JP2009020028A - Liquid level detecting device for liquefied gas in cooling treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level detecting device for a liquefied gas capable of accurately detecting a liquid level of the liquefied gas in a simple configuration in a cooling treatment apparatus, and simply performing working such as air blowing carried out before use. <P>SOLUTION: The outer periphery of a liquid level sensor 12 is doubly covered with an inner cylinder 13 and an outer cylinder 14 consisting of a bottomed cylinder. The device provides an inner cylinder liquid through hole 13a at a downward position rather than a liquid level detection part of the liquid level sensor 12 of the peripheral wall of the inner cylinder 13, and an inner cylinder gas through hole 13b at an upward position respectively. The device provides an outer cylinder liquid through hole 14a at a downward position rather than the inner cylinder liquid through hole of the peripheral wall of the outer cylinder 14 and an outer cylinder gas through hole 14b at an upward position rather than the inner cylinder gas through hole respectively. The device fixes the upper part of the outer cylinder 14 on the ceiling part of a treatment tank 11, encloses an upper end opening part of the outer cylinder 14 with a sealing plug 18 having an inner cylinder holding hole 18a, holds the upper part of the inner cylinder 13 with the sealing plug 18, and connects a purge gas introduction pipe 20 to the inner cylinder 13 extended to the outer part of the treatment tank from the sealing plug 18. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid level detection device for a liquefied gas in a cooling processing apparatus, and more specifically, a surface cooling and hardening process is performed by introducing an object to be processed such as a frozen dessert or a metal product into a liquefied gas stored in a processing tank. The present invention relates to a liquid level detection device for liquefied gas for detecting the level of liquefied gas in the processing tank in a cooling processing device.

Various types of liquid level sensors are used to detect the liquid level in the storage tank, but as a liquid level sensor for detecting the liquid level of low-temperature liquefied gas such as liquefied nitrogen, the difference in the refractive index of light. There is known an optical fiber liquid level sensor utilizing the above. This optical fiber liquid level sensor uses a prism as a liquid level detection unit, and is connected to a transmission optical fiber and a reception optical fiber. The light transmitted from the transmission optical fiber is a prism. Is in the gas, the difference in refractive index between the glass constituting the prism and the gas is greatly different, so that the light is totally reflected and returns to the light receiving element through the receiving optical fiber. When it is in the liquefied gas, the difference in refractive index between the prism and the liquefied gas is relatively small. The surface is detected (for example, refer to Patent Document 1).
JP 2003-214926 A

  However, in a cooling processing apparatus that cools a workpiece by feeding the workpiece into the liquefied gas, the liquefied gas boils vigorously when the workpiece is thrown into the liquefied gas in the treatment tank. Since the surface fluctuates greatly, it has been difficult to accurately detect the liquid level with various liquid level sensors including the optical fiber level sensor as described above. In addition, there is a problem that the liquid level of the liquefied gas cannot be accurately detected when moisture or foreign matters accompanying the object to be processed freeze and adhere to the liquid level detection unit. For this reason, before using the liquid level sensor, it is necessary to remove the liquid level sensor from the processing tank and perform air blow or the like to remove moisture adhering to the liquid level detection unit. Met.

  Therefore, the present invention can detect the liquid level of the liquefied gas in the cooling processing apparatus with a simple structure with high accuracy, and can easily perform the work such as air blow performed before use. The object is to provide a device.

