U.S. patent number 3,709,732 [Application Number 05/171,094] was granted by the patent office on 1973-01-09 for ultrasonic dishwasher.
Invention is credited to Max Thomen.
United States Patent |
3,709,732 |
Thomen |
January 9, 1973 |
ULTRASONIC DISHWASHER
Abstract
Piezoelectric transducers are attached to the bottom wall of an
upwardly open tub of austenitic stainless steel equipped with a
valved inlet in a side wall near the bottom wall, a valved outlet
in the bottom wall, a removable cover provided with a receptacle
for washing compositions, and a vertical row of contacts on the
side wall. After the washer cycle is started by pressing a button,
the washer is further controlled automatically by the opening or
closing of circuits between the contacts and the grounded tub
through the rising or receding liquid in the tub. A safety switch
on the outer tank wall is kept closed by a permanent magnet as long
as the cover is in position, and the receptacle is dropped to
release the washing composition upon retraction of a latch by an
electromagnet on the outer face of the tub side wall.
Inventors: |
Thomen; Max (8202 Kloten,
CH) |
Family
ID: |
4382872 |
Appl.
No.: |
05/171,094 |
Filed: |
August 12, 1971 |
Foreign Application Priority Data
|
|
|
|
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Aug 18, 1970 [CH] |
|
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12422/71 |
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Current U.S.
Class: |
134/57D; 134/184;
134/93 |
Current CPC
Class: |
D06F
39/087 (20130101); A47L 15/50 (20130101); A47L
15/0076 (20130101); B08B 3/12 (20130101); A47L
15/13 (20130101); A47L 2601/17 (20130101) |
Current International
Class: |
A47L
15/13 (20060101); A47L 15/50 (20060101); A47L
15/00 (20060101); D06F 39/08 (20060101); B08B
3/12 (20060101); B08b 003/10 () |
Field of
Search: |
;134/1,57D,58D,93,184 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bleutge; Robert L.
Claims
What is claimed is:
1. A dishwasher comprising:
a. a stainless steel tub having an upright side wall, a bottom
wall, and an open top opposite said bottom wall;
b. a cover movable toward and away from an operative position in
which said cover closes the open top of said tub;
c. transducer means mounted on the outer face of said bottom wall
for imparting ultrasonic vibrations to a liquid in said tub;
d. a plurality of contact elements fixedly mounted on said side
wall and vertically spaced from each other,
1. said contact elements being exposed in said tub for electrical
contact with said liquid,
2. the lowermost of said contact elements being closely adjacent
said bottom wall;
e. a tubular inlet member mounted on said side wall adjacent said
bottom wall and having an axis approximately parallel to said
bottom wall;
f. a receptacle mounted on said cover for movement between a first
position in which said receptacle is capable of retaining a
particulate washing composition and a second position in which said
composition is dropped from said receptacle into said tub;
g. latch means for retaining said receptacle in said first position
against the force of gravity;
h. electrically operated latch releasing means for releasing said
latch means and for thereby permitting said receptacle to move into
said second position thereof,
1. said latch releasing means including an electromagnet mounted on
an outer face of said tub, and
2.
2. said latch means including a ferromagnetic latch member arranged
on said cover for movement in the field of said electromagnet when
said electromagnet is energized;
(i). a tubular drain member on said bottom wall;
(j). electrically operated valve means in each of said tubular
members for opening and closing the associated tubular member;
(k). control means conductively connected to said transducer means,
to said contact elements, to said latch releasing means, and to
said valve means for operating said transducer means, said latch
releasing means, and said valve means in response to conductive
contact between said liquid and said contact elements in timed
sequence; and
1. support means for holding tableware in a predetermined position
in said
tub. 2. A dishwasher as set forth in claim 1, wherein one of said
valve means includes a valve member movable between an opening
position and a closing position, an armature member secured to said
valve member for simultaneous movement, and two electromagnets
oppositely spaced from said armature member in the direction of
movement of the armature member and conductively connected to said
control means.
