US 2621603 A
Description (OCR text may contain errors)
- Dec. 16, 1952 J. B. THOMAS ROTARY PUMP Filed Aug. 31, 1948 4 INVEN J. B THOM ATTORNEY changing the capacity of the pump.
Patented Dec. 16, 1952 UNITED STATES PATENT OFFICE Claims.
This invention relates to pumps and more particularly to a rotary pump in which the rotor may be provided with teeth of any desired length with- :in practical limits whereby the capacity of the pump may be greatly increased without materially increasing the external dimensions thereof.
Rotary pumps of the type employing a hollow internal gear forming a rotor and an idler gear having teeth meshin with the rotor have previously been made with the rotor machined from a solid casting or forging, it being customary to form the teeth of the rotor in a milling machine by the use of an end mill. The faces of these teeth must be accurately machined in order to mesh properly with the teeth of the idler gear and in order to provide an efficient pumping action. The length of these teeth has heretofore been limited by the end mill employed for machining the same since the depth of out which may be taken by an end mill is determined largely by the diameter of the mill, good practice dictating that this depth be not greater than twice the diameter of the mill. Attempts to use end mills of this type in machining surfaces of gear teeth and other articles to a greater depth have resulted in bendin or springing of the mill with consequent inaccurate surfaces being formed which in gear teeth of the type utilized in pumps of the type with which we are here concerned would result in tapered rather than parallel surfaces on the teeth, which parallel surfaces are absolutely necessary for proper and efficient operation of the p p.
The capacity of pumps of this type may be varied by changing the diameter of the rotor, by changing the length of the rotor, and of course, within limits, by changing the speed of rotation thereof. Since in most applications the speed of rotation is that which is optimum for the pump employed and since the speed usually cannot readily be changed, we may for the purposes of this application disregard speed as a factor in In the majority of installations in which these pumps are employed, space is a prime factor and since the diameter of the pump must be increased very materially in order to increase the capacity to any great extent, it is frequently inconvenient if not impossible to incorporate pumps of sufficient diameter in a given apparatus in order to produce the capacity necessary for the operation being performed. On the other hand, the capacity of pumps of this type may be very materially increased by a comparatively small increase in the length-of the teeth on the rotor, and consequently for a given increase in capacity the additional space required when increasing this capacity by lengthenin the teeth is considerably less than when attempting to obtain the same capacity by increasing the diameter.
In present structures utilizing the milling machine method of forming teeth on the rotor, it is possible with a given diameter to obtain a pump having capacities ranging between 5 and gallons per minute, whereas if capacities above this figure are desired it is necessary to increase the diameter materially, which will result in an optimum capacity of approximately 200 gallons per minute. By utilizing longer teeth on the rotor rather than increasing the diameter of the pump it is possible, and by utilizing applicant's invention practical, without materially increasin the weight or size of the pump to obtain any capacity desired between 90 and 200 gallons per minute. The use of longer teeth also materially increases the area of tooth surface which is in frictional contact with the fluid being pumped and when this fluid contains a large percentage of grit, as it does in a great many installations, the life of the pump is materially increased over those in which increased capacity is obtained by enlarging the diameter.
It is therefore an object of this invention to provide a rotary pump in Which the capacity may be determined by providing a rotor having teeth of any desired length and in'which the contour of the teeth is maintained within the necessary tolerances thereby making possible the design of a pump of this type having maximum capacity butminimum size and weight.
It is a further object of this invention to provide a method of constructin a hollow internal gear type pump rotor having teeth of any desired length and in which the surface contour of the teeth may be maintained within the necessary manufacturing tolerances.
Further objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanyign drawings, wherein:
Fig. l is a perspective view of a rotary .pump incorporating the rotor of this invention and with parts broken away for greater clarity;
Fig. 2, a sectional view in elevation showing a rotor of the type previously used in rotary pumps;
Fig. 3, a top plan view of a rotor constructed in accordance with this invention;
Fig. 4,'an elevational view in section taken on theline 4-4 of Fig. 3 and showing the manner of securing the rotor teeth in position; and,
Fig. 5, a perspective View of a tooth prior to assembly with the rotor.
With continued reference to the drawing, there is shown in Fig. 1 a rotary pump I!) having a base II, a discharge outlet I2 and an inlet not shown. The pump I is provided with a generally circular casing I3 provided with a fixed rear wall I4 and a removable front wall I5 which may be secured in place by screw threaded fasteners or the like I6. Internally of the casing I3 there is provided a rotor I! havin a plurality of gear teeth I8 projecting from and secured to a driven plate I9. Plate I9 is maintained on and driven from a shaft rotatably supported in the rear wall M of the housing I3, a suitable bearing and stufling box being provided therefor. Teeth I8 are machined to form an internal gear and these teeth are designed to mesh with the teeth 29 of an idler gear 2I mounted for rotation on a stub shaft 22 which may be secured in the front Wall I5 by a. nut or the like, the idler gear 2I being lubricated by a grease cup or other lubricating means 24.
The idler gear 2I is mounted eccentrically of the rotor I1 and as is common in this type of pump, a partition or baffle 25 is provided between the ends of the idler gear teeth 29 and the internal surface of the rotor teeth I8 in the area in which the idler is spaced from the rotor.
