fig1 illustrates a typical ophthalmic instrument system showing one potential use for a heavy duty support mechanism 10 and a light duty support mechanism 11 , each being constructed in accordance with principles of this invention . mechanisms 10 , 11 are shown affixed to one type of instrument stand 12 , however , it will be understood that many other supports may be used for mechanisms 10 and 11 , as shown in fig1 or mechanisms taking other forms in accordance with the invention . instrument stand 12 generally includes a base 14 which may hold a plurality of instruments 14a , 14b , 14c and which includes an upwardly extending pole 16 . pole 16 may have an overhead light 18 attached at the upper end . as further shown in dotted lines in fig1 support mechanism 11 may carry a lighter weight ophthalmic instrument , such as a vision tester 17 , while mechanism 11 may carry heavier weight structure such as a chin rest 19 and a slit lamp 21 or other instrument ( not shown ). referring now to fig2 instrument support mechanism 10 , which is suitable for heavier duty applications , includes a first arm 20 and a second arm 22 pivotally connected together by means to be described below . a cover 20a is preferably used to conceal the internal components and conventional wiring ( not shown ) associated with arm 20 . a similar cover may be used on arm 11 ( fig1 ) as mentioned below . first arm 20 comprises a first link member 24 and a second , lower link member 26 . link members 24 , 26 are respectively affixed by pivots 28 , 30 to a base member 31 . these pivots 28 , 30 allow the opposite end of arm 20 to be moved vertically with respect to base member 31 . referring briefly to fig3 respective pairs of links 36a , 36b and 38a , 38b assist with the locking of arm 20 in a desired vertical orientation relative to base member 31 . in this regard , links 36a , 36b and 38a , 38b are pivotally connected to first link member 24 . one pivot 40 for securing one end of links 36a , 36b is shown in fig2 with the understanding that a similar pivot connects links 38a , 38b to the same link member 24 . as best shown in fig3 the opposite ends of links 36a , 36b and 38a , 38b include respective slots 42a , 42b and 44a , 44b for reasons to be described below . still referring to fig2 along with the vertical pivoting movement allowed by the pivoting nature of link members 24 , 26 , first arm 20 may pivot about support pole 16 by a pivot connection 46 and second arm 22 may pivot with respect to both the first arm 20 and support pole 16 by a pivot connection 48 . more specifically , pivot connection 46 is made by way of a tube 50 that may be rigidly locked to support pole 16 and which receives a portion of base member 31 thereabout . to act as a stop for pivoting motion about pole 16 , a screw 52 is contained in base member 31 and extends into a slot 54 contained in tube 50 . a conventional screw operated clamp mechanism 56 is used to secure tube 50 rigidly to pole 16 . when lock 56 is in an unlocked position , tube 50 and the attached mechanism 10 may be height adjusted along support pole 16 . at the opposite end of first arm 20 , pivot connection 48 more specifically comprises a pivot support 58 which holds a pivot tube 60 for rotation therein . pivot tube 60 is held for rotation within bearing members or low friction bushings 62 , 64 . a retaining ring 68 holds pivot tube 60 in place within pivot support 58 . retaining ring 68 rests against a washer 66 as shown in fig2 to keep second arm 22 held in place within pivot support 58 . pivot tube 60 may also be used to accommodate wiring ( not shown ) to arm 22 . rotation of tube 60 and , therefore , arm 22 is limited by a screw 69 which engages a stop 71 at a desired limit of rotation . as further shown in fig2 and 2a , counterbalancing springs 70a and 70b help to counterbalance any weight being supported on second arm 22 , or on an additional arm attached thereto , in a generally conventional manner . specifically , springs 70a and 70b are connected to an adjustment screw 72 to allow adjustment of the counterbalancing force . ends 74a , 74b are each connected to a pin which includes an internally threaded bore receiving the adjustment screw 72 . the opposite ends of springs 70a and 70b are connected to pivot pin 34 . still referring to fig2 a locking mechanism 90 operates to lock each of the above described pivot connections in place after mechanism 10 has been adjusted vertically and rotationally to the desired orientation . locking mechanism 90 is operated by a lever 92 which may be moved in a simple and short push or pull manner in a direction extending along the length of first support arm 20 as generally shown by arrow 94 . lever 92 is connected by a pivot 96 to link member 26 and