US2122398A - Air compressor - Google Patents

Description

July 5, 1938. L. D. HARRISON AIR COMPRESSOR Filed June 30, 1937 Hlrr F/Gl

. JNVENTolg.

Patented July 5., 1938 UNITED ASTATES PATENT oFFlci:

My invention relates to air compressorsv of the reciprocating type wherein air is drawnl into a cylinder through an intake valve and discharged through an exhaust valve into a receiving chamber, and its objects are: First, to provide a compressor of the type mentioned wherein both intake and exhaust valves are lmechanically operated in order to secure the proper uniform action to provide mechanism associated with a com; c

thereof, regardless of working pressures; second, to provide a compressor of the type disclosed wherein the valves are mechanically operated so that the pistons-may operate at speeds comparatively much higher than the conventional type heretofore used; third, to provide a compressor of the type disclosed wherein mechanical means is provided to prevent or stop the action of said compressor when desired; fourth, to provide a compressor of the type described wherein leaks around the mechanically operated exhaust valve are prevented; fth, to provide a device of the kind disclosed wherein strain on the exhaust valve due to thepressure built up in the receiver tank is equalized whereby the exhaust valve is not placed on a strain such as to cause its fracture whenoperated at high speeds; and, sixth,

pressor of the type described wherein the exhaust valve opens only after a predetermined pressure has been built up in the working cylinder. Other objects will appear hereinafter. I attain these objects by means of the particular design and construction of the compressor illustrated in the accompanying drawing herewith made a part of this application in which-Fig. 1

is a vertical'mid-sectionof the upper portion of a compressor head embodying my improvements, taken on a plane parallel with theaxis'of the crank shaft; Fig. 2 is a plan view of the cylinder head, as shown in Fig. 1, with the cam lifting mechanism shown in section; Fig. 3 is a vertical section taken substantially on line #-4, 2;

' Fig. 4 is a vertical section taken substantially on line 4 4, Fig. 2; Fig. 5 is a diagrammatic elevation of a cylinder showing the crank'and cam mechanism; and 1""ig.l 6 is a modified form, in section, of an exhaust valve accordion spring.

Similar numerals refer to similar parts in all views.

Heretofore the practice has been to construct air compressors 'with both valves operating automatically from the pressures created by differential air pressures created by the movement of the piston within the cylinder. These valves were variously termed, but are commonly known as weak-spring or flutter valves. The intake valve was positioned so that when a slight vacuum was created it' would open, permitting air to enter the cylinder and would close Whenever pressurewas created by the opposite stroke of the piston within the cylinder. Conversely, the ex- 5 haust valve was constructed so that it would open against the pressure of its closing spring whenever pressure was created within the cylinder greater than that in the receiving tank, and would close under this pressure and by reason of 10 its spring upon the down or outer stroke of the piston. When pressure had been suillciently vbuilt up within the receiver, action of the compressor was stopped, by holding open the intake valve by mechanical lever arrangement. 'I'his 15 practice necessitated the use of heavy, large and slow moving parts in order to furnish compressed air in volumes desired for commercial purposes, since it is impossible to operate these automatic valves beyond a certain speed d'ue to their inertia, 20 etc.

This was particularly true ofthe exhaust valve.

If, on the other hand, this valve was made lighter to minimize the inertia, it was found in practice that it soon hammered itself out of its seat or became entirely broken or crystallized and subject to breakage. This same condition was true of the intake valve to a lesser degree. Due to this drawback, therefore, it was necessary for air compressors to have a large piston displacement and operate at comparatively slow speeds, hardly ever v exceeding 900 R. P. M.

In order to provide mechanism which would furnish an equal volume of air compressed to the required pressure, I have provided the mechanism hereinafterdescribed, and illustrated in the accompanying drawing, in which the valves are caused to--operate mechanically and, therefore, can be made much heavierand larger in order t stand the strain to which they are sub- 40V ject and since these valves do not depend upon differencesof air pressure to cause them to operate, they may be timed to open and close at the 23 leading from the outer air, and exhaust port 2l connected to a compressed air receiver.

With reference to the intake valve, it will be noted that it Vis held shut under me tension of spring 6 in the usual manner, and is mechanically operated by the rocker arm 1, operatively mounted on an eccentrically positioned journal 8 on rocker arm shaft 9. This rocker arm is in turn operated by push rod I from cam 25, operating at the same speed as crank shaft 35 and indicated diagrammatically in Fig. 5.

Exhaust valve is iitted within the head 3 the same as the Vintake valve, which is opposite 'to Ithe conventional manner in which exhfaust valves of air compressors are positioned. Itis held shut under the tension of the spring steel accordion y bellows I2, which is attached to the upper part of the valve stem by: an air-tight seal Il3 and to the cylinderhead 3 by a similarly air-tight seal I4, held in placeby a large bushing I5. This exhaust valve is operated by a rocker arm I6, operatively supported on an eccentrically positioned journal I I on shaft 9, and operated by push rodi 22 from cam 26 revolving at crank shaft speed.

