US3072316A

US3072316A - Rotary pump or expansion engine

Info

Publication number: US3072316A
Application number: US747287A
Authority: US
Inventors: Mossin Kaj Borge
Original assignee: Novo Terapeutisk Laboratorium AS
Current assignee: Novo Terapeutisk Laboratorium AS
Priority date: 1957-07-15
Filing date: 1958-07-08
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08

Description

Jan. 8, 1963 K. B. MOSSIN 3,072,315

ROTARY PUMP OR EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 1 Jan. 8, 1963 K. B. MOSSIN 3,

ROTARY PUMP OR EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 2 /IIIIIIIIIIIIIIIIIII% Jan. 8, 1963 K. B. MOSSIN 3,072,316

ROTARY PUMP 0R EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 3 INVENTOR KQ'Z Barge Moss/A1 ATTORNEYS rates The present invention relates to a rotary pump or expansion engine comprising two rotors rotating in opposite directions in a case which in cross section has the shape of two mutually overlapping circles, one of said rotors having one tooth and being convex in cross section, at any rate as regards the greater part of it, and rotating on an axis eccentric in relation to the geometrical centre of the cross section, while the other rotor has two teeth and rotates on an axis, which is centric in relation to the geometrical centre of the rotor cross section, at a rate of revolution equal to halt the number of revolutions of the former rotor.

Such rotary pump or expansion engine is for example known from the specification of British Patent No. 663,- 928 which in detail describes an embodiment with a singletooth rotor and a triple-tooth rotor, but also discloses that the triple-tooth rotor may be substituted by a doubletooth rotor which in cross section approximately has the shape of a rectangle, the length of which is of the same size as the diameter of the cylindrical working space of this rotor. The two short sides of the rotor cross section are not rectilinear, however, but are formed by circular arcs with a diameter corresponding to the width of the rotor cross section. During the operation, the two co-operating rotors are at any time in contact with each other along at least one line, and each of the teeth on the multi-tooth rotor furthermore forms a line sealing along the wall of the working space of this rotor. The single-tooth rotor may in a similar way be in line contact with the wall of the working space of this rotor, but may also be so formed as to touch the said wall over a sector of egg. about 30.

The construction referred to in the said patent specification is stated to have a smaller clearance space than the rotary pumps or expansion engines known in advance and thus a better efliciency than the latter.

The present invention is based on the cognition that a further considerable reduction of the clearance space may be obtained together with other advantages when the double-tooth rotor in cross section has substantially the form of a double-bitted battle-axe, the crown of each tooth being formed by a circular-arc shaped part of the periphery of the rotor with its centre in the centre of the cross section thereof and with a comparatively considerable extent in the peripheral direction, while the width of the cross section of the tooth at any rate in the outer portion ofeach tooth decreases towards the centre.

An advantage of this construction (in addition to the reduction of the clearance space) consists in that the sealing zone between each of the teeth of the double-tooth rotor and the wall in the associated working compartment extends over a considerable sector or arc, which gives a better sealing between the tooth and the wall than in the case of linear contact for the reason that the tooth is to slide along the wall and therefore can have no firm abutment on or firm contact with the latter. The wide contact face between the crown of the tooth and the wall of the working compartment furthermore opens up the prospect of designing shallow sealing grooves in at least one of the co-operatiug faces for the further increase in the resistance against the passage of the working fluid from the high-pressure side of the tooth to its low-pressure side.

" atent O M Patented Jan. 8, 1963 According to the invention, the periphery of the singletooth rotor preferably comprises a first sector concentric with the axis of rotation of this rotor for cooperation with the circular-arc-shaped crown of each of the teeth of the double-tooth rotor, and an oppositely located second sector which is likewise concentric with the axis of rotation and forms the crown of the tooth of this rotor. During the operation, said first sector will roll or slide on the tooth crowns of the double-tooth rotor, so that at this point a considerable sealing can be obtained, and at the same time the second sector of the single-tooth rotor will over a considerable angle cooperate with the wall of the working compartment of this rotor, so that at this point there will also be a great resistance against passage from the high-pressure side to the low-pressure side.

