Patent Publication Number: US-6217236-B1

Title: Camera crane arm

Description:
This application is a continuation-in-part of Ser. No. 09/092,194, filed Jun. 5, 1998, now U.S. Pat. No. 5,984,536, which in turn is a divisional of Ser. No. 08/514,831, filed Aug. 14, 1995, now U.S. Pat. No. 5,781,814. 
    
    
     BACKGROUND OF THE INVENTION 
     Camera cranes are often used in the motion picture and television industries to position and maneuver cameras. Camera cranes typically have a crane arm supported on a base, with a camera platform at one end of the arm, and a counterweight at the other end. The crane arm can be pivoted by hand to raise and lower the camera, and also to pan to the left or right side. A leveling system is often included to maintain the camera platform in a level orientation. 
     With the advent of remote controlled television and motion picture cameras, filming can be achieved without a camera operator sitting behind the camera. Rather, the camera operator can remain on the ground while the remotely controlled camera is suspended on a crane arm. This allows for more versatile camera positioning. For example, the remotely controlled camera can be positioned at locations where it would be too time consuming, difficult or dangerous to place a traditional camera and operator. Accordingly, there is a need for camera crane arms to match the versatility of remote camera systems. 
     Due to the variety, and occasionally difficult accessibility of filming locations, the camera crane arm should advantageously be portable and lightweight. On the other hand, the arm must be rigid enough, when assembled, to resist bending and sagging, and to avoid excessive whipping motion on the camera during movement. While various camera crane arms have been used successfully in the past, there remains a need for an improved camera crane arm to meet the needs of the television and motion picture industries. 
     SUMMARY OF THE INVENTION 
     To these ends, in a first aspect, a camera crane arm preferably includes a frame pivotally supporting a central box section. A plurality of outer beams are attached to and spaced apart from the central box section. A leveling system is advantageously fixed to the box section in between outer beams, and pivotally linked to a camera platform, to maintain the platform in a level orientation. 
     In a second aspect, the crane arm is most desirably formed of sections having substantially flat ends, with a first end having one or more tapered pin and the second end having a like number of mating tapered holes, with the pins and holes of adjacent sections configured to engage each other when the flat ends of adjacent sections are brought together, thereby forming a secure and rigid attachment between sections. 
     In a third aspect, the beam sections have inclined end faces, to reduce sagging of the arm. 
     In a fourth aspect, the The camera platform is attached to the crane arm at a preset incline angle, to compensate for deflections when loaded. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
     FIG. 1 is a side elevation view of a preferred embodiment of the present camera crane arm; 
     FIG. 2 is an enlarged side elevation view showing the frame section of the crane arm of FIG. 1; 
     FIG. 3 is a top and left side isometric view of a preferred crane arm section; 
     FIG. 3A is a partial section view taken along line  3 A— 3 A of FIG. 3; 
     FIG. 4 is a bottom and right side isometric view of the section of FIG. 3; 
     FIG. 5 is a side elevation view of the back end of the crane arm of FIG. 1; 
     FIG. 6 is a partial plan view thereof; 
     FIG. 7 is a section view taken along line  7 — 7  of FIG. 8; 
     FIG. 8 is a side elevation view of the front end of the camera crane arm of FIG. 1; 
     FIG. 9 is a partial plan view thereof; 
     FIG. 10A is a partial schematic illustration of an arm section, as shown in FIGS. 3 and 4; 
     FIG. 10B is a geometric construction better illustrating the offset and angles of the arm section of FIG. 10A; 
     FIG. 10C is a geometric construction similar to FIG.  10 B and showing an alternative embodiment. 
     FIG. 11 is a partial section view taken along line  11 — 11  of FIG. 2; 
     FIG. 12 is a side elevation view of the supporting frame shown in FIGS. 1 and 11; and 
     FIG. 13 is a side view of an alternative embodiment of the nose piece shown in FIGS.  1  and  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now in detail to the drawings, as shown in FIG. 1, the present crane arm  20  includes arm sections  22 , a counterweight section  24 , a nose or camera platform section  26 , and a central frame section  28 , supported on a frame  30 . The embodiment shown in FIG. 1 includes two arm sections  22  on either side of the frame section  28 , with the arm sections preferably about 24 inches long. Of course, various numbers of arm sections  22  may be used, and the lengths of the arm sections may be varied. Preferably, arm sections are provided in 12 and 24 inch lengths. 
