WO2011032246A1

WO2011032246A1 - Passive device for reducing speed

Info

Publication number: WO2011032246A1
Application number: PCT/BR2010/000308
Authority: WO
Inventors: Sergio Roberto Berteloni; Omar Rachid Murad; Emmanuel Felipe Gonzaga
Original assignee: Whirpool S.A.
Priority date: 2009-09-15
Filing date: 2010-09-15
Publication date: 2011-03-24
Also published as: BRPI0903513B1; WO2011032246A8; BRPI0903513A2; AR078376A1

Abstract

The present invention refers to a passive device for reducing speed (11) of a rotary shaft of a machine comprising at least a rotary container attached to said rotary shaft, where speed control is effected by a geometry proposed for said device. Thus, the device of the present invention comprises a body of elastically deformable material (12) having a inner edge surrounding at least partially said shaft, wherein the inner edge comprises a plurality of grooves (13) angled in the direction of rotation of said shaft (4), and a plurality of deformable teeth (14), each deformable tooth (14) being formed between two consecutive grooves (13).

Description

PASSIVE DEVICE FOR REDUCING SPEED

Field of the Invention

The present invention refers to a speed reduction device for reducing rotation speed of washing machine, dryer or centrifuge shafts, and, more specifically, a speed reduction device functioning in a passive mode with no need for electronic or electromechanical speed control devices.

Background of the Invention

In brief, washing machines or clothes dryers comprise a basket or a tank mounted within a housing, wherein it rotates around a shaft. Generally, time and speed of rotational movement are preprogrammed and depend on the function selected by users and the stage at which machines are.

In some cases, rotational movement should be interrupted at the moment a non-programmed situation occurs, for example, door opened by the user. In these cases, braking means capable of stopping a rotational movement should be provided in view of said non-programmed occurrence.

Known braking solutions involve braking systems assisted by electrical and/or mechanical driving. Door blockers cause a delay in opening the door until a shaft reduces its speed, or electronic control means controlling speed.

These systems already known from the state of the art are very expensive and have a complex construction so that there is still a need for a low-cost speed reduction device of simple construction and high reliability.

Objects of the Invention

In view of the foregoing, one object of the present invention is to provide a low- cost speed reduction device of simple construction and high reliability, whose device operates in a passive mode.

Another object of the present invention is to provide a speed reduction device, wherein speed control is effected by a geometry proposed for said device. Summary of the Invention

The objects of the present invention are accomplished by means of a passive device for reducing the rotary shaft speed of a machine comprising at least a rotary container attached to said rotary shaft (e.g., a clothes washing machine, a clothes dryer or a centrifuge), wherein said device comprises a body of an eiastically deformable material having an inner edge surrounding at least partially said shaft, the inner edge comprising a plurality of grooves angled in the shaft rotation direction, and a plurality of deformable teeth, wherein each deformable tooth is formed between two consecutive grooves.

In a preferred embodiment of the present invention, an eiastically deformable body is substantially cylindrical shaped, and has a recess forming a projection on the outer edge of said body.

Further, in the preferred embodiment, said recess is housed in a web intended for ensuring the device structural strength, wherein said web has an L-shaped cross- section, in which one of the legs projects radially towards the body core, housing inside a cavity formed in said body, and the other leg extends in axial direction of the body.

Such a device may further comprise a spring partially embedded in the body.

Brief Description of Drawings

Figures show:

Figure 1 illustrates a cut view of a washing machine structure incorporating a speed reduction device of the present invention;

Figure 2 illustrates a detailed view of an installation local of a speed reduction device of the present invention;

Figure 3 illustrates a cut view of the installation local of a speed reduction device of the present invention, showing detail D depicted in Figure 2;

Figure 4 illustrates a perspective view of a preferred embodiment of a speed reduction device of the present invention; Figure 5 illustrates a cross-section cut view of the preferred embodiment of a speed reduction device of the present invention;

Figure 6 is a top view of the preferred embodiment of the speed reduction device of the present invention; and

Figure 7 illustrates a cross-section view through A-A section shown in Figure 6.

