US3476308A

US3476308A - Compressor construction

Info

Publication number: US3476308A
Application number: US676107A
Authority: US
Inventors: Theodore W Rundell; Freddie D Randall
Original assignee: Tecumseh Products Co
Current assignee: Tecumseh Products Co
Priority date: 1967-10-18
Filing date: 1967-10-18
Publication date: 1969-11-04
Anticipated expiration: 1986-11-04
Also published as: GB1198584A; NL6814555A; BE722305A; FR1586993A; BR6803189D0; ES359248A1; DE1803504A1

Description

N 1969 T. w. RUNDELL ETAL COMPRES SOR CONSTRUCTION A L 2 L 0 0 T w a my m Vfii v MM M m a a J 4 M a 6 a M 4 ma 0 a a w M M m w J J R 4 0 m F 4 V. w m, a 3 m w w m. m

ATTORNEYS Sheet 5 5 Sheets- F'IG. l2

CONSTRUCTION T. W. RUNDELL ETAL COMPRESSOR ,a 0 Rd 2 Nov. 4, 1969 l NVENTORS 4 4 0001?! IV. ewwzzz ffffifl/f 0. fi/V04ZA ATTORNEYS United States Patent 3,476,308 COMPRESSOR CONSTRUCTION Theodore W. Rundell and Freddie D. Randall, Tecumseh, Mich., assignors to Tecumseh Products Company, Tecumseh, Mich., a corporation of Michigan Filed Oct. 18, 1967, Ser. No. 676,107 Int. Cl. F04b 35/04, 29/00 US. Cl. 230-58 10 Claims ABSTRACT OF THE DISCLOSURE An object of the present invention is to provide an improved compressor construction, preferably of the hermetic type, in which as many parts as possible may be economically mass produced by stamping and/or drawing equipment, and which eliminates the need for the usual reed-type inlet valve in the compressor pump.

Other obiects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a vertical center section through a hermetic motor-compressor unit constructed in accordance with the present invention.

FIG. 2 is a top plan view of the unit of FIG. 1 with a portion broken away and taken in horizontal center section through the pump of the unit.

FIG. 3 is a fragmentary view of the stationary piston and outlet valve of the compressor pump taken in section as in FIG. 1 but on an enlarged scale.

FIG. 4 is a plan view of the outlet valve shown by itself.

FIGS. 58 inclusive are fragmentary center sectional views of the scotch yoke and pump structure of the compressor illustrating in sequence a cycle of operation thereof.

FIG. 9 is a diagrammatic view illustrating the cycle of operation of the scotch yoke-inlet valve mechanism of the unit.

FIG. 10 is a vertical center sectional view illustrating a modified motor-compressor unit also constructed in accordance with the present invention.

FIG. 11 is a horizontal sectional view taken on the line 1111 of FIG. 10.

FIG. 12 is a fragmentary vertical sectional view taken on the line 1212 of FIG. 11.

FIG. 13 is a horizontal sectional view on the line 1313 of FIG. 10.

Referring in more detail to the accompanying drawings, FIGS. 1 and 2 illustrate a motor-compressor unit constructed in accordance with the present invention in which the majority of parts are adapted to be fabricated from sheet metal stock by high-volume production equipment, such as stamping and metal drawing presses, to provide a lightweight, small capacity hermetic compressor at a relatively low cost. The hermetically sealed casing of unit 20 comprises a cylindrical tube 22 closed at each of its opposite ends by top and

bottom covers

24 and 26 respectively. Bottom cover 26 has an axially circular extending rim 28 welded to the bottom of tube 22, and a 3,476,308 Patented Nov. 4, 1969 domed center portion 30 disposed with its convex surface facing downwardly. Top cover 24 likewise has an axially extending rim 32 inserted with a close fit within the upper end of tube 22 and secured thereto by welding, and a domed central portion 34 disposed with its convex surface facing upwardly. Cover 24 also has a conventional electrical connector 36 with leads 38 extending in sealed relation through the cover. The exterior terminals of leads 38 are protected by a small cover 40 removably retained on cover 24 by a spring clip 42 (FIGS. 1 and 2) having a circular bite portion 44 which resiliently expands into a groove 46 provided in rim 32. By squeezing together the

ends

48 and 50 of clip 42 bite 44 may be contracted to remove clip 42 from cover 24 and thereby free cover 40. Cover 40 may also house suitable thermal overload protection devices of known construction.

