Abstract:
Apparatus and methods allow the wheels of a camera dolly to be quickly and easily changed by a single person. A dolly jack may have a leg attached to a foot and pivotable relative to the foot about a first axis. A jack rod is attached to the leg spaced apart from the first axis. An arm may be pivotally attached to the leg as desired, to provide greater mechanical advantage in lifting the camera dolly. Dolly wheels may be changed by inserting a jack rod into a receptacle on one side of the camera dolly, with the foot of the jack on the ground and with the jack leg substantially in a non-vertical position. The jack leg rotated into a second position wherein the jack leg is substantially vertical, with the dolly rolling slightly in the direction of the rotation. This lifts the side of the dolly sufficiently so that the front and back wheels, or wheel pairs, on the one side of the dolly are lifted off of the ground, allowing the wheels to be changed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The field of the invention is camera dollies. More specifically, the application relates to a system for allowing quick change of wheels on a camera dolly. In motion picture or video filming, cameras are often supported on camera dollies, so that camera lens positions, angles, and elevations may be smoothly and easily achieved without interruption. Most camera dollies are pushed by “dolly grips” or camera dolly operators. For use on a relatively smooth and hard surface, such as on a sound stage, or other indoor set, the camera dolly is preferably provided with solid tires having relative high hardness, to reduce rolling friction, and make it easier to push and maneuver the camera dolly. 
         [0002]    For use on more irregular surfaces, for example an indoor surface having small cracks, bumps, etc., a softer solid tire is preferred, to absorb shock impulses, albeit with a small increase in rolling friction. For use on still more irregular surfaces, pneumatic tires are typically used, to provide a higher degree of shock absorption, although with a greater increase in rolling friction. For use on unpaved surfaces, such as grass, sand, etc., or in other applications where a maximum level of smoothness in dolly movement is required, dolly track is laid down, with the dolly wheels rolling on the smooth metal rails of the track. Having a smooth rolling surface, or a way to absorb the shock impacts created when rolling over an irregular surface, is important, as shock impacts generated via the rolling movement of the camera dolly wheels can cause unacceptable movement of the camera lens during filming, resulting in unsteady recorded images. 
         [0003]    It is frequently necessary to change the wheels on the camera dolly, to compensate for change in the ground conditions. For example, if a first part of a film sequence takes place indoors, the hard solid wheels may be used. Then, if the sequence continues outdoors, it may then be necessary to change over to a pneumatic or track wheel. While a combined track/pneumatic wheel, as described in U.S. Pat. No. 4,943,101, incorporated herein by reference, has been successfully used in the past, to avoid wheel changeover when switching between track and pneumatic wheels, it remains necessary to change wheels when the harder solid wheels are needed. In addition, fast wheel changes are assisted by the wheel system described in U.S. Pat. No. 6,349,994 B1, also incorporated herein by reference. 
         [0004]    However, the dolly must still be lifted up to unweight the wheels, before the wheels can be changed. A typical unmotorized camera dolly weighs about 300 to 500 pounds. When loaded with crane arm and accessories, this can increase up to about 1200 pounds. The usual practice is generally for the dolly operators to simply manually lift and chock up one side of the dolly at a time, to change the wheels. While this technique works, it risks injury from heavy lifting. It also requires at least two people. Manual lifting can also damage the camera dolly if the lifting and chocking is not at a structural hard point of the camera dolly. Accordingly, there remains a need for designs which allow fast changeover of camera dolly wheels. 
       SUMMARY OF THE INVENTION 
       [0005]    New apparatus and methods have now been invented which allow for fast changeover of dolly wheels, without the need for lifting the dolly by hand. These new apparatus and methods also allow the dolly wheels to be quickly and easily changed by a single person. In a first aspect of the invention, a dolly jack may include a leg attached to a foot and pivotable relative to the foot about a first axis. A jack rod is attached to the leg and may be substantially parallel to and spaced apart from the first axis. An arm can be pivotally attached to the leg as desired, to provide greater mechanical advantage in lifting the camera dolly. The leg may have fixed upper and lower positions for receiving the jack rod, with the lower position between the leg pin and the upper opening, and with the jack rod attached to the leg by securing it onto the leg at the upper position or at the lower position. 
