GB2396397A

GB2396397A - A spring assembly including at least one torsion bar for controlling the movement of closure members

Info

Publication number: GB2396397A
Application number: GB0229651A
Authority: GB
Inventors: Helmut Mueller; Ralf Hoge
Original assignee: Gencorp Property Inc
Current assignee: Gencorp Property Inc
Priority date: 2002-12-20
Filing date: 2002-12-20
Publication date: 2004-06-23
Also published as: WO2004057143A1; GB0229651D0; AU2003286359A1

Abstract

A spring assembly 15 for controlling movement of a closure member (such as an independently opening car tailgate rear windscreen 9) with respect to a body (such as a tailgate 5) to which the closure member is attached. At least one torsion rod 23a, 23b is mounted in a housing 17. In one embodiment two torsion rods 23a, 23b are provided which cross at a mid-point. This is advantageous when the rear windscreen 9 has a curvature, as it allows the curvature of the torsion rods 23a, 23b to be less than the curvature of the windscreen 9. In another embodiment a torsion rod 30 comprises two generally parallel elongate portions 32a, 32b which are coupled together by cooperating cogs 38a, 38b to allow the twisting force applied to either of the elongate portions to be shared equally with the other of the elongate portions.

Description

CONTROLLING MOVEMENT OF CLOSURE MEMBERS

The present invention relates to a spring assembly for controlling movement of a closure member with respect to a body to which the closure member is attached, for example for controlling the movement of a separately openable rear window in a vehicle tailgate. The present invention also relates to a closure member incorporating such a spring assembly and to a method of manufacturing such a spring assembly.

Many vehicles incorporate an openable tailgate which is pivotally attached to the roof of the vehicle in order to allow access to the load area of the vehicle. Whilst the provision of a tailgate renders the load space easily accessible, because oftheir size, and because they incorporate the rear windscreen ofthe vehicle, such tailgates tend to be heavy, requiring considerable effort to open and close them. Further, if the space behind the vehicle is limited, it can be awkward or impossible to open the tailgate.

To overcome these disadvantages of tailgates, it is increasingly common for vehicle manufacturers to provide the tailgates with a rear windscreen which is openable independently ofthe tailgate. The rear windscreen is typically attached by a hinge or the like to the tailgate at the top of the rear windscreen.

To control movement of such openable rear windscreen, and in particular to allow the rear windscreen to be held in the open position, gas struts are typically employed, one at each of the opposite side edges of the rear windscreen, which connect to the side edges of the rear windscreen opening of the tailgate. However, such gas struts are expensive to manufacture, are highly visible and can obstruct loading of the vehicle.

According to the present invention, there is provided a spring assembly for controlling

: t,:; :e: c:q::e.':r movement of a closure member with respect to a body to which the closure member is attached, comprising at least one torsion rod, mounted in a housing, for coupling to the closure member, the torsion rod having a coupling portion arranged for coupling to the body.

The body may be a vehicle tailgate, and the closure member may be a separately openable rear windscreen pivotally mounted on the tailgate, although it should be understood that the present invention is not restricted to such an arrangement.

The present invention also relates to a closure member having fixed thereto a spring assembly as defined above.

The present invention further relates to a method of manufacturing the spring assembly as defined above.

A spring assembly, a closure member and a method of manufacturing the spring assembly embodying the invention will now be described by way of example with reference to the accompanying schematic drawings, in which: Figure 1 is a view of the internal (in use) side of the glass pane of a vehicle tailgate with the spring assembly shown partially cut away; Figures 2A, 2B and 2C are cross sections respectively taken along lines AA, B-B and C-C of Figure 1; Figures 3A, 3B and 3C show cross-sections corresponding to those of Figures 2A, 2B and 2C of a second embodiment of the present invention;

telll hi; Figure 4 shows a cut-away view of an alternative spring assembly according to a third embodiment of the present invention; Figure 5 shows a cross-section taking along the line D-D of Figure 4; and Figure 6 shows a cross-sectional view, corresponding to the cross section of Figure 5, of an alternative embodiment to that shown in Figures 4 and 5.

Figure 7 shows a perspective view of the rear of a motor car having a rear tailgate with a separately openable rear windscreen glass.

In the drawings, like elements are generally designated with the same reference numeral. Figure 7 shows a car body 1 to the roof 3 of which a tailgate 5 is attached by means of hinges 7.

The rear windscreen 9 of the car is openable separately from the tailgate 5, and is pivotally attached to the tailgate 5 by hinges 1 1. A latch mechanism 13 allows the rear windscreen 9 to be held securely closed when described.

As shown in Figure 7, the rear windscreen 9 is formed of a curved pane of glass in order to provide a pleasing visual appearance and to allow the rear windscreen 9 to conform to the general shape of the tailgate 5.

Embodiments to be described are concerned with a mechanism for allowing controlled movement ofthe rear windscreen 9 with respect to the tailgate 5, and in particular to a mechanism for allowing the rear windscreen 9 to be supported in its fully opened

À À À Àe e À À e e À e ce e c À ',. À e c e e À.... .

position. Previous mechanisms for performing this function include gas struts, as described above. However, gas struts are obtrusive and expensive.

