Abstract:
A machine for bending thin wall electrical conduit having first and second spaced apart forming shoes, each having partial arcuate forming surfaces and a movable arcuate shaped third forming shoe mounted on the tabletop between the first and second forming shoes connected to an actuator for lineal movement forcing a section of tubing against the first and second forming surfaces with quick release retention wheels mounted on a flat plate in a cavity in the tabletop, the cavity having a load-supporting vertical edge for supporting the retention members under load and a pocket on the opposite side from the load supporting edge receiving an edge of the plate preventing it from lifting out of the cavity under load.

Description:
The present invention relates to tube bending and more particularly with apparatus which produces accurately bent electrical conduit tubing in a single operation which reproducible at an increased rate of speed. 
   BACKGROUND OF THE INVENTION 
   Tube bending machines have been designed and used for at least the past one hundred years, as indicated in the prior art. Many of those machines required a single set up for each bend, while more modern machines such as the present invention, performed multiple bends in a single set up. Many of these machines have been relatively large and unwieldy, and not particularly adaptable to on-site construction. Electrical conduit bending in commercial buildings today frequently utilize a set of standard bends, which would include right angle bends, flat saddle bends, round saddle bends and off-set bends. With these uniform bending designs, all of the tubing for a commercial structure can be pre-bent to set dimensions rather than the old method of bending each section of tubing on the site as it is installed, which is far more time consuming. 
   The machine of the present invention will produce all of the above mentioned bends to set dimensions in a matter of seconds for each tube, and then accurately duplicate those bends however many times needed with each one being precisely like the one before. 
   SUMMARY OF THE INVENTION 
   The present invention has an enhanced level of productivity and accuracy over other machines in the marketplace. Once the machine is set up, the bending operation can be accomplished by an electrician&#39;s helper or apprentice, thus, minimizing the labor rate for producing a pre-formed tubing. 
   The set up time to change bends or diameter of tubing, with the present invention, is minimized with its various quick release components. To hold the ends of tubing during bending, a quick release retention wheel is retained in a cavity in the top of the bending table, which quickly releases as it is lifted upward. The retention wheel while in use is capable of substantial horizontal loadings without releasing. The forming shoes, on which the tubing is bent, are freely mounted on an open-ended axle. The axle includes a square-shaped end, which can quickly be engaged by a hand crank for removing the axle so as to change the setting as to the width of a saddle bend. The movable forming shoe, which bends the tubing against other forming shoes, is driven by a screw actuator which causes a slide member to move linearly in a slot in the table until it reaches the preset position of the pointer flag whereupon a micro-switch or an electronic sensor stops the motor at a precise position pre-determined by a pointer flag which is set opposite a scale thus defining the offset distance of the particular tubing being bent. 
   It is, therefore, the object of the present invention is to provide an electrical conduit-bending machine with increased production capability and repeatable accuracy. 
   Another object of the present invention is to provide a bending machine for various diameter conduit which has quick release bending shoes and stops. 
   Another object of the present invention is to provide a portable conduit bending machine electrically powered by a hand-held remote control. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a tube bending machine constructed with the principals of the present invention, set up to form a round saddle bend; 
       FIG. 2  is an isometric view to an enlarged scale of the quick release retention wheel also referred to as the quick brake. 
       FIG. 3  is a sectional view taken along lines  3 — 3  of  FIG. 2  with the supporting plate of the retention wheel positioned in a cavity in the bending machine table; 
       FIG. 4  is an isometric view to an enlarged scale of a quick release axle and an associated hand crank; 
       FIG. 5  is a top plan view of the tube bending machine with the forming shoes and retention wheels positioned to form a round saddle bend; 
       FIG. 6  is a similar view to  FIG. 5  with the forming shoes positioned to form an offset bend; 
       FIG. 7  is a sectional view taken along line  7 — 7  of  FIG. 5 ; 
       FIG. 8  is a sectional view taken along line  8 — 8  of  FIG. 5 ; 
       FIG. 9  is a detailed view of the powered forming shoe to an enlarged scale showing the drive screw actuator and its associated parts taken along line  9 — 9  of  FIG. 7 ; 
       FIG. 10  is a plan view of a flat saddle shoe with its connected shim stop assembly shown removed; and 
       FIG. 11  is a sectional view to an enlarged scale taken along line  11 — 11  of  FIG. 10  with all the shims inserted for a minimum diameter conduit; and 
       FIG. 12  is a schematic plan view of the automatic preset bending apparatus and its sensors. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring in detail to the drawings, the bending machine of the present invention is generally referred to by reference numeral  10  as shown in  FIG. 1 . The machine  10  comprises a table top  13  supported by a four moveable legs  12  which are held in place by set screws  11 . Located at the four corners of the table are retractable handles  14 . The machine  10  is easily transported by two persons with the legs either removed or in place. Located in the center of the table  13  is a bearing slot  15  in which is positioned a slide member  36  which in turn drives a powered forming shoe  34  back and forth in slot  15 . Positioned under slot  15  and parallel thereto is a screw actuator  40 , also referred to as a jack screw, which is rotatably journaled at both ends of the table, as seen in  FIG. 7 , and is powered by a reversible motor  44  through gears  45 . Actuator screw  40  is rotatably supported in journals  46  located at each end of the screw, which in turn are mounted on the sidewalls of top  13 . Slide  36  is connected to a threaded bushing  41 , which moves the slide  36  forwards and backwards depending upon the rotational direction of screw  40 . Slide  36  includes a pin  38 , as seen in  FIG. 7 , which supports round saddle forming shoe  34 , and is essentially half circular in shape. While  FIGS. 1 ,  5 ,  7 , and  9  illustrate a round saddle forming shoe, other types of forming shoes can be utilized such as a flat saddle shoe  56 , as shown in  FIGS. 10 and 11 , and a offset forming shoe  49 , as shown in  FIG. 6 . 
