Patent Publication Number: US-6209374-B1

Title: Roll-forming machine with adjustable compression

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a roll-forming machine having adjustable compression between forming rolls of the forming roll stations. 
     Roll-forming machines typically include a plurality of roll-forming stations that are used to transform a planar sheet of metal into a component having either a C-shaped or Z-shaped cross-sectional area, for example. The component, such as a C-purlin or Z-purlin, typically has a center portion, a pair of leg portions joined to the center portion by a substantially right angle bend formed by the roll-forming machine, and a flange joined to each leg portion by a respective bend formed by the machine. 
     Typically, the flanges of a C- or Z-shaped component are made first by a plurality, such as three, roll-forming stations. The first of these stations makes an initial pair of bends at the desired transverse locations on the sheet, and then the successive stations for forming the flanges increase the previously made bends until the flanges are at the proper angle relative to the center portion of the sheet. The legs of the component are then formed by a plurality of roll-forming stations in a similar manner. 
     Each of the roll-forming stations typically includes a pair of frame members in which a pair of rotatable arbors are journalled, one arbor disposed directly above the other, and a pair of sleeves which cover a portion of the arbors, the sleeves being slidable over the arbors. Each roll-forming station includes at least two pairs forming rolls, two of the forming rolls being fixed to the arbors and the other two forming rolls being fixed to the sleeves. The circumferential ends of the upper and lower forming rolls are vertically spaced apart by a distance corresponding to the thickness of the sheet of material being bent, and the shape or contour of the forming rolls controls the degree to which the sheet is bent. The use of sleeves which are slidable on the arbors and which rotate with the arbors allows the horizontal spacing of the forming rolls on each arbor and sleeve to be varied so that the transverse widths of the center portion and the leg portions of the components being formed can be adjusted. 
     The sheet of material is forced through the roll-forming machine by friction between the sheet and the rotating forming rolls. The forming rolls of a plurality of the roll-forming stations, e.g. the forming rolls of every other station, are rotatably driven to ensure that there is enough driving power to force the sheet through the machine. 
     In the case of a C-shaped component, the flanges are made by bending the transverse ends of the sheet in the same direction, for example, downwards, whereas for a Z-shaped component the flanges are made by bending the transverse sheet ends in opposite directions. After the flanges are formed on the transverse ends of the sheet, the legs are formed by a plurality of roll-forming stations by a similar process. To form a component in the above manner, up to ten or more roll-forming stations may be incorporated in the roll-forming machine. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention is directed to a roll-forming machine having a base structure, a plurality of first roll-forming stations associated with the base structure that form a first component having a Z-shaped cross section and a plurality of second roll-forming stations associated with the base structure that form a second component having a C-shaped cross section. 
     At least one of the roll-forming stations is provided with a first rotatable arbor adapted to support a first pair of forming rolls, a second rotatable arbor adapted to support a second pair of forming rolls, a first support structure, a first bearing assembly associated with the first support structure that rotatably supports a first portion of the first arbor, a second bearing assembly associated with the first support structure that rotatably supports a first portion of the second arbor, a second support structure, a third bearing assembly associated with the second support structure that rotatably supports a second portion of the first arbor, and a fourth bearing assembly associated with the second support structure that rotatably supports a second portion of the second arbor. 
     The roll-forming station also includes a first adjustment mechanism that allows the position of the first bearing assembly to be adjusted relative to the position of the second bearing assembly, a second adjustment mechanism that allows the position of the third bearing assembly to be adjusted relative to the position of the fourth bearing assembly, a first compression assembly that exerts a force upon the first bearing assembly when the first bearing assembly is moved away from the second bearing assembly, and a second compression assembly that exerts a force upon the third bearing assembly when the third bearing assembly is moved away from the fourth bearing assembly. 
     Each of the support structures may comprise a vertically disposed support plate and a slot formed in the support plate, and at least one of the bearing assemblies supported by each support plate may be movable along a vertical direction within the slot. The adjustment mechanisms may be provided in the form of adjustment screws. The compression assemblies may each comprise at least one spring, which may be in the form of a cone-shaped spring member, and a structure that holds the spring in a predetermined position. Each of the compression assemblies may have a non-linear force/displacement curve associated therewith. 
     In another aspect, the invention is directed to a roll-forming station having a first rotatable arbor capable of supporting a first pair of forming rolls, a second rotatable arbor capable of supporting a second pair of forming rolls, a first support structure, a first bearing assembly associated with the first support structure that rotatably supports a first portion of the first arbor, a second bearing assembly associated with the first support structure that rotatably supports a first portion of the second arbor, a second support structure, a third bearing assembly associated with the second support structure that rotatably supports a second portion of the first arbor, and a fourth bearing assembly associated with the second support structure that rotatably supports a second portion of the second arbor. The first and second support structures support the bearing assemblies so that the first and second arbors are movable relative to each other exclusively in a vertical direction so that the first and second arbors are always aligned in a common vertical plane. 
