator
COM's output voltage V _COM changes from "L" to "H". Then, since the two inputs of the NAND circuit NAND1 are both "H", the output voltage V _NAND1 changes from "H" to "L".
Flip-flop FF is inverted to the set state and its output Q becomes "H". As a result, the drive part 7 is actuated, whereby the end of the discharge pipe 4 is moved into the container 3B.
Forced to move to the side. Then, from now on, the weight of container 3B is W _B , and
W _B ′ begins to increase. On the other hand, the container 3A is removed from the balance 14 because its weight W _A has reached the reference value W _S (this time is designated as t ₃ ). the result,
The output voltage V _AMP of the amplifier AMP rapidly decreases, and the output voltage V _COM of the comparator COM is inverted from "H" to "L". Also, from the balance 14 to the container 3A
As a result, the direction of the balance 14 returns to approximately horizontal, and the right end of the balance 14 reaches the stopper 16B.
, the limit switch LSA returns to the off state. When the weight W _B ' of the container 3B reaches a certain level, the balance 14 tilts in the opposite direction, and the left end of the balance 14 comes into contact with the corresponding stopper 16A. As a result, the limit switch LSB turns on and the NAND circuit turns on.
One input of NAND2 becomes "H" (this time is called _t4 ). And from the amplifier AMP, the weight
An output voltage V _AMP of a magnitude corresponding to W _B ′ is generated.
In addition, at an appropriate time, the suspension support shaft 1 on the left end side of the balance 14
7, it is necessary to suspend the empty container 3A.
At time _t5 when the output voltage _VAMP reaches the reference voltage _Vs , the output voltage _VCOM of the comparator COM changes from "L" to "H". Then, this time the NAND circuit NAND2
A state is realized in which both of the two inputs are "H", the flip-flop FF is reset, and its output Q becomes "L". Then, plunger 6
loses its electromagnetic attraction, so the contracting force of the spring 8 causes the end of the discharge pipe 4 to close to the empty container 3A.
The container 3 is moved to the side and returned to the state shown in FIG.
Cement etc. are supplied to A. Thereafter, the above-described operation is repeated. As mentioned above, with such a feeding device, an extremely efficient content feeding operation is realized in which cement, grain, etc. can be continuously fed into a large number of containers one after another without stopping the flow. Ru.
In addition, since one weighing device is used to always measure the weight of the heavier container, there is no need to provide two weighing scales as in the feeding device shown in Figure 1. is simplified, and manufacturing costs can be significantly reduced. Moreover, since one weight measuring device measures the weight of two objects, there is no problem with differences in accuracy, temperature effects, etc. of each measuring device, which would be a problem when using two weight measuring devices. There is no need for initial unbalance adjustment of the weight measuring device and other adjustment operations, and the same measurement result is always obtained no matter which side of the balance the measurement is performed on. As described above, in the weight measuring device of the present invention, one or more strain gauges are attached to the balance, which is supported so as to be rotatable about the central part, and two objects to be measured are attached to the balance. A stopper is provided to reduce the weight by a certain amount and apply it to both ends of the balance, and to prevent the balance from tilting more than a certain angle from a horizontal angle in one rotation direction and in the opposite rotation direction. Become. Therefore, if the weights of the two objects to be measured are unbalanced, the balance will tilt, and the stopper will keep the tilt at a constant angle. Then, for example, the balance receives a bending moment from the heavier object and causes strain, so by detecting that strain with a strain gauge, the weight of the heavier object can always be measured. can do. Therefore, it is ideal for use in a feeding device that performs an alternating operation of feeding cement, etc. into one of two containers and then feeding it into the other container when a predetermined weight is reached, and it has a simple structure and is easy to manufacture. It is also possible to provide a weight measuring device that is inexpensive. In addition, since the weight of the object to be measured is reduced by a certain amount and applied to both ends of the balance using the so-called end weight method, the measurement sensitivity, measurement accuracy, and other performances of the weight measuring device can be significantly improved. Incidentally, a table comparing each characteristic between the case where the fractional amount method is not used (conventional method) and the case where the fractional amount method is used is shown below. In addition, when using the fractional amount method, the fractional amount coefficient K (K=W _A (W _B )/W _A ′(W _B ′)
) is 30.

