JP2013185906A - Float body, liquid level sensor with the same, and manufacturing method for float body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a float body which is composed of a thermoplastic resin including a hollow glass granular material and has a short manufacturing time, a liquid level sensor having the float body, and a manufacturing method for the float body.SOLUTION: A float body 90 is composed of a plurality of partial floats 91 arranged in parallel to each other, so that a shape of each partial float 91 can be made small for one float in a size having desired buoyancy and also the desired buoyancy can be obtained by combining buoyancy of each partial float 91. Therefore, a heating time of a mixture R in which high density polyethylene resin particles P and glass beads G are previously mixed while keeping them in a solid state can be shortened even when the partial float is manufactured by using a manufacturing method in which the mixture R is put in a mold K and compression molding is performed for compressing the mixture by applying a pressure while heating it to a melting temperature of the resin particles P or more.

Description

  The present invention relates to a float body used in, for example, a liquid level sensor that detects a liquid level of a liquid contained in a liquid tank, a liquid level sensor having the float body, and a method for manufacturing the float body. It is.

  In the float type liquid level sensor, the liquid level is detected by detecting the vertical movement of the float floated on the liquid level. Such a float type liquid level sensor may be used for detecting a liquid level in a high pressure liquefied gas such as petroleum liquefied gas (LPG), for example. Furthermore, since the specific gravity of such a liquefied gas is small, a small specific gravity is required for the float to obtain buoyancy.

  For example, when a float is formed of a hollow metal body, the thickness of the metal increases to increase the weight and sufficient buoyancy cannot be obtained to ensure pressure resistance, and the shape is spherical from the point of pressure resistance. There was a problem of being constrained. Even when the float is made of a resin material having a specific gravity smaller than that of metal, the liquid penetrates the resin material in the high-pressure liquid regardless of whether it is a hollow body or foam, and the liquid enters the space in the float. There was a problem that sufficient buoyancy could not be obtained. And the technique which solves such a problem is disclosed by patent document 1. FIG.

  The float described in Patent Document 1 is made of a thermoplastic resin containing a minute hollow body such as a glass microballoon. According to such a float, it was possible to reduce the specific gravity and secure buoyancy without providing a space inside such as a hollow body or a foamed body.

  However, the float of Patent Document 1 is prepared by kneading and extruding a resin heated and melted by an extruder and a glass microballoon to produce a pellet in which these resin and glass microballoon are mixed, and then using this pellet to produce an injection molding machine. However, if the proportion of glass microballoons is increased in order to reduce the specific gravity, the molten resin does not reach between these glass microballoons. The balloons were rubbed and broken, and there was a problem that it was difficult to obtain a float with a small specific gravity. In particular, when a high molecular weight resin having high chemical resistance and rigidity is used, since such a resin has a high viscosity at the time of melting, the molten resin does not spread between the glass microballoons. Was more prominent.

  Therefore, in order to avoid such problems, a mixture in which the thermoplastic resin powder and the glass microballoon are mixed in advance in a solid state is placed in a mold and heated to a temperature equal to or higher than the melting temperature of the resin powder. However, the float was manufactured by the compression molding which compresses by applying pressure. The float manufactured in this way was able to reduce the specific gravity by suppressing the breakage of the glass particles mixed with the resin.

Japanese Patent Laid-Open No. 1-212319

  However, in the above-described compression molding, when the mixture is heated from the surroundings by heating the mold in which the mixture is put, since the glass microballoon is included in the mixture, heat transfer is poor. Therefore, when producing a float of a certain size to obtain the desired buoyancy, it is necessary to heat for a long time in order to sufficiently melt the above mixture to the inside. There was a problem that it was necessary.

  The present invention aims to solve this problem. That is, the present invention aims to provide a float body made of a thermoplastic resin containing hollow glass particles and having a short production time, a liquid level sensor having the float body, and a method for producing the float body. Yes.

