Patent Publication Number: US-6219946-B1

Title: Power shovel with dipper door snubber and/or closure assembly

Description:
FIELD OF THE INVENTION 
     The present invention relates to power shovels and, more particularly, to power shovels having a dipper adapted for excavating earthen material. Specifically, the present invention relates to snubbers and latches for dipper doors. 
     BACKGROUND OF THE INVENTION 
     There are many known earth moving apparatuses or the like. Typical prior art earth moving equipment or excavators use a bucket or dipper assembly on the end of a movable arm which is used to scoop earthen material from horizontal or vertical faces. The bucket or dipper is normally provided with sharp teeth to provide a digging action against the surface being worked and further includes a cavity for collecting the material so removed. Once the earthen material is received within the dipper, the arm is typically moved to another location for transfer of the material. The material is usually discharged into a dump truck, onto a conveyor, or merely onto some other pile. 
     Many such power shovels include a heavy door which is pivotally mounted on a lower end of the dipper. A conventional mechanical latch mechanism secures the door in its closed position and, when released, allows the door to open. Conventional latch mechanisms typically include a trip wire or cable assembly which has one end adapted for control by a power shovel operator and another end connected to a moveable latch lever which is generally located beneath the dipper door. The latch lever is typically coupled to a slidable rod or latch bar which selectively engages a latch keeper extending downward from a front wall of the dipper body of the dipper. The dipper door is held closed when the latch bar is in engagement with the latch keeper. The dipper door is caused to open by tripping the trip cable which moves the latch lever which causes the latch bar to slide away from the latch keeper and disengage from the latch keeper, whereby the dipper door will open under its own weight plus the weight of any material contained within the dipper body. Normally, the door is thereafter closed by swinging the dipper in such a direction so as to cause the dipper door to move by inertia towards its closed position until the latch bar reengages the latch keeper as is conventionally known. 
     As generally known in the art, when the dipper door falls open or slams shut against the dipper body, the impact, if not dampened, can cause damage to the dipper door, dipper body and/or other components of the power shovel. As is commonly understood, devices for dampening the effect of the opening and the closing of a dipper door are typically referred to as snubbers. Many prior snubbers include clutch disk assemblies or brake disk assemblies. 
     BRIEF SUMMARY OF THE INVENTION 
     One problem with conventional mechanical latch closure mechanisms is the tendency for such mechanisms to quickly wear out and require replacement in only a short period of time. Each time the slidable latch bar engages the latch keeper or the like, the tip of the slidable latch bar naturally wears down. In many conventional latch mechanisms, the slidable latch bar is only moved about a half inch to about an inch in order to allow the dipper door to open. Thus, only a very small portion, i.e., the tip, of the slidable latch bar comes into contact with the latch keeper. As the tip of the slidable latch bar wears down over time, it becomes possible for the dipper door to prematurely open before the power shovel operator is ready for the dipper door to open. This, as can be appreciated by those skilled in the art, can create an extremely hazardous and unsafe condition if the power shovel is not properly maintained. 
     Another common problem with the prior mechanical latch closure mechanisms occurs when the excavated material has been discharged from the dipper and the dipper door is inadvertently dragged back across the discharged material as the power shovel operator starts a new digging cycle. Since many of the components of the latch mechanism, in particular, the latch lever, the latch bar and the latch keeper, are located on the bottom side of the dipper door, it is possible for the components of the latch mechanism to be damaged or at least clogged when these components come into contact with the discharged material. Such damage or interference could adversely affect the operation of the latch mechanism thereby preventing the dipper door from properly closing, possibly leading to the premature opening of the dipper door. 
     One problem with the prior clutch disk or brake disk snubber devices is the constant need to adjust the disks to ensure proper operation of the snubbers. As can be appreciated by those skilled in the art, as the clutch or brake disks wear down by virtue of repeated use, they must be readjusted or realigned in order to obtain the desired dampening effect. Although, when properly adjusted, clutch disk or brake disk snubber assemblies provide adequate dampening for a dipper door, the constant need to readjust these assemblies requires significant manpower, time and expense. 
