Abstract:
The invention pertains to a large format, plotter-style automated laser engraver which can be used to engrave various materials. A cabinet body supports a substantially flat work surface which can be raised or lowered as desired. A gantry assembly is mounted in close proximity to such work surface, and facilitates movement of a focused laser assembly to any x/y coordinate along the work surface. A computer controlled wireless focus mechanism is used to regulate the vertical distance between the focused laser assembly and the work surface. Air is provided to cool the work surface during the engraving process.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This application claims the benefit of co-pending non-provisional patent application Ser. No. 10/654,160, filed Sep. 3, 2003. 
   STATEMENTS AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
   None 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a large format, plotter-style automated laser engraver which can be used to engrave various materials. It is an object of the present invention to engrave at high speeds with minimal maintenance requirements and increased engraving productivity. 
   2. Description of the Prior Art 
   Prior to the introduction of automated engraving machines, human engravers were required to have particular knowledge of workpiece selection, cutting speeds, and related matters. Engravers were also required to have some level of manual dexterity in order to physically engrave a workpiece. Development of automated engraving machines has resolved a number of these problems and reduces the overall skill level required of an operator. 
   One common type of automated engraving machine is the laser engraver. Apparatuses utilizing a laser for engraving, or at least writing on, a suitable surface are relatively well known. For example, one such apparatus functions by moving a laser relative to a workpiece which is supported on a work surface and by periodically aiming pulses of collimated coherent light at the workpiece to affect therein an image-wise surface alteration, by a plurality of indentations or pixels selectively placed so that together they form an image. The movement of the laser may be responsive to signals, either directly or by way of a storage, derived from a device which mechanically or optically scans the pattern. The workpiece may consist of any material which is susceptible to the formation of indicia therein as a result of laser beam treatment. 
   Basically, laser printing or engraving is carried out by aiming a laser beam at a workpiece, the laser beam being switched on at every image point (pixel) or off at every blank position, as the case may be, to form an image in the workpiece. Gray-scale images are typically generated by changes in the intensity of the laser beam by modulating its pulse width. An encoder connected to the drive of the laser tool head provides position signals (pulses per angular unit) to a processor which in turn energizes the laser as a function of the pulses. 
   Such automated laser engraving machines have greatly improved the overall quality and efficiency of the engraving process. Notwithstanding this fact, existing automated engraving machines still have certain limitations. Generally, such engraving processes are less than ideal because pixels are directionally displaced; that is, such pixels are typically not aligned in precise columns and/or rows. The difficulties inherent in energizing a laser render it difficult to provide high-speed engraving processes of acceptable precision with cost-efficient x-y plotters. For example, current large format laser engraving machines are limited to engraving speeds of under 100 inches per second, require frequent maintenance, and require multiple operation steps to engrave; such limitations reduce productivity and increase operating costs. Furthermore, currently available automatic engraving machines are frequently very large, and unnecessarily complex with respect to the number of parts required. 
   In light of the foregoing, there is a need for an automated engraving machine that is simple to construct, easy to maintain, and relatively compact in size. The automated laser engraving machine should be able to engrave at high speeds, without requiring frequent maintenance and multiple operation steps. 
   SUMMARY OF THE INVENTION 
   The present invention is an engraving apparatus that substantially obviates limitations and disadvantages associated with prior art engraving machines. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims. 
   In the preferred embodiment, the automated laser engraver of the present invention has a substantially flat work surface which is protected by a hinged cover. Said substantially flat work surface effectively defines an x-axis and a y-axis. An automated gantry assembly is mounted in general proximity to said substantially flat work surface. Said gantry assembly comprises first and second elongate rails, oriented parallel to one another, along the y-axis of said work surface. A third rail, oriented perpendicular to said first and second rails along the x-axis of said work surface, is movably mounted to said first and second rails using traveling bracket members. Said third rail can be moved to various positions along said parallel first and second rails and, thus, along the y-axis of the work surface. A carriage assembly, which is movably received on said third rail, can travel along the length of said third rail between said parallel first and second rails. 
   In the preferred embodiment of the present invention, said traveling bracket members utilize non-recirculating polymer bearings that ride on said first and second rails. Similarly, said carriage assembly also utilizes such non-recirculating polymer bearings that ride on said third rail. Said first, second and third rails are hard coated, anodized rails. Said bearings act to push debris (such as from the engraving process, for example) from said rails, thereby reducing cleaning and maintenance requirements for said gantry assembly. Said non-recirculating polymer bearings riding on said hard coated, anodized rails within the gantry assembly permit the machine to achieve high acceleration and engraving speeds of 120 inches per second and greater with low maintenance requirements. 