Shaft 9 is rotatably supported and journaled to turn in support brackets I8, attached to cylinder head 3. It is provided at one end with a bell crank I9, which may be operated by any convenient leverage means to swing through an arc-.of approximately 90. It is to be noted that theecenter ofthe journal 8 on which the rocker arm I is mounted is'oppositely positioned to Ythat of the journal 'I'I,'on which rocker arm i6 is .mounted When the shaft is in the neutral'position, as illustrated in Figs. 3 and 4, both valve tappets are operative. If, however, it is swung 90 in the directionof the arrow, it ewill be noted that the journal axis of rocker arm-'I is lowered. This has the eiectof holding open the intake valve. ing the exhaust valve rocker arm, is raised so that tained in the receiver by reason of the inoperation of;V the closed exhaust valve. This construction also avoids the possibility of the compressor stopping ata point with the exhaust valve open, which would cause a loss of pressurefrom the receiver ordamage to the drivingY machinery by reason lof ka back .motion of the piston. RockerV arm springs 21 and 23 are connected between the cylinder head and the rocker arms I and I6 respectively, to causethese arms to remain in operative position on, or ride, the upper endsof the push rods, regardless of the position of th `rocker arn shaft or its movements.

The accordion spring I is made with sufcient tensionto hold the exhaust valve 5V'closed, against any predetermined pressure in the receiver. Air

On the other hand, eccentric I1, support- Fig. 6, the accordion 30 may be made of setter, vmetal while the assistant spring 3l is used to furnish the tension and keep the valve closed.

Push rod 22, voperating rockervarm I6, cooperates with-cam 26 in the usual manner. however, is positioned so that exhaust valve 5 is notV opened until the upwardly traveling piston 321'1has approached the upper end of its-stroke as take port'23 through the intake valve, operated by a cam timed to lift so that it fully opens soon after the commencement of the intake stroke and stays open until the piston has practically reached the bottom of its travel. On the up stroke the intake valve closes and the exhaust valve remains closed until the piston reaches a point, as above stated, where the Vpressure in the cylinder approximates that to be maintained in the receiver. At this p :int,the exhaustL valve opens and remains open until -the piston reaches the upper limit or?Y its travcl, when it again closes. Now, if suilicient pressure has been built up in the receiver, and it is desired to momentarily stop compressing, throughout approximately 90 in theV direction of the arrows in Figs. 3 and 4. This shifts the position ofV4 .both of the eccentric portionsf the rocker arm shaft 9, as above explained, and causes the axis of rocker arm I to be lowered so that it remains open even though its push rod operates; On the other hand, the axis of rocker arm I6 raisedso that it does not contact the etop `of the stem of valve 5, although it continues to ride in operative position o n its push rod by Yreason of the tension of spring 38. This simple and eecti-ve means permits the regulation of the Vpressurein the receiver and bell crank I9 may be operated through any convenient lever system either manuallye or by a pressure regulating accordion; diaphragm connected with the receiver.V

tank. e Y Y 'e Since both valves operate mechanically at a predetermined timed position, and the tension of Y their springs may be sumcient tomake a closure at Y all times, itis obvious that this type of mechanism Vof automatically operated valves.

pressure from exhaust port 24 enters the closed i chambern20, through vent opening 29 and, press- Y., ing outwardly, tends to offset the pressure exerted V,against the valve disk 2I, which tends to open it. Therefore, higher pressure thannthat which the spring would otherwise be capable of holding by itself, may be maintained in theY receiver. The

action of the accordion valve spring, therefore is three-fold-First, it prevents pressure from leaking fromthe receiver out throughthe valve-stem;

second, it operates as an offsetchamber to equal-lY ize the pressure on the valve disk and assist inYY Ymaintaining it closed; and, third, it acts as a,

valve spring. In the alternative form shown in is not hampered by inertia which limits the speed For this rea- Its lift,

rocker arm shaft 9 is rotated' son, an air compressor provided with my valve A mechanism may be made of much smaller size, andV by increasing'its crank shaft speed, wiil easily deliver the samevolume of air atthe same pressure as the heavier and more bulkycompressors now` in general use. Whilecompressors' ordinarily do notoperate at a speed greaterfthan 900 RIP. M., .compressors of the type here disclosed may be operated at speeds-.as high as 3,500 R. P. M., thusfpermitti'ng a great saving in space and weight, as'well asmakingit more economical in maintaining'valves in good condition.

