US 2163391 A
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Description (OCR text may contain errors)
June 20, 1939.,
B. S. AIKMAN FLUID ouPnEssfm 2 Sheets-Sheet l Filed March 6, 1937 INVENTOR BURTUN 5. AIKMAN BY A ATTORNEY ,June 20,1939.` v 1 amgm i 2,163,391
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Patented June 20, 1939 UNITED STATES FLUID COMPRESSOR Burton S. Aikman, Wilkinsburg, Pa., assignor to The Westinghouse Air Brake Company,
Wilmerding, Pa., a corporation of Pennsylvania Application March 6, 1937, Serial No. 129,525
-10 an improved construction for a fluid compressor driven by an electric motor, the compressor and motor forming a compact unit, the compressor being constructed so that a standard motor may be employed with a minimum of alterations in f l5 the motor. v
Another object of the invention is to provide a motor driven compressor unit employing a standard electric motor, the motor armature shaft being supported at one end by a bearingl lassociated v20 with the motor frame, and being supported at the other end only by a bearing associated 'with the compressor.
AA further object of the invention is to provide a iiuid compressor having improved means to re- 28 turn to the lubricant chamber, lubricant which is carried from this chamber by the compressor piston.
Another object of the invention is to provide a :Iluid compressor having improved means to mainl tain the lubricant chamber in the compressor at a pressure below atmosphere to prevent leakage of lubricant from this chamber through the joints in the walls of the chamber.
A further object oi.' the invention is to provide 86 an improved portable compressor which. is compact in construction, efllcient in operation, and is provided with convenient means by which" the unit may be carried from one point toanother. .Another object of thel invention is to provide 4o an improved motor driven fluid compressor.
` Other objects ofthe invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings, in which 4I Fig. lis a view, partly in section, of a com pressor unit provided by my invention,
Fig. 2 is a sectional view of the compressor shown in Fig. 1 and showing the compressor piston at a diierent point in its range of move- 5o ment, and
Fig. 3 is a sectional view taken substantially along the line 3 3 of Fig. 1.
Referring to the drawings. the compressor unit shown in Fig. 1 comprises .a compressor indi- 6l cated generally by the reference numeral I, and
(ci. 23o-5s) an electric driving motor indicated generally by the reference numeral 2.
The motor 2 is of standard commercial design, and, as supplied commercially had a frame consisting of a central section 5 to which were se- '5 cured end sections, one of which is indicated at 6. The motor 2 also has an armature having a shaft 8, one end of which is supported by a bearing, such as. a bushing 9, carried by the end section 6. The other end of the armature shaft 8 10 projects from the motor frame and has a reduced portion, indicated at I0, which is adapted to have vmounted thereon a ydriving member for driving mechanism operated by the motor.
The motor 2, as originally designed, included an end section adjacent the end I0 of the armature shaft 8 andl provided with a bearing for supporting this end of the armature shaft. In the compressor construction provided by my invention this end section is not employed, and is replaced by a member I2 to which is'secured by means of cap screws I4 the body of the compressor I. 'I'he member I2 has an opening therein through which the shaft 8 extends, while a. sealing member I5 is secured around the shaft 8 to prevent leak- 25 age of lubricant from the compressor lubricant chamber to the motor 2.
The compressor I comprises a body having a bore therein which serves as a guide for a piston I 1, while a head I8 is secured tothe body of the -30.
compressor by means of bolts I9. 'I'he head I8 has a bore therein adapted to receive the upper end of thepiston I 'Iy to provide a compression chamber 20 at the face of the piston. The bore in the head I8 is o1' somewhat larger diameter 35 than the bore in the bodyof the compressor, and the upper end of the bore inthe compressor body is surrounded by a conical face indicated at 22, the largest portion of whichis slightly larger in diameter than the bore in the head I8 so that 40 any lubricant `which drains from the wall of the bore in the head I8 will drop into the trough formed by the surface 20 and the piston I1.
The head I8 and the body of the compressor cooperate to form an annular inlet chamber 2l 45 surrounding the borein the head I8, while this chamber communicates with the lower end of the bore in the head I8 by means of an annular passage between the lower end oi the wall of the bore in the cylinder head and the upper face of the compressor body. The inlet chamber 24 also communicates with the kbore in the head I8 by means of ports 26 extending through the wall of this bore and spaced apart circumferentially lthereof. 'Ihe ports 26 are so positioned that they 58 open to the bore inthe head I8 at one side of a piston ring 28 carried by the piston I1 as the ring passes over the pjorts on the up stroke of the piston, and so' that they open to the bore in the 6 head I8 at the opposite side of the ring 28 as the ring passes over the ports on the down stroke of the piston.
