GB2101265A

GB2101265A - A V-belt drive pulley system

Info

Publication number: GB2101265A
Application number: GB08218623A
Authority: GB
Inventors: Ronald Clemens; Josef Purrer
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1981-06-29
Filing date: 1982-06-28
Publication date: 1983-01-12
Also published as: FR2508583B1; GB2101265B; FR2508583A1; DE3125545A1

Abstract

A V-belt drive pulley system has a driving pulley (1) and a driven pulley (2) which is adjustable to change the belt tension. Adjustment is carried out by means of a servo-motor (11) which acts via a spring (15) on a support member (7) carrying adjustable V-belt pulley (2) for the purpose of increasing the V-belt tension. A control element (17) controlling the servo-motor (11) and responding to the amount of spring compression is assigned to the spring (15). When the V-belt tension decreases, this control element automatically ensures retensioning of the V-belt (3). Friction wheels (18, 19) (Figure 2) are assigned to the V-belt pulleys (1, 2) coaxially to them and cause a reversal of the sense of rotation when they approach one another and when the V-belt (3) slackens. Consequently, the servo- motor (11) is reversible for the purpose of reversing the sense of rotation. Since this reversal can be effected from the driver's seat of the tractor when the drive is used in field choppers, the drive is of primary importance when the intake feed of the chopping machine is reversed by remote control. <IMAGE>

Description

SPECIFICATION A V-belt drive pulley system The invention relates to a V-belt drive pulley system with a driving V-belt pulley and a driven V-belt pulley, at least one of which is adjustable relative to the other so as to change the belt tension.

In conventional designs, it has proved necessary to ensure a substantially perfect frictional connection between the V-belt and V-belt pulleys by means of an additional third tensioning pulley which constantly stresses one side of the V-belt transversely under spring loading. As a result, however, the V-belt is subjected to an additional change of direction which leads to premature ageing of the belt.

Although it is possible to do without an expensive tensioning-pulley arrangement of this type, nevertheless routine inspection of the belt tension is then necessary so that this can be readjusted in good time in the event of elongation of the belt or signs of wear.

An object of the invention is to modify the V-belt drive pulley system of the type mentioned in the introduction, so that the best possible V-belt tension is ensured automatically, without the V-belt having to undergo an additional change of direction.

According to the invention there is provided a V-belt drive pulley system comprising a driving Vbelt pulley and a driven V-belt pulley, at least one of which is adjustable relative to the other so as to change the belt tension, a support member carrying a said V-belt pulley which is adjustable and mounted on a bearing, a spring, a servo-motor which through the spring acts on the said support member for increasing the V-belt tension when required, and a control element controlling the servo-motor and responding to the degree of spring compression present.

The drive pulley system ensures that, without an additional change of direction, there is always sufficiently great frictional contract between the V-belt and the two V-belt pulleys.

Here, the V-belt pulley can be arranged on a V-belt pulley bearing designed like a slide and permitting linear guidance. However, guidance of the V-belt pulley bearing along a circular arc has proved especially simple in terms of construction, specifically as a result of a design of the drive pulley system in which the said support member constitutes an arm pivotable about the said V-belt pulley bearing.

Even here, it is conceivable to have a construction in which the servo-motor comprises a type of slide guide which enables the pivoting arm to be stressed via the spring. However, it has been shown to be especially simple in construction and functional terms, in a further embodiment, if the said support member is stressable through a pivotable lever connecting the said support member to the servo-motor, the said lever being articulated in the servo-motor. In this case, it is especially favourable in terms of production and construction if the pivotable arm and the said lever are mounted on a common pivot pin.

To allow for the confined conditions of space in the region of the pivoting arm, caused by the V-belt pulleys of relatively large diameter which make it difficult to stress the pivotable arm directly, it has proved highly expedient if the pulley system includes a projecting member projecting transversely from the said support member, the said projecting member being engaged by the said spring, the spring being supported on the said pivotable lever.

