The pulley of a washing machine made of plastic material

Abstract

A pulley (6) made of plastic material for a washing machine drum (3), comprising: a hub, a pulley circumference for receiving a belt (8), a substantially circular dividing rib (14) that divides the pulley into an inner concentric section and an outer concentric section having a plurality of reinforcing ribs (15, 16, 16'), wherein the dividing rib is disposed on a line of a polygon centered on the pulley axis and having corners, and a part of the outermost rib (which is part of the plurality of reinforcing ribs of the inner section) leads from the side facing the hub to the dividing rib, wherein at least a part of these reinforcing ribs leading to the corners of the dividing rib extends along a line of a polygon (preferably a hexagon) that is radially disposed in the inner section and touches each other along one of their sides, and wherein at least one arcuate rib of the outer section originates from at least one of the corners of the dividing rib on the side facing the outer circumference and its free end touches the outer circumference of the pulley.

Description

Field of the Invention

[0001] The subject of the invention is a pulley for a washing machine drum made of plastic material, in particular for a domestic washing machine.

[0002] Technical Problem

[0003] The technical problem is to configure a pulley made of plastic material to have as low a weight as possible and mechanical properties that prevent the pulley from deforming radially and axially. Background Art

[0004] Clothes washing in a washing machine takes place in a drum rotatably arranged in a washing tub of the washing machine. The drum is rotated by a drive assembly which includes: a shaft fixed to the drum and mounted in bearings, a pulley mounted on the shaft, an electric motor having a drive shaft, and a drive belt that transmits the rotation of the electric motor to the drum via the pulley.

[0005] Especially in washing machines with high rotational speeds (e.g., 1400 rpm or higher) and large drum volumes (e.g., 8 kg or larger), due to high mechanical loads, the pulleys are usually made of metal material. The disadvantages of these pulleys are mainly their weight and problematic manufacturing. Therefore, attempts are being made to replace metal pulleys with pulleys made of plastic material, which usually have poor mechanical properties. When a pulley made of plastic is subjected to the belt preload force and the forces associated with a sufficiently firm connection of the pulley to the drum shaft, the pulley made of plastic deforms both during operation and at rest. Attempts are made to compensate for the poor strength characteristics of the material, especially by a more suitable shape of the connecting ribs between the hub and the tread surface of the pulley, on which the drive belt rests.

[0006] Therefore, patent application WO / 2007 / 057234 describes a pulley made of plastic material and having geometric characteristics similar to those of a metal pulley. The pulley has: a central hub, an outer circumference for receiving the belt, and a plurality of radial connecting ribs. To ensure the mechanical properties for transmitting forces during stop and operation, the ribs have a large cross-section, which thus means a large weight of the pulley or the use of a large amount of material, and thus higher manufacturing costs.

[0007] Patent application EP2159314(A1) describes a pulley made of plastic material, which consists of a plurality of radial ribs that are annularly connected from a central hub to an outer circumference for receiving the belt. Even with this technical solution, the sufficient stiffness of the pulley is provided by ribs with a large cross-section. As a result, such a pulley has a very large weight, and thus high requirements for the material used.

[0008] Patent application WO 2013 / 038432 A1 describes a pulley made of plastic material, which includes a central hub, an outer circumference for receiving a belt, an inner section connecting several radial ribs, and an outer section including several circumferential ribs inclined with respect to the radial ribs. This shape of the pulley requires the use of a special plastic material with an elastic modulus exceeding 14,000 MPa. For this purpose, a relatively large proportion of mineral or synthetic fillers is added to the base material, and when the melt solidifies, these mineral or synthetic fillers precipitate at the front end of the casting flow, generating weaker pulley points at the positions where two flows meet, especially on the outer circumference. A large number of ribs supporting the circumference of the pulley reduce the influence of the weak points while ensuring a small radial deformation of the circumference, thus ensuring the stable operation of the belt without periodic excitation. The disadvantage of such a pulley is that the ribs in the first section and the outer section are designed to have a small cross-section, which causes the pulley to bend in a direction outside the plane of action of the radial force. This problem can be solved by using a larger number of ribs or ribs with a larger size, which increases the weight / material consumption in manufacturing.

[0009] CN 106958118 A discloses a plastic pulley configured as a plastic plate, which is strengthened with radial ribs in an inner middle section and an outer middle section.

[0010] To ensure the stable position and correct operation of the belt during operation and at rest, the belt is installed on the pulley with a certain preloading force. As a result, the pulley is loaded with a constant surface pressure on the circumferential surface where the belt rests, which results in a radial force on the pulley. The static load of the pulley can cause permanent deformation of the material due to high stress at high temperatures (especially during storage and transportation stages), resulting in creep. During operation, due to the belt preloading force, the pulley may bend outside the plane of action of the radial force. This type of bending causes the belt to shift on the tread of the pulley and may even cause the belt to fall off in extreme cases.