The periphery between the tooth crowns of the doubletooth rotor is according to the invention advantageously formed by at any rate substantially concave faces with substantially the same curvature as the crown of the tooth of the single-tooth rotor. An advantage of this arrangement is that the pressure of the working fluid on the double-tooth rotor may be distributed tolerably evenly in the position of the rotors corresponding to the highest pressure of the working fluid, and hereby a turning moment on the double-tooth rotor caused by the working fluid can be avoided.

In a preferred embodiment of the rotary pump or the expansion engine according to the invention the crowns of the teeth of the double-tooth rotor continue into the flanks of the teeth through short transition roundings which form line sealing against the single-tooth rotor over the greater part of the periphery of the latter. During the operation of the pump or engine the line of contact between the two rotors will linger at the said transition roundings and so to speak skip the substantially concave faces of the double-tooth rotor.

In an expedient embodiment of the rotary pump or expansion engine it is of the type (known for example from the British patent specification mentioned above) where inlet and outlet channels for the working fluid terminate in the working space through slot-shaped openings in the vicinity of the point of intersection of the circles determining the cross section of the working space, at any rate the one of the said channels, in which the Working fluid is under the highest pressure, terminating in the working compartment for the double-tooth rotor and containing a valve which is located close to the said working compartment and is operated in time with the rotor. In this case the opening of the latter channel is, according to the present invention, advantageously in permanent communication with the working compartment of the single-tooth rotor at a point near this opening. The permanent communication may for example be provided by cutting away parts of the wall of the working compartment of the double-tooth rotor between the opening of the channel and the Working compartment of the single-tooth rotor. This permanent communication will certainly, whether it be provided by the said cutting away or in some other way, entail an increase of the clearance space in the pump or expansion engine, but, firstly, this increase need only be rather insignificant and, secondly, the permanent communication possesses the special advantage that the pressure fluid from the working compartment of the singletooth rotor may flow evenly into the Working compartment of the double-tooth rotor so that no passage losses will occur.

The invention will now be more fully described with reference to the drawing, in which:

FIG. 1 illustrates a diagrammatical cross section through an embodiment of the machine with the two rotors and the associated rotary valve in a first position,

FIGS. 2 and 3 are similar views of the same elements in two other positons during operation,

KG. 4 is a fragmental sectional view of a slightly modified embodiment of the invention, and FIG. 5 is an almost similar fragmental view of a fur ther embodiment.

In the drawing, 1 designates the case of the apparatus which comprises two partly overlapping

cylindrical working compartments

2 and 3. An inlet or admission channel 4 terminates 'in the interior of the case through a slot-shaped opening 5 which in the embodiment shown is in communication with both working

compartments

2 and 3, but may also be in communication with only one of the said two working compartments.

Opposite the inlet opening 5 there is in the wall of the working compartment 3 formed an outlet or discharge opening 6, the communication of which with an outlet channel 7 is controlled by a rotary valve 8 which is suitably accommodated in the outlet channel 7 and the circular-arc-shaped sealing face of which co-operates with comparatively small sealing faces above and below the slot-shaped outlet opening 6, respectively.

In the working compartment 2 there is on a centrally 'journalled shaft l t) mounted a rotor 9, the cross section periphery of which comprises a first sector a, which is concentric with the axis of rotation of the rotor, i.e. the axis of the shaft it), and has a radius which is considerably smaller than half the diameter of the working compartment 2, e.g. about one half of half the diameter of the latter, and a second sector 12 which is concentric with the same axis and the radius of which is equal to half the diameter of the working compartment 2. The two sectors a and b are interconnected through curved portions 11.

Centrallyin the working compartment 3 a shaft 1?; is journalled which carries a double-tooth rotor 13 which in cross section is shaped like a double-bitted battle-axe, the cross section being bounded by two circular arcs 14, which are concentric with the axis of the shaft 12, and two concave arcs 15 connecting the said arcs 14. These concave arcs 15 may be substantially circular-arc-shaped, in which case their radius of curvature is of the same size as or slightly smaller than the radius of the sector b of the single-tooth rotor 9. The tooth crowns 14 of the double-tooth rotor 13 therefore have a considerable extent in the circumferential direction which, as explained in the foregoing, makes possible a particularly effective sealing between these tooth crowns and the wall of the working compartment 3 and, as also mentioned before, this sealing may be further improved by means of shallow grooves or corresponding irregularities on at least one of the cooperating faces. Such grooves extending in the axial direction of the rotor 13 have been indicated in FIG. 4.

