Abstract:
A device for positioning and locking a head clamp in a selective position including a first arm, a second arm and a third arm. The third arm having a free end including both a spherical member carried in a socket and including a mounting tube and a gripping device to restrain movement of said spherical member. The head clamp includes a mounting post for insertion to said mounting tube wherein said mounting tube includes a releasable locking device for engaging and holding said mounting post against rotation and withdrawal of said mounting tube to prevent accidental release of the mounting post.

Description:
FIELD OF THE INVENTION 
     The present invention is an improvement in the apparatus disclosed in my prior U.S. Pat. Nos. 4,964,748 and 5,560,728, both of which are incorporated herein by reference. Each of these patents relate to articulated arms and locking devices for a surgical head clamp such as is used in neurosurgery. 
     BACKGROUND OF THE INVENTION 
     As described in above noted prior U.S. patents, with the use of head clamps for positioning a patient&#39;s head for neurosurgery or other cranial surgery, it is necessary to provide a rigid support for the head and one which can be easily adjusted to allow access by the surgeon to selected portions of the head of the patient during an operation. To this end, my prior structures have provided three articulated arms each with locking levers so that once the head of a patient has been placed in a position as desired by the surgeon, the head can be locked in place. With my structure, selecting any position in space is a continuously variable, analog function. Also, during surgical operations, it is important that the stability and rigidity of the head supporting structure be assured once the position selection has been made. In the past, use of a number of types of head support structures has proven inadequate in terms of the possibility of accidental release of the support structure during a medical procedure. While the locking mechanisms of my prior patents noted above have lessened this possibility, there is a need for a head bracket support that will achieve rapid and secure locking of the head bracket in place without the possibility of rotation of the bracket relative to its support or release of the bracket. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improvement in my prior devices that is easily accomplished yet inexpensive to install and which will positively prevent accidental release of the cranial bracket once placed in position for an operation. In a preferred embodiment, the head bracket is modified in that a single post is integrally formed with or attached to a portion of the bracket with the end of the post provided with recesses for cooperating with a holding device which will grip and lock the post against release as well as rotation once the post is inserted. With this arrangement, a quick release is also provided but one which requires a user to grab both the holding device for the post of the bracket as well as the bracket itself to effect release. Thus, accidental release will be discouraged if not positively prevented in all circumstances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and further advantages of the present invention will become apparent as consideration is given to the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a perspective illustration of the articulated arms of present head clamp support structure which includes elements from my prior support structure; 
         FIG. 1B  is a side view in elevation, partly in section of a preferred version of the locking levers usable in the structure of  FIG. 1A  with a button operated locking device on the locking lever; 
         FIG. 2  is a side view, partly in section, of the device of  FIG. 1  but with the arms rotated to another, selectable position and the levers deleted for clarity; 
         FIG. 3A  is an enlarged, detailed view of the locking device of the present invention with parts broken away and with the post and ball as well as the clamping device in an unlocked condition; 
         FIG. 3   b  is a view similar to  FIG. 3A  but with the post locking device in a locked condition; 
         FIG. 4  is a plan view in elevation of a modified head bracket used in my present invention; and 
         FIG. 5  is a detailed view, partly in section, of the locking device carried by a modified post and ball similar to the structures of  FIGS. 3A and 3B . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1A , there is shown a view of a head positioning device similar to that of my prior U.S. Pat. No. 4,964,748, the disclosure of which is incorporated herein by reference. According to the present invention, the device  10  includes three arms  12 ,  40  and  41  with arm  12  being pivotally mounted on a rod  18  and held in position on the rod  18  by a clamping or gripping device  14  which is actuated by a locking lever  20 . When tightened, the grip of the clamping device  14  on the rod  18  secures the arm  12  against rotation about rod  18  which itself will be attached to a rigid support such as a portion of the operating table. The opposite end of the arm  12  also has a similarly designed clamping device  16  which grips a pin  33  as shown in  FIG. 2  which is connected to a bracket  34  from one face of which the pin  33  and from the other face of which a pin  35  projects. It will be apparent that the gripping action of the clamps  14  and  16  about their respective pivot members  18  and  33  will be substantially simultaneous upon closing of the lever  20 . The same applies to the other arms  40  and  41  since the lever arm  43  activates gripping at both ends of the arm  40  while the lever arm  52  simultaneously activates the gripping device at  53  and the push lock device at  47  to secure locking device  90  in place. The gripping member  36  of the second arm  40  is adjustably positionable about pin  35  until its locking lever  43  (not shown in  FIG. 2 ) is actuated to lock gripping members  36  and  38  on their respective pins  35  and  37 , respectively. Pin  37  projects perpendicularly from one face of bracket  45  and another pin  33 ′ projects from the other face of bracket  45  just as pin  33  projects from bracket  34 . As shown in  FIG. 1A , arm  41  is mounted at one end on the pin of bracket  45  while the free end  47  carries a locking device  90  which is described below. 
