Rotary transmission system with elastic energy accumulation for torque stress reduction

Description

1 / 6 Rotary transmission system with elastic energy storage for torque reduction. INTRODUCTION

[001] The present invention relates to a rotary transmission system applicable, in particular, to rear hub assemblies with ratchet / freewheel for bicycles, incorporating an elastic energy storage subassembly based on a ribbon spring and winding pulley, so as to store energy under selected conditions and return torque under subsequent conditions, reducing peak user effort and / or smoothing torque delivery to the wheel. FIELD OF APPLICATION

[002] The invention is situated in the field of transmission mechanics, encompassing freewheel / ratchet systems and torque damping / regulation solutions by accumulating and releasing elastic energy in rotating assemblies, with preferential application in bicycle rear hubs, and alternative application in other light vehicles and rotating mechanisms with pulsating torque input. TECHNICAL PROBLEM

[003] In pedal-driven transmissions, the input torque is typically pulsating, with peaks during starts, accelerations, climbs, irregularities throughout the pedaling cycle, and sections of lower contribution such as dead spots, requiring peaks of force from the cyclist that increase fatigue and reduce comfort and efficiency. TECHNICAL SOLUTION

[004] The invention solves the problem by means of an assembly that integrates into the ratchet / freewheel system a force reduction subassembly containing a ribbon spring, preferably a flat spiral spring, coupled to a ribbon pulley, so that, during an actuation condition, part of the applied mechanical energy is converted into stored elastic energy, and in a subsequent condition the spring returns torque to the assembly, reducing force peaks and / or smoothing the transmission. STATE OF THE ART Petition 870260017644, dated 25 / 02 / 2026, page 5 / 19 2 / 6

[005] In the state of the art, transmission systems for bicycles are known, such as US patent 6,053,830 entitled “POWER-SPRING ASSIST TO PEDALS OF BICYCLE”, which describes a spring-assist system for bicycles, in which a spring is charged and then released under user control, for example, a throttle-type grip on the handlebars, using a chain and gear transmission assembly coupled to the bicycle frame.

[006] The prior art document above deals with a system external to the hub / ratchet, which requires multiple components, including cable, gears, housing and release mechanism, being aimed at on-demand assistance and not at compact integration into the hub for automatic / local smoothing of torque in the ratchet / freewheel assembly itself. Furthermore, the principle described favors a spring motor with dedicated control, which implies greater complexity and installed mass.

[007] US patent 2,151,324, entitled “IMPROVEMENTS IN OR RELATING TO FREE-WHEEL HUBS WITH COASTER BRAKES”, uses a helical spring to secure coupling / engaging components for the purpose of engaging / disengaging and operating the free-wheel / brake assembly.

[008] In the prior art document above, the spring is used as a functional element for actuating / returning the mechanism, not as an elastic energy accumulator for reducing user torque peaks; nor does it describe a subassembly with a ribbon spring coupled to a winding pulley intended to store energy in peaks and return it in subsequent phases to smooth the transmission. OBJECTIVES OF THE INVENTION

[009] The present invention aims to reduce peak user effort in rotary transmissions by pulsating torque input, store part of the applied torque in the form of elastic energy and return it in the subsequent phase, maintain the freewheel functionality of the assembly, provide a compact and integrated solution to the hub / ratchet with few changes to the assembly architecture, and provide engagement variants, such as unidirectional, as well as stroke limiters to prevent spring overwinding. SUMMARY OF THE INVENTION Petition 870260017644, dated 25 / 02 / 2026, page 6 / 19 3 / 6

[010] The invention provides a wheel hub ratchet assembly, especially for bicycle rear wheels, comprising a hub body, a ratchet body configured to cooperate with the chain, a freewheel mechanism, and a force reduction subassembly that includes a ribbon spring, characterized as a flat spiral spring, coupled to a ribbon pulley. In a drive condition, part of the mechanical energy applied to the ratchet body is converted into elastic energy stored in the spring, and in the subsequent condition the spring develops torque to the rotating assembly, reducing the peak effort of the user and smoothing the torque transmission. The force reduction subassembly further comprises a stroke limiter that prevents over-winding of the ribbon spring, ensuring the durability and safety of the assembly. DESCRIPTION OF THE FIGURES

[011] The invention will be better understood by means of the attached schematic drawings, in which: Figure 1: Cutaway view of the rotary transmission system with elastic energy storage for torque reduction; Figure 2: Perspective view of the rotary transmission system with elastic energy storage for torque reduction; Figure 3: Exploded perspective view of the rotary transmission system with elastic energy storage for torque reduction; Figure 4: Schematic view of the rotary transmission system with elastic energy accumulation for torque reduction, simulating forces. DETAILED DESCRIPTION OF THE INVENTION

