JPH028181Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to a pressure-resistant explosion-proof wasan box that is combined with a pressure-resistant explosion-proof load cell to constitute a multi-load cell weighing machine. 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 is because if the input/output cable connection terminal block and the four-corner error adjustment circuit are simply housed in the same pressure-resistant container, there is a high risk of explosion due to heat, sparks, etc. generated from the electrical components that make up the four-corner error adjustment circuit. It's for a reason. 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 an object to be weighed with a weight of W [Kg] is placed in the center of the platform 4, each load cell LC ₁ to _{LC 4} receives (4/
W) A load of Kg is applied. When the mounting position shifts to the position, the load on the load cells LC ₁ to LC ₃ is 1/2×l/4/l×W=W/8 The load on the 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 summed 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 at the position, E ₁ =E ₃ =k・W/8, E ₂ =E ₄ =k・3/8W ∴E=1/4( 1/8kW+3/8KW+1/8kW+3/8
kW) = kW/4... and the first and second equations are the same. However, if the load-output coefficients are different, for example, if the coefficient of load cell LC ₂ is 0.99 times the coefficient of load cell LC ₁ , then when it is placed in the center, E = 1/4 (k・W/ 4+k・W/4+k・W/4+
1/4 × 0.99kW) = 3.99/16・k・W … When placed at 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, 1/3200k・
An error occurs by W. 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 placement 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 purpose of the invention is to provide a pressure-resistant explosion-proof wasan box that can be used even in an explosive atmosphere without increasing the level of danger due to the provision of a four-corner error adjustment circuit. Composition of the invention The flameproof explosion-proof wasan box of the invention has a terminal block for connecting input/output cables arranged inside the first pressure-resistant container, and a terminal block for connecting the input/output cables.
A four-corner error adjustment circuit is installed inside the pressure-resistant container, and the first
A third pressure container is interposed between the pressure container and the second pressure container, and the terminal block and the four corner error adjustment circuit are connected from the first pressure container through the third pressure container to the second pressure container.
electrically connected by a cable to the pressure vessel,
The load cell circuit outside the first pressure-resistant container and the terminal block are electrically connected via a cable inserted into a pressure-resistant lead-in portion formed in the first pressure-resistant container, thereby providing a four-corner error adjustment circuit that is likely to cause an explosion. It is characterized by being housed in a separate room from the terminal block to reduce the risk of accidents. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on FIGS. 4 to 6. 4 and 5 show an embodiment of the present invention. 5
1 is a first pressure-resistant container, in which a terminal block 6 is attached, and pressure-resistant lead-in portions 7 to 12 for inputting and outputting cables are formed on the outer wall. Reference numeral 13 denotes a second pressure-resistant container, inside which a four-corner error adjustment circuit 14 is attached. Reference numeral 15 denotes an electric conduit serving as a third pressure-resistant container, and the ends thereof are screwed into the connecting portions 16 of the first and second pressure-resistant containers 5 and 13 via connecting fittings 17 and 18. A cable 19 electrically connects the terminal block 6 and the four corner error adjustment circuit 14, and is extended from the first pressure container 5 through the conduit 15 to the second pressure container 13. Reference numerals 20 and 21 are pressure-resistant packings that maintain the pressure resistance between the first pressure-resistant container 5 and the electric conduit 15, and between the second pressure-resistant container 13 and the electric conduit 15. In this way, the four-corner error adjustment circuit 14 is not simply added to the terminal block 6, but the four-even error adjustment circuit 1
4 is housed in the second pressure vessel 13 that is separate from the first pressure vessel 5 that accommodates the terminal block 6, it is possible to prevent an increase in the degree of risk due to the provision of the four corner error adjustment circuit 14. FIG. 6 shows another embodiment. In FIG. 6, the variable resistors of the four corner error adjustment circuit 18 [VR 1 to VR ₁ in FIG.
One end of the operating rotation shaft 22 (equivalent to VR ₄ ) extends to the outside 25 through a shaft hole 24 formed in the lid 23 of the second pressure-resistant container 13. Here, the gap α and the gap depth L between the operating rotating shaft 22 and the shaft hole 24 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-November 1978]
Published on the 15th, author Ministry of Labor Industrial Safety Research Institute] “3231
The bonding surface is specified as shown in Table 1 below.

[Table] In this way, when the rotary operation shaft 22 is extended to the outside 25 so as to satisfy the explosion-proof function, the four-corner error adjustment can be performed in a energized state even in a hazardous location. Effects of the Invention As explained above, the flameproof explosion-proof sum calculation box of the present invention has a terminal block for connecting an input/output cable in the first pressure-proof container, and a four-corner error adjustment circuit in the second pressure-proof container. A third pressure-resistant container is interposed between the first pressure-resistant container and the second pressure-resistant container, and the terminal block and the four corner error adjustment circuit are moved from the first pressure-resistant container to the third pressure-resistant container. electrically connected to the load cell circuit outside the first pressure-resistant container and the terminal block by a cable that reaches the second pressure-resistant container via The terminal block for connecting input/output cables and the four-corner error adjustment circuit were housed in separate rooms, making electrical connection via the
By providing a four-corner error adjustment circuit that is likely to cause an explosion, it is possible to prevent the risk from increasing.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the load conversion section of a multi-load cell type weighing machine, Figure 2 is an explanatory diagram of four corner error adjustment, Figure 3 is an equivalent circuit diagram of Figure 1, and Figures 4 to 6 are the invention of the present invention. FIG. 4 is a vertical cross-sectional view of the pressure-resistant explosion-proof wasan box of the present invention, and FIG.
A' arrow view and FIG. 6 are longitudinal sectional views of another embodiment. LC ₁ to LC ₄ ... Load cell, 5 ... First pressure-resistant container, 6 ... Terminal block, 7 to 12 ... Pressure-resistant lead-in part,
13...Second pressure vessel, 14...Four corner error adjustment circuit, 15...Electrical conduit [third pressure vessel], 19
... Cable, 20, 21 ... Pressure-resistant packing.

Claims (1)

[Scope of utility model registration request] A terminal block for connecting an input/output cable is provided in the first pressure container, a four-corner error adjustment circuit is provided in the second pressure container, and a terminal block is provided between the first pressure container and the second pressure container. A third pressure-resistant container is interposed, and the terminal block and the four-corner error adjustment circuit are electrically connected to each other by a cable extending from the first pressure-resistant container to the second pressure-resistant container via the third pressure-resistant container. A pressure-resistant explosion-proof sum calculation box in which a load cell circuit outside the first pressure-resistant container and the terminal block are electrically connected via a cable inserted through a pressure-resistant lead-in portion formed in the first pressure-resistant container.