Patent Publication Number: US-7210720-B2

Title: Timed rotation tool assembly and actuator

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to fluid-powered actuators and tool assemblies using such actuators, for timed rotational movement of two tool members positioned to cooperate with each other, typically mounted on a boom or arm of a vehicle or stationary platform. 
   2. Description of the Related Art 
   Assemblies such as large grapples, brush rakes, refuse collection tines or fingers, clamshell buckets, and buckets with bucket extensions or lids have been employed in the past for collection and sorting of large and small objects or quantities of material, excavation and picking up refuse containers. Many of these assemblies have two tools or members, which are selectively operable to work together. The assembly is generally attached to a boom or other arm of a platform such as a vehicle. The two tool members of the assembly are positioned to selectively move one toward and away from the other to cooperatively engage, pick up or grasp an object or material. 
   Generally, means are provided to separately supply rotational torque to the tool members in order to rotatable move one tool member relative to the other. The operational limitation of a particular assembly is directly dependent upon the maximum amount of torque that can be supplied to the tool members. If the torque is not sufficient, the object size or the quantity of the object or material to be engaged, picked up or grasped is limited. 
   It will therefore be appreciated that there has long been a significant need for an improved tool assembly and actuator used therewith. The present invention fulfills these needs and further provides other related advantages. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention resides in a fluid-powered rotary actuator for providing timed rotational movement of first and second external members, typically tool members. The actuator includes a body having a longitudinal axis, a first rotatable member, second rotatable member, and a linear-to-rotary force transmitting member. The first rotatable member is rotatably disposed with respect to the body for rotation about a first rotation axis with a portion adapted for coupling to the first external member for rotational movement of the first external member with the first rotatable member as a unit. The second rotatable member rotatably is disposed with respect to the body for rotation about a second axis with a portion adapted for coupling to the second external member for rotational movement of the second external member with the second rotatable member as a unit. 
   The linear-to-rotary force transmitting member is mounted for reciprocal longitudinal movement in response to selective application of pressurized fluid thereto. The force transmitting member engages the first and second rotatable members to translate longitudinal movement of the force transmitting member in a first longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in a first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in a second rotational direction, and to translate longitudinal movement of the force transmitting member in a second longitudinal direction opposite the first longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in a rotational direction opposite the first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in a rotational direction opposite the second rotational direction. 
   In one embodiment of the actuator, the force transmitting member engages the body to translate longitudinal movement of the force transmitting member in the first and second longitudinal directions into rotational movement of the first and second rotatable members about the first and second axes, respectively, relative to the body. 
   The first and second rotational directions may be opposite rotational directions, with rotational movement of the first and second rotatable members in the first and second rotational directions, respectively, in response to longitudinal movement of the force transmitting member in the first longitudinal direction, producing movement of the first and second external members toward each other, and rotational movement of the first and second rotatable members in the rotational directions opposite the first and second rotational directions, respectively, in response to longitudinal movement of the force transmitting member in the second longitudinal direction, producing movement of the first and second external members away from each other. 
   An embodiment of the actuator using third and fourth rotatable members may also be constructed with the third rotatable member rotatably disposed with respect to the body for rotation about a third rotation axis, with the third rotatable member having a portion adapted for coupling to the second external member for rotational movement of the second external member with the third rotatable member as a unit. The fourth rotatable member rotatably may be disposed with respect to the body for rotation about a fourth rotation axis, with the fourth rotatable member having a portion adapted for coupling to the first external member for rotational movement of the first external member with the fourth rotatable member as a unit. The linear-to-rotary force transmitting member may engage the third and fourth rotatable members to translate longitudinal movement of the force transmitting member in the first longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in a third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in a fourth rotational direction, and to translate longitudinal movement of the force transmitting member in the second longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in the rotational direction opposite the third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in the rotational direction opposite the fourth rotational direction. 
   The actuator may be constructed with the first and second rotatable members each having a grooved portion, and with the force transmitting member having a grooved first portion engaging the first rotatable member grooved portion and a grooved second portion engaging the second rotatable member grooved portion to translate longitudinal movement of the force transmitting member in the first longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in the first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in the second rotational direction, and to translate longitudinal movement of the force transmitting member in the second longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in the rotational direction opposite the first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in the rotational direction opposite the second rotational direction. 
   In this embodiment, the actuator includes a third rotatable member rotatably disposed with respect to the body for rotation about a third rotation axis, the third rotatable member having a portion adapted for coupling to the second external member for rotational movement of the second external member with the third rotatable member as a unit, with the third rotatable member having a grooved portion. The actuator of this embodiment further includes a fourth rotatable member rotatably disposed with respect to the body for rotation about a fourth rotation axis, the fourth rotatable member having a portion adapted for coupling to the first external member for rotational movement of the first external member with the fourth rotatable member as a unit, with the fourth rotatable member having a grooved portion. The linear-to-rotary force transmitting member has a grooved third portion engaging the third rotatable member grooved portion and a grooved fourth portion engaging the fourth rotatable member grooved portion to translate longitudinal movement of the force transmitting member in the first longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in a third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in a fourth rotational direction, and to translate longitudinal movement of the force transmitting member in the second longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in the rotational direction opposite the third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in the rotational direction opposite the fourth rotational direction. 
   The actuator may be constructed with the body also having a grooved portion. In this embodiment, the first rotatable member has a grooved portion, and the second rotatable member has a grooved portion. The force transmitting member has a grooved first portion engaging the first rotatable member grooved portion, a grooved second portion engaging the second rotatable member grooved portion and a grooved third portion engaging the body grooved portion to translate longitudinal movement of the force transmitting member in the first longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in the first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in the second rotational direction, and to translate longitudinal movement of the force transmitting member in the second longitudinal direction into rotational movement of the first rotatable member about the first axis relative to the body in the rotational direction opposite the first rotational direction and into rotational movement of the second rotatable member about the second axis relative to the body in the rotational direction opposite the second rotational direction. 
   This embodiment may also include a third rotatable member and a fourth rotatable member, much as described above. The linear-to-rotary force transmitting member has a grooved fourth portion engaging the third rotatable member grooved portion and a grooved fifth portion engaging the fourth rotatable member grooved portion to translate longitudinal movement of the force transmitting member in the first longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in a third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in a fourth rotational direction, and to translate longitudinal movement of the force transmitting member in the second longitudinal direction into rotational movement of the third rotatable member about the third axis relative to the body in the rotational direction opposite the third rotational direction and into rotational movement of the fourth rotatable member about the fourth axis relative to the body in the rotational direction opposite the fourth rotational direction. 
   In at least one embodiment of the actuator, the first rotatable member includes an idler mount portion adapted to rotatably mount a portion of the second external member thereto to allow independent rotation of the second external member relative to the first shaft idler mount portion, and the second rotatable member includes an idler mount portion adapted to rotatably mount a portion of the first external member thereto to allow independent rotation of the first external member relative to the second shaft idler mount portion. 
   In one embodiment of the actuator designed for use with a third external member, the body is adapted for coupling to the third external member for movement of the body with the third external member as a unit. The body includes a central tie rod positioned along the body axis and retaining the first and second rotatable members against longitudinally outward movement relative to each other. The tie rod comprises at least a portion of the body adapted for coupling to the third external member. 
   In one embodiment, the body of the actuator has spaced apart first and second longitudinal end portions, with the portions of the first and second rotatable members adapted for coupling to the first and second external members are both located at the body first end portion. 
   The invention may also be embodied with the actuator having a body with spaced apart first and second longitudinal end portions, with the first and second rotatable members each extending between the body first and second end portions and with the first and second rotation axes thereof in spaced apart arrangement. In this embodiment, the first rotatable member may have first and second end portions, each adapted for coupling to the first external member, and the second rotatable member may have first and second end portions, each adapted for coupling to the second external member. The first end portions of the first and second rotatable members is located at the body first end portion and the second end portions of the first and second rotatable members are located at the body second end portion. The force transmitting member may be a piston sleeve with first and second spaced apart apertures therein and having the first rotatable member extending through the first aperture and the second rotatable member extending through the second aperture. 
   In yet another embodiment of the actuator, the body is a first body and the actuator includes a second body, with the first body being rotatable relative to the second body. Further, the actuator may have another linear-to-rotary force transmitting member mounted for reciprocal longitudinal movement in the first and second longitudinal directions in response to selective application of pressurized fluid thereto. The another force transmitting member engages the first and second bodies to translate longitudinal movement of the another force transmitting member in a third longitudinal direction into one of clockwise or counterclockwise relative rotational movement of the first body relative to the second body and to translate longitudinal movement of the another force transmitting member in a fourth longitudinal direction into the other of clockwise or counterclockwise relative rotational movement of the first body relative to the second body. 
   Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       FIG. 1  is a front perspective view of a clamshell bucket assembly with a fluid-powered rotary actuator embodying the present invention, showing the buckets rotated fully away from each other. 
       FIG. 2  is a side elevational view of the clamshell bucket assembly of  FIG. 1 . 
       FIG. 3  is a front view of the clamshell bucket assembly of  FIG. 1 . 
       FIG. 4  is a side elevational view of a grapple assembly with a fluid-powered rotary actuator embodying the present invention, with the grapples shown in solid line rotated fully away from each other and in broken line rotated fully toward each other. 
