Speed variator for laundry washing machine

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) for 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

[0001] The present invention relates to a speed variator for a laundry washing machine permitting the drum thereof to be rotated at different speeds.

[0002] 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.

[0003] To this effect, the motor advantageously cooperates with a suitable speed variator permitting the drum to be rotated with a variable transmission ratio.

[0004] 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 expanded second position corresponding to the centrifuging speed. In this manner the 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.

[0005] 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 expansion thereof to varying degrees.

[0006] 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 construction and considerable dimensions, so that they are not very practical in use.

[0007] Also known are speed variators of the type defined above, provided with 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.

[0008] 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 expansion of the flyweights for thus varying the 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 continuous'adn progressive manner for rotating the drum at speeds comprised between the laundering and centrifuging speeds. This type of control is obtaiend 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.

[0009] 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 an on the relative position assumed by a hydraulic piston operable to interdict or permit the radial expansion 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.

[0010] 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 certein, 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.

[0011] It is an 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.

[0012] A speed variator of this type is essentially composed of at least one variable-diameter pulley cooperating with radially expandable 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 thereof to varying degrees.

[0013] 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 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.

[0014] These and other objects are attained according to the invention by a speed variator for a laundry washing machine having a laundering tub, a drum mounted for rotation within said tub, and a motor for rotating said drum at a laundering speed and at a centrifuging speed, said speed variator comprising at least one transmission belt operatively connecting a driving pulley of said motor to a driven pulley of said drum, and a number of radially expandable flyweights preferably of cylindrical shape cooperating with at least one of said pulleys, preferably the driving pulley, having a variable effective diameter, said speed variator additionally comprising at least one hydraulic piston or similar device slidingly reciprocating in an associated cylinder connected to the water circulation circuit of the machine through at least one solenoid valve or the like operable to permit the supply to or discharge from said cylinder of a liquid so as to displace said piston to different operating positions, said piston cooperating with said flyweights so as to interdict or to permit to varying degrees the expansion thereof thereby to vary the effective diameter of the associated pulley.

[0015] According to the invention, a speed variator of the type defined above is characterized in that said pulley is formed with at least one internal cavity defined by planar or arcuate surface portions interconnected respectively by inclined ramps or arcuate surface portions of different radius, so that during rotation of said pulley said flyweights are freely displaceable along said surface portions and adapted to be retained adjacent any interconnecting portion between two consecutive surface portions in response to the rotational speed of the pulley and the relative operating position assumed by said piston.

[0016] The characteristics and advantages of the invention will become more clearly evident from the following description of embodiments 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 and 3 show enlarged views in axial section of parts of the speed variator of fig. 1 in two different embodiments of the invention.

[0017] 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.

[0018] 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 copperate to define therebetween at least one internal cavity 15 for accommodating a number of radial-expansion flyweights 16 or preferably cylindrical shape.

[0019] 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 obtained according to the invention by employing a variable-diameter driven pulley 10 in place of, or in combination with, a variable-diameter driving pulles 9.

[0020] Flyweights 16 are designed to radially expand to varying degrees in response to the rotational speed of motor 7. Radial expansion of flyweights 16 causes movable disk 13

[0021] 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.

[0022] 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.

[0023] In addition to the transmission elements descriebd above, the speed variator according to the invention includes at leat one hydraulic piston 17 (sh6wn 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.

[0024] Piston 17, cylinder 18 and the remaining elements associated therewith are of the type descibed in Italian Patent Application No.45737-A/83 filed on 12-23-83 by Applicant. 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 of flyweights 16 to varying degrees for correspondingly varying the effective diameter of driving pulley 9 in the same manner as described in the patent application quoted above. It is of 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.

[0025] Merely by way of example, it is possible to apply the solution descriebd in Italian Patent Application No. 45722-A/84 filed on 9-17-84 by Applicant, 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 lector, the hinged arm is capable of assuming various angular positions under the control of the hydraulic piston, the displacements of which thus determine the radial expansion of the flyweights and thus the effective diameter of the driving pulley.

[0026] Shown in fig. 2 is a particular of a first embodiment of the present invention.

[0027] 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 diskse 11 and 13 in symmetric relationship and interconnected by suitably inclined ramps. The flyweights 16 are thus freely displaceable between the planar surfaces of any pair thereof and come to rest at the inclined ramps interconnecting 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 additional 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.

[0028] 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 descriebd in the abobe quoted patent applications. 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.

[0029] 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 radially expanding by the biasing action of piston 17 on belt 8. As flyweights 16 are not expanded radially, 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 be 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 radially expand 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.

[0030] As a result, flyweights 16 come to rest at this position and are prevented from further expanding in the radial direction, so that disk 13 is supported at a position correspondingly closer to fixed disk 14, thereby to increase the effective diameetr 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 conventional centrifuging steps. In this manner it is possible to eleminiate or to substantially reduce the vibrations of the drum during the centrifuging operation.

[0031] Motor 7 is subsequently rotated at its higher speed for rotating drum 6 at the centrifuging speed.

[0032] In the example under discussion it is thus possible to ob tain 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 permitting flyweights 16 to be displaced within cavity 15 from their position C to the position designated B in the manner descriebd above.

[0033] 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.

[0034] Fig. 3 finally shows a particular of a further embodiment of the speed variator according to the invention.

[0035] According to this embodiment, cavity 15 is defined by arcuate surface portions formed in disks 11 and 13 in a symmetric arrangement as shown at 31, 32, 33, 34 and 35, and interconnected by arcuate portions having a different radius of curvature for displacement and selective retention of flyweights 16 at positions designated A, B and C, or at additional intermediate positions, in the same manner as described with referecne to the first embodiment.

[0036] The speed variator according to the invention is thus of a simple and reliable construction and of reduced dimensions while permitting to obtain accurate control of the various rotational speeds of the drum.

Claims

A speed variator for a laundry washing machine comprising a laundering tub, a drum mounted for rotation within said tub, and a motor for rotating said drum at a laundering speed and a centrifuging speed, said speed variator comprising at least one transmission belt interconnecting a driving pulley of said motor and a driven pulley associated to said drum, at least one of said pulleys, preferably the driving pulley, being provided with a number of radial-expansion flyweights of preferably cylindrical shape, said pulley being of the variable-diameter type, said speed variator further including at least one hydraulic piston or the like mounted for reciprocating displacement in a corresponding cylinder connected to the water supply circuit of the machine through at least one solenoid valve or the like adapted to control the supply and the discharge of a liquid to and from said cylinder, respectively, for displacement of said piston between different operating positions, said piston cooperating with said flyweights so as to interdict or permit the radial expansion thereof to varying degrees to thereby vary the effective diameter of the associated pulley, characterized in that said pulley (9) is provided with at least one internal cavity (15) defined by planar surface portions (25-29) or arcuate surface portions (31-35) interconnected by inclined ramps or arcuate portions of a different radius of curvature, respectively, so that on roation of said pulley (9) said flyweights (16) are freely displaceable along said surface portions (25-29; 31-35) and adapted to be retained at each connecting zone (30) between consecutive surface portions, depending on the rotational speed of said pulley (9) and on the operating position assumed by said piston (17).

Drawing