EP0709515A1 - Driving device for domestic laundry drier - Google Patents

Abstract

The drive unit is for a household laundry dryer with a horizontally rotating laundry drum, which can be driven in one direction or in reverse by a back gear pinion. The pinion (10) is connected to a large belt pulley (9) in a torsion-resistant manner and mounted on a joint axis (8). The pinion (10), in turn, is driven via a back gear belt by the motor pinion (19) of an electric drive motor. The joint axis (8) is guided in a way that permits it to move in an axially parallel manner and is spring loaded in relation to the motor pinion (19) axis and to the drum axis (5).

Description

The invention relates to a drive device for a household tumble dryer with an at least approximately horizontally rotatably mounted laundry drum, which can be driven in one direction or reversibly by a countershaft sprocket by means of a drive belt wrapped around its drum jacket, which is connected in a rotationally fixed manner to a large pulley and is mounted on a common axis and in turn is driven by the motor pinion of an electric drive motor via a countershaft belt.

Such a drive device is known from US Pat. No. 3,382,587. The distances between the axles of the motor pinion and the countershaft as well as between this and the washing drum are fixed. Therefore, the countershaft belt and the drum drive belt must be tensioned by means of an adjusting device during the assembly of the drive device; because the installation dimensions and the length dimensions of the belts are subject to tolerance. For the purpose of maintaining the belt tension required for the required power transmission, the tolerances must be adjusted be balanced. In addition, the belts are subject to permanent elongation over a longer service life, which at fixed center distances reduces the belt tension and thus reduces the transmissible forces and ultimately destroys the belt.

To avoid such differences in length, tensioning rollers have already been used (DE-OS 22 07 372), which are loaded by means of one or more spring-loaded levers on the respective rear of the belt. Apart from such an additional effort and the flexing work that arises in the opposite direction to the pinion encirclement, most of the tensioning pulleys that are not too complicated already have an undesirable property: they lead to the drive pinion or tensioning pulley running onto the incoming belt drum and thereby reduce the transferable forces.

The invention has for its object to avoid the above disadvantages in a drive device defined at the outset and to provide an adjustment-free construction which does not have to be retightened without loss of the transferable forces even after a longer service life of the drive belt.

According to the invention, this object is achieved in that the common axis is guided in an axially parallel manner and is spring-loaded both in relation to the axis of the motor pinion and in relation to the drum axis in the sense of increasing the distance. Such a design of the drive device automatically compensates for tolerances in the system, as well as additional length change tolerances for the belts in the advanced use of the clothes dryer out. In this case, an operation which is otherwise provided for during assembly can be omitted, as a result of which the center distances for the drive belts had to be particularly adjusted. Due to the insensitivity of the drive device according to the invention to long-term length change tolerances of the belts, the number of service calls that are otherwise necessary for retensioning the belts is also eliminated.

According to an advantageous embodiment of the invention, the common axis is located near the free end of a lever with one arm. The combination of the mobility of the common axis in both of the above-mentioned relationships on a single-arm lever simplifies the design compared to known proposals and additionally gains security in compliance with the transmission forces.

To maintain a defined tensioning force in the countershaft belt, a further development of the invention is advantageous in which, in the correct operating situation, the pivot point of the lever and the common axis together with the pivot point of the motor pinion lie at least approximately on a straight line.

The simplicity of the construction with the arrangement on a single-arm lever is particularly evident in the fact that the spring load in relation to the drum axis is represented by a tension spring clamped between a fixed housing part and the extreme free end of the lever.

The simplicity of the design in the spring loading of the countershaft belt can be seen in two alternatives the spring load in relation to the axis of the motor pinion is represented once by a compression spring clamped between the pivot point of the lever and the lever arm and on the other hand by a compression spring clamped between the pivot point of the large pulley and a counterpart fixed to the lever arm. This makes the construction of the lever arm complicated. However, since this consists of an aluminum die-cast part, the complexity is limited to the one-time production of the casting tool.

A single additional component is required in a development of the invention designed in such a way that the fulcrum for the large pulley and the countershaft sprocket is attached to a slide guided at least approximately in the direction of the axis of the motor pinion on the lever.

