Patent Publication Number: US-8109493-B2

Title: Automated truss assembly jig setting system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Application No. 60/804,244, filed Jun. 8, 2006 and entitled Automated Truss Assembly Jig Setting System, the entirety of which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to assembling trusses and more particularly to an automated truss assembly jig setting system. 
     BACKGROUND OF THE INVENTION 
     Prefabricated trusses are often used in the construction of buildings because of their strength, reliability, low cost, and ease of use. An increase in the use of more complex and varied trusses, however, has created manufacturing problems and increased production times. 
     Trusses are generally assembled on a jigging table. Jigging tables typically have a plurality of adjustable stops, or pucks, for indicating the proper positions of the elements of a truss and for holding these elements in position until they can be permanently secured together. The pucks must be repositioned on the jig surface for each different truss. Computer programs generally calculate the position of the pucks from a reference line, such as the edge of the table. Conventionally, an operator would measure the positions of the pucks from the reference line, manually move and secure the pucks into the desired positions, place the truss elements on the table against the pucks, fasten them together, remove the completed truss, and then repeat. Due to great variation and complexity in modern truss designs, a significant amount of production time is spent resetting the positions of the pucks and there is a high likelihood of operator error. Various approaches have been developed to enhance this process. 
     One method that has been developed to increase production efficiency in truss assembly is laser projection. This approach projects the image of a desired truss in actual shape and size onto a jig table. The pucks of the jig table are then simply moved to their corresponding locations as indicated by the laser projection. This minimizes or eliminates the measurement time needed with conventional systems and ensures accurate placement of the pucks. Known laser truss assembly systems are disclosed in U.S. Pat. No. 5,430,662 to Ahonen, U.S. Pat. No. 6,317,980 to Buck and U.S. Pat. No. 6,170,163 to Bordignon et al, which are hereby incorporated by reference. However, these types of systems do not eliminate the need to repeatedly secure and loosen the pucks for each truss design. Although effective in increasing the correctness of assembled trusses, the time it takes for an operator to manually position the pucks with their corresponding projected image is significant. 
     Another approach employs a system that automatically moves the pucks along the surface of the jig. Such systems are disclosed in U.S. Pat. No. 5,854,747 to Fairlie, U.S. Pat. No. 6,712,347 to Fredrickson et al, and U.S. Pat. No. 5,342,030 to Taylor, which are hereby incorporated by reference. The goal of such systems is speed and efficiency greater than prior systems such as manual jig tables and laser projection. For example, the &#39;347 patent criticizes prior laser projection systems as being too slow and expensive. While these systems may speed up the process, they tend to suffer reliability and consistency issues. Because trusses are often made from wood, sawdust and wood chips often pile up on the jigging table. This debris can fall into the slots in which the pucks move, hampering or preventing the pucks from reaching their proper position or preventing the pucks from being properly secured. An operator assembling a truss based on faulty positioning caused by one of these problems may fail to notice when one of the pucks is not in its proper place, possibly leading to an entire batch of improperly aligned trusses. In addition, any error by the software or hardware system controlling the pucks is not likely to be caught by an operator as there is nothing to indicate that there are pucks that are not properly aligned. 
     Existing jigging tables are not readily modifiable to laterally move the puck slots with respect to the overall table. Instead, the slots and the associated pucks are formed integrally with the table and cannot be readily moved. Thus, the flexibility of the table is restricted. Moreover, in known dual puck systems, the two pucks cannot pass each other. 
     Further, although speed and efficiency can be increased with use of such an automated truss assembly table, it often requires a large initial investment to completely replace all existing manual equipment for the automated equipment and a significant prior capital expenditure is wasted in discarding the previously used tables. Accordingly, it would be desirable to be able to easily convert a manual truss assembly table into an automated truss assembly table. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a plank unit for use with a truss assembly jigging table generally comprises a plank having a generally planar top surface, and a drive motor secured to the plank. The drive motor has a rotating output member. A puck assembly includes a puck extending above the top surface of the plank. The puck assembly is operatively coupled to the rotating output member of the motor so that rotational movement of the output member produces translational movement of the puck assembly lengthwise along the top surface of the plank. 