3. A dishwasher as set forth in claim 1, further comprising
selector switch means in circuit with two contact elements upwardly
spaced from said lowermost contact element for selectively
inactivating said two contact elements respectively.
4. A dishwasher as set forth in claim 1, wherein said control means
include a switch mounted on an outer face of said tub and including
a ferromagnetic contact member movable between a circuit closing
and a circuit opening position and yieldably biased toward one of
said positions thereof, said cover carrying a permanent magnet,
said magnet attracting said movable contact member and holding the
same in the other position thereof when said cover is in the
operating position.
5. A dishwasher as set forth in claim 1, wherein said support means
include a support member, a carrier adapted to fixedly hold a
cup-shaped piece of tableware, said carrier being movable on said
support member between a first position in which said cup-shaped
piece is upwardly open and a second position in which said
cup-shaped piece is downwardly open, and operating means responsive
to a change in the level of liquid in said tub for moving said
carrier between said positions thereof.
6. A dishwasher as set forth in claim 5, wherein said carrier
includes a wire frame pivotally secured to said support member for
pivotal movement between said positions thereof, and said operating
means include a float attached to said carrier.
Description
This invention relates to washing machines, and particularly to a
dishwasher equipped with ultrasonic transducers for agitating the
washing liquor in the tub of the dishwasher.
It is common practice to rely on the mechanical action of water
jets for dislodging particles of food and other contaminants from
the surface of tableware in an automatic dishwasher. Water alone,
even when very hot, is not normally effective enough, and strongly
alkaline or oxidizing detergents must be dissolved in the water.
The strong detergents tend to bleach overglazes and other colored
decorations on the tableware, and attack certain types of glass.
Moreover, it is necessary to apply hot air to the washed tableware
after washing and rinsing in order to dry the same.
It is known to use ultrasonic transducers for agitating liquid
cleaning solutions, but the known ultrasonic cleaning devices are
not suitable for household use.
The primary object of this invention is the provision of an
ultrasonic dishwasher which is practical for household use.
A more specific object is the provision of a domestic dishwasher
which need not rely for full cleaning efficiency on aggressive
chemicals and makes it unnecessary to provide hot air for drying
the washed tableware so as to operate in a cycle much shorter than
that of conventional automatic dishwashers.
With these and other objects in view, the invention provides a
dishwasher with a tub of stainless steel having an open top which
may be closed by a movable cover. Transducers are mounted on the
outer face of the tub bottom wall in such a manner that they may
impart ultrasonic vibrations to a liquid in the tub. Contact
elements are fixedly mounted on the side wall of the tub and
vertically spaced from each other. The contact elements are exposed
in the tub for electrical contact with the liquid therein, the
lowermost contact element being closely adjacent the bottom wall of
the tub. A tubular inlet member is mounted on the side wall
adjacent the bottom wall with its axis approximately parallel to
the bottom wall.
A receptacle is mounted on the cover for movement between a first
position in which it is capable of retaining a particulate washing
composition and a second position in which the composition is
dripped from the receptacle into the tub. A latch arrangement
normally retains the receptacle in its first position against the
force of gravity, but it may be permitted to move into the second
position when the latch arrangement is released by an electromagnet
mounted on the outer face of the tub whose field, when energized,
includes a movable ferromagnetic latch member.
The afore-mentioned tubular inlet member and a tubular drain member
on the bottom wall are opened and closed by electrically operated
valves. The valves, the transducers, the latch releasing magnet,
and the contact elements on the side wall are conductively
connected to a central control mechanism which operates the
transducers, the latch releasing magnet, and the valves in response
to electrical contact between the contact elements and the liquid
in the tub. A support is provided for holding tableware in a
suitable position in the tub.