         [0006]    Dolly wheels may be changed using the jack inserting a jack rod into a receptacle on one side of the camera dolly, with the foot of the jack on the ground and with the jack leg substantially in a non-vertical position. The jack leg is moved or rotated into a second position wherein the jack leg is substantially vertical, lifting the side of the dolly sufficiently so that the front and back wheels, or wheel pairs, on the one side of the dolly are lifted off of the ground. The rotation of the jack leg may be achieved by pulling or pushing on the arm, if used. The wheels on the one side of the dolly are changed, and the steps are repeated on the other side of the dolly. Changing the dolly wheels can thus be quickly achieved by a single person, and without heavy lifting. Other objects, features and advantages will become apparent from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In the drawings, the same reference number indicates the same element in each of the views. 
           [0008]      FIGS. 1 and 2  are perspective views of prior art camera dollies. 
           [0009]      FIG. 3  is a side view of a prior art quick change camera dolly wheel as described in U.S. Pat. No. 6,626,117. 
           [0010]      FIG. 4  is a perspective view showing use of the quick change camera dolly wheel design of  FIG. 3 , using a single width wheel ramp, as also described in U.S. Pat. No. 6,626,117. 
           [0011]      FIG. 5  is a side section view of a novel camera dolly jack, shown in the folded position. 
           [0012]      FIG. 6  is a side elevation view of the camera dolly jack as shown in  FIG. 5 . 
           [0013]      FIG. 7  is a front view of the camera dolly jack shown as in  FIG. 5 . 
           [0014]      FIG. 8  is an enlarged side view of the jack rod core shown in  FIG. 5 . 
           [0015]      FIG. 9  is a reduced-scale side view of the camera dolly jack of  FIG. 5  now shown in the unfolded position with the jack rod at the lower position. 
           [0016]      FIG. 10  is a reduced-scale side view of the camera dolly jack of  FIG. 5  now shown in the unfolded position with the jack rod at the upper position. 
           [0017]      FIG. 11  is a schematic side view showing operation of the camera dolly jack shown in  FIGS. 5-9 . 
           [0018]      FIG. 12  is an enlarged detail view of a cover plate on the jack leg. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Turning now in detail to the drawings, as shown in  FIG. 1 , a camera dolly  10  has a chassis  12  with a kingpin  14  at or near each of the corners of the dolly  10 . An inner wheel  18  and an outer wheel  20  are rotatably supported on axles on opposite sides of each kingpin  14 . The inner wheel  18  and outer wheel  20  form a wheel pair. For example, a front right side wheel pair is shown at  28 , and a front left side wheel pair is shown at  38 , in  FIG. 1 . A tire  22  is mounted on each of the wheels. 
         [0020]      FIG. 2  shows another type of camera dolly  30  similar to the camera dolly  30  shown in  FIG. 1  but with legs  32  attached to the chassis via pivot joints  34 . Both types of dollies typically have or may be provided with one or more sockets or receptacles  40  on both sides of the chassis  12 . The receptacles  40  are used to attach accessories to the dolly. The accessories include seats, platforms, sideboards, etc. For example, U.S. Pat. No. 6,719,307, incorporated herein by reference, describes sideboards installed using the receptacles. 
         [0021]      FIGS. 3 and 4  show a side view of a camera dolly quick wheel change design, from U.S. Pat. No. 6,626,117, incorporated herein by reference. This design may be used on the camera dollies  10  and  30  shown in  FIGS. 1 and 2 .  FIG. 3  shows a quick release clip  26  that holds a wheel onto an axle  16 , and that also may be quickly removed by hand, to allow the wheel to be quickly and easily removed from the axle. As shown in  FIG. 4 , with this design, the outer wheel  20  of a wheel pair is rolled up onto a ramp  36  to unweight the inner wheel  20  of the wheel pair. The inner wheel  20  is then removed and replaced. The outer wheel  20  is then rolled up onto the ramp  36 , removed and replaced. With camera dollies having four wheel pairs, and a total of eight wheels, changing the wheels using this technique requires eight movements of the camera dolly onto and off of the ramp  36 . This time consuming operation can be a significant disadvantage. Motion picture or television production often requires a large number of highly skilled professionals, and extensive amounts of equipment and supplies, so that production costs can reach several thousand dollars for each minute. Accordingly, saving even a few minutes in production time is highly significant, in terms of production costs. Moreover, in sequences involving fast changing lighting conditions, the ability to film the sequence as desired may depend on how quickly the equipment, including the camera dolly, can be set up. 
