US3829636A

US3829636A - Overflow control dashpot-type float for a dishwasher switch assembly

Info

Publication number: US3829636A
Application number: US00336397A
Authority: US
Inventors: E Scott
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1973-02-27
Filing date: 1973-02-27
Publication date: 1974-08-13
Anticipated expiration: 1991-08-13
Also published as: AU6550674A; ES423631A1; CA1033435A

Abstract

A float for use in a dishwasher to control an externally mounted overflow switch in response to a potential overflow condition existing within the dishwasher tub. The float is loosely mounted on a vertical guidetube on the bottom of the tub and comprises an inverted cup-shaped member having internal partitions to define a plurality of separate chambers, a post-portion telescopically received over the guide-tube, and a rod extending through the guide-tube to abut the switch. Certain of the chambers provide buoyancy to the float while others act in the manner of a dashpot to stabilize the vertical fluctuations of the float. The post-portion also defines an opening through the wall thereof to prevent a flow path from being maintained in the space between the guide-tube and the post-portion by a syphon effect.

Description

United States Patent 1 Scott OVERFLOW CONTROL DASHPOT-TYPE FLOAT FOR A DISHWASHER SWITCH ASSEMBLY Inventor:

Assignee:

Filed:

Appl. No.:

Eugene W. Scott, Columbus, Ohio Westinghouse Electric Corporation,

Pittsburgh, Pa.

Feb. 27, 1973 References Cited UNITED STATES PATENTS Smith 137/432 73/3225 137/432 X Haggard, Jr, 200/6104 Holderith Doyle 1 1] 3,829,636 Aug. 13,1974

3,610,271 10/1971 Jarvis 137/412 3,721,783 3/1973 Hancock 200/84 R Primary Examiner.lames R. Scott Attorney, Agent, or Firm-F. A. Winans 5 7] ABSTRACT A float for use in a dishwasher to control an externally mounted overflow switch in response to a potential overflow condition existing within the dishwasher tub. The float is loosely mounted on a vertical guidetube on the bottom of the tub and comprises an inverted cup-shaped member having internal partitions to define a plurality of separate chambers, a post-portion telescopically received over the guide-tube, and a rod extending through the guide-tube to abut the switch. Certain of the chambers provide buoyancy to the float while others act in the manner of a dash-pot to stabilize the vertical fluctuations of the float. The postportion also defines an opening through the wall thereof to prevent a flow path from being maintained in the space between the guide-tube and the postportion by a syphon effect.

9 Claims, 4 Drawing Figures OVERFLOW'CONTROL DASHPOT-TYPE FLOAT FOR A DISHWASHER SWITCH ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a float for controlling an overflow switch of a dishwasher and more particularly to such a float having motion damping characteristics to reduce the vertical fluctuation of the float and also having a syphonbreak to prevent that volume between the float and the guide-tube from establishing a syphon flow path.

2. Cross-References to Related Applications This application is related to application Ser. No. 166,385, filed July 27, 1971 now US. Pat. No. 3,721,783 having a common assignee, in the sense that the referenced patent discloses the immediate environment and limited structural detail pertinent to the instant invention.

3. Description of the Prior Art Liquid level responsive switch actuating mechanisms are well known in the prior art; however, such mechanisms have primarily been employed where the liquid is generally quiescent. This prior art has limited appli cability in a dishwasher where water is flung about and generally causes an extremely turbulent condition to exist in the water level being sensed. A more detailed description of the operating conditions and parameters for such a float is set forth in the above-mentioned application, ,but suffice it to say that under the rather adverse turbulent conditions existing within the machine, the float apparatus is required to transmit the effect of relative depth of the water to the external switch within a sufficiently small range to energize the switch when a potential flood condition exists.

US. Pat. No. 3,610,271 is illustrative ofa float apparatus for a dishwasher and, as does the float of the present invention, generally comprises a buoyant chamber supported on a post-portion, which is telescopically received over a vertically extending guide-tube on the bottom of the tub, and a rod member extending through the tube to adjacent an external switch. Thus, as the water level varies within the tub, the effect of the vertical rise and fall of the float is transmitted to the switch through the depending rod.