  In order to achieve the above object, the invention described in claim 1 is a float body made of a thermoplastic resin including hollow glass particles, wherein the float bodies are arranged in parallel with each other. It is a float body characterized by comprising a float.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, each of the partial floats is formed in the same shape.

  To achieve the above object, the invention described in claim 3 is a liquid level sensor comprising a float body and a float arm to which the float body is attached. 2. A liquid level sensor comprising the float body according to 2.

  In order to achieve the above object, the invention described in claim 4 is a method for producing a float body comprising a thermoplastic resin containing hollow glass particles, wherein the thermoplastic resin powder and the hollow A partial float molding step in which a mixture obtained by previously mixing glass particles in a solid state is placed in a mold, and heated to a temperature equal to or higher than the melting temperature of the resin powder to compress and form a partial float. An arrangement step of arranging the plurality of partial floats formed in the partial float forming step in parallel with each other.

  According to the first aspect of the present invention, since the float body is composed of a plurality of partial floats arranged in parallel to each other, each float has a desired buoyancy. The shape of the partial float can be reduced, and the buoyancy of each partial float can be combined to obtain a desired buoyancy. Therefore, the thermoplastic resin powder and the hollow glass particles are in a solid state. Even when the mixture mixed in advance is put into a mold and is manufactured using a compression molding manufacturing method in which pressure is applied while compressing while heating above the melting temperature of the resin powder, the heating time of the mixture is shortened. Therefore, a float body made of a thermoplastic resin containing hollow glass particles can be produced in a short time.

  According to the invention described in claim 2, since each of the partial floats is formed in the same shape, when a plurality of partial floats are molded with one mold, the shape of the cavity provided in the mold is Since it becomes the same shape, manufacture of a metal mold | die becomes easy, Therefore, manufacturing cost can further be reduced. Moreover, a float body can be manufactured in a shorter time by simultaneously molding a plurality of partial floats with one mold.

  According to the invention described in claim 3, since the float body is constituted by the float body according to claim 1 or 2, a float body made of a thermoplastic resin including hollow glass particles is provided. It can be manufactured in a short time, and the manufacturing cost can be reduced.

  According to the invention described in claim 4, there is provided a method for producing a float body made of a thermoplastic resin including hollow glass particles, each of the thermoplastic resin powder and the hollow glass particles. In the partial float molding step, the mixture previously mixed in the solid state is put into a mold, and the partial float molding step is performed by applying pressure and compressing while heating above the melting temperature of the resin powder, and the partial float molding step. And arranging the plurality of molded partial floats in parallel with each other, so that the shape of each partial float is reduced with respect to one float having a desired buoyancy, and the mixture is heated. The time can be shortened and the desired buoyancy can be obtained by combining the buoyancy of a plurality of partial floats. Therefore, a flow made of a thermoplastic resin containing hollow glass particles. Body can be manufactured in a short period of time.

(A) It is a perspective view which shows the float body of one Embodiment of this invention, (b) is a side view (a partial sectional view is included) of the float body of (a). (A), (b) is a figure explaining the mixing process of the manufacturing method of the partial float with which the float body of FIG. 1 is provided. (A)-(f) is a figure explaining the compression molding process of the manufacturing method of the partial float with which the float body of FIG. 1 is provided. It is a front view (partial sectional view is included) which shows the liquid level sensor of one embodiment of the present invention. It is a top view of the liquid level sensor of FIG. It is a partial side view of the liquid level sensor of FIG.

(Embodiment 1)
Hereinafter, the float body of one Embodiment of this invention is demonstrated with reference to FIGS. 1-3. For example, the float body is floated on a liquid such as liquefied petroleum gas stored in a liquid tank, thereby detecting a liquid level (that is, a liquid level and also a liquid level) of the liquid. Used for surface level sensors.

  As shown in FIGS. 1A and 1B, the float body 90 includes a plurality of partial floats 91 and is configured in a cylindrical shape. In the present embodiment, the float body 90 includes three partial floats 91.