   While the previously mentioned forming shoe  34  moves in a linear direction in slot  15  there are also two stationary forming shoes  24  and  25  which are half circular in shape and rotate about fixed axles  28  and  29  as shown in  FIG. 1 . Located on the arcuate surface of forming shoes  24  and  25  is a recessed trough  26  which receives essentially half of the tube or conduit  50  being bent. Forming shoe  34  includes a similar trough  35 . When bending a different diameter conduit such as ½ inch, ¾ inch and 1 inch, a different set of shoes  24 ,  25  and  34  are utilized wherein the trough  26  fits the diameter of the tubing being bent. The shoes for each diameter are typically all painted the same color so that they can be readily identified. 
   While bending tube  50 , as shown in  FIGS. 5 and 1 , the outer ends of the tubing  50  must be supported by retention wheels  16 , also referred to as quick brakes. Once the tubing is formed, as shown, the quick brake  16  are lifted upward by handles  37  so that the formed tube  50  can be removed from the machine. 
   Quick brake  16 , as shown in detail in  FIGS. 2 and 3 , comprises a wheel  17  having a trough therein which freely rotates on axle  20 . The lower end of axle  20 , as shown in  FIGS. 2 and 3 , is threaded into holes  21  in a flat rectangular plate  18 . Plate  18  is positioned in cavity  22  in the top of table  13 , as shown in  FIG. 3  and  FIG. 1 . The forward edge of plate  18  has a beveled edge  19  which is received in a pocket formed by an overlapping plate  23  attached to top  13  while the rear edge of plate  18  butts against the vertical edge of cavity  22 . During bending the load on quick brake  16  is to the right, as seen in  FIG. 3 , with overlapping plate  23  preventing the quick brake from tilting out of cavity  22 . To remove quick brake  16 , the handle of  37  is gripped, lifting the rear edge of plate  18  upward and thereby removing the quick brake  16  from the table. 
   Quick release axle  28 , as shown in  FIG. 4 , is threadably received in any one of a series longitudinal holes  72  spaced in parallel relationship with the length of the tubing  50  being formed, as shown in  FIGS. 5 and 6 . The spacing of these holes  72  permits forming of saddles having different widths. Quick release axles of  28  and  29  include a square head  30  at the upper end, which is engagable by a removable crank  31  thereby permitting a quick repositioning of the longitudinal spacing of axles  28  for various width saddle bends. The three laterally positioned holes  21  in plate  18  permit various size tubing to be inserted between forming shoe  24  and wheel  17  of quick brake  16 . 
   An offset bend conduit  50 ′, as illustrated in  FIG. 6 , utilizes a different forming shoe  49 , with forming shoe  25  and right quick brake  16 . Offset forming shoe  49  includes a slot  51  through which the conduit  50 ′ is inserted. Located on the left side of slot  51  is a retention projection  52 , which takes the place of left quick brake  16 . As the forming shoe  49  begins to move upward, the left end of the tube  50 ′ is held horizontal while the center section of the tube is bent about the arcuate surfaces of shoe  49  and stationary shoe  25 . 
