GB2109495A - Joints between tubular members - Google Patents

Abstract

A joint which provides for relative rotation between two tubes 1,2 comprises enlarged portions 10,20 of the ends of the tubes and disposed one within the other and a series of spring washers 3 mounted within the inner portion 20 to exert a pressure on the walls of the tubes and thereby increase the friction therebetween so that the tubes will remain in an adjusted position. A spring may be employed in place of the washers 3 and the joint is disclosed as being of use in lighting appliances and folding structures including furniture. <IMAGE>

Description

SPECIFICATION A system for articulating movements as applicable to articulated joints Systems are known that provide articulated movements (as for instance in lighting appliances, folding structures and folding furniture), but although these systems are based on mechanical designs or principles, they suffer nonetheless from the following drawbacks: (a) They require complex construction, often with manifold articulated joints; (b) Once they have been constructed, their stiffness cannot be altered, and so they are of use only for a specific kind of requirement; (c) When required to withstand heavy stressing, these articulated joints need to be very large in size.

All these drawbacks are overcome by the articulated movement system covered by this invention which is of a mechanical design (where a friction force is overcome between several bodies iying in contact), and is made using a totally new design that allows a maximum ratio between friction force and area of contact.

Since the structure of the object to which it is desired to embody the articulation is normally tubular, it is on such tube that an articulation centre must be achieved.

This system is based upon the general idea of dividing the tube into two parts, where, by means of sprung components, friction forces are originated between said two parts themselves, or between them and a third which serves as their connection.

The system entails particularly the sprung deformation of two bodies which are generally tubular, where one is deformed to a greater extent than the other so that the latter can be inserted inside the former.

Under an alternative arrangement, the larger deformation is replaced by a third tube in whose inside are inclued the lesser deformations of both the aforementioned bodies.

The deformations may be of any shape at all, and even spherical.

In one particular case the end of the deformation on the inserted body may abut against the inside of the beginning of the enclosing deformation, whereas the end of the enclosing deformation surrounds the outside of the beginning of the inserted deformation.

Pressure pieces, to provide the necessary friction force as required in the articulation, are inserted inside the widened enclosure thus defined.

This flexing force is a function of the flexing deflection, and depends also upon the way in which the washers are positioned, and their physical properties, as detailed hereunder.

This friction force tends to prevent rotation between the tubular bodies, and this articulation remains static so long as there is a force applied which is greater than the aforementioned friction force.

In accordance with another peculiarity of the invention, with one single degree of sprung deformation in the inserted bodies, differing amounts of stiffness can be obtained in the articulation with no further requirement than to alter the number and/or positioning of the spring washers (or, if applicable, the spring flexing constant) fitted in the articulation system.

In accordance with yet another peculiarity of the invention, such articulated joints are obtained by including nuts on the ends of tubular bodies, these being joined together by a portion of greater diameter.

In the following practical explanation of the present invention, the peculiarities and parts included in same are expressed as being applicable, for instance, to the arm of a lighting appliance possessing an articulation in such arm.

Figure 1 shows the section across two bodies (1) and (2) in the area where same comprise an articulation in accordance with the system covered by this invention.

Figure 2 shows a cross section view (where said bodies (1 and 2) are widened in this area) and a plurality of spring washers (3), all parts being in the assembled position.

Figure 3 depicts an articulated joint constructed in accordance with the system covered by the invention.

Figure 4 illustrates an articulated joint which is similar to that shown in the preceding figure, but with the spring washers (3) arranged in a different fashion.

Figure 5 is a construction arrangement of the articulating movement system which is covered by the invention, and this embodies a spring (4) instead of the spring washers (3).

Figure 6 is likewise a construction arrangement of the articulating movement system as covered by the invention, but here a sleeve piece (5) is included for purpose of facilitating the fitting and tightening of the spring washers (3).

Figure 7 is a graph showing the functional interdependence between force (P) and the spring travel (f) for washers (3).

The articulating movement system covered by this invention is now described in conjunction with the accompanying drawings.

There are basically two bodies (1 and 2), and the purpose to be achieved is to provide them with relative motion to one another.

These two bodies (1 and 2) are flexibly deformed at their facing ends, to comprise two widened portions (10 and 20) respectively. These deformations can be carried out by any known method, and particularly be pressing.

Deformations thus made terminate on one of the bodies (1) with the end being bent at an angle, which surrounds the outside of the other body (2) at its angled shoulder at the point (20) where its section becomes larger. The inserted body (2) possesses a straight end which is able to abut inside up against the angled shoulder as defined by body (1) where its section increases (10).

The widened space that is thus provided within this articulated joint accommodates pressure parts which, in this practical construction of the invention shown in Figures 3, 4 and 6, are comprised of some spring washers (3). Said spring washers (3) exert a pressure against the walls of the widened sections, and exert a friction force between the tubes which is greater than the moment created by the body joined articuiatedly by means of arms (1 and 2), so that the articulation remains motionless (arms (1, 2) static with respect to one another) until such time as a greater force than the aforementioned friction force is applied.

