Gas flow control device

A gas flow control device including a body means defining an inlet, an outlet and a gas flow passage therebetween a main valve disposed in the passage and comprising a primary valve movable between a closed position that prevents flow through the passage and an open position that permits flow therethrough; a primary diaphragm operably connected to the primary valve and supported by the body means, the primary diaphragm defining within the body and separating a primary reference chamber from a primary regulator chamber located in the passage and the pressure in the primary reference chamber exerting a force tending to open the primary valve; and a primary bias means biasing the primary valve toward its open position. Also included in the device is a secondary valve disposed in the passage between the primary valve and the outlet, the secondary valve movable between a closed position that prevents flow through the passage and an open position that permits flow therethrough; a secondary diaphragm operably connected to the secondary valve and supported by the body, the secondary diaphragm defining with the body and separating a secondary reference chamber from a secondary regulator chamber located in the passage and the pressure in the secondary regulator chamber exerting a force tending to close the secondary valve; a secondary bias means biasing the secondary valve toward the open position and a control passage providing communication between the primary reference chamber and the outlet.

BACKGROUND OF THE INVENTION 
This application relates generally to a gas flow control device and, more 
particularly, to such a device in which full rated flow is preceded by a 
period of reduced flow that effects limited combustion in a burner. 
The safe operation of many gas burners, particularly those enclosed in 
relatively compact combustion chambers, requires a start-up period of 
reduced gas flow preceding full rated flow. During the period of reduced 
flow, there is developed sufficient draft through the combustion chamber 
to support combustion of the subsequent full rated flow. 
There have been developed and proposed various gas flow control devices, 
commonly known as stepped opening or slow opening valves that can delay 
full rated gas flow to a burner. Although many of these devices 
effectively accomplish the desired delay in full rated flow, they suffer 
from a number of individual and collective disadvantages including, for 
example, critical operation characteristics and high construction costs. 
Examples of stepped opening valves are disclosed in U.S. Pat. Nos. 
3,300,174; 3,386,467; 3,351,085; 3,354,901; 3,502,101; 3,552,430; 
3,578,243; 3,721,263; 3,776,268; 3,800,823; 3,880,186; 3,896,857; 
4,009,861; 4,060,370; 4,217,928 and 4,254,796. 
The object of this invention, therefore, is to provide an improved, 
relatively low cost gas flow control device that efficiently provides an 
initial period of reduced gas flow preceding full rated gas flow. 
SUMMARY OF THE INVENTION 
The invention is a gas flow control device including a body means defining 
an inlet, an outlet and a gas flow passage therebetween a main valve 
disposed in the passage and comprising a primary valve movable between a 
closed position that prevents flow through the passage and an open 
position that permits flow therethrough; a primary diaphragm operably 
connected to the primary valve and supported by the body means, the 
primary diaphragm defining with the body and separating a primary 
reference chamber from a primary regulator chamber located in the passage 
and the pressure in the primary reference chamber exerting a force tending 
to open the primary valve; and a primary bias means biasing the primary 
valve toward its open position. Also included in the device is a secondary 
valve disposed in the passage between the primary valve and the outlet, 
the secondary valve movable between a closed position that prevents flow 
through the passage and an open position that permits flow therethrough; a 
secondary diaphragm operably connected to the secondary valve and 
supported by the body, the secondary diaphragm defining with the body and 
separating a secondary reference chamber from a secondary regulator 
chamber located in the passage and the pressure in the secondary regulator 
chamber exerting a force tending to close the secondary valve; a secondary 
bias means biasing the secondary valve toward the open position and a 
control passage providing communication between the primary reference 
chamber and the outlet. During a start-up period the primary valve 
regulates outlet pressure at a reduced pressure while gas flow between the 
outlet and the primary reference chamber provides a subsequent increase in 
the outlet pressure. 
According to one feature of the invention the control passage comprises a 
check valve providing restricted flow from the outlet to the primry 
reference chamber and full flow from the primary reference chamber to the 
outlet. The restricted flow through the check valve controls the increase 
in outlet pressure while the full flow permits rapid dumping of the 
primary reference chamber after shut-off. 
According to other features of the invention, the device further includes a 
primary actuator coupled to the main valve and operable in a first state 
to prevent flow therethrough and operable in a second state to permit flow 
therethrough, and a secondary actuator coupled to the secondary valve and 
operable in one state to prevent flow therethrough and operable in another 
state to permit flow therethrough. The primary and secondary actuators 
permit control of the device by a thermostat. 
According to one embodiment of the invention, the main valve comprises an 
auxiliary valve disposed in the passage between the inlet and the primary 
valve and the device further includes an actuator coupled to the auxiliary 
valve and operable in a first state to prevent flow therethrough and 
operable in a second state to permit flow therethrough. The auxiliary 
valve facilitates rapid opening of the device by permitting the primary 
valve to remain open during shut-off. 
