US2997862A - dineen - Google Patents

Description

g- 29, 1961 J. J. DINEEN 2,997,862

AIR CYCLE COOLING UNIT Filed Sept. 11, 1959 2 Sheets-Sheet 1 INTAKE INVENTOR 29,196] J. J. DINEEN 2,997,862

AIR CYCLE COOLING UNIFT Filed Sept. 11, 1959 2 Sheets-Sheet 2 lNVENTOR EXPANSION CHAMBERS 2 g Ano RNEYS lNL-EE To EXPANEHONJ NUTLET FROM United States Patent 2,997,862 AIR *CYCLE COOLING UNIT John Drneen, East Northport, N.Y., assignor, by mesne assignments, to Chandler Evans Corporation, West Hartford, Conn a corporation of Delaware Filed Sept. 11, 1959, Ser. No. 839,418 6 Claims. (Cl. 62-403) This invention relates to an air cycle cooling unit,

and particularly such a unit designed for cooling the air in an enclosed space such as the cab of a truck or the interior of a bus or other motor vehicle. It is an object of the invention to prOVide such a coolmg unit of improved efiiciency and compactness, with an expanson cylinder inside the compression cylinder, the compression piston serving as the expansion cylinder, with a combined piston ring and inlet valve, and with other mechanical improvements.

It is a further object to provide a cooling unit in which the air to be cooled is compressed, passed through an air-cooled heat exchanger, expanded, and supplied as relatively cold air to the interior of the truck cab or other space.

It is another object to provide a cooling unit in which the outside air is drawn through the heat exchanger along a path generally counter to the flow of the compressed air to be cooled, and passes also in heat-exchange relation to the wall of the compressor.

It is a further object to provide certain improvements in the form, construction, arrangement and materials of the several parts whereby the above named and other objects may effectively be attained.

A practical embodiment of the invention is shown in the accompanying drawings, wherein:

FIG. 1 represents a vertical axial section through a complete one-cylinder unit in the plane of the drive shaft, parts of the heat exchanger cowling being shown in elevation and parts being broken away, the compressor piston being shown at the bottom of its stroke;

FIG. 2 represents a section as in FIG. 1, omitting part of the heat exchanger and showing the compressor piston substantially at the top of its stroke;

FIG. 3 represents a transverse vertical section on the line IIIIII of FIG. 1;

FIG. 4 represents a detail horizontal sectional view of the combined piston ring and inlet valve, taken on the line IVIV of FIG. 3, and

FIG. 5 represents, somewhat diagrammatically, a transverse cross-sectional view of a plural-cylinder unit.

Referring to the drawings, the unit is shown as comprising a compressor block 1 having a cylindrical compression chamber 2, spaced lower crank-case portions 3, 4 and a valve block 5 within the upper cylindrical crankcase portion '5'. The drive shaft 6 is journaled at 7, 8 in the outer walls of the portions 3, 4, 5' and passes through a horizontal bore 6 in the block 5. The compressor piston 9 has a downwardly projecting inwardly cylindrical part 10 which constitutes the lateral wall of an expansion chamber 11, the top and bottom walls of which are constituted by the under surface of piston 9 and the upper surface of valve block 5. A suitable seal 12 is provided adjacent the upper periphery of block 5 and designed to bear against the inner cylindrical surface of the part alt).

At diametrically opposite points on the outside of the part 10 are mounted the studs 13, alined with eccentrics 14 on the drive shaft, and connecting rods 15 embrace saideccentrics and connect them to the studs 13, with the provision of suitable anti-friction bearings between the connecting rods and the eccentrics and studs.

The valve block is provided with four vertical bores, t e bores '16 and 17 extending downward from the top of the block to the horizontal bore 6 and having their axes in the same vertical plane with the axis of the drive shaft 6, and the bores 18, 19 extending upward from the bottom of the block toward, but not to, the upper surface thereof, said latter bores being so located in the block that they do not intersect any of bores 6, 16 and 17; certain connections being provided, however, as described below.

The upper periphery of the bore 16 is beveled to form a seat for the exhaust valve 20, the stem 21 of which passes through the sleeve 22 and is provided with a yoke 23, axle pin 24 and cam-following roller 25. The sleeve 22 is fixed in the bore 16 by means of a pin 26, and the roller 25 is urged toward its cam 27 (on the drive shaft 6) by a spring 28, the ends of which bear upon the sleeve 22 and yoke 23.

