Abstract:
A body mounted camera support system for isolating the camera from body motion includes two arms linked together. Each of the arms is a four bar linkage with two tension cartridges each extending between two adjacent ones of the links. Two of the links are extended to form the body of the arm. These links are tubular in cross section and receive the tension cartridge. A single pin, in association with a yoke at one open end of the tubular link, locks the cartridge in place. Each tension cartridge includes a draw bar and a canister with a compression spring operatively positioned therebetween. The spring is adjusted to include shims which bias the bowing of the spring under initial compression load. A PTFE coating on the canister and on the coil spring further reduces friction.

Description:
[0001]    This is a division of U.S. application Ser. No. 09/514,882, filed Feb. 29, 2000, which is a division of U.S. application Ser. No. 08/889,208, filed Jul. 7, 1997, the disclosures of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The field of the present invention is motion isolating systems for mounting devices requiring a stable position.  
           [0003]    In the mid-1970&#39;s, mounting systems were developed for motion picture cameras which were used to mount the camera on the body of an operator. These systems were designed to very substantially isolate the motion of the supporting body from the camera. At the same time, the systems provided suspending support for the camera. The supported camera was capable of being lightly guided by the hand of the operator who could move the camera horizontally in all directions either relative to his body or with his body as he moved about. The camera could also be raised or lowered with a relatively light touch. A number of patents have issued on these early systems. They include U.S. Pat. Nos. 4,017,168; 4,156,512; 4,208,028 and 4,394,075. the disclosures of which are incorporated herein by reference.  
           [0004]    More recently, refinements to such systems have been considered. Of particular interest is the versatility of the equipment to accommodate different amounts of load. A number of possible load requirements may be contemplated. A trial video image may be desired which would require a relatively light video camera. A much heavier film camera might then be contemplated for the actual image production. Accessories such as stabilizing flywheels, batteries, monitors and the like also may be needed for particular sequences. Thus, a range of support forces can be required.  
           [0005]    The performance of such support systems under widely varying load conditions is complex. Through preloading of resilient systems such as springs, the static support weight can be easily accommodated. However, the profile of lifting support across a vertical range of motion can be greatly affected by changes in load. These changes can place the response of the system outside of the acceptable range for operation. Reconfiguration and tuning of the system on location to accommodate such changes in load have been found inconvenient and often unacceptable.  
           [0006]    One mechanism which has been devised for adjusting both the load capacity and the profile of load support with vertical motion is disclosed in U.S. Pat. No. 5,435,515, the disclosure of which is incorporated herein by reference. In this system, the support structure geometry is altered through adjustments to the mountings for the resilient force generating elements.  
           [0007]    The load to be carried typically includes a tube chassis with a camera platform at the upper end and batteries and other elements at the other. The tube chassis has a handle for manipulating the assembly. A three-axis gimbal mechanism is attached to the tube chassis near but above the center of gravity. The gimbal mechanism is supported by the support system. One such assembly including a tube chassis and three-axis gimbal mechanism is illustrated in U.S. patent application Ser. No. 08/746,204, filed Nov. 6, 1996, the disclosure of which is incorporated herein by reference.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is directed to a support system used to isolate motion from the load. Four links are pivotally connected to form a structural, articulated arm. Two opposed links include attachments. The other two links are substantially longer than the links with the attachments. A resilient tension cartridge is held at either end to the linkage with one end pivotally held to one of the links and the other end pivotally held to another link. Multiple such arms may be used with such a system in series.  
           [0009]    In a first, separate aspect of the present invention, the support system is arranged with one of the tension cartridge ends being pivotally held to a first link longitudinally outwardly of the pivots of that link. The second end of the tension cartridge is pivotally held to a second link which is pivotally joined to the first link. The tension cartridge thus operates outside of the adjoining pivot between the two links. In this way, a high spring rate on the tension cartridge and substantial moment arm variation on the tension cartridge can be effected in a small area.  
