GB1561639A

GB1561639A - Safety belt retractor fitted with sound insulating bushes

Info

Publication number: GB1561639A
Application number: GB50298/76A
Authority: GB
Original assignee: Britax Ltd
Current assignee: Britax Ltd
Priority date: 1976-12-02
Filing date: 1976-12-02
Publication date: 1980-02-27

Description

(54) SAFETY BELT RETRACTOR FITTED WITH SOUND INSULATING BUSHES (71) We, BRITAX (WINGARD) LIMITED (formerly Wingard Limited), a British Com- pany of Chandler Road, Chichester, Sussex, PO19 2UG, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement : This invention relates to a safety belt retractor which is fitted with sound insulating bushes to prevent noise caused by movement of a shaft or spindle received in respective bearing holes in a supporting frame. Safety belt retractors in accordance with the invention are therefore advantageous in the manufacture of motor vehicles where there is a requirement for a very low sound level within the interior of the vehicle when driven.

More particularly, the present invention provides a safety belt retractor comprising a frame having a pair of oppositely located bearing holes, a shaft or spindle received in said bearing holes, and a sound insulating bush received in each of said bearing holes for supporting the shaft or spindle, each bush comprising an annular member with an inwardly facing surface having three or more inwardly directed portions and an outwardly facing surface with three or more outwardly directed portions, the inwardly and outwardly directed portions being substantially equidistantly spaced with respect to each other about the circumference of the annular member, the outwardly directed portions contacting parts of the frame defining the respective bearing hole and the inwardly directed portions contacting the shaft or spindle.

Preferably, the inwardly and outwardly directed portions of the bush are defined by arcuate regions centred on the true axis of the annular member and thereby forming respective cylindrical surfaces. These arcuate regions may be spaced by lobe-shaped-regions centred on respective points which are slightly offset from the true axis of the annular member. Alternatively, the inwardly or ourwardly directed portions or both such portions, may be defined by raised regions, such as arcuate shoulders, wedge shaped portions, or outwardly or inwardly directed lobes, or said portions may be formed by different combinations of such raised regions.

The annular member preferably includes an outwardly directed flange to improve its rigidity. This is particularly helpful where the bush is of small dimensions, for example, the wall thickness of the bush, (measured radially of the true axis) may be of the order of 30 thousandths of an inch. When a flange is present, cut out portions are preferably provided adjacent the inwardly directed portions so as to provide flexibility at that point.

The annular member may be gapped or split, like a piston ring, to take a circumferferential tolerance when fitted.

Preferably, each bush is made of material which exhibits a hysteresis effect when loaded.

For example, the bushes may be made of thermoplastic acetal resin material.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figs. 1 and 2 are plan and elevational views of a sound insulating bush according to a first embodiment, Figs. 3 and 4 are plan views of bushes according to second and third embodiments, and Figs. 5 and 6 are plan and elevational views of a bush according to a fourth embodiment.

As the general construction of a safety belt retractor is well known, there is no illustration of the same including a frame with oppositely facing bearing holes in which a shaft or spindle is rotatably supported. The shaft or spindle may provide a direct anchorage for a safety belt which is wound on the shaft or spindle, or a reel may be fixed to the shaft or spindle to provide the anchorage and to facilitate belt storage. Therefore, the following description deals mainly with the con struction of sound insulating bushes according to different embodiments of the invention.

Referring to Figs. 1 and 2, a sound insulating bush is in the form of an annular member 1 which is integral with a flange 2.

Member 1 has three inwardly directed portions in the form of either arcuate regions (shown by the broken line 3) which appear to be continuous with the inner surface of member 1, or raised regions 31 which extend towards the true axis 4 of member 1. Regions 3 or 31 are centred at the true axis 4 of member 1.

The respective sections 5, 6, 7 of the inner surface of member 1, which extend between the adjacent regions 3 or 31, are centred on respective off-axis points 8, 9, 10 adjacent the true axis 4. The radius between any one of these off-axis points (e.g. 10) and the corresponding arcuate section (6) is such that a very shallow arcuate recess is provided between adjacent regions 3 or 31. To illustrate this further, which is difficult in view of the small differences between the arcs, one part of the arcuate section 7 is compared with the true cylindrical surface 11 (shown in a broken line) centred on the true axis 4.

It will be appreciated, that the arcuate regions 3 form inwardly directed portions although they appear to be contiguous with the adjacent arcuate sections 5, 6, 7. The raised portions 31 are a modification whereby a greater clearance is provided between a real shaft and the most outwardly directed parts of the arcuate sections 5, 6, 7.

The outer surface of member 1 is similarly formed with arcuate regions 12 centred on the true axis 4 and lobe-shaped regions 13, 14, 15 centred on the respective off-axis points 8, 9, 10. The regions 12 thereby constitute outwardly directed portions which bear against the inner surface of a bearing hole in a frame for supporting one end of a shaft or spindle on which the reel is mounted.