The upper periphery of the bore 17 is beveled to form a seat for the inlet valve 29 which is mounted and operated in the same manner as valve 20 but by means of a cam 30 on the drive shaft 6. Since the air enters the chamber 11 past inlet valve 29 in a compressed state and leaves said chamber past exhaust valve 20 in a relatively expanded state the valve 20 is made larger than the valve 29 and the upper portion of the bore 16 is correspondingly enlarged, the bores 16 and 17 being otherwise the same.

Correspondingly, the bore 18, connected to the upper portion of bore 16 by a lateral passage 31, is larger than the bore '19, connected to the upper portion of the bore 17 by a lateral passage 32.

The compression chamber 2 is defined by the cylindrical wall 33, by the cylinder head 34 and by the upper surface of the compressor piston 9. A check valve is formed in the cylinder head as by the provision of a centrally perforated plate 35 the opening in which is closed by a disc 36, urged toward the plate by the spring 37. The check valve permits passage of air under pressure from the chamber 2 to the compressor outlet 38.

The piston *9 is cut away at a plurality of points around its periphery to form, with the seal ring described below, slots 39 through which air can pass on the downward stroke of the piston, the slot walls being beveled inwardly toward the lower face of the piston as clearly shown in FIGS. 1, 2 and 3. The piston seal ring 40 has a cylindrical part and annular flanges 41, 42 spaced by a distance somewhat greater than the thickness of the piston periphery. On the downward (inlet) stroke of the piston the upper surface thereof moves away from the under surface of the flange 41, permitting passage of air around the edge of flange 42, through the beveled slots 39 and between the piston and flange 41 into the compression chamber 2 (FIG. 1). On the upward (compression) stroke the upper surface of the piston bears firmly against the under surface of flange 41 around the entire periphery of the piston, enabling the ring 40 to act as a seal while the piston compresses the air and forces it under compression past the check valve to the outlet 38 (FIG. 2.). The piston 9, seal ring 40, cylinder head 34 and plate 35 are preferably so shaped and arranged that the volume of the chamber 2 is reduced substantially to zero at the end of the compression stroke.

The compressor outlet 38 communicates with the inlet of an air-cooled heat exchanger 43 which may be of any conventional type such as tube-and-fin, while the outlet of the heat exchanger is connected by the pipe 44 to the lower end of the bore 19. A fan 45 is mounted on the end of the drive shaft 6 and is enclosed in cowling 46 arranged to enable the fan to draw ambient air through the heat exchanger 43 and drive it past the outside of the chamber 2, which may be provided with fins 47. An air intake opening 48 is formed in the wall of the crank case portion 4 and is preferably provided with a dust filter 49. Said intake may merely be open to ambient air, as shown, or may be connected by a suitable conduit to the space to be cooled, for recirculation of the air. The lower end of the bore 18 is connected to the space to be cooled by a pipe 50, which should be larger than the pipe 44.

In order to minimize vibration during operation it is desirable to mount counter-weights 51 on the drive shaft 6 adjacent each of the eccentrics 14, said counterweights being of a size and shape to balance kinetically the eccentrics and the parts associated therewith. Shaft seals 52 are provided each side of the cam 30 in order to prevent leakage of air under pressure in the upper part of bore 17 through said bore into the crank case. Leakage of low pressure air through bore 16 is relatively unimportant so that special steps need not be taken to prevent it.

For simplicity of maintenance it is preferable that the bearings should all be pro-lubricated. The piston seal ring 40 is of a filled Teflon type, intended to run dry and having great durability.