           [0010]    In a second, separate aspect of the present invention, the tension cartridge includes a canister with a draw bar extending from the canister. A compression spring within the canister is operatively arranged between the draw bar and the canister. Use of a compression spring substantially shortens the cartridge and enables it to be used in association with two adjacent links to take advantage of the high spring rate.  
           [0011]    In a third, separate aspect of the present invention, the tension cartridge of the second aspect further includes shims which may be empirically associated with the compression spring to control initial compression forces to avoid substantial bowing. A polymeric anti-friction coating such as PTFE on the inside of the canister as well as such a coating on the spring may be employed to reduce friction, noise and wear in tension cartridge operation.  
           [0012]    In a fourth, separate aspect of the present invention, at least one of the longer links includes a tubular body in cross section with an open end. The tension cartridge extends through this tubular body. This arrangement allows the cartridge(s) to be adjusted for pretension or easily replaced to accommodate substantial changes in the weight of the load. The tubular body and the associated attachment arrangement contributes to torsional rigidity as well.  
           [0013]    In a fifth, separate aspect of the present invention, a method for reducing friction in a compression spring canister is contemplated. A spring is compressed to observe the direction of lateral bow induced in the spring with compression. One or more shims are added to the end or ends of the spring to resist the bowing under initial compression. The ends of the spring and shims are then effectively nonparallel in the relaxed state. The spring is then introduced into the canister.  
           [0014]    In another, separate aspect of the present invention, the combination of any two or more of the foregoing aspects are contemplated to be employed in concert. Further, the use of multiple tension cartridges with an arm and multiple arms linked together are contemplated.  
           [0015]    Accordingly, it is an object of the present invention to provide an improved isolating support system and components therefor. Other and further objects and advantages will appear hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a side view of a body mounted camera support system shown in the unloaded state with one tension cartridge illustrated in each arm.  
         [0017]    [0017]FIG. 2 is a cross-sectional side view illustrating the system of FIG. 1 with the extended links in cross section to illustrate the placement of tension cartridges.  
         [0018]    [0018]FIG. 3 is the system of FIG. 1 slightly rotated for clarity.  
         [0019]    [0019]FIG. 4 is the system of FIG. 1 illustrated through a substantial rotation for clarity.  
         [0020]    [0020]FIG. 5 is a partial cross section of a pivot between links.  
         [0021]    [0021]FIG. 6 is a perspective cross section of a tension cartridge.  
         [0022]    [0022]FIG. 7 is a perspective view of a shim.  
         [0023]    [0023]FIG. 8 is a perspective cross-sectional view of the shim of FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    Turning in detail to the drawings, a body mounted camera support system is illustrated which includes two arms, generally referred to as  10  and  12 . The arms  10  and  12  are pivotally joined through a link  14 . A body mount  16  is associated with one end of the arm  10 . The body mount  16  is intended to be attached to a harness which is positioned on the chest of the camera operator. Such harnesses are commercially available. At the other end of the assembly, a special camera attachment  18  is integrally formed with part of the arm  12 . Any or all of links  14 ,  16  and  18  may include a split clamp or other known device for association with an adjacent pin or member to introduce drag or even locking with the adjacent assembly. In place of or in addition to drag, a return spring may be employed to bias the links to neutral positions.  
         [0025]    Looking to the arms  10  and  12 , the arms are substantially identical with the exception of the camera attachment  18  and certain dimensional changes discussed below. Reference will be made solely to the arm  10  except in these respects. The arm  10  includes two attachment links  20  and  22  and two tubular links  24  and  26 . The attachment links  20  and  22  are identical as are the tubular links  24  and  26 . These four links  20  through  26  are pivotally joined together at pivots  28 ,  30 ,  32  and  34 . The links  20  through  26 , along with the pivots  28  through  34 , define a four bar to linkage which is a parallelogram. The overall structure is preferably of light structural material such as aluminum.  
