GB2175653A - An air cooling and reciprocating type of air compressor without lubricant - Google Patents

Abstract

A cooled compressor is disclosed which needs no lubricant between its piston 3 and its cylinder 2. Piston 3 is driven by rotated shaft 7 via eccentrically located pin 5. Air to be compressed is admitted to the crankcase through a port wherein are located a filter and noise reducing plates. On the piston downstroke air passes through piston port 34 governed by valve 33 and is then compressed during the piston upstroke to the point where spring valve 12 opens to pass the compressed air to outlet 14. Cooling is partly accomplished by the passage of air through the piston, partly by fins 11 and partly by air admitted to funnel 23 being blown around the cylinder. Alternatively water cooling may be used. Piston rings made of polytetrafluoroethylene or graphite may be used to obviate lubrication. <IMAGE>

Description

SPECIFICATION An air cooling and reciprocating type of air compressor without lubricant This invention relates to an air compressor, particularly an air cooling and reciprocating type of air compressor without lubricant.

In the current manufacturing industries and the construction engineering, the pneumatic toal and the pneumatic device have widely been used by engineers; particularly, in the industries such as food, medical, pharmacy, brewer, the control instrument, painting, finish coating, electronic and chemical, etc., the pure air requirement to an air compressor is absolutely rigid, i.e., no oil and other impurities contained therein. The general air compressor without lubricant may indude the axial-flow type, the centrifugal-flow type, and the rotary type. In the reciprocating type of air compressor that can generate higher pressure, its piston has to reciprocate at a high speed in the cylinder, and also has to be in close contact with the cylinder wall in air-tight manner; therefore, a lubricant such as oil has to be added therein so as to lubricate and to cool the friction portion.After a long time operation, the piston ring will suffer from considerable wear and tear to such an extent that it can not be closely in contact with the cylinder wall to rub away the lubricant particles on the cylinder wall upon the piston moving downwards; as a result, the air compressed out contains oil particles, which will adversely affect the quality of the air compressed; usually, the reciprocating type of air compressor has to, after a long time operation, be repaired by boring and replacing the piston ring. The cylinder boring is a rather complicated operation; for example, a minor negligence (such as incorrect clearance measurement, etc.) may result in the air compressor inefficient or being damaged.In case of the lubricant being lost or becoming emulsified, the piston might become sticking as a result of being over-heated; that case is susceptible to happening in the event of not adding lubricant regularly.

The aforesaid air compressors, such as the axial-flow type, the centrifugal flow, and the rotary type, may be operated normally without adding lubricant; however, since the aforesaid air compressors each have their characteristics in terms of the air-flowing direction and the structure, their uses are also different from one another. For instance, the reciprocating type of air compressor has the following advantages: (1) Having high compression rate; (2) The increases of the air pressure not to be affected by the gas being used; (3) The variation between the blowing volume and the pressure having less direct relation, i.e.

having no surging effect to take place; (4) Lower noise.

Consequently, the reciprocating type of air compressor has widely been used in current industry, particularly in the industry which has to use higher air pressure.

In view of the air quality and maintenance problems caused by the use of lubricant in the reciprocating type of air compressor, the inventor has, through endeavoured and repeated studies, developed a reciprocating type of air compressor without using any lubricant during operation. The major feature of this reciprocating type of air compressor is that an opening is furnished at one end of the crank shaft case as an air suction port, an intake check valve is furnished on the top of the piston, and an exhaust valve is furnished on the cylinder head. Upon the piston moving reciprocally, the outer air will be sucked, as a result of the pressure difference, into the crank shaft case, and then compressed through the cylinder and finally into the air tank.Since the air always passes through the crank shaft case and the cylinder, the heated portion of the machine as a result of friction will be cooled. Further, the piston ring is made of teflon (R. T. M.) containing a self-lubrication material, such as fiber glass, bronze powder, and graphitic carbon; the inner wall of the cylinder made of aluminum alloy is coated with a chromium coating or other coating that can increase the rigidity of the aluminum alloy; therefore, the piston and the cylinder would not become sticking because of having the same expansion coefficient; in other words, no lubrication oil is necessary, and there will be no oil element contained in the compressed air.

