A parking brake system

Abstract

A parking brake system 12 for a bicycle, tricycle or other cycle comprises a pulley system 104 operated by a motor through a worm drive to increase the force of application of the brake as the brake i

Description

This invention relates to a parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle. A parking brake or immobiliser once applied, stays on to hold the vehicle stopped until the parking brake or immobiliser is released. The immobiliser can be for a tricycle such as a final mile delivery tricycle or postman's tricycle. The nature of such a tricycle is that it is frequently left unattended for short periods of time while a parcel is being delivered, so a rapid method of securing the vehicle is needed. According to one aspect of the invention, there is provided a parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle to hold the cycle at rest, the system including means to increase the force of application of the brake as the brake is applied. By providing a parking brake system, the cycle will not move while unattended. By including means to increase the force of application of the brake, it can be assured that the cycle is immobilised. This may be particularly important where the cycle is heavy, for example an electric bike, tandem, quadracycle, cargo bike or tricycle, in particular a cargo tricycle. The system may increase the force of application of the brake in any suitable way and in one embodiment, the system includes means to increase the mechanical advantage of the system to increase the force of application of the brake. The means may take any suitable form and may comprise a pulley system. The means may include a part arranged to pivot about an axis. The part may be arranged to pivot through an acute angle to operate the brake. The system preferably includes means to reduce the effective radius of the pulley. The parking brake system preferably includes attachment means arranged to be attached to a brake cable. The attachment means preferably permits the end of the cable to pivot. In this way, the end of the cable is not twisted when the brake cable is pulled. Where there is a pivoting part, the part is preferably arranged to pivot from a position in which a radius from the axis of pivoting to the attachment means is generally perpendicular to the direction of pull. The part may be driven by a gear system. The gear system may drive at a ratio of at least 100 to 1, preferably at least 300 to 1. The gear system may drive at a ratio of less than 1000 to 1. In a preferred embodiment, the gear system is driven at a ratio of about 500 to 1. This gearing means that a relatively small motor can be used to apply adequate braking force to park a fully laden vehicle on a steep hill. Suitably, the part may be driven by a worm drive of the system. The parking brake system may be of any suitable type but is conveniently electrically operated. The parking brake system preferably comprises switch means operable by the user to operate the brake system. The parking brake system is conveniently released by a non contact device such as an RFID system and the parking brake system may be arranged to be released by proximity of an RFID fob. The parking brake system may include a microcontroller to control the system. The parking brake system may include a motor and a current limit may be used to determine when the motor has reached the required torque to provide adequate braking force. The parking brake system may include a limit switch such that, when released, the limit switch indicates that the system has moved back to the disengaged position. The parking brake system may include a mechanical limit stop to prevent overtravel in the reverse direction. The parking brake system may include sensor means to sense when the cycle is moving and means to prevent the parking brake from being applied when the sensor means indicates that the cycle is moving. It is important that the parking brake should not be applied accidentally when the vehicle is moving, in particular for example when pulling out in front of a car, or going round a roundabout. According to another aspect of the invention, there is provided a parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle, the system including sensor means to sense when the cycle is moving and means to prevent the parking brake from being applied when the sensor means indicates that the cycle is moving. The sensor means may take any suitable form and may comprise an accelerometer. According to a further aspect of the invention there is provided the combination of a parking brake system according to any previous aspect of the invention and at least one brake. According to another aspect of the invention, there is provided a bicycle, tricycle or other cycle equipped with a parking brake system according to any preceding aspect of the invention. The parking brake system may operate a brake which is for reducing the speed of the cycle, but in a preferred embodiment, the cycle includes at least one dedicated brake to be operated by the parking brake system which is additional to the or each brake for reducing the speed of the cycle. The cycle may be a tricycle and in that case, in one embodiment, the tricycle is a delta tricycle and the parking brake system may operate a dedicated brake on one rear wheel or preferably on each rear wheel. According to a further aspect of the invention there is provided a parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle, the system comprising switch means operable by the user to operate the brake system, and attachment means arranged to be attached to a brake cable, so that operating the switch means acts on the brake cable to apply the brake. