Abstract:
A mud pump is provided that includes a pump shaft having substantially circular eccentric lobes. Each lobe is rotatably mounted in a connecting rod that, in turn, moves a slide in a horizontal and linearly manner. A piston rod is operatively couples a pump module to one or both sides of each slide frame and a pump module. As the pump shaft turns, each lobe causes the slide to move side to side. As the slide moves side to side, each piston rod operates a pump module whose outputs can be coupled to a common manifold.

Description:
PRIORITY STATEMENT &amp; CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from co-pending U.S. Patent Application No. 61/345,858, entitled “Mud Pump” and filed on May 18, 2010, in the name of Gerald Lesko; which is hereby incorporated by reference for all purposes. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present disclosure is related to the field of pumps in general and, in particular, pumps used in pumping drilling mud or “mud pumps”. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is known to use pumps to provide drilling mud under pressure in the drilling of wells. Pressurized drilling mud is delivered down a hollow drill string as the well is being drilled to carry away cuttings up the annulus surrounding the drill string to ground level. Such drilling operations are well known to those skilled in the art. 
         [0004]    Prior art pumps can use a motor to turn a crankshaft or “pump shaft” to convert rotary motion to a reciprocating motion. The pump shaft moves a connecting rod coupled to a crosshead that moves within a fixed crosshead slide to provide this conversion. The crosshead is coupled to a “pony rod” that, in turn, is coupled to a piston rod that provides the pumping motion in a pump module, as well known to those skilled in the art. 
         [0005]    The above-mentioned mechanical arrangement can be multiplied so that a multitude or plurality of pump modules can be operated from a single pump shaft. The outputs of each pump module can be coupled to a common manifold from which pressurized drilling mud can be provided to the drill string. By coupling the pump module outputs to a common manifold, the pulsing of the pressure of the drilling mud can be reduced or smoothed out, this being a problem well known to those skilled in the art. The disadvantage of this mechanical arrangement is the size and complexity of the components involved to provide a multi-module pump. 
         [0006]    It is also known in the oil and gas industry to drill horizontal wells. These are wells that are initially drilled vertically and, with the use of directional drilling equipment as well known to those skilled in the art, the direction of drilled well becomes horizontal or parallel with the ground surface. It is known to drill horizontal wells 5000 to 7500 feet in length or more. To do so requires the use of “mud motors”, motors that are powered by the delivery of highly pressurized drilling mud pumped through the drill string so as to enable the turning of the drill bit. It is also known that to drill such wells, drilling operators will use at least two or more conventional mud pumps powered by 1000 horsepower or more motors. Each mud pump is housed in its own pump house and occupies space at the drilling site. As each additional pump house increases the number of structures at a drilling site, the number of truckloads required to deliver the necessary equipment to a drilling site also increases. All this additional equipment and number of truckloads to deliver the equipment add cost to the drilling of the well. 
         [0007]    It is, therefore, desirable to provide a pump that can convert rotary motion to reciprocating motion without having to use connecting rods, crossheads, crosshead slides and pony rods to reduce its size, complexity and cost to manufacture. It is also desirable to provide a mud pump that is compact in size but can deliver pressurized mud at a volume equivalent to two or more conventional mud pumps. 
       SUMMARY OF THE INVENTION 
       [0008]    A pump is provided that comprises a pump shaft having at least one eccentric lobe that is substantially circular. A motor is used to provide the rotational power to the pump shaft. In one embodiment, the motor can be coupled directly to the pump shaft. In another embodiment, a transmission can be used between the motor and the pump shaft to reduce the angular speed of the rotational power provided to the pump shaft. In a representative embodiment, a one or two-stage gear transmission can be used. In a further embodiment, the motor can be a  3 -phase AC motor controlled by a variable frequency drive mechanism to control the speed of the motor. 
         [0009]    In one embodiment of the pump, the eccentric lobe can be rotatably disposed within a connecting rod having a substantially circular opening to receive the lobe at one end with the other end rotatably pinned to a slide configured to move in a horizontal and linear manner. In one embodiment, the slide can be slidably disposed within a pair of slide support plates that constrains the slide to move in a linearly and horizontal or side-to-side manner. In one embodiment, slide-bearing mechanisms can be disposed between the slide and the support plates so that the slide can move side-to-side with minimal friction. In a representative embodiment, the slide-bearing mechanism can further comprise means for adjusting a loading force on the slide-bearing mechanism against the slide so that the slide is further constrained to horizontal and linear movement. 
