Molded synthetic resin belt connecting device and method of producing the same

Abstract: This invention provides a molded synthetic resin belt connecting device of the type including a belt attachment member (1) and a fastening member (7) rotatably connected together, wherein a headed pin (31) formed integrally with a rotatable shaft (2) of the belt attachment member (1) and a socket (9) formed integrally with the fastening member (7) are assembled together to form a swivel joint (30) such that a head portion (5) of the headed pin (31) is loosely received in a through-hole (10) in the socket (9), and a neck portion (6) of the headed pin (31) which is smaller in diameter than the head portion (5) is loosely received in a cutout groove (12) at a junction between the cutout groove (12) and the through-hole (10). The belt attachment member (1) and the fastening member (7) are molded of synthetic resin in an assembled condition by a single injection-molding run or cycle. The belt connecting device thus constructed is free from break at a joint portion (30) between the belt attachment member and the fastening member (7) and hence is highly durable in construction and labor-saving in assembly. A method of producing the molded synthetic-resin belt connecting device is also disclosed.

Description: The present invention relates to a molded synthetic-resin belt connecting device, such as a swivel hook, a buckle or the like strap fastener, used for bags, knapsacks and the like articles, and a method of producing the molded synthetic-resin belt connecting device. One known molded synthetic-resin belt connecting device disclosed, for example, in Japanese Patent Publication No. 63-29124 comprises a swivel hook composed of a ring member and a hook member that are molded of synthetic resin in a separate condition and then are assembled together. The hook member has at its one end a split, radially contractible leg composed of a reduced neck portion and an enlarged head portion in the shape of a truncated cone. The split leg is pushed into an attachment hole formed in the ring member while it is radially contracted. When the head portion passes through the attachment hole, the contracted split leg resiliently expands radially outwardly to restore its original shape whereby the hook member and the ring member are rotatably coupled together, with the neck portion rotatably received in the attachment hole. The disclosed swivel hook, however, has a drawback that since the head and neck portions of the hook member which are vertically split will be forcibly fitted in the attachment hole in the ring member, the neck portion is structurally weak and hence is liable to be damaged or broken during assembling operation, and is poor in durability. If an attempt were made to enlarge or thick the neck portion for a purpose of reinforcement, such an enlarged neck portion would hinder smooth snap-fit engagement between the vertically split leg of the hook member and the attachment hole in the ring member. US-A-4 680 837 discloses another belt connecting device 10 having a belt attachment member 16 and a fastening member 18 rotatably connected by means of a swivel joint 24, 36. The swivel joint 24, 36 includes a head 24 with a neck 22 and a socket 34, 36. The fastening member 18 and the belt attachment member 16 are molded by a single run in an assembled condition by a pair of main molds 12, 14 and a pair of auxiliary molds 54, 56. In addition, a pair of pedestals 46, 47 are provided as an integral part of each mold part (cf. Figs. 1 and 4) for molding the head 24 and neck 22. After the molding the fastening member 18 and the belt attachment member 16 are connected by a small tab 42 (Fig. 2 and 3; column 5, lines 9 to 27) which has to be broken at the first use of the connecting device. EP-A-0 099 577 shows still a further belt connecting device 10 comprising a hook 29 and a belt attachment member 11 having a rotatable shaft 15. The hook 29 may be rotatably secured to the shaft 15 by a headed pin 30 received in a hole 28 of the shaft. A mold die assembly includes mold dies 41 for molding end portions 17, 18 of the shaft 15 and holes 19, 20 (cf. page 7, lines 2 to 20; Fig. 7). The belt attachment member 11 and the shaft 15 are molded in an assembled condition in one step. The hook 29 is molded separately therefrom. After molding the hook 29 is mounted to the shaft 15. In view of the foregoing drawback of the prior art, it is an object of the present invention to provide a molded synthetic resin belt connecting device including a belt attaching member and a fastening member rotatably connected together via a swivel joint which is free from rupture or break, highly durable in construction and labor-saving in assembly. Another object of the present invention is to provide a method of producing the molded synthetic-resin belt connecting device. As claimed, a molded synthetic resin belt connecting device is provided which comprises a belt attachment member and a fastening member rotatably connected with the belt attachment member via a swivel joint, the swivel joint including a headed pin formed integrally with one of the belt attachment member and the fastening member, and a socket formed integrally with the other of the belt attachment member and the fastening member and rotatable freely on the headed