GB2249152A

GB2249152A - Adjustable belt tensioning device

Info

Publication number: GB2249152A
Application number: GB9120143A
Authority: GB
Inventors: Armin Schlereth
Original assignee: SKF GmbH
Current assignee: SKF GmbH
Priority date: 1990-10-24
Filing date: 1991-09-20
Publication date: 1992-04-29
Anticipated expiration: 2011-09-20
Also published as: GB2249152B; DE4033777C2; KR920008378A; GB9120143D0; FR2668567B1; DE4033777C5; DE4042745B4; KR940009224B1; FR2668567A1; DE4033777A1

Abstract

In an adjustable tensioning device comprising an eccentric adjusting member 1 pivotally mounted about a fixing bolt 6 on a fixed support 7, an eccentric working member 3 carrying a tensioning roller 4 and pivotally mounted about the eccentric adjusting member, and a spring 8 extending between the working member 3 and a base plate 5, the eccentric adjusting member 1 is rotatable relative to the base plate 5, and the base plate 5 and the fixed support 7 have interengaging means 11 for preventing pivotal movement of the base plate with the eccentric adjusting member 1. Adjustment of the relative angular positions of the two eccentric members is facilitated by means of markings 12, 13. <IMAGE>

Description

i 2249152 A RESILIENTLY ADJUSTABLE TENSIONING DEVICE The invention relates

to a resiliently adjustable tensioning device.

A tensioning device proposed in German Patent Application P 4 015 028.3 includes an eccentric adjusting member which is pivotally disposed on a bolt and can thus be fixed on a motor block. An eccentric working member is pivotally mounted thereon. Provided between the two eccentric members is a torsion spring which provides for an active pivoting of the eccentric working member on the eccentric adjusting member. Provided on the eccentric working member is a tensioning roller which is applied by the torsion spring against a drive belt. This latter acquires the.tension ne eded for operation. As a result of the described embodiment with two eccentric members, there is a large clamping area available.

With this arrangement, by means of the eccentric adjusting member, the spring which acts against the eccentric working member is tensioned by an adjusting tool until a predetermined mean working point is set. This working point is identified by markings on both eccentric members and it indicates a spring force which provides for pre-tensioning of the drive belt-so that in long-run assembly, tolerances in the torsion spring are compensated and evenly tensioned belt transmissions are made possible.

Furthermore, the working paths during pivoting are always the'same even with long-run tolerances, both in the pre-tensioning direction and also in the reverse direction, in the case of the device proposed. The eccentric working member described is pivotably mounted on the shell of the eccentric adjusting member and carries the tensioning roller.

1 0 In the desire for convenient adjustment of the proposed tensioning device, the said markings are provided on both eccentric members. The markings simplify adjustment of a clearly defined previously established tensioning force.

Although the proposed device functions without any shortcomings, particular conditions in the event of a special occasion provide reasons for an improvement. Especially when it is necessary to anticipate tolerances in the length of the drive belt so that in series assembly the major part of the possible adjustment range has to be utilised, it is desirable to adopt further measures so that the.tension defined by the markings can be maintained constant even at an extreme adjustment of the eccentric adjusting member.

The object of the invention is to provide a tensioning device of the type mentioned at the outset in which the pivoted position of the eccentric adjusting member has no effect on the force which acts on the drive belt and in which the position of the markings in relation to the motor block is not essentially altered by the adjusting process, in order to simplify observation during assembly.

According to the present invention, there is provided a resiliently adjustable tensioning device comprising an adjusting eccentric member mounted for pivoting about a fixing bolt on a fixed support, an eccentric working member which is pivotal about the eccentric adjusting member, a spring which extends between the working member and a base plate attached to the adjusting member, and a tensioning roller rotatably mounted on the working member, adjustment of the relative a. ngular positions of the two eccentric members being facilitated by means of markings, wherein the eccentric adjusting member is rotatable relative to the base plate, and the base plate and the fixed support have interengaging means for preventing or substantially preventing a pivoting movement of the base plate with the eccentric adjusting member.