     In another aspect, a truss assembly jigging table generally comprises a table frame, and a plurality of plank units held within the table frame. At least one plank unit is a removable plank unit. The removable plank unit includes a plank comprising a top surface and opposing bottom surface, first and second opposing side surfaces and first and second opposing ends. A plate member extends outwardly from the bottom surface of the plank. A rod is attached to the plate member and runs lengthwise along the plank. A drive motor is attached to the plate member and is configured to rotate the rod. A puck assembly is carried by the rod such that translational motion of the puck assembly is effected when the rod is rotated. 
     In yet another aspect, a method of converting a manual truss assembly jigging table into an automated truss assembly jigging table generally comprises the steps of removing a plank from a truss assembly jigging table, and inserting a removable plank unit into the space previously occupied by the plank. The removable plank unit comprises a plank having a top surface, and a drive motor secured to the plank. The drive motor has a rotating output member and a puck assembly including a puck extending above the top surface of the plank. The puck assembly is operatively coupled to the rotating output member of the motor so that rotational movement of the output member produces translational movement of the puck assembly lengthwise along the top surface of the plank. The removable plank unit is secured to the truss assembly jigging table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a removable plank unit according to an embodiment of the present invention. 
         FIG. 2  is a side elevation of the removable plank unit. 
         FIG. 3  is a front elevation of the removable plank unit. 
         FIG. 4  is a perspective of a truss assembly jig setting table including a plurality of the plank units of  FIG. 1 . 
         FIG. 5  is a top plan of the truss assembly jig setting table. 
         FIG. 6  is a partial top plan of the truss assembly jig setting table with truss members arranged thereon. 
         FIG. 7  is a perspective of another embodiment of a truss assembly jig setting table. 
         FIG. 8  is a perspective of another embodiment of removable plank unit. 
         FIG. 9  is a bottom plan view of the plank unit. 
         FIG. 10  is an enlarged fragmentary perspective taken as indicated in  FIG. 8  showing a puck assembly. 
         FIG. 11  is an exploded view of  FIG. 10 . 
         FIG. 12  is an enlarged perspective of the puck assembly of  FIG. 11 . 
         FIG. 13  is an exploded perspective of the puck assembly of  FIG. 12 . 
         FIG. 14  is a section taken in the plane containing the line  14 - 14  in  FIG. 10 . 
         FIG. 15  is a section taken in the plane containing the line  15 - 15  in  FIG. 8 . 
         FIG. 16  is an enlarged fragmentary perspective taken as indicated in  FIG. 8  showing a rod-supporting assembly. 
         FIG. 17  is an exploded view of  FIG. 16 . 
         FIG. 18  is an enlarged fragmentary perspective; similar to  FIG. 16 , but showing the underside of the plank and with the rod-supporting assembly exploded from the plank unit. 
         FIG. 19  is an enlarged perspective of the rod-supporting assembly. 
         FIG. 20  is an exploded view of the rod-supporting assembly of  FIG. 19 . 
         FIG. 21  is a fragmentary side elevation of the plank unit showing the puck carriage when it first contacts the rod-supporting assembly. 
         FIG. 22  is similar to  FIG. 21  except that it shows the rod-supporting assembly being deflected downward as the puck carriage passes over the rod-supporting assembly. 
         FIG. 23  is similar to  FIG. 21  except that it shows the rod-supporting assembly and the puck assembly after the puck assembly has passed the rod-supporting assembly. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , there can be seen a removable plank unit, generally indicated at  102 , of a truss assembly jig setting system according to an embodiment of the present invention. Removable plank unit includes a plank, generally indicated at  104 , which comprises a top surface  106  and opposing bottom surface  108 , opposite first  110  and second  112  side surfaces, and front (broadly, first)  114  and rear (broadly, second)  116  ends. Planks  104  are typically made of steel, but may be made of any other durable material. Removable plank unit  102  may further include first  154  and second  156  transport members (e.g., threaded eye bolts) attached to plank  104 , which aid in installation and removal of the removable plank unit. Removable plank unit  102  may also include apertures  160  through plank  104  through which fasteners, such as bolts, may be inserted for attaching removable plank unit  102  to a truss jigging table  100  ( FIGS. 4 and 5 ). Alternatively, nails, rods, or any other fastener may be used to secure the removable plank unit  102  to the table  100 . Removable plank units  102  may have different widths and lengths as required for the particular table into which the segments are to be installed. 
