Abstract:
A resin molding is made by integrally joining a first resin molded part configured with a concave portion and a second resin molded part configured with a convex portion so that the concave portion and the convex portion are mated together. The resin molding includes a cavity that is in communication with the convex portion and the concave portion when the convex and concave portions are mated into each other, and a joining resin filled into the cavity. The first and second molded parts and the joining resin are composed of the same resin or similar resins.

Description:
This application is a divisional of application Ser. No. 11/866,531, filed on Oct. 3, 2007, now U.S. Pat. No. 7,467,938, which is a divisional of application Ser. No. 10/767,720, filed on Jan. 30, 2004, now U.S. Pat. No. 7,300,614. 
    
    
     This application claims priority from Japanese Patent Application No. 2003-027511 filed Feb. 4, 2003, which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a resin molding which is difficult to mold integrally and which is obtained by separately molding a plurality of resin molded parts each having a joining portion and mating these joining portions into one another to integrally join the molded parts together, as well as a method of manufacturing this resin molding and a resin injecting apparatus used for this method. 
     2. Description of the Related Art 
     It is contemplated that a resin molding that is difficult to mold integrally may be manufactured by separately pre-molding a plurality of resin molded parts, mating joining portions molded in these molded parts into one another, and injecting an adhesive or a resin into these joining portions to integrate the parts. For example, a cassette type toner cartridge  1  such as the one shown in  FIG. 1 , which is used in an electrophotographic device, comprises a cartridge main body  2  and a side cover  3  disposed at a side of the cartridge main body  2 . It is essentially difficult to mold this apparatus in a single injecting step. Thus, attempts are made to separately inject these parts, integrate the parts together using a joining portion  4 , and fill a molten resin into the joining portion  4  to secure them. 
     Attempts are also made to subject such resin moldings to a recycle process to reuse them as new resin moldings if they are damaged or used. What is important in such a recycle process is that the resin molding is composed substantially of a single material. In this connection, for resin moldings designed so that their joining portions are integrally connected together using an adhesive, the adhesive is foreign to the resin constituting the resin molding. This deteriorates recyclability. Resin moldings obtained by injecting the same molten resin as or a molten resin similar to that of the resin molding into the joining portion are more preferable in terms of recyclability. 
     The use of a hot melting apparatus or an injection molding apparatus is expected as a method of injecting a molten resin into the joining portion between the resin molded parts. 
     When the hot melting apparatus is used, it is necessary to keep a tip portion of an injection gun of the hot melting apparatus in non-contact with the joining portion between the molded parts and to supply a molten resin from the tip of the injection gun to the joining portion between the molded parts. 
     When a common injection molding apparatus  100  such as the one shown in  FIG. 6  is used, a dies set  101  is provided which is composed of a fixed die  101   a  and a movable die  101   b  and formed with a cavity corresponding to the cartridge main body  2  and the side cover  3 , combined with each other. A resin injecting apparatus  103  is provided on a frame  102  of the injection molding apparatus  100 . The resin injecting apparatus  103  comprises a hopper  105  that stores resin pellets  104  in a solid state, a heating cylinder  106  that heats and molds the resin pellets  104 , and a screw driving device  108  that rotates and reciprocates a screw  107  arranged inside the heating cylinder  106 . The screw driving device  108  advances the screw  107  to meter a molten resin  109 . A die open and close driving apparatus  110  comprises a die opening and closing cylinder  111  that reciprocates a movable plate  111   a  in a longitudinal direction in the  FIG. 6 . The fixed die  101   a  is fixed to a fixed plate  111   b . The movable die  101   b  is fixed to the movable plate  111   a.    
     In a molding operation using the injection molding apparatus  100 , the movable plate  111   a  is moved backward, the cartridge main body  2  and the side cover  3  are set in the die  101 , and then the movable plate  111   a  is closed to set the cartridge main body  2  and the side cover  3  in the die  101 . The fixed die  111   a  fixed to the fixed plate  111   b  has a hot runner  112  heated so as not to solidify the molten resin  109 , injected from the heating cylinder  106 , a gate  113  following the hot runner  112 , a gate pin  114  that opens and closes the gate  113 , a gate pin driving cylinder  115  that drives the gate pin  114 , and a cooling fluid passage  116  through which a cooling fluid is passed to cool the gate  113 . Accordingly, after the gate  113  has been opened using the gate pin  114 , the molten resin  109  can be injected into the joining portion  4  between the cartridge main body  2  and the side cover  3 . After the molten resin  109  has completely been injected, the gate pin  114  is advanced to close the gate  113 . Then, the molten resin  109  filled into the joining portion  4  is thus cooled and solidified to integrate the cartridge main body  2  with the side cover  3 . Subsequently, the die opening and closing cylinder  111  is activated to move the movable plate  111   a  backward. The movable die  101   b  fixed to the movable plate  111   a  is thus opened to allow the integrated cartridge main body  2  and side cover  3  to be removed. 
