Abstract:
Structural extending members comprising single-tape and composite-tape structures and the means for forming them. Includes tapes with cross sections containing both concave and convex sides facing in the same direction.

Description:
[0001]    This application claims benefit of U.S. Provisional Application 61/637,123, filed on Apr. 23, 2012. 
     
    
     BACKGROUND 
       [0002]    In many circumstances it would be useful to form a relatively long rigid member from a compact source at one end. For example a robotic arm that can transfer parts through vacuum doors in a multiple chamber vacuum system has proven important in the design of the cluster tools used in the integrated circuit manufacturing industry. In the past such devices have used lead screws, pneumatic or hydraulic cylinders, or pantograph type mechanisms to effect their operation. Robotic extension arms are also useful additions to autonomous or remotely controlled robots in a wide range of applications from those used in planetary exploration to those involved in munitions detection and passivation. 
         [0003]    Structural extending members comprising three flexible tapes have been described in U.S. Pat. Nos. 4,625,475; 3,242,576; and 5,056,278. In U.S. Pat. No. 3,242,576, Wheeler describes a rigid extendable measurement device in which three flexible metal tapes are held together at their edges by means of hook-and-loop material to form a rigid structure with a triangular cross section. In U.S. Pat. No. 4,625,475, McGinnis describes an extensible mast, which is erected from a portable base. The mast comprises a plurality of tapes reinforced with a wrap material. In U.S. Pat. No. 5,056,278, Atsukawa describes an extensible pole in which telescoping cylindrical bodies are extended and retracted by means of band-like plates. The band-like plates are held in place within the cylindrical bodies by partition members having guide slits or guide holes to accommodate the band-like plates. None of these disclosures describe retaining rings that are carried on an extendible structure comprising a plurality of tapes. Most relevant to this disclosure, in U.S. Pat. No. 7,891,145, Bobbio describes a number of designs of compound tapes and spooling mechanisms for use as motion effecting elements in robotic systems. 
       SUMMARY OF THE INVENTION 
       [0004]    U.S. Pat. No. 7,891,145 discloses a lightweight long range extending member formed from assembled tapes such as those used in retractable metal measuring tapes which are widely available in a range of lengths (25 ft typical) and widths (1 inch typical). These tapes are wound about a spring loaded spindle that allows for easy retraction. The cross section of the tapes is curved to lend some rigidity during extension. This rigidity is not uniform. Forces that act toward the convex side of the curve easily kink the tape although the tape is much more resistant to forces acting toward the concave side. A typical tape with its concave side facing upwards can be extended horizontally about seven feet before it collapses under its own weight. A tape with its convex side facing up collapses for much less extension. For widths greater than those available with measuring tapes, spring steel is readily available in much larger sizes though it is usually flat. The methods and structures described herein also apply to larger tapes as well as to those with flat cross sections. 
         [0005]    The strength of an extended structure can be greatly increased by forming a composite structure from individual single tapes. This invention describes various composite structures and the means for forming them. In this disclosure the structures and methods described in U.S. Pat. No. 7,891,145 are extended to include tapes whose cross sections contain both concave and convex sides facing in the same direction and which are thus inherently stronger than those described earlier. Because of the enhanced strength such tapes may be used singly as well as in composites with more than one tape. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1A  shows a plan view of a two-tape embodiment of a composite structure whose cross section is corrugated according to the present invention and a mechanism for forming the structure. The drawing shows two tapes but since the cross section of either tape contains both concave and convex regions a single tape may also be used. 
           [0007]      FIG. 1B  is an isometric view of a two-tape structure in  FIG. 1A . 
           [0008]      FIG. 2A  shows an isometric view of a single tape first embodiment of an extending member whose cross section is circular according to the present invention and a mechanism for forming the structure. Again, the circular cross section contains both concave and convex regions. 
           [0009]      FIG. 2B  shows an isometric view of the end of a second embodiment of an extending member whose cross section is circular. 
           [0010]      FIG. 3  is an isometric view of a composite extending member with retaining pieces distributed at intervals along its length. 
           [0011]      FIG. 4  is an isometric view of the two-tape structure in  FIG. 1B  where a pantograph mechanism has been used to distribute retaining parts at intervals along the length of the extended tapes. 
           [0012]      FIG. 5A  is an isometric view of a two- tape structure disclosed in U.S. Pat. No. 7,891,145 where a pantograph mechanism has been used to distribute retaining parts at intervals along the length of the extended tapes. 
