[0001] The present invention relates to a speed variator for a laundry washing machine for
permitting the drum thereof to be rotated at different speeds.
[0002] In conventional laundry washing machines, the transmission of the driving force from
an electric motor of the commutable pole type to the drum, for rotating the latter
at laundering and centrifuging speeds, is accomplished by means of a V-belt interconnecting
respective pulleys associated with the motor and the drum.
[0003] The drum may additionally be rotated at a further speed lying between the laundering
and centrifuging speeds for executing particular laundering steps, for instance for
establishing the dynamic equilibrium of the drum or for carrying out the centrifuging
operation at a reduced speed.
[0004] To this purpose, the motor may advantageously cooperate with suitable speed variator
means operable to rotate the drum at a variable transmission ratio. Known constructions
of this type include an electromechanic speed variator comprising a variable-diameter
pulley cooperating with a fork member hinged at one end to the housing of the motor
of the machine and connected at its other end to a spring-biased pull member adapted
to be actuated by a solenoid under the control of the program unit of the machine.
[0005] Energization of the solenoid causes the fork member to be arcuately displaced about
its hinged connection with the motor housing to thereby vary the effective diameter
of the pulley.
[0006] As a result,the transmission belt for rotating the drum is shifted to a different
diameter of the driving pulley, so that the drum is further rotated at a different
transmission ratio.
[0007] A speed variator of this type is of complicated and
Lulky construction while its operation is not sufficiently reliable due to the employ
of the solenoid which requires an excessive amount of electric power and is readily
affected by failure or by a tendency to faulty operation.
[0008] Other known speed variators for laundry washing machines include at least one variable-diameter
driving pulley cooperating with a number of radial-expansion flyweights, and at least
one tension roller biased by a spring into engagement with the transmission belt for
rotating the drum and operatively connected to a hydraulic or oleo-dynamic piston
mounted for reciprocating displacement in an associated cylinder connected via at
least one solenoid valve to the water supply circuit of the machine, said solenoid
valve being adapted to be automatically energized and deenergized under the control
of the program unit of the machine.
[0009] The amount of water or other liquid supplied to the cylinder in the manner described
thus determines the displacement of the piston and accordingly, of the tensioning
roller to various operating positions relative to the V-belt so as to bias the tensioning
roller into engagement therewith with a variable compressive force.
[0010] For rotating the drum of the machine at the laundering and final centrifuging speeds,
respectively, the motor is switched from its low speed to its high speed, while the
water or other liquid previously supplied to the cylinder is discharged therefrom
to thereby interdict and then to permit the radial expansion of the flyweights of
the speed variator. It is finally possible to rotate the drum at intermediate speeds
between the laundering and centrifuging speeds and depending on the rotational speed
of the motor, by progressively displacing the piston, and thus the tensioning roller,
to different positions relative to the V-belt in the manner described above.
[0011] Speed variators of this type operate in a satisfactory manner,they suffer from the
disadvantage, however, that the tensioning roller acting on the V-belt tends to set
up vibrations in the entire machine, whereby the operation thereof becomes rather
noisy.
[0012] In addition, the continuous action of the tensioning roller on the V-belt may result
in elastic elongation of the belt, so that the actual rotational speed of the drum
drops below the rated speed, requiring manual adjustments of the driving and/or driven
pulleys to be carried out for re-establishing the correct belt tension.
[0013] It is an object of the present invention to eliminate the disadvantages and shortcomings
of the known embodiments described by providing a speed variator of simple construction
and reduced dimensions, said speed variator having at least one variable-diameter
pulley cooperating with radially expandable flyweights, and at least one hydraulic
or oleo-dynamic piston of the type described, said piston being not, however, provided
with a tensioning roller in the present case while being operable to determine the
rotation of the drum of the machine at different speeds in a manner different from
the one described above.
[0014] A speed variator of this type is characterized in that the motor of the machine,
together with the variable-diameter pulley, is carried by at least one hinged arm
of a suitable configuration having one of its ends hinged to a lower portion of the
laundering tub, while its other end is connected to said piston, said arm being biased
by at least one torsion spring in a direction in which said variable-diameter pulley
tends to keep said transmission belt under tension.
[0015] In this manner, the transmission belt can be shifted to different diameters of the
variable-diameter pulley, depending on the rotational speed of the motor and on the
operative position assumed by the piston, the latter being operable to interdict or
permit the radial expansion of the flyweights to varying degrees so as to cause the
drum to be rotated at variable transmission ratios.
