US2005578A - Compressing machine - Google Patents

Description

June 18, 1935.. 7w D. D E 2,005,578

,QOMPRESSING MACHINE Filed Aug. 6, 1932 5 Sheets-Sheet l June 18, 1935. w. D. DRYSDALE COMPRESSING MACHINE Filed Aug. 6, 1952 5 Sheets-Sheet 2 flzlysdaze,

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Patented June 18, 1935 UNITED STATES, PATIENT." OFFICE COMPRESSING MACHINE William D. Drysdale, Buflalo, N. Y., assignor to Walter J. Sugden, Boston,jMass.

Application August 6, 1932, Serial No. 627,736

I 19 Claims. This invention relates to a compressing machine susceptible of general application, but partioularly useful in connection with mechanical refrigerators, of the compressor, condenser, expander type, and more particularly to a. machine comprising a compressor driven by an electric motor. This invention aims to provide a machine of this class with a direct driving mechanism without a reduction or other ratio between the driving and driven members, and having means whichshall either partially or wholly avoid creating a load on the motor during the starting of the latter, thereby enabling a motor of low starting torque to be employed, without resort to the use of a belt drive, or other means of establishing a ratio permitting the motor shaft to operate at higher speeds than the apparatus it drives through the belt, or a capacitor motor,

to allow the motor to take up the load of the compressor gradually. The invention also aims to p1 ovide a driving mechanism which shall cause the piston of the compressor to maintain the compressor intake closed when the compressor is at rest, thereby preventing therefrigerant from flowing into the compressor cylinder.

The invention will best be understood by reference to the following description, when taken in connection with the accompanying drawings of one specific embodiment thereof, while its scope will be pointed out more particularly in the appended claims.

In the drawings: Fig. l is a plan of a motor-driven compressor embodying the invention;

Fig. 2 is a vertical, longitudinal section, on an enlarged scale, on line 2-2 of Fig. 1;

Figs. 3, 4, 5 and 6, are sectional views, on an enlarged scale, on line 33 of Fig. 1, illustrating the operation of the unloading mechanism;

Fig. 7 an end elevation of the unloading mechanism in its neutral or initial position;

Fig. 8 is a sectional view on line 8-8 of Fig. 2; Fig. 9 is a horizontal, sectional view on line 9-9 of Fig. 3; 1 Fig 10 is a horizontal, sectional view illustrating the inlet for the refrigerant into the motor housing; I r

Fig. 11 is a sectional view illustrating one of the electric terminals for the motor;

Figs. 12 and 13 are end elevations of the unloading mechanism illustrating a slight modification, inwhich the load of the compressor is entirely removed from the motor for starting purpo e 3 Figs. 14-and 15 aresectional views corresponding with Figs. 12 and 13, respectively, and illustrating the means for predetermining the limits of movement of the oscillatory elements of the unloading mechanism; and

Fig. 16 is a sectional view similar to a portion of Fig. 2, showing a slight modification.

Referring to the drawings, and to the embodiment of the invention illustrated therein, and having reference at first more particularly to Fig. 3, there is shown a motor-driven compressor, the latter comprising a cylinder 20 having a lateral intake port 2|, which is covered and uncovered 1 by a piston 22.

through openings 23 in a plate 24, having an annular seat 25 for an outlet valve 26, which, as shown, is a thin, steel, wafer-like disk, normally urged to its seat by a spring 21 within an outlet chamber 23 formed in a cylinder head 29, and communicating with an outlet passage 33, the latter in practice being connected with a condenser. In the present example, the cylinder 20 is in the nature of a sleeve or lining, fixedly mounted in a surrounding support, herein a housing 3i, having a chamber 32 which encloses part of the driving mechanism.

The driving'mechanism, as herein shown, comprises an element such as a crank-pin 33, having an orbital path, and suitably connected to the piston to reciprocate the latter, the connection shown being a shoe or cross-head 34, mounted to slide in a groove extending transversely of the piston, though the invention is not limited to this form of driving connection, but might employ a connecting rod.

The charge drawn into the cylinder and compressed by the piston is discharged Turning now to Fig. 2, the crank-pin is driven by a rotatable element, herein a shaft 36, mounted to rotate in a bearing 31 presented by a plate 38, which constitutes a cover for the chamber 32. The plate 38 constitutes a partition between the r chamber 32 and a motor chamber 39 also formed in the housing 3|, and the other end of this motor chamber is closed and sealed'by a cover-plate 40, thus providing a sealed housing for the entire mechanism.

