Abstract:
A method for cutting or trimming a hollow object having one or more relatively thin walls, the method including an oscillation step that reduces wall deformation at the site of the initial cut to produce a relatively straight leading edge on the object, in combination with a further cutting step that does not include oscillation of a cutting blade. A second oscillation step can be performed after the non-oscillation step that leads to the separation of the object into two pieces and also produces a relatively straight trailing edge. A device for performing the cutting methods is disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for cutting or trimming a hollow object having one or more relatively thin walls, the method including an oscillation step that reduces wall deformation at the site of the initial cut to produce a relatively straight leading edge on the object, in combination with a further cutting step that does not include oscillation of a cutting blade. A second oscillation step can be performed after the non-oscillation step, as the cut begins to exit the part, that leads to the separation of the object into two pieces and also produces a relatively straight trailing edge. A device for performing the cutting methods is disclosed. 
     BACKGROUND OF THE INVENTION 
     Hollow objects or parts having relatively thin walls, such as those formed from plastic, can be difficult to cut or trim to produce a finished part having a relatively straight edge. At the start of a cutting operation, when utilizing a knife or other cutting device with a fixed blade, the material of the object can deflect inwardly and away from the pressure exerted by the blade, generally until the blade enters the material. Once the blade has cut or been passed through a portion of the material, a straight-line cut can be produced until reaching the end point of the object at which time the material thereof may deflect outwardly, away from the cutting pressure, until the blade separates the object or article into two pieces. Thus, in some embodiments the finished part may have a cut-finished end with a scalloped appearance, wherein the leading edge and trailing edge of the object is longer than a central area. 
     Although various cutting devices are known to those of ordinary skill in the art, for example knives, saws, routers, hot knives, ultra sonic knives, and guillotines, the art still needs a method for cutting hollow, relatively thin-walled articles or objects that results in a finished product having a relatively straight edge. 
     SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a method for cutting or trimming a thin-walled, hollow object or article to produce a finished article having a relatively straight-edged surface. 
     Still another object of the present invention is to provide a process for cutting or trimming hollow plastic molded parts using at least two different cutting sequences including an oscillation step wherein a knife or blade, preferably having a straight, non-serrated edge, is oscillated while cutting through a portion of the article, thereby reducing or preventing distortion of the part, and a second step free of the oscillation during cutting. 
     Yet another object of the present invention is to provide an oscillation cutting step, wherein a knife or blade is oscillated during first contact of the knife or blade on an uncut hollow plastic part or object, wherein the oscillation occurs, generally transverse or perpendicular to a cutting axis in one embodiment, while the knife or blade is moved along the cutting axis and further into the part or object. 
     A further object of the present invention is provide a method which discontinues an oscillation of the knife or blade after the knife or blade has entered into the object a desired distance, wherein the knife or blade continues to cut the object as the knife or blade is moved along the cutting axis. 
     Still another object of the present invention is to perform a second oscillation step after a non-oscillation step as the knife or blade approaches an end of the object opposite the first end of the object first cut by the knife or blade. The second, further oscillation step is continued until the object is cut into two pieces or a desired cutting operation has otherwise been performed. 
     In a further aspect, the knife or blade can be oscillated during the entire cutting process. 
     In one aspect of the invention, a method for cutting an object having a wall and at least one hollow portion is disclosed, comprising the steps of obtaining the object; cutting the object using at least two different cutting sequences, including an oscillation step wherein a blade is oscillated while first contacting and cutting into a portion of the object followed by a second step of cutting the object without oscillating the blade. 
     In another aspect of the invention, a cutting method for objects having a hollow portion is disclosed, comprising the steps of: obtaining an object to be cut; obtaining a cutting device comprising a frame and a carriage movable in relation to the frame along a cutting axis, an oscillating device connected to the carriage and arranged to selectively oscillate the carriage on a second oscillating axis arranged from about 35° to 90° in relation to the cutting axis, and a cutting blade having a cutting edge for cutting the object; moving the carriage towards the object along the cutting axis and oscillating the cutting blade prior to and/or during first contact of the object with the cutting blade; and ceasing oscillation of the cutting blade after a period of time and continuing to cut the object with the cutting blade along the cutting axis. 
