fig1 is an elevation view of an embodiment of a remote center positioner in a basic form in accordance with the present invention . a first linkage means is indicated generally by the numeral 21 and a second linkage in the form of a parallelogram is indicated by the numeral 23 . the first linkage means is pivotally mounted on a base plate for rotation about an x - x axis . the second linkage means is pivotally connected to the first linkage means and is adapted to move in a plane parallel to the first linkage . five link members ( including extensions thereof ), 11 , 12 , 13 , 14 , and 15 are connected together with pivot joints 16 - 20 . a portion of element 13 extends beyond pivot 20 of the parallelogram linkage . the parallelogram linkage has an operating end at link member 13 and a driving end at link member 12 . the elongated element 13 may , as desired later , carry a surgical instrument or other device . the pivot joints allow relative motion of the link members only in the plane containing them . a parallelogram linkage is formed by corresponding link members 14 , 15 and link members 12 and 13 . the portions of link members 14 and 15 of the parallelogram are of equal length as are the portions of members 12 and 13 of the parallelogram . these members are connected together in a parallelogram for relative movement only in the plane formed by the members . a rotatable joint generally indicated by the numeral 22 is connected to a suitable base 24 . the rotatable joint 22 is mounted on a base plate 26 adapted to be fixedly mounted to the base support means 24 . a pivot plate 28 is pivotally mounted to base plate 26 by suitable means at , such as , pivots 30 , 32 . thus pivot plate 28 may be rotated about axis x - x through a desired angle θ2 . this may be accomplished manually or by a suitable pivot drive motor 34 . a first linkage is pivotally mounted on the pivot plate 23 of the rotatable joint 22 . the linkage elements 11 , 12 and the link members relatively stiff or inflexible so that they may adequately support an instrument used in surgical operations . rods made of aluminum or other metal are useful as such links . the linkage elements 11 and 12 are pivotally mounted on base plate 28 for rotation with respect to the rotatable joint by pivots 36 and 38 . at least one of the pivots 36 , 38 is positioned so that its axis of rotation is normal to and intersects the x - x axis . movement may occur manually or may occur using a linkage drive motor 40 . the first linkage is also shaped in the form of a parallelogram formed by linkage elements 11 , and 12 ; the portion of link member 15 connected thereto by pivots 16 , 18 ; and base plate 28 . one of the link members 15 is thus utilized in both the first 21 and second 23 linkage means . linkage element 12 also forms a common link of both the first linkage means 21 and the second linkage means 23 . in accordance with the invention , a remote center of spherical rotation 8 is provided by the above described embodiment of apparatus when the linkage element 11 is rotated and / or when pivot plate 28 is rotated about axis x - x . thus the end of element 13 can be moved through desired angles θ1 and θ2 or rotated about its own axis while the remote center of rotation remains at the same location . the preferred embodiment of apparatus assembled in accordance with the present invention is illustrated in fig2 a and 3 . fig2 is an elevation view , fig2 a is an enlarged sectional view taken at a - a of fig2 and fig3 is an end view of the remote positioning apparatus . many of the elements of the preferred embodiment are the equivalent to elements of the fig1 embodiment . these elements will be designated with the same numbers primed in fig2 and 3 . thus a pivot plate 28 ′ is rotatably mounted on a base support means 26 ′ by suitable means such as pivots 30 ′, 32 ′. the pivot plate and the base plate form a rotatable joint 22 ′ which has a rotation axis designated as x - x . the base plate may be fixedly mounted to a suitable base support means 24 ′. two linkage elements 11 ′ and 12 ′ extend from the pivot plate 28 ′. mounting means 36 ′ and 38 ′ are provided to pivotally mount one end of each of the linkage elements to the pivot plate . the axis of rotation of the linkage elements are normal to and intersecting the x - x axis . a channel shaped link member 115 is pivotally connected by suitable pivot joints 16 ′ and 18 ′ to the other ends of linkage elements 11 ′, 12 ′ ( respectively ) equidistant from pivot plate 28 ′. a corresponding link member 15 ′ is located internally of link member 115 and is pivotally connected to the upper end of linkage element 12 ′. a link member 13 ′ corresponding in length to the link member 12 ′ between pivots 17 ′, 18 ′ is pivotally