Packing For Air Compressor Valve

Abstract

In an air compressor, including flapper type blade valves over the inlet and outlet bores of the compressor, the invention is an improved packing for mounting the captured end of each blade valve. Each packing is comprised of a wide, rigid, metal sheet and two thin layers of yieldable material on opposite surfaces of the sheet. The blade is in a recess of and has the same thickness as one of the thin layers.

Parent Case Text

This is a continuation-in-part of application Ser. No. 105,263, now abandoned filed on or about Jan. 12, 1971.

Description

The present invention relates to improved packings for the blade valve of a flapper type air compressor.

In some air compressors the intake and exhaust valves are of the metal blade or flapper type. Such a compressor usually includes a bored plate, having an inlet bore communicating between the inlet to the compressor and the pumping chamber and an outlet bore communicating between the pumping chamber and the outlet from the compressor. An inlet bore blade valve is positioned adjacent to the surface of the bored plate that faces away from both the inlet and the outlet of the compressor. An outlet bore blade valve is positioned adjacent to the surface of the bored plate that faces toward the compressor inlet and outlet.

When air is drawn into the compressor, the outlet bore valve blocks the outlet bore to prevent any back leak of already pumped air. The inlet bore is open so that air may enter the compressor pumping chamber. The incoming air impinges upon the inlet bore valve, which would normally be blocking the inlet bore, and lifts this valve away from the inlet bore, thereby permitting the air to move into the compressor.

Similarly, when the compressor is expelling air, the inlet bore valve prevents leakage back through the inlet bore, whereby all outlet flow is only through the outlet bore. The outgoing air impinges upon the outlet bore valve, which would normally be blocking the outlet bore, and lifts this valve away from the outlet bore, thereby permitting the expelled air to leave only through the outlet bore.

One end of each of the inlet bore blade valve and of the outlet bore blade valve is fixed. The other end is free to shift under the influence of the flowing air. Conventionally, the inlet bore valve is interposed between the bored plate and the cylinder, which contains the moving piston that pumps the air, and the outlet bore valve is interposed between the same bored plate and the compressor head, which contains the inlet and outlet chambers. Each valve normally seats against the surface of the bored plate and is held in place by packings, which seal the compressor. Conventionally, the thickness of the packing determines the length of the stroke of the free end of the blade valve. The stroke must be limited in order to avoid excessive deflection of the valve, which would cause it to unnecessarily rapidly deteriorate.

Conventional packings are formed of a thick layer of resilient gasket material, e.g. asbestos, a rubber-asbestos compound, or the like, which is subject to permanent deformation. As the compressor operates, the packings are continuously flexed as the valves operate. The packings eventually heat up to such an extent that they partially lose their elasticity. As a result of the reduced spring action by the affected packings against the neighboring mating surfaces of the compressor, the airtightness of the seal of the compressor may be impaired. To reestablish the seal, the compressor head to compressor cylinder securing bolts must be periodically retightened, typically after a period of from 20 to 30 hours operation, to restore the airtightness of the seal. Unfortunately, this retightening also reduces the thickness of the packings, and thereby undesirably decreases the stroke of the blade valves, reducing compressor performance.

The present invention overcomes the above-noted drawback of prior packings. In a preferred embodiment of the invention, as is conventional, one of the blade valves is held between the bored plate and the head of the compressor and the other of the blade valves is held between the bored plate and the cylinder of a piston type air compressor. However, the present invention is not limited to a compressor where the blade valves are held between the above mentioned elements. The invention is limited only to compressors where the blade valves are held in the above-noted manner with respect to the bored plate.

In the present invention, each of the packings for each of the blade valves is comprised of a relatively thick, central sheet of an inflexible, nonpermanently deformable material, e.g. steel, aluminum alloy, etc., and of two relatively thinner outer layers of elastic, permanently deformable gasket material, like a fabric, such as felt, or a substantially rigid rubber, or the like. The gasket material layers are interposed on both sides of the central sheet between that sheet and the means engaging the packing. The entire three element packing has proper thickness to permit the desired extent of lift of the free end of each of the blade valves. Only the outer layers of each packing are permanently deformed during operation of the compressor. Because the relative thicknesses of these layers is small as compared with the thickness of the entire packing, the total deformation of the packing due to operation of the blade valves is small, and the sealing features of the packing are not impaired. Therefore, the initial clamping of the parts of the compressor remains assured for a prolonged period.

It is the object of the present invention to provide an improved means for mounting and, in particular, an improved packing for blade valves of an air compressor.

The invention will be further illustrated with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view through the inlet-outlet end of a compressor, in which the present invention is incorporated;

FIG. 2 is a view along the line and in the direction of arrows 2 in FIG. 1;

FIG. 3 is a view along the line and in the direction of arrows 3 in FIG. 1;

FIG. 4 is an enlarged view of a portion of the compressor in FIG. 1, showing the manner of mounting of the compressor blade valves in accordance with the invention.

