US2926683A

US2926683A - Fluid pressure control device

Info

Publication number: US2926683A
Application number: US501294A
Authority: US
Inventors: Frederick N Windsor; Daniel A Green
Original assignee: Mine Safety Appliances Co
Current assignee: MSA Safety Inc
Priority date: 1955-04-14
Filing date: 1955-04-14
Publication date: 1960-03-01
Anticipated expiration: 1977-03-01

Description

March 1960 r F. N WINDSOR arm. 2,926,683

FLUID PRESSURE CONTROL DEVICE United States PatetitO j ice 2 ,926,683 FLUID PRESSURE CONTROL DEVICE Frederick N. Windsor and Daniel A. Green, Penn Township, Pa., assignors to Mine Safety Appliance Company Pittsburgh, Pa., a corporation of Pennsylvania Application April 14, 1955, Serial No. 501,294

u 4 Claims. (Cl. 137-63) This invention relates to fluid pressure controls, and more particularly to those used as inlet valves in breathing equipment.

It is among the objects of this invention to provide a fluid pressure control device which can be used as a demand .valve or inhalation valve for breathing equipment, which can be used as a pressure regulator, and which can be operated by very slight changes in fluid pressure at its outlet side.

In accordance with this invention an axially floating sleeve carries at its rear end an annular valve member. The sleeve is surrounded by ,a housing which is spaced from it. The sleeve extends through the centers of a pair of spaced parallel flexible diaphragms that are secured to it and to the housing. The rear diaphragm has a greater effective area than the front diaphragm. The housing is provided with a fluid pressure inlet communieating with the sleeve and the front diaphragm. Between the valve member and the rear diaphragm, the housing has an internal shoulder that is spaced from that diaphragm and is provided with an annular valve seat for the valve member. The housing also is provided with an outlet communicating with the space between the shoulder and rear diaphragm. The effective area of the front diaphragm is substantially as great as the area of the space surrounded by the valve seat, so that substantially equal forces will be exerted on the sleeve axially thereof in opposite directions by the pressure fluid. The movement of the sleeve is controlled by changes in fluid pressure in the space between the rear diaphragm and valve seat. The valve can normally be held closed by making the diameter of the seat slightly larger than the diameter of the effective area of the front diaphragm, or by the use of a light spring. Or, the valve can normally be held open by a spring urging the sleeve rearwardly.

The preferred embodiment of the invention is illustrated in the accompanying drawings; in which Fig. l is a rear view of our fluid pressure control device;

Fig. 2 is a central axial section taken on the line 11-- II of Fig. 1;

Figs. 3 and 4 are radial sections taken on the lines IIIIII and IV-IV, respectively, of Fig. 2; and

Fig. 5 is a fragmentary detail of a modification.

Referring to the drawings, a circular valve body 1 is provided with an axial passage through it, the rear end of which is closed and sealed by a screwplug 2. Spaced from this plug as well as from the front of the body is an internal shoulder 3, the inner edge of which is encircled by a rearwardly facing valve seat 4. This shoulder divides the central passage into front and rear circular recesses 6 and 7. The front recess 6 has a considerably greater diameter than the other recess, and the outer area of the front recess is connected by a plurality of circumferentially spaced outlet passages 8 with the back of the valve body around the plug 2.

Screwed onto the front of the valve body is a cap 10 that extends across the body some distance in front of 2,926,683 Patented. Mar. 1, 1960 it. Between the front of the cap and the valve body, there is a circular plate 11, the marginal area of which is pressed by the cap against a flexible diaphragm 12 engaging the valve body around its front recess 6. There is a circular opening 13 through the center of the plate. A smaller diaphragm 14 is clamped in a similar manner between the front of this plate and the flange 16 of a nipple 17 that is mounted in a central inlet opening 18 in the cap. 'lhe nipple is adapted to be connected by a hose or the like (not shown) to a source of fluid under pressure, such as an oxygen bottle.

Extending through the centers of the two diaphragms, by which it is supported, is a sleeve 20 that is spaced from all of the other elements described thus far and which form a housing for the sleeve. The inner edge of the large rear diaphragm 12 is clamped between a disc 21 and a ring 22 slidably mounted on the sleeve, and the front diaphragm is similarly clamped between ring 22 and a front ring 23. The rings are pressed toward the disc by a nut 24 screwed onto the front end of the sleeve. Since the sleeve is supported only by the flexible diaphragms, it can move or float axially back and forth in the surrounding housing without frictional resistance.

The rear end of the sleeve is provided with an integral radial flange 26 spaced from valve seat 4. Between the flange and seat there is a valve member in the form of a flexible gasket 27, which encircles the sleeve and engages the flange. When the diaphragms are straight or unflexed, the gasket engages the valve seat.

The rear face of clamping plate 11 is providedwith a a circular recess 30 of substantially the same diameter as the front recess 6 in the valve body. These two recesses are separated by the large diaphragm. The plate recess is connected with the atmosphere by a hole 31 through the plate and another hole 32 through the front of the cap 10. Although the holes are shown in alignment, they need not be because the inside of the cap is provided with a shollow circular recess 33, into which both holes open.

When this device is to be used with a breathing appa ratus facepiece, the rear end of the valve body may have a radial flange 35 so that a groove is formed around the body between the flange and cap 10 for receiving the wall of an opening in the facepiece 36. The cap will clamp the facepiece against the flange to form a seal.