The piston ring 28 is mounted in a ring groove 28 formed in the piston I1, while the ring is held l in engagement with the face of the bore in the head I8 by the inherent resiliency of the material of which it is constructed. The ringgroove" 28 is somewhat wider than the piston ring 28, while the portion of the piston forming thelower is face o! this groove-has recesses, indicated at l2,
formed therein at points spaced apart circumferentially oi' the piston. The piston I1 also has formed therein ports Il which communicate with the compression chamber 28 and with the ring groove 88 at points radially inwardly of the plston ring 28.
The head I8 has an exhaust chamber 28 formed therein which communicates with the compression chamber 20 by way of a passage surrounded 2l by an annular seat rib 28 which is engaged by an exhaust valve in the form of a disc l0, which is yieldingly pressed into engagement with the seat rib 28 by a coil spring l2 which extends between the valve disc and a threaded plugY M which 30 closes the upper end of the exhaust chamber 26. 'I'he plug Il has an annular shoulder 4l formed thereon which is adapted to be engaged by the valve disc 4I) to limit movement of this valve 1 disc away from the seat rib 28.
.1.1 The body of the compressor I has a lubricant chamber 58 formed therein and adapted to contain a quantity of lubricant to lubricate the compressor.V This lubricant chamber has spaced walls having aligned openings therein, one of the Awalls being securedagainst the end section I2 ofthe motor I so that the motor armature shait 8 extends through the opening in this wall. The opening in the other wall of the lubricant chamber Il is closed by means of a cover plate a l2 which is secured in position by means of cap screws 52.
The reduced end portion Il of the armature shaft '8 Vhas secured thereondan velen're't''indicated generally by the reference numeral It, and having a hub portion It which extends into and is supported on a suitable bearing, such as a bush- `ing VI8, mounted in a bore in a boss formed on the cover plate`i2. 'Ihe element i5 is secured on the shaft! by means of a key I8, while the gg cover,` plate 62has a lubricant well Il formed thereon above the bushing 58 and communicating with lubricant passages in the bushing I8 by means of apassage 82.
VThe element l58 includes an eccentric portion o 64 having a peripheral portion which extends over the end oi.' the boss on the cover plate 52 and is provided with a bearing surface on which is mounted the lower end of a connecting rod 86, the upper` end of which is secured to the piston o5 I1 by means of a piston pin 81. The lower end of the connecting rod 86 is provided with an oil dipper 68 which is adapted to extend into lubricant contained in the lower vportion of the lubricant reservoir 50 to supply lubricant to the bear- 70 ing surface on the eccentric il, while lubricant thrown about the lubricant chamber will reach the surfaces of the bore in the compressor body in which the piston I1 reciprocates, and will also reach the lubricant well SII. y The compressor provided by this invention has improved means to maintain the pressure in the lubricant chamber 5I) below the pressure of the atmosphere to prevent leakage of lubricant from this chamber, and to insure the return to this chamber of lubricant which is carried by the 8 piston I1 beyond the top of the bore in the compressor body.
The bore in the compressor body has a groove 18 formed therein and extending from the conical surface 22 to the lubricant chamber I8. If any l0 lubricant is carried by the piston I1 toga'point above the conical surface 22 on the compressor a body this lubricant will ilow to the channel formed by the surface 22 and the face of the piston, and
thence to the passage formed by the groove 18 13 and tothe crankcase chamber 58.
'I'he h ead of the piston I1 has a valve chamber 12 vformed therein in which is mounted a ball valve element 1l, which is adapted to seat upon a seat surrounding a passage 18 communicatins 2o with the region at the lower face oi' the head ci the piston I1 and thereby with the lubricant chamber 58. 'Ihe ball valve 1I is heldin the valve chamber 12 by means of a lretainer 18 having openings th'erein providing communication 25 between the valve chamber 12 and the compression chamber 28 at the upper tace ofthe piston I1.