  The partial float 91 is formed in a cylindrical shape using a thermoplastic resin including glass beads G as hollow glass particles. The partial float 91 is provided with a through hole 92 along the axis. Each partial float 91 is formed in the same shape. Moreover, the thermoplastic resin used for the partial float 91 is determined in consideration of chemical resistance, corrosion resistance, and the like with respect to a liquid or the like on which the partial float 91 floats. In this embodiment, a high-density polyethylene resin is used as the thermoplastic resin.

  The partial floats 91 are arranged coaxially so that one end 72a of a float arm 72 described later is inserted into each through hole 92 and in contact with each other. In the present embodiment, the partial floats 91 constituting the float body 90 are arranged in parallel so as to be in contact with each other, but are not coupled to each other. For example, using a coupling means such as an adhesive The float bodies 90 may be configured by combining the partial floats 91 together.

  Next, an embodiment of the method for manufacturing a float body according to the present invention will be described with reference to FIGS.

  Conventionally, such a float has been manufactured by injection molding using a pellet in which glass microballoons as glass particles are mixed with a molten resin. However, when the mixing ratio of the glass microballoons increases, Since the glass microballoon is broken in this case, the specific gravity cannot be reduced below a certain value. For this reason, for example, a float floated on a liquid having a low specific gravity such as liquefied petroleum gas, dimethyl ether (DME), butane gas, or ammonia It was unsuitable for the production of

  And the float body 90 of this embodiment puts the mixture which mixed the thermoplastic resin powder and the hollow glass particle body beforehand with each solid state in a metal mold | die, and is more than the melting temperature of resin powder. Partial floats manufactured using a manufacturing method by compression molding that compresses by applying pressure while heating are arranged in parallel to each other. Therefore, breakage of the glass particles during production can be prevented, and by forming the float body 90 with the partial float 91, it is possible to manufacture the float body 90 with a low specific gravity that can float on a liquid with a low specific gravity. it can.

  In the float body manufacturing method described below, a cylindrical partial float 91 is formed using thermoplastic resin powder and hollow glass particles as raw materials, and then a plurality of partial floats 91 are formed. A cylindrical float body 90 (FIG. 1) is manufactured in combination. Of course, such a shape is an example, and the shape of the float body 90 is arbitrary as long as it is not contrary to the object of the present invention, such as a rectangular tube shape or an elliptical sphere shape. Further, the number of the partial floats 91 included in the float body 90 is arbitrary as long as it is plural, as long as it is not contrary to the object of the present invention. Further, the partial floats 91 may have different shapes, but the same shape is desirable from the viewpoint of cost reduction.

  As the thermoplastic resin powder, for example, powdered polyethylene (PE) having an average particle diameter of about 100 μm, a specific gravity of 0.95, and a melting temperature of 128 ° C. is used. In this embodiment, high-density polyethylene resin particles P (Sunfine LH-411, manufactured by Asahi Kasei Chemicals Corporation) are used. Of course, regarding the type of resin, in addition to polyethylene, for example, a powdery resin material such as polypropylene (PP) or polyamide (PA) may be used. What is necessary is just to be a magnitude | size of the grade which is not extremely larger than a body and mixes with this glass grain uniformly. In general, there is a correlation between the molecular weight and the melt viscosity in the resin, and even if it is the same kind of resin, the melt viscosity tends to increase as the molecular weight increases, but since it is mixed with the glass particles in the powder state, The melt viscosity does not affect the degree of mixing of the mixture and can be uniformly mixed. Moreover, since the chemical resistance and rigidity increase when the molecular weight of the resin is large, it is advantageous for the production of a high-pressure partial float 91 (that is, the float body 90) having excellent chemical resistance and low specific gravity.