The flange 2 is integral with the annular member 1 and has semicircular cut out portions 16. The flange 2 improves the rigidity of the annular member around substantial portions of its circumference, but the cut out portions 16 relieve this rigidity adjacent the inwardly directed regions 3 or 31.

Assuming that the bush is mounted on a shaft and is located in a bearing hole in a frame, the inwardly directed regions 3, 31 abut the shaft and the outwardly directed regions 12 abut the bearing surface of the hole in the frame. This 3-point suspension centralises the shaft in the bush and the bush in the hole and provides a running clearance over a substantial extent of the respective circumference.

This provides sound insulation without danger of binding between the shaft and the bush. The radial flexibility of the bush is optimised by locating the outwardly directed regions 12 midway between the inwardly directed regions 3 or 31.

The bush may be made of Delrin (Registered Trade Mark).

Fig. 3 is a sketch of a bush without a flange 2 in which the dimensions of the lobeshaped portions 5-7 and 13-15 have been exaggerated to clarify the construction of the bush described above. The drawing shows the "shaft diameter", and "housing diameter" as well as the "shaft clearance" and "housing clearance". The shaft is that which supports a safety belt reel for rotation in a housing or frame. The housing includes bearing holes or bearings for supporting the shaft. This sketch facilitates an appreciation of the radial flexibility of the bush, particularly in the bearing regions or pads 3 and 12.

Fig. 4 is a sketch of a bush of a simplified construction in which similar reference numerals identify similar parts. In this construction, the pads or bearing regions 3 and 12 are formed solely by raised shoulders which extend respectively inwardly and outwardly of the bush. Each of these regions has a cylindrical bearing surface which is centred on the true axis 4. The recesses between each of the regions also defines a cylindrical surface centred on 4. This form of construction may have a flange with cut out portions similar to those identified by reference numerals 2 and 16 in Fig. 1. It is useful where the radial wall is of an adequate thickness.

Figs. 5 and 6 are plan and elevational views of a bush which is similar to that shown in Figs. 1 and 2 with the exceptions that the inner bearing pads or regions 3 are not formed as raised shoulders and that the lobe-shaped recesses (between pads 3 and pads 12 respectively) are of a more pronounced curvature.

In the latter respect the lobe-shaped regions are centred on respective off-axis points 8, 81; 9, 91, and 10, 101 as shown in the drawing. The more radial of said points 81, 91 and 101 are used to strike the arcs between the outwardly projecting portions 12.

The bush is preferably made of a material which exibits a hysteresis effect when loaded, such as thermoplastic acetal material. This assists in providing a damping effect under dynamic conditions.