Detailed Description of the Invention

The present invention will now be described based on working examples represented in the drawings. Although the disclosure below exemplifies a suspension arrangement associated with a clothes washing machine of vertical shaft and top loading, a person skilled in that art will understand that the present invention can be used in other machine types, such as, for example, horizontal shaft and front-loading machines. In the same way, the device of the present invention can be applied to rotary shafts of other machine types, such as centrifuges or clothes dryers.

Figure 1 illustrates a schematic cut view of a clothes washing machine comprising a reduction device of the present invention.

A clothes washing machine generally comprises a structural housing 1 of construction known in the art, within which a basket-tank assembly 2 is suspended to hold wash liquid and the clothes load to be washed. A stirrer responsible for stirring a clothes load to be washed is provided inside said basket. Said stirrer is connected with a shaft 3 that, in turn, is disposed in a centrifugation tube 4 (said tube functioning as a rotary shaft 4). These parts constitute the thus-called "mobile assembly" that is responsible for rotary movement of said basket-agitator assembly and driven by an electric engine 5.

Figures 2 and 3 show more details of a mobile assembly rotary shaft.

Centrifugation tube 4 is arranged in a bearing composed of an upper plate 6 and a lower plate 9, wherein two ball-bearings 7, 8 are disposed between said tube and said bearing. A hood 10 may be disposed above said bearing thus separating the motor assembly ambient from the basket-tank assembly ambient.

A speed reduction device 1 1 of the present invention is preferably disposed between a centrifugation tube 4 and an upper plate of bearing 6; nevertheless, those skilled in the art will understand that said device may be located in another place provided that it remains in contact with said tube or rotary shaft 4.

The preferred embodiment of device 1 1 is better visualized from Figures 4 to 7. The device 1 1 of the present invention comprises an elastically deformable body 12 disposed around rotary shaft 4. Said deformable body 12 comprises grooves 13 spaced around an inner edge of body 12, wherein two consecutive grooves form therebetween a deformable tooth. Deformable teeth 14 contact shaft 14 thus generating a certain extent of mechanical resistance due to attrition occurring between said parts.

As better visualized from Figures 3 and 6, in the preferred embodiment of the present invention, groves 13 are angled, i.e., they form an angle with a radial direction towards the edge of the body 2 and inclined in the rotary direction of said rotary shaft 4. Such an angulation allows for the mechanical resistance created between shaft 4 and teeth 14 to be different depending on the rotary shaft conditions.

When said shaft 4 is in a stationary condition, teeth 14 are in contact with shaft 4 and exerting pressure on it. This pressure generates a compression force that can be equalized with an elastic force.

In fact, in this stationary condition, there is a force that can be represented by equation F_E = k. Δχ, wherein K is an elastic constant of a deformable material of teeth 14 and Δχ is the teeth displacement caused by compression.

When in shaft dynamic condition of the shaft, an attrition force is created between shaft 4 and teeth 14, where said attrition depends on variables such as rotation speed, temperature and superficial roughness of said parts. This attrition force can be represented by equation F_A = μ . N, wherein μ is attrition coefficient and N is normal force/reaction force generated upon contact between the parts. As will be explained below, the presence of angled grooves 13 in the device of the present invention causes the attrition force to decrease as the rotation speed of shaft 4 increases.

In the beginning of shaft movement, the attrition force assumes its maximal value, wherein there is a substantially plenum interference between teeth 14 and the shaft surface.

As the rotation speed increases the attrition force and the reaction force generate a torque on the teeth 14 which deform in the sense of diminishing the reaction force. That is, said teeth 14 deform so that the contact between then and the shaft surface relax (i.e. when in motion said teeth 14 deform towards the shaft movement direction). This deformation is allowed by the bent grooves which create slightly bent teeth 14.

When rotation speed becomes stabilized, a balance is generated and the resistance force assumes a constant value, wherein said system stabilizes in a lower energy condition.

Therefore, said reduction device of the present invention can create a system in which resistance to shaft movement is inversely proportional to shaft rotation speed. This is possible due to the presence of said angled grooves 13 which allow for teeth 14 to deform as the shaft rotation increases, thus decreasing the pressure between said teeth 14 and the surface of shaft 14; as a result, a minor resistance to rotation movement is produced.

Naturally, when the shaft rotates in a direction contrary to the angulation direction of said grooves, adhesion between the surface of shaft 4 and teeth 4 substantially increases thus causing great difficulty of movement. That is, once said deformation of teeth 14 in the shaft rotation direction causes a reduction in pressure between the parts (retention relief), it is expected that rotation in the contrary direction be more difficult. As can be better seen from Figures 5 and 7, which illustrate cut views of a device of the present invention, the elastically deformable body 12 can be formed with a recess 15 thus forming a projection 16 on the radial edge of body 12. Thus, as shown in Figure 7, said recess 15 is defined by a first axial surface 15a formed by an outer wall of the body 12 core, a second axial surface 15b formed by an inner surface of said projection 16.

The recess 15 comprises a web 16 to ensure structural strength of the reduction device. It should be noted that in the preferred embodiment of the present invention, said body 12 is cylindrically shaped whereby said recess 15, projection 16 and web 14 are also circular.

In the preferred embodiment of the present invention, the web 17 has an L- shaped cross-section, where one of legs 17a extends radially towards the body core 12, thereby housing in a cavity formed in the body, and the other leg 17a extends in the axial direction of said body, overlapping the axial surface 15b formed by the inner surface of projection 16.

Further, in the preferred embodiment of the present invention, said device 11 additionally comprises a spring 18 partially embedded into the outer wall of body 12 core (i.e., on the first axial surface 15a of recess 15). This spring is intended to make up for natural wear of said teeth 14 of the device 11 in function of contacting the rotation shaft and, in the preferential embodiment where body 12 is a cylindrical body, it takes the form of a steel ring. In addition, the characteristics of said spring 18 enable to control the value of attrition force, thus affecting the behavior of this assembly.

It should be understood that Figures 1 to 7 show a preferential embodiment of the device of the present invention, wherein the real scope of the object of the invention is defined in the appended claims.

In this sense, it should be understood that the inventive concept subjacent the present invention resides in decreasing the resistance to said rotational movement of shaft 4 as said rotational speed of the shaft increases. Such decrease is provided by the presence of said angled grooves 13 towards the shaft rotation thus allowing for said teeth to deform and as a result pressure exerted by them decreases. Thus, said elastically deformable body 12 can be made of any appropriate, preferably, non-metallic material, such as, for example, elastomers and polymers, and it may have a cylindrical configuration as in the preferred embodiment, or even in an open cylindrical or semi- cylindrical form.

Equally, web and spring included in said reduction device can be fabricated of any material suitable for their use, and the angle of said grooves can be sized in accordance with the performance required for braking.

Claims

1. Passive device for speed reduction (11) of a rotary shaft of a machine comprising at least a rotary container attached to said rotary shaft, said device comprising a body of elastically deformable material (12) having an inner edge surrounding at least partially the shaft, CHARACTERIZED in that a body (1) comprises in its inner edge a plurality of grooves (13) angled towards rotation of shaft (4) and a plurality of deformable teeth (14), wherein each deformable tooth is formed between two consecutive grooves (13).

2. Passive device, in accordance with claim 1 , CHARACTERIZED in that said elastically deformable body (12) has a substantially cylindrical form.

3. Passive device, in accordance with claim 1 or 2, CHARACTERIZED in that said elastically deformable body (12) comprises a recess (15), wherein said recess (15) forms a projection (16) on the outer edge of the body.

4. Passive device, in accordance with claim 3, CHARACTERIZED in that said recess (15) houses a web (17) intended to ensure structural strength of said device (11).

5. Passive device, in accordance with claim 7, CHARACTERIZED in that said web (17) has an L-shaped cross-section, wherein one of legs (17a) extends radially towards the body (12) core, thus being disposed in a cavity formed in the body, and the other leg (17b) extends in the axial direction of said body.

6. Passive device, in accordance with any of claims 1 to 5, CHARACTERIZED in that said body (12) further comprises a spring (18) partially embedded in said body (12).