  As the glass particles, for example, those formed in a hollow sphere having an average particle size of about 35 μm and a specific gravity of about 0.34 are used. In this embodiment, glass beads G for filler (Sphericel 34P30, manufactured by Potters Barotini) are used. The larger the particle size of the glass beads G, the smaller the specific gravity and the lower the pressure resistance. By reducing the specific gravity of the glass beads G, the specific gravity of the partial float 91 molded using the glass beads G can be reduced. However, since the glass beads G are easily broken during production, the partial float 91 having a desired specific gravity can be reduced. It becomes difficult to obtain, and the pressure resistance of the partial float 91 itself is also determined by the pressure resistance of the glass beads G. Therefore, if the specific gravity is too small, the required pressure resistance cannot be obtained. Therefore, the average particle diameter of the glass beads G is adjusted so as to balance the specific gravity and the pressure resistance according to the pressure applied at the time of forming the partial float 91 and the properties of the liquid floating on the partial float 91 (specific gravity, pressure, etc.). decide.

  In the production of the float body 90, first, a predetermined amount of high-density polyethylene resin particles P and glass beads G are weighed and then introduced into a mixer M and mixed as shown in FIGS. 2 (a) and 2 (b). Then, a mixture R in which these raw materials are uniformly mixed is produced (mixing step).

In this mixing step, the ratio of the glass beads contained in the generated mixture R (hereinafter also referred to as the filling rate) matches the application of the float body 90 to be manufactured (that is, the liquid to be floated on the float body 90, etc.). Then, the high density polyethylene resin particles P and the glass beads G are mixed so as to be included in the range of 41 to 73% by volume. The “volume%” here is a value about the volume occupied by the high density polyethylene resin particles P and the glass beads G themselves, which does not include spaces between powders and granules, and these volumes (volume%) are: Calculated from the specific gravity and weight of each raw material. For example, when the high density polyethylene resin particles P (specific gravity 0.95) is 26 g and the glass beads G (specific gravity 0.35) is 17 g, the volume of the high density polyethylene resin particles P is 27.4 cm ³ (= 26 / 0.95) and the glass beads G become 50.0 cm ³ (= 17 / 0.34). When these are mixed, the filling rate of the glass beads G is 65 vol% (= 50.0 / (27.4 + 50.0). )).

  Next, as shown in FIGS. 3A to 3F, the mixture R generated in the mixing step is filled in a mold and compressed while being heated to a temperature higher than the melting temperature of the high-density polyethylene resin particles P ( Compression molding process).

  The die K used in this compression molding process is provided with a plurality of bottomed cylindrical cavities C whose upper ends are opened (FIGS. 3A to 3F show only one cavity). In this cavity C, for example, a mold release process for applying a silicon mold release agent, a fluorine-type mold release agent, or the like is performed in advance. The cavity R is filled with the mixture R and filled with the mixture R until it overflows about 10% from the cavity C. Specifically, the filling of the mixture is performed in a plurality of times by pouring into the cavity C from above in small portions (FIGS. 3A and 3C), and the mixture filled in the cavity C is poured every time the mixture is poured. It compresses with the pressure of about 1 Mpa from the top, and it is performed until it overflows from the upper part of the cavity C, making the space | gap produced in the mixture R small (FIG.3 (b), (d)) (FIG.3 (e)). Then, when the mixture R is filled in the cavity C, the mold K is heated to 180 ° C. by the heater H disposed in the mold K so as to heat the mixture R from all directions, and the mixture R (that is, Resin powder) is melted and the pressure is gradually increased to 5 MPa at a rate of 1 MPa / minute, and the mixture R is compressed for 10 minutes in a state where the pressure of 5 MPa is applied (FIG. 3 (f)). At this time, since the mixture R (that is, molten resin) flows out from the gap between the molds K, the pressure is adjusted so that the pressure applied to the mixture R is maintained at 5 MPa.