SUMMARY OF THE PRESENT INVENTION The float of the present invention, as in the abovedescribed prior-art float, includes buoyant chambers having a centrally located hollow post-portion telescopically receiving a vertical guide-tube on the bottom of the dishwasher and a rod extending through the tube to abut a switch electrically connected in the dishwasher circuit. The float of the present invention also includes chambers which are open both above and below the water line on the float permitting ingress of water into these chambers with the lower opening sized so as to limit the egress of the contained water to effectively damp, as through a dash-pot effect, vertical fluctuations in the float as it rides on the turbulent water. Also, the wall of the hollow central post-portion includes an opening above the water line of the float and below the top of the guide-tube, and, in this instance, communicating with an open chamber, providing a syphon break to the space between the guide-tube and the'post-portion so that that space cannot support a syphon-sustained flow path.

DRAWING DESCRIPTION FIG. 1 is a schematic elevational view of a dishwasher with a portion broken away to show the general location of the float of the present invention;

FIG. 2 is an isometricview of the float of the present invention;

FIG. 3 is a top-plan view of the float; and,

FIG. 4 is a sectional elevational view of the floatas assembled in a dishwasher and taken generally along line IV-IV of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the schematically illustrated dishwasher 10 includes a tub 12 having a forwardly fac- As seen in FIG. 2, the float 20 includes an invertedcup shaped member 22 having a cylindrical peripheral wall 24 and a frusto-conical top 26. A concentric hollow post-portion 28 extends downwardly from the top 26 to below the wall 24 and a concentric rod 29 extends downwardly from the top 26 to well below the post-portion 28.

Equa-angularly disposed vertical walls 30 (also shown in FIG. 2) extend radially between facing surfaces of the post-portion 28 and the cylindrical wall 24 and are contiguous with the top 26 to divide the volume between the post-portion 28 and the wall 24 into separate chambers (6 being shown). The top includes a plurality of apertures 32 permitting air to enter and exit certain of the chambers (i.e., every other chamber 34a) and is continuous over the remaining chambers 34b enabling these chambers to entrap the air and provide the necessary buoyancy so that the float rises and falls in accordance with the level of the water in the tub.

The bottom open face of the inverted cup-shaped member 22 is partly closed by a circular plate 36 which defines a central opening 38 sized to interferingly engage the outer surface of post-portion 28 to maintain it in position against the bottom of the vertical walls 30. The diameter of the plate 36 is somewhat less than the diameter of the cylindrical wall 24 thereby defining bottom facing openings 40 for every chamber. However, it is noted that each opening 40 is substantially less than the cross-sectional areal of each chamber. Accordingly, as seen in FIG. 4, when the float is in operative position, the central post-portion 28 is telescopically received over the vertical guide-tube 42 rising from the bottom of the tub, and the rod 29 extends axially through the tube 42 to abut a switch 43 mounted externally as discussed in the previously referenced copending application. As the water level rises in the dishwasher, the float becomes buoyant once the weight of the water displaced by the float is equal to the weight of the float. This requires the water level on the float to be above the bottom openings 40 which in turn traps air in chambers 34b to displace the water. Thus chambers 34b, although containing a certain amount of water, are referred to as buoyant chambers.

However, chambers 34a associated with the openings 32 in the top 26 are filled with water to the water level on the float as there is no air trapped in these chambers. Because of the limited area of the bottom opening 40 of each such chamber provided between the plate 36 and the wall 24, the water within chambers 24b has restricted ability to egress, thus, the mass of the float for the purpose of its inertia is increased by the water within these chambers and this additional inertial mass provides a damping effect, on the order of a dash-pot, to the movement of the float relative to the turbulent motion of the water within the dishwasher. This reduces the amplitude of the oscillatory motion of the rod 29 and in turn reduces the chances that the switch could be falsely energized by the turbulence to indicate an over-filled condition.

It should be noted that the openings 32 in the top 26 are related in size to the openings 40 in the bottom such that any loose food particles being flung about in the dishwasher that are able to pass through the openings 32 are also able to pass out of openings 40. Also, openings 32 should not permit the water being flung about to enter the chambers 34a at a faster rate than water can egress from the bottom openings 40 or the chambers 34a would eventually become filled with water thereby affecting the water level on the float.

