Patent Publication Number: US-10334665-B2

Title: Underwater heater and manufacturing method therefor

Description:
TECHNICAL FIELD 
     The present invention relates to an immersion heater installed to be immersed under the surface of water and a method of manufacturing the same, and more particularly, to an immersion heater in which a portion of a current supply wire connected to a heater terminal and a sensor terminal is completely waterproofed so that a phenomenon that water flows into the current supply wire, the heater terminal, or the sensor terminal can be prevented, and a method of manufacturing the same. 
     BACKGROUND ART 
     In general, a water tank in which live fishes are accommodated, should be maintained at a constant water temperature so that an inhabited environment of the live fishes can be maintained with good quality. It is not substantially possible to maintain the temperature of a space in which the water tank is installed, at a constant temperature. Thus, an immersion heater that maintains water in the water tank in a set temperature range is installed. 
     When briefly describing a general structure of the immersion heater, the immersion heater includes a heat generation tube for generating heat and a controller that controls an operation of the heat generation tube. Although the shape of the above-described heat generation tube varies according to a required heat generation condition or the size of the water tank, the heat generation tube is mostly wound in the form of a coil having a predetermined diameter, is formed in the range of a length at which the heat generation tube can be installed in the water tank, and is connected to the above-described controller. A water temperature detection sensor for detecting a water temperature and a heat generation tube detection sensor for detecting the temperature of the heat generation tube are respectively installed adjacent to the heat generation tube. 
     The above-described water temperature detection sensor and heat generation tube detection sensor are installed to detect the water temperature and the temperature of the heat generation tube and to stop an operation of the heat generation tube when the detected water temperature and temperature of the heat generation tube are out of an allowable range. For example, the above-described water temperature and heat generation tube detection sensors are configured to have a structure in which well-known sensing members for detecting heat are self-shorted due to the temperature of water or a solution in the heat generation tube or the water tank and a current applied to the heat generation tube is cut off by the above-described controller. 
     In this case, a power wire and a sensor wire, which are disposed to deliver currents and to transmit signals, are connected to the heat generation tube and the detection sensors. However, there is a problem that water flows into a portion into which the power wire and the sensor wire are inserted and a short circuit occurs. Thus, in the conventional immersion heater, the portion into which the power wire and the sensor wire are inserted should be placed on the surface of water. Thus, there is a limitation in utilization. In order to solve the problem, a scheme for sealing the portion into which the power wire and the sensor wire are inserted, with silicone or packing, has been suggested. However, in a currently-suggested sealing technique, the inflow of water along the power wire and the sensor wire cannot be completely prevented. 
     DISCLOSURE 
     Technical Problem 
     The present invention is directed to providing an immersion heater including a portion in which an electric wire and a terminal are connected to each other, can be completely sealed and several portions in which the electric wire and the terminal are connected to each other, can be sealed at one time so that productivity is very high, and a method of manufacturing the same. 
     Technical Solution 
     One aspect of the present invention provides an immersion heater including: a flange; a heat generation tube bent in a U-shape and having both lengthwise ends passing through the flange in an upward direction; a sensor rod having one end passing through the flange in the upward direction; a cap coupled to the flange to cover an end of the heat generation tube and an end of the sensor rod protruding from a top surface of the flange; a power wire having one end inserted into the cap and connected to a power terminal of the heat generation tube; a sensor wire having one end inserted into the cap and connected to a sensor terminal of the sensor rod; and silicone filled in the cap and including a plurality of hardened layers with a time difference. 
     Two or more heat generation tubes may be mounted on the flange, and each of the two or more heat generation tubes may be disposed to be spaced apart from each other. 
     Another aspect of the present invention provides a method of manufacturing an immersion heater, including: a first operation of preparing a heat generation tube bent in a U-shape and a sensor rod; a second operation of passing both lengthwise sides of the heat generation tube and one lengthwise side of the sensor rod through a flange using a fit technique and then connecting a power wire to a power terminal disposed on each of both lengthwise sides of the heat generation tube and connecting a sensor wire to one lengthwise side of the sensor rod; a third operation of coupling a cap to the flange to cover both lengthwise ends of the heat generation tube and one lengthwise end of the sensor rod; a fourth operation of injecting silicone into the cap through an injection hole formed in a ceiling surface of the cap, wherein silicone is injected at a plurality of times with a set time difference; and a fifth operation of fastening a bolt into the injection hole to close the injection hole. 