Unit 20 includes a conventional electric motor 52 with stator windings 54 mounted on an annular core 56 which in turn is suitably fixed to the inner wall of tube 22. A rotor 58 of motor 52 is mounted on a crankshaft 60 for rotation therewith, shaft 60 in turn being journalled Within a tubular bushing 62 which is stationarily mounted concentric with core 56 and tube 22. Shaft 60 has a thrust bearing surface 63 formed as part of the underface of a crank throw 64 and counterweight 66 which are fixed to the upper end of crankshaft 60, surface 63 riding on the upper end surface 68 of bushing 62. Bushing 62 in turn is stationarily supported by a sheet metal spider frame 70 (FIGS. 1 and 2) having a central hub 72 in which bushing 62 is received and welded, and three radially outwardly extending

arms

74, 76 and 78 each having an upturned end 80 secured as by welding to the inner wall of tube 22 at 120 intervals.

The scotch yoke mechanism of unit 20 includes a. cylindrical crank pin 82 fixed on crank throw 64 eccentrically of crankshaft 60 so as to revolve around the axis of shaft 60 as shaft 60 rotates. Pin 82 is rotatably received in a crossbore 84 of a cylindrical slider 86 which slides axially in the throughbore 88 of a cylindrical crosshead 90. Crosshead 90 has a pair of diametrically opposed, axially extending slots 92 and 94 in its upper and lower sides respectively. Lower slot 94 receives pin 82 therethrough and permits lateral travel of the pin axially of crosshead '90 as seen in FIGS. 58, whereas upper slot 92 provides a vent hole for oil discharged from the upper end of an oil passage 96 which extends axially through pin 82 and shaft 60 to a centrifugal impeller tube 98 fixed to the lower end of shaft 60.

Crosshead 90 is fixed at one side thereof to a cuplike cylinder 100 which constitutes the moving part of the compressor pump of unit 20. As best seen in FIG. 1, cylinder 100 has an end Wall 102 with a transverse concavity 104 which receives the side of crosshead 90, cylinder 100 being welded to crosshead 90 at this juncture so to be oriented with its axis perpendicular to the axes of crosshead 90 and crankshaft 60. The cylindrical skirt 106 of cylinder 100 has a close sliding fit on the cylindrical skirt 10 7 of a stationary cup-like piston 108 which constitutes the stationary part of the compressor pump. Piston 108 has a transverse end wall 110 with a transverse groove 112 (FIG. 3) adapted to nest with the transverse convexity of wall 102 to provide essentially zero clearance at the end of the compression stroke of the pump when cylinder 100 is fully telescoped onto piston 108 as shown in FIGS. 1, 2 and 5. Piston 108 is inserted through a circular opening 114 in the side wall of tube 22 and welded to the rim of this opening. The outer end of piston 108 is closed by a plug 116 having an outlet tube 118 mounted therein for communication with a muflier chamber 120 formed by the hollow interior of piston 108.