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig 1 is a perspective view of a tricycle including the parking brake system of the embodiment; Fig 2 is a perspective view of the parking brake system of the embodiment in the rest position with the casing removed; Fig 3 is the view of Fig 2 with the parking brake applied; Fig 4 is a plan view of the parking brake system of the embodiment in the rest position with the casing removed and the top plate omitted for clarity; Fig 5 is the view of Fig 4 with the parking brake applied; Fig 6 is a plan view of the parking brake system of the embodiment in the rest position with the casing removed and the top plate included; Fig 7 is the view of Fig 6 with the parking brake applied; Fig 8 is a plan view of the parking brake system including the casing; Fig 9 is an end elevation of the parking brake system including the casing; and, Fig 10 is a diagrammatic view of the PCB, RFID reader and fob of the embodiment. A tricycle 10 carries the parking brake system 12 of the embodiment. The tricycle 10 is a delta tricycle with two rear wheels 14, 16 and a single front wheel 18 carried by a frame 20 and front forks 22. The tricycle 10 is a tilting tricycle, and the frame 20 comprises a front, tilting part 24, and a rear part 26 arranged so that the front part 24 can tilt with respect to the rear part 26, for example during cornering. The front part 24 comprises a head tube 28, down tube 30 and bottom bracket 32. From the bottom bracket 32 a lower tube 34 extends rearwardly. From the down tube 30 just above the bottom bracket 32 two upper tubes 36 extend rearwardly. The lower and upper tubes 34, 36 connect through a tilting mechanism 38 to the rear part 26, so that the front part 24 can tilt with respect to the rear part 26. The rear part 26 comprises a generally rectangular framework 40, the upper frame loop 42 being generally horizontal to mount a cargo box, not shown. The upper frame loop 42 includes a forwards extending side arm 44, 45 on each side. Four cylindrical pads 47 of elastomeric material are carried by and extend upwardly from the upper frame loop 42, and in use a cargo box, not shown, can be mounted on the pads 47. Each pad 47 is mounted by a bracket 49, 51, 53 which extends outwardly from the upper frame loop 42, the brackets 49 at the rear being at the rear corners of the loop 42 and the brackets 51, 53 at the front being on the forwards extending side arms 44, 45. At the top of the downtube 24 of the tricycle 10 is a button 46, and an RFID reader pad 48. Each rear wheel 14, 16 of the tricycle 10 has a hydraulic disc brake system comprising a brake disc 50, 52 and a brake caliper 54, 56 operated by a lever 58 on the handlebars 24 in the normal way. Each rear wheel 14, 16 also has a mechanical disc brake system using the same disc 50 and a separate dedicated caliper 62, 64 operated by the parking brake system 12. The cable 66, 68 from each parking brake caliper 62, 64 goes to the parking brake system 12. Each parking brake caliper 62, 64 is situated at the rear of each brake disc 50, 52, while each hydraulic brake caliper 54, 56 is situated to the front side. The parking brake system 12 is mounted on one forwards extending side arm 44 of the rear part 26 of the frame 20. The parking brake system 12 includes a weatherproof casing 70. The cables 66, 68 from the parking brake calipers 62, 64 enter the casing 70 on opposite sides 72, 74. The cable 66 passes through an opening (not shown) in the bracket 51 and then diverts through generally a right angle to enter the left side of the parking brake system casing 70. The cable 68 passes through an opening 51 in the bracket 53 and then diverts through generally a right angle to enter the right side of the parking brake system casing 70. The parking brake system 12 comprises a motor 80 driving a worm drive system 84 which drives an axle 88. The axle 88 has a flat 90 on one side. The axle 88 passes through complementary holes 92 in three stacked laser cut plates 100, 102, 104. The worm drive system 84 has a gear ratio of 505 to 1. The first laser cut plate 100 includes a circular cut out adjacent the circumference 112 of the plate 100 and a cut from the circumference 112 to the cut out. A spacer (not shown) is provided between the first laser cut plate 100 and the second laser cut plate 102. The second laser cut plate 102 has a first circular cut out adjacent the circumference 132 of the plate 102 and a cut from the circumference 132 to the first cut out, the first cut out in the second laser cut plate 102 being aligned with the cut out in the first laser cut plate 100. The second laser cut plate 102 also has a second circular cut out 130 on the opposite side of the plate 102 from the first and also adjacent the circumference 132. The second circular cut out 130 is also connected to the circumference 132 by a cut 134. A spacer (not shown) is provided between the second laser cut plate 102 and the third laser cut plate 104. The third laser cut plate 104 includes a circular cut out 160 adjacent the circumference 162 of the plate 104 and a cut 164 from the circumference 162 to the cut out 160, the cut out 160 in the third laser cut plate 104 being aligned with the second circular cut out 130 in the second laser cut plate 102. The first laser cut plate 100 also includes a radially extending arm 170. An upstanding tab 172 is provided on the worm drive housing 174 in the path of movement of the arm 170. A further plate 180 is attached to the top of the third laser cut plate 104 by two screws 182, 184. The further plate 180 extends beyond the circumference of the third laser cut plate 104 to provide a tab 186 with an outer edge 188. A limit switch 190 mounted on a PCB 192 includes a finger 194 to engage the edge 188. The PCB 192 receives wires 200 from the button 46, and RFID reader pad 48 respectively. The PCB 192 mounts an accelerometer 210, a microcontroller 220, an EEPROM 222 and a motor driver 224 for the motor 80. The parking brake cable 66 from one mechanical disc brake caliper 62 terminates in a cylindrical barrel 230, and the parking brake cable 68 from the other mechanical disc brake caliper 64 also terminates in a cylindrical barrel. The first barrel 230 is received in the circular cut outs 130, 160 in the second and third plates 102, 104, so that the cable 66 lies freely between the second and first plates 102, 104, and the barrel 230 can pivot in the circular cut outs 130, 160. The second barrel is received in the second circular cut out of the second