Work holders – Plural holders to hold workpieces relative to each other
Reexamination Certificate
1999-11-23
2001-07-31
Eley, Timothy V. (Department: 3723)
Work holders
Plural holders to hold workpieces relative to each other
C269S910000, C269S303000, C269S305000, C029S281300
Reexamination Certificate
active
06267365
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvements in jigging and pressing systems for the production of timber trusses, such as roof trusses. The invention relates more particularly to locator stops (also known as pucks) for use with a truss table for these systems, and to a truss table having such stops or pucks.
BACKGROUND OF THE INVENTION
Truss tables for truss jigging and pressing systems are well known. Examples are disclosed in U.S. Pat. Nos. 4,943,038 (to Hamden), 5,085,414 (to Weaver), 5,702,095 (to Williams) and 5,553,375 (to Powers). In general, each of these references discloses an elongate truss table including a longitudinal series of table sections in which successive sections are separated by a respective transverse slot. Each table section includes a longitudinal series of transversely disposed relatively narrow panels with successive panels also separated by a respective transverse slot. Some slots, typically those between table sections, have a respective conveyor device able to be raised from a lower, retracted position to a position in which it is operable to move a substantially completed truss laterally off the table. Other slots house either fixed nuts or movable carriers to each of which a respective locator stop or puck is able to be secured on the top surface of the table, by means of a bolt. The stops are able to be secured in an array over the table surface, as required to enable them to accurately position lengths of timber which are to be secured in assembly to form a timber truss of a required configuration in which the timber lengths comprise chords and webs. The timber lengths are at least partially secured at junctions therebetween by toothed truss plates or nail plates which have been pressed to force teeth of each plate into each of the timber lengths forming a respective joint.
The truss or nail plates usually are partially pressed by a relatively light, travelling pressure roller which is passed over the truss table or by a platen press. The resultant partially completed truss then is moved off the table and pressing is completed by a heavier finishing roller. This double pressing procedure is used because the arrangement for securing the locator stops or pucks necessitates use of relatively wide slots between panels of the truss table. The width of the slots is such that if pressure sufficient to complete pressing on the table were to be used, the nail plates would not press satisfactorily or they would be deformed.
In addition to these constraints on pressing, the locator stops or pucks are such that considerable time is expended in securing them in required positions. Usually, each is secured by an Allen bolt tightened relative to a nut or carrier. This needs to be done carefully for each stop in turn to ensure that none of the stops is able to be inadvertently displaced during jigging and pressing.
SUMMARY OF THE INVENTION
The present invention is directed to providing an improved form of locator stop (or puck), and a truss table having such stops or pucks. At least in preferred forms, the stop of the invention enables at least some disadvantages of the known stops to be overcome or alleviated.
A locator stop or puck according to the invention has a body which is adapted to be supported on the upper surface of a truss table, so as to extend across a slot between successive panels of the table. The stop also has locking means which projects below the body so as to be locatable in the slot. The body has a basal surface by which it is supportable on the upper surface of the table, while the locking means has dimensions in two mutually perpendicular directions substantially parallel to the basal surface which respectively are less than the width of the slot and greater than the width of the slot. The locking means is adjustable, by a manual operation performed above the table, whereby the locking means is able to firmly engage at least one of the panels defining the slot and thereby clamp or hold the body on the upper surface, at a required position along the slot.
The body may define an external peripheral surface against which a timber length for a truss bears in use of the stop. The peripheral surface preferably is substantially cylindrical such that the timber length extends tangentially with respect to the peripheral surface. However if required the peripheral surface can be other than cylindrical.
In a first arrangement according to the invention, in which the body defines an outer peripheral surface contactable by a timber length for the truss, the body defines a central bore. The locking means is mounted at the lower end of a stem located in the bore of the body. A transverse pin through the upper end of the stem is journaled in an eccentric, while the eccentric bears on a surface of the body and is rotatable to raise or lower the stem. The locking means, which is raised and lowered with the stem, has a resiliently compressible element carried on a rigid backing member secured to the stem. The arrangement is such that with the eccentric rotated to raise the stem and hence the locking portion, the resilient element is compressed and thereby resiliently engages at least one panel defining the slot and clamps the body on the upper surface of the table.
In a first form of that first arrangement, the locking means is of L-shape, with the backing member thus defining an arm or ledge which extends laterally from the lower end of the stem and on which a resilient element is provided. In use, the ledge extends below one of the panels defining a slot of the table and, as the eccentric is rotated to raise the stem, the resilient element is compressed against the one panel. In a variant of that first form, the locking means is of inverted T-shape, to define two arms or ledges on each of which a resilient element is provided, so each element is compressible against a respective panel. In a second form, the resilient element is located along an upper edge of the backing member and, in use, is located within the slot so as to be compressed against the body portion so as to bulge laterally outwardly. The resilient element may be compressible against the basal surface of the body portion, or against the lower edge of a fin which is defined by the body portion and extends below the basal surface.
In the first form, compression of the resilient element generates a bias acting against lifting of the stem, with this bias causing the body portion to be clamped by being pulled down against the upper surface of the table. In the second form, compression of the resilient element causes it to be squeezed or deformed outwardly so as to bear firmly against, and be held between, respective edges of panels between which the slot is defined.
Rather than define an external peripheral surface against which a timber length for the truss is able to bear, the body in a second arrangement according to the invention is in the form of a hub or top plate. In that case the locator stop preferably includes a housing in which the body is located, and the housing preferably is rotatable relative to the body to actuate the locking means. The housing defines such external peripheral surface, and its peripheral surface preferably is cylindrical.
In a first form of the second arrangement, the housing is in screw threaded engagement with the body. The arrangement is such that, as the housing is rotated in a direction to cause it to advance downwardly onto the body, the housing bears against and moves a force transferring member and thereby generates a force acting to urge the locking means into locking or gripping engagement with at least one of the panels defining the slot. In one embodiment, the force transferring member and the locking means comprise respective arms of a bell-crank lever, in that the arms are at a suitable angle such as generally at right angles and have a common fulcrum at their junction. The fulcrum enables the arms to pivot in unison on an axis which is substantially parallel, and adjacent, to the basal surface of the body. The arrangement pref
Anglin Maurice William
Ash Graham Barry
Cox Gavin
Currie Ian
Kearon Alan
Ajax Technology Centre Pty Ltd.
Eley Timothy V.
Wilson Lee
Wolf Greenfield & Sacks P.C.
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