As best seen in FIGS. 6, 7 and 8 the space between the end walls 102 and 110 of the cylinder and piston forms a variable volume pump chamber 122 which is expanded and contracted by reciprocation of cylinder 100 on piston 108. The inlet pasage to chamber 122 comprises a portion 124 which extends through wall 102 adjacent skirt 106 and which registers with a port 126 which extends through the adjacent side of crosshead 90. The inlet passage is alternately positively opened and closed in synchronism with reciprocation of cylinder 100 by slider 86 as it reciprocates in crosshead 90. As best seen in the sequence of FIGS. 6, 7 and 8 one end wall 128 of the slider moves past port 126 so that the side wall of the slider completely covers port 126 just as cylinder 100 reaches bottom dead center position (FIG. 7). Port 126 remains covered and closed by slider 86 as cylinder 100 moves toward piston 108 on its compression stroke (i.e., the discharge stroke of the pump) and until shortly after the cylinder has bottomed on the piston at the end of the compression stroke. As shown in the diagrammatic illustration of FIG. 9, slider 86 preferably is designed to open the inlet passage for 170 of crankshaft rotation and to close the inlet passage for 180 of crankshaft rotation, the uncovering and covering tolerances being accommodated by the angular increments taken from the suction half of the pump cycle. When port 126 is uncovered by slider 86, communication is established between chamber 122 and the interior of the compressor casing via the adjacent open end of bore 88 and slots 92 and 94 in crosshead 90.

The outlet passage from pump chamber 122 comprises a port 130 extending centrally through end wall 110 of piston 108 to chamber 120. As best seen in FIGS. 3 and 4, port 130 is controlled by an outlet check valve 132 which comprises a thin one-piece stamping of spring steel having a flexible reed valve portion 134 adapted to seat in closed position on a rim 138 formed by machining an annular groove 140 in the inner surface of wall 110 around port 130. Reed 134 is formed by blanking out a keyhole-shaped slot 135 (FIG. 4) from the flat bottom 144 of valve member 132, leaving a connecting stem or hinge 142 so that reed 134 can flex between the closed and open positions thereof indicated in solid and broken lines respectively in FIG. 3. Valve member 132 also includes a pair of

spring fingers

146 and 148 integrally joined to the opposite ends of bottom 144 and each having an outwardly crimped V-shaped detent portion 150 biased by the resilience of the finger so as to snap outwardly into engagement with an annular V-shaped groove 152 (FIG. 3) in the inner wall 154 of piston 108 upon member 132 being slideably inserted endwise through the open end of the piston to thereby securely but removably retain valve member 132 in operative position (FIG. 3).

In operation, motor-compressor unit 20 is energized from a conventional power source through electrical connections (not shown) from connector 36 to rotatably drive crankshaft 60 and this rotational motion is converted by the scotch yoke mechanism into reciprocating motion of cylinder 100 on stationary piston 108 so as to alternately expand chamber 122 to its maximum volume (FIG. 7) and contract it to almost zero volume (FIG. 5). During the suction stroke of the pump (FIGS. 5, 6 and 7) the pressure differential created between

chambers

120 and 122 maintains reed 134 closed, while the

pump inlet passage

124, 126 is opened by the spool valve action of slider 86 in crosshead 90. This causes refrigerant gas to be drawn into chamber 122 from the interior space defined by tube 22 and covers 24 and 26 of the compressor casing. The interior space of the casing in turn communicates via suitable connections (not shown) with the low side of the refrigeration or other system with which it is to be used. As cylinder 100 travels toward top dead center on its compression stroke (FIGS. 7, 8 and 5), the inlet passage is closed by slider 86, and, when the pressure of the compressed gas in pump chamber 122 exceeds that of the gas in muffler chamber 120 and discharge tube 119, reed 134 opens and the compressed gas is expelled from chamber 122 into chamber 120.

From the foregoing description, it will now be apparent that a motor-compressor unit constructed in accordance with the present invention lends itself to high volume low unit cost mass production fabrication equipment and techniques. Except for motor 52 and crankshaft 60, the majority of components are simple in configuration and may be stamped and/ or drawn from sheet metal stock. By having the cylinder 100 arranged externally of the piston and serving as the moving part of the compressor pump, the intake valve of the pump may be formed by the scotch yoke crosshead and slider parts, thereby eliminating one of the two leaf valves hitherto required.

