GB2320746A

GB2320746A - A brake unit with a coiled spring in frictional contact with a housing

Info

Publication number: GB2320746A
Application number: GB9625206A
Authority: GB
Inventors: Guy Timothy Pearson
Original assignee: Adwest Johnson Controls Ltd
Current assignee: AJC Johnson Controls Ltd
Priority date: 1996-12-04
Filing date: 1996-12-04
Publication date: 1998-07-01
Anticipated expiration: 2016-12-04
Also published as: GB9625206D0; GB2320746B

Abstract

A brake unit, e.g.for a seat reclining mechanism, permits rotation of an output shaft 46 by an input shaft (not shown) but prevents rotation of the input shaft by the output shaft and includes a coiled spring 26 normally in frictional contact with a fixed cylindrical housing 12, a rotary drive member 16 connected to the input shaft, and a rotary driven member 40 connected to the output shaft 46. Biasing means 50 urges the drive and driven members in opposite rotary directions so that in the absence of torque applied to the drive shaft the drive and driven members abut against end portion 29 of the coiled spring. Clockwise rotation of the drive member 16 causes, firstly, surface 21 on the member to engage end portion 28 of the coiled spring and reduce the frictional contact, secondly, engagement between portion 28 and surface 53 on the driven member 40, and, thirdly, rotation of the output shaft.

Description

A BRAKE UNIT The present invention relates to a brake unit, in particular but not exclusively, a shaft brake unit for a seat reclining mechanism.

In a seat reclining mechanism which incorporates a rotatable shaft for effecting angular adjustment between the seat cushion and seat back, it is common to provide a shaft brake to retain the adjusted angular position, ie restrain relative angular movement between the seat cushion and seat back caused by reverse loadings applied on the seat back.

Accordingly when adjusting a seat reclining mechanism incorporating such a brake, the brake first has to be disengaged before adjustment can take place. Thus an operative may initially feel a light resistance when first rotating the shaft to cause disengagement of the brake and then a heavier resistance as actual adjustment takes place. This difference in feel is highly undesirable.

A general aim of the present invention is to provide a brake unit for a seat reclining mechanism which provides a consistent feel during disengagement of the brake and actual adjustment of the seat reclining mechanism.

According to one aspect of the present invention there is provided a brake unit for transmitting rotary movement from an input shaft to an output shaft but preventing rotary movement from the output shaft to the input shaft the unit including a cylindrical housing containing a coiled spring defining a generally outer cylindrical surface for frictional contact with the cylindrical housing, the coiled spring having at opposite ends, radially inwardly directed abutment portions, a rotary drive member having opposed abutment faces located out-board of said abutment portions for abutment with outer faces of said abutment portions, the drive member being drivingly connected to the input shaft, and a rotary driven member having opposed abutment faces located in-board of said abutment portions for abutment with inner faces of said abutment portions, the driven member being drivingly connected to the output shaft, the circumferential spacing between the outer faces of said abutment portions being less than the circumferential spacing between said opposed abutment faces of the drive member, the circumferential spring between the inner faces of said abutment portions being greater than the circumferential spacing between the opposed abutment faces of the drive member, and biasing means operatively connected between the drive and driven member to urge the drive and driven member in opposite rotary directions such that in the absence of torque applied to the drive shaft the drive and driven member reside at a biased position whereat the drive and driven member abut on opposite sides against the same abutment portion of the coiled spring.

Various aspects of the present invention are hereinafter described, with reference to the accompanying drawings, in which: Figure 1 is an end of a brake unit according to one embodiment of the present invention; Figure 2 is a perspective view, partly broken away, of the brake unit shown in Figure 1.

The brake unit 10 includes a cylindrical stationary housing 12 which in use is fixed to a frame 14. When used with a seat reclining mechanism, the frame 14 preferably forms part of the seat cushion frame.

Rotatably received within the housing 12 is a part annular drive member 16. The drive member 16 is drivingly connected to the shaft which is to be braked. When used with a seat reclining mechanism, the shaft to which drive member 16 is connected is preferably provided with a hand wheel which an operative can manually grip to rotate the shaft.