Other features, additional objects, and many of the attendant
advantages of this invention will readily be appreciated as the
same is better understood by reference to the following description
of a preferred embodiment when considered in connection with the
appended drawing in which:
FIG. 1 shows a dishwasher of the invention in front elevational
section;
FIG. 2 shows the dishwasher of FIG. 1 built into a kitchen counter,
the view being in front elevation;
FIG. 3 is a fragmentary diagram of the electrical circuits in the
same dishwasher;
FIG. 4 shows a portion of the tableware support in the dishwasher
on a larger scale in elevation and partly in section;
FIG. 5 illustrates the device of FIG. 4 in another operating
position; and
FIG. 6 and FIG. 7 show another portion of the tableware support in
the manner of FIGS. 4 and 5 respectively.
Referring now to the drawing, and initially to FIG. 1, there is
seen the approximately cubical tub 1 of a dishwasher which is deep
drawn from austenitic stainless steel sheet. The open top of the
tub is closed by a removable plastic cover 2. The outer face of the
bottom wall 3 of the tub 1 carries a group of adhesively fastened
barium titanate transducers 4 arranged in a pattern to uniformly
transmit ultrasonic energy to a liquid in the tub when the
transducers are energized at about 25,000 CPS. A housing 5 protects
the transducers.
In the installed condition of the washer, a hot water line is
connected to an inlet tube 6 whose axis is horizontal and thus
parallel to the bottom wall 3 and to the tubular upright wall 12 of
the tub near the juncture of the upright and bottom walls. A drain
tube 7 is provided on the bottom wall 3 and is equipped with a
poppet valve 8 which may be opened and closed by two electromagnets
9, 10 oppositely spaced from a common armature member 11 in the
direction of pivoting movement of the latter on the drain tube 7,
the end portion of the armature member 11 remote from the magnets
being hingedly fastened to the stem of the valve 8.
Three contact elements 13, 14, 15 are mounted in a vertical row on
the upright wall 12. The lowermost contact element 13 is closely
adjacent the bottom wall 3 and barely above the level of the inlet
tube 6, and the topmost contact element 15 is just below the cover
2. Each of the elements consists of a plastic insulating plug and a
Monel wire passing centrally through the plug so that one of its
ends is exposed in the tub 1.
The cover 2 carries a permanent magnet 16 which, in the illustrated
operative position of the cover 2, is aligned with a switch 17
mounted on the outer face of the tub 1 whose material is
non-magnetic. The switch 17 has a fixed contact and a movable
contact sealed in a glass envelope. The movable contact is magnetic
and resilient so that it is normally biased toward the open
position, but closes a circuit when in the field of the magnet
16.
An aperture in the cover 2 is closed in the condition of the
apparatus shown in FIG. 1 by a scoop-shaped receptacle 18 secured
to the bottom face of the cover 2 by a hinge 19, the free end of
the receptacle being held in the illustrated position against the
force of gravity by a latch rod 20 of mild steel biased toward the
operative position by a helical compression spring 21. An
electromagnet 22 is arranged on the outer face of the upright wall
12 in alignment with the latch rod 20. When the magnet 22 is
energized, it attracts the rod 20 against the restraint of the
spring 21, and thereby releases the receptacle 18 to drop its
contents, such as a surfactant, into the tub 1.
As is common practice, the tub 1 may be installed in a freestanding
housing (not shown) mounted on casters, or it may be installed in a
kitchen counter in the manner illustrated in FIG. 2 so that its
open top is vertically aligned with a corresponding aperture, not
visible in the view of FIG. 2, in the counter top 25. The tub is
normally hidden in a sink cabinet which may be flush with another
cabinet 26 and a kitchen stove 27 as is conventional. A nipple 28
on the bottom of the tub 1 connects the drain tube 7 with a siphon
29. A mixing faucet 30 arranged above the open top of the tub
permits the tub to be used as an ordinary kitchen sink if desired.
A panel 31 conceals the ultrasonic generator that energizes the
transducers 4 and carries the several control knobs 32 to 38 and a
timer 39 for automatic operation of the dishwasher. When the tub is
used as a sink, the cover 2 may be stored in a bracket on a wall of
the sink cabinet, and the cabinet also provides space for a basket
40 of wire coated with polyvinyl chloride plastisol which supports
tableware during the automatic washing cycle.