   A first drive mechanism is used to move said first and second traveling brackets (and, accordingly, the third rail) along the length of said first and second rails, respectively. In the preferred embodiment of the present invention, said drive mechanism comprises at least one stepper servo motor and at least one drive belt. Similarly, a second drive mechanism is used to move said carriage assembly along said third rail. In the preferred embodiment, said second drive mechanism comprises at least one stepper servo motor and at least one drive belt. At least one encoder compensates for drive belt flex and maintains the speed of said first and second traveling brackets, as well as said carriage assembly, at desired levels which improves overall quality of the engraving process. Said at least one encoder provides information for motion adjustments and belt flex compensation to the applicable stepper servo motor(s). 
   A beam from an engraving laser is aimed at a workpiece being engraved using an optical assembly mounted on said carriage assembly. As said carriage assembly moves to desired locations relative to a workpiece being engraved, said laser beam engraves the surface of said workpiece. In the preferred embodiment, optics (mirrors and lens) utilized to aim and focus said laser beam are removable for easy cleaning and can be replaced in position without requiring re-alignment. 
   Air is conveyed onto the engraving work surface to cool the workpiece and reduce the possibility of fire. In the preferred embodiment, said air flow is supplied through a tube which is mounted at or near said carriage assembly. Air travels through said tube and passes through a plurality of holes along the length of the tube in the general direction of the area where the laser beam strikes the workpiece. Said tube can be rotated to direct such air flow as desired. 
   In the preferred embodiment, the redirecting and focusing of a laser beam via the gantry assembly and, thus, the engraving on the surface of a workpiece, is controlled via electronics and a computer. A desired design is scanned or otherwise input into the memory of such computer, and this information is supplied to system electronics. Said computer controls aiming of the laser beam relative to said workpiece via the gantry assembly. Said computer also controls laser pulses directed at the workpiece in order to create a surface alteration on the workpiece which is consistent with the desired image. 
   In the preferred embodiment, a computer touch screen, mounted in a convenient location relative to the laser engraver, permits easy data input for management of engraving job(s). Said touch screen can control functions such as focus point determination, job setup, job positioning, speed adjustments, job performance data and job preview zoom. Said computer touch screen also allows an operator to select engraving specifications directly from a host computer&#39;s hard drive and run such jobs on the laser engraving machine. Additionally, in the preferred embodiment, said computer touch screen also allows an operator to determine focus points on a laser table work surface, change operating parameters of the system, position a job on the engraving table work surface and adjust engraving speeds. 
   A wireless focus mechanism controls the distance, or focal length, between the laser and the workpiece being engraved. In the preferred embodiment, said wireless focus mechanism comprises a diode beam and plunger. Said laser diode beam extends horizontally above the work surface along the length of the x-axis. In the event that the plunger, which is attached to the carriage, touches the workpiece, upward movement of the plunger will cause the diode beam to be broken. When this occurs, the substantially flat work surface is automatically set to a position corresponding to the proper engraving focal length for the object to be engraved. 
   In the preferred embodiment, the present invention utilizes two primary focus modes: “auto focus” mode and “bull&#39;s eye focus” mode. When the auto focus mode is initiated, a location on a workpiece (text character, logo, etc.) is targeted as the initial focus point. When the job is sent to the laser, the focus mechanism plunger will move over the designated x,y coordinate of the initial focus point and the substantially flat work surface of the engraving table will move upward to meet said plunger. Once the plunger is engaged, a diode beam is broken sending a signal to the controller to stop the table&#39;s movement. The controller then sends a signal to move the table down reaching the distance of the programmed focal length, thus bringing the object in focus. As soon as the table is focused in this manner, the subject job can begin engraving. 
   The bull&#39;s-eye focus mode allows a user to move a pointer to any point on a workpiece situated on said substantially flat work surface. To set the focus point, a user selects the desired point. In the preferred embodiment, the user will then hear an audible alarm, indicating that the desired point has been set. The auto focus plunger will then move over the selected x,y coordinate point, and the engraving table work surface will move upward to meet the plunger. When the table engages the plunger, a diode beam is broken sending a signal to the controller to stop the table&#39;s movement. The controller then sends a signal to move the table down reaching the distance of the programmed focal length, thus brining the point on the plate to be engraved in focus. Thereafter, the engraving process can start. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts a side perspective view of the laser engraver of the present invention. 
       FIG. 2  depicts a side, partial cut-away view of the laser engraver of the present invention. 
       FIG. 3  depicts an overhead view of the work surface and gantry assembly of the present invention. 
