EP0175218B1

EP0175218B1 - Speed variator for laundry washing machine

Info

Publication number: EP0175218B1
Application number: EP85111188A
Authority: EP
Inventors: Piero Durazzani
Original assignee: Industrie Zanussi SpA
Current assignee: Industrie Zanussi SpA
Priority date: 1984-09-18
Filing date: 1985-09-04
Publication date: 1991-01-23
Anticipated expiration: 2005-09-04
Also published as: IT8445723A1; DE3581461D1; IT1181077B; IT8445723A0; ES288982U; EP0175218A2; EP0175218A3; ES288982Y; ATE60379T1

Abstract

A speed variator for a laundry washing machine comprising a drum (6) mounted in a laundering tub (5) and adapted to be rotated at different speeds by a motor (7) via a transmission belt (8) interconnecting a driving pulley (9) of the motor and a driven pulley (10) associated with the drum. The speed variator includes the driving pulley (9) which is provided with flyweights (16) housed in a cavity (15) of the pulley and radially expandable for varying the effective diameter of the pulley and thus the transmission ratio. The speed variator additionally includes a hydraulic piston (17) guided in a cylinder (18) connected to the water supply circuit of the machine via a solenoid valve (19) displacement between different operating positions, said piston cooperating with the flyweights for interdicting or permitting the radial expansion thereof to varying degrees. The internal cavity (15) of the driving pulley (9) is defined by planar or arcuate surface portions (25-29 and 31-35, respectively) interconnected by inclined ramps or arcuate transitions of different radius of curvature, respectively, permitting the flyweights (16) to radially expand to and be retained in different positions depending on the rotational speed of the driving pulley and the operating position assumed by the piston (17).