         [0010]    As the lobe rotates within the connecting rod opening, the connecting rod slide can move up and down thereby moving the slide linearly and horizontally between the slide support plates. As the slide frame moves side to side, it can move a piston rod in and out to operate a pump module. By virtue of this configuration, the slide can have a piston rod operatively coupled to one or both opposing sides of the slide. Therefore, a single slide can operate one or two pump modules at the same time. In a further embodiment, the pump shaft can comprise a plurality of eccentric lobes thereby allowing a plurality of slides to be operated by the lobes and, hence, a plurality of pump modules to be operated from a single rotating pump shaft. 
         [0011]    Broadly stated, in some embodiments, a mud pump is provided, comprising: a frame; at least one pump module disposed on the frame, the at least one pump module comprising an inlet port and an outlet port; a pump shaft rotatably disposed in the frame for receiving rotational power from a motor, the pump shaft having at least one substantially circular eccentric lobe disposed thereon, the centre of the at least one eccentric lobe displaced or offset from the longitudinal axis of the pump shaft; at least one slide disposed in the frame, the at least one slide operatively configured to move linearly side-to-side within the frame; at least one piston rod assembly operatively coupling the at least one slide to the at least one pump module; and a connecting rod comprising first and second ends operating coupling the pump shaft to the at least one slide, the first end rotatably disposed on the at least one eccentric lobe, the second end rotatably pinned to the at least one slide whereby rotation of the pump shaft causes the slide to move side-to-side that, in turn, causes the at least one piston rod assembly to operate the at least one pump module. 
         [0012]    Broadly stated, in some embodiments, a mud pump is provided, comprising: a platform; a lattice frame disposed on the platform; at least one pump module disposed on the frame, the at least one pump module comprising an inlet port and an outlet port; a pump shaft rotatably disposed in the frame for receiving rotational power from a motor, the pump shaft having at least one substantially circular eccentric lobe disposed thereon, the centre of the at least one eccentric lobe displaced or offset from the longitudinal axis of the pump shaft; a motor operatively coupled to the pump shaft, the motor disposed on the platform; at least one slide disposed in the frame, the at least one slide operatively configured to move linearly side-to-side within the frame; at least one piston rod assembly operatively coupling the at least one slide to the at least one pump module; and a connecting rod comprising first and second ends operating coupling the pump shaft to the at least one slide, the first end rotatably disposed on the at least one eccentric lobe, the second end rotatably pinned to the at least one slide whereby rotation of the pump shaft causes the slide to move side-to-side that, in turn, causes the at least one piston rod assembly to operate the at least one pump module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a rear perspective view depicting a mud pump having three slides, operating six pump modules in total; 
           [0014]      FIG. 2  is a rear elevation view depicting the mud pump of  FIG. 1 ; 
           [0015]      FIG. 3  is a front perspective view depicting the mud pump of  FIG. 1 ; 
           [0016]      FIG. 4  is a front elevation view depicting the mud pump of  FIG. 1 ; 
           [0017]      FIG. 5  is a front cross-sectional elevation view depicting the mud pump of  FIG. 1  with the connecting rod moving upwards; 
           [0018]      FIG. 6  is a front cross-sectional elevation view depicting the mud pump of  FIG. 1  with the connecting rod moving downwards; 
           [0019]      FIG. 7  is a perspective view depicting the frame of the mud pump of  FIG. 1  showing only the slides, the slide bearings, the slide bearing support plates and the piston assemblies; 
           [0020]      FIG. 8  is a perspective sectional view of the mud pump of  FIG. 7  with the frame removed; 
           [0021]      FIG. 9  is a front elevation view of the mud pump of  FIG. 8 ; 
           [0022]      FIG. 10  is a front cross-sectional view of the mud pump of  FIG. 7 ; 
           [0023]      FIG. 11  is a side perspective view depicting the mud pump of  FIG. 7 ; 
           [0024]      FIG. 12  is a side elevation view depicting the mud pump of  FIG. 11  with the pump module mounting plate removed; 
           [0025]      FIG. 13  is a front cross-sectional view depicting one piston rod/liner assembly of the mud pump of  FIG. 10 ; 
           [0026]      FIG. 14  is a perspective view depicting the mud pump of  FIG. 1  installed in a pump house; and 
           [0027]      FIG. 15  is a perspective view depicting the mud pump of  FIG. 1  installed in a pump house. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring to  FIGS. 1 to 13 , one embodiment of a mud pump is illustrated. In this embodiment, mud pump  10  can comprise lattice frame  18  and pump modules  24  mounted thereon. Frame  18  can further comprise mounting tabs  14  for attaching mud pump  10  to a platform, to a skid or to a pump house. 
