Abstract:
A clamp comprises opposed members having clamping surfaces defining a distance therebetween for receiving and clamping an object. An adjustment mechanism is associated with at least one of the members for varying the distance over a continuous range. A spacer assembly being removably associated with at least one of the members for varying the distance by at least one discrete increment.

Description:
FIELD OF THE INVENTION 
   This invention relates to a clamp. In particular, though not exclusively, the invention relates to a clamp used as a base for attaching an item to a surface. 
   BACKGROUND OF THE INVENTION 
   Clamps are used for numerous reasons. In some instances, a clamp is used to hold a work piece in place to be worked on. In other instances, a clamp is used to provide a base to mount an item to a surface. 
   In the case of a table clamp, the clamp can be used as a base for mounting an item on the table. For example, the clamp is fastened to the table; the clamp is adapted to connect to an arm; and an item can be suspended from the arm which is connected to the clamp. Examples of items attached to tables in this manner are task lamps, computer monitors, and various trays for holding items such as office supplies and telephones. 
   A clamp used for such a purpose is typically designed to accommodate tables of varying thicknesses. Such clamps are often C-clamps which include a screw that can be used to adjust the distance between the opposing clamping surfaces of the C-clamp so the clamp may be tightened against the table and thus held in place. The range of thicknesses of tables to which such a C-clamp can attach is limited by the size of the C-clamp and the length of travel of the screw in the C-clamp. To accommodate a greater range of table thicknesses, typically the size of the C-clamp and the length of the screw needs to be increased. 
   SUMMARY OF THE INVENTION 
   In a broad aspect, the invention provides a clamp comprising a frame supporting opposed members having clamping surfaces defining a distance therebetween for receiving and clamping an object; an adjustment mechanism associated with at least one of the members for varying the distance over a continuous range; and a spacer assembly being removably fastenable to at least one of the members for varying the distance by at least one discrete increment. 
   In some embodiments, the opposed members comprise a first member and a second member and the spacer assembly is associated with the first member. 
   In some embodiments, the spacer assembly comprises a block having a thickness and the block and the first member define co-operating protrusions and receiving portions for fastening the block to the second member with the distance decreased by the thickness. 
   In some embodiments, the protrusions comprise the first member having parallel arms which define a channel therebetween and the receiving portions comprise a narrow portion of the block sized to receive the arms. 
   In some embodiments, the narrow portion comprises a post which connects a first portion of the block to a second portion of the block. 
   In some embodiments, the first portion of the block has a first thickness and the second portion of the block has a second thickness different from the first thickness and the block can be reversibly fastened in the first member wherein the distance can be decreased by either the first thickness or the second thickness. 
   In some embodiments, the spacer assembly further comprises at least one block adapter having an adapter thickness wherein the block and the block adapter define co-operating adapter protrusions and receiving portions for fastening the block adapter to the block to further decrease the distance by the adapter thickness. 
   In some embodiments, the adapter protrusions comprise at least one post projecting from the adapter and sized to fit into a hole on the block. 
   In some embodiments, the clamp further comprises at least one second adapter having a second adapter thickness wherein the adapter and the at least one second adapter define further co-operating protrusions and receiving portions for fastening the second adapter to the block adapter to further decrease the distance by the second adapter thickness. 
   In some embodiments, the spacer assembly comprises a rod having spacing elements slidably retained on the rod; a space being movable between the spacing elements by moving the spacing elements on the rod; the first member defining a protrusion for insertion into the space for fastening the spacer assembly to the first member, the distance decreasing by the thickness of the spacing elements inserted into the distance. 
   In some embodiments, the protrusions comprise the first member having parallel arms which define a channel therebetween for receiving a portion on the rod extending through the space. 
   In some embodiments, the spacing elements comprise a plurality of rings of different thicknesses. 
   In some embodiments, the spacing elements further comprise plates fastened on each end of the rod. 
