Description

Truncated conical drum for washers or washer-driers.

The present patent application for industrial invention relates to a drum for washers or washer-driers with increased volume due to truncated conical configuration.

To better understand the problem addressed by the invention and appreciate the advantages offered by the inventive solution, this description continues with reference to the structural and functional configuration of ordinary washers.

In traditional washers the laundry is normally contained in a basically cylindrical drum, which is housed and rotates inside a hermetically sealed cylindrical plastic tank where water and detergents are introduced for washing.

In front-loading washers the drum is composed of a cylindrical sheet. metal shell closed in the back and in the front by two circular flanges, the front flange being provided with a large central hole for laundry loading and unloading, and the back flange being joined in the centre to a motorised shaft with horizontal axis designed to drive into rotation the drum inside the tank, which is stationary during the revolutions of the drum.

The cylindrical shell is covered by a dense series of small holes that allow the water introduced inside the washing tank to penetrate inside the drum during washing, and flow out of the drum during spin drying and final emptying of the tank.

Technically speaking, the assembly of drum and tank is defined as washing assembly or oscillating assembly.

The front circular bottom wall of the circular tank is provided with a large circular opening for laundry front-loading or unloading; the opening is hermetically closed by a circular door that provides access to the internal compartment of the rotary drum.

The circular back bottom of the tank is provided with a central hub for the

motorised shaft connected to the drum.

The said washing assembly with electrical motor is contained in a basically parallelepiped case made of self-supporting sheet metal or composed of a supporting metal frame covered with sheet metal panels. The said case has standardised dimensions: in particular, width is a few millimetres lower than 60 and measures approximately 596 mm. In view of the above, the purpose of the invention is to devise a drum with maximum volumetric capacity, having the same width of the case, whose configuration and dimensions determine the selection of the diameter of the cylindrical washing tank and consequently of the cylindrical drum contained in it.

On the other hand, the increase of the volumetric capacity of the drum is a especially important because of the fact that the larger the free space inside the drum, the higher the washing efficiency will be. The diameter of the cylindrical drum is chosen taking into account the following two phenomena that are generated when the washer is operated. The first phenomenon consists in the lateral displacement of the washing tank, which is hung to a spring system that allows to absorb the stress and vibrations transmitted to the tank through the hub by the motorised shaft inserted in the said hub.

The maximum lateral displacement of the tank occurs during the transient phase, when the drum revolutions increase from 250 to 400 rpm; in order to avoid contacts between the tank and the case during operation, the external diameter of the tank must be such that the empty space between tank and case is wider than the maximum lateral displacement value of the tank measured during the critical transient phase.

The second phenomenon that determines the selection of the maximum diameter of the cylindrical shell of the drum is represented by the oscillations suffered by the rotational axis of the drum during spin drying, when the rotation speed reaches the maximum values.

For purposes of clarity, the description of the second phenomenon continues with reference to the enclosed drawings, whereby:

- fig. 1 is a diagrammatic cross-sectional view of a washer with a horizontal plane passing through the rotation axis of the drum, which is stationary in this figure; for simplicity's sake, this figure illustrates only half of the drum, tank and case. - fig. 2 is the same as fig. 1 , except for the fact that in this figure the drum rotates at the maximum revolution speed, loaded with laundry. The said oscillation is due to the fact that the laundry contained in the drum (1 ) is arranged in a completely accidental position, thus originating an unbalanced rotating mass associated with a centrifugal force that tends to push the drum (1 ) close to the walls of the washing tank (2).

The centre (O) of the oscillation made by the rotational axis (X-X) of the drum (1) is situated in the hub (M) obtained in the tank (2) for the motorised shaft that drives the drum (1) into rotation. As shown in Fig. 2, during spin drying, the rotational axis (X-X) of the drum (1) is subjected to maximum inclination equal to angle (α) with respect to the axis (X'-X ¹ ) of the tank (2) that contains it, passing through the centre (O). In fact, it must be considered that during spin drying both the tank (2) and the drum (1) are subjected to oscillation with respect to a horizontal plane. For example, in the current models of washers the inclination angle (α) of the rotational axis (X-X) of the drum with respect to the axis (X'-X') of the tank varies from 0°40' to 3°. The difference in the inclination angle (α) is related with the maximum number of revolutions and with the length of the drum. Therefore, the maximum radial displacement of the drum (1) occurs in the front flange (3), while the back flange (4) with the hub (M) is not subjected to radial displacement, because it is practically positioned in the oscillation centre (O).

Since the cylindrical drum (1 ) has a constant diameter (D1), today the diameter (D1) of the cylindrical drum (1 ) must be selected in such a way to leave an empty annular space (8) between the drum (1) and the tank (2), having a higher width (h) than the maximum radial displacement value of the front flange (3) measured during spin drying.