       FIG. 5A  is a front perspective view of a refuse container handling assembly with a fluid-powered rotary actuator embodying the present invention, shown mounted on a refuse truck with refuse collection tines grasping and dumping a refuse container. 
       FIG. 5B  is an enlarged, sectional view of the area of  FIG. 5A  encircled by line  5 B. 
       FIG. 5C  is an enlarged, sectional view of the area of  FIG. 5A  encircled by line  5 C, showing an alternative design for attachment of the refuse collection tines. 
       FIG. 6  is an enlarged, sectional side elevational view of the actuator and refuse collection tines of  FIG. 5A . 
       FIG. 7  is a sectional, top plan view of the actuator and refuse collection tines of  FIG. 6 . 
       FIG. 8  is an enlarged, sectional, side elevational view of the fluid-powered rotary actuator of  FIG. 1  with coaxial timed rotation members for attachment of tool members at opposite longitudinal ends of the actuator. 
       FIG. 9A  is a fragmentary, sectional, side elevational view of an alternative embodiment of the fluid-powered rotary actuator of  FIG. 8  using splines for attachment of clamshell buckets or other tool members. 
       FIG. 9B  is an end view of the actuator of  FIG. 9A . 
       FIG. 10  is a sectional, side elevational view of an alternative embodiment of a fluid-powered rotary actuator embodying the present invention with coaxial timed rotation members showing attachment of two tool members at the same longitudinal end of the actuator. 
       FIG. 11  is a sectional, side elevational view of an alternative embodiment of a fluid-powered rotary actuator embodying the present invention with two timed rotation members showing attachment of two tool members at each of the opposite longitudinal ends of the actuator. 
       FIG. 12  is a sectional, side elevational view of an alternative embodiment of a fluid-powered rotary actuator embodying the present invention with timed rotation members for attachment of tool members at opposite longitudinal ends of the actuator and utilizing a central tie rod member. 
       FIG. 13A  is a sectional, side elevational view of an alternative embodiment of a fluid-powered rotary actuator embodying the present invention with two laterally separated timed rotation members. 
       FIG. 13B  is an end view of the actuator of  FIG. 13A . 
       FIG. 14A  is a sectional, side elevational view of an alternative embodiment of a fluid-powered rotary actuator embodying the present invention with radially inward positioned timed rotation members for attachment of tool members at opposite longitudinal ends of the actuator and a radially outward positioned rotation member. 
       FIG. 14B  is an end view of the actuator of  FIG. 14A . 
       FIG. 15  is a sectional, side elevational view of another alternative embodiment of a fluid-powered rotary actuator embodying the present invention with radially outward positioned timed rotation members for attachment of tool members at opposite longitudinal ends of the actuator and a radially inward positioned rotation member. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in the drawings for purposes of illustration, the present invention is embodied in a fluid-powered tool assembly  10  and a fluid-powered rotary actuator  12  used therewith for timed rotation of first and second tool members  14  and  16 . As shown in  FIGS. 1–3 , the tool assembly  10  is usable with a boom arm  18  connected to a support platform such a vehicle (not shown). The support platform may also be a stationary platform. The boom arm  18  may have multiple boom arm sections pivotally connected together, and is typically pivotally mounted at its lower end to the vehicle or stationary platform, although non-pivotal mounting may be used if desired. Conventional hydraulic cylinders, rotary actuators or other actuation means (not shown) may be used for raising and lowering the boom arm  18 , extending the boom arm and moving the boom arm laterally with respect to the support platform. 
   A boom mounting member  20  is pivotally connected to the upper end of the boom arm  18 , and if desired, can be rotated relative to the boom arm using conventional hydraulic cylinders, rotary actuators or other actuation means (not shown). The tool assembly  10  is rigidly attached to the boom mounting member  20  for movement therewith. In other applications, the tool assembly  10  may be mounted to other mounting surfaces, platforms or frames, as appropriate to perform the work desired using the tool assembly. 
   A first embodiment of the tool assembly  10  is illustrated in  FIGS. 1–3 , with the tool members  14  and  16  being two opposing clamshell buckets. It should be understood that the present invention may be practiced using other tool members, and is not limited to buckets or other collection tools and devices. These may include grapples as shown in  FIG. 4 , refuse collection tines as shown in  FIGS. 5A–5C ,  6  and  7 , brush rakes, and buckets with bucket extensions or lids (not shown), to name a few. These tools are often employed for collection and sorting of large and small objects or quantities of material, excavation and picking up refuse containers 
   The first and second tool members  14  and  16  are connected to the actuator  12  for timed rotational movement of the first and second tool members, often toward and away from each other. Other tools may have different timed rotational movement. The actuator provides rotational torque to the first and second tool members. 
   Referring to the tool assembly  10  of  FIGS. 1–3 , operation of the actuator  12  causes the first and second tool members  14  and  16  to simultaneously rotate about a longitudinal axis  22  of the actuator relative to the boom mounting member  20  to provide timed rotational movement of both tool members, not just rotational movement of one tool member relative to the other. As shown in  FIG. 1 , the actuator  12  can be selectively operated to simultaneously produce clockwise rotation of the first tool member  14 , as indicated by arrow  24 A, and counterclockwise rotation of the second tool member  16 , as indicated by arrow  24 B, relative to the boom mounting member  20 , to cause the first and second tool members to rotationally move toward each other for grasping of an object therebetween or picking up material in the buckets. Similarly, the actuator  12  can be selectively operated to simultaneously produce counterclockwise rotation of the first tool member  14 , in the rotational direction opposite arrow  24 A, and clockwise rotation of the second tool member  16 , in the rotational direction opposite arrow  24 B, to cause the first and second tool members to rotationally move away from each other for releasing of a grasped object or releasing material within the buckets. 
   While the tool assembly  10  of  FIGS. 1–3  is designed for one of the first and second tool members  14  and  16  to move clockwise when the other moves counterclockwise, thus to simultaneously move them toward or away from each other, in other embodiments, the tool assembly may have the first and second tool members simultaneously move clockwise together or simultaneously move counterclockwise together, either by the same or different amounts. 
   The construction of the actuator  12  and the attachment of the first and second tool members  14  and  16  thereto are shown in  FIG. 8 . As can be seen in  FIG. 8 , the actuator  12  has an elongated housing or body  42  with a cylindrical sidewall  44  and first and second longitudinal ends  46  and  48 , respectively. Separate first and second rotatable drive members or output shafts  50  and  52 , respectively, are coaxially positioned within the body  42  and supported for rotation relative to the body. The first shaft  50  extends axially out of the body  42  at the first body end  46 , and has an attachment portion  50 A at the first body end. The second shaft  52  extends axially out of the body  42  at the second body end  48 , and has an attachment portion  52 A at the second body end. The first shaft  50  further includes a flange portion  50 B positioned within the body  42  inward of the first body end  46  adjacent to an axially outward facing first shoulder  54  of the body sidewall  44 . Similarly, the second shaft  52  further includes a flange portion  52 B positioned within the body  42  inward of the second body end  48  adjacent to an axially outward facing second shoulder  56  of the body sidewall  44 . 
   Exteriorly threaded first and second annular retainer nuts  58  and  60  are positioned within the body  42 . The first retainer nut  58  is threadably attached to an interiorly threaded portion of the body sidewall  44  toward the first body end  46  and the second retainer nut  60  is threadably attached to an interiorly threaded portion of the body sidewall  44  toward the second body end  48 . The first and second retainer nuts  58  and  60  are located axially outward of the corresponding first and second shoulders  54  and  56  of the body sidewall  44 , with the flange portion  50 B of the first shaft  50  positioned between the first shoulder  54  and the first retainer nut  58  to prevent axial movement of the first shaft within the body  42 , and the flange portion  52 B of the second shaft  52  positioned between the second shoulder  56  and the second retainer nut  60  to prevent axial movement of the second shaft within the body. The first and second shaft nuts  58  and  60  are locked in place against rotation with the first and second shafts  50  and  52 . 
   Thrust bearings  62  are disposed between the first and second shaft flange portions  50 B and  52 B, and both of the corresponding first and second shoulders  54  and  56 , and the first and second retainer nuts  58  and  60  to support the first and second shafts against longitudinal thrust loads. A radial bearing  64  is positioned between each of the first and second shafts  50  and  52  and the corresponding first and second retainer nuts  58  and  60  to support the shafts against radial loads. Seals  66  are disposed between the first and second shaft nuts  58  and  60 , and both of the corresponding first and second shafts  50  and  52 , and the body sidewall  44  to provide a fluid-tight seals therebetween. 
   The exterior end surfaces of the attachment portions  50 A and  52 A of the first and second shafts  50  and  52  are flat and each have a plurality of threaded apertures  70  and  72 , respectively, which threadably receive attachment bolts  74 . The first tool member  14  has a first side projecting attachment portion  14 A and a second side projecting attachment portion  14 B, and the second tool member  16  has a first side projecting attachment portion  16 A, and a second side projecting attachment portion  16 B for attachment of the first and second tool members to the actuator  12 . In the case of the illustrated clamshell buckets, these comprise portions of the right and left sidewalls of each bucket. 