     The roll-forming station also includes a first adjustment mechanism that allows the position of the first bearing assembly to be adjusted exclusively in a vertical direction relative to the position of the second bearing assembly, a second adjustment mechanism that allows the position of the third bearing assembly to be adjusted exclusively in a vertical direction relative to the position of the fourth bearing assembly, a first compression assembly that exerts a force upon the first bearing assembly when the first bearing assembly is moved away from the second bearing assembly in a vertical direction within the common vertical plane, and a second compression assembly that exerts a force upon the third bearing assembly when the third bearing assembly is moved away from the fourth bearing assembly in a vertical direction within the common vertical plane. 
     In a further aspect of the invention, the first and second adjustment mechanisms may be adjusted to support each of the first and third bearing assemblies in an initial position so that there is a predetermined initial gap between the forming rolls supported by the first arbor and the forming rolls supported by the second arbor when the first and third bearing assemblies are disposed in the initial positions. Each of the compression assemblies may be disposed in a pre-loaded condition so that each has a discontinuous force/displacement curve in order to cause each compression assembly to exert no force when its associated bearing assembly is disposed in its initial position and to cause the force exerted by each compression assembly to increase discontinuously to a non-zero force as soon as its associated bearing assembly is moved from its initial position to a displaced position. 
     The invention is also directed to a method of processing a sheet of material having a thickness with a roll-forming station, the roll forming station having a first rotatable arbor, a pair of forming rolls supported by the first rotatable arbor, a second rotatable arbor, a pair of forming rolls supported by the second rotatable arbor, first and second adjustment mechanisms that allow the position of the first arbor to be adjusted vertically relative to the position of the second arbor, and a compression assembly. 
     The method includes the steps of: (a) adjusting the first adjustment mechanism to an initial position so that the vertical gap between one of the forming rolls supported by the first arbor and one of the forming rolls supported by the second arbor is less than the thickness of the sheet of material, (b) adjusting the second adjustment mechanism to an initial position so that the vertical gap between one of the forming rolls supported by the first arbor and one of the forming rolls supported by the second arbor is less than the thickness of the sheet of material, and (c) passing the sheet of material between the forming rolls supported by the first and second arbors with the first and second adjustment mechanisms disposed in the initial positions so that the initial gap between the forming rolls disposed on the first arbor and the forming rolls on the second arbor is increased from the initial gap to a distance substantially equal to the thickness of the sheet of material, the increase in the initial gap causing a compression force to be applied to the sheet of material by the compression assembly. 
     The method may also include the step of using a compression assembly that provides a non-linear compression force and/or the step of adjusting the compression assembly to provide a non-zero compression pre-load prior to step (c). 
     The features and advantages of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a schematic side view of a portion of a preferred embodiment of a roll-forming machine that forms components having C-shaped cross-sections; 
     FIG. 1B is a schematic side view of a portion of a preferred embodiment of the roll-forming machine that forms components having Z-shaped cross-sections; 
     FIG. 2 is a schematic end view of the roll-forming machine of FIGS.  1 A and  1 lB; 
     FIGS. 3A-3F illustrate portions of a number of roll-forming stations used to form C-shaped components; 
     FIGS. 4A-4E illustrate portions of a number of roll-forming stations used to form Z-shaped components; 
     FIGS. 5-8 illustrate a first type of adjustment mechanism for adjusting the vertical position of an annular forming roll; 
     FIG. 9 illustrates a second type of adjustment mechanism for adjusting the vertical position of an annular forming roll; 
     FIGS. 10-12 illustrate structure for adjusting the position of three vertically movable plates which supports the adjustment mechanisms shown in FIGS. 5-9; 
     FIGS. 13A,  13 B,  14  and  15  illustrate a first structure for pivotably supporting a plurality of contact rollers; 
     FIGS. 16A-16B illustrate a second structure for pivotably supporting a plurality of contact rollers; 
     FIG. 17 is a side elevational view of one of the frame members  20  shown generally in FIG. 2; 
     FIG. 18 is a cross-sectional view of one of the bearing assemblies used support an arbor; 
     FIGS.  19 A and l 9 B. illustrate an anchor mechanism and a compression mechanism; and 
     FIGS. 20A and 20B illustrate force/deflection curves provided by a compression mechanism. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A and 1B illustrate a schematic side view of a preferred embodiment of a roll-forming machine  10  in accordance with the invention. The roll-forming machine  10  is similar to that disclosed in allowed U.S. Ser. No. 09/154,853 filed Sept. 17, 1998, which is incorporated herein by reference in its entirety. Referring to FIG. 1A, the roll-forming machine  10  has a plurality of roll-forming stations  12   a-   12   j  supported by a base  13 . The roll-forming stations  12   a-   12   j  are used to form a C-shaped component, such as a C-purlin, from a flat sheet of metal at room temperature. 
     The metal sheet enters the roll-forming station  12   a  first and passes between a pair of upper forming rolls  14   a ,  16   a  (see FIG. 3A) supported by a spindle or arbor  18   a  rotatably journalled in a pair of frame members  20   a  and a pair of lower forming rolls  22   a ,  24   a  (see FIG. 3A) supported by an arbor  26   a  rotatably journalled in the frame members  20   a . The transverse shape of the forming rolls  14   a ,  16   a ,  22   a ,  24   a  is illustrated in FIG. 3A, which shows a pair of initial bends being formed in a metal sheet  30  to form a pair of flanges  32  at the transverse ends of the sheet  30 . 