         [0029]    For the purposes of this specification, and as shown specifically in the figures, each pump module  24  can comprise inlet port  25 , outlet port  35 , top access port  37  and side access port  36 . Pump module  24 , as illustrated, can be any suitable pump module that is readily available to the mud pump industry and is well known to those skilled in the art. As shown in  FIG. 1 , pump module  24  is shown as a singular device having three pump units disposed therein. It is obvious to those skilled in the art that pump module  24  can comprise one or more pump units use in combination. Representative examples of pump module  24  are pump modules having an 800 horsepower rating as manufactured by Continental Emsco in the U.S.A. or their equivalent. Such pumps have interchangeable liners of different diameters whereby the volume of mud handled by a pump module per pump cycle can be adjusted upwards or downwards depending on the diameter of the liner. Generally speaking, the smaller the volume per pump module, the greater the pressure the mud can be pumped at. 
         [0030]    Referring to  FIG. 1 , mud pump  10  is shown having cover  20  disposed on top of lattice frame  18 . Input shaft  12  can be connected to a motor (not shown) to provide rotational input power to mud pump  10 . In some embodiments, an internal combustion motor can be used to provide rotational input power to mud pump  10 . In other embodiments, an electric motor of suitable power rating can be used. In further embodiments, a variable frequency drive mechanism (not shown) as well known to those skilled in the art can be used to control the electrical power provided to the electric motor thereby controlling the rotational speed the motor operates at to supply rotational input power to mud pump  10 . 
         [0031]    In one embodiment, mud pump  10  can comprise transmission  22  to couple shaft  12  to the operating components of mud pump  10 . Transmission  22  can be a single-stage or dual-stage gear transmission to reduce the rotational speed of input shaft  12  to the required rotational speed for proper operation of pump shaft  30  rotatably disposed in mud pump  10 . In other embodiments, transmission  22  can comprise a planetary gear transmission. In further embodiments, transmission  22  can comprise helical gears. In yet other embodiments, transmission  22  can comprise spur gears. Intake manifold  52 , comprising inlet  54 , is shown attached to pump module inlet ports  25 . Outlet manifold  58 , comprising couplers  62  and end caps  66 , is shown attached to pump module outlet ports  35 . In one embodiment, frame  18  can comprise return lines  68  that provide communication from galleys  38  to reservoir  70 . When in operation, lubricating oils are used to lubricate the moving components of mud pump  10 . These oils will collect in galleys  38  and return to reservoir  70  through return lines  68  to be re-circulated through mud pump  10 . 
         [0032]    Referring to  FIG. 2 , a rear elevation view of mud pump  10  is shown. In this figure, piston rod support bushings  31  are shown disposed on sidewalls  19  of frame  18 . Piston liners  26  are shown disposed between pump modules  24  and support bushings  31 . Couplers  41  can be used to couple liners  26  to support bushings  31 . As noted above, liners  26  can be comprised of various diameters depending on the volume and the pressure drilling mud is to be produced by mud pump  10 . 
