WO1980001508A1

WO1980001508A1 - Support leg construction

Info

Publication number: WO1980001508A1
Application number: PCT/SE1980/000017
Authority: WO
Inventors: T Johansson
Original assignee: Safac; T Johansson
Priority date: 1979-01-22
Filing date: 1980-01-21
Publication date: 1980-07-24
Also published as: SE7900546L

Abstract

In known support leg constructions of the type where the displacement of the support leg is carried out by means of a threaded rod, it is necessary that the pitch of the thread be not too steep as otherwise a rotation of one revolution of the rod requires too great a force. It is the object of the present invention to provide a support leg construction where the support leg is driven at a substantially greater rate when not loaded. The support leg construction of the invention is characterized in that the externally threaded rod (4; 4') has two portions (4a, 4b; 4a', 4b') with opposed pitch directions, one portion (4a;4a') being received in an internally threaded bore (12; 12') which is detachably non-rotatably connected with a holding means adapted to the supported means (2; 2') while the other portion (4b; 4b') carries an internally threaded element (6; 6'), to which one end of the support leg (7; 7') is pivotably adapted, and that a brace (10; 10') is pivotably attached with its ends to the support leg (7; 7') and to a means of attachment fixed relative to the supported means (11; 11').

Description

Support leg construction

This invention relates to a support leg construction.

Known support leg constructions, where the very support leg is displaced by means of rotation of a threaded rod, have certain apparent shortcomings.

In order that rotation of the threaded rod should not require too great a force when the support leg is loaded the rotation of the threaded rod one revolution cannot correspond to too great a displacement of the free end of the support leg. Thus, the pitch must not be too steep.

What has been stated above as to the pitch means that the transfer of the support leg from its position of rest to active position takes rather a long time. The threaded rod must be rotated several revolutions in order that the free end of the support leg should cover the relative way. It is the object of the present invention to provide a support leg construction where the support leg is operated at an essentially greater rate when not loaded. When the support leg is then loaded the drive is automatically shifted so that a rotation of one revolution of the threaded rod corresponds to a substantially less displacement of the free end of the support leg.

This is effected by means of a device that has been given the characteristic features set forth in the following claims. One illustrative example of the invention will be described below with reference to the enclosed drawings, where Fig. 1 shows a schematical lateral view of a support leg construction according to the invention, Fig. 2 shows a detail of the construction according to Fig. 1; Fig. 3 shows a lateral view of an alternative embodiment of the invention, and Fig. 4 shows a detail according to Fig. 3.

The support leg construction 1 shown in Fig. 1 comprises a holding means 2 open downwards, which is rigidly secured to the underside of the means 3, preferably a caravan, to be supported. In the holding means 2 a threaded rod 4 is received, which has an eye 5 at its outward end. The construction of the threaded rod 4 will be described more in detail in connection with Fig. 2. On the threaded rod 4 an internally threaded case 6 is adapted, to which one end of the very support leg 7 is articulately connected. At its other end the support leg is provided with a pivotable disc-shaped foot 8, which is intended to be in contact with the foundation 9 in the active position of the support leg 7.

About in the middle of the support leg 7 one end of a brase 10 is articulately connected, the other end of which is also articulately connected to a means of attachment 11. It is apparent from the lateral view of the threaded rod 4 shown in Fig. 2 that the threads have an opposite pitch direction on the outer and interior portion 4a; 4b, respectively, of the rod 4. The outer portion 4 a passes an internally threaded bushing 12, preferably of steel, which is made in an opening 13 in the holding means 2. As is most apparent from Fig. 2 the bushing 12 is provided with collars 14 a and 14 b to retain it in the opening 13. The collar 14 is then displaced to make contact with the holding means 2. Between the other collar 14 a and the holding means 2 a ring 15 of lead bronze or teflon, another ring 16, preferably of steel, and a washer 17 of spring steel are adapted.

Thus, the interior portion 4b has a pitch direction which is contrary to that of the outer portion 4a. The interior portion of the threaded rod 4 means is rotatably connected (not shown) in the holding means 2.

The construction described above operates in the following way.

