Patent Description:
Document <CIT> discloses a winder comprising a torsion bar (<NUM>), a spindle (<NUM>-<NUM>) coaxially mounted around the torsion bar (<NUM>), and two end covers (<NUM>-2a, <NUM>-2b) provided respectively on two ends of the combination of the torsion bar (<NUM>) and the spindle (<NUM>-<NUM>), wherein the spindle (<NUM>-<NUM>) engages with a middle portion of the torsion bar (<NUM>) through a teethed structure.

In a seat belt system of a vehicle, a webbing fastened on a vehicle occupant is connected to a conventional retractor for ensuring safety of the occupant. In emergency, the webbing connected to the spool assembly of the conventional retractor can be locked and is in a tensioned state for fastening a body of the vehicle occupant.

In the conventional retractor, the spool assembly is connected to the webbing and is locked by a brake assembly. With reference to <FIG>, the spool assembly has a shaft <NUM>, a spool member <NUM> coaxially mounted around the shaft <NUM>, and two ratchets <NUM> fixed on two axial ends of a combination of the shaft <NUM> and the spool member <NUM>. The webbing is connected to the spool member <NUM>. The two ratchets <NUM> can be locked or unlocked by the brake assembly. The conventional retractor is used in the seat belt system of the vehicle that provides safety protection for the vehicle occupant. The strength of the spool assembly of the conventional retractor can sustain the loading that the webbing applies to the spool member <NUM>.

When the conventional spool assembly is used as a tie-down of a heavy wheelchair in a vehicle, under a high load, especially in case of a collision of the vehicle, the strength of the conventional spool assembly is inadequate, and is prone to failure. The webbing connected to the spool member <NUM> of the spool assembly is loaded and is in under tension. The loading exerted by the webbing on the spool member <NUM> includes radial loading, linear loading, torque, and bending. <FIG> show that the radial loading is exerted on the spool member <NUM> of the spool assembly at different positions. Radial force is borne by the spool member <NUM> and spool tabs <NUM> of the spool member <NUM>, wherein end portions of each one of the spool tabs <NUM> are connected to the two ratchets <NUM>. <FIG> show that the linear loading is exerted on the spool member <NUM> of the spool assembly at different positions. Linear force is borne by a combination of the shaft <NUM> and the spool tabs <NUM> of the spool member <NUM>. As shown in <FIG>, when the torque is exerted on the spool member <NUM> of the spool assembly, torque loading is borne by the spool tabs <NUM> of the spool member <NUM>. <FIG> shows a state in which the spool member <NUM> of the spool assembly bears the loading exerted by bending.

As mentioned above, the stress on the spool tabs <NUM> connected to the spool to the ratchets <NUM> resulting from the radial force exerted on the spool assembly is not the same as the stress on the spool tabs <NUM> resulting from the linear force. With reference to <FIG>, shear stress generated by the radial force on the spool member <NUM> is almost evenly distributed along a periphery of the spool member <NUM>. One exception is that the spool member <NUM> is mostly a tube having a slot. The area with greater stress is located at two ends of the spool member <NUM> facing an axial slot <NUM>.

Shear stress generated by the linear force on the spool member <NUM> is substantially evenly distributed on the opposite side of a pulling direction of a pulling force applied by the webbing <NUM> to the spool member <NUM>. With reference to <FIG>, when the pulling direction is upward, the shear stress is located on a lower half of the spool member <NUM> and is changeable with a relative distance between the axial slot <NUM> of the spool member <NUM> and the webbing <NUM>. With reference to <FIG>, the lower half of the spool member <NUM> is borne by two of the spool tabs <NUM>, and the stress borne by each of the two spool tabs <NUM> is greater. With reference to <FIG>, the lower half of the spool member <NUM> is borne by three of the spool tabs <NUM>, and the stress borne by each of the three spool tabs <NUM> is less.

As known from the above analysis of the stress borne by the spool assembly under a tensioned state of the webbing <NUM>, a fixing connecting structure between each one of the spool tabs <NUM> and a body of each one of the two ratchets <NUM> is crucial regarding whether the mechanical strength of the reinforced spool assembly can sustain the loadings.