The'motor chamber 39 houses an electric motor comprising a stator 4! fixed in the housing,

and a rotor l2 suitably secured to theshaft 36, as

by providing the latter with a reduced portion 43, to which the rotor is secured, as by a key 44 and by a nut 45 threaded onto a further reduced portion 46. The nut urges the rotor, and a suitable thrust washer 61 toward a shoulder 48 presentedby the body oithe shaft, said washer resting against the adjacent endof' the-bearing 31.

The rotor is slightly offset axially with relation to the stator in a. direction opposite to the bearing, thereby to utilize the magnetic flux to eliminate any tendency of the rotor to move endwise. The stator has three-lead wires 49, attached respectively to lead-in plugs 50, one of which is shown in detail in Fig. 11, the same comprising a conductor 5| for attachment to the wire, and a tapered, threaded, insulating shell 52, which is screwed into the housing 3|. The details of this plug have no necessary bearing upon the present invention, and therefore require no further description.

Referring now to Fig. 10, in the embodiment shown, the refrigerant to be compressed. instead of entering the chamber 32 directly, enters the motor chamber 39, as by 'means of a plug 58 threaded into the housing, and provided with passages 54 and 55, the former being connected as usual with an expander. The refrigerant, after entering the motor chamber 39, enters the lower end of a conduit 56 (see Fig. 2), and passes thence through passages 51 and 58 in the plate 33 into the chamber 32. From this chamber, the gas passes upwardly through a passage 59 in the housing 3| (see Fig. 3, and thence through a port 60 in registration with the lateral intake port 2| of the cylinder 28. Thus, the refrigerant on its way to the cylinder, passes through the motor chamber, and cools the motor, as well as the shaft and its bearing.

The unloading mechanism'will now be described, reference being had at first to Fig. 2. In

general, the mechanism imparts to the piston a reciprocatory motion of variable amplitude, varying from'a zone in which the piston covers and uncovers the lateral intake port and causes gas to be admitted through said port and discharged past the outlet valve toa zone within which the piston maintains said port closed. In the first zone, a full stroke is imparted to the piston, while in the second zone, the stroke is either reduced to one of small amplitude, or if desired may be reduced to zero. In' the form shown in Figs. 2 to 8, inclusive, the stroke is reduced to one of small amplitude, while in the form shown in Figs. 12 to 15, inclusive, the stroke is. reduced to zero. The amount of reduction of the stroke is determined by the amount of eccentricity of the oscillatory element now to be described.

Referring to Fig. 2, the crank-pin which has been referred to as an element having an orbital path is carried by an oscillatory element, herein a rockshaft 6|, having an axisof. oscillation eccentric to the axis of rotation of the rotatable element, namely, the shaft 36. When, therefore, the rockshaft 6| is turned about its axis, the radius of the orbit of the crank-pin is varied from a radius in which the piston is effective to cover and uncover the lateral intake port of the cylinder to a radius in which the piston is ineffecthe motor to start tive to uncover said port, and, furthermore, this change of radius changes the load of the compressoron the motor from full load, in which the piston is at full stroke, to a reduced load or no load at all, depending, as has been stated, upon the of the rockshaft. This reduction, or total elimination of the load, enables and to get up to speed partially or wholly free from load, and therefore a motor of low starting torque can be employed, with a direct drive, instead of using other expedientsheretofore employed.

. As herein shown, the eccentricity of the rockshaft SI and corresponding eccentricity of the .Fig. 8), having a reduced portion 64, which is received in asegmental groove 65 in the rockshaft. If desired, the screw and the slot may be located near the inner end of the rockshaft, as shown in Fig. 16. The screw and slot, while employed primarily to prevent endwise movement of the rockshaft, also serve as one means to limit turning movement offthe rockshaft. However, as they are near the axis, I prefer to employ other stops presently to be described, much farther from the axis, to limit turning movement of the rockshaft. I

While the weight 62 might be relied upon without other aid to control the turning of the rockshaft, under the influence of variations in the speed of the motor, I prefer to employ a spring 66 (see Fig. 2) to assist the weight.- This spring can be arranged to present a yielding resistance tothe weight 62 in either direction,- that is to say, it may be utilized either to increase orto decrease the, eccentricity of the crank-pin; but in the embodiment shown, the

spring is arranged to have a neutral position in which it is not stressed, and in which position the stop screw 63 (see Fig. 8) is in the center of the segmental slot 65 when the machine is at rest, the intake port being closed. This is simply a matter of securing the ends of the spring in the desired relationship to the parts which they connect. As shown in Fig. 2, one end of the spring is wound about and secured to a plug 61, having a tongue 68 which is received in a slot 69 in the shaft 36, and; the other end of the spring is wound about and securedtoa simiiar plug 10, having a tongue ll received in a slot 12 in the rockshaft 6|. As herein shown, these slots are conveniently formed by making drilled holes, into which the tongues extend laterally.