     After passing through the roll-forming station  12   b , the sheet enters the roll-forming station  12   c , where the two bends made to form the flanges  32  are increased. In the station  12   c , the sheet passes between a pair of upper forming rolls  14   c ,  16   c  (see FIG. 3B) supported by an arbor  18   c  rotatably journalled in a pair of frame members  20   c  and a pair of lower forming rolls  22   c ,  24   c  (see FIG. 3B) supported by an arbor  26   c  rotatably journalled in the frame members  20   c.    
     After passing through the roll-forming station  12   d , the sheet enters the roll-forming station  12   e , where two new bends are started to form a pair of legs  34  and a center portion  36  of the sheet or component  30 . In the station  12   e , the sheet passes between a pair of upper forming rolls  14   e ,  16   e  (see FIG. 3C) supported by an arbor  18   e  rotatably journalled in a pair of frame members  20   e  and a pair of lower forming rolls  22   e ,  24   e  (see FIG. 3C) supported by an arbor  26   e  rotatably journalled in the frame members  20   e . Stations  12   f  (and any stations disposed between station  12   e  and  12   f ) are used to increase the bends that separate the leg portions  34  of the component  30  from its center portion  36 . 
     At station  12   g , the component  30  passes between a pair of upper forming rolls  14   g ,  16   g  (see FIG. 3D) supported by an arbor  18   g  rotatably journalled in a pair of frame members  20   g  and a pair of lower forming rolls  22   g ,  24   g  (see FIG. 3D) supported by an arbor  26   g  rotatably journalled in the frame members  20   g . Station  12   g  also includes a third pair of annular forming rolls  40   g ,  42   g  that have a central hollow portion through which the lower arbor  26   g  passes. The annular forming rolls  40   g ,  42   g  have a pair of cylindrical surfaces  44   g ,  46   g , each of which makes flush contact with a respective flange  32  of the component  30 . 
     As described below, each of the annular forming rolls  40   g ,  42   g  is supported by a respective cradle mechanism, one of which is shown in FIG. 1A to include three support rollers  50   g . The vertical position of the cradle mechanism, and thus of the annular forming rolls  40   g ,  42   g  is adjustable so that the cylindrical surfaces  44   g ,  46   g  may always make flush contact with the flanges  32  of the component  30  being formed, regardless of the length of the legs  34  of the component  30 . 
     At station  12   h , the component passes between a pair of upper forming rolls  14   h ,  16   h  (see FIG. 3E) supported by an arbor  18   h  rotatably journalled in a pair of frame members  20   h  and a pair of lower forming rolls  22   h ,  24   h  (see FIG. 3E) supported by an arbor  26   h  rotatably journalled in the frame members  20   h . Station  12   h  includes a pair of annular forming rolls  40   h ,  42   h  having a central hollow portion through which the lower arbor  26   h  passes. The annular forming rolls  40   h ,  42   h  have a pair of cylindrical surfaces  44   h ,  46   h , each of which makes flush contact with a respective flange  32  of the component  30 . Each of the annular forming rolls  40   h ,  42   h  is supported by a respective cradle mechanism, one of which is shown in FIG. 1A to include three support rollers  50   h.    
     At station  12   i , the component passes between a pair of upper forming rolls  14   i ,  16   i  (see FIG. 3F) supported by an arbor  18   i  rotatably journalled in a pair of frame members  20   i  and a pair of lower forming rolls  22   i ,  24   i  (see FIG. 3F) supported by an arbor  26   i  rotatably journalled in the frame members  20   i . Station  12   i  includes a pair of annular forming rolls  40   i ,  42   i  each having a central hollow portion through which the lower arbor  26   i  passes. The annular forming rolls  40   i ,  42   i  have a pair of cylindrical surfaces  44   i ,  46   i , each of which makes flush contact with a respective flange  32  of the component  30 . Each of the annular forming rolls  40   i ,  42   i  is supported by a respective cradle mechanism, one of which is shown in FIG. 1A to include a lower support roller  52   i  and a pair of side support members  54   i.    
     The final station  12   j  may be used to apply an additional driving force to force the component  30  out of the roll-forming machine  10 , and not to make any additional bends in the component  30 . 
     FIG. 1B illustrates a second portion of the roll-forming machine  10  which forms a component  56  having a Z-shaped cross section from a flat sheet of metal. As shown in FIGS. 4C-4E, the component  56  has a center portion  57 , a pair of leg portions  58  joined to the center portion  57 , and a pair of flanges  59  joined to the leg portions  58 . 
     Referring to FIG.  1 B and FIGS. 4A through 4E, the Z-shaped component  56  is formed by successively feeding the metal sheet through a plurality of roll-forming stations  60   a  through  60   i . The roll-forming stations  60  include a plurality of upper forming rolls  64   a-   64   i ,  66   a-   66   i  supported by a plurality of upper arbors  68   a-   68   i  rotatably journalled in a plurality of frame members  70   a-   70   i  and a plurality of lower forming rolls  72   a-   72   i ,  74   a-   74   i  supported by a plurality of lower arbors  76   a-   76   i  rotatably journalled in the frame members  70   a-   70   i . The final station  60   j  may be used to apply an additional driving force to force the component  56  out of the roll-forming machine  10 , and not to make any additional bends in the component  56 . 
