Threaded – headed fastener – or washer making: process and apparat – Apparatus for making externally threaded fastener or...
Reexamination Certificate
1999-08-31
2001-01-30
Tolan, Ed (Department: 3725)
Threaded, headed fastener, or washer making: process and apparat
Apparatus for making externally threaded fastener or...
C470S072000, C451S120000, C451S218000, C408S013000, C408S204000
Reexamination Certificate
active
06179718
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a fastener-forming machine and, more particularly, to a secondary fastener-forming machine.
BACKGROUND OF THE INVENTION
Secondary fastener forming machines take cylindrical workpieces, such as headed fastener blanks that have been formed in a primary fastener forming process, and perform additional operations on the workpieces such as tapering the ends. To perform additional operations such as pointing on the blanks, some secondary forming machines drive the blanks axially along a linear forming stroke into engagement with cutters mounted on a cutting head. It is highly desirable that secondary fastener forming machines of this type include means for adjusting the length of each forming stroke to accommodate fastener blanks and other workpieces of various lengths. It is also desirable that such machines include a mechanism that senses when a blank has reached the end of its forming stroke and causes the machine to reverse and disengage the formed workpiece from the forming tool.
Optical Boring Company, the assignee of the present invention, manufactures a secondary fastener forming machine (the OBC machine) that forms pointed ends onto headed fastener blanks. The OBC machine includes a reciprocator in the form of a 2-piston hydro-pneumatic cylinder that reciprocates a reciprocating portion of the assembly including a fastener gripper upward to a fully retracted “remote” position and downward through a cutting stroke to a fully extended “proximate” position. During the lower portion of the cutting stroke the lower end of a fastener blank held in the gripper axially engages a rotating cutting tool at a cutting tool rotational axis. The cutting tool includes carbide cutting blades that are positioned around the cutting tool axis to cut a tapered conical tip on the fastener blank. One piston within the cylinder is hydraulically dampened leaving no hard linkages between the forming machine and the fastener blank being worked. This lack of hard linkages allows the downward travel of the fastener blank and gripper to slow with increased resistance during the cutting stroke and to slow further or even stop completely in response to excessive resistance. After cutting, the cylinder lifts the gripper and extracts the fastener from the cutting tool, completing a cutting cycle. The OBC machine also includes a part transfer mechanism that inserts and ejects parts. The reciprocal motion of one of the pistons within the hydro-pneumatic cylinder drives the part transfer mechanism.
An adjustable screw axially engages a limit switch whenever a fastener has reached the end of its forming stroke. When the limit switch is thus activated it signals the reciprocator to reverse the reciprocating portion of the assembly and disengage the newly-tipped fastener from the cutters. The screw may be advanced or retracted to adjust the reversal point of the cylinder at the end of the cutting stroke.
While a reciprocator of this type provides many advantages it cannot consistently terminate the downward forming/cutting stroke at the same proximate position within acceptable tolerances. If cycle speed is increased for any reason, the reciprocating portion of the assembly and the fastener blank can overshoot the proximate position resulting in a deeper cut on the fastener. Conversely, if cycle speed decreases for any reason, the reciprocating portion may undershoot the desired reversal point resulting in a shallower cut on the fastener. Cycle speed will tend to decrease over time as the cutters begin to get dull from repeated cutting cycles. The cycle speed slows because the force required to advance each fastener blank into the cutters increases while the pneumatic pressure supply remains relatively constant. In addition, small variations in pneumatic pressure supply are common with most industrial air compressor systems and can result in cutting depth variations that are unacceptable in certain applications.
What is needed is a hydro-pneumatically driven fastener forming machine that, without hard linkages, moves fastener blanks through a forming stroke while positively and consistently maintaining the end-of-stroke stopping position, i.e., the “proximate” position of each workpiece relative to the forming tool. What is also needed is such a machine that can accommodate bolts of various lengths.
SUMMARY OF THE INVENTION
In accordance with the present invention a hydro-pneumatically driven fastener forming apparatus for forming fasteners from cylindrical workpieces comprises a positive stop. The positive stop prevents a reciprocating portion of the apparatus from causing workpieces to overshoot or undershoot a proximate position relative to a forming tool. The apparatus includes a workpiece gripper supported for reciprocal movement along a forming axis and configured to releasably grip and carry a generally cylindrical workpiece in a coaxial disposition along the forming axis. The forming tool is spaced from the gripper along the forming axis. At least one of the part gripper and tool is supported for relative reciprocal motion along the axis between a remote position and the proximate position. The gripper and tool are disposed farther apart in the remote position than in the proximate position. The assembly also includes a workpiece transfer mechanism configured to sequentially transfer a series of workpieces into the workpiece gripper and to drive preceding workpieces out of the workpiece gripper and onto an exit path. A reciprocator is operatively connected to the reciprocating portion of the apparatus. The reciprocating portion of the apparatus comprises one of the workpiece gripper and tool. The reciprocator drives one of the workpiece gripper and tool between the extended and retracted positions. The reciprocator has a stationary end connected to a stationary support and a reciprocating end operatively connected to the reciprocating portion of the apparatus. The stationary end is hydro-pneumatically coupled to the reciprocating end. The motion of the reciprocating end and the reciprocating portion of the apparatus are hydraulically dampened. The positive stop includes a reciprocating stop surface disposed on the reciprocating portion of the apparatus in a position to engage a stationary stop surface when the workpiece gripper and tool are in the proximate position.
In accordance with another aspect of the invention the reciprocating stop surface is disposed on a reciprocating stop that is adjustably connected to the reciprocating portion of the apparatus. The position of the reciprocating stop relative to the reciprocating portion of the apparatus is adjustable in a direction parallel to the forming axis to allow an operator to adjust the extended position.
In accordance with another aspect of the invention the reciprocator includes a lower limit switch disposed in the path of the reciprocating portion of the apparatus. The lower limit switch is actuable by contact with the reciprocating portion of the apparatus in the extended position. The lower limit switch is configured to send a signal in response to actuation that causes the reciprocator to reverse direction.
In accordance with another aspect of the invention the lower limit switch is supported adjacent the stationary stop. The lower limit switch includes a plunger actuator that extends through an aperture in the stationary stop surface.
In accordance with another aspect of the invention the reciprocator includes a compound hydro-pneumatic cylinder connected between the stationary end and the reciprocating end of the reciprocator.
In accordance with another aspect of the invention the hydro-pneumatic cylinder is connected to a stationary support. A reciprocating piston rod extends from a piston within the cylinder and operatively connects to the workpiece gripper.
In accordance with another aspect of the invention reciprocal motion of the reciprocator drives the workpiece transfer mechanism.
In accordance with another aspect of the invention a rotator is operatively connected to one of the workp
Custer Dennis F.
Linthorst Jan A.
Marchionni Ronald W.
Morath Lawrence A.
L & M Machining and Manufacturing, Inc.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Tolan Ed
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