That is to say, the width h must satisfy the following relation: h > L * sin (α)

where L is the length of the drum.

A close examination of the aforementioned considerations has resulted in the idea of increasing the volumetric capacity of the drum by giving it a truncated conical configuration, in which the external diameter of the annular shell measured in the back flange is higher than the one measured in the front flange, it being provided that the lower diameter is determined in compliance with the said width (h).

For purposes of clarity, the description of the drum of the invention continues with reference to the enclosed drawings, which are intended for purposes of illustration only and not in a limiting sense, whereby:

- fig. 3 is a diagrammatic cross-sectional view of a washer provided with the truncated conical drum of the invention with a horizontal plane passing through the rotational axis of the drum, which is stationary in this figure; for simplicity's sake, this figure illustrates only half of the drum, tank and case; - fig. 3A is an enlarged detail of Fig. 3;

- fig. 4 is the same as fig. 3, except for the fact that in this figure the drum rotates at the maximum revolution speed, loaded with laundry;

- fig. 5 is the same as fig. 3, except for the fact that it refers to a different embodiment of the drum; - fig. 6 is a diagrammatic axonometric view of the truncated conical drum of the invention in the embodiment illustrated in fig. 5.

- fig. 7 is a diagrammatic axonometric view of the truncated conical drum of the invention in a further embodiment.

With reference to figures 3 and 4, the drum (10) of the invention is traditionally formed of an annular shell (50) and two circular bottom flanges

(30 and 40), the front flange (30) being provided with a large central opening

(30a) for laundry front loading and unloading, while the back flange (40) is joined in the centre to a motorised shaft with horizontal axis (90) designed to drive the drum (10) into rotation inside the tank (2) that remains stationary while the drum (10) rotates.

The main characteristic of the drum (10) of the invention is the truncated conical configuration, in which the external diameter of the annular shell (50)

measured in the back flange (40) has a higher value (D) than the value (d) measured in the front flange (30).

The coning angle (β) of the drum (10) is basically identical to the angle (α) of maximum oscillation of the rotational axis (X-X) of the drum during spin drying.

Therefore, the coning angle (β) of the drum can be selected, for example, in the range from 0°40' to 3°, preferably 2°, according to the oscillation of the axis of the drum.

As shown in Fig. 3A, the external annular border with higher diameter (D) of the drum can be situated very close to the internal surface of the tank (2), for example at a distance (ITl) lower than 10 mm, preferably about 4 mm.

This means that the drum (10) can be dimensioned according to the internal diameter (Dv) of the tank (2) in order to satisfy the following relation:

Dv - D = 2 ^* h1 from which the maximum diameter (D) of the drum is obtained.

The following relation is applied to calculate the minimum diameter (d) of the drum:

D - d = 2 * L ^* sin (β) where L is the length of the drum and β is the coning angle. According to the preferred embodiment of the invention shown in figures 3 and 4, the two bottom flanges (30 and 40) have the same external diameter

(D3 and D4) equal to the aforementioned value (d) so that the annular shell

(50) is suitably shaped and enlarged to reach the increased diameter value

(D) at the end facing the back flange (40). It must be noted that the back opening of the annular shell (50) is shaped in such a way to have a first diverging section (50a) that joins the point (P1 ) used for connection to the border of the back flange (40) and the point (P) with the maximum external diameter (D) of the shell (50).

Fig. 4 shows the maximum angle (α) of the oscillation made by the rotational axis X-X of the drum (10) during spin drying, when the generatrix of the shell

(50) is basically in parallel position to the cylindrical wall of the washing tank

(2) due to the oscillation suffered by the shaft (90) and the drum (10) joined to

the shaft itself.

With the tank (2) having the same configuration and size, the truncated conical drum (10) of the invention has a higher volumetric capacity than a traditional cylindrical drum (1 ) that is basically equal to the volume of the toroidal revolution solid generated by the rotation around axis X-X of the triangular area (T) shown as a broken line in figs. 3 and 4. According to the alternative embodiment of the invention shown in fig. 5, the back flange (40) has a higher diameter (D4) than the diameter (D3) of the front flange (30), so that the profile of the shell (50) is perfectly rectilinear from the back opening to the front opening.

In this case, the diameter (D4) is the same as the aforementioned diameter (D), and the diameter (D3) is the same as the aforementioned diameter (d). Without leaving the inventive concept and the patent protection scope, the drum (10) of the invention may be given a truncated conical configuration interrupted by longitudinal areas (11) without truncated conical profile, so that the said truncated conical profile is only provided in one or more circular sectors (S1 , S2...) of the drum (10) as shown in fig. 7.