In the conventional spool assembly, the spool tabs <NUM> at two axial ends of the spool member <NUM> are riveted and fixed to the bodies of the two ratchets <NUM>. A body of the spool member <NUM> and a connecting portion between the adjacent spool tabs <NUM> at the two axial ends of the combination of the shaft <NUM> and the spool member <NUM> cannot be supported substantively. Even though the spool tabs <NUM> riveted on the ratchets <NUM> are further welded with outer surfaces of the bodies of the ratchets <NUM>, the ratchets <NUM> support the spool tabs <NUM> merely in radial positions of supporting portions, which are located between the shaft <NUM> and the spool tabs <NUM> of the spool member <NUM>, of the bodies of the ratchets <NUM>. With reference to <FIG>, a shear line L1, which acts on the spool tabs <NUM> of the spool member <NUM> and is located at an inner surface of one of the ratchets and the supporting portions, is perpendicular to a central axis of the shaft <NUM>. A cross-sectional area of the loading is too small. When the conventional spool assembly is used as a tie-down of a heavy wheelchair, during an accident, the heavy wheelchair is trusted forward and the webbing <NUM> is tensioned to generate the loading on the spool member <NUM> of the spool assembly. This could easily cause that unit-area stresses in fixing portions between the ratchets <NUM> and the spool member <NUM> are too large. The mechanical strength of the conventional spool assembly may be insufficient to withstand the high loading generated by the heavy wheelchair, such that the spool assembly of the tie down mechanism is prone to deformation or breakage. In order to prevent such a failure, it is necessary to improve a structure of the conventional spool assembly. The objective of the invention is to provide a reinforced spool assembly that can solve the problem that the mechanical strength of the conventional spool assembly of wheelchair tie down cannot sufficiently withstand the high loading created by a heavy wheelchair during an accident. The reinforced spool assembly has a shaft, a spool member, and two ratchets. The spool member is coaxially mounted around the shaft. A spacing is formed between an inner wall of the spool member and an outer wall of the shaft. Each one of the two ratchets has a body mounted on and around the outer surface of the spool member and having an inner surface and multiple teeth formed around a periphery of the body. The two inner surfaces of the two bodies face each other.

Two axial ends of the shaft (<NUM>) protrude through the bodies of the two ratchets respectively. In each one of the two ratchets, the body has a reinforced supporting structure. The reinforced supporting structure is located between the outer wall of the shaft and the inner wall of the spool member. The reinforced supporting structure is offset from the inner surface of the body. An imaginary extension plane of the inner surface of the body is perpendicular to a central axis of the shaft and passes through the reinforced supporting structure.

The reinforced spool assembly can be adapted to a retractor of a seat belt system or a tie down of a heavy wheelchair and has the following advantages:.

With reference to <FIG> and <FIG>, a first embodiment and a second embodiment of a reinforced spool assembly <NUM> in accordance with the present invention comprises a shaft <NUM>, a spool member <NUM>, and two ratchets <NUM>.

With reference to <FIG> and <FIG>, the shaft <NUM> is a circular rod with a predetermined length. The shaft <NUM> has a central axis <NUM> extending along an axial direction of the shaft <NUM>. With reference to <FIG> and <FIG>, the spool member <NUM> is a circular tube with a predetermined length. The spool member <NUM> is coaxially mounted around the shaft <NUM>. An inner diameter of the spool member <NUM> is larger than an outer diameter of the shaft <NUM>. A spacing is formed between an inner wall of the spool member <NUM> and an outer wall of the shaft <NUM>. The spacing is set according to product requirements for the reinforced spool assembly <NUM>. The spool member <NUM> has multiple spool tabs <NUM> respectively formed on two axial ends of the spool member <NUM> and located around the shaft <NUM> at spaced intervals.

With reference to <FIG> and <FIG>, the spool member <NUM> is a circular tube, which is formed by bending a metal plate, having a slot. The slot of the circular tube extends axially. A distance between two adjacent spool tabs <NUM> adjacent the slot is relatively wider, and a distance between the other two adjacent spool tabs <NUM> is relatively narrower. With reference to <FIG>, a rough, non-slip surface <NUM> is formed on an outer surface of the spool member <NUM> for ensuring connection stability between the spool member <NUM> and a webbing <NUM>. The webbing <NUM> can remain flat and evenly apply a loading to the spool member <NUM>.