Another feature of this invention is the radiating flanges being provided on the outer surface of the cylinder head, the cylinder, and the crank shaft case so as to accelerate the radiation.

A still another feature of the present invention is that a water jacket is provided around the cylinder head, the cylinder, and the crank shaft case so as to cool the cylinder head and the crank shaft case by means of a circulating water in the water jacket.

A further feature of the present invention is that an air cooling pipe may be mounted around the cylinder or the cylinder head to cool the cylinder to external air circulating in the pipe.

A still further feature of this invention is the air suction port mounted in the opening end of the crank shaft case; that air suction port is furnished therein with a noise reduction and filter means so as to minimize the machine noise and to filter the impurities out of the air compressed.

Therefore, the prime object of this invention is to provide a recipocating type of air compressor that needs no lubricant, and the output air of this compressor will contain no oil element absolutely so as to meet the requirement of any industry that needs absolutely pure compressed air.

Another object of this invention is to provide an air compressor that needs no lubricant so as to prevent from the care of oil leaking or oil emulsified, and to save the maintenance problem and the operation cost.

A still another object of this invention is to provide an air compressor, of which the piston is made of a material containing lubricant nature; the cylinder and the piston of the compressor are made of the similar material (aluminum alloy), and the inner wall of the cylinder is coated with a rigid coating so as to have the cylinder and the piston generate the same expansion coefficient; then, the piston would not have a sticking condition during operation so that the running load is reduced, and the compression efficiency will be increased.

A further object of this invention is to provide an air compressor, in which the wear and tear of the piston ring and the inner wall of the cylinder can be minimized so as to increase the serviceable life of the air compressor.

A still further object of this invention is to provide an air compressor, in which no oil can be leaked out to pollute the cylinder head and the high pressure air pipe so as to minimize maintenance problems.

The aforesaid and other objects and features of this invention are described in detail, with reference to the drawing attached, herein after.

Figure 1 is a radial sectional view of the first embodiment of the present invention, showing the structure, the intake and exhaust valves thereof.

Figure 2 is an axial sectional view of the first embodiment of the present invention, showing the structure, the transmission mechanism, and the air intake port thereof.

Figure 3 is a radial sectional view of the second embodiment of the present invention.

Figure 4 is an axial sectional view of the second embodiment of the present invention-.

Figure 5 illustrates a top view of the cylinder mechanism of the first embodiment, in which the X-X line shows an axial sectional view, while the Y-Y line shows a radial sectional view.

Figure 6 is a top view of the cylinder mechanism of the second embodiment, in which the X'-X' line shows an axial sectional view, while the Y'-Y' line shows a radial sectional view.

Figure 7 illustrates the reciprocating movement of the piston in the cylinder, in which (A) shows the intake stroke, (B) shows the compression stroke, and (C) shows the exhaust stroke.

Referring to Fig. 1, there is shown a radial sectional view of the first embodiment of the present invention, showing the related positions of the structure, the intake valve and the exhaust valve. The outer surface of the cylinder head 1 is provided with radiating flanges 11; the connecting portion between the cylinder head 1 and the cylinder 2 is furnished with an exhaust valve 12, which controls the opening and closing operation of an exhaust portion 13, and which may be a flexible valve plate or a valve being pressed in closed condition with a spring. At one side of the cylinder head 1, there is furnished with an outlet 14 to be connected with a high pressure tube (not shown) so as to transmit the high pressure air out.The outer surface of the cylinder 2 is furnished with a plurality of radiating flanges 21, the inner surface of the cylinder 2 is not provided with a cylinder liner; instead, the inner surface of cylinder is coated with chromium or other electroplated coating to increase the rigidity of the cylinder 2 (further details will be described herein after). In the cylinder 2, there is mounted with a piston 3, of which the outer surface is furnished around with several grooves for installing and piston rings 32 supported with spring rings 31 respectively; the piston ring 32 can closely contact with the surface of the cylinder 2 for airtight effect. The piston 3 is different from the conventional piston for having an inlet valve 33 being pressed with a spring, and the valve 33 controls the open/close of the intake port 34 (there may be more than one intake port).The piston 3 is connected with the connecting rod 4 with a piston pin 35 at the bottom portion of the piston, and the bottom end of the connecting rod 4 is connected, as usual, with an eccentric shaft 5, a cam 6, and an input shaft 7, which form the transmission mechanism, whereby the connecting rod 4 and the piston 3 will be able to move reciprocatingly in the cylinder 2.