           [0013]      FIG. 5B  is an isometric view of the structure shown in  FIG. 5A  with the addition of lateral guides and a termination that facilitates attachment to one of the extended tapes. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]      FIG. 1  shows a first embodiment of this invention. In the mechanism of  FIG. 1  two tapes are simultaneously extended or retracted from the same spool by forces that act in the circumferential direction upon the interior ends of the tapes. The tapes in  FIG. 1  have a corrugated cross section and thus contain both convex and concave portions facing in the same direction and could also be used in a single tape structure. The tapes are joined together outside the spooling structure to form a mechanically robust extending structure.  FIG. 1A  shows a plan view of the interior of mechanism and  FIG. 1B  an overall perspective view. In  FIG. 1A  two metal tapes,  701  and  702 , are wound, overlapping each other, on a spool piece,  703 . The tapes are rigidly fixed to each other and to the periphery of the spool piece using fasteners like small machine screws or a strong adhesive at  704  in the figure. The spool piece,  703 , is fastened to an axle,  705 , that is also connected to some mechanical means (e.g. a motor or hand crank) that can impart rotary motion to the spool piece. Clockwise motion of the spool,  703 , that results in extension of the composite structure is illustrated by a circular arrow in  FIG. 1A . The support structure is composed of seven plates ( 710 ,  720 ,  721 ,  722 ,  723 ,  730 , and  740  in  FIG. 1B ) of a low friction plastic material such as UHMW polyethylene, fluorinated ethylene propylene (FEP), or polytetrafluoroethylene (PTFE). The plates are separated by spacers and held together with fasteners (e. g. machine screws and nuts) through the plates and the centers of the spacers. In  FIG. 1  a typical spacer is shown at  750  and a typical fastener is shown at  760 . All of the plates of the support structure are not the same. Plate  710  simply serves as a low friction retainer for the tapes to bear upon. Plate  740  serves the same purpose as plate  710  but also serves as a mounting plate for the mechanical means that effects the rotary spooling motion. In  FIG. 1B  the mechanical means is an electric motor,  770 , mounted to plate  740 . Plates  720 ,  721 ,  722 ,  723 , and  730  are identical and, in addition to being a part of the support structure, also serve as segmented versions of a low friction compressible layer. The low friction layer is composed of rollers,  725 , that rotate on axles,  726 , supported in frame pieces,  727 . The frame pieces in  FIG. 1  are an integral part of the plates  720 ,  721 ,  722 ,  723 , and  730 . The frame pieces are connected to the rest of the plates,  720 ,  721 ,  722 ,  723 , and  730  by narrow regions, such as  715  in  FIG. 1A , that act as springs and allow the frame pieces and rollers to move in order to accommodate the changing diameter of the coiled tapes,  701  and  702 , as they wind or unwind on the spool piece,  703 . 
         [0015]    In many cases (e. g. small spooling structures and light external loading) the axles,  726 , and rollers,  725 , may be replaced by simple spacers that join plates  720 ,  721 ,  722 ,  723 , and  730  together at the frame pieces,  727 . These frame pieces then contact the tape,  701 , directly and, if they are made of a low friction material, may provide enough friction reduction to eliminate the need of a roller. Similarly, if the tapes are not excessively long and are not heavily loaded in the axial direction toward the spool, rigid roller support plates may be substituted for the compliant plates  720 ,  721 ,  722 ,  723 , and  730  in  FIG. 1B  The two tapes,  701  and  702 , enter or exit the spooling structure though a slot,  780 , in plates  720 ,  721 ,  722 ,  723 , and  730 . If the tapes are of the type used as measuring tapes (thin spring steel) they may be preformed to have a corrugated cross section and will naturally bend into the corrugated cross sectional shapes outside the spooling structure and the cross sections will flatten as they are wound around the spool,  703 . The cross sectional corrugation is shown clearly in the isometric view in  FIG. 1B . 
         [0016]    The support piece,  790 , is attached to plates  710  and  740  and the composite extending structure (formed from tapes  701  and  702 ) passes through it. The support piece in  FIG. 1  is made of a low friction material (e. g. UHMW polyethylene, fluorinated ethylene propylene (FEP), or polytetrafluoroethylene (PTFE)) that does not impede the passage of tapes  701  and  702 . The two tapes that form the composite structure in  FIG. 1  are joined together at the end of the extension using a joining piece,  800 . Because the tapes are rigidly joined at the point labeled  704  in  FIG. 1A  they cannot both be rigidly joined to the joining piece. Each turn of tape  701  on the spool,  703 , is at a larger circumference than the corresponding turn of tape  702 . For a given number of clockwise rotations of the spool,  703 , the left end of tape  701  will move further than the left end of tape  702 . Thus the joining piece is made of a low friction material, such as UHMW polyethylene, fluorinated ethylene propylene (FEP), or polytetrafluoroethylene (PTFE), that allows tape  701  to slide easily through it while tape  702  is rigidly attached to the joining piece using fasteners like small machine screws or a strong adhesive at  810  in  FIG. 1A . Mechanical attachment of an external system to the composite structure may be accomplished by means of a rigid coupling of that system to the joining piece,  800 . If only a single tape is wound around about the spool piece,  703  in  FIG. 1A  the joining piece,  800  would not be required. 
