Metal working – Means to assemble or disassemble – Overedge assembling means
Reexamination Certificate
2001-05-21
2002-12-24
Jones, David (Department: 3725)
Metal working
Means to assemble or disassemble
Overedge assembling means
C029S715000, C411S361000
Reexamination Certificate
active
06497024
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fastening system including two-piece swage fasteners and more particularly to pull type swage fasteners with the present invention directed to a construction in which the tensile or relative axial loads required to swage the fastener are reduced permitting the use of smaller, lighter weight installation tools while providing a fastener having a preselected strength and a desirable weight and size.
BACKGROUND OF THE INVENTION
The present invention relates to two-piece swage type fasteners or lockbolts generally of the type illustrated in U.S. Pat. No. 2,531,048 to L. Huck, issued Nov. 21, 1950, and U.S. Pat. No. 3,215,024 to Brilmyer et al issued Nov. 2, 1965; there are numerous other variations of swage type fasteners such as U.S. Pat. No. 3,915,053 to J. Ruhl, issued Oct. 28, 1975, U.S. Pat. No. 4,472,096 to J. Ruhl and R. Dixon, issued on Sept. 18, 1984 and U.S. Pat. No. 5,090,852 to R. Dixon, issued Feb. 25, 1992.
In many commercial applications, two-piece threaded or swaged fasteners are used and are designated by a grade indicative of a particular strength level. For example, a ⅝ inch Grade 5 fastener will have a ⅝ inch diameter pin or bolt shank portion for use in a nominal ⅝ inch diameter workpiece opening and will have a strength level indicated by the grade level, i.e. Grade 5. A Grade 8 bolt, on the other hand, will have higher strength characteristics than the Grade 5 bolt while a Grade 9 bolt will have even higher strength characteristics. For example the strength of a Grade 5 fastener is determined by the strength of the material of the bolt or pin as set by SAE J429 or ASTM A-325 with a minimum material tensile strength of 120 KSI while a Grade 8 is set by SAE J429 or ASTM A-490 at 150 KSI.
A typical swage type fastener includes a pin and a collar with the pull type fastener having a pin shank having a locking portion with lock grooves and a pull portion with pull grooves. The pull grooves are adapted to be gripped by matching teeth in chuck jaws of an installation tool having a swage anvil adapted to engage the collar whereby a relative axial force can be applied between the pin and collar to move the anvil over the collar to swage it into the lock grooves. Here the relative axial force is a tensile load on the pin via the chuck jaws and a compressive load on the collar via the tool swage anvil.
In many swage fasteners the pull portion is connected to the lock groove portion by a breakneck groove of reduced strength which is adapted to fracture at a preselected magnitude of axial or tensile force greater than that required to swage the collar whereby the pull portion, or pintail, will be severed and removed from the pin shank after completion of swaging. Other swage fasteners, however, have pull portions which remain on the pin after completion of installation. See for example U.S. Pat. No. 5,315,755 to Fulbright et al, issued May 31, 1994 where a threaded pull portion is utilized which is not severed from the pin.
In many instances, with swage fasteners of relatively high strength, in order to fully swage the collar the magnitude of applied tensile load can be quite high requiring an installation tool of relatively large size and weight. This is especially significant where manually operated installation tools are used. Such tools typically include hydraulic and/or pneumatic piston-cylinder constructions the size and weight of which will vary with the necessary magnitude of tensile load to be applied. Such tools can be of the type shown in U.S. Pat. No. 4,597,263 to R. Corbett issued Jul. 1, 1986 and U.S. Pat. No. 4,878,372 issued Nov. 7, 1989 to Port et al.
In addition with fasteners including pins having the pull grooves on a severable pintail the breakneck groove must also be of sufficient strength to withstand the high tensile load for swaging and the pull grooves must be similarly of sufficient strength to accept the relative axial pull load applied by the engaged teeth of chuck jaws on the installation tool. This routinely requires that the pull portion be of a relatively large diameter so as to have sufficient material to provide the necessary size and strength for the breakneck groove and also to inhibit fracturing of the pull grooves instead of the breakneck groove. This also adds to the size and weight of the components of the tool to engage the pull grooves and to provide the tensile load on the pin for fracture of the breakneck groove.
In the present invention, a two-piece swage type fastener is provided which can be installed at a lower swage load than a conventional swage type fastener of comparable grade but when installed has the physical properties of essentially the same values such as tensile strength, clamp load and the like on the workpieces being connected. This permits the use of a smaller, lighter weight installation tool in comparison to similar swage type fasteners having the same Grade capability for providing similar physical properties. At the same time with pins having a severable pintail, the breakneck groove and pull grooves can be correspondingly reduced in strength. This permits the pull portion or pintail of the pin shank to be reduced in diameter thus reducing the amount of metal in the pin and at the same time reducing the weight and material cost. The reduced diameter pintail also facilitates the manufacture of the lower strength breakneck groove by roll forming.
However, with pull type swage fasteners having threaded pull portions which are not severed, as in the '755 patent, supra, the present invention facilitates the engagement of fewer threads on the pull portion since the extra force required to fracture a breakneck is not required. This causes less stress on the engaged threads of the mating threaded thimble or nut member on the pull tool resulting in longer life. This also permits the use of a shorter, less expensive pin since less pin protrusion is required for the fewer pull grooves to be gripped. Also the installation tool can be smaller and hence lighter and less expensive since lower applied loads are required for final installation. This also facilitates the use of an internal drive of the type illustrated in FIGS. 17 and 18 of the '755 patent which as shown involves the use of a threaded pull rod or spindle engageable with pull grooves provided by a threaded bore in the end of the shank of the pin or bolt. The use of an internal drive will permit a reduction in protrusion relative to the external drive thereby providing for a more efficient final fit and appearance.
One form of a conventional swage type fastener is shown herein in
FIGS. 7 and 7A
. This type of fastener is used primarily in industrial applications such as buildings, bridges, trucks and the like. Such fastener also requires the application of a relatively high axial force for swaging and for final installation and accordingly requires a relatively large and heavy installation tool. Thus, in the present invention, the swage type fastener which comprises a pin and a collar is for use in applications similar to that of the fastener of
FIGS. 7
,
7
A but, in contrast, the pin and collar are adapted to be set at a relatively low axial force and with a substantially smaller and lighter weight tool.
SUMMARY OF THE INVENTION
In one form of the invention the lock grooves in the pin are constructed to have wide or elongated roots which are of a simulated streamlined shape generally as shown in the '852 patent (supra). The crests of the shoulders of the lock grooves are contoured to facilitate the flow of the collar material as it is swaged to reduce the magnitude of tensile or swage load required to swage. Also the lock grooves are substantially wide relative to the width of adjacent crests which further promotes the flow of collar material during swage. As will be seen, however, the overall structure and operation of the fastener of the present invention is substantially different from that of the '852 patent and its commercial form. In this regard, and
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