     A first motor plate  122  is affixed to bottom surface  108  of plank  104  near first end  114 , and a first drive motor  118  is affixed to the first motor plate  122 . Similarly, a second motor plate  124  with a second drive motor  120  affixed thereto is secured to the bottom surface  108  of the plank  104  near the second end  116 . Alternatively, both drive motors  118 ,  120  may be attached to one of the motor plates near either end of the plank  104 . 
     First and second threaded rods  128 ,  126  extend between the first and second motor plates  122 ,  124  and are rotatably secured thereto by bearings (only bearing  129  associated with the rod  128  is shown in the drawings). The bearings  129  allow the rods  126 ,  128  to rotate about their longitudinal axes, for reasons explained below. Preferably, the rods  126 ,  128  are arranged in a side by side configuration. In the alternative, the rods  126 ,  128  may be arranged vertically adjacent to one another. At least a portion of each rod  126 ,  128  is preferably disposed directly beneath the bottom surface  108  of plank  104 , although the rods may be located entirely laterally of the plank without departing from the scope of the invention. 
     A pulley system, generally indicated at  150 ,  152 , connects each drive motor  118 ,  120  to one of the rods  126 ,  128  in order to rotate the rods about their longitudinal axes. Each pulley system  150 ,  152  comprises an endless belt  162  wrapped around a first pulley  164  mounted on an output shaft  165  of the motor  118 ,  120 , and a second pulley  166  mounted on the rod  126 ,  128 . 
     A pair of puck assemblies, generally indicated at  130 ,  132 , are operatively engaged with the rods  126 ,  128  so that rotation of the rods produces translational movement of the puck assemblies along the lengths of the rods. Each puck assembly  130 ,  132  comprises a puck  134 ,  136  secured to a puck carriage  142 ,  144  by a bolt  146 ,  148  extending through bores in the puck and puck carriage. Each puck carriage  142 ,  144  has a threaded aperture (not shown) through which the respective rod  126 ,  128  is inserted to mount the carriage on the rod. The thread of each aperture is a suitable complementary thread for transferring power, such as, for example, an acme or square thread. Accordingly, rotational movement of the rods  126 ,  128  produces translational movement of the respective puck carriages  142 ,  144  and the pucks  134 ,  136  along the length of the rod. Each puck  134 ,  136  sits atop respective puck carriage  142 ,  144  with an optional washer  138 ,  140  therebetween. The pucks  134 ,  136  are preferably made of steel, but may be made of any other durable material. The bottommost surface of each puck/washer combination is a wear surface that rests on top surface  106  of plank  104 . The washer  138 ,  140  protects the puck  134 ,  136  from wear and can be replaced without replacing the puck. The washer  138 ,  140  can be made of a suitable low friction material such as a nylon. It is to be understood that the puck assemblies may have other configurations within the scope of the present invention. 
     The location of puck assemblies  130 ,  132  in different slots on adjacent sides of the plank  104  of each removable plank unit  102 , rather than within a single slot through the plank, allows for a more versatile and flexible puck setting system. Two pucks  134 ,  136  can thus typically be positioned along the length of even the shortest truss member. This also makes it easier to position more pucks  134 ,  136  nearer to either end of the table. In addition, because one puck  134 ,  136  is located on each side of each plank  102 , the actual distance between pucks on adjacent planks is less than the “on-center” distance (the distance from the center of one plank to the center of a next plank) between planks. 
     In operation, activation of drive motor  118  in a first rotational direction produces rotation of rod  126  in the first rotational direction due to pulley system  150 . Rotation of rod  126  in first direction causes translational motion of puck assembly  130  in a first translational direction along rod  126 . For example, the first rotational direction may be clockwise, and the first translational direction may be away from the associated mounting plate  122 . Rotation of drive motor  118  in the opposite direction accordingly causes translational motion of puck assembly  130  in an opposite, second translational direction along the rod  126 . For example, the second rotational direction may be counterclockwise, and the second translational direction may be toward the associated mounting plate  122 . Movement of puck assembly  132  is carried out in a like manner. Because each puck assembly  130 ,  132  is associated with a separate drive motor  118 ,  120 , movement of puck assemblies  130 ,  132  may be carried out independent of one another. One of skill in the art will recognize that rotation of the drive motor may be translated to linear movement of the puck assembly by various other means, such as, for example, by a gear system. 