Still referring to H0. 4, the float is further characterized by an opening 44 in an area of the post-portion residing in one of the buoyant chambers 34a. Opening 44 is disposed so as to provide an open area above the water level on the float and below the top of the guidetube 42. Thus, opening 44 places that space between the guide-tube 42 and the post-portion 28 in communication with'ambient pressure within the tub through opening 32 in the top 26. (As is known, tub 12 is vented so that ambient pressure is present in the tub.) This opening 44 serves as a syphon-break in the following manner. The height of the guide-tube 42 on which the float telescopically rides is generally just greater than the maximum permitted depth of the water in the tub. Under normal conditions, this height will be sufficient to prevent any water from escaping out the tube 42; however, in rare instances, such as during a rapid buildup of pressure within the tub, water could be forced to overflow the top of the tube 42 and out onto the floor. An example of such a condition is referred to in the art as an explosion effect" and occurs most often when the door of the dishwasher is opened and then quickly closed, such as to add an item to be washed, during the washing cycle and after the tub, dishes, and water therein have reached an elevated temperature. Opening the door permits the tub to fill with relatively cool air which, because of the abundance of hot surface areas, rapidly expands. Closing the door confines the air to escape through a vent; however, the rapid increase of pressure, in addition to causing air to be expelled suddenly through the vent, forces water over the tube.

With the float in place over the tube 42 as shown in FIG. 4, the water, to get to the top of the tube, must flow upwardly in the space between the tube and the post-portion 28. As this previously defined a closed volume, once flow such as has been described was initiated it was possible for it to continue by a syphoning effect, even after the air pressure within the tub returned to ambient. This would result in a quantity of water being deposited beneath the dishwasher.

The opening 44 in the post-portion 28, to act as a syphon-break, must be positioned so as to make some intermediate portion of the space defining the flow path open to ambient pressure. Thus, the opening 44 includes at least a portion which is above the water level on the float and below the top of the guide tube 42 and, in the specific embodiment shown, is in an area of the post-portion facing into a dash-pot chamber 34a which, because of the opening 32 in the top, is at ambient pressure. Therefore, in this position, opening 44 destroys the integrity of the flow path by opening it up to ambient pressure and prevents the space between the post-portion 28 and the guide tube 42 from supporting a syphon effect. And, in the condition previously described where water could be momentarily forced over the top of the guide-tube 42, once this condition has ceased, so will any flow out of the tube.

1 claim:

1. In a dishwasher in which water is flung about the interior of the washing tub, an improved float apparatus for controlling the energization of an externally mounted switch in accordance with the depth of the liquid within the tub, andin which the tub includes a bottom wall supporting a substantially vertical guidetube terminating in an open end at a height above the permitted depth of the water, wherein the improvement of said float apparatus comprises;

means defining at least one chamber providing buoyancy to said float apparatus;

means defining at least one dash-pot chamber having an upper opening at a level above the water level on said float apparatus to place the interior of said dash-pot chamber in communication with the tub space above the water level, and a lower opening in communication with the water in said tub, said lower opening being of an area substantially less than the cross-sectional area of said chamber so that water egress thereout of in response to a tendency for rapid elevation of said float apparatus under an agitated water condition is restricted and variations in float elevation thereby dampened, said upper opening being of an area relative to the area of said lower opening that water ingress through said upper opening in the normal operating environment is at a lower rate than water egress out of said lower opening to prevent filling said dash-pot chamber to a level above the water level on said float apparatus, a vertically disposed hollow post-portion having a sufficiently large internal diameter to telescopically receive said guide-tube in freely movable relation; and,

rod means disposed internally of said post-portion and of the sufficiently limited size so as to be received within said guide-tube for extension therethrough to adjacent said externally mounted switch.

2. The float apparatus of claim 1 wherein said postportion defines an opening to provide a syphon-break to the space between said post-portion and said guidetube, said opening having a portion disposed above the water level on said float apparatus and below the top of said guide-tube, and providing communication between said space and ambient pressure within said washing tub.

3. The float apparatus of claim 2 wherein said means providing buoyancy and said means defining at least one dash-pot chamber include separate chambers within an inverted cup-shaped member having a generally continuous top, said top defining at least one said upper opening for each dash-pot chamber, and said post-portion extends downwardly from said top.

4. The float apparatus of claim 3 wherein said postportion includes an area disposed within said at least one dash-pot chamber and wherein said opening providing a syphon break is disposed in said area.

5. The float apparatus of claim 1 wherein the size of said lower opening is related to the size of said upper opening to the extent \that any particle able to enter said dash-pot chamber through said upper opening can exit said chamber through said lower opening.

6. The float apparatus of claim 5 wherein the size of said upper opening is further related to the size of said lower opening such that, in the normal operating environment, water can egress through said lower opening at a greater rate than can ingress through said upper opening.

7. The float apparatus of claim 1 wherein said lower opening is disposed in the lowermost portion of said dash-pot chamber to permit the generally complete evacuation of water therefrom in the absence of water within the washing tub.