   In some embodiments, the adjustment mechanism is associated with the second member. 
   In some embodiments, the adjustment mechanism comprises a threaded opening in the second member and a threaded bolt axially moveable therein in a direction of the distance. 
   In some embodiments, the bolt comprises an orifice opposite the direction, the orifice being sized to receive a post for mounting the post thereto. 
   In some embodiments, the post is a post of a table lamp for mounting the table lamp to a table. 
   In some embodiments, the clamp further comprises a removable sleeve encircling a head of the bolt. 
   In some embodiments, the adjustment mechanism further comprises a plate mounted to swivel on the end of the bolt for clamping the object. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be described with reference to the attached drawings in which: 
       FIG. 1  is a perspective view of a clamp according to an embodiment of the invention in which a spacer is removed from the clamp; 
       FIG. 2  is a side view of the embodiment of  FIG. 1  in which the spacer is attached to the clamp in a first position; 
       FIG. 3  is a side view of the embodiment of  FIG. 1  in which the spacer is attached to the clamp in a second position; 
       FIG. 4  is a top view of the embodiment of  FIG. 1 ; 
       FIG. 5  is a front view of the embodiment of  FIG. 2 ; 
       FIG. 6  is a rear view of the embodiment of  FIG. 3 ; 
       FIG. 7  is a side view of a second embodiment of the invention; 
       FIG. 8A  is a side view of a spacer adjustment of the embodiment of  FIG. 7 ; 
       FIG. 8B  is a side view of the spacer of the embodiment of  FIG. 7 ; 
       FIG. 8C  is a side view of another spacer adjustment of the embodiment of  FIG. 7 ; 
       FIG. 8D  is a top view of the spacer of the embodiment of  FIG. 7 ; 
       FIG. 9  is a perspective view of a clamp according to a third embodiment of the invention; 
       FIG. 10  is a side view of the embodiment of  FIG. 9 ; 
       FIG. 11A  is a front view of the spacer of the embodiment of  FIG. 9 ; 
       FIG. 11B  is a sectional view of the spacer of  FIG. 11A  taken along line A-A of  FIG. 11A ; 
       FIG. 12  is a perspective view of a fourth embodiment of the invention in which the spacer is removed from the clamp; 
       FIG. 13  is an exploded perspective view of the spacer of  FIG. 12 ; 
       FIG. 14  is a side view of the embodiment of  FIG. 12  with the spacer attached to the clamp in a first position; and 
       FIG. 15  is a side view of the embodiment of  FIG. 13  with the spacer attached to the clamp in a second position. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIGS. 1 to 6  show a clamp  10  in three possible configurations. The three possible configurations change the distance between the clamping surfaces. The distance is changed in increments by the presence and orientation of a spacer  12 . The distance can also be varied by the use of an adjustment mechanism at the opposite end of the clamp. The adjustment mechanism includes a bolt or screw  14  connected to a clamping plate  16 . Travel of the screw  14  into and out of the clamp interior will adjust the position of the clamping plate  16  over a continuous range of the travel of the screw  14  and thereby also change the distance between the clamping surfaces. 
   Turning to the clamp in further detail, the clamp  10  includes a supporting frame or body  18 . The body  18  is made up of two spacer arms  20  connected to two connecting arms  22  which in turn are connected to two head arms  24 . In this embodiment, the arms  20 ,  22  and  24  have a square cross-section shape. The head arms  24  in turn connect to a head  26 . As can be seen in the drawings, the embodiment of  FIGS. 1 ,  2  and  3  is C-clamp. In other words, the arms  20 ,  22  and  24  define a squared C-shaped frame. In this embodiment, the spacer arms  20  are parallel to and spaced from the head arms  24  by the length of the connecting arms  22 , with the connecting arms  22  being perpendicular to both the spacer arms  20  and the head arms  24 . The arms  20 ,  22  and  24  consist of two parallel arms spaced by a constant gap. 
