US3019964A - Vacuum pump - Google Patents

Description

Feb. 6, 1962 o. H. GRISWOLD 3,019,964

VACUUM PUMP Filed March 10, 1960 3 Sheets-Sheet 1 HOUSING HOUSING SPHERICAL THROW CONE SEGMENT AXIS l p I 4 l 1 i SHAFT Axls l CRANK L \l BEARINGS NUTATING DISK B3 F /g./

OUTLET SEPARATG NOTCH c A SHAFT a DISK B THROW AXES HOUSING TRACK 0F POINT P SHAFT ROTATATION Fly. 2

4 F/g. 3Q

2 F A 1 I K MW B r SHAFT AXIS K 2 THROW AXIS INVENTOR.

c l OWEN H. GRISWOLD Y WW ATTO R N EYS Feb. 6, 1962 o. H. GRISWIOLD 3,019,964

VACUUM PUMP Filed March 10, 1960 5 Sheets-Sheet 2 3 IN VEN TOR.

I OWEN H. GRISWOLD ATTORNEYS Feb. 6, 1962 o. H. GRISWOLD 3,019,964

VACUUM PUMP Filed March 10, 1960 3 Sheets-Sheet 3 IO 9 3. Q 1 I T I I2 I? /8 BEN J 3 9 s| 23 29 I6 34 I 240 38 24 48 INVENTOR.

OWEN H. GRISWOLD MfW ATTORNEYS United states Patent 3,019,964 VACUUM PUMP Gwen H. Griswold, Westwood, NJ. Filed Mar. 1%, 1960, Ser. No. 14,992 4 Claims. (Cl. ass-14s) This invention relates generally to vacuum pumps, but has reference more particularly to a pump which is especially adapted for use in connection with a tape recorder for an IBM computer.

The tape recorder of such a computor requires a vacuum source of 18 in. water maximum or 60 c.f.m. maximum. The maximum diameter of the pump must be 9.5 inches, with 8.5 inches preferred, and the maximum speed is 3600 rpm. The noise level of the pump is required to be low.

Efforts to develop or design a pump or blower to meet these requirements have not proven satisfactory, until an approach to a solution of the problem was made through design of a positive displacement type pump, having the simplicity of a centrifugal pump, that is, one having no contact between parts other than bearings, and having no valves.

The design in question stems from observation of rotary disc meters of the type which are generally used for metering cold water on domestic and commercial water service lines. Such a meter consists of a circular metering chamber, with a conical roof and floor divided into two compartments by a nutating disc. The disc does not rotate about its own axis, but the shaft on which it is mounted generates a cone with its apex downward. Motion of the disc is guided by two half-balls mounted upon it, and with each revolution, a fixed volume of water passes through. The circular motion of the upper end of the disc shaft operates the counting gears of the water meter.

The theory in designing a pump, based on the above principle of operation may be described in connection with FIGS. 1 to 3b inclusive of the accompanying drawings.

In FIG. lot the drawings, a pump is diagrammatically shown, utilizing a crank shaft, with its throw inclined, so that its axis intersects the axis of the driving shaft. The throw axis describes a cone when the shaft is rotated, said cone having its apex at the intersection of the axes and its centerline or cone axis coincidental with the shaft axis. Now if a plate or disc is mounted on the centerline of the throw axis at the intersection of this axis with the shaft axis by means of a hearing so that it can rotate, it is possible to restrain the disc from rotating about its axis, and to make it nutate by rotating the shaft. The volume swept by such a disc is defined by two cones having axes coincidental with the shaft axis and having their apices at the point of intersection of the shaft and throw axes. This volume will be bounded annularly by a spherical segment, such as that taken from the center of a sphere. The walls forming the boundary of this volume form the housing of the pump.

Referring to FIG. 2 of the drawings, if a notch is cut in the nutating disc and a separator or wall is placed across the housing, separating the inlet and outlet openings, fluid will be drawn into the housing through the inlet, when the shaft is rotated in a counterclockwise direction, and will be exhausted through the outlet opening. The inlet and outlet or exhaust may be located either in the annular spherical part of the housing or in either of the conical parts of the housing, or in a combination of these parts. Reversing rotation of the shaft reverses the flow of the fluid. It may be noted, in this connection, that the pump produces both positive and negative pressures. It may also be noted that this is a reversible process, and that the pump becomes a motor by forcing fluid into either side of the separator, thus making the motor easily "ice and quickly reversible and permit braking action on the output shaft.

Having reduced the pumping theory to practice, it was found that there was considerable vibration, and therefore noise, in the unit, requiring an investigation of the causes for this.

