FLUID-POWER DEVICE WITH ROLLER

Abstract: A fluid-powered device having a body (12) with interior helical grooves, and output shaft (20) with exterior helical grooves, a plurality of rollers (84) having circumferential grooves, and an axially receiprocating piston sleeve (50) mounted within the body (12) and retaining the rollers (84) in fixed axial and circumferential position relative to the piston sleeve (50) during powered operation of the device. The rollers (84) are retained by the sleeve portion of the piston sleeve (50) in circumferentially distributed arrangement between the grooved body and shaft surface portion with a first plurality of the rollers (84) in seated engagement with the grooved body and a second plurality of the rollers (84) in seated engagement with the grooved output shaft for transmitting force between the body (12), output shaft (20) and piston sleeve (50). In alternative embodiments, the rollers include a single set of rollers mounted on spindles carried by the piston sleeve, two sets of axially separated rollers positioned in windows of the piston sleeve and mounted on spindles therein, and two sets of radially staggered rollers in both nested and spaced-apart arrangements. The rollers may be an integral unit or comprised of a plurality of rollers disk, and may be axially offset from adjacent rollers or be axially skewed at a skew angle. The spindles are axially adjustable to eliminate backlash.

Description: The present invention relates to a fluid-power device as outlined in the preambles of claims 1 and 30. A fluid-powered device of this type is disclosed in US-A-4 590 816. The known actuator or fluid-power device comprises torque-transmitting helical races for carrying a plurality of balls. Ball bearings, however, are difficult to mount since the balls of the known device cannot and are not adapted to be retained in fixed axial and circumferential position. In the past, rotary helical splined actuators have been employed to achieve the advantage of high-torque output from a simple linear piston-and-cylinder drive arrangement. The actuator typically uses a cylindrical body with an elongated rotary output shaft extending coaxially within the body, with an end portion of the shaft providing the drive output. An elongated piston sleeve is disposed between the body and the shaft and coaxially receives the shaft therein. The piston sleeve has a sleeve portion splined to cooperate with corresponding splines on the body interior and the output shaft exterior. The piston sleeve 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 piston sleeve. As the piston sleeve linearly reciprocates in an axial direction within the body, the outer splines of the sleeve portion engage the splines of the body to cause rotation of the sleeve portion. The resulting linear and rotational movement of the sleeve portion is transmitted through the inner splines of the sleeve portion 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. While such an arrangement produces a relatively high-torque output, the capability of the actuator is inherently limited by the use of splines. Splines having certain characteristic limitations relating to the number of turns, pitch, surface contact drag and free play between the corresponding splines which limit the axial and radial loads that the shaft can be subjected to and the operating efficiency of the actuator. For high-torque, high-efficiency applications, the rigid splined helical actuators have been found to have an undesirably high frictional coefficient and large loads can cause binding between the corresponding spline. While actuators using balls to transmit torque have been manufactured and are an improvement upon the splined actuator, further improvement is desirable. It will therefore be appreciated that there has been a significant need for a fluid-powered actuator and other devices such as pumps which are capable of handling increased axial and radial shaft loads while decreasing the weight and size of the device and decreasing the difficulty and expense of manufacturing the device. Fluid-power devices fulfilling this need show the features of claims 1 and 30. The fluid-power device or actuator could be used as a pump or for any further purposes requiring the axial movement of a piston to result or to be produced by relative rotational or linear movement between a body and an output member. The device of the present application has a low friction design to increase efficiency, an uncomplicated and strong design to increase reliability, and is useable for heavy duty applications. Preferably the device will provide a higher output efficiency by using force transmission components producing rolling friction which is less than the sliding friction of splines. At least some embodiments should provide backlash elimination adjustment means to reduce the need for exceptionally accurate machining, to facilitate easy assembly of the device, and to eliminate the slack that produces backlash after the device is assembled. The present invention fulfills these needs and further provides other related advantages. The first and second pluralities of rollers are in fixed radial and circumferential position relative to the reciprocating member with the first rollers being axially positioned spaced away from the grooved drive member outward surface portion and radially positioned to engage the grooved body inward surface portion, and the second rollers being axially positioned spaced away from the grooved body inward surface portion and radially positioned to engage the grooved drive member outward surface portion. In another embodiment, the first and second pluralities of rollers are positioned next to each other. Embodiments of the present invention are hereinafter descibed with reference to the accompanying drawings. Brief Description of the Drawings Figure 1 is a side elevational, sectional view of a fluid-powered roller rotary actuator embodying the present invention, taken substantially along the line 1-1 of Figure 2. Figure 2 is a sectional view of the actuator taken substantially along the line 2-2 of Figure 1. Figure 3 is an isometric view of a circumferentially grooved roller of the type used in the actuator of Figure 1. Figure 4 is a partial side elevational, sectional view of an alternative embodiment of the invention similar to the embodiment of Figure 1 but with the fluid compartments separated from the force-transmitting parts. Figure 5 is a partial fragmentary side elevational, sectional view of another alternative embodiment of the invention utilizing two roller sets for backlash elimination. Figure 6 is an isometric view of an enlarged windowed sleeve of the type used in the actuator of Figure 5 and showing an alternative backlash elimination adjustment design. Figure 7 is a side elevational, partial sectional view of another embodiment of the invention utilizing cantilevered axially skewed rollers. Figure 8 is a reduced size, end view of a spindle support plate used in the embodiment of Figure 7, shown removed from the actuator. Figure 9 is a fragmentary, partial side elevational, sectional view of an alternative embodiment of the rollers. Best Mode for Carrying out the Invention As shown in the drawings for purposes of illustration, the present invention is embodied in a fluid-power device. A first embodiment of the device is a rotary actuator 10 shown in Figures 1 and 2. The actuator 10 includes a elongated housing or body 12 having a cylindrical sidewall 14 and first and second ends 16 and 18, respectively. An elongated rotary output shaft 20 having a hollow center bore 21 is coaxially positioned within the body 12 and supported for rotation relative to the body. An annular first end cap 22 is positioned at the first body end 16 and has a threaded outer perimeter portion 24 threadably attached to a threaded end portion 26 of the body 12. The first end cap 22 has a central aperture 28 to receive an axially outward end portion 30 of the shaft 20. The shaft 20 has a radially outward extending flange portion 32 positioned toward the first body end 16 between the end cap 22 and a stop ring 34. The stop ring 34 is held in place in the body 12 against axial movement by an interior axially outward facing stop shoulder 36 of the body and an axially inward projecting cylindrical flange portion 38 of the first end cap 22. The shaft 20 is rotatably held in place against axially thrust by thrust bearings 40 disposed between the shaft flange portion 32 and the stop ring 34 and between the shaft flange portion and the end cap flange portion 38. A second end cap 44 is positioned at the second body end 18 and has a threaded outer perimeter portion 46 threadably attached to a threaded end portion 48 of the body 12. The shaft end portion 30 has a splined shaft extension 49 for coupling to an external device (not shown), however, any conventional means of attachment may be used. The body 12 is adapted for attachment to a stationary support frame (not shown), by a plurality of threaded recesses 41 circumferentially spaced about a radially outward flanged portion 42 of the body sidewall 14. It is to be understood that the invention may be practiced with the shaft 20 rotatably driving an external device, or with the shaft being held stationary and the rotational drive being provided by rotation of the body 12. A piston sleeve 50 is coaxially and reciprocally mounted within the body 12 coaxially about the shaft 20. The piston sleeve 50 has a head portion 52 positioned toward the second body end 18, and a cylindrical sleeve portion 54 fixedly attached to the head portion and extending axially therefrom toward the