Field of the Invention

This invention relates to an arrangement in a sup- porting leg of the type that is mountable on a vehicle and comprises an upper member pivotable about an articu¬ lation between an inoperative, swung-up position and an operative, swung-down position, and a lower member extend¬ ible from said upper member and adapted to be applied against the ground when the supporting leg is in the swung-down position. In actual practice, the upper leg member consists of a hollow or tubular section in which a lower leg member in the form of a smaller hollow or tubular section is telescopically movable by means of a hydraulic cylinder incorporated in the upper leg member. Normally, the lower leg member ends in a supporting foot. Background of the Invention

Usually, supporting legs of this type are mounted at the free end of a supporting beam, which is telesco- pically movable in relation to the vehicle frame, and occupy, when not in operation, a position in which they usually, albeit not necessarily, are directed vertically upwards from the free end of the supporting beam. From the inoperative position, the supporting legs are pivoted downwards through 180° to a position in which they are directed vertically downwards from the beam and in which the lower member can be extended from the upper member and applied with the supporting foot against the ground. In some constructions, the supporting leg is pivoted upwards but 60-90° from the operative to the inoperative position. Prior-art supporting legs have been shifted between the inoperative and the operative position either entirely by hand or partly by hand, using a hoist which facilitates raising the leg and counteracts uncontrolled movements of the supporting leg when swung down to the operative posi¬ tion. Since the supporting legs are fairly heavy and may weigh up to 100-150 kg, there is a considerable risk of

accidents happening when swinging the supporting leg up or down, especially when this operation is entirely manual, but also when a hoist is used as auxiliary means. Moreover, it is difficult to incorporate known hoists in the supporting beam of the leg. Summary of the Invention

This invention aims at obviating the above inconve¬ niences of known supporting leg constructions and provid¬ ing an arrangement enabling simple and reliable operation of the supporting leg. Thus, a basic object of the inven¬ tion is to provide an arrangement which is easy to mount on the supporting leg and which rapidly and reliably can pivot the supporting leg from its operative, swung-down position to its inoperative, swung-up position. Another object of the invention is to provide an arrangement which also enables the supporting leg to be swung down in a simple, reliable and controlled manner. In an additional aspect, the invention also concerns an operating device utilising, for its operation, the same hydraulic system that is required for displacing the lower leg member in relation to the upper one.

According to the invention, at least the basic object is achieved by an arrangement having the features recited in the characterising clause of appended claim 1. Advanta- geous embodiments of the invention are defined in appended claims 2-7. Brief Description of the Drawings

In the drawings, FIG. 1 is a schematic side view of an inventive support- ing leg when swung down;

FIG. 2 is a front view of the supporting leg when swung down; FIG. 3 is a similar front view of the supporting leg when swung up; and FIG. 4 is a simplified diagram illustrating a hydraulic system connected to the supporting leg.

Description of a Preferred Embodiment

In Figs 1-3, reference sign 1 generally designates a supporting leg which in known manner comprises an upper member 2 and a lower member 3 having a supporting foot 4 at its free lower end. In actual practice, the two mem¬ bers 2, 3 suitably consist of hollow or tubular sections, of which the former is larger than the latter. A hydrau¬ lic cylinder 5 is incorporated in the upper leg member 2 and enables the lower leg member 3 to be telescopically extended from and retracted into the upper leg member 2. In its entirety, the supporting leg 1 is mounted on the free end of a supporting beam 6, more precisely by means of an articulation 7 permitting the supporting leg to pivot in relation to the beam 6 between an operative position in which it is swung down (Fig. 2) and an inope¬ rative position in which it is swung up (Fig. 3). The sup¬ porting beam 6 is in turn mounted on the frame of a vehi¬ cle (not shown) at right angles to the longitudinal extent of the vehicle, the beam being telescopically displaceable in relation to the frame, so that the supporting leg can be removed from an inoperative position close to one side of the vehicle to an operative position remote therefrom. At the free end, the supporting beam 6 is equipped with a vertical plate 8. In order to lock the supporting leg in either of the two positions illustrated in Figs 2 and 3, there is pro¬ vided a locking mechanism in the form of locking pin 10 which is incorporated in a sleeve 9 and which can be brought into engagement with one or the other of two holes 11, 12 provided in the plate 8 and positioned on diametri¬ cally opposite sides of the centre of the pivotal articu¬ lation 7 equidistantly therefrom.

A power mechanism, generally designated 13, of vari¬ able length is arranged on the upper leg member 2. In the preferred embodiment illustrated, the power mechanism 13 is a hydraulic cylinder comprising a cylinder 14 and a piston rod 15 axially movable in relation thereto. In this

embodiment, the cylinder 14 is attached to the upper leg member 2 by a bracket 16. At its free end 15\', the pis¬ ton rod 15 is connected to one end of a flexible trac¬ tion means 17, whose opposite end is connected to an attachment 18 (see Fig. 2) provided on the plate 8 and forming a fixed point of attachment for the traction means. For instance, the traction means 17 may be a chain, a line, a wire, a rope, a band or suchlike. In the area between its two opposite points of attachment 15\', 18, the traction means 17 is passed round a runner 19 which here consists of a drum or a sleeve forming part of the arti¬ culation 7. In this embodiment, the drum 19 has a fairly large diameter, as compared with the thickness of the sup¬ porting leg, and the traction means 17 will thus move in a substantially semicircular path at a relatively ^" large dis¬ tance from the centre of the articulation 7. In addition, that run of the traction means which extends between the drum 19 and the point of attachment 15\' is here passed round a guide pulley 20 mounted approximately in line with one side of the supporting leg. —

Although it is preferred, in this embodiment, to use the drum 19 forming part of the articulation 7 as runner for the traction means 17, other alternatives are of course conceivable. Thus, the runner might be composed of one or more guide pins or guide pulleys spaced apart from the centre of the articulation 7.