Referring to FIGS. 10-13 inclusive, a second embodiment 200 of a motor-compressor unit of the invention is illustrated which is similar in most respects to unit 20, corresponding parts being given like reference numerals with a prime suflix. Unit 200 differs from units 20 primarily in the supporting frame for motor 52 and crankshaft 60. Thus, in place of the three-legged spider 70, a cup-like frame member 202 is provided for supporting stator 54' of motor 52' in fixed position in casing 22' and for supporting the crankshaft bushing 62' adjacent the upper end of crankshaft 60. Frame 202 has a cylindrical rim 204 which has a close fit against the inner wall of tube 22' and is welded thereto. The side wall of frame 202 is generally conically shaped so as to taper inwardly and upwardly from rim 204 up to the top end wall 206 of the frame. Four openings 208 are struck out at intervals around the side wall of frame 202 (FIG. 13), and four tabs 210 are bent down from the material taken from the side wall in forming these openings so as to extend in wardly at right angles to tube 22 to provide hangers to which stator 54 is secured by fasteners 212.

The central portion of top wall 206 is depressed downwardly to form a frusto-conical wall 214 and a radial flange 216 the inner margin of which defines a central opening through whichbushing 62' is inserted so that a flange 63 thereof rests on and is fixed to flange 216.

The supporting framework for the motor and crankshaft of unit 200 also includes a U-shaped strut 218 (FIGS. 10, 11 and 12) with a pair of

arms

220 and 222 bent up one from each of the opposite ends of a straight central portion 224 which extends horizontally and diametrically across the lower end of casing 22. Each

arm

220 and 222 is secured by a fastener 212 to the underside of stator 54. As best shown in FIGS. 10 and 11, the lower end of crankshaft 60' extends through a bushing 226 which serves as an outboard bearing for the crankshaft spaced remote from the inboard bearing 62. Bushing 226 is formed integrally from the central portion 224 of the strut by a suitable piercing and drawing operation.

The compressor pump of unit 200 differs from that of unit 20 in that outboard end of the stationary piston 108' is completely closed by a plug 230 (FIG. 10), the discharge tube' 118 being connected through the skirt of piston 108' and extending therefrom internally of the casing to an auxiliary muffler 232 which in turn is connected to an outlet opening 236 in the side wall of casing tube 22.

Unit 200, like unit 20, thus has a majority of its components fabricated from stamped and/or drawn sheet metal parts for economy of manufacture, and the com pressor pump thereof requires only one reed valve 132.

It is to be understood that the above described motor compressor units of the invention may be disposed for operation with the axis of rotation of the crankshaft of the unit orientated horizontally rather than vertically as illustrated by way of example herein. The only modification required for horizontal operation is the substitution of a suitable oil pump for the previously described pick-up tube 98, and for this purpose, well-known positive displacement type gear rotor or rotary vane oil pumps or the like may be used in conjunction with a suitable dip tube for conducting oil from the oil sump to the pump inlet, as in the manner indicated in United States Patents 1,967,035; 2,185,473 and/or 2,283,024.

We claim:

1. In a motor-compressor unit, the combination comprising a casing, a support frame connected to said casing, a motor mounted in said casing, a crankshaft supported by said frame and rotatably driven by said motor, a compressor pump disposed in said casing including a piston connected in a fixed relation to said support frame, a cylinder externally slidably received on said piston and defining with said piston a pump chamber, drive means operably connecting said crankshaft with said cylinder for reciprocating said cylinder on said piston in response to rotation of said crankshaft and means forming intake and discharge passages and valves for said pump chamber, said drive means comprising a scotch yoke mechanism including a crank pin eccentrically mounted on said cranckshaft, a slider carried on said crank pin and a crosshead slidably connected with said slider and connected in fixed relation to said cylinder, said crosshead having a surface along which said slider travels, said intake passage means comprising a passage extending through said cylinder and said crosshead between said pump chamber and said surface of said crosshead, said intake valve means comprising said slider alternately closing and opening said intake passage during reciprocation of said slider on said crosshead in response to rotation of said crankshaft.