first body end 16. The shaft 20 has an axially inward end portion 56 which extends axially toward the second body end 18 to within the sleeve portion 54, but terminates short of the head portion 52. The head portion 52 carries conventional seals 58, disposed between the head portion and a corresponding interior smooth wall portion 60 of the body sidewall to define fluid-tight compartments 62 and 64 to each side of the head portion toward the first body end 16 and the second body end 18, respectively. The smooth sidewall portion 60 of the body sidewall has sufficient axial length to accommodate the full stroke of the head portion 52 within the body 12. Reciprocation of the piston sleeve 50 within the body 12 occurs when hydraulic fluid or air under pressure selectively enters through one or the other of a port 66 located in the sidewall 14 and a port 68 located in the second end cap 44. As used herein "fluid" will refer to hydraulic oil, air or any other fluid suitable for use in the actuator 10. The ports 66 and 68 each communicates with one of the fluid-tight compartments 62 and 64, respectively. Conventional seals 70 are disposed between the first and second end caps 22 and 44 and the body 12 and between the shaft end portion 30 and the first end cap 22 to prevent fluid leakage from the compartments. The application of fluid pressure to the compartment 62 produces axial movement of the piston sleeve 50 toward the second body end 18. The application of fluid pressure to the compartment 64 produces axial movement of the piston sleeve 50 toward the first body end 16. The actuator 10 provides relative rotational movement between the body 12 and the shaft 20 through the conversion of linear movement of the piston sleeve 50 into rotational movement of the shaft, as will be described in more detail below. An inward facing surface portion 72 of the body sidewall 14 toward the first body end 16 has cut therein a plurality of helical grooves 74 having the same lead angle and a uniform and axial pitch. The helical body grooves 74 extend about the sidewall 14 and have helical ridges 76 therebetween. An outward facing surface portion 78 of the shaft end portion 56 has cut therein a plurality of helical grooves 80 having the same lead angle and a uniform lead and axial pitch. The helical shaft grooves 80 extend about the shaft 20 and have helical ridges 82 therebetween. The outward shaft surface portion 78 is located generally opposite the grooved inward body surface portion 72 and spaced apart radially inward therefrom to define a circumferential space 79 therebetween. The helical body grooves 74 have an opposite hand or direction of turn from the helical shaft grooves 80. In the embodiment of Figure 1, the helical body grooves 74 are left hand, and the helical shaft grooves 80 are right hand. As will be discussed in more detail below, the number of grooves or groove starts comprising the plurality of helical body and shaft grooves 74 and 80 varies from design to design. As used herein "lead angle" is the helix angle of a helical groove, "lead" is the linear advance resulting from one full revolution along a helical groove, "pitch" is the axial distance between adjacent helical grooves, and "pitch diameter" is the diameter of the grooved part measured from the groove half-depth position. The actuator 10 is provided with a set of elongated force transmitting rollers 84 disposed in a circumferentially aligned row in the circumferential space 79 between the grooved inward body surface portion 72 and the grooved outward shaft surface portion 78. As best shown in Figure 3, the rollers 84 each have cut in the outward facing surface thereof a plurality of circumferential grooves 86 with circumferential ridges 88 therebetween. The circumferential grooves 86 extend about the roller 84 in parallel spaced apart radial planes. The circumferential grooves 86 of the rollers 84 have substantially the same axial pitch as the helical body and shaft grooves 74 and 80. The rollers 84 have a pitch diameter (PD3) sized based upon the first pitch diameter PD1 of the grooved inward body surface portion 72 and the second pitch diameter PD2 of the grooved outward shaft surface portion 78, substantially according to the relationship: The relationship of the pitch diameters is best illustrated in Figure 2. If desired, the circumferential grooves 86 and ridges 88 of the rollers 84 may be axially spaced apart to skip certain of the helical body and shaft grooves 74 and 80. When using rollers with the same axial position within the actuator (i.e., with the corresponding ridges 88 of each roller in the same plane), the number of grooves on the shaft must be equal to the number of rollers or must be an integer multiple thereof, assuming the rollers are circumferentially distributed with equal inter-roller spacing. For example, if there are eight rollers or at least eight equally spaced roller positions, the shaft must have 8, 16, 24 or 32 grooves, etc. In any event, the groove spacing of the roller must correspond to the axial pitch or groove spacing of the shaft and body with which the roller grooves mesh. As will be described below, in alternative embodiment shown in Figures 14, 15 and 16, the rollers 84 may be axially offset to permit further flexibility in the selection of the number of shaft and body grooves which can be used for a particular number of rollers. The rollers 84 are rotatably retained in fixed axial and circumferential position relative to the piston sleeve 50 as the piston sleeve reciprocates within the body 12 during fluid-powered operation of the actuator 10 by a plurality of cylindrical shaft spindles 90. Each of the spindles 90 has a coaxially extending and integrally formed support arm portion 92. The support arm portions 92 are disposed in a plurality of bore holes 94 formed in an axially outward end wall 96 of the sleeve portion 54 facing toward the first body end 16. The bore holes 94 are evenly circumferentially spaced-apart about the sleeve portion 54 and axially extending fully through the sleeve portion 54 and the head portion 52, and O-ring seals 97 are provided in grooves in the support arm portions 92 to prevent fluid leakage between the compartments 63 and 64. The support arm portion 92 has an exterior threaded end portion 98 threadably received in an interior threaded end portion 100 of its corresponding bore holed 94. The support arm threaded end portion 98 may be threaded into the bore holed threaded end portion 100 by turning the spindle 90 using a slot 102 cut in the axial end face thereof. The support arm portion 92 has a radially outward extending flange 104 which engages the sleeve portion end wall 96 when the support arm portion is fully threaded into the bore hole 94. As will be described below, certain of the support arm portions 92 are adjusted so as to not be fully seated against the flange 104 for backlash elimination purposes. The spindles 90 project into the circumferential space 79 and hold the rollers 84 restrained against axial movement relative to the spindles for rotation about the spindles on axes in parallel axial alignment with the body 12. The spindles 90 also retain the rollers 84 in circumferentially distributed, spaced apart positions within the circumferential space 79 about the shaft 20 with each of the rollers in seated engagement and coacting with the helical body grooves 74 and the helical shaft grooves 80 for transmitting force between the body 12, the shaft 20 and the piston sleeve 50. Each ridge 88 of the rollers 84 is positioned for rolling travel in corresponding grooves of both the helical body grooves 74 and the helical shaft grooves 80, and the corresponding ridges 88 of adjacent rollers are axially positioned in generally the same plane. As will be described below, in alternative embodiments the rollers can be axially offset from one another. The spindles 90 are arranged in parallel axial alignment with the body 12 and each have one of the roller 84 coaxially and rotatably retained thereon and retrained against axial movement relative to the spindle. The rollers 84 each have longitudinally extending coaxial roller bore 106 therethrough for rotatably receiving one of the spindles 90. the axial roller bore 106 is defined by an interior sidewall 108, and the corresponding roller bore sidewall and spindle exterior surface have formed thereon a plurality of confronting and corresponding ball races 110 and 112, respectively, defining a plurality of ball channels extending circumferentially thereabout. A plurality of balls 114 are seated in each of the ball channels formed by the ball races 110 and 112 to prevent axial movement of the roller 84 relative to the spindle 90 against axial thrust encountered during powered operation while permitting free rotation of the roller on the spindle. Preferably, the circumferential roller ball races 110 are formed on the roller bore sidewall 108 radially inward from and axially positioned corresponding to the circumferential roller ridges 88 so that the cutting of the roller ball races does not adversely affect the roller strength. A sufficient number of balls and ball channels must be used to handle extremely large axial loads encountered during operation. The balls 114 can be inserted into the ball channels with the rollers 84 positioned on the spindles 90 using a ball filler hole 116 extending radially through each of the roller ridges 88 and communicating with the corresponding ball race 110. After a sufficient number of balls 114 are inserted through the filler hole 116 to fill the ball race 110, a sealer plug 118 is inserted into the hole to prevent passage of the balls out of