8. In a dishwasher in which water is flung about the interior of a washing tub, an improved float apparatus for controlling the energization of an externally mounted switch in accordance with the depth of the liquid within the tub, and in which the tub includes a bottom wall supporting a substantially vertical guidetube terminating in an open end at a height above the permitted depth of the water, wherein the improvement of said float apparatus comprises:

means providing buoyancy to said float apparatus;

a vertically disposed hollow post-portion attached to said buoyant means, open at its lower end and having a sufficiently large internal dimension for telescopic receipt thereinto of said guide-tube in freely movable relation, said post-portion being closed at the upper end in the area generally vertically over the open end of said guide-tube thereby preventing water from being flung into said guide-tube;

rod means extending downwardly from adjacent said closed end and internally of said post-portion and of sufficiently limited size so as to be received within said guide-tube for extension therethrough to adjacent said externally mounted switch; and air passage means providing communication between ambient air within the tub and the space between the post-portion and said guide-tube irrespective of whether said lower end of said post-portion is submerged, for a syphon break to said space.

9. Structure according to claim 8 wherein said air passage means terminates at one end in an opening into said space between said post-portion and said guidetube, with said opening disposed above the water level on said float and below the open end of said guide-tube. l l

Claims

1. In a dishwasher in which water is flung about the interior of the washing tub, an improved float apparatus for controlling the energization of an externally mounted switch in accordance with the depth of the liquid within the tub, and in which the tub includes a bottom wall supporting a substantially vertical guidetube terminating in an open end at a height above the permitted depth of the water, wherein the improvement of said float apparatus comprises; means defining at least one chamber providing buoyancy to said float apparatus; means defining at least one dash-pot chamber having an upper opening at a level above the water level on said float apparatus to place the interior of said dash-pot chamber in communication with the tub space above the water level, and a lower opening in communication with the water in said tub, said lower opening being of an area substantially less than the cross-sectional area of said chamber so that water egress thereout of in response to a tendency for rapid elevation of said float apparatus under an agitated water condition is restricted and variations in float elevation thereby dampened, said upper opening being of an area relative to the area of said lower opening that water ingress through said upper opening in the normal operating environment is at a lower rate than water egress out of said lower opening to prevent filling said dash-pot chamber to a level above the water level on said float apparatus, a vertically disposed hollow post-portion having a sufficiently large internal diameter to telescopically receive said guide-tube in freely movable relation; and, rod means disposed internally of said post-portion and of the sufficiently limited size so as to be received within said guide-tube for extension therethrough to adjacent said externally mounted switch.

2. The float apparatus of claim 1 wherein said post-portion defines an opening to provide a syphon-break to the space between said post-portion and said guide-tube, said opening having a portion disposed above the water level on said float apparatus and below the top of said guide-tube, and providing communication between said space and ambient pressure within said washing tub.

4. The float apparatus of claim 3 wherein said post-portion includes an area disposed within said at least one dash-pot chamber and wherein said opening providing a syphon break is disposed in said area.

5. The float apparatus of claim 1 wherein the size of said lower opening is related to the size of said upper opening to the extent that any particle able to enter said dash-pot chamber through said upper opening can exit said chamber through said lower opening.

8. In a dishwasher in which water is flung about the interior of a washing tub, an improved float apparatus for controlling the energization of an externally mounted switch in accordance with the depth of the liquid within the tub, and in which the tub includes a bottom wall supporting a substantially vertical guide-tube terminating in an open end at a height above the permitted depth of the water, wherein the improvement of said float apparatus comprises: means providing buoyancy to said float apparatus; a vertically disposed hollow post-portion attached to said buoyant means, open at its lower end and having a sufficiently large internal dimension for telescopic receipt thereinto of said guide-tube in freely movable relation, said post-portion being closed at the upper end in the area generally vertically over the open end of said guide-tube thereby preventing water from being flung into said guide-tube; rod means extending downwardly from adjacent said closed end and internally of said post-portion and of sufficiently limited size so as to be received within said guide-tube for extension therethrough to adjacent said externally mounted switch; and air passage means providing communication between ambient air within the tub and the space between the post-portion and said guide-tube irrespective of whether said lower end of said post-portion is submerged, for a syphon break to said space.

9. Structure according to claim 8 wherein said air passage means terminates at one end in an opening into said space between said post-portion and said guide-tube, with said opening disposed above the water level on said float and below the open end of said guide-tube.