2. The combination set forth in claim 1 wherein said discharge valve means comprises a discharge passage connecting said pump chamber with the interior of said piston and a thin metallic generally U-shaped valve member having a flat central portion containing a reed valve and further having a pair of spring arms with detent portions, said piston having means in engagement with said detent portions to thereby removably retain said valve member in operative position in said piston with said reed valve thereof acting as a discharge check valve controlling said discharge passage.

3. In a motor-compressor unit, the combination comprising a casing, a support frame connected to said casing, a motor mounted in said casing, a crankshaft supported by said frame and rotatably driven by said motor, a compressor pump disposed in said casing including a piston connected in a fixed relation to said support frame, a cylinder externally slidably received on said piston and defining with said piston a pump chamber, drive means operably connecting said crankshaft with said cylinder for reciprocating said cylinder on said piston in response to rotation of said crankshaft and means forming intake and discharge passages and valves for said pump chamber, said crankshaft being joumalled in a bushing adjacent one end of said crankshaft, and wherein said frame comprises a sheet metal frame disposed transversely of said casing and having a central hub portion receiving said bushing therethrough, said frame being fixedly secured to said bushing and extending radially outwardly from said hub portion to fixed connections with said casing.

4. The combination set forth in claim 3 wherein said frame comprises a generally flat central portion surrounding said hub portion and a plurality of angularly spaced arms connected at their inner ends to said central portion and each having a mounting portion bent at right angles to the outer end of the arm and Welded to said casing.

5. The combination set forth in claim 3 wherein said frame comprises a generally cup-like member having a circular rim portion secured to said casing, a side wall of generally frusto-conical configuration and an end wall joined to said side wall, said hub portion comprising said end wall receiving said bushing therethrough and providing the support therefor to form an inboard bearing for said crankshaft, and further including an outboard bearing for said crankshaft comprising a generally U-shaped strut having a central portion extending diametrically of said crankshaft and having a hub portion journalling said crankshaft near the end thereof remote from said one end, said strut having a pair of arms one at each opposite end thereof fixedly connected to said cup-like member.

6. The combination set forth in claim 5 wherein said cup-shaped frame member has a plurality of circumferentially spaced openings in said side wall thereof and a tab bent inwardly in each of said openings, and wherein said motor has an annular stator secured to said tabs of said frame member.

7. The combination set forth in claim 6 wherein said crankshaftis oriented with its axis upright and said hub portion of said end wall of said cup-like frame member has a downwardly depressed portion in the center thereof whereby said inboard bearing is supported at an elevation below the uppermost portion of said end wall so that oil collecting on said end wall drains toward said inboard bearing.

8. The combination set forth in claim 3 wherein said casing comprises a cylindrical tube with a circular end plate inserted at each of the opposite ends thereof and hermetically closing said opposite ends.

9.In a motor-compressor unit, the combination comprising a casing, 21 support frame connected to said casing, a motor mounted in said casing, a crankshaft supported by said frame and rotatably driven by said motor, a compressor pump disposed in said casing including a piston connected in a fixed relation to said support frame, a cylinder externally slidably received on said piston and defining with said piston a pump chamber, drive means operably connecting said crankshaft with said cylinder for reciprocating said cylinder on said piston in response to rotation of said crankshaft and means forming intake and discharge passages and valves for said pump chamber, said piston comprising a cup-shaped member closed at one end by an integral end wall and having its other end secured in an opening of said casing, said cylinder also comprising a cup-shaped member closed at one end by an integral end wall and receiving said piston with a sliding seal fit through the other open end of said cylinder member, said discharge passage extending through said integral end wall at said one end of said piston to the interior of said piston.

10. The combination set forth in claim 9 wherein said piston is closed at said other end thereof by a plug member and said outlet valve is disposed within said piston adjacent said end wall thereof so that the interior of said piston forms a muffler chamber adjacent said discharge valve means.

References Cited UNITED STATES PATENTS 1,445,252 2/1923 Weiss 230174 2,435,108 1/1948 Touborg 23058 2,628,765 2/ 1953 Anderson 23058 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 230174