When comparing Figs 2 and 3, it is evident that the hydraulic cylinder unit or power mechanism 13 is of maxi¬ mum length when the supporting leg is swung down, the pis- ton rod 15 then extending maximally from the cylinder 14. By shortening the mechanism 13, i.e. retracting the piston rod 15 into the cylinder 14, the supporting leg will be pivoted through 180° about the articulation 7 from the swung-down position to the vertical swung-up position (shown in Fig. 3).

Fig. 4 schematically illustrates the cooperation of the two hydraulic cylinders 5, 13 with a hydraulic system including two main lines 21, 22 which, by a directional control valve 23, are alternately connectible to a pump 24 and a tank 25. The hydraulic cylinder 5 for displacing the lower leg member 3 in relation to the upper leg member 2 will hereinafter be referred to as the main cylinder, while the hydraulic cylinder 13 for pivoting the support¬ ing leg will be referred to as the secondary cylinder. The line 22 is connected to the piston side of the main cylin¬ der 5, and the line 21 is connected to the piston-rod side thereof. When hydraulic oil is pumped through the line 22 to the piston side of the cylinder (the line 21 then serves as return line), the upper leg member 3 will thus be extended from the upper leg member so as to apply the supporting foot 4 against the ground. Conversely, the lower leg member 3 is retracted into the upper member when oil is pumped through the line 21 to the piston-rod side of the cylinder (the line 22 then serves as return line). As described thus far, the hydraulic system is of conven¬ tional type.

According to the invention, the secondary cylinder 13 is connected to the line 22 by a first branch line 26 including a first throttle or constant-flow valve 27. A second branch line 28, including a second throttle or con¬ stant-flow valve 29, extends between the first branch line 26 and the line 21. The valve 29 should in practice have twice the rate of flow of the valve 27. For instance, the valve 29 may have a rate of 6 1/min, while the valve 27 has a rate of 3 1/min.

Function of the Inventive Arrangement

The supporting leg is swung down from the inoperative position shown in Fig. 3 in the following manner. First, the supporting beam 6 is extended from its parking site close to the vehicle frame, to a position remote there¬ from, whereupon the locking pin 10 is released from the hole 11. Then, a force in the direction indicated by the

arrow A in Fig. 3 is applied by hand to the supporting leg in order to pivot it clockwise about the articulation 7. The point of attachment 15\' of the traction means 7 will then begin to move along a circular-arc-shaped path about the articulation 7, but since the length of the traction means is constant, the piston rod 15 will be drawn out of the associated cylinder 14. As a result, the cylinder 14 is evacuated of hydraulic oil, which is conducted through the branch line 26 to the line 22 in a flow throttled by the valve 27. To be more specific, throttling of the flow ensures that the supporting leg cannot fall in uncontrol¬ led manner under its own weight down towards the operative position, but is forced to move at an even angular velo¬ city restricted by the rate of flow (say 3 1/min) of the throttle valve 27. In other words, the supporting leg is prevented from falling rapidly and in uncontrolled manner. When the supporting leg, having pivoted through 180°, comes to occupy the position shown in Fig. 2, the locking pin 10 is inserted in the hole 12, and is there mechani- cally locked to prevent any further pivotal movement.

Regardless of the setting of the directional control valve 23, only the main cylinder 5 will thereafter be affected by the hydraulic system in conventional manner, either such that the lower leg member 3 is extended from the upper leg member, or vice versa. When the main cylin¬ der is shortened, i.e. the lower leg member is moved into the upper leg member 2, a pressure will certainly build up in the secondary cylinder 13, but this will not cause the supporting leg to pivot, being as it is locked by means of the locking pin 10.

In the inverse operation, i.e. when the supporting leg is pivoted from the operative position shown in Fig. 2 to the inoperative position shown in Fig. 3, the locking pin 10 is released, and the directional control valve is so set that the lower leg member 3 is retracted into the upper leg member. Once the lower leg member has reached its inner end position in the upper leg member, continued

pumping of oil into the main line 21 results in that the flow of oil is switched to the branch line 28. After the constant-flow valve 29, permitting a rate of flow of say 6 1/min, the flow is divided at the junction 30 into two part flows, one to the secondary cylinder 13 and one to the constant-flow valve 27 whence it is finally recycled to the tank via the line 22. The part flow to the secon¬ dary cylinder 13 causes this cylinder to be shortened, meaning that the supporting leg 1 is forced to pivot anti- clockwise about the articulation 7 back to its inoperative position, in which it is directed upwards and is again locked by means of the pin 10. The valve 29 having twice the rate of flow of the valve 27, the supporting leg 1 will, when raised, move at the same angular velocity as when it was swung down. Finally, the supporting beam 6 is again moved close to the vehicle frame.

The advantages of the invention are obvious. Both when swung down and when swung up, the supporting leg is pivoted at an even and uniform angular velocity, the lifting operation requiring no manual force at all, while the lowering operation requires but a slight manual pres¬ sure before the supporting leg can be gently swung down to the operative position under its own weight. Conceivable Modifications of the Invention It goes without saying that the invention is by no means restricted to the embodiment described above and shown in the drawings. Thus, other power mechanisms than a hydraulic cylinder can be used for moving the support¬ ing leg between its two end positions, e.g. a screw-nut mechanism. Further, the guide means for the traction means can be modified in many ways, e.g. by using one or more spacers about which the traction means can be passed, regardless of whether these are centred with respect to the centre of rotation of the supporting leg or not. It should also be pointed out that the invention is applic¬ able to supporting legs that are pivotable through other angles than 180° between the operative and the inoperative position, e.g. 90° or even less.