         [0033]    Referring to  FIGS. 3 and 4 , front views of mud pump  10  are shown. In this embodiment, pump modules  24  are shown with outlet ports  35  exposed having no output manifold attached thereon to show valve mechanism  39  disposed therein. In one embodiment, pump module  24  can comprise “sucker-cup” pump mechanisms as well known to those skilled in the art. In the illustrated embodiment, an output manifold (not shown) can be attached to the shown outlet ports  35  to collect drilling mud pumped by pump module  24 , in addition to outlet manifold  58  shown in  FIGS. 1 and 2 , or it can be capped with a cover (not shown). Input ports  25  can be coupled together with intake manifold  52  that directs drilling mud into pump modules  24 . In one embodiment, coolant pump  34  can be used to circulate coolant through piston liners  26  and oil pump  32  can be used to pump lubricating oil through support bushings  31  to lubricate the moving components therein, as described in more detail below and as shown in  FIG. 13 . 
         [0034]    Referring to  FIGS. 5 and 6 , front cross-section views of mud pump  10  are shown revealing the internal components of the embodiment shown therein. In this embodiment, pump shaft  30  rotates as a result of input rotational power applied to input shaft  12  that is operatively coupled to pump shaft  30  via transmission  22  as shown in  FIG. 4 . In one embodiment, pump shaft  30  can comprise eccentric  80  disposed thereon and affixed thereto with pin  82 . Rotatably disposed on eccentric  80  is connecting rod  84 . In another embodiment, eccentric bearing  83  is disposed between eccentric  80  and connecting rod  84 . In a further embodiment, connecting rod  84  is rotatably pinned to slide  28  via pin  86 . In yet another embodiment, bearing  85  can be disposed between pin  86  and connecting rod  84 . In  FIG. 5 , eccentric  80  is shown rotating clockwise thereby moving connecting rod  84  upwards and to the right in this figure. In so doing, slide  28  is being pushed to the right. In one embodiment, slide  28  is disposed between upper support plate  44  and lower support plate  46  to help keep slide  28  moving in a horizontal linear path, and to resist the bending moment caused by the rotation of pump shaft  30  and eccentric  80 . In another embodiment, upper slide bearing  43  can be disposed between upper plate  44  and slide  28 , and lower slide bearing  45  can be disposed between lower plate  46  and slide  28  as a means to reduce the friction between slide  28  and upper and lower plates  44  and  46  as slide  28  moves side-to-side. 
         [0035]    As slide  28  moves to the right, it pushes piston rod  27   a  and, hence, piston  40   a  to the right in liner  26   a  to push fluids in pump chamber  42   a  out through valve  39   ao  to outlet ports  35  (not shown) and outlet manifold  58  (not shown). In so doing, piston rod  27   b  also pulls piston  40   b  in liner  26   b  to the right thereby drawing in fluid through valve  39   bi  from intake manifold  52 . 
         [0036]    In  FIG. 6 , eccentric  80  is shown rotated further clockwise (from  FIG. 5 ) thereby moving connecting rod  84  downward and to the left. In so doing, piston  40   a  is being pulled to the left thereby drawing in fluid into pump chamber  42   a  through valve  39   ai  from intake manifold  52  while piston  40   b  is pushed to the left thereby pushing fluid out of pump chamber  42   b  through valve  39   bo  to outlet ports  35  (not shown) and outlet manifold  58  (not shown). In this figure, the connecting rods  84  of two adjacent stages rising above the top of frame  18 . 
         [0037]    Referring to  FIG. 7 , mud pump  10  is shown without pump modules  24 , cover  22 , piston liners  26 , pump shaft  30 , slides  28  and connecting rods  84 . In this illustrated embodiment, frame sidewalls  19  are visible as are removable caps  17 , which are configured hold pump shaft  30  in place in frame  18 . Also visible are piston rods  27 , rod support bushings  31 , couplers  41  and pistons  40 . In one embodiment, mud pump  10  can comprise means for applying a loading force to upper support plates  44  to keep slide  28  confined to a horizontally linear range of motions. In some embodiments, these means can comprise a plurality of setscrew rails  48  disposed on frame  18  near sidewalls  19  and disposed on caps  17 . In further embodiments, setscrew rails  48  can comprise a plurality of setscrews  47  threadably attached to and through said setscrew rails. Setscrews  47  can be tightened to apply forces to various locations on upper support plates  44  whereby the loading force applied to upper support plates can be adjusted at each location of setscrews  47  to ensure that slide  28  is constrained to horizontal linear movement. While the illustrated embodiment shows setscrews  47  as being manually adjustable for applying force to slide  28 , it is obvious to those skilled in the art that mud pump  10  can comprise further means for monitoring the movement of slides  28  and for automatically adjusting setscrews  47  with electro-mechanical servo motors, or the like, so that setscrews  47  are dynamically adjusted in real-time to ensure that proper force is being applied to slide  28  at all times to keep its movement linearly horizontal. 
