A RESIN CASE PROVIDING COMPATIBILITY BETWEEN AIR PERMEABILITY AND WATER PROOFING, A DIE FOR PRODUCING SUCH A CASE, AND A METHOD FOR PRODUCING SUCH A CASE

Abstract: A through hole (50) with an annular groove (52) provided about its periphery is formed in a resin case (10). The through hole (50) is covered with a water/oil-repellent film (40) comprising a porous film (44). The through hole (50) makes the resin case (10) gas-permeable, and the water/oil-repellent film (40) prevents entry of external water and oil, etc.

Description: TECHNICAL FIELD The present invention relates to a resin case required to be gas-permeable and waterproof, such as a connector-integrated case, etc. housing electric and electronic parts inside. BACKGROUND ART Circuits including electronic parts such as transistors, etc., and electric parts such as motors, etc. used for computers and their peripherals, are designed on substrates. These substrates, etc. are housed in resin cases (hereafter called "connector-integrated cases") wherein connectors are integrally formed. Terminals connected to the substrates, etc. protrude from the connectors to the outside of the boxes so that the terminals can be attached to other parts through the connectors. Fig. 13 is a perspective view of a conventional connector-integrated case 100. Fig. 14 is a cross-sectional view of a connector-integrated case 100' having the same construction as the connector-integrated case 100 except that it has a through hole 500 provided in a lid 300, and is equivalent to a cross-sectional view along the line 14-14 in Fig. 13. The connector-integrated case 100 comprises a box 200 and a lid 300 made of resin such as plastic, etc. Inside a connector C provided on one side of the box 200, there is a plurality of terminals T protruding from within to the outside of the box 200 (see Fig. 14). This terminal T is connected, at one end, to a circuit of a substrate B secured in the box 200 and is attachable, at the other end, to another member through the connector C. After securing a substrate B inside the box 200, a seal packing (not shown) is placed between an end face of the box 200 and the lid 300. Then, the box 200 and the lid 300 are secured with screws, etc (not shown). The connector-integrated case 100 like this has to be completely watertight so that moisture may not enter inside. When there is communication between outside air and the inside of the connector-integrated case 100, conditions of the outside air such as outside air temperature and humidity, etc. may influence the substrate B inside the connector-integrated case 100. In particular, when humid outside air is taken into the connector-integrated case 100, metal parts such as circuits, etc. of the substrate B are corroded by moisture contained in the outside air, often causing electrical contact failures. Therefore, the connector-integrated case 100 must be highly airtight. On the other hand, when electric and electronic parts in use inside the connector-integrated case 100 generate heat and the temperature inside the connector-integrated case 100 increases, the inside air may expand to produce high pressure. Further, under certain conditions, the internal pressure may become lower than atmospheric pressure, that is, it may become subatmospheric. In order to cope with the thus-produced difference in pressure between the interior and exterior of the connector-integrated case 100, it is necessary to provide a through hole in the connector-integrated case 100. However, provision of such a through hole inevitably lowers the waterproof quality and airtightness. Therefore, in the past, as shown in a cross-sectional view of Fig. 14, a through hole 500 is formed in an upper surface of the lid 300 or in a side face of the box 200. The through hole 500 was covered with woven fabric, etc. preventing moisture and oil content from passing through, and allowing only air to pass, to equalize the internal and external pressures while maintaining a waterproof quality and airtightness. An example of a woven fabric preventing moisture and oil content from passing through and allowing only air to pass is a porous film 400 made of fluorocarbon resin, etc., which is bonded to the box 200 or to the lid 300 by a double-sided tape or by an adhesive. Since the porous film 400 covering the through hole 500 is made of fluorocarbon resin and the like, the double-sided tape and adhesive, etc. cannot achieve sufficient adhesion, and, as a result, the porous film 400 sometimes peels in use. Therefore, in a certain connector-integrated case, the porous film 400 is cut into a circular shape and fitted into a metal ring, which is crimped to hold the porous film - 400. Then the porous film 400, fitted in the metal ring, is secured to the required position on the box 200 or the lid 300 by insert molding or further crimping. The porous film 400 is sometimes bonded at the required position on the box 200 or lid 300 by heat sealing or laser seizing. However, it requires processing time to crimp a metal ring to the periphery of the porous film 400. Further, excessively