FOLDABLE BICYCLE FRAME

Abstract: A foldable bicycle frame comprising: a lower frame (1) provided at its intermediate portion with a hunger bracket (3) having a hunger portion (2); a front frame formed integrally with a head tube (8) and rotatably supported by a shaft attached to the front end of said lower frame (1), said lower frame (1) having claws (10) supporting a rear wheel axle (11); a seat tube (15) rotatably supported by a shaft attached to said hunger bracket (3); a front support stay (18) rotatably supported between the shaft (16) attached to said seat tube (15) and a shaft (17) attached to said front frame; a seat stay separated into an upper seat stay (20) and a lower seat stay (25) so as to be able to be bent upwardly at its mid portion, each of said seat stay being composed of a pair of members, said upper seat stay (20) being pivotally secured at its outer end to a portion of said seat tube (15) near the upper end of the latter while said lower seat stay (25) being pivotally secured at its lower end to said claws (10) of said lower frame (1); a locking plate (24) interconnecting the inner ends of said upper (20) and lower seat (25) stays in such a manner that the inner end of said lower seat stay (25) being directly fixed to said locking plate (24) while the inner end of said upper seat (20) stay being secured rotatabiy and slidably by means of a connecting shaft (23) inserted to said locking plate (24); a compression spring (26) acting on said connecting shaft (23) so as to spread said upper seat (20) stay outwardly, said locking plate (24) being provided at its both sides with clamping portions (27) fittingly holding the connecting ends of said upper seat stay (20); and a stopper (28) provided on said locking plate (24) and adapted to prevent an excessive sliding of only one of a pair of members of said upper seat stay, said seat stay is pressed by a force exceeding the force of said compression spring (26).

