EP1107901A1

EP1107901A1 - Worm wheel transmission

Info

Publication number: EP1107901A1
Application number: EP99941870A
Authority: EP
Inventors: Derk Frans Thijs; Lambert Johan Thijs
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-28
Filing date: 1999-08-26
Publication date: 2001-06-20
Also published as: WO2000012378A1; AU5534599A; NL1009960C2

Abstract

The invention concerns a variable transmission, particularly for human powered vehicles, by means of at least one Snek (snail wheel) (14) which exists of a drum with on it a non cylindric, in most cases more or less conical helicoidally shaped guiding path an d a cable like means of propulsion which rolls on and off said guiding path with the charateristic that the length of said guidingpath is substantially larger than the maximum stroke of the back and forth going means of propulsion and that a shifting mechanism(15) can alter the part of the Snek (14) where the means of propulsion is rolling on and off and thus change the gear ratio due tothe non cylindric shape of the Snek (14).

Description

Snek transmission

The invention concerns a variable transmission by means of a Snek (fusee) of which the groove is substantially longer than the stroke .

In this way, for example, it is possible to transmit a back and forth going movement into a rotating movement.

The invention was born on the Rowing bike, a human powered vehicle which is propelled by a back and forth going movement similar to the movement as for example on some vehicles for disabled people and on the Flying Dutchman. On the Rowing bike as shown on figure 1 and 2 the steering bar (8) is pivoting around a horizontal axle just above the head set; The foot slider (6) can move linear over the bow sprit (5) and is connected to the steering bar by the armstrokecable (9) which rolls over one of the two bow pulleys (10) . By pulling the steering bar backwards and pushing the click pedals (7) mounted on the foot slider forward the bike is propelled. During the recovery stroke the bike is freewheeling and the rider returns the foot slider, steering bar and propulsion cable (11) in begin position by means of a return cable (12) . The propulsion and return cable system is held on tension by an elastic cord (13) .

Until now the rear wheel was propelled by means of a chain on sprocket wheels mounted on a freewheel that could be chosen by a derailleur or by means of a steel cable witch rolls on and off a cilindrical drum mounted on a hub with internal gearing system and freewheel.

The problems in the existing systems were in the chain version: The undesireable presence of a chain which is always dirty. The changing of gear with a back and forth going chain causes problems with the standard available derailleur systems. The transmission by means of a chain is quite angular, not fluid. In the cable driven version the problems are that the gear changing is done in a gear hub; the efficiency of gear hubs is very poor due to so many moving parts all having their resistance. Also the freewheel in gear hubs engages the rear wheel only after a large free stroke, this also is a loss of energy and driving comfort. Both systems have the disadvantage that during a stroke the gear ratio is constant while the rider has smaller force in the beginning of the stroke and more force at the end of it.

These problems are solved by a transmission according to claims 1 and 2. Transmission according to the preamble of claim 1 are known for example from British patent no. 6225 A.D. 1911 and DE- C-947858. Patent GB-A-200385 even shows a similar transmission combined with a system to shift gear. This gear system changes the ratio between pedal movement and cable movement. This ratio is not easy to change on the Rowing bike as the propulsion cable is directly mounted on the linear moving foot bench.

The transmission according to the invention is only applicable for back and forth moving propulsion cables as the cable would screw itself of the Snek when only moved in one direction.

The Snek transmission can be effected with any means of propulsion like for example steel cable, rope, cord, belt, chain or toothed belt.

A lot of rotating power sources like for example the pedal shaft of a bicycle or the crank shaft of an Otto fuel engine find their origin in a back and forth going movement. The invention of the Snek transmission gives the opportunity to new solutions and designs in which forces can be transmitted more efficient, directer, cleaner and smoother. In the figurers 8 to 13 I show 6 of the possible solutions in a schematic way.

Figure 8 shows in a schematic way how the invention is carried into effect on the Rowing bike as shown in figures 1 to 6. Besides the explanation given above the following explanation of the numbered parts will clarify things.

