Presses – Methods
Reexamination Certificate
1999-03-19
2001-06-26
Gerrity, Stephen F. (Department: 3721)
Presses
Methods
C072S455000, C100S046000, C100S25800A
Reexamination Certificate
active
06250216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for controlling deflections in the work surfaces of a mechanical press. The method and apparatus of the current invention may be used to alter the deflection in the work surface of, for example, the slide or the bed of a mechanical press. The method and apparatus of the current invention may be employed to alter deflections prior or not prior to machining the work surface of a press member and/or during press operation.
2. Description of the Related Art
Mechanical presses, for example, stamping presses and drawing presses, comprise a frame having a crown and a bed with a slide supported within the frame for motion toward and away from the bed. Such mechanical presses are widely used for stamping and drawing operations and vary substantially in size and available tonnage depending upon the intended use.
Conventional press machines employ a tooling apparatus in the form of a die assembly to shape a workpiece, such as in a stamping or drawing operation. The die assembly particularly includes a lower die attached to the work surface of a non-moveable bed or bolster and an upper die or punch attached to the work surface of a reciprocating slide. The upper and lower dies, which are installed in opposing spaced apart relation to one another, cooperate during press machine operation to mutually engage the workpiece at respective sides thereof to thereby effect the desired forming activity.
Repeated stamping operations of a mechanical press cause deflections in portions of the press. For example, press operation causes deflections in the bed and the slide of the mechanical press. Bed and slide deflections are typically within the range of 0.002″ per foot to 0.005″ per foot of slide or bed width. In some production environments, such deflections will cause scrapping of stamped product which leads to increased cost and production time.
The working surfaces of the slide and the bed are typically machined to produce substantially uniform work surfaces. Having to re-machine these work surfaces is undesirable due to the necessary press down time and the wear to the work surfaces caused by additional machining. Replacing deflected work surfaces is undesirable due to the necessary press down time and substantial expense.
What is needed in the art is an apparatus and method to minimize the deflection experienced by portions of the mechanical press during press operation. What is additionally needed in the art is an apparatus and a method to monitor deflections experienced during press operation and to provide a means for automatically adjusting deflections during press operation.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus which works to eliminate deflection experienced in members of a mechanical press.
The present invention places members of a mechanical press in a prestressed condition to minimize deflection in the work surface of the press member. Further, the present invention can be utilized to monitor deflections experienced during press operation and to automatically adjust deflection during press operation.
The invention, in one form thereof, comprises a mechanical press including a press member which has a work surface that experiences deflection during press operation. A deflection controller is provided and controls the deflection of the work surface of the press member. The press member can be, for example, a slide or a bed.
The invention, in another form thereof, includes a deflection controller which comprises a tie rod that is connected to a press member and is maintained in tension. In one form of the current invention, the tie rod is connected to the work surface of the press member.
In one form of the current invention, the deflection controller comprises a tie rod which is connected by a pair of tie rod nuts to a press member. The tie rod nuts are threadedly connected to the tie rod and are selectively actuatable. When actuated the tie rod nuts increase the tension in the tie rod which correspondingly alters the deflection in the press member.
The invention, in another form thereof, comprises a deflection controller for controlling the deflection in the work surface of a press member which includes a tie rod connected to the press member and which is maintained in tension. A pair of tie rod nuts are threadedly connected to the tie rod so that when actuated the tie rod nuts increase the tension in the tie rod and correspondingly alter the deflection in the press member. A deflection measuring means which can be, for example, a strain gage or a non-contacting optical or electrical sensing means measures the deflection of the press member. A display device is provided and is communicatively connected to the deflection measuring means and displays the deflection measured by the deflection measuring means. The display device may also display a predetermined desired deflection. In this way, the deflection experienced in a press member may be compared to a predetermined desired deflection so that the tie rod nuts may be actuated when the measured deflection deviates from the predetermined desired deflection. In this way, the deflection experienced during press operation may be altered.
The invention, in another form thereof, comprises a deflection controller for controlling the deflection of the work surface of a mechanical press member. In this form, the deflection controller comprises a tie rod connected to the press member by a pair of pressure activated tie rod nut assemblies such that the tie rod is in tension. When the tie rod nut assemblies are activated, they increase the tension in the tie rod and correspondingly alter the deflection in the press member. A feedback means is connected to a deflection measuring means and to the tie rod nut assemblies for comparing a predetermined desired deflection to a measured deflection. The feedback means activates the tie rod nut assemblies when the measured deflection deviates from the predetermined desired deflection.
The invention, in another form thereof, includes pressure activated tie rod nuts. The pressure activated tie rod nuts each include a cylinder block which has a cylinder bore fit about a tie rod. A piston is threadedly engaged about the tie rod and slidingly disposed within the cylinder bore thereby forming an inner chamber. A plurality of seals are operatively located between the piston and the cylinder block to seal the inner chamber. A tie rod nut is threadedly engaged about the tie rod, engaging the piston, so that when the inner chamber is pressurized with a liquid, the increase in pressure forces the piston and tie rod nut away from the cylinder block and thereby increases the tension in the tie rod. In one form of the current invention, a tube encases the tie rod and is in compression.
The invention, in another form thereof, includes a feedback means which activates the pressure activated tie rod nut assemblies by altering the pressure within the inner chamber. The feedback means comprises: pressurizing means connected to the pressure activated tie rod nut assemblies and a comparator. The pressurizing means is activated by a control signal and changes the pressure of liquid communicated to the tie rod nut assemblies in response to the control signal. The pressurizing means can be, for example, a pump, a hydraulic cylinder, or a hydraulic power unit. The comparator has input lines for a measured deflection from a deflection measuring means and for a predetermined desired deflection. The comparator further includes an output line connected to the pump. The comparator causes a control signal to be formed on the output line on the basis of a comparison between a measured deflection and a predetermined desired deflection.
The invention, in another form thereof, comprises a press in which a crown and bed are connected together by a frame. A slide is connected within the frame for reciprocating movement in opposed relation to the bed. Both the bed and the slide have w
Gerrity Stephen F.
Knuth Randall J.
The Minster Machine Company
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