     FIG. 2 shows the central frame section  28  on the frame  30 , without any arm sections  22 . A nose section  26  and a counterweight section  24  may be attached directly to the central frame section  28 , to form the shortest embodiment. 
     As shown in FIGS. 3 and 4, each arm section  22  includes a female end  32  and a male end  34 . The section ends are preferably flat, so that with the sections fitted together, the ends fit flush all around. Each arm section  22  includes outer beams  38  joined to a central box section  36 , with the arm sections having a substantially I-shaped cross section. The box section  36  is preferably hollow, to reduce weight. The arm sections may be manufactured as aluminum weldments. The upper and lower surfaces  37  and  39  are preferably flat. 
     The female end  32  includes threaded holes  42  closest to the upper and lower surfaces  37  and  39 . A center hole  48  optionally extends centrally into the box section  36 , to reduce the weight of the arm section  22  and to allow for cable routing within the arm  20 . Pin receiving holes  44  and  46  are advantageously located on opposite sides of the center hole  48 , as shown in FIG.  3 . Referring to FIG. 4, bolts  52  are provided at the male end  34  of the arm sections  22 , in alignment with the threaded holes  42 , when adjacent sections are mated together. Upper and lower pins  54  and  56  extend from the flat face of the male end  34 , similarly in alignment with the holes  44  and  46 . The pins  54  and  56  advantageously have different diameters, so that the arm sections  22  cannot be assembled in a reversed or upside down manner. In the embodiment shown, the upper pin  54  is larger than the lower pin  56 , with the upper pin having a base diameter of 1 inch and tapering at a 6° included angle to a substantially smaller end diameter, and with the lower pin  56  having a base diameter of ¾ inch and similarly tapering to a substantially smaller end diameter. The pin receiving holes  44  and  46  are also tapered and configured to engage with the pins  54  and  56  as the male end  34  of one arm section engages a female end  32  of an adjacent section. Because of the taper of the pins  54  and  56 , no engagement force is needed to assemble adjacent arm sections  22 , i.e., the attachment is engagement free until the flat facing surfaces meet. 
     Referring to FIG. 2A, an undercut  58  is provided to the root diameter on a section of the threads of the bolts  52 . Once installed, the bolts  52  are captive within the arm sections  22  by set screws  60 , (FIG. 3) which allow the bolts  52  to turn, and slide forward and back, but prevent the bolts  52  from being removed from the arm section. 
     Referring still to FIG. 3, each arm section  22  includes upper and lower leveling rods  64  and  65 . The ends of the leveling rods at the female end of the arm section  22  have a clevis  70  including a slot  72 . Correspondingly, the ends of the leveling rods  64  at the male end  34  of each arm section  22  include tabs  74 , which mate into the slots  72  (of an adjacent arm section  22 ). The leveling rods  64  are mounted on bolts  68  extending through bushings  71 , with the bolts threaded into pivot arms  66 . The bushings  71 , preferably stainless steel, are slightly wider than the leveling rods, so that the bolts  68  clamp down on the bushings  71 , but not on the leveling rods, which remain free to pivot on the bushings  71 . The pivot arms are similarly mounted on bolts  67  passing through bushings  73  slip fit into, and slightly wider than, the box section  36  and retained by washer  77  and nut  75 , so that the pivot arms  66  can freely pivot with respect to the box section  36 . Referring momentarily to FIG. 1, quick release pins placed through holes in the clevis  70  and slot  72  at the ends of the leveling rods  64  and  65  allow the leveling rods of adjacent arm sections to be securely attached to each other. Storage holes  78  may be provided through the leveling rods at the female ends, to conveniently store the quick release pins  76  when not in use. The leveling rods are external on the arm  20 , yet are within the envelope  79  of the cross section of the arm. Accordingly, they are easily and quickly accessible for assembly and disassembly of the arm, yet they are shielded from damage via dropping, collision, etc. 