The motor-compressor assembly may have associated therewith a reservoir 88 having a cham- 30 ber therein adapted to receive fluid under pressure, while this chamber communicates with an opening surrouded by a mounting face which is adapted to be secured against a similar mounting face surrounding an exhaust e 82 formed in the head I8 and leading from the exhaust chamber u. 'I'he reservoir I8 is also adapted to be securedto the cover plate l2 by means of a bolt 8l, while a'discharge pipe 88 is secured in a threaded opening in a wall of the reservoir".` Il
'Ihis motor-compressor assembly has associated therewith means by which it may be readily carried fromv one location to another. This means comprises a tubular body. such as a piece of pipe indicated at 88, having one end thereof secured 45 in a hollow member 8l which is secured by means of bolts, not shown. to the body oi'- the compressor I so that the passage through the pipe Il and the member 88 communicates with the inlet chamber 28,. 'Ihe other end of the pipe 88 has 60 secured thereon an air strainer and silencer indicated generally' by the reference numeral 82. The device 82 may be of any suitable well known construction. In addition.. the end oi' the pipe i to which the air strainer v82 is secured is eon- 88 nected by means of a member Il to one `of the bolts by which the fram'e end section 8 o! the motor 2 is secured to the motor central frame portion 5. The pipe 88 is spaced from the adjacent portion of the motor 5 so that a workmans iin- -00 gers may readily pass between the pipe Il and the motor 2 in order that the workman may grasp the pipe 88 to carry the motor-compressor assembly.
In the operation of the device, the num to be es4 compressed by the compressor is drawn through the air strainer 82 and the pipe 88 so that the pipe 88 is constantly cooled and will always remain substantially at atmospheric temperature and will not become heated as the result of operation -70 of the compressor so that it is uncomfortable to grasp.
A base plate 88 is secured to the feet ofthe motor central frame section l and extends beneath the compressor I and terminates in a 1s l ao shown, and on rotation of the motor armature the shaft 8 turns the eccentric element 55 which is supported from the cover plate 52 by means of the bushing 58. On rotation of the eccentric element the piston I1 is moved downwardly from the position in which it is shown in Fig. 1 l
of the drawings. On initial downward movement of the piston I1 the ring 28 is maintained in the positionin which it is shown byits engagement with the" inner face ofthe bore in the head I8 until the piston I1 is moved downwardly relative tothe ring I1 far enough for the upperface of the ring groove 30 to engage theupper face of the ring 28. As a result of this movement of the piston I1 relative to the ring 28 communication is opened between the inlet chamber 24 and the compression chamber 20 by way of the passage 25, the space intermediate the piston I1 and the face of the bore in the cylinder head I8, the recesses 32 in the pston I1, past the ring 28 to the portion of the ring groove 30 radially inwardly of the piston ring 28, and thence through the ports 34. Asa result, on downward movement of the piston I1, fluid from the atmosphere supplied through the air strainer 92 and the pipe 88to the inlet chamber 24, flows therefrom to the compression chamber 20. A y
In addition, on downward movement of the piston I1 there is a reduction in the volume of the chamber 50, and the gaseous fluid contained in z the'upper portion of this chamber is .subjected to a small pressure with the result that iluid flows throughthe passage 18 in the piston I1, unseats the valve 14 and flows tothe valve chamber 12. from which it flows to the compression chamber 0nk movement of the compressor piston I1 to a point adjacent the lower end of its range of. movement, the piston ring 28 -is moved past the ports 26 in the wall of the bore in the head I8 so that communication is opened from the inlet chamber 24 to the compression chamber 2II through the ports 26, and fluid is thereafter supplied from the inlet chamber 24 to the compression chamber 28 through the ports 28.
On movement of the piston I1 to the lower end A of its range of movement, and upon further rotation of the armature shaft 8 the piston I1 is caused to move upwardly in the bore in the head I8. On initial upward movement of the piston I1, the piston ring 28 is held in the position to which it has been moved because of engagement of the ring with the face of the wall of the bore in the head I8. As a result the piston I1 will be moved relative to the ring 28 until the lower surface of the ring groove 30 inthe piston engages the lower face of the ring to thereby prevent the flow of iiuld from the compression chamber 20 to the inlet chamber 24 through the ports 34 in the piston,`the space radially inwardly of the ring 28, and the recesses 32 in the piston.
On upward movement`o`f the piston I1 to a predetermined point in its range of movement, the piston ring 28 is moved past the ports 26 to thereby cut off communication between the inlet chamber 24 and the compression chamber 20 through these ports. Upon further upward movement of the piston I1 the fluid contained in the compression chamber 20 is subjected to pressure and causes the exhaust valve 40 to be moved away from the. seat rib n against the spring n so that fluid from the compression chamber 2l flows to the exhaust chamber Ji and thence byway of the exhaust passage 8 2 to the reservoir 88.V i
Upon upward movement'of the v'piston' i1, and on the increase in the pressure of the fluid-in the compression chamber 20, the ball valve 14l is moved to the seated position to prevent the flow of fluid from the compression chamber'28 through the passage 16 to the lubricant .chamber 58. As`
a result of upward movem'erxhof the piston I1 there is an increase in the' volume of the lubricant chamber 50, and a corresponding decrease in the pressure of the fluid containedin this chamber.