strong crimping gives rise to the problem of damage to the porous film 400. Further, bonding the porous film 400 by heat sealing or laser seizing, requires special equipment, resulting in additional cost. Also, during such procedures, it is difficult to locate the porous film 400 at the proper position with respect to the through hole 500. Further, since it is not possible to exert pressure to the porous film 400, sufficient bonding strength cannot be obtained. DE-A-197 02 685 discloses a plastic casing which may be used in a motor vehicle windscreen wiper assembly. The plastic casing has a vent opening for air exchange between the interior and the surroundings. A gas-permeable membrane covers the opening and prevents water entering. Enclosure of the gas-permeable membrane periphery is achieved by using the plastic material of the casing. DISCLOSURE OF THE INVENTION The present invention provides a sealed resin case having a through hole provided therein, said through hole being covered with a water/oil repellent film which is permeable to air but does not allow liquids to pass, said water/oil-repellent film being a porous film and being bonded to said resin case by molten resin entering pores of said porous film, characterised by a cross-section of the case around the through hole comprising a tip end portion and an annular groove being provided around the through hole, and said water/oil-repellent film being bonded to an upper end face of the tip end portion when said resin case is injection-moulded by using molten resin. The present invention further provides a die for manufacturing a resin case as defined in claim 5 and a method for manufacturing a resin case as defined in claim 7. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a connector-integrated case of a first embodiment of the present invention; Fig. 1 (a) is a perspective view; Fig. 1 (b) is a vertical cross-sectional view along the line b-b in Fig. 1 (a); and Fig. 1 (c) is an enlarged fragmentary view of Fig. 1 (b). Fig. 2 is a vertical cross-sectional view of a connector-integrated case of a second embodiment of the present invention. Fig. 3 is a vertical cross-sectional view of a connector-integrated case of a third embodiment of the present invention. Fig.4 shows an automobile light case, which is a resin case in accordance with the present invention; Fig. 4 (a) is a perspective view; and Fig. 4 (b) is a cross-sectional view along the line b-b in Fig. 4 (a). Fig. 5 shows a motor case, which is a resin case in accordance with the present invention; Fig. 5 (a) is a perspective view; and Fig. 5 (b) is a cross-sectional view along the line b-b in Fig. 5 (a). Fig. 6 shows a cellular phone case, which is a resin case in accordance with the present invention; Fig. 6 (a) is a perspective view; and Fig. 6 (b) is a cross-sectional view along the line b-b in Fig. 6 (a). Fig. 7 shows an outdoor lamp case, which is a resin case in accordance with the present invention; Fig. 7 (a) is a perspective view; and Fig. 7 (b) is a cross-sectional view along the line b-b in Fig. 7 (a). Fig. 8 shows a copier toner case, which is a resin case in accordance with the present invention; Fig. 8 (a) is a perspective view; and Fig. 8 (b) is a cross-sectional view along the line b-b in Fig. 8 (a). Fig. 9 is an enlarged fragmentary cross-sectional view of a resin case using a water/oil repellent film made up of a porous film only. Fig. 10 shows dies for manufacturing the connector-integrated case of Fig. 1; Fig. 10 (a) is a cross-sectional view showing a condition in which the dies are opened; and Fig. 10 (b) is a cross-sectional view showing a condition in which the dies are closed. Fig. 11 shows a die designed to relieve pressing force against the water/oil-repellent film; Fig. 11 (a) is an enlarged fragmentary cross-sectional view in which a pocket is provided in a central region of an end face of the protrusion of the second die; Fig. 11 (b) is an enlarged fragmentary cross-sectional view in which a pocket is provided in a central region of a recess of the first die; and Fig. 11 (c) is an enlarged fragmentary cross-sectional view in which pockets are provided in the protrusion of the second die and in the recess of the first die. Fig. 12 is a view illustrating the flow of resin in a cavity; Fig. 12 (a) is an enlarged fragmentary cross-sectional view of a connector-integrated case molded by the first die with an annular protrusion; and Fig. 12 (b) is an enlarged fragmentary cross-sectional view of a connector-integrated case molded by the first die without an annular protrusion. Fig. 13 is a perspective view of a conventional connector-integrated case. Fig. 14 is a cross-sectional view of another conventional connector-integrated case. BEST MODE FOR CARRYING OUT THE INVENTION Fig. 1 shows a resin case 10 of the first embodiment of the present invention; Fig. 1 (a) is a perspective view of a box 20; Fig. 1 (b) is a cross-sectional view along the line b-b in Fig. 1 (a), in which the substrate B is housed in the box 20 and a lid 30 is attached; and Fig. 1 (c) is an enlarged fragmentary