  Then, cooling for solidifying the mixture R into a molded product is performed. That is, the heater H is turned off while holding the mold K, and natural cooling is performed until the mold temperature (that is, the temperature of the mixture R) reaches 100 ° C., and further, the mold K is held. Cooling water is circulated through a pipe line (not shown) provided in the mold K to perform cooling until the mold temperature reaches 40 ° C. (cooling process). The process including the mixing process and the compression molding process described above corresponds to the partial float molding process in the claims.

  Then, the molded product is taken out from the mold K, and the partial float 91 is obtained. The plurality of partial floats 91 obtained in this way are arranged coaxially so as to be in contact with each other (arrangement step), and the float body 90 is completed.

  An example of the relationship between the filling rate (that is, the mixing ratio) of the glass beads G into the high-density polyethylene resin particles P and the specific gravity of the partial float 91 that is a molded product is shown below.

  For example, the average particle size is 100 μm (particle size range 80 to 150 μm), the specific gravity is 0.95, the high temperature polyethylene resin particles P having a melting temperature of 128 ° C., the average particle size is 35 μm (particle size range 10 to 50 μm), These raw materials are mixed in a solid state using glass beads G having a specific gravity of 0.34 and a pressure resistance of 20 MPa.

  Then, (A) a mixture R in which the filling rate of the glass beads G is 41 to 73% by volume is generated, and the mixture R is filled in a mold K and compression-molded at a pressure of 5 MPa. (1) Dimethyl ether Partial float 91 having a specific gravity suitable for each of (liquid specific gravity 0.67), (2) ammonia (liquid specific gravity 0.64), and (3) liquefied butane gas (liquid specific gravity 0.58) (ie, float 90) Can be manufactured.

  Alternatively, (B) by producing a mixture R in which the filling ratio of the glass beads G is 51 to 71% by volume, filling the mixture R into a mold and compression molding at a pressure of 5 MPa, (2), A float 90 having a specific gravity suitable for each of (3) can be manufactured.

  Alternatively, (C) a mixture in which the filling ratio of the glass beads G is 64 to 66% by volume is generated, and the mixture is filled in a mold and compression-molded at a pressure of 5 MPa, which is suitable for the above (3). A float body 90 having a specific gravity can be manufactured. In particular, by setting the filling rate of the glass beads G to 65%, it is possible to manufacture a float having a specific gravity of 0.55 to 0.57 that could not be manufactured by the conventional manufacturing method disclosed in Patent Document 1. it can.

  As described above, according to the present embodiment, since the float body 90 is configured by the plurality of partial floats 91 arranged in parallel to each other, each float with a desired buoyancy is provided for each float. The shape of the partial float 91 can be reduced, and the desired buoyancy can be obtained by combining the buoyancy of each partial float 91. Therefore, the thermoplastic resin powder (high-density polyethylene resin particles P) and the hollow shape can be obtained. Production by compression molding in which a mixture R in which the glass particles (glass beads G) are mixed in advance in a solid state is placed in a mold K and compressed by applying pressure while heating to a temperature higher than the melting temperature of the resin powder. Even when manufactured using the method, the heating time of the above mixture can be shortened. Therefore, the float 90 made of a thermoplastic resin containing hollow glass particles can be shortened. In can be produced.

  Further, since each of the plurality of partial floats 91 is formed in the same shape, when the plurality of partial floats 91 are formed with one mold K, the shape of the cavity C provided in the mold K is the same shape. Therefore, the mold K can be easily manufactured, and the manufacturing cost can be further reduced. Moreover, the float body 90 can be manufactured in a shorter time by simultaneously molding the plurality of partial floats 91 with one mold K.

  In addition, the above-described manufacturing method of the float body 90 is a method in which a mixture of thermoplastic resin powder and hollow glass particles previously mixed in a solid state is put in a mold, and the melting temperature of the resin powder or higher is reached. A step of forming a partial float 91 by applying pressure and compressing while heating, and a step of arranging a plurality of the partial floats formed in the step in parallel with each other. In addition to reducing the shape of each partial float 91 for one float, the heating time of the mixture can be shortened, and the buoyancy of the plurality of partial floats 91 can be combined to obtain a desired buoyancy. Therefore, the float body 90 made of a thermoplastic resin containing hollow glass particles can be manufactured in a short time.