     The lower surface of the upper leveling rod  64 , and the upper surface of the lower leveling rod  65  include recesses  62 , to allow a greater range of movement, without interference from the pins  67  or needle bearings  71 . 
     Turning to FIGS. 7,  8  and  9 , the nose section  26  includes an armature  80  having a flat rear surface male end  81  similar to the arm sections  22  (but without the outer beams). The armature has a round forward end  82  with flat sides and a through bore  91  having a central step  93 . A U-plate  85  has inner and outer disk legs  89  and  90 , a flat forward plate  105 , and a shaft section  99 . The shaft section  99  extends through the bore and bearings  94  in the bore. An L-plate  84  has a disk leg  98  joined at a right angle to a forward plate  106 . As shown in FIG. 7, the end of the shaft section  99  is supported in a counterbore in the disk leg  98 . A bolt  86  extends through the L plate  84  and shaft section  99  and threads into disk leg  90 . Bolts  83  attach the forward plates  105  and  106  to an attaching plate  87 . A nose plate  92  is attached to the attaching plate  87  via a stud  95  extending from the attaching plate through the vertical leg of the nose plate  92 , and a washer  96  and a nut  97  on the stud  95 . The front ends of the nose leveling rods  101  and  103  are pivotally attached via dowels and bearings to the U-shaped plate  85  between the disk legs  89  and  90 . 
     Dowel pin  107  locates plate  92  every 90 degrees, as the plate  92  is relocated by revolving around stud  95 . The nut  97  is loosened ¼ inch, then plate  92  is moved out ¼ inch, allowing dowel  107  to be rotated in 90 degree increments around stud  95 . The incremental rotation change may also of course be set at 45°, 30°, or other angles, as the need may require. 
     Referring to FIGS. 5 and 6, the counterweight section  24  includes a bucket mounting plate  111  having a pyramid-like trapezoidal mounting lug  113 . A weight bucket or cage  115  advantageously has a chassis  117  for holding counterweights  116 , which can be secured by a door  119  hinged onto the chassis  117 . A chassis receptacle  112  having a trapezoidal slot is provided on the chassis  117 , so that the chassis  117  of the weight bucket  115  can be engaged onto the mounting plate  111 . A quick release pin  114  extends through aligned holes in the mounting lug  113  and chassis  117 , to secure the weight bucket  115  onto the arm  20  while allowing for rapid weight bucket installation and removal. The pyramid lug and slot, each having four angled sides, are self-aligning. Alternative weight bucket designs may also be used. For example, the weight bucket may be split into two smaller spaced apart weight buckets, with a television monitor positioned in between them, along with controls for directing a remote camera. 
     Referring to FIG. 10A, a 24 inch arm section  22  is provided with an angled end face, to help compensate for vertical deflection of the crane arm. Specifically, when assembled, the female end  32  of the arm section  22  is offset vertically above the male end  34 . The male end face is vertical, while the female end face is inclined (upwardly) toward the male end face by angle BC, preferably about 0.5 degrees. This 0.5 degree angle on the end face creates a rise of about 0.2 inches over a 24 inch arm segment. The threaded bolt holes  42  and pin holes  44  and  46  are (as well as the bolts and pins) preferably perpendicular to surfaces B and C. 
     FIG. 10B schematically shows an unloaded assembly of the section shown in FIG. 10A, with the vertical positions and angles greatly exaggerated for clarity of illustration. The two female ends of the frame section  28  are preferably vertical. The faces of the female ends  32  on the two sections  22  adjoining the frame section  28  are inclined upwardly at an angle BC, preferably about 0.5 degrees for the embodiment shown. As additional sections  22  are added for a longer arm  20 , the angles BC, and rises provided by the angles BC, accumulate. Without any load, the ends of the beam are slightly above the frame section  28 . However, when loaded with a camera on the nose plate  92  and counterweights in the weight bucket  115 , the ends of the beam deflect downwardly, so that the arm  20  is substantially straight and the nose plate  92  is substantially level. When loaded under ordinary conditions, surfaces B and C become substantially parallel and angle BC becomes substantially zero, i.e., the end faces become vertical, as a result of bending deflection of each section  22 . 
