GB2300686A

GB2300686A - Drum drive belt tensioning in a laundry drier

Info

Publication number: GB2300686A
Application number: GB9609655A
Authority: GB
Inventors: Jens Thomas; Wilfried Kluge
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-11
Filing date: 1996-05-09
Publication date: 1996-11-13
Anticipated expiration: 2016-05-09
Also published as: ITMI960763A0; DE19517372C2; DE19517372A1; GB9609655D0; ITMI960763A1; IT1283622B1; GB2300686B

Description

1 DRUM DRIVE BELT TENSIONING IN A LAUNDRY DRIER 2300686 The present

invention relates to a laundry drier and has particular reference to drum drive belt tensioning in such a drier.

In DE 75 15 298 there is disclosed a laundry drier in which a tensioning roller, which is rotatably mounted at one end of a lever which itself is mounted to be pivotable coaxially with a pinion shaft of a motor, is drawn resiliently at one side into a run of a drive belt.

Drive belts increase in length with increasing age. In order that the run at the roller side of an old belt does not touch the run at the other side, the length of a new belt and the force of the spring tensioning the roller must take this circumstance into account and be dimensioned so that sufficient play remains between the two runs to accommodate increasing length of the belt. This play must also take is into consideration that the run, which departs from the pinion in the one direction of rotation of the drum, draws the roller out of the run running off whilst moving away from the run running on, but in the other direction of rotation of the run the roller draws into the run in the case of a run running towards the pinion and the run running towards the pinion thus moves towards the run now running off. The runs must have a safety spacing from each other even in this case of drive.

These considerations lead tc the afore-mentioned parameters being such that a new belt cannot be drawn by the tensioning roller very far into the run at the roller side. As a result, however, the looping angle at the pinion, which should be as large as possible for the transmission of the greatest possible forces, is too small for a factory-new laundry drier. This looping angle is also too small when the run at the roller side runs off the pinion, because the tensioning roller in that case moves further towards the drum and widens the angle between the two runs.

This disadvantage can be eliminated by a double-roller tensioning mechanism such as described in DE 31 41 384 Al. For this purpose, a bearing bridge with two rollers disposed at both sides of the runs running on and off is so mounted at a spring-loaded lever that the rollers arranged tension both runs. The spacing of the rollers can be so that the tensioned runs between the pinion and the rollers are parallel. The looping angle at the pinion can therefore always amount to 1800 constantly, independently of age and length of the drive belt. The safety spacing between the two runs is thus maintained automatically.

However, a constant angular setting of the parallelly running runs relative to the drum axis is obtainable only by a complicated lever tensioning mechanism. However, notwithstanding such an advantage, which requires elements which are not components of conventional double-roller tensioning mechanisms, this system appears to be too expensive for commercial application in the consumer goods industry.

Nevertheless, the need for the other advantages of this known doubleroller tensioning mechanism remains without wanting to take over its expensive construction. It would thus be desirable to provide a construction which combines the advantages intrinsic to the double- roller tensioning mechanism, in respect of the geometry independent of ageing in the region of the runs running on and off, with an invariable angular setting of the runs with respect to the drum axis.

3 - According to the present invention there is provided a laundry drier with a laundry drum driven by a belt looped around its casing and with a drive motor, the pinion of which is borne in a loop of the belt in a space underneath the drum, and with a roller tensioning mechanism which tensions one of the two belt runs between the pinion and the drum by a force component acting perpendicularly on the drum, characterised in that the roller is mounted to be running freely at one end of a plunger, the other end of which is loaded by a tensioning spring, which urges 'Lhe roller into the run, and that the plunger is rectilinearly guided at a firmly clamped-in guide element to be longitudinally movable in the running direction of the opposite run. Such an arrangement can fulfill the required tasks completely. The tensioning mechanism is relatively simple, in that it essentially consists simply of a plunger, a guide element, a spring and a roller with axle.

In a particularly advantageous development, the spring is a helical compression spring clamped between the plunger and a counterbearing mounted at the guide element. The fixedly located guide element ensures a constant looping angle of 1800 at the pinion by the constant orientation parallel to the belt run running stretched. Thus, the forces which can be transmitted by the belt are independent of length changes due to, for example, ageing. The tension produced by the spring-loaded roller compensates for such tolerances by a position of the plunger which is set to a greater or lesser extent to the roller side run of the belt.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side view of a laundry drier embodying the invention; and Fig. 2 is a partly sectioned schematic side view, to an enlarged scale, of a tensioning device in drier.