       FIG. 4  depicts a side perspective view of the work surface and gantry assembly of the present invention. 
       FIG. 5  depicts a detailed side view of a second traveling bracket and encoder of the present invention. 
       FIG. 6  depicts a side view of a first traveling bracket and carriage assembly of the present invention. 
       FIG. 7  depicts an end view of a carriage mechanism of the present invention with optical components installed. 
       FIG. 8  depicts a side perspective view of a carriage mechanism of the present invention with an optical component removed. 
       FIG. 9  depicts a detailed view of the plunger of the wireless focus mechanism of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , the automated laser engraver  100  of the present invention has cabinet body  101  and cover  102 . In the preferred embodiment, cover  102  is hinged and can be opened to provide access to engraving table work surface  200  (not shown in  FIG. 1 ), or closed to protect said work surface. Said cover  102  can be supported by gas-charged struts for easy opening and closing of said cover and, in the preferred embodiment, has see-through window  102   a  included therein. Laser engraver  100  also has removable panels  103  with ventilation ports  104  to permit access to the inside of cabinet body  101 . Castors  105  permit laser engraver  100  to be easily moved as desired. Panel face  106  and computer touch screen  107  are presented along the front surface of cabinet body  101  for easy access by an operator. 
   Referring to  FIG. 2 , cabinet body  101  defines a support frame for shelves  108  and  109 , as well as fixed upper surface  120 . Removable panels  103  are also installed along the rear of cabinet body  101  to provide access to the inside of said cabinet body  101  from the rear of laser engraver  100 . Substantially planar engraving table  220  having upper work surface  200  is disposed below cover  102 . Automated elevation mechanism  110  can be used to raise or lower said engraving table  220 , and thus work surface  200 , to a desired level within cabinet body  101 . Computer unit  111  is situated within cabinet body  101 , and is used to control the various functions of laser engraver  100  via electronics. In the preferred embodiment, laser tube  112  is situated on shelf  109  within cabinet body  101 . Laser tube  112  emits a laser beam which is used to engrave a workpiece supported on work surface  200 . 
   Referring to  FIG. 3 , an automated gantry assembly is mounted on fixed upper surface  120  of cabinet body  101 . Said gantry assembly is situated in a fixed position in general proximity to movable engraving table  220  and work surface  200 . Said gantry assembly comprises first elongate rail member  201  and second elongate rail member  202 . First and second elongate rail members are oriented parallel to one another, and together define a y-axis component of work surface  200 . Third elongate rail member  203  is oriented perpendicular to said first elongate rail member  201  and second elongate rail member  202 , thereby defining an x-axis component of work surface  200 . Entire third elongate rail member  203  is movably mounted to said first and second rail members using traveling bracket members  204  and  205 . Said third elongate rail member  203  can be moved to various positions along the length of said parallel first and second elongate rail members  201  and  202  and, thus, along the y-axis of work surface  200 . Carriage assembly  206 , which is slidably disposed on said third elongate rail member  203 , can travel along the length of said third elongate rail member  203  between said traveling bracket members  204  and  205 . 
   In the preferred embodiment of the present invention, said first and second elongate rail members  201  and  202  comprise single cylindrical rods. Said third elongate rail member  203  comprises tandem cylindrical rods. Each of said first and second elongate rail members are supported by horizontal support members  218  which are attached to upper surface  120 . Third elongate rail member  203  is supported by horizontal support member  219 , which is affixed to traveling bracket members  204  and  205 . Traveling bracket members  204  and  205  are slidably received on first and second elongate rail members  201  and  202 , respectively. In the preferred embodiment, said traveling bracket members  204  and  205  utilize non-recirculating polymer bearings that ride on the external surface of said first and second elongate rail members  201  and  202 , respectively. 
   Carriage assembly  206  is slidably received on third elongate rail member  203 . Said carriage assembly  206  also contains non-recirculating polymer bearings that ride on the external surface of said third elongate rail member  203 . In the preferred embodiment, first, second and third elongate rail members are constructed of hard coated, dual anodized rails. Said bearings act to push debris (such as from the engraving process, for example) from said elongate rail members, thereby reducing cleaning and maintenance requirements associated with laser engraver  100 , generally, and work surface  200 , in particular. Said non-recirculating polymer bearings riding on said hard coated, anodized rail members within the gantry assembly of the present invention permit laser engraver  100  to achieve high acceleration and engraving speeds of 120 inches per second and greater with low maintenance requirements. 