the hole during operation of the actuator 10. As will now be described, linear reciprocation of the piston sleeve 50 produces rotation of the piston sleeve and the shaft 20 through the force-transmitting capability of the rollers 84. As the piston sleeve 50 linearly reciprocates between one or the other axial directions within the body 12 through application of fluid pressure to the fluid-tight compartments 62 and 64, torque is transmitted by the rollers 84 to the piston sleeve through their coaction with the helical body grooves 74. The axial force created by fluid pressure on the head portion 52 causes the rollers to roll along the helical body grooves 74 and transmit torque to the piston sleeve 50. The transmitted torque causes the piston sleeve 50 to rotate as it moves axially. By way of example, since the helical body grooves 74 are left hand, the piston sleeve 50 rotates counterclockwise when viewed from the first body end 16 as the piston sleeve moves from the first body end to the second body end 18 when fluid pressure is applied to the compartment 62 through the port 66, as shown by arrow A in Figure 2. As the piston sleeve 50 rotates counterclockwise, the rollers 84 roll along the helical body grooves 74 and themselves rotate clockwise, as shown by arrow B. The resulting linear and rotational movement of the piston sleeve 50 transmits both axial and rotational force to the shaft 20 through the coaction of the rollers 84 with the helical shaft grooves 80. The transmitted force causes the shaft 20 to rotate relative to the body 12 since axial movement of the shaft is restricted by the thrust bearings 40. As such, axial movement of the piston sleeve 50 produced by fluid pressure is converted into relative rotational movement between the body 12 and the shaft 20. The resulting movement when viewed from the body ends is much like the movement of a planetary gear arrangement. Continuing the example discussed above, since the helical shaft grooves 80 are right hand, the axial movement of the piston sleeve 50 toward the second body end 18 causes the shaft 20 to rotate counter clockwise relative to the piston sleeve, as shown by arrow C in Figure 2. As the shaft 20 rotates counterclockwise, the rollers 84 roll along helical shaft grooves 80 with a clockwise rotation. Since this is the same roller rotation as caused by the rollers rolling along the helical body grooves 74, no scuffing or slippage of the rollers occurs and the advantage of rolling friction rather than sliding friction is enjoyed. As noted above, since both the piston sleeve 50 and the shaft 20 rotate counterclockwise in response to the application of fluid pressure to the compartment 62, the resulting relative rotation between the body 12 and the shaft is the sum of the rotation of the piston sleeve relative to the body and the rotation of the shaft relative to the piston sleeve. It is noted that the rotational directions described above are merely reversed when the piston sleeve 50 moves from the second body end 18 to the first body end 16 when fluid pressure is applied to the compartment 64 through the port 68. It is further noted that it is necessary to utilize the opposite hand turn for the helical body and shaft grooves with the embodiment of the invention shown in Figure 1 to avoid the rollers 84 scuffing or slipping as result of the rollers tending to rotate in one direction due to the piston sleeve rotation and opposite direction due to the shaft rotation. If the rollers do not roll with the surface they engage, they will slide with respect to the surface and produce disadvantageous sliding friction much like that of splines. Thus, the sometimes advantageous arrangement of using the same hand turn for the helical body and shaft grooves to produce differential rotation is not possible while achieving the benefit of rolling friction. Still referring to the embodiment of Figure 1, the actuator 10 is provided with means for eliminating backlash in the force-transmitting parts and for axially preloading of the piston sleeve 50 and the rollers 84 positioned therein, which transmit force between the body and the shaft through the piston sleeve. Backlash occurs as the piston sleeve 50 moves from one axial direction to the other within the body as it reciprocates. As previously described, the spindle support arm portion 92 has a threaded end portion 98 threadably received in an interior threaded end portion 100 of the sleeve bore hole 94. Circumferentially alternate support arm portions 92 are fully threaded into the sleeve 54 with the flange in seated engagement with the sleeve portion end wall 96, and not moved. Preferably every other of the support arm portions 92 is intended to be selectively and adjustably movable in their sleeve bore holes 94 for the purpose of backlash elimination prior to commencing fluid powered operation. The adjusting axial movement of every other of the support arm portions 92, and thus the spindles 90 extending therefrom and the rollers 84 rotatably retained thereby, relative to the stationary support arm portions, and thus the spindles extending therefrom and the rollers rotatably retained thereby, tends to eliminate backlash by reducing the slack between the rollers and the helical body and shaft grooves 74 and 80 which coact with the rollers. When all slack between either the rollers and the helical body grooves or the rollers and the shaft grooves has been eliminated, further axial adjustment will apply an axial preloading force on the piston sleeve and the rollers. The rollers 84 associated with the support arm portions 92 which are maintained stationary with respect to the piston sleeve 50 are designated in Figures 1 and 2 by the reference numeral 84a, while the rollers associated with the support arm portions which are adjustably moved with respect to the piston sleeve to eliminate backlash are designated 84b. To lock the support arm portions 92 in position once axially adjusted to eliminate backlash, each adjusted support arm portion is provided with a locking set screw 120 extending through a threaded bore hole 122 in the head portion 52 and into the sleeve bore hole 94. The set screw 120 engages and applies an axial outward locking force to the end of the support arm portion 92. Should usage of the actuator 10 cause wear of the grooves or the rollers seated therein, or should slack occur for any other reason, the slack can be removed in the same manner described above by further axial adjustment of the support arm portions. With the present invention, the grooves may be machined using conventional machining techniques with standard tolerances, and the slack which creates the backlash problem can be eliminated by adjustment prior to fluid-powered operation of the actuator 10. Furthermore the grooves can be machined with a size to permit easy assembly of the actuator and the slack thereby introduced can be eliminated by adjustment. It is noted that the backlash elimination described will eliminate an equal amount of slack between the rollers and the helical body and between the rollers and the shaft grooves. A significant advantage with the present invention is the reduction in machining time and cost by utilizing helical grooves 74 and 80 only on the body 12 and the shaft 20, rather than the four helical grooved surfaces required for force transmission using conventional helical splines or ball races. Cutting of grooves on the piston sleeve 50 has been completely eliminated. As such, the number of helical grooves which must be cut with the expensive and slow precision equipment required to cut helical grooves are reduced, thus reducing the expense and time of manufacture. Moreover, the roller 84 can be simply turned on a lathe to cut their circumferential grooves 86. By utilizing backlash elimination, the parts need not be manufactured to extremely close tolerances, further reducing the expense of manufacture. The rollers 84 of the present invention achieve the benefit of reduced friction by using rolling friction, as do balls, rather than the sliding friction of splines, yet the friction reduction over splines can be achieved with rollers using less axial length than balls. Moreover, since the surface contact for rollers is spread over a greater area than with balls, the walls of the grooves with which the rollers coact can be cut thinner while still retaining adequate strength. This also allows the grooves to be placed closer together for more dense packing of the rollers than can be achieved than with balls. As a result of these benefits, the overall actuator weight can be reduced compared to a ball actuator of equivalent power rating and a more reliable actuator produced. Compared to splines, the rollers also provide the benefit of serving as roller bearing to reduce frictional drag and to provide aligning support for the body, piston sleeve and shaft. This facilitates easy shaft rotation and reduces shaft binding under extreme loads. It is to be understood that while the described embodiment of Figure 1, as well as all embodiments of the invention which will be described hereinafter are described as fluid-powered rotary actuators, devices of the same general construction utilizing the invention may be manufactured for use as linear actuators, fluid pumps, shock absorbers and the like. In the situation of a linear actuator, the shaft 20 is partially or completely restrained against rotation but permitted to move axially relative to the body 12 in response to reciprocation of the piston sleeve 50. In the situations of pumps or shock absorbers, the shaft 20 is rotated as the input member and the resulting reciprocal movement of the piston sleeve 