Field of Invention

[01] Non-tilting steering system for reverse trike.

Background of Invention

[02] It is obvious that reverse trikes are more safe and stable than bikes as well as

conventional trikes. Reverse trikes have many mechanical advantages over conventional trikes which include stability, traction in uphills and steerability. But providing an efficient steering mechanism for reverse trikes is a challenge. In recent past many models of reverse trikes have come up in the public domain offering tilting steering system. Tilting steering system has many issues which includes traction as well as ground clearance while cornering around a turn. Non-tilting steering system for reverse trikes have drawn little attention as it is understood by majority of folks that rack and pinion steering mechanism used in cars is sufficient for the purpose. But it has its own issues which includes big reduction ratio and too complex mechanism to handle on a trike. Newton trike provides non-tilting steering mechanism using kingpin assembly. It employs pitman arm to swing the kingpin attached to spindle mounted on each of the two front steer wheels.

Technical Problem

[03] Non-tilting steering mechanism in Newton reverse trike, applies the steering torque on the two wheels either from the front side of the head tube or rear side of the head tube due to which force gets exerted on the head tube rearward or forward direction respectively, thus making it difficult to operate as compared to steering system for a bicycle. In bicycles steering torque applied on the wheel is symmetric along the head tube.

[04] In Newton trike, head tube of the left and right front wheels are connected sideways to the central head tube, due to which the weight of the rider pulls the wheels downwards along the transverse direction, thereby impeding the forward motion. Summary of Invention

[05] One of our objectives is to provide steering system for reverse trike which is as

ergonomic to operate as that of a bicycle.

To achieve this objective steering system for reverse trike is designed such that two front wheels can be transversely rotated using coupled torque. Steering torque is applied on each of the front wheels symmetrically on both ends of the axle and symmetrically on front and rear side of the steerer rods, thereby providing easy and stable maneuverability to the steering system. Head tube is proportional to the length of steerer rod to provide sturdiness to steerer rod. Over steering, that is steering rotation beyond 90 degrees in clockwise as well as in anticlockwise direction is prevented by central rod in the central pivot crank.

[06] One of our objectives is to provide steering support mechanism which can promote forward motion and has special provision to leverage the advantages of using smaller front wheels. Larger rear wheel with smaller front wheels make the reverse trikes more stable on uneven roads and easier to steer while cornering around a turn while mileage is almost equal to that of reverse trikes with larger front wheels.

This objective is achieved by connecting the head tubes of left and right front wheels at their rear sides to the top tube via backward slanting upward extending tube. Also the top tube which connects the upper end of seat tube to the central head tube is bent to form a downward slope towards the front side.

Brief Description of Drawings

[07] [Fig. 1] Reverse trike with coupled torque steering system according to this invention.

[08] [Fig. 2] Reverse trike with steering system according to prior art.

[09] [Fig. 3] and [Fig 4] Front and back view respectively of coupled torque steering system according to this invention.

[10] [Fig. 5] Steering support mechanism, for Newton trike.

[11] [Fig. 6] Central steering system with steering support mechanism

[12] [Fig. 7] Central steering system with steer transmission arms [13] [Fig. 8] Central pivot crank

[14] [Fig. 9] Right and left front wheel steering system

[15] [Fig. 10] Steering support mechanism

[16] [Fig. 11] Right and left top tube arms

[17] [Fig. 12] Reverse trike with rotated front wheels due to steering action by steering system according to this invention.

[18] [Fig. 13] Schematic diagram illustrating the effect of weight of rider on the steering support mechanism according to this invention.

[19] [Fig. 14] Schematic diagram illustrating the effect of weight of rider on the steering support mechanism of Newton trike.

[20] [Fig. 15] Multi-point coupled torque steering system without top tube arms according to this invention.

[21] [Fig. 16] Front view of multi-point coupled torque steering system, without steering support mechanism, according to this invention.

Description of Embodiments

[22] As shown in [Fig. 1] and [Fig. 3], coupled torque steering system for reverse trike (1) with top tube (TT) and down tube (DT), according to this invention comprises central steering system (CSS), left wheel steering system (LSS), right wheel steering system (RSS), steering support mechanism (SSM).

Front wheel steering system

[23] As shown in [Fig. 3] and [Fig. 9], right wheel steering system (RSS) comprising a wheel (RW), steering fork (RSF), and crank rod (RCR) and left wheel steering system (LSS) comprising a wheel (LW), steering fork (LSF), and crank rod (LCR) are located on the right side and left side respectively on the front part of the reverse trike with each of them wherein

wheel is preferably of diameter less than or equal to that of rear wheel; steering fork is a suspension fork with steerer rod connected at its crown and fork blades at their ends holding the wheel at the ends of its axle;

crank rod is a horizontal straight rod of length preferably around 8-12 inch, perpendicular to the plane of said steering fork extending from rear side of steerer rod to front side steerer rod of the corresponding wheel is attached at its middle to the lower side of the said steerer rod just above the crown of the said steering fork.

