Field of the invention

The present disclosure relates to a laundry washing machine comprising a rotatable drum, carried by and adapted to rotate in relation to a drum frame, and a suspension arrangement, carrying the drum frame in relation to a base structure, located under the washing machine and on which the washing machine rests.

Technical background

Such washing machines are widely used and generally give good washing results.

Problems associated with washing machines of this type include how to make them, lighter, more silent, and to avoid that they move on the floor or the like, e.g. during an extraction phase of a washing cycle, when the drum rotates at high speed.

Summary of the invention

One object of the present disclosure is therefore to provide a washing machine which is one or more of lighter, more silent or less prone to move during extraction. This object is achieved by means of a laundry washing machine as defined in claim 1. In a washing machine of the initially mention kind there may then be provided more specifically at least one vibration absorber arrangement being attached to the drum frame and forming a spring-mass system having a resonant frequency. The vibration absorber arrangement may comprise a carrier rod and a mass, wherein a proximal end of the carrier rod is attached to the drum frame at an attachment point, the mass is suspended by the carrier rod at a distance from the attachment point.

In such a washing machine, the vibration absorber arrangement may be tuned to resonate at for instance a frequency corresponding to the extraction speed of the drum. This means that the vibration absorber arrangement absorbs the drum frame’s vibrations to a great extent by vibrating out of phase therewith. The result is a more silent machine where the drum frame can be made lighter, and/or where the amount of forces being transmitted from the drum to the ground is reduced, such that the risk of the machine ‘wandering’ is more or less eliminated.

The above-mentioned distance may be variable to change said resonant frequency. Such a vibration absorber arrangement can thus be tuned to follow the instantaneous rotation speed of the drum, thereby substantially reduce drum vibrations and transmission of forces to the base structure, which could otherwise cause the machine to move. It also becomes possible for a given allowed level of vibration to reduce ballast weights of the drum frame, thereby providing an overall lighter machine.

The proximal end of the carrier rod may be fixedly attached to the drum frame at the attachment point, and the mass may be moveable on the carrier rod.

Alternatively, the proximal end of the carrier rod is slideably attached to the drum frame at the attachment point, and the mass may be fixedly attached to the carrier rod.

Typically, a vibration absorber may be placed in each corner of the drum frame.

The washing machine may comprise a sensing device, providing a speed signal corresponding to the rotation speed of the drum, and an adjusting device, adjusting the resonant frequency of the vibration absorber arrangement in response to the speed signal.

The present disclosure also considers a laundry washing machine comprising a rotatable drum, carried by and adapted to rotate in relation to a drum frame, a suspension arrangement carrying the drum frame in relation to a base structure, located under the washing machine and on which the washing machine rests, wherein at least one vibration absorber arrangement is attached to the drum frame forming a spring-mass system having a resonant frequency, a sensing device, providing a speed signal corresponding to the rotation speed of the drum, and an adjusting device, adjusting the resonant frequency of the vibration absorber arrangement in response to the speed signal.

The present disclosure further considers a method for controlling a laundry washing machine comprising a rotatable drum, carried by and adapted to rotate in relation to a drum frame, a suspension arrangement carrying the drum frame in relation to a base structure, located under the washing machine and on which the washing machine rests. The washing machine comprises at least one vibration absorber arrangement being attached to the drum frame forming a spring-mass system having a resonant frequency. The method includes providing a speed signal corresponding to the rota tion speed of the drum and adjusting the resonant frequency of the vibration absorber arrangement in response to the speed signal.

Brief description of the drawings

Fig 1 shows a perspective view of a washing machine.

Fig 2 shows a perspective view of a drum frame.

Fig 3 illustrates schematically a conventional suspension arrangement with dampers and springs.

Fig 4 shows a vibration absorber arrangement with a carrier rod and a mass.

Fig 5 illustrates how such vibration absorber arrangement can be attached to a drum frame carried by a suspension arrangement.

Fig 6 and 7 illustrate schematically different ways of accomplishing a tunable vibration absorber.

Fig 8 illustrate ground force transmission over a frequency range, with and without tunable vibration absorbers.

Detailed description

The present disclosure relates generally to a washing machine 1 , an example of which is shown in fig 1. The washing machine comprises an outer housing 3 and rests on a base structure 5, which is typically a floor, but in principle could be a rack or another machine, for instance. At a front side 7 of the washing machine, there is located a door 9 through which the interior of a drum is accessible. There also exist machines where laundry is inserted from the top of the machine, and the present disclosure is equally relevant to such machines.

Fig 2 shows a perspective view of a drum frame 11 , used in a machine of the type shown in fig1. The drum frame comprises a frame base 13 and metal straps 15 that are designed to firmly connect an outer, fixed drum (not shown) configured to contain water during washing, and in which an inner drum is configured to rotate and contain laundry being processed.

Fig 3 illustrates schematically a conventional suspension arrangement for a drum frame 11 of this kind. As mentioned, the drum frame 11 carries an outer drum 17, in which an inner drum 19 is rotatable. The drum frame 11 in turn is connected via a suspension arrangement 23, 25 to a bottom plate 21 , or the like, which in turn rests on the aforementioned base structure 5. The suspension arrangement typically comprises a number of dampers 23 and springs 25. Which together provide properties to the dynamic system formed inside the washing machine.