     It will be appreciated that removable plank unit  102  carries a completely self-contained puck movement system. This provides substantial flexibility to the table manufacturer in locating pucks  134 ,  136  on a new table, so that customized tables can be made at reasonable cost. Moreover, this allows removable plank units  102  to be retrofit to existing truss assembly jigging tables to create an automated truss assembly jig setting system without the expense of constructing or purchasing a completely new table. Removable plank unit  102  need only be connected to a power system and a computer control system to be suitable for automated puck positioning. It is understood that it is also advantageous to manufacture an original jigging table including the removable board segments  102 . 
     Referring now to  FIGS. 4 and 5  there can be seen a truss assembly jigging table  100  that has been retrofit with removable plank units  102  to create an automated truss assembly jig setting table. As can be seen, truss assembly table  100  comprises a table frame  158  fitted with a plurality of plank units in numbered positions  1 - 8 . Note that tables with greater or fewer plank units may also be placed according to the present invention. Originally, table  100  would have included traditional plank units  103  in all positions. To retrofit the table for an automated truss assembly jig setting system, planks  103  in positions  1 ,  3 ,  6 , and  8  were removed and removable plank units  102  were inserted. This creates a table having one puck assembly  130  or  132  between each pair of adjacent plank units. This allows each puck assembly  130 ,  132  the ability to be positioned anywhere along the length of the table  100 . It will be understood that the table  100  can be originally manufactured in the configuration illustrated in  FIGS. 4 and 5 . Alternatively, removable plank units  102  may be inserted into any other combination of positions  1 - 8  as assembly of a particular truss design may dictate. For example, removable plank units  102  may be inserted into all of the positions  1 - 8 , in which case each adjacent pair of plank units would have two puck assemblies there between. Although depicted as being retrofitted across the width of a table, removable segments  102  can be configured to be installed lengthwise or at an angle across a table. 
     Because the puck assemblies  130 ,  132  of the plank unit  102  are on opposite sides of the board and are independent of each other, both puck assemblies of a single board may engage either the top of bottom chord members  168  of the truss. For example, as seen in  FIG. 6 , the puck  134 ′ of the of the middle plank  102 ′ is disposed to the left of a pitch break  178  in the upper truss chord and the other puck  136 ′ is disposed to the right of the same pitch break. Because the width of the plank unit  102  is preferably between about 6 in (15 cm) and about 10 in (25 cm), the pucks  134 ′,  132 ′ engage the truss chord members adjacent to the pitch break  178  to improve accuracy of manufacture of the truss. Further, the pucks  134 ,  136  may be positioned within the interior of the perimeter of the truss so that the pucks engage interior surfaces of the chord members, as seen by puck  136 ″ of plank unit  102 ″ in  FIG. 6 . It is understood that one of the pucks  134 ,  136  of the plank unit  102  may be positioned within the interior of the truss, both of the pucks, or neither of the pucks, within the scope of the present invention. 
     It is understood that the distance between removable plank units  102  may be varied. In addition, the width of the removable plank units  102  themselves can vary. This allows puck assemblies  130 ,  132  to be optimally placed depending on the locations of the particular truss members  168  of a given truss. This also allows removable plank units  102  to be fitted to a greater variety of existing truss tables, as a particular table layout is not required in order to retrofit removable plank units  102 . 
     Referring to  FIG. 4 , truss assembly table  100  need only be connected to a power system  170  (connection being shown schematically by solid lines) and a computer control system  172  (connection being shown schematically by dashed lines) having software capable of positioning the pucks to create an automated truss assembly jig setting table. Software programs are well known and generally available that can calculate the positions of the pucks on the table and activate the drive motors to move the pucks to their proper positions. Typically, the shape of a truss is known and its details are fed into the control system, which then activates the drive motors and moves the pucks into their desired positions. 
     Referring to  FIG. 7 , another embodiment of a truss assembly table is generally indicated at  200 . This table is similar to the prior embodiment  100 , and therefore, like components are indicated by corresponding reference numerals plus  100 . The difference between this table  200  and the prior embodiment  100  is that the present table has a laser projection system, generally indicated at  201 , that projects a laser image of a desired truss in actual shape and size on the work surface, which ensures greater accuracy in truss assembly (not shown). Some fragment(s) of the truss or component part(s) may be projected onto the upper surface of the table without departing from the scope of the present invention. The laser projection system  201  may be interfaced with the same computer control system  272  as the removable plank units  202 , or may be interfaced with a different controller. The laser projection system  201  may also be electrically connected to the same power system  270  as the plank units  202 . Known laser truss assembly systems are disclosed in U.S. Pat. No. 6,317,980 (owned by the owner of this application), the entirety of which is herein incorporated by reference for providing complete disclosure. 
