Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Manipulation of liquid
Reexamination Certificate
2001-05-24
2003-06-17
Stinson, Frankie L. (Department: 1746)
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Manipulation of liquid
C068S012020, C068S012060, C068S012120
Reexamination Certificate
active
06578225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to pre-balancing methods and apparatus, and in particular to pre-balancing methods and apparatus useful for domestic and commercial washing machines.
2. Brief Description of the Related Art
The need for balancing of washing machine baskets is well known. In a typical washing machine, upon the completion of the wash cycle, the excess water is extracted from clothes during the so-called spin cycle. During a spin cycle, the clothes held in the wash basket are rotated at high speeds. The excess water, acted upon by the centrifugal forces generated by this spinning, is forced out of the clothes and to the outside of the wash basket, where it forced out through the perforations in the walls of the wash basket and into the drain. An efficient water extraction from the clothes is beneficial as it reduces the drying times for clothes.
The efficiency of the water extraction depends on the spin speeds. It is a well-known fact that the higher the spin speed, the higher the water extraction. It is therefore beneficial to afford high spin speeds in washing machines. However, high spin speeds give rise to high levels of vibration caused by imbalances in the wash basket due to uneven distribution of clothes during spinning. Such imbalances randomly change from one wash to the next and their exact magnitudes and locations relative to wash baskets are not known prior to spinning. The difficulty in dealing with such imbalances is further exacerbated by the fact that as the process of water extraction takes place during the spinning operation, the imbalances change. The problem of imbalance and vibration during spinning is undesirable due to stress and damage to the machine and its various components. Furthermore, excessive vibration during the spinning can adversely affect the efficiency of water extraction, result in unwanted noise, and in some cases, cause damage to the sub-floor.
A number techniques have been proposed to deal with the problem of imbalance in wash baskets. The most commonly used technique relies on attaching heavy counterweights to the outer tub, which houses the rotating wash basket. Such counter-weights are typically made of steel, concrete, or some other heavy material, and are intended to reduce vibration by increasing the weight of the suspended assembly. The main disadvantages of such a technique are the increased weight and cost of the machine, as well as the fact that the rotating components are still subjected to the same damaging stresses due to imbalance.
Various alternate techniques have been proposed that counteract the unknown and changing imbalances in wash baskets of washing machines. These techniques are based on the concept of the so-called automatic balancing. Herein, the balancing is achieved by operably mounting an apparatus on the rotating member, which includes an annular cavity containing a balancing fluid or a plurality of movable masses. As sufficient rotational speeds of the rotating member are reached, the balancing fluid or the movable masses position themselves as to counteract the imbalance of the rotating member. One such apparatus is described in U.S. Pat. No. 4,433,592 (Tatsumi et al.). Tatsumi et al. describe a vertical axis washing machine including a wash basket rotatable about its axis of rotation and operably mounted inside the outer tub. The apparatus further includes an annular groove or a race provided in the top plane of the wash basket containing a plurality of freely movable counterbalancing weights. As the wash basket reaches its spin speed, the counterbalancing weights position themselves as to counteract any imbalances in the wash basket.
A similar type of structure is described in the U.S. Pat. No. 2,984,094 (Balaieff). Balaieff describes a front loading, horizontal axis washing machine assembly having annular races or grooves placed at each end and at the outer periphery of the rotating wash basket and concentric with its axis of rotation. The apparatus further includes pluralities of freely movable balls disposed in each of the annular grooves. During the operation of the rotating member, such balls position themselves so as to compensate for any unbalanced static and dynamic loads.
Another type of apparatus is described in U.S. Pat. No. 5,448,979 (Ryan et al.). Ryan et al. describe a wash basket with two balancing rings including annular grooves partially filled with a balancing fluid, such as water. The annular grooves are placed at the opposite ends of the wash basket. During operation, the balancing fluid flows into the direction so as to counteract the imbalance forces.
Further, a similar structure is described in U.S. Pat. No. 5,345,792 (Farrington et al.). This document describes an apparatus including a plurality of annular grooves disposed at each end of the wash basket and containing pluralities of balancing fluids.
Yet further types of apparatus are described in U.S. Pat. No. 5,850,748 (Kim et al.). Kim et al. describes a wash basket of a front loading horizontal axis washing machine including two concentric annular races placed at each end of the wash basket, each pair of annular races containing compensating weights of different size with the inner races having smaller weights than the outer races.
Such prior devices provide compensation for imbalance at the spin speeds; however, these devices have certain disadvantages. It is well known to those skilled in the art that automatic balancers counteract the imbalance forces in rotating members at speeds which are above the so-called resonant or critical speed of the suspended assembly. In typical washing machines, and indeed in most washing machines, such critical speeds are lower than the design spin speeds of rotation of the wash baskets. Therefore, automatic balancers, such as those described in the above prior documents, are able counteract the imbalances at spin speeds. However, automatic balancers are ineffective for rotating speeds below the critical speeds and actually can add to the imbalance forces. A consequence of this limitation is that during the entire time that the wash basket is accelerated from its initial position of rest to the operating speed, the wash basket remains severely unbalanced. Furthermore, upon start-up, as the speed of rotation approaches the critical speed of the suspended wash assembly, violent resonant oscillations occur resulting in the assembly often hitting the cabinet of the washing machine. In fact, it has been observed that such resonances are often more severe in cases when automatic balancers are deployed. Correspondingly, heavy counterweights must be utilized to control such resonances and on occasion larger washing machine cabinets are required. This, in turn, results in higher cost of the machine, higher transportation costs, and inconvenience to the end user.
Furthermore, most modem machines come equipped with imbalance sensors and/or trip switches to protect the fragile electronic systems. Therein, if sufficiently large imbalances, or excessive vibration levels during start-up, are detected, the washing machine will not begin the spin cycle. As a result, water extraction will not take place until the user manually rearranges the wet laundry inside the wash basket. Herein lies a significant disadvantage of the above prior devices. Since imbalance detection takes place at low speeds, which are below the resonant speeds, greater imbalances will typically be sensed with automatic balancers. Similarly, as the machine accelerates through its resonant speed, higher levels or resonant vibrations will typically result with automatic balancers. Consequently, such systems can be detrimental to the proper engagement of spin cycles.
One solution to overcome the disadvantages of the above prior art is through so-called pre-balancing. It is known to those skilled in the art that some type of pre-balancing of the wash loads is required prior to engaging the spin cycle, regardless of whether the machine is equipped with automatic balancers or not. Pre-balancin
Burns Doane , Swecker, Mathis LLP
SKF AutoBalance Systems AB
Stinson Frankie L.
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