Field of the invention

The invention relates to a device for locking a belt at predetermined belt tension at a machine arrangement of the kind set out in the preamble of claim 1.

Background of the Invention

At machines provided with belt drives with one or more V- belts/belts (in the description below termed belt) between a motor with or without transmission (in the description below termed engine/transmission) and a driven shaft/driven shafts (in the description below termed driven shaft) of a machine a tensioning device for tensioning the belt is used.

More particularly, the belt tension is normally adjusted by a force being applied between the engine/transmission having a driving pulley and a driven pulley of a machine, and at adequate belt tension the distance between the pulleys

relative to each other is locked by a threaded locking device, for instance.

Today, the belt tension is adjusted at most belt drives by means of threaded elements, threaded rods and adjusting nuts, for instance, which are rotated when the belt tension is increase/decrease, whereupon the setting is fixed by a locking nut. For this adjustment a tool and a measuring instrument is needed to verify the belt tension every time the belt is changed/adjusted .

A disadvantage, when threaded elements are used to obtain the belt tension, is that with this typically means at least two points of adjustments have to be adjusted. With this method, the alignment must be done with the instrument each time the belt tension is released. This is not always done in practice.

A further disadvantage is that after a period of time the threads are usually damaged due to corrosion and/or

mechanically, which means that it is not possible to

reduce/increase the tension of the belt without replacing the damaged threaded elements.

Replacement of threaded elements is an additional maintenance cost and in many cases this means a long downtime of the machine, and it is not unusual with loss of production as a result .

To minimize loss of production, it sometimes happens that the belt is replaced by tools in a non-proper way which may damage the belt and reduce the useful life of the belt. One way is to force the belt by a tool onto the pulleys by extending it too much so as to mount the belt onto the pulleys. Then there is a risk of losing the control of the belt tension and the

alignment .

Wrong belt tension and non-aligned pulleys means that the belt drive runs with unnecessarily high energy consumption and poor efficiency and the useful life of the belt is shortened.

Summary of the Invention

The purpose of the invention is to wholly or partly overcome the above-mentioned disadvantages, such as long downtime and loss of production, since with a device according to the invention it is possible to maintain the belt drive in a relatively short period of time and always with the belt tension correctly set, whereby the energy consumption and efficiency of operation is optimized and provides conditions for a normal life of the belt.

According to the invention, this object is achieved by a device for locking at least one belt at predetermined belt tension, which belt is arranged at a machine arrangement with belt drive, which machine arrangement comprises a stand having legs placed on a base, at least one driving pulley which is arranged on a drive shaft, and at least one driven pulley, which pulleys are aligned relative to each other, the legs being articulately attached to at least one of the stand or the base, characterized in that at least two of the legs comprises longitudinally adjustable tension legs, that each of the longitudinally adjustable tension leg comprises a first tension leg part having a wedge box arranged to receive a wedge having a grooved surface and a second tension leg part having a grooved surface directed towards said wedge box, that the first and second tension leg parts are adapted to lock in relation to each other by cooperation between the grooved surface of the wedge and the grooved surface of the second tension leg part when the wedge is adapted to wedge in wedge box .

Further features of the device according to the invention for locking the belt at a predetermined belt tension are indicated in the dependent claims.

Brief Description of the Drawing

The invention is described in more detail below in the form of a non-limiting example with reference to the accompanying drawing, on which

- Fig. 1 is a side view of a machine arrangement with belt drive, comprising a device according of the invention for locking at least one belt at predetermined belt tension, the machine arrangement comprising a stand having legs disposed on a base, wherein at least one driving pulley and at least one driven pulley are aligned relative to each other,

- Fig. 2 is a view obliquely from above of the machine

arrangement of Fig. 1,

- Fig. 3 is an enlarged view of the portion within the circle designated A in Fig. 2 of a tension leg included in the device according to the invention for locking the belt at a

predetermined belt tension,

- Fig. 4 is a perspective view of a wedge forming part of the device for locking a belt in Fig. 3, and

- Fig. 5 is a exploded view of a first (to the left) and a second (to the right) tension leg part included in a tension leg disposed between the stand and the base. Detailed description of preferred embodiment

At the first assembly of the device according to the invention the pulleys are aligned between the motor/transmission and the driven shaft by means of measurement equipment (not shown) . This setting is made with slack belt which means that the motor and shafts are aligned without bending stresses and deformations .

A machine arrangement 1 with belt drive according to Fig. 1 comprises a stand 3 having legs 2, said stand with its legs is placed on a base 4. In the illustrated embodiment, a

motor/transmission with a driving pulley 5 arranged on a drive shaft 5b is placed on the stand and a driven shaft 6b with driven pulley 6 is placed on the base, but it is obvious that the engine/ transmission with driving pulley 5 and the driven shaft 6b with the driven pulley 6 can be placed vice versa. The driving pulley 5 and the driven pulley 6 are aligned relative to each other. It is noted that in an embodiment not shown one or more belts 10 may run over more than two pulleys.