[0016] This solution thus lacks the above described tensioning roller, resulting in the
elimination of the vibrations and noises set up by such a roller in the entire washing
machine.
[0017] In addition, as the transmission belt is always kept under tension by the hinged
arm, the distance between the driving and driven pulleys of the washing machine does
not require any manual adjustment.
[0018] These and other objects are obtained according to the invention by a speed variator
for a laundry washing machine comprising a laundering tub, a drum mounted for rotation
within the tub, and a motor for rotating said drum at the laundering and centrifuging
speeds, said speed variator including at least one transmission belt interconnecting
a driving pulley of said motor and a driven pulley associated with said drum, and
a number of flyweights associated with at least one of said pulleys, preferably the
driving pulley, the effective diameter of which is variable, said flyweights being
adapted to expand radially at the centrifuging speed of said motor so as to correspondingly
vary the effective diameter of the associated pulley, 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 via
a three-way valve and at least one solenoid valve or the like operable to control
the supply and discharge of a liquid to, or from, respectively, said cylinder for
displacement of said piston to different operating positions.
[0019] According to the invention, this speed variator is characterized in that said motor,
together with said variable-diameter pulley, is carried by a hinged arm having one
of its ends hinged to a lower portion of said tub while having its other end connected
to said piston, Said arm being biased by resilient means in a direction causing said
variable-diameter pulley to continually tension said belt, irrespective of the radial
expansion of said flyweights, said piston being adapted to act on said hinged arm
so as to interdict or to permit to a variable degree the radial expansion of said
flyweights depending on the respective operating position assumed by the piston.
[0020] The characteristics and advantages of the invention will become more clearly evident
from the following description given by way of example with reference to the accompanying
drawings, wherein:
fig. 1 shows a partially sectioned rear view of a laundry washing machine provided
with a speed variator according to the invention, the latter being in a first operating
position,
fig. 2 shows a top plan view of the speed variator according to fig. 1 as sectioned
along the line I-I in fig. 1, and
fig. 3 shows a view similar to that shown in fig. 1, with the speed variator in a
second operating position.
[0021] With referecne to figs. 1 and 2, there is diagrammatically shown a laundry washing
machine 4 having a laundering tub 5 and a rotatable drum 6 mounted within tub 5 and
adapted to be rotated by an electric motor 7 via at least one transmission V-belt
8 interconnecting a driving pulley 9 of motor 7 and a driven pulley 10 associated
with tub 6.
[0022] In particular, driving pulley 9 is of the variable-diameter type essentially composed
of a disk 11 fixedly secured to a shaft 12 of motor 7, and a further disk 13 mounted
on shaft 12 for displacement towards and away from fixed disk 11 and operatively connected
to a number of radially expandable flyweights 14.
[0023] Energization of motor 7 thus causes driving pulley 9 to be rotated together with
flyweights 14. Merely by way of example, motor may be designed to rotate drum 6 at
different speeds, namely, a reduced laundering speed of for instance about 50 rpm,
and an increased centrifuging speed of about 800 rpm. A satisfactory result may also
be obtained when only driven pulley 10 or both pulleys 9 and 10 are of the variable-diameter
type, these modifications being also included within the scope of the invention.
[0024] Flyweights 14 are dimensioned so as to expand to the full radial extent at the maximum
rotational speed of motor 7. This radial expansion of flyweights 14 causes movable
disk 13 to be displaced towards fixed disk 11 so as to vary the effective diameter
of pulley 9. In this manner, transmission belt 8 is shifted to different effective
diameters of driving pulley 9 for rotating drum 6 at variable transmission ratios.
[0025] In particular, the belt may be shifted in this manner from the laundering speed position
shown in fig. 1 to the centrifuging speed position shown in fig. 3.
[0026] The laundering tub 5 of the present invention has its lower portion provided with
brackets 15 and 16 for connection to conventional vibration dampeners (not shown)
and with two identical mounting arms 17, 18 of reduced thickness secured to the bottom
portion of tub 5 parallel to one another.
[0027] Also provided is a rigid arm 19 of an arcuate profile corresponding to the circumferential
shape of motor 7, the width of arm 19 being somewhat smaller than the axial length
of motor.