     When the hot melt apparatus is used to fill the molten resin into the joining portion  4  between the cartridge main body  2  and the side cover  3  as shown in  FIG. 1 , a tip portion of an injection gun of the hot melt apparatus must be kept in non-contact with the joining portion  4  between the cartridge main body  2  and the side cover  3 . Thus, depending on the shapes of a cavity in the joining portion  4  into which the molten resin is filled or the viscosity of the molten resin, it may be difficult to completely fill the molten resin into these cavitys or appropriately maintain the esthetics of the surface of the joining portion after the injection. 
     On the other hand, when the injecting molding apparatus  100  as shown in  FIG. 6  is utilized to inject the molten resin  109  into the joining portion  4  between the cartridge main body  2  and the side cover  43 , such inconveniences do not occur as occur if the above-described hot melt apparatus is used. However, the injection molding apparatus  100  for molding and injecting the resin pellets  104  into the joining portion  4  further incorporates the hot runner  112  that guides the molten resin  109  to the joining portion  4 , and the like. The injection molding apparatus  100  also requires the dies set  101  for holding the toner cartridge  1 . Thus, disadvantageously, a dedicated facility is required, thus increasing installation spaces and facility costs. Furthermore, the injection molding apparatus itself is expensive and cumbersome to handle. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is a method of manufacturing a resin molding made by integrally joining a first resin molded part and a second resin molded part together via their joining portions, the method comprises a step of molding a concave portion as the joining portion when molding the first molded part, a step of molding a convex portion which has a through-hole in a central portion thereof as the joining portion when molding the second molded part, a step of mating the concave portion of the first molded part with the convex portion of the second molded part so that a cavity being in communication with one end of the through-hole is configured between the concave portion and the convex portion, a step of holding, with a jig, the first and second molded parts mating the concave portion with the convex portion so as to form the cavity therebetween, a step of connecting a tip of an injection nozzle to the other end of the through-hole, the injection nozzle being used to inject a molten resin into the cavity between the first and second molded parts held by the jig, and a step of filling the molten resin into the through-hole and the cavity from the injection nozzle so that the concave and convex portions are integrally joined by the molten resin. 
     In the method according to the first aspect of the present invention, the resin molding is obtained by mating the convex portion formed in the first molded part with the corresponding convex portion formed on the second molded part, holding the mated first and second molded parts by the jig, then connecting the injection nozzle with one end of the through-hole which the other end is in communication with the cavity, injecting the molten resin into the through-hole and the cavity from the injection nozzle, and integrally joining the first and second molded parts, as the resin molding, via the concave and convex portions by the resin. 
     According to the present invention, the resin molding of a complicated shape can be efficiently and inexpensively manufactured without using any special dies or the like. Consequently, a very recyclable resin molding can be manufactured. 
     In the method of manufacturing a resin molding according to the first aspect of the present invention, the first molded part, the second molded part, and the molten resin may be made of the same resin or similar resins in that the resin molding can be easily processed for recycling. In terms of material costs and handling easiness, these same or similar resins are particularly preferably polystyrenes, polypropylenes, polyethylenes, ABS resins, modified PPE resins, or composite resins of ABS and polycarbonate. 
     The method of manufacturing the resin molding may further comprise a step of interposing a thermal insulating bush between the injection nozzle which is connected to the other end of the through-hole in order to inject the molten resin into the cavity from the through-hole, and the convex portion to suppress a rise in temperature of the second resin molded part. In this case, the method of manufacturing the resin molding may further comprise a step of flowing a coolant through the thermal insulating bush so that a temperature of the thermal insulating bush is lower than that of the molten resin. For this reason, it is possible to prevent the second molded part from being disadvantageously thermally deformed. 
     A second aspect of the present invention is a resin molding made by integrally joining a first resin molded part configured a concave portion and a second resin molded part configured a convex portion so that the concave portion and the convex portion are mated together, the resin molding comprises a cavity that is in communication with the convex portion and the concave portion when the convex and concave portions are mated into each other, and a joining resin filled into the cavity, and wherein the first and second molded parts and the joining resin are composed of the same resin or similar resins. 