Description

The present invention relates to a speed variator for a laundry washing machine permitting the drum thereof to be rotated at different speeds.
In conventional laundry washing machines, the driving power from the motor, usually of the commutable pole type, is transmitted to the drum by means of a V-belt connected to respective pulleys of the motor and the drum for rotating the latter at the washing and centrifuging speeds. The drum may in addition be rotated at other speeds between the washing speed and the centrifuging speed for carrying out certain phases of the laundering cycle, for instance for achieving dynamic equilibration of the drum or for reduced- speed centrifuging of the laundry.
To this effect, the motor advantageously cooperates with a suitable speed variator permitting the drum to be rotated with a variable transmission ratio.
Known speed variators for laundry washing machines include at least one variable-diameter pulley cooperating with flyweights adapted to be shifted between a contracted first position corresponding to the laundering speed of the machine, and a radially displaced second position corresponding to the centrifuging speed. In this manner the effective diameter of the pulley is rapidly varied when passing from the laundering speed to the centrifuging speed, resulting in the V-belt being lifted to a greater diameter for driving the drum at a different transmission ratio.
For permitting the drum to be rotated at speeds between the laundering and centrifuging speeds, a speed variator of this type is additionally provided with suitable electromechanical or purely mechanical actuating means cooperating with the flyweight-equipped pulley of the laundry washing machine and acting directly on the flyweights thereof so as to interdict or permit the radial displacement thereof to varying degrees.
The employ of a device of this type is nevertheless not very convenient for various reasons. In particular, both the electromechanical and the purely mechanical actuating means are of complicated structure and considerable dimensions, so that they are not very practical in use
In EP-A-0 147 625 which belongs to the prior art according to Art. 54(3) EPC, a speed variator of the type defined above is disclosed, comprising flyweights and at least one tensioning pulley biased into engagement with the V-belt with a variable compression force generated by a hydraulic piston connected to the water supply circuit of the machine via at least one solenoid valve.
By the displacement of the hydraulic piston the tensioning pulley is biased into engagement with the V-belt with a variable force, so as to variably interdict or permit the radial displacement of the flyweights for thus varying the effective diameter of the pulley and thereby the rotation of the drum between the laundering speed and the centrifuging speed. This piston permits the rotating speed of the drum to be varied in a continous and progressive manner for rotating the drum at speeds comprised between the laundering and centrifuging speeds. This type of control is obtained by repeatedly energizing the solenoid valve at predetermined intervals so as to define for each desired rotational speed of the drum a relative equilibrium condition between the compressive force exerted on the V-belt by the hydraulic piston and the reactive force exerted by the belt on the piston.
According to a further known embodiment of a flyweight speed variator, there is also provided a hydraulic piston connected to a pivotable arm carrying the motor of the machine, this arm being hinged to a lower portion of the washing tub and biased by a torsion spring towards a position whereat a variable-diameter driving pulley driven by the motor keeps the transmission belt for rotating the drum under tension. In this manner the transmission belt extends around the variable-diameter pulley at varying diameters thereof, depending on the rotational speed of the motor and on the relative position assumed by a hydraulic piston operable to interdict or permit the radial expansion displacement to varying degrees of flyweights associated with the pulley. The displacement of the piston permits the rotational speed of the drum to be varied in a continuous and progressive manner, so that the drum operates at the laundering and centrifuging speeds and at different speeds lying therebetween. Although these types of speed variators operate in a satisfactory and reliable manner, they are particularly critical as regards the control of the drum rotation at the intermediate speeds.
In this case the displacement of the piston between its various operating positions is likewise brought about by admitting different quantities of water to the associated cylinder, i.e. by repeatedly energizing the solenoid valve at predetermined intervals under the control of a program control unit of the machine or of other per se known control apparatus. As the cooperation between these components is affected by existing play and certain, albeit minimal delays in response, it is practically impossible to always position the piston accurately at its desired operating positions, as would be required for constantly obtaining accurate control of the rotational speed of the drum and thus optimum execution of the different laundering phases.
From DE-A-2 045 732 a speed variator for a washing machine is known, which is provided with a driving pulley connected to the motor of the washing machine and associated with flyweights able to vary the effective diameter of the pulley and therefore the speed ratio of the drum, driven by the driving pulley through a transmission belt.
Each flyweight is formed by a ball which is slidable along curved portions of walls provided in each part of the associated driving pulley. The variation of the effective diameter of the pulley is obtained by a relative rotational movement between both parts of the pulley obtained by temporarily reversing the mutual direction of rotation of these parts. The speed variator requires an electric motor able to rotate at different speeds for permitting radial displacement of the balls of the flyweights in the different radial positions along the curved portions of the walls of the wall of the pulley part so as to vary the diameter of the pulley. A hydraulic piston or the like for permitting the displacements of the flyweights in different positions is missing.
It is the object of the present invention to eliminate the disadvantages and shortcomings of the above discussed solutions by the provision of a simple and reliable flyweight speed variator of reduced dimensions and designed to ensure operation of the drum of the laundry washing machine at all times accurately at the required rotational speed.
A speed variator of this type as defined by the claim is essentially composed of at least one variable-diameter pulley cooperating with radially outwardly displaceable flyweights and at least one conventional hydraulic piston or the like connected to the water supply circuit of the machine and acting on the flyweights so as to interdict or permit the radial expansion displacement thereof to varying degrees.
In particular, the variable-diameter pulley is designed to permit the displacement of the flyweights not only between positions corresponding to the laundering and centrifuging rotational speeds of the drum, but also to at least one intermediate position corresponding to a further rotational speed of the drum residing between the laundering and the centrifuging speeds. In this manner, the flyweights are capable of being displaced to and retained at different radial operating positions, even if, for the reasons set forth above, the piston fails to be displaced accurately to the respective operating positions. As a result, the present speed variator is capable of accurately maintaining different transmission ratios and thus different rotational speeds of the drum residing between the laundering and the centrifuging speeds.
The characteristics and advantages of the invention will become more clearly evident from the following description of an embodiment thereof, given by way of example with reference to the accompanying drawings, wherein:

Fig. 1 shows a partially sectioned diagrammatical sideview of a laundry washing machine provided with a speed variator according to the invention,
Fig. 2 shows an enlarged view in axial section of parts of the speed variator of Fig. 1.