     Referring still to  FIG. 7 , the removable plank units  202  of the type described above are advantageously placed in the truss assembly table  200 . Placing removable plank units  202  in the table  200  creates a table that utilizes both laser projection and automated puck positioning. Use of an automated system dramatically increases the speed and efficiency of the system relative to standard laser projection systems. In addition, placing the automated system in a laser projection system, rather than a standard table, provides a check on the automated system such that an operator can easily tell whether it is functioning accurately and reliably. 
     Referring now to  FIGS. 8-21 , another embodiment of a removable plank unit is generally indicated at  302 . This embodiment is similar to the plank unit  102 , and therefore, like components are indicated by corresponding reference numerals, plus  200 . Referring to  FIGS. 9 ,  11  and  14 , a pair of laterally spaced apart elongate struts, generally indicated at  380 , extend along the length of the plank  304  and are secured to the bottom surface  308  of the plank to provide structural support against bending when large loads are applied to the upper surface  306  during assembly of a truss. As seen best in  FIGS. 11 and 14 , each strut  380  includes a generally U-shaped body, generally indicated at  382 , having spaced apart inner and outer legs  384 A,  384 B, respectively, extending downward from the bottom surface  308  of the plank  304  and a web member  382  extending between and connecting lower ends of the legs. An L-shaped arm  390  extends laterally outward from an upper end of each outer leg  384 B of the U-shaped bodies  380 . For purposes explained below, the outer leg of  384 B of each base  382  and the respective L-shaped arm  390  together constitute a track defining an inverted channel  392  for receiving a portion of a corresponding puck assembly. 
     The plank  304  includes apertures  360  for attachment of the plank unit  302  to the table. Three openings  360 ′ at each longitudinal end of the plank are roll pin openings for receiving roll pins (not shown) through the plank into connection with a mounting plate of the table to fix the plank unit in position after it has been aligned and calibrated. An opening in the mounting plate of the table (not shown) is drilled only after the alignment and calibration is completed. If it later becomes necessary to remove the plank unit  302  for repair (for example), the plank unit  302  can be removed and then replaced by inserting roll pins through the same openings  360 ′ previously drilled in the table mounting plate. This permits the plank unit  302  to be reinstalled without requiring re-calibration. 
     Referring to  FIGS. 10-15 , the puck assemblies  330 ,  332  of the present embodiment are substantially identical in structure, and therefore, only puck assembly will be described in detail. The puck carriage  344  (indicated generally) of the puck assembly  332  includes a base  396  having a threaded bore  400  for receiving and threadably engaging the rod  328  ( FIG. 10 ) and a mount  398  on which the puck  336  and the washer  340  are mounted. In one example, the base  396  is formed from an oil impregnated nylon material, such as NYLATRON, although other materials may be used. The mount  398  may be formed from aluminum, although other materials may be used. 
     A longitudinal guide slot  402  is formed in an upper portion of the base  396  adjacent to an inner side  404  of the base. Referring to  FIG. 14 , the guide slot  402  receives the free end of the L-shaped arm  390  of the corresponding strut  380  so that an upper, longitudinal portion  406  of the base  396  is received in the inverted channel  392 , as described briefly above. An upper portion  408  ( FIGS. 14 and 12 ) of the slot  402  tapers downward to facilitate insertion of the L-shaped arm  390  into the slot. As seen best in  FIG. 14 , the puck assembly  344  is further guided and its rotation restricted by virtue of a lower portion  412  of the inner side wall  404  of the base  396  the outer leg  384 B of the strut  380 . During use, the track defined by the L-shaped arm  390  and the base  382  of the strut  380  guides the puck assembly  344  along the length of the rod  328  and prevents rotation of the base  396  with the rod to thereby ensure that puck assembly moves linearly along the rod as the rod rotates. Other ways of guiding and preventing rotation of the puck assemblies is within the scope of the invention. 