cross-sectional view of Fig. 1 (b). The resin case 10 is a connector-integrated case comprising the injection molded plastic box 20 and the lid 30, wherein the connector C is provided on one side of the box 20. Hereafter, the resin case 10 is called a "connector-integrated case". In the connector C, there is a plurality of terminals T protruding outwardly from the inside of the box 20. A conventionally known porous film is , a polytetrafluoroethylene (PTFE), which allows gases such as air to pass through but repels liquids such as water and oil. An example of such PTFE porous films is one having micropores of about 0.1 - 3 µ , formed at a density of several billion pores/cm 2 . Examples of specific products on the market are "Microtek", etc. films, of Nitto Denko Corp. This PTFE porous film 44 is laminated on a backing 42 comprising a polyethylene terephthalate (PET) non-woven or woven fabric with a water/oil-repelling property imparted to it to form a water/oil-repellent film 40. A circular through hole 50 is formed in a bottom portion of the box 20 and, on an inner surface of the bottom portion, an annular groove 52 is provided around the through hole 50. Consequently, as shown in Fig. 1 (c), the cross section around the through hole 50 becomes substantially L-shaped, and it comprises a tip end (vertical thin wall) 20a extending in the shape of L, a mid-portion (horizontal thin wall) 20b below the annular groove 52, and a base end portion (general portion) 20c. On the inner surface of the bottom portion, i.e., on the upper end face of the tip end portion (vertical thin wall) 20a, the above described water/oil-repellent film 40 is fusion-bonded so as to cover the through hole 50. Since the through hole 50 for providing communication between interior of the case and outside air is formed in the connector-integrated case 10, there is no difference in pressure between the interior and exterior of the connector-integrated case 10. Further, since the through hole 50 is covered with the water/oil-repellent film 40 which allows air to pass but prevents liquids such as water and oil, etc. from passing through, oil content and moisture in the atmosphere do not enter the case 10. Fig. 2 is a cross-sectional view of a resin case 12 of a second embodiment of the present invention. The resin case 12, like the one in the first embodiment, is a connector-integrated case comprising a box 22 and a lid 32, wherein a connector is provided on one side of the box 22 and, in addition, a through hole 50a and an annular groove 52a are provided in the lid 32. Also, the through hole 50a is covered with the same water/oil-repellent film 40 as described above. Fig. 3 is a cross-sectional view of a resin case 14 of the third embodiment of the present invention. This resin case 14 also is a connector-integrated case, like the one described above, comprising a box 24 and a lid 34. However, a through hole 50b and an annular groove 52b are provided in one side of the box 24 and the through hole 50b is covered with the water/oil-repellent film 40. These connector-integrated cases 12 and 14 also have the through holes 50a, 50b in the lid 32 or box 24 so that there is no difference in pressure between the interior and exterior of the connector-integrated cases 12 and 14. Further, since the through holes 50a, 50b are covered with the water/oil-repellent film 40, moisture, etc. in the atmosphere do not enter the connector-integrated cases 12, 14. As described above, since it is possible to achieve gas-permeability and waterproof quality compatibly, the resin case of the present invention is suitable not only for connector-integrated cases but also for other applications. Figs. 4 through 8 show an automobile light case 100a, a motor case 100b, a cellular phone case 100c, an outdoor lamp case 100d and a copier toner case 100e. Further, in Figs. 4 through 8, (a) is a perspective view and (b) is a cross-sectional view along the line b-b in (a). A light L is housed in the automobile light case 100a in Fig. 4, and a power cable D protrudes externally of the case. Further, reference characters R and A denote a reflector and a lens, respectively. A motor is housed in the motor case 100b of Fig. 5, and the power cable D protrudes externally of the case. An electric/electronic substrate B, etc. are housed in the cellular phone case 100c shown in Fig. 6. The outdoor lamp case 100d of Fig. 7 comprises a main unit 200d of the case and a lid 300d, and the light L is housed inside. The copier toner case 100e of Fig. 8 is filled with toner, which is stirred by a rotating screw S. These cases 100a, 100b, 100c, 100d and 100e have, like the previously described connector-integrated cases, through holes 500a, 500b, 500c, 500d and 500e, which are covered with the water/oil-repellent film 40. The positions of the through holes differ according to the cases. In the drawings, the through holes are provided in the side faces of the automobile light case 100a and the motor case 100b. Also, the through holes are provided in bottom surfaces of the cellular-phone case 100c and the outdoor lamp case 