50 causes the head portion 52 to pump fluid through the ports 66 and 68. For ease of understanding, the components of the alternative embodiments of the invention described hereinafter will be similarly numbered with those of the first embodiment when of a similar construction. Only the differences in construction will be described in detail. An alternative embodiment of the invention very similar to the embodiment of Figure 1 is shown in Figure 4. In this embodiment, the piston sleeve 50 has an elongated, axially extending neck portion 124 extending between the sleeve portion 54 and the head portion 52. The head portion 52 is formed in two pieces, and includes an interiorly threaded ring 126 threadably attached to an exteriorly threaded end portion 128 of the piston sleeve neck 124. The piston head ring 126 carries the seal 58, and a seal 130 is provided between the ring and the neck portion 124 to prevent fluid leakage. In the embodiment of Figure 4, the cylindrical sidewall 14 is formed in two parts 14A and 14B securely connected together in fixed relation by an interiorly positioned annular connector plug 132. The connector plug 132 has exterior threads which are threadably attached to a threaded end portion 134 of the sidewall part 14A and a threaded end portion 136 of the sidewall part 14B. The plug 132 has a central aperture 138 through which the neck portion 124 of the piston sleeve 50 slides as the piston sleeve reciprocates. The plug 132 divides the interior of the body 12 into a first chamber 140 to a side of the plug toward the first body end 16 within which the sleeve portion 54 and the spindle 92/roller 84 assembly is positioned, and a second chamber 142 to a side of the plug toward the second body end 18 within which the head portion 52 is positioned. The plug 132 has conventional seals 144 disposed between the plug and the sidewall parts 14A and 14B, and between the plug and the piston sleeve neck portion 124. The first body chamber 142 is divided by the head portion 52 into the two fluid-tight compartments 62 and 64 with which the ports 66 and 68 communicate. The compartments 62 and 64 are sealed from the second body chamber 140 by the plug 132 and seals 144 to prevent the fluid used to power the actuator 10 from entering the first chamber 140. A port 146 is provided to the first chamber 140 for applying lubrication oil or grease to the force-transmitting compartments contained therein. Except for the separation of the fluid compartment 62 and 64 from the force-transmitting parts, and several other minor changes, the actuator 10 of Figure 4 is structurally and operatively identical to the actuator of Figure 1. In the alternative embodiments of the invention shown in Figures 5 and 6, the sleeve portion 54′ of the piston sleeve 50 has a first set of circumferentially spaced apart windows or sidewall openings 148 and a second set of circumferentially spaced apart windows or sidewall openings 150. The first set of sidewall openings 148 are axially spaced apart from the second set toward the first body end 16, inward from the outward end wall 96 of the sleeve portion 54′. The first and second sidewall openings 148 and 150 extend fully through the cylindrical sidewall of the sleeve portion 54′, and are each sized to receive one of the rollers 84 therewithin. The sidewall of the sleeve portion 54′ has a wall thickness sufficiently thin such that the rollers 84 extend radially inward and outward beyond the sidewall to seat in both the helical body and shaft grooves 74 and 80, and coact therewith for transmitting force between the body 12, the shaft 20 and the piston sleeve 50, in the manner described above for the embodiment of Figure 1. By the use of two sets of rollers 84, the thrust handling capacity of the actuator is effectively doubled. The rollers 84 are rotatably retained in the sidewall openings 148 and 150 in fixed axial and circumferential position relative to the piston sleeve 50 as the piston sleeve reciprocates within the body 12 during fluid powered operation of the actuator by a plurality of spindles 90′. One spindle 90′ is disposed in each of the sidewall openings 148 and 150 in parallel axial alignment with the body 12 and has one of the rollers 84 coaxially and rotatably retained thereon and restrained against axial movement relative to the spindle. The rollers are retained on the spindles 90′ in the manner previously described using a plurality of confronting and corresponding ball races 110 and 112 with a plurality of balls 114 seated in each of the ball channels formed by the ball races. Each sidewall opening 148 of the first set of sidewall openings has a corresponding axially spaced apart sidewall opening 150 of the second set of sidewall openings, with the corresponding sidewall openings have the same circumferential position on the sleeve portion 54′ to provide a plurality of pairs of corresponding axially spaced apart sidewall openings. Each of the spindles 90' disposed in the sidewall openings 148 and 150 has a longitudinally extending coaxial spindle bore 152 therethrough for slidably receiving an alignment pin 154. Each alignment pin 154 extends straight through both sidewall openings 148 and 150 of a corresponding pair of axially spaced apart sidewall openings, and through the spindle bore 152 of each of the spindles 90′ disposed in the pair of sidewall openings. The alignment pins 154 are restrained by the sleeve portion 54′ circumferential and radial movement relative to the sleeve portion, and restrain the spindles 90' against circumferential and radial movement within the sidewall openings 148 and 150. The sidewall openings 150 of the second set of sidewall openings have an axial length substantially equal to the axial length of the spindles 90' disposed therein, with the axially outward end faces of the spindles engaging the axially inward end walls of the sidewall openings. As such, the rollers 84 retained on the spindles 90′ in the sidewall openings 150 are restrained against axial movement in the sidewall openings. The rollers 84 have an axial length less than that of the spindles 90′ and hence do not engage the end walls of the sidewall openings and remain free to rotate of the spindles. For backlash elimination purposes, the sidewall openings 148 of the first set of sidewall openings have an axial length sufficiently greater than the axial length of the spindles 90′ disposed therein to allow adjustable axial movement of the spindles, and hence the rollers 84 mounted thereon, within at least a limited range. The actuator 10 further includes a plurality of exteriorly threaded adjustment set screws 156, each threadably and adjustably received in an interiorly threaded set screw bore hole extending between the axially outward facing end wall 96 of the sleeve portion 54′ and one of the sidewall opening 148 of the first set of sidewall openings. The set screw 156 projects into the corresponding first sidewall opening 148 and slidably engages an axially outward facing end wall of the spindle 9′ disposed therein. The set screws 156 are selectively extendable to exert an adjustable axial force on the engaged spindles 90′ to selectively and adjustably axially move the engaged spindle on its alignment pin 154, and thus the roller 84 retained by the spindle, by an amount within the limited range for spindle movement. This moves the roller of the engaged spindle relative to the roller retained by the spindle in the axially corresponding sidewall opening 150 of the second set of sidewall openings to reduce the slack between the two rollers and the helical body and shaft grooves 74 and 80 with which they coact and allows axial preloading. A set screw 156 is provided for each axially corresponding pair of sidewall openings. Each of the set screws 156 is provided with an axially outward opening hexagonal aperture 158 for adjustably turning the set screw with a tool. In this embodiment of the invention, threaded recesses 159 in the shaft end portion 30 are used for attachment of the shaft 20 to an external load. The recesses 159 extend fully through a radially outward extending flange portion 160 of the shaft 20 positioned toward the first body end 16. The recesses 159 are also used to provide access to the set screws 156 within the body 12, and are positioned to correspond to the set screws 156 for their adjustment without disassembling the piston sleeve 50 from the body 12. Each of the recesses 159 is sealed against fluid leakage when not opened for making adjustments by a threaded plug 162 carrying an O-ring 164. The shaft flange portion 32 projects outward from the flange portion 160 and utilises balls as the thrust bearings 40. In the embodiment of Figure 5, the alignment pins 154 each have a smooth shank portion 166 which is slidably disposed in a smooth bore 168 extending fully through a sidewall portion 170 of the sleeve portion 54′ dividing the pairs of axially corresponding sidewall openings of the first and second sidewall openings 148 and 150. A smooth bore 172 extends from each of the second sidewall opening 150 into an adjacent sidewall portion 174 of the sleeve portion 54′ to slidably receive a smooth end portion 175 of the alignment pin 154. The alignment pin 154 is further provided with a distal threaded end portion 176 threadably received in a longitudinally extending, threaded coaxial bore 178 in the corresponding set screw 156. As such, the alignment pin 154 travels with the set screw 156 as it is adjusted axially inward and outward for backlash elimination, with the smooth shank portion 166 and end portion 175 slidably moving in the smooth bores 168 and 172. Alternatively, the adjustment pin may