A design which has been shown to be very advantageous from an operational point of view is one in which the servo-motor comprises an electric motor which drives a spindle and in the electric circuit of which is located a limit switch constituting the said control element. Instead of this, it is also possible to design a favourable construction which is characterised in that the servo-motor constitutes a hydraulically actuable piston/cylinder unit, in the pressure medium circuit of which is located a control valve constituting said control element.

In a further design, an expedient form of the invention concerns a drive pulley system including a pair of friction wheels arranged so as to cause a reversal of the sense of rotation of the pulleys when they approach one another and when the Vbelt consequently slackens. In this case, according to the invention, the servo-motor is reversible for the purpose of reversing the said rotational sense.

This makes it possible, as a result of a simple reversal of the sense of rotation of the servomotor, to cause the friction wheels of the pair of friction wheels to approach one another until they touch one another after an immediately preceding slackening of the V-belt. Whereas both drive pulleys rotate in the same sense when the V-belt is tensioned and therefore effective, bringing the friction wheels into operation results in a reversal of the sense of rotation of the driven drive pulley, When the drive pulley system according to this preferred form of the invention is used, this reversal of the sense of rotation is possible in a way which is especially simple in terms of control and which is economical in terms of construction.

In a further embodiment of the drive pulley system, it has been shown to be very advantageous if there is included a pole-changing switch allowing the sense of rotation to be reversed, the said pole-changing switch being located in the circuit of the servo-motor, which circuit includes a direct-current motor.

Appropriately, the break in the circuit caused by the limit switch is ensured in a simple way by connecting a diode in parallel with the limit switch constituting the said control element, the limit switch being connected after the pole-changing switch.

The reversal of the sense of rotation, possible in the way explained above, is especially important when the intake feed of chopping machines is reversed. In this case, when the drive pulley system is designed according to the invention the change-over gear, for example in trailed appliances, can be located far from the tractor seat but can nevertheless be easily operated remotely by the driver, even in an enclosed driver's cab. Since the reversing operation lasts for only a short time, the slipping of the V-belt on the V-belt pulleys which occurs at the same time can be allowed for without any disadvantages.

By way of example only, a preferred embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 shows a diagrammatic side view of a drive pulley system of the invention, Figure 2 shows a front view of the drive pulley system according to Figure 1 and Figure 3 shows a circuit diagram to illustrate the servo-motor circuit involved.

As is evident from the drawings, the V-belt drive pulley system comprises a fixedly mounted driven V-belt pulley 1 and a driving V-belt pulley 2.

A V-belt 3 is guided in a conventional way over the two V-belt pulleys. The driving V-belt pulley 2 is driven from a shaft 5 via a universal joint 4. The universal joint 4 allows the driving V-belt pulley 2 to be adjusted transversely to its axis, that is to say relative to the driven V-belt pulley 1, so that the tension of the V-belt 3 can be adjusted.

The driving V-belt pulley 2 has a V-belt pulley bearing 6 which is provided at one end of a support member in the form of a pivoting arm 7.

The arm 7 is mounted pivotably about a fixed pivot pin 8. In the vicinity of the pivot pin 8, the pivoting arm 7 is provided with a transversely projecting member 9. A lever 10, on the free end of which a servo-motor 11 engages, is also mounted pivotably on the pivot pin 8. In the example illustrated, the servo-motor consists of a directcurrent motor 1 2 which via a back gear 1 3 drives a spindle 14, the free end of which is articulated to the lever 10. Inserted between the lever 10 and the projecting member 9 is a helical spring 1 5 via which, when the spindle 14 is extended, the projecting member 9 is stressed from the servomotor 11 for the purpose of pivoting the pivoting arm 7, thereby tensioning the V-belt 3.A screw bolt 16 passes through the helical spring 1 5 and couples the lever 10 to the projecting member 9 in such a way that when the servo-motor 11 is retracted the projecting member 9 is brought with it by the lever 10.