   Other orientations of the arms could be utilized with corresponding changes made, if needed, to the spacer  12  and the clamping plate  16 . This invention is also applicable to other styles of clamps which are not C-clamps and could have different configurations for supporting the spacer  12  and the opposing clamping surface, such as the clamping plate  16  of this embodiment. 
   The head  26  in this embodiment, is connected to the head arms  24  at the opposite end of the head arms  24  from the connecting arms  22 . It would be appreciated, that the head arms  24  can be completely eliminated if the head  26  were of a sufficiently large diameter. The head  26  is internally threaded with complimentary threads to the threads of the screw  14  so that the screw  14  can be screwed to move the clamping plate  16  into and out of the interior of the clamp  10  to shorten or lengthen a distance X 1  between the clamping surfaces. 
   The clamping plate  16  of this embodiment is generally ring shaped with an extension  32  which is smaller in diameter than the body of the clamping plate  16  and is roughly of the same diameter as the screw  14 . However, such an extension is not essential. The clamping plate  16  is connected to the screw  14  by a smaller screw  30  which extends through a hole in the center of the clamping plate  16  and screws into the screw  14 . The clamping plate  16  also has a depression  34  in the clamping surface. This depression  34  may be tapered or another shape depending on the shape of the head of the connecting screw  30 . This depression ensures that the clamping surface of the clamping plate  16  contacts the surface to be clamped rather than the head of the connector screw  30 . Additionally, when the connector screw  30  is screwed tightly into the clamping plate  16 , the clamping plate  16  can still ride freely on the screw  30 . In other words, the clamping plate  16  can rotate around on the screw  30 . 
   Other means of securing the clamping plate  16  may also be used. For example, plate  16  may ride on a pin that is snap fit into the screw  14 . 
   It will be appreciated that the clamping plate  16  and the screw  30  may be totally eliminated. The clamping surface on this side of the clamp would then be provided by the end of the screw  14 . The clamp  10  may have to be held more securely for mounting in this configuration to prevent the contact between the rotating end of the screw  14  and the surface being clamped from causing the clamp  10  to travel along the surface. A protective material may also be used to protect the surface being clamped. 
   The screw  14  has a screw head  15 . A screw cap  28  can be used to cover the screw head  15  and the upper threads of the screw  14 . In this embodiment, the screw cap  28  is generally cylindrical. However, numerous other shapes may be used which are decorative such as triangular, octagonal or patterned screw caps. The screw cap  28  is a sleeve which covers the head of the screw  14  and it will be appreciated that the screw cap  28  may be completely eliminated. In this embodiment, the screw cap is retained by a press fit onto the screw head  15 . Other retaining means such as a retaining screw through the cap  28  and the head  15  could also be used. 
   As best seen in  FIG. 4 , there is a hole  36  which extends through the screw cap  28  and down into the screw  14 . This hole  36  is a blind hole in this embodiment. In other words, it will typically not extend through the end of the screw  14 . However, it could extend the entire length of screw  14 . The hole  36  is for mounting an item on the clamp. For example, a task lamp may have a cylindrical end that is sized to fit within the hole  36 . The positioning of the hole  36  is also visible in FIGS.  5  and  6 . The hole  36  need not extend through the screw  14 , for example, there may be a block of material mounted above or on the back of the arms  22  and the hole  36  may extend through that block. 
   Although the hole  36  and a complementary post at the bottom of a lamp could be used to mount a lamp on the clamp, any other fastening means known in the art may be used. For example, the clamp  10  could have a plate with holes on the arm  24  and an item to be fastened could have complementary holes for screwing to the plate. The advantage of the use of the clamp  10  in such a configuration is to avoid the necessity of drilling screw holes in, for example, the table. 