   As can best be seen in  FIG. 8 , the first attachment portion  14 A of the first tool member  14  is positioned in contact with the end surface of the first attachment portion  50 A of the first shaft  50  and rigidly attached thereto by the attachment bolts  74  for rotational movement with the first shaft. The first attachment portion  14 A of the first tool member  14  is clamped between a first end support member  76  and the first shaft attachment portion  50 A by the attachment bolts  74  which extend through apertures in the first end support member  76  and the first attachment portion  14 A of the first tool member  14  and are threadably received in the threaded apertures  70 . The first attachment portion  16 A of the second tool member  16  is rotatably mounted (idle mounted) on the first end support member  76  so that it can rotate freely, independent of the first shaft  50  to which the first end support member is rigidly attached, but yet be supported by the first end support member for transmitting radial and axial loads during use. This is accomplished by providing the first attachment portion  16 A of the second tool member  16  with an aperture  16 C through which the first end support member  76  projects. An axially outward retainer flange  76 A allows independent rotation of the second tool member  16  but retains it in place on the first end support member  76 . Bearings may be used to facilitate the rotation. As will be described in greater detail below, the first shaft  50  provides rotational drive to the first tool member  14 , and the second shaft  52  provides rotational drive to the second tool member  16 . 
   Similarly, the second attachment portion  16 B of the second tool member  16  is positioned in contact with the end surface of the attachment portion  52 A of the second shaft  52  and rigidly attached thereto by the attachment bolts  74  for rotational movement with the second shaft. The second attachment portion  16 B of the second tool member  16  is clamped between a second end support member  78  and the second shaft attachment portion  52 A by the attachment bolts  74  which extend through apertures in the second end support member  78  and the second attachment portion  16 B of the second tool member  16  and are threadably received in the threaded apertures  72 . The second attachment portion  14 B of the first tool member  14  is rotatably mounted (idle mounted) on the second end support member  78  so that it can rotate freely, independent of the second shaft  52  to which the second end support member is rigidly attached, but yet be supported by the second end support member against loads encountered during use by the first tool member. This is accomplished by providing the second attachment portion  14 B of the first tool member  14  with an aperture  14 C through which the second end support member  78  projects. An axially outward retainer flange  78 A which allows independent rotation of the first tool member  14  but retains it in place on the second end support member  78 . Bearings may be used to facilitate the rotation. This construction provides a straddle mounting of the first and second tool members  14  and  16  to the actuator  12  which for a wide tool like the clamshell buckets illustrated in  FIGS. 1–3  provides a stronger and more durable mounting arrangement that can handle the loads on the buckets encountered when digging or grasping a non-uniform object while still providing rotary drive to each bucket from only one end of the actuator body  42 . 
   As shown in  FIG. 8 , the actuator  12  includes an elongated splined piston  82  coaxially and reciprocally mounted generally within the body  42  coaxial with the first and second shafts  50  and  52 . The piston  82  has a first end portion  84 , which extends into an axially inward open chamber  50 C of the first shaft  50 , and a second end portion  86 , which extends into an axially inward open chamber  52 C of the second shaft  52 . The piston first end portion  84  has outer helical splines  88  over a portion of its length which mesh with inner helical splines  90  of the first shaft chamber  50 C, and the piston second end portion  86  has outer helical splines  92  over a portion of its length which mesh with inner helical splines  94  of the second shaft chamber  52 C. The piston  82  has a mid-portion  96  with outer helical splines  98  over a portion of its length which mesh with an interior ring gear portion  100  of the body sidewall  44  having inner helical splines  102 . 
   The meshing splines can be threaded in the direction (e.g., left-handed or right-handed) and with the lead desired to produce simultaneous counter-rotation of the first and second tool members  14  and  16  in a desired amount per unit of axial motion of the piston  82 , as would typically be the case for the clamshell buckets illustrated in  FIGS. 1–3 , but also may be splined to produce simultaneous rotation of the first and second tool members in the same rotational direction. 
   In the actuator  12  of  FIG. 8 , the piston  82  includes an annular piston head portion  104 , which is threadably attached to the mid-portion  96  of the piston with a seal  106  disposed therebetween. Seals  108  are disposed between the piston head portion  104  and a smooth interior wall portion  110  of the body sidewall  44  to provide a fluid-tight seal therebetween. A radial bearing  65  is positioned between the piston head portion  104  and the smooth interior wall portion  110  of the body sidewall  44  to support the piston  82  against radial loading. 
   As will be readily understood, reciprocation of the piston  82  within the body  42  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of a first port P 1  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion  104  toward the first body end  46  or through a second port P 2  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion toward the second body end  48 . As the piston head portion  104  and the piston  82 , of which the piston head portion is a part, linearly reciprocates in an axial direction within the body  42 , the outer splines  98  of the piston mid-portion  96  engage or mesh with the inner splines  102  of the body sidewall  44  to prevent rotation of the piston, where both the outer splines  98  and the inner splines  102  are straight. If desired, the splines  98  and  102  may be helical to also cause rotation of the piston  82  as it linearly reciprocates within the body  42 . The linear and rotational movement of the piston  82  is simultaneously transmitted through the outer splines  88  and  92  of the piston to the inner splines  90  and  94 , respectively, of the first and second shafts  50  and  52  to cause the shafts to simultaneously rotate. The smooth interior wall portion  110  of the body sidewall  44  has sufficient axial length to accommodate the full end-to-end reciprocating stroke travel of the piston  82  within the body  42 . As noted above, longitudinal movement of the first and second shafts  50  and  52  is restricted, thus linear movement of the piston  82  is converted into rotational movement of the first and second shafts. The amount of rotation and the output torque produced depends on the slope and direction of turn of the various splines, and the fluid pressure used. 
   In more detail, the application of fluid pressure to the first port P 1  produces axial movement of the piston  82  toward the second body end  48 . The application of fluid pressure to the second body port P 2  produces axial movement of the piston  82  toward the body first end  46 . The actuator  12  provides simultaneous rotational movement of the first and second shafts  50  and  52 , relative to the body  42  (and hence relative to the boom mounting member  20  to which attached) through the conversion of linear movement of the piston  82  into rotational movement of the shafts. The first and second shafts  50  and  52  are selectively rotated by the application of fluid pressure, and the rotation is transmitted to the first and second tool members  14  and  16  to selectively rotate the first and second tool members about the axis  22  of the actuator  12  relative to the body  42 . The rotary drive to the first tool member  14  is transmitted by the first shaft  50  by its rigid attachment thereto at the first body end  46 , and the rotary drive to the second tool member  16  is transmitted by the second shaft  52  by its rigid attachment thereto at the second body end  48 . 
   The body  42  of the actuator  12  has mounting flanges  112  by which the body is attached to a mounting face  114  of the boom mounting member  20  using attachment bolts  116 , as best seen in  FIGS. 1–3 . In such manner, the first and second tool members  14  and  16  simultaneously rotate relative to the body  42  and the boom mounting member  20  to which the body is attached when the piston  82  is moved linearly by the application of fluid pressure to one of the first and second body ports P 1  and P 2 . 
   An alternative actuator  12  is shown in  FIGS. 9A and 9B  where the attachment portion  50 A of the first shaft  50  at the first body end  46  and the attachment portion  52 A of the second shaft  52  at the second body end  48  use a different construction to attach the first and second tool members  14  and  16  thereto. In this embodiment, the attachment portions  50 A and  52 A have splines  118  about their perimeter by which they transmit rotary drive to the first attachment portion  14 A of the first tool member  14  and to the second attachment portion  16 B of the second tool member  16 , respectively, rather than using the attachment bolts  74  of the embodiment of  FIG. 8 . Of course, the first attachment portion  14 A and the second attachment portion  16 B have corresponding mating splines. The first and second end support members  76  and  78  are still used to rotatably mount and retain the first attachment portion  16 A and the second attachment portion  14 B to the first and second shafts  50  and  52 , respectively, as described above for the embodiment of  FIG. 8 . 
   An alternative embodiment of the fluid-powered tool assembly  10  is shown in  FIG. 4  as a grapple using basically the same actuator  12  as described above for  FIG. 8 . In this embodiment the first and second tool members  14  and  16  are fingers or tines. Each of the first and second tool members may comprise a single tine or multiple tines. As described above, the first and second tool members  14  and  16  are connected to the actuator  12  for timed rotational movement toward and away from each other, for grasping items between the cooperating tines. If the first and second tool members  14  and  16  are each a single tine, each can have an axially inward bend so that the tines of the first and second tool members are each offset axially inward to rotate through a transverse plane (or closely positioned together individual planes) approximately midway between the first and second body ends  46  and  48  of the actuator  12 , much as shown in  FIGS. 5B and 7  for a refuse can collection embodiment which will be described below. 
   If appropriate for the work to be performed, especially if each of the first and second tool members has multiple tines (such as 2, 3 or 4 spaced apart along the length of the actuator) and the loads on the actuator  12  would be too great, the first and second tool members may be straddle mounted on the actuator much as described above for the clamshell buckets of  FIGS. 1–3 . With straddle mounting, each of the first and second tool members  14  and  16  may have spaced apart first and second attachment portions (not shown, but somewhat like the first and second attachment portions  14 A and  16 A, and  14 B and  16 B of the clamshell buckets), with one attachment portion of each tool member being supplied rotary drive by a corresponding one of the first and second shafts  50  and  52  at one end of the actuator and with the other attachment member being idle mounted to the other of the first and second shafts at the other end of the actuator. 
