Abstract:
A retrofit kit for a printing press adjustment hydraulic actuator. The hydraulic actuator is maintained to benefit from its mounting position and alignment, but the hydraulic fluid is removed. A hydraulic actuator shaft is attached to a mechanism that converts the rotary motion of an electric motor to linear motion. The electric motor provides faster and more accurate control of the hydraulic actuator shaft than the hydraulic fluid, providing for faster adjustment of the printing press.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of a prior U.S. Provisional Application No. 61/147,820, filed Jan. 28, 2009. The entire teachings of the above application are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Some printing presses, such as the Goss “Metro Color” printing press, use hydraulic actuators to adjust the circumferential and lateral registers of each color print roller on the press. The hydraulic systems cause two problems: inaccurate adjustments and slow adjustment times. The inaccuracies are caused by continued movement of the hydraulic actuator after a control input has ceased. Also, the hydraulic controls are limited to a relatively large minimum adjustment such that an operator often has to overshoot an adjustment in one direction to “dial in” the adjustment in the opposite direction. The slow adjustment times are caused by incapability of the hydraulic supply system to simultaneously actuate several different actuators. 
         [0003]    Because the printing press is printing paper during the adjustment period after start-up, the printing press is generating waste until the printer is calibrated. Delays in calibration caused by the inaccuracies and slow adjustment times described above are significant contributors to the amount of generated waste. Also, printing presses tend to require periodic adjustments to the register during a print run. Again, the delays in calibration result in significant waste. 
       SUMMARY OF THE INVENTION 
       [0004]    An example embodiment of the present invention include a motor and assembly that attaches to existing hydraulic actuators and replaces the hydraulic power operating the actuator with electrical power. The electrically-powered actuators can be operated simultaneously with each other, enabling faster calibration than hydraulically powered actuators, which must be operated individually. Also, the electrically-powered actuators are more accurate than the hydraulic-powered actuators because they can take smaller steps than the hydraulic-powered actuators and because they do not overshoot, i.e., tend to continue actuating after the control signal ends. These benefits of electrically-powered actuators significantly reduce the time required to calibrate the register of a color printing press, thereby increasing the time available to run a printing job and decreasing the amount of waste generated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
           [0006]      FIG. 1  is a side view of a printing press adjustment gear and its hydraulic actuator; and 
           [0007]      FIG. 2A  is a bottom view of a hydraulic actuator retrofit to be driven by an electric stepper motor according to an embodiment of the invention; 
           [0008]      FIG. 2B  is a perspective view of the hydraulic actuator retrofit of  FIG. 2A ; 
           [0009]      FIG. 2C  is an exploded view of the hydraulic actuator retrofit of  FIGS. 2A and 2B ; 
           [0010]      FIG. 3  is a flow chart of integration of a dedicated control system with a third party system; 
           [0011]      FIG. 4  is a flow chart showing operation of dedicated programmable logic controller and third party programmable logic controller; and 
           [0012]      FIG. 5  is a schematic wiring diagram for a dedicated programmable logic controller. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    A description of example embodiments of the invention follows.  FIG. 1  shows a prior art hydraulically actuated printing press adjustment  100 . A gear  104  is mounted to a frame member  102  of a printing press and the axis of rotation  103  of the gear  104  is connected to an adjustment mechanism (not shown) of the printing press. For example, gear  104  may be connected to a mechanism that adjusts one of lateral or circumferential position of a printing press cylinder (not shown). The gear has teeth  118  (partially shown), which mesh with corresponding gears  116  on a rack  106 . An end of the rack  106  is attached to a hydraulic actuator shaft  108   a . The hydraulic actuator shaft  108   a  passes through a housing  110  and an opposite end of the hydraulic actuator shaft  108   b  extends from the opposite end of the housing  110 . The housing includes a cylinder wall  120  and two end caps  112   a ,  112   b . The end caps  112   a ,  112   b  are pressed against the ends of cylinder wall  120  by threaded rods  114   a ,  114   b . Note that  FIG. 1  only shows two threaded rods  114   a ,  114   b . Typically, the end caps  112   a ,  112   b  are pressed against the ends of cylinder wall  120  by four threaded, but only two of the four threaded  114   a ,  114   b  are visible in  FIG. 1 . Hydraulic lines  122   a  and  122   b  feed hydraulic fluid under pressure into respective ends of the hydraulic cylinder  120  via the end caps  112   a ,  112   b  to push the hydraulic actuator shaft  108   a ,  108   b  in a direction towards or away from the gear  104 . For example, adding hydraulic fluid at hydraulic line  122   b  into end cap  112   b  pushes the hydraulic actuator shaft  108   a ,  108   b  towards the gear  104 . Conversely, adding hydraulic fluid at hydraulic line  122   a  into end cap  112   a  pushes the hydraulic actuator shaft  108   a ,  108   b  away from the gear  104 . Thus, by controlling the flow of hydraulic fluid, an operator can cause the hydraulic actuator shaft  108   a ,  108   b  to turn the gear  104  via the rack  106 . 