Turning to the drawings, and particularly FIG. 1, air compressor 10 is of the conventional piston type, including an elongated hollow cylinder 12, having a sealed reciprocating piston 14 located therein. Conventional means (not shown) reciprocate piston 14. Above piston 14 is compressor pumping chamber 16, which alternately increases and decreases in volume as piston 14, respectively, descends and ascends.

Secured by conventional bolts 19 to cylinder 12 is compressor head 20, which includes intake chamber 22 that communicates, through inlet conduit 24, with the source of air or other gas to be pumped, and includes exhaust chamber 26 that communicates, through outlet conduit 28, with the means receiving air. Chambers 22, 26 are separated by divider 32, which extends across the entire interior of head 20.

Head 20 and its chambers 22, 26 are separated from cylinder pumping chamber 16 by rigid, metallic plate 40, the upper surface 42 of which seals against packing 70, described below. Passing completely through plate 40 are intake bore 44, which joins intake chamber 22 with pumping chamber 16, and exhaust bore 46, which joins pumping chamber 16 with exhaust chamber 26.

In order to obtain compression, as piston 14 descends enlarging chamber 16, bore 44 must be open to permit air to be drawn into pumping chamber 16 from inlet 24 and bore 46 must be sealed to prevent back leakage of air, which has already passed through exhaust chamber 26. Similarly, as piston 14 ascends, decreasing the volume of chamber 16 and expelling air, bore 46 must be open to permit air to exit through chamber 26 and outlet 28, and bore 44 must be sealed to prevent return of the air in chamber 16 through intake chamber 22.

Referring to all of the Figures, when piston 14 is descending, in order to seal bore 46, outlet bore blade valve 50 is provided. Valve 50 is formed of resilient material and is held at one end 51 and is free to move toward and away from plate 40 at its free opposite end 52. The valve is of a length such that its free end is between the base 53 of the divider 32 of head 20 and plate 40, and these two elements control the maximum stroke of the valve. Valve 50 includes a blocking surface, which seals outlet bore 46. Valve 50 is normally positioned so as to be substantially in engagement with upper surface 42 of bored plate 40, thereby to seal bore 46 when piston 14 descends. Once valve 50 covers bore 46, when piston 14 is descending, the pressure differential between chambers 16 and 26 seals valve 50 against bore 46 to prevent leakage. During the exhausting of air from chamber 16, the pressure in chamber 16, which on intake was lower than the pressure in exhaust chamber 26, now exceeds the pressure in chamber 26. The increased pressure developed in bore 46 raises valve 50 from bored plate surface 42 to its dotted line position in FIG. 1 and permits the compressed air in pumping chamber 16 to pass through bore 46, exhaust chamber 26 and outlet 28.

A similar type of inlet bore blade valve 60 seals bore 44 during exhausting of air from pumping chamber 16 when piston 14 is ascending. Valve 60 is comprised of similar material to valve 50 and is held in a manner similar to blade 50 at one end 61. It has a free shiftable end 62. Similarly to valve 50, valve 60 is of a length such that its free end is between the end surface 63 of cylinder 12 and plate 40 and these two elements control the maximum stroke of the valve.

Valve 60 extends past bore 44 and is normally held so as to be substantially in engagement with surface 66 of bored element 40. When piston 14 ascends, the pressure within chamber 16 exceeds the pressure in intake chamber 22. This pressure differential seals valve 60 against bore 44, ensuring that air exhaust from the compressor is only through exhaust chamber 26. During intake of air into chamber 16, the pressure in chamber 16, which on exhaust was higher than in intake chamber 22, now is below the pressure in chamber 22. The increased pressure developed in bore 44 shifts valve 60 down from plate surface 66 to its dotted line position in FIG. 1 and permits intake of air through bore 44 into chamber 16.

Because valve 60 should not interfere with the exhausting of air from chamber 16, it has an opening 64 therethrough, which is aligned with bore 46 and permits the free passage of air through that bore.

The significant aspect of the invention relates to the means by which blade valves 50 and 60 are mounted. Valve 50 is held by packing 70, which is interposed between bored plate 40 and head 20, and valve 60 is held by packing 80, which is interposed between bored plate 40 and cylinder 12.

Packings 70 and 80 are similarly constructed, with an exception noted below. As can be seen in FIGS. 2 and 3, they are annular rings, and are multilayer, as shown in FIGS. 1 and 4. Packing 70 includes a crossbar 71, which is identically layered to the remainder of the packing and which completes the seal between chambers 22, 26 by securely meeting divider 32 on one side and plate 40 on the other.

Packings 70, 80 include respective, relatively thick central metal plates 72, 82. Plates 72, 82 are disposed between respective, relatively thin and more yieldable, outer layers 74, 84 and inner layers 76, 86 of gasket material. These layers may be deformed by movement of valves 50, 60, but they are sufficiently resilient to restore the valves to their normal positions against respective surfaces 42, 66 of element 40. Layers 74, 76, 84, 86 assure the airtight seal of the mounting of the compressor blade valves.