     Such resin molding can be collectively processed during recycling and are thus suitable for recycling. In particular, when polystyrenes, polypropylenes, polyethylenes, ABS resins, modified PPE resins, or composite resins of ABS and polycarbonate as the same resin or similar resins are used, the resin molding which can be easily processed at low cost is obtained. 
     In the above-mentioned resin moldings, the resin molding may comprise a plurality of joining portions in order to increase a bonding strength of the first and second molded parts. 
     A third aspect of the present invention is a resin injecting apparatus which comprises a resin injecting nozzle for injecting a molten resin into a cavity configured between a first resin molded part and a second resin molded part connected to the first molded part, from a through-hole configured in the second molded part, an ejection plunger for ejecting a predetermined amount of molten resin from the resin injecting nozzle, a thermal insulating bush attached to the resin injecting nozzle, a coolant passage which is formed in the thermal insulating bush and through which a coolant is passed, and coolant supplying means for supplying the coolant to the coolant passage. 
     According to the resin injecting apparatus of the present invention, the thermal insulating bush can prevent heat from the resin injecting nozzle or radiant head from being transmitted to the second resin molded part. This prevents the molten resin from leaking from pressed-against surfaces of the other end of the through-hole and the injecting nozzle to the exterior of the through-hole. 
     In the resin injecting apparatus according to the third aspect of the present invention, the thermal insulating bush may have a cylindrical portion surrounding a circumference of the through-hole, and a bottom surface of the cylindrical portion may abut on an end surface of the second molded part in which the other end of the through hole is open. This enables the resin injecting nozzle to be positioned relative to the through-hole. It is thus possible to prevent the molten resin from leaking from pressed-against surfaces of the other end of the through-hole and the injecting nozzle to the exterior of the through-hole. 
     In the above-mentioned resin injecting apparatus, the resin injecting apparatus may further comprise a thermal insulating member provided on the thermal insulating bush and abutted on the first molded part. In this case, the thermal insulating bush and the thermal insulating member can reliably insulate heat from the resin injecting nozzle. This makes it possible to prevent the second molded part from being thermally deformed. 
     The resin injecting apparatus may further comprise a jig for holding at least one of the first and second molded parts. In this case, the resin injecting nozzle can be positioned relative to the through-hole. This also makes it possible to prevent the molten resin from leaking from the through-hole. 
     The number of the resin injecting nozzles and the number of the ejection plungers may correspond to the number of through-holes configured in the second molded part. Workability and working efficiency can be improved by simultaneously injecting the molten resin through all the through-holes. 
     The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjoining portion with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a projection view illustrating the appearance of a toner cartridge to which the present invention is applied; 
         FIG. 2  is a sectional view illustrating the structure of the joining portion between a cartridge main body and a side cover constituting the toner cartridge shown in  FIG. 1 ; 
         FIG. 3  is a sectional view illustrating an operation of joining the joining portions shown in  FIG. 2  using the resin injecting apparatus shown in  FIG. 4 ; 
         FIG. 4  is a projection view illustrating the appearance of essential components of a resin injecting apparatus that joins the joining portions shown in  FIG. 2 ; 
         FIG. 5  is a sectional view illustrating an operation of joining the joining portions shown in  FIG. 2  using another embodiment of a resin injecting apparatus; and 
         FIG. 6  is a sectional view schematically showing a conventional operation of joining portions of two resin molded parts using an injection molding apparatus. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1 to 5 , a detailed description will be given of an embodiment in which a method of manufacturing a resin molding according to the present invention is applied to the toner cartridge  1  of the electrophotograhic device as shown in  FIG. 1 . However, the present invention is not limited to this embodiment. It is possible to subject the embodiment to all alterations or modifications included in the concept of the present invention described in the specification. Thus, naturally enough, the present invention is applicable to other techniques belonging to the spirits of the present invention. 
       FIG. 1  shows the appearance of the toner cartridge  1  according to the present embodiment.  FIG. 2  shows the sectional structure of the joining portion  4  between the cartridge main body  2  and the side cover  3 . As described previously, the toner cartridge  1  according to the present embodiment comprises the cartridge main body  2  and the side cover  3  disposed at the side of the cartridge main body  2 . The cartridge main body  2  and the side cover  3  are separately injected and then integrated into the toner cartridge  1 . 