         [0022]      FIGS. 5-7  show a camera dolly jack  50  having a resilient pad  54  on the bottom surface of a foot  52 . As shown in  FIG. 5 , a screw  56  is threaded into the bottom end of the leg  60  and clamps a metal pad plate  55  into a recess in the pad  54 . The metal pad plate  55 , if used, helps to securely hold the pad  54  onto the leg  60 . The pad  54 , which may be rubber, may also be attached to the leg  60  by adhesives, or by other techniques. A leg or lower section  60  is pivotally attached to the foot  52 , for example via a pin  58 . The leg  60  has a lower socket  66  and an upper socket  70 . Each socket has an outer counter bore and an inner threaded hole  66 . 
         [0023]    An arm  64  may be used and pivotally attached to the leg  60  by a hinge fitting  62 . In this example, as shown in  FIG. 5 , the hinge fitting  72  may be attached to the top end of the leg  60  by a bolt  72  with the arm attached to the hinge fitting  62  by an arm pin  74 . This attachment may have sufficient drag to prevent the arm  64  from swinging freely, or a detent may optionally be used hold the arm  64  into desired positions. The foot  52 , the leg  60  and the arm  64  may be metal. For example, the leg  60  and the arm  64  may be a ¾ inch diameter round aluminum bar or a square bar. For use with most camera dollies, the leg  60  may be 10-20 inches long. The arm  64 , if used, may be the same length as the leg, or slightly shorter, to provide maximum leverage without increasing the overall folded length of the jack  50 . 
         [0024]    As shown in  FIGS. 5 and 8 , a jack rod or segment  75  may have a metal core  76  including a knurled knob or shoulder wheel  80 , a shoulder pin  82  and a threaded stud section  84 . Bushings  88 , such as DU bushings, are pressed into a metal sleeve  86 . A Teflon (fluoropolymer) washer  96  is positioned on the core  76  next to the knob  80 . The sleeve  86  with the bushings  88  is placed onto the core  76  and held on the core  76  via a Teflon end cap  90  and a cap screw  92 . The sleeve  86  and core  76  may be stainless steel. The sleeve  86  can rotate on the core  76 . The stud section  84  may be threaded into an opening in the end of the arm  64 . A slot  98  may be provided in the back surface of the leg  60  to provide clearance for the knob  80  when the jack is in the folded position as shown in  FIGS. 5 and 6 . The camera dolly jack  50  as shown in  FIGS. 5-7  is accordingly compact and lightweight. As a result, the jack  50  may be permanently stored on the camera dolly. The dolly operator then need not move away from the dolly, for example to a remotely stored dolly accessory kit, to have access to the jack. 
         [0025]    Referring now to  FIGS. 9-11 , in use, the jack rod  75  is removed from the handle  64  by turning the knob counterclockwise. The jack rod  75  is then placed into the upper socket  70  or the lower socket  66  matching the height of the receptacle  24  on the camera dolly to be lifted.  FIG. 9  shows the jack rod  75  in the lower socket  66  for use in lifting the type of dolly  10  shown in  FIGS. 1 and 11 . The engagement between the pin shoulder  82  on the jack rod  75  and the counter bore in the socket  66  or  70  aligns the stud section  84  on the jack rod  75  with the threaded hole  68  in the socket. The jack rod  75  is then turned to thread the stud section  84  into the threaded hole  68  to securely attach the jack rod  75  to the leg  60 . 
         [0026]    The alignment between the pin shoulder  82  and the counter bore helps to provide a secure structural attachment between the jack rod  75  and the leg  60 . The sockets  66  and  70  may be blind holes or through holes. If through holes are used, the openings on the back side of the leg  60  may be covered over, e.g., with a cover plate  102  and screws  104 , as shown in  FIG. 12 , to prevent the operator from inadvertently trying to install the jack rod  75  onto the back side of the leg  60 . A label reminding the operator to fully insert and tighten the jack rod  75  into the leg  60  may be provided on the leg, as shown in  FIG. 7 . 
         [0027]    As shown in  FIG. 11 , the jack rod  75  is inserted into a receptacle  24  on the camera dolly, with the leg  60  in a non-vertical position. In  FIG. 11 , the leg  69  is initially about 10 to 40° from vertical. The foot  52  is correspondingly at an angle to the ground, generally with only one side or edge of the foot  52  contacting the ground. The pivot axis between the foot  52  and the leg  60 , or the axis of the foot pin  58 , extends parallel to the front/back direction of the dolly chassis. Consequently, the foot  52  remains perpendicular to the leg  60 , in the front/back axis F/B shown in  FIG. 11 . 
