Webbing length adjustor

FIELD OF INVENTION

This invention relates to a webbing length adjustor, and in particular to adjustors which use clamping elements that have cam shaped surfaces to clamp webbing with respect to the adjustor.

BACKGROUND OF THE INVENTION

Such adjustors are commonly used with restraint and seat belt webbing. The webbing which passes through the adjustor has tension applied on one side of the adjustor which locks the webbing with respect to the adjustor. Pulling the webbing on the other side of the adjustor will release the clamping force and allow the webbing to be pulled through the adjustor.

For example, a shoulder harness in a child restraint or safety seat uses such an adjustor to allow tensioning of the shoulder straps. A locking cam in the adjustor is shaped so that applying tension to the free end of the webbing will cause rotation of the arm to release the webbing. The webbing can then be pulled through the adjustor to tighten the shoulder straps.

After adjusting the webbing, the cam is caused to rotate to a locking position to apply clamping force to the webbing.

The rotation of the cam is assisted by a spring which moves the cam in the required direction to clamp the webbing. The surface of the cam has a series of ridges which bite into the webbing surface. The cam is shaped so that further tension applied to the webbing causes it to rotate further and to thereby increase the clamping force.

Known adjustors have a manual actuator which enables rotation of the cam to release the clamping force and allow the webbing to move in either direction through the adjustor. This enables loosening of the webbing when increased length is required for a seat belt or shoulder harness. A spring is required to ensure that the cam rotates far enough to enable the serrated edges of the cam to abut against the webbing. This engagement will then ensure that the clamping force applied to the webbing will increase as the tension applied to the webbing increases.

The aim of this invention is to provide an alternative arrangement of adjustor and to have an adjustor which has a reduced number of components with an improved ease of manufacture and assembly.

BRIEF DESCRIPTION OF THE INVENTION

The invention is therefore said to reside in a webbing length adjustor adapted to clamp webbing having a free end and a tension end when tension is applied to the tension end of the webbing, the adjustor comprising;

a webbing guide,

a clamp element pivotally mounted with respect to said webbing guide,

a locking cam on said clamp element which in a locked position clamps said webbing between said locking cam and said webbing guide to prevent movement of said webbing through said adjustor when said tension is applied to the tension end,

a release actuator to cause rotation of said clamp element to move said locking cam to a position where said webbing is released to allow it to move in either direction through said adjustor, and

a projection on said clamp element that abuts against the webbing between the locking cam and the tension end thereof so that said webbing when tensioned exerts a force against said projection which urges or causes rotation of said clamp element in a direction that holds or moves said locking cam in or into said locked position.

As can be seen from the above description, the invention avoids the need for the use of a spring to rotate the locking element into a position where it engages the webbing. Instead, the projection causes a deflection of the webbing when the clamp element rotates to an unlocked position. Tension applied to the webbing acts to straighten the deflected webbing. This causes a force to be applied to the projection which rotates the clamp element and locking cam towards the webbing.

The projection can be designed to always slightly deflect the webbing, even when the clamp element is in its locked position. This will ensure that there is some positive force urging the locking cam towards the webbing. Rotation of the clamp element by application of tension onto the webbing will cause further gripping of the locking cam against webbing. The greater the deflection of the webbing, the more force is applied to the projection when tension is re-applied to the webbing.

The webbing guide may comprise a bracket which has a surface over which the webbing locates. The locking cam acts to clamp the webbing against the surface. In a case of child restraints, the bracket may be adapted to be attached to the molded shell of the restraint.

Alternatively, where the webbing length adjuster is associated with a child safety seat, the shell of the child safety seat may be molded to form the required webbing guide. The clamp element can then be pivotally attached with respect to the molded webbing guide.

Preferably, the locking cam has a surface designed to grip or otherwise positively catch against the surface of the webbing. This surface may have knurling or a plurality of saw tooth projections that extend the width of the locking cam surface. Each saw tooth projection has a sharp edge which will dig into and grip the surface of the webbing.

The release actuator preferably comprises a manual actuator. This may be a flange which is lifted or pushed by a person's fingers. By lifting or pushing the flange, the clamping element may be rotated to release the webbing.

Alternatively, the release actuator comprises a button actuator which may be used to cause rotation of the clamp element.

The projection on the clamp element may be of an arcuate flange that extends away from the axis of rotation of the clamp element.

The webbing guide may be provided with a recess into which the projection locates. The webbing is pushed into the recess by the projection so that its path from the locking cam is into the recess, around the end of the projection and back out of the recess and onto a surface of the webbing guide. This can result in a more positive force being applied by the webbing to the projection when tension is applied to the webbing.