A rotor of the type heretofore used in these pumps is shown by way of illustration in Fig. 2 and comprises a solid cast or forged body 23 having a drive shaft 21 secured thereto by a key or the like 28, the teeth 29 being formed by an end mill operating vertically to machine the side faces 30 to the contour desired. It will be noted from A rotor constructed in accordance with this invention is shown in detail in Figs. 3 and 4 in which the plate I9 is secured to a drive shaft 3| by a key or the like 32 and a collar 33 welded or brazed to the plate I9 at 34. Plate I9 serves to support and drive a plurality of gear teeth I8 and these teeth are formed with longitudinal surfaces 35 of the proper contour for engagement with teeth 20 of the idler gear 2|. Teeth I9 may be machined separately in any desired manner, such as by use of a form cutter on a planer or milling machine and a single individual tooth I3 is shown in perspective in Fig. 5 and as will be seen from an inspection of this figure the tooth is provided at its inner end with a reduced cylindrical portion 36 adapted for reception in an aperture 31 in plate I9. Reduced portion 35 is of such a diameter as to have a relatively tight fit in aperture 3'! thus properly positioning the tooth I9 coaxially with the shaft 3 I.
The necessary number of teeth I8 are machined and positioned in their corresponding recesses 31 in plate I9 whereupon the loosely assembled rotor is inserted in a jig or fixture to properly orient the teeth so that the surfaces 35 thereof will be in position to properly engage teeth 20 of idler gear 2| and while held in the assembly jig a hole 38 is drilled radially into the peripheral edge 33 of the plate I9 through the reduced portion 36 of the tooth I9 and into the material of the plate at the opposite side of the aperture 31. Tightly fitting dowel pins 40 are then driven into these holes to lock the teeth I8 in position in the plate I9. The rotor is then removed from the assembly jig or fixture and the teeth I8 permanently secured in place by brazing, welding or otherwise adequately securing the reduced portion 36 to the plate I9 at 4 I.
It will be noted from an inspection of Fig. 4 that the teeth I8 are considerably longer than twice the minimum distance between adjacent teeth and as a matter of fact these teeth may be made any desired length within the strength characteristics of the material employed for the teeth. Consequently a rotor with considerably longer teeth than those heretofore possible may be constructed and utilized in a rotary pump of the type described above to materially increase the capacity thereof without increasing the diameter and only slightly increasing the length thereof.
It has been found that pumps utilizing rotors constructed in accordance with this invention, while having a greater capacity than heretofore possible within the same dimensions also possess much longer wearing qualities in that the tooth area in contact with the fluid being pumped is considerably greater, thus reducing the wear per unit area and furthermore the load is distributed over a considerably larger area rather than being concentrated thus further reducing strain and wear.
It will thus be seen that by this invention there has been provided a relatively simple and eificient rotor for the purpose intended which is economical to produce and which exhibits increased wearing characteristics, thus resulting in the production of pumps of relatively small weight and dimensions yet having high pumping capacities and relatively long life.
It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and. therefore the invention is not limited by that which is shown in the drawings and described in the specification but only as indicated in the appended claims.
1. A rotary pump comprising a casing, a driven toothed rotor rotatably mounted in said casing and an idler gear rotatably mounted in said casing and having teeth meshing with the teeth on said rotor, said rotor comprising an end plate, a driving shaft secured to said plate centrally thereof and extending from one side only, a plurality of apertures in said plate disposed in a circle adjacent the outer edge thereof, a plurality of gear teeth having reduced extensions disposed in said apertures and extending axially of said plate to form a hollow gear, said extensions being secured in said apertures by dowels and brazing, the length of said teeth being greater than twice the minimum distance between tWo adjacent teeth.
2. A rotary pump comprising a casing, a, driven toothed rotor rotatably mounted in said casing and an idler gear rotatably mounted in said casing and having teeth meshing with the teeth on said rotor, said rotor comprising a driven end plate and a plurality of teeth removably secured to said plate and extending axially thereof the length of said teeth being greater than twice the minimum distance between two adjacent teeth.
3. In a rotary pump having a casing, a hollow gear type rotor and an idler gear meshing with said rotor, the improvement consisting in providing said rotor with individually formed and removably attached teeth of a length greater than twice the minimum distance between two teeth whereby the capacity of said pump may be varied by utilizing rotors having teeth of different lengths.
4. A method of making a hollow gear type pump rotor comprising providing an end plate, formin a plurality of apertures in said plate disposed in a circle adjacent the outer edge thereof, machining a plurality of teeth of the desired contour and of a length greater than twice the minimum distance between two adjacent teeth, forming a reduced extension on one end of each tooth, assembling said teeth with said plate by inserting said extensions in said apertures, accurately positioning and holding said teeth while inserting dowels through said extensions into said plates and finally brazing said extensions to said plate.
5. A method of making a hollow gear type pump rotor comprising providing an end plate, forming a'plurality of apertures in said plate disposed in a circle adjacent the outer edge thereof, machining a plurality of teeth to the desired contour and of a length to provide the desired pump capacity, forming a reduced extension on one end of each tooth, assembling said teeth with said plate by inserting said extensions in said apertures, accurately positioning and holding said teeth while inserting dowels through said extensions into said plate and finally brazing said extensions to said plate.
JULIAN B. THOMAS.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS