EP0761157A1

EP0761157A1 - Power increase of PTC heating element via spray jet

Info

Publication number: EP0761157A1
Application number: EP96111705A
Authority: EP
Inventors: John Dries
Original assignee: White Consolidated Industries Inc
Current assignee: White Consolidated Industries Inc
Priority date: 1995-09-06
Filing date: 1996-07-19
Publication date: 1997-03-12
Also published as: CA2180064A1

Abstract

An apparatus for increasing the power draw of a positive temperature coefficient heating element (400) in a washer (10) when the heating element is not submerged in fluid. The washer includes the heating element (400), a tub (20) with a sump (28), a hub (40), a pump (80) and a spray arm (100). The pump circulates the fluid from the sump throughout the tub. Disposed around the sump is the heating element. Projecting upward from the sump is the hub which has a passage for conveying fluid from the pump to the top of the hub. The spray arm is substantially hollow and is rotatably mounted to the top of the hub. The spray arm receives fluid from the passage in the hub and projects sprays of fluid into the tub, causing the spray arm to rotate. At least one of the sprays (340,380) is directed downward onto the heating element (400) during the rotational travel of the spray arm so as to substantially wet the heating element when the heating element is not submerged in fluid, thereby cooling the heating element and increasing its power draw.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to washers in general and, more particularly, to dishwashers having a positive temperature coefficient resistive heating element.

2. Description of the Related Art

Positive temperature coefficient (PTC) resistive heating elements are commonly used in washers to heat fluid for the wash and rinse cycles and to heat air for the drying cycle(s). PTC resistive heating elements are ideally suited for use in washers because they have a high power draw when they are cooled by fluid and a low power draw when they are exposed to air. A high power draw is desired for the wash and rinse cycles in order to rapidly bring the temperature of the fluid up to a required level. A low power draw is desired for the drying cycle in order to avoid heat damage to the tub which is commonly made from plastic.
As is well known, a PTC resistive heating element has a high temperature coefficient of resistance. At low temperatures, a PTC resistive heating element has a low resistance, permitting a high current flow therethrough. At high temperatures, a PTC resistive heating element has a high resistance, permitting only a low current flow therethrough. Since the voltage (V) applied to the PTC resistive heating element is constant, the power (P) varies proportionately with changes in current (I) pursuant to the well known relationship: $P=V × I$
Accordingly, a PTC resistive heating element has a high current flow therethrough and, thus, a high power draw when it is cooled by fluid in a washer tub. Conversely, a PTC resistive heating element has a low current flow therethrough and, thus, a low power draw when it is exposed to air. These characteristics of a PTC resistive heating element in a washer are disclosed in expired U.S. Patent No. 3,207,164 to Fay, incorporated herein by reference.
Typically, the PTC resistive heating element is mounted near the bottom of the washer tub. In older washer models, the PTC resistive heating element was submerged in fluid at the beginning of the wash and rinse cycle(s). However, current fluid conserving washers do not have a substantial amount of standing fluid in the lower portion of their tub during any cycle of their operation. In such fluid conserving washers, the PTC resistive heating element is typically not submerged before or during the wash and rinse cycle(s) and only makes incidental contact with fluid falling from the wash area above, i.e., the fluid is not purposefully directed onto the PTC resistive heating element.
For a given power draw, an unsubmerged PTC resistive heating element heats fluid for the wash and rinse cycle(s) just as well as a submerged PTC resistive heating element because washers are essentially closed systems. However, for a given PTC resistive heating element, the power draw will be less if the PTC resistive heating element is unsubmerged than if it is submerged because an unsubmerged PTC resistive heating element will be hotter and, thus, will have more resistance to the flow of current than a submerged PTC resistive heating element. As a result, the fluid heating rate for the wash and rinse cycle(s) in a fluid conserving washer will be less than in an older model washer for a given PTC resistive heating element.
Currently, the fluid heating rate in a fluid conserving washer can be increased is to increase the capacity of the PTC resistive heating element. However, if the capacity of the PTC resistive heating element is increased too much, the PTC resistive heating element may draw too much power during the drying cycle(s), causing heat damage to the tub. Accordingly, it would be advantageous to have a method and apparatus for increasing the power draw of a PTC resistive heating element when the PTC resistive heating element is not submerged in fluid. The present invention is directed to such a method and apparatus.

