Abstract:
An adjustable viewing frame ( 27 ) for use by artists to help compose a view comprises two frame members ( 10,11 ) each having two frame links ( 21,22,23,24 ) at right angles to one another. The frame links ( 21,22,23,24 ) have a rib ( 30 ) along one edge over which two C-shape clips ( 20 ) engage to hold the two frame members ( 10,11 ) together where they overlap. The force exerted by the clips ( 30 ) is sufficient to hold the two frame members ( 10,11 ) together against disturbances so that the frame ( 27 ) thus formed can be held in one hand for viewing purposes, but allows adjustments to be made easily by hand to change the size and/or relative proportions of the frame ( 27 ). A scale ( 40 ) marked on the frame member ( 10 ) allows specific relative proportions to be achieved with certainty and precision.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to an adjustable viewing frame of a type used by artists and others to help to compose a view. One known such frame comprises no more than a piece of card with a square or rectangle cut out of it. Another known such frame comprises a piece of glass or transparent plastic with a square or rectangle marked on it. Such frames are light and easy to make, but they are not readily adjustable to form apertures of different sizes or proportions.  
           [0002]    Adjustable frames are known for cropping pictures or photographs. These are usually made from two L-shape pieces of cardboard, plastic, metal or the like which are either separate or mounted to be carried on a board. It is not easy to hold up two separate pieces in just one hand for framing a field of view, which would be useful for an artist, especially in the absence of any means for holding their two pieces in a fixed position relative to one another. The picture-cropping frame cannot be used for this purpose, however because of its weight, which inhibits the user from carrying them, and, especially from holding them up in one hand while drawing or painting with the other.  
           [0003]    The prior art also includes the frame described in U.S. Pat. No.  1 , 183 , 977  which comprises four rectilinear arms with elongate central slots in them. The arms are held together in pairs by respective nuts and bolts, and the two structures thus formed are held together but threaded pins passing through the slots onto which are screwed thumb nuts to clamp a so-called spider into the slots. This device has the advantage that it can be folded into a compact space, but the disadvantage that it is complex, involving many parts, and requires that the two thumb nuts be slackened to allow adjustment and then re-tightened when the adjustment is made. It is also difficult to set this up with the corners exactly square.  
         OBJECTS OF THE INVENTION  
         [0004]    One aspect of the present invention is to provide an adjustable viewing frame which is an improvement over the prior art.  
           [0005]    Another aspect of the invention is to provide a viewing frame, which is quick and simple to adjust, light in weight and economical to produce.  
           [0006]    Still another aspect of the invention is to provide a viewing frame which can be easily adjusted to a predetermined ratio of side sizes to form a viewing aperture of selected shape.  
           [0007]    A further aspect of the invention is a viewing frame which can be held in one hand for use or easily mounted on an easel or other support for use by an artist.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides an adjustable viewing frame comprising at least two frame members having arms forming substantially rectilinear frame limbs, in which the frame members are held together by a frictional force which is sufficient to retain the frame members in a selected adjusted position but which can be overcome to effect adjustment. The frictional force can be applied by retainer members. Such retainer members may be resiliently biased into engagement with the said frame members.  
           [0009]    In one embodiment the retainer members are generally C-shape and engage respective frame members from opposite sides thereof.  
           [0010]    Each limb of a frame member preferably has a respective shoulder extending at least along a part of the length thereof. Such shoulder is engageable by the retainer members in order to hold the frame members together.  
           [0011]    The said shoulders of the frame limbs may comprise the side wall of an upstanding ridge or rib extending longitudinally at least part of the way along the frame limb. If the frame limbs are laminar or sheet like elements the longitudinal ridge or ribs may be located substantially along one edge thereof. Alternatively, the said shoulder may be formed by an elongate, longitudinally extending, slot, groove or channel in each frame limb. In such case the retainer members may have heads engaged in the said slot, groove or channel of respective frame limbs whereby to hold them together to form the said frame.  
           [0012]    The frictional engagement of the two frame members is preferably achieved by resilient deformation of the retainer members. Such resilient deformation may be flexure, extension or compression.  
           [0013]    The present invention also comprehends an adjustable viewing frame comprising at least two frame members having arms forming substantially rectilinear frame limbs, in which the frame members are held together by magnetic attraction sufficient to generate a frictional force which retains the frame members in a selected adjusted position, but which can be overcome to effect adjustment.  