     Thus, there exists a need in the art for a latch mechanism which does not require replacement in only a very short amount of time. There is also a need in the art for a snubber which does not require frequent readjustment. The invention provides an apparatus which acts as a closure device for a dipper door and which does not utilize conventional mechanical latch devices. The invention also provides an apparatus which is capable of acting not only as a closure device, but also as a snubber device, thereby providing a simple and inexpensive alternative to prior assemblies. Accordingly, the present invention provides a hydraulic assembly which acts as a closure mechanism and/or a dampening device for a dipper door of a power shovel. 
     The hydraulic assembly is provided with a hydraulic cylinder and a piston which is movable within the hydraulic cylinder. The piston divides the hydraulic cylinder into a first chamber and a second chamber wherein the volumes of the chambers change as the piston moves back and forth within the hydraulic cylinder. A piston rod is attached to the piston and extends through the hydraulic cylinder. Either the hydraulic cylinder or the piston rod is connected to the dipper body and the other is connected to the dipper door itself. 
     In one embodiment of the present invention, a restricted flow conduit is provided to connect the first chamber of the hydraulic cylinder with the second chamber of the hydraulic cylinder. By “restricted” it is meant that the conduit is constructed such that when hydraulic fluid flows between the chambers as the dipper door is opening or closing, the hydraulic fluid does not flow too quickly, and the hydraulic assembly thereby dampens or slows down the movement of the dipper door so as to substantially ensure that the dipper door does not bang or slam against the dipper body or other components of the power shovel. 
     In the preferred embodiment of the present invention a valve controls the hydraulic fluid flow through the conduit from one of the chambers to the other chamber. In this way, when the valve is closed, the hydraulic fluid is prevented from flowing between the chambers so that the dipper door is prevented from moving. When the valve is opened, the hydraulic fluid is allowed to flow between the chambers such that the dipper door is allowed to move. Thus, preferably, the hydraulic assembly is both a snubber device and a closure mechanism. 
     In a highly preferred embodiment, the power shovel does not include a conventional mechanical latch mechanism, and only includes the hydraulic assembly. 
     In an alternative embodiment, the conduit is not restricted but has the valve therein, and the hydraulic assembly acts only as a latch mechanism. 
     Accordingly, a feature of the present invention is to provide a power shovel which includes an apparatus adapted to effectively dampen the opening and closing of a dipper door to prevent damage to the dipper door and/or power shovel which would occur if the dipper door is not dampened. 
     Another feature of the present invention is to provide a power shovel which includes an apparatus adapted to effectively close a dipper door to prevent undesirable opening of the door thereby eliminating or, at least minimizing, hazardous or unsafe conditions which are virtually inevitable when a dipper door prematurely opens. 
     A further feature of the present invention is to provide a power shovel which includes an apparatus adapted to act both as a snubber device and a locking mechanism for a dipper door, thereby eliminating the complex assemblies of the prior art which typically include both a snubber assembly and a mechanical latching mechanism. 
     The apparatus according to the present invention is a simple, inexpensive assembly which is also capable of solving many of the problems attributable to the more complicated, costly designs of the prior art. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a power shovel embodying the present invention. 
     FIG. 2 is a cross-sectional view of the hydraulic assembly. 
     FIG. 3 is a cross-sectional view of an alternative hydraulic assembly. 
     FIG. 4 is an enlarged portion of FIG. I showing the hydraulic assembly with the dipper door closed. 
     FIG. 5 is a view similar to FIG. 4 wherein the dipper door is open. 