     The fourth operation may be performed by injecting silicone at a plurality of times with a time difference of 24 hours. 
     In the fourth operation, an amount of silicone to be first injected may be an amount such that a point at which the heat generation tube and the power wire are connected to each other and a point at which the sensor rod and the sensor wire are connected to each other, are capable of being buried. 
     The flange and the cap may be coupled to each other in a screw coupling structure, and the second operation may further include welding a portion of a top surface of the flange through which the heat generation tube and the sensor rod pass, and the third operation may further include welding between the top surface of the flange and a bottom end of an outside surface of the cap. 
     Advantageous Effects 
     In an immersion heater according to the present invention, a portion in which an electric wire and a terminal are connected to each other is completely sealed so that the immersion heater can be used in a state in which it is fully immersed in water. Also, by using a method of manufacturing the immersion heater according to the present invention, the portion in which the electric wire and the terminal are connected to each other can be completely sealed only through the injection of silicone and all of several portions in which the electric wire and the terminal are connected to each other can be sealed at one time so that productivity of the immersion heater can be improved. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of an immersion heater according to the present invention. 
         FIGS. 2 through 6  are cross-sectional views sequentially showing an operation of manufacturing an immersion heater according to the present invention. 
         FIG. 7  is a view showing the stage of use of the immersion heater according to the present invention. 
         FIG. 8  is a view of an immersion heater according to a second embodiment of the present invention. 
     
    
    
     MODES OF THE INVENTION 
     Hereinafter, a method of manufacturing an immersion heater according to an embodiment of the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a cross-sectional view of an immersion heater according to the present invention. 
     The immersion heater according to the present invention that is a kind of an electric heating device for heating water filled in a water tank using a current supplied from the outside, is characterized by having a complete waterproof structure in which a short circuit does not occur due to water that flows into the immersion heater even though the whole of the immersion heater is immersed in water. That is, the immersion heater according to the present invention includes a flange  100  that serves as a body, a heat generation tube  200  and a sensor rod  300 , which are mounted to pass through the flange  100  in an upward direction, a cap  500  coupled to the flange  100  to cover an end of the heat generation tube  200  and an end of the sensor rod  300  that protrude toward a top surface of the flange  100 , a power wire  410  having one end inserted into the cap  500  and connected to a power terminal  210  of the heat generation tube  200 , a sensor wire  420  having one end inserted into the cap  500  and connected to a sensor terminal  310  of the sensor rod  300 , and silicone  600  filled in the cap  500  and stacked in the form of a plurality of layers, as illustrated in  FIG. 1 . 
     The heat generation tube  200  is configured to be bent in a U-shape, to have both lengthwise ends coupled to each other to pass through the flange  100  in the upward direction, and to generate heat due to a current delivered from the power wire  410 . The sensor rod  300  is configured to deliver signals for turning on/off the heat generation tube  200  according to a water temperature to a controller (not shown) so as to prevent a phenomenon that water in a water tank is overheated. In this way, the heat generation tube  200  for generating heat and the sensor rod  300  for generating a control signal for the heat generation tube  200  according to the water temperature are substantially applied to the conventional immersion heater. Thus, detailed descriptions thereof will be omitted. 
     In this case, the feature of a configuration of the immersion heater according to the present invention is that an inside of the cap  500  for covering the power terminal  210  and the sensor terminal  310  is filled with silicone  600  so as to prevent a phenomenon that water in the water tank flows into the power terminal  210  or the sensor terminal  310  along the power wire  410  and the sensor wire  420 . That is, because, in the conventional immersion heater, waterproofing is performed only at an inlet of a hole into which the power wire  410  and the sensor wire  420  are inserted, when a waterproof material coated on the inlet of the hole into which the power wire  410  and the sensor wire  420  are inserted, is damaged, water in the water tank flows into the power terminal  210  or the sensor terminal  310  so that a short circuit occurs. However, the immersion heater according to the present invention has an advantage that the whole of a space in which the power wire  410  and the sensor wire  420  are connected to the power terminal  210  and the sensor terminal  310 , as well as the hole into which the power wire  410  and the sensor wire  420  are inserted, are filled with silicone  600  so that a phenomenon that water flows into the power terminal  210  or the sensor terminal  310  does not occur. 