     Referring to  FIG. 13 , the mount  398  of the puck assembly  344  is secured within a notch  416  extending through an outer side wall  418  and the upper surface  414  of the base  396 . As seen best in  FIG. 14 , a section of the mount  398  engaging the base  396  has a cross-section that is generally an inverted L-shape so that the mount rests substantially flush against the upper surface  414  of the base and surfaces  420  defining the notch  416  and so that an outer side surface  422  of the mount extends up from and is substantially coplanar with the outer wall  418  of the base. As seen best in  FIG. 13 , the mount  398  is secured to the base  396  by three fasteners  423  extending through the outer side surface of the mount  422  and threaded into one of the surfaces  420  defining the notch  416 . Referring still to  FIG. 13 , an elongate finger  424  of the mount  398  extends rearward from an upper portion of the L-shaped section. A top surface  426  of the finger at a free end margin where the puck  336  and the washer  340  are mounted is generally coplanar with the top surface  306  of the plank  304 . Other ways of securing the mount to the base and/or making the carriage assembly are within the scope of the invention. 
     Referring now to  FIGS. 13 and 15 , a shoulder bolt  430  secures the puck  336  and the washer  340  to the finger  424  of the mount  398 . A threaded, free end margin  432  of the shank of the bolt  430  is threaded into a blind bore  434  of the finger  424  so that the remaining non-threaded portion of the shank extends upward through bores  436 ,  438  in the washer  340  and the puck  336  and into a counter-bore  440  in the puck. A compression spring  442  disposed around the non-threaded portion of the shank of the bolt  430  is captive within the counter-bore  440  of the puck  336  by a bottom surface defining the counter-bore and the head of the bolt. The spring  442  biases the puck  336  and the washer  340  downward in contact with the top surface  306  of the plank  304  and allows the puck and the washer to move upward and downward along the axis of the bolt  430  as the puck is driven linearly along the length of the plank. In this way, the puck assembly  332  may be used with a plank having somewhat non-linear upper surface that slopes along its length because the vertical position of the puck compensates for any irregular, non-linear portions of the top surface on which it is riding. Other ways of varying the vertical position of the puck as it moves along the plank to compensate for irregularities of the plank are within the scope of the present invention. 
     Referring back to  FIGS. 8 and 9 , a plurality of rod-supporting assemblies, generally indicated at  450 , extend laterally outward from each of the struts  380  below the plank  304  and engage the rods  328 ,  326 . Corresponding generally aligned rod-supporting assemblies  450  support each rod  328 ,  326  to substantially prevent sagging or bowing of the rods due to gravity and to maintain the general linearity of the rod as the rod rotates about its axis. In the illustrated embodiment, three rod-supporting assemblies  450  are spaced equally apart along the length of each rod (the rod-supporting assemblies associated with the rod  326  are not visible in  FIG. 8 ), although it is understood that the plank unit may have more or fewer rod-supporting assemblies within the scope of the invention. 
     The rod-supporting assemblies  450  are substantially identical, and therefore, only one rod-supporting assembly will be described in detail. Referring to  FIGS. 16-23 , the rod-supporting assembly  450  includes a base plate  452  having an inner end margin secured to the web  386  of the respective strut  380  and a saddle block, generally indicated at  454 , cantilevered from an outer end margin of the base by a resiliently elastic bar  455 . The bar  455  exerts an upward force on the block  454 , which is transferred to the rod  328  to maintain the linearity of the rod. The rod-supporting assemblies  450 , by way of the saddle block  454  and resiliently flexible cantilever bar  455 , and the spring  442  of the resiliently movable pucks  334 ,  336  together act to dampen vibrations and noise of the system as the rods are rotated and the pucks are moving linearly along the rods. 
     As seen best in  FIG. 18 , the base plate  452  is secured to the strut  380  using threaded fasteners  456  (e.g., bolts) extending through openings  458  in the base plate and threaded into in bores  460  in the web  386 . Referring still to  FIG. 18 , the web  386  has a plurality of such bores  460  spaced along the length of the strut  380  for securing the rod-supporting assemblies  450  at selective longitudinal positions. 