   Another alternative embodiment of the fluid-powered tool assembly  10  is shown in  FIGS. 5A–5B ,  6  and  7  as a refuse can collection assembly using basically the same actuator  12  as described above for  FIG. 8 . In this embodiment the fluid-powered tool assembly  10  is mounted to a refuse collection truck  120  having a refuse collection dump bin  122  with a refuse collection bin opening  124 . An arm or boom  126  is pivotally connected at its lower end to the dump bin  122  at the bin opening  124  and has the boom mounting member  20  rigidly attached to an upper end of the boom. The tool assembly  10  is attached to the boom mounting assembly by the mounting flanges  112  of the body  42  of the actuator  12 . 
   In this embodiment, the first and second tool members  14  and  16  are a pair of opposing curved fingers or tines sized to grasp and pickup a refuse container  128 . As described above, the first and second tool members  14  and  16  are connected to the actuator  12  for simultaneous timed rotational movement toward and away from each other, for grasping and releasing the refuse container  128  therebetween. The lower end of the boom  126  is pivotable by an operator  130  that can pivot the boom to a position to operate the tool members  14  and  16  to grasp the refuse container  128  when containing refuse, then pivot the boom to the position illustrated in  FIG. 5A  whereat the refuse container is inverted to dump the refuse contained therein through the bin opening  124  for collection of the refuse in the dump bin  122 . The operator  130  can then be operated to pivot the boom  126  to return the emptied refuse container  128  to the position where originally picked up and the tool assembly  10  operated to rotate the first and second tool members  14  and  16  away from each other to release the refuse container. 
   In the refuse collection embodiment illustrated, the first and second tool members  14  and  16  are each a single tine having an axially inward bend  132  so that the tines of the first and second tool members are each offset axially inward to rotate through adjacent transverse parallel planes approximately midway between the first and second body ends  46  and  48  of the actuator  12 . 
   An alternative embodiment of the first and second tool members  14  and  16  usable with the tool assembly  10  for refuse collection is shown in  FIG. 5C , with the first and second tool members each straddle mounted to the actuator  12 , generally as illustrated in  FIG. 8  for the clamshell bucket embodiment. As with the clamshell buckets described above, each of the first and second tool members  14  and  16  has first end attachment portions  14 A and  16 A axially spaced apart from corresponding second end attachment portions  14 B and  16 B. The actuator  12  supplies rotary drive to the first attachment portion  14 A of the first tool member by the first shaft  50  and rotary drive to the second attachment portion  16 B of the second tool member by the second shaft  52 . The second attachment portion  14 B of the first tool member and the first attachment portion  16 A of the second tool member are idle mounted to the second shaft  52  and the first shaft  50 , respectively, as described above for the straddle mounting of the clamshell buckets of  FIG. 8 . 
   Another embodiment of the actuator  12 , in many ways similar to the embodiment of  FIG. 8 , is shown in  FIG. 10 . In this embodiment, the first and second shafts  50  and  52  are located at the first longitudinal body end  46  (the left end as viewed in  FIG. 10 ). The separate first and second shafts  50  and  52  are coaxially positioned within the body  42  and supported for rotation relative to the body  42 , with the first shaft  50  being in the form of a sleeve having a central opening  50 D extending axially fully therethrough. The second shaft  52  is concentrically, rotatably mounted within the central opening  50 D of the first shaft  50 . The first shaft  50  extends axially out of the body  42  at the first body end  46 , and has an attachment portion  50 A at the first body end  46 . The second shaft  52  also extends axially out of the body  42  at the first body end  46 , extending outward beyond the end of the first shaft  50 , and has an attachment portion  52 A at the first body end. 
   The attachment portions  50 A and  52 A each have splines  118  by which they transmit rotary drive to the attachment portion  14 A of the first tool member  14  and to the first attachment portion  16 A of the second tool member  16 , respectively, rather than using the attachment bolts  74  shown in  FIG. 8 . Of course, the first attachment portion  14 A and the second attachment portion  16 A of the first and second tool members  14  and  16  to be used with the actuator  12  will have corresponding mating splines. As noted above, the tool members may comprise various type work tools, including grapples or refuse can collection fingers or tines, to name a few. If the tool members have second attachment members, they may be idle mounted to the actuator body  42  or elsewhere. The actuator of  FIG. 10  is particularly desirable for providing rotary drive to the first and second tool members  14  and  16  from the same end of the actuator  12  at adjacent locations. 
   In the embodiment of the actuator  12  shown in  FIG. 10 , the first shaft  50  includes a radially outward flange portion  50 B, much as with the embodiment of  FIG. 8 . The outward flange portion  50 B is positioned at the first body end  46  adjacent to the axially outward facing first shoulder  54  of the body sidewall  44 . The first shaft  50  further includes a radially inward flange portion  50 E positioned at the first body end  46 . An annular end cap  134  is positioned at the first body end  46  and attached to an end flange  136  of the body  42  by a plurality of bolts  138 . The end cap  134  is located axially outward of the outward flange portion  50 B of the first shaft  50 , with the flange portion  50 B positioned between the first shoulder  54  of the body sidewall  44  and the end cap  134  to prevent axial movement of the first shaft within the body  42 . The end cap  134  has a central aperture  140  through which the first and second shafts  50  and  52  extend axially outward beyond the end cap. 
   The second shaft  52  has an axially inward facing shoulder  142  positioned axially outward of the radially inward flange portion  50 E of the first shaft  50 . An interiorly threaded annular retainer nut  144  is positioned within the body  42 , and is threadably attached to an exteriorly threaded portion of the second shaft  52  toward the first body end  46  to position the retainer nut  144  axially inward of the second shaft shoulder  142 . The radially inward flange portion  50 E of the first shaft  50  is positioned between the second shaft shoulder  142  and the retainer nut  144  to prevent axial movement of the second shaft  52  within the central opening  50 D of the first shaft  50 , and hence prevent axial movement of the second shaft relative to the body  42 . The retainer nut  144  is locked in place for rotation with the second shaft  52 . 
   Much as with the first discussed embodiment, thrust bearings  62  are disposed between the first shaft flange portion  50 B of the first shaft  50 , and both of the first shoulder  54  of the body sidewall  44  and the end cap  134  to support the first shaft against longitudinal thrust loads. Additionally, thrust bearings  62  are disposed between the radially inward flange portion  50 E of the first shaft  50 , and both of the second shaft shoulder  142  and the retainer nut  144  to support the second shaft  52  against longitudinal thrust loads. Radial bearing  64  are positioned in this embodiment between the first shaft  50  and the body sidewall  44  and between the radially outward face of the first shaft flange portion  50 B and the body sidewall axially outward of the first shoulder  54  to support the first shaft against radial loads. Additionally, radial bearing  64  are positioned between the first and second shafts  50  and  52  and between the retainer nut  144  and the first shaft to support the second shaft against radial loads. Seals  66  are disposed between the first shaft  50  and both the end cap  134  and the body sidewall  44 , and between the first and second shafts  50  and  52  to provide a fluid-tight seals therebetween. 
   The piston  82  used in the actuator  12  of the embodiment of  FIG. 10  is coaxially and reciprocally mounted generally within the body  42  coaxial with the first and second shafts  50  and  52 . In this embodiment, however, the piston  82  has an annular first end portion  146  toward the first body end  46  in the form of a splined sleeve, and a second end portion  148  toward the second body end  48 . An end of the first shaft  50  toward the second body end  48  has inner helical splines  90  over a portion of its length, and spaced apart radially inward thereof, an end of the second shaft  52  has outer helical splines  94  over a portion of its length. The first end sleeve portion  146  of the piston  82  extends within the central opening  50 D of the first shaft  50 , between the splined ends of the first and second shafts  50  and  52  (radially inward of the first shaft and radially outward of the second shaft). The piston first end sleeve portion  146  has outer helical splines  88  over a portion of its length which mesh with the inner helical splines  90  of the first shaft  50 , and inner helical splines  92  over a portion of its length which mesh with the outer helical splines  94  of the second shaft  52 . The second end portion  148  of the piston  82  has outer straight splines  98  over a portion of its length which mesh with the interior ring gear portion  100  of the body sidewall  44  having inner straight splines  102 . The splines  98  and  102  may be helical if desired. In the actuator  12  of  FIG. 10 , the annular piston head portion  104  is threadably attached to the second end portion  148  of the piston toward the second body end  48  with the seal  106  disposed therebetween. The seal  108  is disposed between the piston head portion  104  and the smooth interior wall portion  110  of the body sidewall  44  to provide a fluid-tight seal therebetween. 
   The meshing splines can be threaded in the direction (e.g., left-handed or right-handed, or straight, as appropriate) and with the lead desired to produce simultaneous counter-rotation of the first and second shafts  50  and  52 , and hence the first and second tool members  14  and  16  attached thereto, in a desired amount per unit of axial motion of the piston  82 , but also may be splined to produce simultaneous rotation of the first and second tool members in the same rotational direction. 