In the cycle of operation, the air to be cooled enters the upper cylindrical part of the crankcase through the intake 48, being drawn in by upward movement of the piston 9, the periphery of which is tightly sealed against the lower surface of flange 41 on seal ring 40. When the piston 9 reaches the top of its stroke (FIG. 2) the volume of chamber 2 is nearly zero; thus, on the downward stroke, with valve 36 closed, the air in the crank-case is drawn through the slots 39 into the chamber 2 until the latter attains its maximum volume--at the bottom of the stroke. As the piston moves upward again the air in the chamber 2 is compressed and driven out past valve 36 into the compressor outlet 38, the air being at a somewhat elevated temperature corresponding to its compression, and exceeding any normal ambient temperature The heated and compressed air flows to and through the heat exchanger 43, where it is cooled somewhat without much pressure drop, and thence through pipe 44 and bore 19, past valve 29, to the expansion chamber 11. Valve 29 remains open for part of the stroke and then closes permitting expansion to take place. The closing point is computed so that at the end of the expansion stroke the pressure in the cylinder is approximately ambient. Since the expansion chamber is formed in or carried by the compressor piston, the expansion of air in chamber 11 is simultaneous with the compression of another charge in chamber 2, and the force of expansion, urging the piston upward, serves to recoup a substantial part (e.g., 45%) of the energy required to compress the air above the piston and drive the several moving parts. As the air expands, its drop in pressure is accompanied by a drop in temperature so that, at the top of the stroke, the chamber is filled with cool air at low pressure; the outlet valve 20 then opens (FIG. 2), and the cooled expanded air is driven out during the downward stroke at low pressure through bore 18 and pipe 50 to the space to be cooled. The ambient air, moved by fan 45, picks up some heat on its passage through the heat exchanger 43 but is still normally capable of having some further cooling effect as it passes the fins 47 around the compression chamber 2.

As a matter of thermodynamics it might be preferable to mount the fan downstream from the compression chamber (as, at the right of FIGS. 1 and 2), so that both the heat exchanger and the compressor would be cooled by air under suction, but the improvement in efiiciency from such an arrangement is seldom suflicient to justify the increased cost of cowling and enlargement of the over-all dimensions of the device.

While a single-cylinder unit is shown and described herein as being a practical embodiment of the invention for eifectively cooling small spaces, it will be understood that a plurality of cylinders (2, 3 or more) could be coupled axially or otherwise for more heavy duty installations. A 3 cylinder radial unit is illustrated diagrammatically in FIG. 5, each cylinder being substantially of the type described in detail herein and utilizing a common drive shaft, fan and heat exchanger, while master connecting rods 53 (corresponding to rods 15) for operating one piston are operatively coupled by links 54 to the other pistons.

In a small unit the drive shaft 6 may be actuated by a flexible shaft drive from the vehicle engine fan belt, but a separate combustion or electric drive may be used if desired. The source of power, being no part of the present invention, is not shown. Typical performance of a unit substantially as shown and described calls for operation at a speed of 1000 rpm, with the 1.25 inch stroke giving a piston speed of 208 feet/min. Assuming at least volumetric efliciency the air flow would then be approximately 34 c.f.m. On a dry air basis, with air entering the expansion chamber at 115 F., the temperature drop would be 154 with a 3 to 1 expansion ratio. Assuming 70% adiabatic efiiciency, the temperature drop is 108, representing a cooling load on a F. day of 65 B.t.u./min., or .32 tons. Moisture in the air will raise the outlet temperature somewhat but the cooling capacity in B.t.u.s will remain the same. Control may be efi ected simply for example, by providing a manual valve (not shown) for bypassing part of the air flow around the expansion cyclinder to reduce pressure at the expansion cylinder inlet.

What I claim is:

1. An air cycle cooling unit comprising, an air compression cylinder, a piston movable in said cylinder, an air expansion cylinder connected to said piston and movable therewith, a valve block located in and extending across the air expansion cylinder, means for supplying air to the compression cylinder, a conduit including a heat exchanger connecting the compression cylinder to the expansion cylinder, means for conducting air from the expansion cylinder to a space to be cooled, and means for reciprocating said piston and expansion cylinder to eflfect compression in the compression cylinder and expansion in the expansion cylinder.

2. An air cycle cooling unit according to claim 1 in which the expansion cylinder is integral with the piston.

3. An air cycle cooling unit according to claim 2 which includes a drive shaft and at least one eccentric fixed on said shaft, and in which said eccentric is operatively connected to the expansion cylinder and piston.

4. An air cycle cooling unit according to claim 3 in which there are two eccentrics operatively connected to the expansion cylinder and piston at diametrically opposite points thereof.

5. An air cycle cooling unit according to claim 3 which includes an inlet valve controlling the admission of air to the chamber within the expansion cylinder, a valve controlling the exhaust of air from said chamber to the space to be cooled, and cams on the drive shaft for operating said valves.

6. An air cycle cooling unit according to claim 5 in which the valves are lift valves having stems lying in the same plane with the axis of the drive shaft.

References Cited in the file of this patent UNITED STATES PATENTS 196,253 Root Oct. 16, 1877 1,495,663 Belluzzo May 27, 1924 2,415,618 West Feb. 11, 1947 2,873,061 Kodra Feb. 10, 1959

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