A study of the nutating disc reveals (see FIG. 3a) that all forces tending to cause rotation or oscillation are balanced within the disc. It is further seen that all centrifugal forces are balanced and therefore the forces causing unbalance are all normal to the plane of the disc and are due to acceleration. To demonstrate these forces acting on the disc due to acceleration let us consider all of the points on the disc at a given radius, say at the periphery. With reference to FIG. 3a, a side view of a nutating disc, the points B and B, have attained constant velocity and therefore their acceleration and the resultant force is zero. The points A and C have zero velocityv and maximum acceleration because they are changing direction and their resulting forces are in the direction as shown by FIG. 3b a view taken at to FIG. 3a. From A to B (and from C to B the points are being accelerated and their resultant forces are in the same direction as at point A (and 'C) and decrease in magnitude from A to B (and from C to B as shown in FIG. 312. From B to C (and from B, to A) the points are being decelerated and the resultant forces reverse direction at the B 13 axis and increase from zero at B (and B to a maximum at C (and A) as shown by FIG. 3b. We now see that we have no force along the disc axis B 13 and that the forces increase in magnitude from this axis to a maximum at A and C.

The summation of the forces on one side of axis B -B can be made equal to a single force F acting on an axis perpendicular to B -B through the center of the disc. Similarly, forces acting on the other side of B -B may be replaced by a single force F It may now be seen that the forces acting on the nutating disc are equal to a couple acting about the axis B B As the driving shaft rotates, the axis B +B and the force couple rotates with it, even though the disc does not rotate.

Further development shows that the aforesaid theory is true for any thin disc of symmetrical mass. The magnitude of the forces F or F varies as the square of the angular velocity of the rotating shaft and directly with the mass and the radius of the center of mass, according to the formula:

This is also the formula for centrifugal force, and therefore two centrifugal Weights W and W attached to the rotating shaft will balance the inertial forces F A and F providing they meet the following conditions:

(1) Their centers of gravity must be in the plane containing F and F (2) The product of their mass times the distance to their center of gravity must be equal, as indicated at the right in FIG. 3b, and as expressed by the following formula:

produced by F times the distance from F to F (see FIG. 3b), as expressed in the following formula:

In applying the aforesaid balance theory to a pump, to be presently described, it has been found that the mass of the nutating disc is asymmetrical, due to the notch or recess through which the separator plate passes. Since the opposed centrifugal moment is constant (for a given speed) then the inertia of the disc and its moment must be a constant. To accomplish this, balancing slugs must be added to the disc or its hub such that the inertia is the same on any axis in the plane of the disc. It is also desired to emphasize that the disc cannot be balanced by substracting mass from the heavy side as in the case of static or dynamic balancing, since this would increase the difference in moments, resulting in increased vibration.

In FIGS. 4, and 6 of the drawings, there is illustrated a pump embodying the theories which have been developed and described above with reference to such a pump. In these views,

FIG. 4 is a top plan view of the pump;

FIG. 5 is a bottom plan view of the pump, and

FIG. 6 is a view, partly in elevation, and partly in section, taken on the line 6-6 of FIG. 4.

Referring more particularly to FIGS. .4, 5 and 6 of the drawings, a pump is disclosed, which comprises a housing consisting of an upper portion 1 and a lower portion 2, which are secured to each other by means of circumferentially-spaced bolts 3 and nuts 4. The housing, as thus provided, includes an upper conical wall 5, a lower conical wall 6 and an outer wall 7 in the form of a spherical segment, which interconnects the walls 5 and 6.

Extending upwardly from the upper portions 1 of the 1 housing is a series of circumferentially-spaced posts 8, to the upper ends of which a cover plate 9 is secured, as by means of screws 10. The plate serves as a mounting for the housing 11 of an electric motor, the housing being properly located with respect to the plate as by means of a pilot boss 12 of the housing 11 which extends into a central opening 13 in the plate 9. The housing 11 is secured to the plate 9 by means of bolts 14.

The motor, as shown, is disposed with its shaft 15 in a vertical position, and afiixed to the shaft 15, as by means of a pin 16 and a key 17, is a crank 18.

The crank 18 is made as a single casting, which consists of a part 19 and a part 20. The part 20 serves as a housing for a bearing 21, which is retained in the housing 29 by means of a plate 22, which is supported in position by means of bolts 23 which extend through the housing 2i).

Disposed within the bearing 21 is the upper portion of a shaft assembly or unit, generally designated by reference numeral 24, and consisting of a lower hemispherical sealing portion 25, a mutating disc 26, a hemispherical seal 27 which clamps the disc 26 (to the portion 25, a spacer 28, which spaces the seal 27 from the bearing 21, a washer 29 disposed above the bearing 21, and a nut 30 which is secured to a threaded extension 31 of the shaft and which holds the assembly together and also locates the assembly in the bearing.

