JPH028248B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a pressure-resistant explosion-proof wasan box that constitutes a multi-load cell weighing machine in combination with a pressure-resistant explosion-proof load cell. Conventional configuration and its problems Conventionally, there has been no pressure-resistant explosion-proof sum calculation box as described above, and the current situation is that a multi-load cell type weighing machine cannot be constructed in an explosive gas atmosphere. This means that four-corner error adjustment cannot be performed in a hazardous location simply by housing the four-corner error adjustment circuit in the same pressure-resistant container as the input/output cable connection terminal block. This is because the risk of explosion increases due to heat, sparks, etc. generated from the electrical components that make up the four-corner error adjustment circuit. First, the necessity of the terminal block and the four-corner error adjustment circuit will be explained with reference to FIGS. 1 to 3. Terminal block 1 connects the outputs of load cells LC ₁ to LC ₄ in parallel.
The four corner error adjustment circuit 2 composed of variable resistors VR ₁ to VR ₄ corrects differences in individual characteristics of the load cells LC ₁ to _{LC 4} . 3 is a casing. FIG. 2 shows a plan view of a platform scale in which the four corners of the platform 4 are supported by the load cells LC ₁ to _{LC 4} of FIG. 1. In such a platform scale, when a heavy object to be weighed with a weight of W [Kg] is placed on the central part () of the platform 4, a load of W/4 Kg acts on each load cell LC ₁ to LC ₄ . do. When the mounting position shifts to the position (), the load on load cells LC ₁ and LC ₄ is 1/2×l/4/l×W=W/8 The load on load cells LC ₂ and LC ₄ is , 1/2×3/4l/l×W=3/8W. Here, the internal resistances of each load cell LC ₁ to LC ₄ are all the same r as shown in Fig. 3, and the load -
If the output coefficients k are all the same, the sum output E is E = 1/4 (E ₁ + E ₂ + E ₃ + E ₄ ), so if it is placed in the center (), E ₁ = E ₂ = E ₃ = E ₄ = k・W/4 … Also, when placed in the position (), E ₁ = E ₃ = k・W/8, E ₂ = E ₄ = k・3/8W ∴E= 1/4 (1/8kW+3/8kW1/8kW+3/8
kW) = kW/4... and the first and second equations are the same. However, if the load-output coefficients are different, for example, the coefficient of load cell LC ₂ is 0.99 of load cell LC ₁ .
If it is double the size, then when it is placed in the center (), E=1/4 (k・W/4+k・W/4+K・W/4+1
/4×0.99k・W)=3.99/16・k・W… When placed in the position (), E=1/4(k・W/8+3/8×0.99・k・W+k・
W/8+3/8・k・W)=7.97/32・k・W... From the third and fourth equations, an error of 1/3200 kW occurs between () and (). Therefore, the variable resistors VR ₁ to _{VR 4} of the four-corner error adjustment circuit 2 are adjusted to adjust the voltage applied to each load cell LC ₁ to _{LC 4} individually to equalize the load-output coefficient, and to adjust the weight of the heavy object to be weighed. This is intended to compensate for errors in the summed output voltage E caused by the mounting position. As described above, the multi-load cell type weighing machine requires the four-corner error adjustment circuit 2, but simply making the casing 3 of a pressure-resistant and explosion-proof type does not ensure sufficient safety for the reasons mentioned above. Purpose of the Invention The present invention provides a pressure-resistant explosion-proof suma box that does not increase the level of danger due to the provision of a four-corner error adjustment circuit and is capable of adjusting four-corner errors even in an explosive atmosphere. The purpose is to Structure of the Invention The pressure-resistant explosion-proof wasan box of the present invention is configured such that a partition wall is provided to divide the inside of the pressure-resistant container into two chambers, a first and a second chamber, and these two chambers can be opened and closed using separate lid bodies. At the same time, the input/output cable connection terminal block disposed in the first chamber and the four corner error adjustment circuit disposed in the second chamber are electrically connected via a cable inserted into the pressure-resistant lead-in portion of the partition wall. The load cell circuit outside the pressure-resistant container and the terminal block are connected through a cable inserted into a pressure-resistant lead-in portion formed at a predetermined location on the wall of the first chamber excluding the partition wall and the lid of the first chamber. The degree of danger due to the provision of the four corner error adjustment circuit through electrical connection is reduced, and one end of the operating rotation shaft of the four corner error adjustment circuit is connected to the above-mentioned pressure-resistant It is extended to the outside of the container, and the gap and the depth of the gap between the operating rotating shaft and the shaft hole are set to satisfy explosion-proof function, so that the four-corner error can be adjusted in a energized state even in a hazardous location. It is characterized by DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 4 to 6. Reference numeral 5 denotes a casing body, which has a partition wall 6 in the center and divides the inside into a first chamber 7 and a second chamber 8.
Reference numerals 9 and 10 are first and second lids that close the upper openings of the first chamber 7 and the second chamber 8, respectively; bolts 11,
12 to the casing body 5. Reference numeral 13 denotes an O-ring installed in an annular groove 14 formed on the outer periphery of the upper opening of the second chamber 8 to ensure tight airtightness between the casing body 5 and the second lid 10. 15, 16, and 17 are terminal blocks disposed in the first chamber, and 18 is a four-corner error adjustment circuit disposed in the second chamber. Reference numeral 19 denotes a push-fit fitting that is installed through the partition wall 6, and the terminal block 15,
A cable 20 is inserted between a predetermined one of the four corners 16 and 17 and the four corner error adjustment circuit 18, and an epoxy resin is filled between the cable 20 and the push-in fitting 19 for pressure-resistant fixation. 21
26 are cable lead-in portions formed on the side walls 27 and 28 of the first chamber 7, and input/output cables 29 are connected to predetermined ones of the terminal blocks 15, 16, and 17.
is drawn into the first chamber 7 through this, and communication between the first chamber 7 and the outside 31 is cut off at the cable lead-in portions 21 to 26 by rubber packings 30. Unnecessary cable lead-in portions 21 to 26 are appropriately closed off with plugs 32. Further, as shown in FIG. 6, the terminal block 15,
16 and 17, the terminal block 16 located in the center is installed lower than the terminal blocks 15 and 17 on both sides,
Correspondingly, the cable lead-in portions 21, 22, 2
Cable lead-in part 2 of 3, 24, 25, 26
1, 23, 24, 26 are cable lead-in parts 22, 2
5, and is designed to make it easier for the input/output cables drawn in from the cable lead-in sections 22 and 25 to pass under the terminal blocks 15 and 17 on the front side and connect to the terminal block 16 in the center. ing. Furthermore, as shown in FIG.
One end of the operation rotation shaft 33 of the variable resistor No. 8 (corresponding to VR ₁ to VR ₄ in FIG. 1) is connected to the shaft hole 3 of the second lid body 10.
4 and extends to the outside 31. Here, the gap α and the gap depth L between the operating rotation shaft 33 and the shaft hole 34 are set so as to satisfy the explosion-proof function. In other words, Technical Guidelines of the Institute of Industrial Safety [Report of the Institute of Industrial Safety, RIIS-TR-79-1 1978
They are specified as shown in Table 1 below based on "3231 Joint Surface" published by the Ministry of Labor, Industrial Safety Research Institute, published on November 15th.