1 frame 18 spokes

2 front fork 19 freewheel housing

3 wheel 20 disk rear wheel

4 seat 21 main groove in Snek

5 bow sprit 22 diagonal groove in Snek

6 foot slider 23 Snek for fixed cable

7 click pedal 24 Snek without diagonal groove

8 steering bar 25 contra Snek

9 arm stroke cable 26 stroke

10 bow pulley 27 (foot slider) drum

11 propulsion cable 28 pull spring

12 return cable 29 radial spring

13 elastic cord 30 locking device

14 Snek 31 Snek brake

15 derailleur 32 cable tensioner

16 rear hub 33 elastic cord drum

17 qquuiicckk rreelleeaassee Figure 3 and 4 show the rear hub (16) of the Rowing bike with a Snek version as described in the claims 1, 2, 7 and 11: the propulsion cable (11) is turned around the Snek (14) one and a half time to ensure sufficient traction. It is possible that in other versions the propulsion cable needs to be turned around the Snek more or less times. This is a delicate play between shape and hardness of means of propulsion cable and Snek as well as the tension put on the propulsion system for example by means of a shock cord.

In the design of the total apparatus, in this case the Rowing bike, when one wants to change gear by shifting the cable to another part of the Snek for example by means of a derailleur (15) one has to take notice of the fact that the maximum contact length of the cable on the Snek, occurring when in lowest gear, should be shorter than the maximum stroke; otherwise the changing of gear cannot be completed. Changing to a higher gear is effected by pushing with the derailleur that part of the propulsion cable which is, seen from the foot slider, positioned after the Snek during the beginning of the stroke to the outward part of the Snek, where the Snek gets smaller in diameter. The cable will flip over to a next groove through a diagonal Snek groove (22) or other interruption in the side walls of the main groove specially taken out of the Snek for this purpose. After 1,5 rotation of the Snek , when the cable leaves the diagonal groove, the shifting of gear is completed.

Shifting to a lower gear is effected during the recovery stroke. On the end of the stroke one pushes, with the derailleur, that part of the cable witch is, seen from the foot slider, on the foot slider side of the Snek to the inside part of the Snek where its diameter is bigger. The cable takes a sidestep through a diagonal groove and after 1,5 rotation of the Snek shifting gear has completed.

Figure 5 and 6 show The Snek with its main groove (21) and its diagonal grooves (22) or other interruptions in the side wall of the main groove that are necessary in case shifting gear is effected by means of a kind of derailleur. When looked upon the section of the Snek it has a hollow line. Due to this hollow shape the difference in gear ratio during one stroke is practically the same in the lowest gear as it is in the highest gear. When a hyperbolic curve is used this effect is 100 % achieved.

Figure 7 shows an alternative shape of the Snek witch is barely conical in the lowest gear. A shape like this can be desireable for specific practical use, for example on a rowing bike for steep hills. Any ergonomically desired curve can be made!

Figure 9 shows a version in which the propulsion cable is attached to the smallest part of the Snek for fixed cable attachment (23) . On this Snek a narrow elastic cord drum (33) is attached whereon the elastic cord(13) rolls on and off. On the foot slider (6) a narrow twin drum is attached wherein one drum the propulsion cable can be rolled on and at the same time the return elastic cord (13) can be rolled off or otherwise around. Besides fluctuation of length of the propulsion and return cable system caused by shifting gear, fluctuations can occur caused by voluntary rolling over each other of cables in the several drums. To cope with these length differences a return cable is completely replaced by a return elastic cord. In this version shifting to a heavier gear is effected by always simultaneously de-locking the locking device (30) of the foot slider drum (27) and activating the Snek brake (31) . When now the foot slider is recovered the propulsion cable will roll on and the return elastic cord will roll off the foot slider drum. Before the next stroke the foot slider drum locking device is simultaneously locked with the de-activation of the Snek brake and thereby the shifting of gear is completed.

The shifting to a lower gear is effected in the same way but then by making a fake stroke in stead of above mentioned fake recovery.