SUMMARY OF THE INVENTION

It therefore would be desirable, and is an object of the present invention, to provide an apparatus for increasing the power draw of a PTC resistive heating element in a washer when the PTC resistive heating element is not submerged in fluid. In accordance with the present invention, the washer includes the heating element, a tub, a pump and a means for directing fluid. The tub is adapted to receive objects to be washed and has a sump for collecting fluid. The pump circulates the fluid from the sump throughout the tub. The fluid directing means directs fluid from the pump onto the heating element so as to wet the heating element when the heating element is not submerged in fluid, thereby cooling the heating element and increasing its power draw.
The fluid directing means includes a hub projecting upward from the sump and a spray arm rotatably mounted to the hub. The hub has a passage for conveying fluid from the pump to the top of the hub. The spray arm has first and second arm portions extending out from the hub in opposite directions. The spray arm is generally hollow and receives the fluid from the passage in the hub. The spray arm has a plurality of openings that emit sprays of fluid into the tub. The openings are arranged such that the sprays create a reaction force that rotates the spray arm about the hub. One of the openings is downwardly directed and adapted to emit one of the sprays of fluid onto the heating element during the rotational travel of the spray arm so as to substantially wet the heating element when the heating element is not submerged in fluid.
It is also desirable, and is a further object of the present invention, to provide a method for increasing the power draw of a PTC resistive heating element when washing objects in a washer that has a tub with a sump for collecting fluid. In accordance with the present invention, the tub is filled with fluid to a level below the heating element and the heating element is energized. The fluid in the sump is pressurized to form a pressurized fluid flow. A portion of the pressurized fluid flow is directed onto the objects to be washed, while another portion of the pressurized fluid flow is directed onto the heating element so as to wet the heating element when the heating element is not submerged in fluid, thereby cooling the heating element and increasing its power draw. The heating element is then de-energized.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig.1 shows a front sectional view of a portion of a washer in accordance with the present invention;
Fig.2 shows a front perspective view of a portion of the washer in accordance with an embodiment of the present invention; and
Fig.3 shows a front perspective view of a portion of the washer in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to Fig 1., there is shown a front sectional view of a fluid conserving washer 10, such as a dishwasher, having the apparatus of the present invention. The washer 10 generally includes a tub 20, a hub 40, a coarse filter 60, a pump 80, a spray arm 100, a positive temperature coefficient (PTC) resistive heating element 400 and a fine filter having a downwardly sloping section 65a and an annular vertical section 65b. The tub 20 is made from molded plastic and has a wash area (or compartment) 22 with a rack 24 for holding objects such as dishes, silverware, glasses and cookware that are to be washed. The lower portion of the tub 20 defines a sump 28 from which the hub 40 projects. The spray arm 100 is rotatably mounted to the hub 40 so as to have the same vertical center line as the hub 40. The pump 80 is mounted at the bottom of the sump 28.
Referring now to Fig.2, there is shown a perspective view of a portion of the washer 10. The PTC resistive heating element 400 is a rod formed into a substantially rectangular configuration with perpendicular end portions. The PTC resistive heating element 400 is mounted to the bottom of the tub 20 with the perpendicular end portions projecting through the tub 20. A power supply (not shown) is connected to the perpendicular end portions on the other side of the tub 20. In characteristic fashion, the PTC resistive heating element 400 has a low resistance at low temperatures and a high resistance at high temperatures. Thus, the PTC resistive heating element 400 has a high current flow when it is cooled by fluid and a low current flow when it is exposed to air.