         [0014]    As discussed above, there are several disadvantages of a hydraulic system. First, the hydraulic system is relatively inaccurate. Second, due to constraints on the hydraulic pressure supply, only one or a small number of hydraulic actuators can be operated at one time. 
         [0015]      FIGS. 2A-2C  show an example embodiment of a retrofit kit  200  according to the present invention that replaces hydraulic fluid with an electric motor  232  to actuate the hydraulic actuator shaft  208   a ,  208   b . The hydraulic cylinder  220 , end caps, and hydraulic actuator shaft  208   a ,  208   b  are left in place mounted to a frame member of the printing press (not shown). Hydraulic lines (not shown in  FIGS. 2A-2C , but see  122   a - b  in  FIG. 1 ) are disconnected from the end caps  212   a ,  212   b  and hydraulic fluid (not shown) inside the hydraulic cylinder  220  is drained. With the hydraulic cylinder  220  drained of hydraulic fluid (not shown), the hydraulic actuator shaft  208   a ,  208   b  can move freely. Nuts  215   a - d  are temporarily removed from threaded rods  214   a - c  (a fourth threaded rod is not visible in  FIGS. 2A-2C ), and stationary bracket  230  is mounted next to end cap  212   b . The nuts  215   a - d  are reassembled onto threaded rods  214   a - c  (and the fourth rod, which is not visible in  FIGS. 2A-2C ) to also hold bracket against end cap  212   b . Threaded rods  214   a - c  (and the fourth threaded rod not visible in  FIGS. 2A-2C ) may be replaced with longer threaded rods to accommodate the thickness of the stationary bracket  230 . Hydraulic actuator shaft  208   b  passes through a hole  231  in the stationary bracket  230 . 
         [0016]    The stationary bracket  230  extends past a side of end cap  212   b  and electric motor  232  mounts to the stationary bracket  230  at the extension. The motor  232  may be mounted to stationary bracket  230  by bolts  219   a - d , rivets (not shown), or any other commonly-used fastening mechanism. Optionally, a space plate  221  may be included between the motor  232  and the stationary bracket  230 . Typically, the electric motor  232  is a two-phase stepper motor having at least  200  steps per revolution (1.8 degree increments). A two-phase electric stepper motor having  400  steps per revolution may also be used to achieve even higher degrees of accuracy. If a stepper motor having  400  steps per revolution is used, software in a controller  250  can provide for larger step increments, such as  200  steps per revolution when larger adjustments to the printing press are required. 
         [0017]    An output shaft  234  of the motor  232  extends through a hole  233  in the stationary bracket. In the embodiment shown in  FIGS. 2A-2C , the output shaft  234  is threaded. The threaded output shaft  234  may be a separate piece connected to the output shaft of the electric motor  232 . When the end cap  212   b  and electric motor  232  are both attached to the bracket  230 , the threaded output shaft  234  and hydraulic actuator shaft  208   b  are parallel to each other. A movable bracket  236  is attached to the hydraulic actuator shaft  208   b  and electric motor output shaft  234 . The movable bracket  236  is attached to the end of hydraulic actuator shaft  208   b  with a bolt  238  that passes through hole  237  in the bracket  236  and threads into a threaded hole (not shown) in the end of the hydraulic actuator shaft  208   b . The hole (not shown) in the hydraulic actuator shaft  208   b  may need to drilled and tapped. The threaded output shaft  234  is threaded through a threaded hole  239  in the movable bracket  236 . 
         [0018]    With the movable bracket  236  attached to the end of the hydraulic actuator shaft  208   b  and threaded onto the threaded output shaft  234  of the electric motor  232 , rotation of the threaded output shaft  234  causes the movable bracket  236  to move towards or away from the electric motor  232  and hydraulic cylinder  220 . The movement of the movable bracket  236  causes the hydraulic actuator shaft  208   a ,  208   b  to also move with respect to the hydraulic cylinder  220 . The rack  206  attached to the end of hydraulic actuator shaft  208   a  moves beneath the printing press adjustment gear  204 . 
         [0019]      FIGS. 2A-2C  also show a guide shaft  240  attached to the stationary bracket  230  and passing through a hole  235  in the movable bracket  236 . The movable bracket  236  slides over the guide shaft  240 , the guide shaft  240  keeping the movable bracket  236  perpendicular to the axes of the hydraulic actuator shaft  208   b  and the electric motor  232  output shaft  234 , thereby preventing the movable bracket  236  from binding on the threaded shaft. A bushing  242  may be fitting inside the hole  235  in the movable bracket  236  such that the guide shaft  240  is in sliding contact with the bushing  242  rather than the hole  235  in the movable bracket  236 . The bushing  242  may improve the effectiveness of the guide shaft  240  to prevent binding between the movable bracket  236  and the threaded output shaft  234 . The bushing  242  may be installed and fixed in place with nut  243 . 
