Abstract:
A portable, folding camera dolly track is assembled from a number of folding track sections, each track section having a parallel pair of rails, each rail having a base and a cylindrical wheel-supporting rail element, and a transverse spacer. A continuous, removable, resilient cap is provided on each wheel-supporting rail element to provide a smooth ride over joints formed by adjoining rail elements.

Description:
TECHNICAL FIELD 
     The invention relates to railed tracks for supporting and transporting wheeled vehicles, and more particularly, but not exclusively, to portable tracks for camera dollies. 
     BACKGROUND 
     In motion picture, video and television production, smooth camera movement is achieved using a wheeled camera support platform referred to as a dolly, which typically runs on two parallel dolly tracks or rails. The tracks or rails provide a solid fixed path for the wheeled dolly to follow to thereby provide a precise, smooth moving camera shot. When filming on location, away from the studio, portable dolly tracks must be used. 
     In existing portable dolly tracks, there are typically provided a number of removably connected track sections, each having two tubular parallel rail sections pivotally joined by transverse spreaders. See for example U.S. Pat. No. 5,887,787 Saldana. The rails are supported on the spreaders, which pivot to permit folding. When unfolded, latches or fasteners extend between two adjacent spreaders between the rails and are tightened to maintain the rails in parallel relation. 
     Since the rails span the space between adjacent spreaders in existing portable dolly tracks, there can be a sag in the rail as the heavy dolly rolls over it, causing undesirable vertical movement in the camera shot. Also the location of the latches between the rails can interfere with movement of the wiring and cables connected to the camera as the dolly rolls and can interfere with the feet of the dolly operator or focus puller. Further, the metal surface of the rails can become dented or pitted which may harm a smooth camera shot. Consequently there is a need for a portable, collapsible dolly track which avoids the foregoing problems. 
     SUMMARY OF INVENTION 
     The present invention therefore provides a folding track section for a wheeled vehicle, comprising: i) a parallel pair of rails, each rail having a horizontal base, an upper cylindrical wheel-supporting rail element, and a vertically extending element joining the base and the upper wheel-supporting rail element; ii) male and female joining elements in the ends of the rails; iii) a transverse spacer element extending between and pivotally secured at each end to the rails further provided on each rail element with a removable, resilient cap and wherein the upper wheel-supporting element is configured to prevent the cap from rotation about its length-wise axis. 
     The present invention further provides a folding track section for a wheeled vehicle, comprising: i) a parallel pair of rails each rail having a horizontal base, an upper cylindrical wheel-supporting rail element, and a vertically extending element joining the base and the upper wheel-supporting rail element wherein the vertical element is provided with an aperture adjacent one end; ii) male and female joining elements in the ends of the rails; iii) a transverse spacer element extending between and pivotally secured at each end to the rails; and iv) a latch member secured to the rail and having a hooked end for engaging an aperture in the vertical member of an adjoining section. 
     The present invention further provides a folding track section for a wheeled vehicle, comprising: i) a parallel pair of rails, each rail having a horizontal base, an upper cylindrical wheel-supporting rail element, and a vertically extending element joining the base and the upper wheel-supporting rail element; ii) male and female joining elements in the ends of the rails; iii) a transverse spacer element extending between and pivotally secured at each end to the rails through a vertical pivot axis on the base element; wherein the vertical pivot axis comprises a horizontal support extending from and secured to the vertical element. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In drawings which illustrate a preferred embodiment of the invention: 
     FIGS. 1A,  1 B and  1 C are perspective views of a dolly track section according to the invention in 8-foot, 4-foot and 2-foot sections respectively; 
     FIG. 2 is an end perspective view of the track section shown in FIG. 1, in detail; 
     FIG. 3 is a detail of the spreader connection for the track section shown in FIG. 1; 
     FIG. 4 is a side perspective view of the invention, with protective cap removed for purposes of illustration, illustrating a connection of two track sections; 
     FIG. 5 is a side perspective view of the invention with protective cap removed showing two joined track sections; 
     FIG. 6 is cross-section view of the plastic cap; 
     FIGS. 7A and 7B are perspective views of the male and female end pieces; and 
     FIG. 8 is a cross-section taken along lines  6 — 6  of FIG.  1 . 
    
    
     DESCRIPTION 
     Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
     With reference to FIG. 1, an 8-foot track section  10  is shown having parallel rails  13 ,  14  and transverse spreaders  16 . While an 8-foot section preferably has four spreaders  16  spaced at equal intervals, 4-foot section  11  having two spreaders  16  and 2-foot section  12  having a single spreader  16  are also used to permit combinations of sections having the desired length. The sections of different lengths are otherwise identically constructed. 
     As shown in FIG. 8, rails  13 ,  14  are formed of anodized extruded aluminum and have a lower horizontal base  18 , a vertical element  20  and a tubular member  22 . The rails are formed of aluminum which is anodized black to reduce reflection from lighting. The tubular member  22  has a vertical cross-member  24  for strengthening and rigidity. Cross-member  24  has a central widening  25 , circular in cross-section, to receive a screw  26  to secure the end pieces  28 ,  30 . End pieces  28 ,  30  are stainless steel. There are female end pieces  28  which receive corresponding male end piece  30  on the adjoining track element. The cross-members  24  are drilled out of the ends of the tubular members  22  to a depth equal to the depth of the extensions  32  beyond collars  33  of the end pieces  28 ,  30  so that the end pieces can be slid into the tubular members and secured to the cross-members by screws  26 . Preferably the same ends of rails  13 ,  14  of one track section will have complementary end pieces, that is, one will be male and one female. 
     Spreaders  16  are lengths of aluminum tubing which are pivotally secured at either end by pivot connections  34 . A rod end bearing  38 , or other horizontally extending support is secured to vertical element  20  by a screw  40 . Nut  42  is screwed onto a threaded bolt  45  which extends through base  18 . Friction-reducing  30  washers  43 , made of Teflon or the like, facilitate the pivoting of the spreaders  16 . 
     Latch members  44  are provided at opposite ends of rails  13 ,  14  and comprise a hooked bar  46  having hooked end  48  and opposite end  50  which is pivotally secured at  51  to handle  52 , which in turn has one end pivotally secured at  54  in an over-center relationship so that when adjacent rail sections are connected as in FIG. 5, and hooked end  48  is placed through hole  56  in vertical element  20 , the pivoting of handle  52  causes the two sections to be drawn tightly and securely together, and handle  52  is biased in the closed position shown in FIG. 5 until force is applied to pivotally release it. 
     To provide protection for the upper surface  58  of the rails and a smoother motion for the dolly wheels, a plastic cap  60  is snapped onto the tubular section  22 . It is shown in section in FIG.  6 . Preferably it is molded of high density polyvinyl chloride (PVC) of a thickness about 0.07 inches so that it is flexible to bend over the track and is open along arc  62  to receive the track. It is preferably provided in 2-foot, 4-foot, 8-foot or 16-foot lengths. The extruded tubular member  22  has lengthwise ribs  64  which prevent cap  60  from rolling over the side of tubular member  22 . The cap is preferably positioned so that the joints between cap sections do not overlie the joints between the track sections. 
     In operation, each track section is folded for transportation by pivoting the spreaders  16  so that rails  13 ,  14  come into close parallel contact. At the desired location, the desired number and length of track sections are unfolded, and secured end to end using latch members  44 . The appropriate length of plastic cap  60  is then snapped onto the upper surface  58  of the rails. Preferably the cap  60  extends over the joints  66  between adjacent sections. 
     As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.