  In order to achieve the above object, the liquid level detecting device for liquefied gas in the cooling processing apparatus of the present invention is a cooling processing apparatus for performing cooling processing of a processing object by putting the processing object into a processing tank storing liquefied gas. In the liquefied gas level detecting device for detecting the level of the liquefied gas by inserting a level sensor into the processing tank, the outer circumference of the level sensor is an inner cylinder and an outer cylinder made of a bottomed cylinder. The inner cylinder liquid passage hole is provided at a position below the liquid level detection portion of the liquid level sensor on the peripheral wall of the inner cylinder, the inner cylinder gas passage hole is provided at an upper position, and the outer wall of the outer cylinder is further covered. An outer cylinder liquid passage hole is provided below the inner cylinder liquid passage hole, an outer cylinder gas passage hole is provided above the inner cylinder gas passage hole, and the upper part of the outer cylinder is fixed to the ceiling portion of the processing tank. And sealing the upper end opening of the outer cylinder with a sealing plug having an inner cylinder holding hole and the sealing plug The upper part of the cylinder is held, and a purge gas introduction pipe is connected to the inner cylinder that extends from the sealing plug to the outside of the processing tank, and the liquid level sensor includes a prism unit that is a liquid level detection unit, A transmission optical fiber and a reception optical fiber each having a distal end connected to the prism portion through the inner cylinder, and a detection unit to which the proximal ends of the transmission optical fiber and the reception optical fiber are connected. In addition, it is preferable that the liquid level sensor is provided with the liquid level detection unit at two locations, a high liquid level and a low liquid level.

  In the liquid level detection device of the present invention, since the outer periphery of the liquid level sensor is doubly covered with the inner cylinder and the outer cylinder made of a bottomed cylindrical body, the liquid level is detected even if the liquefied gas in the processing tank fluctuates greatly. Since the liquid level in the inner cylinder housing the sensor does not vary greatly, the liquid level in the processing tank can be detected with high accuracy. In addition, since the purge gas introduction pipe is connected to the inner cylinder extending to the outside of the processing tank, air blowing with nitrogen gas or dry air can be performed without removing the liquid level sensor from the processing tank.

  FIG. 1 is an explanatory view showing an example of a liquid level detecting device for a liquefied gas according to the present invention, and FIG.

  The liquid level detecting device 10 for liquefied gas cools the object to be processed by putting the object to be processed into a processing tank 11 storing liquefied gas, for example, liquefied nitrogen, and bringing the liquefied nitrogen and the object to be in direct contact with each other. An inner cylinder that is used in a cooling processing apparatus that performs processing, and that has a liquid level sensor 12 inserted into the processing tank 11 and a double pipe structure provided so as to cover the outer periphery of the liquid level sensor 12 13 and the outer cylinder 14. The liquid level sensor 12 includes a prism unit 15 which is a liquid level detection unit disposed at two positions, a transmission optical fiber 16a having a tip connected to the prism unit 15 through the inner cylinder 13, and a reception unit. The optical fiber 16b is formed by the detection unit 17 to which the base ends of the transmission optical fiber 16a and the reception optical fiber 16b are connected.

  The outer cylinder 14 is a bottomed cylindrical body formed of a material having a low thermal conductivity, for example, a synthetic resin such as polyvinyl chloride or polypropylene, and is inserted into the processing tank 11 from an insertion port provided in a ceiling portion of the processing tank 11. The upper end is fixed to the insertion slot. The upper end opening of the outer cylinder 14 is sealed by a sealing plug 18 having an inner cylinder holding hole 18a for holding the inner cylinder 13, and the inner cylinder 13 is held at a predetermined position by the sealing plug 18. It becomes.

  The inner cylinder 13 is a bottomed cylindrical body formed of a metal such as stainless steel, for example, and is inserted from the inner cylinder holding hole 18a of the sealing plug 18 to the vicinity of the bottom wall in the outer cylinder 14 and protrudes from the outer cylinder 14. A detection unit 17 is provided at the upper end, and a purge gas introduction pipe 20 having a valve 19 is connected between the detection unit 17 and the sealing plug 18.