Advantageously, the slide has a chamber with a spring support for the compression spring, which is located at a distance from the fulcrum and whose fixed counterpart on the lever is close to an elongated hole in the guide of the slide for penetrating the lever with the countershaft.

Fig. 1

eine erfindungsgemäße Antriebseinrichtung mit einem einseitig gelagerten Hebel, der an seinem Lagerpunkt längsverschieblich unterbrochen ist und mit einer Druckfeder zum Spannen des Vorgelege-Riemens versehen ist,

Fig. 2

eine das Vorgelege gemäß Fig. 1 betreffende Einzelheit zur Erläuterung der Kraftverhältnisse an der gemeinsamen Achse und

Fig. 3

eine anders als in Fig. 1 und 2 ausgebildete Antriebseinrichtung, bei der die gemeinsame Achse auf einem im Hebel geführten und federbelasteten Schlitten angeordnet ist.

The invention is explained below using two exemplary embodiments shown in the drawing. Show it

Fig. 1

a drive device according to the invention with a lever mounted on one side, which is displaceably interrupted at its bearing point and is provided with a compression spring for tensioning the countershaft belt,

Fig. 2

a detail relating to the transmission according to FIG. 1 to explain the force relationships on the common axis and

Fig. 3

a differently than in Fig. 1 and 2 designed drive device, in which the common axis is arranged on a guided in the lever and spring-loaded carriage.

The base 2 of a floor assembly is installed in the lower area of the housing 1 of a tumble dryer. The drive motor 3 for the laundry drum 4 rests therein, which in turn is rotatably mounted on the axis 5 on a housing component (not shown) which is arranged at a distance from the base 2. In the fulcrum 6 of the base part 2, a lever 7 is also supported with one arm, in the operating position of which the axes of the fulcrum 6 and the drive motor 3 lie on a straight line 22 with the common axis 8 of the large pulley 9 and the countershaft sprocket 10. The common axis 8 is arranged in the vicinity of the free end 11 of the single-arm lever 7. At the free end 11 of the lever 7 engages a tension spring 12, the other end of which is hooked into a hook 13 of the base part 2. The countershaft sprocket 10 is pulled into the drive belt 14 for the laundry drum 4 by this spring 12. As a result, the belt 14 remains under tension without any adjustment being required. The drum cross-sectional circular area 15 represents the drum pulley which is wrapped by the belt 14 and which is automatically in the same plane as the countershaft sprocket 10.

The lever 7 is stretched by a compression spring 16 which is guided in a double-walled sleeve 17 so that the large pulley 9 has its lay belt 18 between them and the motor pinion 19 stretches. As a result, the countershaft belt 18 remains constantly tensioned without adjustment.

The tension of the belts 14 and 18 is determined in part by the geometry of the countershaft parts and essentially by the tensioning forces of the springs 12 and 16.

To explain the force relationships, the feed area from FIG. 1 is shown enlarged in FIG. 2. The rotational forces required for transmission from the motor to the large pulley 9 and from the countershaft sprocket 10 to the casing of the drum 4 determine the tension required for the belts 18 and 14. The tension for belt 18 is represented by vector F18 and the tension for belt 14 is represented by vector F14. From these two known quantities and from the distance LT from the fulcrum 6 of the lever 7 to the fictitious point of application 20 of the force F12 of the tension spring 12 on the straight line 22 and the distance LV from the fulcrum 6 to the point of application of the tension of the belt 14 in the common axis 8 of the The required spring forces can be calculated as follows:

Darin ist α der Winkel zwischen der Rienenspannung F14 und der Normalkraft F4 auf die Gerade 22.The tensioning force F14 of the belt 14 acts on the axis 8 and lies precisely on the connecting line 21 between the axis 8 and the axis 5 of the drum 4. If this force vector F14 is broken down into the normal forces F1 and F4, then another vector F1 pointing in the direction of the pivot point 6 of the countershaft lever can be determined. This vector results from the following formula: $$\mathit{\text{<figure-callout id="1" label="F" filenames="imgf0001.png" state="{{state}}">F</figure-callout>}}\text{1 =}\mathit{\text{<figure-callout id="14" label="F" filenames="imgf0001.png,imgf0002.png" state="{{state}}">F</figure-callout>}}\text{14 × sinα.}$$

Therein, α is the angle between the line tension F14 and the normal force F4 on the straight line 22.