connected to link member 15 ′ at pivot 19 ′ and to link member 115 at pivot 20 ′. an instrument mounting means 44 is fixedly mounted to link member 13 ′ for movement therewith . the axis of an instrument held in the instrument mounting means 44 intersects the x - x axis of the rotating joint 22 ′. thus an instrument held in the mounting means would have a remote center of spherical rotation about the position indicated by the numeral 8 ′ in fig2 . a drive motor 434 incorporating a shaft - angle position sensor is operably connected to the pivot plate 28 ′. a second drive motor 440 incorporating a shaft - angle position sensor is operably connected to linkage element 11 ′. suitable motor drive and control circuits may be connected to motor / sensor 440 and motor / sensor 434 via power and sensor cables 436 and 435 ( respectively ) to operate the present apparatus under open - loop or closed - loop servo control . the details of the mounting arrangement for the instrument mounting means are shown in fig2 a which is a sectional view taken at a - a of fig2 . as there shown the mounting means 44 is fixedly connected via multiple - axis force and torque sensor 400 and pin member 118 to link member 13 ′ for movement therewith . link member 13 ′ is pivotally connected at pivot 20 ′ to the channel shaped link member 115 by bearing means 116 , 117 formed about pin member 118 . link member 15 ′ is pivotally connected to link member 13 ′ at 19 ′ by means of bearing means 120 and pin member 121 . a suitable sensor interface circuit may be connected to the force and torque sensor 400 via cable 401 so that sensor signals arising from forces and torques applied to an instrument supported in the mounting means 44 can be detected and used for monitoring or controlling operation of the present apparatus . for example , the sensor signals can be used as feedback signals in master - slave force - reflecting telerobotic servo control of the invention such that the input control device responds to forces exerted on the supported instrument and is not affected by inertial loads , gravity forces , or external forces acting on linkage elements other than mounting means 44 . an apparatus is provided for moving an instrument about a spherical center of rotation at a desired location of the instrument . a base support means is adapted to be fixedly mounted to a surface . first linkage means 11 ′, 12 ′ are pivotally mounted on the base plate for rotation about an axis . a holding means 44 is provided for holding an instrument in a position so that the desired remote center of spherical rotation of the instrument intersects the axis and a second linkage means 15 ′, 115 and 13 ′ is connected to the holding means and pivotally connected to the first linkage means by pivots 17 ′, 18 ′, 16 ′ whereby the remote center of spherical rotation of the instrument is maintained at the desired location . fig4 is a schematic elevation view of another embodiment of apparatus assembled in accordance with the present invention . in many instances it may be desirable to have a means of adjusting the remote center of rotation 8 ′ relative to the mounted position of base plate 26 ′. thus it would be desirable to axially extend or retract the horizontal members 14 ′, 15 ′ of the parallelogram linkage . the length of the two corresponding members 14 ′, 15 ′ must be increased or decreased in equal amounts to maintain the parallelogram geometry of the linkage . the axial length adjustment could be provided in many ways . for example , as shown in fig4 , a portion of members 14 ′, 15 ′ are provided with racks 42 , 44 . tubular members 46 , 48 enclose members 14 ′, 15 ′. the members 14 ′, 15 ′ are extended or retracted by suitable means such as drive motor 50 , motor lead 51 and drive belt 52 . other means for axially extending or retracting the members are available . for example , coupled lead screws could be used or the members could be manually fixed into the desired position in the tubular members using ratchets , pins or spring detents . fig5 illustrates an embodiment of apparatus assembled in accordance with the invention wherein a motor driven arrangement is positioned on the operating end of the parallelogram linkage . a drive unit 60 is connected by power and control cable 62 to a source of power and control and a cannula 64 is provided which may be passed through a patient &# 39 ; s abdominal wall . an instrument 66 is attached to an operating element 68 and may be manipulated as indicated in fig5 . the remote center positioners as described heretofore will maintain the center of spherical rotation at position 80 while the instrument 66 is being manipulated . fig6 is an elevation view illustrating a manual application of the remote center positioner of the