Abstract:
An actuating mechanism for spectacles which include two variable focus lens units. The mechanism mounts on the spectacle bridge; and includes two elongated drive levers mounted near opposite ends of the bridge, each extending toward the other end of the bridge. The free end of each driving lever is connected to its corresponding lens unit through a linkage. The driving levers are caused to rotate simultaneously, but in opposite directions, by a cam that is driven by a sliding member that slides along the bridge. By positioning the sliding member as desired, the spectacles wearer causes the cam to rotate, thereby causing the driving levers to rotate, and both lens units to change focal length.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an actuating mechanism for simultaneously adjusting the optical powers of each of the two lens units in a pair of variable focus spectacles. The invention is described in relation to lens units of the general type disclosed in U.S. Pat. No. 5,138,494 (embodiment of FIG. 9 thereof), U.S. Pat. No. 5,371,629, and U.S. Pat. No. 5,688,620. The disclosures of all of said patents are relevant hereto, and are accordingly incorporated herein by reference. 
   Variable focus spectacles inherently include two lens units; it is accordingly desirable that an actuation means be provided to simultaneously control the optical powers of both. The present invention is intended to provide such a means. 
   SUMMARY OF THE INVENTION 
   For convenience in explaining the present invention, a lens unit embodiment is assumed which is comprised of 1) a front ring assembly {including a front ring and a distensible membrane stretched across the field of view of the lens unit}, 2) a rear ring assembly {including a rear ring that holds a rigid lens positioned across the field of view of the lens unit}, 3) a transparent liquid filling the space between the front and rear ring assemblies, 4) a sealing bellows {which keeps the liquid from escaping, yet allows relative motion between the front and rear ring assemblies}, and 5) hinging means between the front and rear ring assemblies {that allows the rear ring assembly to rotate with respect to the front ring assembly}. To form variable focus spectacles, two such lens units are connected by a bridge. This connection may be accomplished, for example, by laser welding one end of the bridge to the front ring of one lens unit, and the other end of the bridge to the front ring of the other. 
   As the front and rear ring assemblies of such a lens unit are moved closer and further apart (by rotation of the rear ring assemblies about the hinging means) the focal length of the lens unit is decreased or increased (i.e., its optical power is increased or decreased). More details of the construction and operation of such lens units may be had by reference to the aforementioned patents. 
   The invented actuating mechanism is contained within the bridge of the spectacles, and causes the rear ring assemblies of the lens units to rotate about their respective hinges responsive to the position of a user-operated sliding member (the “slider”). The slider operates a cam, which in turn causes two elongated levers (the “driving levers”) to rotate in a horizontal plane simultaneously, but in opposite directions. Each driving lever is connected, via a linkage, to a rear ring assembly. Movement of the slider causes both rear ring assemblies to rotate, thereby causing a change in optical power of each of the lens units. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a rear view of a pair of spectacles including two variable focus lens units and an actuator according to the present invention. 
       FIG. 2  is a top view of the spectacles of  FIG. 1 . 
       FIG. 3  is an enlarged top sectional view of a first embodiment of the invented actuator taken at section  3 — 3  of  FIG. 6 . The slider is shown positioned for distance viewing. 
       FIG. 4  is an enlarged sectional view of the invented actuator as in  FIG. 3 , except that the slider is positioned for intermediate distance viewing, and part of the left driving lever and cam are cut away to provide a better view of the right driving lever. 
       FIG. 5  is an enlarged rear view of the invented actuator as shown in  FIG. 1 . The ends of the driving levers and cam which otherwise would be visible from the rear are omitted in  FIG. 5  for clarity. 
       FIG. 6  is a cross sectional side view of the first embodiment of the invented actuator taken at  6 — 6  of  FIG. 5 . 
       FIG. 7  is a fragmentary plan view showing one style of linkage that can be used to connect a driving lever to the rear ring of a lens unit. 
       FIG. 8  is a fragmentary sectional side view of the linkage of  FIG. 7  taken at  8 — 8  of  FIG. 7 . 
       FIG. 9  is a fragmentary plan view showing a second style of linkage that can be used to connect a driving lever to a rear ring of a lens unit. 
       FIG. 10  is a fragmentary sectional side view of the linkage of  FIG. 9  taken at  10 — 10  of  FIG. 9 . 
       FIG. 11  is a fragmentary plan view showing a third style of linkage that can be used to connect a driving lever to the rear ring a lens unit. 
       FIG. 12  is a fragmentary sectional side view of the linkage of  FIG. 11  taken at  12 — 12  of  FIG. 11 . 
       FIG. 13  is an enlarged top sectional view of a second embodiment of the invented actuator, taken at  13 — 13  of  FIG. 14 . 
       FIG. 14  is cross sectional view of the second embodiment of the invented actuator taken at the same section as was  FIG. 6 , namely at a position corresponding to position of  6 — 6  of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  show top and rear views of a pair of variable focus spectacles in which a first embodiment of the invented actuation mechanism is installed. Primarily for cosmetic reasons, the spectacles may include a cover  10  that effectively hides the mechanism from view. For clarity, the cover  10  is not shown other than in  FIGS. 1 ,  2 ,  6 , and  14 . A fragment of temples  11  and  12  that are attached to the spectacles may be seen in  FIG. 2 . 
   The spectacles are comprised of two lens units  13  and  14  connected by a bridge  15 . The actuator of the present invention is contained within the bridge. Only so much of the construction and operation of the lens units as is deemed necessary for an understanding of the invention is included herein, but further constructional details and an explanation of lens unit operation can be found in the referenced patents (U.S. Pat. Nos. 5,138,494, 5,371,629, and 5,688,620). 
   Each lens unit contains a front ring assembly ( 16  and  17 ) that is attached by laser welding, or otherwise, to the bridge  15 . Rear ring assemblies  18  and  19  are hingedly attached to the respective front ring assemblies, as by leaf hinges  20  and  21 . Approximately diagonally across each lens unit from the hinges, and attached to the rear ring portion of the rear ring assemblies, are linkage anchors  22  and  23 . As explained in the reference patents, the focal length of a lens unit is changed by rotating the rear ring assembly with respect to the front ring assembly about the hinge. In the present invention, such rotation is accomplished by connecting the invented actuator to each rear ring assembly via the linkage anchors, and displacing the anchors in a forward or rearward direction. For purposes of this document, the direction “forward” means away from the wearer&#39;s eyes. Left and right are directions from the perspective of the spectacle wearer, as are the directions up and down. 
     FIGS. 3 and 4  are top sectional views of the invented actuator.  FIG. 3  shows the slider positioned for distance viewing, while  FIG. 4  shows it positioned for viewing an intermediate distance. For viewing closer distances, e.g., reading distance, slider  24  would be positioned further yet to the right. Slider  24  slides along channel  25  in bridge  15  (as best seen in  FIG. 6 ). The wearer positions slider  24  by manipulating lip  24 ′, which is preferably a portion of slider  24  that projects above cover  10 , where it can easily be reached and positioned by the wearer. Pin  26 , which may be pressed into slider  24 , carries bushing  28  and (preferably toothed) roller  27 . For long wear life, bushing  28  may, for example, be fabricated from Torlon 4301, and pin  26  from hardened steel. Torlon is a tradename of Solvay Advanced Polymers of Alpharetta, Ga. for a polyamide-imide plastic product. Roller  27  is preferably toothed to assure that it turns as the slider is moved, thereby minimizing frictional wear. Roller  27  is also preferably hardened. 
   Roller  27  runs on cam surface  29 ′ of cam  29  and causes the cam to rotate about pivot pin  30  as slider  24  is moved. Pivot pin  30  is preferably pressed into bridge  15 . As the slider  24  is moved to the right, cam  29  rotates counterclockwise. It will be appreciated that the directions of motion described herein are the directions corresponding to the particular embodiment illustrated, and that other embodiments may have some or all of the motions reversed. As cam  29  rotates, drive pin  31 , which is pressed through and fixedly mounted to cam  29 , bears against the rear edge of left driving lever  32  and the rear edge of right driving lever  33 . The terms “left” and “right”, as applied to the driving levers, are meant to indicate which lens unit is driven by the respective drive lever. As cam  29  rotates counterclockwise (about the pin  30 ), right driving lever  33  rotates also counterclockwise about pivot pin  30 . At the same time, left driving lever  32  rotates clockwise about pivot pin  34 . The right hand portions of cam  29  and left driving lever  32  are cut away in  FIG. 4  so that right driving lever  33  can be clearly seen. 
   As seen in the figures, the cam surface  29 ′ appears straight. However, this surface may be straight, or it may be curved gently (thereby altering the shape of the functional relationship between cam rotation and slider position). For example, it may be desired that the change in optical power with respect to change in slider position be lower near the distance viewing position of the slider than near the reading position of the slider. Changing the shape of cam surface  29 ′ can accomplish that objective. 
   In the embodiment of the invention shown in  FIGS. 3 and 4 , the free ends of driving levers  32  and  33  are coupled to the linkage anchors  22  and  23  utilizing strips of ribbon  35  and  36 . The fragmentary views of the free end of driving lever  33  and linkage anchor  23  shown in  FIGS. 7 and 8  illustrate the connection. The ribbon is shown stippled in  FIG. 8  for clarity. It will be appreciated that each lens unit includes liquid under pressure, and therefore the lens units provide an inherent restoring force. Hence only a unidirectional actuating force (i.e., pulling) need be applied. The ribbon strips are preferably fabricated from high strength steel. The size of the ribbon section will depend on many factors in the design of the spectacles, but for illustrative purposes a section about 0.0015 thick by about 0.009 wide might be considered typical. One end of a ribbon may, for example, be laser or spot welded to the free end of a driving lever, and the other end similarly welded to the corresponding linkage anchor. As shown, each ribbon is attached to a linkage anchor ( 22  or  23 ) extending from the rear rings. The illustrated construction is a matter of convenience. Each ribbon could alternatively be attached directly to a rear ring, and in that case, linkage anchors would not used. 
   There are many other possible configurations for the links between the driving levers and the rear rings. Two such alternate configurations are illustrated in  FIGS. 9 through 12 . In  FIGS. 9 and 10 , a wire  36 ′, preferably having a round cross-section, is shown looped over the driving lever  33 ′, and laser welded to linkage anchor  23 ′. In  FIGS. 11 and 12  a hook  36 ″, fabricated from a metal strip, is hooked over driving lever  33 ″ and laser welded to linkage anchor  23 ″. Other configurations are also possible, as will be appreciated by those skilled in the art. 
   Installing the linkages between driving levers and the lens units is preferably the last step in the production of the spectacles prior to final filling with optical fluid. Various methods of installing the links are possible; an illustration of a presently preferred method of installation is described below. For convenience of description, all reference is explicitly to ribbon links. It will be understood, however, that other types of link may be installed using similar procedures. 
   First, a length of ribbon longer than is ultimately required is welded to each driving lever tip. The slider  24  is positioned to its closest view position using lip  24 ′ (all the way to the right as seen in  FIGS. 1 and 2 ). The rear ring assembly of each lens unit is then rotated maximally forward, for example by applying a force on the rear ring near the corresponding linkage anchor. Rearward tension is applied to each ribbon, and it is welded to the appropriate linkage anchor. Excess ribbon may be cut off, and the installation is then complete. 
   After the linkages are installed, the lens units may be filled with liquid. For this operation, the slider is positioned for distance viewing (all the way to the left) and liquid is injected into each lens unit until the lens focal length is the desired value for distance viewing. This portion of the manufacturing process is then complete. 
   A second embodiment of the invention is illustrated in  FIGS. 13 and 14 . The second embodiment requires fewer parts than the first embodiment, however, the first embodiment has the advantage that the driving levers can be made symmetrical, and if so made, displacement errors due to bending of the driving levers tend to balance out. The parts of the second embodiment that are substantially identical to the corresponding parts of the first embodiment are given the same numeric designation as the first embodiment parts. The difference between the two embodiments resides only in that the right driving lever  33  and the cam  29  of the first embodiment are combined into one part, cam/driving lever  50 . Left driving lever  32  is shown broken away in  FIG. 13  so that cam/driving lever  50  may be clearly seen. Left driving lever  32  rotates about pivot pin  34  while the cam/driving lever  50  rotates about pivot pin  30 . Pin  31 , pressed through cam/driving lever  50  drives driving lever  32  clockwise as the cam/driving lever is rotated counterclockwise. 
   Two embodiments of the invented actuator have been described above but those skilled in the art will no doubt appreciate that other embodiments and variants of the above embodiments are possible within the spirit of the invention. Such other embodiments and variants are intended to be covered by the following claims.