Flow noise reduction

A flow noise reduction assembly having a fixed flow limiting orifice or an inlet pressure responsive flow control washer having a flow limiting orifice. A conically faced diverter is disposed closely adjacent the downstream face of the orifice and an expansion chamber is disposed downstream of the flow diverter for noise attenuation.

BACKGROUND OF THE INVENTION 
The present invention relates to devices for controlling the flow rate in a 
conduit and particularly to flow control of water to the inlet of a 
household appliance such as a dishwasher, clothes washer, or refrigerator 
ice maker. In providing flow rate control to household appliances 
connected to municipal water supplies, it is desired to provide a 
generally constant flow rate to the appliance inlet in the face of wide 
variations in the water supply pressure. Various types of flow control 
devices have been employed for this purpose; and, a particularly well 
known device is an elastomeric washer which deforms resiliently under 
increasing supply pressure to restrict the flow orifice size, thereby 
maintaining a constant flow rate. 
However, in providing flow control to the water inlet of an appliance, 
problems have been experienced in excessive noise, where the restrictions 
of the flow control device have produced cavitation. In cases where the 
flow control is applied at the inlet of an electrically operated water 
inlet valve, the noise problem has been particularly exacerbated by the 
flow cavitation causing resonant vibration of the surrounding valve body 
structure. This problem has been particularly troublesome in appliance 
water inlet valves having body structure rigidly secured to a surrounding 
metal frame or cabinet of the appliance. 
Where an appliance water inlet flow control device is required to control 
substantial restriction to accommodate relatively high water supply 
pressures for maintaining a constant flow rate to the appliance inlet, 
severe high frequency vibration has been encountered as cavitation 
occurred at the flow control device; and, the resulting noise is perceived 
to be quite objectionable to the appliance user. It has thus been desired 
to find an inexpensive way or means of controlling the noise associated 
with flow control devices employed for controlling the rate of flow at the 
inlet of an appliance. 
SUMMARY OF THE INVENTION 
The present invention provides a flow control assembly which may be 
employed in a conduit or at the inlet of a valve for controlling flow to 
an appliance or at the inlet or outlet of an appliance connected directly 
to a source of pressurized fluid. The flow control assembly of the present 
invention employs, in its simplest form, a flow control orifice plate 
disposed in the body of the assembly, with a transversely enlarged 
expansion chamber formed on the downstream or discharge side of the 
orifice plate, and with the outlet port of the expansion chamber 
substantially smaller than the width of the chamber. In the simplest form 
of the invention, a flow diverter having a tapered face, in the form of a 
cone having a preferably obtuse included apex angle is disposed spaced 
closely adjacent the discharge face of the orifice plate, with the apex of 
the cone extending into the orifice formed in the plate. However, in a 
more complex embodiment the orifice plate has the downstream side thereof 
tapered to form a diffuser with the diffuser having the included angle 
thereof generally common to the included angle of the diverter cone. 
Preferably, the diverter has a secondary conically tapered surface 
disposed concentrically with the tapered surface of obtuse angle, with the 
secondary cone having a generally right angle included apex angle. The 
diverter creates a pressure drop which minimizes cavitation and the 
expansion chamber attenuates noise. Optionally, a resilient elastomeric 
flow control washer may be disposed in a conduit on the upstream face of 
the orifice plate. In this arrangement, the central orifice of the flow 
control washer is chosen to be less than the diameter of the orifice in 
the orifice plate. 
The present invention thus provides a unique and novel flow control 
assembly, which may be employed at the inlet of an appliance for diverting 
flow through the flow control orifice in a manner causing a pressure drop 
at the diverter to limit cavitation and an expansion chamber to attenuate 
flow noise. The present invention is readily employed as an in-line device 
or attached to the inlet or outlet of a water inlet valve.