Fig. 2 illustrates an axial sectional view of the first embodiment of this invention, which mainly includes the structure, the transmission mechanism and the air intake port. The transmission mechanism further includes an input shaft 7, a cam 6, and an eccentric shaft 5. Upon the input shaft 7 being driven with a driving means (not shown) for circular rotation at an equal speed, the connecting rod 4, a follower parts, will move up and down through the transmission mechanism of the cam 6 and the eccentric shaft 5. Of course, the transmission mechanism may be replaced with a crank shaft, which is adaptable to a multi-cylinder or multi-stage air compressor. (The present invention may, in accordance with the same theory and structure, be designed into a single cylinder or multi-cylinder, or one-stage or multi-stage air compressor according to the different requirement of the blowing pressure.) In case of using a crank shaft, the air suction port 8 should be provided at one side of the shaft instead of the present position.When the air suction port 8 being designed at one side of the crank shaft case 9, the port 8 may include a base 81 having several holes 811, an outer cover 82 having several air intake holes 821 to be attached to the case 81 with a screw bolt 84, and a filter bed 83 being sandwiched between the base 81 and the outer cover 82; the filter bed 83 may be made of sponge or other like and known materials. On the edge portion of the base 81, there is furnished with at least one ringshaped noise reduction plate 812; inside the outer cover 82, there is furnished with the same number of noise reduction plate 822 as that of the plate 812.Upon the piston 3 moving upwards, the crank shaft case 9 will generate a pressure drop to cause the outer air to enter into the air suction port 8 through the several air intake holes 821 on the outer cover 82; then, the air will pass through a muffler channel formed by the noise reduction plates 812 and 822 (to reduce more noise than the conventional air compressor), and through a filter bed 83 and the holes 811 on the base 81 before entering into the crank shaft case 9.

During the piston 3 in motion state, the top portion of the cylinder 2 will incur the highest air pressure; therefore, the top portion of cylinder 2 is susceptible to high temperature during the piston in motion state. In order to reduce the temperature of the cylinder 2, the top of the cylinder 2 is, in addition to the raidating flanges 21, furnished with an air cooling pipe 22 (as shown in Fig. 1, 2, and 5), or a water jacket 25 (as shown in Fig. 3, 4, and 6). The air cooling pipe 22 or the water jacket 25 may be pre-built in the cylinder 2 during manufacturing, or furnished directly on the top of the cylinder 2. The air cooling pipe 22 or the water jacket 25 is to be built around the top portion of the cylinder 2 so as to cool the cylinder 2 directly upon the circulation of air or water.

One end of the air cooling pipe 22 is furnished with a trumpet-shaped opening 23 for receiving the external air; a motor or a fly wheel may be used for blowing air into the trumpetshaped opening 23; an additional blower may be installed to accelerate the cooling effect. The other end of the air cooling pipe 22 is furnished with an outlet 24.

Both ends of the water jacket 25 are furnished with an inlet 26 and an outlet 27 respectively with inner threads therein so as to connect with the external water pipe (not shown). According to the present invention, the running water for general family use may be connected with the water jacket 25 for cooling purpose. For a large air compressor, a pump and a cooling apparatus may be installed to form an inner circulating and cooling system by expanding the outer wall of the cylinder, the cylinder head 1 and the crank shaft case 9.

Fig. 3 and 4 show respectively a radial sectional view and an axial sectional view of the second embodiment of the present invention; the second embodiment is good for ia larger air compressor, which is similar to the structure of the first embodiment except the water jacket 25 on the cylinder 2 top instead of an air cooling pipe 22. Naturally, water cooling method to a cylinder 2 is better than an air cooling method. According to experiments, the air cooling method can reduce the temperature of a cylinder by 8% to 13%, while the water cooling method can reduce the temperature of a cylinder by 18% to 25%; therefore, the second embodiment is adaptable to a large air compressor for a long time running.