To ensure that, when the servo-motor 11 is moved, it is switched off automatically as soon as the V-belt 3 has reached the desired tension, a control element in the form of a limit switch 1 7 is provided on the projecting member 9.

Figure 3 shows that the limit switch 1 7 is located in the circuit of the direct-current motor 12. The spring 1 5 is compressed by the servomotor 11 when the V-belt 3 is tensioned. When the compression reaches the amount corresponding to the desired V-belt tension, the limit switch 1 7 responds and opens the circuit via its switching contact. Depending on the wear or the elongation of the V-belt 3 during its use after a certain period, the pivoting arm 7 can give way under the effect of the spring 1 5. The distance between the projecting member 9 and the lever 10 also increases correspondingly, and the V-belt decreases when the V-belt tension falls below a specific value, the contact of the limit switch 1 7 closes, and the latter ensures automatic retensioning of the V-belt 3 via the servomotor 11.

Figure 2 shows most clearly that a pair of coaxial friction wheels 1 8 and 1 9 is assigned to the V-belt pulleys 1 and 2. When they approach one another and when the V-belt 3 slackens, the friction wheels 1 8 and 1 9 come into contact with one another and cause a reversal of the sense of rotation.

To control the reversal of the sense of rotation by means of the servo-motor 1 the latter is reversible for the purpose of reversing the rotational sense. Consequently, the curcuit of the direct-current motor 1 2 contains a pole-changing switch 20. As shown in Figure 3, the poles of the direct-current source 21 can be interchanged in relation to the terminals of the direct-current motor 1 2 by means of this switch 20.

So that the direct-current motor 12 can be started with the opposite sense of rotation even when the limit switch is actuated, that is to say when the limit-switch contacts are open, a diode 22 is connected in parallel with the limit switch 1 7.

Claims

1. A V-belt drive pulley system comprising a driving V-belt pulley and a driven V-belt pulley, at least one of which is adjustable relative to the other so as to change the belt tension, a support member carrying a said V-belt pulley which is adjustable and mounted on a bearing, a spring, a servo-motor which through the spring acts on the said support member for increasing the V-belt tension when required, and a control element controlling the servo-motor and responding to the degree of spring compression present.

2. Pulley system according to Claim 1, wherein the said support member constitutes an arm pivotable about the said V-belt pulley bearing.

3. Pulley system according to Claim 1 or Claim 2, wherein the said support member is stressable through a pivotable lever connecting the said support member to the servo-motor, the said lever being articulated to the servo-motor.

4. Pulley system according to Claim 3, wherein the said support member and the said pivotable lever are mounted on a common pivot pin.

5. Pulley system according to Claim 3 or Claim 4, which includes a projecting member projecting transversely from the said support member, the said projecting member being engaged by the said spring, the said spring being supported on the said pivotable lever.

6. Pulley system according to any preceding claim, wherein the servo-motor comprises an electric motor which drives a spindle and in the electric circuit of which is the said control element in the form of a limit switch.

7. Pulley system according to any one of Claims 1 to 5, wherein the servo-motor constitutes a hydraulically actuable piston/cylinder unit, in the pressure-medium circuit of which is located the said control element in the form of a control valve.

8. Pulley system according to any preceding claim, including a pair of friction wheels arranged so as to cause a reversal of the sense of rotation of the pulleys when they approach one another and the V-belt slackens, the servo-motor being reversible for the purpose of reversing the said rotational sense.

9. Pulley system according to Claim 8, including a pole-changing switch allowing the said rotational sense to be reversed, the said polechanging switch being located in the servo-motor circuit, which circuit includes a direct-current motor.

10. Pulley system according to Claim 9, wherein a diode is connected in parallel with the said control element, which is in the form of a limit switch, the limit switch being connected after the pole-changing switch.

1 A V-belt drive pulley system substantially as herein described with reference to the accompanying drawings.