With reference to Fig. 1, there is shown a laundry washing machine 4 having a laundering tub 5 and a drum 6 mounted for rotation within tub 5 and adapted to be rotated by an electric motor 7 with the aid of at least one V-belt 8 operatively connecting a driving pulley 9 of motor 7 to a driven pulley 10 associated to drum 6.
In particular, driving pulley 9 is composed of a disk 11 fixedly secured to a shaft 12 of motor 7, a further disk 13 mounted for axial displacement relative to fixed disk 11, and another disk 14 secured to the end portion of shaft 12, said disks 13 and 14 cooperating with one another to define therebetween a V-shaped groove for receiving V-belt 8 therein. On the other hand, disks 11 and 13 cooperate to define therebetween at least one internal cavity 15 for accommodating a number of radial-expansion flyweights 16 of preferably cylindrical shape.
Motor 7 thus drives driving pulley 9 in unison with flyweights 16. Motor 7 is advantageously designed to operate at two different speeds for rotating drum 6 selectively at a laundering speed of about 58 rpm, and at a centrifuging speed of about 800 rpm, these speeds being of course given merely by way of example. This result may likewise be obtained according to the invention by employing a variable-diameter driven pulley 10 in place of, or in combination with, a variable-diameter driving pulley 9.
Flyweights 16 are designed to radially displace to varying degrees in response to the rotational speed of motor 7. Radial expansion displacement of flyweights 16 causes movable disk 13 to be axially displaced towards fixed disk 14 to thereby increase the effective diameter of driving pulley 9. As a result, V-belt 8 is shifted between different effective diameters of driving pulley 9 for rotating drum 6 at correspondingly varying transmission ratios.
In particular, V-belt 8 is capable of being shifted between a minimum diameter and a maximum effective diameter of driving pulley 9 for rotating drum 6 at the laundering and centrifuging speeds, respectively.
In addition to the transmission elements described above, the speed variator according to the invention includes at least one hydraulic piston 17 (shown in Fig. 1 in a front end view) reciprocably slidable in a cylinder 18 connected via a solenoid valve 19 and a tube 20 to a three- way valve 21 included in a water supply conduit 22 of the machine, conduit 22 itself being connected to a detergent distributor 23 and to the water supply mains through a further solenoid valve 24.
Piston 17, cylinder 18 and the remaining elements associated therewith are of the type described in EP-A-0 147 625 published on 10.07.1985, mentioned above. Also in the present case, piston 17 is thus connected to at least one tensioning roller (not shown) acting on V-belt 8 with a compressive force depending on the operating position assumed by piston 17 in response to the supply or discharge of water or another suitable liquid to, or from, respectively, cylinder 18 by repeatedly energizing solenoid valve 19 at predetermined intervals. Depending on the operating position of piston 17 it is thus, possible to interdict or permit the radial expansion displacement of flyweights 16 to varying degrees for correspondingly varying the effective diameter of driving pulley 9 in the same manner as described in EP-A-0 147 625 quoted above. It is course also possible to control the radial expansion of flyweights 16 in another manner and/or by different conventional means, without thereby leaving the scope of the present invention.
Merely by way of example, it is possible to apply a solution, according to which a hydraulic piston 17 of the type described above is connected to a hinged arm carrying the motor and the variable-diameter pulley, said arm being hinged to a lower portion of the laundering tub of the machine and biased by a torsion spring. Depending on the rotational speed of the motor, the hinged arm is capable of assuming various angular positions under the control of the hydraulic piston, the displacement of which thus determines the radial displacement of the flyweights and thus the effective diameter of the driving pulley.
Shown in Fig. 2 is a particular of an embodiment of the present invention.
According to this embodiment, the cavity 15 formed between disks 11 and 13 is defined by planar surface portions 25, 26, 27, 28 and 29 formed on disks 11 and 13 in symmetric relationship and connected with each other, forming different inclinations. The flyweights 16 are thus freely displaceable between the planar surfaces of any pair thereof and come to rest corresponding to each connection zone interconnecting two consecutive planar surface portions. In this embodiment, each cylindrical flyweight 16 is thus displaceable from a position A corresponding to the minimum or laundering speed to a position B corresponding to the maximum or centrifuging speed, and to an intermediate position C resting against connection zone 30 for rotating drum 6 at a speed lying between the laundering and centrifuging speeds. It is of course possible to form cavity 15 with addditional planar surface portions, so that flyweights 16 may come to rest at the respective connecting zones therebetween for thus obtaining additional intermediate rotational speeds of the drum.
The described speed variator operates as follows:
At the beginning of a laundering cycle, water is supplied from the mains to laundering tub 5 and to cylinder 18 in the manner described above. As a result, piston 17 is placed to its completely extended position with respect to cylinder 18, so that the associated tensioning roller (not shown) is forced into contact with belt 8 to keep it tensioned. Piston 17 is retained in this position by preventing the water from escaping from cylinder 18.
Under these conditions, motor 7 is energized to rotate at its lower speed for rotating drum 6 at the laundering speed of for instance 58 rpm. During rotation of driving pulley 9 at this speed, flyweights 16 are retained within cavity 15 at their position designated A, and are prevented from being radially outwardly displaced by the biasing action of piston 17 on belt 8. As flyweights 16 are not displaced outwardly, disks 13 and 14 are at their largest spacing, resulting in driving pulley 9 having its smallest effective diameter. As motor 7 continues to rotate at the same speed, part of the water contained in cylinder 18 may discharged into tub 5, so that piston 17 is pushed back into cylinder 18 by the tension of belt 8. As a result, the tension of belt 8 under the action of piston 17 is reduced, permitting flyweights 16 to be radially outwardly displaced within cavity 15 to the position designated C. In this position there is established an equilibrium condition between the axial components of the centrifugal force exerted by flyweights 16 and the force exerted by belt 8 on disk 13.
As a result, flyweights 16 come to rest at this position and are prevented from being further outwardly displaced in radial direction, so that disk 13 is supported at a position correspondingly closer to fixed disk 14, thereby to increase the effective diameter of driving pulley 9 to rotate drum 6 at a different transmission ratio. In the present example, this results in drum 6 being rotated at a speed of about 85 rpm for advantageously establishing a short phase for evenly distributing the laundry within drum 6, while there is still water in tub 5, prior to initiating the conventioanl centrifuging steps. In this manner it is possible to eliminate or to substantially reduce the vibrations of the drum during the centrifuging operation.
Motor 7 is subsequently rotated at its higher speed for rotating drum 6 at the centrifuging speed.
In the example under discussion it is thus possible to obtain an intermediate centrifuging speed of about 509 rpm and a maximum speed of about 800 rpm for the final centrifuging operation by retaining the water in cylinder 18 or by discharging it therefrom, respectively, the latter per- miting flyweights 16 to be displaced within cavity 15 from their position C to the position designated B in the manner described above.
With this type of a speed variator it is of course possible to obtain additional rotational speeds of the drum in between the laundering and centrifuging speeds by displacing piston 17 to further operating positions and by preferably providing further planar surface portions and associated ramps within cavity 15 for determining further rest positions of flyweights 16 at the respective connecting zones.