The embodiments provide a mechanism for controlling movement of the rear windscreen which is a relatively low cost, is simple to manufacture and is unobtrusive. It should, of course, be appreciated that the invention, and the arrangements described in the embodiments, are not restricted to a mechanism for use with an openable window of a tailgate. The mechanism described could be employed to control the movement of any closure member, whether it is formed of glass or some other material. However, the embodiments to be described are particularly advantageous when used to control movement of a glass or other transparent panel because they are relatively unobtrusive.

Figure 1 shows a rear windscreen 9 to which a spring assembly 15 in accordance with the first embodiment ofthe invention is attached. The spring assembly 15 comprises a plastics housing 17 having an elongate main body 19 from which two limbs 21 extend generally perpendicularly with respect to the elongate portion] 9.

Located within the housing 17 are two torsion rods 23a and 23b, formed in this example of resiliently deformable metal. Each ofthe torsion rods 23a, 23b comprises a main elongate portion 25a, 25b from which extends at one end an integral relatively short coupling portion 27a, 27b lying generally perpendicular to the main elongate portion 25a, 25b. The respective coupling portion 27a, 27b are attached to a suitable point on the inside of the roof 3 of the car 1 near the hinges 7. At the opposite end of

8, t 8 8 8 8 8 8 8 8, 8

8 8 À t 1 8 the elongate portions 25a, 25b to the coupling portions 27a, 27b is an integral mounting portion 29a, 29b located within the respective limbs 21a,21b ofthe housing 17. Torsion rods are conventional devices and have previously been employed to control the movement of closure members. However, conventional torsion rods cannot be satisfactorily employed where it is desired to unobtrusively mount them on a curved closure member. If a conventional torsion rod is accommodated in a housing which follows the contour ofthe curved closure member, this will cause the elongate portion of the torsion rod to have the same curvature as the curvature ofthe closure member.

The forced curvature of the torsion rod causes lateral forces to act on the walls of the housing making movement of the closure member stiff end generating noise.

According to the first embodiment ofthe invention, the elongate portions 25a, 25b of the torsion rods 23a, 23b are arranged such that the elongate portions 25a, 25b cross one another at the central region thereof. The respective elongate portions 25a, 25b do not exactly follow the curvature of the rear windscreen 9. The elongate portions 25a, 25b are inclined with respect to the axis of symmetry (along which cross section B-B is taken) ofthe rear windscreen 9. For example, the elongate portion 25a, 25b are inclined by 80 to the axis of symmetry of the rear windscreen 9. This allows the elongate portions 25a, 25b to have a lower curvature than the curvature of the rear windscreen 9 at the point at which the housing 17 is mounted thereon.

Figure 2A shows a cross-section taken along line A-A through the limb 21b. Figure 2B is a cross-section taken along line B-B through the central region of the elongate portions 25a, 25b. Figure 2C is a cross-section taken along the line C-C at the end region of the elongate portions 25a, 25b.

À ' r Àe e.e e?; À À

In Figure I the outer surface of the housing 17 (that is the surface furthest from the rear windscreen 9) is shown cut away so that the torsion rods 23a, 23b can be seen.

As is clear from the cross sections of Figures 2A, 2B and 2C, the housing includes an outer surface which conceals the torsion rods 23a, 23b when viewing the spring assembly 15 from the inside surface of the rear windscreen 9, in use. When viewed from the outside surface ofthe rear windscreen 9, the elongate part 19 ofthe housing 17 will be obscured by a blackened area at the top part of the rear windscreen 9, applied in the conventional manner.

The housing 17 may be made by a suitable moulding operation. The torsion rods 23a, 23b are then located at the appropriate recesses formed by the moulding operation, and the assembled spring assembly is then fixed to the interior surface of the rear windscreen 9 by any suitable means, such as by an adhesive. When the housing 17 is fixed to the interior surface of the rear windscreen 9, movement of the torsion rods 23a, 23b, other than the twisting action, is prevented.

The physical characteristics of torsion rods are such that: 1. The spring force and the tension in the material of the torsion rods both increase in proportion to the square of the diameter of the torsion rods; 2. the turning rate behaves in a converse manner with respect to the square ofthe diameter; 3. increasing the length of the elongate portion 25a, 25b of the torsion rods improves the linearity with which the torsion forces are provided by the torsion rods, but of course, the length of the elongate portions 25a, 25b is restricted by the dimensions of the rear windscreen 9; and

ÀÀ À 1

À À

À À ÀÀ À 1

À as Ie I I À 7 ' "

À ' ' À ' '

4. the friction between the springs and the recesses in the housing 17 dissipates some of the spring force generated by the torsion rods.

In some applications it may be advantageous to replace the single torsion rod 23a with multiple generally parallel torsion rods, and to replace the single torsion rod 23b with multiple generally parallel torsion rods. Figure 3A, 3B and 3C show cross sections corresponding to Figures 2A, 2B and 2C taken through a spring assembly where torsion rod 23a is replaced by two generally parallel torsion rods, and torsion rod 23b of Figure 1 is replaced by two generally parallel torsion rods.