Alternatively, the invention may include any form of projection that deflects the line of the webbing so that a rotation force is applied to the cam element when tension is applied to the webbing.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to fully understand the invention, preferred embodiments will now be described. However, it will be realised that the scope of the invention is not restricted to the features of these embodiments. The embodiments are illustrated in the accompanying drawings in which:

FIG. 1

shows a cross sectional view of an adjustor with the clamp element in an unlocked position,

FIG. 2

shows a cross sectional view of an adjustor with the clamp element in a locked position,

FIG. 3

shows a plan view of an adjustor,

FIG. 4

shows a cross sectional view of a second embodiment of an adjustor incorporating a push button actuator,

FIG. 5

shows a third embodiment showing an alternative push button actuator,

FIGS. 6

to

8

show cross-sectional views of a second embodiment of an adjustor,

FIG. 9

shows a plan view of the embodiment shown in

FIGS. 6

to

8

,

FIGS. 10 and 11

show cross-sectional views of a third embodiment of an adjustor, and

FIG. 12

shows a child car seat with an integrally formed webbing guide according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to

FIGS. 1

to

3

the adjustor

10

comprises a webbing guide which in this embodiment is a metal bracket

11

. A clamp element

12

is pivotally mounted to the bracket

11

via shaft

13

. The bracket

11

is U-shaped and comprises a webbing guide surface

14

and a pair of side walls

15

on either side of the guide surface

14

. There is an aperture

18

between the guide surface

14

and a guide bar

19

. The shaft

13

locates through a pair of apertures within the side walls

15

. The shaft

13

has a head

20

at one end and either a swaged end or threaded nut

21

which holds the shaft

13

in place in the bracket

11

.

The clamp element

12

comprises has a manual actuator, which in this embodiment is flange

23

that is manually lifted to cause rotation of the clamp element

12

. The clamp element

12

has a locking cam

24

with an arcuate surface comprising saw tooth ridges

25

. The center of the part circle forming the arcuate surface of the locking cam

24

is displaced from the longitudinal axis of the shaft

13

. Downward movement of the flange

23

will result in the surface of the locking cam

24

moving towards the guide surface

14

as shown in FIG.

2

.

The clamp element

12

also has a projection

27

that comprises an arcuately shaped flange that extends away from the locking cam

24

and the shaft

13

. The projection

27

moves downwardly into the aperture

18

when the clamp element

12

is rotated by lifting flange

23

.

Both FIG.

1

and

FIG. 2

show the path taken by the webbing

28

through the adjustor

10

. Webbing

28

passes between the guide surface

14

and the locking cam

24

and passes over the aperture

18

and guide bar

19

. Referring to

FIG. 2

, the webbing

28

is to be prevented from moving when tension is applied to the tension end

28

a

of the webbing

28

on the left hand side of the actuator. The webbing

28

extending on the right hand side of the actuator

10

is a free or loose end

29

which is used to adjust the length of the webbing

28

on the left hand side of the adjustor

10

. When the free end webbing

29

is pulled, a turning movement is applied to the clamp element

12

which moves the locking cam

24

away from the webbing

28

to release the clamping force. This enables the webbing

28

to be adjusted without having to manually manipulate the clamp element

12

.

Rotation of the clamp element

12

into the unlocked position, as shown in

FIG. 1

, results in the projection

27

pressing onto and deflecting webbing

28

through the aperture

18

. When tension is again applied to the left hand side or tension end

28

a

of the webbing

28

, the deflected portion of the webbing is pulled upwardly and applies a force to the projection

27

. This in turn rotates the clamp element

12

into the locked position. As soon as the saw tooth ridges

25

abut against the webbing

28

, further movement of the webbing

28

will result in the locking cam

24

rotating into the locked position. This is shown in FIG.

2

. Even in the position shown in

FIG. 2

, there is a slight depression of the webbing

28

into the aperture

18

. This will ensure that the webbing

28

on the tension side of the adjustor

10

will always be urging the clamp element

12

to rotate into the locked position.

The projection

27

avoids the need for a spring between the shaft

13

and the clamp element

12

. This reduces the number of components needed for the adjustor

10

. This simplifies both manufacture and assembly and reduces the cost of the adjustor

10

.

FIGS. 4 and 5

show two variations for manual actuation of the adjustor

10

. In each case, a button is positioned to operate a flange on the clamp element. In the embodiments shown in

FIG. 4 and 5

, load is applied to the webbing

28

a

on the right-hand side of the adjustor

10

shown in these figures. The webbing

29

on the left-hand side is a free end.

In the embodiment shown in

FIG. 4

, the button

30

has a ramped surface

31

which abuts against the end of the flange

23

. Depression of the button

30

results in an upward lift being applied to the flange

23

.

In

FIG. 5

, the flange

35

is orientated vertically with the end of the button

36

abutting against the flange

35

.