Fig. 7 illustrates the reciprocating movement of the piston in the cylinder, showing the intake, eduction, and compression strokes of the piston. Fig. 7A shows an intake stroke; upon the piston 3 moving downwards, there is generated a pressure difference between the cylinder 2 and the crank shaft case 9, i.e., the high pressure air in the crank shaft case 9 will cause the intake valve 33 to open to enter into the cylinder 2; in that moment, the air pressure is not strong enough to open the exhaust valve 12 that is normally closed.Fig. 7B shows a compression stroke; upon the piston 3 moving upwards from the lower dead point, the air pressure in the cylinder 2 will force the intake valve 33 to open; simultaneously, the air pressure in the cylinder 3 is insufficient to open the exhaust valve 12; therefore, upon the piston 3 moving upwards, the air confined in the cylinder 2 will be compressed to become a high pressure air.

Upon the piston 3 moving upwards, a pressure drop will take place in the crank shaft case 9, since the space in the case 9 is increased; as a result, new and fresh air will be sucked into the crank shaft case 9. Fig. 7C illustrates the eduction stroke; upon the piston 3 continuously moving upwards, the air inside the cylinder 2 will be compressed to such a pressure that its force can open the exhaust valve 12, and the high pressure air will be exhausted out of the exhaust port 13; simultaneously, the crank shaft case 9 continues to such in the air. Upon the piston 3 moving downwards from its upper dead point, the exhaust valve 12 will be closed as a result of the pressure in the cylinder 2 -being dropped, i.e. restoring to the intake stroke as shown in Fig. 7A.

According to the aforesaid description, the air passes through the air suction port, the crank shaft case, the piston and then enters into the cylinder; therefore, it will provide a better cooling effect to the various running and friction parts, such as the input shaft, the cam, the eccentric shaft, the bearing, the connecting rod, the piston, the piston ring, and the cylinder wall, etc.; in other words, the present invention needs no lubricant except the running parts such as the bearing. That air cooling method can be used for the cylinder made of many kinds of materials, such as aluminum alloy, aluminum alloy with case hardening process, cast iron, steel, aluminum alloy with cast iron cylinder liner, or other metals.Since the thermal conduction coefficient of air (approximate 0.022Kcal/m.hr"C) is lower than that of the lubricant, the rotation speed of the air compressor must be limited properly (ranging from 400-700 rpm) in case of the cylinder being made of cast iron, steel and aluminum alloy with cast iron cylinder liner so as to avoid the piston to be sticking because of high temperature. In case of requiring the present invention to run at a high speed, the material of the piston and the cylinder must be considered appropriately. Generally, an aluminum alloy having better casting nature and rapid radiation (having a thermal conduction coefficient about 175 Kcal/m.hr C) may be used therefor.In case of using aluminum alloy for making cylinder, the inner surface of the cylinder has to be processed with case hardening because of the aluminum alloy being not hard enough as the cast iron to withstand wear and tear; in other words, the inner surface of the cylinder may be electroplated with a chromium coating or other coating that can increase the hardness of the aluminum alloy (instead of mounting a cast iron cylinder liner in the cylinder so as to minimize the assembling problem, and to avoid the cylinder liner becoming loose after being heated).Since both the piston and the cylinder are made of aluminum alloy, they will have a rapid radiation and the same expansion coefficient, whereby the air compressor can withstand a high temperature and run at a high speed. (Note: The method of electroplating chromium on the aluminum alloy is that, first, an electrolyte containing a chromium acid and water mixture having a density of 200-250 g/l is prepared, and a sulfur acid having a density of 0.6-1.0 g/l and a potassium fluosilicate having a density of 20-45 g/l are added in the water mixture; the area of the negative electrode should be two to three times larger than that of the positive electrode, and then start an electrolysis by putting nothing in the electrolyte for over 17 hours before putting the aluminum alloy parts therein; then, effect a rapid electroplating with a current density of 50-250 A/dm2.) The piston ring according to the present invention has to be made of teflon (R.T.M.) or graphitic carbon containing a self-contained lubricant (such as glass fiber, graphite, or bronze powder, etc.) so as to withstand friction. Since the intake valve and the exhaust valve according to the present invention are installed along the center line of the piston, the air convection would have no eccentric effect to the piston (in the conventional air compressor, the air convection does have eccentric effect to the piston); therefore, wear and tear between the piston ring and the inner wall of cylinder may be reduced.According to the present invention, the wear extent of the piston ring is shown in Table 3, in which the data are obtained through experiment, Embodiment No. 1 According to the structure of the first embodiment, the inventor has developed a sample, of which the piston is made of aluminum alloy 152 (including 7.00% Cu, 5.5% Si, and 0.3% Mg), the piston ring is made of teflon (R.T.M.) added with glass fiber, and the cylinder is made of aluminum 356 (including 7.0% Si, 0.3% Mg), and the inner wall of the cylinder is coated with chromium. The specification of the air compressor according to the present invention is shown in Table 1 as follows:

MOTOR CYLINDER DIAMETER NUMBER OF SPEED PISTON DISPLACEMENT AIR TANK X STROKE CYLINDER CAPACITY HP mm rpm 1/mien liter 42 X 34 1 1700 80 9 After experimental running with the aforesaid sample of air compressor, a number of data thereof are shown in Table 2 as follows:

2 CURRENT TEMPERATURE MAX. AIR TIE REQUIRED FRO Okg/Cm2 OF CYLINDER PRESSURE TO MAX. AIR PRESSURE Amp C kg/cm2 Sec WITHOUT 6.6 LOAD 7.5 85-69 WITH FULL 7.6 59 LOAD After a long period of experimental running according to the present invention, the data of wear extent of the piston ring are shown in Table 3 as follows::

TESTING TIMES OF RUNNING THE POINTS WHERE THE THICKNESS OF REMARKS DATE FROM Okg/cm2 THE PISTON BEING MEASURED (mm) TO 7.5 Kg/cm2 (1) (2) (3) (4) (5) (6) (7) 85-1-5 199 3.980 3.988 4.00 3.996 3.998 3.995 3.992 UPON IT 85-1-7 200 3.973 3.982 3.994 3.990 3.992 3.989 3.986 RUNNING FROM 85-1-8 200 3.968 3.976 3.989 3.985 3.987 3.984 3.980 Okg/cm2 TO 85-1-9 196 3.963 3.971 3.984 3.980 3.982 3.979 3.975 7.5 Okg/cm2, 85-1-10 194 3.958 3.966 3.980 3.976 3.977 3.974 3.970 IT WAS STOPPED 85-1-11 195 3.954 3.963 3.976 3.972 3.973 3.970 3.966 FOR 150 85-1-12 200 3.951 3.959 3.973 3.969 3.970 3.967 3.963 SECONDS. 85-1-14 198 3.948 3.956 3.970 3.966 3.966 3.964 3.960 85-1-15 198 3.945 3.953 3.967 3.963 3.963 3.961 3.957 85-1-16 185 3.943 3.950 3.964 3.961 3.960 3.958 3.955 85-1-17 191 3.940 3.948 3.961 3.958 3.958 3.953 3.952 85-1-18 195 3.937 3.945 3.959 3.955 3.956 3.951 3.949 85-1-19 195 3.935 3.943 3.957 3.954 3.954 3.949 3.946 85-1-21 199 3.932 3.941 3.955 3.951 3.952 3.948 3.943 85-1-22 200 3.929 3.938 3.952 3.948 3.949 3.945 3.940 85-1-23 200 3.926 3.935 3.949 3.945 3.946 3.943 3.937 85-1-24 197 3.924 3.933 3.947 3.943 3.943 3.940 3.934 85-1-25 197 3.920 3.930 3.945 3.941 3.941 3.937 3.931 85-1-26 198 3.917 3.927 3.941 3.938 3.938 3.934 3.928 85-1-28 190 3.914 3.924 3.939 3.936 3.935 3.931 3.925