         [0026]    Each of the links  20  and  22  defines four pivot axes. Three of these axes are parallel while the fourth is at right angles to the other three. On the link  20 , two of the axes locate the axes of the pivots  28  and  30 . Similarly, on link  22 , these axes locate pivots  34  and  32 . Another axis on each of these links defines an attachment point for one end of a tension cartridge. In each case, this axis is defined by a clevis hitch including lugs  36  and  38  for attachment of the tension cartridge by a pin  40 . The pin  40  is a bolt with a smooth shank and a threaded end to receive a nut or to thread directly into the lug  38 . The threads are preferably fine to contribute a self locking character. Another set of clevis lugs  42  and  44  defines the axis at right angles to the other three axes. A clevis pin  46  cooperates with the lugs  42  and  44  to define an attachment to which the body mount  16  or the link  14  may be pivotally associated. The clevis pin  46  includes a head  47 , a smooth shank  48  and a threaded end  49 . The smooth shank  48  provides a bearing surface to pivotally engage the two lugs  42  and  44  and holes on the split ends of the body mount  16 . The link  22  is inverted in its orientation on the arm as compared with the link  20 . However, it is configured to accommodate the pin  46  in the upright orientation. This is intended for ease of assembly.  
         [0027]    The tubular links  24  and  26  are identical. Each includes open ends to receive a tension cartridge at one end and to receive the lugs  36  and  38  associated with the links  20  and  22  at the other. At the pivots  28 ,  30 ,  32  and  34 , the tubular links  24  and  26  extend longitudinally to pairs of wings  52 . These extensions  52  provide operatively elongated links and also provide a wide mounting arrangement to enhance the stability of the pivots  28  through  34 . Naturally, the tubular structures themselves provide substantial torsional resistance relative to their weight.  
         [0028]    Looking specifically at FIG. 5, the pivot  28 , representative of the pivots  28 ,  30 ,  32  and  34 , includes a horizontal pin  53  extending across the pair of wings  52  at the open end of the tubular link  24  adjacent the attachment link  20 . A horizontal pin cap  54  receives the pin  53 . Both are inset in the wings  52  to avoid obstructions on the outside of the arm which could interfere with use of the system. Both the head of the pin  53  and the cap  54  are arranged to transfer compression to the wings  52  when the pin  53  is tightened in place. The attachment link  20  includes floating bearings  55  aligned to receive the pin  53 . A bearing spacer  56  is located between the bearings  55 ; and thrust washers  57  are placed outwardly of the bearings  55 . As the pin  53  is tightened, the entire assembly is brought into compression. In this way, the pivot is stabilized. Further, the tubular link  24  is strengthened against torsional loads as the wings  52  are unable to move relative to one another.  
         [0029]    A tension cartridge, generally designated  58 , is located in one of the two tubular links  24  and  26 . A second cartridge  58  may be similarly located in the other of these tubular links depending upon the load carried by the camera mount  18 . The tension cartridges  58  act cumulatively with one another in each arm. Cartridges  58  of varying spring rate may be selected to accommodate a range of mounting loads. Combinations of cartridges  58  of different spring rates can also be used to provide a variety of load weight ranges for the arm. The same combination of cartridges  58  is preferably used in both arms  10  and  12  to obtain a uniform response from the overall support system.  
         [0030]    A tension cartridge  58  is best illustrated in FIG. 6. The cartridge includes a tubular canister  60 . The canister  60  is threaded at each end to receive two end caps  62  and  64 . The interior wall  66  of the canister  60  is provided with a polymeric anti-friction coating such as PTFE. Located within the tubular canister  60  is a draw bar  68 . The draw bar extends from the end of the canister  60  to an eye  70 .  
