Abstract:
A skate truck for interposition between two mutually facing parts of a flexible cable guide is composed of plural skate units interconnected to one another by interconnecting members that allow both vertical articulation and lateral movement of the skate units relative to the interconnecting members and relative to adjacent skate units.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority on the basis of Japanese patent application 2006-153741, filed Jun. 1, 2006. The disclosure of Japanese application 2006-153741 is hereby incorporated by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates generally to cable protection and guide devices, hereinafter referred to for brevity as “cable guides,” for protecting and guiding flexible cables. More specifically, the invention relates to an improved rolling skate truck, composed of a plurality of interconnected skate units, for interposition between two mutually facing parts of a folded cable guide in order to promote smooth flexing movement of the cable guide, and to prevent damage resulting from frictional contact or collision between the parts, and thereby extending the useful life of the cable guide. 
       BACKGROUND OF THE INVENTION 
       [0003]    The term “flexible cable,” as used herein, means any flexible, elongated, energy or fluid-conducting device, such as a cable composed of one or more electrical wires or optical fibers, a fluid-conducting hose for conducting compressed air or a hydraulic fluid used as a medium for transmission of motive power, a flexible conduit used to convey a gas, a liquid, or another fluid material for use in a machine or industrial process, a flexible actuator such as a Bowden wire, or a flexible rotating shaft with or without a non-rotating sheath. Such flexible cables are used, for example, to connect relatively moving parts of a machine such as a machine tool, an industrial robot, or a conveyor or other material-handling or material-carrying machine, such as a hoist or other machine used in a civil engineering application. 
         [0004]    When a flexible cable is connected to a moving part, torsion, flexion, and tensile forces applied to the cable as a result of movement of the moving part can result in damage to, or distortion of, the cable, and interfere with smooth movement of the cable and of components connected to the cable. Cable guides have been used to avoid damage and distortion of the cables, and to promote smooth movement. 
         [0005]    A typical cable guide G is shown in  FIG. 6 . The guide is composed of a plurality of flexibly interconnected links forming an elongated channel though which a cable C extends. The guide, which has a fixed end part G 1 , a movable end part G 5 , and an intermediate folded part G 3 , is configured so that a lower part G 2  of the guide is in mutually facing, opposed, relationship to an upper part G 4  of the guide. The particular links which constitute the folded part G 3 , of course, depend on the relationship between the upper part and the lower part. 
         [0006]    Each of the links of the cable guide comprises a pair of side plates Ga disposed on opposite sides of the cable C and a pair of connecting elements Gb, bridging the side plates, one plate Gb of each link being on the outer side of the cable, i.e. on the top side of the upper part, the bottom side of the lower part or the outer side of the folded part. The side plates are hinged to one another so that the guide can bend at least in a single plane, and, preferably, the side plates are configured to limit flexion of the guide to a specific minimum radius of curvature in order to avoid kinking of the cable C. 
         [0007]    Where a cable guide of sufficient length is folded on itself, it is possible for two portions of the guide to come into face-to-face contact with each other. Friction between the contacting parts of the guide can obstruct smooth reciprocating motion. Moreover, frictional contact over time can cause wear and eventual breakage of the cable guide. Breakage can also result from interference between projecting portions of the two facing parts of the guide. 
         [0008]    Skate trucks, such as skate truck  400  in  FIG. 7 , have been used to avoid contact between the mutually facing parts of a folded cable guide. The skate truck  400  of  FIG. 4  is sandwiched between the lower parts G 2  and the upper parts G 4  of two cable guides. A typical skate truck is described in United States Patent Application Publication No. 2005/0155337, published on Jul. 21, 2005. 
         [0009]    The conventional skate truck  400  of  FIG. 7  is composed of a number of connected skate units  410 , as shown in  FIG. 8 . Each skate unit  410  includes four rollers  412 , sandwiched between upper and lower parts of the cable guide, a first pair of rollers being rotatably mounted disposed on a left frame member  413  on one side of the skate unit and a second pair of rollers being rotatably mounted on a right frame member  413  on the opposite side of the skate unit. Connecting blocks  414 , which join the adjacent truck units in series, keep the right and left frame members  413  at the required spacing from each other. As shown in  FIG. 8 , the frame members  413  are rigidly secured to the connecting blocks by bolts  415 , which are threaded into threaded holes in the connecting blocks. 
