Pressure compensation valve arrangement

A pressure compensation valve arrangement for opening automatically with the occurrence of a pressure difference on opposite sides of a dividing wall including a valve stem having a valve head at one end biassed into sealing relationship against an annular valve seat by a compression valve spring acting at the side of the dividing wall remote from the head and at a flange at the other end of the valve stem. The valve stem at its other end has a hollow cavity and has laterally recessed openings between vertically shaped connecting ribs. The cavity and openings communicate with a passageway bounded by the valve seat when the pressure on the valve stem exceeds a predetermined safety value.

BACKGROUND OF THE INVENTION 
The present invention relates to pressure compensation valve arrangements 
for valve stems which are provided with valve heads biassed under spring 
pressure into sealing engagement against a rigid annular valve seat of a 
support. The valve stem passes through the valve hole and is movable 
therethrough by spring pressure acting against the other side of the valve 
support such that with the occurrence of excess or vacuum pressure the 
valve is opened automatically and operates to automatically ensure 
pressure compensation. 
It has been proposed in U.S. Pat. Nos. 1,378,724 and 3,080,995 
(CURTISS-WRIGHT) or German Offenlegungsschrift Nos. 1,580,140 and 
2,028,383 in fuel tanks of automotive vehicles to use automatically acting 
valves within the closure caps of such tanks. These valves are retained 
tightly sealed subject to compression spring force and, with the 
occurrence of excess or reduced pressure in the tank, a respective valve 
opens automatically and again seals automatically tightly subject to 
spring force after pressure compensation has occurred. A serious 
disadvantage of such automatically acting pressure compensation valves 
resides in that, especially with the occurrence of large pressures during 
the opening of the valve, the compression springs located intermediate the 
valve hole and the interior of the fuel tank inadequately effect automatic 
opening and closing of the valve for gas pressure compensation. A more 
adverse effect particularly results if with the occurrence of increased 
pressure within the sealed fuel tank, the valves open correspondingly 
further against spring pressure forces which consequently produce a 
stronger compression of the springs. The cross-sectional flow area towards 
the valve hole will become forcibly constricted with the increased opening 
of the valve head. Eventually a fully compressed spring will block all gas 
flow towards the valve hole. 
SUMMARY OF THE INVENTION 
It is thus an object of the invention, generally and independently of the 
given intended uses for valves having tappet-like acting valve stem 
members, to control gas flow towards the valve hole. At the beginning of a 
valve opening a sufficient cross-sectional flow area is immediately 
produced which then, particularly for adaptation of large pressures, 
becomes greater so that with valves opening to a larger extent against 
spring forces, a correspondingly greater gas pressure compensation is 
ensured in a relatively short time. 
According to the present invention there is provided a valve arrangement 
for opening automatically with the occurrence of a pressure difference on 
opposite sides of a dividing wall or valve support. The arrangement 
includes a valve stem having a valve head at one end biassed into sealing 
relationship against a rigid ring valve seat of the dividing wall by a 
compression valve spring. One end of the spring acts on the side of the 
dividing wall remote from the head and the other end of the spring acts 
against a flange end of the valve stem. The spring is operative to seal 
the valve hole when equal pressure conditions exist on both sides of the 
valve head. The valve stem is hollow for forming a cavity having a large 
cross-sectional flow area and has laterally recessed openings between 
vertically extending shaped connecting ribs. The ribs project radially 
outwards, are equidistantly spaced about the stem, and extend to the end 
flange for the valve control spring. The connecting ribs have dome-shaped 
lower portions at the end flange. 
The technical progress according to the invention compared with known 
pressure compensation valves resides in that now, due to the partly hollow 
construction of the valve stem, a larger flow cross-section as connection 
to the outside immediately occurs during opening of the valve. Gas flows 
not only through the convolutions of the spring but also through the 
hollow cavity of the valve stem itself and into the lateral recesses of 
the ribs of the valve stem. The dome-shaped lower rib portions are 
connected to the end flange to support a valve control spring acting on 
the other side of the wall. Furthermore, this novel configuration forcibly 
provides a larger outer connecting cross-section beyond the cavity in the 
interior of the valve stem itself the more the valve head opens on the 
other side of the valve hole. As the end flange of the valve stem 
approaches the valve hole with increasing spring force, a larger portion 
of the recesses and cavity establishes communication with the valve hole. 
Once pressure compensation has occured, and in order to ensure an automatic 
satisfactory re-sealing closure of the valve seat, the invention is 
further characterized by the feature that an elastic or resilient sealing 
plate is centrally retained between the stem and the valve head and is 
pretensioned in the region of its outer circumference into an arcuate 
disk-shaped form by abutting against a rounded annular collar on the valve 
head. The collar is of somewhat larger inner diameter relative to the 
smaller outer diameter of the rounded seat of the valve hole. The collar 
is centrally retained and pressed in position all around over the raised 
rounded seat of the valve hole. 
