Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
  • F15B15/02—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member
  • F15B15/06—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member for mechanically converting rectilinear movement into non- rectilinear movement
  • F15B15/068—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member for mechanically converting rectilinear movement into non- rectilinear movement the motor being of the helical type

Definitions

• the present invention relates generally to actuators, and more particularly, toizid-powered actu-
• ⁇ 4 Q ators of the type in which axial movement of a piston produces relative rotational movement between a body and an output member.
• Rotary helical splined actuators have been employ ⁇ ed in the past to achieve the advantages of high-torque output from a simple linear pi s ton-and-cylinder drive arrangement.
• the actuators typically employ a cylindrical body with an elongated rotary output shaft extending from
• a separate ring gear attached to the body may be used.
• the piston is reciprocally mounted within the body and has a head for the application of fluid pressure to one or the other opposing sides thereof to produce axial movement of
• the sleeve is elongated and coaxially receives the shaft therein.
• the outer splines of the piston sleeve engage.
• the splines the body or ring gear to cause rotation of the sleeve.
• the resulting linear and rotational movement of the sleeve is transmitted through the inner splines of the sleeve to the splines of the shaft • to cause the shaft to rotate.
• Bearings are typically supplied to rotatably support one or both ends of the shaft relative to the body.
• a fluid-powered rotary actuator with relatively small size and a thin-walled construction at an economical price.
• Such an actuator is desirable for use in robotics and other situations in which a light, small sized, and inexpensive actuator operating on air or hydraulic fluid at pressures up to about 1500 psi is required.
• the actuator should be manuf acturable in large quantities without requiring as much precision machining as do existing actuators.
• the actuator should also be provided with precisely adjustable stops for setting the rotational limits of the output shaft while reducing any binding these stops might cause on the piston.
• the stops should be adjustable without requiring complete disassembly of the actuator. While using thin-walled construction, the actuator body must be sufficiently strong and durable. Another problem encountered with conventional actuators is backlash.
• the actuator should not require exceptionally accurate machining of the torque-transmitting parts to eliminate slack that produces backlash, and the actuator should be easy to assemble.
• the design of an actuator ' must incorporate a certain amount of slack, but the slack results in undesirable backlash during operation.
• Means should be provided for substantially complete elimination of the slack causing the backlash problem.
• accurate machining reduces slack initially, should the torque- transmi tti ng parts wear during usage or otherwise lose their original tolerances, means should be provided for elimination of the slack that develops.
• Elimination of the slack should be accomplished in a simple manner and with an adjustment which simultaneously remove the slack existing between all the torque-transmitting parts within the body which translate linear movement of the piston into rotational movement of the output member.
• the actuator should be usable with torque-transmitting means other than splines to avoid the undesirably high frictional coefficient of splines.
• actuators have been constructed using balls and helical ball races, and provide a higher output efficiency due to the rolling friction of the balls being less than the sliding friction of the splines
• conventional helical ball screw actuators require recirculation of the balls as the ball carrier reciprocally moves within the actuator cylinder.
• the recirculation allows the balls to roll relatively unrestricted within the ball races to avoid the balls scuffing along the races.
• the use of recirculation eliminates most of the ball scuffing problem, it is difficult and expensive to manufacture an actuator with a recirculation path; and no recirculation path can provide a totally unrestricted flow of the Balls.
• the actuator must be made wider than ordinarly necessary since recirculation requires that the recirculation path double back over the ball races carrying the balls.
• the present invention resides in a fluid-powered actuator, including a body having a chamber with a smooth bore interior sidewall, and first and second ends; and a piston mounted within the chamber for endwise reciprocal movement therein responsive to the application of fluid pressure to one or the other opposing sid " es thereof.
• the piston has an endwise extending aperture therethrough eccentric with the chamber
• the actuator further includes adjustment means for selectively moving one of the member or the piston relative to the other to endwiae preload the member and the piston.
• the adjustment means provides sufficient adjustment to place the member and piston into sliding lateral engagement withthe chamber interior sidewall to thereby substantially eliminate backlash in the piston and member torque-transmitting means.
• the adjustment means includes means for adjustably rotating or endwise moving one of the member or piston relative to the other b a selected amount to endwise preload them.