     As schematically shown in FIGS. 4D and 4E, the roll-forming stations  60   h  and  60   i  include a plurality of rollers  80   h ,  80   i ,  82   h ,  82   i  which make rolling contact with the Z-shaped component  56  at the intersections of the center and leg portions  57 ,  58  of the component  56 . The purpose of the rollers  80   h ,  80   i ,  82   h ,  82   i  is to enable the formation of sharp bends at those intersections. 
     The rollers  80   h ,  80   i ,  82   h ,  82   i  are supported by a support structure shown schematically in FIG.  1 B. Referring to FIG. 1B, that support structure includes a horizontal support bar  84  mounted to the two outer or “outboard” frame members  70   h ,  70   i , a horizontal support bar  86  mounted to the two inner or “inboard” frame members  70   h ,  70   i , three upper adjustment mechanisms  88  fixed to the support bar  84  for pivotally adjusting the position of the rollers  80   h ,  80   i , and three lower adjustment mechanisms  90  fixed to the support bar  86  for pivotally adjusting the position of the rollers  82   h ,  82   i . 
     FIG. 2 is a view of the roll-forming machine  10  (the forming rolls and other components not being shown) showing the general construction of two roll-forming stations  12 ,  60 . The detailed structure of each of the roll-forming stations of the roll-forming machine  10  is described in a subsequent section of this patent. 
     Referring to the right-hand portion of FIG. 2, a sleeve  96  is disposed around the right-hand portion of the upper arbor  18 , and a sleeve  98  is disposed around the right-hand portion of the lower arbor  26 . Each of the sleeves  96 ,  98  has a keyed portion (not shown in FIG. 2) which extends into a respective slot (not shown in FIG. 2) formed in each of the arbors  18 ,  26  so that the upper arbor  18  and the sleeve  96  are forced to rotate together within bearings  97  (schematically shown) and so that the lower arbor  26  and the sleeve  98  are forced to rotate together within bearings  99  (schematically shown). 
     One of the upper forming rolls  16  (not shown in FIG. 2) is mounted to the left-hand side of the arbor  18  between the frame members  20 , and the other upper forming roll  14  (not shown in FIG. 2) is mounted to the sleeve  96 . Two lower forming rolls  22 ,  24  (not shown in FIG. 2) are similarly mounted to the lower arbor  26  and sleeve  98 . The lower arbor  26  has a coupler  100  attached to its left end which mates with a horizontally movable coupler  102  that may be rotatably driven by a drive mechanism  104 . The upper arbor  18  is rotatably driven via an upper gear  106  fixed to the upper arbor  18  and a lower gear  108  fixed to the lower arbor  26 . As is well known, not all of the arbors of roll-forming stations need to be rotatably driven by the drive mechanism  104 . 
     Referring to the right-hand side of FIG. 2, the inboard (left) frame member  20  is supported by a block  110  fixed to the machine base  13 , and the outboard frame member  20  is supported by a base  112  slidably supported by a slide fixture  114  mounted on the machine base  13 . By horizontally sliding the outboard frame member  20 , the horizontal distance between the forming rolls mounted to the arbors  18 ,  26  and sleeves  96 ,  98  can be varied (to vary the transverse lengths of the center portion and leg portions of a component to be formed) since the sleeves  96 ,  98  slide horizontally along the arbors  18 ,  26  in response to movement of the outboard frame member  20 . 
     The construction of the roll-forming stations  60  used to form Z-shaped components, shown in the left-hand side of FIG. 2, is substantially the same as the construction just described. The particular construction of the roll-forming stations  12 ,  60 , which could take many forms in accordance with the invention, could be in accordance with U.S. Pat. No. 5,644,942 entitled “Roll Stand Raft Assembly,” which is incorporated herein by reference. 
     FIGS. 5 through 8 illustrate the manner in which one of the annular forming rolls  42   g  is adjustably supported. Referring to FIG. 5, the annular forming roll  42   g  is supported by the three support rollers  50   g  shown schematically in Fig.  1 A. Each of the support rollers  50   g  is mounted to an upper metal plate  120  by a respective bolt  122 . The support rollers  50   g  include internal bearings (not shown) which allow them to freely rotate. 
     The plate  120  is pivotally connected to a mounting member  124  via a pivot member  126  connected to the plate  120  which passes through a cylindrical bore formed in the mounting member  124 , the pivot member  126  being pivotally secured within the bore in the mounting member  124  via a collar  128 . The mounting member  124  is fixed to the machine base  13  via a plurality of bolts  130 . 
     The upper plate  120  has a U-shaped opening  132  formed therein to facilitate the passage of the arbor  26   g  and a sleeve  98   g  disposed around the arbor  26   g . The upper plate  120  is connected to a lower plate  134 , at an angle to the lower plate  134 , via a pair of brackets  136  welded to both of the plates  120 ,  134 . The lower plate  134  has a U-shaped opening  138  formed therein to accommodate the lowermost roller  50   g  (see FIG.  5 ). 