The seals and 27 do not make contact with the pump housing into which they extend, but instead, small clearances are provided as indicated at 3-2. Likewise, there is a small clearance between the disc 26 and the housing faces along their apparent areas of contact, as indicated at 33. There is also a small clearance between the periphery of the disc 26 and the outer Wall 7 of the pump housing, as indicated at 34.

The disc 26 is restrained against rotation about its axis by a flexible shaft assembly or unit, which consists of a shaft, comprising an intermediate, portion 35, which can bend or flex, and solid fittings 36 and 37 which are brazed or swaged to the ends of the portion 35. The fitting 36 is fixed to the upper end of the shaft assembly 24 by means of a pin 38, which, as shown in FIG. 6, extends diametrically through the fitting 36 and into openings 24a and 24b which extend diametrically through the shaft assembly 24. The fitting 37 is frictionally clamped be tween a clamp portion 39 of the housing portion 2 and a clamp element 40 (see FIG. 5), the clamp element 40 being secured to the clamp portion 39 by means of bolts 41 and nuts 42. To further insure against rotation of the fitting 37 in the clamp portion 39 and clamp element 49, the fitting 37 is provided with a pin 38a which extends diametrically through the fitting and is provided with ends which extend into the space between the clamp portion 39 and clamp element 40.

Since the fitting 36 is thus fixed to the upper end of the shaft assembly 24, the upper end of the flexible shaft cannot rotate relatively to the shaft assembly 2-4, and since the shaft assembly 24 includes the nutating disc 26 which is clamped between the sealing portion 25 and seal 27, which are part of the shaft assembly 24, it follows that the upper end of the flexible shaft is fixed to the nutating disc 26 and cannot rotate relatively to the latter.

Since the fitting 37 is fixed between the clamp portion 39 of the housing portion 2 and the clamp element 40, in the manner described above, it follows that the lower end of the flexible shaft is fixed to the pump housing and cannot rotate relatively to the latter.

As stated above, the disc 26 is restrained against rotation about its axis by the flexible shaft assembly or unit, which has been described, so that the disc is confined to a purely nutating movement.

The mutating disc 26 has a V-shaped notch or recess 43 therein, and this notch or recess is located in fixed and proper position relatively to the pump housing by means of a pin 44, which extends through the disc and the portion 25 of the shaft assembly 24.

Extending transversely between the pump housing parts is a separator plate 45, this plate extending through the central portion of the notch or recess 43 in the disc 26, and radially inwardly to the portions '25 and 27 of the shaft assembly 24. The separator plate also extends through an opening 46 in the wall 7 of the pump housing and is secured to lugs 47 extending from the housing parts 1 and 2, as by means of bolts 48 and nuts 49.

The pump inlet opening 50 is located in the conical wall 6 of the pump housing at one side of the separator plate, while the portion of the opening 46 behind the separator plate shown in FIG. 6, constitutes the exhaust or outlet opening of the pump.

The pump is resiliently mounted on a base plate 51 by means of an extruded rubber P ring 52, and is secured to the base plate by means of three bolts 53, washers 54 and rubber pads 55 being interposed between the heads of these bolts and the base plate. The P ring 52, and pads 55 also serve as gaskets and seals for the chamber 56 between the pump housing and the base plate, which chamber is a part of the intake system of the pump.

A pipe 57 is provided as an intake connection to the pump, and in this case, a rubber hose (not shown) connects the pipe 57 to the computer to which reference has been made.

The base plate 52 is provided with a multiplicity of circumferentially-spaced bosses 58 having tapped holes, which are used to bolt the pump to a computer mounting plate 5?. The pipe 57 extends through an opening in the computer mounting plate to .a compartment (not shown) below this plate. The use of a separate base plate 51 not only permits resilient mounting of the pump, but also facilitates adaptation of the pump to other uses or applications where the configurations of inlets and mounting holes are different than those shown.

The part 19 of the crank casting 18 acts as the centrifugal weight W which has been described in connection with FIG. 3b of the drawings. To provide additional mass for the part 19 of the crank casting, if necessary, a round lead slug (not shown) may be inserted in such part of the casting. This additional mass may also be provided in the form of an iron balance weight (not shown) which may be clamped to the part 19 of the casting by means of a separate saddle clamp, bolts and nuts.

The part 20 of the crank casting 18, together with the bearing 21 and part of the shaft assembly 24, constitutes r the centrifugal weight W which has been described in connection with FIG. 3b of the drawings.