With this arrangement, the base plate and thus the end of the spring which is anchored therein remain virtually immovable even during the adjustment process. By reason of the fact that the setting of the device is completely separate from the function of the eccentric working member, always the same tensioning forces are assured in the position identified by the markings, even in series assembly and even if greatly varying adjustment positions result from considerable length tolerances in the drive belt.

Furthermore, apart from their position in relation to one another, and regarded as an observation point, the mrkings are always in the same position in relation to the motor block and can therefore be conveniently used without altering the direction of view and without the risk of being masked by other components.

The invention will be described hereinafter with reference to an example shown in the accompanying drawings in which:

Figure 1 is a longitudinal section through a tensioning device with an eccentric adjusting member and an eccentric working member; Figure 2 is a plan view of the assembly surface of the device in Figure 1; and 4.11 z Figure 3 is a partial enlargement of the region of fitment of the eccentric adjusting member.

The tensioning device shown in the drawings consists essentially of an eccentric adjusting member 1, an eccentric working member 3 disposed to pivot thereon via a plain bearing bush 2, and a clamping roller 4 rotatably mounted thereon. The eccentric adjusting member is seated on a base plate 5, is pivotable about a fixing bolt 6 and can be secured by this latter on a motor block 7. A coil spring 8 has one end 9 anchored in the eccentric working member 3 while its other end 10 is anchored on the base plate 5.

As can be seen from Figures 1 and 2, the base plate 5 is radially lengthened and has an outwardly bent projection 11 which engages the motor block. A notch 12 constitutes a marking which cooperates with a further marking in the form of a point 13 which is disposed on a radial tongue 14 on the eccentric working member 3. As shown in Figure 3, the eccentric adjusting member 1 is axially and form-lockingly connected to the base plate 5 but is freely rotatable.

When the present device is tensioned against a drive belt 15, as shown in Figure 2, the fixing bolt 6 is slightly slackened. The device is pivoted against the drive belt 15 by an adjustment tool which engages a hexagonal socket 16 in the eccentric adjusting member 1. The member 1 pivots about the fixing bolt 6 and rotates in the base plate 5 while this latter remains substantially immovable in relation to the motor block 7. In Figure 2, the position is reached in which the drive belt 15 is stretched but is not yet tensioned. In this position, the coil spring 8 is still relaxed and the markings 12, 13 are remote from one another.

Upon further pivoting of the eccentric adjusting member 1 in the direction of the arrow, a pivoting movement of the eccentric working member 3 towards the eccentric adjusting member I commences, so that the coiled spring 8 is tensioned. The eccentric adjusting member 1 is pivoted until such time as the two markings, the point 13 and the notch 12, coincides.

In the case of a relatively long drive belt 15, caused by tolerance, the eccentric adjusting.member 1 would have to be pivoted still further in the direction of the arrow. However, this has no effect on the active lever arm of the eccentric working member 3 which is always the same in all possible positions of the eccentric adjusting member 1 and when the markings 12, 13 coincide. As the base plate 5 is substantially immovable, the notch 12 and, after adjustment, also the point 13, is always at the same location in all adjusted positions.

Claims

1. A resiliently adjustable tensioning device comprising an adjusting eccentric member mounted for pivoting about a fixing bolt on a fixed support, an eccentric working member which is pivotal about the eccentric adjusting member, a spring which extends between the working member and a base plate attached to the adjusting member, and a tensioning roller rotatably mounted on the working member, adjustment of the relative angular positions of the two eccentric members being facilitated by means of markings, wherein the eccentric adjusting member is rotatable relative to the base plate, and the base plate and the fixed support have interengaging means for preventing or substantially preventing a pivoting movement of the base plate with the eccentric adjusting member.

2. A tensioning device according to Claim 1, wherein the markings are respectively provided on the base plate and on the eccentric working member in order to pre-select a specific tensioning force.

3. A tensioning device according to Claim 1 or 2, wherein the interengaging means comprise a projection on the base plate for engagement in a depression in the fixed support.

4. A tensioning device constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.