100d, and in an upper surface of the copier toner case 100e, respectively. Since these resin cases 100a, 100b, 100c, 100d and 100e have the through holes 500a, 500b, 500c, 500d and 500e, electric/electronic parts such as lights and motors, etc. housed inside do not generate heat. Further, even when outdoor temperature changes, there is no difference in pressure produced between the interior and exterior of the cases. Further, since the through holes 500a, 500b, 500c, 500d and 500e are covered with the water/oil-repellent film 40, moisture in the atmosphere does not enter the case. Particularly, with regard to the automobile light case 100a, the cellular phone case 100c and the outdoor lamp case 100d, moisture does not enter the cases even when such cases are used outdoor and get wet in rainwater, etc. Also, with regard to the copier toner case 100e, the toner does not scatter externally of the case even when the screw S provided inside rotates. Next, the die for manufacturing the resin case of the present invention will be described with reference to a die for manufacturing a connector-integrated case. Further, the connector-integrated cases 10, 12, 14 of the embodiments 1 through 3 are of the same construction except for the positions of the through holes 50, 50a, 50b as described above, and are manufactured by the same method. Therefore, in the following paragraphs, a manufacturing method of the connector-integrated case 10 of the first embodiment alone will be described. Fig. 10 is an enlarged cross-sectional view of a die comprising a first die 60 and a second die 70; Fig. 10 (a) shows a condition in which both dies 60, 70 are opened; and Fig. 10 (b) shows a condition in which both dies 60, 70 are closed. A circular recess 64 surrounded by an annular protrusion 62 is provided in the first die 60, and a cylindrical protrusion 72 located at the central portion of the recess 64 of the first die 60 is provided on the second die 70. As shown in Fig. 10 (b), a cavity 80 is formed between the two closed dies 60, 70. When the dies 60 and 70 are opened, the water/oil-repellent film 40 is fitted in the recess 64 of the first die 60 (see Fig. 10 (a)) so that an inner surface of the recess 64 and a surface of the porous film 44 of the water/oil-repellent film 40 come into contact with each other. Then the two dies 60, 70 are closed. When molten resin is injected into the cavity 80 formed between the two dies 60, 70, the backing 42 of the water/oil-repellent film 40 fitted into the recess 64 of the first die 60 is melted by the heat of the resin and becomes integral with the resin to be injection-molded (insert molding). As described above, by using the die for manufacturing the connector-integrated case of the present invention, the water/oil-repellent film 40 becomes integral with the box 20 when the box 20 is injection-molded. Therefore, the process of attaching the water/oil-repellent film 40 can be omitted. Further, it is easy to position the water/oil-repellent film 40 with respect to the through holes 50, 50a and 50b. Further, since the water/oil-repellent film 40 is melted by heat for bonding to the box 20, the bonding strength thereof is sufficient to prevent the film 40 from peeling. Further, during the injecting-molding, the water/oil-repellent film is evenly pressed by the molten resin under high pressure (300 kgf/cm 2 or more), the molded box 20 and the water/oil-repellent film 40 are strongly bonded. As a resin for injection molding when manufacturing the connector-integrated case, it is desirable to use a resin whose temperature when being molded is higher than the melting point of the backing 42 making up the water/oil-repellent film 40. If PET (whose melting point is 264 °C) is used for the backing 42, a resin having a temperature of 264 °C or higher when being molded, such as (polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) and polycarbonate (PC), etc. are suitable as resins for injection molding. The porous film 44 making up the water/oil-repellent film 40 is easily destroyed when pressed from the outside. Therefore, when the protrusion 72 of the second die 70 is pressed against the water/oil-repellent film 40 placed inside the recess 64 of the first die 60, the porous structure of the water/oil-repellent film 40 may be crushed and pores thereof may be closed. Therefore, it is desirable to provide a pocket in the recess of the first die and/or in the protrusion of the second die so as to relieve the pressing force against the water/oil-repellent film. Fig. 11 is a fragmentary enlarged cross-sectional view of the die having a structure in which the pressing force against the water/oil-repellent film 40 is relieved; Fig. 11 (a) shows that a pocket 76 is provided in a central region of an end face of the protrusion 72' of the second die 70'; Fig. 11 (b) shows that a pocket 66 is provided in a central region of the recess 64' of the first die 60'; and Fig. 11 (c) shows that pockets 66, 76 are provided in the recess 64' of the first die 60' and in the protrusion 72' of the second die 70', respectively. If the