[0011] The problem of pulley bending is usually solved by using a large number of ribs or ribs with a larger cross-section. Due to the use of a large amount of material, this solution leads to an increase in the weight of the pulley, which in turn results in higher weight and higher manufacturing costs.

[0012] The common disadvantage of all these solutions is that they cannot optimize the distribution of internal stress in the pulley, so the pulley manufactured by injection molding is deformed. Summary of the Invention

[0013] This technical problem is solved by a pulley made of plastic material and having the features defined in independent claim 1.

[0014] A pulley for a washing machine drum, especially for a household washing machine, the pulley being made of plastic material and comprising: a central part of the pulley, which is formed as a hub through which the pulley is fixed to the drum shaft; a circumference of the pulley, which is arranged concentrically with respect to the hub and defines the pulley and receives a belt on its outer surface; a substantially circular dividing rib, which is arranged concentrically with respect to the circumference of the pulley so as to divide the pulley into two concentric sections, namely a first inner section closer to the hub and a second outer section defined by the circumference of the pulley, wherein a corresponding plurality of reinforcing ribs are arranged in the inner and outer sections, wherein the dividing rib is arranged on a line of a polygon centered on the pulley axis and having corners, and a part of the outermost reinforcing rib leads from the side facing the hub to the dividing rib, the outermost reinforcing rib being part of a plurality of inner reinforcing ribs, wherein at least a part of these reinforcing ribs leading to the corners of the dividing rib extends along a line of a polygon (preferably a hexagon), the polygon being arranged radially in the inner section and contacting each other along one of their sides, wherein at least one arcuate reinforcing rib, preferably two arcuate reinforcing ribs, of the outer section originate from at least one of the corners on the side of the dividing rib facing the circumference, forming a pair of mirror-image arcuate reinforcing ribs, and the free ends of the arcuate reinforcing ribs contact the circumference of the pulley.

[0015] The reinforcing ribs in the inner section extending along the line of the polygon form a honeycomb, thereby achieving greater radial strength in the inner section.

[0016] The pair of arcuate reinforcing ribs in the outer section can have a second pair of arcuate ribs with axially mirror-image distribution.

[0017] The reinforcing ribs in the outer intermediate section are arcuate, and the size of the arcuate radius of the reinforcing ribs is approximately equal to or greater than the radius of the pulley.

[0018] The reinforcing ribs in the inner section are arranged radially to form a honeycomb. In this case, the honeycomb cells symmetric with respect to the pulley axis have the same size. The size of the honeycomb cells increases as their distance from the axis increases.

[0019] The high stiffness of the honeycomb and thus the small deformation under load are also reflected in the smaller deformation of the intermediate dividing rib, the second intermediate section, and the circumference of the pulley itself. The radial deformation is more uniform. The result of the smaller radial deformation is to minimize the periodic excitation of the belt, which causes the belt to run more evenly along the circumference of the pulley or the tread, which prevents the possibility of the belt falling off the pulley.

[0020] In the production of pulleys, stresses and thus deformations also occur during the cooling of the plastic material. The arcuate configuration of the ribs helps to reduce the deformations, especially those of the circumference of the pulley. During cooling, the material shrinks. Due to the arcuate configuration of the ribs in the outer intermediate section, these ribs shrink or deform in such a way that their curvature decreases or their radius increases. The stresses generated by the shrinkage of the arcuate ribs are transmitted to the circumference of the pulley to a much lesser extent, so that the local deformation of the circumference of the pulley in the radial direction is greatly reduced compared to the local deformation that would exist in the case of straight ribs. Due to the relatively large number of ribs, the relative deformation of the circumference of the pulley is further reduced.

[0021] Another advantage of the pulley according to the invention is evident during the injection molding production process. During the injection molding of circular products similar to pulleys, where it is necessary to maintain the center or circular shape on the circumference, the liquid material is usually supplied to the mold at a position on the axis or in a position adjacent to the axis, where a uniform flow of the liquid material into all parts of the mold should be provided. The configuration of the ribs according to the invention and of the entire pulley causes the liquid material supplied axially to flow essentially radially towards the circumference during the entire flow step, all the way to the outer circumference of the pulley. The individual strands of the melt join together on the outer circumference of the pulley. The fillers present in the material and representing weak points are eliminated at the joining points. The fewer the number of joining points, the more fillers are eliminated at this point. Therefore, the aim is to increase the number of contact points. This is achieved by the pulley according to the invention because there are a large number of ribs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The pulley according to the invention will be described in more detail below by way of examples and the drawings presented.