• the adjustment means includes an adjustable element extending between and engaging each of the member and the piston. The adjustable element provides ' an adjustable and oppositely directed endwise force on the member and the piston to move one of the member or piston relative to the other for endwise directed preloading of the member and piston.
• the actuator body includes endwalls defining the first and second ends of the chamber and limiting endwise movement of the member and piston therein.
• the piston and member each have a projecting stop adjustably extendable generally endwise outward therefrom to engage the corresponding endwall of the body and limit travel of the member and piston toward the endwalls.
• the extent of linear travel of the member and piston toward the first and second ends can be selectively controlled, thereby setting precise preselected rotational movements on the shaft.
• each of the endwals has a projecting stop adjustably extendable generally endwise inward therefrom to engage a corresponding one of the member or piston and limit travel thereof toward the endwalls.
• the adjustable stops are located toward the axial center of the member and piston. and an exterior sidewall in sliding laterial engagement ⁇ with the interior sidewall of the chamber for transmitting torque between the piston and the body.
• a shaft is eccentirally positioned within the chamber and extends 5 through the piston aperature for rotation of the shaft about a longitudinal axis eccentric with the chamber.
• the piston aperture is sufficiently out of concentricity with the chamber to prevent rotation of the piston within the body as the piston reciprocates.
• the shaft is supported for rotation relative to the body and connnectable to an external device.
• Piston torque-transmitting means are provided for transmitting torque between the piston and the shaft, and for producing
• a member is also mounted within the chamber for endwise reciprocal movement
• An endwise extending eccentric aperture is provided in the member generally corresponding to the piston aperture.
• the member is independently rotatable from the piston within at least a limited range sufficient to place the member and
• the actuator further includes . j . member torque-transmitting means for transmitting torque between the member and the shaft, and for producing relative rotational movement between the shaft and the body 35 in response to endwise movement of the piston corresponding to the rotational movement produced by the piston torque-transmitting means.
• the piston and member torque-transmitting means includes ball races and stops arranged to permit substantially unimpeded rolling travel of the balls within the channels defined thereby and to engage and limit travel of the balls along the ball races.
• the torque-transmitting means are innermeshing splines.
• An alternative embodiment of the actuator utilizes a chamber with a non-cylindrical interior sidewall.
• the piston and member are mounted generall coaxially within the chamber and have an exterior shape and size preventing rotational movement within the chamber beyond a limited range.
• the shaft may be concentrically positioned within the chamber.
• Figure 1 is an isometric view of a fluid-powered actuator embodying the present invention utilizing an eccentric shaft with a cylindrical body.
• Figure 2 is an enlarged, side elevational, sectional view of the actuator of Figure 1.
• Figure 3 is a sectional view taken substantially along the line 3-3 of Figure 2.
• Figure 4 is a schematic end view of the sleeve member and piston sleeve of the actuator of Figure 1 shown rotated to place them in lateral sliding engagement with the interior sidewall of the body, with the extent of rotation exaggerated for the purposes of illustration.
• Figure 5 is a fragmentary side elevational, sectional view of a first alternative embodiment of the invention utilizing a splined piston and shaft arrangement and adjustable stops mounted in the end wall.
• Figure 6 is a side elevational, partial sectional view of a second alternative embodiment of the invention utilizing a concentric shaft with an elliptical body.
• Figure 7 is a sectional view taken substantially along the line 7-7 of Figure 6.
• Figure 8 is a fragmentary, isometric view of a third alternative embodiment of the invention utilizing an eccentric shaft and thin wall construction.
• the present invention is embodied in a fluid-powered rotary actuator, indicated generally by reference numeral 10.
• the preferred embodiment of the actuator 10 is shown in Figures 1 through 4.
• the actuator 10 includes an elongated housing or body 12 having a generally cylindrical sidewall 14 with a smooth bore interior sidewall surface 16.
• a first end cap 18 is attached to the body 12 at a first end 20, and a second end cap 22 is attached to the body at a second end 24.
• the end caps 20 and 22 are attached to the sidewall 14 by threaded
• the sidewall 14 and the end caps 20 and 22 define a generally cylindrical chamber 26 within the body 12.
• a rotary output shaft 28 is positioned within the body 12 for rotation about a longitudinal axis eccentric with the chamber 26, and is supported for rotation relative to the body 12.
