Rotary kinetic fluid motors or pumps – Including additional means causing or controlling fluid flow... – Means subjected to or is working fluid
Reexamination Certificate
2001-10-23
2004-05-18
Verdier, Christopher (Department: 3745)
Rotary kinetic fluid motors or pumps
Including additional means causing or controlling fluid flow...
Means subjected to or is working fluid
C415S177000, C415S178000, C415S206000, C415S214100, C219S543000, C219S544000, C392S479000, C392S480000, C392S485000, C392S487000
Reexamination Certificate
active
06736598
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a pump, particularly for washing machines, dishwashing machines and the like, having a housing and a heating device for the continuous heating of a liquid, particularly water, in which the heating device is constructed as the circumferential wall of the housing.
BACKGROUND OF THE INVENTION
For heating the water necessary for operation, it is known to place in the interior of such devices heating elements such as heating coils. However, not only are the design and assembly costs also in conjunction with possible repairs, but also the direct contact of the heating elements with the water to be heated, which in particular with highly calcareous waters lead to significant reductions in the service life and efficiency of the heating coils are disadvantageous or can make necessary further constructional measures. Frequently mechanical damage occurs to the heating coils through dropping objects.
It is also known to position upstream of said devices a boiler or a separate hot-water heater, where the water is heated to the necessary temperature. However, such additional units require extra space, so that the devices either have larger dimensions or their useful volume is correspondingly reduced and are in part complicated from the design standpoint and correspondingly cost intensive.
It has finally been proposed to place a heating device on the outside of the sump container housing, but this does not lead to a uniform heating of the water.
DE 199 03 951 A1 describes a pump for washing machines, dishwashers, etc. having a housing and a heating device for continuous liquid heating, the latter having a heater located on the outside of the pump housing and a heat distributing plate positioned between the pump housing wall and the heating device for the uniform distribution of the heat produced by the heating device over the pump housing. Although this leads to a uniform heating of the water whilst avoiding the aforementioned disadvantages, it is disadvantageous in the case of the known pump that the entire pump housing is made from metal for thermal conductivity reasons and consequently requires relatively high material and manufacturing costs.
DE 197 36 794 C2 discloses a circulating pump for a dishwasher, where the pump housing is formed by heating coils embedded in a sleeve-like heater.
The upper end of the heater is circumferentially surrounded by a bearing stud of a bearing element for a spray arm, whereas the lower face terminates in free, spaced manner with respect to a bearing plate, through which only pass the heater connections. The overall construction is complicated and costly.
The problem of the invention is to propose a simple, inexpensive pump of the aforementioned type which, whilst avoiding the aforementioned disadvantages, ensures a uniform, continuous liquid heating.
SUMMARY OF THE INVENTION
According to the invention this problem is solved with a pump of the aforementioned type in that on one face of the heating device is placed in sealing manner a base and on another face of the heating device is placed in sealing manner a cover of the housing.
In the case of the pump according to the invention the heat supply consequently does not take place by indirect heating of the pump housing via heat distributing plates and instead the heating device forms part of the pump housing, whereas the remaining housing part constituted by the base and the cover is preferably made from plastic, which can be inexpensively obtained and in particular inexpensively processed. These housing parts can be made from random thermoplastic or thermosetting materials, such as polyolefins (polyethylene, polypropylene, etc.), polyamides, polyesters, polyacetates, polycarbonates, vinyl polymers, polyurethanes, etc. or from polymer blends, which have an adequate thermal stability for pump use.
In order to ensure a high efficiency of the heat transferred by the heating device to the liquid flowing through the pump, the heating device is appropriately located on an area of the housing where, for flow reasons, the formation of a temperature gradient in the liquid is avoided. The heating device is preferably located between a housing base and cover, so as to form a substantially annular housing circumferential wall. Thus, particularly with the centrifugal pumps used for liquid heating of washing machines, dishwashers, etc., where the liquid delivered by the pump passes over a circular path, it is ensured that the heat supply takes place in a high turbulence area of the liquid leading to a high heat transfer. Through the formation of an annular side wall a simply designed pump housing structure is obtained, the housing cover and housing base being made from plastic and the annular side wall can be e.g. separately manufactured.
In a preferred embodiment, the heating device has a metal ring forming at least part of the housing side wall, said ring preferably being made from high-grade steel, particularly high-grade sheet steel, or from aluminium. In the latter case the aluminium ring can e.g. be a casting or an extruded part and then the inside is coated. Alternatively the heating device can have a ring of heat conductive plastic forming at least part of the housing side wall. Then, in particular electrically conductive plastics can be provided.
Advantageously, for heating the ring forming the housing side wall, the heating device has a thick film resistor externally in contact with the ring or a tubular heater externally in contact with the ring, which is located around at least a partial circumference of the ring and consequently at least partly surrounds the same.
In the case of a heating device having a tubular heater, the ring advantageously has a corrugation at least partly receiving the tubular heater, so as on the one hand to securely and permanently fix the tubular heater to the outside of the ring and on the other so as to ensure an increased heat exchange surface between the tubular heater and the ring. Alternatively or additionally a heat distributing plate, preferably from aluminium, can be positioned between the ring and the tubular heater.
If the ring is made from an electrically conductive plastic, there is no need for the actual heating element, e.g. in the form of a tubular heater or thick film resistor and the plastic ring is then directly electrically heated.
Whereas in the case of a thermoplastic housing the ring can be directly injection moulded into the latter, when the housing is made from a thermosetting material it can be moulded into the housing. The ring can be bonded to the housing or, optionally accompanied by the interposing of seals, can be pressed with the housing.
In order to provide corrosion protection with aluminium rings, the pump heating device is preferably provided with a coating on the inside. It is also possible to provide temperature regulating devices in contact with the heating device in order to individually adjust the desired liquid temperature.
As stated, the pump is preferably a centrifugal pump.
In order to secure the connection of heating device and housing parts, according to a preferred development of the invention a retaining device embraces extensions of the housing parts. This reliably prevents any leaks of the connection, particularly if the heating element ring is a metal part and the remaining parts of the housing are made from plastic, because then as a result of the heating and cooling processes stresses can arise between the heating device and the plastic housing due to the different expansion coefficients of the materials and over a long period of time could lead to leaks at the connection. Moreover, within the pump, due to the liquid flow, an elevated pressure prevails all round, which on the one hand acts perpendicularly on the heating device and therefore presses the latter outwards and on the other the pressure also acts perpendicularly on the adjacent housing base and cover. Therefore the connection between the heating device and housing is burdened in two directions. These forces are also abso
Kleemann Martin
Nauerth Helmut
Uhrner Klaus-Jürgen
Antonelli Terry Stout & Kraus LLP
Eichenauer Heizelemente GmbH & Co. KG
Verdier Christopher
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