With regard to point 3 above, it will also be understood by those skilled in the art that if a torsion rod is twisted beyond a predetermined amount, the torsion rod will be damaged and will no longer behave elastically. The amount oftwisting that a torsion rod of a given diameter and of a given material can endure without being damaged is proportional to the length of that torsion rod (all other factors being equal).

The limitation in length of the torsion rod, due to it having to be accommodated within the dimensions of the rear windscreen 9, is a particular problem because the rear windscreen 9 may have to rotate through approximately 150 with respect to the tailgate 5 in order that a rear windscreen 9, when opened, can be held in a position where it does not cause an obstruction to a person wishing to load or unload the car 1.

Figures 4 and 5 show a third embodiment ofthe invention. In this embodiment torsion rod 30 comprises two generally parallel elongate portions 32a and 32b. Elongate portion 32a terminates in a coupling portion 34 similar to the coupling portion 27a of the first embodiment. The other elongate portion 32b terminates in a portion 36 corresponding to the mounting portion 29a of the first embodiment. The other ends of

À À À À À

t c t t - -

- t eta Àr À the elongate portions 32a, 32b each have fixed thereto a respective cogwheel 38a, 38b. These cog wheels 38a, 38b act such that, when a turning force is applied to one ofthe two elongate portions 32a, 32b, this turning force is shared substantially equally with the other of the two elongate portions 32b, 32a by the coupling action of the mated teeth ofthe cogs 38a, 38b. The interaction ofthe cogs 38a, 38b allows the two elongate portions 32a, 32b to have similar characteristics to a single elongate portion having twice the length of either of the elongate portions 32a, 32b. Therefore, improved characteristics ofthe spring assembly are provided despite the constraint of the dimensions of the rear windscreen 9. A second torsion rod 39, similar to the torsion rod 30, may be provided in the housing.

Figure 6 shows a cross section corresponding to the cross section of Figure 5 of a fourth embodiment of the invention. According to the fourth embodiment, the elongate portion 32b has a crank or cam 40 fixed thereto and extending therefrom.

The cam 40 acts against a recessed surface 42 the generally C-shaped part 44 fixed to the elongate portion 32a. The action ofthe cam 40 on the surface 42 serves to cause twisting force applied to one of the two elongate portions 32a, 32b to be shared equally with the other of the two elongate portions 32b, 32a, in a similar manner to the third embodiment.

Other mechanical linkages between the elongate portions 32a, 32b, providing similar functionality, such as levers, could alternatively be used.

Claims

À es:: he e-: l À À CLAIMS

1. A spring assembly for controlling movement of a closure member with respect to a body to which the closure member is attached, comprising at least one torsion rod mounted in a housing, for coupling to the closure member, the torsion rod having a coupling portion arranged for coupling to the body.

2. The assembly of claim 1, wherein the closure member has a curved surface having an axis of symmetry and the housing is fixed to the curved surface and has the same access of symmetry as the curved surface.

3. The assembly of claim 2, wherein the torsion rod comprises a main elongate portion extending obliquely with respect to the access of symmetry.

4. The assembly of claim 2 or 3, including first and second torsion rods arranged within the housing such that the rods cross one another.

5. The assembly of claim 4, wherein the first and second torsion rods have a lower curvature and the curved surface of the closure member.

6. The assembly of claim 5, wherein a circle of curvature ofthe closure member is inclined with respect to a circle of curvature of the first and second torsion rods.

7. The assembly of any one of claims 2 to 6, modified in that the first torsion rod comprises a plurality of torsion rods and in that the second torsion rod comprises a plurality of torsion rods.

À À t À

8 The assembly of any one of the preceding claims, wherein the at least one torsion rod comprises two elongate portions mounted side by side and coupled together at one end thereof via coupling means, the other ends ofthe elongate portions being arranged for coupling to respective ones of the closure member and the body

9. The assembly of claim 8, wherein the coupling means allows torsion applied to one of said elongate portions to be applied to the other of said elongate portions.

10. The assembly of claim 8 or 9, wherein the coupling means causes twisting of one of said elongate means to apply a twisting force to another of said elongate means.

1 1. The assembly of claim 8, 9 or 10, wherein the coupling means comprises two interlocking cogs, fixed to respective ones of the elongate portions.

12. The assembly of claim 8, 9 or 10, wherein the coupling means comprises a crank fixed to one of the elongate portions, the other of the elongate portions having fixed thereto a member shaped to receive the crank.

13. A closure member having fixed thereto a spring assembly according to any one of the preceding claims.

14. The closure member of claim 13, wherein the closure member comprises an openable window.

15. The closure member of claim 14, wherein the closure member is pivotally attached to the body.

a:. t' c::: À À

16. The closure member of claim 15, wherein the body is the tailgate of a vehicle and the window is the rear window of the tailgate.

17. A method of manufacturing the spring assembly of any one of claims 1 to 12, including locating the torsion rod in the housing, fixing the housing to the closure member, fixing the closure member to the body, and coupling the coupling portion of the torsion rod to the body.

18. A spring assembly substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the . accompanying drawings.

l9. A closure member substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the . accompanying drawings.

20. A method of manufacturing a spring assembly, substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.