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter and the equivalents thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Illustrated in FIG. 1 is a power shovel  10  embodying the present invention. It should be understood that the present invention is capable of use in other power shovels known in the art and power shovel  10  is only provided as an example of one such power shovel. The power shovel  10  comprises a frame  14  supported for movement over the ground. Specifically, frame  14  is a revolvable upper frame mounted on a mobile base such as crawler tracks  18 . A fixed boom  22  extends upwardly and outwardly from the frame  14 . A dipper handle  26  is mounted on the boom  22  for movement about a rack and pinion or crowd drive mechanism  30  for pivotal movement relative to the boom  22  about a generally horizontal dipper handle axis  32 , and for translational (non-pivotable) movement relative to the boom  22 . The dipper handle  26  has a forward end  34 . A dipper  38  is mounted on the forward end  34  of the dipper handle  26  in a manner further described below. An outer end  42  of the boom  22  has thereon a sheave  46 , and a hoist cable or rope  50  extends over the sheave  46  from a winch drum  54  mounted on the frame  14  and is connected to the dipper  38  for pivotal movement relative thereto about a horizontal pivot axis  58 . 
     The dipper  38  will be further described with continued reference to FIG. 1 in which the dipper handle  26  is shown in a generally horizontal position. The dipper  38  is generally of a box shape having a main body  62  which includes a back wall  66 , opposite side walls  68  extending forwardly from and substantially perpendicular to the back wall  66 , and a front wall  70  which is generally parallel to the back wall  66 . Digging teeth  74  extend outwardly from an upper end of the front wall  70 . The main body or dipper body  62  defines a material receiving opening  78  (FIG. 4) and a material discharging opening  82  (FIG.  5 ). The dipper  38  further includes a dipper door  86  pivotally connected to the back wall  66  adjacent the lower end thereof about a dipper door axis  90 . The dipper door  86  is movable between open and closed positions as will be further described below. The back wall  66  of the dipper  38  is connected to the forward end  34  of the dipper handle  26 . The back wall  66  (and thus the dipper  38 ) is connected to the dipper handle  26  for pivotal movement relative thereto about a generally lower horizontal dipper axis which corresponds to dipper door axis  90 . Thus, in the illustrated construction, the lower dipper axis is coaxial with the axis  90  of pivotal movement of the door  86  relative to the dipper  38 . These axes need not, however, be coaxial. 
     Still referring to FIG. 1, the tooth cutting angle of the dipper  38  is controlled by a pair of attenuators  94  (only one is shown) connected to the dipper  38  and the dipper handle  26 . Such attenuators  94  are typically mounted on each side of the dipper  38  and are preferably variable pitch braces or shock attenuators as described in U.S. Pat. No. 5,499,463 which is hereby incorporated herein by reference. The dipper  38  pivots relative to the dipper handle  26  and about the lower dipper axis  90  coincident with extension and contraction of a spring (not shown) in the attenuators  94 . It should be understood that the dipper  38  can be connected to the dipper handle  26  in any number of ways known to those skilled in the art and still benefit from the use of the present invention. 
     The power shovel  10  also comprises (see also FIG. 2) a hydraulic assembly  98 . While only a single hydraulic assembly  98  is shown in the drawings, a second hydraulic assembly may be spaced apart from the first hydraulic assembly  98  on the opposite side of the dipper handle  26 . 
     Referring to FIG. 2, the hydraulic assembly  98  includes a hydraulic cylinder  102  mounted on the dipper body  62 . Any suitable mounting can be employed. Typically, hydraulic cylinder  102  includes a main body  106  and a pair of opposing end walls  110  conventionally attached to the main body  106  with screws  114 . The end walls  110  include respective holes  118 . 
     The hydraulic assembly  98  also includes a piston  122  which is movable within the hydraulic cylinder  102  and which divides the hydraulic cylinder into a first chamber  126  and a second chamber  130 . As can be appreciated, as the piston  122  moves within the hydraulic cylinder  102 , the volumes within the chambers  126  and  130  vary accordingly. As can also be appreciated by those skilled in the art, located on either side of piston  122  is hydraulic fluid. A piston seal  134  is provided to move with the piston  122  between the piston  122  and inside wall of the hydraulic cylinder  102  to prevent or inhibit passage of the hydraulic fluid from one chamber  126  to the other chamber  130 , or vice versa, between the piston  122  and inside wall of the hydraulic cylinder  102 . 
