Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2002-05-20
2003-11-25
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C425S144000
Reexamination Certificate
active
06654661
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mechanical press, and, more particularly, to an auto-positioning control system for maneuvering a press machine slide into a resting state at any selectable location along the slide path.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction that includes a movable slide guided by a frame structure having a crown and a bed. The frame structure supports the slide in a manner enabling reciprocating movement of the slide towards and away from the bed. These press machines are widely used for a variety of workpiece operations and employ a large selection of die sets. Accordingly, the press machines vary considerably in size and available tonnage depending upon its intended use.
A flywheel and clutch assembly are utilized to transmit mechanical energy from a main drive motor to the press crankshaft. The flywheel assembly serves as the primary source of stored mechanical energy and rotary driving power. Standard press configurations have the flywheel located between the main drive motor and clutch, with the flywheel being mounted on either the driveshaft, crankshaft or press frame by use of a quill.
The main drive motor replenishes the flywheel with rotational energy as it becomes depleted during the course of press working strokes as the clutch engages the flywheel and establishes a driving connection between the flywheel and the crankshaft. In particular, when the crankshaft and flywheel are engaged in driving relationship, the flywheel energy is converted into mechanical work to power the press components, namely, the reciprocating slide. During engagement of the clutch, the flywheel drops in speed as the press driven parts are brought up to running speed.
Maneuvering the slide into a particular stroke position along the slide path is useful during tooling setup as well as stock material feed setup. For example, the slide can be positioned along the slide path by manually rotating an otherwise stationary flywheel with the clutch engaged or by pulsing the clutch while the flywheel is rotating to intermittently engage the flywheel.
Manual rotation of the flywheel can be accomplished by inserting a lever such as a long metal bar into bores within the flywheel. Raising or lowering the bar will then manually rotate the flywheel and cause the slide to correspondingly move up or down.
However, this method of flywheel adjustment is time consuming and requires that flywheel motion be stopped, making this process inapplicable to operational situations that require slide repositioning during a press running mode. Additionally, this manner of slide adjustment is prone to imprecision and positional inaccuracies since it is based upon visual indication of slide position as perceived by the press operator. Generally, most forms of manual adjustment produce sub-optimum results due to a lack of precise reproducibility arising from human errors inherent in any task predominated by manual manipulation.
The intermittent engagement or pulsing of the clutch is likewise an inferior approach to slide adjustment since the frequent engagement and disengagement of the clutch causes excessive wear to the clutch components. Additionally, this method of slide adjustment produces inconsistent slide displacement values per pulse since the distance the slide moves per pulse is dependent upon, for example, counter balance settings and slide position. Typically, there is not provided any compensation scheme to account for the variability introduced by such factors as counter-balance settings and slide position.
Since pulsing a clutch in equal time intervals typically will not produce correspondingly equivalent units of slide movement, this method of achieving a stop position for the slide of a mechanical press is inaccurate, as it is based upon visual indications of slide position as perceived by a press operator and unequal increments of slide movement.
What is needed in the art is a method and apparatus for allowing a press operator to choose an absolute dimensional value at which the mechanical press may be stopped, namely, an exact specific slide location at which the slide will come to rest.
What is further needed in the art is a system for locating the slide of a mechanical press at a specific absolute resting position that does not require manual intervention vis-à-vis the press components, and which does not excessively wear the clutch and brake components of the press.
What is further needed in the art is a means for repositioning the slide that minimizes the time interval between the submission of the repositioning request and placement of the slide into its fully resting state at the selected slide position.
What is further needed in the art is a compensation strategy useful in repositioning the slide that comprehensively accounts for all of the temporal factors that contribute to lessening the reactivity and responsivity of the repositioning system, such as processing delay, scan time delay, and communication delay.
SUMMARY OF THE INVENTION
According to one form of the present invention, there is provided a control system to enable a press operator to selectively position the slide at a specific resting location corresponding to an absolute dimension of the slide travel path. In one form, the resting location for the slide may represent a specific angular value, such as a degree measure (0-359°) relative to the top dead center (TDC) position of the press machine crankshaft.
The slide positioning process may be facilitated by a programmable limit switch module that suitably manages the operation of a brake-clutch combination by commanding a clutch control circuit to actuate disengagement of the clutch at the proper moment so that the slide will come to rest at the selected resting location.
According to another form of the invention, the slide control system is implemented with a programmable limit switch module that is suitably configured to optimally minimize the operational delays that typically exist in applications involving the coordinated interaction among various discrete components connected over a distributed platform. For example, the programmable limit switch module is provided in a form that aims to reduce the scan time related to the retrieval of press speed information by integrating all of the functionality of the slide positioning process within a single, self-contained, stand-alone modular unit.
In one form, the programmable limit switch module includes a programmable limit switch device connected to a press speed resolver and a dedicated processor connected directly to the programmable limit switch device and/or resolver. The processor may be a special purpose computer or computational device such as a programmable logic controller (PLC) or a general purpose computer or computational device that has been configured with the appropriate processing software.
In one form, the processor is configured with an algorithm that computes the precise clutch drop-out condition based upon various input variables, such as press slide speed. For this purpose, the algorithm performs a function that addresses speed-related compensation to account for variable advancement of the clutch drop-out position based upon slide speed.
The programmable limit switch module is suitably configured, for example, to minimize the scan time related to retrieval of press speed information by the processor.
The invention, in one form thereof, is directed to a system for use with a press machine environment having a slide and an apparatus to selectably control movement of said slide. The system includes, in combination, an input device and a unit operatively associated with the apparatus. The input device is configured to enable a user to selectively indicate a resting location for the slide corresponding to an absolute slide position. The unit is configured to control operation of the apparatus using a resting location indication operatively re
Knuth Randal J.
Picard Leo
Swindell W. Russell
The Minster Machine Company
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