When the pressures on the opposite sides of the large diaphragm are equal, the position of sleeve 20 in the housing will be determined by the relation of the area of the space surrounded by the valve seat to the effective (exposed) area of the small diaphragm. If those areas 4 are equal, the fluid pressure at the opposite ends of the sleeve will act against it axially in opposite directions with equal force and have no effect on the sleeve. In such a case, to assure that the valve member will engage its seat firmly, it may be necessary to insert light compression spring means (not shown) between the screw plug and the adjacent end of the sleeve. Such springs can be avoided, however, by making the area of the space surrounded by the valve seat slightly greater than that of the effective area of the small diaphragm. The'total fluid pressure against the rear end of the sleeve then will be just enough 'greater than the pressure in the opposite direction against the front end of the sleeve to normally hold the valve closed, no matter what position the fluid control device may be in. In either case, the valve is opened the moment the fluid pressure in front recess 6 is reduced a slight amount, such as by inhalation by the wearer of a facepiece incorporating this device. Such a reduction in pressure will cause the large diaphragm to move toward shoulder 3 and thereby move the sleeve rearwardly to retract the valve member from its seat. As soon as suflicient incoming fluid flows across the valve seat from the rear to the front recess in the valve body to restore normal pressure in the front recess, the large diaphragm will move the sleeve forward again to close the valve. V p At high altitudes where the pressure of the ambient atmosphere is low, pressurized breathing can be maintained by connecting a suitable source of compressed air (not shown) to hole 32 in order to maintain the pressure between the two diaphragms at sea level pressure.

This device cantalso be used as a pressure regulator by soldering tension spring 40, as shown in Fig. 5, between the screw plug and sleeve. The spring should pull the sleeve toward the plug with a predetermined force and thereby require a predetermined fluid pressure against the back side of the lar e diaphragm to move the sleeve-forward until the valve member engages the seat. If the pressure in front recess 6 starts to fall, the springs will open the valve'to restore that pressure. In this way a desired fluid pressure can be maintained at the outlet side of the control device or regulator.

This pressure control device, in which the sleeve is supported only by flexible diaphragms and can float back and forth without any fritcional resistance, is very sensitive. As the difference between the area of the space surrounded by the valve seat and the effective area of the small diaphragm is very slight at the most, such difference, even if multiplied by a fairly large pressure of the fluid entering the device, still gives only a slight differe'nce in the pressures applied to the opposite ends of the sleeve. Consequently, the change in pressure in front recess 6 that is required to operate the valve is always very small. 3

Where the claims herein refer to the effective areas of the front diaphragm being substantially as great as the area'of the space surrounded by the valve set, it is meant that the two areas are the same, or only slightly different, as pointed out in the preceding para-graph.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. A breathing apparatus fluid pressure control device, comprising an axially floating sleeve carrying at its rear end an annular valve member, a housing surrounding the sleeve and spaced therefrom, and a pair of spaced parallel flexible diaphragms mounted in the housing around the sleeve in front of the valve member and secured to the sleeve for moving it, the rear diaphragm having a greater effective area than the front diaphragm, the housing being provided with a fluid pressure inlet communicating with the sleeve and the front of the front diaphragm, the housing having between said valve member and the rear diaphragm an internal shoulder spaced from that diaphragm and provided with an annular valve seat for the valve member, the housing being provided with an outlet communicating with the space between said shoulder and rear diaphragm, and the effective area of the front diaphragm being substantially as great as the area of the space surrounded by the valve seat so that substantially equal forces will be exerted on the sleeve axially thereof in opposite directions by said pressure fluid, the movement of the sleeve being controlled by changes in fluid pressure in the space between the rear diaphragm and valve seat.

2. A fluid pressure control device according to claim 1, in which said housing is provided with a passage extending from the space between the diaphragms to the outside of the housing.

3. A breathing apparatus fluid pressure control device, comprising an axially floating sleeve carrying at its rear end an annular valve member, a housing surrounding the sleeve and spaced therefrom, and a pair of spaced parallel flexible diaphragms mounted in the housing around the sleeve in front of .the valve member and secured to the sleeve for moving it, the rear diaphragm having a greater effective area than the front diaphragm, the housing being provided with a fluid pressure inlet communicating with the sleeve and the front of the front diaphragm, the housing having between said valve member and the rear diaphragm an internal shoulder spaced from that dia phragm and provided with an annular valve seat for the valve member, the housing being provided with an outlet communicating with the space between said shoulder and rear diaphragm, and the effective area of the front diaphragm being only slightly less than the area of the space surrounded by the valve seat, whereby the valve member can be moved away from the seat by only a slight reduction in fluid pressure in the space between the rear diaphragm and valve seat.

4. A breathing apparatus fluid pressure control device, comprising an axially floating sleeve carrying at its rear end an annular valve member, a circular valve body formed for mounting in a face mask and provided in its front with a rearwardly extending opening containing the rear portion of the sleeve in spaced relation with the body, said opening having an internal central shoulder separating the opening into front and rear recesses, the shoulder being provided with a valve seat for said valve member, the diameter of the front recess being greater than the rear recess, said body being provided with an outlet communicating with the front recess, a cap screwed onto the front of said body and provided with a fluid pressure inlet, a flexible rear diaphragm, a plate encircling the sleeve and spaced therefrom, the plate being pressed against the diaphragm by said cap to clamp it against the front of said body, a flexible front diaphragm spaced from the other one and having its outer portion clamped between said cap and plate, the diaphragms being provided with axially aligned openings receiving the sleeve, and means securing the diaphragms to the sleeve, the front diaphragm having an area open to said inlet, said area being smaller than the area of the rear diaphragm covering said front recess, and the diameter of said area of the front diaphragm being substantially as great as the diameter of the valve seat.

References Cited in the file of this patent UNITED STATES PATENTS