Pipe joints or couplings – Packed – Externally with clamp
Reexamination Certificate
2002-09-11
2004-05-25
Hewitt, James M. (Department: 3679)
Pipe joints or couplings
Packed
Externally with clamp
C285S004000, C285S404000, C285S421000, C411S004000, C411S005000, C411S375000, C411S372600, C411S373000
Reexamination Certificate
active
06739631
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a torque-limiting bolt-and-nut assembly which is capable of being tightened only to a selected torque, especially for use in securing pipe ends together.
Bolt-and-nut assemblies are used to secure pipe ends together at a pipe junction. In that regard, attention is directed to
FIG. 1
depicting a conventional pipe junction holder
10
for securing together the ends of two pipes
12
,
14
. Such a holder, disclosed in U.S. Pat. No. 4,092,036, includes a plurality of bolts
16
(only one depicted) which connect a ring
18
to a flange
20
of one of the pipes
12
. The ring
18
carries a plurality of inclined bolts
22
(only one shown). Each bolt is connected to a respective pipe pressing member
24
to force edges
26
,
28
thereof against an outer periphery of the pipe
14
. Each inclined bolt
22
includes a flange
30
which bears against a slant surface
32
of the ring
18
. By manually rotating the drive heads
33
of the bolts
22
, the pressing members
24
are tightened against the ring, causing the ring
18
to press a packing member
34
against the ends of the two pipes to sealingly secure the pipe ends together. The slant surface
32
is inclined relative to the pipe axis, such that if the pipe ends try to separate axially from one another, the pipe pressing members
24
will be urged more forcefully against the pipe
14
to more vigorously resist the separation.
It will be appreciated that if the inclined bolts
22
are excessively rotated by a technician, the pressing member
24
may be forced too hard against the pipe
14
, producing damage thereto. To prevent that from occurring, it has been proposed to utilize bolts that possess a torque-limiting structure. Exemplary of such bolts are those disclosed in U.S. Pat. Nos. 3,595,124; 3,812,757; and 4,627,774, wherein the driving head of the bolt is designed to shear-off when a predetermined torque level is exceeded.
In addition, as shown in U.S. Pat. No. 4,627,744, and in
FIGS. 2 and 3
herein, it is conventional to provide an overlying protective nut on the shearable drive head to prevent that shearable drive head from breaking off prematurely if subjected to an accidental impact. In that regard, and with reference to
FIGS. 2 and 3
, a bolt
40
includes a threaded shank
42
, a collar
44
, a cylindrical intermediate segment
46
extending through a respective hole
45
formed in the flange
30
, a secondary head
48
, a shearable drive head
50
, and a retaining rivet
52
for retaining the protective nut
54
in place. The nut
54
includes a recess
56
configured correspondingly to the drive head
50
to transmit torque to the drive head when the nut is rotated by a turning tool (e.g., a wrench). The nut extends axially sufficiently far to enable a free end thereof to overlie a portion of the cylindrical intermediate segment
46
.
Among the shortcomings of such prior art is the fact that if the rivet
52
becomes broken and the nut
54
becomes accidentally dislodged from the bolt
40
, the turning torque necessary to rotate the drive head must be applied directly to the drive head. However, the drive head
50
has a cross-sectional shape which is not of the traditional shape for which standard wrenches are designed, (i.e., a rectangular shape formed by two long sides
57
joined by two short sides
58
). Thus, the drive head is not adapted to be gripped by wrenches of the type normally found in the tool box of a typical technician. Since the technician will be located in the field where the pipes are to be joined, it may be difficult for the technician to locate a wrench that is adapted to the shape of the drive head. As a result, the technician may resort to applying torque to the secondary drive head
48
which has a more traditional shape, but which is not of the shearable type, thereby giving rise to the risk of overtightening the pipe pressing member, as discussed earlier herein in connection with FIG.
1
.
Therefore, it would be desirable to provide a torque-limiting bolt-and-nut assembly having a shearable drive head which can be driven by tools that are traditionally found in technicians toolboxes. It would also be desirable to provide a simpler way of attaching a protective nut to the bolt of such an assembly.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a torque-limiting bolt-and-nut assembly. The bolt includes a connector portion including a threaded shank, a secondary drive head integrally joined to an end of the connector portion, and a shearable drive head integrally joined to the secondary drive head by a shear-off section designed to be sheared-off by a torque exceeding a predetermined value. A recess is formed in the bolt between the shearable drive head and the secondary drive head. A nut is affixed on the shearable drive head and is configured for transmitting torque to the shearable drive head from a tool.
Preferably, the nut includes a connection structure extending into the recess for resisting dislodgement of the nut from the bolt.
Also, preferably, the shearable drive head has at least four sides as viewed in a cross-sectional plane oriented perpendicular to a center axis of the bolt. All of the sides of the drive head are of equal length, and the number of sides is an even number.
REFERENCES:
patent: 3191486 (1965-06-01), Gibbens
patent: 3370341 (1968-02-01), Allsop
patent: 3595124 (1971-07-01), Lindstrand et al.
patent: 3602976 (1971-09-01), Grube
patent: 3728933 (1973-04-01), Grube
patent: 3812757 (1974-05-01), Reiland
patent: 3897112 (1975-07-01), Walther et al.
patent: 4092036 (1978-05-01), Sato et al.
patent: 4484849 (1984-11-01), Klimowicz
patent: 4627724 (1986-12-01), Cameron
patent: 4627774 (1986-12-01), Bradley
patent: 4779900 (1988-10-01), Shumard
patent: 4848808 (1989-07-01), Pannell et al.
patent: 4896903 (1990-01-01), Shumard
patent: 4902036 (1990-02-01), Zander et al.
patent: 5228250 (1993-07-01), Kesselman
patent: 5287029 (1994-02-01), Krouse
patent: 5544922 (1996-08-01), Shumard et al.
patent: 5630687 (1997-05-01), Robinson
patent: 5772252 (1998-06-01), Malani
patent: 5947527 (1999-09-01), Carter
patent: 37 38 409 (1989-05-01), None
“Mechanical Joint 360° Wedge Type Restraint System Designed for Ductile Iron and C900 PVC Pipe”, Allgrip™ Series 3600 and PVCGrip™ Series 3500, Starpipe Products, pp. 5, 6, and 9.
Smith Radford S.
Woody Roger D.
Burns Doane , Swecker, Mathis LLP
Hewitt James M.
LandOfFree
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