be otherwise fixedly attached to the set screw or be formed as an integral part of the set screw. The sleeve portion 54′ is best shown in Figure 6 with an alternative arrangement for the alignment pins and set screws. Although otherwise identical in structure and function, the set screws 15′ in Figure 6 have a slot 179 in the axially outward end face thereof for adjustably turning the set screw with a tool and a smooth axial bore 178′ with an axially outward facing radial shoulder 180. The alignment pin 154′ is slidably received in the set screw bore 178′ and has a head 182 engaging the shoulder 180. A distal end portion 184 of the alignment pin 154′ is threaded and threadably received in a threaded bore hole 186 formed in a plug 188 extending transversely through the sidewall portion 174 of the sleeve portion 54′. With this embodiment, after the set screw 156′ is adjusted to eliminate backlash, the set screw can be locked in position by turning the alignment pin 154′ with a tool using a hexagonal aperture 190 in the pin head 182 to apply an axially inward force on the set screw through engagement of the head with the set screw shoulder 180. Yet another embodiment of the invention is shown in Figures 7 and 8. In this embodiment, the body sidewall 14 is formed in first and second body halves 454 and 456, respectively, which each have a threaded inward end portion 458 threadably connected to the inward end portion of the other body half. Rather than using end caps, the body 12 has first and second end annular body flange portions 460 and 462 projecting radially inward from the body sidewall 14 at the first and second body ends 16 and 18, respectively. The shaft 20 is held in place against axial thrust by the first and second end ball races 412 and 414, respectively, and the balls 410 disposed therein. The first end ball races 412 are formed in the first end body flange portion 460 and a corresponding portion of the shaft 20 toward the first body end 16. The second end ball races 414 are formed in the second end body flange portion 462 and a corresponding portion of the shaft 20 at the second body end 18. Conventional seals 463 are disposed between the first and second body end flange portions 460 and 462 and the shaft 20 to prevent fluid leakage. In this embodiment, a single annular piston head portion 464 is utilized and carries an inner seal 466 to provide a fluid-tight seal between the piston head portion and the smooth wall shaft portion 416 of the shaft 20. As with the previously described embodiment of Figure 14, the piston sleeve 50 does not carry an outer seal, but rather a seal 468 is positioned stationary within a groove 470 in the first body halve 454 toward the mid-portion of the body sidewall 14. The piston sleeve 50 has a smooth outer wall portion 471 which is sealably engaged by the seal 468 and slides past the seal as the piston sleeve reciprocates within the body 12. The smooth outer wall portion 471 has sufficient axial length to accommodate the full stroke of the piston sleeve 50. By not requiring the piston sleeve to carry both inner and outer seals in order to form the fluid-tight chambers 62 and 64, the overall length of the actuator 10 is shortened and placement of the port 66 is made easier, as will be described in more detail for another embodiment. Also, the use of the split housing using body halves 454 and 456 is made possible where the first body half can be manufactured from a less expensive casting since the first body half has no grooves or expensive interior finishing, and only serves as a simple pressure vessel. Although less expensive, it has been found undesirable to use a casting where a smooth wall interior surface must be machined for engagement by a sliding seal. This is because of the voids found in even the better castings which when exposed by the machining causes the interior surface to be somewhat abrasive, and results in undesirable seal wear. In the embodiment of Figure 7, the problems of bending and possible failure under large loads inherent with cantilevered spindles is reduced for the straight spindles 92 at the second body end 18 by the use of an annular spindle support plate 483. The plate 483 has holes 485 circumferentially spaced apart around the plate and sized to receive the free end portions of each of the spindles, as shown in Figure 8 with the plate removed from the actuator 10. The plate 483 is positioned on the free end portions of the spindles 92, axially outward of the outermost roller disk 208 comprising each of the rollers 84 and inward of the split rings 230 on the spindles. As with the individual retainer rings 226 used in the embodiment of Figure 13, the side of the plate 483 toward the disks 208 has an axially inward opening ball groove 487 formed concentric with each of the plate holes 485 and corresponding to the ball groove 216 of the outermost roller disk 208. The ball groove 487 and the ball groove 216 of the roller disk form a complete roller ball race. The plate 483 ties the free end portions of the spindles 92 together and thereby provides them with lateral support and improves their ability to withstand bending and failure under loading. In Figure 9, an alternative embodiment of a roller 600 is shown which is usable with any of the actuators described using spindles. The roller 600 is shown mounted on a spindle 602 engaged with the helical shaft grooves 80 of the shaft 20. The roller 600 includes a pair of annular roller disks 604, indicated by the reference letters a and b, disposed on the spindle 602 in axially adjacent position and operating together to form the roller. Each of the roller disks 604 has a coaxial opening 606 therethrough sized to slide axially onto the spindle 602 during assembly and for free rotation about the spindle during powered operation. However, the roller disks 604 of this embodiment also have several important differences which provide improved performance. The roller disks 604a and 604b each have axially outward and oppositely facing first and second sidewalls 608 and 610, respectively, which form the roller surfaces for contact with the helical grooves. The disks also include first and second annular extensions 612 and 614, respectively. The first and second extensions 612 and 614 extending axially outward from the first and second sidewalls 608 and 610, respectively, and space the adjacent roller disks 604a and 604b axially apart to provide the desired roller pitch. By increasing the axial length of the first and second extensions 612 and 614 used, the roller pitch can be increased as needed without impacting the size and shape of the first and second roller sidewalls 608 and 610, which may be designed for optimum groove contact. By increasing the spacing between the sidewalls of adjacent disks 604a and 604b, the roller disks 604a and 604b can project deeper into the helical grooves. This is because the interference inherent in the closely spaced adjacent disks of Figure 9 and 10 is avoided. As such, the helical grooves can be cut wider and the disks 604 will still contact the helical grooves at the groove half-depth position. In addition, with the disks 604 of Figure 9 the first and second sidewalls 608 and 610 can be machined with a larger radius of curvature for improved groove contact without undesirable contact of the edges of the rollers with the ridges of the helical grooves, which has been a particular problem when using axially skewed rollers. To select the curvature of the first and second sidewalls 608 and 610, the surfaces of the helical grooves are diagramatically extended to determine the location of a sharp peak position 611 for the ridge of the helical groove and a sharp valley position 613 for the groove, as shown by the projection lines 616 in Figure 9. A center position 618, half way between the peak and valley positions 612 and 614, is next determined. This mid-point establishes a pitch line 615 (i.e., the point used to determine the pitch diameter of the helical grooves). A line 620 is then projected at a right angle to the grooved surface, as shown in Figure 9 for the first sidewall surface 608 of the roller 604b for purposes of illustration. To determine the center of curvature to be used for the roller sidewalls 608 when not axially skewed, a second line 622 is positioned parallel to the line 620 and spaced laterally therefrom along the pitch line toward the roller disk by the clearance to permit the out of alignment positioning of the roller in the grooves (the roller is shown in Figure 9 aligned with the groove). This establishes a point 624 on the roller surface and the line 622 is a radial line used for determining the center of curvature of the roller, with the center of curvature being at a point 626. When in engagement with the groove, the roller will contact the groove along the pitch line 615, at the point 624 on the roller and the point 618 on the groove. This provides rolling engagement much like a spherical ball bearing having a radius equal to the radius of curvature selected for the roller surface. The radius of curvature is selected as large as possible, but small enough to avoid edge contact (i.e., contact between the roller and the grooves along parts of the roller surface outward of the point 624). Edge contact is minimized by further providing the roller surface with a reverse radius of curvature using a point 627 as the center of curvature. This is to provide an enlarged space between the roller and the groove to make certain any edge contact and the wear resulting therefrom is avoided. It is noted that the grooves used with the rollers 600 have truncated ridges 628 to further minimize edge contact.