(Embodiment 2)
Next, a liquid level sensor according to an embodiment of the present invention will be described with reference to FIGS. The liquid level sensor of this embodiment is used for detecting a liquid level such as liquefied petroleum gas, for example.

  As shown in FIGS. 4 to 6, the liquid level sensor 1 includes a case 10, a pointer mechanism unit 30, a drive mechanism unit 50, and a float unit 70.

  The case 10 is made of, for example, a metal having corrosion resistance such as stainless steel, and the upper case portion 11 and the lower case portion 21 are fixed to each other by screws 12.

  The upper case portion 11 includes a substantially bottomed cylindrical upper portion 11a and a substantially cylindrical lower portion 11b having a smaller diameter than the upper portion 11a coaxially stacked on the bottom surface of the upper portion 11a. It has been.

  The upper case 11 has a first accommodating chamber 14 that is a substantially cylindrical space opened upward as an inner space of the upper portion 11a, that is, downward as an inner space of the lower portion 11b. And a second storage chamber 15 which is an open substantially cylindrical space. In the first storage chamber 14, a pointer mechanism unit 30 described later is stored. The second storage chamber 15 stores a drive magnet 52 described later.

  The lower case portion 21 is formed in a cylindrical shape that is long and has a smaller diameter than the lower portion 11b. Bearing portions 22 and 23 that pivotally support a shaft 51 of a drive mechanism portion 50 to be described later are provided inside the one end portion 21 a and the other end portion 21 b of the lower case portion 21. Further, a flange 24 is provided on one end 21 a of the lower case portion 21 over the entire outer peripheral surface. The outer diameter of the flange 24 is formed to be the same as the outer diameter of the one end portion 11 c of the upper case portion 11 (that is, the outer diameter of the lower portion 11 b of the upper case portion 11).

  The flange 24 is superimposed on the one end portion 11 c of the upper case portion 11, and is fixed to the one end portion 11 c with the screw 12. Thereby, the opening of the second storage chamber 15 is closed by the lower case portion 21.

  The pointer mechanism unit 30 includes a base 31, a pointer unit 35, and a cover 49.

  The base 31 is formed in a disk shape having the same outer diameter as that of the first storage chamber 14 using, for example, a synthetic resin. On the peripheral edge of the upper surface 31a of the base 31, an index 31c such as a scale line or a number indicated by a pointer unit 35 described later is formed. In addition, a pointer unit accommodation chamber 32 which is a substantially cylindrical space opened upward is formed at the center of the upper surface 31a of the base 31. A columnar convex portion 33 is formed on the bottom surface 32 a of the pointer unit accommodation chamber 32. The lower surface 31 b of the base 31 is formed in the same shape as the bottom surface of the first storage chamber 14, and when the base 31 is stored in the first storage chamber 14, the lower surface 31 b of the base 31 is changed to the first storage chamber 14. Closely overlaps the bottom. The base 31, the pointer unit accommodation chamber 32, and the convex portion 33 are arranged so as to be coaxial with each other. The base 31 is fixedly stored in the first storage chamber 14.

  The pointer unit 35 includes a pointer portion 36 and a driven magnet 41.

  The pointer portion 36 includes a pointer portion main body 37 and a pointer 40 that are integrally formed using, for example, a synthetic resin. The pointer unit body 37 is formed in a substantially bottomed cylindrical shape having an outer diameter slightly smaller than the diameter of the pointer unit accommodation chamber 32. A concave portion 38 in which the convex portion 33 of the pointer unit accommodation chamber 32 is rotatably fitted is provided at the central portion of the bottom wall 37 a of the pointer portion main body 37. Further, a bottom wall through hole 39 into which a later-described stop pin 47 is inserted is provided at the center of the bottom wall 37a. The pointer 40 is extended in a rod shape toward the radially outer side of the pointer portion main body 37 at the opening side end portion of the peripheral wall 37 b of the pointer portion main body 37.