Therotor 13 has in the embodiments shown short transition roundings 16 between each of the tooth crowns 1'4 and the tooth flanks 15.

Between the outlet opening 6 and the working compartment 2 a permanently open passage 17 is provided for the purpose explained in the foregoing. In the illus trated embodiments, this passage is formed by one or more recesses extending through the portion or" the casing 1 separating the opening 6 from the compartment 2.

When the apparatus shown is to operate as a rotary pump, the

rotors

9 and 13 and the rotary valve are caused to rotate in the directions indicated by the arrows and in such a way that the rate of revolution for the rotor 13 is half the rate of revolution for the rotor 9, the rate of revolution of which is equal to the rate of revolution for the rotary valve 8.

In the position in FIG. 1, the sector b of the singletooth rotor has just cut off the communication from theinlet channel 4- to the compression chamber in the cylinder or compartment 2, and the right-hand lower transition rounding of the double-tooth rotor 13 is in 41. sealing contact with the right-hand curved portion 11 of the single-tooth rotor h. At the same time the opposite tooth crown on the [rotor 13 has cut of? the communication from the inlet channel 4 to the chamber above the rotor This chamber is, however, via the outlet opening a, which is obstructed by the rotary valve 8, and the recess 17 in permanent communication with the compression chamber in the cylinder or compartment 2, so that during the rotary motion of the rotors a uniform rise in pressure will occur in the intercommunicating chambers. If the recess 17 were not provided, the right-hand tooth of the (rotor 13 would form a separation between the two chambers during the first part of the compression stroke, and the passage of the working fluid from the compartment 2 to the compartment 3 would not commence until a pressure of a certain value had been produced in the compartment 2, and therefore the sudden opening for the passage would be accompanied by a certain throttling loss.

FIG. 2 shows the position of the different parts after the single-tooth rotor 9 and the rotary valve 8 have turned about 180 from the position in FIG. 1, while at the same time the double-tooth rotor 13 has turned slightly less than In the position in FIG. 2 the rotary valve has opened the outlet opening 6, and the working fluid is being forced out into the outlet channel 7, the lower tooth crown 14 on the double-tooth rotor meanwhile being in sealing contact with the circular sector a of the single-tooth rotor 9. The opening point for the rotary valve 8 may be adapted to the pressure which it be desired to produce.

In FIG. 3 the different parts approach their positions at the termination of the compression stroke. The circular section b of the single-tooth rotor 9 still seals against tie wall of the working compartment 2, and the lefthand curved portion 11 of this rotor is in line contact with the left-hand lower corner rounding of the doubletooth [rotor 13. The rotary valve 8 has partly obstructed the outlet opening 6, but pressure fluid may still how out through this opening. From the position in FIG. 3 the parts turn on, and the left-hand end of the circular-arc-shaped sector b reaches the lower, left-hand corner rounding lid of the double-tooth rotor 13, so that the space between the two rotors, ie. the clearance space of the machine, has reached its minimum. At this point, the rotary'valve 3 completely obstructs the outlet opening 6, and the whole of the concave, downwards-facing side or flank 15 of the double-tooth rotor 13 will be loaded with the pressureof the working medium so that the latter exerts no unbalanced stress on this rotor. During a very short further turning of the parts the line of contact between the two rotors 9 and 113 skips to the right-hand lower corner rounding 16 of the rotor 13, which rounding will during the further turning slide on the right-hand curved portion 11 of the single-tooth rotor 9. The parts have now arrived into a position corresponding to that shown in FIG. 1.

It will be obvious that the apparatus illustrated in the drawing may also work as an expansion engine, this only necessitating that the rotary valve 8 is given a rotary motion in the opposite direction to the arrow shown and that pressure fluid is supplied to the channel 7. The two

rotors

9 and 13 will then by the pressure medium be given a rotary motion in the direction opposite to the arrows shown.

