192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
1999-07-29
2001-06-12
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
Reexamination Certificate
active
06244412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for monitoring the necessary energy and/or tonnage for a particular application of a mechanical press and for adjusting clutch torque to achieve this necessary energy and/or tonnage. Adjusting clutch torque to achieve the minimum necessary operating tonnage lessens possible press damage caused by a die wreck.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction which includes a frame structure having a crown and a bed and which supports a slide in a manner enabling reciprocating movement toward and away from the bed. The slide is driven by a crankshaft. A connecting rod is operatively connected to the crankshaft and slide. The connecting rod is operative to transmit the rotational energy of the crankshaft into reciprocal movement of the slide. These press machines are widely used for a variety of workpiece operations and employ a large selection of die sets with the press machine varying considerably in size and available tonnage depending upon its 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 bed or bolster and an upper die or punch attached to the slide. The upper and lower dies are installed in opposing spaced-apart relation to one another and cooperate during press machine operation to mutually engage the workpiece at respective sides thereof to thereby effect the desired forming activity.
Press operational problems occur when foreign material enters the die set. Large pieces of foreign material entering the die set can cause a die wreck in which the die set of the mechanical press can be significantly damaged. Additionally, contacting large pieces of foreign material or debris during press operation will create excessive vibration throughout the press.
Many mechanical presses employ a hydraulic overload protection device which serves to alleviate problems associated with foreign objects entering the die set. Such hydraulic overload protection devices are of limited utility as they commonly provide protection only with respect to foreign objects small in height. Larger foreign objects would exceed the capacity of the overload protection device and cause die or press damage.
What is needed in the art is a method and apparatus for preventing or lessening the effect of die destruction and associated problems which can occur when large foreign objects enter the die set.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for determining the necessary or lowest operating tonnage for a mechanical press and for adjusting clutch torque to achieve such necessary operating tonnage. In this way, any foreign object entering the die set will receive only the minimum operating tonnage of the mechanical press and as the foreign object forces the press to exceed this necessary tonnage, the clutch of the mechanical press will slip, thus limiting the tonnage transferred to the foreign object and thus limit the associated damage caused thereby.
The present invention provides a clutch slip monitoring device in the form of measuring devices which measure the angular displacement of both the flywheel and the clutch. These angular displacements can then be compared to determine whether the clutch is slipping relative to the flywheel. Such a clutch slip monitoring device is communicatively connected to a clutch pressure adjusting device and signals changes in applied clutch pressure depending upon measured clutch slippage. In this way, the pressure of engagement between the clutch and the flywheel (or, more generally drive and driven members) may be regulated so that clutch slip is eliminated and the necessary tonnage for the particular application is achieved. With such a device in place, the mechanical press will be without an excess surplus of applied operating tonnage.
The invention, in one form thereof, comprises an apparatus for automatically controlling the clutch torque of a mechanical press. The apparatus of this form of the current invention includes a clutch slippage monitor and a clutch pressure adjuster which is communicatively connected to the clutch slippage monitor.
The invention, in another form thereof, comprises a mechanical press having an automatic clutch torque control. The press of this form of the current invention includes a flywheel, a clutch, a clutch slip monitoring device, and a clutch pressure adjusting device. The clutch is operative to selectively engage the flywheel and has an adjustable clutch engagement pressure. The clutch slip monitoring device is operable to monitor clutch slippage and is operatively connected to the clutch. The clutch pressure adjusting device is operative to vary the clutch engagement pressure and is communicatively connected to the clutch slip monitoring device and operatively connected to the clutch.
In one form of the current invention, the clutch slip monitoring device includes a first measuring device for monitoring the angular displacement of the flywheel. A second measuring device is provided and monitors the angular displacement of the clutch. A high speed counter module is communicatively connected to both the first measuring device and the second measuring device. The high speed counter module is operative to evaluate the angular displacement of the flywheel and the angular displacement of the clutch to determine the extent of clutch slippage relative to the flywheel. The first and second measuring devices can be, for example, a first pulse generator and a second pulse generator respectively. The first pulse generator is affixed to the flywheel while the second pulse generator is connected to the clutch. The second pulse generator may be affixed to the crankshaft of the mechanical press, which is operatively connected to the clutch. In one form of the current invention, both the first pulse generator and the second pulse generator are resolvers.
An output module is communicatively connected to the high speed counter module and to the pressure adjusting device. The pressure adjusting device is operatively connected to the clutch and is operative to control the adjustable clutch engagement pressure. The output module is communicatively connected to the pressure adjusting device so that the output module is operative to control the adjustable clutch engagement pressure based upon clutch slippage as determined by the high speed counter module. In one form of the current invention, the output module is operative to produce a zero to ten VDC signal operative to vary the clutch engagement pressure provided by the pressure adjusting device.
In one form of the current invention, the pressure adjusting device includes a proportional pressure relief valve which is communicatively connected to the output module. The pressure adjusting device further includes a pressure reducing valve which is operative to control the adjustable clutch engagement pressure. The proportional pressure relief valve is operatively connected to the pressure reducing valve and is operative to communicate a pilot pressure to the pressure reducing valve whereby the pilot pressure controls the adjustable clutch engagement pressure. Pressure is provided to the pressure reducing valve by way of a pressurizing pump.
The invention, in another form thereof, comprises a method of operating a mechanical press at the necessary tonnage for the particular application of the mechanical press. The method of this form of the current invention includes the steps of: monitoring the required operating tonnage for the press application and adjusting the press operating tonnage in real time to achieve the required operating tonnage.
The invention, in another form thereof, comprises a method of automatically controlling the clutch torque of a mechanical press to achieve the necessar
Bonck Rodney H.
Knuth Randall J.
The Minster Machine Company
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