         [0038]    Referring to  FIG. 8 , the mud pump  10  of  FIG. 7  is now shown with frame  18  removed to reveal slides  28 . In this embodiment, slides  28  can comprise openings  29  for pump shaft  30  (not shown) to pass through and pin openings  88  configured to receive connecting rod pins  86  (not shown). In some embodiments, mud pump  10  can further comprise one or more eccentric rods  49  disposed beneath lower support plates  46  for applying upwards force thereto for ensuring that slide  28  is constrained to horizontal linear movement. This is also shown in  FIGS. 9 ,  10 ,  11  and  12 . In some embodiments, eccentric rods  49  can be rotated or adjusted and then set into position by turning rod adjusters  50 . While the illustrated embodiment shows eccentric rods  49  as being manually adjustable for applying force to slide  28 , it is obvious to those skilled in the art that mud pump  10  can comprise further means for monitoring the movement of slides  28  and for automatically adjusting eccentric rods  49  with electro-mechanical servo motors, or the like, operatively coupled to rod adjusters  50  so that eccentric rods  49  are dynamically adjusted in real-time to ensure that proper force is being applied to slide  28  at all times to keep its movement linearly horizontal. 
         [0039]    Referring to  FIG. 13 , a cross-section view is shown of the internal pumping mechanism of mud pump  10 . In some embodiments, piston rod  27  can be coupled to slide  28  by threading piston rod  27  into threaded opening  91  disposed on slide  28 . In other embodiments, piston rod  27  can be further secured with lock nut  101  threaded on piston rod  27  and tightened against slide  28 . In yet further embodiments, piston rod stud  92  can be disposed in an opening disposed through piston rod  27  and secured to slide  28  in threaded opening  93 . In some embodiments, piston rod stud  92  can further comprise flange  95  that can rest against shoulder  94  disposed within piston rod  27 . Piston rod stud  92  can also serve as means for mounting piston  40  and piston retaining caps  96  and  97  thereon. Nut  98  can be used to secure piston  40  and caps  96  and  97  on piston rod stud  92 . 
         [0040]    In some embodiments, mud pump  10  can comprise means for circulating coolant in piston liner  26  behind piston  40  to prevent overheating of the mechanism when in operation. As shown in  FIG. 13 , coolant can be pumped by coolant pump  34  (as shown in  FIG. 4 ) into liner chamber  106  through coolant inlet  102  via lines, hoses or piping (not shown). Coolant can the flow through, and circulate within, chamber  106  and then exit through coolant outlet  104 . Lines, hoses and piping (not shown) can be coupled to outlet  104  so that the heated coolant can be collected, cooled and re-circulated. In other embodiments, inlet  102  and outlet  104  can further comprise one-way valves, such as ball-valves as one example obvious to those skilled in the art, such that coolant can be drawn into chamber  106  through inlet  102  as piston  40  is moving towards pump module  24  (not shown), and then expelled from chamber  106  through outlet  104  and piston  40  is moving away from pump module  24 . 
         [0041]    In some embodiments, mud pump  10  can comprise means for circulating lubricating oil to piston rod  27  as it reciprocates back and forth through support bushing  31 . As shown in  FIG. 13 , lubricating oil can be pumped by oil pump  32  (as shown in  FIG. 4 ) into oil inlet  108  where it can flow into annulus  110  between piston rod  27  and support bushing  31  thereby maintaining a layer of lubricating oil therebetween. Oil can then flow out of annulus  110  into galleys  38  (as shown in  FIG. 1 ) where the oil can be collected and re-circulated. In other embodiments, barrier seals  99  and ice-breaker wear band  100  can be disposed between piston rod  27  and support bushing  31  as sealing means to separate and isolate chamber  106  from annulus  110  so that coolant does not intermingle with and contaminate the lubricating oil, and vice-versa. 