The turning valve 8 in the outlet channel 7 shown in FIGS. 1-3 oifers favorable discharge possibilities, but also valves of other types may be used. Thus, in FIG. 4 a spring-loaded non-return valve 18 has been shown which is hinged as at 19 to a portion of the casing 1 and is permanently urged towards its closed position by means of a compression spring 20 inserted between an appropriate part of a casing 1 and an arm 22 rigidly connected with the valve plate 18.

In FIG. 5' a transversely displaceable gate valve 22 has been shown. By an appropriate mechanism (not shown) of conventional type, this gate valve or slide valve may be moved between a closing position and an open position indicated by broken lines in FIG. 5.

FIG. 4 also indicates that provisions may be made for cooling the machine during its operation, particularly when the machine is a high pressure rotary pump. Thus,

reference numerals

23 and 24 in PEG. 4 designate cooling fluid passages provided in the casing 1 of the machine.

Finally should be mentioned that due to the spcciai cross sectional shape of the double-tooth rotor with comparatively deep cuts between the teeth the singletooth rotor may have an especially high ratio between its largest radius (sector 11) and its smallest radius (sector a), which results in a correspondingly large cross sectional area for the compression chamber or the expansion chamber and consequently a high output per unit of length of the rotors.

I claim:

1. A rotary pump or expansion engine, having a casing enclosing a working space comprising two intersecting compartments of circular cross-sectional shape, a first rotor journalled for rotation Within one of said compartments about the axis thereof and having a peripheral surface of cylindrical formation, the cross section of which is composed of a first sector concentric with said axis and of a radius considerably smaller than the radius of the particular compartment, a second sector concentric with said axis and of substantially the same radius as said compartment, and two convex further smoothly curved sections interconnecting the respective ends of said first and second sectors, said further sections having end portions extending tangential to respective ends of said first and second sectors, a second rotor journalled for rotation within the other one of said compartments about the axis thereof and having a peripheral surface of cylindrical formation, the cross section of which is that of a double bitted battle-axe and composed of a first pair of opposite sectors concentric with the axis of said other compartment and of substantially the same radius as this compartment, and a second pair of opposite sectors of a generally concave formation interconnecting the respective ends of the sectors of said first pair of opposite sectors, each sector of said second pair of opposed sectors having a generally flat central portion and arcuate end portions, the spacing of said axes being equal to the combined radii of said first rotor first sector and said second rotor first sector, a driving connection between said two rotors causing said second rotor to revolve in operation in the opposite direction from that of said first rotor and with a rotational speed equal to one half of the rotational speed of said first rotor, the shapes of said second sector and said further sections of the first rotor and said second pair of opposite sectors of the second rotor being interrelated in such a manner that during operation the rotors contact each other at least along a single line at all times, inlet and outlet ducts in said casing located one on each side of the second rotor and communicating with said working space and sealed from each other by the rotors, and a control valve disposed in that one of said ducts in which the highest working pressure prevails during operation.

2. A rotary machine as claimed in claim 1, wherein each central portion of each sector of said second pair of sectors of said second rotor has substantially the same curvature as said second sector of said first rotor.

3. A rotary machine as claimed in claim 1, wherein each of the sectors of said first pair of o osite sectors of said second rotor continues into the adjacent ends of said second pair of sectors through short transition roundings which form line contact with said further sectors of said first rotor during operation.

4. A rotary machine as claimed in claim 1, wherein one of the inlet and outlet ducts in which the highest working pressure prevails during operation communicates with said other compartment of the working space through a slot-shaped opening in the vicinity of one of the points of intersection of said compartments, a rotary valve controlling said opening and being located in close proximity to said other compartment and operated in properly timed relation with said rotors, and said opening below said valve communicating with the compartment within which said first rotor operates, through at least one permanently open passage terminating in the latter compartment in the vicinity of said point of intersection.

5. A rotary machine as claimed in claim 1, wherein the peripheral faces of said second rotor, corresponding with said first pair of opposite sectors, are roughened.