  Further, the inner cylinder liquid passage holes 13a and 13a are provided in the peripheral wall of the inner cylinder 13 at a position below the prism portion 15 on the low liquid level side, and the inner cylinder gas passage holes are provided on a position above the prism portion 15 on the high liquid level side. 13b are provided, and the outer cylinder 14 has an outer cylinder liquid passage hole 14a at a position below the inner cylinder liquid passage hole 13a, and an outer cylinder gas at a position above the inner cylinder gas passage hole 13b. Each through hole 14b is provided. The inner cylinder gas passage hole 13b and the inner cylinder liquid passage hole 13a are formed to have a small diameter, for example, about 2 mm in diameter, in order to reduce the influence of external liquid level fluctuations, and the outer cylinder gas passage hole 14b and the outer cylinder liquid passage hole 14a. Is formed to have a diameter that facilitates the flow of gas and liquid while suppressing the influence of liquid level fluctuation, for example, about 8 mm in diameter. Further, the inner diameter of the inner cylinder 13 and the interval between the outer peripheral surface of the inner cylinder 13 and the inner peripheral surface of the outer cylinder 14 are set to dimensions of about 10 mm so that the liquefied nitrogen flows smoothly and the ripples are reduced. Yes.

  The cooling processing apparatus provided with the liquefied gas level detector 10 thus formed is liquefied so that the liquid level is positioned between the high liquid level prism portion 15 and the low liquid level prism portion 15. Nitrogen is supplied. That is, the measurement light transmitted from the detection unit 17 of the liquid level sensor 12 to the transmission optical fiber 16a is mostly the measurement light when the prism unit 15 is in nitrogen gas above the liquid level. When the optical fiber 16b is reflected and returns to the receiving optical fiber 16b, a strong optical signal is detected by the detection unit 17, and the prism unit 15 is in liquefied nitrogen, most of the measurement light is caused by the difference in refractive index between the gas and the liquid. Is radiated into the liquefied gas, and the optical signal detected by the detection unit 17 after returning to the reception optical fiber 16b becomes weak. Therefore, when the detection unit 17 detects an optical signal of a predetermined intensity, the prism unit 15 is in the gas. When the optical signal having the predetermined intensity is not detected, it can be detected that the prism portion 15 is in the liquid.

  Therefore, when the liquid level is lowered below the low liquid level side prism unit 15 due to the cooling process, when the detection unit 17 detects a strong optical signal from the low liquid level side prism unit 15, liquefaction (not shown) is performed. Supply of liquefied nitrogen from the nitrogen supply pipe into the treatment tank 11 is started. The liquid level in the processing tank 11 rises due to the supply of liquefied nitrogen, the high liquid level prism unit 15 enters the liquid, and the detection unit 17 detects a strong optical signal from the high liquid level prism unit 15. If not, the supply of liquefied nitrogen is stopped. As a result, the liquid level in the processing tank 11 is held between the low liquid level prism portion 15 and the high liquid level prism portion 15.

  Then, when an object to be processed, such as a metal part, is put into the liquefied nitrogen in the processing tank 11, the liquefied nitrogen is vigorously vaporized and the liquid level largely fluctuates. The inner and outer cylinders 13 and 14 having a double-pipe structure are housed in the inner cylinder 13 and the outer cylinder 14, and the flow of liquefied nitrogen into and out of the cylinder is mainly performed in the outer cylinder liquid passage hole 14a and the inner cylinder liquid passage hole 13a. Therefore, even if the liquid level in the processing tank 11 is greatly swung by inserting metal parts, the liquid in the processing tank 11 is not greatly transmitted to the inner cylinder 13. The surface can be detected accurately and reliably. Therefore, the control range of the liquid level can be reduced, and the utilization efficiency of liquefied nitrogen can be greatly improved.

  Further, the decrease in the liquid level due to the consumption of liquefied nitrogen and the increase in the liquid level due to the supply of liquefied nitrogen cause the outer cylinder liquid through hole 14a, the inner cylinder liquid through hole 13a, the inner cylinder gas through hole 13b, and the outer cylinder gas through hole. Since liquefied nitrogen and nitrogen gas are slowly circulated through 14 b and are transmitted into the inner cylinder 13, liquefied nitrogen can be reliably supplied into the processing tank 11. Furthermore, even if water or the like adhering to the metal parts freezes and floats on the liquid surface, they can be prevented from entering the inner cylinder 13, so that the liquid level sensor can be prevented from malfunctioning.