The PTC resistive heating element 400 is disposed around the hub 40 such that the vertical center line of the spray arm 100 is centrally located within the rectangular configuration. The front side 410 and rear side 420 of the rectangular configuration are equal in length to the spray arm 100. Accordingly, the ends of the spray arm 100 are directly above the curved edge of the PTC resistive heating element 400 when the spray arm 100 is parallel to the front and rear sides 410,420 of the rectangular configuration. For reasons more fully explained later, the PTC resistive heating element 400 may be formed into a circular configuration having a circumference directly underlying the circumference of a circular path of the spray arm 100.
Referring back to Fig.1, the coarse filter 60 is also disposed around the hub 40. The coarse filter 60 prevents loose objects and other large articles from entering the sump 28. The downwardly sloping section 65a of the fine filter is attached to the coarse filter 60. Preferably, the fine filter is composed of molded mesh screen having 4 mm (.015 in.) openings. Below the annular vertical section 65b of the fine filter is an inner wall 27 of the sump 28 that has a downwardly sloping component 27a. The inner wall 27 defines an extension of the fine filter and separates the sump 28 into a collection chamber 70 and a pump chamber 75.
Fluid, such as wash water, enters the sump 28 through the coarse filter 60. Large articles of debris, such as food and loose silverware, are entrained by the coarse filter 60. Large biodegradable articles will eventually be eroded and dissolved until they pass through the coarse filter 60. Other large articles will remain until they are manually removed. From the coarse filter 60, the fluid either enters the collection chamber 70 or passes through the sloping section 65a of the fine filter and enters the pump chamber 75. When the fluid level in the collection chamber 70 is high enough, some of the fluid in the collection chamber 70 flows through the vertical section 65b and into the pump chamber 75. Thus, only fluid that has passed through the coarse filter 60 and the fine filter can enter the pump chamber 75. In this manner, full flow filtration of the fluid is provided.
When fluid passes through the fine filter, particles suspended in the fluid are entrapped by the fine filter. The sloping section 65a of the fine filter and the sloping component 27a of the inner all funnel the particles into the collection chamber 70 where they are macerated. At the end of the wash and rinse cycle(s), the minced particles are pumped out of the collection chamber 70 along with used fluid by a drain pump (not shown). The amount of fluid used in the wash and rinse cycle(s) is small in order to conserve fluid. Accordingly, the fluid level in the washer 10 does not rise to a level where the PTC resistive heating element 400 is submerged in fluid.
At the bottom of the pump chamber 75 is an inlet to the pump 80 which is driven by a horizontally mounted motor. An outlet of the pump 80 is in communication with the hollow interior of the hub 40. The hub 40 has a bottom opening and a top opening with a threaded shaft 42 projecting therefrom. Rotatably fastened to the threaded shaft 42 is the spray arm 100. The spray arm 100, which is substantially hollow, has a central opening (not shown) that overlays the top opening in the hub 40. The hub 40 provides a passageway for fluid to travel from the pump 80 up to the spray arm 100.
The spray arm 100 is comprised of first and second oppositely directed arm portions 140, 180. First arm portion 140 has a top surface 142 and a bottom surface 144 while second arm portion 180 has a top surface 182 and a bottom surface 184. Respectively disposed along the top surfaces 142, 182 are a plurality of openings 200, 250 through which sprays of fluid project. Portions of the openings 200, 250 are upwardly directed and portions are outwardly directed. The sprays of fluid from the upwardly-directed portions of the openings 200, 250 enter the wash area 22 and impinge upon the objects in the rack 24, loosening particles adhering thereto.
The outwardly-directed portion of the openings 200 and the outwardly-directed portion of the openings 250 face opposite directions. As a result, a net reaction force is created by the sprays of fluid projecting from the outwardly-directed portions of the openings 200, 250. The net reaction force rotatably drives the spray arm 100 at a predetermined rate.
Projecting downward from the bottom surface 144 of the first arm portion 140 is an outer spray nozzle 240 having an orifice 245 directed inward towards the hub 40. The outer spray nozzle 240 is located near the end of the first arm portion 140. Projecting downward from the bottom surface 184 of the second arm portion 180 are an inner spray nozzle 280 and an outer spray nozzle 290. The inner spray nozzle 280 is located close to the hub 40 and has a downwardly-directed orifice 285. The outer spray nozzle 290 is located near the end of the second arm portion 180. An orifice 295 in the outer spray nozzle 290 is directed inward towards the hub 40.