     A wheel support bracket  140  is connected to the bottom end of the lower plate  134  via a plurality of bolts  142 . The bracket  140  has a roller  144  rotatably mounted to it via a nut and bolt assembly  146 . As shown in FIG. 5, the roller  144  rests on a horizontal plate  150  that may be moved up and down within an enclosure formed by a number of walls  152 . 
     By moving the plate  150  up or down, the position of the annular forming roll  42   g  may be adjusted up or down so that its edge surface  46   g  may make flush contact with the flanges  32  of the component  30 , as shown in FIG. 3D, regardless of the length of the legs  34  of the component  30 . Referring to FIG. 5, when the plate  150  is forced upwards, the roller  144  and the plates  120 ,  134  to which it is connected are forced upwards in an arc, due to the upper plate  120  being pivotably connected to the stationary mounting fixture  124 . Upward movement of the plate  120  causes upward movement of the rollers  50   g  which support or cradle the annular forming roll  42   g , thus forcing the annular forming roll  42   g  upwards (for the case where the component  30  has relatively short legs  34 ). The upward and downward movement of the annular forming roll  42   g  is limited by the diameter of its central circular opening  154  through which the arbor  26   g  and sleeve  98   g  pass. 
     The structure for adjustably supporting the annular forming roll  40   g  shown in FIG. 3D is the same as that shown in FIGS. 5 through 8, except that components  124  and  136  are modified so that the forming roll  40   g  is supported at an angle symmetric to that of the forming roll  42   g , as shown in FIG.  3 D. The structure for adjustably supporting the annular forming rolls  40   h  and  42   h  shown in FIG. 3E is substantially the same as that shown in FIGS. 5 through 8, except that the component  124  is modified (by making its upper portion vertical instead of angled) and the components  136  eliminated (the lower plate  134  being welded directly to the upper plate  120 ) so that the forming rolls  40   h  and  42   h  are supported in a substantially vertical position, as shown in FIG.  3 E. 
     FIG. 9 illustrates the structure for adjustably supporting the annular forming roll  40 i of roll-forming station  12   i . Referring to  9 , that structure is similar to that shown in FIG. 5, except that the relatively large roller  52   i  shown schematically in FIG. 1 is used to support the bottom of the annular forming roll  40   i , and the sides of the forming roll  42   i  are maintained in place by side support members  54   i , which make sliding contact with the forming roll  40   i . The bottom roller  52   i  is rotatably supported between a pair of plates  160  which are pivotally connected to a mounting fixture  162  as described above in connection with FIG.  5 . Each of the side support members  54   i  is mounted to a respective mounting plate  164 , each of which has a lower end connected between the plates  160 . A positioning roller  166  may be used to aid in the positioning of the component  30  before it arrives at the roll-forming station  12   i.    
     FIGS. 10-12 illustrate one manner of raising and lowering the plate  150  on which the rollers (e.g. roller  144  shown in FIG. 5) of the annular forming roll support mechanisms rest. Referring to FIG. 10, the plate  150  is snugly supported for vertical movement within an enclosure formed by the walls  152  and two additional walls  170 . Four angled members  172  are bolted to the underside of the plate  150 , and four similarly angled members  174  are bolted to the upper side of a horizontally shiftable plate  176 , which rests on a base plate  178  to which the walls  152  are bolted. 
     A horizontally translatable rod  180  is connected to the shift plate  176  via a bracket  182  fixed to the upper side of the shift plate  176 . For example, the end of the rod  180  may be threaded into a bore  184  (FIG. 12) formed in the bracket  182 . The rod  180  may be horizontally translated into and out of a cylinder  184  under the control of a drive mechanism  186 , such as a screw jack drive. The drive mechanism  186  may include a pair of coupling rods  188  disposed in a direction transverse to the rod  180 , to facilitate interconnection of a plurality of the structures shown in FIG. 10, such as the assembly shown in FIG.  11 . 
     FIG. 11 illustrates the interconnection of three drive mechanisms  186  via a plurality of couplers  190  and drive shafts  192 , the right-most coupler  190  being connected to the drive shaft of a motor  194 . With the construction shown in FIG. 11, the vertical position of the annular forming rolls  40   g ,  40   h ,  40   i  of the roll-forming stations  12   g ,  12   h ,  12   i  may be simultaneously adjusted via the motor  194 . 
     In the operation of the roll-forming machine  10  described above, a sheet of material may be fed to a plurality of roll-forming stations to cause the flanges  32  and legs  34  of a C-shaped component  30  to be formed, the C-shaped component having a first leg length. After the formation of a number of such components, the roll-forming machine  10  can be reconfigured in a simplified manner to produce C-shaped components having different leg lengths. 
     This reconfiguration is accomplished by shifting the outboard frame members  20  in a horizontal direction, as described above in connection with FIG. 2, and then adjusting the vertical position of the three annular forming rolls  40   g ,  40   h ,  40   i , as described above in connection with FIGS.  5  and  9 - 11 . After such adjustments are made, C-shaped components having different leg lengths than the original C-shaped components can be formed. 
