WO1989002042A1

WO1989002042A1 - Self-centering drum

Info

Publication number: WO1989002042A1
Application number: PCT/SE1987/000391
Authority: WO
Inventors: Sven-Göran ERIKSSON
Original assignee: Artic Nova
Priority date: 1986-03-06
Filing date: 1987-09-01
Publication date: 1989-03-09
Also published as: SE8601040L; SE8601040D0; SE451492B

Abstract

The present invention relates to a belt drum to counteract the lateral movement of a belt running about the drum in relation to the drum, comprising two opposite ends (2), an axle (3) extending through said ends (2) and adjustable means surrounding said axle (3). The invention is characterized in that said means consists of rollers (5) connected to the ends (2) by means of pivots (4) or through shafts (9) journalled in said ends (2), said pivots (4) or said through shafts (9) having their rotary axis in parallel with the said drum axle (3) while the rotary axis of each roller (5) deviates from the rotary axis of the pivots or of the through shafts (9) in a diametrical plane.

Description

SELF-CENTERING DRUM

The present invention relates to a belt drum for counteracting lateral displacement in relation to the drum by a belt extending round the drum,which includes two opposing end walls, a shaft passing through the end walls and adjustable means surrounding the shaft.

The usual method of guiding the belt in relation to the drum is by cambering. A cambered drum has a conically shaped shell, with the greatest diameter of the drum in the region of its central portion.

A disadvantage with conventional cambering is that an uneven stress distribution occurs in the belt. The camber causes a considerable rise in the maximum belt stress, which can have a damaging effect, above all on the central portion of the belt.

The object of the present invention is to achieve a belt drum which does not have the mentioned disadvantages, and this object is attained by the belt drum being given the distinguishing features disclosed in the claims.

In accordance with the invention cambering is not required for guiding the belt. The inventive belt drum is a simple, but effective solution to the problem of guiding the belt. Nearly all the lateral displacements of the belt are counteracted as soon as they arise, and the belt stesses occurring are distributed across the entire belt width.

An embodiment of the invention will now be described as an example, and with reference to the accompanying drawings, where Figure 1 is a schematical cross section of an inventive belt drum, Figure 2 is a schematical section along the line II-II in Figure 1, and Figure 3 is a schematical, longitudinal section of another embodiment of a belt drum in accordance with the invention.

Referring now to Figures 1 and 2, the drum 1 includes two end walls 2, which are suitably unrotatably mounted on a shaft" 3 passing through the end walls. The shaft 3 is mounted in suitable bearings 6, which are in turn carried by supports 7 resting on a substructure 8. It is also conceivable to have the shaft 3 fixed and the end walls rotatably mounted on the shaft. The end walls 2 are provided with through holes at uniform circumferential spacing, pins 4 being rotatably mounted in the holes parallel to the shaft 3.

In the axial direction of the drum 1 , the pins 4 carry preferably tubular cylinders or rolls 5, the central axes of these rolls deviating from those of the pins 4 in a diametral plane, i.e. the rolls 5 are eccentric to the pins 4. This eccentricity can vary, depending on how large a deviation is permitted between the central axes of pins and rollers. A plurality of rolls, here eight, serve as the cylindrical shell of the drum. The number of rolls may be greater, although it must be ensured that the rolls can not come into mutual contact for maximum eccentricity.

In Figure 1, a first position of two rolls is shown by full lines, and a second position for these rolls is shown in dashed lines. The rolls have been rotated 180° from the first position to obtain the second position. Only two rolls are shown in the Figure for the sake of clarity.

In Figure 3 there is illustrated another embodiment of the invention. Here the rolls 5 are carried eccentrically by through shafts 9 rotatably mounted in the end walls 2 and parallel to the shaft 3.

In the embodiments decribed above, the rolls 5 are unrotatably mounted on pins 4 or shafts 9, but it is also conceivable to have the rolls 5 rotatably mounted in fixed pins 4 or shafts 9.

The function of the belt drum 1 will now be explained in the following. In the first position of the rolls illustrated in Figure 1, a belt (unillustrated) engaging against the rolls has been displaced to the left, with the result that the rolls 5 have been inclined in a radial direction relative the shaft 3. In this position of the belt, the lefthand end of the drum has a less diameter than its righthand end. AS it is a well-known fact that with cambered rolls the belt strives to move laterally towards the part of the roll that has the greatest diameter, it will be understood that the belt will move to the right in Figure 1. When the belt has centered on the rolls 5, no force acting to incline them acts on them, and they assume their normal positions, with their generatrices parallel to the shaft 3.

In the second position of the rolls 5 illustrated in Figure 1, a belt has been displaced towards the righthand end wall 2. In a corresponding way to the first position the belt will move to the left in the Figure until it centers on the rolls 5, which then assume an attitude with their generatices parallel to the shaft 3.

The function decribed above assumes that the rolls 5 not engaging the belt have taken up the same position as the rolls engaging against the belt, since the drum 1 revolves the whole time at relatively high speed, and no repositioning of the rolls takes place during the time from when the rolls lose contact with the belt to when they once again come into contact with it.

The invention is in no way restricted to the embodiments described above, and can be freely varied within the scope of the following claim.

Claims

CLAIM

Belt drum for counteracting lateral displacement in relation to the drum by a belt extending round the drum, which includes two opposing end walls (2), a shaft (3) passing through the end walls and adjustable means surrounding the shaft (3), characterised in that the means comprise rolls (5) connected to the end walls (2) with the aid of pins (4) or through shafts (9) mounted in the end walls, the rotational axes of the pins (4) or through shafts (9) being parallel to the shaft (3), whereas the rotational axes of the rolls (5) deviate from the rotational axes of the pins (4) or the through shafts (9) in a diametral plane.