[012] In one embodiment, the invention is implemented in a bicycle rear hub (1), designed to support the wheel and rotatably mounted relative to the axle by means of at least one bearing (2). The axial positioning of the components is ensured by spacers (3, 4) and retention / closure by a locking cap (5), which may include usual fastening and locking elements. The assembly comprises a rotating subassembly associated with the hub (1) and configured to cooperate with the bicycle chain. In one configuration, the cooperation is achieved by an internal gear (6) associated with a transmission cover (7); additionally, it may be provided Petition 870260017644, dated 25 / 02 / 2026, page 7 / 19 4 / 6 an external gear (11), for direct cooperation with the chain in conventional operation. The transmission cover (7) acts as a torque transmission element and as a functional support for the ribbon spring (9) described below. The system incorporates a freewheel mechanism, which operates with a ratchet, capable of: (i) transmitting torque in the drive direction from a drive body / ratchet, and (ii) allowing relative rotation in the opposite direction and / or in overspeed, when the wheel rotates faster than the drive, so that the bicycle can accelerate without dragging the pedals. This ratchet mechanism can be implemented, for example, by pawls and toothed ring, one-way roller clutch or technical equivalent, provided that it preserves the freewheel decoupling function.A cassette (10) comprising the ratchet assembly / body that receives one or more gears (6, 11) or the equivalent functional component that cooperates with the chain and the freewheel mechanism is fitted / coupled to the assembly by an appropriate mechanical interface, for example, splines, thread, locking ring or other equivalent means, being able to cooperate with the freewheel mechanism for torque transfer to the hub (1) in the drive direction. The assembly further comprises a sub-assembly for accumulating and returning elastic energy, which includes a ribbon spring (9) mounted coaxially to the rotating assembly. A first end (9A) of the ribbon spring (9) is fixed / anchored to the inner surface of the transmission cover (7), preferably in an internal geometry that acts as a pulley / winding reel.A second end (9B) of the ribbon spring (9) is coupled to a reaction element that remains stationary, or substantially stationary, relative to the axis, such as the bearing (2), so that the relative rotation between the drive housing (7) and the reaction element causes controlled winding / unwinding of the ribbon spring (9). In a drive condition, for example, starting, climbing, resuming, or any phase of the pedaling cycle with peak torque, the torque from the chain is applied to the drive assembly, for example, via the outer gear (11) and / or via the inner gear (6). This torque is then transmitted to the hub (1) by the freewheel mechanism, via the cassette (10), propelling the wheel. Simultaneously, by design effect, at least a fraction of this torque produces relative rotation involving the drive housing (7) and. Petition 870260017644, dated 25 / 02 / 2026, page 8 / 19 5 / 6 the reaction element, resulting in the elastic loading of the ribbon spring (9). In practice, part of the excess instantaneous torque is converted into elastic energy stored in the ribbon spring (9), reducing the peak effort perceived by the user. In a subsequent condition, for example, after overcoming the peak torque or in a complementary phase of the pedaling cycle in which the user's torque decreases, the ribbon spring (9) tends to unwind, returning torque to the transmission housing (7) and to the rotating assembly. In this phase, the internal gear (6) is driven by the transmission housing (7) under the action of the ribbon spring (9), so that the torque returned by it is effectively delivered to the freewheel assembly and the hub (1), promoting assisted wheel rotation and smoothing of torque delivery resulting in reduced jerking.The external gear (11), when present, can maintain the normal transmission function of the bicycle without the aid of the ribbon spring (9), that is, operating conventionally when torque is supplied directly by the chain. In this configuration, the design provides that the torque return by the ribbon spring (9) acts preferentially on the internal path: cover (7) / gear (6) / freewheel mechanism / hub (1), while the external gear (11) remains in typical freewheel / ratchet operation, including the possibility of overspeed, minimizing the tendency for unwanted torque return to the chain / pedals. In a constructive variant, the cassette (10) is a component mountable on the assembly by fitting / splines / locking ring, as in usual architectures.In another variant, the transmission cover (7) itself is shaped to perform a function equivalent to the cassette (10) / ratchet, incorporating an interface for the chain and / or functional engagement elements of the freewheel mechanism, so that, under this architecture, the cover (7) replaces the cassette (10) and begins to perform the function of the ratchet / cassette body, reducing the number of parts and / or allowing specific coupling conditions. Preferably, so that loading occurs only under selected conditions and to preserve freewheel behavior, the assembly may include at least one unidirectional coupling between rotating components, for example, between the cover (7) and the functional ratchet / cassette body (10) and / or a mechanical stroke limiter that prevents the... Petition 870260017644, dated 25 / 02 / 2026, page 9 / 19 6 / 6 over-winding of the ribbon spring (9). The assembly can also be sealed by a protector (12), reducing the entry of contaminants and assisting in lubrication retention.