   As previously explained, the distance between the clamping surfaces may be varied by screwing the screw  14  in the head  26  inwards to the interior of clamp  10  and outwards from the interior of the clamp  10 . In this example, the other way of altering the distance between the clamping surfaces is by use of the spacer  12 . The geometry of the spacer  12  is best seen in the front view in  FIG. 5 . The spacer  12  is made up of a thin portion  38 , a thick portion  40  and a narrow portion  42 . In this embodiment, the thin portion  38  and the thick portion  40  are both cylindrical in shape and are connected by the narrow portion  42 . The width of the narrow portion  42  of this embodiment is sized to fit within the width of the distance between the connecting arms  22  by being substantially the same width. Similarly, the space between the thin portion  38  and the thick portion  40 , in other words the height of the narrow portion  42 , is sized to fit around the thickness of the spacer arms  22  by being substantially the same width. With this sizing, the spacer  12  can be press fit onto the spacer arms  22  as shown in  FIGS. 2 ,  3 ,  5  and  6  and thus retained in position. The particular shape of the spacer  12  is not essential. For example, the narrow portion  42  may be narrower and still have a press fit which retains the position. Other means of removably fastening the spacer in position may also be used, including a loose positioning that is secured by the clamping of clamp  10  when used. The spacer  12  may be any shape of block which, with the body  18 , define co-operating protrusions and receiving portions for mounting the spacer block to the body  18 . 
   As can be seen by comparing the distances X 1 , X 2 , and X 3  in  FIGS. 1 ,  2  and  3 , the distance X 1  and by extension the thickness of an item which can be clamped, is the maximum of the three distances when the spacer is totally removed as in  FIG. 1 . When the spacer  12  is press fit into the clamp with the thin portion  38  inside the clamp as shown in  FIG. 2 , the clamping distance is decreased to the distance X 2  by the thickness of the thin portion  38 . When the spacer  12  is press fit into the clamp  10  in the orientation shown in  FIG. 3 , the distance is reduced to the distance X 3  by a larger amount namely by the thickness of the thick portion  40 . 
   It will be appreciated that the use of the spacer  12  allows the distance to be decreased in increments based on the thickness of the portion of the spacer  12  which is added to the interior of clamp  10  inside of the spacer arms  20 . The opposed, in other words the oppositely facing parallel clamping surfaces, are provided by the inner face of the clamping plate  16  and the inner face of the spacing arms  20  in  FIG. 1 , the inner face of the thin portion  38  in  FIGS. 2 and 5  and the inner face of the thick portion  40  in  FIGS. 3 and 6 . 
   The use of the spacer  12  in conjunction with the screw  14  allows the screw  14  to be of a shorter length than if the spacer assembly was not available. In other words, for the clamp  10  to clamp to a thin item, the screw  14  only needs to be of sufficient length to travel the distance X 3  depicted in  FIG. 3  rather than the longer distance X 1  depicted in  FIG. 1 . In some embodiments the travel of the screw  14  is ⅜ inches. 
   Other embodiments of the invention will now be discussed. The further embodiments will be discussed only to the extent that they differ from the embodiments of  FIGS. 1 to 6 . Like reference characters will be used for the same parts and the same parts will not be described in detail. 
     FIG. 7  and  FIGS. 8A to 8D  show a different spacer assembly which can be used with the clamp body  18  described with respect to  FIGS. 1 to 6 . A spacer  44  has the same basic configuration as the spacer  12 . In particular, the spacer  44  has a thin portion  46  connected to a thick portion  48  by a narrow portion  50 . As with spacer  12 , the spacer  44  is sized to be press fit onto the spacer arms  20  of the body  18  of the clamp  10 . The spacer  44  differs from the spacer  12  in that the spacer  44  has a hole  52  defined on the outer flat side of the thin portion  46  and a hole  54  defined on the outer flat side of the thick portion  48  as seen in  FIG. 8B . The hole  52  may be square but it also may be other shapes and may not be exactly centered on the surface. 