• the end portions of the shaft 28 extend through an eccentric aperture 30 in each of the end caps 18 and 22, and the shaft is supported by axial thrust bearings 32 positioned between the caps and the shaft to prevent axial movement of the shaft.
• a circumferential ball race 34 is formed on each end portion of the shaft 28, and the caps 18 and 22 each have inserts 36 with axially inward opening ball races 38 extending about the apertures 30 and confronting the corresponding ball race on the shaft.
• the invention may be practiced with the shaft 28 rotatably driving an external device (not shown), or with the shaft being held stationary and the rotatable drive being provided by rotation of the body 12.
• the shaft 28 is provided with keyways 40 formed on the end portions of the shaft for attachment to an external device. Other means may be used for attachment of the external device to the shaft or the body.
• a cylindrical piston sleeve 42 is mounted within the chamber 26 for endwise or axially directed reciprocal movement therein, and has an eccentric endwise extending aperture 44 t erethrough, located to generally corresponding to the eccentric aperture 30 in each of the end caps 18 and 22.
• the shaft 28 projects through the piston sleeve aperture 44 and the aperture is sufficiently out of concentricity with the chamber 26 to prevent rotation of the piston sleeve within the chamber beyond a limited range.
• the piston sleeve 42 is provided with keyways 40 formed on the end portions of the shaft for attachment to an external device. Other means may be used for attachment of the external device to the shaft or the body.
• a cylindrical piston sleeve 42 is mounted within the chamber 26 for endwise or axially directed reciprocal movement therein, and has an eccentric endwise extending aperture 44 t
• the head portion 46 has a head portion 46 positioned toward the first end 20 of the body 12 and a sleeve portion 48 extending generally axially inward therefrom toward the second end 22.
• the head portion 46 carries conventional inner and outer seals 50 disposed between the head portion and the cor espo ding smooth-walled portions of the body sidewall 14, and between the head portion and a smooth surface portion of the shaft 28 to define fluid-tight compartments to each side of the head portion.
• the smooth-walled portion of the body sidewall 14 and smooth surface portion of the shaft 28 have su ficient axial length to accommodate the full stroke of the piston sleeve 42 within the chamber 26.
• Conventional seals 51 are disposed between the shaft 28 and the end caps 18 and 22 to prevent fluid leakage from the body 12. Reciprocation of the piston sleeve 42 within the body 12 occurs when hydraulic fluid or air under pressure selectively enters through one or the other of a pair of ports 53, located to opposing sides of the head portion .10
• a sleeve 52 is reciprocally mounted within the chamber 26, generally coaxial with the sleeve portion 48 of the piston sleeve 42, for endwise reciprocal movement therein.
• the sleeve 52 is positioned between the sleeve portion 48 and the second end 22 of the body 12.
• the sleeve 52 also has an eccentric endwise extending aperture 54, located to generally corresponding to the apertures 30 in each of the end caps 18 and 22, and the aperture 44 in the piston sleeve 42.
• the shaft 28 projects through the aperture 54, and the aperture is sufficiently out of concentricity with the chamber 26 to prevent rotation of the sleeve within the chamber beyond a limited range.
• the piston sleeve 42 and the sleeve 52 are independently rotatable in opposite directions within at least a limited range, sufficient to place a portion of the exterior sidewalls thereof into sliding lateral engagement with the smooth bore ' interior sidewall surface 16 of the body sidewall 14 for transmitting torque therebetween and for backlash elimination purposes.
• the piston sleeve 42 and the sleeve 52 have an exterior diameter sufficiently less than the interior diameter of the chamber 26 to provide for the limited rotation.
• the actuator 10 utilizes no torque-transmitting splines or balls/ball races between the body 12 and the piston sleeve 42 and the sleeve 52.
• a split nylon bearing 55 is positioned about the piston sleeve 42 and sleeve 52, and between them and the sidewall 14 of the body 12, which expands and contracts in circumference as the piston sleeve and sleeve are rotated relative to each other to eliminte backlash, as will be described in more detail below.
• the bearing 55 reduces the sliding friction as the piston and sleeve 42 and sleeve 52 reciprocate within the chamber 26 in sliding engagement into the body sidewall surface 16, and further improves the operation of the actuator 10 by eliminating the large 11
• a circular plate 56 Positioned between the axially inward facing end walls of the sleeve portion 48 of the piston sleeve 42 and 5 the axially inward facing end wall of the sleeve 52 is a circular plate 56 with an eccentric aperture for the shaft 28.
