Abstract:
The present invention is a method for advancing and cutting tube blanks into desired lengths and ejecting the unusable piece of tubing remaining after all of the usable cuts have been made. The machine for cutting the tubes of the present invention is preferably a standard supported shear type cutting machine and the ejection of the tube is accomplished via a pusher that is mounted for reciprocation on a carriage such that when the last piece of usable tubing has been cut from the tube blank the pusher may be activated to eject the tubing from the cutting machine.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the field of specification tube cutting machinery and methods used to produce tubes and tubular pieces from longer stock tubes and, more particularly, to an apparatus and method for advancing and cutting a long tube and ejecting the remaining scrap tube from the cutting machine after the last specified piece is cut, thereby increasing the efficiency of the cutting operation and eliminating a time consuming and dangerous work step from the tube cutting process. In particular, the invention provides a gripper for securely holding the tube during the cutting operation. The gripper is attached to a carriage which is horizontally translatable with respect to the cutting apparatus. Additionally, a pusher is provided for automatically ejecting the last piece of cut tubing from the machine. The pusher is mounted on the carriage and reciprocates forward once the last specified piece of tubing has been cut in order to eject the end piece of tubing from the cutting machine. Preferably the tube cutting machine described herein is used in combination with a shear cutting device, although other methods of cutting tubing are known and would be considered operable in the present invention. 
     Methods for cutting long tubular stock into pieces of specified length are known. For example, in U.S. Pat. No. 2,837,156 to Brehm a conventional machine for cutting continuously advancing tubing is disclosed. This method, known as the Brehm method, is an example of a cutting method that is useful with the invention disclosed herein. In brief, the Brehm method involves the use of two dies, an inner die for contacting the inner surface of the tubing to be cut and an outer die for contacting the outer surface of the tubing to be cut. In order to cut the tubing, one die (generally the outer die) is moved with respect to the other die thereby “shearing” the tubing. This method for cutting tubing is preferred over other prior art methods that involve “sawing” the tubing because very little of the tubing is destroyed. Furthermore, the use of the Brehm method creates tube ends that are generally smooth and burr free. 
     Over the years, there have been many attempts to improve on the Brehm method in order to improve the quality and efficiency of the cutting process. For example, U.S. Pat. No. 4,205,569 to Horn et al. discloses a tube cutting apparatus using the Brehm method wherein multiple tube segments may be cut in a single shearing operation. After the tubing is cut, the slices of cut tubing are advanced onto an ejector rod that is then retracted to allow the cut tubing to fall into a collection bin. Additionally, the Horn et al. patent discloses dies that define inclined planes in order to cut tubes on a bias. 
     Similarly, U.S. Pat. No. 5,406,870 to Suitts et al. also discloses an improvement to the basic Brehm method in which the loader and feeder mechanisms for the cutting machine are integrated into one piece of equipment. In particular, in the Suitts et al. patent, a method and apparatus for cutting tubing is disclosed using the shear cutting method wherein the tubing is fed automatically to the cutter and is gripped and advanced to the cutting station. The cut tube is advanced along an arbor and is dropped off into a bin at the end of the arbor. The cutting machine of the Suitts et al. patent is equipped with an infrared sensing system that works in conjunction with computer programming to discard the scrap materials separately from the specification milled tubing without the need for a mechanical stop finger to determine the tube cutoff length. 
     Thus, while several prior art methods exist for continuously loading and cutting tubing while discarding any scrap created thereby, these methods tend to be complex and expensive, requiring the use of infrared sensing equipment, etc. Additionally, they also require the use of an arbor that extends past the end of the die and various forms of expensive and elaborate equipment add ons. 
     Accordingly, there exists a need for a method and apparatus for cutting tubing and automatically ejecting any leftover scrap tubing after all of the usable tubing has been cut that is mechanically simple and relatively inexpensive to fabricate and operate and which does not require the use of overly expensive or elaborate equipment to implement. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved method and apparatus for advancing and cutting tube blanks into desired lengths and ejecting the unusable piece of tubing remaining after all of the usable cuts have been made. The machine for cutting the tubes of the present invention is preferably a standard supported shear type cutting machine. 
