Transmission device for a chainless bicycle

• US 6,478,323 B2
• Filed: 03/05/2001
• Issued: 11/12/2002
• Est. Priority Date: 03/05/2001
• Status: Expired due to Fees

• Current Assignee: Chin-Hsing Tsai, Su-Mei Chang
• Original Assignee: Chin-Hsing Tsai, Su-Mei Chang
• Inventors: Chang, Shih-Hsing
• Primary Examiner(s): Dickson, Paul N.
• Assistant Examiner(s): Lum, L.
• Application Number:
  US09/799,741
• Publication Number:
  US 20020121761A1
• Time in Patent Office: 617 Days
• Field of Search: 280/260, 280/259, 280/262
• US Class Current: 280/260
• CPC Class Codes: B62M 17/00 Transmissions characterised by use of rotary shaft, e.g. cardan shaft

Abstract

A chainless transmission device for a bicycle has a front casing, a rear casing, a crank axle and a transmission assembly. The transmission assembly has a transmission shaft, a drive gear, a front gear, a rear gear and a driven gear. A tube is connected between the front casing and the rear casing to receive the transmission shaft. Two ears extend from the front casing. A connector is secured to each ear to connect to the bottom bracket of the bicycle. The transmission device can directly be mounted on a conventional bicycle frame. To install the transmission device on the frame becomes easier. In addition, the transmission shaft can slightly move and rotate relative to the rear gear. This can prevent the transmission from being bent when the bicycle is being ridden. The transmission efficiency and the useful life of the chainless transmission device are improved.

Claims

1. A transmission device for a bicycle having a frame, a bottom bracket mounted on the frame and a hub with a rear wheel axle, the transmission device comprising:

a front casing;

a crank axle rotatably mounted in the front casing and having two ends each extending out from the front casing to be adapted to be connected with a pedal;

a drive gear rotatably attached to the crank axle;

a tube securely connected to the front casing with one end of the tube;

a rear casing securely connected to the other end of the tube;

a transmission shaft rotatably received in the tube and having a first end extending into the front casing and a second end extending into the rear casing;

a front gear rotatably attached to the first end of the transmission shaft and received in the front casing to mate with the drive gear;

a rear gear rotatably attached to the second end of the transmission shaft and received in the rear casing; and

a driven gear rotatably received in the rear casing and engaging with the rear gear to be adapted to be attached to the hub;

wherein two ears extend from the front casing;

a connector is secured to each ear and has a circular protrusion adapted to be fit into one end of the bottom bracket; and

multiple bolts extend through the ears, the connectors and a nut screws onto each bolt to attach the front casing to the bottom bracket by the connectors.

2. The transmission device as claimed in claim 1, wherein teeth are formed on the first end of the transmission shaft;

and

a stub extends from one side of the front gear and has inner teeth to engage with the teeth on the transmission shaft.

3. The transmission device as claimed in claim 2, wherein a bearing is received in the front casing and attached on the stub on the front gear,

thereby the front gear can rotate freely relative to the front casing.

4. The transmission device as claimed in claim 1, wherein the first end of the transmission shaft extends through the front gear and has a threaded hole defined in the first end;

and

a bolt extending through a washer is screwed into the threaded hole of the transmission shaft to securely attach the front gear to the first end of the transmission shaft.

5. The transmission device as claimed in claim 1, wherein a neck with a diameter smaller than that of the transmission shaft is formed on the second end of the transmission shaft;

a ball with a diameter larger than that of the neck is formed on a free end of the neck;

a through hole is laterally and radially defined through the hole;

a stub extends from one side of the rear gear to connect with the transmission shaft;

a central hole with a diameter larger than that of the neck on the transmission shaft is defined in the stub on the rear gear to receive the ball and the neck;

a gap is defined between an inner surface of the central hole and the neck;

a through hole is defined in the stub and aligns with the through hole of the ball; and

a pin extends through the through holes in the stub and the ball to pivotally connect the ball to the stub,

thereby the rear gear is pivotally connected to the second end of the transmission shaft.

6. The transmission device as claimed in claim 5, wherein a bearing is received in the rear casing and attached on the stub on the rear gear,

thereby the rear gear can rotate freely relative to the rear casing.

7. The transmission device as claimed in claim 6, wherein a groove is defined around an outer periphery of the stub;

and

a fastener is secured in the groove to securely hold the bearing.

8. The transmission device as claimed in claim 1, wherein a base is formed on the front casing and is adapted to have a chain stay rested thereon.