The spray nozzles 240, 280, 290 operate to project filter cleaning sprays of fluid onto the coarse filter 60 and fine filter. Horizontal sprays of fluid project inwardly from the openings 245, 295 in the outer spray nozzles 240, 290 and impinge upon the coarse filter 60 and fine filter, propelling particles entrained therein towards the hub 40. The particles dislodged by the horizontal sprays are propelled downward towards the collection chamber 70 by a downwardly directed spray of fluid projecting from the opening 285 in the inner spray nozzle 280. Naturally, the scope of the present invention is not limited in any manner by the spray nozzles 240, 280, 290.
In addition to the spray nozzle 240, the bottom surface 144 of the first arm portion 140 has a downwardly-directed opening 340 located at the outer end of the first portion 140. Similarly, the bottom surface 184 of the second arm portion 180 has a downwardly-directed opening 380 located at the outer end of the second arm portion 180. The openings 340, 380 are respectively positioned along the first and second arm portions 140, 180 so as to be directly above the PTC resistive heating element 400 when the spray arm 100 is parallel to the front and rear sides 410,420 of the rectangular configuration of the PTC resistive heating element 400. The openings 340,380 are formed so as to project fairly broad sprays of cooling fluid onto the PTC resistive heating element 400. It should be noted that the fluid is not necessarily "cool" in an absolute sense, but is "cool" in a relative sense, i.e., the fluid is at a temperature lower than the PTC resistive heating element 400.
As the spray arm 100 rotates, the cooling sprays of fluid substantially wet the PTC resistive heating element 400, thereby lowering the temperature of the PTC resistive heating element 400. As a result, the power draw of the PTC resistive heating element 400 increases and the fluid is heated more rapidly. In another embodiment of the present invention, one of the openings 340, 380 can be eliminated. The spray of fluid provided by one of the openings 340, 380 would be sufficient to fully wet the PTC resistive heating element 400 during the travel of the spray arm 100.
In another embodiment of the present invention shown in Fig.3, the PTC resistive heating element 400 is formed into a circular configuration having the same diameter as the spray arm 100. With this configuration, the PTC resistive heating element 400 is disposed around the hub 40 such that the circumference of the circular path of the spray arm 100 directly overlies the circumference of the PTC resistive heating element 400. In this manner, the openings 340, 380 are located so as to be directly above the PTC resistive heating element 400 at all times during the circular travel of the spray arm 100. With this orientation of the openings 340, 380, the PTC resistive heating element 400 is fully wetted by narrow streams of fluid emanating from the openings 340, 380.
It should be appreciated that in other embodiments of the present invention, the PTC resistive heating element 400 may be submerged for a portion of the wash and/or rinse cycle(s). Although the present invention would have no effect on the power draw of the PTC resistive heating element 400 during the period the PTC resistive heating element 400 was submerged, the present invention would effectively increase the power draw of the PTC heating element 400 during the portion of the wash and/or rinse cycle(s) that the PTC resistive heating element 400 was not submerged.
Finally, it should be appreciated that the present invention can be practiced without using the spray arm 100. Instead of spraying fluid onto the PTC resistive heating element 400 from the openings 340,380 in the rotating spray arm 100, fluid can be sprayed onto the PTC resistive heating element 400 from stationary jets mounted around the periphery of the PTC resistive heating element 400. Such jets could be connected by piping to the outlet of the pump 80.
It is to be understood that the description of the preferred embodiments are intended to be only illustrative, rather than exhaustive, of the present invention. Those of ordinary skill will be able to make certain additions, deletions, and/or modifications to the embodiments of the disclosed subject matter without departing from the spirit of the invention or its scope, as defined by the appended claims.