Da F12 nicht bekannt ist, muß auch diese Kraft zunächst errechnet werden. Sie ergibt sich aus der Formel $$\text{F12 =}\frac{\mathit{\text{F}}\text{2}}{\text{cosβ}}\text{.}$$

Auch F2 ist nicht bekannt, aber durch folgende Formel errechenbar: $$\text{F2 = F4 ×}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{;}$$

denn da die am Ende des Hebels 7 angreifenden Kräfte im Gleichgewicht stehen müssen, muß das Drehmoment an der Achse 8 über den Hebelarm LV gleich sein mit dem Drehmoment am Angriffspunkt 20 über dem Hebelarm LT. Daraus und aus (2) bis (4) ergibt sich für die Kraft F19 folgende Formel $$\text{F19 =}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{×}\mathit{\text{F}}\text{14 ×cosα ×}\frac{\text{sinβ}}{\text{cosβ}}$$

oder $$\text{F19 =}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{×}\mathit{\text{F}}\text{14 ×cosα ×tan β .}$$

Schließlich lassen sich die gegebene Riemenspannkraft F18 und die gefundenen Kraftkomponenten F1 und F19 gemäß (1) und (6) zu einer gemeinsamen Kraftkomponente addieren, der sich die durch die Druckfeder 16 des Hebels 7 aufzubringende Kraft F16 gleichgewichtig entgegenstellen muß: $$\text{F16 = F18 + F1 + F19 .}$$

Fig. 3 zeigt ein anderes Ausführungsbeispiel für eine erfindungsgemäße Antriebseinrichtung. Darin ist nicht der einarmig gelagerte Hebel 23 an seinem Drehpunkt 6 selbst federnd gelagert; der Hebel 23 ist in sich starr. Er hat aber in der Nähe seines Hebelendes 11 eine Kulissenführung 24, dem Mittelachse in Betriebsstellung des Hebels 23 in etwa auf die Achse des Motors 3 zeigt. Die Kulissenführung 24 nimmt einen Schlitten 25 auf, an dem das Lager für die große Riemenscheibe 9 und für das Vorgelege-Ritzel 10 befestigt ist. Mit diesem Schlitten 25 kann das Vorgelege-Lager daher in Richtung der Mittelachse der Kulissenführung 24 hin- und herbewegt werden. Der Schlitten 25 hat an seinem aus dem Hebel 23 ragenden Ende 26 eine Gegenlagerbrücke 27 für eine Druckfeder 28, die sich an einer Lagerplatte 29 des Hebels 23 abstützt. Die Druckfeder 28 zieht daher die große Riemenscheibe 9 über das Vorgelege-Lager und den Schlitten 25 in den Riemen 18. Gleichzeitig wird durch die Zugfeder 12 am Ende 11 des Hebels 23 das Vorgelege-Ritzel 10 in den Riemen 14 gezogen.The spring force F12 is broken down into the vector F2, which is the corresponding normal force on the straight line 22 at the point of application 20 of the point of intersection of the imaginary axis of the spring 12 and the straight line 22, and the vector F19, which ultimately results from the existing triangle of forces at the angle can be calculated. In it $$\text{F19 = F12 × sin β.}$$

Since F12 is not known, this force must also be calculated first. It results from the formula $$\text{F12 =}\frac{\mathit{\text{F}}\text{2nd}}{\text{cosβ}}\text{.}$$

F2 is also unknown, but can be calculated using the following formula: $$\text{F2 = F4 ×}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{;}$$

since the forces acting on the end of the lever 7 must be in balance, the torque on the axis 8 via the lever arm LV must be the same as the torque on the point of application 20 above the lever arm LT. From this and from (2) to (4), the following formula results for the force F19 $$\text{F19 =}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{×}\mathit{\text{<figure-callout id="14" label="F" filenames="imgf0001.png,imgf0002.png" state="{{state}}">F</figure-callout>}}\text{14 × cosα ×}\frac{\text{are}}{\text{cosβ}}$$

or $$\text{F19 =}\frac{\mathit{\text{LV}}}{\mathit{\text{LT}}}\text{×}\mathit{\text{<figure-callout id="14" label="F" filenames="imgf0001.png,imgf0002.png" state="{{state}}">F</figure-callout>}}\text{14 × cosα × tan β.}$$

