KR20220127554A - Method for float use in level sensor - Google Patents

Abstract

The present invention relates to a method for manufacturing a float for a level sensor, and more specifically, to a method for manufacturing a float for a level sensor, which is made of rubber material and is partially submerged in a liquid to be used for liquid level measurement. The method for manufacturing a float for a level sensor comprises: a step of introducing an FMB sheet including rubber material into a primary molding die having a temporarily molded cavity of a predetermined shape, and forming the FMB sheet into a temporarily molded float of a predetermined shape in the temporarily molded cavity while thermally pressing the FMB sheet by a press; and a step of introducing the temporarily molded float into a secondary molding die having a cavity molded in a predetermined shape, and manufacturing a finished float of a predetermined shape through foaming while thermally compressing the float at a predetermined temperature for a predetermined period of time by the press. The press transfers heat to the first and second molding dies by a heat medium heating method. The present invention converts the float molding press mold into a heat medium heating method, thereby reducing temperature deviations throughout the entire mold to mold a high-quality float, and improving the stability even during long-term use in a urea solution. Moreover, the present invention minimizes product molding defects caused by internal pressure by smoothly discharging the gas generated during the float molding process to the outside of the mold and discharging smoothly the gas generated from the inside of the magnet groove formed as a blade hole to the lower part of a protrusion for forming a magnet groove.

Description

Method for manufacturing a float for a level sensor {Method for float use in level sensor}

The present invention relates to a method for manufacturing a float for a level sensor, and more particularly, to improve the quality of a float product used in a level sensor for measuring the level of urea water in an SRC system, and to improve the quality of a float product generated in a mold during float molding. It relates to a manufacturing method of a float for a level sensor that can smoothly discharge the product to minimize product molding defects.

The level sensor (gauge) is used in various industrial fields such as vehicle fuel senders, rollover valves, fuel vent valves, LPG level gauges, and liquid level sensing industries. It includes a stem 20 coupled to the float, and other components for measurement are further configured.

In addition, as the standard (Euro-6) for the emission of diesel vehicles is the same as that of Europe, the installation of emission reduction devices is mandatory, and the development of parts related to the SCR system (Selective Catalyic Reduction System) has expanded. is becoming Among the SRC system parts, the float used for the level sensor for measuring the level of urea in the urea tank should not have any external deformation such as swelling or bursting due to being immersed in urea for a long time, and it should have oil resistance within 5% of the weight change. It should have, and the surface should not be melted by the number of urea.

Therefore, in order to improve oil resistance, pressure resistance, and chemical resistance, an NBR (acrylonitrile-butadiene rubber)-based foam float is mainly used. These NBR floats are rigid foams containing independent pores (or cells), have strong oil resistance and pressure resistance, and can be manufactured in various shapes and uses depending on the molding mold. These NBR floats have strong oil resistance compared to floats made of other materials such as metal, polypropylene, and urethane, and are widely used in fuels containing alcohol in addition to gasoline and diesel.

2 is a photograph of a state in which the cross section of the NBR float used in the conventional urea level sensor is cut. As shown in the photograph, the conventional NBR float forms a pinhole (p) by a drilling method, such a drilling method can adjust the size of the pinhole (p) as needed, but there is a possibility that eccentricity of the hole may occur during processing, and dust generated during drilling may remain inside and cause defects.

In addition, the float used for the level sensor in the fuel tank for urea storage in diesel vehicles has a lot of temperature variation in the mold temperature with the conventional electric heater heating method, so sensitive working conditions such as uniform heat conduction and uniform pressure It is difficult to meet the requirements, and it is difficult to manufacture high-quality floats.

And Figure 3 is a view showing the cross-sectional structure of the blind hole (h) into which a magnet is inserted into the NBR float used in such a conventional urea number level sensor. A hole (h) is required, and the blind hole (h) does not have a gas discharge space, so it is disadvantageous to discharge gas generated during molding of a rubber product, so that product molding is not performed well, resulting in a number of unmolded defects.