   Positioned laterally on table top  13 , as seen in  FIGS. 5 and 6 , is a scale  48  which determines the lateral offset dimension of the particular tube being bent. Positioned in slot  15  is a pointer flag  43 , as seen in  FIGS. 1 ,  5 ,  6 ,  7  and  8 . A pointer flag  43  includes a pointer, which is aligned with the scale  48  to define the inches of offset the bending machine is to form. Attached to the underside of pointer flag  43 , as seen in  FIGS. 8 and 12 , is a flat metal plate  66 . A first sensor means  67  is mounted on slide  36  underneath the table and moves with bending shoe  34 , as shown in  FIGS. 7 ,  9  and  12 . When the sensor means  67  passes under the edge of flat plate  66 ; the sensor  67  opens a relay and screw actuator motor  44  is stopped at the precise offset distance required for the bend. The sensors  67  and  68  are inductive proximity sensors well known in the prior art such as Cutler Hammer Model 182A505-A. The operator controlling the machine moves a hand held switch, not shown, to the retract position, wherein screw motor  44  is activated in the reverse direction and slide  36  and forming shoe  34  are returned to the initial position, whereupon a vertical metal plate  70  moving with the slide member  36  passes a second stationary sensor  68  and stops the rotation of the screw actuator  40  as shown in  FIG. 12 . Second sensor  68  is stationary and mounted on the underside of tabletop  13 . 
   The bending shoes  24 ,  25  and  34  all require a trough  26  and  35  in the shoe that corresponds with the diameter of the conduit being bent. The supports for all the above-mentioned shoes are all sliding fits permitting a quick removable and substitution for shoes having different width troughs. For example, both shoes  24  and  25  are merely lifted off their support axles  28  and  29 , while forming shoe  34  is slid horizontally off of pin  38 . If the width of the offset bend needs to be widened, axles  28  and  29  are quickly removed by hand crank  31  and reset in a series of longitudinally spaced threaded holes  72 , as seen in  FIGS. 5 and 6 . Shoes  24  or  25  when rotated 180 degrees, releases the conduit section  50  for removal. The offset bend conduit shown in  FIG. 6  is removed from the machine by rotating forming shoe  25 , 180 degrees and then sliding conduit  50 ′ to the right until the left end of the conduit clears offset forming shoe  49 . 
   The retention wheel  17  of quick brake  16  does not require a precise diameter trough in their contact since the tubing  50  is not being bent about those arcuate surfaces of wheel  17 , but rather merely held in place while the bending of the tubing is taking place on the larger diameter forming shoes  24 ,  25 ,  34  and  49 . To accommodate different tubing diameters, the quick brakes  16  must be slightly adjusted laterally from forming shoes  24  and  25 . This lateral adjustment takes place by resetting axles  20  in quick brake  16  in one of three holes as illustrated in  FIGS. 2 and 3 . In the prior art, this is achieved by a second and third row of holes  72  laterally spaced in the table top  13 . The wheels  17  and the quick brakes  16  are easily reset in different holes  21  in the mounting plate  18  as seen in  FIG. 2  and by handle  23 . All of the adjustments on the bending machine of the present invention are achieved manually without any additional tools, thus decreasing the change time between different bends, different diameter tubing, and different width saddles. 
   A flat saddle bend is achieved by replacing round saddle-bending shoe  34  of  FIG. 1  with forming shoe  56  as shown in  FIG. 10 . A flat saddle bend includes two arcuate sections  57  joined by a straight section  55 , as seen in  FIG. 10 . To achieve this bend, it is necessary to retain the conduit in bending shoe  56  at the center of the shoe so it retains a straight section in the bend rather than one large circular section. This is achieved with the use of shim assembly  64 , as shown in  FIGS. 10 and 11 . Shim assembly  64 , as best seen in  FIG. 11 , includes three varying thickness shim plates  61 ,  62  and  63  which are adjusted for the diameter of tubing being bent so that the tubing  50 ′ is held within trough  57 . Shim assembly  64  is inserted in shoe  56  through slot  58  on the right side as seen in  FIG. 11  with the thinnest shim  61  extending across  57  to the opposite side through a slot  60 . The shape of the shims and thickness, of course, could be varied to handle additional diameter tubing as required. The shim assembly  64  is held together by an eyebolt and cable  65  so that it is not separated from forming shoe  56  when not in use. 
   The electrical control of the machine, which is not shown, can be any type of forward and reverse switch that can be mounted in the body of the table top  13  or on an electrical cable which the operator can hand hold while moving around the table. 
   In the typical operation, the operator will set the pointer flag  43  in alignment with scale  48  at the precise offset of the bend that is desired. Pointer flag  43  has an attached metal plate  66  positioned under the table as seen in  FIGS. 8 ,  9  and  12 . Attached to slide  36  and forming shoe  34  is a sensor  67 , which moves with the forming shoe  34  and when sensor  67  passes the front edge of plate  66 , a relay stops motor  44  at that precise offset position. When the controller switches to the return position, motor  44  is energized in the opposite direction and retracts the forming shoe assembly to its retracted position which is determined by the stationary second sensor  68  located under the table and energized by a vertical plate  70  passing thereby. 
   Although this invention has been disclosed in the context of certain preferred embodiments in examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically embodiments to other alternative embodiments and obvious modifications and equivalents. According to the way it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described upon, but should be determined only by a fair reading of the claims that follow.