pocket 76 is provided in the end face of the protrusion 72' of the second die 70' as in Fig. 11 (a) and the pocket 66 is provided in the recess 64' of the first die 60' as in Fig. 11 (b), pressing forces at the inner surface of the recess of the first die and the end face of the protrusion of the second die can be relieved when the first die and the second die are closed. Therefore, the porous structure of the central portion of the water/oil-repellent film 40 is not crushed. Further, as in Fig. 11 (c), when the pockets 66, 76 are provided in both the recess 64' of the first die 60' and the end face of the protrusion 72' of the second die 70', the pressing force against the water/oil-repellent film 40 can be more effectively relieved. The annular protrusion 62 of the first die 60 not only makes it easy to position the water/oil-repellent film 40 but also causes the pressure of resin to be exerted perpendicularly against the water/oil-repellent film 40 when the resin is injected into the cavity 80, thus making it possible to fusion-bond the water/oil-repellent film 40 reliably. Fig. 12 (a) is an enlarged cross-sectional view illustrating a flow of resin in the cavity of the connector-integrated case of the invention molded by using the first die 60 with the annular protrusion 62, and Fig. 12 (b) is an enlarged cross-sectional view illustrating flow of resin in the cavity of the connector-integrated case of the invention molded by using a first die 600 without an annular protrusion. If the first die is not provided with the annular protrusion, it is difficult to position the water/oil-repellent film 40, as shown in Fig. 12 (b). Besides, since the molten resin flows parallel to the water/oil-repellent film 40 as shown by the arrow in Fig. 12 (b), an end portion of the water/oil-repellent film 40 may be deformed by the pressure of the resin. On the other hand, as shown in Fig. 12 (a), when the annular protrusion 62 is provided on the first die 60, the molten resin flows in perpendicularly to the water/oil-repellent film 40, as shown by the arrow in the drawing, so that the water/oil-repellent film 40 and the resin are efficiently fusion-bonded. When looking at this from the aspect of the shape of the connector-integrated case to be molded, the periphery of the through hole and the melted joint of the water/oil-repellent film form a U-shaped cross-section, which was as described in claim 5. As shown in Figs. 10 and 11, using the die of the present invention, the annular protrusion 62 is provided on the first dies 60, 60', and the water/oil-repellent film 40 is fitted and retained in the recesses 64, 64' surrounded by the annular protrusion 62, so that it is easy to position the water/oil-repellent film 4.0, and prevent it from sliding when the dies 60, 60', 70, 70' are closed. In the above-described resin case, a water/oil-repellent film 40 comprising a backing 42 with a porous film 44 laminated thereon is used. However, it is possible to bond the porous film 44 alone without using the backing 42. In this case, it is possible to use dies shown in Figs. 10 and 11. Since the porous film 44 is made of PTFE having a melting point of 327 °C or higher, it is not melted by the heat of the molten resin (whose melting point is 264 °C in the case of PET) injected into the cavity. The injected molten resin enters pores of the porous film 44 to be integral with it and, as a result of this, the porous film 44 is bonded to the resin case. Fig. 9 is an enlarged fragmentary cross-sectional view of the resin case using a water/oil-repellent film 40' comprising the porous film 44 alone. It is needless to say that the die for manufacturing the connector-integrated case of the present invention described above can be used when forming the connector-integrated cases 12, 14 of the second and third embodiments shown in Fig. 2 and 3. Further, when manufacturing the resin case shown in Figs. 4 through 8, a die having a shape suitable for the resin case may be used. INDUSTRIAL APPLICABILITY As described above, the resin case of the present invention is made so as to be both gas-permeable and waterproof by the through hole and the water/oil-repellent film covering the through hole. Thus, while there is no difference in pressure between the interior and exterior of the case, moisture from the outside does not enter the case. By using the die for manufacturing the resin case according to the present invention, it is possible to injection-mold the case and integrally bond the water/oil-repellent film covering the through hole. Therefore, the water/oil-repellent film can be attached without additional equipment and processes. Since the annular protrusion is provided on the first die, it is easy to position the water/oil-repellent film. Also, since the water/oil-repellent film is placed inside the first die before being pressed by the second die, it will not slide during the injection molding. Further, since the water/oil-repellent film is bonded to a bonding surface of the case by the perpendicular pressure of the resin, it can be bonded with high bonding strength.