[0028] As particularly shown in fig. 2, arm 19 serves for carrying motor 7 together with
driving pulley 9, to which purpose motor 7 is provided with lugs 21 welded to its
upper portion and secured to arm 19 by means of bolts and nuts 20 or similar fastener
elements. The arm may also be integrally connected to motor 7. In the embodiment shown,
arm 19 is formed with parallel upstanding sidewalls 22 and 23 having one end thereof
hingedly mounted between support arms 17 and 18 by means of a transversely extending
bolt 24 threaded into corresponding bores formed in the support arms and sidewalls
and fixed to the support arms in a per se known manner.
[0029] Adjacent bolt 24 there is provided at least one torsion spring 25 having its free
ends 26 and 27 anchored respectively to one of the support arms, for instance support
arm 18, and one of the upstanding sidewalls, for instance sidewall 23 of carrier arm
19.
[0030] Torsion spring 25 is provided for permanently biasing carrier arm 19, and thus motor
7 together with driving pulley 9, in the direction indicated by arrow A in fig.1,
so that transmission belt 8 is always kept under tension irrespective of its being
shifted to different effective diameters corresponding to the respective positions
assumed by flyweights 14. As a result, there is no need for manual adjustment of the
spacing between driving and driven pulleys 9 and 10, respectively, as in prior art
machines.
[0031] For ensuring proper movement of carrier arm 19 over a limited range and without lateral
displacement, the sidewalls of carrier arm 19 and the adjacent mounting arms are operatively
interconnected by a slot and pin system 28.
[0032] In addition to the components descriebd, the speed variator according to the invention
includes at least one hydraulic or oleo-dynamic piston 29 mounted for reciprocating
displacement in an associated cylinder 30 secured to bracket 16 of tub 5 and connected
through a solenoid valve 31 and a pipe 32 to a three-way connector 33 provided in
the water supply circuit 34 of the machine, supply circuit 34 itself being connected
to a detergent distributor 35 and to the external water supply mains through a further
solenoid valve 36.
[0033] The same result may be obtained by connecting cylinder 30 to a separate pressurized
container (not shown accommodated within the housing of the machine.
[0034] Three-way connector 33 may advantageously be provided with a conventional filtering
element (not shown) for ensuring proper operation of piston 29 by once again filtering
the water derived from the supply circuit of the machine.
[0035] Piston 29 is operatively connected to the free end of carrier arm 19 by a rod 37
for adjustment to different operating positions by sliding displacement in cylinder
30 in the same manner as described in Italian Patent Application No. 45737-A/83 filed
on 12-23-83 by the present applicant, according to which patent application the piston
is connected to a tensioning roller for biasing it into pressure engagement with the
transmission belt of the machine.
[0036] The purpose of piston 29 is to interdict or permit the radial expansion of flyweights
14 to varying degrees determined by the operating position of the piston for permitting
belt 8 to be shifted to correspondingly varying effective diameters of driving pulley
9 so as to rotate drum 6 at different transmission ratios.
[0037] The speed variator according to the invention operates as follows:
At the beginning of a laundering cycle solenoid valves 36 and 31 are energized for
supplying mains water to tub 5 via distributor 35 and supply circuit 34 and to cylinder
30 via pipe 32 (cf. fig. 1).
[0038] When cylinder 30 is completely filled with water, solenoid valve 31 is closed so
as to prevent the water from escaping from cylinder 30.
[0039] The pressure of the water in cylinder 30 is effective to displace piston 29 to its
fully extended position so as to cooperate with torsion spring 25 in rotating carrier
arm 19 in the direction of arrow A to a position determined by the tension of belt
8. Carrier arm 19 is then stably retained in this position irrespective of the rotational
speed of motor 7, because the force exerted by piston 29 on carrier arm 19 overcomes
the oppositely directed force acting thereon as a result of the tendency of flyweights
14 to radially expand. Consequently the effective diameter of pulley 9 remains unchanged
even at the maximum rotational speed of motor 7. During the initial phase of the washing
cycle, however, motor 7 rotates only at the laundering speed, at which the flyweights
14 are not radially expanded, so that driving pulley 9 is maintained at its minimum
effective diameter.
[0040] During a subsequent phase, motor 7 is switched to its centrifuging speed, at which
flyweights 14 tend to expand radially, such radial expansion being still prevented
from occurring, however, by the action of piston 29 on carrier arm 19 precluding its
rotation about bolt 24.
[0041] As a result, drum 6 is now rotated at a higher speed than previously, without however
being able to attain the maximum centrifuging speed.