         [0010]    Since the adjacent skate units  410  are rigidly secured to the connecting blocks by bolts  415 , the skate truck is unable to adapt to flexion of the cable guide in the vertical direction. Nor is it able to adapt to snaking movement of the cable guide in horizontal directions transverse to the direction of advancing movement of the skate truck. Thus, when horizontal or vertical flexion of the cable guide occurs, excessive force can be generated in the skate units  410 , resulting in deformation or damage to the cable guide. 
         [0011]    Accordingly, an object of this invention is to provide a skate truck having flexibility, enabling it to adapt smoothly to vertical movements of a cable guide as well as to lateral horizontal movement of the cable guide relative to the direction of movement of the skate truck. 
       SUMMARY OF THE INVENTION 
       [0012]    The skate truck according to the invention comprises a plurality of skate units. Each skate unit comprising a frame and a plurality of rollers. The rollers are rotatably mounted on the frame on parallel horizontal axes for rolling contact with mutually facing parts of a cable guide. The skate units are connected to one another in a series extending along a direction of elongation by connections which allow both vertical articulating movement of the skate units relative to one another, and horizontal lateral movement of the skate units relative to one another in directions transverse to the direction of elongation of the skate truck. 
         [0013]    Preferably, the adjacent skate units in the series are joined by connectors, and the skate units joined by each connector are both capable of vertical articulating movement relative to the connector, and also capable of horizontal lateral movement relative to the connector. 
         [0014]    The skated units preferably comprised frames having side members maintained at a predetermined spacing from each other. The connectors can have different forms, and can comprise connecting blocks, for example, or sets of connector plates. 
         [0015]    Where the connectors comprise connecting blocks, the widths of the connecting blocks are less than the spacing between the side members of the frames of the skate units. Because of the difference between the widths of the blocks and the spacing of the side members, gaps are provided which allow relative lateral movement of the connecting blocks and their adjacent skate units. The side members of each of said adjacent skate units can be connected by rods which extends through the connecting blocks. Alternatively, cantilevered rods fixed to the connecting blocks can extend laterally therefrom and slidably through holes in the side members of adjacent skate units. 
         [0016]    In the case where connector plates are used, the side members of each of the adjacent skate units in the series on one side of the skate truck are joined by connectors, and the side members of adjacent skate units in the series on the opposite side of the skate truck are also joined by connectors. Each of these connectors comprises a pair of connector plates spaced from each other. The side members joined to each other by each connector extend into the space between the plates thereof, and a pair of pins extends through both plates of each connector. Each pin of the pair also extends through one of the side members joined by the connector. Each of the connecting pins is slidable in at least one of the connector plates and side member through which it extends. So long as both pins of each connector are not rigidly connected to both of the connected side members and also to a single connector plate, the joined side members are laterally movable relative to each other and therefore the joined skate units are movable laterally relative to each other. 
         [0017]    The skate truck can flex in the vertical direction, and the connected skate units can move relative to one another laterally. The skate truck can assume a zigzag shape in the vertical direction to accommodate flexion of the portion of the cable guide extending between the bend of the cable guide and the movable end of the guide. Furthermore, horizontal relative movement of the skate units can accommodate snaking of that portion of the cable guide. Thus, strain in the cable guide, and in the skate truck, is avoided, deformation and damage to the skate units can be prevented, and the burden of maintaining the skate truck and of the cable guide is significantly reduced. 
