Abstract:
A lock down apparatus for use with an oil well pumping unit of the walking beam type. It includes upper and lower clamps for attachment to the walking beam and to the bottom frame of the unit, respectively, and an adjustable tensioning arrangement extending between the two clamps. Part of the tensioning unit is a wire rope with plastic buttons pressed onto the rope at suitably spaced intervals. A coupler for latching to the particular button which is selected for adjustment for the distance between the walking beam and its frame is provided. Once the tensioning unit is in place, a turnbuckle is tightened to increase the tension to hold the walking beam in a lowered position, against inadvertent release of the pumping unit safety brake.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No.: 60/115,812, filed Jan. 14, 1999. 
    
    
     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 hairpin connector. This narrower portion of the hairpin connector is sized to receive the wire rope, but will not permit passage of the buttons on the wire rope. 
     After the wire rope has been transferred from the open portion to the engaging portion of the hairpin connector, the “eye” of the wire rope portion is lifted to engage the hook affixed to the pump arm. The lower end of the apparatus is attached to the bottom clamp and thereafter the threaded adjustment portion of the present invention, a single turnbuckle in the preferred embodiment, is adjusted to tighten the lock down apparatus. Once the threaded adjustment portion has been adjusted to apply tension to the lock down apparatus, the safety brake may be released so that the full tensional load of the pump arm is taken up by the lock down apparatus. The safety brake is then reapplied and work may proceed in safety. 
     All portions of the lock down apparatus of the present invention are engineered and tested to withstand loads in excess of four times greater than those likely to be encountered in the field, thereby providing a great degree of safety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention may be realized from a consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic representation, partially broken away, of a conventional oil well pumping unit with which embodiments of the present invention are designed to be used; 
     FIG. 2 is an exploded view of a beam clamp assembly which is one particular portion of the present invention; 
     FIG. 3 is a schematic view of the beam clamp assembly of FIG. 2, shown installed on the pump arm beam; 
     FIG. 4 is a schematic perspective view, partially broken away, of one particular portion of the present invention shown installed on the base frame of the pumping unit of FIG. 1; 
     FIG. 5 is a schematic side view corresponding to the portion depicted in FIG. 4; 
     FIG. 6 is a schematic representation of a portion of the embodiment of the present invention which is used for adjusting the tension of the lock down apparatus after installation; and 
     FIG. 7 is a schematic view, partially broken away, of a section of wire rope or cable shown with a lifting pole for attaching the lock down apparatus to the upper beam of the pumping unit of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of the lock down apparatus  10  of the present invention is shown in structural detail in FIGS. 2-7 and is designed to be installed on a pumping unit, such as that which is represented in FIG. 1, generally designated by the numeral  12 , in the manner indicated by the block portion of the diagram. Pumping unit  12  includes a walking beam  14  pivotably supported by a samson post  16  for pivotal movement about a generally horizontal axis defined by a center bearing assembly or saddle bearing  18 . The beam has a pitman assembly or crank rods  20  connected to the beam  14  near the end  15  where a counterbalance weight  17  is attached. The pitman assembly is driven to cause the beam  14  to oscillate or pivot in a vertical plane about the transverse horizontal axis of the saddle bearing  18 . 
     The other end of the beam  14  has a horsehead  22  connected thereto. The horsehead  22  is of conventional construction and includes a pair of side plates  24  and an arcuate outer face or plate  26 . A wire line assembly  28 , sometimes called a wire rope bail, is attached to the horsehead by a conventional wire line hanger  30  at the upper end of the arcuate member  26 , with the cables or wire lines  32  engaged by the arcuate member  26  during swinging movement thereof to maintain the line of force exerted by the wire line assembly  28  in proper alignment with a polished rod  34  so that it will properly reciprocate a sucker rod or pump rod associated with a downhole pump (not shown). The cable  32  is connected to the polished rod by a carrier bar and polished rod clamp  36  in a conventional manner. All of the aforementioned structure except for the lock down apparatus  10  is conventional and forms no particular part of the present invention except for the association of the lock down apparatus  10  therewith. 
     The lock down apparatus  10 , the structural details of which are shown in FIGS. 2-7, is represented in FIG. 1 by three connected blocks. The upper and lower blocks  10 A and  10 C are devices for clamping to the walking beam of the pump unit and one of the beams making up the base frame of the unit, respectively. Block  10 B represents the intermediate portion of the lock down apparatus extending between the clamp devices  10 A and  10 C. 