Therefore, it overcomes the manufacturing problems of the NBR float used in the conventional urea level sensor, reduces the occurrence of defects due to additional processing by allowing the shape of the finished product to be manufactured in the molding process, and furthermore, improves the mold structure to foam There is an increasing demand for a method for manufacturing a float for a level sensor that allows the gas generated in the process to be smoothly discharged and the shape of the blow hole is stably formed, thereby minimizing defects in the product manufacturing process.

Korea Patent Publication No. 0000-00000000

The present invention has been devised to solve the above problems, and an object of the present invention is to reduce the mold heating temperature deviation so that a high-quality float can be manufactured, and the finished product shape of the float can be molded during the molding process, This is to minimize the defect rate in the product manufacturing process.

Another object of the present invention is to improve the mold structure to facilitate the discharge of gas generated in the blind hole forming process of the float for a level sensor.

According to one aspect of the present invention for achieving the above object, in the manufacturing method of a float for a level sensor that is partially immersed in a liquid as a rubber material and used for liquid level measurement, an FMB sheet comprising a rubber material is formed into a predetermined shape. Putting the FMB sheet into a primary forming mold in which the provisional forming cavity of Putting it into a secondary molding mold having a molding cavity of a shape, thermocompression bonding for a predetermined temperature and time by a press to produce a finished float of a predetermined shape while foaming, wherein the press is heated in a hot oil heating method Heat is transferred to the first and second molding molds.

Here, the secondary molding mold is separably stacked on the top of the base plate of the press, and a pin for forming a pinhole is installed on the upper surface in a cylindrical shape, and spaced apart from the pin by a predetermined distance to form a magnet groove is a circular arc. A bottom plate in which a plurality of installation holes are respectively formed to be installed at regular intervals along It is provided including a middle plate formed to be accommodated, and a cover plate separably stacked on top of the middle plate and formed to cover the molding cavity while being stacked on the middle plate.

Here, the installation hole is formed vertically through the bottom plate so that the protrusion for forming the magnet groove is inserted, and the gas generated in the foaming process of the provisional float is downwardly through between the projection for forming the magnet groove and the installation hole. is emitted

In addition, an insertion hole communicating with the installation hole is formed and further comprising a core plate interposed between the bottom plate and the base plate, wherein gas generated in the foaming process of the provisional float is discharged between the bottom plate and the core plate make it possible

Furthermore, the projection for forming the magnet groove has a groove-forming surface protruding into the molding cavity at an upper end to form a groove-forming surface for forming the magnet groove, and a lower end of the groove-forming surface has a conical cross-sectional structure of upward and downward light. A movement guide surface is formed and inserted into the installation hole, and an extension surface extending downwardly and inserted into the insertion hole is formed at the lower end of the gas movement guide surface.

In addition, the installation hole formed in the bottom plate is made of an inclined surface extending downward to correspond to the gas movement guide surface.

In addition, the protrusions for forming the magnet grooves are formed in a rectangular parallelepiped shape, and magnetic grooves having a shape corresponding to the protrusions for forming the magnet grooves are respectively formed in the completed float, and the shape corresponding to the magnet grooves is formed inside each of the magnet grooves. Inserting each magnet, injecting a resin into each of the magnet grooves is provided further comprising the step of hardening the magnets inside the magnet grooves.

According to the present invention as described above, the float molding press mold is converted to a heat-heating method, and the heating temperature deviation is reduced throughout the mold, thereby forming a high-quality float, and improving stability even after long-term use in urea water there is

In addition, the gas generated during the float molding process is smoothly discharged to the outside of the mold, and the gas generated inside the magnet groove formed by the blow hole can be smoothly discharged to the lower part of the protrusion for forming the magnet groove, thereby reducing the internal pressure. It has the effect of minimizing product molding defects caused by