     The joining portion  4  between the cartridge main body  2  and the side cover  3  is composed of a cylindrical concave portion  21  projected from the cartridge main body  2 , a convex portion  31  projected from the side cover  3 , and a joining resin  41  filled into a cavity configured between the concave portion  21  and the convex portion  31 , i.e. a space S when the portions  21  and  31  are fitted into each other. In the present embodiment, the cartridge main body  2 , the side cover  3 , and the joining resin  41  are all formed of the same material. 
     The convex portion  31 , molded integrally with the side cover  3 , comprises a pedestal  32  projecting from a surface of the side cover  3  and having a cylindrical cross section, a fitting sleeve  34  projecting further outward from an inner end surface  35  of the pedestal  32 , and a cylindrical gate bush  36  projecting from the inner end surface  35  of the pedestal  32  in the direction opposite to that of the fitting sleeve  34  and located inside the pedestal  32 . In the present embodiment, the outer diameter of the fitting sleeve  34  is set to be smaller than that of the pedestal  32 . The outer diameter of the gate bush  36  is set to be further smaller than that of the fitting sleeve  34 . A molten resin  41 ′ is supplied via the gate bush  36 . 
     The concave portion  21 , injected integrally with the cartridge main body  2 , comprises a fitting sleeve  22  projecting from the side wall of the cartridge main body  2  and a projection  23  projecting from the side wall of the cartridge main body  2  concentrically with the fitting sleeve  22 . The outer diameter dimension of the fitting sleeve  34  of the convex portion  31  and the inner diameter dimension of the fitting sleeve  22  of the concave portion  21  are appropriately set so that the fitting sleeve  34  of the convex portion  31  can be closely fitted into the fitting sleeve  22  of the concave portion  21 . Moreover, after the fitting sleeve  34  of the convex portion  31  has been fitted into the fitting sleeve  22  of the concave portion  21 , the tip of the fitting sleeve  22  of the concave portion  21  abuts on an outer end surface  33  of the pedestal  32  of the convex portion  31 . Furthermore, an appropriate spacing is formed between the inner peripheral surface of the fitting sleeve  34  of the convex portion  31  and the outer peripheral surface of the projection  23  of the concave portion  21  as the space S so as to allow the molten resin  41 ′ to be filled into the space S through a tapered hole  37  in the gate bush  36  which is a through-hole according to the present invention. 
       FIG. 3  shows the appearance of a resin injecting apparatus according to the present embodiment which forms the joining portion  4 .  FIG. 3  shows the sectional structure of a tip portion of the resin injecting apparatus together with the cartridge main body  2  and the side cover  3 , provided as a work piece. A resin injecting apparatus  50  according to the present embodiment comprises a hopper (not shown) for storing resin pellets (not shown), a heating cylinder (not shown) for heating and melting the resin pellets accommodated in the hopper, a pellet supplying section (not shown) for supplying the heating cylinder with the resin pellets stored in the hopper, a resin injecting portion  51  for injecting the molten resin  41 ′ from the heating cylinder, and a positioning jig  52  on which the cartridge main body  2  connecting to the side cover  3  via the joining portion  4  is supported. An injecting operation of the molten resin  41 ′ using the resin injecting apparatus  50  is performed while the cartridge main body  2  connecting to the side cover  3  is mounted on the positioning jig  52 . 
     The resin injecting portion  51  according to the present embodiment, in which a heater (not shown) for thermal insulation is incorporated, comprises a metering section  54  having an injection pin  53  driven when the molten resin  41 ′ is injected, a resin injection nozzle  55  through which the molten resin  41 ′ is injected, a nozzle pin  56  that opens and closes the resin injection nozzle  55 , and a thermal insulating bush  57  attached to a tip portion of the resin injection nozzle  55 . When the nozzle pin  56  is moved backward to open the resin injection nozzle  55 , the communication between the above-described pellet supplying section and heating cylinder is blocked. The movement stroke of the injection pin  53  is set in association with the volumes of the space S and the tapered hole  37 . As the pellet supplying section supplies the resin pellets to the heating cylinder, the injection pin  53  is moved backward (in  FIG. 3 , upward) to its backward end. A coolant passage  58  through which a coolant such as water or air is passed is formed in the thermal insulating bush  57 , which surrounds the resin injection nozzle  55 , so as to surround the resin injection nozzle  55 . Coolant supplying means (not shown) is connected to the coolant passage  58 . The coolant is passed through the coolant passage  58 . The thermal insulating bush  57  according to the present embodiment has a cylindrical portion  59  that can be fitted into the pedestal  32  of the convex portion  31  of the side cover  3 . The thermal insulating bush  57  is set so that by abutting the proximal surface of the gate bush  36 , fitted into the cylindrical portion  59 , against the bottom surface of the cylindrical portion  59 , the outer peripheral end of the resin injection nozzle  55  is closely abutted on the inner peripheral surface of the tapered hole  37  in the gate bush  36 . A thermal insulating member  61  surrounding the cylindrical portion  59  is further attached on a surface of the thermal insulating bush  57 . When the molten resin  41 ′ is injected, the insulating member  61  is abutted against the side cover  3  to stabilize the relative position of the resin injection nozzle  55  of the resin injecting apparatus  50  relative to the side cover  3 . This also minimizes the thermal deformation of the side cover  3 . 