The invention will be described further, by way of example, with reference 
to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the drawings, a section of a partition wall or valve support 1 is shown 
having a valve hole or passageway 3 therein provided with a raised annular 
valve seat 2 having a sealing rounded edge. A stem tappet 4 is located in 
the valve hole 3 and carries a valve head 10 mounted on one side of a 
sealing element or plate 11. Stem 4 extends through the hole 3 to the 
other side of the wall 1. Annular end flange 5' serves as abutment support 
for the compression spring 9 acting against the wall 1. The valve is shown 
slightly opened by being displaced against the force of a compression 
spring 9 so that valve head 10 and sealing valve plate 11 are slightly 
raised from the seat 2, so that with respect to the pressure compensation 
hitherto possible, a substantially larger pressure compensating 
cross-section is provided laterally outwards towards the hole 3, due to 
the hollow cavity 6 at the valve stem exposed end 5, and the lateral 
recesses 7 located between vertical rib portions 8 and 8'. 
Besides provision of a considerable compensating cross-section resulting 
from only a slight opening of the composite valve plate 10, 11, there is 
provided a further important advantage according to the invention. As the 
end flange 5' approaches the valve hole 3, the lateral openings 7 between 
the ribs open to an increasing extent. With increasing opening of the 
valve, increased gas flow from the hollow cavity 6 and the recesses 7 
occurs directly towards the valve hole 3. Upper rib portions 8' are 
mounted vane-like on the solid stem portion 4 as shown in the left-hand 
half of FIG. 2 and are arranged within the valve hole 3 with a lesser 
guide clearance relative to the axially drawn-in tubular wall portion 2'. 
For guiding the valve tappet 4 within the valve hole 3, three vane-like 
ribs 8,8' are used and spaced equidistantly over the circumference of the 
stem with their outer edges 8" having slight spacing relative to the 
drawn-in hole wall 2' as is evident from the left-hand half of FIG. 2 and 
also in part elevation of FIG. 1. 
It can be appreciated that hitherto a pressure compensation could only 
occur in unfavourable manner with the use of a solid stem tappet with the 
valve head providing only a small valve opening through the spacings 
between thread convolutions of a control compression spring 9 towards 
valve hole 3. Furthermore, with the occurrence of greater pressure 
differences with the valve opened widely against spring force, the 
cross-sectional passage area between these spring convolutions become 
constantly constricted or even completely sealed with adjacently abutting 
spring convolutions, whereas in such condition a particularly large 
cross-sectional passage area is desired. 
The invention provides a partially hollow valve tappet and dome-shaped 
connecting ribs 8, 8' which extend in a vertical direction from the end 
flange edge 5' for supporting a compression spring 9. This feature 
automatically and quickly compensates for large pressure differentials 
existing at opposite ends of the valve stem. There is thus obtained a 
larger cross-sectional flow area for the pressurized fluid flowing towards 
the valve hole 3 even with only a slight opening of the valve head 10, 11. 
Furthermore, with increased opening of the valve, the pressure 
compensating cross-section accordingly also increases because of the 
hollow cavity 6, since the size of the recesses 7 between lower rib 
portions 8 of dome-shaped configuration at the hollow ring 5' likewise 
increase. When the control compression spring 9 is in a fully compressed 
state, compensation can still occur because gas flows from the hollow 
cavity 6 via the laterally larger openings 7 to the valve hole 3. Thus an 
even swifter compression compensation can occur and the valve is also able 
to more swiftly close hermetically subject to the restoring action of the 
control spring 9. 
The solid material portion of the stem tappet 4 has a stepped, knob-like 
end portion 4' by which it is retained with snap fit and loosely guided in 
a correspondingly hollowed out mounting recess 10' in the centre of the 
valve head 10. Between the valve head 10 and a supporting shoulder 4" of 
the valve stem 4, a plate 11 of rubber, synthetic rubber or the like 
sealing material is provided for sealing relative to the seat 2 of the 
valve hole 3 and is inserted so that it abuts with pretension in a 
dish-shaped concave form against the collar 10" of the valve head. 
Further according to the invention and for providing centered seating of 
this sealing plate 11 and also of the valve head 10 seated on the valve 
tappet 4 relative to the valve aperture 3 or its valve seat 2, the sealing 
plate 11 is mounted under pretension in an arcuate shape on the valve head 
10. The plate 11 is shaped by collar 10". Collar 10" has a somewhat larger 
inside diameter than the outside diameter of the seat 2 of the hole. The 
collar 10" presses the plate 11 all around the seat 2. This causes the 
sealing plate 11 over its outer circumference by means of the collar 10" 
to be tightened, sealed and centered on the valve head 10. The somewhat 
larger outer diameter of the collar 10" relative to the seat 2 which is of 
somewhat smaller diameter provides a particularly good sealing effect. 
Moreover, the dish-shaped sealing plate 11 retained under pretension by 
the collar 10" is pressed flat with the valve seat closed, and will then 
be in flat abutment accordingly relative to the seat 2 on the valve hole 
3. 
The valve portions may be constituted by synthetic plastic material or by 
metal material.