GB2247870A - Pedal cycle and pedal assisting means - Google Patents

Abstract

A pedal cycle (10) has respective sensors (46) for detecting when great force is applied to the pedals (26) and actuating power supply to respective solenoids (34), thus urging displacement of the solenoid plungers (36) to assist the work of pedalling. The power supply may take DC from a battery (40); convert it to AC with a power inverter; increase the voltage with a transformer; and rectify the result to provide a high voltage DC supply for the solenoids (34). <IMAGE>

Description

PEDAL CYCLE AND PEDAL ASSISTING MEANS The present invention relates to a device to assist the rider of a pedal cycle, by providing power, when required, to assist the working of the pedals.

The bicycle, powered solely by human energy is a very convenient and economical method of transport particularly in heavily built up areas with much traffic congestion. Moreover, it does not add to the so-called "green-house" effect and its use is to be encouraged in cities and built-up areas in . order to cut down the emission of carbon dioxide by internal combustion engines.

However, some cities have very steep hills and it requires much effort to bicycle up these, even if the bicycle is provided with a three or multi-speed gear.

It is thus an object of the present invention to provide assistance to the pedals of a pedal cycle, which assistance is ecoiogically friendly to the environment.

According to the present invention there is provided a device to assist the rider of a pedal cycle, including: (a) a pair of solenoids whose plungers are respectively associated with the cranks of the pedal cycle; (b) a re-chargeable battery; (c) means for detecting when the pressure applied to the respective pedals of the bicycle exceeds a given pressure; and (d) means for energizing respective solenoids from said re-chargeable battery, when said pressure on respective pedals exceeds said given value; whereby actuation of the plungers of the respective solenoids on the cranks of the respective pedals assists the propulsion of the pedal cycle.

The power for the energization of the solenoids may be obtained through a power inverter including an oscillator, a flip-flop circuit" and a power amplifier.

The means for detecting when the pressure on the pedals exceeds a predetermined value is preferably a pair of pressure sensors, each in the form of a sensitive switch mounted on a pedal or the bicycle.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings wherein: Fig. 1 is a circuit diagram of the power inverter forming part of the device for providing motorized assistance to a pedal cycle; Fig. 2 is a circuit diagram of the solenoids which are energized with power from the power inverter when sufficient pressure is applied to the pedals of the bicycle; and Fig. 3 is a schematic view of a bicycle embodying the invention.

Fig. 3 shows a bicycle 10 having two wheels 12,14 and a frame 16 (including a seat tube 17). The frame carries handlebars 18, a saddle 20, and luggage carrier 22.

The rear wheel 12 is drivable. via a crankset comprising a pair of cranks 24 rotatably mounted to the frame 16, a pair of pedals 26 mounted to respective cranks 24; a front chainwheel 28 coaxial with the cranks; a rear chainwheel 30 coaxial with the rearwheel 12; and a chain 32 coupling the chainwheels. This much is conventional: but the cycle further includes pedal assisting means. These include a pair of solenoids 34 mounted to the seat tube 17. Each has a displaceable plunger 36 pivotally coupled at its lower end to a connecting rod 38, whose other end is pivotally connected to a respective crank 24. The luggage carrier 22 bears a battery 40 and circuitry 42 which is described below.

The handlebars 18 carry an on/off switch 44. Each pedal 26 bears a pressure sensitive switch 46.

Figs. 1 and 2 give details of the circuitry.

Referring specifically to Fig. 1, the power inverter is powered by means of a 12 volt rechargeable battery B.

The power inverter includes an oscillator 0, a flip-flop F and a power amplifier A. The oscillator 0 is an LM555 integrated circuit device provided with associated resistors R1 to R3 and capacitors C1 to C3. It is designed to oscillate at a frequency of 120Hz when energized from the battery B through a main-switch Si.

The output from the oscillator 0 is applied to the clock input of the flip-flop F. The flip-flop F is a 74C74 integrated circuit device and is designed to divide the oscillator output by a factor of 2 thereby producing complementary outputs of 60Hz on its Q and Q outputs 5 and 6 respectively.

The power amplifier A comprises transistors Q1 to Q6, resistors R4 to R15 and a capacitor C4. The two outputs from the Q and Q outputs of the flip-flop F are applied to the respective base electrodes of the transistors Q1 and Q2 through respective resistors R4 and R5. The outputs from the collector electrodes of respective transistors Q1 and Q2 are applied to the base electrodes of respective transistors Q3 and Q4 through respective resistors R7 and R9. The collector electrodes of the transistor Q1 and Q2 are also connected to the positive terminal of the battery B through respective resistors R6 and R8, whilst the emitter electrodes are earthed.The collector electrodes of the transistors Q3 and Q4 are connected to the opposite sides of a resistive bridge network A comprising resistors R10 to R13. The other corners of the bridge network A are earthed. the base electrodes of transistors Q5 and Q6 are connected to the collector electrodes of the respective transistors Q3 and Q4. The emitter electrodes of the transistors Q5 and 06 are connected to opposite ends of the primary winding of a transformer T through respective resistors R14 and R15, whilst the collector electrodes of these transistors are connected to the positive terminal of the battery B.

Referring now to Fig. 2 the opposite ends of the secondary winding of the transformer T are connected to opposite corners of a full wave rectifier bridge Z. The energizing windings of a pair of solenoids L1 and L2 are connected in series with respective switches S2 and S3, these being the pressure sensitive switches attached to respective pedals of the bicycle. Protective diodes D1 and D2 are provided in parallel with respective solenoid windings L1 and L2 and a capacitor C5 is provided in parallel with the complete solenoid circuits, across the other two corners of the rectifier bridge Z.