  The driven magnet 41 is formed in a substantially cylindrical shape having the same outer diameter as the inner diameter of the pointer part main body 37, and is fixedly housed inside the pointer part main body 37. A magnet through hole 42 is provided in the axial direction at the center of the driven magnet 41. When the driven magnet 41 is accommodated in the pointer part main body 37, the magnet through hole 42 overlaps the bottom wall through hole 39 of the pointer part main body 37 and communicates with each other. The driven magnet 41 is magnetically coupled (magnetically coupled) to a drive magnet 52 described later.

  The pointer unit 35 is accommodated in the pointer unit accommodating chamber 32 such that the convex portion 33 is positioned inside the concave portion 38. Then, when the stop pin 47 is inserted into the magnet through hole 42 and the bottom wall through hole 39 and the tip of the stop pin 47 is fixed to the convex portion 33 of the base 31, the pointer unit 35 is attached to the base 31 in a freely rotatable manner. It is done. The pointer 40 of the pointer unit 35 is disposed on the upper surface 31a of the base 31, and indicates an index 31c corresponding to the rotation position (that is, the measurement amount). The pointer unit 35 is rotated in accordance with the rotation of the drive magnet 52 that is magnetically coupled to the driven magnet 41.

  The cover 49 is made of, for example, a transparent synthetic resin and is directed downward over the disk-shaped upper wall portion 49a having the same outer diameter as the first storage chamber 14 and the entire periphery of the upper wall portion 49a. The peripheral wall part 49b stood up and the shielding part 49c provided in the center part of the upper wall part 49a are provided. The cover 49 is housed in the first housing chamber 14 so that the front end of the peripheral wall portion 49b (that is, the end opposite to the upper wall portion 49a) faces the base 31. The cover 49 is made of light-shielding paint so that the indicator 31c formed on the upper surface 31a of the base 31 and the pointer 40 of the pointer unit 35 are visually recognized when viewed from above, and the pointer body 37 and the driven magnet 41 are not visually recognized. The formed shielding part 49c is provided in the central part of the upper wall part 49a.

  The drive mechanism unit 50 includes a shaft 51, a drive magnet 52, a first gear 53, and a second gear 54.

  The shaft 51 is formed in a long cylindrical shape using, for example, a metal having corrosion resistance such as stainless steel. The shaft 51 is pivotally supported on the inner side of the lower case portion 21 by the bearing portions 22 and 23 of the lower case portion 21 so as to be rotatable coaxially with the lower case portion 21. One end portion 51 a of the shaft 51 protrudes from one end portion 21 a of the lower case portion 21 and is positioned in the second storage chamber 15, and the other end portion 51 b protrudes from the other end portion 21 b of the lower case portion 21. It is positioned outside the case portion 21.

  The drive magnet 52 is formed in a disc shape (that is, a flat cylindrical shape), and is fixedly attached to one end portion 51 a of the shaft 51. The center of the drive magnet 52 is disposed on the rotation axis of the shaft 51.

  The first gear 53 is fixedly attached to the other end 51 b of the shaft 51. The rotation shaft of the first gear 53 is disposed on the rotation shaft of the shaft 51. The second gear 54 is extended to the other end 21 b of the lower case portion 21 so that the rotation axis thereof is orthogonal to the rotation axis of the first gear 53 (that is, the rotation axis of the shaft 51). The gear bearing 25 is pivotally supported by the gear bearing 25.

  The float unit 70 includes a float arm 72 and a float arm assembly 71 including the float body 90 described above, and a balancer 73.