         [0018]    Where connecting blocks are used, the gaps between the connecting block and the side members of the skate unit frames allow lateral movement of the skate units relative to the conneting blocks and relative to one another. Where connectors comprising pairs of connector plates and pins are utilized, the skate units can shift laterally relative to one another with limits determined by the lengths of the pins. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic elevational view showing a use skate truck according to the invention in use between upper and lower mutually facing parts of two cable guides, and including an enlarged view of a portion of the skate truck; 
           [0020]      FIG. 2  is a top plan view of a portion of the skate truck shown in  FIG. 1 , and includes an enlarged view of a portion of the skate truck; 
           [0021]      FIG. 3  is a cross-sectional view taken on section plane III-III of  FIG. 2 ; 
           [0022]      FIG. 4  top plan view of a portion of a skate truck in accordance with a second embodiment of the invention, and includes an enlarged view of a portion of the skate truck; 
           [0023]      FIG. 5  is a top plan view of a skate truck according to a third embodiment of the invention; 
           [0024]      FIG. 6  is perspective view of a cable guide; 
           [0025]      FIG. 7  is schematic side elevational view of a conventional skate truck used to prevent direct contact between upper and lower parts of pair of cable guides, and including an enlarged view of a portion of the cable guide and skate truck assembly; and 
           [0026]      FIG. 8  is a top plan view of a conventional skate truck. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    The skate truck  100 , shown in  FIG. 1 , cooperates with a pair G of opposed cable guides. Each of the two cable guides corresponds to the cable guide depicted in  FIG. 6 , and comprises a series of articulably interconnected links, each link comprising a pair of side plates Ga disposed on both sides of a cable C and connecting elements Gb, bridging the side plates, one plate Gb of each link being on the outer side of the cable, i.e. on the top side of the upper part, the bottom side of the lower part or the outer side of the folded part. The side plates are hinged to one another so that the guide can bend at least in a single plane, and, preferably, the side plates are configured to limit flexion of the guide to a specific minimum radius of curvature in order to avoid kinking of the cable C. 
         [0028]    The cable C can be any flexible cable such as an electric cable, optical fiber cable, mechanical drive, fluid supply hose or the like, or a plurality of electrical conductors, fiber cables, hoses, etc. or combinations thereof. The cable is safely and reliably protected and guided, while it is being moved, because the cable is disposed within a the guide, and the folded portion of the cable is situated with a folded part G 3  of the guide, situated between a fixed end G 1  and a movable end G 5 , as shown in  FIGS. 1 and 6 . 
         [0029]    The skate truck  100  comprises a plurality of skate units  110 , connected to one another. The skate truck cooperates with the pair of cable guides, and moves on the lower portions of the cable guides, while the upper portions of the cable guides are in engagement with, and move on, the skate truck. Thus, the skate truck is disposed on inner side of folded parts of the cable guides. As the movable ends G 5  of the cable guides move back and forth, i.e., from left to right and from right to left in  FIG. 1 , the skate truck  100  travels in the same direction as the direction of travel of the movable ends of the cable guides, but at half the speed, and through only half the distance. The skate truck prevents mutual contact between the lower portions G 2  and the upper portions G 4  of the guides. 
         [0030]    As shown in  FIGS. 1 to 3 , each of the skate units comprises a frame having side members  111  on which plurality of rollers  114  are mounted rotatably. These rollers  114  are sandwiched between the lower and upper parts G 2  and G 4  of the cable guide. Connecting blocks  112 , each having a U-shaped cross-section and being preferably formed of sheet steel, are disposed between the side members adjacent the ends thereof, and each connecting block  112  extends between the side members  111  of two adjacent skate units. A connecting rod  113  is inserted through holes formed in the side members and extends through holes formed in the upright side walls of the U-shaped connecting blocks. The rods are secured by screws  116 , which extend through washers  115  on both ends of the connecting rods  113 , thereby establishing a maximum spacing between the side members  111  of each skate unit. The side members are held apart from each other by lateral connecting members also shown in  FIG. 2 . 
         [0031]    As shown in  FIG. 2 , the connecting rods can rotate in the openings of the side walls of the connecting blocks  112 . The rotatability of the connecting rods in the side walls of the connecting blocks allows flexion of the skate truck in the vertical direction. The enlargement portion of  FIG. 2  shows that gaps X are provided between the connecting blocks  112  and the side members  111 . Since the connecting blocks are free to move along the connecting rods within the ranges defined by gaps X, lateral movement of the skate units relative to the connecting blocks, and therefore, lateral movement of the skate units relative to one another, is permitted. Thus, in the skate truck  100 , of the embodiment shown in  FIGS. 1 ,  2  and  3 , the connection of the skate units to one another, which is indicated generally by the letter J, allows mutual flexion of the skate units  110  in the vertical direction (that is, the vertical direction in  FIG. 1 ), and relative horizontal, lateral movement of the skate units with respect to the general direction of movement of the skate truck  100 . 