     FIGS. 13A and 13B illustrate the structure of one of the upper adjustment mechanisms  88  shown schematically in FIG.  1 B. Referring to FIGS. 13A and 13B, each adjustment mechanism  88  includes a pair of spaced-apart side plates  200  bolted to the top of the support bar  84  (shown schematically in FIG.  1 B). A pivot arm  202  is pivotably disposed between the side plates  200  via a bolt  204  and a nut  206  threaded onto the bolt  204 . The lower end of each pivot arm  202  is connected to a mounting bar  208  via a plurality of bolts  210  which are threaded into a plurality of holes  212  (see FIG. 14) formed in the mounting bar  208 . As shown in FIG. 14, the rollers  80   h ,  80   i  (one of which is shown schematically in FIG.  4 D and one of which is shown schematically in FIG. 4E) are rotatably supported by the mounting bar  208  within a respective elongate slot  214  formed in the mounting bar  208 . The position of the rollers  80   h ,  80   i  relative to the forming rolls  66   h ,  72   h , respectively, is adjustable so that different gap distances may be provided between those components  80   h ,  80   i ,  66   h ,  72   h  to accommodate the formation of Z-shaped components  56  having different thicknesses. 
     The angular position of the pivot arm  202 , and thus of the rollers  80   h ,  80   i  is adjustable via an adjustment mechanism  216  connected to an upper plate  217  bolted to the top of the side plates  200 . The adjustment mechanism  216  includes a headless screw  218 , an adjustable collar assembly  220 , and a nut  222  welded to the bottom end of the screw  218 . 
     The structure of the adjustable collar assembly  220  is shown in FIG.  15 . Referring to FIG. 15, the collar assembly  220  has a first component  224  having a cylindrical head  226 , a cylindrical body portion  228 , a threaded portion  230 , and a nut portion  232 , all of which are formed from a single piece of metal. The nut portion  232  has an internal threaded bore  234  formed therein, and the head and body portion  226 ,  228  have a smooth internal bore  236  formed therein coaxially with the threaded bore  234 . 
     The collar assembly  220  has a second component in the form of an annular collar  238  that is threaded onto the threaded portion  230 . One or more set screws  240  may be provided in the collar  238  to prevent the collar  238  from turning on the threaded portion  230  of the component  224 . 
     Referring also to FIGS. 13A and 13B, the collar assembly  220  is installed on the top plate  217  by rotatably adjusting the position of the collar  238  until the space between the collar  238  and the head  226  is just sufficient to allow rotation of the collar assembly  220 , and then the set screw(s)  240  in the collar  238  are tightened. Consequently, with the headless screw  218  passing through the threaded portion  234  of the nut  232 , rotation of the nut  232  will cause the entire collar assembly  220  to rotate, which will cause vertical displacement of the screw  218  and the nut  222  welded to its bottom end. Neither the screw  218  or the nut  222  rotates since the nut  222  is provided within a narrow slot  240 , formed in a lower surface of the pivot arm  202 , which is just wide enough to accommodate the nut  222 . 
     A bolt  242  is disposed through a threaded bore in the top plate  217  and has a lower end which abuts an upper surface of the pivot arm  202 . A lock nut  244  is threaded onto the bolt  242  to lock its position. After the mechanism  216  has been adjusted to correspond to the desired position of the pivot arm  202  and the rollers  80   h ,  80   i , the bolt  242  is rotated to move it in a downward direction until the lower end of the bolt  242  forces the left-hand end of the pivot arm  202  downwards so that it firmly abuts the nut  222  welded to the screw  218 . 
     FIGS. 16A and 16B illustrate the construction of the lower adjustment mechanisms  90  (schematically shown in FIG. 1B) which are used to adjustably support the rollers  82   h ,  82   i  schematically shown FIGS. 4D and 4E. Referring to FIGS. 16A and 16B, each adjustment mechanism  90  has a pair of lower side plates  250  bolted to the bottom of the support bar  86  (shown schematically in Fig.  1 B). A pivot arm  252  is pivotably disposed between the lower side plates  250  via a bolt  254  and a nut  256  threaded onto the bolt  254 . The lower end of each pivot arm  252  is connected to a mounting bar  258  (which is substantially the same as the mounting bar  208  shown in FIG.  14 ), via a plurality of bolts  260 . 
     A pair of upper side plates  262  are connected to a horizontally disposed plate  264  bolted to the top of the support bar  86 . A top plate  266  is bolted to the upper side plates  262 . An adjustment mechanism  270  substantially the same as the adjustment mechanism  216  described above in connection with FIGS. 13A,  13 B and  15  is connected to the top plate  266 . The adjustment mechanism  270  includes the collar assembly  220  described above. A headless screw  272  is threaded through the collar assembly  220  into the top of an elongate rod  274  having a square cross section and is secured to the rod  274  by a locking nut  276 . The elongate rod  274  passes through a rectangular slot  278  (FIG. 16A) formed in the plate  264  that prevents the rod  274  from rotating. The bottom portion of the rod  274  is disposed in a similar rectangular slot  280  (FIG. 16A) formed in an upper surface of the pivot member  252 , and the bottom end of the rod  274  is provided with a cylindrical member  282  which is disposed within a cylindrical bore  284  in the pivot member  252 . 