Referring now to the drawings, there is shown in Fig. 1 a laundry drier comprising a laundry drum 2, which is mounted horizontally in the housing 1 and driven by a belt 3 by way of its casing. An electrical motor 4 is installed in a fixed location in the lower part of the drier and the belt 3 is looped around a drive pinion 5 or pulley of the motor by a looping angle of about 18C. In the case of rotation of the drum 2 in the direction indicated by the arrow 6, the stretched length of the belt 3 between the pinion 5 and the drum 2 is the run 7 running of,' the pinion 5. The run 8, which runs towards the pinion, of the belt 3 is displaced by a tensioning roller 9 so as to extend parallel to the run 7 as far as the roller 9 because of the looping angle X = 1800.

The tensioning roller 9 is, as indicated in Fig. 2, mounted to be freely rotatable on an axle 10 at the upper end of a plunger 11. The plunger has a longitudinal bore 12 at its lower end (shown in section) for the guidance of a pin 13 of a guide element 14, which at the lower end is connected in fixed location by means of a block 15 with for example, a pedestal 16 of the motor 4. A helical spring 19, which here is a compression spring, is clamped between a counterbearing 17 at the plunger 11 and a counterbearing 18 at the block 15. The spring urges the plunger 11 upwardly and thereby the roller 9 against the belt run 8.

Since the pin 13 of the guide element 14 extends parallelly to the belt run 7, the rectilinear guidance of the plunger 11 similarly has such a parallel orientation. However strongly the run 8 of the belt 3 bears against the roller 9, the rectilinear guidance of the plunger 11 always guides the run 8 parallelly to the run 7. Consequently, the belt Tooping angle around the pinion 5 always remains about 180. No particularly high demands are imposed on the play in the rectilinear guidance between the plunger 11 and the pin 13 if these two parts consist of synthetic materials with an appropriate coupling.

The advantage of an invariable looping angle is also present when the direction of rotation of the pinion 5 changes in order to drive the drum 2 in reverse. If the rotation of the drum is in the direction according to the arrow 6 in Fig. 1, the single tensioning roller in prior art tensioning devices would be drawn into the run 8, which is at the roller side and then running towards the pinion, increase the belt tension and in some circumstances dangerously reduce the spacing between the runs at the roller side and the other side. Conversely, in the case of the tensioning device shown in Figs. 1 and 2 a change in the belt tension, for whatever reason it comes into being, would at most lead to parallel displacement of the plunger 11, which would only shorten or lengthen the run 8 at the roller side, but not change its angular setting.

The described arrangement for belt tensioning in a laundry drier is appreciably cheaper than the two-roller tensioning mechanism known from the state of the art. This is readily evident from the comparison of the number of the components needed. Moreover, the tensioning device in a drier embodying the invention is substantially more simple to assemble because, apart from the additional effort involved in the assembly of several components in the known two-roller tensioning mechanism, the two-roller arrangement must be threaded over the pinion already looped around by the belt and brought by force into a position for insertion of the spring. By comparison, the components of the present tensioning device need only be plugged together. Af ter assembly of the tensioning device, only the belt has to be laid over the single tensioning roller with transient compression of the spring. Moreover, the belt geometry does not change with changes in length of the belt.

The invention is not restricted to the illustrated embodiment. The tensioning device can, of course, engage at the other run. For this purpose, only the geometry of the tensioning device has to be appropriately adapted. Moreover, in place of the compression spring, a tension spring can be utilised for biassing the tensioning roller with kinematic reversal by comparison with that evident from Figs. 1 and 2. In that case, the tensioning roller is not pushed, but pulled, into the run.

Claims

1. A laundry drier comprising a laundry drum, a drive belt extending around and drivingly coupled to the drum, a motor having a drive element drivingly coupled to the belt in a loop thereof below the drum, and a tensioning device tensioning one of two runs of the belt between the drum and the drive element and comprising a tensioning roller engaging said one of the belt runs, a plunger carrying the roller and resiliently biassed to urge the roller against said one of the belt runs, and fixedly located guide means rectilinearly guiding the plunger to be longitudinally movable substantially parallel to the running direction ofthe other one of the belt runs.

2. A laundry drier as claimed in claim 1, wherein the plunger is biassed by a compression spring acting between the plunger and support means at the guide means.

3. A laundry drier substantially as hereinbefore described with reference to the accompanying drawings.