         [0017]    If tapes with preformed cross sections are unavailable, tapes that are inherently flat may also be used. Flat spring steel is readily available in a wide variety of thicknesses, widths, and lengths. In this case retaining parts ( 1710 ,  1720 , and  1730  in  FIG. 3 ) may be used to form and retain the corrugations in the extended tapes as well as to contribute to the assembly if more than one tape is used. The retaining pieces are formed of a low friction material and are provided with slots in the shape of the desired cross section (e.g. corrugations). The retaining parts are not rigidly fixed to any of the flexible tapes but are held in place by friction. They may be moved along the tapes and are positioned at intervals along their length. Three representative retaining parts ( 1710 ,  1720 , and  1730 ) are shown in position in  FIG. 3 . One mechanism (a pantograph) for positioning retaining parts on extending tapes will be discussed in this disclosure. Other mechanisms have been proposed and discussed in U.S. Pat. No. 7,891,145. 
         [0018]      FIG. 2  shows a second embodiment of the invention. In this case the extended cross section is circular and so also contains both convex and concave parts facing in the same direction.  FIG. 2A  shows an isometric view of a spooling structure that is identical to the structure shown in  FIG. 1  except that the support piece,  1790 , is lengthened to allow the substantial deformation required to form the circular cross section from one that is originally flat. Ideally, the cross section of tape,  1700 , would be preformed to be a circle and it would flatten during spooling. On the contrary, if the relaxed shape of the cross section is flat, retaining pieces similar to the ones shown by  1710 ,  1720 , and  1730  in  FIG. 3 , but with circular apertures, might be used. For the circular cross section shown in  FIG. 2A , the included angle from one edge of the tape to the other is  360  degrees. A stronger structure is shown in  FIG. 2B  where the included angle is  540  degrees and the edges of the extended tape  1701  overlap. The additional strength is gained at the expense of a wider tape and larger deformation required in the transition from the spooled to the extended form. In a preferred embodiment the included angle is between  270  and  360  degrees, including the end points. In another preferred embodiment, the included angle is between  360  and  450  degrees, including the end points. In another preferred embodiment, the included angle is between  450  and  540  degrees, endpoints included. 
         [0019]      FIG. 4  illustrates a pantograph mechanism for positioning retaining parts on the tape assembly shown in  FIG. 1B . The mechanism is conventionally composed of bars such as those shown by  1120  and  1130  and pins such as the pin shown at  1110  in the figure. The pins join the bars together in such a way that they may smoothly rotate about the pins. The bars are also joined to low friction retaining pieces (at  1010 ,  1020 ,  1030 , in the figure) by pins such as the one shown by  1140  in  FIG. 4 . Here again, the bars are free to rotate about the pins although the pins themselves are firmly anchored in the retaining pieces. One end of the pantograph is held to the frame of the extension mechanism by pins such as the one shown at  1150  in the figure. The other end of the pantograph is attached to the joining piece  800  which in turn is rigidly attached to one of the plurality of extending tapes such as the one shown by  701 . The other tapes in the plurality, such as  702 , are free to slide through the joining piece  800 . All the tapes in the plurality are free to slide through the retaining pieces ( 1010 ,  1020 ,  1030 ). As the tapes extend, the joining piece  800  is pulled and this, in turn stretches the pantograph along the length of the extended tapes thereby distributing all the retaining pieces along the length.  FIG. 5A  shows the same pantograph mechanism applied to a spooled coiled actuator as described in U.S. Pat. No. 7,891,145 in which two tapes (one concave,  791 , and the other convex,  792 ) are used to form the composite extended structure 
         [0020]    The composite extended structure consisting of one or a plurality of tapes, retaining pieces, and pantograph is significantly more rigid than either the pantograph or extended tapes separately. The separate pantograph flexes substantially and extends out in a bowed way, even when very lightly loaded. The separate tape composites are much less bowed but have a very low torsional spring constant for rotation around the axis of the extended tapes. The tape-pantograph composite ameliorates both issues. Although it should be mentioned that the low spring constant is sometimes an advantage. For example, in applications where the extended end is used to actuate something that has its own mechanical constraints, it allows the extended end to adapt to the constraints but still produce substantial force in the axial direction. 
         [0021]      FIG. 5B  shows the same actuator as  5 A with some practical additions that improve operation and assembly. The actuator shown in  FIG. 5B  is the same as the one in  FIG. 5A  with the addition of two frame extension assemblies ( 1220  ,  1210  and  1225 ,  1215 ), two support elements ( 1230  and  1235 ) and two rigid attachment posts ( 1240  and  1245 ). The extension assemblies are rigid structures containing a slot. The pins attaching the pantograph to the retaining piece  1010  have been modified with the addition of low friction posts or cylindrical rollers ( 1230  and  1235 ) that bear in the slots and provide additional support for the extended composite. It is desirable that the surfaces of the support elements facing the pantograph be low friction. For example, the inner surfaces of aluminum support elements might be covered with thin strips UHMW polyethylene, fluorinated ethylene propylene (FEP), or polytetrafluoroethylene (PTFE). The joining piece ( 800 ) has been provided with two rigid posts ( 1240  and  1245 ) to which the upper tape in the composite ( 791 ) may be securely attached; for example by screw fasteners through tape  791  and into the posts.