In order to oifset or, balance the weight lost by formation of the notch or recess 43 of the nutator disc 26, a balancing slug or weight 60 is added to the portion 25 of the shaft assembly 24. Such balancing slugs may also be added to the portion 27 of the shaft assembly, if necessary. Instead of such balancing slugs, lead buttons (not shown) may be inserted on each side of the notch in disc 26, for offsetting or balancing the weight lost by formation of the notch or recess 43.

A metal band or collar 61 may also be secured to the posts 8 of the housing, for concealing the crank mechanism and to improve the appearance of the pump, as a whole.

The use and operation of the pump, as described, will be apparent, and a detailed description thereof is believed to be unnecessary.

The pump, in tests, fully meets the requirements set forth at the beginning of the application, and develops a pressure of 19 inches water.

Due to the provision of the various weights, as described, the pump is properly balanced, and is substan-- tially free from vibration and noise, in operation.

While a given point on the disc nutates from the top of the housing to the bottom of the housing and vice versa, as shown by the track of point P in FIG. 3a, successive points around the disc come very near to the conical surfaces of the housing, thereby having the effect of rolling the disc around the conical section of the housing, and squeezing the fluid ahead of it on both sides. Due to the clearances provided, the disc and housing do not come into contact at any time, nor does the disc ever come into contact with the separator plate.

The V-shape of the notch in the disc is the most efficient shape, although the notch does not necessarily have to be V-shaped. The V-shape permits the greatest angular clearance over the separator, while permitting maximum disc area for pumping. The notch can be of uniform width, but must be wider than the combined thickness of the separator plate and the width of the track of point P, as shown in FIG. 3a, in order to avoid contact of the disc with the plate.

It is to be understood that the form of my invention, herewith shown and described, is to be taken as a preferred example of the same, and that various changes may be made in the shape, size and arrangement of parts thereof, without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a pump of the character described, a housing having end walls of conical shape and having a common conical axis, and a side wall of spherical shape interconnecting the peripheral edges of said end walls, a separator plate extending transversely between said end walls at one side of said common conical axis, a disc disposed between said conical walls and adapted to nutate therebetween, said disc having a recess therein through which said separator plate extends, means for nutating said disc, said means comprising a drive shaft coaxial with said common axis, and crank means driven by said drive shaft, said crank means being weighted at one side of said common axis to statically counterbalance the weight of said crank means at the other side of said common axis, said weight being axially displaced relatively to said crank means an amount to deliberately produce a dynamic unbalance or force couple equal in magnitude but opposite in direction to the force couple produced by the forces of acceleration of the nutating disc, and means associated with said disc for balancing the unbalanced inertia forces in said disc due to the recess therein through which said separator plate extends.

2. In a pump of the character described, a housing having end Walls of conical shape and having a common conical axis, and a side wall of spherical shape interconnecting the peripheral edges of said end walls, a separator plate extending transversely between said end walls at one side of said common conical axis, a disc disposed between said conical walls and adapted to nutate therebetween, said disc having a recess therein through which said separator plate extends, means for nutating said disc, said means comprising a drive shaft coaxial with said common conical axis and a shaft assembly aflixed to the central portion of said disc and extending from said disc at an angle to said common conical axis, and a flexible shaft having one end connected to said shaft assembly and its other end connected to said housing, whereby said flexible shaft, during mutation of said disc, prevents said disc from rotating about its own axis.

3. A pump, as defined in claim 2, in which said flexible shaft extends through said shaft assembly and through the said disc, and is connected to said housing at a point along said common conical axis.

4. In a pump of the character described, a housing having end Walls of conical shape and having a common conical axis, and a side wall of spherical shape interconnecting the peripheral edges of said end walls, a separator plate extending transversely between said end walls at one side of said common conical axis, a disc disposed between said conical walls and adapted to nutate thcrebetween, said disc having a recess therein through which said separator plate extends, said disc having an axial opening, a shaft assembly clamped to the central portion of said disc and extending at an angle to said common conical axis, said shaft assembly comprising a portion which extends through said disc opening and has a cavity therein, means for nutating said disc, said means comprising a shaft coaxial with said common conical axis and means connecting said shaft with said shaft assembly, and a flexible shaft having one end connected to said portion of said shaft assembly, said flexible shaft extending through said cavity and having its other end connected to said housing at a point along said common conical axis, whereby said flexible shaft, during nutation of said disc, prevents said disc from rotating about its own axis.

References Cited in the file of this patent UNITED STATES PATENTS 1,638,183 Bylger Aug. 9, 1927 2,083,070 Krueger June 8, 1937 2,773,453 Gemeinhardt Dec. 11, 1956 2,887,059 Cornelius May 19, 1959 FOREIGN PATENTS 15,766 Switzerland Nov. 30, 1897 341,903 France of 1904

Images