According to another embodiment of the invention, the device includes a 
vent valve connected between atmosphere and the primary reference chamber 
and adapted to normally vent the primary reference chamber and to close 
and allow a pressure increase therein in response to movement of the main 
valve to the open position. The vent valve facilitates rapid cycling of 
the device by both bleeding off pressure from the primary reference 
chamber and preventing the existence of a vacuum therein during quick 
re-starts of gas flow.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Constructed in accordance with one embodiment of the invention is a gas 
flow control device 11 shown in FIG. 1. A casing body 12 defines an inlet 
13 for connection to a source of gas, an outlet 14 for connection to a 
combustion burner and a gas flow passage 15 therebetween. Disposed within 
the passage 15 for controlling gas flow therethrough is a main valve 16 
assembly including a primary valve 17 and an auxiliary valve 18. The 
series connected primary valve 17 and auxiliary valve 18 are accommodated, 
respectively, by valve seats 19 and 21 defined by the body 12. Also 
disposed in the gas flow passage 15 between the primary valve 17 and the 
outlet 14 is a secondary valve 22 accommodated by a valve seat 23. 
Operably connected to a stem 20 of the primary valve 17 is a primary 
diaphragm 25 retained by the body 12. Together the primary diaphragm 25 
and the body 12 define a primary regulator chamber 26 within the gas flow 
passage 15 and a primary reference chamber 27 separated therefrom by the 
primary diaphragm 25. In response to pressure induced movement of the 
diaphragm 25, the primary valve 17 is moved between a closed position 
engaging the seat 19 and preventing gas flow through the passage 15 and an 
open position permitting gas flow therethrough. A primary bias spring 29 
extends between the body 12 and the primary diaphragm 25 and exerts 
thereon a force tending to open the primary valve 17. 
Operatively connected to a stem 30 of the secondary valve 22 and supported 
by the body 12 is a secondary diaphragm 31. Together the body 12 and the 
secondary diaphragm 31 define a secondary regulator chamber 32 disposed in 
the flow passage 15 and a secondary reference chamber 33 separated 
therefrom by the secondary diaphragm 31. In response to pressure induced 
movement of the secondary diaphragm 31, the secondary valve 22 is moved 
between a closed position engaging the seat 23 and preventing gas flow 
through the flow passage 15 and an open position permitting flow 
therethrough. Extending between the secondary diaphragm 31 and an 
adjustable threaded plug 35 in the body 12 is a secondary bias spring 36. 
Produced on the secondary diaphragm 31 by the secondary bias spring 36 is 
a force tending to open the secondary valve 22. Atmospheric pressure is 
maintained in the secondary reference chamber 33 by a vent orifice 37. 
A control passage 38 has one end communicating with the outlet 14 and an 
opposite end communicating with the primary reference chamber 27. Located 
in the control passage 38 is an assembly 41 for controlling pressure 
within the primary reference chamber 27. An enclosure 42 joins a section 
43 of the control passage 38 connected to the primary reference chamber 27 
and a section 44 connected to the outlet 14. Retained by the enclosure 42 
is a check valve 45 urged by a bias spring 46 toward a closed position 
that closes the section 43. Extending centrally through the check valve 45 
is a restriction orifice 47. 
A primary solenoid actuator 51 has a plunger 52 coupled to the auxiliary 
valve 18. In a first deenergized state of the primary solenoid 51, the 
plunger 52 retains the auxiliary valve 18 in a closed position to prevent 
gas flow through the passage 15. In a second energized state of the 
solenoid 51, the plunger 52 is withdrawn allowing opening of the auxiliary 
valve 18 to permit flow to the passage 15. A secondary solenoid actuator 
55 has a plunger 56 operatively coupled to the secondary valve 22. In one 
deenergized state of the solenoid 55, the plunger 56 retains the secondary 
valve 22 in a closed position to prevent fuel gas flow through the passage 
15. In another energized state of the solenoid 55 the plunger is withdrawn 
to permit opening of the secondary valve 22 by the secondary spring 36 and 
the secondary diaphragm 31. 
OPERATION 
In the absence of a call for gas at a burner (not shown) connected to the 
outlet 14, the deenergized primary solenoid 51 and secondary solenoid 55, 
respectively, retain the auxiliary valve 18 and the secondary valve 22 in 
closed positions that prevent gas flow through the flow passage 15. At 
such time, the same atmospheric pressure exists in the primary flow 
chamber 26 and the primary reference chamber 27 and the primary spring 29 
retains the primary valve 17 in an open position. 
