Tools – Wrench – screwdriver – or driver therefor – Machine
Reexamination Certificate
2000-12-06
2003-06-03
Smith, James G. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Machine
C081S057150, C081S090500
Reexamination Certificate
active
06571667
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
None.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the use of latches to hold jointed sections of manual pipe tongs as deployed in the oilfield industry together. More particularly, the invention relates to the addition of a secondary safety latch to a set of manual pipe tongs to prevent the undesired opening of the tong jaws.
2. Description of the Related Art
Manual pipe tongs are used throughout the oilfield industry to transmit torque to various tubular components of generally cylindrical shape. This assisted transmission of torque is most often used to secure, tighten (make-up), and loosen (break-out) the threaded connections of drill pipe, drill collars, casing, and tubing. Pipe tongs typically function by incorporating a cantilevered configuration that holds the workpiece in a grip that tightens as more torque is applied to the lever arm.
FIG. 1
shows a typical prior art manual tong assembly
10
as used in oilfield drilling operations to secure or rotate a generally cylindrical workpiece
12
. This particular example of a manual tong assembly
10
includes a long jaw
14
, a short jaw
16
, a lug jaw
18
, and a lever arm
20
all connected together at pivot points
22
. A latch
24
is pinned to one end of the long jaw
14
and fits into a receiver step
26
at the end of the lug jaw
18
.
FIGS. 2
a
and
2
b
show how different workpiece
12
sizes can be accommodated by adjusting the lengths and configurations of lug jaw
18
.
FIG. 2
a
shows a lug jaw
18
that includes an array of mounting locations
28
and a choice of receiver steps,
26
and
30
, that may be used to adjust to various workpiece diameters (e.g. pipe diameters). Similarly,
FIG. 2
b
details a hinged lug jaw
32
that is greater in length than lug jaw
18
and includes a hinged portion
34
attached to a lug portion
36
by means of a hinge
38
to allow even larger diameter workpieces to be accommodated by tong assembly
10
.
Referring again to
FIG. 1
, jaws,
14
,
16
, and
18
are positioned around workpiece
12
and locked into place with latch
24
. Each jaw may contain one or more sets of sharpened teeth
40
(tong dies) that are used to “bite” into workpiece
12
and prevent slippage when manual tong
10
is engaged. Once latch
24
is engaged, lever arm
20
can be rotated in direction &agr; so that latch
24
is loaded in tension and tool
10
engages and applies torque to workpiece
12
in the &agr; direction. Rotating lever arm
20
in direction &ohgr; will loosen jaw's
14
,
16
, and
18
and allow latch
24
to be released. Several handles such as
42
and
44
, are typically placed about the periphery of manual tong assembly
10
to provide locations for rig workers to guide tong assembly
10
during operations.
Manual tong
10
, as illustrated, is configured to only grip workpiece
12
when torque is applied on the &agr; direction. Typical rig operations incorporate two sets of manual tongs, with each one being the mirror image of the other, so that one tightens in clockwise direction and the other in a counter-clockwise direction. Each can tighten or loosen the pipe threads, depending on whether it is installed in the upper position for rotating the pin (male) connection or the lower position for holding the box (female) connection. The number of tongs used in an operation and their position on the workpiece relative to each other depends on the operation being performed and the type of additional rig equipment used.
It has been found that conventional tongs sometimes allow the undesired release of latch
24
when the tong is rotated in direction &ohgr;. After workpiece
12
has been positioned, it sometimes becomes necessary to slidably rotate manual tong
10
backwards (counter-clockwise as drawn, in the &ohgr; direction) about workpiece
12
, in a manner similar to a ratchet, so that the engagement and rotation steps can be repeated. Latch
24
of
FIG. 1
is designed to engage when the manual tong device is loaded in direction &agr;. If the load applied in direction &agr; were slackened, or if the tong is rotated in direction &ohgr;, the latch device can release undesirably, allowing tong jaws
14
,
16
, and
18
to rotate and swing free of workpiece
12
. Because jaws,
14
,
16
and
18
are typically quite massive, such undesired openings can be hazardous, as well as requiring that operations cease until they are repositioned and secured. Any improvement made in latch
24
of manual tong
10
that is able to reduce such undesired openings would increase safety and reduce down-time and the costs associated therewith.
In addition, manual tong components occasionally work themselves loose during operations, which can cause the tong apparatus to open unexpectedly and rapidly. This undesired failure has great potential to cause physical harm to operators and nearby support personnel. This potential for injury can be greatly magnified if the tong is being operated under high loads at the time of the undesired opening. For this reason, a system that maintains the jaws in a closed configuration in the event of such a failure is highly desirable.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, the issues noted above are addressed by providing a latch device for a manual tong that incorporates a secondary catch mechanism. Such a secondary catch assists in maintaining the tong assembly in its closed position during a reversing operation or at a time when load applied to the manual tong device in the gripping direction is very low. Additionally the secondary catch provides protection from undesired release by holding some components of the tong assembly together in the event of a failure of certain tong components. The mechanism of the secondary catch is spring loaded and is deactivated by swinging a handle in a direction that corresponds to the operator's natural motion to open the lug jaw.
REFERENCES:
patent: 1125554 (1915-01-01), Keck
patent: 1675748 (1928-07-01), Bunker
patent: 1763135 (1930-06-01), Cox
patent: 1925970 (1933-09-01), Pennington
patent: 4095493 (1978-06-01), Hayes
patent: 4167128 (1979-09-01), Chandler et al.
patent: 5192105 (1993-03-01), Walker
patent: 5542318 (1996-08-01), Wesch
patent: 6058811 (2000-05-01), Stuart
patent: 6119558 (2000-09-01), Foley
patent: 6279426 (2001-08-01), Neves
Macon William Harold
Miller Richard Harland
Price Herman Paul
Conley & Rose, P.C.
National-Oilwell L.P.
Smith James G.
LandOfFree
Manual tong safety latch does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manual tong safety latch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manual tong safety latch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3090895