Piston for rotary pumps
US 587907 A
Description (OCR text may contain errors)
W L AMES & T GRAY PISTON FOR ROTARY PUMPS, BLOWERS, &c.
No. 587,907. Patented Aug. 10,1897.
71 12172656 5. J/ZMM 7 UNITED STATES PATENT OFFICE.
WILLIAM L. AMES AND THOMAS GRAY, OF TERRE HAUTE, INDIANA.
PISTON FOR ROTARY PUMPS, BLOWERS, 800.
SPECIFICATION forming part of Letters Patent No. 587,907, dated August 10, 1897. Application filed July 8, 1893. Serial No. 479,976. on model.)
T0 ail whom it may concern:
Be it known that we, WILLIAM L. AMES, a citizen of the United States, and THOMAS GRAY, a subject of the Queen of Great Britain, residing at Terre Haute, in the county of Vigo and State of Indiana, have invented certain new and useful Forms of Pistons or Revolvers for Rotary Pumps, Blowers, Gas-Exhausters, Meters, and the Like, of which the following is a specification. p
The object of our invention is to provide pistons of the class mentioned which have such an outline of cross-section, taken at right angles to the axis of rotation, that they may either be made with greater accuracy or with less labor than the pistons now in use for such purposes, or that the form of cross-section may be adapted to specific purposes, or that either one or all these advantages may be obtained. We accomplish these results by making use of odontoidal surfaces, so arranged as to form a working surface for a rotary piston, which'under proper conditions is coacting with another piston the working surface of which has a like form.
By odontoidal surfaces we wish to be understood as meaning surfaces of such contour that when they have their axes of rotation in proper position and are rotated about these axes with proper and uniform angular velocities they will keep in perfect contact continuously throughout the extent of the coacting pairs of surfaces.v Our method of arrangement and construction of these surfaces is illustrated in the accompanying drawing,
which represents the cross-section of a pair of pistons, the section-outline being generated by rolling outside and inside the pitchcircle a closed curve of unequal diameters.
Describing our invention more fully by aid of the drawing, the outline of the piston-section is generated in like manner to that of the continuous epicycloidal outline generated by alternately rolling a'circle on the inside and outside of the pitch-line, but differs therefrom in that the rolling or generating curve is not a circle, but has unequal diameters.
As a particular case the drawing represents a section-outline 35 36, generated by rolling on the pitch-circle an ellipse Z, having its perimeter equal to one-fourth that of the pitch-circle and (in this case) having the describing point at the end of the major axis. When a piston of this outline is used in conjunction with a piston of like outline, perfect contact is kept up throughout a complete revolution.
By properly selecting the describing point (which may be any point of the rolling curve) the outline of the section may be varied to suit certain particular applications. For example, by taking the describing point at the end of the major axis of the ellipsealong and relatively thin section is obtained,thus adapting the pump to a larger capacity for low pressures. By taking the describing point at the endof the minor axis ashort and broad section is obtained which may be made to swell around the shaft, thus permitting the use of a large shaft and adapting the pump to high pressures.
Although we have used the ellipse as a particular case of rolling or generating curve for describing our invention, we do not confine ourselves to the use of the ellipse, but may use any other suitable closed curve excepting the circle.
Having fully described our invention, what we claim, and desire to secure by Letters iatent, is
Rotary pistons having as section-outlines odontoidal curves generated by rolling outside and inside the pitch-circle-a closed curve having unequal diameters-and having a periphery equal to one-fourth that of the pitchcircle, substantially as described.
WM. L. AMES. THOMAS GRAY;
' P. NIELSEN,