     To ensure stability, the ends of lever arms  20 ,  43  and  52  will be provided with catch tabs  200 , as shown in  FIG. 1B  which are arranged to receive a projection carried on the end of the levers opposite their pivotal attachment to their respective arms. The tongues  63 ,  64  will carry a spring biased ball detent to engage a recess on the projection of the respective arm to hold the arm in their locked positions. In a preferred form, the locking of the lever arms may be accomplished by the structure shown in  FIG. 1B  a variation of which is described in my co-pending application Ser. No. 10/941,944 which is incorporated herein by reference. In  FIG. 1B , the locking lever  52 ′ is pivotally mounted on a pin  62  extending between two walls, one of which is shown at  64 , of a gap provided at the end of arm  40 ′. Also mounted on pin  62  is a rod  66  which extends through a bore formed in arm  40 ′. The opposite end of rod  66  is threaded to cooperate with an anchoring nut  70  which can be rotated to adjust the force exerted when the lever  52 ′ is pivoted on pin  62  to bring the leg members  72  and  74  of arm  40 ′ in gripping condition relative to the surfaces of pins  35 ′ and  37 ′. The arm  40 ′ is provided with a receiving cup  78  into which a shaft  76  can be inserted and which is provided with a detent arrangement, such as that described and shown in my copending application Ser. No. 10/941,944, so that once captured, release can only be effected by a conscious effort in pushing on the button  80  that extends through a bore in the lever  52 ′. Other types of arrangements to capture the locking lever arms will be apparent to those skilled in this art. 
     With reference to  FIGS. 1A and 2 , arm  41  is pivotable about a pin  33 ′ similar to pin  33  but projecting perpendicularly from the face of the bracket  45  which is identical to bracket  34 . Arm  41  can be locked in a position by actuation of the lever arm  52  (not shown in  FIG. 2 ) and such actuation will lock gripping member  53  on the pin  33 ′ of bracket  45  and at the same time will actuate the gripping function of locking device  90  at the free end of arm  41  as viewed in  FIGS. 1A and 2  and which will now be described with reference to  FIGS. 3A and 3B . 
     The locking device  90  at the free end of arm  41  will operate to engage and hold the ball  84  from which post  86  extends and with which it is integrally formed. The post  86  is thus adjustably positionable in a socket  88  defined by the cover  91  which is rotatably carried on locking device  90  by the threaded housing  89  attached to body  91  formed on the end of arm  41 . The post  86  is thus free to be positioned at any point relative to the axis of arm  41  through 360° of rotation about the axis of arm  41  and 180° of rotation about socket  88 . A recess  87  is formed on the end of arm  41  to receive the toggle actuator  85  formed on the end of lever arm  52 . An apertured plate  95  cooperates with toggle member  99  to move into or out of contact with the socket body to effect or release locking of the ball  84  in its housing. In  FIG. 3A , the ball  84  is released while in  FIG. 3B , the ball  84  is in its locked position. The shaft  104  operates in the same manner as shaft  66  described in conjunction with  FIG. 1B  in so far as the clamping device  53  is concerned so that the movement of the lever  52  will effect gripping of the pin  33 ′ while at the same time moving toggle member  99  upwardly as viewed in this figure to lock the ball  84  in a selected orientation. To this end, the toggle actuator  85  includes a pin  97  which extends through the upper end of shaft  104 . The opposite end of shaft  104  engages the gripping member  53  as shown. 