In order that the rotating parts shall be in balance after the full speed of the motor is attained, I provide the rotatable shaft 36 with a fly-wheel 13, having a weight 14, which is opposite to the weight 62 when the latter is fully advanced. The counterweight 14 balances the weight 62, as well as the rockshaft with its crankpin. This ensures smooth running, without noticeable vibration, as the two weights under this condition constitute together a balanced flywheel. The fly-wheel I3 is provided with stops l6 and 11 (see Fig. 7), to be engaged by opposite edges of the weight 62 to limit turning movement of the rockshaft 6! in opposite directions.

The operation of the unloading mechanism will readily be understood from a comparison of Figs. 3 to 8, inclusive. Fig. 3 shows what may be termed theretarded position, in which .the radius of the crank-pin is at minimum and the stroke of the piston is correspondingly at minimum. As herein'before stated, in the initial position of the crank-pin, when parts are at rest, the crank-pin may have a slight throw, as shown in Figs. 3 to 8, inclusive, or its axis may be coincident with the axis of the rotatable shaft 36, in which it has no throw at all, as shown in theform illustrated in Figs. 12 to 15, inclusive. The form illustrated in Figs. 3

to 8, inclusive, is preferred, because of the small'- er radius through which the crank-pin and the rqckshaft turn in advancing and retarding. This short radius gives the eccentric weight an inin the compression chamber.

creased leverage in throwing the crank-pin to its position of maximum throw, and in maintaining the piston at full stroke, and hence at maximum pumping eficiency. When the piston is in its maximum operating position, that is at the full stroke, the main shaft, rockshaft' and crank-pin centers are preferably directly over each other in the order named. This pro-. vides a positive drive, so that the piston operates just as efficiently in this position as if no starting relief were provided. Furthermore, as hereinafter suggested, until this full stroke of the piston is reached, the piston may fall back and cushion any excess burden imposed by oil slugs When the'rockshaft is in its neutral position and when the machine is at rest, the lateral intake port. 2| is covered by the piston 22, and no refrigerant can enter the cylinder. When the port is closed, the refrigerant in the cylinder is simply compressed slightly, and then expanded, thus imposing no material load upon the motor. When the motor starts, there is only a slight load, or none at all, depending of course upon the amount of eccentricity of the rockshaft 6|. With the first form, the stroke of the piston, when the motor starts to run, is shown by a comparison of Figs. 3 and 4, Fig. 3 showing the piston at the bottom of its stroke, and Fig. 4 showing the piston at the top of its stroke.

As the speed of the motor increases, the eccentricity of the crank-pin increases, until in the 'full running position shown in Figs. 5 and 6,

the piston has its maximum stroke, Fig. 5 showing the piston at the bottom of 1 its stroke with the port 2| uncovered by the piston, and Fig. 6 showing the piston at the top of its stroke with a slight clearance, amounting in practice to a few thousandths of an inch. During the increase of the piston stroke and before the full stroke is reached, if an oil slug should happen to be taken into the cylinder, no damage will result, because the resistance which is encountered will naturally cause ,a slight retardation in the position of the crank-pin, and a corresponding momentary shortening of the stroke of the piston.

It might be supposed that it would be more desirable to have the setting of the spring 66 such that the latter would tend toretain the crankpin 33 in its fully retarded position,-that is, in the position in which the crank-pin'has its shortestthrow; Such setting of the spring has been found to produce satisfactory results, but it has been found more desirable to set the spring so that it tends to restore the-crankin to its mid position. With the latter. setting of the spring, the crankpin is at mean position when l the machine is at rest and the intakeport' is closed,

. When'the motor starts, the weight 62 will by its inertia lag behind the shaft 36, and will thus bring the crank-pin momentarily to its minimum throw, in opposition tothe resistance of the spring. When, however, the shaft acquires sufiicient speed, the centrifugal effect of the weight, due to its eccentric mounting, results in the weight being thrown outwardly with relation to the shaft. During the first half of this movement,the spring. which is under stress assists the weight in moving-outwardy with relation to the shaft.

