Presses – Reciprocating press construction – With mechanical force multiplier
Reexamination Certificate
1999-05-11
2001-02-13
Gerrity, Stephen F. (Department: 3721)
Presses
Reciprocating press construction
With mechanical force multiplier
C072S450000, C072S455000, C083S615000, C083S632000, C100S214000, C100S299000, C184S006140, C384S099000, C384S114000
Reexamination Certificate
active
06186061
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to mechanical press machines and, more particularly, to a press bearing lubrication system that provides both hydrostatic and hydrodynamic bearing support at press wrist pins and other journal bearings characterized, for example, by oscillatory motion, relatively little rotation, and/or slow rotational speeds.
2. Description of the Related Art
Mechanical presses of the type performing industrial activity such as stamping and drawing operations have a conventional configuration including a frame with a crown and bed portion and a slide supported within the frame for reciprocating movement toward and away from the bed. A crankshaft rotatably disposed within the crown is arranged in driving connection with the slide using a connecting arm assembly. A flywheel assembly rotatably driven by a drive mechanism is selectively connectable with the crankshaft for driving rotation thereof, utilizing a clutch/brake combination to make the driving connection. These mechanical presses are used in a wide variety of workpiece operations employing a large selection of die sets, with the press machine varying substantially in size and available tonnage depending upon the intended use.
The primary source for stored mechanical energy in mechanical presses is the flywheel, which is conventionally located between the main drive motor and the clutch. The flywheel and its associated bearing are mounted on either the driveshaft, crankshaft, or the press frame by use of a quill. The main drive motor replenishes the energy lost from the flywheel during press stamping operations when the clutch couples the flywheel to the press driven parts. During engagement of the clutch, the flywheel drops in speed as the press driven parts are brought up to press running speed. The flywheel rotates in unison with the engaged clutch while the flywheel bearings have no relative rotation, except for the case of a quill arrangement whereby relative rotation is always present.
One of the critical demands in mechanical presses concerns providing adequate lubrication to the system parts to safeguard their structural integrity, promote durability, and avoid premature device failure. Efforts aimed at addressing this problem have focused on developing bearing arrangements that adequately support the principal rotary components throughout their operating cycle, namely the flywheel and crankshaft. However, what has been overlooked by such efforts, and consequently absent from the accompanying press design work, is the need to provide similar bearing protection at other press machine sites which, while not representing principal sources or recipients of work-related rotational energy, nevertheless exhibit relative motion between press parts that necessarily invokes a lubricating requirement. Examples of such machine sites include wrist pins and other journal bearings where there exists relatively little rotation, oscillation, and/or slow rotational speeds.
One conventional approach aimed at providing bearing support to these secondary motion sites proposes to create a hydrodynamic effect between the bearing surfaces of the associated devices. Generating such hydrodynamic activity requires a sufficient amount of relative rotation between the devices to mobilize or activate the oil film injected into the clearance space. For components such as wrist pins, however, developing a lubricating system that relies exclusively upon adequate relative rotation to produce the needed bearing support is not a complete or satisfactory solution. Accordingly, despite the availability of hydrodynamic assistance, problems still attend such press machine sites because of their dependence upon an operating condition, namely sufficient relative rotation, that does not manifest to any suitable degree.
A bearing support system based solely on hydrodynamic activity is ineffective in lubricating devices experiencing a low order of rotational or sliding motion. These devices are therefore typically characterized by high wear rates and sometimes premature failure of the bearing due to the minimal or non-existent hydrodynamic effect which otherwise is intended to accommodate the sliding motion occurring between the bearing surfaces. In terms of power requirements, the absence of adequate lubrication means that a relatively high torque is needed to rotate the bearings due to large frictional forces caused by the bearing surfaces sliding across each other. A larger drive system is therefore required due to the reduced efficiencies in power conversion. The elevated torquing action is accompanied by related increases in the thermal energy of the lubricating area, raising the operating temperature of the bearing and causing the oil viscosity to decrease, thereby reducing the load-carrying capacity of the bearing.
Bearing support limited to hydrodynamic activity still presents certain difficulties even if the rotational speeds are sufficient to create the intended hydrodynamic effect. In particular, as the devices commence their operation from a static condition and appreciable hydrodynamic activity appears, a “lift-off” effect occurs in which the bearing surfaces yield to an displacing pressure generated by the oil film as it undergoes hydrodynamic activity. This lift-off of the bearing surfaces causes a change in position of the crankshaft, pins, and linkages, resulting in a change in the press ram position at the bottom of each stroke relative to when the press is in a static condition. This ram displacement must be taken into account when installing the ram tooling or otherwise poor part quality and damaged tooling may result.
SUMMARY OF THE INVENTION
According to the present invention a plurality of hydrostatic bearing pads are each integrally formed in a respective pin or journal member being used within a mechanical press machine. The hydrostatic bearing pads are supplied with pressurized fluid sufficient to create a combined hydrostatic and hydrodynamic effect between the opposed bearing surfaces of the pin and an associated bushing. The hydrostatic bearing pads are preferably used in conjunction with rotational and oscillating bearings in which relatively little rotation, oscillation, or slow rotational speeds exist. These types of bearings, for example, are associated with crankshaft and connection journal bearings, connection pins that couple the press slide or weight assembly to the crankshaft which provides reciprocating motion, connection pins and pivot pins used by a rocker-type coupling assembly that couples a weight assembly to the piston assembly that drivingly reciprocates the press slide.
The invention, in one form thereof, includes a press comprising, in combination, a frame structure with a crown and a bed; a slide associated with the frame structure for reciprocating movement in opposed relation to the bed; a drive means associated with the frame structure for reciprocating the slide, the drive means including a piston assembly coupled to the slide; a balance means associated with the frame structure for balancing the slide; and a coupling means for coupling the balance means to the piston assembly, the coupling means comprising: a rocker assembly including a plurality of pivot pins, a first link assembly for coupling the piston assembly to the rocker assembly including a first plurality of connection pins, and a second link assembly for coupling the balance means to the rocker assembly including a second plurality of connection pins. The press further comprises a plurality of hydrostatic bearing pads each integrally associated with a respective pin from among the first plurality of connection pins, the second plurality of connection pins, and the plurality of pivot pins and each arranged to facingly oppose the bearing surface of an associated bushing disposed about the respective pin; and a means for providing each one of the plurality of hydrostatic bearing pads with pressurized fluid at least sufficient to create a hydrostatic bearing between the
Burns Bradley A.
Daniel Edward A.
Watercutter Brian A.
Gerrity Stephen F.
Knuth Randall J.
The Minster Machine Company
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