The present disclosure relates to a method and arrangement, mostly intended for professional washing machines, but also applicable for domestic use, that lowers both force transmission from the drum and drum oscillations.

In a washing machine, the non-uniform mass distribution of the laundry inside the rotating drum generates centrifugal forces acting on the drum system. This produces drum oscillations and force transmission to the ground which should be limited in order to reduce noise and the risk of the machine wandering.

The dynamic responses of washing machines provide resonance peaks, at which both force transmission and drum oscillation are the highest. The resonance para meter is an intrinsic feature of the dynamic mechanical configuration of the appliance, although weight and distribution of the laundry in the drum gives some variation. In order to lower the resonance frequency, so as to reduce the total force transfer to the ground and to lower the drum oscillation at maximum speed, ballast masses 27 of. fig 5 are fixed to the drum frame, thereby increasing inertia and lowering the resonance frequency. Typically, this is done to lower the resonance frequency further away from the frequencies induced by the drum rotating at a speed suitable for extracting water from the laundry.

Such a solution is simple to implement but increases significantly the final weight of the appliance and its cost.

In the present disclosure, there is introduced one or more vibration absorber arrange ments, which are attached to the drum frame and comprise a suspended mass. Typically, one may be arranged at each corner of the machine, although other con figurations are possible. The vibration absorber arrangement forms a spring-mass system having a resonant frequency. When the drum frame vibrates at a frequency reaching the resonant frequency of the vibration absorber arrangement, the mass begins to resonate, i.e. swing, with an amplitude that may be substantially greater than the drum frame’s vibration amplitude, but out of phase therewith. This means that the vibration absorber arrangement substantially dampens the vibration of the drum frame itself.

Fig 4 shows a vibration absorber arrangement 29 with a carrier rod 33 and a mass 31. The mass 31 may here be made of a material with relatively high density such as Lead or Zink, for instance. The carrier rod 33 on which the mass 31 is suspended is elastic and has well-defined spring characteristics. It may be solid or hollow and typically made of steel. The proximal end of the carrier rod 33, i.e. the end closest to the drum frame, is attached to a base plate 35 by means of a clamp 36 forming an attachment point. The base plate may be screwed or welded to the drum frame of the washing machine.

In this configuration, if the carrier rod 33 is horizontally oriented, the mass 31 will swing up and down with a significant movement when the drum frame vibrates at the resonant frequency. As mentioned, one vibration absorber arrangement 29 may be located in each corner of the machine, as illustrated in fig 5, which shows the drum frame 11 carrying the drum 19, and in turn being suspended by suspension arrange ments 23, 25, comprising dampers 23 and springs 25, in relation to a base plate 21. The horizontal orientation of the carrier rod 33 is not necessary, and the orientation may be selected based on predicted vibration amplitude directions.

In addition to just providing a vibration absorber arrangement 29, the vibration absorber arrangement may be made controllable such that its resonance frequency is adapted to the movements of the drum. Such controlling may be based on the drum speed or its acceleration, angular or linear, or both. This may further lower the drum’s oscillation and transmission of forces to the ground. The dynamic response of the appliance is strongly related to the frequency of excitation established by the rotating speed of the drum.

Fig 6 and 7 illustrate schematically different ways of accomplishing a tunable vibra tion absorber arrangement. In a first version, shown in fig 6, the mass 31 is moveable on the rod 33, in order to obtain different distances d to the base plate 35 as illustrat ed with an example in dotted lines. Generally, a shorter distance implies a higher resonance frequency. In this embodiment, a mechanism is provided to move the mass 31 on the rod 33, typically using a hollow carrier rod 33. In the version illustrated in fig 7, the mass 31 is fixedly attached to the carrier rod 33, and instead, the rod 33 is made linearly moveable in relation to the point at which it is attached to the drum frame. This can be accomplished for instance by means of a linear actuator. It is also possible e.g. to provide a threaded portion on the exterior of the rod 33 in engagement with a corresponding thread in the opening of the base plate 35, and use a stepping motor 37 to rotate the rod 33, thereby changing the distance d. Regardless of how this mechanical arrangement is provided, it may be controlled by a control unit 39 which receives information regarding the rotation speed of the drum from a sensor 40. This sensor 40 may be devised in different ways. It is possible for instance to use accelerometers located on the drum, a dedicated rpm meter or to use driving motor currents to determine the drum speed and a corresponding target tuning frequency for the tunable vibration absorber arrangements. Such a sensor and controller may be used also in an arrangement as shown in fig 6.

The distance d between the mass and the attachment point can thus be made vari able, such that the vibration absorber arrangement can always resonate at the frequency implied by the instantaneous drum rotation speed, which provides excel lent damping of drum vibrations.

Fig 8 illustrate ground force transmission over a frequency range, with and without tunable vibration absorbers following the drum rotation speed. As shown, the trans mission of forces to the ground drops significantly compared to the corresponding machine without the vibration absorbers. As can be seen in fig 8, this drop in ground force transmission of the drum frame with a vibration absorber arrangement 43 compared to a system without dampers 41 arises significantly already at about 10 Hz, the initial peak being the resonance frequency of the drum itself. The extraction speed may correspond to several hundred Hertz.

The present disclosure is not restricted to the above-described embodiment and may be varied and altered in different ways within the scope of the appended claims.