  When starting the cooling process, it is easy to remove the moisture adhering to the prism portion 15 by air blowing by opening the valve 19 and introducing dry air or nitrogen gas into the inner cylinder 13 from the purge gas introduction pipe 20. Can be done. Further, if necessary, the inner cylinder 13 can be pulled out from the outer cylinder 14 together with the sealing plug 18 to perform work such as air blow or the inspection of the liquid level sensor 12.

  The material and dimensions of the inner cylinder and the outer cylinder, the diameter of the gas passage holes and the liquid passage holes, and the number of installations can be arbitrarily set, the configuration of the liquid level sensor is also arbitrary, and the detection of the liquid level can be performed continuously or What is performed in multiple stages can also be employed. Moreover, the liquid level detection apparatus for liquefied gas of the present invention can also be applied to a cooling processing apparatus that performs cooling processing of various articles, for example, surface cooling and curing processing of frozen confectionery such as ice candy with a stick.

It is explanatory drawing which shows the example of 1 form of the liquid level detection apparatus for liquefied gas of this invention. It is explanatory drawing of a liquid level detection part similarly.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Liquid level detection apparatus for liquefied gas, 11 ... Processing tank, 12 ... Liquid level sensor, 13 ... Inner cylinder, 13a ... Inner cylinder liquid passage, 13b ... Inner cylinder gas passage, 14 ... Outer cylinder, 14a ... Outer Cylinder liquid passage hole, 14b ... outer cylinder gas passage hole, 15 ... prism part, 16a ... transmission optical fiber, 16b ... reception optical fiber, 17 ... detection part, 18 ... sealing plug, 18a ... inner cylinder holding hole, 19 ... Valve, 20 ... Purge gas introduction pipe

Claims (3)

Liquefaction that detects the liquid level of the liquefied gas by inserting a liquid level sensor into the processing tank of the cooling processing apparatus that cools the processed object by putting the processing object into the processing tank in which the liquefied gas is stored. In the gas level detection device for gas, the outer periphery of the liquid level sensor is doubly covered with an inner cylinder and an outer cylinder made of a bottomed cylindrical body, and is positioned below the liquid level detection part of the liquid level sensor on the peripheral wall of the inner cylinder The inner cylinder liquid passage hole is provided at the upper position, the inner cylinder gas passage hole is provided at the upper position, the outer cylinder liquid passage hole is provided at a position lower than the inner cylinder liquid passage hole in the peripheral wall of the outer cylinder, and the inner cylinder gas passage hole is provided. An outer cylinder gas hole is provided at a higher position, the upper part of the outer cylinder is fixed to the ceiling of the processing tank, and the upper end opening of the outer cylinder is sealed with a sealing plug having an inner cylinder holding hole. The upper portion of the inner cylinder is held by the sealing plug, and a purge gas is introduced into the inner cylinder extending from the sealing plug to the outside of the processing tank. To attachment cooling treatment liquefied gas liquid level detection device in the apparatus according to claim. The liquid level sensor includes: a prism unit that is a liquid level detection unit; a transmission optical fiber and a reception optical fiber each having a tip connected to the prism unit through the inner cylinder; the transmission optical fiber and the reception optical fiber; The liquid level detecting device for liquefied gas in the cooling processing device according to claim 1, further comprising: a detecting unit to which a base end of the optical fiber for use is connected. 3. The liquid level detection for a liquefied gas in the cooling processing apparatus according to claim 1, wherein the liquid level sensor is provided with the liquid level detection unit at two locations, a high liquid level and a low liquid level. apparatus.

Images