[Table] In this way, the four corner error adjustment circuits 18 are not simply added to the terminal blocks 15, 16, 17, but the first chamber 7 that houses the terminal blocks 15, 16, 17 has four corner error adjustment circuits 18. Since it is housed in a separate second chamber 8, it is possible to prevent an increase in the degree of risk caused by the provision of the four corner error adjustment circuit 18. Further, since the rotary operation shaft 33 of the four-corner error adjustment circuit 18 protrudes from the second lid 10, the four-corner error adjustment can be performed in a energized state even in a dangerous location. Effects of the Invention As explained above, the pressure-resistant explosion-proof wasan box of the present invention divides the inside of the pressure-resistant container into two chambers, a first and a second chamber, by providing a partition wall, and each of these two chambers is provided with a separate lid body. The terminal block for connecting input/output cables disposed in the first chamber and the four corner error adjustment circuit disposed in the second chamber are connected to a cable inserted into the pressure-resistant type lead-in portion of the bulkhead. The load cell circuit outside the pressure-resistant container and the terminal block are electrically connected through a pressure-resistant lead-in portion formed at a predetermined location on the wall of the first chamber excluding the partition wall and the lid of the first chamber. Since the input/output cable connection terminal block and the four-corner error adjustment circuit are electrically connected via a cable and housed in separate rooms, it is possible to reduce the risk of providing the four-corner error adjustment circuit, which is likely to cause an explosion. Moreover, since the inside of the container is divided into two chambers by the partition wall, the shape is compact. Furthermore, one end of the operating rotation shaft of the four-corner error adjustment circuit is extended to the outside of the pressure vessel through a shaft hole drilled in the lid of the second chamber, and a gap is formed between the operation rotation shaft and the shaft hole. Since the width and the gap depth are set to satisfy the explosion-proof function, the four-corner error adjustment can be carried out in a energized state even in a hazardous location, and the adjustment can be completed in a short time.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the load conversion section of a multi-load cell type weighing machine, Fig. 2 is an explanatory diagram of four corner error adjustment, Fig. 3 is an equivalent circuit diagram of Fig. 1, and Figs. 4 to 6 are the invention of the present invention. FIG. 4 is a longitudinal cross-sectional view of a pressure-resistant explosion-proof wasan box of the present invention, and FIG.
A' arrow view, FIG. 6 is a sectional view of the main part of FIG. 5. LC ₁ to LC ₄ ... Load cell, 5 ... Casing body, 6 ... Partition wall, 7 ... First chamber, 8 ... Second
Chamber, 9...First lid, 10...Second lid, 1
1, 12... Bolt, 15, 16, 17... Terminal block, 18... Four corner error adjustment circuit, 19... Push-in fitting, 20... Cable, 21-26... Cable lead-in part, 33... Operation rotation Shaft, 34...shaft hole,
α...Like, L...Depth of like.

Claims (1)

[Claims] 1 A partition wall is provided to divide the inside of the pressure vessel into two chambers, a first and a second chamber, and each of these two chambers is configured to be opened and closed by a separate lid, and the input/output cables installed in the first chamber are The connection terminal block and the four corner error adjustment circuit arranged in the second chamber are electrically connected via a cable inserted through the pressure-resistant lead-in part of the partition wall, and the load cell circuit outside the pressure-resistant container and the terminal block are electrically connected. and,
Electrical connection is made via a cable inserted through a pressure-resistant lead-in portion formed at a predetermined location on the wall of the first chamber excluding the partition wall and the lid of the first chamber, and further connected to one end of the operating rotation shaft of the four corner error adjustment circuit. is extended to the outside of the pressure vessel through a shaft hole drilled in the lid of the second chamber, and the gap and the depth of the gap between the operating rotation shaft and the shaft hole are adjusted to satisfy an explosion-proof function. A pressure-resistant explosion-proof wasan box.