• the piston sleeve 42 and the sleeve 52 are in sliding engagement with each other through the plate 56.
• a helical ball race 58 is formed on the
• the ball races 58, 60 and 61 have substantially identical lead and pitch, and form a pair of laterally confined, variable length ball channels defined by the area of coincidence of the
• One or more balls 62 are disposed in each of the ball channels for transmission of torque between the sleeve portion 48 of the piston sleeve 42 and the shaft 28, and between the sleeve 52 and the shaft.
• 25 56 serves as a ball stop, as do certain of the blocked ends of the ball races 58, 60 and 61, to engage and limit travel of the balls 62 and to regroup the balls, as will be described in more detail below. While for ease of understanding the ball races 58, 60 and 61 are described
• the ball races may be multiple-start ball races each with a corresponding ball race to form a ball channel and with one or more balls disposed therein.
• the more balls and ball races utilized the greater will be
• the dashed lines indicate the linear extent of the ball races and the manner of termination of the ball races.
• the ball races 60 and 61 each have an axially outward end which terminates in a blocked end.
• the ball races 60 and 61 extend in the axially inward direction to the end of the piston sleeve and the sleeve, and terminate in an open end running out into the interior chamber 26 of the body 12. Both ends of the ball race 58 formed on the shaft 28 terminate in a blocked end 66.
• the apertures 44 and 54 of the piston sleeve 42 and the sleeve 52 are diametrically sized to produce minimal inner spacing between the piston sleeve and sleeve and the shaft 28 to increase ball contact with the ball channels and promote improved torque transmission by the balls 62 carried therein.
• the plate 56 projects radially inward toward the shaft 28 sufficient to engage and limit the travel of balls
• the plate 56 also blocks the open ends of the ball races 60 and 61 to prevent the balls 62 from passing out of the open end of one of the ball races into the open end of the other ball race. It is noted that the plate 56 will only operate to regroup the balls 62 in the ball channels should they not roll fully against the stops formed by the blocked ends 66 of the ball race 58, which limit travel of the balls 13
• the ball race 61 on the sleeve extends over an axial length of the sleeve projecting beyond the blocked end 66 of the ball race 58 toward the second end 24, at least one-half of the distance of the end-to-end axial travel of the sleeve within the chamber 26.
• the balls 62 disposed in the ball channel travel along the channel as they roll approximately one-half the distance the sleeve travels with respect to the body 12.
• the ball race 61 must extend over a sufficient length of the sleeve 52 beyond the stop provided by the blocked end 66 of the ball race 58 to allow free rolling of the balls within the inner channel during the entire sleeve travel between its end limit at the * second end 24 to its end limit at the first end 20 to avoid scuffing of the balls.
• the ball race 60 on the piston sleeve extends over an axial length of the piston sleeve projecting beyond the blocked end 66 of the ball race 58 toward the first end 20, at least one-half of the distance of the end-to-end axial travel of the piston sleeve within the chamber 26.
• the ball race 58 extends unblocked over a sufficient axial length of the shaft 28 to each side of the plate 56, as measured with the piston sleeve 42 and sleeve 52 positioned at either end limit of theiraxial travel within the chamber 26, by at least one-half of the distance of the end-to-end axial travel of the piston sleeve and sleeve within the chamber. 14
• the actuator 10 provides relative rotational movement between the body 12 and the shaft 28 through the conversion of fluid-actuated reciprocal linear movement of the piston sleeve 42 and the sleeve 52 into rotational movement of the shaft.
• torque is transmitted by the balls 62 through the coaction of the ball race 58 on the shaft 28 with the ball race 60 on the piston sleeve 42 and the ball race 61 on the sleeve 52.
• the transmitted torque causes the shaft 28 to rotate relative to the body 12 since the axial movement of the shaft is restricted by the thrust bearings 32.
• the transitted torque also tends to apply a counter-directed torque on the piston sleeve 42 and the sleeve 52 which is transmitted to the sidewall 14 of the body 12.
• the counter-directed torque is prevented from rotating the piston sleeve and sleeve within the chamber 26.
• the linear movement of the piston sleeve 42 and the sleeve 52 is converted into rotation of the shaft 28.