is further connected to a connecting link 98 by a pin 100 extending from connecting link 98 and into a slot 102 contained in the end of lever 92 . connecting link 98 is pivotally attached at opposite ends to respective short links 104 , 106 by respective pivots 108 , 110 . the opposite end of each short link 104 , 106 is connected to rotate a respective screw 112 , 114 . as will be described below , these screws operate to simultaneously lock pivot connections 46 and 48 as well as the general pivot connection formed by pivots 28 , 30 , 32 , 34 allowing arm 20 to move vertically with respect to base member 31 . referring now to fig3 to lock pivot connection 48 in place , a clamp member 116 is provided around pivot tube 60 . thus , it will be appreciated that when clamp member 116 is tightened against pivot tube 60 , pivot tube 60 will not be capable of rotating and , therefore , second arm 22 will not be capable of rotating with respect to first arm 20 . as more specifically shown in fig3 clamp member 116 includes a first portion 118 having an internally threaded insert 120 and a second portion 122 having a hole 124 . threaded insert 120 receives a threaded portion 112a of screw 112 , while hole 124 receives an unthreaded portion 112b of screw 112 with clearance to allow rotation of screw 112 . preferably , the threaded portion 112a is a double helical thread . most preferably , screws 112 , 114 are 3 / 8 &# 34 ;-- 10 double lead screws . additional clamp members 126 , 128 are provided for locking the above described vertical movement of first arm 20 with respect to base member 31 ( fig2 ). these clamp members 126 , 128 each include flange portions 126a , 128a that serve to clamp links 36a , 36b and 38a , 38b against a portion of pivot support 58 to prevent any movement of links 36a , 36b and 38a , 38b and thereby prevent any vertical movement of first arm 20 with respect to base member 31 ( fig2 ). it will further be appreciated that in an unlocked state , tubular portions 126b , 128b act as guides that ride within slots 42a , 42b and 44a , 44b during the vertical movement of first arm 20 with respect to base member 31 . the tubular portion 128b is preferably internally threaded and carries threaded member 130 to provide adjustment capability and a force bearing surface . washers 134 , 136 are located about tubular portion 126b and between pivot support 58 and link member 36b and link members 36a and 36b . likewise , washers 138 , 140 are located between pivot support 58 and link 38b and links 38a , 38b . turning now to fig4 pivot connection 46 more specifically comprises a clamp member 150 having a first portion 152 with a threaded insert 154 and a second portion 156 with a hole 158 . in a manner similar to pivot connection 48 , threaded insert 154 contains a double helically threaded portion 114a of screw 114 and hole 158 receives an unthreaded portion 114b of screw 114 with clearance to allow rotation of screw 114 . clamp member 150 is disposed about tube 50 and , therefore , when clamp member 150 is tightened , no rotation of base member 31 about tube 50 may take place . a set screw 159 allows adjustment in the clamping action . as further shown in both fig3 and 4 , short links 104 , 106 are rigidly connected to screws 112 , 114 at intermediate locations thereon with retainer pins 160 , 162 . thus , a review of fig2 - 4 will indicate that moving lever 92 away from base member 31 in the direction of arrow 94 will result in connecting member 98 moving toward base member 31 and short links 104 , 106 rotating screws 112 , 114 clockwise as viewed in fig2 . as shown in fig3 this will cause screw 112 to move in the direction of arrow 163 to urge clamp member 126 against links 36a , 36b until they are wedged against washers 134 , 136 and pivot support 58 . this will lock up and down motion of first arm 20 with respect to base member 31 ( fig1 ). simultaneously , clamp 116 will be rotated slightly around pivot tube 60 and move generally in the direction of arrows 164 , 165 . this will urge clamp member 128 against links 38a , 38b and clamp these links against washers 138 , 140 and against pivot support 58 to further assist in locking vertical movement of arm 20 . as clamp portion 118 moves further toward clamp portion 122 , pivot tube 60 is locked against any rotational movement . as long as short links 104 , 106 ( fig2 ) are maintained in the position shown , mechanism 10 will be locked completely in place by the friction of screws 112 , 114 . to unlock mechanism 90 , lever 92 is moved in the direction of arrow 95 toward base member 31 ( fig5 ). this moves short links 104 , 106 to an oppositely angled position and rotates screws 112 , 114 counterclockwise to reverse and unlock the various clamping movements