Asthespeedof the shaft increases, the weight carries the rdckshaft andthe crank-pin past the neutral position of the spring, and thereafter the spring is stressed in the opposite direction, and yieldingly resists outwardmovement of the weight. When the weight, the rockshaft and the crank-pin reach their extreme outward position, the crank-pin has its greatest throwand the piston its greatest stroke. a

When the current is cut off from the motor, and the speed of the shaft is reduced, the weight commences to lag-behind the shaft, and is assisted by the spring during the first half of this backward movement with relation to theshaft. During this time, the throw of the crank-pin is reduced, the stroke of the piston is correspondingly decreased and the load on the motor is diminished, inasmuch as the piston has little or no work to do, depending of course upon whether the design shown in Figs. 3 to 8, inclusive, or that which is shown in Figs. 12 to 15, inclusive, is used. Moreover, it is to be noted that only a very slight shortening of the stroke of the piston is required to prevent the latter from uncovering the intake port. This means a definite and quick relief of compression stresses and consequent load on the motor.

Observation of the operation of the design illustrated in Figs. 3 to 8, inclusive, shows that sometimes when the motor stops, the crank-pin has returned to its position of minimum throw in opposition to the spring, while at other times, it returnsonly to the mid position in which the spring is neutra1,-that is, not under stressf Observation has also shown that if the machine stops with the crank-pin at mid throw, when the motor starts again, the lag of the weight will bring the crank-pin momentarily to its minimum throw, and then as the speed of'the motor increases, the crank-pin throw will be increased'to maximum, as the motor speed approaches or reaches maximum.

Having thus described one embodiment of the invention, but without limiting myself thereto,

outlet valve, to a zone within which said piston maintains said port closed.

2.- In a refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working insaid cylinder and adapted to cover and uncover said port, means to reciprocate said piston, said means including an element having an orbital path, 'and means to change the path of said element to vary the stroke of said piston from a full stroke during which said piston covers and uncovers saidport to a condition during which said piston maintains said port covered.

3. In a-refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder andadapted to cover and uncover said port, means to reciprocate said piston, said means including an element having an orbital path, and means to vary the radius of the orbit of said element from a radius in which said piston is effective to cover and uncover said port to aradius in which said piston is ineffective to uncover said port.

4. In a refrigerant pump, the combination of a cylinder having a lateral intake pcrt, an outlet -valve, a piston working in said cylinder and 'first-mentioned element from a path in which the latter is effective to cause said piston to cover and uncover said port to a path in which the firstmentioned element is ineffective to cause said piston to uncover said port.

5. In a refrigerant pump, the combination of a cylinder having alateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable element carried by said oscillatory element inan orbital path during the rotation of said rotatable element, and means to cause said oscillatory element to oscillate about its axis to shift said orbitallymovable element toward and from the axis rotatable element, an orbitally movable element of aaid rotatable element.

6. In a refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover saidport, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable ele ment carried by said oscillatory element in an orbital path during the rotation of said rotatable element, biasing means normally to retain said oscillatory elementin an initial position adapted to yield to permit said oscillatory element to move about its axis, and means to cause said oscillatory element to move in opposition to said biasing means.

7. In a refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable element carried by said oscillatory element in an orbital path during the rotation of said rotatable element, biasing meansnormally to retain said oscillatory element in an initial position and adapted to yield to permit said oscillatoryelement to move about its axis, and speed-responsive means to cause said oscillatory element to move in opposition to said biasing means.

8. In a refrigerant pump, the co i'nbination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable element carried by said oscillatory element in an orbital Path during the rotation ofsaid rotatable element, means to limit the oscillatory movement of said oscillatory element, and speed-responsive means to cause said oscillatory element to oscillate in accordance with variations in the speed of rotation of said rotatable element.

9. In a refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder and adapted to coverand uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable element carried by said oscillatory element in an orbital path during the rotation of said rotatable element, means to limit the oscillatory movement of said oscillatory element, speed-responsive means to cause said oscillatory element to oscillate in accordance with variations in the speed of rotation of said rotatable element, and a spring which resists oscillatory movement of said oscillatory element and restores said oscillatoryel-ement to its initial position as the speed of rotation of said rotatable element is reduced.