In operation, provided the cyclist's pressure on the pedals does not exceed a given pressure value, the windings of the solenoids L1 and L2 are not energized as the respective pressure sensitive switches S2 and S3 remain open. This occurs on level or down-hill gradients when no great pressure on the pedals is required to propel the bicycle. However, the power inverter is ready to produce the necessary power to energize the solenoids provided the main switch S1 is closed. This switch is conveniently provided on the handle bars of the pedal cycle for operation by the cyclist when required.

Desirably an energised solenoid can provide a force of 2Kg or more via its plunger.

When the main switch S1 is closed, the oscillator 0 is set to oscillate at 120Hz. The flip-flop F divides this by 2 so that two oppositely phased square waves at a frequency of 60Hz appear at the base electrodes of the respective transistors Q1 and Q2. These oppositely phased square waves are separately amplified by the respective circuits comprising transistors 91, Q3, Q5 and transistors Q2, Q4, Q6. The outputs from transistors Os and Q6 again in phase opposition are applied to the primary winding of the transformer T. The output of the secondary winding of the transformer T is capable of producing a power of 120 watts at 220 volts A.C. and is applied across the rectifier bridge Z.This will tend to charge up the capacitor C5, if the sensor switches S2, S3 are both closed. If the cyclist applies sufficient force to the pedals, e.g. because he encounters an up-hill gradient at a given point in the downward movement of each pedal, the given pressure is exceeded and the pressure sensitive switch S2 or S3 closes to energize the respective solenoid winding L1 or L2, for that.part of the downward movement of the pedal at which the given pressure is exceeded. The capacitor C5 partly discharges through the respective solenoid. The solenoids L1 and L2 act alternately and their plungers apply mechanical pressure to the respective cranks of the pedals to assist in the propulsion of the pedal cycle.As stated above, each solenoid is capable of applying a force equivalent to 2Kg to the pedal crank. As soon as the brow of the hill has been reached, the pedal pressure is reduced below that at which the pressure sensitive switches operate, and the solenoids become inoperative. The cyclist may then switch off the battery power by opening the main switch S1.

When the bicycle is not in use, the battery B can be recharged by connecting it to a normal car battery charger.

It should be noted that if more power capacity is required two additional power transistors may be provided in parallel with the respective output transistors Q5 and Q6, each additional power transistor having an associated resistor analogous to respective resistors R14 and R15.

The device for motorized assistance to pedal cycles is robust and easy to operate. Moreover, it makes the use of bicycles more pleasant and less hard work in hilly terrains, thus encouraging city dwellers to make more or full use of their pedal cycles thus cutting down on the emission of carbon dioxide into the atmosphere. In addition more use of the pedal cycle is a healthy form of cardiovascular exercise which lowers the blood pressure and is especially beneficial to people subjected to high stress, reducing the risk of heart attacks. The utilization of the device of the present invention thus encourages lazy people to take more exercise.

Claims (9)

Claims

1. A pedal cycle having a frame, ground engaging wheels mounted thereto; wheel driving means coupled to a drivable one of said wheels and comprising a pair of pedals coupled to said drivable wheel so that application of force to the pedals urges rotation of said drivable wheel; pedal assisting means comprising a pair of solenoids mounted to said frame and associated with respective pedals, each solenoid having a body and a displaceable plunger; means fpr applying power to a selected one of said solenoids; and sensing means arranged to sense when force applied to a pedal exceeds a predetermined threshold value; said sensing means being coupled to said power applying means so that detection of force applied to a pedal actuates the application of power to the associated solenoids, which urges displacement of its plunger which urges said rotation of the drivable wheel.

2. A pedal cycle according to claim 1 wherein said driving means further includes a pair of pedal cranks rotationally fast with respective pedals; and wherein said solenoid plungers are coupled to respective pedal cranks.

3. A pedal cycle according to claim 1 or 2 wherein said power applying means comprises power inverter means for producing an alternating current from a direct current supply; a transformer coupled to the power inverter for producing an output at a higher voltage; and rectifying means for rectifying said higher voltage output.

4. A pedal cycle according to any preceding claim wherein said sensing means comprise pressure sensitive switches mounted to respective pedals.

5. A pedal cycle substantially as herein described with reference to and as illustrated in the accompanying drawings.

6. Pedal assisting means for a pedal cycle having a frame, ground engaging wheels mounted thereto; and wheel driving means coupled to a drivable one of said wheels and comprising a pair of pedals coupled to said drivable wheel so that application of force to the pedals urges rotation of said drivable wheel, said pedal assisting means comprising a pair of solenoids, each solenoid having a body and a displaceable plunger; means for mounting said solenoids to a cycle frame so that displacement of a plunger in one sense urges rotation of the drivable wheel; means for applying power to a selected one of said solenoids; and sensing means adapted to be mounted to a cycle so that in use they sense when force applied to a pedal exceeds a predetermined threshold value; said sensing means being coupled to said power applying means so that detection of force applied to a pedal actuates the application of power to the associated solenoid, which urges displacement of its plunger.

7. Pedal assisting means according to claim 6 wherein said power applying means comprises power inverter means for producing an alternating current from a direct current supply; a transformer coupled to the power inverter for producing an output at a higher voltage; and rectifying means for rectifying said higher voltage output.

8. Pedal assisting means according to claim 6 or 7 comprising pressure sensitive switches adapted to be mounted to respective pedals.

9. Pedal assisting means substantially as herein described with reference to and as illustrated in the accompanying drawings.