     Meanwhile, when silicone  600  for filling the cap  500  is injected once and then is hardened, silicone may be spaced apart a very short distance from the power wire  410  or the sensor wire  420  when silicone  600  is contracted during the hardening operation, or silicone  600  may be spaced apart a very short distance from an inside surface of the cap  500 . In this way, when a separation space is formed between the power wire  410  and the silicone  600 , between the sensor wire  420  and the silicone  600  and between the inside surface of the cap  500  and the silicone  600 , water in the water tank may flow into the power terminal  210  or the sensor terminal  310  through the separation space and may be in contact with the power terminal  210  or the sensor terminal  310 . 
     In order to solve the above-described problem, the immersion heater according to the present invention is characterized in that, when silicone  600  is injected into the cap  500 , the cap  500  is not filled with silicone  600  at one time but silicone  600  is injected into the cap  500  at several times with a predetermined time difference. An operation of injecting silicone  600  into the cap  500  at several times and effects thereof will be described in detail with reference to  FIGS. 2 through 6 . 
       FIGS. 2 through 6  are cross-sectional views sequentially showing an operation of manufacturing an immersion heater according to the present invention. 
     When the immersion heater is manufactured by a method of manufacturing the immersion heater according to the present invention, first, after the heat generation tube  200  bent in the U-shape and the sensor rod  300  are prepared, as illustrated in  FIG. 2 , both lengthwise sides of the heat generation tube  200  and one lengthwise side of the sensor rod  300  pass through the flange  100  using a fit technique through an insertion hole  110  formed in the flange  100 . When the heat generation tube  200  and the sensor rod  300  are simply inserted into the insertion hole  110 , the heat generation tube  200  and the sensor rod  300  may be detached and removed from the flange  100  due to an external force. Thus, a portion of a top surface of the flange  100  through which the heat generation tube  200  and the sensor rod  300  pass, is welded to form welded beads B, as illustrated in  FIG. 3 . When the heat generation tube  200  and the sensor rod  300  are stably coupled to the flange  100 , the power wire  410  is connected to the power terminal  210  disposed at each of both lengthwise sides of the heat generation tube  200 , and the sensor wire  420  is connected to one lengthwise side of the sensor rod  300 . 
     When connection of the power wire  410  and the sensor wire  420  is completed, as illustrated in  FIG. 4 , the cap  500  is coupled to the flange  100  to cover both lengthwise ends of the heat generation tube  200  and one lengthwise end of the sensor rod  300 . In this case, the power wire  410  and the sensor wire  420  pass through the cap  500  and are drawn toward an outside of the cap  500 . When a female screw thread  510  formed on a bottom end of the inside surface of the cap  500  is screw-coupled to a male screw thread  120  formed at an upper side of the flange  100 , the cap  500  is integrally coupled to the flange  100 . An additional welding operation may be added so that screw coupling between the cap  500  and the flange  100  is not loose due to vibration or shock applied from the outside. Due to the welding operation, the welding beads B are formed between the top surface of the flange  100  and a bottom end of an outside surface of the cap  500 . Thus, the flange  100  and the cap  500  are completely integrally coupled to each other, and a coupled portion therebetween is completely sealed. In this case, for improvements in a sealing property of a welded portion, preferably, the flange  100  and the cap  500  are welded by Argon welding in which the welded portion is smooth and a worker can do work while seeing the welded portion with naked eyes. 
     When coupling of the flange  100  and the cap  500  is completed, silicone  600  is injected into the cap  500  through an injection hole  520  formed in a ceiling surface of the cap  500  so that a connection portion of the power wire  410  and the heat generation tube  200  and a connection portion of the sensor wire  420  and the sensor rod  300  can be sealed. In this case, when the whole of the cap  500  is filled with silicone  600  by injecting silicone  600  at one time, silicone  600  is contracted while being hardened. Thus, a minute separation space may be formed, and through the separation space, water in the water tank flows into the cap  500  so that there is a possibility that a short circuit will occur. 
     Thus, when silicone  600  is injected into the cap  500 , as illustrated in  FIG. 5 , only a predetermined amount of silicone  600  is injected into the cap  500  so that a first silicone layer  610  having a predetermined thickness can be formed, and then, an operation of waiting until injected silicone  600  is hardened and then injecting silicone  600  having a predetermined amount into the cap  500  is repeatedly performed at several times so that a plurality of silicone layers  610  to  670  can be formed, as illustrated in  FIG. 6 . 