discussed above . referring now to fig6 the lighter duty instrument support mechanism 11 is shown in more detail . mechanism 11 works on very similar principles to those discussed above with respect to mechanism 10 . mechanism 11 comprises a first arm 170 and second arm 172 which are pivotally connected to one another in a manner to be described below . first arm 170 may have a cover 170a ( fig7 ) to conceal internal components . first arm 170 is also pivotally connected to a base member 174 to allow vertical , pivoting movement with respect thereto as will also be described below . first arm 170 comprises a first link member 176 and a second link member 178 . first and second link members 176 , 178 are connected to base member 174 by respective pivots 180 , 182 which allow vertical pivoting motion with respect to base member 174 in a vertical orientation as shown in fig6 i . e ., when support pole 16 extends in a vertical orientation . links 188a , 188b are connected at a pivot 190 to first link member 176 as shown in fig6 . as further shown in fig7 links 188a , 188b include respective slots 192a , 192b for reasons similar to those described above with respect to mechanism 10 as will be described in more detail below . again referring to fig6 in addition to the pivot connections allowing generally vertical movement of the outer end of first arm 170 with respect to base member 174 , pivot connections 194 , 196 are provided to respectively allow pivoting motion of mechanism 11 about support pole 16 and pivoting motion of second arm 172 with respect to first arm 170 . for height adjustment , like the first embodiment , a tubular support member 198 is provided to hold mechanism 11 on support pole 16 and may be locked in place by a conventional screw locking clamp mechanism 200 when positioned at the desired height along pole 16 . referring now to fig6 and 7 , pivot connection 196 more specifically comprises a cylindrical rod 206 received within a pivot support or housing 208 and connected to second arm 172 by a connecting member 210 . as best shown in fig7 cylindrical rod 206 is preferably contained within a low friction sleeve or bearing member 211 which , in turn , is disposed within a clamp member 212 . as further shown in fig6 a retainer 214 keeps the cylindrical rod 206 held within pivot support or housing 208 . link members 176 , 178 of first arm 170 are attached to housing 208 by pivots 184 , 186 . still referring to fig6 like the first embodiment , a counterbalancing spring 216 is preferably provided and connected to an adjustment screw 218 at one end for allowing adjustment in the counterbalancing force to be made upon initial assembly or by the user . one end 220 of spring 216 is connected to a threaded member 222 which receives adjustment screw 218 for threaded adjustment therein . the other end 224 of spring 216 is connected to pivot pin 186 . as further shown in fig6 a locking mechanism 230 is provided for locking the various pivot connections of arm 11 . locking mechanism 230 is similar to locking mechanism 90 of instrument support mechanism 10 . specifically , a lever 232 operates generally in the direction of arrow 234 to lock pivot connections 194 and 196 as well as the general pivot connection made between base member 174 and first arm 170 which allows vertical adjustment of first arm 170 with respect to base member 174 . more specifically , lever 232 is connected by a pivot 236 to second link member 178 and is further connected to a connecting link by a pin 240 extending therefrom and into a slot 242 in the end of lever 232 . short links 244 , 246 are connected at respective ends of connecting link 238 by pivots 248 , 250 . the opposite end of each short link 244 , 246 is rigidly affixed to respective screws 252 , 254 by retainer pins 256 , 258 . thus , it will be appreciated that when lever is pulled away from base member 174 to the position shown in fig6 short links 244 , 246 will rotate screws 252 , 254 clockwise to simultaneously lock the various pivot connections as will be described . preferably , screws 252 , 254 are each 3 / 8 &# 34 ;-- 10 double lead screws . referring now more specifically to fig7 the locking mechanism 230 preferably operates clamp member 212 to selectively allow or prevent rotation of cylindrical rod 206 . specifically , a first portion 260 of clamp member 212 includes a threaded insert 262 for receiving threaded portion 252a of screw 252 . a second portion 264 of clamp member 212 interacts with an adjustable screw stop 266 . finally , similar to the first embodiment , a clamp member 268 including a flange portion 268a and a tubular portion 268b is operated by one end of screw 252 to selectively allow and prevent movement of links 188a , 188b . as also provided