         [0031]    The draw bar  68  is divided into two assemblies  72  and  74 . The assembly  72  includes a threaded nut  76  fixed to a hollow tube  77 . A threaded shaft  78  on the assembly  74  mates with the threaded nut  76 . Rotation of the shaft  78  relative to the nut  76  lengthens or shortens the draw bar  68 . The shaft  78  is rotatably mounted relative to a hub  80 . This hub  80  includes an outwardly extending flange  82 . The hub  80  and flange  82  are slidably arranged within the canister  60  and can move through the canister  60  either as part of an adjustment through rotation of the threaded shaft  78  or through extraction of the draw bar  68  by force applied to the eye  70 . Adjustments are made through the end cap  64 . A passage  84  extends inwardly through the end cap  64  to a hexagonal socket associated with the head  86  of the threaded shaft  78 . Insertion of a hexagonal wrench through the passage  64  to engage the head  86  to rotate the shaft  78  effects adjustment of the draw bar  68 . An elastomeric cover with a slit may be used at the entrance to the passage  64  to avoid contamination of the interior of the cartridge  58 .  
         [0032]    The end cap  62  includes an annular cavity  88  to define a spring seat in opposition to the spring seat defined by the flange  82  on the hub  80  of the draw bar  68 . A draw bar bearing  90  is positioned inwardly of the annular cavity  88  to accommodate axial motion of the draw bar  68  therethrough. An annular seat  92  is also provided on the end cap  62 . This seat  92  cooperates with a stack of conically shaped spring washers  93  associated with the nut  76  around the draw bar  68 . A cushion is thus defined for reducing the impact when the tension cartridge  58  reaches its limit.  
         [0033]    A compression spring  94  is located within the tubular canister  60  and is operatively positioned between the canister  60  and the draw bar  68  by locating the ends of the spring  94  in the annular cavity  88  and against the flange  80 . This spring is preferably a coil spring coated with a polymeric anti-friction coating such as PTFE in order that it might experience low friction, low noise and low wear in movement across the interior wall  66 , also coated with PTFE.  
         [0034]    A stop  96  is provided on the second assembly  74  of the draw bar  68 . This stop  96  cooperates with a seat  98  on the first assembly  72  to limit preload adjustment. The stop  96  is positioned such that the spring  94  is not fully compressed upon full extension of the tension cartridge  58  with maximum pretensioning. In this way, the compression spring cushion  93  is not defeated.  
         [0035]    The spring  94  is assembled with shims  100  as seen in FIGS. 7 and 8. These shims  100  are circular and have end surfaces which are not parallel. The shims  100  are located at the ends of the spring  94  in a preassembly set of aligned spring seats. The end caps are drawn together to observe bowing within the spring  94 . Once observed, the shims  100  are rotated relative to the spring  94  until bowing is minimized. At this point, the shims  100  are tacked to the spring  94 . A notch  102  in the shim  100  is simply an indicator of the point of maximum thickness on the shim  100  to assist in orientation during empirical testing. Thus, the assembly of the shims  100  and the spring  94  does not have parallel ends when fully relaxed. The spring  100  is then placed in a cartridge  58 .  
         [0036]    A phenomenon is being employed through the use of the shims  100 . It has been observed that a substantial lateral force of bowing exists with the spring  94  moderately compressed. As the spring  94  becomes more severely compressed, the lateral force of bowing decreases greatly. Thus, control of bowing under moderate compression through the use of the shims  100  is sufficient to greatly reduce the side load resulting in rubbing friction between the spring  94  and the interior wall  66  of the canister  60 . Under greater compression, the side loads are sufficiently low that excessive rubbing is not experienced. In spite of the relative length to diameter of the relaxed spring  94 , which is 6.1:1 in the heaviest spring and 5.2:1 in the lightest as employed in the embodiment, the spring  94  and canister  60  exhibit little wear from rubbing because of bowing under these constrained conditions. The load characteristics of the system depend on the tension cartridges  58 . Two adjustments can be effected for establishing these characteristics. First is the selection of the cartridges  58 . Second is the pretensioning of the cartridges  58  selected. In each arm  10  and  12 , one or two cartridges  58  may be used. As noted above, the cartridges  58  in each arm act cumulatively.  