   As described above for the embodiment of the actuator  12  shown in  FIG. 8 , reciprocation of the piston  82  within the body  42  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of the first port P 1  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion  104  toward the first body end  46  or through the second port P 2  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion toward the second body end  48 . As the piston head portion  104  and the piston  82 , of which the piston head portion is a part, linearly reciprocates in an axial direction within the body  42 , the outer splines  98  of the piston second end portion  148  engage or mesh with the inner splines  102  of the body sidewall  44  to prevent rotation of the piston, where both the outer splines  98  and the inner splines  102  are straight. The linear movement of the piston  82  is simultaneously transmitted through the outer splines  88  and the inner splines  92  of the piston first end sleeve portion  146  to the inner splines  90  of the first shaft  50  and the outer splines  94  of the second shaft  52 , respectively, to cause the shafts to simultaneously rotate. In such manner, the first and second tool members  14  and  16  attached to the first and second shafts simultaneously rotate relative to the body  42  and to the boom mounting member  20  or other mounting surface, platform or frame to which the body is mounted when the piston  82  is moved linearly by the application of fluid pressure to one of the first and second body ports P 1  and P 2 . The smooth interior wall portion  110  of the body sidewall  44  has sufficient axial length to accommodate the full end-to-end reciprocating stroke travel of the piston  82  within the body  42 . 
   As noted above, longitudinal movement of the first and second shafts  50  and  52  is restricted, thus linear movement of the piston  82  is converted into rotational movement of the first and second shafts. The amount of rotation depends on the lead of the various splines and the stroke of the piston, and the output torque produced depends on the slope and direction of turn of the various splines, and the piston force generated by the fluid pressure. 
   The mounting flanges  112  of the actuator  12  of  FIG. 10 , by which the body is attached to the mounting face  114  of the boom mounting member  20  or some other mounting surface, platform or frame, are located at the second body end  48  of the body  42 . The attachment bolts  116  may be used to accomplish the mounting. 
   Another embodiment of the actuator  12  is shown in  FIG. 11  using straddle mounting but with simultaneous rotary drive provided to the first and second tool members  14  and  16  at both ends of the actuator  12  (i.e., idle mounting is not used). This is useful when it is desirable to provide rotary drive to both the first and second side projecting attachment portions  14 A and  14 B of the first tool member  14 , and to both the first and second side projecting attachment portions  16 A and  16 B of the second tool member  16 . This can be compared to the embodiment of the actuator  12  shown in  FIG. 8  where rotary drive is only provided to the first side projecting attachment portion  14 A of the first tool member  14  and to the second side projecting attachment portion  16 B of the second tool member  16 , with the second side projecting attachment portion  14 B and the first side projecting attachment portion  16 A being idle mounted. For example, with the embodiment of the actuator shown in  FIG. 11  used with clamshell buckets, both the right and left sidewalls of each clamshell bucket can be simultaneously supplied torque by the actuator. 
   Much as described above for the embodiment of  FIG. 10 , the embodiment of the actuator  12  shown in  FIG. 11  has the first and second shafts  50  and  52  located at the first longitudinal body end  46  (the left end as viewed in  FIG. 11 ). The first and second shafts  50  and  52  are described above with respect to the embodiment of  FIG. 10  and that description will not be repeated here. However, in the actuator  12  of  FIG. 11 , similar separate first and second shafts  50 ′ and  52 ′ are also located at the second longitudinal body end  48  (the right end as viewed in  FIG. 11 ), essentially the design described above for the left end of the actuator of  FIG. 10  is repeated at the right end of the actuator. 
   The separate first and second shafts  50 ′ and  52 ′ are coaxially positioned within the body  42  and supported for rotation relative to the body  42 , with the first shaft  50 ′ being in the form of a sleeve having a central opening  50 D extending axially fully therethrough. The second shaft  52 ′ is concentrically, rotatably mounted within the central opening  50 D of the first shaft  50 ′. The first shaft  50 ′ extends axially out of the body  42  at the second body end  48 , and has an attachment portion  50 A at the second body end. The second shaft  52 ′ also extends axially out of the body  42  at the second body end  46 , extending outward beyond the end of the first shaft  50 ′, and has an attachment portion  52 A at the second body end. The attachment portions  50 A and  52 A each have splines  118  by which they transmit rotary drive to the second attachment portion  14 B of the first tool member  14  and to the second attachment portion  16 B of the second tool member  16 , respectively. Of course, the second attachment portion  14 B and the second attachment portion  16 B of the first and second tool members  14  and  16  to be used with the actuator  12  will have corresponding mating splines. As noted above, the tool members may comprise various type work tools, including clamshell buckets, brush rakes, grapples or refuse can collection fingers or tines, to name a few. 
   In the embodiment of the actuator  12  shown in  FIG. 11 , the first shaft  50 ′ includes a radially outward flange portion  50 B, the same as the first shaft  50  described above for the embodiment of  FIG. 8 . The outward flange portion  50 B is positioned at the second body end  48  adjacent to the axially outward facing first shoulder  56  (similar to the first shoulder described with respect to  FIG. 8 ) of the body sidewall  44  located toward the second body end. The first shaft  50 ′ further includes a radially inward flange portion  50 E positioned at the second body end  48 . An annular end cap  134  is positioned at the second body end  48  and attached to an end flange  136  of the body  42  by a plurality of bolts  138 . The end cap  134  is located axially outward of the outward flange portion  50 B of the first shaft  50 ′, with the flange portion  50 B positioned between the second shoulder  56  of the body sidewall  44  and the end cap  134  to prevent axial movement of the first shaft  50 ′ within the body  42 . The end cap  134  has a central aperture  140  through which the first and second shafts  50 ′ and  52 ′ extend axially outward beyond the end cap. 
   The second shaft  52 ′ has an axially inward facing shoulder  142  positioned axially outward of the radially inward flange portion  50 E of the first shaft  50 ′. An interiorly threaded annular retainer nut  144  is positioned within the body  42 , and is threadably attached to an exteriorly threaded portion of the second shaft  52 ′ toward the second body end  48  to position the retainer nut  144  axially inward of the second shaft shoulder  142  of the second shaft  52 ′. The radially inward flange portion  50 E of the first shaft  50 ′ is positioned between the second shaft shoulder  142  of the second shaft  52 ′ and the retainer nut  144  to prevent axial movement of the second shaft  52 ′ within the central opening  50 D of the first shaft  50 ′, and hence prevent axial movement of the second shaft  52 ′ relative to the body  42 . The retainer nut  144  is locked in place for rotation with the second shaft  52 ′. As with the first and second shafts  50  and  52  described with respect to  FIG. 10 , thrust bearings  62 , radial bearing  64  and seals  66  are provided. 
   The piston  82  used in the actuator  12  of the embodiment of  FIG. 11  is coaxially and reciprocally mounted generally within the body  42  coaxial with the first and second shafts  50  and  52  at the first body end  46  and with the first and second shafts  50 ′ and  52 ′ at the second body end  48 . In this embodiment, however, not only does the piston  82  have the annular first end portion  146  toward the first body end  46  in the form of a splined sleeve, but the second end portion  148  toward the second body end  48  is also in the form of a splined sleeve. The first and second shafts  50  and  52  are described above with respect to the embodiment of  FIG. 10  and that description will not be repeated here. With respect to the first shaft  50 ′ at the second body end  48 , it has an end toward the first body end  46  with inner helical splines  90  over a portion of its length, and spaced apart radially inward thereof, the second shaft  52 ′ has an end with outer helical splines  94  over a portion of its length. The second end sleeve portion  148  of the piston  82  extends within the central opening  50 D of the first shaft  50 ′, between the splined ends of the first and second shafts  50 ′ and  52 ′ (radially inward of the first shaft  50 ′ and radially outward of the second shaft  52 ′). The second end sleeve portion  148  has outer helical splines  88  over a portion of its length which mesh with the inner helical splines  90  of the first shaft  50 ′, and inner helical splines  92  over a portion of its length which mesh with the outer helical splines  94  of the second shaft  52 ′. As in the embodiment of the actuator  12  shown in  FIG. 8 , the mid-portion  96  of the piston  82  has outer straight splines  98  over a portion of its length which mesh with inner straight splines  102  of the interior ring gear portion  100  of the body sidewall  44 . Alternatively, the splines  98  and  102  may be helical. The annular piston head portion  104  of the actuator  12  is threadably attached to the mid-portion  96  of the piston  82 . 