pin. The belt attachment member and the fastening member are molded of synthetic resin in an assembled condition for allowing the headed pin to be freely rotatably received in the socket. The headed pin includes a neck portion integral with one of the belt attachment member and the fastening member, and a head portion having a diameter larger than that of the neck portion, and the socket has a through-hole extending in a first direction and loosely receiving therein the head portion, and a cut-out groove loosely receiving the neck portion and extending in a second direction which is different from the first direction and intersects the through-hole. According to the invention the head portion is cut out at diametrically opposite positions thereof to provide a pair of flat surfaces extending in parallel with inner surfaces of opposite side walls of the through-hole, and the opposite side walls have a pair of aligned holes thereon in confrontation with the head portion. According to a preferred embodiment, the belt attachment member includes a rotatable shaft, the headed pin is integral with a central portion of the rotatable shaft and extending at right angles to a longitudinal axis of the rotatable shaft, the fastening member includes a base portion, and the socket is integral with the base portion of the fastening member. In another preferred embodiment, the belt attachment member includes a rotatable shaft, the socket is integral with a central portion of the rotatable shaft, the fastening member includes a base portion, and the headed pin is integral with the base portion of the fastening member and extending at right angles to a longitudinal axis of the rotatable shaft. It is preferable that the first and second directions are perpendicular to one another. The fastening member may be a hook or one of a male member and a female member of a buckle. As claimed, further a method of producing a molded synthetic resin belt connecting device is provided which includes a belt attachment member having a belt attachment portion and a rotatable shaft, and a fastening member rotatably connected with the shaft of the belt attachment member via a swivel joint, the swivel joint being composed of a headed pin having an enlarged head portion and a reduced neck portion formed integrally with one of the shaft of the belt attachment member and the fastening member, and a socket formed integrally with the other of the shaft of the belt attachment member and the fastening member and rotatable freely on the headed pin. The method comprises the steps of: providing a mold assembly which is composed of a pair of opposed, relatively movable main molds having respective mold surfaces jointly defining a mold cavity for molding the belt attachment member, and the socket of the swivel joint, and a pair of opposed first auxiliary molds assembled in the main molds, respectively, from a first direction for molding opposite end portions of the shaft and a pair of aligned bearing holes in the belt attachment member such that the opposite end portions of the shaft are loosely received in the corresponding bearing holes, and injecting a molten synthetic resin material into the cavity in the mold assembly in a closed condition, thereby forming the belt attachment member. The main molds further define a mold cavity for molding the fastening member, and the mold assembly is further composed of a pair of opposed second auxiliary molds assembled in the main molds, respectively, from the first direction for molding the neck portion of the headed pin such that the neck portion is loosely received in the socket, and a pair of opposed third auxiliary molds assembled in the main molds, respectively, from a second direction different from the first direction for molding the head portion of the headed pin such that the head portion is loosely received in the socket. Thereby the belt attachment member and the fastening member are molded in an assembled condition by a single injection-molding run, with the headed pin freely rotatably received in the socket. Preferably, the pair of opposed first auxiliary molds are integral with the main molds. The above and other objects, features and advantages of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example. FIG. 1 is a plan view of a molded synthetic resin belt connecting device according to an embodiment of the present invention; FIG. 2 is a side view of FIG. 1 with parts broken away for clarity; FIG. 3 is an enlarged perspective view showing a swivel joint of the belt connecting device composed of a headed pin and a socket rotatably receiving therein the headed pin; which swivel joint has holes in the sides of the socket; FIG. 4 is a top view showing a modified form of the headed pin of the swivel joint; FIG. 5 is a fragmentary plan view, with parts broken away for clarity, of a modified belt connecting device including a belt attachment member having a rotatable shaft with which a socket of the swivel joint is integrally formed; FIG. 6 is a plan view, partly in cross section, of the modified belt attachment device used as a male member of a snap-fit buckle or strap fastener; FIG. 7 is a diagrammatical plan view, with parts in cross section, of a mold assembly used for injection-molding the belt connecting device shown in FIG. 1; and FIG. 8 is a diagrammatical view, with