Claims

A dishwasher for washing dishes with wash water, said dishwasher comprising:
a tub adapted to receive the dishes to be washed and having a sump for collecting wash water;

a pump for circulating wash water from the sump throughout the tub;

a positive temperature coefficient resistive heating element for heating the wash water, said heating element being disposed around the sump;

a hub projecting upward from the sump, said hub having a passage for conveying wash water from the pump to the top of the hub; and

a spray arm rotatably mounted to the top of the hub and having first and second arm portions extending out from the hub in opposite directions, said spray arm being generally hollow and receiving the wash water from the passage in the hub, said spray arm having a plurality of openings that project sprays of wash water into the tub, said openings being arranged such that the sprays create a reaction force that rotates the spray arm about the hub, a first one of the openings being located in the first arm portion and being downwardly directed and adapted to project a first one of the sprays of wash water onto the heating element during the rotational travel of the spray arm so as to wet the heating element when the heating element is not submerged in wash water, thereby cooling the heating element and increasing its power draw.
The dishwasher of claim 1 wherein a second one of the openings is located in the second arm portion of the spray arm and is downwardly directed and adapted to project a second one of the sprays of wash water onto the heating element.
The dishwasher of claim 2 wherein the first one and the second one of the sprays of wash water do not contribute to the reaction force that rotates the spray arm about the hub.
The dishwasher of claim 2 further comprising a filter for removing debris from the wash water, said filter being disposed around the hub beneath the spray arm.
The dishwasher of claim 4 wherein the spray arm further comprises downward projecting spray nozzles having orifices adapted to emit jets of wash water onto the filter to rinse the debris therefrom.
The dishwasher of claim 2 wherein the heating element is disposed around the hub in a substantially rectangular configuration with first and second opposite sides having a length not greater than the length of the spray arm.
The dishwasher of claim 6 wherein the first one and the second one of the openings are located laterally along the spray arm so as to be directly above the heating element when the spray arm is parallel to the first and second sides of the substantially rectangular configuration of the heating element.
The dishwasher of claim 7 wherein the first one and the second one of the sprays of wash water are broad enough to project onto the heating element during a substantial portion of the rotational travel of the spray arm.
The dishwasher of claim 2 wherein the heating element is evenly disposed around the hub in a substantially circular configuration having a diameter not greater than the diameter of the spray arm.
The dishwasher of claim 9 wherein the first one and the second one of the openings are located laterally along the spray arm so as to be directly above the heating element during the entire rotational travel of the spray arm.
The dishwasher of claim 10 wherein the first one and the second one of the sprays of wash water are narrow enough to project onto substantially only that portion of the heating element over which the first one and the second one of the openings pass during the rotational travel of the spray arm.
A washer having a positive temperature coefficient resistive heating element, said washer comprising:
a tub adapted to receive objects to be washed and having a sump for collecting fluid;

a pump for circulating fluid from the sump throughout the tub; and

means for directing fluid from the pump onto the heating element so as to wet the heating element when the heating element is not submerged in fluid, thereby cooling the heating element and increasing its power draw.
The washer of claim 12 wherein the means for directing fluid comprises a sprayer for projecting both a downward spray of fluid onto the heating element and an upward spray of fluid onto the objects to be washed.
The washer of claim 13 wherein the sprayer comprises:
a hub projecting upward from the sump, said hub having a passage for conveying fluid from the pump to the top of the hub; and

a spray arm mounted to the hub and having first and second arm portions extending out from the hub in opposite directions, said spray arm being generally hollow and receiving the fluid from the passage in the hub, said spray arm having an upwardly-directed opening adapted to emit the upward spray of fluid and having a downwardly-directed opening adapted to emit the downward spray of fluid.
The washer of claim 14 wherein the spray arm is rotatably mounted to the hub and has a plurality of other openings that emit other sprays of fluid into the tub, said other openings being arranged such that the other sprays create a reaction force that rotates the spray arm about the hub.
The washer of claim 15 wherein the heating element is disposed around the hub in a substantially rectangular configuration with first and second opposite sides having a length not greater than the length of the spray arm.
The washer of claim 16 wherein the downwardly-directed opening is located laterally along the spray arm so as to be directly above the heating element when the spray arm is parallel to the first and second sides of the substantially rectangular configuration of the heating element.
The washer of claim 17 wherein the downward spray of fluid is broad enough to project onto the heating element during a substantial portion of the rotational travel of the spray arm.
The washer of claim 15 wherein the heating element is evenly disposed around the hub in a substantially circular configuration having a diameter not greater than the diameter of the spray arm.
The washer of claim 19 wherein the downwardly-directed opening is located laterally along the spray arm so as to be directly above the heating element during the entire rotational travel of the spray arm.
The washer of claim 20 wherein the downward spray of fluid is narrow enough to project onto substantially only that portion of the heating element over which the downwardly-directed opening passes during the rotational travel of the spray arm.
A method for washing objects in a washer having a tub and a positive temperature coefficient resistive heating element, said tub being adapted to receive objects to be washed and having a sump for collecting fluid, said method comprising the steps of:
filling the tub with fluid to a level below the heating element;

energizing the heating element;

pressurizing fluid in the sump to form a pressurized fluid flow;

directing a portion of the pressurized fluid flow onto the objects to be washed;

directing another portion of the pressurized fluid flow onto the heating element so as to wet the heating element when the heating element is not submerged in fluid, thereby cooling the heating element and increasing its power draw; and

de-energizing the heating element.