     In this way, silicone  600  is injected into the cap  500  with a set time difference at several times so that, when the plurality of silicone layers  610  to  670  are formed, each of the silicone layers  610  to  670  has a different environment condition at a hardening time. Thus, contracted patterns of the silicone layers  610  to  670  are different from each other. That is, even when part of the silicone layers  610  to  670  is spaced apart from the power wire  410  and the sensor wire  420 , the other part thereof are closely adhered to the power wire  410  and the sensor wire  420 , and even when another part of the silicone layers  610  to  670  is spaced apart from the inside surface of the cap  500 , the other part thereof is closely adhered to the inside surface of the cap  500 . Thus, neither a phenomenon that water flows into the cap  500  along the power wire  410  and the sensor wire  420 , nor a phenomenon that water flows into the cap  500  along an inner wall of the cap  500 , occurs. 
     In addition, even when a gap is formed while a previously-injected silicone layer is hardened, silicone  600  in a gel state to be subsequently injected fills the gap. Thus, the inside of the cap  500  can be filled with silicone  600  so that a waterproof performance can be remarkably improved. In this case, a hardening time for silicone  600  is generally about 24 hours. Thus, preferably, second silicone  600  is injected after about 24 hours elapse since first silicone  600  has been injected. That is, as illustrated in the current embodiment, when silicone  600  filled in the cap  500  includes seven silicone layers silicone  600  has to be injected for seven days. 
     Meanwhile, when the amount of silicone  600  to be first injected is not sufficient to bury both the power terminal  210  and the sensor terminal  310 , i.e., when a connection portion of the power wire  410  and the power terminal  210  or a connection portion of the sensor wire  420  and the sensor terminal  310  is located at a higher position than a top surface of a first silicone layer  610 , the connection portion of the power wire  410  and the power terminal  210  or the connection portion of the sensor wire  420  and the sensor terminal  310  may be damaged while hardening of the first silicone layer  610  is waited. Also, when the power terminal  210  and the sensor terminal  310  are buried with the first silicone layer  610  and ends (bottom ends in  FIG. 6 ) of the power wire  410  and the sensor wire  420  are buried with a second silicone layer  620 , a hardened pattern of the first silicone layer  610  and a hardened pattern of the second silicone layer  620  are different from each other so that the power wire  410  and the sensor wire  420  may be separated from the power terminal  210  and the sensor terminal  310 . 
     Thus, preferably, the amount of silicone  600  to be first injected is set to an amount such that a point at which the heat generation tube  200  and the power wire  410  are connected to each other and a point at which the sensor rod  300  and the sensor wire  420  are connected to each other, can be buried. 
     Also, when injection of silicone  600  is completed, a bolt  700  is fastened into the injection hole  520  formed in the cap  500  so that the injection hole  520  can be closed. In this case, preferably, the bolt  700  is a stripper bolt so that the bolt  700  does not protrude toward an outside of the cap  500 . 
       FIG. 7  is a view showing the stage of use of the immersion heater according to the present invention, and  FIG. 8  is a view of an immersion heater according to a second embodiment of the present invention. 
     In the immersion heater according to the present invention manufactured by the method of manufacturing the immersion heater, both a point at which the power wire  410  is connected to the heat generation tube  200  and a point at which the sensor wire  420  is connected to the sensor rod  300 , are completely sealed. Thus, the immersion heater may be used while being put on the bottom of a water tank  10 , as illustrated in  FIG. 7 . Also, even when water in a water tank is somewhat reduced, the immersion heater is maintained in an immersed state until water in the water tank drains completely. Thus, a problem that the heat generation tube  200  is locally heated can be prevented. Thus, the problem caused by local heating does not occur in the immersion heater according to the present invention. Thus, as illustrated in  FIG. 8 , two or more heat generation tubes  200  are inserted into one flange  100  so that the entire heat generation capacity can be increased. 
     In  FIG. 8 , only a case where three heat generation tubes  200  are mounted on one flange  100  is illustrated. However, the number of mounting the heat generation tube  200  may be changed in various ways. Also, the heat generation tube  200  is not limited to the U-shape illustrated in the current embodiment but may be changed in various shapes. Of course, when a plurality of heat generation tubes  200  are mounted on one flange  100 , the heat generation tubes  200  have to be installed to be spaced apart from each other so as to prevent overheating. 
     Meanwhile, even when a plurality of heat generation tubes  200  are mounted on one flange  100 , as mentioned above, all portions in which the power wire  410  is connected to each of the heat generation tubes  200 , are sealed through the injection of silicone  600  at one time. Thus, the effect of improving productivity of the immersion heater can be attained. 
     INDUSTRIAL APPLICABILITY 
     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.