plate 102 and in the circular cut out in the first plate 100, so that the cable 68 lies freely between the first and second plates 100, 102, and the barrel 232 can pivot in the circular cut outs. In the rest position, the radius R from the axle 88 to the first barrel 230 is generally perpendicular to the direction of pull to the cable 66, and the opposite radius from the axle 88 to the second barrel 232 is perpendicular to the direction of pull to the cable 68. In use, the rider can bring the tricycle 10 to a halt and then press the button 46 to turn on the parking brake 12 and immobilize the tricycle 10. A signal from the button 46 will pass down a wire (not shown) in the down tube 30 to the microcontroller 220. The microcontroller 220 will instruct the motor driver 224 to actuate the motor 80. The motor 80 will drive the worm drive system 84 turn the axle 88 to rotate the plates 100, 102, 104 through an acute angle. Rotation of the plates 100, 102, 104 will pull the barrels 230, 232 to pull the brake cables 66, 68 to actuate the parking brake calipers 62, 64. A current limit is used to determine when the motor 80 has reached the required torque to provide adequate braking force. It is seen from in particular Figures 4 and 6, that as the plates 100, 102, 104 rotate, the parking brake cables 66, 68 come closer to the axle 88, thereby reducing the effective radius of pull from R to r (Fig 5) and therefore increasing the force applied to pull the cables 66, 68. At the same time, for each degree of rotation, the distance each cable 66, 68 is pulled reduces. Thus, the plates 100, 102, 104 act as a pulley system. Because the shape of the pulley system is such that the cable ends 230, 232 can rotate freely, and the spacer plates (not shown) are shaped to allow the cable to move without spooling, as the pulley rotates in direction of rotation the effective pulley radius (perpendicular to the cable) can reduce from R to r, increasing the resulting force on the cable for a fixed torque at the gearmotor 84 output shaft 88. In the case of the present design, the maximum change in radius is from 10mm to 5mm, which results in up to a doubling of the cable pull force as the brake reaches full engagement (force is doubled assuming minimum effective radius is reached, this depends on how the brakes are adjusted and overall cable travel) As the plates 100, 102, 104 rotate, the outer edge 188 of the tab 186 will come into contact with the finger 194 of the limit switch 190 to activate the limit switch 190 and via the microcontroller 220 stop the motor driver 224 to stop the motor 80. In case of failure of this system, the arm 170 will engage the upstanding tab 172 on the worm drive housing 174 in the path of movement of the arm 170, and the tab 172 will act as a stop to prevent further rotation of the plates 100, 102, 104. To release the parking brake system 12, the rider will bring a fob 240 adjacent or onto the RFID reader pad 48. This will send a signal though a wire (not shown) in the down tube 30 to the microcontroller 220 to release and reverse the motor 80 and return the plates 100, 102, 104 to their starting positions. In this way, a parking brake system 12 is provided which will increase the force of application of the parking brake calipers 62, 64 as the brake actuates to assure that the tricycle 10 is effectively immobilised and will not move while unattended. Other benefits of the design are that by allowing this freedom for the end 230 of the cable to rotate, and the reducing radius of the pulley towards the engaged position, the cable 66, 68 is subjected to much less bending which significantly improves the life of helical steel cables. The rising mechanical advantage also means that a smaller gearmotor 80 may be used to achieve the desired force on the cable 66, 68 sufficient to brake the vehicle 10 which reduces power consumption and system weight. When the parking brake button 46 is pressed, the microcontroller 220 checks for a signal from the accelerometer 210. If a signal is present from the accelerometer 210 to indicate that the tricycle 10 is moving, the microcontroller 220 does not actuate the motor 80 to activate the parking brake. This ensures that the tricycle 10 is not accidentally braked suddenly if the button 46 is mistakenly pressed while cycling along. The worm drive 84 prevents the motor 80 from being back driven. The tricycle 10 of the embodiment has two brake calipers 62, 64, but in a variation of the embodiment, the parking brake acts on only one rear wheel 14 so only one brake caliper 62 is provided. Equally, in a further variant, the parking brake system 12 could operate on all three wheels 14, 16, 18, by including an additional brake caliper on the front wheel 18 with a brake cable to an additional plate. The tricycle could be a tadpole tricycle, rather than a delta tricycle, in which case the parking brake would act on the two front wheels, or on just one wheel, or on all three wheels. Instead of the button 46 and RFID reader pad 48, the parking brake system 12 could be operated by a key. Alternatively, the parking brake system 12 could be arranged to be operated by the user's phone. If security is not an issue, the parking brake system 12 can just be operated and released by the button 46. This means the tricycle 10 could be ridden off by someone who just releases the parking brake by pressing the button 46, but if the rider will always be close to the tricycle 10 in use, then that may be acceptable. Other variants of the design would be differing pulley sizes to accommodate for different brake calipers, and alternative gearmotor options for higher or lower brake forces as required. In the depicted embodiment the gear ratio is 505:1 but could vary depending on application e.g. for larger brake systems on heavier vehicles or single brake systems on a single tracked vehicle i.e. a bicycle. Instead of the accelerometer, it would be possible to use a wheel speed sensor to detect if the vehicle is moving. This would have the advantage over the accelerometer as the accelerometer might be triggered by e.g. wind causing the vehicle to move.