Inner layers 76, 86 of packings 70, 80 are recessed back from the edges of their respective neighboring plates of the packings to provide respective openings 77, 87 to receive and support valves 50, 60. Inner layers 76, 86 are of a thickness corresponding to the thickness of their respective valves 50, 60. This ensures that the valves are held securely and that the seal at the respective secured ends 51, 61 of these valves is airtight.

While the thickness of outer layers 74, 84 is not as critical as the thickness of inner layers 76, 86, the former layers may be substantially identical in thickness to the latter layers. However, it is best to make layers 74, 84 as thin as possible.

All layers of crossbar 71 of packing 70 are recessed at 79 to receive free end 52 of valve 50. In this recess, end 52 moves between base 53 of head 20 and surface 42 of plate 40. Similarly, all layers of packing 80 are recessed at 89 to receive free end 62 of valve 60. In the recess, end 62 moves between end surface 63 of cylinder 12 and surface 66 of plate 40.

Upon securing together the various parts of the compressor, blade valves 50, 60 are clamped against plate 40. Since the relatively thick respective metal plate 72, 82 of each packing 70, 80 is held between relatively thinner layers of yieldable packing material, the total non-elastic yielding of each completed packing is contained within limits that do not jeopardize the effectiveness of the valve clamping and of the seal. This minimizes the permanent yielding of each entire packing 70, 80, when the entire compressor is assembled and the packings are squeezed. Therefore, even through prolonged use, there is little deterioration in the secureness of the clamping of valves 50, 60 or in the yieldable packing material layers 74, 76, 84, 86.

A particular example showing the benefits of the present invention is now described. A conventional 2 mm. thick, single-layer packing, which is formed of a material having a 20 percent permanent set, will reduce in thickness to 1.6 mm. after a short period of compressor operation. Frequent retightening of the compressor sealing means will be required, and the stroke of the flapping blade valves will be greatly reduced.

A corresponding packing in accordance with the present invention would have a 1 mm. thick central, nonyieldable layer and outer yieldable layers each 0.5 mm. thick, with only the outer layers having a 20 percent permanent set. After a period of compressor operation, the thickness of the entire packing will reduce only to 1.8 mm. This thickness reduction requires no retightening to maintain the compressor seal.

With the present invention, an improved means of clamping the blade valve of a blade valve or flapper type air compressor is provided.

Although this invention has been described with respect to its preferred emboodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art. It is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

I claim:

1. In an air compressor comprising an intake chamber, an exhaust chamber, a pumping chamber, means for varying the volume of said pumping chamber, an intake bore connecting said intake chamber with said pumping chamber and an exhaust bore connecting said pumping chamber with said exhaust chamber;

an exhaust bore blade valve positioned to block said exhaust bore when air is being drawn into said pumping chamber through said intake bore;

an intake bore blade valve positioned to block said intake bore when air is being exhausted from said pumping chamber through said exhaust bore;

the improvement comprising,

a first packing securing a first end of said exhaust bore valve, thereby permitting the other end of said exhaust bore valve to be shifted alternately from a blocking to an unblocking position with respect to said exhaust bore; and

a second packing securing a first end of said intake bore valve, thereby permitting the other end of said intake bore valve to be shifted alternately from a blocking to an unblocking position with respect to said intake bore;

each said packing comprising a central, substantially nonyieldable sheet and a layer on each side of said sheet comprised of a relatively more yieldable material; means supporting each said packing in said compressor by way of engaging said outer layers of each said packing,

whereby the structure of each said packing reduces to a minimum the permanent yielding of the packing during flexing of its respective said valve.

2. In the air compressor of claim 1, said intake and said exhaust bores being provided in an appropriately bored plate which is disposed within said compressor between said pumping chamber, on the one hand, and said intake and said exhaust chambers, on the other hand;

the improvement further comprising, said packing for said exhaust bore valve being interposed between said bored plate and a head which contains both said intake and said exhaust chambers; said packing for said intake bore valve being interposed between said plate and a cylinder means containing said pumping chamber, wherein said head is in engagement with one of said yieldable layers of said packing for said exhaust bore valve and said bored plate is in engagement with the other said yieldable layer of that said packing; said bored plate is in engagement with one of said yieldable layers of said packing for said intake bore valve, and said cylinder means is in engagement with the other said yieldable layer of that said packing.

3. In the air compressor of claim 2, the improvement further comprising, said thinner layers of said packing and said central nonyieldable sheet thereof having the capacity of airtight sealing of said compressor.

4. In the air compressor of claim 2, the improvement further comprising, that said yieldable layer of each said packing which is in engagement with said bored plate is also provided with a recess for receiving the respective said valve; and that said yieldable layer is of a thickness corresponding to the thickness of the respective said valve,

whereby each said valve is held securely in position between said bored plate and the said central sheet of its respective said packing.

5. In the air compressor of claim 1, the improvement further comprising the total thickness of each packing is chosen so as to define a desired lift of the respective said blade valve.

6. In the air compressor of claim 1, the improvement further comprising, said nonyieldable sheet having a thickness greater than each of its associated said yieldable layers.

7. In the air compressor of claim 6, the improvement further comprising, said nonyieldable sheet being approximately twice as thick as each said yieldable layer.