   Referring to  FIG. 4 , a first drive mechanism is used to move said first and second traveling brackets  204  and  205  (and, accordingly, entire third elongate rail member  203 ) along the length of said first and second elongate rail members  201  and  202 , respectively. In the preferred embodiment of the present invention, said drive mechanism comprises at least one electric stepper or servo motor  210  and drive belts  208  and  209 . Said drive belts  208  and  209  advance along pulleys mounted within hubs  214 ,  215 ,  216  and  217  (obscured from view in  FIG. 4 ). In  FIG. 4 , pulleys  214   a  and  216   a  are deployed within hubs  214  and  216 , respectively. Although not shown in  FIG. 4 , similar pulleys are mounted within hubs  215  and  217 . Similarly, a second drive mechanism is used to move said carriage assembly  206  substantially along the length of said third elongate rail member  203 . In the preferred embodiment, said second drive mechanism comprises at least one stepper or servo motor  207  and at least one drive belt  211 . At least one servo motor encoder  212  compensates for drive belt flex and maintains the accuracy of said carriage assembly  206  at desired levels. Said encoder provides information for motion adjustments and belt flex compensation to the applicable stepper or servo motor  207 . 
   Referring to  FIG. 5 , horizontal support members  218  are mounted to upper surface  120  of cabinet body  101  and provide support for elongate rail member  202 . Traveling bracket  205  is slidably mounted on elongate rail member  202 . Encoder  212  is situated on traveling bracket  205  opposite drive motor  207 . Due to the high-g acceleration and speed of carriage assembly  206 , drive belt  211  could flex and stretch during motion. Encoder  212 , attached to shaft  213   a  of carriage assembly pulley  213 , reads directly off of drive belt  211  and compensates for unwanted movement of carriage assembly  206 , thereby increasing overall engraving quality. 
   Referring to  FIG. 6 , horizontal support member  218  is mounted to upper surface  120  of cabinet body  101  and provides support for elongate rail member  201 .  FIG. 6  depicts a detailed view of traveling bracket  204  and carriage assembly  206 . Carriage assembly  206  has a lightweight design, and drive belt  211  is attached to the carriage assembly  206  at the center of moment, thus enabling high-g accelerations. Said drive belt  211  is vertically mounted to said carriage assembly  206 , which reduces debris collection on the teeth of said belt. Belt tension is adjustable utilizing a setscrew. 
   Still referring to  FIG. 6 , carriage optical assembly  300  is mounted to said carriage assembly  206 . As said carriage assembly  206  moves to desired locations relative to work surface  200 , and any workpiece situated thereon, said carriage optical assembly  300  directs and focuses a laser beam to engrave the surface of such workpiece. In the preferred embodiment, optics  301  and  302  (a reflector and lens, respectively, obscured from view in  FIG. 6 ) for said carriage optical assembly are removable for easy cleaning and can be snapped back into place without requiring re-alignment. Reflector  301  is mounted within optic casing  301   a,  while lens  302  is mounted within optic casing  302   a.    
     FIG. 7  depicts an end view of carriage assembly  206  of the present invention. Referring to  FIG. 7 , carriage optical assembly  300  is attached to said carriage assembly  206 . Bearings  221  are used to slidably mount carriage assembly  206  to third elongate rail member  203 . Although not shown in this drawing, such bearings are likewise used to movably mount traveling brackets  204  and  205  to first and second elongate rail members  201  and  202 , respectively. Optic casing  301   a,  and thus reflector  301 , is mounted within mounting bracket  303  on carriage optical assembly  300 . Similarly, lens casing  302   a , and thus lens  302  (obscured from view in  FIG. 7 ) is mounted within mounting bracket  304  of carriage optical assembly  300 . Spring loaded, nylon tipped set screw  305  can be employed to firmly hold said reflector casing  301  a and lens casing  302   a  in place within their respective mounting brackets. 
   Mounting brackets  303  and  304  allow optic placement and removal for cleaning and inspection. When casing  301   a  and  302   a  are installed into said mounting brackets, the optics within said casings can be automatically returned to a position that does not require realignment. Said casings  301   a  and  302   a  are ideally constructed of aluminum and utilize an anodized color code to instruct proper placement within mounting brackets  303  and  304 . 
     FIG. 8  depicts a side view of carriage assembly  206  and carriage optical assembly  300 , with reflector  301  and associated casing  301   a,  removed. Lens  302 , and associated casing  302   a , are installed within lens mounting bracket  304 . A wireless focus mechanism controls the vertical distance, or focal length, between the carriage optical assembly  300  and a workpiece being engraved on work surface  200  of engraving table  220 . In the preferred embodiment, said wireless focus mechanism comprises a diode beam which works in conjunction with plunger  306 . A diode laser beam is directed from port  305  on traveling bracket member  204  shown on  FIG. 6 . Said diode laser beam is directed across work surface  200  along the length of third elongate rail member  203 . Said diode beam is focused through a port  307  extending through plunger  306  and towards detector  330  on traveling bracket member  205  (shown on  FIG. 5 ). 