[Table] Total accuracy at=√ ₁ ² + ₂ ² + ₃ ² + ₄ ² +
a ₅ ² + a ₆ ² + a ₇ ² . As is clear from the above table, the characteristics of the strain gauge section and the characteristics of the amplifier can be significantly improved by using the fractional method.
A weight measuring device with very good performance can be obtained even by simply attaching a commercially available, inexpensive gauge to a balance and simply coating it (waterproofing it). For example, according to a simple coating, if the strain gauges SG are connected in parallel to each other in a bridge, the equivalent insulation resistance will drop to about 50MΩ instead of ∞, resulting in a strain of 7×10 ^-6 For example, if the rated output is 4000 x 10 ^-6 strain, the effect of the reduction in insulation in the bridge cannot be ignored, as the figure of 0.175% FS shows. However, if the fractional amount method is used as in the present invention, the effect can be reduced to 1/K, that is, 0.0058% FS according to the numerical example described above, and an error of this degree does not become a problem. It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made. for example,
Although we have shown an example in which the force of a spring is used so that a gravitational force that is a certain amount smaller than the weight of the object to be measured is applied to both ends of the balance, a weight may also be used as shown in FIG. 7. That is, in Figure 7, 2
1 and 22 are weights, whose weight W _O is _the lever 22,
It acts on the hanging support shafts 17, 17 via 22. The levers 22, 22 have one end connected to the intermediate part of the hanging support shafts 17, 17, and the other end have a weight 21,
21 is suspended, and levers 22, 22
An intermediate portion of the fulcrum is rotatably supported by fulcrums 23, 23. l ₃ is the distance between the fulcrum 23 and the end where the weight 21 is suspended, l ₄ is the distance between the fulcrum 23 and the suspension shaft 17
is the distance between the ends connected to the In this example, W (W _A or W _B ) <
When W _O ·l ₃ /l ₄ , the upper end of the hanging support shaft 17 does not come into contact with the engaging portion 14a of the balance 14 . Then, when W (W _A or W _B )>W _O・l ₃ /l ₄ , the weight W′ of the magnitude W (W _A or W _B )−W _O・l ₃ /l ₄ is at the end of the balance 14. join. In each of the above embodiments, an example was shown in which the weight of the heavier container was always measured.
If two stoppers are placed below the balance rather than above, so that the end of the balance on which the heavier container is suspended comes into contact with the stopper, the balance will receive the bending moment caused by the lighter container. You can do it like this. Therefore, by detecting the strain on the balance, the weight of the lighter container can be measured. Further, in the above-described embodiments, a configuration example was shown in which containers containing objects to be measured were suspended from both ends of the balance, but the containers may be placed above both ends of the balance. In this case, in order to avoid overturning the container and measurement errors due to eccentric loads, it is preferable to use a so-called Roberval parallel motion mechanism. It should be noted that what is shown in the drawings is merely one embodiment and one application example of the present invention, and the present invention can be implemented in various forms and applied to various things.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a conventional example, FIGS. 2 to 7 are diagrams for explaining an embodiment of the present invention, and FIG. 2 is a diagram of a feeding device using the weight measuring device of the present invention. 3 is a circuit diagram of a bridge circuit composed of strain gauges, FIG. 4 is a circuit diagram of a control circuit, FIG. 5 is a plan view of a modified example of the present invention, and FIG. The figure is a time chart showing the operation of the control circuit, and FIG. 7 is a front view schematically showing the configuration of another embodiment of the present invention. 3A, 3B...Container of the object to be measured, 4...Discharge pipe, 5...Switching mechanism, 6...Plunger, 7...
...Drive unit, 8...Spring, 9...Wire,
11... Guide tool, 12... Socket, 13A, 13B
... Branch guide pipe, 14 ... Balance, 14A, 14B
...Engagement piece, 15... Rotating shaft, 16A, 16B...
...Stopper, 17, 17... Hanging support shaft, 17a, 1
7a... U-shaped portion, 18, 18... Spring support body, 19, 19... Coil spring, 20,
20... Connection plate, 21, 21... Weight, 22, 22
...Lever, 23, 23...Fulcrum, SGa~SGd...
Strain gauge, AMP...amplifier, COM...
Comparator, NAND1 to NAND4...NAND circuit,
FF...Flip Flop.

Claims (1)

[Claims] 1 One or more strain gauges are attached to a balance that is rotatably supported around the central part, and the weight of two objects to be measured is reduced by a certain amount and applied to both ends of the balance. None, on the other hand, a stopper is provided to prevent the balance from being tilted by more than a certain angle from a horizontal angle in one rotation direction and in the opposite rotation direction, and the balance is prevented from being tilted by an unbalanced weight of the two objects to be measured. When the tilted balance comes into contact with one of the stoppers and is prevented from tilting any further, the strain produced in the balance due to the load of the heavier or lighter object to be measured is detected by the strain gauge. 1. A weight measuring device characterized in that it is configured to always measure the weight of a heavier or lighter object.