     In an alternative embodiment shown in FIG. 10C, the angle BC is split equally on the male and female ends  32  and  34 , with each end having an end face angle CD of about 0.25 degrees. The two female end faces  32  of the frame section  28  may also be similarly angled upwardly. 
     Of course, the amount of end face angle on each arm section  22  required to have the crane arm  20  remain straight without sagging when under load, will vary with the length of the arm  20  (i.e., on how many arm sections  22  are used), the loads applied, and the moment of inertia of the arm  20 ). Although as arm length increases, the cumulative offset provided with each section also increases, arm deflection will vary with the cube of the length of the arm, whereas the built-in offset or rises of the arm sections accumulates linearly with increasing length. The maximum preferred arm length, measured from the center post  160  to the bearings  94  in the nose section, is about 26 feet, for best performance. The approximate 0.5 degree inclination angle, and 0.2 inch rise per segment for the embodiment of FIG. 10A, are selected to provide a straight beam  20  with a camera payload of about 100-180 pounds, with close to the maximum arm length. 
     Referring to FIGS. 1 and 2, the frame section  28  has two female ends. Accordingly, the male ends  34  of the arm sections  22  are engaged into both sides of the frame section  28 , so that the built-in offset of the arm  20 , on either side of the frame section  28  is in the upward direction. 
     Referring to FIGS. 2 and 11, the frame section  28  includes a box section  120 , similar to box section  36 , but tapering outwardly towards the center of the frame section  28 . The slash lines  25  in FIG. 2 schematically illustrate the position of the leveling rods when the arm is titled fully up. Referring specifically to FIG. 11, a tilt axle  130  extends through a right cap  136 , a right spindle  142 , the box section  120 , a left spindle  152 , and is held in place by an axle bolt  156  passing through a left cap  154 . Inner and outer washers  138  and  140  separate the right cap  136  and right spindle  142  from the right upper arm  143  of the U-shaped frame  30 . A tilt brake knob  132  is attached to the tilt axle  130  and spaced apart from the right cap by a thrust bearing  134 . The right spindle  142  is attached, preferably welded, to the box section  120 . A spindle bearing  144  and a box section bearing  145  pivotally support the frame section  28  on the tilt axle  130 . The tilt axle  130  is fixed on the frame  30 . DU bushing  131  allows sliding adjustment when the tilt brake knob  132  is rotated on the O.D. threaded end of axle  130 . The frame section  28  of the arm  20  rotates about axle  130 . 
     A disk washer  148  separates the left side of the box section  120  from a leveling rod disk  146 . The washers  138 ,  140  and  148  are preferably Teflon or Delrin or a similar material. A spacer tube  150  around the axle  130  maintains spacing between the left spindle  152  and the leveling rod disk  146 , so that the leveling rods cannot become clamped between the left spindle  152  and the disk  146 , as the arm pivots vertically to raise and lower a camera. Preferably, the leveling rod disk  146 , the spacer tube  150 , and the left spindle are machined from a single bar, leaving them connected for added rigidity and strength. As shown in FIG.  2 , clamping bolts  135  are advantageously provided to clamp the left cap  154  and spindle  152  to the frame  30 . 
     Upper and lower leveling rod pins  122  extend through the left cap  154  and left spindle  152 , through holes in the upper and lower leveling rods  64  and  65  on the frame section  28 , and into the leveling rod disk  48 . Thus, the left spindle  152 , leveling rods  64  and  65 , and leveling rod disk  146  are fixed in position on the left upper arm  141  of the frame  30 . Bearings may be provided to reduce friction between the pins  122  and the leveling rods, as they pivot about the pins. The pins  122  fix the center of rotation of the leveling rods, causing the ends of the leveling rods to remain vertically aligned, despite vertical pivoting arm movement. 