With reference to <FIG> and <FIG>, the two ratchets <NUM> are respectively and fixedly mounted on two axial ends of a combination of the shaft <NUM> and the spool member <NUM> with the two axial ends of the shaft (<NUM>) protruding through the bodies (<NUM>) of the two ratchets (<NUM>) respectively. Each one of the two ratchets <NUM> has a body <NUM> having an inner surface 31a mounted on and around an outer surface of the spool member <NUM> and multiple teeth <NUM> formed around a periphery of the body <NUM>. The body <NUM> has an inner surface 31a and an outer surface 31b opposite to the inner surface 31a. The inner surface 31a is perpendicular to a central axis <NUM> of the shaft <NUM>. In the two ratchets <NUM>, the two inner surfaces 31a of the two bodies <NUM> face each other. In each one of the two ratchets <NUM>, an imaginary extension plane <NUM> is perpendicular to the central axis <NUM> of the shaft <NUM>. The body <NUM> has a reinforced supporting structure 33A, 33B. The reinforced supporting structure 33A, 33B is located between the outer wall of the shaft <NUM> and the inner wall of the spool member <NUM>. The reinforced supporting structure 33A, 33B is offset from the inner surface 31a of the body <NUM>. The imaginary extension plane <NUM> passes through the reinforced supporting structure 33A, 33B.

With reference to <FIG> and <FIG>, in each one of the two ratchets <NUM>, the reinforced supporting structure 33A, 33B is offset from the inner surface 31a of the body <NUM>. The imaginary extension plane <NUM>, which extends along the inner surface 31a of the body <NUM> and is perpendicular to the central axis <NUM> of the shaft <NUM>, passes through the reinforced supporting structure 33A, 33B. Shear line L, which acts on the spool tabs <NUM> of the spool member <NUM>, is located at the inner surface 31a of the body <NUM>, and extends to an inner surface of the reinforced supporting structure 33A, 33B, is offset and inclined for increasing a cross-sectional area. Load acting on the spool tabs <NUM> is effectively distributed on the larger cross-section area. Stress per unit area in a conjunction between each one of the ratchets <NUM> and the spool member <NUM> is reduced. Mechanical strength of the reinforced spool assembly is increased in bearing higher loadings. Based on the above-mentioned conception, the reinforced supporting 33A, 33B of the reinforced spool assembly <NUM> can be utilized in many feasible embodiments. For ease and conciseness in description, technical features of the reinforced spool assembly <NUM> are elaborated in conjunction with the drawings of the preferred embodiments, but not limited thereto.

With reference to <FIG> and <FIG>, in each one of the two ratchets <NUM>, the body <NUM> has a center hole <NUM> located at a center of the body <NUM>, a supporting area <NUM> located around the center hole <NUM>, and multiple fixing holes <NUM> disposed around the supporting area <NUM>. An edge of each one of the fixing holes <NUM> is adjacent to an outer periphery of the supporting area <NUM>. Two axial ends of the shaft <NUM> are respectively and fixedly inserted into the two center holes <NUM> of the two ratchets <NUM>. The spool tabs <NUM> respectively located on the two axial ends of the spool member <NUM> are respectively and fixedly inserted into the fixing holes <NUM> of the two ratchets <NUM>.

With reference to <FIG>, in each one of the two bodies of the two ratchets <NUM>, the reinforced supporting structure <NUM> A has a supporting ring <NUM> mounted around the shaft <NUM> and located in the supporting area <NUM>, which is between the shaft <NUM> and the spool tabs <NUM> of the spool member <NUM>. The supporting ring <NUM> is offset from the inner surface 31a of the body <NUM>. The center hole <NUM> is located on the supporting ring <NUM> and is offset from a side, which faces a middle of the shaft <NUM>, of one of the fixing holes <NUM>. The supporting ring <NUM> abuts against the shaft <NUM> and the spool tabs <NUM> of the spool member <NUM>.