Claims: A fluid-power device (10), comprising: a body (12) having a plurality of helical grooves (74) with ridges (76) therebetween formed on an inward facing surface portion (72) thereof; an axially extending drive member (20) supported for rotational movement relative to said body (12) and connectable to an external device, said drive member (20) having a plurality of helical grooves (80) with ridges (82) therebetween formed on an outward facing surface portion (78) thereof positioned within said body (12); a plurality of roller means (84); an axially reciprocating member (50) reciprocally mounted within said body (12), said reciprocating member (50) rotatably retaining said roller means (84) between said grooved body inward surface portion (72) and said grooved drive member outward surface portion (78) in seated engagement with said grooved body inward surface portion and said grooved drive member outward surface portion; and at least one piston (52) mounted for reciprocal movement and operatively engaging said reciprocating member (50), characterized by said roller means comprising a plurality of elongated rollers (84) having circumferential grooves (86) with ridges (88) therebetween; and said reciprocating member (50) rotatably retaining said rollers (84) in fixed axial and circumferential position relative to said reciprocating member (50) during powered operation of the fluid-power device (10), said rollers (84) being retained by said reciprocating member in circumferentially distributed arrangement between said grooved body inward surface portion (72) and said grooved drive member outward surface portion (78) with at least a first plurality of said rollers in seated engagement with said grooved body inward surface portion and at least a second plurality of said rollers in seated engagement with said grooved drive member outward surface portion for transmitting force between said body (12), drive member (20) and reciprocating member (50), each ridge (88) of said rollers being positioned for rolling travel in the corresponding grooves (74 and 80) of said body or said drive member. The device of claim 1 wherein said body helical grooves (74) have a first lead and said drive member helical grooves (80) have a second lead, with said drive member helical grooves (80) having a hand turn opposite the hand turn of said body helical grooves (74) and having substantially the same axial pitch as said body helical grooves (74), said roller grooves (86) having an axial pitch corresponding to the axial pitch of said body and drive member helical grooves, and wherein each of said rollers (84) in said first and second pluralities of rollers are in seated engagement with both said grooved body inward surface portion (72) and said grooved drive member outward surface portion (78). The device of claim 1 wherein said piston (52) is positioned within said body (12) and with said reciprocating member (50) forms a piston sleeve. The device of claim 1 wherein the number of said plurality of drive member helical grooves (80) is an integer multiple of the number of equally spaced circumferentially adjacent positions for rollers (84) for engagement therewith, and the number of said plurality of body helical grooves (74) is an integer multiple of the number of equally spaced circumferentially adjacent positions for rollers (84) for engagement therewith. The device of claim 1 wherein the lead of said body helical grooves (74) and said drive member helical grooves (80) are selected substantially according to the relationship: groove lead = groove axial pitch x number of grooves. The device of claim 1 wherein said piston (52) is positioned in a fluid-tight chamber (140) sealed to prevent leakage of fluid into a chamber portion (142) of said body (12) with said grooved body inward surface portion (72) and within which said grooved drive member outward surface portion (78) and said rollers (84) are disposed. The device of claim 2 wherein said reciprocating member (50) includes a plurality of spindles (90), each with an attached end portion (92) connected to said reciprocating member (50) and a free end portion positioned in a circumferential space (79) between said grooved body and drive member surface portions (72 and 78), said spindle free end portion being circumferentially distributed within said space (79) about said drive member (20), said spindles (90) each having at least one of said rollers (84) coaxially and rotatably retained on said free end portion to provide a cantilevered support and retained against axial movement relative to said free end portion, said spindles (90) being retained by said reciprocating member (50) to prevent axial movement of said spindles (90) relative to said reciprocating member (50) during powered operation of the fluid-power device (10). The device of claim 7 wherein said rollers (84) retained on said spindles (90) each have a longitudinally extending substantially coaxial roller bore (106) therethrough rotatably receiving one of said spindles (90). The device of claim 8 wherein each of said rollers (84) retained on said spindles (90) is defined by a plurality of rings (604) disposed on one of said spindles (90), each of said rings (604) having a radially outward facing surface portion (608) and (610) shaped to form in combination with the other of said plurality of rings said roller grooves and ridges (86 and 88). The device of claim 9 wherein each of said rings (604) has a central opening (606) forming in combination with the central openings of the other of said plurality of rings said roller bore (106), said ring central openings (606) being sized to slide axially on said spindle (90) during assembly. The device of claim 7 wherein each of said spindle attached end portions (92) is supported by a coaxially extending support arm (98) and said reciprocating member (50) includes a sleeve portion (54) having a plurality of circumferentially spaced-apart and axially extending bore holes (94) therein, said spindle support arms being disposed in said sleeve bore holes (94). The device of claim 11 wherein at least one or more of said spindle support arms (98) are selectively and adjustably axially movable in said sleeve bore holes (94), and the device further includes means (102) for selectively and adjustably axially moving said movable spindle support arms (98) in an axial direction relative to the others of said spindle support arms within at least a limited range to axially move said rollers (84) rotatably retained on said movable spindles (90) relative to said rollers (84) rotatably retained on the other of said spindles and thereby eliminate backlash resulting from said rollers coacting with said body and drive member helical grooves (74 and 80) as said piston (52) moves from one axial direction to the other within said body (12) as it reciprocates. The device of claim 12 wherein said movable spindle support arms (98) and said sleeve portion bore holes (92) are correspondingly threaded, and said movable spindle support arms (98) are adjustably axially moved by rotation thereof, and the fluid-power device (10) further includes lock means (120) for locking said movable spindle support arms (98) against rotation during powered operation of the fluid-power device (10). The device of claim 13 wherein said locking means includes an adjustment element (120) projecting into said sleeve portion bore hole (94) and slidably endwise engaging one of said movable spindle support arms (98), said adjustment element (120) being selectively extendable to exert an axial locking force on said engaged support arm. The device of claim 12 wherein at least one or more of said spindle support arms (98) are axially fixedly retained within their corresponding sleeve bore holes (94), with said movable support arms and said fixed support arms being circumferentially alternately positioned. The device of claim 11 wherein said sleeve portion is coaxially positioned within said body (12) and has a generally cylindrical sidewall (54') receiving generally coaxially therewithin said drive member (20), said sleeve sidewall extending into said circumferential space (79) and having a plurality of circumferentially spaced-apart sidewall openings (148, 150) extending fully therethrough and each sized to receive at least one of said rollers (84), said rollers (84) being rotatably disposed in said sidewall openings (148, 150) on said spindles (90) and restrained against axial and circumferential movement therewithin during powered operation of the fluid-power device (10). The device of claim 1 wherein said reciprocating member (50) includes a generally cylindrical sleeve sidewall (54') coaxially positioned within said body (12) and receiving generally coaxially therewithin said drive member (20), said sleeve sidewall (54') extending into said circumferential space (79) and having a plurality of circumferentially spaced-apart sidewall openings (148, 150) extending fully through said sleeve sidewall, each of said sidewall openings (148, 150) being sized to receive at least one of said rollers (84), said rollers (84) being rotatably disposed in said sidewall openings (148, 150) and restrained against axial and circumferential movement