US3513754A - Fluid operated actuator with adjustment means - Google Patents

Description

FLUID OPERATED ACTUATOR WITH ADJUSTMENT MEANS Filed May 27, 1968 JAMES W. JOHN W INVENTOR.

A TTO/PA/ Y3 United States Patent 3,513,754 FLUID OPERATED ACTUATOR WITH ADJUSTMENT MEANS James W. John, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed May 27, 1968, Ser. No. 732,374 Int. Cl. F0111 3/00 US. Cl. 9231 1 Claim ABSTRACT OF THE DISCLOSURE A compact, relatively simple fluid operated actuator or motor comprising a cylindrical member closed at both ends with an output shaft rotatably extending through one end in a fluid tight manner. The output shaft has a coaxial helical bore extending from the inner end thereof toward the outer end. A piston is mounted for sliding movement in the cylinder and has a helical shaft fixedly connected to and extending from one face thereof which engages the helical bore in the output shaft. A guide pin prevents rotation of the piston in the cylinder so that motion of the piston and helical shaft longitudinally of the cylinder rotates the output shaft.

Background of the invention The present invention is directed to a fluid operated actuator or motor and, more particularly, to an actuator which converts pneumatic or hydraulic pressure into rotary motion.

Fluid operated actuators or motors of the prior art are generally complex, large and expensive. Often the motor cost and size substantially exceeds that of the apparatus being actuated. In some instances the cost of the motor is several times that of the driven apparatus. Additionally, many actuators have undesirable hysteresis loss characteristics because of the complex linkages used, so as to preclude their use for accurate apparatus positioning. Also, because of the complexity of the parts in many presently available actuators, the cost of mainte nance is prohibitive.

In US. Pat. No. 3,253,517, a simple, economical, an defficient actuator or motor is disclosedwhich overcomes many of the foregoing disadvantages. It comprises v a cylinder having a piston driveable therein by a pressure differential thereacross. The piston is provided with a helical bore which engages a helical drive shaft. The piston is arranged so that at least a portion of the 'drive shaft is continuously engaged by the helical bore whereby longitudinal movement of the piston rotates the shaft. The outer end of the drive shaft is provided with a socket or the like for engaging the apparatus, such as a valve stem, which is to be operated. The piston itself is non-rotatably secured to the end of the cylinder op- Summary of the invention Accordingly, the present invention provides a fluid operated actuator which is simpler and less expensive to construct than those of the prior art. Moreover, while retaining the desirable features of the actuators of the prior art, the present motor is also smaller and lighter.

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Specifically, the present invention provides a fluid operated actuator comprising a cylindrical member closed at both ends. An output shaft extends through one end of the cylinder in a fluid tight manner and is rotatable therein. The output shaft is provided with a coaxial helical bore extending from the inner end thereof toward the outer end. A piston is mounted for sliding movement in the cylinder and has a helical shaft fixedly connected to and extending from one face thereof. The shaft engages the helical bore in the output shaft. Means is provided for preventing rotation of the piston in the cylinder. Means is provided for admitting an operating fluid into the cylinder to move the piston and helical shaft longitudinally of the cylinder thereby rotating the output shaft.

' Furthermore, the invention provides a cylinder which is formed of a cup-shaped member and a cylindrical plug member arranged to close the open end thereof. The cylindrical plug is adjustably positionable in the cupshaped member to vary the stroke and/ or initial orienta tion of the piston. I

In addition, the present invention provides a pin extending parallel to the shaft from the same face of the piston. The pin engages the end of the cylinder to prevent rotation of the piston therein. n

The various features of novelty which characterize the present invention are pointed out with particularity in the claim annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and the specific objects obtained by its use, reference should be had to the accompanying drawing and descriptive matter in which a preferred embodiment of the present invention is illustrated and described.

Brief description of the drawing The drawing illustrates a longitudinal view, generally in section, of a preferred embodiment of the present invention.

Description of the preferred embodiment Referring to the drawing, the actuator, or motor, comprises a cup-shaped cylinder member 10 having an integral end wall 12 provided with a tapped fluid port 14 therethrough. The opposite end of the cylinder member 10 is provided with internal threads 16 which engage external threads 18 disposed on the periphery of a cylindrical plug closure member20. The cylindrical plug closure member 20 is screwed into the open end of cylinder member 10, forming a chamber 22 therein. A substantially-flat, cylindrical piston member 24, having'an outer diameter substantially equal to the inner surface 25 of cylinder member 10, is arranged for slidingmo tement within chamber 22.

The cylindrical plug closure member 20 is provided with an axial bore 26 therethrough in which an output shaft 28 is sealingly journaled for rotary motion. The output shaft has a flange portion 30 on the inner end thereof which is substantially coplanar with the inner end 32 of plug member 20. The output shaft 28 is supported for rotary motion by a pair of. sleeve bearings 34 and 36 disposed in a standard mannerin-bore 26 of the plug closure member 20. The flange 30 of the output shaft also bears upon the inner end of bearing 34, as shown. The output shaft 28 is retained within the plug closure member 20 by a retaining clip 38 and washer 40, which bears against the outer end of bearing 36. A tapped fluid port 21 is also provided through the cylindrical plug closure member 20.

