US1846700A - Fluid apparatus provided with cooperating rotary pistons - Google Patents

Description

Feb. 23, 1932. G. A. UNGAR 1,846,700

FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONS Filed June 11, 1930 5 Sheets-She et l INVENTOR @0577; v5 0N6? ATTORNEYS Feb. 23, 1932. G. A. UNGAR 1,846,700

FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONS Filed June 11, 1930 3 Sheets-Sheet 2' m g. 1o

INVENTOR G'usT/I vs A. UMG/uf ZWQ 5 ATTORNEYS Feb. 23, 1932.

G. A. UNGAR FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONS Filed June 11, 1930 I5 Sheets-Sheet 3 lN GUSTAV VENTOR a ,4. (/NGAR BY v o 5 ATTORNEYS tion in which cross sections taken plston Patented Feb. 23, 1932 G'OSTAVE .A. UNGAR, OF PELEAM MANOR, PATENTS INCORPORATED, OF NEW YORK,

N. Y., A CORPORATION OF NEW YORK FLUID APPARATUS PROVIDED WITH COOPERA'I'ING ROTARY PISTONS Application filed June 11,

My invention relates to pumps and other apparatus through which a fluid is caused to pass, and more particularly to apparatus of the type provided with co-operating rotary pistons. In apparatus of this type as constructed hitherto, all cross sections of the piston taken in planes perpendicular to the axis of rotation, at different points of such axis, cut the outline or periphery of the piston in profile lines which are similar, for each such cross section, bothas to shape and position; or, to express this differently, successive longitudinal or axial sections of the piston as constructed hitherto, cut the outline or periphery of the piston along lines of the same shape, generally (when theperipheries of the pistons are cylindrical, in the broad mathematical sense of the term) straight lines parallel to the axis. With these prior constructions, rotation of the pistons at a constant angular velocity has corresponded to considerable irregularities in the rate of the flow of the fluid through the apparatus. Such irregularities will occur with pistons which are cylindrical in the mathematical sense (or straight pistons, as they may be called, since their peripheral surfaces may be genera-ted by' the motion of a straight line), what- .ever profile such pistons may have. The irregularities or fluctuations will increase with an increase in the ratio betweenthe greatest and the smallest radius of the said peripheral surface. The object of my present invention is to remedy this drawback and to obtain a condition i which a practically uniform rate of fiow of time fluid will correspond to a constant angular velocity of the pistons.

For this purpose, I have devised a constructhrough a at successive points of its axis of rotation, will vary gradually from one end of the piston to the other, and in which successive axial sections of the piston likewise will cut the outline or along varyinglines.

Several satisfactory examples of my invention are shown, as examples, in the accompanying drawings, in which Fig. 1 shows one form of my invention in axial section, on line 1-1 of Fig. 2, the latter being a diagramperiphery of the piston 1930. Serial No. 460,309.

matic'cross section, substantially on line 22 of Fig. 1; Fig. 3 is a diagrammatic end view of one of the pistons shown in Fig. 2, and Fig.

NEW YORK, ASSIGNOR 'ro commaoxar.

4 is a corresponding side view, with a representation of the helical or spiral path of a point at which the two pistons come in contact; Figs. 5 and 6 are diagrams showing two difierent positions of narrow or differential slices of co-operating pistons which have an irregular output when rotating at a constant angular speed; Figs. 7, 8 and 8* are diagrammatic views, hereinafter referred to, showing that a uniform output is obtained with my invention; Fig. 8 is a section substantially on line 8"8 of Fig. 7 Fig. 9 is an axial section, and Fig. 10 is a cross section illustrating a second embodiment of my invension; Fig. 11 is a cross section of a third In Figs. 2 and 10, I indicates the inlet and i O the outlet of the casing C having two cylindrical chambers concentric with the parallel shafts S, S of the rotary pistons P, P, shown as of similar construction, except that one of them is right-hand and the other lefthand, as explained hereinafter. These pis tons are adapted to rotate in opposite direc- 1 tions at equal angular velocities, as by mounting on the shafts S, S, spur gears .G, ,G' of. equal diameters. Each piston has end faces of approximately elliptical or oval shape, the major axis ofthe ellipse or oval bein approximately equal to the diameter 0 chamber in which the piston rotates. The end faces of the same piston are alike in shape, but differ in them relative position; the major axis of one end being in a position at 9O from the major axis of the other" end, as will be seen best in Fig. 2. The minor radius half-axis) of the ellipse or oval is obtaine by subtracting the major radius the from the distance separating the centers of h the shafts S, S. The piston portion between its ends is of what may be termed of screw formation, that is to say, there. is a gradual twist from one end to the other, and any cross section of the piston (perpendicular to the axis of rotation) will be of the same oval shape as the ends, but with the axes of the ellipse shifting in position gradually as cross sections are taken at successive points lengthwise of the axis of rotation. The twist is left-hand for one of the pistons (say the lower piston P), and right-hand for the other. 7

In practice, I prefer that the pistons P, P should not come into actual contact, but leave a small clearance between the points of closest approach. This clearance will be constant in all positions of the pistons, and the line of contact, or rather of closest ap proach, will "at all times be continuous from one end face of the pistons to the other; thus there will at no time be any direct communication, or bypass, between the inlet I and the outlet 0, but the fluid has to follow an arcuate path along the inner walls of the casing chambers during the rotation of the pistons.