     Referring to FIGS. 2 and 3, details of the upper beam clamp,  10 A of FIG. 1, are shown. In the exploded view of FIG. 2, the clamp is shown comprising a pair of symmetrical, generally C-shaped, half-clamps  40 , each of which is attached, as by welding, to a corresponding side plate  42 . Between the two side plates  42  is a mounting block  44  which is provided with a first set of holes for attachment to the two side plates  42  and with a second set of holes for mounting a cable hook  46 . These parts are shown assembled in FIG. 3 with the half-clamps  40  firmly engaging the lower flanges of the I-beam  14  of the pump unit of FIG.  1 . Bolt heads  48  and nuts  49  are shown as used in attaching the two side plates  42  to the central block  44 . Additional bolts  50  are shown attaching the hook  46  to the central block  44 . This arrangement of the beam clamp of the invention is designed to be permanently installed on the walking beam  14 , thereby avoiding the hazard of requiring maintenance personnel to climb up on the walking beam whenever arrangements of the invention are to be used for locking down the pumping unit. 
     Structure making up the lower clamp  10 C (FIG. 1) is shown in FIGS. 4 and 5. This mainly comprises a gripping element  60  which is shaped with a cutout in the lower portion which permits the element  60  to be slid over the end of a lower frame rail  62  and up against the edges of a cross rail or beam  64 . Safety hooks  66  are provided to retain the element  60  against the rail  64 . These are held in position, once the element  60  is in place, by threaded nuts  68 . The element  60  is shown having a large opening  70 . This is for the purpose of receiving the clevis  72  when the lock down apparatus is set up for use. 
     In FIG. 5, the clevis  72  is shown placed through the opening  70  with its clevis pin  74  retaining one end of a turnbuckle  80 . The upper end  82  of the turnbuckle  80  is attached by another clevis  84  with associated clevis pin  86  to the loop  88  of a “hairpin” coupler  90 . The opposite ends of the loop or link  88  are attached, as by welding, to an inverted cylindrical cup  92  which is provided with a slot  94  extending up one side and across to about the center of the upper end of the cup  92 . The width of the slot is sufficient to receive an associated wire rope or cable (FIG. 7) therein. 
     The wire rope  100  is shown in FIG. 7 as having a loop  102  at its upper end and a series of regularly spaced buttons  104  mounted thereon. The buttons  104  are preferably formed of plastic and are pressed onto the wire rope  100  at approximately 20″ spacing in order to permit adjustment of the operative length of the wire rope  100 . The spacing of the buttons  104  is selected to correspond to the adjustment range of the turnbuckle  80 . FIG. 7 shows the wire rope  100  with the lowermost button  104  retained within the cup  90 . The slot  94  receives the wire rope  100  therein and the projecting sides of the plastic button  104  are gripped by the upper face  92  of the cup  90 . As indicated in FIG. 6, the loop  88  will be attached to the remainder of the lock down apparatus by a clevis  84 . 
     FIG. 7 also shows a lifting pole  110  with a hook  112  on the end thereof suitable for releasably gripping a button  104  so that the lock down apparatus may be lifted to the point where the loop  102  is slipped over the end of the hook  46  that is attached to the walking beam  14  of the pumping unit  12 . The lifting pole  110  may conveniently comprise a pole commonly used with swimming pool brushes and like pool implements, generally having a length of about 12 feet and being light enough in weight but strong enough to lift the upper end of the lock down apparatus to engagement with the hook  46 . 
     When the lock down apparatus  10  is to be placed in use, the turnbuckle  80  is swivelled to the extended position, the lower end  78  is connected to the bottom clamp  60  by the clevis  72  and the retaining hooks  66  are adjusted to firmly hold the clamp member  60  against the cross beam  64 . One of the buttons  104  is placed within the cup  90  to be retained in the slot  94  and the upper end of the apparatus is lifted by the lifting hook  110  to place the loop  102  on the hook  46 . If there is too much slack in the apparatus as thus installed, the loop  102  is removed from the hook  46  and a different button  104  is positioned within the cup  90 , after which the loop  102  is again placed over the hook  46 . After proper adjustment in this fashion, the turnbuckle  80  is swivelled to take up the remaining slack and render the lock down apparatus taut. Following installation in this manner, the safety brake of the pump unit (not shown) is released momentarily so that the lock down apparatus holds the walking beam  14  in a safe position against the weight of the counterbalance  17 . The safety brake may then be again applied for added safety. 
     With this arrangement, the lock down apparatus of the invention serves to hold the beam  14  against release, even if the safety brake should somehow slip or be inadvertently released. The lock down apparatus is easy and simple to use, is constructed of components which for the most part are readily available and of relatively low cost. Thus, a most effective, simple, reliable lock down apparatus is provided to fill the need which is common with the conventional oil well pumping units of the type described. 
     Although there have been described hereinabove various specific arrangements of a PUMPING UNIT LOCK DOWN APPARATUS in accordance with the invention for the purpose of illustrating the manner in which the invention may be used to advantage, it will be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art should be considered to be within the scope of the invention as defined in the annexed claims.