         [0032]    Whereas, in the case of a rigid skate truck, vertical movement of the folded part G 3  of the cable guide, and of the movable end portion G 5  of the cable guide, could exert a strain tending to damage the cable guide, the vertical movement can be accommodated by the ability of the skate units of the skate truck to articulate relative to one another in the vertical direction. Because adjacent skate units are joined by connectors to which both of the adjacent skate units are pivoted, the skate truck can even assume a zigzag configuration (in side elevation), if necessary. Thus, damage to the cable guide due to vertical flexing movement can be prevented. 
         [0033]    Furthermore, even if snaking, i.e. lateral flexion, occurs in the upper part G 4  of the cable guide, i.e. the part between the folded part G 3  and the movable end G 5 , the lateral flexion is accommodated by horizontal relative movements of the skate units and their connecting blocks within the range afforded by gaps X. Consequently, the skate truck exhibits lateral flexibility as well as vertical flexibility. Therefore, the skate truck, by virtue of its flexibility can prevent damage to the cable guide as well as damage to itself due to excessive deformation. The flexibility of the skate truck also makes it possible to carry out maintenance of the cable guide and the skate truck more easily, since the skate units can be more easily moved both laterally and vertically. 
         [0034]    In a second embodiment of the invention, shown in  FIG. 4 , a skate truck  200 , which is used with a cable guide in the same manner as the skate truck of the first embodiment, is composed of a plurality of skate units  210  connected to one by connections J, which allow flexion of the skate truck in the vertical direction, and also allow relative lateral horizontal movements of the skate units. 
         [0035]    Rollers  214  are rotatably mounted on side members  211  of the skate units  210 , and these rollers are sandwiched between the lower and upper parts of the cable guides. The connecting blocks  212  are provided with cantilevered shafts which extend through holes formed in the side members of the skate units. The cantilevered shafts are constituted by unthreaded cylindrical portions of the shanks of bolts  213 , which are threaded into the connecting blocks  212 . The heads of the bolts are spaced from the sides of the connecting blocks, and the side members  211  of the skate units are not only rotatable about the bolts but also movable laterally along the bolts. The distance between the heads of the bolts and the sides of the connecting blocks is such that a gap X is provided, as shown in the enlarged part of  FIG. 4 , allowing for limited lateral movement of the skate units relative to the connecting blocks and relative to one another. The length of the gap X is equal to the difference between the length of the cylindrical portion of a bolts and the thickness of a side member of a skate unit. 
         [0036]    In the embodiment of  FIG. 4 , as in the first embodiment, vertical flexion and snaking are accommodated, and maintenance is facilitated, by the ability of the skate truck to flex vertically and by the ability of the skate units to move laterally relative to one another. 
         [0037]    In a third embodiment, as shown in  FIG. 5 , a skate truck  300  is composed of a plurality of skate units  310  connected to one another by connections J, which allows vertical flexion of the skate truck as well as relative lateral horizontal movement of the skate units. 
         [0038]    Rollers  314  are mounted rotatably on side members  311  of the skate units  310 , and are sandwiched between upper and lower parts of folded cable guides as in the previously described embodiments. Adjoining skate units are connected by two pairs of plates  312 . The plates  312  of a first pair are disposed on opposite sides of left side members  311  of two successive skate units, and plates  312  of a second pair are disposed on opposite sides of the right side members  311  of the same two successive skate units. The plates  312  of each pair are joined by two connecting pins  313 , which extend loosely through holes in the side members in these members. Split pins  315  are used to prevent the plates  312  from becoming disenaged from pins  313 . The connecting pins  313  allow the adjoining skate units to articulate vertically relative to each other, and the positions of the split pins are such that the ajoining skate units can move laterally in a horizontal direction relative to each other by an amount corresponding to the gap X described with reference to the first and second embodiments. 
         [0039]    In the embodiment of  FIG. 4 , as in the first and second embodiments, vertical flexion and snaking are accommodated, and maintenance is facilitated, by the ability of the skate truck to flex vertically and by the ability of the skate units to move laterally relative to one another.