         [0028]    To lift the dolly, the leg  60  is then rotated from the starting position, shown in dotted lines in  FIG. 11 , to the upright vertical position shown in solid lines in  FIG. 11 . This movement is achieved by manually pushing or pulling on the unfolded arm  64 . During this movement, the dolly rolls (slightly forward in  FIG. 11 ) and the jack rod  75  moves in an arc, forwardly and upwardly, as shown in  FIG. 11 . The leading edge of the pad  54  tends to catch against the floor and hold the jack  50  in place against sliding. If necessary, on a lower friction floor surface the operator can prevent any sliding of the foot  52  by placing the operator&#39;s foot in front of the jack foot  52 . 
         [0029]    The upward movement of the jack rod  75  lifts the right side front and rear wheel sets  28  up off of the ground. As shown in  FIG. 11 , when lifted by the jack  50 , the right side wheels  28  are up and off of the ground  90  by for example ½ to 2 inches, and the left side wheels  38  on the opposite side of the camera dolly remain on the ground  90 . The sleeve  86  on the jack rod  75  can rotate about the core  76  as the dolly is lifted. The sleeve need not rotate relative to the receptacle  24  on the dolly, thereby avoiding scoring or scraping the interior surfaces of the receptacle. Rotation of the sleeve  86  about the core  74  also prevents the jack rod  75  from becoming over-tightened into the socket  66  or  70  as the camera dolly is jacked up. As a result, the jack rod  75  can be removed from the socket by hand, even after being used to lift heavy loads. 
         [0030]    With the leg  60  in the vertical position, the width of the foot  52  (e.g., 2-3 inches) in the front/back direction F/B, helps to stabilize the lifted dolly. If the dolly is equipped with wheel brakes, one or more of the brakes may optionally be set on, to further help to prevent inadvertent movement of the lifted dolly. Referring to  FIG. 11 , since the camera dolly is lift from one side, during the lifting movement, the receptacle moves forward and up along the arc AA shown in dotted lines in  FIG. 11 . The receptacle  24  also moves away from the jack  50  along the arc BB shown in  FIG. 1 . Movement on the arc BB tends to move the receptacle away from the jack rod  75 , with the receptacle oriented upwardly about 1° to 5° when a typical dolly is fully lifted up. 
         [0031]    However, as shown in  FIG. 5 , since the foot pin  58  is aligned in the front/back direction F/B, the leg  60  can lean in towards the dolly, as the dolly is lifted. This movement can help to keep the jack rod  75  fully inserted into the receptacle  24  and also reduce stress on the attachment between the jack rod and the leg  60 . With the dolly lifted as shown in  FIG. 9 , all four wheels on the right side are off of the ground and can be changed over. The procedure described above is then repeated on the left side of the dolly. All eight wheels can therefore be changed with only two lifts using the jack  50 . 
         [0032]    Referring to  FIGS. 2 and 10 , for use with camera dolly having a receptacle higher up off of the floor, such as the dolly  30  shown in  FIG. 2 , the jack rod  75  is placed into the upper socket  70 . The jack  50  then lifts the dolly  30  in the same way as described above. With the dolly  30  jacked up, the positions of the legs  32  may also be easily changed. The jack  50  can be used to lift any dolly having a receptacle  24 . The jack may be used by a single camera dolly operator, without any tools needed. 
         [0033]    As is apparent from  FIGS. 5 and 11 , the position of the jack rod  75  on the leg is selected based on the height of the receptacle  24  of the camera dolly to be lifted. Generally, the dimension from the bottom of the foot to the centerline of the jack rod  75  is ½ to 2 or 3 inches greater than the dimension from the floor  90  to the centerline of the receptacle  24 . 
         [0034]    The arm  64  acts as an extended lever on the leg  60 , and it is also foldable into a convenient compact form. Other forms of arms  64  without any hinge attachment may also be used. For example, the arm  64  may be inserted into or slide over the top end of the leg  60 . Alternatively, the leg  60  may simply be extended to a length that provides the desired amount of leverage. In another alternative design, the jack rod  75  may be stored as a separate piece, not attached to the arm  64 . The jack rod  75  may also alternatively be permanently attached to the leg  60  at the upper or lower socket position, or a jack rod  75  may be attached at both positions. It is also possible to provide multiple sockets or other attachments for the jack rod  75  on the leg  60 , so that the camera dolly jack  50  may be used with various camera dollies having receptacles at different vertical positions. 
         [0035]    Thus, novel apparatus and methods have been shown and described. Various changes and substitutions may of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be limited, except by the following claims and their equivalents.