The version according to figure 9 can be simplified by attaching the return elastic cord to a fixed point in stead of over a pulley to the foot slider drum. The elastic cord length has to be long enough to cope with al length differences. Figure 10 shows a version wherein the apparently endless propulsion cable clamps itself on the Snek by means of one or a few rotations around the Snek and wherein shifting of gear is effected by locking the foot slider (6) on a different part of the propulsion cable. The necessary tension on the cable is realised by the bow pulley witch is fixed by means of a draw spring(28). Just like the previous version when shifting gear the locking device of the propulsion cable on the foot slider is de-locked and simultaneously the Snek brake is activated. The shifting of gear is effected in exactly the same way.

Figure 11 shows a second system wherein an endless cable or cord can be used. In this version a contra Snek (25) is used which shape is such that it exactly compensates for the length differences that occur when the cable is rolled on and off the Snek. A cable tensioner or a elastic cord can take care for the necessary tension. Again shifting gear is effected in the same way. Of course the propulsion cable can be rolled around the Snek one or several times for sufficient traction.

Figure 12 shows a version wherein the shifting of gear is effected with a derailleur (15) again. The recovery of the system as well as the tension on the system is effected by one single elastic cord which is drawn as one single line but of course it may be necessary to have it running over a or a few pulley (s) to house the necessary length.

Figure 13 shows a Snek with fixed cable that is recovered in completely rolled up beginning position by means of an axial spring. Shifting of gear is effected by pulling in the propulsion cable (11) towards the foot slider (6) (shift to higher gear) or rolling off the cable (shift to a lower gear) before locking it on the foot slider with the locking device (30).

An other version of the gear shifting system can be that the propulsion cable is fixed to Snek as well as to the foot bench but that the propulsion cable is rolled off the Snek further (shifting to higher gear) or rolled on the Snek (shifting to a lower gear) by means of enlarging or shortening the cable length or distance from foot bench to the Snek.

It is also possible to transmit two or more eventually coupled back and forth going movements through several Snek systems in a rotating movement. A somewhat more conventional bicycle with a freewheel and Snek on each side of the rear wheel for the eventually coupled movement of the right and left leg can be an example for this version. Hereby a continuing propulsion can be achieved.

A next method to propell a more conventional leg propelled bike by one Snek is to couple the movements of the two pedals to each other in such way that strokes are made alternate to each other left and right, to mount the propulsion cable decoupleable to both pedals in such manner that at the end of the stroke of one pedal the propulsion cable is de-locked from that pedal and thereupon is pulled back fast by a spring or elastic cord in the beginning position of the stroke and in that position is automatically locked to the second pedal to make the next stroke etc. In this way an almost continuous propulsion can de achieved with only one Snek and freewheel.

With the invention the reversible transmission from rotating to back and forth going movement is also possible. The freewheel (s) than has (have) to be exchanged for a locking device that at the end of each stroke de-couples the relating Snek from the incoming rotating axis. The locking and de-locking of one or more Snek(s) could be activated by some kind of an eventually adjustable device at the beginning and end of each stroke. The recovery can be effected by coupling to a second Snek or by a spring or elastic cord.

The invention can also be applied for more conventional Snek (fusee) applications like the compensation of a certain balance between for example the weight of an up and down movable lift or storage device and a draw spring or like the balance between the force of a human being and a counterweight or spring in a fitness machine.

By means of the invention it is possible to use a similar gear ratio shifting device as described above on a intermediate axle to adjust torques and thereby in mentioned examples compensate different loads in the lift or storage device or give a fitness machine a heavier or lighter adjustment or give a stroke on a fitness machine a different ergonomical curve. When a cable is stranded or rope is woven wherein a periodically thickening is made and the shape of the groove on the Snek corresponds with this shape traction of the propulsion cable on the Snek is granted. In many cases it will not be necessary to wind the propulsion cable more than a half rotation around the Snek.

These periodically thickened cable or rope is technically not very hard to produce; you can weave a rope around a periodically thickened core or design an applicable weaving method.

In fact in this way the negative of a chain is born; a tooth rope or tooth cable. Next step is the negative toothed wheel; A Snek wherein in stead of one helicoidally shaped groove one or several cilindrical grooves are made. The periodically thickened rope can be made endless and at the wished length. The negative chain and negative tooth wheels can replace their their less clean relatives directly!

In claims 14 and 15 production methods for Snek and negative tooth wheels are described.