Upon a call for gas, the primary solenoid 51 and secondary solenoid 55 are 
energized to withdraw, respectively, the plungers 52 and 56 and thereby 
open the auxiliary valve 18 against the spring 53 and permit opening of 
the secondary valve 22 by the secondary spring 36. Resultant gas flow from 
the inlet 13 through the open auxiliary and primary valves 18, 17 
increases the pressure in the primary regulation chamber 26. In response 
thereto, the primary diaphragm 25 and the primary spring 29 function as a 
regulator to maintain a given pressure in the chamber 26. For example, the 
primary diaphragm 25 and the primary spring 29 can be selected to provide 
a given initial pressure in the primary flow chamber 26 of approximately 
11/2 inches water column (W.C.). The secondary valve 22 also is controlled 
by the secondary diaphragm 31 and the secondary spring 36 to regulate 
pressure in the secondary regulator chamber 32. Preferably the secondary 
diaphragm 31 and the secondary spring 36 are selected to limit the 
pressure in the secondary regulator chamber 32 to a predetermined greater 
pressure of, for example, 31/2 inches W.C. Thus, the initial given 
pressure in the primary flow chamber 26 less any line pressure drop is 
transmitted by the secondary valve 22 to the outlet 14. 
Gas at the outlet 14 is fed to both a connected burner (not shown) and the 
primary reference chamber 27 through the control passage 38 and the 
restriction orifice 47 in the check valve 45. Resultant increasing 
pressure in the primary reference chamber 27 increases the opening force 
applied by the primary diaphragm 25 to the primary valve 17 causing the 
pressure to increase in the primary flow chamber 26 and correspondingly at 
the outlet 14. The outlet pressure increases until approximately 31/2 
inches W.C. is reached and retained by the secondary valve 22. At that 
time, the pressure in the primary regulator chamber 26 and the inlet to 
the secondary valve 22 is maintained at a pressure determined by the 
combined forces applied to the primary diaphragm 25 by the primary bias 
spring 29 and the pressure then existing in the primary reference chamber 
27. For the example given above, that operating pressure in the primary 
regulator chamber 26 will approximate 5 inches W.C. 
Any subsequent deenergization of the primary solenoid 51 and the secondary 
solenoid 55 results in closure of the auxiliary valve 18 and the secondary 
valve 22 to interrupt gas flow between the inlet 13 and the outlet 14. The 
check valve 45 responds to the difference in pressure between the primary 
reference chamber 27 and the outlet 14 by moving against the spring 46 to 
open the section 43 of the control passage 38. Accordingly, gas pressure 
in the primary regulator chamber 27 is quickly dumped into the outlet 14 
to reestablish atmospheric pressure within the primary reference chamber 
27. The return to atmospheric pressure in the primary reference chamber 26 
allows the primary spring 29 to maintain the primary valve 17 in an open 
position prepared for a reopening of the auxiliary valve 18. 
Illustrated in FIG. 2 is another embodiment 60 in which parts identical to 
those of the embodiment 11 shown in FIG. 1 bear the same reference 
numerals. In the embodiment 60, the check valve 41 and the auxiliary valve 
18 of FIG. 1 are replaced by a vent valve 61 connected between the primary 
reference chamber 27 and the outlet 14 by a vent passage 62. Also, the 
plunger 52 of the primary solenoid actuator 51 is coupled directly to the 
primary valve 17 and the primary reference chamber 27 communicates with 
the outlet 14 via a control passage 63 having a restriction orifice 64. A 
spring 65 extends between the body 12 and a skirt 66 on a stem 67 of the 
valve 61. The spring 65 exerts a closure force on the valve 61 and an 
annular seal 68 prevents flow between the inlet 13 and the primary 
reference chamber 27. Operatively connecting the vent valve 61 to the 
solenoid 51 is an arm 71 mechanically coupled between the plunger 52 and 
the valve stem 67. The coupling between the primary solenoid 51 and the 
vent valve 61 is such that in response to a call for gas, the secondary 
valve 22 and the primary valve 17 are opened after which the vent valve 61 
is closed. 
Operation of the embodiment 60 is similar to that described for the 
embodiment 11. However, in the absence of the check valve 41, the vent 
valve 61 functions to relieve pressure in the primary reference chamber 27 
after closing of the primary valve 17 and thereby permit a rapid recycling 
thereof. In addition, the open vent valve 61 facilitates opening of the 
primary valve 17 by preventing an initial vacuum in the primary reference 
chamber 27. Subsequent closing of the vent valve 61 permits a gradual 
pressure increase in the primary reference chamber 27 via the restricted 
orifice 64 in the control passage 63. Thus, the restricted orifice 64 and 
the vent valve 61 provide for the embodiment of FIG. 2 a stepped flow 
operation similarly provided in the embodiment of FIG. 1 by the check 
valve 41. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is to be understood, 
therefore, that the invention can be practiced otherwise than as 
specifically described.