US2471484A - Piston and cylinder construction for reciprocating hydraulic motors - Google Patents

Description

y 1949- g L. E. GODFRIAUX 2,471,484

PISTON AND CYLINDER CONSTRUCTION FOR RECIPROCATING HYDRAULIC MOTORS Filed Sept. 20, 1944 3 Sheets-Sheet 1 FIGJ.

Louis E. Godfrz'dmt INVENTORE' ATTORNEY. Y

May 31, 1949 L. E. GODFRIAUX PISTON AND CYL 2,471,484 INDER CONSTRUCTION FOR Filed Sept. 20, 1944 REC I PROCAT ING HYDRAULI C MOTORS 3 Sheets-Sheet 2 FIG. 3.

MOTOR Louis 2.60 rzaux SUM? 4 ms-rmzu'roa REVERSIHG' VALVE PUMP i INV NTOR.

' ATTORNEY May 31, 1949.

. L. PISTON AND CYLINDER CONSTRUCTION FOR RECIPROCATING HYDRAULIC MOTORS Filed Sept.- 20, 1944 3 Sheets-Sheet 3 A LoubEGad/rz'aux INVENTOR.

ATTORNEY E. GODFRIAUX 2,471,484

Patented May 31, 1949 I PISTON AND CYLINDER CONSTRUCTION FOR RECIPROCATING HYDRAULIC MOTORS Louis E. Godi'riaux, Madison, .Wis., .assignor to Gisholt Machine Gompany,-. Madison, Wis., a corporation of Wisconsin Application September 20, 1944, Serial No. 554,883

3 Claims. (01. 121120) This invention relates to a hydraulic motor of high torque efficiency at low speeds.

The invention has as its principal object the construction of motors adapted to operate with a substantially constant torque output with any given pressure over a very wide range of speeds, as, for instance, from onlya fraction of a revoluper minute to over a hundred revolutions a minute.-

Another object of the invention is to provide a small compact hydraulic motor of relatively high torque output.

A more specific object is to provide a multicylinder piston type hydraulic motor employing individual rotary cam members for transforming the power stroke of each piston into rotary motion.

A further specific object is to provide a rotary cam member capable of delivering a substantially constant torque force to the shaft during the working stroke of its respective piston.

Another object is to reduce the overlap of the torque force of successive cylinders to obtain a more uniform torque output for the motor.

In carrying out the invention the rotary cam member secured on the motor shaft is designed to be turned or rotated approximately uniformly 'as the piston moves uniformly in its working stroke, and a suflicient number of pistons are employed to engage either the same cam member or similar individual cam members to provide a substantially constant torque force for the motor shaft. The cam members are further designed to provide a nearly constant torque force during the overlap between the successive working strokes of the several pistons when the latter are accelerating and decelerating.

An embodiment of the invention is illustrated in the accompanying drawings in which:

Figure 1 is a longitudinal central section through the motor axially of its shaft;

Fig. 2 is a transverse section through the motor taken on line 22 of Fig. 1 centrally of one of the cylinders;

Fig. 3 is a schematic illustration of the fluid circuit for the motor; and

Fig. 4 is an enlarged diagrammatic illustration of the method of laying out the cam. v

The motor comprises, in general, a motor shaft i and a plurality of power cylinders 2 disposed in a housing 3. A suitable distributor 4 is geared to the shaft l to be driven in synchronism with the motor for controlling the distribution of pressure fluid to the cylinders 2.

The shaft l is mounted to rotate in bearings 5 in housing 3, and to extend from the housing at one end where a worm gear 6 secured upon the shaft drives a suitable-power shaft 1.

r The shaft I has a plurality of cam members 8 integral therewith and disposed in axially spaced relation correspondingwith the spacing of the centersof cylinders 2.

Each cylinder 2 has apiston 9 operating therein and carrying a roller III which is mounted on suitable bearings at the outer end of the piston. The roller ID of each piston is adapted to engagethe corresponding cam member 8 and to drive the same during the working stroke of the piston.

The pistons 9 are driven upwardly in succession by the timed admission of pressure fluid into the corresponding cylinders 2 through the port II for each cylinder. The distributor furnishes and controls the inlet of pressure fluid to the respective cylinders in order to raise the corresponding pistons therein successively and provide the power strokes for the pistons.

Just after the piston 9 for each cylinder reaches its uppermost position the supply of pressure fluid beneath the same is cut off by distributor 4 and the distributor then exhausts fluid through port H. The piston 9 thereupon lowers partially by its own gravity, but more particularly by the engagement of the back side'of cam member 8 with roller l0 driving it downwardly.

The cam members 8 are constructed of curved cam contour having a major and minor axis representing the outer and inner extremity of the piston movement, respectively. The shape or contour of the cam in that portion of the movement of the piston representing the power stroke is such that for each increment of vertical movement of the piston there will be a corresponding increment of rotation of the'cam and the roller I I! will be kept'in pressure contact with the cam throughout the movement. The shape or contour of the cam in the remaining portion of its surface is relatively unimportant, although it is preferable to provide a similar curve on the back side of the cam so that the motor can be reversed in direction of operation.