• the piston sleeve 42 and the sleeve 52 are independently rotatable within at least a limited range for backlash adjustment purposes.
• the actuator 10 is provided with a plurality of axially extendable, circumferentially spaced apart set screws 70 each threadably received in a threaded bore 72 extending endwise through the sleeve 52.
• the set screws 70 are axially inwardly adjustable to project from the sleeve 52 and engage the plate 56 positioned between the sleeve and the piston sleeve 42.
• the set screws 70 thereby apply an adjustable and oppositely directed, axially outward force on each of the piston sleeve 42 and the sleeve 52 to force movement of the piston sleeve relative to the sleeve for axially preloading them. It is noted that while the force 15
• the piston sleeve and sleeve are in contact with the expandable split bearing 55, rather than in direct contact with the sidewall surface.
• the piston sleeve 42 and the sleeve 52 may be manufactured with a slightly oblong cross-section by relieving the sides of each in the area where they contact the sidewall 14 through the bearing 55 to enlarge the contact area between the piston sleeve and sleeve, and the sidewall.
• the adjustment of set screws 70 may be accomplished before the assembly comprising the shaft 28, piston sleeve 42 and sleeve 52 is inserted into the body chamber 26, or afterward if appropriately placed access parts are provided in the end cap 22 to gain access to the set screws 70.
• the same adjusting movement may be achieved by providing means for direct rotation of the piston sleeve 42 and sleeve 52 relative to each other to eliminate backlash since the helical ball channels produce both axial and rotational movement regardless of same movement may be achieved by providing means for direct rotation of the piston sleeve 42 and sleeve 52 to eliminate backlash since the helical ball channels produce both axial and rotational movement regardless of whether an axial or rotational force is applied to the piston sleeve and sleeve.
• the same movement to eliminate backlash may be accomplished whether the set screws 70 apply opposite axially outwardly directed force on the piston sleeve and sleeve, or the piston sleeve and sleeve are spaced apart and the set screws are arranged to provide axially inward directed forces on the piston sleeve and sleeve to pull them toward each other. In both situations, the resultant oppositely directed axial and rotational movement of the piston sleeve and sleeve operates to eliminate the slack between the ball races of the ball channels.
• the piston sleeve 42 and the sleeve 52 move in unison, with substantially all backlash eliminated as the piston sleeve and the sleeve reciprocate within the chamber 26.
• the slack can be easily removed in the same manner described above by further adjustment of the set screws 70.
• the ball races may be machined using conventional machining techniques with standard tolerances and sufficient slack to facilitate assembly of the actuator 10. The slack, which otherwise would create backlash problems can be simply eliminated by adjustment of the set screws 70 prior to fluid-powered operation of the actuator.
• piston sleeve 42 and sleeve 52, and the body sidewall 14, a smaller diameter, lighter and less expensive actuator may be manufactured.
• a molded or tubular body may be used and precision machining of the body is eliminated. This facilitates easy and quick manufacture and assembly and reduces cost.
• a thin wall body design is also made possible since no machining of splines or ball races is required on the body sidewall.
• the body sidewall need only have sufficient strength to withstand the forces transmitted on the wall by the counter-directed torque of the piston sleeve 42 and the sleeve 52.
• the piston sleeve and sleeve do not require machining of splines or ball races, also reducing the size of the actuator.
• this allows the manufacture of extremely small sized actuators of relatively high torque-transmitting capacity using tubular stock for the body sidewall 14. It is expected that an actuator can be made using the present invention with a .875 inch outer diameter using a plastic tube as the body sidewall.
• the split bearing 55 can be eliminated.
• the invention is not limited to such small sized actuators, it does allow the construction of an actuator in a size which might otherwise be impossible to achieve if splines or ball races were required to be cut on the interior wall of the body sidewall.
• the use of a smooth bore body against which the piston sleeve and sleeve slide substantially eliminates the large sliding friction encountered with helical splines.
• the actuator 10 is further provided with a pair of axially extendable stops 76 which limit the endwise linear travel of the piston sleeve 42 and sleeve 52 for setting precise preselective rotational limits on the shaft 28.
• One of the stops 76 is threadably received in an endwise extending threaded bore 78 in each of the piston sleeve 42 and the sleeve 52, and is axially outwardly 18
• a threaded access port 73 is provided in the second end cap 22 for access to one of the stops 76 for its adjustment without further disassembling the actuator 10.