With reference to <FIG>, in each one of the two ratchets <NUM>, the reinforced supporting structure 33B has multiple supporting blocks <NUM> surrounding the supporting area <NUM>. Each one of the supporting blocks <NUM> has a block surface. The block surface is a side surface of the supporting block <NUM> and faces the middle of the shaft <NUM>. The supporting blocks <NUM> and the spool tabs <NUM> are equal in amount, and the supporting blocks <NUM> respectively correspond to the spool tabs <NUM> in position. Each one of the supporting blocks <NUM> is offset from the inner surface 31a of the body <NUM>, is located in the supporting area <NUM>, and is located between the shaft <NUM> and the corresponding spool tab <NUM>. Preferably, each one of the supporting blocks <NUM> abuts against the shaft <NUM> and the corresponding spool tab <NUM> of the spool member <NUM>.

The amounts of the supporting blocks <NUM> and the spool tabs <NUM> can also be different in other embodiments, and the supporting blocks <NUM> can be not positioned corresponding to the spool tabs <NUM>. Increasing the amount the supporting blocks <NUM> can enhance the support.

As mentioned above, the mechanical strength of the reinforced spool assembly <NUM> is obviously enhanced. The reinforced spool assembly <NUM> is not only applicable to a retractor of a seat belt system in a vehicle for protecting an occupant. With reference to <FIG> and <FIG>, the ratchets <NUM> of the reinforced spool assembly <NUM> are locked by a brake assembly of the retractor. The webbing <NUM> fastened on the wheelchair is in a tensioned state. The spool member <NUM> connected to the webbing <NUM> has the reinforced supporting structures 33A, 33B disposed on the two bodies <NUM> of the two ratchets <NUM> for effectively distributing the loading exerted on the spool tabs 21on the larger cross-section area. Stress per unit area between the ratchets <NUM> and the spool member <NUM> is reduced. The mechanical strength of the reinforced spool assembly <NUM> is increased in bearing higher loadings, sufficiently satisfying safety requirements for the retractor of the seat belt system.

In addition, the reinforced spool assembly <NUM> is also used in a tie-down <NUM> fixing a heavy wheelchair <NUM> carried by vehicles, such as rehabilitation buses and public transportation vehicles allowed to carry wheelchairs. The tie-down <NUM> having the reinforced spool assembly <NUM> is mounted on a floor of the vehicle by a fixed fixing mechanism or a fixing mechanism <NUM>. The webbing <NUM> connected to the reinforced spool assembly <NUM> is pulled out of a shell of the tie-down <NUM>. A clasp mounted on a distal end of the webbing <NUM> is hooked to a frame of the heavy wheelchair <NUM>. Four tie-downs <NUM> are disposed at two sides of a front end and a rear end of the heavy wheelchair <NUM> for fixing the heavy wheelchair <NUM> on the floor of the vehicle. During transportation, the four tie-downs <NUM> disposed around the heavy wheelchair <NUM> provide a balanced and stable traction force to ensure that the heavy wheelchair <NUM> remains fixed to the floor of the vehicle.

Claim 1:
A reinforced spool assembly (<NUM>), and characterized in that the reinforced spool assembly (<NUM>) comprises:
a shaft (<NUM>);
a spool member (<NUM>) coaxially mounted around the shaft (<NUM>), wherein a spacing is formed between an inner wall of the spool member (<NUM>) and an outer wall of the shaft (<NUM>);
two ratchets (<NUM>), each one of the two ratchets (<NUM>) having
a body (<NUM>) mounted on and around an outer surface of the spool member (<NUM>) and having an inner surface (31a); and
multiple teeth (<NUM>) formed around a periphery of the body (<NUM>);
wherein the two inner surfaces (31a) of the two bodies (<NUM>) face each other, and two axial ends of the shaft (<NUM>) protrude through the bodies (<NUM>) of the two ratchets (<NUM>) respectively; and
wherein the body (<NUM>) has a reinforced supporting structure (33A, 33B), the reinforced supporting structure (33A, 33B) is located between the outer wall of the shaft (<NUM>) and the inner wall of the spool member (<NUM>), the reinforced supporting structure (33A, 33B) is offset from the inner surface (31a) of the body (<NUM>), an imaginary extension plane (<NUM>) of the inner surface (31a) of the body (<NUM>) is perpendicular to a central axis (<NUM>) of the shaft (<NUM>) and passes through the reinforced supporting structure (33A, 33B).