One or more bores 42 are formed from the inner surface 32 partially through plug closure member 20 and extend parallel to the axial bore 26. The piston 24 is 3 provided with one or more pins 44 extending outwardly from the face 46 thereof adjacent the inner end 32 of the plug closure member. The pins 44 are threadedly connected to the piston 24 and are arranged to slide in bores 42. These pins prevent rotation of the piston 24 within chamber 22, as will become apparent hereinbelow.

The piston 24 is provided with an axial bore 48 through which a shaft 50 (shown in full) is sealingly and nonrotatably connected via nut 52 and collar 54. The portion of the shaft 56 extending from the face 46 of the piston has a generally square cross-section and is formed as a helix. An axial bore 58 is provided in output shaft 28, which is filled with a coaxial plastic or metal insert 60 having a helically formed inner surface 62 which engages the helical shaft 56. The depth of the helically formed inner surface is substantially equal to the length of shaft 56 whereby movement of piston 24 within chamber 22 causes shaft 56 to move into or out of the insert 60. The piston 24 is moved within chamber 22 by means of a hydraulic or pneumatic fluid introduced into the chamber through either port 14 or port 21, with fluid exhaust occurring through the other port, in a manner well known to those skilled in the art. Inasmuch as the piston 24 is prevented from rotating by pins 44, and since the helical shaft is non-rotatably connected to the piston, the helical shape of the shaft 56 and the inner surface 62 of insert 60 causes the output shaft 2 8 to rotate as the piston is moved in the cylinder. This output shaft may be connected to any device which it is desired to operate. The cylinder closure plug 20 is provided with a flange 64 extending outwardly therefrom to permit attachment to a support or to the device to which output shaft 28 is connected.

In order to assure the lowest possible hysteresis loss in the movement of shaft 56 in bore 62, it has been found desirable to mold the insert 60 in bore 58 with the shaft 56 centered therein. In such a molding operation the respective surfaces are prepared so that the insert 60 adheres to the bore 8 and not to the shaft 56. Knurling of the inner surface of bore 58 and lubrication of the outer surface of shaft 56 is one method of accomplishing this.

To maximize the efliciency of the present actuator, and to reduce leakage of the operating fluid, O-ring type seals 66 are provided about the periphery of the piston 24, the flange 30 of the output shaft, and the cylinder plug closure member 20. It will be also be noted that the present arrangement provides an actuator wherein the piston 24 is fully penetrated only by the shaft 50', and that in a liquidtight manner. Thus, the possibility of fluid bypassing the piston with a concomitant reduction in actuator efficiency is substantially eliminated.

The initial orientation of the piston 24 and output shaft 28 may be simply and readily adjusted by turning the cylindrical closure plug member 20' within the end of the cup-shaped cylinder member 10. In order to positively maintain the desired orientation once it is achieved, a set-screw 6'8 is provided through the wall of the cylinder member 10, which engages the outer periphery of the closure plug member 20. Thus, the present invention provides all of the latitude available in the prior art apparatus even though the complexity and number of parts utilized is substantially reduced. Moreover, with the present arrangement the overall dimensions of the actuator are minimized by combining the piston orientation adjustment with the assembly connection. Thus, external tie- 4 rods or thicker wall sections to accept connecting bolts are eliminated.

It will be noted from the foregoing that the present actuator is composed of a plurality of relatively simple, easily fabricated elements. Specifically, the elements of the present actuator are substantially simpler and less expensive to fabricate than those of the actuator disclosed in the above-identified patent. Moreover, it will be noted that by connecting the helical shaft to the piston and disposing the helical bore within the output shaft the thickness of the piston may be greatly reduced as well as providing a substantial reduction in the overall size of the actuator. This is particularly important in many arrangements where size and weight are of major concern.

Accordingly, it will be seen that the present invention provides an actuator capable of efiiciently and reliably performing all of the operations of actuators of the prior art and at the same time is lighter and more compact, and is fabricated from simpler, less-expensive components.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereina'bove and as defined in the appended claim.

I claim:

1. A fluid operated actuator comprising a cup-shaped cylinder member having a threaded open end, a cylindrical plug member arranged to adjustably engage the threaded open end of said cylinder member and cooperating therewith to form a cylindrical chamber, an output shaft extending axially through said cylindrical plug member in a fluid tight manner, said output shaft being rotatable in said cylindrical plug member and having a coaxial helical bore extending from the inner end thereof toward the outer end, a piston mounted in said cylindrical chamber in sliding engagement with the inner cylindrical surface of said cylinder member, a helical shaft fixedly connected to said piston and extending from one face thereof in engagement with the helical bore in said output shaft, means for preventing rotation of said piston and said helical shaft in said cylinder, means for admitting an operating fluid into said cylinder to move said piston and helical shaft longitudinally of said cylinder thereby rotating said output shaft, and means to selectively position said plug member in the end of said cup-shaped cylinder to selectively angularly position said output shaft.

References Cited UNITED STATES PATENTS 1,828,965 10/1931' Fuller 9233 XR 2,373,385 4/ 1945 Davie 92-31 XR 1,747,306 2/ 1930 Kolodzie 9231 XR 2,755,069 7/1956 Mosby 92-33 XR 2,974,646 3/ 1961 Miller et al. 9233 XR 2,987,888 6/1961 Crowell 923'3 3,253,517 5/1966 John et al. 92-33 XR 3,274,901 9/1966 Yost 92--3l XR 3,428,298 2/ 1969 Powell 9233 XR MARTIN P. SCHWADRON, Primary Examnier L. I. PAYNE, Assistant Examiner US. Cl. X.R. 9233

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