It will be noted from Figs. 2, l0 and 11 that the inlet 1 and the outlet 0 are diametrically opposite each other, and these inlet and outlet ports or connections, may extendpractically the full length of the pistons, as clearly indicated by the dotted rectangles in Figs. 1 and 8 The flow of the fluid both to the interior of the casing C and away therefrom, will be substantially radial and circumferential, and will not be axial as it is in certain prior devices.

If the pistons were made of approximately oval cross section, but without the longitudinal twist or screw formation described above (that is, if the pistons were shaped as oval or elliptical cylinders), the rate of the flow of the fluid, with a'constant angular velocity of the pistons, would not be uniform but attain a minimum when the major axes of the two ellipses are perpendicular to each other (Fig. 5), and a maximum when they a're parallel'to each other (Fig. 6). These minima occur in piston positions 90 apart, while the maxima occur in positions at &5" from the minima positions. This inequality in the rate of flow 'withpistons shaped as elliptical cylinders, increases with the eccentricity of the ellipse, or in other words, with the difference between the radii of the ellipse. The une en rate of flow, at a constantangular velocity of the pistons, will be understood best by a consideration of the diagrammatic Figs. 5 and 6. Fig. 5 shows the pistons A, B or slices perpendicular to the axis of rotation in a position in which their major axes are erpendicular to each other, it being understood that these pistons or slices have no twist ing the equal I with the area of the sector D, it will be obsuch as those described with reference to Figs; 1 and 2. If the pistons A, B rotate through an'angle 5, the output or delivery of piston A will momentarily be nil, since the point of contact or of closest approach'of the two pistons is at a circular arc of minimum radius. The output or delivery of piston B will be a zone sector, within the angle 5, the inner radius 1' of said sector being the minimum radius of the piston profile, and the outer radius R of said zone beingthe maximum radius of said profile. Let us designate the area of said zone sector as D, and this indicates the pump output or delivery in the position shown in Fig. 5. When the pistons A, B are in a position in which their major axes are parallel, as in Fig. 6, their rotation through the same angle 5 will produce an output or delivery equal to D D each of these two areas D and, D being a zone sector, within the angle 9, the inner radius of such sector being equal to the arithmetical mean,

is equal to the maximum radius R. Compar areas of the sectors D and D vious, since the sector D narrows uniformly toward its inner end, that the outer portions D, D are of larger area than the inner portions indicated at D In other words, each area D or D is greater than one-half of the entire sector area D, and consequently, D+D D. Thus, rotation of the pistons A, B through the same angle 5 will produce a smaller (minimum) pump delivery D in the vicinity of the position Fig. 5, and a greater (maximum) pump deliveryD'-l-D in the vicinity of the position Fig. 6. In positions intermediate between those shown in Figs. 5 and 6, the output or rate of flow will have a gradually changing intermediate value. It will thus be evident'that with straight or cylindrical pistons or slices (Figs. 5 and 6),

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the rateof flow 'will not be uniform when the pistons are rotated at a constant angular velocity, but will fluctuate between a maximum and a minimum, which are attained in piston positions 45 apart. This fluctuation increases with increase in the ratio The inequalities in the rate of fib w, at con" consideration of the diagrammatic Figs. 3.

and 4. Fig. 3 shows the piston P in the same position as Fig. 2, the point of contact with, or of closest approach to, the other piston (not shown in this view) being indicated at Y. If we consider a position 90 before reaching the one shown in Fig. 4, the point of piston P at which it was in contact with, or closest to, the other piston, would be the one indicated at X. The points X and Y areat equal distances (R) from the center or axis of the piston, but at opposite ends of the piston, as will be evident from Fi 4. Thus, during the rotation of the piston through an angle of 90?, the shifting point of contact, or of closest approach, of the two pistons would describe, on the piston P, a helical line X, Y. In other words, such point of contact or of closest approach will shift from one end of the piston to the other, during rotation through an angle of 90, and back to the first-mentioned end, during the rotation through the next 90. The path of the point of contact, or of closest approach, on the other piston, would be 'similar to the one illustrated, except that the helix would run in the opposite direction. Fig. 4 also illustrates the extension of the helical line Y X through Y, X, Y" to the full'360, showing that L, the lead of pitch of the said helical line, equals four times the width WV of the piston body.