in the first embodiment , washers 270 , 272 are respectively disposed between pivot support housing 208 and link 188b and between links 188a and 188b . thus , when screw 252 is rotated by short link 244 to move in the direction of arrow 274 , clamp member 268 will move upwardly as viewed in fig7 and flange portion 268a will clamp links 188a , 188b against washers 270 , 272 and the inside of pivot support or housing 208 . this will prevent movement of links 188a , 188b by way of slots 192a , 192b riding along tubular clamp portion 268b and thereby prevent any articulating up and down movement of first arm 170 ( fig6 ). at the same time , portion 260 of clamp member 212 will move generally in the direction of arrow 276 and , as portion 264 is stopped against threaded stop member 266 , this will clamp cylindrical pivot rod 206 against any rotation . referring now to fig8 a clamp member 280 is provided at the opposite end of first arm 170 to selectively allow or prevent rotation of first arm 170 and any attachments about support pole 16 . specifically , clamp member 280 includes a first portion 282 having a threaded insert 284 for receiving threaded portion 254a of screw 254 . a second portion 286 of clamp member 280 includes a hole 286a which receives an unthreaded portion 254b of screw 254 with clearance for rotation . thus , when short link 246 is rotated by connecting link 238 in a clockwise direction as viewed in fig6 screw 252 will move in the direction of arrow 288 and bear against the inside of base member 174 . this will cause portion 282 of clamp member 280 to move in an opposite direction and , as portion 286 bears against adjustment screw 290 , a clamping action will take place against tubular support member 198 . like the other adjustment screws , screw 290 allows adjustment in the clamping action . therefore , base member 174 will not be able to rotate about tubular support member 198 . generally referring to fig6 - 8 , and to summarize the operation of mechanism 11 , when lever 232 is pulled in the direction of arrow 234 away from base member 174 , short links 244 , 246 will be rotated by connecting link 238 and thereby rotate screws 252 , 254 in a clockwise direction as viewed in fig6 . as shown in fig7 this will move screw 252 in the direction of arrow 274 to clamp links 188a , 188b against any movement and further move first clamp portion 260 in the direction of arrow 276 to prevent any rotational movement of pivot rod 206 . in this manner , pivoting of second arm 172 with respect to first arm 170 is prevented and vertical movement of first arm 170 with respect to base member 174 is also prevented . at the same time and referring more specifically to fig8 screw 254 will be moved in the direction of arrow 288 and thereby clamp member 280 against support tube 198 in the manner described above to prevent any rotational movement of mechanism 11 about support pole 16 . as schematically shown in fig9 movement of lever 232 in an opposite direction toward pole 16 will rotate screws 252 , 254 in a counterclockwise direction thereby unlocking all of the pivot connections described above and allowing readjustment of mechanism 11 to a desired position . while the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail , it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail . as an example , the various features of the mechanisms described herein in detail may be combined or substituted in various manners . additional advantages and modifications will readily appear to those skilled in the art . the invention in its broader aspects is therefore not limited to the specific details , representative apparatus and methods as shown and described . this has been a description of the present invention , along with the preferred methods of practicing the present invention as currently known . however , the invention itself should only be defined by the appended claims , wherein
a medical instrument support mechanism , particularly suitable for ophthalmological instruments , including first and second support arms and a suitable base member in which the first arm is vertically pivotal with respect to the base member and the base member is pivotal with respect to another support member , such as a support pole . the second arm is also pivotally connected to the first arm . a locking mechanism is operatively connected to each of the pivot connections to allow an operator to selectively lock and unlock the pivot connections substantially simultaneously by operating a lever movable in a direction extending along the length of the first support arm . this lever is preferably disposed along a lower side of the first support arm and specifically operates screw locking mechanisms and respective clamp members .