• the access port 73 is closed with a sealed threaded plug 74 when not in use to prevent the leakage of fluid therefrom.
• Access to the other stop 76 is through another threaded access port 79 provided in the first end cap 18.
• a sealed threaded plug 80 closes the access port 79 when not in use to prevent the leakage of fluid.
• the eccentric ' shaft design of ' the actuator 10 with the shaft 28 located off center permits location of the stops 76 toward the axial center of the piston sleeve 42 and the sleeve 52.
• the force aplied on the piston sleeve 42 and the sleeve 52 is more concentric than otherwise possible with a concentric shaft and a single contact stop.
• the usual resulting off-center force realized when using a concentric shaft and a single off-center stop which tends to cock and bind the piston sleeve and sleeve within the chamber is reduced or avoided.
• the actuator 10 utlilizes an eccentric shaft having splines 82 formed on the shaft 28 intermeshing with splines 83 formed on each of the piston sleeve 42 and the sleeve 52 to transmit torque therebetween.
• splines are- used instead of the ball races and balls described above.
• a pair of stops 84 are provided, each threadably received in an endwise extending threaded bores 86 in one of the end caps 18 and 22.
• the stops 84 are axially inwardly adjustable to project from the end caps 18 and 22, and engage the 19
• the eccentric shaft design of the actuator permits location of the stops 84 toward the axial center of the piston sleeve 42 and the sleeve 52 to reduce or eliminate binding.
• the actuator 10 utilizes a relatively thick body sidewall 14 and is usable for high-pressure operation.
• the thickness of the sidewall can be reduced for lower pressue operation.
• an alternative design can be employed using tie rods. Such an eccentric shaft actuator is shown in
• the actuator of Figure 6 and 7 is shown having a thin-wall construction, with the body sidewall 14 having its end portions set in correspondingly shaped recesses 92 in each of the end caps 18 and 22.
• the end caps 18 and 22 are square in shape and the corner portions extend radially outward beyond the body sidewall 14.
• An aperture 94 is provided through each of the four corner portions of each of the end caps 18 and 22 outward of the body sidewall 14.
• tie rods 96 extending between and attached to each of the end caps.
• the body 12 of the actuator 10 shown in Figures-6 and 7 has a non-cylindrical sidewall 14 with a smooth bore interior sidewall surface 16.
• the output shaft 28 is positioned within the body 12 for rotation about a longitudinal access concentric with the chamber 26.
• the apertures 30 in the end caps 18 and 22, and the apertures 44 and 54 and the piston sleeve 42 and the sleeve 52, respectively, are concentric with respect to the chamber 26. While this embodiment does not utilize the eccentric shaft previously described, the use of splines, ball channels, ring gears and other space consu ming torque-transmitting means to transmit torque between the piston sleeve 42 and sleeve 52, and the body sidewall 14 is similarly eliminated.
• the piston sleeve 42 and the sleeve 52 are prevented from rotating within the chamber 26 by the use of the non-cylindrical interior sidewall 14 in conjunction with the piston sleeve 42 and sleeve 52 having a corresponding shape and size which permits their sliding lateral engagement with the smooth bore interior sidewall surface 16, but prevents their rotation under the counter directed torque produced during fluid-powered operation of the actuator.
• the shaft 28 may be concentrically positioned within the body and the bending moments experienced on the eccentric shaft of the previously described embodiments, as a result of the eccentric positioning of the shaft are eliminated. This embodiment does, however, maintain many of the benefits of the eccentric shaft actuator described above, including the ability to utilize a thin-wall design and to eliminate backlash, among others.
• the bearing plate 56 is in the form of a ring and the set screws 70 for the elimination of backlash bear directly on the face of the piston sleeve 42. While the cross-sectional shape of the body sidewall 14 is shown as oblong or elliptical, other non-cylindrical shapes may be used. 21

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Transmission Devices (AREA)

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• 1986
  • 1986-07-15 EP EP19860904688 patent/EP0229833A1/de active Pending
  • 1986-07-15 WO PCT/US1986/001490 patent/WO1987000590A1/en unknown
  • 1986-07-15 AU AU61380/86A patent/AU6138086A/en not_active Abandoned

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