Variable diameter sprocket assembly

• US 4,952,196 A
• Filed: 10/14/1988
• Issued: 08/28/1990
• Est. Priority Date: 10/21/1987
• Status: Expired due to Fees

• Current Assignee: Autra-Bike Company Incorporated
• Original Assignee: Autra-Bike Company Incorporated
• Inventors: Malahowski, Robert J., Chilcote, Keith C.
• Primary Examiner(s): Massie, IV, Jerome W.
• Assistant Examiner(s): SMITH, MATTHEW J
• Application Number:
  US07/256,336
• Time in Patent Office: 683 Days
• Field of Search: 474/70, 474/80, 474/82, 474/102, 474/109, 280/236-238, 280/804, 364/424.1
• US Class Current: 474/70
• CPC Class Codes: B62M 9/08 involving eccentrically- mounted or elliptically-shaped driving or driven wheel; with expansible driving or driven wheel
• CPC Class Codes: G01P 1/10 for indicating predetermined speeds
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

A rotatable sprocket assembly transmits force from a chain into rotation of a wheel on a bicycle. A plurality of sprocket segments having peripheral teeth are mounted on a pair of sprocket housings so that the combined periphery of the sprocket segments is substantially circular. The sprocket segments are slidable relative to the housing in a substantially radial direction so as to vary the diameter of the combined sprocket segments. Each sprocket segment is formed from a plurality of hinged subsegments, with each subsegment having a single tooth thereon. The sprocket segments of one housing overlap the adjacent sprocket segments on the other housing so that the pairs of overlapping teeth combine to effectively form a single tooth. The sprocket segments are movable angularly relative to the sprocket housings, so that in combination with the radial displacement of the sprocket segments, the total number of effective teeth on the sprocket assembly can be varied in increments of one tooth. The sprocket segments are retained in a desired radial position by a disengageable latch mechanism. A shift actuator contacts the latch mechanism to cause disengagement of the latch and angular displacement of the sprocket segments to a desired position. Movement of the shift actuator is accomplished manually or automatically through a motor and an electronic control system. The wheel and sprocket assembly are rotatable about a hub assembly which permits removal of the wheel from the bicycle without requiring removal of the sprocket assembly.

Claims

1. A device that automatically controls the gear selection of a multi-gear shifting mechanism of a bicycle, comprising:

an electric motor engageable with the shifting mechanism so that rotation of said electric motor causes said shifting mechanism to shift from one gear to another gear, the motor operational in a first direction to cause said shifting mechanism to select a higher gear, said motor operational in a second direction to cause said shifting mechanism to select a lower gear;

a transducer that generates a transducer output signal having a characteristic that varies in accordance with the rotation rate of one of the wheels of said bicycle;

a strain gauge that detects the strain applied to said bicycle when being pedalled by a rider, said strain gauge providing a strain gauge output signal responsive to the detected strain; and

an electrical circuit that receives said transducer output signal and said strain gauge output signal, and that generates a motor power signal to operate said electric motor, said electrical circuit comparing the characteristic of said transducer output with first and second ranges of characteristics for the currently selected gear, said first and second ranges of characteristics varying in response to said strain gauge output signal, said electrical circuit generating said motor power signal with a first polarity to operate said electric motor in said first direction to select a higher gear when said transducer output is within said first range of characteristics, said electrical circuit generating said motor power signal with a second polarity to operate said electric motor in said second direction to select a lower gear when said transducer output is within said second range of characteristics.

2. The device as defined in claim 1, wherein said characteristic is the time interval between successive pulses generated by said transducer.

6. The device as defined in claim 1, wherein said electrical circuit comprises a microprocessor, said microprocessor receiving said pulses from said transducer as a first input and receiving a second input indicative of the current gear of said multi-gear shifting mechanism, said microprocessor selectably outputting a signal to operate said electric motor in response to said first and second inputs, said microprocessor counting the number of said pulses per unit time and comparing said number with an associated range of numbers for the current gear of said shifting mechanism and operating said electric motor to select a higher gear when said number of pulses is greater than said associated range of numbers and operating said electric motor to select a lower gear when said number of pulses is less than said associated range of numbers.

3. A device that automatically controls the gear selection of a multi-gear shifting mechanism of a bicycle, comprising:

an electric motor engageable with the shifting mechanism so that rotation of said electric motor causes said shifting mechanism to shift from one gear to another gear, the motor operational in a first direction to cause said shifting mechanism to select a higher gear, said motor operational in a second direction to cause said shifting mechanism to select a lower gear;

a transducer that generates a transducer output signal having a characteristic that varies in accordance with the rotation rate of one of the wheels of said bicycle; and

an electrical circuit that receives said transducer output signal and that generates a motor power signal to operate said electric motor, said electrical circuit comparing the characteristic of said transducer output with first and second ranges of characteristics for the currently selected gear, said electrical circuit generating said motor power signal with a first polarity to operate said motor in said first direction to select a higher gear when said transducer output is within said first range of characteristics, said electrical circuit generating said motor power signal with a second polarity to operate said electric motor in said second direction to select a lower gear when said transducer output is within said second range of characteristics, said electrical circuit comprising;

a pulse generator that generates a pulse having a time duration that varies in accordance with the currently selected gear;

a counter that counts the number of pulses generated by said transducer during said time duration and provides a count output corresponding to the number of pulses; and

a decoder that decodes the count output of said counter and that generates a first signal when said count output is within a first range of counts and that generates a second signal when said count output is within a second range of counts.

