GB2279918A

GB2279918A - Treadle-cycle

Info

Publication number: GB2279918A
Application number: GB9314808A
Authority: GB
Inventors: Arthur Entwistle
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-15
Filing date: 1993-07-15
Publication date: 1995-01-18
Also published as: GB9314808D0

Abstract

Pedals 22 are guided for linear movement in slotted tubes 18 and are coupled via flexible members 24 to one-way clutch or free wheel 27 which in turn rotates drive wheel 28. The pedals can be operated independently, a return spring acting to return them to the upper position. Alternatively the pedals can be interconnected so downward movement of one returns the other to the upper position. <IMAGE>

Description

A PEDAL POWERED MECHANISM This invention relates to pedal powered mechanisms and to a vehicle driven thereby.

With a conventional pedal drive, as used on bicycles, the final torque is dependent on the angle of the pedals. When the pedals are respectively placed at the top and bottom of the stroke the application of a downward force gives zero drive. When the pedals are at 90 degrees to the operating force, the maximum torque is applied to the final drive. The force curve is cyclic, rising from zero to a maximum at 90 degrees again to zero at 180 degrees maximum again at 270 degrees and finally zero at 360 degrees. It is well known that in order to pedal away, it is necessary to start out with the drive pedal on the downward stroke.

The human body is capable of producing more useful power from the legs than from the arms.

With both legs straight out from the body, raising one knee puts the moving foot in a position just below the other knee. This is the best staring point for an energy stroke. When the foot is pushed away from the body, the energy is given over the full stroke, ie. from the knee position of the straight leg to the foot position. Approximately 16" on the average person.

According to one aspect of the present invention there is provided a pedal powered mechanism including a pedal, pedal guide means adapted to guide the pedal for substantially linear movement, a rotary member and a linear-to-rotary movement conversion means interconnecting the pedal and the rotary member, whereby said substantially linear movement of the pedal causes rotation of the rotary member.

Preferably the pedal guide means includes a straight slide member along which the pedal slides.

Conveniently, the linear-to-rotary converter includes a chain or toothed belt connected at one end to the pedal and passed round a chain wheel or toothed wheel respectively, either of said wheels being connected to drive said rotary member through a one-way clutch or freewheel.

Advantageously, said pedal powered mechanism includes two of said pedals, a parallel pair of said pedal guide means and each said pedal connected through one of said linear-to-rotary movement conversion means to the rotary member.

Preferably, the mechanism includes pedal retraction means adapted to restore the or each pedal from the end position of a pedal power stroke to the start position of the pedal power stroke.

According to another aspect of the invention there is provided a pedal powered vehicle including at least one of said pedal powered mechanisms.

The vehicle may be a bicycle and is conveniently a reclining-type bicycle preferably fitted with a seat for the driver, the seat conveniently having a back rest.

One embodiment of the invention is described by way of example only with reference to the accompanying drawings, in which.

Figure 1 is an elevation of a bicycle incorporating pedal powered mechanism, according to the invention, and Figure 2 is a perspective view of a pedal powered mechanism according to the invention.

In the drawings, a bicycle has front and rear wheels 10, 11 the front wheel 10 being mounted on forks 12 through a steering head 13 to handlebars or a complete or partial steering wheel 14.

The steering head 13 forms part of a frame 15 having rear forks 16 on which the rear wheel 11 is mounted.

At either side of the frame 15 a pair of parallel pedal slides 17 are fastened as shown in Figure 2, each pedal slide 17 comprises a cylindrical tube 18 having a longitudinal slot 19 along the outer face thereof. A cylindrical slug 20 is a sliding fit in the tube 18. A spindle protrudes from the slug 20 through the slot 19 and carries a pedal 22 pivoted thereon, the pedal 22 being mounted outwardly from the tube 18.

The upper end of each slug 20 has an eye 23 to which one end of a roller chain 24 is fastened.

Each chain 24 passes over a chain wheel 25 running on a drive shaft 26 and connected thereto by a one-way clutch or freewheel 27. The one-way clutch or freewheel 27 is typically a friction drive type, such as a sprag type, or a a ratchet and pawl type. Between the chain wheel 25 and affixed to the drive shaft 26 is a drive wheel 28 connected by a loop of chain 29 driving a sprocket 30 on the rear wheel 11 or on a further drive shaft 31. A helical or similar return spring may interconnect the chain wheel 25 and stationary structure, so as to re-wind the chain 24 at the end of each downward pedal stroke and thereby raise the pedal 22 to the top of its stroke.

Instead of chains 24, 29, and chain wheels 25, 28, 30 toothed belts and correspondingly toothed wheels can be used or even other suitable belts or cables. A conventional multi-ratio drive may be used between the wheels 28, 30 such as a derailleur type 32 or a hub type 33, In the bicycle shown in Figure 1, the pedal slides 17 are almost horizontal but lower at the front.

A cycle rider 33 sits on a seat 34 mounted low on the frame 15, the layout being such that the path of the pedals 22 in alignment with a comfortable movement of the riders foot between retracted and extended positions of his legs 36. The seat 34 has a back rest 37 to absorb the reaction forces of the rider 33 on the pedals 22.

After the rider 33 has extended his leg 36 in a power stroke the pedal 22 can be returned to the beginning, where his leg is retracted by a toe clip on the peel 22 or by a return spring or other suitable means., Where movement of the pedals 22 is kept independent, both pedals 22 can be pushed out together in simultaneous power strokes of the legs 36, or the pedals 22 can be used alternatively for a smoother mode of riding.

A suitable length for the travel of the pedal 22 is around 500mm with the diameter of the chain wheel 25 being around 175mm. Obviously shorter riders can use as much of the pedal travel as suits them.

Although the invention has been described as applied to a pedal cycle, it is also applicable to other pedal driven equipment, such as for man-powered flight.

Instead of the pedals 22 being able to operate independently of each other, they can be coupled such that as one pedal moves down the other moves correspondingly up. For example, they can be coupled by a cable extending upwardly from one pedal 22 around a pulley and down to the other pedal.

It will be seen that in all positions of the pedal 22 the torque applied to the wheel 11 is proportional to the force on the pedal, whereas in a conventional rotary crank pedal mechanism the relationship between pedal force and torque is substantially sinusoidal.

Thus, in a pedal powered mechanism, according to the invention, the work expended by a rider in one stroke of the pedal is equal to the product of the constant torque which he generates by his constant force on the pedal and the angle of rotation of the rotary member. If torque is plotted against angle the area under the curve is a rectangle.

On the other hand, with a conventional pedal mechanism the work expended by the rider is equal to the product of the sinusoidal torque distribution and the angle. The plot of these is half a sine curve, which for a given constant pedal force has an area equal to 0.707 of the work expended in the present invention. Thus the work available for propelling the cycle or for other purposes is around 41% greater than when using a conventional pedal mechanism

Claims

CLAIMS 1. A pedal powered mechanism including a pedal, pedal guide means adapted to guide the pedal for substantially linear movement, a rotary member and a linear-to-rotary movement conversion means interconnecting the pedal and the rotary member, whereby said substantially linear movement of the pedal causes rotation of the rotary member.
2. A pedal powered mechanism according to claim 1, adapted to produce a substantially constant torque on the rotary member from a constant force on the pedal in the direction of said substantially linear movement.
3. A pedal powered vehicle including at least one pedal powered mechanism according to claim 1 or claim 2.
4. A pedal powered mechanism constructed and arranged and adapted to operate substantially as described herein and as shown in the accompanying drawings.