Workpiece clamping tool

Details Workpiece clamping tool Workpiece clamping tool

1999-07-12

2001-03-20

Scherbel, David A. (Department: 3723)

Work holders

Relatively movable jaws

With means for 'hold-down' component of force

C264S029300, C269S025000

Reexamination Certificate

active

06202996

ABSTRACT:

FIELD OF THE INVENTION
The present invention is generally related to clamps suitable for use in machining and woodworking. More specifically, the present invention is related to a workpiece edge clamp capable of applying a simultaneous horizontal and downward force to a workpiece.
BACKGROUND OF THE INVENTION
Clamps are commonly used for securing workpieces to machine tables during machining operations such as drilling and milling. Edge clamps and toe clamps are frequently used. Machine operations can apply large vertical, lateral, and torquing forces on the workpiece or part being machined. The large tool forces require large counteracting clamping forces to prevent the part being machined from moving out of tolerance or flying off the machine table entirely. The clamping force requirement is exaggerated in the case of small parts being machined. In the first place, the small part typically has only a small surface area upon which a clamping force can be brought to bear. In the second place, the size of the clamping device may be of large size relative to the part being machined and can obscure tool access to a significant portion of the part, especially the part sides.
In one device, the ADVANT-EDGE™ edge clamp, a body having an inclined surface is provided along with means for securing the body to a T-slot. A nominally rectangular clamping element, having a small bore hole therethrough and a larger round surface recess, is disposed on the incline and held in place upon the incline with a bolt extending through the recess and bore hole. The bolt has a round head mounted on the end of the bolt shaft and off center from the shaft. This mounting provides a small distance from shaft center to head outside edge on one side, and a large distance from shaft center to head outside edge on the opposite side. As the head is rotated, the bolt is drawn in at an angle perpendicular to the incline, and the wider portion of the head rotates as a cam down the incline, and toward the workpiece being held. The clamping element is forced slightly downward and toward the workpiece. There are several drawbacks with this design. First, to allow the bolt to rotate, the clamping element must be spaced above the incline surface with a gap therebetween to allow the bolt to turn, otherwise the bolt would be bound. This results in tilting or deflection of the clamping element from vertical as it is advanced into contact with a workpiece, which translates into a less than firm grip on the workpiece. Second, the bolt increases force on the workpiece only through 180°. Further turning of the bolt decreases the applied force over the next 180° and the clamping element cannot be drawn tight to the incline surface.
In U.S. Pat. No. 4,049,253 to Mandel, a toe clamp is described including a work-engaging member, a nut, an inclined clamping screw for tightening the work-engaging member to the bolt, and an inclined shoulder bolt having a non-threaded region disposed within the work-engaging member and a threaded region disposed within the nut. The toe clamp described has the work-engaging member apart from, and not received by, the nut. Only the shoulder bolt threaded lower region is received by, and receives any support from, the nut. Finally, the work-engaging member is disposed totally above the table top. The toe clamp work-engaging member described is believed to be prone to some tilting or deflection about the screw and shoulder bolts. The work-engaging member resides totally above the work table surface, blocking machine tool access to a substantial part of the workpiece, as can be seen from inspection of
FIG. 4
of the reference.
What would be desirable is a workpiece clamp having improved support for the workpiece engaging member, which eliminated or reduced any deflection of the clamping element from vertical while contacting the workpiece to provide consistent workpiece placement. What would further be desirable is a workpiece clamp having most of the structure disposed below the work table surface, enabling machine tool access to a substantial portion of any parts being machined, while achieving improved support for the workpiece. What would also be desirable is a workpiece clamp having improved workpiece-holding characteristics.
SUMMARY OF THE INVENTION
The present invention provides a workpiece edge clamp for holding a workpiece or part during operations such as machining and wood working. The workpiece can be positioned between the clamp and a lip on a fixture block or work table. The clamp supplies a downward and lateral force to the piece being held. The clamp preferably has a small profile above the surface of the fixture block or work table, enabling the tool being used to access a substantial portion of the piece being machined, including all of the sides.
In preferred embodiments, the clamp includes a body having an angled recess, means for securing the body to a fixture block, an insert adapted to be slidably received within the body recess at such angle, means for drawing the insert into the body recess along the angled path defined by the recess, and a workpiece contact face secured to or formed on the insert. The body can be secured to the fixture block or work table, the workpiece placed on the fixture block or work table between a fixture block lip or work table shoulder, and the insert contact face. The insert can then be drawn into the body along a path defined by the angle of the recess, such that the contact face is simultaneously forced downward and toward the workpiece at a constant rate, thereby contacting with constantly increasing force the workpiece to secure the workpiece between the lip and contact face.
The body is preferably adapted to fit within a surface cavity in the fixture block or work table, at a suitable distance from a lip or shoulder on the fixture block or work table. The upper surface of the body in one preferred clamp is flush with the surface of the fixture block or work table. A mounting hole in one embodiment is used to secure the body to the fixture block with or without using a mounting bolt. The body has an angled recess for receiving the insert. The insert slides along the recess, as defined by the recess walls, at such angle downward and toward the workpiece. The body recess preferably has an angled threaded bore in the lower portion, which extends parallel to and beyond the recess for receiving a threaded tension bolt through the insert.
The insert has a workpiece contact face extending upward from the insert when the insert is inserted in the recess. In such position, at least a portion of the contact face extends above the work plane or work surface of the fixture block or work table, while substantially the entire body and the vast majority of the insert are below the work table or fixture block surface. This combination provides tool access to substantially the entire part during machining. The insert is sized to be received by the body recess, such that the insert receives support and proper alignment from the recess walls throughout its range of travel. With this configuration, tilting or flexing of the insert and associated workpiece contact face from vertical is minimized. This is true because the body recess cylindrical back and side walls provide substantial area for close tolerance contact with the insert while allowing desired workpiece contact face rotation for alignment with the part. The insert upper portion is preferably sized to slidably receive a tension bolt, such that when the tension bolt is rotated and tightened into the body, the insert is drawn at a continuous rate into the body and fixture block along the angle. The insert contact face is thus drawn both downward and toward the workpiece at a continuous rate, applying increasing downward and lateral force against the workpiece with each incremental rotation of the tension bolt, securing the workpiece to the fixture block.
The tension bolt is preferably concentrically disposed within the insert, and the insert concentrically disposed within the body recess, such that the tens

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