The friction force generated is dependent upon the physical properties of each spring washer (3), and each one of same exerts a spring force that is determined by the following general formula:

where: P = Spring force exerted by washer (3).

D = Outside diameter.

d = Inside diameter.

s = Thickness.

h = Inside height of the truncated cone, with no load applied.

f = Spring travel range.

a =Characteristic value (depending on the ratio D/d).

The friction force (P) generated is a function of the spring travel (f), and depends too upon the fitting of the spring washers (3).

Hence, when as shown in Figure 7, values of the spring travel (f) are plotted on the horizontal scale against force values (P) on the vertical scale, and where ,8 is the angle formed by the functional value for each point with respect to the horizontal axis, we have: - For a single spring washer (3): tgp P/f = 1.

- For spring washers (3) all placed facing the same way (see either of the symmetrical haives in Figure 4): tgp = P/f ) 1.

- For spring washers (3) placed so as to face in different directions with respect to one another (see Figure 3): tgp = P/f < 1 (whether said washers are alone or in groups).

Experimental tests have shown that the arrangement where the best use is made of the spring washers (3) is that depicted in Figure 4, and additionally a more even distribution of forces is achieved with this arrangement. In this case, tgp = P/f 2: 0.25.

In accordance with the system covered by this specification, the articulated joint terminates in end ridges (101) provided on the arm (1) and prevent any axial travel between it and the other, while the end area (201 ) of the other arm (2) abuts against the shoulder of the widened portion (see Figures 3 to 6).

The present invention also envisages the inclusion of a spring (4), or any other similar flexible member, instead of the spring washers (3) hereinbefore described, without entailing any alteration whatsoever to the peculiarities hereof (see Figure 5). By including a spring (4) in this invention, the generation of forces is displaced, these being concentrated in the areas at the ends of the housing defined by widened sections (10, 20) where the end ridges (101, 102) are formed.

In yet a further practical construction of this invention as is shown in Figure 6, it is envisaged that a sleeve piece (5) be included. Moreover, another sleeve piece may be fitted in the arm (2).

Such sleeve piece (5), which is either tapered or possesses a varying diameter, is preferably arranged in such a manner that one of its ends, whose diameter is "d", is essentially the same as that of one of the arms (1), while the diameter "D" of its opposite end is the same as that of the widened section of the other arm (2) (see Figure 6). In this way, by inserting said sleeve piece (5), the fitting and tightening up of the spring washers (3) is facilitated, these being in a compressed condition inside the widened section.

Claims (10)

1. A system for articulating movements as applicable to articulated joints, peculiar inasmuch that it comprises: a) Two bodies to be articulated together, the sections of whose ends are widened; b) Means of joining the two widened ends; c) Spring elements arranged in compression between the two widened ends.

2. A system for articulating movements as applicable to articulated joints, in full accordance with the preceding claims, and peculiar insofar as the means of joining the two widened ends comprise a tubular piece, each of whose ends surrounds the widened ends of the bodies that are to be articulated together.

3. A system for articulating movements as applicable to articulated joints, in full accordance with the first claim, and peculiar insofar that the widening at the ends of the two bodies differs in section on one from that on the other, the larger being such that the small can be inserted inside it.

4. A system for articulating movements as applicable to articulated joints, in full accordance with the first and third claims above, and peculiar wherewith the joining means comprise a deformation on the end of the longer widened section, which closes back upon itself forming an angle, and surrounding the beginning of the smaller deformed section.

5. A system for articulating movements as applicable to articulated joints, in full accordance with the first claim, and peculiar inasmuch that the spring members are a set of spring washers arranged one against another inside the housing defined by the two widened ends, so that the friction generated varies in function to the spring travel range, this being dependent on: (a) the physical properties of each spring, and (b) the arrangement of the springs.

6. A system for articulating movements as applicable to articulated joints, in full accordance with the fifth claim, and peculiar wherewith the friction force from each spring washer is defined as follows:

where: P = Spring force exerted by each washer.

D = Outside diameter.

d = Inside diameter.

s = Thickness.

h = Inside height of the truncated cone, with no load applied.

f= Spring travel range.

a = Characteristic value depending on the ratio D/d.

7. A system for articulating movements as applicable to articulated joints, in full accordance with the preceding claims, and peculiar insofar that p/f > = 1,where: P = Spring force exerted by each washer.

f = Spring travel range.

8. A system for articulating movements as applicable to articulated joints, in full accordance with the preceding claims, and peculiar insofar that p/f > - 1,where: P = Spring force exerted by each washer.

f = Spring travel range.

9. A system for articulating movements as applicable to articulated joints, in full accordance with the first claim above, and peculiar insofar as the spring means are a spring.

10. A system for articulating movements as applicable to articulated joints, in full accordance with the aforegoing claims, and peculiar inasmuch that the friction force is evenly and continuously distributed along the length of the inside wall of the widened section.

1 A system for articulating movements as applicable to articulated joints, in full accordance with the above claims, and peculiar insofar that it is fitted with a variable section sleeve which is placed at the beginning of at least one of the widened sections, and against which the spring ends abut.

1 2. A system for articulating movements as applicable to articulated joints.