[0042] In the example described, the drum is now rotated at a speed of about 400 rpm prior
to carrying out the centrifuging step at the maximum rotational speed.
[0043] For attaining this maximum speed, motor 7 is kept switched to high speed operation,
and solenoid valve 31 is energized for permitting the water contained in cyclinder
30 to be discharged therefrom into tub 5 via pipes 32 and 34 and detergent distributor
35.
[0044] As a result, carrier arm 19 is no longer retained by piston 29 in its previous position,
and is now rotated in the direction indicated by arrow B by the force resulting from
the radial expansion of flyweights 14 in opposition to the bias of spring 25, this
rotation of carrier arm 19 being limited by the slot and pin system 28 (cf. fig. 3).
[0045] In this operating condition, carrier arm 19 has pushed piston 29 completely back
into cylinder 30, while driving pulley 9 assumes its maximum effective diameter for
rotating drum 6 at the maximum centrifuging speed.
[0046] In a similar manner it is also possible to rotate the drum at intermediate speeds
between the laundering and centrifuging speeds by permitting the water previously
supplied to cylinder 30 to be gradually discharged therefrom into the tub for displacing
piston 29 to different operating positions. This may be done by energizing solenoid
valve 31 repeatedly and at predetermined intervals.
[0047] The present speed variator is of simple construction and reduced dimensions, permitting
it to be readily installed in a restricted space within the housing of a laundry washing
machine.
[0048] The speed variator also permits the drum to be reliably rotated at different rotational
speeds between the laundering and centrifuging speeds while eliminating the generation
of vibration and noise caused in prior art machines by the employ of tensioning rollers
acting on the transmission belt.
[0049] The speed variator finally ensures proper tensioning of the transmission belt 8 at
all times, irrespective of the rotational speed of motor 7 and thanks to the spring-biased
mounting of carrier arm 19, without the need for manual adjustments.
1. 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 laundering
and centrifuging speeds, said speed variator including at least one transmission belt
interconnecting a driving pulley and a driven pulley of said motor and said drum,
respectively, and a number of flyweights associated with at least one of said pulleys,
preferably the driven pulley, said pulley being of the variable-diameter type, said
flyweights being adapted to expand radially at the centrifuging speed of said motor
so as to correspondingly vary the effective diameter of the associated pulley, said
speed variator further including at least one hydraulic piston or the like mounted
for reciprocating displacement in an associated cylinder connected to the water supply
circuit of the machine through a three-way connector and at least one solenoid valve
or the like adapted to control the supply and the discharge of a liquid to, and from,
respectively, said cylinder so as to displace said piston to different operating positions,
characterized in that said motor (7) together with said variable-diameter pulley (9)
is supported by at least one rotatable carrier arm (19) having one of its ends hinged
to a lower part of said tub (5) while its other end is connected to said piston (29),
said carrier arm (19) being biased by resilient means (25) towards a position whereat
said variable-diameter pulley (9) constantly maintains said belt (8) in a tensioned
state against the action of the radial expansion of said flyweights (14), said piston
(29) being adapted to act on said carrier arm (19) in a manner to interdict or permit
the radial expansion of said flyweights (14) to varying degrees depending on the operating
positioon assumed by said piston (29).
2. A speed variator according to claim 1, characterized in that said rotatable carrier
arm (19) is of an arcuate configuration having the same profile and a slightly smaller
width than said motor (7) for permitting said carrier arm (19) to be fitted and secured
to the top portion of said motor.
3. A speed variator according to claim 1, characterized in that said rotatable carrier
arm (19) is integrally connected to said motor (7).
4. A speed variator according to any of claims 1 to 3, characterized in that said
rotatable carrier arm (19) is formed with upstanding sidewalls (22, 23) extending
parallel to one another and adapted to be connected to rigid mounting arms (17, 18)
secured in proximity thereto to the lower portion of said tub (5) by means of respective
slot and pin systems (28).
5. A speed variator according to claim 4, characterized in that said resilient means
comprise at least one torsion spring (25) or the like disposed adjacent an articulating
bolt (24) of said carrier arm (19) and having its ends (26, 27) anchored to one (18)
of said mounting arms and the adjacent sidewall (23) of said carrier arm, respectively.
6. A speed variator according to any of claims 1 to 5, characterized in that said
three-way connector (33) may be provided with at least one filter element of conventional
type.