[013] Figure 4 schematically illustrates the distribution of forces and the torque path in the system, highlighting the coexistence of a conventional transmission path and an elastic assistance path. In normal operation, the pedaling torque T_pedal is applied by the external transmission assembly, cooperating with the conventional external gear (11) mounted on the cassette (10) / ratchet assembly, which transmits torque to the freewheel mechanism, which in turn delivers torque to the hub (1) in the propulsion direction.During conditions of higher torque demand, a portion of the torque T_pedal is diverted to elastic loading (T_carga), promoting relative rotation between the transmission housing (7) and the bearing (2) acting as a reaction element, so that the ribbon spring (9) is wound, storing elastic energy, with the end (9A) of the spring (9) remaining attached to the housing (7) and the end (9B) remaining attached to the reaction element associated with the bearing (2). In a subsequent condition, when the pedaling torque decreases, the spring (9) unwinds and applies a return torque T_mola on the transmission housing (7), imposing rotation on the internal gear (6) and transferring torque to the freewheel mechanism and hub (1) in the propulsive direction, so that the internal gear (6) is driven by the energy previously stored in the ribbon spring (9), assisting the wheel rotation and reducing the valleys between peaks of user torque.As illustrated, the assist gear (6) and the cassette (10) / ratchet are arranged coaxially and juxtaposed on the transmission side, allowing the elastic assist path to act internally without interfering with the conventional function of the external gear (11), which remains able to operate in normal transmission mode without direct assistance from the ribbon spring (9), preserving the freewheel behavior. Petition 870260017644, dated 25 / 02 / 2026, page 10 / 19

Claims

1 / 2 CLAIMS 1) ROTARY TRANSMISSION SYSTEM WITH ELASTIC ENERGY ACCUMULATION FOR TORQUE EFFORT REDUCTION, applicable to a bicycle rear hub, characterized by comprising: a hub (1) rotatably mounted by means of at least one bearing (2); a drive assembly configured to cooperate with a chain, including a transmission cover (7) associated with a gear (6); a cassette (10) / ratchet body attachable to the assembly; a freewheel mechanism configured to transmit torque from the cassette (10) / ratchet body to the hub (1) in the drive direction and allow relative freewheel rotation;and a flat spiral ribbon spring (9), having a first end (9A) anchored to the transmission cover (7) and a second end (9B) anchored to a reaction element, so that, under peak torque conditions, elastic loading of the spring (9) occurs by relative rotation involving the cover (7) and, under elastic unloading conditions, the spring (9) returns torque to the cover (7) to drive the gear (6) and assist the rotation of the hub (1) via a freewheel mechanism, reducing peak user effort. 2) ROTARY TRANSMISSION SYSTEM WITH ELASTIC ENERGY ACCUMULATION FOR TORQUE EFFORT REDUCTION, according to claim 1, characterized in that the reaction element comprises the bearing (2) and / or component integral to the shaft, and in that the transmission cover (7) internally defines a pulley / spool geometry for controlled winding and unwinding of the ribbon spring (9). 3) ROTARY TRANSMISSION SYSTEM WITH ELASTIC ENERGY ACCUMULATION FOR TORQUE EFFORT REDUCTION, according to any of the preceding claims, characterized by comprising at least one unidirectional coupling and / or mechanical stroke limiter configured to (i) allow selective loading of the ribbon spring (9) under a predetermined drive condition and (ii) prevent over-winding of the ribbon spring (9). 4) ROTARY TRANSMISSION SYSTEM WITH ELASTIC ENERGY ACCUMULATION FOR TORQUE EFFORT REDUCTION, according to any of the preceding claims, characterized by further comprising an external gear (11) for cooperation with the chain in conventional operation, wherein the external gear (11) operates without direct assistance from the ribbon spring (9), while the torque return of the ribbon spring (9) acts on the internal path involving the transmission cover (7) and the gear (6) for partial assistance to the drive of the hub (1).

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