           [0014]    For this purpose at least part of at least one of the said frame members may be magnetised and at least part of the other frame member may be made of ferromagnetic material. The magnetic attraction may be effected, of course, by the introduction of appropriate magnetic materials into otherwise non-magnetic members or elements such as plastics. Alternatively, plastics or other non-magnetic materials having magnetic or magnetised particles imbedded therein may be employed.  
           [0015]    The adjustable frame of the invention may further include mounting means for mounting the frame to an easel, stand, tripod, table or other support. Such mounting means may also be used as a hand grip by which the frame may be held for viewing.  
           [0016]    According to another aspect the present invention provides an adjustable viewing frame comprising two generally L-shape frame members, each having two substantially orthogonal rectilinear frame limbs, and means for retaining the two members together in a selected relative position to form a relatively rectangular frame, in which the frame limbs of at least one frame member bear a scale including indicia representing different dimensional ratios to which the viewing frame may be adjusted.  
           [0017]    The invention will be more easily understood from the following detailed descriptions thereof with reference to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a perspective view of a first embodiment of the invention;  
         [0019]    [0019]FIG. 2 is a partially sectioned detail view of the embodiment of FIG. 1 taken on the line II-II of FIG. 1;  
         [0020]    [0020]FIG. 3 is a plan view of the embodiment of FIG. 1 illustrating the use of the proportioning scale;  
         [0021]    [0021]FIG. 4 is an enlarged view of a part of the embodiment of FIG. 3 illustrating the proportioning scale on a larger scale;  
         [0022]    [0022]FIG. 5 is a perspective view of an alternative embodiment illustrating slot and link interconnection of the frame members;  
         [0023]    [0023]FIG. 6 is a sectional view through the embodiment of FIG. 5 taken on the line VI-VI of FIG. 5;  
         [0024]    [0024]FIG. 6 a  is a sectional view of a link for retaining the two frame members in the embodiment of FIGS. 5 and 6;  
         [0025]    [0025]FIG. 7 is a schematic view of an alternative embodiment of the invention utilising four identical frame members;  
         [0026]    [0026]FIG. 8 is a schematic view of a frame member suitable for use in the embodiment of FIG. 7; and  
         [0027]    [0027]FIG. 9 is a perspective view of a further embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    Referring first to FIG. 1 of the drawings, this shows a frame  27  comprising two L-shape frame members  10  and  11 , typically made of plastic, metal, cardboard, composites, wood or other suitable material; which may be opaque, semi-transparent or transparent. The two L-shape frame members  10  and  11  each have two frame limbs  21 , 22  and  23 , 24 , with one frame limb  21 , 23  of each frame member being longer than the other (although in other embodiments these arms may be of equal length as will be described below). In use of the illustrated embodiment the two L-shape frame members  10 , 11  will for preference be so positioned that the long frame limbs  21 , 23  of the two frame members  10 , 11  are opposite each other, in the position shown in FIG. 1.  
         [0029]    The two L-shape frame members  10  and  11  are held together by two retainers  20  in the form of clips, one positioned at the outside edge of each of the two corners where the frame limb of one L-shape frame member crosses the frame limb of the other L-shaped frame member: as shown in FIG. 1.  
         [0030]    The two L-shape frame members  10  and  11  are each formed with a ridge  30  along one edge of each frame limb  21 , 22  and  23 , 24 . The L-shape frame members are so made that the face which contacts the other L-shape frame member is flat, with the ridge  30  being on its other side. The clips  20  pass over the two ridges  30 . A cross-section of this arrangement is shown in FIG. 2. The ridges  30  terminate a short distance from the elbow  12  of the L-shape frame member  10  or  11 , and at the free end  13 , 14  of each frame limb the ridges  30  each have a transverse stop end or shoulder  15 ,  16 . This facilitates introduction of the clips  20  at the elbow  12  upon assembly and ensures that upon enlargement of the frame  27  the clips  20  cannot pass beyond the free ends  13 ,  14  to allow the two L-shape frame members  10 ,  11  to become separated.  
         [0031]    The clips  20  are so formed that, when the user of the frame  27  wishes to adjust it, the two L-shape frame members  10 , 11  will slide easily over each other; but at the same time, the clips  20  exert enough force to hold the two L-shape frame members in the same position relative to each other when released. The clips  20  achieve this by being made of resilient material and being shaped so that they are stressed when engaged in position. The clips  20  may be made of plastics; metal, composites, or other suitable materials, or of a combination of materials. A separate resilient element may be used to provide the resilient stress in other embodiments (not shown).  