In designing the cam 8, the curvature is laid out by taking determined increments-of movement of roller l0 along the radius of shaft I, and plotting the surface of the cam for corresponding increments of rotation of the shaft, the surface of the cam being located at the point of contact of the roller l0 so that the latter will always be in contact with the cam during the working stroke.

A specific method of laying out one quadrant ofthe cam 8 is illustrated in Fig.4 in which line A-A is the longitudinal center line for the cam and line B-B is the transverse center line at right angles to line A-A. C is the center of the cam and is located at the intersection of lines A-A and B-B. The ends of the cam are first drawn as short arcs with C as the center and with a radius equal to one-half the proposed length of the cam.

LineC-D is then drawn at an angle of 10 to line A-A and point E is located on the line at the center of the roller it when the latter rides on the end of the cam at itsmaximum distance from C.

Line C-F is then drawn at an angle of 60 to line -D and point G is located on'the line at the center of the roller l0 when the latter is at its minimum distance from point C in the operation of the motor, as determined by the layout of the working stroke for the piston 9.

The point E is transposed to line C-F and the distance E-G is then divided into six equal spaces to provide intermediate points H, I, J, K and L, reading outwardly from point G.

The 60 angle between 0-1) and C-F is divided into six equal angles of each to provide intermediate lines C-M, C-N, C-O, C-P and C-Q, reading from line CF toward C-D.

Point H on line 0-1 is then transposed to the adjacent line C-M; point I is transposed to the next line C-N; point J is transposed to line C-0; point K is transposed to line 0-1; and point L is transposed to line CQ. These points represent respective locations for the center of roller H) as the latter rides along the cam.

The several locations for roller III are then outlined with the original points E and G and the transposed points H, I, J, K and L as centers.

The curve of the cam 8 representing the working stroke is then drawn tangent to the roller at the several positions referred to to constitute the cam surface Rr-S- R is the point at which the cam surface intersects the end are of the cam. S is the point of the working cam surface nearest 0.

A central curve S-S is drawn to connect the working cam surfaces of two adjacent quadrants of cam 8. The end arcs R-R represent idling arcs when the piston 9 is retracted to the lower end of its cylinder while the arcs S-S represent the idling arcs when the piston 9 is extended from its cylinder and at the top of its stroke.

The curves R,-S in alternate quadrants of the cam 8 represent the working cam surfaces for the motor by which the cam is driven by piston 9, and those in the intermediate quadrants represent the cam surfaces for the return strokes of the piston. Each cam surface R-S is active for a little over 60 of rotation of the cam 8 and since there are three cylinders, each having two working strokes per revolution of the cam, a substantially constant torque is provided for the entire 360 of revolution of the cam. The slight amount of overlap provided by the movement of roller in when its center approaches point E is suflicient to join the power strokes of successive pistons. When the center of roller l0 leaves point G the curve S-S preferably causes the roller to stop in its inward movement except for a slight overla in transmitting the torque load to the next active piston 9.

Two working strokes of the piston III are obtained for each revolution of the cam by providing the latter with two diametricaly opposite cam projections of major axis, as shown in Fig. 2.

The curve of the cam 8 in the region of contact of roller l0 during the working stroke of the piston produces a constant torque or turning moment on shaft 1 when a constant pressure of oil is applied to the piston 9. The speed of movement or of rotation of shaft I is dependent upon the volume of oil supplied to the cylinder in a given time.

In order to apply a constant torque to shaft I, the three cylinders have their corresponding cams ofiset circurnferentially on shaft 1 so that each working stroke of a piston drives the shaft through slightly more than one-sixth of a revolution and the several pistons operate in succession ,sion of power strokes necessary in driving the shaft. The sequence of admission and exhaust of oil from the respective cylinders should correspond with the positioning of the respective cams to provide the required succesto apply a continuous torque to the shaft. It is possible to provide a larger number of cylinders, each corresponding to a smaller portion of the rotation of the shaft. Where two cylinders only, are employed there is some difllculty in obtaining sufficient overlap to have a constant torque forthe motor.

Three cylinders have been found to be most satisfactory since with that number it is possible to provide eificient cams for transforming the radial movement of the pistons into rotary movement of the shaft with a minimum of overlap between successive pistons. The actual overlap may be considerably less than 15% of the total cycle of movement and is controlled by the cam contour to provide a cumulative effect during overlap approximately equal to the desired constant torque value.

While the cylinders have been described as being disposed side by side in parallel relationship in a common plane, it is possible to arrange them in other relationships wherein they act upon one or more cam members to apply the desired torque to the motor shaft. However, for compactness of structure, it is preferred to mount the cylinders in an axial plane as shown, wherein each piston engages a separate cam member.

There is a key l2 extending through each cylinder wall and into a longitudinal slot l3 in the corresponding piston 9 to prevent rotation of the pistons on their respective axes, so that the rollers Ill are maintained parallel to the shaft l.