therewithin during powered operation of the fluid-power device (10). The device of claim 17 wherein said reciprocating member (50) further includes a spindle (90') positioned in each of said sidewall openings (148, 150) with at least one of said rollers (84) coaxially and rotatably retained thereon. The device of claim 18 wherein said rollers (84) retained on said spindles (90') each have a longitudinally extending substantially coaxial roller bore (106) rotatably receiving one of said spindles (90'), said axial bore (106) being defined by an interior sidewall (108), corresponding ones of said roller bore sidewalls (108) and spindles (90') having formed thereon a plurality of confronting and corresponding ball races (110 and 112) defining a plurality of ball races extending circumferentially thereabout, and the device further includes a plurality of balls (114) seated in said ball races (110 and 112) to restrict axial movement of said rollers (84) relative to said spindles (90') while permitting free rotation of said rollers on said spindles. The device of claim 17 wherein said sleeve sidewall openings (148, 150) include first and second sets of sidewall openings, said sidewall openings (148) of said first set being axially spaced apart from said sidewall openings (150) of said second set, at least one of said rollers (84) in said first or second set of sidewall openings (148, 150) being selectively and adjustably axially movable within at least a limited range relative to another of said rollers (84) in the other of said first or second set of sidewall openings for backlash elimination, and the device further includes backlash adjustment means (156, 156') for selectively and adjustably axially moving said movable roller for backlash elimination. The device of claim 20 wherein each sidewall opening (148) of said first set having a corresponding axially spaced-apart sidewall opening (150) in said second set with the same general circumferential position to provide a plurality of pairs of corresponding axially spaced-apart sidewall openings, and said reciprocating member (50) further includes a spindle (90') positioned in each of said sidewall openings (148, 150) with said roller (84) disposed therein coaxially and rotatably retained thereon. The device of claim 20 wherein said sidewall openings (148) of said first set have an axial length sufficiently greater than the axial length of said rollers (84) disposed therein to allow for adjustably moving said rollers (84) within at least a limited range for backlash elimination, and said rollers (84) disposed in said first set of sidewall openings (148) are selectively and adjustably axially movable within said first set of sidewall openings, said backlash adjustment means providing for selective and adjustable axial movement of said rollers (84) in said first set of sidewall openings (148) in an axial direction relative to said rollers (84) in said second set of sidewall openings (150) within said limited range to eliminate backlash resulting from said rollers coacting with said body and drive member helical grooves (74 and 80) as said piston (52) moves from one axial direction to the other within said body (12) as it reciprocates. The device of claim 22 wherein each sidewall opening (148) of said first set has a corresponding axially spaced-apart sidewall opening (150) in said second set with the same general circumferential position to provide a plurality of pairs of corresponding axially spaced-apart sidewall openings, and said reciprocating member (50) further including a spindle (90') positioned in each of said sidewall openings (148, 150) with said roller (84) disposed therein coaxially and rotatably retained thereon and restrained against axial movement relative to said spindle (90'), and a plurality of alignment members (154, 154') retained by said sleeve sidewall (54'), each of said alignment members (154, 154') extending through both sidewall openings (148, 150) of a corresponding pair of axially spaced-apart sidewall openings and through an axial through-bore (152) of said spindles (90') disposed in said pair of axially spaced-apart sidewall openings, said spindles (90') disposed in said first set of sidewall openings (148) being selectively and adjustably axially movable therewithin for axially moving said rollers (84) for backlash elimination. The actuator of claim 23 wherein said backlash adjustment means includes a plurality of adjustment members (156, 156') adjustably attached to said sleeve sidewall (54') and selectively and adjustably axially movable, each of said adjustment members (156, 156') engaging one of said spindles (90') in said first set of sidewall openings (148) for providing a selectable axial force on said engaged spindle to move said engaged spindle axially relative to said spindles (90') in said second set of sidewall openings (150) by an amount within said limited range to eliminate backlash. The device of claim 24 wherein each of said adjustment members (156, 156') is an adjustment element projecting toward and slidably endwise engaging one of said engaged spindles (90'), said adjustment element being selectively extendable to exert an axial force on said engaged spindle. The device of claim 25 wherein said adjustment members (156, 156') are exteriorly threaded adjustment setscrews, each threadably received in one of a plurality of threaded setscrew bore holes in said sleeve sidewall (54'), each setscrew bore hole extending between an axially outward facing end wall (96) of said sleeve sidewall (54') and one of said first set of sidewall openings (148, 150), said adjustment setscrew projecting from said setscrew bore hole into said sidewall openings (148, 150) to engage the one of said spindles (90') disposed therein. The device of claim 26 wherein said adjustment setscrews (156') each have a smooth axial bore hole (178') therethrough with one of said alignment members (154') extending therethrough, said setscrew bore hole (178') having an axially outward facing radial shoulder (180) and said alignment member (154') having a head (182) engaging said shoulder (180) and a distal threaded end portion (184) threadably received in a threaded bore hole (186) in said sleeve sidewall (54'), whereby said adjustment setscrew (156') can be locked in position after being adjusted to eliminate backlash by tightening of said alignment member (154') to apply an axially inward force on said adjustment setscrew (156') through engagement of said alignment member head (182) with said shoulder (180). The device of claim 26 wherein said adjustment setscrews (156) each have one of said alignment members (154) attached thereto for movement therewith, said alignment member (154) having a distal end portion (175) slidably received in a smooth bore hole (172) in said sleeve sidewall (174). The device of claim 1 wherein at least said first or second pluralities of rollers (84) are axially positioned in generally coplanar relation, and the number of corresponding grooves of said plurality of body or drive member helical grooves (74 and 80) is an integer multiple of the number of equally spaced circumferentially adjacent positions for rollers for engagement therewith. A fluid-power device (10), comprising: a body (12); an axially extending drive member (20) supported for rotational movement relative to said body (12) and connectable to an external device, one of said body (12) or said drive member (20) having at least one helical groove (74 or 80) formed on a surface portion (72 or 78) thereof positioned within said body (12); roller means (84); an axially reciprocating member (50) reciprocally mounted within said body (12), said reciprocating member rotatably retaining said roller means (84) in seated rolling engagement with said grooved surface portion (72 or 78); means (84) for transmitting torque between said reciprocating member (50) and the other of said body (12) or said drive member (20); and at least one piston (52) mounted for reciprocal movement and operatively engaging said reciprocating member (50), characterized by said roller means comprising at least one roller (84) having at least one circumferential ridge (88); and said reciprocating member (50) rotatably retaining said roller (84) in fixed axial and circumferential position relative to said reciprocating member (50) during powered operation of the fluid-power device (10) with said roller (84) in seated rolling engagement with said grooved surface portion (72 or 78) for transmitting force between said reciprocating member (50) and the one of said body (12) or said drive member (20) having said grooved surface portion, said ridge (88) of said roller (84) being positioned for rolling travel in said helical groove (74 or 80) of said grooved surface portions (72 or 78). The device of claim 30 wherein said at least one groove (74 or 80) includes a plurality of helical grooves with ridges therebetween and said et least one roller (84) includes a plurality of rollers, with each ridge (88) of said rollers being positioned for rolling travel in one of said helical grooves (74 or 80), and wherein the number of said plurality of helical grooves is an integer multiple of the number of equally