parts in cross section, illustrative of the manner in which a head portion of the headed pin of a swivel joint is formed by a pair of auxiliary molds. Certain embodiments of the present invention will be described below in greater detail with reference to the accompanying drawings. FIGS. 1 and 2 show a molded synthetic resin belt connecting device according to an embodiment of the present invention. The molded synthetic resin belt connecting device is produced by a single run or cycle of the injection molding process using a reinforced plastic of the class called as "engineering plastics", such as nylon, polyacetal, polycarbonate and the like, and is composed of a belt attachment member 1 and a fastening member 7 rotatably connected with each other via a swivel joint 30. The belt attachment member 1, as shown in FIG. 1, includes a generally U-shaped frame 1-1, and a shaft 2 rotatably supported by the U-shaped frame 1-1 transversely across an opening of the U-shaped frame 1-1, with opposite end portions 2-1, 2-1 rotatably received in a pair of aligned bearing holes 3, 3 in the U-shaped frame 1-1. The U-shaped frame 1-1 includes a belt attaching portion or bar 4 parallel spaced apart from the shaft 2 and adapted to be connected to a looped end of a belt or strap attached to a bag, a knapsack or the like. The rotatably supported shaft 2 has a central portion with which a headed pin 31 of the swivel joint 30 is integrally formed. The headed pin 31 is solid and free from a slit, and it has a reduced neck portion 6 integral with the central portion of the rotatable shaft 2, and an enlarged circular cylindrical head portion 5 having a diameter greater than that of the neck portion 6. The fastening member 7, as shown in FIG. 1, is composed of a hook 8 adapted to catch or hook an end of another belt or strap. The hook 8 has a base portion 8-1 with which a socket 9 of the swivel joint 30 is integrally formed, and the headed pin 31 of the swivel joint 30 is rotatably received in the socket 9. The socket 9 has a generally rectangular box-like shape having a through-hole 10 extending centrally through the rectangular box-like socket 9 and loosely receiving therein the head portion 5 of the headed pin 31, as shown in FIG. 2. The socket 9 has a top wall 11, and a cut-out groove 12 extending across the top wall 11 in a direction perpendicular to the direction of the through-hole 10, as shown in FIG. 2. The through-hole 10 and the cut-out groove 12 intersect with each other and hence communicate with each other via a central rectangular opening 13 (FIG. 2) in which the neck portion 6 of the headed pin 31 is loosely and rotatably received. As shown in FIG. 3 and 4, the head portion 5 which is larger in diameter than the neck portion 6 has an end face 14 engageable with an inner surface of the grooved top wall 11 so that the head portion 5 is prevented from displacing off the socket 9. With this construction, since the fastening member 7 is connected with the rotatable shaft 2 of the belt attachment member 1 via the swivel joint 30, the hook 8 is rotatable freely about an axis of the headed pin 31 and also is turnable freely about the axis of the shaft 2. More in detail, the form of the headed pin 31 and the socket 9 of the swivel joint 30 is the following : The headed pin 31 includes a head portion 5a which is cut out at diametrically opposite positions thereof to provide a pair of flat surface portions 23, 23 extending in parallel with the inner surfaces of opposite side walls 15 of the through-hole 10. With the cut-out flat surface portions 23, 23 thus provided, it is possible to enlarge the maximum diameter of the head portion 5a. The socket 9 includes a pair of aligned holes 16 communicating with the through-hole 10 and formed in confrontation with the head portion 5a at respective central portions of the opposite side walls 15 of the socket 9 which are free from open ends of the through-hole 10. The aligned holes 16 formed at the opposite side walls 15 allow the head portion 5a to rotate about the neck portion 6 in the socket 9 . FIGS. 5 and 6 illustrate a modified belt connecting device according to another embodiment of this invention. The modified belt connecting device includes a belt attachment member la having a rotatable shaft 2a, and a fastening member 7a rotatably connected with the belt attachment member la via a swivel joint 30a which is composed of a headed pin 31a formed integrally with a base portion 7a-1 of the fastening member 7a, and a socket 9a formed integrally with a central portion of the shaft 2a of the belt attachment member la. The belt attachment member la and the fastening member 7a are injection-molded of synthetic resin in an assembled condition in which an enlarged circular head portion 5b and a reduced neck 6a portion of the headed pin 31a are rotatably received in the socket 9a. As shown in FIG. 6, the fastening member 7a is composed of a male member 18 of a snap-fit buckle or strap fastener 17. It will be appreciable that the fastening member 7a may be a female member 25 of the strap fastener 17. FIGS. 7 and 8 diagrammatically illustrate a mold assembly used for injection-molding the synthetic resin belt connecting device of this invention shown in FIGS. 1 and 2. The mold assembly is composed of a pair of opposed, relatively movable nain molds 19 (only