The dashed position of the support leg 7 shown in Fig. 1 is its position of rest and transport. The threaded rod 4 is then completely threaded into the holding means 2. By turning the threaded rod 4 in a suitable direction, which can e.g. be carried out by placing a crank in the eye 5, the outer portion 4 a is displaced and, consequently, the whole rod 4 outwards relative to the bushing 12 , which is non-rotatably connected with the holding means 2 through the frictional engagement between the holding means 2 and the collar 14 b caused by the spring 17. Due to the turning of the rod 4 in this direction the case 6 will also be displaced relative to the rod outwards towards the eye 5. Thus, a so-called double drive of the case outwards towards the bushing 12 will be obtained. The support leg 7 will be folded down towards the foundation 9 relatively quickly.

When the disc-shaped foot 8 will get into contact with the foundation 9 the support leg 7 will actuate the treaded rod 4 with a force lengthwise of the support leg 7. The component force in the longitudinal direction of the treaded rod 4 will then displace the threaded rod 4, against the action of the spring 17, towards the centre of the caravan 3.

Due to this the frictional engagement of the collar 14 b with the holding means 2 will cease at the same time as the steel ring 16 and the lead bronze ring 15 will be pressed more hardly against the collar 14 a by the spring 17. However, the friction between the collar 14 a and the lead bronze ring 15 is so low, in spite of the increasing pressure force of the spring 17, that the whole bushing 12 with the collar 14 a rotates relative to the rings 15, 16 and the spring 17. Thus, the friction between the threads of the outer portion 4a of the rod and the interrior threads of the bushing is greater than the friction between the collar 14 a and the lead bronze ring 15. Therefore the bushing 12 is brought along when the rod 4 is rotated. There is no risk that the threaded rod 4 re-enters its position according to Fig. 2 by the actuation of the spring 17 as the force in the longitudinal direction of the support leg 7 will increase the greater the load on the support leg 17 will be.

As the collar 14 b has lost its frictional engagement with the holding means 2 the threaded rod 4 will not be displaced relative to the bushing 12 but only the case 6 will be displaced relative to the rod 4.

At this so-called simple drive a turning of one revolution of the rod 4 will bring less displacement of the disc-shaped foot 8 of the support leg 7, substantially vertically, than at the so-called double operation. It is then realized that a reduced force is required at a loaded support leg 7 to turn the threaded rod 4 if the simple drive is connected than if the double drive is connected.

During the whole period when the support leg 7 raises the caravan 3 the simple drive is connected. It has been described above how the simple drive is connected when the support leg 7 gets into contact with the foundation 9. When the support leg 7 is to be transferred from its active position to transport position the rod 4 is rotated in an opposite direction as compared with the support leg 7 being folded down.

When the support leg 7 is put up the double operation is connected directly as soon as the rod 4 is rotated in a desired direction. The friction between the inner thread in the bushing 12 and the outer portion 4 a is substantially lower when the leg 7 is put up than when it is folded down. This is due to the fact that at rotation of the rod 4 in the direction at which the support leg 7 is put up no lifting effect is obtained which increases the friction between the inner thread of the bushing 12 and the outer portion 4 a. In Fig. 3 an alternative support leg construction 1 is shown, which like the device according to Figs. 1 and 2 comprises a holding means 2' downwardly open, which is rigidly secured to the underside of the means 3', preferably a caravan, to be supported.

The constructive basic principle of the embodiment according to Figs. 3 and 4 agrees with the embodiment according to Figs. 1 and 2 described above.What differs the two embodiments is the constructive design of the bushing. The busing 12' shown in Figs. 3 and 4 is in the position shown in Fig. 4 non-rotatably connected to the holding means 2' in such a way that a nut 18 rigidly secured to the bushing 12' is retained in an opening 13' in the holding means 2' by means of springs 19 a and 19 b, which opening has a form corresponding to that of the nut 18.

As in the embodiment according to Figs. 1 and 2 the support leg 7' will actuate the threaded rod 4' with a force lengthwise of the support leg 7', when the disc-shaped foot 8' will get into contact with the foundation 9'. The component force in the longitudinal direction of the threaded rod 4' will then displace the threaded rod 4', against the action of the spring 19a, towards the centre of the caravan 3'.