The control panel 31 obscures not only the afore-mentioned
ultrasonic generator, but also relays and other circuit elements of
a control unit 41 (FIG. 3) which are connected with the drain
magnets 9, 10, the contact elements 13, 14, 15, the reed switch 17
and the magnets, not shown, which operate the non-illustrated valve
in the inlet tube 6 in the manner illustrated with reference to the
valve 8. The tub 1 provides a common ground connection for the
several electrical devices mounted thereon, and is connected by a
ground lead 42 with the circuit elements on and behind the control
panel 31.
The current supply to the electrically operated elements of the
dishwasher is controlled by a contactor operated by the reed switch
17. All current is shut off when the cover 2 is removed. The push
button 32 operates the main switch of the machine. The push buttons
33 to 35 permit a fully automatic or semi-automatic washing cycle
to be selected or a mode of operation in which a load is washed
only, but not dried. The push buttons 36, 37 are arranged in series
with the contact elements 14, 15 so that they may inactivate one of
the two contact elements but only one. The button 38 when
depressed, starts a selected washing program. The timer 39 may be
set to determine the period during which the non-illustrated
high-frequency generator energizes the transducers 4.
The circuitry of the control unit 41, not shown in detail, is
controlled by a drum switch operated by means of a small
synchronous motor as is customary in automatic washing machine. In
operating the machine, when loaded with dishes to be washed, the
cover 2 is closed first to operate the safety switch 17. One of the
buttons 33 to 35 is pushed to set the desired program, the main
switch is closed by pushing the button 32, and the desired water
level during washing is set by pushing one of the buttons 36, 37.
The period of ultrasonic agitation is set on the timer 39 depending
on the amount and kind of soil on the dishes, and the button 38 is
pressed last to start the cycle.
Assuming that the button 33 was pressed before the button 38 for
automatic operation, the valve 8 is closed, the non-illustrated
valve in the inlet tube 6 is opened, and the magnet 22 is energized
briefly to dump a particulate surfactant from the receptacle 18
into the whirling water discharged from the tube 6. When a circuit
is closed between the lowermost contact element 13 and the tub 1,
the non-illustrated high-frequency generator is energized. As the
water level reaches the contact element 14 or 15 which has remained
active, the water flow from the tube 6 is shut off, and the timer
39 is started. It may be set to open the drain valve 8 30 seconds
to 6 minutes after the desired maximum level is reached, and the
ultrasonic generator is shut off as the descending water level
passes the lowermost contact element 13. Opening of the circuit
through the element 13 also causes the inlet tube 6 to be opened
briefly after a delay of approximately 5 seconds to flush debris
from the bottom of the tub 1 into the drain tube 7. 20 seconds
later, the valve 8 is shut automatically, the inlet tube 6 is
opened and the second period of the cycle, similar to the first
period, is started. If it is desired to use a surfactant in the
second period also, the receptacle 18 may be returned manually to
the illustrated position and again charged with washing composition
at any time during the first period.
When the second period approaches its end, the inlet tube 6 is not
opened again, and the valve 8 remains open as long as current is
supplied to the machine. The cover 2 may then be removed, and the
washed dishes withdrawn.
The surfactant employed has the dual function of facilitating the
release of gas bubbles, more specifically air bubbles, from the
liquid in the tub, and of dispersing or emulsifying the soil
particles dislodged from the tableware by cavitation under the
influence of ultrasonic oscillations in the liquid after the air
bubbles are released. Because the ultrasonic treatment is continued
while the washing liquid is discharged through the drain tube 7,
the surfactant-bearing liquid is drained completely from the
tableware in the basket 40 if the pieces of tableware are
positioned so as not to trap water. The oscillation during draining
also prevents redisposition of soil on the tableware, particularly
in the second period of the cycle. The tableware, when properly set
in the basket 40, is withdrawn dry and clean from the tub 1.