[24] As shown in [Fig. 3] and [Fig. 7] central steering system (CSS) comprises central

steering shaft (CST), front steer transmission arm (FSA), back steer transmission arm (BSA), central pivot crank (CPC), handle (HN) and four ball bearing pivot hinges.

[25] As shown in [Fig. 3] and [Fig. 7] handle (HN) is preferably dutch style parallel

handlebars with its stem connected to the upper end of central steering shaft (CST), is located above the front end of the top tube (TT) of reverse trike at a height around the height of seat.

[26] As shown in [Fig. 8] central pivot crank (CPC) consists of

a pair of coaxially parallel horizontal circular plates, upper circular plate (CPC1) and lower circular plate (CPC2) each of diameter equal to the length of crank rod (RCR) and fixedly connected to each other at their centers via a central rod (CPC3) which is a vertical rod of length 6-8 inch, coaxial to the said circular plates, with its midpoint is midpoint of the line joining midpoints of the crank rods (RCR) and (LCR) of right and left front wheel steering system and

a pair of pivot crank rods which are vertical straight rods, one (CPC4) at the front and other (CPC5) at the rear side of said central rod (CPC3), journalled to the periphery of said circular plates via ball bearings so that midpoint of front pivot crank rod is midpoint of the line joining front ends of the crank rods (RCR) and (LCR) of right and left front wheel steering system and midpoint of rear pivot crank rod is midpoint of the line joining rear ends of the crank rods (RCR) and (LCR) of right and left front wheel steering system.

[27] As shown in [Fig. 3] and [Fig. 7] central steering shaft (CST) is a straight cylindrical tube backward slanting by an angle, preferably, of 5-20 degrees to the vertical with a height approximately equal to the height of the handle (HN) minus the height of the upper circular plate (CPC1) of central pivot crank (CPC) and is connected at its upper end to the stem of the handle (HN) and is connected at its lower end coaxially to center of the upper circular plate (CPC1) of the central pivot crank (CPC).

[29] As shown in [Fig. 3] and [Fig. 7] front steer transmission arm (FSA) and back steer

transmission arm (BSA) are parallel horizontal straight tubes, attached at their mid points to the mid points of front (CPC4) and rear pivot crank rods (CPC5), respectively, wherein front steer transmission arm (FSA) is hinged at its right and left ends on its lower side to the front ends of the upper side of the crank rods (RCR) and (LCR) of the right and left wheel steering system via ball bearing pivot hinges (FSA2) and (FSA3), respectively; back steer transmission arm (BSA) is hinged at its right and left ends on its lower side to the rear ends of the upper side of the crank rods (RCR) and (LCR) of the right and left wheel steering system, via ball bearing pivot hinges (BSA2) and (BSA3), respectively.

Steering support mechanism

[30] As shown in [Fig. 10] steering support mechanism (SSM) comprises top tube (TT),

central head tube (CHT), left head tube (LHT), right head tube (RHT), central top tube arm (CTTA), left top tube arm (LTTA) and right top tube arm (RTTA).

[31] As shown in [Fig. 6] and [Fig. 10] central head tube (CHT) is a cylindrical tube of length proportional to the central steering shaft, whose upper end is located at a point between the stem of the handle (HN) and front end of top tube (TT) and lower end is located at 1- 2 inches above the upper circular plate (CPC1) of central pivot crank (CPC), holds central steering shaft coaxially with the help of a pair of ball bearings at its upper and lower ends.

As shown in [Fig. 4] central head tube (CHT) is connected at its rear side at a point in the upper half to the front end of the top tube (TT), at a point in the middle region to the front end of central top tube arm (CTTA) and at a point on the lower half to the front end of down tube (DT).

As shown in [Fig. 4] top tube (TT) is a horizontal cylindrical tube which connects upper end of seat tube to the central head tube (CHT) and is bent at its rear half to form a downward slope towards the front side making an angle, preferably, of 5-10 degrees with the horizontal.

As shown in [Fig. 4] and [Fig. 10], left head tube (LHT) is a cylindrical tube which holds steerer rod of left wheel steering fork coaxially with the help of a pair of ball bearings at its upper and lower ends.

As shown in Fig. 4 and Fig. 10, right head tube (RHT) is a cylindrical tube which holds steerer rod of right wheel steering fork coaxially with the help of a pair of ball bearings at its upper and lower ends.

As shown in [Fig. 4] and [Fig. 10], central top tube arm (CTTA) is an L-shaped rod whose horizontal arm is connected at its front end to the rear side of central head tube (CHT) and upward extending arm is backward slanting by an angle, preferably, of 10-15 degrees with the vertical and is connected to top tube (TT) at a point on its front half.