   The spacer assembly of  FIGS. 7 and 8A  to  8 D also includes a thin spacer adapter  56  and a thick spacer adapter  58 . The thin spacer adapter  56  has a protrusion  62  which is sized to fit within either the hole  52  or the hole  54 . Similarly, the thick spacer adapter  58  has a protrusion  60 . The adapters  56  and  58  also have holes  61  and  63  sized to fit the protrusions  60  and  62 . It will be appreciated the spacer adapters  56  and  58  can be press fit onto the spacer  44  by inserting the protrusion  60  or  62  into the hole  52  or  54 . The adapters can therefore be used to vary the thickness of the portion of the spacer assembly which is internal to the clamp  10  and therefore vary the distance between the clamping surfaces by increments other than the thickness of the thin portion  46  or the thick portion  48 . Each of the adapters  56  and  58  may in turn have holes  61  and  60  on the opposite face from the protrusion so that further adapters may be connected to the adapters to allow further spacing increments. It will be appreciated that other co-operation protrusions and receiving portions for connecting the adapters to the spacer may be used. For example, the adapters may be screwed into position or have edge connectors for snapping into position. It will also be appreciated that the adapters need not be circular or of uniform size. Although the upper and lower surfaces of the adapters  56  and  58  and the spacers  12  and  44  are parallel, and the clamping surfaces are parallel, it will be appreciated that other configurations may be used. For example, if the clamp is to be attached to a pipe, the clamping surfaces may be concave. 
     FIGS. 9 ,  10 ,  11   a  and  11   b  depict another embodiment of the invention. The side view in  FIG. 10  appears much the same as the embodiment depicted in  FIGS. 1 to 8D , however, it will be appreciated from the perspective view in  FIG. 9  that a clamp  63  depicted in  FIGS. 9 and 10  differs from the clamp  10  depicted in  FIGS. 1 to 3 . In particular, the clamp body  64  of the clamp  63  is made up of a single piece rather than two parallel members. Clamp body  64  is made up of a head arm  66  connected to a connecting arm  68  which in turn is connected to a spacer arm  70  in the same manner as arms  20 ,  22  and  24 . The screw cap  28 , the head  26 , the screw  14  and the clamping plate  16  of the clamp  63  are the same as the components in  FIGS. 1 to 8 . 
   Because the spacer arm  70  of the clamp  63  is a single piece, a spacer  72  of the clamp  63  differs from the spacer  12  of the clamp  10 . The spacer  72  is made up of a thin portion  74  and a thick portion  76  similar to the thin portion  38  and the thick portion  40  described with respect to spacer  12 . However, the thin portion  74  and the thick portion  76  are connected by a different means. Rather than having a narrow portion  42  which is press fit between two spacer arms  20 , in this embodiment, there are connecting posts  78  on the sides of the spacer  72 . These connecting posts  78  connect the thin portion  74  and the thick portion  76  as shown in  FIGS. 11A and 11B . As can be seen from  FIG. 9 , the positioning of the connecting posts  78  allow the spacer arm  70  to be inserted between these connecting posts to fasten the spacer  72  in position. In other words, the thickness of the spacer arm  70  substantially equals length of the connecting posts  78  and the width between the connecting posts  78  substantially equals the width of the spacer arm  70  so that the spacer  72  is press fit into position around the spacer arm  70 . A press fit is not essential and other configurations may be used. For example, one connecting post may be eliminated if the remaining connecting post is sufficiently rigid. The connecting posts  78  may be separate components which are attached to the thin portion  74  and the thick portion  78 , for example, by an adhesive. Alternatively, the entire spacer  72  may be machined from a single block of material. 
   The spacer  72  could also be used with the clamp  10  and fitted to the outside of the spacer arms  22 . The use of adapters as shown in  FIGS. 7 to 8D  could also be made to the spacer  72  of  FIGS. 9 to 11B . The arms  22  and  24  may also be a single arm like arms  64  and  66 . 