  The float arm 72 is made of, for example, a metal having corrosion resistance such as stainless steel, and is formed in a substantially L-shaped cylindrical bar shape. One end portion 72a of the float arm 72 corresponds to a portion on the short side of the L shape, and the float body 90 is attached thereto. The other end 72b of the float arm 72 corresponds to a portion near the tip of the long side of the L shape, and a balancer 73 described later is fixedly attached.

  The float body 90 is formed to be slightly shorter than the length of the L-shaped short side of the float arm 72. The float body 90 has the one end 72a of the float arm 72 inserted through the through-hole 92, and the push nut 93 is fixedly attached to the tip of the one end 72a. And it is attached in a state of being sandwiched between the L-shaped bent portion 72c of the float arm 72. Of course, not limited to this, the float body 90 may be fixedly attached to the one end portion 72a by a fixing member such as an adhesive.

  The balancer 73 is made of, for example, a metal having corrosion resistance such as stainless steel, and is formed in a substantially cylindrical shape, and has a balancer through-hole 74 through which the other end 72b of the float arm 72 is inserted along the axis. Is provided. The balancer 73 is fixed to the other end portion 72 b of the float arm 72 by brazing 77 at both ends thereof.

  The liquid level sensor 1 described above is attached to a liquid tank that contains a liquid. Then, when the float body 90 of the liquid level sensor 1 is floated on the liquid surface of the liquid in the liquid tank and the float body 90 is moved up and down as the liquid level rises and falls, this vertical movement is the first. The drive magnet 52 is rotated according to the amount of movement of the float body 90, that is, the amount of liquid in the liquid tank, sequentially transmitted to the second gear 54, the first gear 53 and the shaft 51. Then, the driven magnet 41 is rotated by the rotation of the drive magnet 52, and accordingly, the pointer portion 36 is also rotated, so that the pointer 40 provided on the pointer portion 36 has an amount of liquid in the liquid tank. The index 31c corresponding to the is indicated.

  As mentioned above, according to this embodiment, since it has the float body 90 mentioned above, the float body 90 which consists of a thermoplastic resin containing a hollow glass particle body can be manufactured in a short time, Therefore, a liquid level The sensor 1 can also be manufactured in a short time, and the manufacturing cost can be reduced.

  In the above-described embodiment, the float body used for detecting the liquid level of the liquefied petroleum gas and the liquid level sensor having the float body are described. However, the present invention is not limited to this, and the liquefied petroleum is not limited thereto. In addition to gas, it may be used for highly corrosive chemicals such as sulfurous acid and ammonia, and high-pressure liquefied gases such as propane gas and butane gas, and the type of liquid whose liquid level is to be detected is arbitrary. In this case, the float arm assembly is configured using a material having corrosion resistance to the liquid to be detected. Further, the liquid level sensor of the present invention may be mounted on a moving body such as a vehicle and used for measuring the remaining amount of fuel in the fuel tank, and the use is arbitrary as long as it does not contradict the purpose of the present invention. It is.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Liquid level sensor 71 Float arm assembly 72 Float arm 72a One end part 90 Float body 91 Partial float 92 Through-hole P P High density polyethylene resin particle (thermoplastic resin powder)
G Glass beads (hollow glass particles)
K mold C cavity H heater R mixture

Claims (4)

In a float body made of a thermoplastic resin containing hollow glass particles,
The float body is composed of a plurality of partial floats arranged in parallel to each other.   The float body according to claim 1, wherein each of the partial floats is formed in the same shape. In a liquid level sensor having a float body and a float arm to which the float body is attached,
The said float body is comprised with the float body of Claim 1 or 2, The liquid level sensor characterized by the above-mentioned. A method for producing a float body comprising a thermoplastic resin containing hollow glass particles,
A mixture in which the thermoplastic resin powder and the hollow glass particles are mixed in advance in a solid state is placed in a mold, and compressed by applying pressure while heating to a temperature higher than the melting temperature of the resin powder. A partial float forming process for forming a partial float;
And a disposing step of arranging the plurality of partial floats formed in the partial float forming step in parallel with each other.

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