1 is a diagram schematically showing the structure of a conventional level sensor.
2 is a photograph of a state in which the cross section of the NBR float used in the conventional urea water level sensor is cut.
Figure 3 is a view showing the cross-sectional structure of the formation of the blind hole in which the magnet is inserted inside the NBR float used in the conventional urea level sensor.
4 is a flowchart illustrating a manufacturing process of a float for a level sensor according to the present invention.
5 is a perspective view and a single-year structure diagram showing the shape of the finished product of the float for a level sensor according to the present invention.
6 is a diagram schematically illustrating a procedure in which a provisional molding float is formed by the primary molding die according to the present invention.
7 is a view schematically showing a sequence in which a finished float is formed by the secondary molding die according to the present invention.
8 is a diagram schematically illustrating a discharge path of gas generated in the secondary molding mold according to the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a flowchart illustrating a manufacturing process of a float for a level sensor according to the present invention, FIG. 5 is a perspective view and a single-year structure diagram showing the shape of a finished product of a float for a level sensor according to the present invention, and FIG. 6 is 1 according to the present invention It is a view schematically showing the order in which the provisional float is formed by the secondary forming die, and FIG. 7 is a view approximately showing the order in which the finished float is formed by the secondary forming die according to the present invention.

As shown in FIG. 5, the float for a level sensor manufactured by the present invention is a cylindrical body having a circular pinhole formed on the inside, and a plurality of magnet grooves Fm are formed on the outside by being spaced apart from the pinhole by a predetermined distance, and the magnet grooves Fm ) inside the magnet (M) is installed.

The float for a level sensor according to the present invention is a rubber material, which is partially immersed in a liquid and used to measure the liquid level. It is manufactured through a step (S410), a step of inserting a magnet into the magnet groove (S410), and a step of curing the resin in the magnet groove (S410).

In the provisional molding float manufacturing step (S410), the FMB sheet (S) containing a rubber material is put into the primary molding mold 100 in which the provisional molding cavity 140 of a certain shape is formed, and the FMB sheet (S) is pressed by the press. ) is hot-pressed so that the FMB sheet (S) is formed into a falsely formed float (f) of a specific shape in the provisional forming cavity (140).

This primary molding mold 100 puts the FMB sheet (S) inside the sheet receiving groove 110 in the primary molding mold 100 as shown in FIG. 6 , and the upper pressing plate 120 is pressed downward. Thus, the FMB sheet (S) is filled into the provisional forming cavity 140 through the material transfer hole 130 so that the provisional forming float (f) is manufactured.

At this time, the FMB sheet (S) used as a molding material is mixed with sulfur, cured resin, accelerator, vulcanization accelerator, foaming agent, foaming aid, etc. in CMB (carbon master batch) prepared by mixing NBR (nitrile butadiene rubber) and carbon. After that, it is cut into a sheet shape of a certain size. NBR is called nitrile rubber or Buna_N, and can be a generic term for oil-resistant rubber produced by copolymerizing acrylonitrile and butadiene, which are monomers. Carbon is used as a reinforcing agent and filler, and is a fine particle mainly composed of carbon with a particle diameter of microns, and may contain less than 1% of sulfur and ash as impurities.

In the finished float manufacturing step (S420), the provisional molding float (f) prepared as described above is put into the secondary molding mold 200 in which the molding cavity 221 of a predetermined shape is formed, and is heated for a predetermined temperature and time by pressing. As it is compressed and foamed, it is made into a finished float (F) of a certain shape.

As shown in FIG. 7 , the secondary molding mold 200 includes a bottom plate 210 , a middle plate 220 , and a cover plate 230 such that a cavity having a predetermined shape is formed on the inside.

The bottom plate 210 is detachably stacked on the top of the base plate of the press, and the pin 250 for forming a cylindrical pinhole is installed on the top surface. And the outside of the pin 250 is spaced apart from each other by a predetermined interval, so that a plurality of projections 260 for forming a magnet groove are installed at predetermined intervals along a circular arc, the installation holes 211 are respectively formed at predetermined positions. These installation holes 211 are formed through the bottom plate 210 so that the protrusions 260 for forming the magnet grooves are inserted, so that gas in the manufacturing stage of the completed float forms the projections 260 and the installation holes 211 for forming a magnet groove. ) to be discharged downward through the gap. That is, a large amount of gas generated when the magnet groove (Fm) is foamed in the form of a blow hole cannot escape from the inside of the hole, so that the gas is smoothly discharged downward so that unmolding does not occur.

