Patent Publication Number: US-3967540-A

Title: Rotor, pistons, piston shoes and associated means in fluid handling devices

Description:
BACKGROUND OF THE INVENTION 
     There are many radial piston pumps and motors, which have piston shoes and pistons associated thereto and where the piston shoes are guided inwards and outwards and mostly also endwards. Such devices work satisfactorily and reliably at certain sizes, pressures and revolutions. They are known for example from my U.S. Pat. Nos. 3,223,046; 3,270,685; 3,277,934; 3,304,883 and from many other patents. 
     Such radial piston pumps however, insofar as they had long piston strokes, had guide means for the piston shoes axially of the cylinders or of portions thereof, which resulted in relatively large axial dimensions of the device, so that the number of piston groups therein remained limited, because otherwise the fluid passages in the rotor would become too long for effective work. And further, those devices commonly had a rotary actuator means for the actuation of the piston stroke, which was revolvably mounted in bearings. 
     More recently, however, it is desired that radial piston pumps for example, operate with the rotary velocity of gas-turbines or of high speed revolving combustion engines. At those high rotary revolutions, however, the heretofore used guide means for the piston shoes are often unsatisfactory because the forward and backward acceleration forces on the piston shoes are becoming so high at such speeds, that the piston shoes tend to tilt a little in their guide means, which at very high speeds leads to welding between the guide faces of the piston shoes and of the guide means thereof. Also, the bearings for the actuator means are not able to revolve at such high revolutions, because their diameters are large in radial piston devices so that the velocity of the balls or rollers of the bearing would exceed their allowed maximum speed, if the pump runs at the speed of gas turbines or of high speed combustion engines. The bearings would then break. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a rotary fluid handling device which is simple to be built, inexpensive, safe and effective in operation and which overcome the limitations of the angular rotary velocity of the former fluid handling devices, while at same time the novel device of the invention reduces friction on the piston shoes and thereby increases the efficiency and power of the device. 
     The object of the invention is realized by the provision of one or more means of the invention, which for example, are: 
     a. The provision of a recess in the rotary fluid handling body for the reception of a portion, especially a forward portion of the piston shoe to enable the piston shoe to enter into the fluid handling rotor itself for obtaining a large piston stroke with a correspondingly large rate of flow of fluid through the device, to thereby increase the power of the device. At same time the diameter of the guide face of the actuator means can be kept small, so that the relation of the large piston stroke compared to the small diameter of the actuator face of the actuator means for the piston stroke gives a high efficiency of the device; 
     b. The provision of a forward extension of the piston shoe for making possible a high speed forward velocity of the piston shoe relative to the guide face of the actuator means, and at the same time to provide space for the reception of fluid by hydrodynamic action between piston shoe and guide face or for the provision of space for the location of fluid pressure balancing recesses in the forwardly extending outer face of the piston shoe in order to get stable sliding of the piston shoe along the guide face of the piston shoe actuator; 
     c. The sizing of the piston shoe so that it is smaller than the recess in the rotor wherein to it enters; 
     d. The provision of space between the ends of the piston shoes and the walls of the recesses in the rotor, or of the walls attached to or provided on the rotor for the securing of the axial location of the piston shoes so that excessive axial dislocation of the piston shoes is prevented, while said spaces prevent sliding of piston shoe faces on wall faces and thereby eliminate friction by end guides of the piston shoes, which increases the efficiency of the device; 
     e. The provision of a backward shoulder in the piston and of a backward neck on the piston shoe, which piston shoe shoulder extends radially almost to the outer face of the piston shoe so that a limited space is provided between said shoulder and said neck whereby the piston shoe can pivot in its seat in the piston forward and backward only to a limited extent, so that excessive backward inclination of the piston shoe is prevented and stopped by said neck and said shoulder. Thereby, the need to provide the heretofore used inner guides for the piston shoes is eliminated and consequently their friction is spared, which in turn improves the efficiency and power of the device; 
     f. The provision of the piston shoe pivot seat in the piston head and an opening extending therefrom at an inclination radially outward and forward, while the piston shoe itself is provided with a seat portion extending through said opening into said seat in said piston, whereby the piston can pivot in said piston to a limited extent and the piston shoe has a desired maximum of strength in the radial outward and forward direction, which is the direction of greatest load on the piston shoe, whereby the forward motion of the piston shoe is ideally borne by said piston; 