[32] As shown in [Fig. 10] left top tube arm (LTTA) consists of three tubes as three sections namely front section, middle section and rear section, which are serially joined where in front section (LTTA1) is horizontal tube connected at front end to rear side to the left head tube;

middle section (LTTA2) is a tube extending upwards slanting backwards by angle 5- 10 degrees and is connected at its bottom to the rear side of the front section (LTTA1);

rear section (LTTA3) is a tube extending upwards slanting backwards and inclining towards the top tube such that it is connected at its bottom end to the upper end of the middle section (LTTA2) and upper end is connected to the top tube and it make an angle of 5-10 degrees in backward direction with respect to the plane containing middle section (LTTA2) and normal to the frame of the bicycle.

Right top tube arm (RTTA) comprises of three tubes (RTTA1), (RTTA2) and (RTTA3) serially joined and attached to the frame such that (RTTA) forms mirror reflection of the left top tube arm (LTTA) with respect to plane of the frame.

Steer operation

[33] On rotation in clockwise direction, handle causes central pivot crank (CPC) to rotate in clockwise direction, thereby causing the front steer transmission arm (FSA) to push the front half of the front right wheel (RW) towards right side, pull the rear half of the front right wheel (RW) towards left side, push the rear half of the front left wheel (LW) towards left side, pull the front half of the front left wheel (LW) towards right side. Over steering, that is steering rotation beyond 90 degrees in clockwise as well as in

anticlockwise direction is prevented by central rod in the central pivot crank.

Effect of rider’s weight [34] As shown in [Fig. 14], in the steer support mechanism according to prior art resultant force denoted by dashed arrow caused by weight of the rider denoted by vertical arrow and pulling force on the head tube denoted by horizontal arrow, pulls the front wheels downwards along the plane transverse to direction of motion thereby impeding the forward motion.

[35] As can be observed from [Fig. 11] and [Fig. 13], in the steer support mechanism

according to this invention, component of the weight of the rider in plane transverse to the direction of motion is minimal and large part is along the direction of motion denoted by double arrow in form of horizontal component W _H direction of which is denoted dashed arrow.

Multi-point steering system

[36] Coupled torque steering system described in paragraphs [22]-[35] may be modified to function as multi-point steering system. In this modification steering action applied on the steerer rod of left and right wheel at three points, upper, middle and lower point of steerer rods. As shown in [Fig. 15], [Fig. 16], multi-point steering system consists is a single point steering system described in paragraphs [22]-[35] with the modification that a) each of steer transmission arms, front steer transmission arm (FS A) and back steer transmission arm (BSA), are branched at both their ends to form trident rod on both sides; b) steerer rod (RSR) at right wheel is attached with three crank rods, one (RCR1) at the top, one (RCR2) at the middle and one (RCR3) at the bottom of the steerer rod; c) steerer rod (LSR) at left wheel is attached with three crank rods, one (LCR1) at the top, one (LCR2) at the middle and one (LCR3) at the bottom of the steerer rod; d) top middle and bottom branch on the right side of front steer transmission arm (FS A) at their right end are connected to front end of crank rods (RCR1), (RCR2) and (RCR3) respectively; e) top middle and bottom branch on the right side of back steer transmission arm (BSA) at their right end are connected to rear end of crank rods (RCR1), (RCR2) and (RCR3) respectively via ball bearing pivot hinges; f) top middle and bottom branch on the left side of front steer transmission arm (FSA) at their left end are connected to front end of crank rods (LCR1), (LCR2) and (LCR3) respectively via ball bearing pivot hinges; g) top middle and bottom branch on the left side of back steer transmission arm (BSA) at their left end are connected to rear end of crank rods (RCR1), (RCR2) and (RCR3) respectively via ball bearing pivot hinges; h) head tube (RHT) for the right wheel has two sections, one (RHT1) coaxially holding right wheel steerer rod (RSR), between top (RCR1) and middle (RCR2) crank rods, via ball bearings and (RHT2) coaxially holding right wheel steerer rod (RSR), between middle (RCR2) and bottom (RCR3) crank rods, via ball bearings with both sections of head tube connected to each other at their right and left sides via C-shaped rods; i) head tube (LHT) for the left wheel has two sections, one (LHT1) coaxially holding left wheel steerer rod (LSR), between top (LCR1) and middle (LCR2) crank rods, via ball bearings and (LHT2) coaxially holding left wheel steerer rod (LSR), between middle (LCR2) and bottom (LCR3) crank rods, via ball bearings with both sections of head tube connected to each other at their right and left sides via C- shaped rods; j) Horizontal rod of front steer transmission arm (FSA) and back steer transmission arm (BSA), on the right and left side of central pivot crank are coupled with each other using a straight rods (CPL1) and (CPL2), respectively, via ball bearing pivot hinges.