References Cited in the file of this patent UNITED STATES PATENTS 508,574 Lambing Nov. 14, 1893 595,227 Wattles Dec. 7, 1897 1,698,802 Montelius Jan. 15, 1929 1,821,523 Montelius Sept. 1, 1931 2,198,786 Montelius Apr. 30, 1940 2,698,130 Mossin Dec. 28, 1954 2,920,610 Breelle Jan. 12, 1960 FOREIGN PATENTS 20,174 Great Britain of 1909 663,928 Great Britain Dec. 27, 1951 604,302 France Jan. 25, 1926 323,492 Italy Dec. 24, 1934 721,481 Germany Feb. 19, 1943

Claims

1. A ROTARY PUMP OR EXPANSION ENGINE, HAVING A CASING ENCLOSING A WORKING SPACE COMPRISING TWO INTERSECTING COMPARTMENTS OF CIRCULAR CROSS-SECTIONAL SHAPE, A FIRST ROTOR JOURNALLED FOR ROTATION WITHIN ONE OF SAID COMPARTMENTS ABOUT THE AXIS THEREOF AND HAVING A PERIPHERAL SURFACE OF CYLINDRICAL FORMATION, THE CROSS SECTION OF WHICH IS COMPOSED OF A FIRST SECTOR CONCENTRIC WITH SAID AXIS AND OF A RADIUS CONSIDERABLY SMALLER THAN THE RADIUS OF THE PARTICULAR COMPARTMENT, A SECOND SECTION OF WHICH IS COMPOSED OF A FIRST SECTOR CONCENTRIC SAME RADIUS AS SAID COMPARTMENT, AND TWO CONVEX FURTHER SMOOTHLY CURVED SECTIONS INTERCONNECTING THE RESPECTIVE ENDS OF SAID FIRST AND SECOND SECTORS, SAID FURTHER SECTIONS HAVING END PORTIONS EXTENDING TANGENTIAL TO RESPECTIVE ENDS OF SAID FIRST AND SECOND SECTORS, A SECOND ROTOR JOURNALLED FOR ROTATION WITHIN THE OTHER ONE OF SAID COMPARTMENTS ABOUT THE AXIS THEREOF AND HAVING A PERIPHERAL SURFACE OF CYLINDRICAL FORMATION, THE CROSS SECTION OF WHICH IS THAT OF A DOUBLE BITTED BATTLE-AXE AND COMPOSED OF A FIRST PAIR OF OPPOSITE SECTORS CONCENTRIC WITH THE AXIS OF SAID OTHER COMPARTMENT AND OF SUBSTANTIALLY THE SAME RADIUS AS THIS COMPARTMENT, AND A SECOND PAIR OF OPPOSITE SECTORS OF A GENERALLY CONCAVE FORMATION INTERCONNECTING THE RESPECTIVE ENDS OF THE SECTORS OF SAID FIRST PAIR OF OPPOSITE SECTORS, EACH SECTOR OF SAID SECOND PAIR OF OPPOSED SECTORS HAVING A GENERALLY FLAT CENTRAL PORTION AND ARCUATE END PORTIONS, THE SPACING OF SAID AXES BEING EQUAL TO THE COMBINED RADII OF SAID FIRST ROTOR FIRST SECTOR AND SAID SECOND ROTOR FIRST SECTOR, A DRIVING CONNECTION BETWEEN SAID TWO ROTORS CAUSING SAID SECOND ROTOR TO REVOLVE IN OPERATION IN THE OPPOSITE DIRECTION FROM THAT OF SAID FIRST ROTOR AND WITH A ROTATIONAL SPEED EQUAL TO ONE HALF OF THE ROTATIONAL SPEED OF SAID FIRST ROTOR, THE SHAPES OF SAID SECOND SECTOR AND SAID FURTHER SECTIONS OF THE FIRST ROTOR AND SAID SECOND PAIR OF OPPOSITE SECTORS OF THE SECOND ROTOR BEING INTERRELATED IN SUCH A MANNER THAT DURING OPERATION THE ROTORS CONTACT EACH OTHER AT LEAST ALONG A SINGLE LINE AT ALL TIMES, INLET AND OUTLET DUCTS IN SAID CASING LOCATED ONE ON EACH SIDE OF THE SECOND ROTOR AND COMMUNICATING WITH SAID WORKING SPACE AND SEALED FROM EACH OTHER BY THE ROTORS, AND A CONTROL VALVE DISPOSED IN THAT ONE OF SAID DUCTS IN WHICH THE HIGHEST WORKING PRESSURE PREVAILS DURING OPERATION.