Moreover, in the present invention, the core plate 240 is interposed at the lower end of the bottom plate 210 so that the gas discharge is further improved. In the core plate 240 , an insertion hole 241 communicating with the installation hole 211 is formed under the bottom plate 210 to be interposed between the bottom plate 210 and the base plate. In this way, the core plate 240 allows the gas generated during the foaming process of the finished float manufacturing step, that is, the provisional float f, to be discharged between the bottom plate 210 and the core plate 240, so that the gas is discharged more smoothly. let it go

In addition, the protrusion 260 for forming a magnet groove has a hexahedral shape, is inserted into the bottom plate 210 and the core plate 240, and the upper end protrudes into the molding cavity 221 to form a magnet groove in the provisional float foaming step ( Fm) is formed, and the lower end of the groove forming surface 261 has a conical cross-sectional structure of upward and downward light. The gas movement guide surface 262 is formed to move to the , and the gas movement guide surface 262 is inserted into the installation hole 211 . In this case, the installation hole 211 is formed of an inclined surface that is enlarged downward to correspond to the gas movement guide surface 262 . And the lower end of the gas movement guide surface 262 is extended downwardly extending surface 263 to be inserted into the insertion hole 241 is formed.

The gas generated in the forming cavity 221 by the magnetic groove forming protrusion 260 having the above shape is a middle plate 220 to be described later at the boundary between the groove forming surface 261 and the gas movement guide surface 262. The gas remaining along the gas movement guide surface 262 is discharged to the outside through between the bottom plate 210 and the core plate 240 while allowing the gas to be discharged to the outside through the space between the bottom plate 210 and the bottom plate 210 . and the remaining gas is smoothly discharged between the base plate and the core plate 240 of the press through the extension surface 263 .

The middle plate 220 is separably stacked on the top of the bottom plate 210 so that the molding cavity 221 is formed therein. At this time, the forming cavity 221 is formed at an end of the protrusion 260 for forming the magnet groove at a predetermined height to be accommodated in the forming cavity 221 .

In the state in which the middle plates 220 are stacked in this way, the provisional molding float f is seated inside the molding cavity 221 , and then the cover plate 230 is covered thereon.

The cover plate 230 is detachably stacked on top of the middle plate 220 , and is formed to cover the molding cavity 221 in a stacked state on the middle plate 220 , so as to cover the cover plate 230 . Next, the provisional molded float (f) accommodated inside the molding cavity (221) is foamed by thermal pressurization, so that the molding cavity (221) and the finished float (F) having a corresponding shape are manufactured.

In addition, the press to which the primary and secondary molding molds 100 and 200 are applied adopts a heat oil heating method to minimize the mold heating temperature deviation. This thermal oil heating method has very high thermal conductivity compared to the electric heater heating method. In particular, in terms of temperature deviation, the electric heater method shows a temperature deviation of ±7℃, but the thermal oil heating method has a temperature deviation of within ±2℃. , it is very effective in manufacturing a high-quality float having water resistance, ammonia resistance, and low weight change rate as in the present invention.

In the magnet insertion step in the magnet groove, the magnet (M) is inserted into the plurality of magnet grooves (Fm) formed at the top of the completed float (F). The magnet groove (Fm) is formed in a shape corresponding to the protrusion 260 for forming the magnet groove, and the corresponding rectangular parallelepiped magnet (M) is inserted into the magnet (M).

In the resin curing step, the resin is injected so that the magnet (M) inserted into the magnet groove (Fm) is hardened from the inside to finish the surface.

8 is a diagram schematically illustrating a discharge path of gas generated in the secondary molding mold 200 according to the present invention. The gas generated in the molding process in the float for the level sensor manufactured as described above is the same as in FIG. Similarly, the gas generated in the magnet groove Fm is discharged to the connection portion between the cover plate 230 and the middle plate 220 and the connection portion between the middle plate and the bottom plate 210 and the bottom plate 210 ) and the connection part of the core plate 240, the core plate 240 and the base plate connection part, in particular, to be smoothly discharged along the open bottom gas movement guide surface 262 of the magnet groove Fm, so that in the foaming process The gas generated from the inside of the mold is smoothly discharged to the outside, so that the defective product is minimized by the internal pressure.