In both embodiments shown in

FIGS. 4 and 5

, a spring

32

pushes the button

30

,

36

away from the adjustor

10

and acts to return the button

30

,

36

to this position after it is depressed.

A fourth embodiment is shown in

FIGS. 6

to

9

. In this embodiment, the adjustor

110

has a bracket

111

. The bracket

111

is U-shaped and has a pair of side walls

115

and a base wall

116

. An aperture

118

is located in the base wall

116

. The clamp element

112

is pivotally mounted to the bracket

111

via shaft

113

in a similar manner to the first embodiment.

The clamp element

112

has a flange

123

which is pushed to cause rotation of the clamp element

112

. The clamp element

112

has a locking cam

124

with an arcuate surface comprising saw-tooth ridges

125

. As in the first embodiment, the center of the part circle forming the arcuate surface for locking cam is displaced from the longitudinal axis of the shaft

113

. Clockwise rotation of the clamp element

112

will result in the saw-tooth ridges

125

moving towards the base wall

116

.

FIGS. 6

to

8

show the path taken by webbing

128

through the actuator

110

. The webbing

128

passes firstly through the aperture

118

and between the saw-tooth ridges

125

of the locking cam surface

124

and the base plate

116

. The webbing

128

locates around the clamp element

112

so that it can then pass back through the aperture

118

.

The clamp element

112

has a projection

127

and the webbing

128

passes over the projection

17

.

The actuator

110

is shown in a partly locked position in FIG.

6

. When tension is applied to the webbing

128

which is located on the left-hand side of the adjustor

110

as shown in

FIGS. 6

to

8

, the clamp element

112

is caused to rotate in an anti-clockwise direction. The movement into a locking position is illustrated in

FIGS. 6 and 7

where the clamping element

112

moves from a partially locked position in

FIG. 6

to a fully locked position in FIG.

7

. The tension force applied to the webbing

128

pulls against projection

127

which causes rotation of the clamp element

112

in the counter-clockwise direction.

Continued application of tension within the webbing

128

on the left-hand side of the adjustor

110

will maintain the clamp element

112

in its locked position.

The right-hand side of the webbing shown in

FIGS. 6

to

8

is also known as the free end

129

. The clamp element

112

can be released from the locking position by pulling the free end

129

of the webbing

28

. By pulling the free end

129

, the clamp element

112

is rotated in a clockwise direction. Provided that all tension is released from the left-hand side of the webbing

128

, this rotation will unlock the clamp element

112

thereby allowing the webbing

128

to be pulled through the adjustor

110

.

Alternatively, as shown in

FIG. 8

, the flange

123

can be depressed to fully rotate the clamp element

112

to an unlocked position. In this position, the webbing

128

can be freely pulled through the adjustor

110

in either direction. Any tension applied to the left-hand side of the webbing

128

shown in

FIG. 8

will cause a downward force to be applied to the projection

127

. This will in turn cause rotation of the clamp element

112

into a locked position. Pulling the free end

129

as shown in

FIG. 8

will tend to maintain the clamp element

112

in an unlocked position.

FIGS. 10 and 11

show a variation of the embodiment shown in

FIGS. 6

to

9

. The same adjustor

110

can be used as an inline belt length adjustor. In this case, the webbing

128

approaches and leaves from the same side of the adjustor

110

which in this embodiment, is the right-hand side as shown in

FIGS. 10 and 11

. On the left-hand side of the adjustor

110

, there is provided an aperture

133

in the base wall

116

which enables attachment of webbing

134

. The adjustor

10

shown in

FIGS. 9 and 10

function exactly in the same way as the adjustor shown in

FIGS. 6

to

8

.

Although all of the above described embodiments of the invention will function without a torsion spring acting between the bracket

11

,

111

and the clamp element

12

,

112

a spring may be incorporated within these embodiments to improve the tactile feel of the clamp element

12

,

112

when it is rotated using the flange

23

,

123

.

FIG. 12

shows a child car seat with an integrally formed webbing guide according to another embodiment of the present invention.

In this embodiment a child car seat

40

has a back

41

which is formed as a plastics material molding. The seat is restrained in a vehicle by a tether strap

43

which includes a attachment arrangement

44

by which the seat can be fastened to a anchor point. The tether strap is fastened at one side of the back of the seat back

41

at

46

and at the other side of the seat back

41

there is an integral webbing length adjuster

50

according to this invention. In this arrangement the webbing guide comprises a portion of the shell of the seat molded to form the webbing guide and an actuating button

51

is provided to operate the webbing length adjuster to enable release of the tether strap to adjust the length. Tension applied to the tether strap

43

will cause the webbing length adjuster

50

to grip the tether strap to restrain movement.

Throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.

Throughout this specification and the claims that follow unless the context requires otherwise, the words ‘comprise’ and ‘include’ and variations such as ‘comprising’ and ‘including’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.