   Reciprocation of the piston  82  within the body  42  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of the first port P 1  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion  104  toward the first body end  46  or through the second port P 2  which is in fluid communication with a fluid-tight compartment within the body to a side of the piston head portion toward the second body end  48 . As the piston head portion  104  and the piston  82  linearly reciprocates in an axial direction within the body  42 , the outer splines  98  of the piston mid-portion  96  engage or mesh with the inner splines  102  of the body sidewall  44  to prevent rotation of the piston, where both the outer splines  98  and the inner splines  102  are straight. The linear and rotational movement of the piston  82  is simultaneously transmitted through the outer splines  88  and the inner splines  92  of the piston first end sleeve portion  146  to the inner splines  90  of the first shaft  50  and the outer splines  94  of the second shaft  52 , respectively, and simultaneously transmitted through the outer splines  88  and the inner splines  92  of the piston second end sleeve portion  148  to the inner splines  90  of the first shaft  50 ′ and the outer splines  94  of the second shaft  52 ′, respectively, to cause the first and second shafts  50  and  52  and the first and second shafts  50 ′ and  52 ′ to all simultaneously rotate. The splines are selected to cause the first shafts  50  and  50 ′ to rotate in the same direction, and the second shafts  52  and  52 ′ to rotate in the same direction, but typical opposite or counter to the direction of rotation of the first shafts so that the first and second tool members  14  and  16  attached to the shafts selectively rotate toward and away from each other. The shafts rotate relative to each other and each rotates relative to the body  42  and the boom mounting member  20  or other mounting surface, platform or frame to which the body is mounted when the piston  82  is moved linearly by the application of fluid pressure to one of the first and second body ports P 1  and P 2 . 
   The longitudinal movement of the first and second shafts  50  and  52  and the first and second shafts  50 ′ and  52 ′ is restricted, thus linear movement of the piston  82  is converted into rotational movement of the shafts. 
   As with the embodiment of  FIG. 8 , the mounting flanges  112  of the actuator  12  of  FIG. 11 , by which the body is attached to the mounting face  114  of the boom mounting member  20  or some other mounting surface, platform or frame, are located along the body sidewall  44 . 
   Yet another embodiment of the actuator  12  is shown in  FIG. 12 . This embodiment is similar to the embodiment of  FIG. 8  with the first and second shafts  50  and  52  located at the first and second ends  46  and  48 , respectively, of the body  42 . However, rather than using first and second retainer nuts  58  and  60  to retain the shafts within the body  42  against axial movement, the body  42  of the actuator  12  includes a central tie rod  150  positioned along the longitudinal axis  22  of the actuator. The first and second shafts  50  and  52  are in the form of sleeves having central openings  50 D and  52 D, respectively, extending axially fully therethrough, and have the tie rod  150  extending through the central openings. The tie rod  150  retains the first and second shafts  50  and  52  from axially outward movement relative to each other and the body sidewall  44 , as will be described below. 
   As with other embodiments, the first and second shafts  50  and  52  are coaxially positioned within the body  42  and supported for rotation relative to the body. The first shaft  50  extends axially out of the body  42  at the first body end  46 , and has an attachment portion  50 A in the form of a flange located axially outward of the first body end  46  to which the first tool member  14  may be connected. The second shaft  52  extends axially out of the body  42  at the second body end  48 , and has an attachment portion  52 A in the form of a flange located axially outward of the second body end  48  to which the second tool member  16  may be connected. The first shaft  50  further includes an axially inward facing end wall portion  50 F positioned within the body  42  inward of the first body end  46  adjacent to the axially outward facing first shoulder  54  of the body sidewall  44  to prevent axial inward movement of the first shaft  50 . Similarly, the second shaft  52  further includes an axially inward facing end wall portion  52 F positioned within the body  42  inward of the second body end  48  adjacent to the axially outward facing second shoulder  56  of the body sidewall  44  to prevent axial inward movement of the second shaft  52 . 
   The first and second shafts  50  and  52  each further include a radially inward flange portion  50 E and  52 E, respectively. The radially inward flange portion  50 E is positioned axially outward of the first body end  46 , and the radially inward flange portion  52 E is positioned axially outward of the second body end  48 . The tie rod  150  includes a head portion  152  positioned axially outward of the radially inward flange portion  52 E of the second shaft  52  and adjacent thereto to prevent axial outward movement of the second shaft  52 . The tie rod  150  further includes an elongated shaft portion  154  extending along the longitudinal axis  22  of the actuator  12  and having an exteriorly threaded end portion  156  positioned axially outward of the radially inward flange portion  50 E of the first shaft  50 . A tie rod retainer nut  158  is threadably attached to the tie rod threaded end portion  156 . An annular end cap  160  is positioned axially outward of the radially inward flange portion  50 E of the first shaft  50  and adjacent thereto to prevent axial outward movement of the first shaft  50 . The end cap  160  has a central aperture through which the tie rod shaft portion  154  extends axially outward beyond the end cap. The tie rod retainer nut  158  prevents axial outward movement of the end cap  160 . The tie rod retainer nut  158  is locked in place against rotation on the tie rod threaded end portion. As with the embodiments described above, thrust bearings  62 , radial bearing  64  and seals  66  are provided. 
   The actuator  12  of  FIG. 12  is attached to the mounting face  114  of the boom mounting member  20  or some other mounting surface, platform or frame by attachment of the tie rod  150  thereto using mounting flanges (not shown). The mounting flanges are connected to the tie rod  150  by attachment bolts threadably received in a plurality of threaded apertures  162  in the end of the tie rod head portion  152  and in a plurality of threaded apertures  163  in the tie rod end cap  160 . 
   The piston  82  used in the actuator  12  of the embodiment of  FIG. 12  is in the form of a piston sleeve having a central opening  82 A extending axially fully therethrough, with the tie rod shaft portion  154  extending through the central opening  82 A. The piston  82  is coaxially and reciprocally mounted generally within the body  42  coaxial with the first and second shafts  50  and  52 . Instead of using a threadably attached annular piston head portion as in the embodiments described above, the actuator  12  of  FIG. 12  integrates the piston head function into the sleeve by providing seals  164  carried by the piston  82  between the exterior and interior walls thereof and the smooth interior wall portion  110  of the body sidewall  44  and a smooth exterior wall portion  166  of the tie rod shaft portion  154  to provide fluid-tight seals therebetween. 
   In the embodiment of  FIG. 12 , the piston  82  has a first end portion  168  toward the first body end  46 , and a second end portion  170  toward the second body end  48 . An end of the first shaft  50  toward the second body end  48  has inner helical splines  90  over a portion of its length, and an end of the second shaft  52  toward the first body end  46  has inner helical splines  94  over a portion of its length. The first end sleeve portion  168  of the piston  82  extends within the central opening  50 D of the first shaft  50 , and has outer helical splines  88  over a portion of its length, which mesh with the inner helical splines  90  of the first shaft  50 . The second end sleeve portion  170  of the piston  82  extends within the central opening  52 D of the second shaft  52 , and has outer helical splines  92  over a portion of its length which mesh with the inner helical splines  94  of the second shaft  52 . Unlike the previously described embodiments with the body sidewall having a splined interior ring gear portion, in the embodiment of  FIG. 12  the tie rod shaft portion  154  (forming a part of the body  42 ) has outer straight splines  102  at its end toward the second body end  48 . The piston  82 , within the central opening  82 A thereof at an end toward the second body end  48 , has inner straight splines  98  over a portion of its length that mesh with the outer straight splines  102  of the tie rod shaft portion  154 . The splines  98  and  102  may be helical if desired. 
   As before, the meshing splines can be threaded in the direction (e.g., left-handed or right-handed) and with the lead desired to produce simultaneous counter-rotation of the first and second shafts  50  and  52 , and hence the first and second tool members  14  and  16  attached thereto, in a desired amount per unit of axial motion the piston  82 , but also may be splined to produce simultaneous rotation of the first and second tool members in the same rotational direction. 
   As described above for other embodiments of the actuator  12 , reciprocation of the piston  82  within the body  42  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of the first port P 1  which is in fluid communication with a fluid-tight compartment within the body toward the first body end  46  or through the second port P 2  which is in fluid communication with a fluid-tight compartment within the body toward the second body end  48 . In the embodiment of  FIG. 12 , the first and second ports P 1  and P 2  are formed in the tie rod  150  at the ends thereof toward the first and second shafts  50  and  52 , respectively. As the piston  82  linearly reciprocates in an axial direction within the body  42 , the inner splines  98  of the piston  82  engage or mesh with the outer splines  102  of the tie rod shaft portion  154  to prevent rotation of the piston, where both the inner splines  98  and the outer splines  102  are straight. The linear movement of the piston  82  is simultaneously transmitted through the outer splines  88  and  92  of the piston to the inner splines  90  of the first shaft  50  and the inner splines  94  of the second shaft  52 , respectively, to cause the shafts to simultaneously rotate. In such manner, the first and second tool members  14  and  16  attached to the first and second shafts simultaneously rotate relative to the tie rod  150  (which forms a part of the body  42 ) and to the boom mounting member  20  or other mounting surface, platform or frame to which the body/tie rod is mounted when the piston  82  is moved linearly by the application of fluid pressure to one of the first and second ports P 1  and P 2 . The smooth interior wall portion  110  of the body sidewall  44  has sufficient axial length to accommodate the full end-to-end reciprocating stroke travel of the piston  82  within the body  42 . 
   Since longitudinal movement of the first and second shafts  50  and  52  is restricted, linear movement of the piston  82  is converted into rotational movement of the first and second shafts. 