     In a preferred embodiment, the present invention consists of a cutting machine, such as a supported shear type cutting machine, for cutting a tubular workpiece and a base upon which the cutting machine is mounted. A carriage is mounted either on the base, or in close proximity thereto, in a manner that allows the carriage independent movement with respect to the base. The carriage is operatively connected to a motor, preferably a stepper motor, so that the carriage may be automatically moved precise distances during the cutting process. The carriage is also equipped with a device, such as grippers, for securing and advancing the tubular workpiece with the carriage. A pusher, shaped to engage the end of the tubular workpiece, is mounted on the carriage for reciprocal movement with respect to the carriage. The pusher includes a sensor, such as a contact switch, positioned on a portion of the carriage so that the position of the pusher with respect to the carriage may be ascertained at at least one point along the reciprocation route of the pusher. 
     The tube advancer, cutter, ejector of the present invention is preferably operated by selecting a tubular workpiece to be cut and positioning the workpiece on a cradle in the base in alignment with the cutter. After the cutting machine is programmed to make cuts at the desired lengths, the machine is activated. The carriage then begins to travel forward, thereby contacting the pusher with the back end of the tubular workpiece. The contact of the pusher with the tubular workpiece causes relative rearward movement of the pusher with respect to the carriage while the carriage continues to move forward. During this time the grippers, in an open position, continue to move with the carriage in a position coaxial with the tubular workpiece. Then, after the grippers have traveled a predefined distance down the length of the workpiece whereby they can securely grip and advance the workpiece, a sensor is activated sending a signal to activate the grippers to grip the tube and stop the pusher from further relative rearward movement with respect to the carriage. This signal can be sent via an infrared sensor or the like, but preferably is activated by a contact on the back of the pusher. 
     The carriage continues forward, now with the workpiece secured thereto, a designated cutting length and stopped. This length can be controlled using a stepper motor, various sensors, or other methods known in the art. The cutting machine is activated to make the desired cut and the carriage is moved again the designated length and the desired cut is made. This process continues until all of the desired lengths of tube have been cut from the tubular workpiece. The controller for the carriage, having calculated the number of cuts that have been made, then deactivates the grippers, thereby releasing hold of the remaining scrap piece of the tubular workpiece. The opening of the grippers signals the pusher to stroke forward, thereby ejecting the remaining piece of the workpiece through the cutting machine. The carriage then cycles back to the rear end of the base and is reset to cut another workpiece. 
     Accordingly, it is an object of the present invention to provide a tube advancer, cutter, ejector for cutting tubes of desired lengths from tubular workpieces which is mechanically simple and relatively inexpensive to fabricate and operate and which does not require the use of overly expensive or elaborate equipment to implement. 
     Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a preferred embodiment of the tube advancer, cutter, ejector of the present invention; 
     FIG. 2 is a detail top plan view of the carriage in the tube advancer, cutter, ejector of FIG. 1; 
     FIG. 3 is a cut away side elevational view of the carriage taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a side elevational view of the carriage of FIG. 2 showing the activation of the grippers for securely holding a tubular workpiece; 
     FIG. 5 is a side elevational view of the carriage of FIG. 4 showing the deactivization of the grippers for releasing the tubular workpiece; 
     FIG. 6 is a detail side elevation view of the carriage/pusher assembly for use with the tube advancer, cutter, ejector of FIG. 1 showing the pusher in a fully retracted position; 
     FIG. 7 is a detail side elevation view of the carriage/pusher assembly of FIG. 6 shown in a tube ejecting position; 
     FIG. 8 is a side perspective view of the carriage/pusher assembly of FIG. 6; and 
     FIG. 9 is a side perspective view of the carriage/pusher assembly of FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     In accordance with a preferred embodiment of the present invention, as shown best in FIG. 1, the present invention consists of a cutting machine (not shown), such as a supported shear type cutting machine, for cutting a tubular workpiece  10  into tubes of desired lengths. The cutting machine includes a base  12  upon which the cutting machine is mounted having a cradle  14  for holding the tubular workpiece  10  during the cutting process and a control panel  16  for controlling operation of the cutting machine, and a carriage  20 . The carriage  20  is mounted either on the base  12 , or in close proximity thereto, in a manner that allows the carriage  20  independent movement with respect to the base  12 . As best shown in FIG. 3, the carriage  20  is preferably mounted on a track or rail system  22  so that the carriage  20  may be moved longitudinally with respect to the base  12 . The carriage  20  is operatively connected to a motor (not shown), preferably a stepper motor, so that the carriage  20  may be automatically moved precise distances during the cutting process. 