     Turning to FIG. 12, a center post  160  is rigidly attached to a camera dolly or crane arm base, such as shown in my U.S. Pat. No. 4,360,187 or U.S. Pat. No. 5,312,121, incorporated herein by reference, so that the arm  20  has a mobile base which can preferably be moved into different positions on a floor, track or other surface. A Teflon ring  170  around a base  162  is clamped by a split ring  164 . Referring to FIG. 11, a pan brake handle  168  is attached to a pan brake bolt  166  which extends through the split ring  164 . As the pan brake handle  168  is turned, the sides of the split ring  164  are pulled together and clamp onto the base  162 , to stop panning rotation movement. 
     The frame  30  and base  162  are pivotally supported on the center post  160  via upper and lower center bearings  180  and  176 . A frame ring  178  and post cap  182  secure the upper center bearing  180 . A post cap bolt  184  holds the frame ring  178  and the frame  30  down onto the center post  160 . 
     In use, the frame  30  carrying the frame section  28 , as shown in FIG. 2, is bolted onto a center post  160  of a dolly or mobile base via the post cap bolt  184 . Alternatively, if the frame  30  is provided with a center post  160 , as shown in FIGS. 2 and 12, then the center post  160  is securely attached to the dolly or mobile base. The appropriate number of arms sections  22  are then fitted together on either side of the frame  30 , to achieve the desired arm length. Specifically, the pins  54  and  56  are aligned with and moved into the holes  44  and  46 , with adjoining sections moved together until the flat ends touch. The bolts  52  are then turned in to hold adjoining sections together. Due to the flat end surfaces, matching pin and hole contours, and precise machining, even tightening the bolts  52  by hand provides for a rigid arm  20 . However, tightening the bolts  52  with a wrench prevents the bolts from becoming inadvertently loosened. As the frame sections are brought together, the holes in the leveling arm clevis  70  and tab  74  align with each other. Locking pins  114  are inserted through the holes, to securely link the upper and lower leveling rods  64  and  65  of adjoining arm sections  22 , as shown in FIG.  1 . The attachment of arm sections  22  to the frame section  28  is achieved in a similar way, except that the frame section  28  has two female ends. The weight bucket and nose section are attached at opposite ends, in a similar manner. Weights are placed into the weight bucket to balance the arm. 
     In a preferred embodiment, with the arm sections having a height of about 8.2 inches, a width of about 6 inches, a box section wall thickness of about ¼ of an inch, and a moment of inertia I of about 44 inches 4 , each 24 inch arm section weighs about 22 pounds. The arm  20  can therefore be readily assembled by attaching the arm sections to the frame section supported on a dolly or mobile base. Alternatively, multiple sections can first be attached together and then attached to the frame section  28 , although this requires the lifting of greater weight. The outer beams  38  serve as handles for lifting and maneuvering individual arm sections  28 , as well as maneuvering the entire arm  20  during filming. 
     The leveling system is next to the box section and in between the left side outer beams. In this position, the leveling system (i.e., the leveling rods and their supports and attachments) is shielded from damage and abuse (e.g., dropping arm sections), allows for a more compact design, and is out of the way during use. In addition, as the leveling system is well inside of the envelope  79 , the outer beams may be grasped and used as handles away from any potential pinch points. 
     To lock the arm  20  against vertical movement (i.e., pivoting movement about the tilt axle  130 , the tilt brake knob  132  is turned, causing the tilt axle  130  to act as a draw bar and being secured by the axle bolt  156 . Correspondingly, the upper arms  141  and  143  of the frame  130  are moved slightly towards each other, clamping the right spindle  142  against the inner Teflon washer  140  and the upper arm  143 , and at the same clamping the left side of the box section  120  against the disk washer  148  and the leveling rod disk  146 , to the point where friction smoothly resists pivoting movement. When the tilt brake knob  132  is backed off, the clamping force on the frame section  28  is released and the low friction washers  138 ,  140 , and  148  allow the beam  20  to freely pivot vertically. To prevent panning motion, the pan brake handle  168  is similarly tightened, drawing the split ring  164  together and clamping it on the base  162 . 