[0023] Figure 1 For the components of a washing machine tub.

[0024] Figure 2 For the pulley according to the invention. DETAILED DESCRIPTION

[0025] A washing machine includes a tub assembly 1, the tub assembly including a washing tub 2 and a drum 3 rotatably disposed therein. The drum 3 is rotated by a drive assembly 4, the drive assembly including: a shaft 5, which is fixed to the drum 3 and mounted on bearings, the shaft allowing the drum 3 to rotate freely about its axis; a pulley 6, which is disposed on the shaft 5; an electric motor 7, which has a drive shaft; and a drive belt 8, which connects the drive shaft of the electric motor 7 and the pulley 6, thereby transmitting rotation from the electric motor 7 to the washing machine drum 3.

[0026] The pulley 6 of the washing machine drum includes

[0027] - a central portion 9 formed as a hub, through which the pulley 6 is fixed to the shaft 5;

[0028] - The circumference 10 of the pulley, which is arranged concentrically with respect to the hub and defines the pulley 6, and receives the belt 8 on the outer surface of its substantially tread;

[0029] - A substantially circular separating rib 14, which is arranged concentrically with respect to the circumference 10 of the pulley at 1 / 3 to 2 / 3 of the radius of the circumference 10 of the pulley, preferably at approximately half of the radius of the circumference 10 of the pulley, so as to divide the pulley 6 into two concentric sections, namely an inner section 12 and an outer section 13, in which a corresponding plurality of reinforcing ribs 15, 16 are arranged.

[0030] The separating rib 14 is arranged along the line of the polygon 11 in such a way that its center is on the axis of the pulley 6 and has an angle 21. A plurality of reinforcing ribs 15 are arranged in the inner section 12 of the pulley 6. A part of the reinforcing rib 15 that is closer to the separating rib 14 or farthest from the hub 9 converges into the angle 21 of the separating rib 14 on the angular side facing the hub 9. In this embodiment, two ribs 15 of the inner section converge at each angle 21, which is not a mandatory feature. The convergence of the reinforcing ribs 15 can also be carried out only in a certain limited number of angles 21, and it is not mandatory for the two reinforcing ribs 15 farthest from the hub to converge into a single angle 21.

[0031] At least a part of the reinforcing rib 15 that converges into the angle 21 (in this embodiment, all the ribs 15 that converge into the angle 21) extends along the line of the polygon 17 (preferably a hexagon). The polygon 17 is arranged radially in the inner section 12 and contacts each other along one of their sides. The ribs 15 of the inner section 12 that extend along the line of the polygon 17 form a honeycomb 19. The size of the cells of the honeycomb 19 increases as their distance from the said axis increases.

[0032] The angle 21 of the separating rib 14 forms a starting point 18, and at least one arcuate rib 16, preferably two arcuate ribs 16, 16' of the outer section 13 emerge from this starting point, so as to form a pair 20 of mirror arcuate reinforcing ribs 16, 16', and the free ends of this pair of mirror arcuate reinforcing ribs contact the outer circumference 10 of the pulley 6.

[0033] In this embodiment, the second pair 20' of arcuate reinforcing ribs 16, 16' is axially mirror to each pair 20 of arcuate reinforcing ribs 16, 16' of the outer section 13, which is not a mandatory feature.

[0034] The number of pairs 20 of the arcuate reinforcing ribs 16, 16' in the outer section 13 is equal to the number of angles 21 of the separating rib 14. The number of pairs 20 of the reinforcing ribs 16, 16' depends on the required strength of the pulley 6 and increases as the strength requirement increases.

[0035] The ribs 16, 16' of the outer intermediate section 13 are arcuate, and the dimension of the radius of the arcuate shape of the ribs 16, 16' is approximately equal to or greater than the radius of the pulley 6.

[0036] Due to the honeycomb shape, the rib system formed by the ribs 15 has high axial and radial stiffness, which ensures high stiffness of the pulley 6 in the inner section 12 under axial and bending loads, thereby reducing the bending deformation of the pulley 6. The high stiffness of the honeycomb 19 and the resulting small deformation are also reflected in the smaller deformation of the separating ribs 14.

[0037] The height of the reinforcing ribs 15, that is, the dimension of the ribs in the axial direction of the axis of the pulley 6, increases towards the central part 9 of the pulley 6. As the height of the reinforcing ribs 15 or the height of the cell walls of the honeycomb 19 increases, the pulley 6 obtains higher strength or stiffness in the central part, which is required due to the large compressive force in this area.