Description: Detailed Description of the Invention The present invention relates to a foldable bicycle frame capable of being assembled instantaneously to get ready for use and folded easily and simply to facilitate the storing when the bicycle is not used. In the conventional foldable bicycles, the folding and assembling are generally difficult and require specific tools and troublesome works for rotating levers for many times and so forth, resulting in an impractically long time. In addition, it takes a considerable.time to fold the bicycle for ttansportation or when the bicycle is not used. Accordingly, an object of the invention is to provide a foldable bicycle frame having a rigid construction and capable of being easily and promptly folded or assembled. The invention will be described hereinunder in more detail with reference to the accompanying drawings. A hunger bracket 3 having a hunger portion 2 is provided on the mid portion of a lower frame 1. A front frame 9 formed integrally with a head pipe 8 is rotatably supported by a shaft 4 attached to the front end of the frame 1. Claws 10 provided at the rear end of the lower frame 1 supports a rear wheel axle 11. A shaft attached to the hunger bracket 3 rotatably supports a seat tube 15. A front support stay 18 is rotatably supported between a shaft 16 attached to the seat tube 15 and a shaft 17 attached to the front frame 9. A seat stay is divided into an upper seat stay 20 and a lower seat stay 25 so as to be able to be bent and flexed at its mia. portion. Each of the upper and lower seat stays is constituted by a pair of members. The outer end of the upper seat stay 20 is pivotally secured to a portion of the seat tube 15 near the upper end of the latter, while the lower seat stay 25 is pivotally secured to the claws 10 provided at the rear end of the lower frame 1,. The inner ends of the upper seat stay 20 and the lower seat stay 25 are connected to each other by means of a locking plate 24. More specifically, the inner end of the lower seta stay 25 is fixed to the locking plate 24, while the inner end of the upper seat stay 20 is rotatably and slidably secured by means of a connecting shaft inserted to the locking plate 24. A compression spring 26 acts on the connecting shaft 23 so as to spread the upper seat stay 20 outwardly. The connecting ends of the upper seat stay 20 are fittirigly supported by gripping portions 27 provided at both sides of the locking plate 24. The locking plate 24 is provided with a stopper 28 which prevents an excessive sliding movement of only one of the members of the upper seat stay 20 when said members are pressed toward each other overcoming the force of said compression spring 26. The folding and assembling of this foldable bicycle frame are made in the following manner. Both members of the upper seat stay 20 fitting in the grapping portions 27 of the locking plate 24 by the action of the compression spring 26 and opposing to each other are gripped by one hand as shown in Fig. 4, so that both members of the upper seat stay are slided inwardly overcoming the force of the compression spring 26., into contact with the stopper 28 of the locking plate 24. The connecting ends of the upper seat stay then come off from the gripping portions 27 of the locking plate 24, so that the upper seat stay 20 comes to be able to rotate around the connecting shaft 23. The outer end of the upper seat stay 20 is pivotally secured to the portion of the seat tube 15 near the upper end of the latter, while the lower end of the seat tube 15 is pivotally secured to the hunger bracket 3. The lower seat stay 25 is also pivotally secured to the claws 10 of the lower frame 1. Thus, the lower frame 1, front stay 18, upper seat stay 20 and the lower seat stay 25 in combination constitute a quadrilateral link. As the upper seat stay 20 is rotated in the direction of arrow A in Fig. 2, the lower seat stay 25 and the seat tube 15 are rotated in the directions of arrows B and C, respectively, so that the frame is folded in auch a manner that the seat tube 15 is inclined rearwardly until it comes into contact with the rear wheel axle 22. To the contrary, when the frame is assembled from the folded state, one of the uyper seat stay 20, lower seat stay 25 and the seat tube 15 is rotated in the direction opposite to the arrow in Fig. 2, until the upper and lower seat stays 20 and 25 come to form a substantially straight line. * Since the connecting ends of the upper seat stay 20 are spread outwardly by the force of the compression spring 26, the connecting ends are put into engagement with the gripping portions 27 of the locking plate 24 thus completing the assembling. As has been described, according to the invention, all of the constituents of the frame are formed of metallic materials having a high mechanical strength and, hence, a high reliability, and can be folded and assembled easily and instantaneously without requiring any specific tool. Namely, the folding and assembling can be made by a simple and single action of lifting and depression of the upper seat stay 20. In addition, any excessive bending at the juncture between the upper seat stay 20 and the seat tube 15 is effectively prevented by the action of the stopper 28 to ensure a stable folding and assembling operation and a high durability of the foldable bicycle frame. 4. Brief Description of the Drawings Fig. 1 is a side elevational view of an embodiment of the invention; Fig. 2 shows the embodiment shown in Fig. 1 in the state during the folding; Fig. 3 shows the embodiment shown in Fig. 1 in the state after the folding; Fig. 4 is a top plan view of the embodiment shown in Fig. 1, showing the state in which an upper seat stay is being disengaged from the gripping portions of the locking plate by a gripping action by a hand; Fig. 5 is a bottom plan view of a seat stay and a locking plate; Fig. 6 is a top plan view of a locking plate; and Fig. 7 is a bottom plan view of the locking plate. 1: lower frame, 2: hunger portion, 3: hunger bracket, 4: shaft, 5: handle post. 6: front wheel axle, 7: front fork, 8: head pipe, 9: front frame, 10: claw, 11: rear wheel axle, 12: shaft, 13: saddle, 14: seat post, 15: seat tube, 16: shaft, 17: shaft, 18: front support stay, 19: bolt, 20: upper back fork, 21: front wheel, 22: rear wheel

Claims: Claim A foldable bicycle frame comprising: a lower frame provided at its intermediate portion with a hunger bracket having a hunger portion; a front frame formed integrally with a head tube and rotatably supported by a shaft attached to the front end of said lower frame, said lower frame having claws supporting a rear wheel axle; a seat tube rotatably supported by a shaft attached to -aid hunger bracket; a front support stay rotatably supported between the shaft attached to said seat tube and a shaft attached to said front frame; a seat stay separated into an upper seat stay and a lower seat stay so as to be able to be bent upwardly at its mid portion, each of said seat stay being composed of a pair of members, said upper seat stay being pivotally secured at its outer end to a portion of said seat tube near the upper end of the latter while said lower seat stay being pivotally secured at its lower end to said claws of said lower frame; a locking plate interconnecting the inner ends of s#id upper and lower seat stays in such a manner that the inner end of said lower seat stay being directly fixed to said locking plate while the inner end of said upper seat stay being secured rotatably and slidably by means of a conbecting shaft inserted to said locking plate; a compression spring acting on said connecting shaft so as to spread said upper seat stay outwardly, said locking plate being provided at its both sides with clamping portions fittingly holding the connecting ends of said upper seat stay; and a stopper provided on said locking plate and adapted to prevent an excessive sliding of only one of a pair of members of said upper seat stay when said seat stay is pressed by a force exceeding the force of said compression spring.

Inventors: ISHIBASHI, HIDEYUKI, TAKAMIYA, KIKUZO
Applicants: BRIDGESTONE CYCLE CO., LTD.
Application year: 1982
Main classification: B62K15
IPC codes: B62K15