         [0037]    The spring constants of the cartridge or cartridges  58  are selected to provide a certain range of capacity to each arm  10  and  12 . These cartridges  58  are then adjusted for preload as noted above so that a neutral position is established at the preference of the operator. To provide convenient flexibility, the cartridges  58  are easily replaced. To this end, the cartridges  58  include trunnions  104  on the end cap  64 . The tubular links  24  and  26  provide an open end for receipt of the tension cartridge  58 . Recesses  106  are formed into this open end to receive the cartridge trunnions  104 . The pin  40  is then positioned through the eye  70  of the draw bar  68  and the clevis lugs  36  and  38  of the link  20  and secured. The tubular links  24  and  26  include access holes  108  for placement of the pin  40 . The appropriate camera or other load is then positioned through the camera attachment  18  on the second arm  12 . The attachment  18  is shown to have two vertically oriented holes  110  for receipt of a camera mounting gimbal assembly or the like. Any appropriate attachment may be used depending on the configuration of the load attachment.  
         [0038]    The arm  10  is to support the arm  12  as well as the camera and equipment load. It is possible to create substantially the same response in both arms  10  and  12  by increasing the capacity of the tension cartridges  58  in the arm  10 . This would make the necessary cartridge sets different for each arm  10  and  12 . Instead, the cartridges  58  remain interchangeable between arms  10  and  12 . To obtain this result, the attachment points at the pin  40  on the attachment links  20  and  22  are at different locations on each arm. On the arm  10 , the pin  40  is located 1.10 inches beyond the pivot axis of the pivot  28  as measured along the pivot plane of the link defined by the axes through the pivots  28  and  30  and 0.135 inches laterally of that plane in a displacement away from the tubular link  24 . On the arm  12 , the corresponding dimensions are 1.03 inches and 0.120 inches, respectively. The offset laterally of the pivot plane of the link affects “operator input” which is the load profile as the mount moves vertically.  
         [0039]    The spring constants in the cartridges  58  are high. Spring constants in the range of 48 pounds per inch to 60 pounds per inch are employed in the embodiment. Use of such stiff springs results in the cartridges  58  being quite compact. This allows the cartridges  58  to extend along a single link and fit within the tubular body thereof. A spring diameter of 1.70 inches is contemplated with relaxed spring lengths of 10.37 inches for a heavier spring to 8.84 inches for a lighter spring. In turn, two lifting triangles are able to be associated with each arm and the assembled arms have a smooth and compact profile.  
         [0040]    To accommodate a high spring constant with the tension cartridges  58 , the distance between, for example, the pivot  28  and the line between the pivot attachments at  40  and  104  of the tension cartridge  58  is designed to be small. This distance is a maximum of 1.11 inches for the arm  10  and 1.04 inches for the arm  12  in the current design. The moment arm resulting from the weight of the load is at a maximum with the arm  10 ,  12  extending in a horizontal orientation. Consequently, the distance between the pivot  28  and the line of action of the tension cartridge  58  is at a maximum with the arm at or near horizontal depending on the lifting profile desired. The length of the tubular link  24  between pivots  28  and  32  is 9.25 inches.  
         [0041]    The higher spring constant also contributes to greater latitude in adjustment. By having a high spring constant, smaller changes in precompression of the spring effect the same change in preload. Lower spring constants make a lower slope on the lifting profile easier to achieve. However, other of the foregoing features would require compromise. Even so, a lifting profile having about three pounds of up force at the lower extreme and the same down force at the upper extreme has been achieved. This profile varies across the load range accommodated by adjustment of the cartridges  58  by no more than about a pound either way. With two of the heavier spring cartridges  58  used per arm  10 ,  12 , such a range of lifting profiles is achieved for a load range of 50 pounds to 72 pounds. With the lighter spring cartridges  58 , a load range of 29 pounds to 55 pounds is similarly accommodated. As noted above, only one cartridge  58  need be used. With one heavier spring cartridge  58 , the range is 24 pounds to 34 pounds. With one lighter spring cartridge  58 , the range is 13 pounds to 24 pounds. Additionally, a spring index of from 6.14 to 6.80 has been found to provide sufficient maximum load and load adjustment.  
         [0042]    Accordingly, an improved body mounted camera support system is disclosed. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.