present invention . a handle 71 for operating a surgical instrument 73 is connected to the operating end of the remote center positioner . movement of the cannula 75 will be constrained to rotation about the center 80 ′ of spherical rotation . fig7 is an elevation view and fig7 a is a sectional view taken at a - a of fig7 of an embodiment of the invention which utilizes a flexible drive element in the linkage of the remote center positioner . a rotatable joint is indicated by the numeral 122 . the rotatable joint rotates about an x - x axis . thus pivot plate 128 can be rotated about pivots 130 , 132 through a desired angle θ2 with respect to base plate 126 . a linkage element 111 is pivotally mounted on the pivot plate by pivot 133 . the pivot 133 is positioned so that its axis of rotation is normal to and intersects the x - x axis . a pulley 101 is positioned to be coaxial with the axis of rotation of the pivot 133 . it is evident that the term pulley can include wheels , sprockets or the like . the pulley is fixedly connected to the base plate 128 by suitable means such as screws 105 , 107 . thus the pulley will not rotate with respect to the base plate 128 . a link member 114 is pivotally connected by pivot joint 116 to linkage element 111 . a second pulley 121 coaxial with pivot 116 is fixedly connected to link member 114 by screws 146 and 147 . a flexible drive link 135 such as a belt , chain , or a cable is connected around the pulleys 121 , 101 in a non slip mode such as a bicycle chain or timing belt . pulleys 121 and 131 are of equal diameter as are pulleys 142 and 137 . a link member 140 is pivotally connected to the operating end of link member 114 by means of pivot joint 141 . a third pulley 137 coaxial with pivot 141 is fixedly connected to link member 140 by means of screws 143 , 145 . a fourth pulley 142 coaxial with pivot 116 is fixedly connected to link element 111 by screws 160 and 16 . 1 . a second flexible drive link 150 is connected around pulleys 137 and 142 in non slip relationship . thus when linkage element 111 is rotated about pivot 133 by linkage drive motor 149 for example , the motion is transmitted by the pulleys to link member 140 which is constrained to move in parallel relationship with element 111 . in this manner a remote center of rotation is maintained as indicated by 180 in fig7 . fig8 is an elevation view and fig8 a is a sectional view taken at a - a of fig8 of another embodiment of the present invention . a rotatable joint is shown and is indicated generally by the number 222 . the rotatable joint rotates about a x - x axis . thus pivot plate 228 can be rotated around pivots 230 , 232 through a desired angle θ2 . a linkage element 211 is pivotally mounted on the pivot plate 228 by pivot 233 . the axis of the pivot 233 is located normal to and intersecting the x - x axis of rotation . a pulley 201 is positioned to be coaxial with the axis of rotation of the pivot 233 . the pulley is fixedly connected to the base plate by suitable means such as screws 205 , 207 . a pair of link members 214 , 215 are pivotally connected to linkage element 211 by pivots 212 and 216 respectively . the other end of the link members 214 and 215 are pivotally connected to an instrument holding means or the like indicated by 240 by suitable pivot joints 241 , 242 . a second pulley 231 is fixedly connected to link element 215 by suitable screws 251 , 252 . the pulley 231 is mounted coaxially with the axis of rotation of the pivot joint 216 . a flexible drive link 260 is connected around both pulleys 201 and 231 in non slip relationship . the effect of this construction constrains link members 215 and 214 to remain parallel with the x - x axis during movement and also constrains element 240 to remain parallel with linkage element 211 during movement , thus causing the center of spherical rotation of the instrument or the like to remain at point 280 . the principles , preferred embodiments and modes of operation of the present invention have been described in the foregoing specification . however , the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed . the embodiments are to be construed as illustrative rather than restrictive . variations and changes may be made by others without departing from the spirit of the present invention . accordingly , all such variations and changes which fall within the spirit and scope of the present invention as defined in the following claims are expressly intended to be embraced thereby .
the invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation , remote from any bearings or mechanical supports , at a desired location of the instrument . the remote center positioner is particularly useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the abdominal wall .