As shown in Fig. 2, the frame 3 in the embodiment shown is provided with four legs 2 extending between the stand and the base. The legs 2 are preferably pivotally attached to at least one of the stand or the base. The drive shaft 5b of the engine/transmission has an axis B-B with the same longitudinal direction as the longitudinal direction of the driven shaft 6b. The legs 2, which are placed perpendicular to the

longitudinal direction of said axis B-B and on the same side of the stand, are formed of longitudinally adjustable tension legs 20, each longitudinally adjustable tension leg comprising a first 21 and a second 22 tension leg part. More

particularly, a first end 21a of the first tension leg part 21 is pivotally attached to the base 4, and a first end 22a of the second tension leg part 22 is pivotally attached to the stand 3.

The first tension leg part 21 extending from the base towards the stand is provided with a wedge box 30 adapted to receive a wedge 31 having a grooved surface 32. The second tension leg part 22 extending from the stand towards the base is provided with a grooved surface 23, wherein the grooves of the surfaces 23, 32 have complementary shape. The second tension leg part 22 is slidably disposed in and through the wedge box 30.

From Fig. 3 it can be inferred that the first 21 and second 22 tension leg parts are arranged to slide along each other and in the longitudinal direction thereof for tensioning/slacking the belt 10. In order to lock the first 21 and second 22 tension leg parts relative to each other in a fixed and repeatably position, the wedge box 30 is fixedly attached to the first tension leg part 21 and directed towards said side of said tension leg part against which the second tension leg part abuts. The wedge box 30 is formed of two parallel tongues 33 extending perpendicularly to the longitudinal direction of the first tension leg part and a crosspiece 34 connecting the parallel tongues 33 so that the wedge box 31 forms a wedge enclosing means. The crosspiece 34 is angled relative to the longitudinal direction of the two tension leg parts so that the distance at a first end 35 of the crosspiece directed towards the base between said first end and the second tension leg part 22 is shorter than a distance at a second end 36 of the crosspiece directed towards the stand between said second end and the second tension leg part 22.

The first tension leg part 21 is at a second end 21b, which is directed towards the stand 3, preferably provided with a cramp 25, through which the second tension leg part 22 is, with a clearance fit, slidably disposed so as to improve the lateral stability of the tension leg 20.

Mounting and applying tension

The following describes the mounting of a belt 10 to the machine arrangement 1 and applying belt tension. The belt 10 is mounted in slacked state on the pulleys 5,6, after which a jack 40 or any other suitable tensioning device is placed in position between the stand 3 and the base 4 so as to apply a force so that the belt 10 is tensioned to the desired tension. Thereafter, the wedge 31 is placed in the wedge box 30 of the respective tension leg 20 with its grooved surface 32 toward the grooved surface 23 of the second tension leg part 22 so that said surfaces abut against each other. Then the jacket is release and the desired belt tension is obtained and is automatically locked by the wedge being wedged in the wedge box, the first 21 and second 22 tension leg parts being locked in relation to each other by the grooved wedge surface of the wedge cooperating with the grooved surface of the second tension leg part. The wedge will abut against on one hand the crosspiece 34 and on the other hand the grooved surface 23. Locking takes place through the dead weight of the machine arrangement 1 and the tension of the belt 10, or only by the tension of the belt, optionally in combination with the friction between constituent parts, i.e. the wedge/wedge box/ tension leg part with and without wedge box.

Slacking of belt tension

When slacking the tension of the belt the jack 40 is placed in position and force is applied between the stand 3 and the base 4, whereupon the inventive friction locking is neutralized, i.e. wedge action between the grooved surface 32 of the wedge 31 and the grooved surface of the second tension leg part 22 stops. More specifically, by the applied force, the both tension leg parts of respective tension leg 20 will be

displaced relative to each other, i.e. tension legs 20 are extended, whereby the wedge 30 may be removed, in the

embodiment shown lifted slightly from its wedging position. The wedge can then easily be lifted/removed and the mechanical locking is non-existing. Then, the jack 40 is lowered and the belt 10 is slacked to the position where it can be easily removed .

By the device according to the invention it is possible to obtain a repeatable accuracy of the belt tension and the alignment between the engine/transmission and the driven shaft during maintenance.

Although, in the illustrated embodiment, the longitudinally adjustable tension legs 20 is provided vertically at a machine arrangement of the type shown, it is obvious to those skilled in the art that the legs can be arranged horizontally at a different type of machine arrangement. In this case, the locking by the wedge 31 is achieved only by the tension of the belt 10, optionally in combination with the friction between constituent parts, i.e. wedge/wedge box/tension leg part with and without wedge box.

It is further apparent to those skilled in the art that the belt in the above description and figures can be a multi- groove belt or a toothed belt, for instance.