     The adjustment of the angular position of the pivot arms  252  and the rollers  82   h ,  82   i  is performed by rotating the collar assembly  220  in the same manner as described above in connection with FIGS. 13A and 13B. No locking assembly is necessary to lock the position of the pivot arms  252  since the weight of the left-hand ends of the pivot arms  252  and the support bar  258  forces the right-hand end of the pivot arms  252  upwards against the bottom end of the square portion of the elongate rod  274 . 
     It should be noted that, in addition to being pivotably adjustable, the position of the rollers  80  relative to the rollers  82  is also horizontally adjustable in a linear direction since the frame members  70  to which the adjustment mechanisms  88  are mounted are laterally movable, as described above in connection with FIG.  2 . 
     Although the roll-forming machine  10  described above forms the flanges of the Z- and C-shaped components before forming the legs of those components, the machine  10  could be modified so that the legs of the Z- and/or C-shaped components are formed before the flanges. 
     Detailed Structure of Roll-Forming Stations 
     The structure of each of the roll-forming stations of the roll-forming machine  10  is shown in more detail in FIGS. 17-19A. FIG. 17 is a side elevational view of one of the roll-forming stations shown generally in FIG.  2 . Referring to FIG. 17, each roll-forming station may be provided with a pair of vertically disposed support plates  300 , each of which acts as a support structure to support an end portion of each of the arbors  18 ,  26 . Each support plate  300  may be provided with a rectangular slot  302  in which the upper bearing assembly  97  (shown schematically in FIG. 2) is disposed. 
     Referring to FIGS. 17 and 18, the bearing assembly  97  may be provided with an outer bearing cap  304  and an inner bearing cap  306 . Referring to FIG. 17, each of the bearing caps  304 ,  306  has a width that is greater than the width of the slot  302 . The bearing caps  304 ,  306  are bolted on either side of a bearing block  308  via a plurality of bolts  310 . As shown in the lower right portion of FIG. 18, the bearing block  308  may have the same thickness as the support plate  300 , and the width of the bearing block  308  may be slightly smaller than the horizontal width of the slot  302  (see FIG. 17) so that the bearing block  308  may be moved smoothly within the slot  302  in a vertical direction. 
     Referring to FIG. 18, the bearing assembly  97  also includes an annular outer bearing cone  312  mounted on the sleeve  96 , an annular inner bearing cone  314  mounted on the sleeve  96  adjacent the outer bearing cone  312 , an annular outer bearing cup  316  mounted within an internal aperture formed in the bearing block  308 , an annular inner bearing cup  318  mounted within the internal aperture formed in the bearing block  308 , and a plurality of cylindrical roller bearings  320  rotatably disposed between the bearing cones  312 ,  314  and the bearing cups  316 ,  318 . 
     An annular inner spacer  322  is mounted on the sleeve  96  adjacent the inner bearing cone  314 , and an annular outer spacer  324  is mounted on the sleeve  96  adjacent the outer bearing cone  316 . An annular locking collar  326  is threaded onto a threaded portion of the sleeve  96 . The sleeve  96  also includes a key portion  330  which is disposed within a slot formed in the arbor  18  to ensure that the arbor  18  and the sleeve  96  always rotate together. 
     Referring to the upper portion of FIG. 18, an adjustment screw  340  is threaded into the upper portion of the bearing block  308 . A jam nut  342  is disposed on the adjustment screw  340 , and the adjustment screw  340  is locked in place within the bearing block  308  via a locking pin  344  which extends through a bore  346  drilled through the bearing block and through the center of the adjustment screw  340 . 
     Referring to FIGS. 17,  19 A and  19 B, the adjustment screw  340  passes through an unthreaded lower bore  348  formed in a cylindrical anchor member  350 , and the adjustment screw  340  is threaded into a threaded upper bore  352  formed in the anchor member  350 . The anchor member  350  is disposed within a bore formed in the upper portion of the support plate  300 , and a retaining collar  354  is threaded onto the upper portion of the anchor member  350  over a washer  356 . The retaining collar  354 , which has a diameter larger than the diameter of the bore formed in the upper portion of the support plate  300 , retains the anchor member  350  and the adjustment screw  340  which is threaded into the bore  352 , to the upper portion of the support plate  300 . 
     Since the upper bearing assembly  97  is slidable within the slot  302  and supported by the adjustment screw  340 , the vertical position of the upper bearing assembly  97  can be is adjusted by rotating the anchor  350  relative to the adjustment screw  340  to change the degree to which the adjustment screw is threaded into the anchor  350 . The upper portion of the anchor  350  is hexagonally shaped at  358  (see FIG. 19B) to facilitate rotational adjustment of the anchor  350 . 
     Referring to FIGS. 19A and 19B, a compression assembly  360  is supported by the anchor  350 . The compression assembly  360  may include a lower washer  362  supported by an enlarged lower portion of the anchor, a plurality (e.g. four) of cone-shaped springs  364  (e.g. Bellville washers) disposed on top of the lower washer  362 , an upper washer  366 , and an annular cover  368 . 
     The compression assembly  360  is installed on the roll-forming machine  10  by tightening the retaining collar  354  to at least such an extent that the upper washer  366  firmly abuts the upper surface of the slot  302  and so that the spring members  364  are in contact with the upper washer  366  and each other, and so that the lowermost spring member  364  is in contact with the lower washer  362 . 