With the twisted'form of piston explained in connection with Figs. 3 and 4, the rate of flow at constant angular speed of rotation 1s no longer fluctuating as in the slices shown in Figs. 5 and 6,.but practically uniform, since, as will also appear from Fig. 1, the pistons P, 1?, considered in axial section, have their active surfaces closer to their respective axes of rotation at one end of the.

piston than at the other, and this relation is reversed for the two pistons. Thus in Fig. 1 the active surface at the right-hand end of piston P is closer to the axis of rotation than the one at the left-hand end, while the active surface of piston P is closer to,the axis of rotation at the left-hand end of the piston than at the right-hand end. a At each moment therefore, the sum or integral of the deliveries made by all the narrow zones or slices ofthe pistons (slices perpendicular to the axes of rotation) will be constant, and

therefore the output of the ump will be constant when the pistons P, rotateat a constant angular Velocity. v

Figs. 7, 8 and 8 further illustrate these conditions, Fig. 7 showing the pistons P, P

in a position in which their major axes are parallel (45 from the position shown in Fig. 2). Within the angles or, the piston outline (in end view or cross section) is a circular arc, and the corresponding helical bands 0, c are portions of circular cylinders, the inner bands 0 being portions of a circular cylinder with the radius 1', While the outer bands 0 are portions of a circular cylinder with the radius R. The provision of cylindrical surface portions as at 0 and c, is of advantage in that it enables me to preserve at all times, adjacent to the inlet I and the I outlet 0, a suflicient amount of overlap Lto insure an eflicient seal at these points and to j prevent any short-circuiting or direct flow from the inlet I to' the outlet 0. The inter-' mediate portions 0" of the outer or active piston surfaces are twisted, or non-cylindrical. The diagram Fig. 8 shows a development of the piston circumference, and (at the right) a developed profile of the rotor or piston. Fig.- 8 is a diagram illustrating the fluid'delivery of the two pistons in the longitudinal plane indicated atww in Fig. 8.

While within such plane the delivery, or rate through the axes of both pistons when the major axes of their corresponding elliptical end faces are perpendicular to each other,

will show the line of contact, or-of closest approach, as a reverse curve one end of which is nearer to the axis of one piston than the other end. If transverse sections were taken in positions of the pistons intermediate between those just referred to, they would show a gradual transition in the longitudinal shape of the line of contact, or of closest approach.

Asa variant of the one-piece pistons the outlines of which ,have a continuous twist or screw-shape from one end to the other, I have devised a construction of such pistons in cylindrical laminations .or slices alike in shape, but secured together to form an approximation to the screw-shape shown in Figs. 1 to 4. Such approximation can be increased by using a greater number of slices, of correspondingly reduced thick ness. Figs. 9 and 10 illustrate this con- 'struction of built-up pistons. Each of the slices p or p is of the same shape, viz. that of a thin plate or slice of the form of an approximatey elliptical or oval cylinder, and can be manufactured readily by stamping sheet metal, or other inexpensive methods. The individual plates'or laminations of the same pistons are of equal thickness, and would be set in positions shifted or displaced angularly to each othen, by equal amounts, in such a manner that the angular shifting of the lastlamination relatively to the first will amount to 90, in the particular case illustrated. The laminations may be held in the proper position in any suitable manner, for instance by means of a key passing through properly positioned keyways in the iii successive laminations. If there are n laminations, the angular lead of each over its neighbor will be in the particular case referred to; for instance; with nine laminations, the angular lead, from one lamination to the next, will be 10. It is true that, considering each lamination alone, the piston outline, within that lamination, will have the shape of an ellipticalcylinder; yet the succession of these short elliptical cylinders, in somewhat step-like arrangement, as shown, will form a close approximation to the exact theoretical twisted or screw-surface described in connection with the first form of my invention. In practice, especially with a large number of laminations, this built-up construction of pistons will yield avirtually uniform rate of flow of the fluid, with a constant angular velocity of the pistons.

My invention is not restricted to pistons of elliptical or oval outline, but various other shapes may be employed. The piston outline, however, should always be symmetrical to the axis of rotation, and selected so as to provide rolling of the profile of one piston on the other, or with a constant clearance (1. c. without actual contact) when the two pistons are rotating in opposite directions with equal angular velocities. An example of such other shapes is shown in Fig. 11, where the piston hasa screw-shape, with a lead of 90 from one end to the other, as in Figs, 1 to 4 and 7 to 10, but the piston outline includes circular arcs a and a,v (for instance of 30) centered upon the axes of the respective pistons, and suitable connecting portions 6. With outlines formed partly of circular arcs, I am enabled to use circumferentially wider inlet and outlet openings at I and 0 respectively, but otherwise this form of my invention has the same advantages as the constructions described above.