4. The device as defined in claim 3, wherein said time duration is selected by a plurality of timing resistors, one of said timing resistors corresponding to each gear selection provided by said shifting mechanism.

7. A device that automatically controls the gear selection of a multi-gear shifting mechanism of a bicycle, comprising:

a transducer for generating a sequence of pulses at a rate that varies in accordance with the rotation speed of the rear wheel of said bicycle;

a gear position indicator that generates a gear position indicator signal that varies in accordance with the current gear of said multi-gear shifting mechanism;

an electric motor that provides power to shift said multi-gear shifting mechanism, said electric motor responsive to current flowing in a first direction to shift said multi-gear shifting mechanism from a lower gear to a higher gear, said electric motor responsive to current flowing in a second direction to shift said multi-gear shifting mechanism from a higher gear to a lower gear;

a motor control circuit responsive to a first signal to generate current to said electric motor in said first direction in response to a first shift signal and to generate current to said electric motor in said second direction in response to a second shift signal;

a microprocessor that receives said sequence of pulses from said transducer and said gear position indicator switch from said gear position indicator and generates said first and second shift signals to said motor control circuit responsive thereto, said microprocessor comparing the number of pulses that occur in a predetermined amount of time with a range of numbers associated with the current gear position indicator signal and generating one of said first and second shift signals when said number of pulses is outside said range of numbers; and

a strain gauge that detects the strain applied to said bicycle when being pedalled by a rider, said strain gauge generating an output signal that is provided as an input to said microprocessor, said microprocessor responsive to said strain gauge output signal to adjust said range of numbers associated with the current gear position indicator so that said range of numbers is increased when additional strain is applied by said rider.

5. The device as defined in claim 7, wherein said characteristic of said transducer output is the number of pulses generated by said transducer.

8. A device that automatically controls the gear selection of a multi-gear shifting mechanism of a bicycle, comprising:

a transducer for generating a sequence of pulses at a rate that varies in accordance with the rotation speed of the rear wheel of said bicycle;

a gear position indicator that generates a gear position indicator signal that varies in accordance with the current gear of said multi-gear shifting mechanism;

an electric motor that provides power to shift said multi-gear shifting mechanism, said electric motor responsive to current flowing in a first direction to shift said multi-gear shifting mechanism from a lower gear to a higher gear, said electric motor responsive to current flowing in a second direction to shift said multi-gear shifting mechanism from a higher gear to a lower gear;

a motor control circuit responsive to a first signal to generate current to said electric motor in said first direction in response to a first shift signal and to generate current to said electric motor in said second direction in response to a second shift signal;

a microprocessor that receives said sequence of pulses from said transducer and said gear position indicator switch from said gear position indicator and generates said first and second shift signals to said motor control circuit responsive thereto, said microprocessor comparing the number of pulses that occur in a predetermined amount of time with a range of numbers associated with the current gear position indicator signal and generating one of said first and second shift signals when said number of pulses is outside said range of numbers; and

a timer circuit, said timer circuit generating a periodic timer output signal when said timer circuit is enabled, said timer output signal causing said microprocessor to be reset to known predetermined conditions, said timer circuit being disabled whenever said microprocessor generates one of said first and second shift signals so that said reset signal is precluded for a predetermined amount of time after each of said first and second shift signals.

9. A method of controlling an automatic shifting mechanism in a bicycle, comprising the steps of:

generating a sequence of pulses having a pulse repetition rate responsive to the rotation speed of a bicycle wheel;

counting the number of said pulses in said sequence in a predetermined amount of time;

comparing said counted number of pulses with a predetermined range of pulses for the currently selected gear of said shifting mechanism;

shifting said shifting mechanism to a selected one of a higher or a lower gear when said counted number of pulses is outside said predetermined range of pulses for the currently selected gear;

measuring the strain applied to the rear wheel of said bicycle by a rider on said bicycle; and

adjusting said predetermined range of pulses for the currently selected gear in response to the magnitude of said measured strain so that said shifting step occurs when said counted number of pulses is outside said adjusted predetermined range of pulses.

10. An apparatus for sensing the force applied to a drive chain of a bicycle that has a frame and a drive wheel rotating about an axle mounted within said frame, said apparatus comprising:

a force sensing device that provides an output that is sensitive to an applied force;

an axle strap having a first end and a second end, said first end having an opening that receives one end of said axle, said one end of said axle mounted so that it is free to move with respect to said frame of said bicycle, said second end of said axle strap coupled to said force sensing device to that force applied to said drive chain is coupled from said drive chain through said axle and said axle strap to said force sensing device.

11. The apparatus as defined in claim 10, wherein said output is an electrical signal having a characteristic responsive to the magnitude of said force.

12. A method for sensing the force applied to the chain of a bicycle by a drive sprocket, comprising the steps of:

mounting the drive wheel of the bicycle in the frame of the bicycle so that one end of the axle of the wheel is loosely mounted with respect to the frame;

interconnecting said one end of the axle to a force transducer so that force applied to said chain is coupled through said axle to said force transducer; and

sensing the force applied to said force transducer and providing an output responsive thereto.