Due to this the nut 18 of the bushing 12' will be moved out of the opening 13' and lose its engagement with this. There is no risk that the threaded rod 4' due to the influence of the spring 19 b will return to its position according to Fig. 4 as the force in the longitudinal direction of the support leg 7' will increase the greater the load on the support leg 7' will be.

As the nut 18 has lost its engagement with the hole 13' the threaded rod 4' will not be displaced relative to the bushing 12' but only the case 6' will be displaced relative to the rod 4'.

At this so-called simple drive a rotation of one revolution of the rod 4', as in the embodiment according to Figs. 1 and 2, will cause less displacement of the disc-shaped foot 8 of the support leg 7, substantially in vertical direction, than at the so-called couble drive.

Thus, through the support leg constructions described above support legs 7, 7 ' with disc-shaped foots 8, 8' will be rapidly folded down until a contact is obtained between the disc-shaped foot 8, 8' and the foundation 9, 9'. After this a slower raising of the support leg 7, 7' is obtained by connecting the simple drive, which is necessary in order that too great a force should not be needed to turn the threaded rod 4, -4' at a loaded support leg 7, 7'. If the support leg 7, 7' has almost taken its vertical position before it gets into contact with the foundation 9, 9' it may happen that the displacement of the threaded rod 4, 4' will not be automatical. In that case the operator can assist in connecting the simple drive by applying a force, e.g. by a crank, lengthwise of the rod 4, 4' towards the middle of the caravan 3 , 3'. An outwardly directed force can be applied to the rod 4, 4' in a corresponding way unless shifting from a simple to a double drive is effected automatically when the support leg 6, 6' loses its contact with the foundation 9, 9'.

The invention is by no means limited to the illustrative example described above but can be freely varied within the scope of the following claims.

Claims

Patent Claims

1. Support leg construction, characterized in that it comprises an externally threaded rod (4; 4') which has two portions (4a, 4b; 4a', 4b') with opposed pitch directions, one portion (4a; 4a') being received in an internally threaded bushing (12; 12-') which is detachably, non-rotatably connected with a holding means (2, 2') adapted to the supported means while the other portion (4b; 4b') supports an internally threaded element (6; 6') which is displaceably longitudinally guided in the holding means ( 2 ; 2' ) , the upper end of the support leg (7; 7') being pivotably adapted to the internally threaded element (6; 6') in active position and that a brace (10; 10') is pivotably attached with its ends to the support leg (7; 7') and to a means of attachment (11; 11') fixed relative to the supported means .

2. The support leg construction as claimed in claim 1, characterized in that the detachable, non-rotatable connection beween the bushing (12) and the holding means (2) is obtained by pressing a first collar (14b) of the bushing (12) by means of a spring (17) towards the holding means (2) for frictional engagement between the collar (14b) and the holding member.

3. The support leg construction as claimed in claim 2, characterized in that a ring (15) of a material with a low coefficient of friction is adapted between the spring (17) and a second collar (14a) of the bushing (12).

4. The support leg construction as claimed in claim 1, characterized in that the detachable, non-rotatable connection between the bushing (12') and the holding means (2') is obtained by holding a nut (18) fixed on the busing (12') by means of resilient means (19a: 19b) in position in an opening (13') in the holding means (2') corresponding to the nut (18).

5. The support leg construction as claimed in one or any of the preceding claims, characterized in that one end of the brace (10; 10') is adapted about at the centre of the support leg (7; 7') in its longitudinal direction, while the means of attachment (11; 11') of the other end of the brace (10; 10') is adapted in the vicinity of the bushing (12; 12'

6. The support leg construction as claimed in one or any of the preceding claims, characterized in that a disc-shaped foot ( 8 ; 8') is pivotably connected with the support leg

(7; 7') at its free end.

7. The support leg construction as claimed in one or any of the preceding claims , characterized in that the threaded portions (4a, 4b; 4a', 4b') with opposed pich directions each take up about half the length of the rod (4; 4').