I wish to be limited only by the following claims. -j e' I claim:

1.Va.lve mechanism for air Ycompressors of the reciprocating piston type comprising. incombinato open inwardly into said cylinder chamber, in-

tion a cylinder head lbeing ported and provided with valve seats for an intake and exhaust valve take and exhaust valves seated therein having their stems protruding outward from said cylinder head, a helical spring intermediate said cylinder headand the outer end of said intake valve, an accordion spring intermediate said cylinder head and the outer end of the stem of said exhaust valve, means for sealing. said accordion spring to the cylinder head and the place of its attachment on the stem of said exhaust valve respectively, rocker arms adapted to operatively open said valves supported on the rocker arm shaft attached to said cylinder head with the journal supporting said intake valve eccentrically positioned relative to the axis of said rocker arm shaft and the journal supporting said exhaust valve rocker arm eccentrically positioned relative to the axis of said rocker arm shaft, the axes of said eccentrically positioned journals being oppositely positioned relative tothe axis of said rocker arm stem protruding outwardly through lsaid cylinder head and a spring normally holding said valve shut intermediate said cylinder head and the outer' end of said valve stem, anexhaust valveY seatedvin said exhaust valve port seat having an outwardlyI extending stem, a spring consisting of a resilient accordion cylinder annularly surrounding said exhaust valve stem and provided with an air-tight seal at its outer Aend to the outer end of the valve stem of said exhaust valve and a seal at its lower end forming an air-tight closure tov said cylinder head, together with mechanism for mechanically operating said valves at predetermined intervals. v

3. Valve mechanism for reciprocating air compressors comprising a cylinder head provided with an intake port and exhaust port and valve seats communicating therewith to receive inwardly opening poppet valves, an intake valveoperative in said intake port .valve seat having its stem protruding outwardly through said cylinder head and a spring normally holding said valve shut intermediate saidcylinder head and the outer end of said valve stem, an exhaust valve seated in said exhaust Avalve port seat having an outwardly extending stem, a spring consisting of a resilient accordion cylinder annularly surrounding said exhaust valve stem and provided with an airtight seal at its outer end to the outer end of the valve stem of said exhaust valve and a seal at its lower end forming an air-tight closure to said cylinder head, together with mechanism 'for alternately operating said valves at predetermined intervals comprising rocker arms, push rods and cam-operatively associated with the crank shaft of said compressor, said rocker arms being supported on a rotative rocker arm shaft and having bearings operative on journals eccentrically positioned relative to the axis of said rocker arm shaft, the' centers of said eccentric journals being disposed at uniform distances on either side of the axis of said rocker arm shaft, and means for distance whereby to shift the axes of said eccentrically positioned rocker arm journals.

4. Valve mechanism for reciprocating air compressors comprising a' cylinder head provided with an intake port and exhaust port'and valve seats communicating therewith to receive inwardly opening poppet valves, an intake valve operative in said intake port valve seat having its stem protruding outwardly through said cylinder head and a spring normally holding said valve shut intermediate said cylinder head and the outer end of said valve stem, an exhaust valve seated in said exhaust valve port seat havingl an outwardly extending stem, a spring consisting of a resilient accordion cylinder annularly surrounding said exhaust valve stem and provided with an air tight seal at its outer end to the outer end of the valve stem of said exhaust valve and a seal at its lower end forming an air-tight closure to said cylinder head, together with mechanism for alternately operating said valves at predetermined intervals comprising rocker arms, push rods and cams operatively associated with the crank shaft of said compressor, said rocker arms being supported on a rotative rocker arm shaft and having bearings operative on journals eccentrically positioned relative to the axis of said -rocker arm shaft, the centers of said eccentric l predetermined distance whereby to shift the axes of said eccentricaily positioned rocker arm jour- 5. In a reciprocating air compressor, valves and associated'mechanism comprising inwardly opening poppet intake and exhaust valves communieating with `the compressor cylinder, positive means for opening said valves at pre-determined intervals, including rocker arms, push rods and cams operative from the compressor crank shaft, a combined valve closing spring and sealing means vsurroundingr the exhaust valve stem adapted to prevent leakage from the compressed air receiver back through the valve stem chamber, and passageways communicating air pressure from said receiver to said sealing means whereby back pressure froni4 said receiverl pushing outward tends to hold said inwardly opening exhaust valve means for opening said valves at pre-determined intervals, including vrocker arms, push rods and cams operative from the compressor crank shaft,

a combined valve closing spring and sealing means surrounding the exhaust valve stem adapted to prevent leakage from the compressed air receiver back through the valve stem chamber, land passageways communicating air pressure from said receiver to said sealing means whereby back pressure from said receiver pushing outward tends to hold said inwardly open-v ing exhaust valve closed, togetherwith means for rendering said valves inoperative by holding said intake valve open and permitting said exhaust valve to remain closed, comprising a rotatable rocker arm shafthaving eccentrically posiltioned rocker arm journals thereon with their eccentric centers substantially oppositely positioned relative to the axis of said rocker a shaft.v

LAURENCE D. HARRISON. Il

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