     In yet another aspect of the invention, a cutting device is disclosed, comprising a frame and a carriage movable in relation to the frame along a cutting axis, and oscillating device connected to the carriage and arranged to selectively oscillate the carriage on a second oscillating axis arranged at an angle of about 35° to 90° in relation to the cutting axis, and a cutting blade having a cutting edge for cutting the object operatively connected to the carriage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and other features and advantages will become apparent by reading the detailed description of the invention, taken together with the drawings, wherein: 
         FIG. 1  is a perspective view of one embodiment of a cutting device of a present invention suitable to perform the cutting methods described herein; 
         FIG. 2  is a front view of the device illustrated in  FIG. 1 ; 
         FIG. 3  is a top view of the device illustrated in  FIG. 1 ; and 
         FIG. 4A ,  FIG. 4B ,  FIG. 4C  and  FIG. 4D  visually illustrate one embodiment of a cutting method of the present invention wherein  FIG. 4A  shows a first stage wherein the carriage is located at a home position prior to being advanced toward the article,  FIG. 4B  shows a second stage wherein the carriage has been advanced towards the article and is oscillated while cutting through a first portion of the article,  FIG. 4C  shows a third stage illustrating the cutting knife or blade cutting the article along the cutting axis while no oscillation is being performed, and  FIG. 4D  shows a fourth stage wherein oscillation is resumed as the cutting knife or blade approaches the second or distal end of the article opposite the first end of the object cut by the knife or blade. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This description of preferred embodiments is to be read in connection with the accompanying drawings, which are part of the entire written description of this invention. In the description, corresponding reference numbers are used throughout to identify the same or functionally similar elements. Relative terms such as “horizontal,” “vertical,” “up,” “upper”, “down,” “lower”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and are not intended to require a particular orientation unless specifically stated as such. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. 
     The methods or processes of the present invention for cutting hollow, thin-walled objects or parts, such as plastic parts utilize two or more cutting steps in sequence, including a first cutting step wherein a straight, non-serrated knife or blade is oscillated in a direction other than along a cutting axis and contacted with a leading edge of the part at a location desired to be cut. The second cutting step is a non-oscillation cutting procedure that is performed by pushing or pulling the knife or blade through a portion of the part along the cutting axis after the first cutting step has been performed. In a preferred embodiment, a second oscillation cutting step is performed after the non-oscillation step as the knife or blade approaches a distal end of the part. The second oscillation step is continued until the part is cut into two pieces. 
     The methods of the present invention solve various problems of the prior art methods that are encountered when cutting an object or part into a final shape. Relatively thin-walled, hollow, plastic parts such as formed by blow molding, rotational molding or other process are only semi-rigid in some embodiments. When pressure from a knife or blade is exerted onto the outside of a hollow plastic part, the knife or blade can deform the part, sometimes to the extent that the part is no longer within manufacturing tolerances. The manufacturing tolerances may vary with different applications, but can be relatively small. The methods of the present invention provide an economical cutting process that reduces deformation of the plastic part and provides a straight or square edge to the finished part. 
     Referring now to the drawings,  FIGS. 1-3  illustrate a cutting device  10  including a base or frame  12  having a mounting surface  14  that is adapted to be placed upon and/or connected to a support surface via a fastener or other suitable attachment element(s). Support gussets  16  are utilized in some embodiments to provide rigidity to cutting device  10 . 
     A guide rail assembly  20  is connected to the frame  12  for moving carriage along a linear cutting axis  18 . The cutting axis utilized allows the cutting knife or blade  60  to cut or trim a desired object or part into two or more separate pieces. Guide rail assembly  20  includes one or more guide rails  21  that direct carriage  30  along cutting axis  18  and engage with one or more carriage bearings  32  of carriage  30  that comprise linear bearings in one embodiment. Carriage bearings  32  provide low friction travel of the carriage  30  on the guide rail assembly  20 . 
     A drive system  22 , a screw drive in one embodiment, is present on the guide rail assembly. Drive system  22  includes a servo motor  23  operatively connected to a screw  24  that is connected to the guide rail assembly  20  by two bearings supports  25 . A screw drive nut  27  operatively connected to screw  24  is connected to carriage  30 , in one embodiment by connecting a suitable bracket between the screw drive nut  27  and carriage  30 . The screw drive nut  27  drives the carriage  30  forward or backward along cutting axis  18  when the servo motor  23  is actuated. 
     A carriage mount plate  33  connected to carriage bearings  32  includes a carriage guide rail assembly  40 , see  FIG. 3 , having a carriage guide rail  34  fixedly connected to mount plate  33 . Carriage guide rail assembly  40  additionally includes oscillating axis bearings  35 , which are linear bearings in one embodiment. Carriage guide rail  34  and oscillating axis bearing  35  are arranged so that the carriage  30  can be moved or oscillated on an axis  19 , transverse or perpendicular to cutting axis  18  in one embodiment. In some embodiments, the axis  19  is arranged at an angle a from about 35° to 90° and desirably from about 45° to 90° in relation to cutting axis  18  in order to provide a desired oscillating motion. 