         [0032]    In the embodiment of the invention, shown in FIG. 3 the two frame members  10 , 11  have limbs  2 , 22  and  23 , 24  of equal length. One L-shape frame member  10  carries a scale  40 , marked upon it by engraving, printing or other means, which enables the user to set the opening defined between the frame members to form a rectangle (or square) in which one side bears a specified ratio to the other, whatever the size of the opening.  
         [0033]    The scale includes ratios commonly used, in the paper industry or in art, such as for example 1:{square root}2, 1:1.5, etc. This scale  40  is also shown in FIG. 4, and comprises a plurality of longitudinal graduations lines  39  spaced at distances determined by the set proportions as represented by ratio legends  41 . A plurality of intersection lines  42 , by reference to which the proportions of the frame may be set, extend at an angle from regular gradation positions marked with a scale  43  representing specific dimensions, for example centimeters.  
         [0034]    The scale is used by placing the edge of frame limb  24  of the L-shaped frame member  11  over a desired figure on the scale  43 , and positioning the other arm of L-shaped frame member  11  over the appropriate intersection line  42  on the other arm of the scale, as shown in FIG. 3. By selecting the appropriate intersection point between a longitudinal graduation line  39  representing the ratio and the inclined line  42  associated with the gradation number  43  corresponding to that against which the other frame limb  23  is set, the user may construct a desired rectangle in either landscape or portrait format. As can be seen in FIG. 3 the frame limb  23  is set at 6 marked on the frame limb  22  and the frame limb  24  is set to the corresponding size at a ratio of 1:1.5 (represented on the scale by 1½) by selecting the intersection of the inclined line extending from 6 and the longitudinal graduation line  39  marked 1½ on the frame limb  21 .  
         [0035]    In a further embodiment of the invention, shown in FIGS. 5 and 6, two L-shape frame members  60 ,  61  are held together by different means, as follows. Each of the rectilinear limbs  62 ,  63  of the L-shape frame member  60  has a respective elongate slot  64 ,  65  which, as can be seen in FIG. 6, has a T-shape cross section with an enlarged head portion  66  and a narrow neck portion  67 .  
         [0036]    The frame limbs  68 ,  69  of the L-shape frame member  61  have corresponding identically shaped slots as can be seen in FIG. 6.  
         [0037]    A retainer member in the form of a linking stud  70  having two mushroom heads  71 ,  72  on opposite ends of a central stem  73  fits into the intersection between two grooves or slots  64 ,  65  at the point where two frame limbs  62 ,  68  or  63 ,  69  overlap. As can be seen in FIG. 6 a  the mushroom heads  71 ,  72  are slightly domed so that, when fitted into the head section  66  of a slot, with the stem  73  residing in a neck portion  67 , the head is slightly flexed to give a frictional interengagement between the linking stud  70  and the slots to achieve the same frictional contact as described in relation to the C-shape clips of the earlier embodiments. The embodiment of FIGS. 5 and 5 has the advantage of avoiding the need for external clips.  
         [0038]    The embodiment of FIGS. 7 and 8 is different from the earlier embodiments in that it comprises four identical elongate frame limbs  80 ,  81 ,  82 ,  83  each, as illustrated in FIG. 8, having an elongate slot  84  of T-section extending from one end  85  to a point close to the other end  86  at which there is a T-shape projection  87  which, in assembling the frame, is engaged in a slot of an adjacent member. The four frame elements can be pushed towards one another or pulled apart to reduce or enlarge the size of the frame opening.  
         [0039]    [0039]FIG. 9 illustrates a final embodiment of the invention in which a frame  92  comprising two identical L-shape frame elements  90 ,  91  are made from magnetised or magnetisable material, or at least material such as a geomagnetic material, which is influenced by magnetic attraction so that they are retained in the selected position simply by magnetic attraction holding the two facing surfaces with sufficient force to generate a frictional engagement which is enough to ensure that the frame  92  remains in the selected adjustment when in use, but not so great that it cannot be overcome by manual exertion when it is desired to vary the adjustment.  
         [0040]    In any embodiment of the invention, one of the two L-shaped frame members may be equipped with a mounting device such as a handle, an arm or bracket  99 , which enables the frame to be either directly or indirectly mounted on an easel, stand, tripod, table, or other support. An example is shown in broken outline in FIG. 3.