Although the present invention has been described with reference to the above-mentioned preferred embodiments, various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the appended claims shall cover such modifications and variations as fall within the scope of the present invention.

100: 1st molding die
110: seat receiving groove 120: pressure plate
130: material transfer hole 140: false mold cavity
200: secondary molding die
210: bottom plate 211: installer
220: middle plate 221: molding cavity
230: cover plate
240: core plate 241: insertion hole
250: pin for forming a pinhole
260: protrusion for forming a magnet groove 261: groove forming surface
262: gas movement guide surface 263: extended surface
f : pseudotype float
F : Complete float Fm : Magnet groove
M: Magnet
S: FMB sheet

Claims (7)

In the manufacturing method of a float for a level sensor that is partially immersed in a liquid as a rubber material and used for liquid level measurement,
An FMB sheet made of a rubber material is put into a primary molding mold having a provisional forming cavity of a certain shape, and the FMB sheet is hot-pressed by a press, and the FMB sheet is formed into a provisional forming float of a certain shape in the provisional forming cavity. being formed;
The provisional molding float is put into a secondary molding mold having a molding cavity of a predetermined shape, and is thermocompressed by a press for a predetermined temperature and time to be foamed and manufactured into a finished float of a predetermined shape,
The press is a method of manufacturing a float for a level sensor, characterized in that the heat is transferred to the first and second molding molds in a hot oil heating method.
The method of claim 1,
The second molding mold is
Doedoe stacked separably on the top of the base plate of the press, a pin for forming a pinhole is installed on the upper surface in a cylindrical shape, and a plurality of protrusions for forming a magnet groove are installed at regular intervals along an arc by being spaced apart from the outside by a predetermined distance. a bottom plate in which installation holes are formed, respectively;
a middle plate separably stacked on top of the bottom plate to have the forming cavity formed therein, and an end of the protrusion for forming a magnet groove is formed to be accommodated in the forming cavity;
A method of manufacturing a float for a level sensor, comprising a cover plate that is detachably stacked on the middle plate and formed to cover the molding cavity in a state of being stacked on the middle plate.
3. The method of claim 2,
In the bottom plate, the installation hole is vertically penetrating so that the protrusion for forming the magnet groove is inserted, and the gas generated in the foaming process of the provisional float is discharged downward through the space between the magnet groove forming projection and the installation hole. A method of manufacturing a float for a level sensor, characterized in that.
4. The method of claim 3,
The insertion hole communicating with the installation hole is formed, further comprising a core plate interposed between the bottom plate and the base plate,
A method of manufacturing a float for a level sensor, characterized in that the gas generated in the foaming process of the provisional float is discharged between the bottom plate and the core plate.
5. The method of claim 4,
The protrusion for forming the magnet groove is
A groove-forming surface protruding into the molding cavity to form the magnet groove is formed at the upper end, and a gas movement guide surface is formed at the lower end of the groove-forming surface to have a cross-sectional structure of upward and downward light in a conical shape. The method of manufacturing a float for a level sensor, characterized in that the lower end of the gas movement guide surface is extended downwardly and an extension surface to be inserted into the insertion hole is formed.
6. The method of claim 5,
The method of manufacturing a float for a level sensor, characterized in that the installation hole formed in the bottom plate is formed of an inclined surface that is enlarged downward to correspond to the gas movement guide surface.
7. The method of claim 6,
The protrusions for forming the magnet grooves are formed in a rectangular parallelepiped shape, and magnet grooves having a shape corresponding to the protrusions for forming the magnet grooves are respectively formed on the completed float,
inserting each magnet having a shape corresponding to the magnet groove inside each of the magnet grooves;
hardening the magnets inside the magnet grooves by injecting a resin into each of the magnet grooves; Method of manufacturing a float for a level sensor, characterized in that it further comprises.

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