   Another embodiment of the actuator  12  is shown in  FIGS. 13A and 13B  using straddle mounting with simultaneous rotary drive provided to the first and second tool members  14  and  16  at both ends of the actuator  12 . In this embodiment, first and second end caps  172  and  174  are positioned at the first and second body ends  46  and  48 . The first end cap  172  is attached to the end flange  136  of the body  42  by a plurality of bolts  176 . The second end cap is attached to the body sidewall  44  at the second body end  48  by a plurality of bolts  178 . The first and second shafts  50  and  52  each extends fully between the first and second end caps  172  and  174 , and each has first and second end portions with splines  118  extending axially beyond the first and second end caps to receive and provide rotary drive to the first and second tool members  14  and  16  (not shown in  FIGS. 13A and 13B ) at positions axially outward of the end caps. The first and second end portions of the first shaft  50  both simultaneously supply torque to the first tool member  14 , and first and second end portions of the second shaft  52  both simultaneously supply torque to the second tool member  16 . The first and second shafts  50  and  52  are in laterally spaced apart relation, each mounted in the body  42  for rotation on a separate axis of rotation not coaxial with the other or the body. 
   The piston  82  of the embodiment of  FIGS. 13A and 13B  has two apertures  82 B therethrough. Each piston aperture  82 B has one of the first and second shafts  50  and  52  extending therethrough. The portion of each of the first and second shafts  50  and  52  extending through the piston aperture  82 B has outer helical splines  180  over a portion of its length which mesh with inner helical splines  182  of the piston  82  formed within the piston aperture. While the piston may also be supplied with outer splines arranged to mesh with the splines of an interior ring gear portion of the body sidewall  44  as used with some of the previously described embodiments, such is not necessary to achieve operation of the actuator  12  unless required to reduce binding during operation of the actuator. As with the embodiments described above, thrust bearings, radial bearing and seals are provided as needed. The body  42  is shown in  FIG. 13A  mounted to a mounting frame  184  located at the first body end  46 . Alternatively, the actuator  12  may be mounted using mounting flanges attached to the body sidewall  44  of the body  42  as described above for other embodiments. 
   Reciprocation of the piston  82  within the body  42  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of the first port P 1  which is in fluid communication with a fluid-tight compartment within the body toward the first body end  46  or through the second port P 2  which is in fluid communication with a fluid-tight compartment within the body toward the second body end  48 . As the piston  82  linearly reciprocates in an axial direction within the body  42 , the inner splines  182  of the piston  82  located within the piston apertures  82 B engage or mesh with the outer splines  180  of the first and second shafts  50  and  52  to cause rotation of the first and second shafts. Since the first and second shafts  50  and  52  are laterally spaced apart, the piston  82  cannot rotate as it moves longitudinally within the body  42 . As such, and since longitudinal movement of the first and second shafts  50  and  52  is restricted, the linear movement of the piston is simultaneously transmitted through the inner splines  182  of the piston to the outer splines  180  of the shafts to cause the shafts to simultaneously rotate. In such manner, the first and second tool members  14  and  16  (not shown in  FIGS. 13A and 13B ) attached to the first and second shafts simultaneously rotate relative to the body  42  and to the mounting frame  184  to which the body is mounted when the piston  82  is moved linearly by the application of fluid pressure to one of the first and second ports P 1  and P 2 . 
   Another embodiment of the actuator  12  is shown in  FIGS. 14A and 14B . This actuator is essentially the actuator of  FIG. 8 , referred to here as the inner actuator, usable to provide simultaneous rotary drive to the first and second tool members  14  and  16  (not shown in  FIGS. 14A and 14B ) such as to rotate the first and second tool members toward and away from each other to provide a grabbing action, positioned within a rotary actuator, referred to here as the outer actuator, that is operable to rotate the inner actuator and the first and second tool members as a unit, as will be described below. 
   In particular, the actuator  12  has an elongated outer housing or body  186  with a cylindrical sidewall  188  and first and second longitudinal ends  190  and  192 , respectively. The outer body  186  has the mounting flanges  112  for mounting of the body the mounting face  114  of the boom mounting member  20  or some other mounting surface, platform or frame. The body  42  of the inner actuator, described above for the actuator of  FIG. 8  and referred to here as the inner body  42 , is positioned coaxially within the outer body  186 . The inner and outer bodies  42  and  186  are arranged coaxial with the longitudinal axis  22 . As with the actuator of  FIG. 8 , the separate first and second end rotatable drive shafts  50  and  52  of the inner actuator are coaxially positioned within the inner body  42  and supported for rotation relative to the inner body, with the first shaft  50  extending axially out of the inner body  42  at the first body end  46 , and the second shaft  52  extending axially out of the inner body  42  at the second body end  48 . For brevity, the complete physical description of the inner actuator will not be repeated here. 
   In the embodiment of the actuator  12  of  FIGS. 14A and 14B , the exteriorly threaded first annular retainer nut  58  is positioned between the inner and outer bodies  42  and  186 , at the first body ends  46  and  190 , and is threadably attached to an interiorly threaded portion of the body sidewall  188  of the outer body  186  at the first body end  190 . Similarly, the exteriorly threaded first annular retainer nut  60  is positioned between the inner and outer bodies  42  and  186 , at the second body ends  48  and  192 , and is threadably attached to an interiorly threaded portion of the body sidewall  188  of the outer body  186  at the second body end  192 . In this embodiment of the actuator, the first and second retainer nuts  58  and  60  are located axially outward of the axially outward facing ends of the first and second body ends  46  and  48  of the body sidewall  44 , with the flange portion  50 B of the first shaft  50  positioned between the axially outward facing end of the first body end  46  and the first retainer nut  58  to prevent axial movement of the first shaft within the inner body  42 , and with the flange portion  52 B of the second shaft  52  positioned between the axially outward facing end of the second body end  48  and the second retainer nut  60  to prevent axial movement of the second shaft within the inner body  42 . 
   The exterior end surfaces of the attachment portions  50 A and  52 A of the first and second shafts  50  and  52  are flat and each have threaded apertures  70  and  72  to allow attachment of the first and second tool members  14  and  16  thereto. The first and second end support members  76  and  78  described above for the actuator of  FIG. 8  may be used to idle mount one of the attachment portions of the first and second tool members if desired to achieve a straddle mounting of the first and second tool members  14  and  16  to the actuator  12  of  FIGS. 14A and 14B . 
   The construction and operation of the inner actuator is generally as described above for the actuator of  FIG. 8 , with reciprocation of the piston  82  within the inner body  42  occuring when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of a first port P 1  which is in fluid communication with a fluid-tight compartment within the inner body  42  to a side of the piston head portion  104  toward the first body end  46  or through a second port P 2  which is in fluid communication with a fluid-tight compartment within the inner body  42  to a side of the piston head portion toward the second body end  48 . It is noted that in the actuator  12  of  FIGS. 14A and 14B , the first and second ports P 1  and P 2  extend through the outer body  186 , toward the first and second body ends  190  and  192  thereof, respectively, and communicate with the fluid-tight compartments within the inner body  42  though channels  58 A and  60 A in the retainer nuts  58  and  60 , respectively. As the piston head portion  104  and the piston  82 , of which the piston head portion is a part, linearly reciprocates in an axial direction within the inner body  42 , the outer splines  98  of the piston mid-portion  96  engage or mesh with the inner splines  102  of the body sidewall  44  to prevent rotation of the piston, where both the outer splines  98  and the inner splines  102  are straight. Helical splines  98  and  102  may be used if desired. The linear movement of the piston  82  is simultaneously transmitted through the outer splines  88  and  92  of the piston to the inner splines  90  and  94 , respectively, of the first and second shafts  50  and  52  to cause the shafts to simultaneously rotate. Since the longitudinal movement of the first and second shafts  50  and  52  is restricted, linear movement of the piston  82  is converted into rotational movement of the first and second shafts. 
   The actuator  12  of  FIGS. 14A and 14B  further includes an elongated, annular splined outer piston  194  positioned within the annular space between the inner body  42  and the outer body  186  for axial reciprocal movement within the outer body  186  coaxial with the inner body  42  and first and second shafts  50  and  52 . The outer piston  194  has an annular piston head portion  195 . The outer piston  194  further includes outer helical splines  196  over a portion of its length which mesh with inner helical splines  198  of the outer body sidewall  188  (formed on a radially inward facing side thereof), and inner straight splines  200  over a portion of its length which mesh with outer straight splines  202  of the inner body sidewall  44  (formed on a radially outward facing side thereof). The splines  200  and  202  may be helical if desired. Alternatively, the splines  196  and  198  may be straight and the splines  200  and  202  helical, or the splines  196  and  198  may be helical and the splines  200  and  202  straight. The meshing splines can be threaded in the direction (e.g., left-handed or right-handed, or straight, as appropriate) and with the lead desired to produce rotation of the inner actuator (including the inner body  42 , the first and second shafts  50  and  52 , and the first and second tool members  14  and  16  attached to the shafts as a unit) relative to the outer body  188  in a desired amount per unit of axial motion of the outer piston  194 . As with the embodiments described above, thrust bearings, radial bearing and seals are provided as needed. 