DETAILED DESCRIPTION 
Referring to FIG. 1, the flow control assembly is indicated generally at 10 
and has a body or housing 12 with an inlet passage 14 formed therein, 
through which flow enters in the direction indicated by the black arrow in 
FIG. 1. The inlet passage 14 communicates with an enlarged cavity 16 which 
has an orifice plate 18 disposed therein, and secured peripherally 
therearound in any suitable manner as, for example, by snap-locking into 
groove 20, provided in the wall of the cavity 16. Orifice plate 18 has a 
flow limiting orifice 22 formed centrally therethrough, and preferably has 
the downstream or discharge face thereof conically tapered to form a 
diffuser cone 24. 
The downstream side of orifice plate 18 communicates with an enlarged 
expansion chamber 26, which preferably has the largest dimension thereof 
transverse to the flow direction, or the diameter thereof, at least five 
multiples of the diameter of the orifice. The chamber has a substantially 
increased volume; and, in the present practice has its length not less 
than one-third the transverse dimension thereof established as described 
aforesaid. The increased volume of the chamber 26 aids in dissipating 
cavitation and attenuation of flow noise and is an essential feature of 
the invention with respect to noise reduction. 
The chamber 26 is closed by a cover or outlet member 28 received over the 
body 12 and secured thereon in any suitable manner as, for example, 
non-metallic weldment about parting line 30. 
The cover 28 has a boss or nipple 32 provided thereon, which has outlet 
passage 34 formed therethrough and communicating with the expansion 
chamber 26. In the presently preferred practice of the invention, the 
outlet 32 has the transverse dimension thereof in the direction of the 
flow, not greater than 1/2 the diameter of the transverse dimension of the 
expansion chamber. 
Referring to FIGS. 1, 2, and 3, a flow diverter, indicated generally at 36, 
is shown as disposed in the expansion chamber immediately adjacent the 
downstream face of orifice diffuser cone 24. Diverter 36 has the face 38 
thereof adjacent the diffuser cone 24 orifice formed in a conical 
configuration, and has a generally obtuse apex angle corresponding to the 
included apex angle of the diffuser cone 24. The base diameter of the 
conical diverter face 38 is, in the present practice of the invention at 
least 11/2 multiples of the diameter of the flow control or limiting 
orifice 22, 122, 252. The outer periphery of diverter 36 is registered 
against the downstream face of the orifice plate 18, and is secured into 
the body by the cover 32. 
Referring particularly to FIGS. 2 and 3, the diverter 36 has a plurality of 
circumferentially equally spaced radial spokes 42 extending between the 
cone 38 and the outer rim 40 of the diverter, which ribs form the 
plurality of arcuate passages 44 about the circumference of the cone 38. 
The ribs each have a streamlined or tapered configuration 46 provided on 
the upstream edge thereof as shown in FIG. 3. 
The diverter face cone 38 is spaced a distance from the downstream face of 
the orifice plate or diffuser cone 24 by an amount or distance expressed 
as a ratio of the orifice diameter in the range of 0.08 to 0.14 in the 
presently preferred practice of the invention. The diffuser cone 24 and 
diverter cone 28, in the presently preferred practice, have an included 
apex angle on the order of 150 degrees. 
The conical face 38 of the diverter, in cooperation with the diffuser cone 
18, or the downstream face of the orifice plate 118 provides increased 
surface area for the pressure drop across the orifice and thus functions 
to minimize cavitation. 
Referring to FIG. 4, another embodiment of the invention is illustrated 
generally at 100, having a body 112 with inlet 114 communicating with 
inlet chamber 116, having an orifice plate 118 provided therein, 
registered in a groove 120 in the body, and having a central flow limiting 
orifice 122 formed therein. The downstream face of the orifice plate 118 
has a tapered conical diffuser surface 124 communicating with an expansion 
chamber 126, which is formed in a cover 128 attached to body 112 and 
sealed thereabout along parting line 130, preferably by non-metallic 
weldment. Cover 128 has boss or nipple 132 formed thereon with an outlet 
passage 134 therethrough communicating with expansion chamber 126. The 
sizing of the expansion chamber 126 and outlet 134 is similar to that 
described above with respect to the embodiment of FIG. 1. 
The embodiment of FIG. 4 has a diverter indicated generally at 136, which 
has the upstream face thereof disposed adjacent the diffuser cone 124; 
and, the upstream face 138 of the diverter 136 has a conically tapered 
surface having an obtuse included apex angle. 
An auxiliary or secondary conically tapered surface, indicated at 139 is 
formed concentrically with the surface 138 and the auxiliary conically 
tapered surface 139, has a generally right angled included apex angle, and 
extends into the orifice 122. The location and spacing of the diverter 136 
from the diffuser cone 124 is similar to that described above with respect 
to the embodiment of FIG. 1. 
Referring to FIG. 5, another embodiment of the invention is indicated 
generally at 200, and has a chamber 216 formed on the upstream face of the 
orifice plate 218. The chamber 216 has disposed therein a resilient 
elastomeric control washer indicated generally at 250, which has the 
thickness and diameter thereof conformed to the walls of chamber 216, and 
has a flow control orifice 252 formed centrally therein. It will be 
understood that the flow control orifice 252 is not greater than the 
diameter of the flow limiting orifice 222 provided in the orifice plate 
218. The assembly 200 includes a diverter 236 disposed adjacent the 
downstream side of orifice 222 in an expansion chamber 226 communicating 
with an outlet 234 formed in cover 228. It will be understood that the 
structural configuration of the embodiment 200 of FIG. 5 is otherwise 
identical to that of FIG. 4. 
In the present practice of the invention, at a flow rate of 1.75 gallons 
per minute, a noise level reduction of 6 decibels on the "A" scale from 
the level of the known present technology has been achieved in a flow 
control assembly made in accordance with the invention and employing a 
single orifice elastomeric flow control washer having a pressure drop of 
60 psi (414 KPa) thereacross. 
Referring to FIG. 6, values of noise level in decibels, measured at a 
distance of 2 inches (51 mm) from the source of noise, are plotted as 
ordinates for differing values of the pressure drop .DELTA.P across the 
assembly resulting from varying inlet pressures plotted as abscissa. The 
upper graph in FIG. 5 represents measurements taken for a flow-through 
device employing only a single orifice elastomeric flow control washer 
without the present invention. The middle graph represents measurements 
taken for flow through a device having only a tri-orifice (3 hole) 
elastomeric flow control washer without the present invention. The lower 
graph represents a flow control device employing a single orifice 
elastomeric flow control washer with the diverter and expansion chamber of 
the present invention disposed immediately downstream of the flow control 
washer. From the graph of FIG. 5, it will be seen that the present 
invention provides at least 3 decibels, or fifty percent (50%) noise 
reduction for .DELTA.P greater than 20 psi (130 KPa). 
The present invention thus provides a unique and novel flow control 
assembly for an appliance water inlet which employs a conically tapered 
diverter immediately adjacent the downstream face of the flow control 
orifice. The diverter has an obtuse included apex angle in its simplest 
form, and an auxiliary generally right angled conically tapered surface 
for controlling pressure drop immediately adjacent the downstream edge of 
the orifice plate for diverting flow and reducing cavitation as the flow 
enters the expansion chamber which attenuates flow noise. The present 
invention thus provides a convenient and low cost way of reducing flow 
noise in a flow control device. 
Although the invention has hereinabove been described with respect to the 
illustrated embodiments, it will be understood that the invention may be 
modified and varied by those having ordinary skill in the art, and is 
intended as limited only by the scope of the following claims.