     Prior head brackets similar to head bracket  95  ( FIG. 4 ) would include a hollow tube into which post  86  will be inserted and usually held by a threaded bolt provided in the tube to hold the post  92  in place. The bolt is tightened against the post  86  but any loosening of the threaded bolt will result in rotation of the bracket about the post  86  which is undesirable. In my co-pending U.S. application Ser. No. 10/941,944, a locking device for the levers and the unnumbered lever for the head bracket is provided. The present invention provides a secure mounting in place of the post  86  of a head bracket similar to the bracket shown in my U.S. Pat. No. 5,560,728 but where the head bracket is modified as shown in  FIG. 4  to cooperate with the locking feature of  FIG. 5 . 
     As shown in  FIG. 4 , there is shown a conventional head bracket  95  where the mounting post  92  has been modified to include an annular array of spaced apart recesses  94  to cooperate with a holding device  100  as described below. The recesses  94  are preferably adjacent one end of the post  92 . The device  100 , as shown in  FIG. 5 , replaces the post  86  shown in  FIGS. 3A and 3B  on the end of arm  41 . The arm  41 , shown in  FIG. 5 , is provided at its end with a head  110  about which the locking device  100  is positioned and which carries a washer  150  rotatably supported between two seal rings  152  and  154 . The locking device  100  is provided at one end with a peripheral flange  132  which extends radially inwardly toward the neck of the washer  150 . The interior wall of the locking device  100  is provided with a radially inwardly extending flange  156  which supports the coil spring  160  on its upper side as shown in  FIG. 5 . The lower portion of the head  110  is also provided with a radially outwardly extending flange  158  which on its upper side supports one end of a coil spring  160  which acts between the flanges  156  and  158  to constantly urge the body  162  of the locking device  100  away from the arm  41  in an axial direction. 
     At a specific distance from the upper end of the arm  41 , apertures  194  are formed in the wall of the arm  41  with each aperture carrying a detent ball  166 . The apertures  194  will be shaped to limit the extent to which the individual balls may project into the interior  168  of the arm  41 . Preferably, there are at least four apertures and corresponding balls and more preferably, six apertures and balls are used. As shown, the interior of the body  162  is formed with a radially inwardly projecting camming member  170  which has an annular, inner sloping cam surface  172  for engaging the balls  166 . As viewed in  FIG. 5 , the lower portion of the surface  172  projects radially inwardly a greater extent than the upper sloping portion. With this arrangement, with the body  162  moved by the coil spring  160  away from the bracket  90  when the post  92  is inserted as shown, the balls are permitted to move away from the post  92 . However, with the post  92  inserted and the body  162  moved downwardly by a user and then released, the lower portion of the camming surface  172  will urge the balls to each engage one of the recesses  94  formed adjacent the end of the post  92 . This action will effectively lock the post  92  in device  100  as well as prevent relative rotation between the post  92  and the arm  41 . Release of the post  92  and the bracket  90  is effected by a user grasping the bracket  90  and then moving the device  100  away from the bracket  90  to allow the upper portion of the camming surface  170  to move downwardly as viewed in  FIG. 5  to allow the balls to be pushed back from their projecting position by the force applied by the movement of the post  92 . 
     With this arrangement, it will be evident that accidental release of the post  92  is effectively prevented. It will also be apparent that the camming action of the locking device  100  may take a number of forms in addition to the one illustrated. For example, the locking function may be achieved by moving the camming surface axially away from the bracket  12  where the slope of member  70  is opposite to that shown. Another alternative may involve requiring relative movement between two annular members to position or change the position of the camming surface. Further, for increased resistance to accidental release, one can make the spring constant of spring  160  larger than conventional for surgical clamps. 
     Having described the invention, it will be apparent to workers in this field that various modifications can be made without departing from the spirit of this invention.