     Referring to  FIGS. 16 ,  19  and  20 , the saddle block  454  has a concave, upper support surface  466  extending longitudinally through upwardly sloping front and rear faces  468 A,  468 B of the block. The support surface  466  partially receives a longitudinal portion of the rod  328  therein, and may, for example, extend about 180 degrees around a circumference of the rod. The concave shape of the support surface  466  retains the rod  328  in the saddle  454  as the rod  328  rotates so that the saddle continuously engages and supports the rod as the rod rotates during use. Thus, the linearity of the rod is maintained during use and allows the rods to be rotated at higher rates. The saddle may be formed from NYLATRON, although it may be made from other materials. 
     As seen best in  FIGS. 19 and 20 , a first end of the cantilever bar  455  is secured to the base plate  452  using a compression plate  464  secured to the base plate using fasteners  469  (e.g., bolts) so that the bar is sandwiched between the base plate and the compression plate. The cantilever bar  455  is secured to a bottom of the saddle block  454  by a threaded fastener  470  (e.g., bolt,  FIG. 20 ) extending through a hole  472  in the bar  455  and threaded into the block. The cantilever bar  455  may be formed from metal or other material. A tension-adjustment member  474  is threaded through a nut  475  and a bottom of the compression plate  464  and contacts a bottom of the cantilever bar  455 . Selectively setting the length of the tension-adjustment member  474  extending above the compression plate  464  respectively decreases and increases the upward force of the bar  455  that is exerted on the rod  328 . 
     In addition to providing the upward force on the rod  328  to maintain the linearity of the rod, the resiliently flexible bar  455  allows the puck carriage  344  to move past the saddle block  454  as the puck carriage is moving longitudinally along the rod. Referring to  FIGS. 21-23 , a sequence of the puck carriage  344  passing the rod-supporting assembly  450  as the carriage is moving to the left along the rod  328  is illustrated. As will be appreciated by those skilled in the art, the sequence is substantially similar when the carriage  344  is moving to the right along the rod  328 . In the position illustrated in  FIG. 21 , a beveled lead edge of the base  396  of the carriage  344  first contacts the sloped rear face  468 B of the saddle block  454 . Referring to  FIG. 22 , as the carriage  344  continues its movement, the force of the carriage deflects the cantilever bar  455  deflects so that the saddle block  454  moves downward. The upwardly sloping rear face  468 B of the block  454  acts as ramp to allow a bottom surface  480  of the carriage base  396  to ride along the face of the block as the bar  455  continues to deflect and the block continues to move downward. The bottom surface  480  of the carriage base  396  slopes from each of the front and rear ends toward the center of the base to further facilitate engagement with the saddle block  454 . After the puck carriage  344  moves past the saddle block ( FIG. 23 ), the bar elastically rebounds and the saddle  454  moves upward, back to its original position of engagement with the rod  328 . Accordingly, where each bar  328 ,  326  has two or more rod-supporting assemblies  450  associated with it, each rod is continuously supported and retained within at least one of the saddles, thus maintaining the linearity of the rod and prohibiting the rod from deflecting as it rotates. 
     Removable plank units  102 ,  202  may also be packaged in a truss assembly jigging table automated retrofitting kit. Such a kit includes one or more removable plank units  102 ,  202  and may include a plurality of fasteners for affixing removable plank units  102 ,  202  to a truss assembly jigging table, tools necessary for removing planks and inserting removable plank units  102 ,  202 , cords for connecting removable plank units  102 ,  202  to a power system and a computer control system, and/or software to be installed on a computer control system. Removable plank units  102 ,  202  may come fully assembled, as shown in  FIGS. 1-3 , or may come disassembled so that the number, location, and configuration of the various components, such as drive motors, rods, and puck assemblies, can be varied upon assembly as required for a particular application. 
     As may be apparent from the above description of the illustrated embodiment, an advantage of the preferred embodiment is increased efficiency and cost savings. Removable plank units allow a manual truss assembly jig setting table to be quickly converted into an automated table. This increases the speed and efficiency of truss assembly. In addition, a significant capital expenditure is saved by converting the old tables into automated tables, rather than having to throw out the old tables and purchase completely new ones. 
     Another advantage of the illustrated embodiment is flexibility. Because of the removable nature of removable plank units, varying numbers of such segments may be used at any one time. The width of segments and the distance between segments may also be varied. This allows different numbers and configurations of puck assemblies to be used depending on the requirements of a particular truss. 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions, products, and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.