         [0042]    In the embodiments illustrated the figures herein, there are three slides  28  shown, each coupled to two pump modules  24  thereby resulting in the operation of six pump modules. It is obvious to those skilled in the art that fewer or more slides mechanisms can be implemented to either decrease or increase the number of pump modules that can be operated. It is also obvious to those skilled in the art that a slide frame can be releasably coupled to a single piston rod to, therefore, operate a single pump module. 
         [0043]    Referring to  FIG. 6 , pump shaft  30  is shown turning three connecting rods  84 . This necessarily requires pump shaft  30  having three eccentric lobes  80 . In this configuration, the lobes can be displaced nominally 120° apart from each other such that the lobes can be substantially spaced equally apart around the circumference of pump shaft  30 . In embodiments where pump shaft  30  comprises two eccentric lobes  80 , the lobes can be displaced nominally 180° apart. In other embodiments where pump shaft  30  comprises two lobes  80 , one lobe  80  can be displaced 178° from the other lobe  80  so that pump shaft  30  can more easily turn from a dead stop. In other embodiments where additional eccentric lobes are disposed on pump shaft  30 , the lobes can be substantially spaced equally apart on pump shaft  30 . For example, for a four-lobe shaft, each lobe  80  can be displaced 90° nominally from each other lobe  80 . If five lobes are disposed on pump shaft  30 , the lobes can be displaced nominally 72° apart on pump shaft  30 . For six lobes disposed on pump shaft  30 , the lobes can be displaced nominally 60° apart, and so on. 
         [0044]    In operation, mud can be supplied to inlet  54  on intake manifold  52  from an external pump (not shown) drawing mud from a mud tank (not shown) as well known to those skilled in the art. As slides  28  operate pump modules  24 , mud is drawn into pump modules  24  from intake manifold  52  and pumped out of pump modules  24  into outlet manifold  58  via outlet manifold couplers  62  disposed between pump modules  24  and outlet manifold  58 . The pumped mud can exit outlet manifold  58  via outlet  60  that can be connected to a mud delivery pipe and/or hose for use on a drilling rig (not shown) as well known to those skilled in the art. In one embodiment, the diameter of inlet  54  and the pipe that make up intake manifold  52  can be nominally ten inches whereas the diameter of outlet and the pipe that make up outlet manifold  58  can be nominally four inches. In another embodiment, outlet manifold  58  can comprise couplings (not shown) for connection with a pressure gauge to provide a visual indication of the pressure of the mud being pumped and/or a pressure relief valve to provide means to limit the pressure of the mud being pumped by mud pump  50 . It is obvious to those skilled in the art that the diameters of inlet  54 , intake manifold  52 , outlet manifold  58  or outlet  60  can be increased or decreased depending on the volume and pressure of drilling mud required in the drilling of a well. 
         [0045]    In operation, it is expected that mud pump  10  can operate up to 65 revolutions per minute using a 1000 horsepower motor, which translates up to 130 pump module strokes per minute per slide frame mechanism given that each slide frame can be coupled to two pump modules. It is also anticipated that mud pump  10  can pump up to 800 gallons or 4 cubic metres of drilling mud per minute. Using 7-inch liners in the pump modules, it is expected that mud pump  10  can pump mud up to 1500 pounds per square inch in pressure. It is also expected that mud pump  10  would weigh approximately 45,000 pounds and deliver the equivalent volume and pressure of drilling mud as a conventional mud pump powered by a 1600 horsepower motor weighing up to 120,000 pounds. 
         [0046]    Referring to  FIG. 14 , mud pump  10  is shown positioned in pump house  56 , a structure used to house mud pumps at drilling sites. Access to mud pump  10  is done through doorways  64 . In this configuration, mud pump  10  is positioned “lengthwise” in pump house  56 . Referring to FIG.  15 , mud pump  10  is shown in pump house  56  rotated 90 degrees. The compactness of mud pump  10  can allow it to be installed in this manner in pump house  56  whereby access to the inlet and outlet to mud pump  10  is through doorway  64 . In addition, more than one mud pump  10  can be installed in pump house  56  thereby reducing the number of pump houses required at a drilling site if the well being drilled requires a volume of pressurized drilling mud greater than what one mud pump  50  can provide. 
         [0047]    Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.