Still another form of my invention is shown in Figs. 12 to 17-. Here cross sections taken through the same piston at different points. along. its axis of rotation are not of like outline, as in the constructions described above, but such outline varies lengthwise of said axis. Yet, in this form also, I use a screw formation or longitudinal twist on certain portions of the co-operating piston outlines. Each piston 19 p has cylindrical por tions 1), 19* respectively of circular cross section and of the same diameter, the axes of these portons coinciding with the axes of the respective pistons. Each pistdn 22 p furthermore has cylindrical portions p, p respectively, likewise of circular cross section,

but of a diameter smaller than that of the portions 12 ,17 and co-axial therewith. The portions p p and p, p are connected by ,corresponding to the aeaaaoo helical surfaces 12 10 respectively constitutportions 17 p respectively. The helical portions 20 p are of uniform pitch from one end face of each piston to the other, and the lead is 90 from one end to the other, as in the forms described above. On one piston, the outer or relatively raised portions p are of diamond shape in developed view (Fig. 13) and the inner or relatively depressed portions 39 are triangular, with their-bases at the ends of the piston, and their apices at its median transverse plane. On the other piston, the arrangement is reversed,.the triangular raised portions 2 matching the depressed triangular portions 19 of theother cylinder, while the diamond-shaped depressed portions 2 match the like raised portions 19*. It will be evident that the outline of each piston, in successive cross sections taken along its axis of rotaton, will vary gradually from one end of the piston to the other. The formation of the helical surfaces 39 ,7) is such that during the rotation of the two pistons their. points of contact, or of closest approach, will at all times form a continuous line from one endof the piston to the other.

Fig. 13 is a developed view, being virtually a section taken in the cylindrical surfaces (pitch surfaces) indicated in Figs. 10, 11 and 12 by the dotted circles between those inner surfaces 29 p and to the outer surfaces 10 p respectively. The left half ofFig. 13 shows the piston p arid the right half shows the piston 79 It will'be obvious that at any particular moof. three quantities: First, the quantity Q. at.

such points where the outer portion 29 of the piston p cooperates with the inner portion p of the other piston 22 second, the quantity Q at such points where the inner portion p of the piston 19 co-operates with i the outer portion 19 of the other piston 77; and third, the quantityQ, at those points where the helical portions of the two pistons co-operate. If we consider the slightly changed condition obtaining after the pistons have rotated through an angle (,0, the relative contributions to the quantities Q, and Q (Q being constant) will. have varied, but the total amount Q Q+Q +Q, remains the same, thus showing that a uniform rate of flow corresponds to a constant angular velocity of the pistons.

The construction illustrated by Figs. 12 to 17 is what may be termed a device provided with rotary pistons each having two teeth of a cross section varying lengthwise of the axis. This form of my invention might be carried out in other ways, as long as the sum of the individual flow quantities Q, Q Q, remains constant, which will be the case when the flanks of the teeth form helical surfaces of constant pitch;

I desire it to be understood, however, that my invention is not limited to a construction in which the pistons are each provided with two portions of large diameter and two portions of small diameter, or, in other words, with two teeth; the invention is applicable to constructions in which the piston has more than two teeth or points, or portions of large diameter, and particularly to the form of pumps known as gear pumps, whose pistons resemble gear wheels.

In practice, the shaft of one of the co-operating pistons (in any embodiment of my invention) is extended so that power may be applied to the device when it is used as a pump or for similar purposes, or that power may be taken from the device if it is driven by the flow of fluid.

The toothed form exemplified by Figs. 12 I to 16 gears one piston to the other and enables me to dispense with gears such as shown at G G in Fig. 1; yet even in connection with this toothed form, I consider the employment of gears (corresponding to G, G) desirable,

in order to prevent wear of the co-operating pistons.

I claim:

1. A fluid apparatus comprising a casing having an inlet and an outlet diametrically opposite to said inlet, and cooperating pistons mounted in said casing to rotate about axes located in a plane substantially perpendicular to the line joining the inlet and the outlet, said pistons having helical portions of substantially uniform pitch extending axial- 1y thereof, said inlet and outlet being substantially as wide as the axial length of said pistons, whereby a constant volume flow is obtained.

2. A fluid apparatus according to claim 1, in which the helical piston portions have a lead of from one end of a piston to the other. I

3. A fluid apparatus according to claim 1,

in which the plston is built up of laminations,

transverse to the axis of notation, said laminations being of substantially elliptical outline of like shape, but with their axes shifted by. equal angles from one lamination to the a next, to produce a helical surface.

my hand,

4. A fluid apparatus accordin to claim 1, in which the cross section of eac piston has an outline composed of circular arcs of two di erent radii and connecting portions between arcs of difi'erent radii.

In testimony swhereoef I have hereunto set GUSTAVE A. UNGAR.

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