         [0020]      FIG. 2A  also shows a controller  250  attached to the electric motor  232  via wires or cables  252 . The controller  250  may be a programmable logic controller (PLC) and is configured to send electrical signals to the electric motor  232 , causing the motor  232  to turn the threaded output shaft  234  in either a clockwise or counterclockwise direction. The controller for the removed hydraulic system may be repurposed to control the electric motor  232 . Alternatively, a new controller  250  may be installed with the above-described assemblies. The controller may be configured to accept commands from a human operator, e.g., the human operator may push a first button that causes the motor to turn clockwise or push a second button that causes the motor to turn counterclockwise. The controller may also be automated and computer controlled, responding to sensor readings to determine when an adjustment needs to be made and automatically making the required adjustment. The sensor is typically a camera pointed at a color register on each print page that indicates alignment of the print rollers for the different colors with respect to each other. When the camera detects a misalignment of a print roller, a computer coupled to the camera and receiving the misalignment information instructs the controller  250  to turn the motor  232  to adjust the print roller. 
         [0021]    The controller also may control other types of actuators, e.g., a motor coupled to a hand adjustment wheel as described in U.S. Pat. Nos. 7,208,904 and 7,408,316, both titled “Multiple Motor Position Control,” U.S. Pat. No. 7,321,212, titled “Restricted Motion Motor Control with Visual Indication,” U.S. application Ser. No. 11/344,867, titled “Quick Disconnect Motor Mount,” and U.S. application Ser. No. 11/344,866, titled “Flexible Cantilever Motor Mount,” all of which are incorporated herein by reference. 
         [0022]    A typical printing press has a total of eight printing rollers, one roller for each of the four colors printed on each side of a piece of paper. Each roller has two adjustments: circumferential adjustment, i.e., clocking the print roller with respect to the other print rollers, and lateral adjustment, i.e., moving the print roller with respect to the other print rollers. Thus, there are a total of sixteen gears, such as gear  104  on a printing press, and a total of sixteen retrofit kits, such as retrofit kit  200  in  FIG. 2 , may be used to upgrade a printing press. The electric motor  232  of each retrofit kit  200  may be controlled by a dedicated controller  250  or all sixteen motors  232  of the sixteen retrofit kits  200  may be controlled by a single controller  250 . 
         [0023]      FIGS. 3-5  show how a dedicated programmable logic controller (PLC) may be incorporated into a third party system already operating on a printing press. As described in step  1   a . of  FIG. 3 , the third party PLC maintains control of color registration adjustments unless it is disabled (by failure or by being taken off line on purpose). If the third party system is disabled, the dedicated PLC automatically takes control of the color registration adjustments (as described in Steps  1   b . to  1   h .). Embodiments of such a dual PLC systems include a safeguard to ensure that both the dedicated PLC and third party PLC are not simultaneously enabled. 
         [0024]      FIG. 4  shows a schematic diagram of a third party PLC  402  and a dedicated PLC (labeled “IMC PLC”)  404  simultaneously connected to a motor driver  406 . If the third party PLC  402  is in control, then the dedicated PLC  404  does not control the stepper motors  408 . However, the dedicated PLC  404  does monitor the positions of stepper motors  412  and any system alarms  410 . 
         [0025]      FIG. 5  shows a schematic diagram how a dedicated PLC  500  may be connected to a motor driver  502 . Signals representing direction of motor driving (Pins  17  and  18 ), signals representing number of motor driving pulses (Pins  19  and  20 ), and signals representing alarms (Pins  25  and  26 ) are always provided to the dedicated PLC  500 . Also, the dedicated PLC  500  can clear alarms via Pins  21  and  22  if the 3 rd  party PLC 9not shown in  FIG. 5 ) is not capable of controlling electric motors.  FIG. 5  also shows a relay switch  504  that connects either the dedicated PLC  500  or the third party PLC (not shown) to the motor driver  502  (Pins  9  and  10  for motor direction and Pins  11  and  12  for motor activation). Normally, the relay switch  502  closes an electrical circuit with the third party PLC (not shown) such that the dedicated PLC  500  cannot send control signals to the motor driver  502 . In the event the third party PLC (not shown) is disabled, the relay switch  504  closes the circuit to the dedicated PLC  500  so the dedicated PLC  500  may send control signals to the motor driver  502 . 
         [0026]    While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.