The total running times are 3927, and the thickness (mm) worn away are (1) 0.066, (2) 0.064, (3) 0.061, (4) 0.060, (5) 0.063, (6) 0.064, (7) 0.067; the average thickness worn away is 0.0636 mm. If the average time required for one period of running from 0kg/cm2 to 7.5 Kg/cm2 is 90 seconds, the total running time are 98.175 hours, while the average wear and tear of the piston ring within a unit of time is 0.6475 u/hr. It has been proved according to the aforesaid experimental data that the present invention will not have any oil in the output air, and can also increase the compression efficiency of the compressor without increasing the running load in comparison with the conventional air compressor in the same specification; moreover, the wear and tear to the piston ring and the inner wall of the cylinder will also be minimized.

According to the aforesaid description, the present invention has attained an object designed and expected by the inventor thereof. It is naturally that the present invention may be modified, in the outer shape and structure, by any person skilled in the art without deviation from the substantial spirit of the invention. In accordance with the actual blowing volume and pressure required, the present invention may, with the same theory and structure, be embodied to include a single or multi-cylinder, or a one-stage or multi-stage air compressor.

Claims (9)

1. An air cooling and reciprocating type of air compressor without lubricant, comprising: cylinder with radiating flanges furnished on the outer surface thereof; cylinder head attached to the open end of said cylinder; and at the bottom center or nearing said center of said cylinder head, there is furnished with an exhaust valve having a check valve function; and said cylinder head is also furnished with an outlet for releasing the compressed air; an air suction port being furnished over the opening of the crank shaft case, and inside said air suction port, there are provided with a plurality of noise reduction plates and a filter bed for eliminating noise and filtering the air sucked in; a piston with several grooves around its outer wall surface for mounting a number of piston rings supported with spring rings respectively; and said piston ring having self-lubrication effect, and being closely in contact with the inner wall of said cylinder for air-tight function; and at the top center or nearing said center of said piston, there is furnished with a check valve as an intake valve.

a connecting rod being connected with the bottom of said piston; and a transmission mechanism being connected perpendicularly with said connecting rod, and said transmission mechanism being mounted in said crank shaft case so as to make said connecting rod moving back and forth; and since said piston moving reciprocally in said cylinder, a pressure difference will be generated respectively in said crank shaft case and said cylinder so as to have the air enter into said crank shaft case through said air suction port, and then the air will pass through said intake valve on said piston to enter into said cylinder, wherein the air is to be compressed into a high pressure air and exhausted through said exhaust valve; and therefore such circulated air has a cooling effect to the running parts and friction parts without adding any lubricant in the machine.

2. A reciprocating type of air compressor as claimed in claim 1, wherein the transmission mechanism is a crank shaft.

3. A reciprocating type of air compressor as claimed in claim 1, wherein said transmission mechanism includes an input shaft that is driven with a driving means for rotation, a cam being attached to said input shaft, and an eccentric shaft being connected with said cam and said connecting rod.

4. A reciprocating type of air compressor as claimed in claim 1, wherein said piston ring is made of teflon (R.T.M.), being added with a glass fiber, a graphite and a bronze powder, etc

5. A reciprocating type of air compressor as claimed in claim 1, wherein said piston ring is made of a graphitic carbon, being added with a glass fiber and a bronze powder.

6. A reciprocating type of air compressor as claimed in claim 1, wherein the inner wall of said cylinder is treated with a case hardening method, i.e. to electroplate with a chromium coating or other coating that can increase the rigidity of the cylinder wall.

7. A reciprocating type of air compressor as claimed in claim 1, wherein the inner wall of said cylinder is covered with a cylinder liner made of cast iron or other material that can withstand wear and tear.

8. A reciprocating type of air compressor as claimed in claim 1, wherein the top portion of said cylinder is furnished with a sunk and ring-shaped air cooling pipe, of which one end is mounted with a trumpet-shaped opening, while the other end is furnished with an outlet.

9. A reciprocating type of air compressor as claimed in claim 1, wherein the top portion of said cylinder is furnished with a sunk and ring-shaped water jacket, of which one end is provided with an inlet, while the other end is provided with an outlet.