Claims

CLAIMS :

1. Variable transmission, particularly for human powered vehicles, by means of at least one Snek (fusee), which exists of a drum with on it a non cilindric, more or less conical, sloping upwards helicoidally shaped guiding path, a cable like means of propulsion which is rolled on and off said guiding path with the characteristic that the length of said guiding path is substantially larger then the maximal stroke of said back and forth going means of propulsion and the transmission further has to its disposal a shifting mechanism that can make the said means of propulsion roll on and off several parts of the guiding path on the Snek which results in a different gear ratio due to the non cilindric shape of the guiding path.

2. Transmission according to claim 1 with the characteristic that a back and forth going movement through the means of propulsion cable is transmitted into a rotating movement in such way that a Snek is mounted rotatably on an outgoing axis and propels said axis by means of a freewheel.

3. Transmission according to previous claims with the characteristic that the transmission is effected by several eventually coupled Snek transmissions by which a continue transmission is achieved.

4. Transmission according to claim 1 and 2 with the characteristic that two coupled back and forth going movements propel an outgoing axis through one Snek; the means of propulsion is decoupled at the end of the stroke of one movement; is pulled back by a spring or elastic cord in the beginning position of the second movement whereas it is coupled to this second movement to begin the next stroke and so forth.

5. Transmission according to conclusion 1 with the characteristic that a rotating movement is transmitted in a back and forth going movement through that every Snek is mounted rotatably on the incoming axis by means of a clutch mechanism which is activated and deactivated at the end and beginning of each stroke; the recovery of the stroke is activated by coupling to another Snek or any other means of recovery as for example a spring.

6. Transmission according to conclusion 1 with the characteristic that there is no incoming or outgoing rotating axis but that the transmission between two movements or balance between two forces is transmitted by means of a snek transmission with a gear ratio shift mechanism on an intermediate axle.

7. Transmission according to one of previous claims with the characteristic that the means of propulsion is a cable with a rigidly shaped cross section and the shape of the guiding path is adapted to the shape of the cable in such way that the cable when brought on tension by a tensioning device and turned around the Snek one or several times clamps itself in the guiding path.

8. Transmission according to one of the claims 1 to 6 with the characteristic that the guiding path on the Snek has a sharp, eventually teethed, v groove in such way that a rope cord or belt, when brought on tension by a tensioning device, clamps itself on the Snek and in this way works as means of propulsion.

9. Transmission according to one of the claims 1 to 6 with the characteristic that the guiding path on the Snek exists of a teethed path so that a chain or teethed belt can be used.

10. Transmission according to one of previous claims with the characteristic that the means of propulsion is fixed at one end of the Snek guiding path and that a means of recovery is installed which returns the Snek and said cable in fully rolled on position when the gear shifting device is ordering hereto.

11. Transmission according to one of the previous claims with the characteristic that shifting gear is effected by a shifting mechanism that moves the means of propulsion diagonaly and is eventually helped or enabled by a diagonal groove or other interruption in the side walls of the guiding path specially made into the Snek for this purpose.

12. Transmission according to one of previous claims with the characteristic that an apparently endless round going means of propulsion is used and that the gear shifting mechanism can alter and lock the means of propulsion at any desired position at a back and forth going object so that the distance of unrolling of the cable on the Snek determines the gear ratio.

13. Transmission according to one of the previous claims with the characteristic that the means of propulsion exists of a periodically thickened rope, cord, cable, line or belt and that the guiding path on the Snek has a corresponding shape.

14. Production method for a Snek according to conclusion 1 wherein a copying lathe with adjustable axial pitch and several shaped chisels are used with the characteristic that the shape of the chisels determine the shape of the guiding path, the radial movement of the guiding path is determined by the shape of the copying mould, the pitch of the guiding path is determined by the pitch of the lathe and a profiled wheel made out of material substantially harder than the Snek material can be run through the guiding path to bring the appropriate surface or periodically thickening in the guiding path.

15. Production method for a Snek according to conclusion 1 with the characteristic that the periodically thickened profile in the guiding path is made by means of a milling cutter and the distance between each miller cutting in the guiding path is determined by a guiding wheel running through the guiding path while Snek or negative toothed wheel can turn around their axis freely.