     FIG. 13 shows an alternative embodiment crane arm  200  having a nose or camera platforms section  201  which provides for improved leveling of the camera, when the camera is mounted on the assembled and balanced arm  200 . As shown in FIG. 13, the nose section  201  has armature  80  and an attaching plate  202  with an upwardly inclined end face pivotably attached to the armature  80 . The line V in FIG. 13 represents the vertical direction. The end face of the attaching plate  202  is at an inclined angle, preferably in the range of 1-3 degrees, and preferably 2 degrees in the embodiment shown. The inclined angle extends to the rear of the crane arm, above the crane arm centerline, so that the camera platform or nose plate is tilted backwards, or in a counterclockwise direction. In other words, the front of the platform is elevated above the back of the platform. 
     As shown ins FIG. 13, the top plate or camera support plate  205  of the nose section  201  is preferably attached at 90 degrees to the side plate  203  of the nose section  201 . A gusset  206  braces the top and side plates  205  and  203  at right angles. As the side plate  203  is clamped flush against the inclined end face of the attaching plate  202 , via the stud  95  and the nut  97 , and locked into a straight up angular position via the dowel pin  107 , the side plate is angled rearwardly at angle I. Correspondingly, the top plate  205  is also inclined rearwardly at angle I. 
     In use, for most filming sequences, the camera  207  (and specifically the camera lens) must be level or horizontal. With the camera  207  attached to the nose section  201  by itself, the camera would be looking up at angle I, instead of being level. However, when the nose section is attached to an assembled camera crane arm, as shown e.g., in FIG. 1, and with the arm balanced using counterweights in the weight bucket  24 , the leveling rods  64  and  65  deflect. The upper leveling rods  64 , in all of the crane arm sections, stretch under the tensile stress of the camera and counterweights. Similarly, the lower leveling rods  65 , in all of the crane arm sections, compress, under an equivalent compressive stress. For a smaller camera crane, of the type shown in FIG. 1, having relatively small leveling rods which are closely spaced together, the deflection can be significant. This deflection of the leveling rods causes the camera support plate  205  to rotate slightly clockwise, typically about 2 degrees. Thus, with the built in incline of the plate  205  in the unloaded condition, the plate moves into a horizontal, or very near horizontal position, when the camera crane arm in loaded and put into use. Consequently, a separate camera leveling head is not needed on the plate  205 . If the mobile base on which the crane is mounted is level, the camera will also be level. This reduces the set up time of the camera on the arm, and the need to provide a leveling head. 
     The preferred 2 degree incline angle is selected based on a median expected number of arm sections and on a median camera payload weight. The incline angle can be adjusted for variations in arm length and/or camera payload weight. To help reduce deflection of the leveling rods  64  and  65 , expanding quick release pins  209 , similar to the pins  78  described above, are used, to take play out of the leveling rod linkages, when the arm is assembled. 
     Referring still to FIG. 13, the height of the side plate  203  is selected so that the center of gravity of the camera  207  is at or near the centerline C of the crane arm. Alternatively, the side plate  203  can have several vertically spaced apart holes, so that use of one of the holes will locate the center of gravity of the camera at or near the arm centerline. Having the camera closer to the crane arm centerline, in contrast to the embodiment shown in FIG. 1, reduces twisting or torquing of the arm, especially during rapid arm movements. The crane arm therefore provides more stable support for the camera. 
     With the camera positioned more centrally relative to the crane arm, crane operation is also improved. For example, if the crane must be maneuvered to move the camera through a window or other opening, there is more clearance around the camera, in all directions. The cross section of camera and crane arm is reduced, as the crane arm falls entirely within the cross section of the camera. This provides greater flexibility of camera movement. 
     Thus, a novel camera crane arm and camera crane arm section having been shown and described. Many changes and modifications can of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be restricted, except by the following claims.