     A cutting blade mount plate  36  is connected to oscillating axis bearings  35  and oscillating device  37 , such as an air cylinder in one embodiment is connected to cutting blade mount plate  36 . The oscillating device  37  includes an actuating rod  38  connected to an actuator end  39 . The oscillating device  37  provides the oscillation by using two limit sensors  70 , which sense the location of the cylinder. By using sensors  70 , the frequency of the oscillation can be adjusted by moving the sensors. The oscillation process is started in one embodiment when the carriage  30  reaches a pre-programmed position along guide rail  21 . Once this position is reached, the oscillation device  37  is activated, causing the carriage  30  to move to a second position, see  FIG. 4B ) for example. Once the carriage  30  reaches the other sensor it is sent back to the first position by oscillation device  37 . The oscillation device  37  oscillates the carriage  30  while it is moving forward. Once the carriage reaches a desired position, the first oscillation is ceased, see  FIG. 40 ) for example, preferably at the first position, prior to the oscillation. The carriage  30  is moved along cutting axis  18  without oscillation and continues to cut through the portions of article  80  that the blade  60  encounters. At a time prior to the blade  60  severing the article  80  into two pieces or otherwise completing a cutting operation, the oscillation device  37  is restarted thereby oscillating carriage  30  in a desired manner, generally along axis  19  perpendicular to the cutting axis  18  in a preferred embodiment. The second oscillation step, see  FIG. 4D ) for example, is continued until the cutting operation is finished and the desired finished article  80  is produced. After the cutting operation is performed, the carriage can be returned to its initial starting point, see  FIG. 4A ). 
     One or more arms  42  are connected to the cutting blade mount plate  36 . The cutting knife or blade  60  is connected to arm  42 . As illustrated in the figures, blade  60  is connected between two arms  42 . Blade  60  has a cutting edge  62  that is linear in a preferred embodiment, and is situated at a desired angle with respect to cutting axis  18 . The cutting knife or blade  60  can be connected to the arm  42  in a manner so that the cutting edge  62  has an axis that is situated at an angle of about 80° to about 110°, desirably from about 85° to about 105°, preferably from about 90° to about 100° in relation to the cutting axis  18 . In one embodiment, the blade  60  has a cutting edge that has either a single bevel or double bevel in order to provide the desired cutting action. In one embodiment, the cutting edge  62  has an axis that is situated along axis  19  that is perpendicular to cutting axis  18 . Blade  60  is connected to arms  42  utilizing any suitable method. For example, in one embodiment, the blade  60  is bolted to the blades, but obviously other fastener connections can be utilized. 
     Methods of utilizing the device of the present invention will now be explained utilizing  FIG. 4  as a guide. An article  80  to be processed is located adjacent cutting device  10 , and preferably secured utilizing a suitable fixture, if desired or necessary, see  FIG. 4A ). The article  80  has a leading edge or first end  82  positioned adjacent the cutting edge  62  of blade  60  and a trailing edge or second end  84  generally opposite the first end  82 . The carriage  30  is advanced along cutting axis  18  towards article  80  and upon or prior to engagement of cutting edge  62  with the first end  82  of article  80 , carriage  30  is oscillated with oscillating device  37 . First oscillating contact of cutting edge  62  with first end  82  of article  80  is illustrated in  FIG. 4B ). The arrows illustrate the movement of carriage  30  forward along cutting axis  18  as well as lateral oscillating movement of carriage  30 . After the cutting edge  62  has performed the desired cutting operation along cutting axis  18  with oscillation, the oscillation operation is ceased, see  FIG. 4C ), and the carriage  30  is moved further forward along cutting axis  18  and through the desired portion of article  80 . Once the carriage  30  reaches a location near the second end  84 , a second oscillation step is performed such as illustrated in  FIG. 4D ) while the forward motion is maintained along axis  18  and the cutting edge of blade  60  severs or otherwise cuts through the desired portion of article  80 . After the cutting operation has been performed, the carriage is returned to an initial or desired position, see  FIG. 4A ) for example. 
     In various embodiments, the first oscillation step can be performed until the knife edge has entered the part reaching a point where the cutting direction is inline with the wall being cut. Cutting edge has cut through up to 45%, and desirably up to 20% of the length of article  80  measured along the cutting axis  18 . Likewise, the second oscillation step can be initiated prior to 45%, and desirably less than 20% of the length of article  80  remaining to be cut along axis  18 . 
     Utilizing the methods of the present invention, finished, hollow, articles having at least one open end are formed having a clean, substantially straight edge about the opening formed by the multiple step cutting methods of the present invention. 
     In accordance with the patent statutes, the best mode and preferred embodiment have been set forth; the scope of the invention is not limited thereto, but rather by the scope of the attached claims.