     FIGS. 12 to 15  depict another embodiment of the invention. In particular, these Figures depict a clamp  80 . The basic configuration of the clamp body  81  is the same as described with respect to  FIGS. 1 to 6 . In particular the clamp  80  is made up of a body  81  comprising spacer arms  87  connecting arm  83  and head arms  85 . In this embodiment, these arms are depicted as having a tubular rather than square shape. The continuous adjustment assembly is comprised of the head  26 , the screw  14  and the clamping plate  16  as previously described. In  FIG. 12 , the screw cap  28  is removed so that the screw head  15  is visible. 
   This embodiment includes a spacer  84 . The spacer  84  is made up of first spacer end  86  in a second spacer end  88 . The spacer ends  86  and  88  are connected by a rod  90 . On the rod  90  between the spacer ends  86  and  88  are spacer elements which are thin spacer rings  92  and thick spacer rings  94 . The spacer rings  92  and  94  each have a hole through them which is larger than the diameter of the rod  90 . This allows the spacer rings  92  and  94  to move freely along the rod  92  within the limits of travel imposed by the spacer ends  86  and  88 . 
   The entire rod  90  is not occupied by spacer rings  92  and  94 . It will be appreciated that there will always be a blank area or gap on the rod  90  as shown in  FIG. 12 . This area can be repositioned along the spacer  84  by sliding the spacer rings  92  and  94 . For example,  FIG. 15  depicts the gap in one position and  FIG. 14  depicts the gap in another position. The size of this gap in this embodiment is about the same as the thickness of the spacer arms  20  so that the spacer arms  20  can be press fit between any two successive spacer rings  92 ,  94  or between a spacer end  86  or  88  and the next adjoining spacer ring  92  and  94 . This allows for a wide range of incremental spacer thicknesses to be added to the interior of the clamp  80 . For example, in  FIG. 14 , the distance has been decreased to a distance X 4  by the cumulative thickness of the spacer end  86 , three thin spacer rings  92  and two thick spacer rings  94 . In contrast, in  FIG. 15  the distance has been reduced to a distance X 5  only by the thickness of the spacer end  86  and the thickness of one thin spacer ring  92  and one thin spacer ring  94 . 
   It will be appreciated that the spacer  84  may have an effective thickness within the clamp  80  equal to the thickness of any successive grouping of spacer rings  92  and the associated spacer end  86  or  88 . The spacer ends  86  and  88  may be smaller and fit within a recess in the end most spacer rings so they do not add to the effective thickness. Any thickness of rings and ends and positioning the spacer rings may be employed. For example, the rod  90  may be telescoping so that no gap is left and the rod is expanded to allow the insertion of the spacer arms  20  into the spacer  84 . Alternatively, there may be multiple gaps. It would also be appreciated that spacer  84  may be configured similar to the spacer  72  of  FIGS. 9 to 11B  with peripheral rods rather than a central rod. 
   Although the embodiments depicted show circular spacers, it would be appreciated that other shapes may be employed. The spacers also may be screwed in or slid in from the sides rather than the front. The spacer, rather than the screw can have a hole or other protrusion or receiving portion to which an object can be mounted. 
   Although the embodiments depicted show the continuous adjustable screw assembly at one end of the clamp and the spacers at the opposite end of the clamp, it will be appreciated that spacers could also be attached to the clamping plate or be used in line in the connecting arms  22  as extensions. 
   An adjustable assembly other than a screw may be used as the complementary adjustment assembly to the spacer assembly. For example, a cam assembly may be used. The screw  14  may be replaced by a shaft connected to a cam. The cam in turn is connected to a rod. When the cam is in a released position, the shaft would slide freely up and down inside the head. When the rod is rotated to the engaged position, the cam will press against the shaft, holding it in place. 
   The parallel connecting arms  22  may also be used to facilitate a tracking system. For example, the arms may be extended to a much greater length than depicted in the figures and elements fixed between these parallel tracks or arms. 
   Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.