The drive member 16 includes a pair of opposed, radially extending abutment faces 21, 22 which define therebetween a recess 23.

A coiled spring 26 is located within the cylindrical housing 12 such that the outer periphery of the spring 26 is normally biased into frictional surface contact with the inner cylindrical face of the housing 12.

The spring 26 includes a pair of end abutment portions 28, 29 which project radially inwardly into recess 23 by a distance sufficient to lie in the path of rotary movement of faces 21, 22.

The maximum angular distance A between the end portions 28, 29 is chosen to be less than the angular distance B between opposed faces 21, 22 by a distance C. This ensures that in the static condition of the brake unit 10, the spring portions 28, 29 are able to move apart in an unrestricted manner to ensure that the spring 26 is biased into contact with the inner cylindrical face of the housing 12.

Located within the recess 23 so as to be capable of abutting engagement with the inner faces 31, 32 of the end portions 28, 29 is a rotary driven member 40. The driven member 40 is for example an arm 42 which is connected to a shaft 46. When used in a seat reclining mechanism, shaft 46 is preferably arranged to drive the gear transmission of the reclining mechanism.

Biasing means 50, preferably in the form of a 'C' shaped spring is provided for biasing the drive member 16 and driven member 40 in opposite rotary directions.

As seen in Figure 1, in the static condition, the biasing force of the biasing means 50 is sufficiently strong to ensure that both the abutment face 52 of driven member 40 is in abutment with face 32 of end portion 29 and abutment face 22 of drive member 16 is in abutment with end portion 29. Accordingly, rotation of drive member 16 is in an anticlockwise direction immediately causes a similar movement of the driven member 40. Accordingly the operative senses no difference in feel when adjusting in this direction.

Movement in this direction is permitted by the spring 26 since displacement of the end portion 29 in an anti-clockwise direction tends to wind the spring 26 and thereby reduce its diameter and thereby relieve frictional engagement between the spring 26 and housing 12.

Adjustment in the opposite direction, ie rotation of drive member 16 in a clockwise direction, requires the drive member 16 to rotate through an initial angular displacement (equivalent to distances C and D) before the drive member 16 abuts the abutment face 53 (via end portion 28) to positively displace the driven member 40 in a clockwise direction.

The biasing force of the biasing means 50 is chosen to be sufficiently strong such that the operator perceives a consistent resistance to rotary movement as the drive member 16 travels through said initial angular displacement and thereafter causes displacement of the driven member 40. On release of the hand wheel driving drive member 16, the biasing means 50 acts to move the driven member 16 in an anti-clockwise direction and driven member 40 in a clockwise direction to resume the position shown in Figure 1.

Claims

CLAI1%

1. A brake unit for transmitting rotary movement from an input shaft to an output shaft but preventing rotary movement from the output shaft to the input shaft the unit including a cylindrical housing (12) containing a coiled spring (26) defining a generally outer cylindrical surface for frictional contact with the cylindrical housing, the coiled spring having at opposite ends, radially inwardly directed abutment portions, a rotary drive member (16) having opposed abutment faces (21, 22) located outboard of said abutment portions for abutment with outer faces of said abutment portions, the drive member being drivingly connected to the input shaft, and a rotary driven member (40) having opposed abutment faces (52, 53) located in-board of said abutment portions for abutment with inner faces of said abutment portions, the driven member being drivingly connected to the output shaft, the circumferential spacing between the outer faces of said abutment portions being less than the circumferential spacing between said opposed abutment faces of the drive member, the circumferential spacing between the inner faces of said abutment portions being greater than the circumferential spacing between the opposed abutment faces of the drive member, and biasing means (50) operatively connected between the drive and driven member to urge the drive and driven member in opposite rotary directions such that in the absence of torque applied to the drive shaft the drive and driven member reside at a biased position whereat the drive and driven member abut on opposite sides against the same abutment portion of the coiled spring.

2. A brake unit substantially as herein described with reference to and as illustrated in any of the accompanying drawings.