     FIG. 9  depicts a see-through view of plunger  306  of the wireless focus mechanism of the present invention. Plunger  306  consists of outer body  308 , internal shaft  309  and port  307 . Although not depicted in  FIG. 9 , an optional spring can be used to bias internal shaft  309  downward away from port  307 . In the event that internal shaft  309  comes in contact with a workpiece situated on work surface  200 , internal shaft  309  is directed upward within outer body  308 . Internal shaft  309  blocks port  307 , thereby interrupting said diode beam and preventing said diode beam from reaching detection sensor  330  on traveling bracket member  205 . The computer controller recognizes this as the “pre-set” focus point and automatically adjusts the engraving table  220  and work surface  200  to the correct focal distance relative to carriage optical assembly  300 . The process can be directed by an operator through software or through the touch screen keypad. 
   A laser beam from laser tube  112  is aimed and focused at a workpiece to be engraved on work surface  200  using a series of reflectors and/or lens. Referring to  FIG. 2 , a beam from laser tube  112  is emitted from port  112   a . Said beam is redirected upward toward upper surface  120  using at least one aimed reflector (not shown in  FIG. 2 ). In the preferred embodiment, said beam is thereafter aimed at reflector  340 , shown on  FIG. 3  which is situated at or near upper surface  120 . Said beam is re-directed by reflector  340 , and aimed at reflector  350 , positioned on traveling bracket  205 . Said beam is again reflected using reflector  350 , and redirected through port  351  towards carriage optical assembly  300  mounted on carriage  206 . Referring to  FIG. 6 , said beam passes through port  352 , towards reflector  301 . The beam is reflected by reflector  301  and aimed downward through lens  302  at work surface  200  (and any workpiece situated thereon). As can be seen from the various drawings, in this manner said beam can be re-directed (reflected) and focused as desired at different positions on said work surface  200 . 
   Air is conveyed onto work surface  200  to cool a workpiece being engraved. In the preferred embodiment, said air flow is supplied through a tube which is mounted at or near carriage assembly  206 , such as tube  400  on  FIGS. 5 and 6 . Air travels through said tube and passes through a plurality of holes  401  extending through the tube  400  in the general direction of the area where a focused laser beam strikes the workpiece. 
   Forced air is used to minimize unwanted flame from engraving certain materials, and pushes debris to a vacuum plenum. In the preferred embodiment, said tube  400  allows for full air flooding onto the material, also helping to cool the engraving material, thereby reducing adverse impact to the material. By rotating the tube, a user can direct the airflow in the desired direction. 
   In the preferred embodiment, the movement of the carriage via the gantry assembly and, thus, the engraving on the surface of a workpiece, is controlled via electronics and a computer. A desired design is scanned or otherwise input into the memory of such computer, and this information is supplied to system electronics. Said computer controls movement of a laser beam relative to said workpiece via the gantry assembly described herein. Said computer also controls laser pulses directed at the workpiece in order to create a surface alteration on the workpiece which is consistent with the desired image. 
   In the preferred embodiment, a computer touch screen  107 , mounted in a convenient location relative to the laser engraver  100 , permits management of an engraving job. Said touch screen can control functions such as focus point determination, job setup, job positioning, speed adjustments, and job performance data. Said computer touch screen allows an operator to select engraving jobs directly from a host computer&#39;s hard drive and run such jobs on the laser engraving machine. Additionally, in the preferred embodiment, said computer touch screen also allows an operator to determine focus points on a workpiece situated on work surface  200 , change operating parameters of the system, position a workpiece for engraving, and adjust engraving speed. 
   Referring back to  FIG. 1 , computer touch control screen  107  is mounted to the front upper panel of the cabinet body  101  and acts as the control interface for the laser engraver of the present invention. Jogging of the gantry assembly, setting home positions, setting job offsets, job preview with zoom, determining focus points, turning on and off air assist, setting blower delay, controlling the audible notifications, turning on the diode laser pointer, toggling between metric and imperial units, using the mottle function, enabling HPGL use, setting the focus offset, accessing test engraving jobs, selecting display languages, pausing, changing power, changing speed, and performing maintenance functions can all be performed by using computer control touch screen  107 . 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the construction of this engraving apparatus without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.