Dishwashing machine with single-motor pump unit

Abstract: Dishwashing machine with single-motor pump unit comprising a circulating centrifugal pump (7) of the action type and a peripheral outflow drain pump (10) whose respective impellers (11,12) are connected to a reversible drive shaft (13) of said motor (16) to alternately deliver a fluid. The two pumps are connected with one another through relevant calibrated openings (17,18) intercommunicating via an annular chamber (21). This latter is connected with the washing water circuit of the machine through a vent pipe (23). In the annular chamber (21) is provided a further impeller (24) keyed on the drive shaft (13) and forming a further centrifugal pump with the annular chamber.

Description: The present invention relates to a dishwashing machine provided with a single-motor pump unit for circulation and discharge of the washing liquid. More particularly, the present invention relates to a dishwashing machine provided with a pump unit of the type disclosed in US-A-4 799 855, wherein the impellers of a water circulating pump and a water drain pump are keyed on a common reversible shaft of a drive motor to alternately operate the relevant pumps, according to the direction of rotation of the common shaft. The circulating pump is a so-called "action" centrifugal pump, whereas the impeller of the drain pump is of the peripheral outflow type. The two pumps are separated by a partition provided with a calibrated annular opening defined around a hub which is common to the impellers of both pumps. The above pump unit enable the whole energy consumption, vibrations and hydraulic noise occurring during operation of the machine to be remarkably reduced. Furthermore, the annular opening mentioned above, which provides communication between the washing water circuit and the drain water circuit of the dishwashing machine, advantageously enables water collected in both water circuits to be discharged during every discharge phase. However, during the washing phases the direct communication between the drain and the washing water circuits provided by the above annular opening undesirably causes agitation of the dirt particles deposited in correspondence of the suction side of the drain pump. As it is known, it is on the contrary desirable that the dirt particles stagnate under quietness conditions during the washing phases, in order to prevent the dirt particles deposited at said suction side from polluting the washing water circuit. It is to be noted, moreover, that during the washing phases the impeller of the drain pump is rotated in a direction which is opposite to its normal direction of operation, so that the pump chamber of the drain pump is filled with air. As a consequence, at the beginning of every subsequent discharge phase the drain pump is under substantially poor priming conditions, which undesirably affect its performances. It is a scope of the present invention to provide a dishwashing machine with a single-motor pump unit capable of automatically discharging water from both washing and drain water circuits without causing, during the washing phases, agitation of the dirt particles collected in the drain circuit. Another scope of the present invention is to provide a dishwashing machine with a pump unit of the kind mentioned above in which the operation of the drain pump substantially is not affected under priming conditions. According to the invention, these scopes are attained in a dishwashing machine with single-motor pump unit embodying the features recited in the appended claims. The characteristics and advantages of the invention will be more apparent from the following description, given only by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 diagrammatically shows the main components of the dishwashing machine according to the invention; Figure 2 shows in an enlarged scale a longitudinal section of a preferred embodiment of the pump unit provided in the dishwashing machine as in Figure 1; and Figure 3 diagrammatically shows a cross section, taken along line III-III, of the pump unit as in Figure 2. With reference in particular to Figure 1, the dishwashing machine according to the invention basically includes a wash tub 4 (shown only partially) provided at its lower part with a filtering arrangement, generally illustrated at 22, and a water collecting sump 5 the bottom of which communicates with the suction side 6 of a circulating pump 7. This latter is able to feed with water at least a rotary spray arm 8 to spray the crockery to be washed in known manner. In a per se known manner, the wash tub 4 communicates also with the suction side 9 of a drain pump 10. With reference also to Figure 2, the relevant impellers 11 and 12 of pumps 7 and 10, respectively, are keyed on a common reversible shaft 13 of an electric drive motor 16 and are arranged to alternately deliver to the delivery sides 14, 15 of the associated pumps 7, 10, respectively, the water taken in correspondence of the relevant suction sides 6, 9. More particularly, either the circulating pump 7 or the drain pump 10 is alternately operated, respectively during a washing phase or a discharge phase, when the drive shaft 13 is driven in a first or a second direction of rotation. The pumps 7 and 10 are substantially arranged as described in the above-mentioned US-A-4 799 855; accordingly, they form part of one single-motor pump unit in which the drain pump 10 is of the peripheral outflow type, whilst the circulating pump 7 is a centrifugal pump provided with an impeller of the so-called "action" type, i.e. including blades oriented forwardly with respect to its normal direction of rotation to perform a crockery washing phase. The circulating pump 7 and the drain pump 10 are mutually coaxial and adjacent, and communicate with one another through annular openings 17, 18 provided in the relevant pump chambers 19, 20 in correspondence of the drive shaft 13. According to an aspect of the invention, the pump chambers 19 and 20 define a substantially annular chamber 21 therebetween, which annular chamber communicates with the circulating pump 7 and the drain pump 10 through the relevant annular openings 17 and 18, respectively. The annular chamber 21 further communicates, through at least a vent pipe 23, with the washing water circuit of the dishwashing machine, particularly with the area of the sump 5 which is defined between the filtering arrangement 22 and the suction side 6 of the circulating pump 7. The vent pipe 23 preferably has a calibrated cross section and branches off the top of the side wall of the annular chamber 21. The pump unit described above provides the same advantages, and substantially operates in a similar manner, with respect to the one disclosed by the already mentioned US-A-4 799 855. Attention is however directed to the fact that during the washing phases, in which the circulating pump 7 feeds the rotary spray arm 8 with water drawn from the sump 5, the pump 7 itself causes a small amount of water to flow towards the drain pump 10 through the annular opening 17, the annular chamber 21 and the annular opening 18. This amount of water, therefore, tends to enter the drain pump 10, whose impeller 12 (which during the washing phases rotates in a reverse direction) would tend to project it towards the suction side 9, undesirably causing in this way agitation of the dirt particles collected thereat. This drawback is advantageously minimized by the provision of the vent pipe 23, through which the water flowing from the circulating pump 7 into the annular chamber 21 is substantially "vented" into the washing water circuit of the dishwashing machine before entering the drain pump 10. The operational performances of the dishwashing machine according to the invention may be improved by the provision, inside the annular chamber 21, of a further impeller 24 keyed on the drive shaft 13. As it is shown in Figure 3, the impeller 24 is preferably of the per se known kind comprising radial blades 25 and forms a centrifugal pump together with the annular chamber 21. Furthermore, the blades 25 are preferably provided on the side of the impeller 24 facing the drain pump 10. During the washing phases, the impeller 24 provides an effective hydraulic barrier between the circulating pump 7 and the drain pump 10, causing a centrifugally forced expulsion, through the vent pipe 23, of the water which otherwise could flow from the annular chamber 21 into the drain pump 10, as stated before. During the discharge phases the circulating pump 7 (rotating in a reverse direction) keeps producing a water flow towards the annular chamber 21 and the pipe 23, which water flow has a reduced pressure and is substantially negligible, in this way not affecting the general performances of the pump unit. On the other hand, thanks also to the reduced head of the circulating pump 7, during the discharge phases the impeller 24 draws into the annular chamber 21, and vents through the pipe 23 the air formerly trapped into the drain pump 10 during a preceding washing phase. Thus, the drain pump 10 (which rotates in a forward direction) advantageously is under the best priming conditions for a correct operation. Of course, it is to be understood that a number of modifications may be made to the described dishwashing machine without departing from the scope of the present invention. As shown in Figure 3, for example, baffle means 26 are preferably provided in the annular chamber 21. Such baffle means substantially have an inverted Y, or inverted T configuration and are positioned in correspondence of the mouth of the vent pipe 23, on the side wall of chamber 21. The baffle means 26 make it possible to obtain an improved conveyance to the vent pipe 23 of a part of the fluid circulated inside the annular chamber 21 by the impeller 24 when this latter is driven in either direction of rotation.