spaced circumferentially adjacent positions for rollers for engagement therewith. The device of claim 30 wherein said at least one groove includes a plurality of helical grooves with ridges therebetween and said at least one roller (84) includes a plurality of rollers, with each ridge (88) of said rollers being positioned for rolling travel in one of said helical grooves, and wherein said reciprocating member (50) includes a plurality of spindles (90) extending into a circumferential space (79) adjacent to said grooved surface portion (72 or 78) and circumferentially distributed thereabout, said spindles (90) each having at least one of said rollers (84) coaxially and rotatably retained thereon and retained against axial movement relative to said spindles, said spindles (90) being retained by said reciprocating member (50) to prevent axial movement of said spindles relative to said reciprocating member during powered operation of the fluid-power device (10). The device of claim 32 wherein said rollers (84) retained on said spindles (90) each have a longitudinally extending, substantially coaxial roller bore (106) therethrough rotatably receiving one of said spindles. The device of claim 33 wherein said rollers (84) retained on said spindles (602) each have a plurality of said circumferential ridges (88) with a groove (86) between adjacent pairs of said ridges, and are defined by a plurality of rings (604) disposed on one of said spindles, each of said rings having a radially outward facing surface portion (608 and 610) shaped to form in combination with the other of said plurality of rings (604) said roller grooves and ridges (86 and 88). The device of claim 32 wherein said rollers (84) retained on said spindles (602) each have a plurality of said circumferential ridges (88) with a groove (86) between adjacent pairs of ridges, and are defined by a plurality of annular rings (604) coaxially aligned and positioned together on one of said spindles (602), each of said rings (604) having a radially outward facing surface portion (608 and 610) shaped to form in combination with the other of said plurality of rings said roller grooves and ridges (86 and 88), at least one of said rings (604) further including at least one annular skirt (612, 614) coaxial with said one ring and axially extending therefrom toward the next adjacent one of said rings, whereby said surface portions of said plurality of rings (604) can be axially spaced apart to provide a desired roller pitch. The device of claim 35 wherein each said ring (604) includes annular first and second skirts (612, 614), one of said first or second skirts extending axially to each side thereof, and said first and second skirts (612, 614) each having an axially outward opening circumferential ball groove formed thereon. The device of claim 36 wherein said first and second skirt ball grooves are axially spaced apart so that one of said skirt ball grooves corresponds to and cooperates with one of said skirt ball grooves of an adjacent one of said rings (604) to define a roller ball race to receive a ball (114). The device of claim 32 wherein each of said spindles (90) is supported by at least one support arm (92). The device of claim 38 wherein said reciprocating member (50) includes a sleeve portion (54) having a plurality of circumferentially spaced-apart bore holes (94) therein, said spindle support arms (92) being disposed in said sleeve bore holes. The device of claim 32, further including means (102) for selectively and adjustably axially moving at least one or more of said spindles (90) in an axial direction within at least a limited range to axially move said rollers (84) rotatably retained on said spindles relative to said reciprocating member to eliminate backlash resulting from said rollers' coacting with said helical grooves (74 or 80) as said piston (52) moves from one axial direction to the other within said body (12) as it reciprocates. The device of claim 30 wherein said at least one groove (74 or 80) includes a plurality of helical grooves with ridges therebetween and said at least one roller (84) includes a plurality of rollers, with each ridge (88) of said rollers being positioned for rolling travel in one of said helical grooves (74 or 80), and wherein said rollers (84) are axially positioned in generally coplanar relation and the number of helical grooves of said grooved surface portion (72 or 78) is an integer multiple of the number of equally spaced, circumferentially adjacent positions for rollers for engagement therewith. The device of claim 30 wherein said grooved surface portion (72 or 78) of said body (12) or said drive member (20) has a plurality of helical grooves (74 or 80) with an axial pitch and a lead angle with a left- or right-hand turn, wherein said rollers (84) are retained by said reciprocating member (20) relative to said body (12) or drive member (20) with which engaged, and wherein said reciprocating member (50) includes a plurality of spindles (90) each rotatably and coaxially retaining at least one roller (84) of said rollers positioned adjacent to said grooved surface portion (72 or 78), said spindles (90) being circumferentially distributed about said grooved surface portion (72 or 78) to position said rollers (84) in seated rolling engagement therewith, said spindles (90) retaining said rollers (84) against axial movement relative thereto, said spindles (90) being retained by said reciprocating member (20) to prevent axial movement of said spindles relative to said reciprocating member during powered operation of the fluid-power device (10). The device of claim 42 wherein each of said spindles (90) is supported at one end by a cantilever support arm (92) rigidly attached thereto, and said reciprocating member (50) includes a sleeve portion (54) having a plurality of circumferentially spaced-apart bore holes (94) formed in an end portion thereof, each said bore hole (94) being sized to receive one of said support arms (92), said support arms (92) being disposed in said sleeve bore holes (94) with said spindles (90) supported thereon and positioned axially beyond said end portion of said sleeve portion (54). The device of claim 42 wherein said spindles (90) each have a free, unattached first end portion (92) extending into a circumferential space (79) adjacent to said grooved surface portion (72 or 78) and circumferentially distributed thereabout, said spindle free end portions each having at least one of said rollers (84) coaxially and rotatably retained thereon and retained against axial movement relative to said spindles (90), each said spindle (90) having a second end portion (98) attached to said reciprocating member (50) to support said first end portion in cantilevered manner and to prevent axial and circumferential movement of said spindle, said reciprocating member (20) retaining said spindle free first end portions (92) and said rollers (84) rotatably retained thereon in fixed axial and circumferential position relative to said reciprocating member (20) during powered operation of the fluid-power device (10), said rollers (84) on said spindles (90) being retained by said reciprocating member (50) in circumferentially distributed arrangement in seated rolling engagement with said grooved surface portion (72 or 78) for transmitting force between said reciprocating member (50) and the one of said body (12) or said drive member (20) having said grooved surface portion, and further including an annular spindle support plate (483) having a central opening through which said drive member (20) extends and a plurality of circumferentially distributed spindle openings (485), each said spindle opening (485) receiving one of said spindle free first end portions therethrough and providing support thereto against lateral forces on said spindles (90), said support plate (483) being attached to said spindles (90) for travel therewith during powered operation of the fluid-power device (10). The device of claim 42 wherein each of said spindles (90) is supported between first and second support arms (92), and said reciprocating member (50) includes at least one recess (148, 150), with at least one of said rollers (84) positioned therein and projecting radially beyond said reciprocating member (50) to rollingly engage said grooved surface portion (72 or 78), said recess (148, 150) having a pair of opposed and axially spaced-apart wall portions, with each of said wall portions supporting one or the other of said first and second support arms (92). The device of claim 45 wherein said first and second support arms (92) for each spindle (90) are coaxial, and said support arms and spindle for each said roller (84) are attached together in coaxial relation. The device of claim 45 wherein said recess (148, 150) is a window extending transversely fully through said reciprocating member. The device of claim 45 wherein said reciprocating member (50) includes a plurality of said recesses (148, 150) circumferentially spaced apart, each said recess having at least one of said rollers (84) positioned therein.

Inventors: WEYER, PAUL P.
Applicants: WEYER, PAUL P.
Application year: 1987
Main classification: F15B15
IPC codes: F16H25, F15B15