     When a sheet of material having a variable thickness is processed by the roll-forming machine  10 , thicker portions of the sheet of material may cause the forming rolls supported by the upper arbor  18  to move upward, which in turn would cause the upper arbor  18 , the bearing assembly  97 , and the adjustment screw  340  to move upward as well. Such upward movement of the adjustment screw  340  would cause the anchor  350  to move upward relative to the support plate  300 , which in turn would compress the springs  364  between the upper washer  366  (which is forced against the upper surface of the slot  302  and which does not move) and the lower washer  362  (which moves with the anchor  350 ). Consequently, a compression force would be applied to the sheet of material, the amount of which depended upon the force/deflection curve associated with the springs  364 . 
     One example of a non-linear force/deflection curve is illustrated in FIG.  20 A. Referring to FIG. 20A, when the springs  364  are not deflected at all, there would be zero compression force applied to the sheet of material. As the springs became compressed or deflected, the compression force would increase at a non-linear rate, until the maximum compression force was reached at maximum compression or deflection of the springs  364 . 
     As an alternative, the compression assembly  360  could be installed on the roll-forming machine  10  to provide a desired amount of compression pre-load. Such a pre-load would be provided by tightening the retaining collar  354  so that the enlarged bottom portion of the anchor  350  caused the springs  364  to become compressed between the lower washer  362  and the upper washer  366 . In that case, the springs  364  would always apply a minimum compression force, and would always be compressed or deflected by a minimum amount, regardless of the vertical position of the upper arbor  18  and the bearing assembly  97 . 
     The compression force applied by the springs  364  in the case of such a compression pre-load is shown in FIG. 20B, which shows a discontinuous force/deflection curve. Referring to FIG. 20B, without any upward movement of the upper bearing assembly  97  caused by passage of a sheet of material through the roll-forming station, no compression force would be applied by the pre-loaded springs  364 . However, as soon as the upper bearing assembly  97  is forced upwards by the sheet of material, thus forcing further deflection of the springs  364 , the compression force immediately jumps to a non-zero value, corresponding to the amount by which the springs  364  are pre-loaded. As used herein, the term “discontinuous” means a force or curve that changes instantaneously (i.e. has a vertical slope) from one value to another. 
     Referring to FIGS. 17 and 19A, it should be noted that rotation of the anchor  350  (via the nut  358 ) will cause the adjustment screw  340  to move within the threaded portion  352  of the anchor  350 , and will thus change the position of the bearing assembly  97  and the initial gap between the forming rolls disposed on the arbors  18 ,  26 . 
     In order to change the pre-load generated by the springs  364 , the retaining collar  354  is rotated, which will either pull the anchor  350  upwardly or will allow the anchor  350  to move downwardly. It should be noted that when the pre-load is changed by rotating the retaining collar  354 , the initial gap between the forming rolls will also change since any change in vertical position of the anchor  350  will also result in a change in vertical position of the adjustment screw  340 . Thus, for example, in order to change the initial gap between the forming rolls while retaining a predetermined pre-load (or zero pre-load), the anchor  350  can be rotated by a desired amount (to change the gap) and the retaining member  354  is rotated by the same amount (to maintain the same pre-load). 
     The roll-forming machine  10  described above can be used to process sheets of material having non-uniform thicknesses, such as a sheet of material having a relatively small thickness and a relatively large thickness. The roll-forming machine  10  can also be used to process sheets of material having uniform thickness. The roll-forming machine  10  can also be used to continuously process different sheets of material, where each sheet has a uniform but different thickness, without the need to change the initial vertical gap between the forming rolls. 
     In one method of using the roll-forming machine  10 , the position of each of the adjustment screws  340  of each roll-forming station may be adjusted to an initial position so that the vertical gap (preferably a non-zero gap) between the forming rolls of the roll-forming stations is less than the thickness of a sheet of material, and then the sheet of material may be passed between the forming rolls supported by the arbors  18 ,  26  so that the initial gap between the forming rolls disposed on arbors  18 ,  26  is increased from the initial gap to a distance substantially equal to the thickness of the sheet of material to cause a compression force to be applied to the sheet of material by the compression assembly  360 . 
     Although the compression assembly  360  of each roll-forming station has been described above as including a plurality of cone-shaped springs, alternative compression assemblies could be utilized. For example, springs of other shapes could be utilized. Alternatively, instead of using springs, other structures that would generate a desired compression force could be utilized, such as pneumatic cylinders or hydraulic systems provided with appropriate bleed valves. 
     The compression assemblies described above could also be used in connection with other forming rolls, or rollers, incorporated in the roll-forming machine  10 . For example, the compression assemblies could be used in connection with the rollers  80 ,  82  which are designed to contact the corners of a sheet of material, as shown in FIGS. 4D and 4E for example. In that case, the compression assemblies could be incorporated in the structure which supports the rollers  80 ,  82 , such as the structures shown in FIGS. 13A,  13 B,  16 A and  16 B. 
     Numerous additional modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. This description is to be construed as illustrative only, and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.