Claims: Dishwashing machine with single-motor pump unit comprising a circulating centrifugal pump (7) of the action type and a peripheral outflow drain pump (10) whose respective impellers (11,12) are keyed on a reversible drive shaft (13) of said motor (16) to alternately deliver a fluid drawn from a washing water circuit and a drain water circuit, respectively, of the machine, said circulating and drain pumps communicating with each other through relevant calibrated openings (17,18), characterized in that between the circulating pump (7) and the drain pump (10) is provided a substantially annular chamber (21) through which said calibrated openings (17,18) communicate with each other, said annular chamber further communicating with said washing water circuit through at least one vent pipe (23). Dishwashing machine according to claim 1, characterized in that inside the said annular chamber (21) is provided a further impeller (24) keyed on said reversible drive shaft (13) and forming a further centrifugal pump with the annular chamber. Dishwashing machine according to claim 2, characterized in that said further impeller (24) comprises radial blades (25) provided on the side thereof facing said drain pump (10). Dishwashing machine according to claim 2, characterized in that baffle means (26) are provided in the annular chamber (21) in correspondence of the mouth of the vent pipe (23), said baffle means being capable of conveying to said vent pipe a part of the fluid circulated inside said annular chamber by said further impeller (24). Dishwashing machine according to claim 1, characterized in that said annular chamber (21) is coaxial with and adjacent to said circulating pump (7) and drain pump (10).

Inventors: FAVRET UGO, SANTAROSSA GIANNI, TASSOTTI SERGIO, FAVRET, UGO, SANTAROSSA, GIANNI, TASSOTTI, SERGIO
Applicants: ZANUSSI ELETTRODOMESTICI, ZANUSSI ELETTRODOMESTICI S.P.A.
Application year: 1991
Main classification: A47L15
IPC codes: A47L15