Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Reexamination Certificate
1999-12-14
2001-07-03
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
C074S532000, C024S0680CT, C024S0690WT, C248S072000, C248S228100, C254S234000
Reexamination Certificate
active
06253631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to safety devices used to secure equipment in place and enable the performance of maintenance or other work on such equipment with safety. More particularly, the invention relates to lock down devices used to preclude movement of a loaded oil well pumping unit and thereby permit work on it to be performed safely.
2. Description of the Related Art
In industry, motor-driven machinery and other equipment frequently require securing in order to permit maintenance and/or modifications to be performed in complete safety, free from the concern that the equipment could move suddenly. Precautionary measures, such as the applying of brakes and the shutting off of engines or electrical power, are common means of increasing workplace safety. Such safeguards and practices occasionally fail or are overlooked, so multiple redundant systems are often used.
In the petroleum industry, a variety of methods are used for extracting oil from underground reservoirs. Perhaps one of the most common of these methods is an oil well pumping unit known as the “walking beam” type. With some imagination, these walking beam pumping units resemble giant grasshoppers, each one seesawing its giant pump arm up and down as it lifts oil from underground.
In the course of regular maintenance or modifications, a lift rod connected to the head of the pump arm must be disconnected. To perform this operation, the pump arm is operated through its up-down cycle until the pump arm brings the pump head down to its lowest position, closest to the ground. At this point the unit is stopped and a safety brake is applied.
In current practice, a chain is passed over the pump arm and secured to the platform or base of the pump unit. The addition of this secured chain provides an added degree of safety, should the safety brake mechanism fail. Such an arrangement is similar to that set forth in U.S. Pat. No. 4,525,914 issued to Bryan et al. The Bryan patent uses chain for securing the horsehead of an oil well pump, but does not provide the additional ease and safety afforded by the present invention.
The installation and securing of a chain over a pump arm requires rig personnel to climb up on the pump unit in order to manually pass the chain over the pump arm. As maintenance and repair operations are performed in the field, the rig personnel must scale the pump unit, frequently without safety gear or other fall protection devices, all the while at considerable distance from emergency medical care. Additionally, if the chains used for this purpose are not regularly inspected and tested, they may fail without warning. The failure of a chain may allow the pump arm to spring upward suddenly and cause substantial damage to the pump unit and other rig equipment, as well as seriously injure rig personnel. Commonly used walking beam pump units require rig personnel to scale the unit to heights of 20 to 30 feet in order to pass a safety chain over the pump arm. A slip or fall from such height could easily result in serious injury. U.S. Pat. No. 4,092,872 issued to McClure disclosed a safety attachment for an oil well horsehead utilizing jointed parallel straps. The McClure patent does not teach the lock down safety features of the present invention.
Several patents disclose clamping arrangements for attaching to a flanged beam. Examples of such clamping arrangements are taught in U.S. Pat. Nos. 2,877,974 of Estes, U.S. Pat. No. 3,084,893 of Ruth and U.S. Pat. No. 4,799,639 of Riley. However, none of these patents teaches or suggests the structural combination of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a lock down apparatus for securing structural members or heavy machinery. The lock down apparatus may be used generally to secure structural members and/or heavy machinery during maintenance or modification in order to permit safe work thereon. The lock down apparatus is particularly useful when applied to the walking beam type oil pumping units commonly used in the petroleum industry.
The advantages of the present invention are substantial. The lock down apparatus of the present invention eliminates the need for rig personnel to scale the pump arm, thereby greatly reducing the risk of injury from falls. The lock down apparatus may be installed while personnel remain at ground level. Arrangements of the present invention are designed to support the load of the pump arm or beam against its counterweight and, in so doing, become a primary safety feature while relegating the safety brake to secondary safety feature status. The present invention enables rig workers to secure the pump arm at one of a number of desired positions or heights without any need for the worker to leave the ground. The use of wire rope in the present invention permits ready visual inspection of the structural integrity of the lock down apparatus in marked contrast to prior art methods involving the use of chain.
One particular arrangement of the present invention employs an upper secured clamp which may be installed directly and permanently to the wide flange portion of the “I” beam comprising the pump arm. Since the installation of the upper clamp is permanent, wear and risk of damage to the pump arm is reduced and the security and safety afforded by the present invention are improved. The present invention greatly reduces both the possibility of damaging the pump and the risk of great bodily harm resulting from some alternative arrangement slipping or shifting position under load
The present lock down apparatus is safe and simple to use. Initially, an upper clamping device is used to permanently affix a top assembly hook to the pump arm. The clamping device attaches securely to the wide flange portions of the “I” beam comprising the pump arm.
When maintenance schedules require a pump arm to be secured, rig personnel stop the pump unit with the pump arm horsehead in its desired, lowered position. The safety brake is then applied, and rig personnel install the lock down apparatus as follows. A bottom bracket is installed to provide a lower securing point below the upper clamp assembly permanently installed on the pump arm. The bottom bracket or clamp slides over and engages a section of “I” beam used as a base for the pump unit or, as is frequently found, molded into the concrete pad upon which the pump unit sits. The bottom bracket may be equipped with hooks to engage an orthogonally situated “I” beam in order to prevent the bottom bracket from moving out of position.
A cable portion of the lock down apparatus is made up from suitable wire rope material, such as ⅝″ diameter wire rope. An “eye” is provided at one end, either through braiding or the use of a cable crimp or a preformed loop connector to which the wire rope is swaged or otherwise connected. The resulting “eye” engages the hook of the upper assembly which is clamped to the pump arm.
Starting at the “eye” and proceeding down the length of the cable portion, one encounters a series of “buttons” or stops affixed to the wire rope at selected intervals. These buttons are securely pressed onto the wire rope or otherwise secured to prevent their movement or slippage under strain, and can be selected as the attaching element connected to the remainder of the lock down apparatus. The relatively close spacing of these buttons enables quick and easy incremental adjustment of the secured positioning of the pump arm, thereby varying the effective length of the flexible cable portion of the overall tensioning assembly of the lock down apparatus.
A threaded adjustment portion of the lock down apparatus is secured at its lower end to the bottom clamp while the opposite, upper end is terminated with a “hairpin” connector for engaging a selected button of the wire rope portion.
To use the present lock down apparatus, the lower end of the wire rope is passed through the large open portion of the hairpin connector and a selected button is engaged in the narrower engaging portion of the hairp
Lewis Donald J.
McCain Gary Richard
McCain James Robert
Bac-Lamb Wire Line Services
Bissell Henry M.
Bissell, IV Henry M.
Herrmann Allan D.
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