Claims

1. A parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle to hold the cycle at rest, the system including means to increase the force of application of the brake as the brake is applied.

2. A parking brake system as claimed in claim 1, wherein the system includes means to increase the mechanical advantage of the system to increase the force of application of the brake.

3. A parking brake system as claimed in claim 1 or claim 2, wherein the means comprises a pulley system.

4. A parking brake system as claimed in any of claims 1, 2 and 3, wherein the means includes a part arranged to pivot about an axis.

5. A parking brake system as claimed in claim 4, wherein the part is arranged to pivot through an acute angle to operate the brake.

6. A parking brake system as claimed in any of claims 3 to 5, wherein the system includes means to reduce the effective radius of the pulley.

7. A parking brake system as claimed in any preceding claim, wherein the system includes attachment means arranged to be attached to a brake cable.

8. A parking brake system as claimed in claim 7, wherein the attachment means permits the end of the cable to pivot.

9. A parking brake system as claimed in claim 7 or claim 8, when dependent on claim 4 or claim 5, wherein the part is arranged to pivot from a position in which a radius from the axis of pivoting to the attachment means is generally perpendicular to the direction of pull.

10. A parking brake system as claimed in claim 4, 5 or 9, wherein the part is driven by a gear system.

11. A parking brake system as claimed in claim 10, wherein the gear system drives at a ratio of at least 100 to 1.

12. A parking brake system as claimed in claim 10, wherein the gear system drives at a ratio of at least 300 to 1.

13. A parking brake system as claimed in claim 10, 11 or 12, wherein the gear system drives at a ratio of less than 1000 to 1.

14. A parking brake system as claimed in claim 10, wherein the gear system drives at a ratio of about 500 to 1.

15. A parking brake system as claimed in any of claims 10 to 14, wherein the part is driven by a worm drive of the system.

16. A parking brake system as claimed in any preceding claim, wherein the parking brake system is electrically operated.

17. A parking brake system as claimed in any preceding claim, the system comprising switch means operable by the user to operate the brake system.

18. A parking brake system as claimed in any preceding claim, wherein the parking brake system is released by a non contact device.

19. A parking brake system as claimed in claim 18, wherein the parking brake system includes an RFID system and the parking brake system is arranged to be released by proximity of an RFID fob.

20. A parking brake system as claimed in any preceding claim, wherein the parking brake system includes a microcontroller to control the system.

21. A parking brake system as claimed in any of claims 17 to 20, wherein the system includes a motor.

22. A parking brake system as claimed in claim 21, wherein a current limit is used to determine when the motor has reached the required torque to provide adequate braking force.

23. A parking brake system as claimed in any of claims 17 to 22, wherein the system includes a limit switch and is such that, when released, the limit switch indicates that the system has moved back to the disengaged position.

24. A parking brake system as claimed in any of claims 17 to 23, wherein the system further includes a mechanical limit stop to prevent overtravel in the reverse direction.

25. A parking brake system as claimed in any preceding claim, wherein the system includes sensor means to sense if the cycle is moving and means to prevent the parking brake from being applied when the sensor means indicates that the cycle is moving.

26. A parking brake system for a bicycle, tricycle or other cycle for operating a brake on the cycle, the system including sensor means to sense if the cycle is movingand means to prevent the parking brake from being applied when the sensor means indicates that the cycle is moving.

27. A parking brake system as claimed in claim 25 or claim 26, wherein the sensor means is an accelerometer.

28. The combination of a parking brake system as claimed in any preceding claim and at least one brake.

29. A bicycle, tricycle or other cycle equipped with a parking brake system as claimed in any of claims 1 to 27.

30. A bicycle, tricycle or other cycle as claimed in claim 29, wherein the cycle includes at least one dedicated brake to be operated by the parking brakesystem.

31. A tricycle as claimed in claim 30, wherein the tricycle is a delta tricycle and the 5 parking brake system operates a dedicated brake on each rear wheel.

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