     The positioning jig  52  according to the present embodiment, which acts as supporting means, comprises a base plate  62  and a plurality of (in the illustrated example, three) locating blocks  63  projected from the base plate  62  to allow the cartridge main body  2  to be mounted on the base plate so as to position the respective predetermined areas of the cartridge main body  2  and the side cover  3 . Considerations are given for the mount positions, support positions, and the like of these locating blocks  63 , which support the cartridge main body  2  and the side cover  3 , so as to prevent the cartridge main body  2  and the side cover  3  from moving relative to the positioning jig  52  when the molten resin  41 ′ is injected. 
     In the injecting operation, the cartridge main body  2  connecting to the side cover  3  via the joining portion  4  is placed on the positioning jig  52  at a predetermined position. In this state, the positioning jig  52  is moved and held as shown in  FIG. 3  so that the gate bush  36  of the side cover  3  is mated into the cylindrical portion  59  of the thermal insulating bush  57  of the resin injecting apparatus  50 . Then, the nozzle pin  56  is moved backward to move the injection pin  53  from its backward end to its forward end (toward the nozzle pin  56 ). The molten resin  41 ′ is thus completely filled into the space S from the resin injection nozzle  55  via the tapered hole  37  in the gate bush  36 . Once the injection pin  53  reaches its forward stroke end, the nozzle pin  56  is moved forward to block the resin injection nozzle  55 . Thus, the filling operation of the molten resin  41 ′ is finished. In this case, the thermal insulating bush  57  is covered over the tip portion of the resin injection nozzle  55 . Accordingly, the resin injection nozzle  55  can be efficiently cooled by the thermal insulating bush  57 . The molten resin  41 ′ injected into the tapered hole  37  can thus be easily separated from the tip of the resin injection nozzle  55 . 
     The molten resin  41 ′ filled into the tapered hole  37  and the space S is cooled and solidified to complete integrating the concave portion  21  with the convex portion  31 . Then, the positioning jig  52  is separated from the resin injection apparatus  50  to separate the tip of the resin injecting nozzle  55  in the resin injecting apparatus  50  from the joining resin  41  filled into the tapered hole  37 . 
     In the resin injecting apparatus  50 , shown in  FIG. 4 , the thermal insulating member  61  abutting on the surface of the side cover  3  is mounted on the thermal insulating bush  57  to hinder the side cover  3  from being thermally deformed. However, it is also effective to thermally insulate the side cover  3  from the resin injecting portion  51  by forming a gap between the surface of the side cover  3  and the thermal insulating bush  57 . 
       FIG. 5  shows the sectional structure of essential components of another embodiment of the resin injecting apparatus  50  together with the above-described cartridge main body  2  and side cover  3 . Elements having the same functions as those of the above-embodiment are denoted by the same reference numerals with their duplicate description omitted. After the resin injecting apparatus  50 , shown in  FIG. 5 , has been positioned on the side cover  3 , the thermal insulating bush  57  has only the bottom surface  60  of its cylindrical portion  59  abutted on the end surface of the gate bush  36  of the side cover  3 . A thermal insulating gap G is formed between the surface of the side cover  3  and the thermal insulating bush  57 . In the present embodiment, to stably support the cartridge main body  2  and the side cover  3  when the molten resin  41 ′ is, injected, a locating block  64  and a pair of locating blocks  65  are further provided on a base plate  62  of the positioning jig  52 . The locating block  64  contacts with the opposite surface of the concave portion  21  of the cartridge main body  2  and the pair of locating blocks  65  supporting the side cover  3  so that its front and back surfaces are both sandwiched between the blocks. 
     The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the apparent claims to cover all such changes and modifications as fall with in the true spirit of the invention.