Claims: A sealed resin case (10) having a through hole (50) provided therein, said through hole (50) being covered with a water/oil repellent film (40) which is permeable to air but does not allow liquids to pass, said water/oil-repellent film (40) being a porous film and being bonded to said resin case (10) by molten resin entering pores of said porous film (40), characterised by a cross-section of the case (10) around the through hole (50) comprising a tip end portion (20a) and an annular groove (52) being provided around the through hole (50), and said water/oil-repellent film (40) being bonded to an upper end face of the tip end portion (20a) when said resin case (10) is injection-moulded by using molten resin. A resin case (10) according to Claim 1, wherein said resin case (10) comprises a box (20) and a lid (32) covering an opening of said box (20), and said through hole (50) is provided in said box (20) and/or said lid (32). A resin case (10) according to Claim 1 or 2, wherein said water/oil-repellent film (40) is made by laminating a backing (42) comprising a thermoplastic material and said porous film (40), and said backing (42) is melted to be bonded to said resin case (10). A resin case (10) according to any preceding claim, wherein a joint of a periphery of said through hole (50) and said water/oil-repellent film (40) form a U-shaped cross-section. A die for manufacturing a resin case (10) comprising: a first die (60) having an annular protrusion (62) on its inner surface, and a second die (70) having a cylindrical protrusion (72) received in said annular protrusion (62), wherein a water/oil-repellent film (40), which is permeable to air but does not allow liquids to pass, may be fitted into a recess (64) surrounded by said annular protrusion (62) of said first die, and said first die (60) and second die (70) may then be closed so that resin can be injected between the two dies (60, 70), characterised by a cavity (80) being formed between the first and second dies (60, 70) when the dies (60, 70) are closed; and the annular protrusion (62) of the first die (60) causing the pressure of the resin to be exerted perpendicularly against the water/oil-repellent film (40) when the resin is injected into the cavity (80). A die according to Claim 5, wherein a pocket (66) is provided in said recess (64) of said first die (60) and/or in an end face of the cylindrical protrusion (72) of said second die (70). A method of manufacturing a sealed resin case (10), comprising the steps of: providing a first die (60) having an annular protrusion (62) on its inner surface and a second (70) die having a cylindrical protrusion (72) which may be received in said annular protrusion (62); fitting a water/oil-repellent film (40), which is permeable to air but does not allow liquids to pass, into a recess (64) surrounded by said annular protrusion (62) of said first die (60); closing the first and second dies (60, 70); and injecting resin between the two dies (60, 70), characterised by the steps of: forming a cavity (80) between the first and second dies (60, 70) when the dies (60, 70) are closed; and the annular protrusion of the first die (60) causing the pressure of the resin to be exerted perpendicularly against the water/oil-repellent film (40) when the resin is injected into the cavity (80).

Inventors: FUKUNISHI ATSUSHI, HARA KOUICHI, KATSUURA TAKAHITO, FUKUNISHI, ATSUSHI, HARA, KOUICHI, KATSUURA, TAKAHITO
Applicants: TOKAI KOGYO CO LTD, TOKAI KOGYO CO. LTD.
Application year: 2000
Main classification: H05K5
IPC codes: H05K5, B29C45