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.
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.
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.
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.
A description of example embodiments of the invention follows.
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.
The stationary bracket 230 extends past a side of end cap 212b 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 219a-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.
An output shaft 234 of the motor 232 extends through a hole 233 in the stationary bracket. In the embodiment shown in
With the movable bracket 236 attached to the end of the hydraulic actuator shaft 208b 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 208a, 208b to also move with respect to the hydraulic cylinder 220. The rack 206 attached to the end of hydraulic actuator shaft 208a moves beneath the printing press adjustment gear 204.
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.
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
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.
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.
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Number | Date | Country | |
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61147820 | Jan 2009 | US |