Technical Field

The invention relates to the field of air dryers, and more particularly devices which use a filter bed to remove moisture from a stream of air.

Background Art

Prior art air dryers typically have used a filter bed of desiccant material to remove moisture from the air stream. For example, US patent 3,465,503 Henderson describes an air dryer in which the air flows upwardly through a desiccant bed of drying materials such as silica gel or calcium chloride. US patent 913,325 Touzimsky similarly discloses an air dryer which uses a bed of desiccant material, namely calcium chloride to dry the air. The air flow in this device is around the outside of a central cylinder of the desiccant bed.

US patent 5,061,300 Alexander, III describes a coalescer filter which removes liquid from air. It relies on the air passing first upwardly through a fibrous metal¬ lic coalescing material, and then downwardly through a filter material.

Canadian Patent No. 1,125,671 issued to John R. McKenzie entitled NATURAL GAS FILTERING DEVICE discloses a device for filtering moisture and impurities from natural gas. It provides baffles and a porous filter bed of gravel within a filter tank. The baffles deflect the gas flow so as to cause turbulence and assist the porous filter bed in filtering impurities. Perforations are placed in the baffles to permit gas flow through the baffles. The preferred embodiment shows a non-permeable baffle at either end of the tank and two permeable baffles near either end to deflect the gas flow. The gravel particles are dis- closed to be greater than one inch in diameter.

Disclosure of Invention

The present invention therefore provides an air dryer comprising: i) a hollow tank having first and second

ends; ii) an air inlet into the tank adjacent the first end thereof; iii) an air outlet adjacent the second end there¬ of; iv) a non-porous gravel bed filling the section of the tank between the inlet and outlet, consisting substantially of particles 3/8 inch in diameter or less; v) compression means extending across the tank in contact with the gravel bed; vi) means for biasing the compression plate against the gravel bed; and vii) drainage means for draining water from the tank.

Brief Description of Drawings

In drawings which disclose a preferred embodiment of the invention:

Fig. 1 is a perspective view of the invention; Fig. 2 is a cross-sectional view of the invention taken along line 2-2 of Figure 1; and

Fig. 3 is a cross-sectional view of the invention taken along line 3-3 of Figure 2 (with gravel bed removed for clarity of illustration) .

Best Mode(s) For Carrying Out the Invention

The air dryer of the invention is designated generally by 15. It comprises a hollow cylindrical tank 17 with closed ends 16, which is mounted on saddles 12 sup- ported on legs 22. Tank 17 is substantially filled with a non-porous crushed material 20 such as gravel, the size of the particles of gravel being largely between 3/32 inches and 3/8 inch in diameter. Granite is the preferred form of gravel, being hard and therefore resistant to wear from the air stream. A solid circular metal plate 9, typically 3/8 inches thick, is located adjacent one end of the tank 17 to pack the gravel 20 tightly by bearing against the body of gravel 20 in the tank. Plate 9 has a central hole 18 which rides on ready rod 8 extending through the centre of the plate 9, and is under pressure from a spring 10 which is mounted by nut 11 on ready rod 8. Rod 8 is welded at one end to a bar 7 extending transversely across the interior

of the tank 17. The outer circumference of plate 9 has a diameter slightly less than the inner diameter of tank 17. Stop blocks 14 fixed to the inner surface of tank 17 limit the extent of travel of plate 9. The source of moist air to be dried enters tank

17 through air inlet 1 on the top of the tank 17 adjacent one end 16. Inlet 1 is covered by a perforated screen 5. The air outlet 2 is also on the top of the tank 12 adjacent the other end 16. The inlet 1 extends downwardly into the tank 17 and connects with elbow 6, the lower outlet end 13 of which faces plate 9 and is spaced from plate 9 by approximately 3/4 inches. Disruptor plates 40 are welded to the upper inner surface of the tank 17.

The outlet 2 is connected to elbow 3, the inlet end of which is also covered by a perforated screen 4. The other end 19 of elbow 3 faces the end of the tank 16. A perforated screen 21 also covers end 19. Inspection ports 24, 26, which are plugged during operation, are provided at either end, covered by perforated screens 25, 27 A circular opening 50, covered by perforated screen 52 is provided in the lower central section of tank 17 to empty water which has precipitated from the air stream. Opening 50 communicates with a cylindrical pipe or boot 54 closed at its lower end 56. Drain 58 can be opened by a valve (not shown) to remove the water, and liquid can also be removed from boot 54 at nozzle 62.

In operation, the moist air is forced through the inlet 1, flows through the non-porous, sharp-edged gravel bed 20, and dry air exits from the outlet 2. Disruptor plates 40 prevent the air stream from taking a short route to the outlet along the upper inside surface of the tank 17 rather than circulating through the gravel. Acceleration and deceleration of the air as it passes among the cavities between the gravel particles, changes in velocity and formation of low pressure areas causes the water to form into droplets which eventually precipitate from the air. The dry air exits through outlet 2. Water which has pre-

cipitated from the air collects in the bottom of tank 17 and flows through opening 50 into boot 54 at the bottom of the tank which is drained through nozzle 62, and boot 54 can also be cleaned out through drain 58. As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.