one being shown), and three auxiliary mold pairs 20, 21, 22. Using the mold assembly, the belt connecting device is molded by a single injection-molding run or cycle. The main molds 19 in FIG.7 have respective mold surfaces recessed to define a mold cavity for molding the belt attachment member 1 including a main portion or body of the shaft 2, the fastening member 7, and the socket 9 of the swivel joint 30 as shown in FIG. 1 and 2. The pair of opposed first auxiliary molds 20 are inserted in the main molds 19 from the left and right sides, respectively, of the main molds 19 as shown in FIG. 7 for simultaneously molding the opposite end portions 2-1 of the shaft 2 and the corresponding bearing holes 3 in the belt attachment member 1 such that the opposite end portions 2-1 of the shaft 2 are loosely received in the corresponding bearing holes 3 as shown in FIG. 1 and 2. Similarly, the pair of opposed second auxiliary molds 21 are inserted in the main molds 19 from the left and right sides, respectively, of the main molds 19 as shown in FIG. 7 for simultaneously molding the neck portion 6 of the headed pin 31 and the cut-out groove 12 in the socket 9 such that the neck portion 6 is loosely received in the socket 9 as shown in FIG. 1 and 2. On the other hand, the pair of opposed third auxiliary molds 21 are inserted in the main molds 19 from the front and rear sides, respectively, of the main molds 19 as shown in FIG. 8 for simultaneously molding the head portion 5 of the headed pin 31 and the through-hole 10 in the socket 9 such that the head portion 5 is loosely received in the socket 9 as shown in FIG. 1 and 2. The main molds 19 are closed together, with the first, second and third auxiliary molds 20, 21, 22 properly assembled in the main molds 19 to complete the mold assembly, and while keeping the mold assembly 19-22 in the closed condition, a molten synthetic resin material is injected from a sprue (not shown) into the mold cavity in the mold assembly whereby a molded synthetic resin belt connecting device can be produced by a single run or cycle of the injection-molding process. With this injection-molding, since the belt attachment member 1 and the fastening member 7 of the belt connecting device arc molded in assembled condition via the swivel joint 30, a conventional assembling work for the belt attachment member and the fastening member can be omitted. The third auxiliary molds 22 for molding the head portion 5 may be provided integrally with the corresponding main molds 19 instead of being assembled in the main molds 19. It is apparent from the foregoing description that since the swivel joint can be formed by a single injection molding run or cycle in an assembled condition in which the headed pin is loosely and rotatably received in the socket, a separate work or process for assembling the belt attachment member and the fastening member can be omitted. The headed pin is by no means required to have a particular arrangement, such as a split radially contractible construction, so the assembling between the belt attachment member and the fastening member will be facilitated. Thus, the joint portion between the belt attachment member and the fastening member is very strong in construction with the result that the belt connecting device is excellent in durability. The same advantageous effects can be attained when the headed pin of the swivel joint is formed integrally with the fastening member and the socket of the swivel joint is formed integrally with the belt attachment member. It is, therefore, possible to select the combination of the headed pin and the socket with the belt attachment member and the fastening member in an adequate manner according to the form and structure of the belt attachment member and the fastening member. By using the auxiliary molds which are assembled in the main molds for molding the opposite end portions of the shaft of the belt attachment member, the neck portion of the headed pin and the head portion of the headed pin, the belt connecting device can be produced by a single injection-molding run or cycle such that the belt attachment member and the fastening member are rotatably connected together. With this molding method of the present invention, a work for assembling the belt attachment member and the fastening member can be omitted, thus making it possible to abridge labor and improve the production efficiency. Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims: A molded synthetic resin belt connecting device comprising: a belt attachment member (1, 1a); and a fastening member (7; 7a) rotatably connected with the belt attachment member (1; 1a) via a swivel joint (30; 30a), the swivel joint (30; 30a) including a headed pin (31; 31'; 31a) formed integrally with one of the belt attachment member (1; 1a); and the fastening member (7; 7a), and a socket (9; 9'; 9a) formed integrally with the other of the belt attachment member (1; 1a) and the fastening member (7; 7a) and rotatable freely on the headed pin (31; 31'; 31a), the belt attachment member (1; 1a) and the fastening member (7; 7a) being molded of synthetic resin in an assembled condition for allowing the headed pin (31; 31'; 31a) to be freely rotatably received in the socket (9; 9'; 9a), wherein the headed pin (31; 31'; 31a) includes a neck portion (6; 6a) integral with