     g. The provision of a fluid containing fluid pressure balancing recess in the outside face of the piston shoe, extending forward in said piston shoe extension, and the association of a fluid pressure balancing recess thereto between the piston shoe seat and the piston shoe seat portion and thereby between the respective piston and piston shoe, for the reduction of friction between the piston and the piston shoe, the respective recesses being communicated by passages through said piston shoe and said piston to the respective associated cylinder; 
     h. The provision of a tangential fluid pressure balancing recess in the back wall of the piston for the reduction of friction between the piston wall and the cylinder wall, which said recess is communicated by a passage means with the other recesses in the piston and piston shoe for thereby increasing the power and efficiency of the device and also the pressure handling capability of the device; 
     i. The provision of annular grooves in the actuator means for the partial reception of radial extensions or walls of the rotor or rotor assembly, for assuring a large piston stroke and thereby a large rate of flow of fluid through the device and thereby a large power of the device and/or: 
     k. The provision of wall means on the rotor extending axially of the actuator means and partially radially beyond the inner face thereof, for providing a securing means against excessive axial dislocation of the piston shoes over a large radial piston stroke range. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view through an embodiment of the invention, 
     FIG. 2 is a cross sectional view through FIG. 1 on the line II -- II; 
     FIG. 3 is a fragmentary section through FIG. 1 on the line III -- III. FIG. 4 is a fragmentary longitudinal sectional view through a piston-piston shoe assembly of the invention; 
     FIG. 5 is a front view of FIG. 4; 
     FIG. 6 is a cross-sectional view through FIG. 4; 
     FIG. 7 is a longitudinal sectional view through an embodiment of a multi cylinder group rotor of the invention with the thereto associated walls and actuator means; and 
     FIG. 8 is a fragmentary developed view of the rotor in FIG. 7. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Housing or actuator means 11 has an inner face 22 for guiding the piston stroke of the piston shoes 1 and pistons 4 radially into and out of the cylinders 14 in rotor body 8. Body 8 is the fluid handling body for the reception of fluid to flow therethrough. Body 8 may have a shaft 17 for rotation in the housing, the body 8 or shaft 17 being supported in the housing 11 or in the covers thereof. 
     Passages 15 and/or 16 may lead the fluid through the covers into and out of the cylinders 14 of the rotary fluid handling body 8. 
     According to the invention, the rotary fluid handling body 8 is provided with recesses 5 for the temporary reception of all or a portion of a respective piston shoe 1 or its front extension 3. The recess 5 of the invention is bounded by walls 24 for the prevention of excessive axial dislocation of the piston shoes 1 relative to pistons 4. Each piston 4 and piston shoe 1 are connected together by a piston head seat 9 so that the associated extension 3 is pivotable. A smaller front portion 7 and a wider back portion 6 of the respective piston 4 embrace the piston head seat 9 a little, so that it cannot radially disassemble. The narrowed portion between the piston shoe head 2 and the seat 9 extends radially outward and forward in an inclined direction through an opening 10 of the piston head. The front extension 3 enters into the respective recess 5 for obtaining the desired large piston stroke, and the piston shoe head 2 is shorter than the portion 6, but slightly spaced therefrom, so that the piston shoe 1 can pivot a little on piston head seat 9. The piston shoe head 2 has also the outer face 23 which slides along the actuator means 11, inner actuator face 22. The pistons 4 and the associated piston shoes 1 each have a passage 20 for the transfer of fluid from the associated cylinder into and through the balancing recess 19 between piston and piston shoe and into the outer balancing recess 21 which may be directed forward and radially outward at an inclination selected for the most suitable high speed operation of the device. A tangentially directed balancing recess 40 may be formed in the portion 6 of the piston 4 and be communicated with passage 20 or recess 19 for exerting fluid pressure against the wall of cylinder 14 to reduce friction between the piston 4 and such wall. Balancing recesses 12 may be provided on the cover and rotor 8 in order to assure the suitable floating of the rotor 8 during revolution between fields of fluid of equal dimension or force on both ends of the rotor FIGS. 7 and 8. 
     The device of the invention can also be a multi-piston group or a multi-flow device. Such an embodiment is shown in FIG. 7. It has a rotary control face 37 for engagement with a stationary control face on a respective control body. Cylinder group 14 has recesses 5 of the invention and walls 35 and 34 for the prevention of excessive dislocation of the piston shoes. Cylinder groups 38 and 39 are so closely together in rotor 30, that they may need only the two walls 34 and 35 for operation of both piston shoe groups. The piston shoes will then have axial extensions 36 for preventing excessive axial dislocation of the piston shoes. Actuator ring 32, along the inner face of which the outer faces 23 of the piston heads 2 slide, may have an annular groove 33 for the partial reception of wall means 35 and be short enough so that the wall 34 can extend radially beyond the inner face 22 of actuator ring 32, for the purpose of obtaining the desired very large piston stroke of the device of the invention. 
     In actual tests the device of FIG. 7 had a diameter of 70 mm only and a length of about 60 mm; at a weight of only 1800 grams this device developed 80HP.