Mild, non-foaming surfactants and emulsifiers are adequate for
operation of the illustrated dishwasher since they are not needed
for releasing soil from the tableware. Such surfactants are staple
articles of commerce and do not affect overglaze or sensitive
glass. The washing cycle in fully automatic operation takes only
about 10 to 15 minutes since it does not include the hot-air drying
period of conventional dishwashers.
When the button 34 is pressed to set the washing program, the
second period is omitted. The drain valve 8 remains open after the
first washing period. This is sufficient for lightly soiled
tableware. When the button 35 is pushed, the ultrasonic generator
is shut off by the timer 39 while the valve 8 remains closed and
the liquid level in the tub 1 is maintained at its maximum value
set by the button 36 or 37. This mode of operation may be selected
for cleaning heavily soiled kitchen utensils for which the
last-described individual cycle may precede a normal automatic
cycle, or when it is desired to add more tableware after a first
washing.
The armature member 11 is preferably mounted on the drain tube 7
with sufficient friction to maintain its angular position when the
magnets 9, 10 are deenergized. The valve 8 is thus opened or closed
by a brief electrical pulse transmitted from the control unit 41 to
the magnets 9, 10 respectively, and remains open or closed
thereafter. The valve 8 is held closed by the pressure of the
liquid in the tub 1, but it is preferred that the magnet 10 receive
pulses repeated from time to time as long as the valve 8 is desired
to remain open.
The only movable mechanical elements in the illustrated dishwasher
are the valves in the inlet and drain tubes, and the receptacle 18.
Additional movable elements are provided in the basket 40 for
effective cleaning of tumblers or other cup-shaped pieces of
tableware as is shown in FIGS. 4 to 7.
Referring initially to FIGS. 4 and 5, there is seen a support
member 45 which is a normally stationary element of the basket 40.
Two open-meshed wire grids 46 respectively act as carriers for two
tumblers 50. One end of each grid 46 is pivotally attached to the
support member 45 for movement through an angle determined by two
abutments 47, 48. The other end of each grid is provided with
entegral hooks 49 which retain the corresponding tumbler 50 in a
fixed position relative to the grid 46. The far end of the grid
also carries a tube 51 whose ends are sealed and which is filled
with air to act as a float.
When the tub 1 is empty of water, the grids 46 engage the lower
abutments 47 whereby the open ends of the tumblers 50 are directed
downwardly. When the tub 1 is filled with water to its operating
level, the floats 51 raise the grids 46 so that the tumblers 50 are
open in a direction which has an upward component.
During washing, the tumblers 50 are thus held in the position seen
in FIG. 5 in which no gas can be trapped within the tumblers, and
the liquid wets all internal and external tumbler surfaces and
exposes them to the action of the ultrasonic oscillation. When the
water level drops, the tumblers are drained as they move toward the
position shown in FIG. 4. Because the ultrasonic oscillations
continue during most of the draining period, no droplets of water
are left behind on the glass surfaces to stain the same after
drying.
A correspondingly operating portion of the basket 40 suitable for
carrying coffee or tea cups provided with a handle is shown in
FIGS. 6 and 7.
A member 52 of the basket 40 pivotally supports a carrier frame 53
equipped with hooks 54 from which cups 55 are suspended by their
handles. The hooks 54 cooperate with transverse members 56 of the
frame 53, which act as stops for the cups 55, to maintain a fixed
position of the cups on the carrier frame 53. A float 57, different
from the afore-described float 51 in its dimensions only, pivots
the carrier frame 53 and the cups suspended therefrom from the
position of FIG. 6 to that of FIG. 7 as the liquid level in the tub
1 rises, while abutments 47, 48 on the supporting member 52 limit
the angle of pivoting movement between the two terminal positions
illustrated in which the cups are open downwardly for draining
liquid or upwardly for release of gas, as described with reference
to the tumblers 50 in FIGS. 4 and 5.
It should be understood, of course, that the foregoing disclosure
relates only to a preferred embodiment of the invention, and that
it is intended to cover all changes and modifications of the
example of the invention herein chosen for the purpose of the
disclosure which do not constitute departures from the spirit and
scope of the invention set forth in the appended claims.
* * * * *