. The pressure of the fluid in this chamber will be reduced to a value substantially'below atmospheric pressure and the higher pressure of v the atmosphere present in the inlet chamber 24 ex-` erted on. any lubricant which has collected in the trough formed by the surface 22 will'cause this lubricant to flow through the groove 10 to the lubricant chamber 50. This will insure return to the lubricant chamber of any lubricant which has been carriedput of the bore in thel compressor body by the piston l1.
As the mancantchamber so is maintained atA in the wallof the -lubricant chamber- 58, .and
will therefore, tend to prevent the escapeof lubrif cant through these joints.
On movement of thepiston Il;tothe".lippenA end of its range'of movement, .which is subiy stantially vthe position irrwhich'.I the piston is` shown in Fig. 1 of thedrawngs, the 'valve disc 40 is moved tothe `seated position bythe spring 42A to prevent back flowwo'f fluidi-from the arserf. voir 88` to the compressionchamber` A2li, while upon further rotationofhthe" motor 'armature shaft 8 and subsequent downward movement 'of the piston I1 thecycleofoperationdescribedgin* detail above is againrepeatedi. -v
It willbe seen ,that .the motorfcompressorl sembly provided `byAthisfinventlon emliiys an" electric motor of standard design andconstruction. and that the armature shaft of this motor,
is supported at one end by a bearing associated with the motor, while the armature shaft is supported at the other end 'only by a bearing asso` ciated with 'the compressor.
It will be seen also that the eccentric for reciprocating the compressor`piston is directly supported on a bearing so that the motor armature shaft is not subjected to forces generated during reciprocation of the compressor piston.
In addition, it will be seen that the compressor incorporates improved means to maintain the lubricant chamber of the compressor at a pressure below the atmosphere to thereby prevent leakage of lubricant from this chamber through the joints in the casing sections forming the lubricant chamber or through the opening through- -made without departing from the scope of the following claims.
Having now described my invention. what I claim as new and desire to secure by Letters Patent, is:
1. In a compressor adapted to be driven by an electric motor of a type provided with a frame having a central portion having end sections secured on opposite sides thereof, the motor being also provided. with an armature having a shaft supported by bearings carried by said end sections, the compressor comprising a member adapted to be secured to the motor frame central portion in place of one of said end sections and having an opening therein through which the armature shaft is adapted to extend, a compressor body associated with said member and having a bore therein, a piston reciprocable in said bore, the compressor body having therein a chamber having spaced walls, one of which is adjacent the motor andhaving an opening therein through which the armature shaft is adapted to extend and the othervof which is disposed at the end of said armature shaft, an element adapted to be mounted on said armature shaft within said chamber and being supported only by a bearing'carried by the chamber wail at the end of the armature shaft. vsaid element being adapted to provide the only support for an end of the motor amature shaft, said element having means thereon for reciprocating said piston, said element and means being spaced from therst mentioned wall adjacent the motor.
2. In a compressor adapted to be driven by an electric motor comprising a frame having a centrai portion and an end section at one side of said central portion, the motor including an armature having a shaft supported at oneI end on a .bearing carried by said end section, the compressor comprising a member adapted to be secured to the motor frame central portion at the side thereof opposite from said end section and serving as an end section of said motor frame,A a compressor body vassociated with said member and having a bore therein, a piston reciprocable in said bore, said member and said compresso!" body having openings therein through which the motor armature shaft is adapted to extend, and an element adapted to be secured on the end of the motor armature shaft for reciprocating said piston, said element being supported on a bearing carried by the compressor body at the adjacent end of the motor armature shaft beyond said element and being adapted to provide the only support for that end of the motor armature shaft.
3. In a compressor adapted to be driven by an electric motor comprising a frame having a central portion and an end section at one side of said central portion, the motor including an armature having a shaft supported at one end on a bearing carried by said end section, the com*- presscr comprising a member adapted to be secured to the motor frame central portion at the side thereof opposite from said end section and serving as an end sectionof said motor frame, a compressor body secured to said member, said body having a bore therein and having therein a chamber having spaced walls. said member and the wall of said chamber adjacent the motor having openings therein through which the motor armature is adapted to extend without bearing relationship,'and an element positioned within said' chamber and adaptedfto be secured on the end of the motor amature shaft for reciprocating said piston, said element being supported only onl a bearing carried by the wall loi' the chamber in the compressor body remote from said motor and being adapted to provide the only support for an end of said motor amature shaft.
BURTON S. AIKIIAN.