   Reciprocation of the outer piston  194  within the outer body  186  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of a third port P 3  which is in fluid communication with a fluid-tight compartment within the outer body  186  to a side of the piston head portion  195  toward the first body end  190  or through a fourth port P 4  which is in fluid communication with a fluid-tight compartment within the outer body  186  to a side of the piston head portion  195  toward the second body end  192 . As the piston head portion  195  and the outer piston  194  linearly reciprocates in an axial direction within the outer body  186 , the outer splines  196  of the outer piston  194  engage or mesh with the inner splines  198  of the outer body sidewall  188  to cause rotation of the outer piston, where both the outer splines  196  and the inner splines  198  are helical. The rotational movement of the outer piston  194  is transmitted through the inner splines  200  of the outer piston to the outer splines  202  of the inner body sidewall  44  of the inner body  42  to cause the inner body, and the first and second shafts  50  and  52 , to rotate as a unit relative to the outer body  186 . In such manner, the first and second tool members  14  and  16  attached to the first and second shafts  50  and  52  rotate relative to the outer body  186  and to the boom mounting member  20  or other mounting surface, platform or frame to which the outer body is mounted when the outer piston  194  is moved linearly by the application of fluid pressure to one of the third and fourth ports P 3  and P 4 . By way of example using grapples as the first and second tool members  14  and  16 , the resulting movement by operation of the inner actuator is timed rotation of the grapple tines about the axis  22  serving much like grabbing with the fingers of a hand, and the resulting movement by operation of the outer actuator is rotation of the grapple tines as a unit about the axis  22  much like the rotation of a wrist to provide a high torque articulated tool. 
   Another embodiment of the actuator  12  is shown in  FIG. 15 . This actuator is essentially the actuator of  FIG. 12  (although without the tie rod) referred to here as the outer actuator usable to provide simultaneous rotary drive to the first and second tool members  14  and  16  (not shown in  FIG. 15 ) such as to rotate the first and second tool members toward and away from each other to provide a grabbing action, with a rotary actuator referred to here as the inner actuator positioned within the outer actuator. The inner actuator is operable to rotate the outer actuator and the first and second tool members as a unit. 
   In particular, rather than using the central tie rod of the embodiment of  FIG. 12 , the actuator  12  of  FIG. 15  has an elongated inner housing or body  204  with a cylindrical sidewall  206  and first and second longitudinal ends  208  and  210 , respectively. The inner body  204  is positioned coaxially within the body  42 , described above for the actuator of  FIG. 12  and referred to here as the outer body  42 . The outer and inner bodies  42  and  204  are arranged coaxial with the longitudinal axis  22 . As with the actuator of  FIG. 12 , the separate first and second end rotatable drive shafts  50  and  52  of the outer actuator are in the form of sleeves and are coaxially positioned within the outer body  42  and supported for rotation relative to the outer body, with the first shaft  50  extending axially out of the outer body  42  at the first body end  46 , and the second shaft  52  extending axially out of the outer body  42  at the second body end  48 . For brevity, the complete physical description of the outer actuator will not be repeated here. 
   In the actuator  12  of  FIG. 15 , the axially inward facing end wall portion  50 F of the first shaft  50  is positioned within the outer body  42  inward of the first body end  46  adjacent to the axially outward facing first shoulder  54  of the body sidewall  44  to prevent axial inward movement of the first shaft  50 . Similarly, the axially inward facing end wall portion  52 F of the second shaft  52  is positioned within the outer body  42  inward of the second body end  48  adjacent to the axially outward facing second shoulder  56  of the body sidewall  44  to prevent axial inward movement of the second shaft  52 . 
   The radially inward flange portion  50 E of the first shaft  50  is positioned axially outward of the first body end  46 , and the radially inward flange portion  52 E of the second shaft  52  is positioned axially outward of the second body end  48 . The inner body  204  has first and second annular retainer nuts  212  and  214  threadably attached to outer threaded portions of the first and second body ends  208  and  210 , respectively, of the inner body. The retainer nut  212  is positioned axially outward of the radially inward flange portion  50 E of the first shaft  50  and adjacent thereto to prevent axial outward movement of the first shaft  50 . The retainer nut  214  is positioned axially outward of the radially inward flange portion  52 E of the second shaft  52  and adjacent thereto to prevent axial outward movement of the second shaft  52 . 
   The attachment portion  50 A of the first shaft  50  is in the form of a flange located axially outward of the first body end  46  to which the first tool member  14  may be connected. The attachment portion  52 A of the second shaft  52  is in the form of a flange located axially outward of the second body end  46  to which the second tool member  16  may be connected. 
   The inner body  204  further has third and fourth annular retainer nuts  216  and  218  threadably attached to inner threaded portions of the first and second body ends  208  and  210 , respectively, of the inner body. The third and fourth retainer nuts  216  and  218  each has a central aperture  220  through which a shaft  222  extends for positioning the shaft  222  along the longitudinal axis  22  of the inner actuator within the inner body  204 . The shaft  222  has first and second end portions  224  and  226  that extend axially outward beyond the third and fourth retainer nuts  216  and  218 , respectively. The first and second end portions  224  and  226  of the shaft  222  have splines  228  by which the shaft  222  may be attached to a mounting surface, platform or frame. 
   The construction and operation of the outer actuator is generally as described above for the actuator of  FIG. 12 , with reciprocation of the piston  82  within the outer body  42  occurring when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of a first port P 1  which is in fluid communication with a fluid-tight compartment within the outer body  42  toward the first body end  46  or through a second port P 2  which is in fluid communication with a fluid-tight compartment within the outer body  42  toward the second body end  48 . It is noted that in the actuator  12  of  FIG. 15 , the first and second ports P 1  and P 2  extend through the first and second shafts  50  and  52 . As the piston  82  linearly reciprocates in an axial direction within the outer body  42 , the inner splines  98  of the piston engage or mesh with outer splines  102  of the inner body  204  (formed on a radially outward facing side thereof) to prevent rotation of the piston, where both the inner splines  98  and the outer splines  102  are straight. The splines  98  and  102  may be helical if desired. The linear movement of the piston  82  is simultaneously transmitted through the outer splines  88  and  92  of the piston to the inner splines  90  and  94 , respectively, of the first and second shafts  50  and  52  to cause the shafts to simultaneously rotate. Since the longitudinal movement of the first and second shafts  50  and  52  is restricted, linear movement of the piston  82  is converted into rotational movement of the first and second shafts. 
   The actuator  12  of  FIG. 15  further includes an elongated, annular splined inner piston  230  positioned within the annular space between the inner body  204  and the shaft  222  for axial reciprocal movement within the inner body  204  coaxial with the outer body  42  and the first and second shafts  50  and  52 . The inner piston  230  has an annular piston head portion  232 . The inner piston  230  further includes inner helical splines  234  over a portion of its length which mesh with outer helical splines  236  of the shaft  222 , and outer helical splines  238  over a portion of its length which mesh with inner helical splines  240  of the inner body sidewall  206  of the inner body  204  (formed on a radially outward facing side thereof). The meshing splines can be threaded in the direction (e.g., left-handed or right-handed) and with the lead desired to produce rotation of the outer actuator (including the outer body  42 , the first and second shafts  50  and  52 , and the first and second tool members  14  and  16  attached to the shafts as a unit) relative to the inner body  204  in a desired amount per unit of axial motion of the inner piston  230 . As with the embodiments described above, thrust bearings, radial bearing and seals are provided as needed. 
   Reciprocation of the inner piston  230  within the inner body  204  occurs when hydraulic oil, air or any other suitable fluid under pressure selectively enters through one or the other of a third port P 3  which is in fluid communication with a fluid-tight compartment within the inner body  204  to a side of the piston head portion  232  toward the first body end  208  or through a fourth port P 4  which is in fluid communication with a fluid-tight compartment within the inner body  204  to a side of the piston head portion  232  toward the second body end  210 . As the piston head portion  232  and the inner piston  230  linearly reciprocates in an axial direction within the inner body  204 , the inner splines  234  of the inner piston  230  engage or mesh with the outer splines  236  of the shaft  222  to cause rotation of the inner piston, where both the inner splines  234  and the outer splines  236  are helical. The linear and rotational movement of the inner piston  230  is transmitted through the outer splines  238  of the inner piston to the inner splines  240  of the inner body sidewall  206  of the inner body  204  to cause the inner body, which carries the outer body  42  and the first and second shafts  50  and  52  therewith, to rotate as a unit relative to the shaft  222 . In such manner, the first and second tool members  14  and  16  attached to the first and second shafts  50  and  52  rotate relative to the shaft  222  and to the boom mounting member  20  or other mounting surface, platform or frame to which the shaft  222  is mounted when the inner piston  230  is moved linearly by the application of fluid pressure to one of the third and fourth ports P 3  and P 4 . Again by way of example using grapples as the first and second tool members  14  and  16 , the resulting movement by operation of the outer actuator is timed rotation of the grapple tines about the axis  22  serving much like grabbing with the fingers of a hand, and the resulting movement by operation of the inner actuator is rotation of the grapple tines as a unit about the axis  22  much like the rotation of a wrist to provide a high torque articulated tool. This is the reverse of the actuator of  FIGS. 14A and 14B . 
   It should be understood that while splines are shown in the drawings and described herein, the principle of the invention is equally applicable to any form of linear-to-rotary motion conversion arrangement, such as balls or rollers, and that the splines can include any type of groove, thread or channel suitable for such motion conversion. 
   It will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 
   All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.