10. In a refrigerant pump, the combination of a cylinder havinga lateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said of said rotatable element, and a spring which resists oscillatory movement of said oscillatory element and tends to restore said oscillatory element to an initial position between said limits as the speed of rotation of said rotatable element is reduced.

11. In a refrigerant pump, the combination of a cylinder having a lateral intake port, an outlet valve, a piston working in said cylinder and adapted to cover and uncover said port, a rotatable element, an oscillatory element carried by said rotatable element and having an axis of oscillation eccentric to the axis of rotation of said rotatable element, an orbitally movable element carried by said oscillatory element in an orbital path during the rotation of said rotatable element, a weight carried by said oscillatory element to cause the latter to oscillate about its axis in response to variations in the speed of said rotatable element to shift said orbitally movable element toward and from the axis of said rotatable element, and a weight carried by said rotatable element to counterbalance the first-mentioned weight when said orbitally movable element is at its greatest distance from the axis of said rotatable element.

12. In a refrigerating machine, the combination of a compressor to compress the refrigerant, said compressor including a cylinder having a lateral intake port, a piston reciprocating in said cylinder and covering and uncovering said port, a motor to drive said compressor, and driving mechanism connecting said motor and said compressor, and comprising means responsive to the speed of said motor to vary the amplitude of the stroke of said piston from a zone in which the piston covers and uncovers said port to a zone in which said piston maintains said port closed.

13. In a refrigerating machine, the combination of a compressor to compress the refrigerant, a rotatable element to drive said compressor, and positive driving mechanism connecting said element to said compressor, said driving mechanism including a revoluble element which is revoluble about an axis other than its own, and means responsive to variations of the speed of said rotatable revoluble element to move said element toward the axis of said rotatable element when the speed of said rotatable element is reduced, and to move said revoluble element from the axis of said rotatable element when the speed of said rotatable element is increased.

14. In a refrigerating machine, the combination of a compressor to compress the refrigerant, a rotatable element to drive said compressor, and positive driving mechanism connecting said element to said compressor, said driving mechanism includin a crank-pin which drives said compressor, and means responsive to variations of the speed of said rotatable element to move said crank-pin toward the axis of said rotatable element when the speed of said rotatable element is reduced, and to move said crank-pin from the axis of said rotatable element when the speed of said rotatable element is increased.

15. In a refrigerating machine, the combination of a compressor to compress the refrigerant,said compressor including a cylinder and a piston to reciprocate therein, a rotatable element to drive said piston, and driving mechanism between said element and said piston, said driving mechanism including stroke-changing means responsive to changes of the speed of said element to diminish the length of the stroke of said piston as the speed of said rotatable element diminishes, and to increase the length of said stroke as the speed of said rotatable element increases.

16. In a refrigerating machine, the combination of a compressorto compress the refrigerant, a shaft to operate said compressor, and driving mechanism connecting said shaft and said compressor, said mechanism including a crank-pin, and means responsive to the speed of said shaft to move said crank-pin toward the axis about which it revolves when the speed of said shaft diminishes, and to move said crank-pin from said axis as the speed of said shaft increases.

17. In a refrigerating machine, the combination of a compressor to compress the refrigerant, an electric motor, and driving mechanism at all times connecting said motor to said compressor, said mechanism including means to increase the mechanical advantage as the speed of said motor diminishes and to decrease the mechanical advantage as the speedof said motor increases, said means including a weight which tends to lag behind said motor when said motor starts, and to lag behind said motor when the speed of said motor diminishes.

13. In a refrigerating machine, the combination of a compressor to compress the refrigerant, an electric motor, and driving mechanism at all times connecting said motor to said compressor, said mechanism including means automatically to change the driving relationship between said motor and said compressor in accordance with differences between the power of said motor and the load of said compressor, said means including a weight which causes the eifective load to be at minimum when the power of said motor is at minimum, and which causes the effective load to be at maximum when the power of said motor is at maximum.

19. In a refrigerating machine, the combination of a compressor to compress the refrigerant, an electric motor, and gearless speed-responsive mechanism at all times connecting said motor and said compressor to increase the mechanical advantage asthe speed and torque of said motor' diminish and to decrease the mechanical advantage as the speed and torque of said motor increase.

M D. DRYSDAIE.

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