one of the belt attachment member (1; 1a) and the fastening member (7; 7a), and a head portion (5; 5a; 5b) having a diameter larger than that of the neck portion (6; 6a), and the socket (9; 9'; 9a) has a through-hole (10) extending in a first direction and loosely receiving therein the head portion (5; 5a; 5b), and a cut-out groove (12) loosely receiving the neck portion (6; 6a) and extending in a second direction which is different from the first direction and intersects the through-hole (10), characterised in that the head portion (5; 5a; 5b) is cut out at diametrically opposite positions thereof to provide a pair of flat surfaces (23, 23) extending in parallel with inner surfaces of opposite side walls (15) of the through-hole (10), and the opposite side walls (15) have a pair of aligned holes (16) thereon in confrontation with the head portion (5; 5a; 5b). A molded synthetic resin belt connecting device according to claim 1, wherein said belt attachment member (1) includes a rotatable shaft (2), said headed pin (31; 31') is integral with a central portion of said rotatable shaft (2) and extending at right angles to a longitudinal axis of said rotatable shaft (2), said fastening member (7) includes a base portion (8-1), and said socket (9) is integral with said base portion (8-1) of said fastening member (7). A molded synthetic resin belt connecting device according to claim 1 or 2, wherein said belt attachment member (1a) includes a rotatable shaft (2a), said socket (9a) is integral with a central portion of said rotatable shaft (2a), said fastening member (7a) includes a base portion (7a-1), and said headed pin (31a) is integral with said base portion (7a-1) of said fastening member (7a) and extending at right angles to a longitudinal axis of said rotatable shaft (2a). A molded synthetic resin belt connecting device according to any of claims 1 to 3, wherein said first and second directions are perpendicular to one another. A molded synthetic resin belt connecting device according to any of claims 1 to 4, wherein said fastening member (7) is a hook (8). A molded synthetic resin belt connecting device according to any of claims 1 to 5, wherein said fastening member (7a) is one of a male member (18) and a female member (19) of a buckle (17). A method of producing a molded synthetic resin belt connecting device which includes a belt attachment member (1; 1a) having a belt attachment portion (4) and a rotatable shaft (2; 2a), and a fastening member (7; 7a) rotatably connected with the shaft (2; 2a) of the belt attachment member (1; 1a) via a swivel joint (30; 30a), the swivel joint (30; 30a) being composed of a headed pin (31; 31'; 31a) having an enlarged head portion (5; 5a; 5b) and a reduced neck portion (6; 6a) formed integrally with one of the shaft (2; 2a) of the belt attachment member (1; 1a) and the fastening member (7; 7a), and a socket (9; 9'; 9a) formed integrally with the other of the shaft (2; 2a) of the belt attachment member (1; 1a) and the fastening member (7; 7a) and rotatable freely on the headed pin (31; 31'; 31a), the method comprising the steps of: providing a mold assembly which is composed of a pair of opposed, relatively movable main molds (19, 19) having respective mold surfaces jointly defining a mold cavity for molding the belt attachment member (1; 1a), and the socket (9; 9'; 9a) of the swivel joint (30; 30a), and a pair of opposed first auxiliary molds (20, 20) assembled in the main molds (19, 19), respectively, from a first direction for molding opposite end portions (2-1) of the shaft (2; 2a) and a pair of aligned bearing holes (3) in the belt attachment member (1; 1a) such that the opposite end portions (2-1) of the shaft (2; 2a) are loosely received in the corresponding bearing holes (3, 3), injecting a molten synthetic resin material into the cavity in the mold assembly in a closed condition, thereby forming the belt attachment member (1; 1a), characterised in that the main molds (19, 19) further define a mold cavity for molding the fastening member (7; 7a), and the mold assembly is further composed of a pair of opposed second auxiliary molds (21, 21) assembled in the main molds (19, 19), respectively, from the first direction for molding the neck portion (6; 6a) of the headed pin (31; 31'; 31a) such that the neck portion (6; 6a) is loosely received in the socket (9; 9' 9a), and a pair of opposed third auxiliary molds (22, 22) assembled in the main molds (19, 19), respectively, from a second direction different from the first direction for molding the head portion (5, 5a; 5b) of the headed pin (31; 31'; 31a) such that the head portion (5; 5a; 5b) is loosely received in the socket (9; 9'; 9a), whereby the belt attachment member (1; 1a) and the fastening member (7; 7a) are molded in an assembled condition by a single injection-molding run, with the headed pin (31; 31'; 31a) freely rotatably received in the socket (9; 9'; 9a). A method according to claim 7, wherein said first direction and said second direction are perpendicular to one another. A method according to claim 7 or 8, wherein said first auxiliary molds (20, 20) are integral with said main molds (19, 19).

Inventors: TAKAHASHI YOSHINOBU, TAKAHASHI, YOSHINOBU
Applicants: YKK CORP, YKK CORPORATION
Application year: 1995
Main classification: F16B45
IPC codes: F16G15, B29C45, F16B45