Finally, the given belt tensioning force F18 and the found force components F1 and F19 according to (1) and (6) can be added to a common force component which must be counterbalanced by the force F16 to be applied by the compression spring 16 of the lever 7: $$\text{F16 = F18 + F1 + F19.}$$

Fig. 3 shows another embodiment for a drive device according to the invention. Therein, the one-armed lever 23 is not resiliently mounted at its pivot point 6; the lever 23 is rigid in itself. However, in the vicinity of its lever end 11 it has a link guide 24, which shows the central axis in the operating position of the lever 23 approximately on the axis of the motor 3. The link guide 24 receives a carriage 25 on which the bearing for the large pulley 9 and for the countershaft sprocket 10 is fastened. With this slide 25, the countershaft bearing can therefore be moved back and forth in the direction of the central axis of the link guide 24. The carriage 25 has at its end 26 protruding from the lever 23 a counter bearing bridge 27 for a compression spring 28 which is supported on a bearing plate 29 of the lever 23. The compression spring 28 therefore pulls the large pulley 9 over the countershaft bearing and the slide 25 into the belt 18. At the same time, the countershaft sprocket 10 is pulled into the belt 14 by the tension spring 12 at the end 11 of the lever 23.

Due to completely different dimensions compared to the exemplary embodiment according to FIGS. 1 and 2, the result shown in FIG. 3 illustrated embodiment other spring tensions. The basic structure of the drive device according to the invention and the calculation process for the spring forces are, however, of the same type.

Claims (8)

Drive device for a household tumble dryer with an at least approximately horizontally rotatably mounted laundry drum, which can be driven in one direction or reversibly by a countershaft sprocket by means of a drive belt wrapped around its drum jacket, which is rotatably connected to a large pulley and mounted on a common axis and in turn is driven by a countershaft belt from the motor pinion of an electric drive motor, characterized in that the common axis (8) is guided so as to be axially parallel and both in relation to the axis of the motor pinion (19) and in relation to the drum axis (5) is spring-loaded in the sense of increasing the distance. Drive device according to claim 1, characterized in that the common axis (8) is located in the vicinity of the free end (11) of a lever (7, 23) with one arm. Drive device according to claim 2, characterized in that in the correct operating situation the pivot point (6) of the lever (7, 23) and the common axis (8) together with the pivot point of the motor pinion (19) at least approximately on a straight line (22) lie. Drive device according to claim 2 or 3, characterized in that the spring load in relation to the drum axis (5) is clamped by a between a fixed housing part (2, 13) and the outermost free end (11) of the lever (7, 23) Tension spring (12) is shown. Drive device according to one of claims 2 to 4, characterized in that the spring loading in relation to the axis of the motor pinion (19) by a compression spring clamped between the pivot point (6) of the lever (7) and the lever arm (7, 17) (16) is shown. Drive device according to one of Claims 2 to 4, characterized in that the spring loading in relation to the axis of the motor pinion (19) is provided by a bearing plate (fixed to the lever arm (23) between the pivot point (8) of the large pulley (9) and 29) clamped compression spring (28) is shown. Drive device according to claim 6, characterized in that the fulcrum (8) for the large pulley (9) and the countershaft sprocket (10) is guided on the lever (23) at least approximately in the direction of the axis of the motor pinion (19) Carriage (25) is attached. Drive device according to claim 7, characterized in that the slide (25) has a chamber-shaped end (26) with a counter-bearing bridge (27) for the compression spring (28) which is mounted at a distance from the pivot point (8) and whose fixed bearing plate (29) is on the Lever (23) is located near an elongated hole (30) in the guide (24) of the slide (25) for the penetration of the lever (23) with the countershaft.

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