Claims

A speed variator for a laundry washing machine comprising a laundering tube (5), a drum (6) mounted for rotation within said tub (5), and a motor (7) for rotating said drum (6) at a laundering speed and a centrifuging speed, said speed variator comprising at least one transmission belt (8) interconnecting a driving pulley (9) of said motor (7) and a driven pulley (10) associated to said drum (6), at least one of said pulleys, preferably the driving pulley (9), being provided with a number of radially displaceable flyweights (16) of preferably cylindrical shape, said pulley (9) being of the variable-diameter type, said speed variator further including at least one hydraulic piston (17) or the like mounted for reciprocating displacement in a corresponding cylinder (18) connected to the water supply circuit (22) of the machine through at least one solenoid valve (19) or the like adapted to control the supply and the discharge of a liquid to and from said cylinder (18), respectively, for displacement of said piston (17) between different operating positions, said piston (17) cooperating with said flyweights (16) so as to interdict or permit the radial expansion displacement thereof to varying degrees to thereby vary the effective diameter of the associated pulley (9), said pulley (9) being provided with at least one internal cavity (15) defined by planar inclined surface portions (25-29) interconnected by connection zones (30) forming different inclinations, said flyweights (16) being freely displaceable along said surface portions (25-29) as to come to rest only at each connection zone (30), depending on the respective operating position of said piston (17) and on the rotational speed of said pulley (9).