     The carriage  20  includes a device for securing and advancing the tubular workpiece  10  with the carriage  20  towards the cutting machine. As best shown in FIGS. 4-9, in a preferred embodiment, the device is a pair of grippers  24  that are operated by a motor to either a closed postion (FIGS. 4,  6 ,  8 ) thereby securing the tubular workpiece  10  for movement with the carriage  20 , or to an open position (FIGS. 5,  7 ,  9 ) thereby allowing movement of the tubular workpiece  10  between the grippers  24 . A pusher  26 , is also mounted on the carriage  20  and is shaped to engage the end of the tubular workpiece  10 . In a preferred embodiment, the pusher  26  is mounted on the piston  28  of a solenoid assembly  30  so that the pusher  26  may move axially with respect to the workpiece  10  and be stroked independently of the carriage  20  to eject an unused portion of the tubular workpiece  10 . 
     The carriage  20  includes a sensor so that the position of the pusher  26  with respect to the carriage  20  may be ascertained at at least one point along the reciprocation route of the pusher  26 . In a preferred embodiment, this sensor is a contact switch assembly  32  that includes a contact  34  mounted on the back of the pusher  26  that contacts the switch  36  part of the assembly  32 . Thus, when the carriage  20  moves forward and the pusher  26  contacts the end of the tubular workpiece  10 , further forward movement of the pusher  26  is prevented while the carriage  20  continues forward until the contact  32  contacts the switch  36 . As will be discussed in greater detail below, the contact of the contact  32  with the switch  36  signals the grippers  34  to close upon the tubular workpiece  10 , thereby advancing the workpiece  10  with the carriage  20 . 
     The advancer, cutter, ejector of the present invention is preferably operated by selecting a tubular workpiece  10  to be cut and positioning the workpiece on the cradle  14  in the base  12  in alignment with the cutting machine (not shown). After the cutting machine is programmed to make cuts at the desired lengths, the machine is activated at the control panel  16 . The carriage  20  then begins to travel forward, thereby contacting the pusher  26  with the back end of the tubular workpiece  10 . The contact of the pusher  26  with the tubular workpiece  10  causes relative rearward movement of the pusher  26  with respect to the carriage  20  while the carriage  20  continues to move forward. During this time, as shown best in FIG. 5, the grippers  24 , in an open position, continue to move with the carriage  20  in a position coaxial with the tubular workpiece  10 . Then, after the grippers  24  have traveled a predefined distance down the length of the workpiece  10  whereby they can securely grip and advance the workpiece  10 , a sensor, such as a contact switch assembly  32 , is activated sending a signal to activate the grippers  24  to grip the tube  10  and stop the pusher  26  from further relative rearward movement with respect to the carriage  20 . If a contact switch assembly  32  is used in connection with a solenoid assembly  30 , as in the preferred embodiment depicted herein, the switch  36  can act as a “stop” to prevent further relative rearward movement of the pusher  26 . However, in other embodiments, it would be possible to have a sensor send a signal to the pusher assembly to prevent further relative rearward movement of the pusher  26 . Of course, in any embodiment, the grippers  24  should not be closed until they have passed the pusher  26 , and only should be closed once they can securely hold the workpiece  10  for advancing and cutting. 
     The carriage  20  continues forward, now with the workpiece  10  secured thereto, a designated cutting length and stopped. As discussed above, the movement of the carriage  20  may be controlled in a number of different ways, such as through the use of standard motor and corresponding sensors, hydraulics, etc. Preferably, however, the carriage  20  is moved along the tracks or rails  22  using a stepper motor (not shown) that is precisely controlled by a controller (not shown). 
     Next, once the tubular workpiece  10  has been positioned to make a cut of the desired length, the cutting machine is activated and the carriage  20  is moved again the designated length and the desired cut is made. This process continues until all of the desired lengths of tube have been cut from the tubular workpiece  10 . The controller for the carriage  20 , having calculated the number of cuts that have been made, then deactivates the grippers  24 , thereby releasing hold of the tubular workpiece  10 . The opening of the grippers  24  signals the solenoid assembly  30  to stroke forward, thereby ejecting the remaining piece of the workpiece  10  through the cutting machine. The carriage  20  then cycles back to the rear end of the base  12  and is reset to cut another workpiece  10 . 
     While the form of the apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.