Each of the cylinders 2 is of substantial length and the corresponding pistons 9 are long to provide for a substantial bearing surfacebetween the pistons and the cylinder walls and preventwear from side thrust of the cams 8 against the rollers Ill. The pistons 9 are tubular at their inner ends and telescope over a central tubular plug [4 secured to the end of the cylinder around the corresponding port II. The movement of the piston downwardly during the exhaust stroke effects a rapid flow of the liquid over the upper edge of plug l4 and down therethrough to port I l and tends to drive out any gas bubbles that may have formed in the cylinder.

Referring to Fig. 3, the distributor 4 has a connecting passage l5 leading to each port II. An inlet pipe l6 supplies power fluid to the distributor 4, and an exhaust pipe l1 receives exhaust fluid from the distributor 4. In operation the motor may be reversed by valve means l8 for reversing the connections to pipes l 6 and 11 so that pipe ll may be utilized to supply power fluid to distributors 4 and pipe l6 utilized to exhaust fluid from distributor 4. This reversal of operation of the having a port therein for the admission and exhaust of pressure liquid for the cylinder, a piston disposed in said cylinder, a cylindrical skirt for said piston extending from the piston crown toward said head and of substantial thickness to provide for a reasonably tight fit of the skirt with the cylinder walls without binding under the infiuence of the liquid pressures on the inside of the skirt, and a tubular scavenging plug extending from said head into said piston to provide a scavenging passage between the plug and piston skirt during movement of the piston toward the head, the free end of said plug extending to a position close to the crown of the piston when the latter has moved to its nearest position, the passage in said plug opening toward said piston crown and communicating with said port to supply power liquid to said cylinder and exhaust liquid therefrom, and the flow of liquid being displaced by the thick end of the piston skirt through said scavenging passage providing a scavenging action upon the inside of said piston and efiecting removal of any entrapped air bubbles during exhaust of the liquid from the cylinder through the passage in said plug.

' 2. In a hydraulic motor of the class described, a cylinder disposed with its axis vertical, a head at the lower end of said cylinder having a port axially of the cylinder for the admission and exhaust of pressure liquid for the cylinder, a piston disposed in said cylinder, a cylindrical skirt for said piston extending downwardly from the piston crown toward said head and of substantial thickness to provide for a reasonably tight fit of the skirt with the cylinder walls without binding under the influence of the liquid pressures on the inside of the skirt. and a tubular scavenging plug extending upwardly from said head axially of the cylinder into said piston to provide an annular scavenging passage between the plug and piston skirt during downward movement of the piston, the upper end of said plug terminating close to the piston crown when the latter is in its extreme lower position, the passage in said tubular plug opening axially upward toward the piston crown and communicating with said port to supply power liquid to said cylinder and exhaust liquid therefrom, and the flow of liquid being displaced by the thick end of the piston skirt through said scavenging passage providing a scavenging action upon the inside of said piston crown and effecting removal of any entrapped air bubbles during exhaust of the liquid-from the cylinder through the passage in said plug.

3. In a fluid motor of the class described, a vertically disposed cylinder of substantial length, a head at the lower end of said cylinder, 2. piston near the top of said cylinder and closing the same, a central tube extending upward from said head through which motive liquid is supplied to and exhausted from said cylinder near the top thereof, a piston skirt extending downward from the crown of said piston between the tube and cylinder wall and of a thickness to provide a substantial displacement of liquid at the lower end of the cylinder during the downward stroke of,

said piston, and to provide an, annular passage around said tube for the passage of said displaced liquid upwardly against the piston crown to scavenge air bubbles which may collect in theupper end of the cylinder and fiow the same outwardly LOUIS E. GODFRIAUX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS through said tube.

Number Name Date 423,515 Colborne Mar. 18,- 1890 603,173 Clay Apr. 26, 1898 871,634 Rothchild Nov. 19, 1907 1,039,448 Schwarz Sept. 24, 1912 1,206,387 Sundh Nov. 28, 1916 1,309,257 Martens July 8, 1919 1,414,495 Bangs May 2, 1922 1,531,748 Johnson Mar. 31, 1925 1,653,960 Halstead et al Dec. 27, 1927 1,667,213 Marchetti Apr. 24, 1928 1,711,260 Caminez Apr. 30, 1929 1,774,087 Dunn Aug, 26, 1930 1,775,108 Omo Sept. 9, 1930 1,781,416 Sundstrand Nov. 11, 1930 1,873,396 Hallenbeck Aug. 23, 1932 1,890,244 Barrett et al 1 Dec. 6, 1932 1,938,772 Ernst et a1 Dec. 12, 1933 2,081,760 Nardone May 25, 1937 2,086,835 Adkisson et al. July 13, 1937 2,107,456 Trapp Feb. 8, 1938 2,304,903 Eppens Dec. 15, 1942 2,316,408 Dawson Apr. 13, 1943 FOREIGN PATENTS Number Country Date 2,625 Great Britain May 25, 1910 529,508 Germany L. July 21, 1931

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