[0038] The arcuate form of the reinforcing ribs 16, 16' in the outer section 13 allows for good transmission of radial loads, thereby allowing small radial deformation of the circumference 10 of the pulley 6. At the same time, the arcuate ribs 16, 16' in the outer section 13 allow for good transmission of the radial loads generated due to the assembly of the belt 8 along a part of the circumference 10 of the pulley 6 to the separating ribs 14 and the inner section 12. The shape of the arcuate reinforcing ribs 16, 16' in the outer section 13 can transmit torque loads well during the acceleration and deceleration of the drum 3, because the arcuate ribs 16, 16' follow the loads on the pulley 6 during the acceleration and deceleration of the washing machine drum 3. In this way, axial loads mainly appear in the ribs 15, 16, 16', and no bending load will cause the reinforcing ribs 15, 16, 16' to bend in the axial direction of the pulley 6. Due to the large number of arcuate reinforcing ribs 16, 16' and thus smaller openings or air channels between the ribs 16, 16' in the outer section 13, a more uniform air flow is achieved between the pulley 6 and the tub 2 of the washing machine during the rotation of the pulley 6, which results in lower pneumatic noise.

Claims

1. A pulley (6) of a washing machine drum (3), the pulley being made of a plastic material, the pulley comprising: The central part of the pulley, which is formed as a hub (9), and the pulley (6) is fixed to the drum shaft (5) through the central part; the circumference (10) of the pulley, which is arranged concentrically with respect to the hub (9) and receives the belt (8) on its outer surface; a substantially circular dividing rib (14), which is arranged concentrically with respect to the circumference (10) of the pulley so as to divide the pulley (6) into two concentric sections, namely a first inner section (12) closer to the hub (9) and a second outer section (13) defined by the circumference (10) of the pulley, wherein a corresponding plurality of reinforcing ribs (15, 16, 16') are arranged in the inner section (12) and the outer section (13), characterized in that the dividing rib (14) is arranged on the line of a polygon (11), the center of the polygon is on the axis of the pulley (6) and the polygon has corners (21), the farthest part of the reinforcing rib (15) from the hub (9) leads to the dividing rib from the side facing the hub (9), the reinforcing rib (15) is part of the plurality of reinforcing ribs (15) in the inner section (12), wherein at least a part of the reinforcing rib (15) leading to the corner (21) of the dividing rib (14) extends along the line of a polygon (17), the polygon is hexagonal in shape and is arranged radially in the inner section (12), and the polygons are in contact with each other along one of their sides, at least one arcuate reinforcing rib (16) originates from at least one of the corners (21) on the side of the dividing rib (14) facing the circumference (10), and the free end of the at least one arcuate reinforcing rib contacts the circumference (10) of the pulley (6).

2. The pulley according to claim 1, characterized in that, Two arcuate reinforcing ribs (16, 16') in the outer section (13) originate from at least one corner (21) on the side of the dividing rib (14) facing the circumference (10), forming a pair (20) of mirror-image arcuate reinforcing ribs (16, 16') and the free ends of the pair of mirror-image arcuate reinforcing ribs contact the circumference (10) of the pulley (6).

3. The pulley according to any one of the preceding claims, characterized in that, The dividing rib (14) is arranged concentrically with respect to the circumference (10) of the pulley (6) at 1 / 3 to 2 / 3 of the radius of the circumference (10) of the pulley (6).

4. The pulley according to claim 1 or 2, characterized in that, The reinforcing ribs (15) in the inner section (12) extending along the line of the polygon (17) form a honeycomb (19).

5. The pulley according to claim 4, characterized in that, The size of the cells of the honeycomb (19) increases as the distance of the cells of the honeycomb from the axis of the pulley (6) increases.

6. The pulley according to claim 1 or 2, characterized in that, The size of the radius of the arcuate reinforcing ribs (16, 16') is equal to or greater than the radius of the pulley (6).

7. The pulley according to claim 2, characterized in that, A second pair (20') of arcuate reinforcing ribs (16, 16') is axially mirror-image to the pair of arcuate reinforcing ribs (16, 16') in the outer section (13).

8. The pulley according to claim 1 or 2, characterized in that, The height of the reinforcing ribs (15) extending in the axial direction of the pulley (6) increases towards the central part of the pulley.

9. The pulley according to claim 1 or 2, characterized in that, The number of the pair (20) of arcuate reinforcing ribs (16, 16') in the outer section (13) is equal to the number of the corners (21) of the dividing rib (14).

10. The pulley according to claim 1, characterized in that, The pulley (6) is a pulley of a washing machine drum of a household washing machine.

11. The pulley according to claim 3, characterized in that, The dividing rib (14) is arranged concentrically with respect to the circumference (10) of the pulley (6) at approximately half of the radius of the circumference (10) of the pulley (6).

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