WHAT WE CLAIM IS: 1. A safety belt retractor comprising a frame having a pair of oppositely located bearing holes, a shaft or spindle received in said bearing holes, and a sound insulating bush received in each of said bearing holes for supporting the shaft or spindle, each bush comprising an annular member with an inwardly facing surface having three or more inwardly directed portions and an outwardly facing surface with three or more outwardly directed portions, the inwardly and outwardly -directed portions being substantially equidistantly spaced with respect to each about the circumference of the annular member, the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. struction of sound insulating bushes according to different embodiments of the invention. Referring to Figs. 1 and 2, a sound insulating bush is in the form of an annular member 1 which is integral with a flange 2. Member 1 has three inwardly directed portions in the form of either arcuate regions (shown by the broken line 3) which appear to be continuous with the inner surface of member 1, or raised regions 31 which extend towards the true axis 4 of member 1. Regions 3 or 31 are centred at the true axis 4 of member 1. The respective sections 5, 6, 7 of the inner surface of member 1, which extend between the adjacent regions 3 or 31, are centred on respective off-axis points 8, 9, 10 adjacent the true axis 4. The radius between any one of these off-axis points (e.g. 10) and the corresponding arcuate section (6) is such that a very shallow arcuate recess is provided between adjacent regions 3 or 31. To illustrate this further, which is difficult in view of the small differences between the arcs, one part of the arcuate section 7 is compared with the true cylindrical surface 11 (shown in a broken line) centred on the true axis 4. It will be appreciated, that the arcuate regions 3 form inwardly directed portions although they appear to be contiguous with the adjacent arcuate sections 5, 6, 7. The raised portions 31 are a modification whereby a greater clearance is provided between a real shaft and the most outwardly directed parts of the arcuate sections 5, 6, 7. The outer surface of member 1 is similarly formed with arcuate regions 12 centred on the true axis 4 and lobe-shaped regions 13, 14, 15 centred on the respective off-axis points 8, 9, 10. The regions 12 thereby constitute outwardly directed portions which bear against the inner surface of a bearing hole in a frame for supporting one end of a shaft or spindle on which the reel is mounted. The flange 2 is integral with the annular member 1 and has semicircular cut out portions 16. The flange 2 improves the rigidity of the annular member around substantial portions of its circumference, but the cut out portions 16 relieve this rigidity adjacent the inwardly directed regions 3 or 31. Assuming that the bush is mounted on a shaft and is located in a bearing hole in a frame, the inwardly directed regions 3, 31 abut the shaft and the outwardly directed regions 12 abut the bearing surface of the hole in the frame. This 3-point suspension centralises the shaft in the bush and the bush in the hole and provides a running clearance over a substantial extent of the respective circumference. This provides sound insulation without danger of binding between the shaft and the bush. The radial flexibility of the bush is optimised by locating the outwardly directed regions 12 midway between the inwardly directed regions 3 or 31. The bush may be made of Delrin (Registered Trade Mark). Fig. 3 is a sketch of a bush without a flange 2 in which the dimensions of the lobeshaped portions 5-7 and 13-15 have been exaggerated to clarify the construction of the bush described above. The drawing shows the "shaft diameter", and "housing diameter" as well as the "shaft clearance" and "housing clearance". The shaft is that which supports a safety belt reel for rotation in a housing or frame. The housing includes bearing holes or bearings for supporting the shaft. This sketch facilitates an appreciation of the radial flexibility of the bush, particularly in the bearing regions or pads 3 and 12. Fig. 4 is a sketch of a bush of a simplified construction in which similar reference numerals identify similar parts. In this construction, the pads or bearing regions 3 and 12 are formed solely by raised shoulders which extend respectively inwardly and outwardly of the bush. Each of these regions has a cylindrical bearing surface which is centred on the true axis 4. The recesses between each of the regions also defines a cylindrical surface centred on 4. This form of construction may have a flange with cut out portions similar to those identified by reference numerals 2 and 16 in Fig. 1. It is useful where the radial wall is of an adequate thickness. Figs. 5 and 6 are plan and elevational views of a bush which is similar to that shown in Figs. 1 and 2 with the exceptions that the inner bearing pads or regions 3 are not formed as raised shoulders and that the lobe-shaped recesses (between pads 3 and pads 12 respectively) are of a more pronounced curvature. In the latter respect the lobe-shaped regions are centred on respective off-axis points 8, 81; 9, 91, and 10, 101 as shown in the drawing. The more radial of said points 81, 91 and 101 are used to strike the arcs between the outwardly projecting portions 12. The bush is preferably made of a material which exibits a hysteresis effect when loaded, such as thermoplastic acetal material. This assists in providing a damping effect under dynamic conditions. WHAT WE CLAIM IS:

1. A safety belt retractor comprising a frame having a pair of oppositely located bearing holes, a shaft or spindle received in said bearing holes, and a sound insulating bush received in each of said bearing holes for supporting the shaft or spindle, each bush comprising an annular member with an inwardly facing surface having three or more inwardly directed portions and an outwardly facing surface with three or more outwardly directed portions, the inwardly and outwardly -directed portions being substantially equidistantly spaced with respect to each about the circumference of the annular member, the

outwardly directed portions contacting parts of the frame defining the respective bearing hole and the inwardly directed portions contacting the shaft or spindle.

2. A retractor according to claim 1 wherein said inwardly and outwardly directed portions are defined by arcuate regions centred on the true axis of the annular member, thereby forming respective cylindrical surfaces.

3. A retractor according to claim 2 wherein said arcuate regions are spaced by lobe-shaped regions centred on respective points which are offset from the true axis of the annular member.

4. A retractor according to claim 1 wherein the inwardly, or outwardly directed portions, or both of said portions, are defined by raised regions.

5. A retractor according to claim 4 wherein said raised regions are arcuate shoulders.

6. A retractor according to claim 4 wherein said raised regions are wedge shaped.

7. A retractor according to claim 4 wherein said raised regions are in the form of outwardly or inwardly directed lobes.

8. A retractor according to any one of the preceding claims wherein the annular member includes an outwardly directed flange.

9. A retractor according to claim 8 wherein cut-out portions are provided in said flange adjacent the inwardly directed portions so as to provide flexibility at that point.

10. A retractor according to any one of the preceding claims wherein the annular member is gapped or split.

11. A retractor according to any one of the preceding claims wherein the bush is made of material which exhibits a hysteresis effect when loaded.

12. A retractor according to claim 11 wherein the bush is made from thermoplastic acetal resin material.

13. A safety belt retractor comprising a frame having a pair of oppositely located bearing holes, a shaft or spindle received in bearing holes, and a sound insulating bush received in each of said bearing holes for supporting the shaft or spindle, each bush being substantially as herein described with reference to Figs. 1 and 2, or Fig. 3, or to Fig.

4, or to Figs. 5 and 6 of the accompanying drawings.