     The hydraulic assembly  98  further includes a piston rod  138  attached to the piston  122 . Generally, the piston rod  138  travels through a centrally located bore in the piston  122  and is attached to the piston  122  via retainer rings  142  or the like. The piston rod  138  extends through the hydraulic cylinder  102  through holes  118  such that one end  146  of piston rod  138  extends outward of one end wall  110  of the hydraulic cylinder  102  and is pivotally connected to the dipper door  86  in a suitable manner. The other end  150  of piston rod  138  extends outward of the other end wall  110  of the hydraulic cylinder  102 . A pair of piston rod seals  154  prevent or at least minimize leakage of the hydraulic fluid from the chambers  126  and  130  between the piston rod  138  and end walls  110 . 
     While in the illustrated construction, as best shown in FIGS. 4 and 5, the piston rod  138  is connected to the dipper door  86  and the hydraulic cylinder  98  is connected to the dipper body  62 , it should be understood that the piston rod  138  could be connected to the dipper body  62  and the hydraulic cylinder  102  could be connected to the dipper door  86 . As shown, end  146  of piston rod  138  is pivotally connected to a trunnion mount  170  located on a back portion of the dipper door  86  near the dipper door axis  90 . The hydraulic cylinder  102  is securely mounted to the back wall  66  of the dipper body  62  with bracket  174 . As shown, when end  146  of piston rod  138  extends farther out from the hydraulic cylinder  102  as compared to end  150  of piston rod  138 , the connection between the end  146  of piston rod  138  and the trunnion mount  170  causes the dipper door  86  to be closed according to the principles of the present invention. However, when end  150  of piston rod  138  extends farther out from the hydraulic cylinder  102  as compared to end  146  of piston rod  138  because the piston  122  (and therefore, the piston rod  138 ) moves in an opposite direction within the hydraulic cylinder  102 , the connection between the end  146  of piston rod  138  and the trunnion mount  170  causes the dipper door  86  to move. While the end  150  of the piston rod preferably extends through the wall  110  for support, this is not always necessary. 
     Referring back again to FIG. 2, the hydraulic assembly  98  includes a restricted flow conduit  158  which connects the first chamber  126  with the second chamber  130 . Preferably, as shown, the conduit  158  is external of the hydraulic cylinder  102 . However, the conduit  158  could extend through the wall  106  of the hydraulic cylinder  102 . Opposite ends  162  of conduit  158  are respectively attached to the end walls  110  of the hydraulic cylinder  102  in any number of suitable ways so long as the first chamber  126  is capable of communication with the second chamber  130  via conduit  158 . 
     A valve  166  controls the hydraulic fluid flow through the conduit  158 . The valve  166  can be a conventional on/off valve generally known to those skilled in the art and readily available from numerous commercial sources, but may be of any type of valve suitable for use according to the principles of the present invention. Preferably, the valve  166  is a solenoid valve which is controlled by way of a remote switch (not shown) operated by the power shovel operator. Such valves are commonly known to those skilled in the art and are also readily available from numerous commercial sources. 
     FIG. 3 shows an alternative hydraulic assembly  98 ′. In this embodiment, the conduit  158 ′ extends through the piston  122 ′ to connect the first chamber  126  to the second chamber  130 . In all other aspects, the hydraulic assembly  98 ′ of FIG. 3 is practically the same as the hydraulic assembly  98  of FIG.  2 . 
     The operation of the hydraulic assembly will now be further described with particular reference to FIGS. 4 and 5, it being understood that the hydraulic assembly  98 ′ of FIG.  3  and equivalent hydraulic assemblies can replace the hydraulic assembly  98  as shown in FIGS. 4 and 5. As generally known, a digging or excavating cycle of the power shovel  10  begins with the dipper  38  in a tucked position and the dipper door  86  in a closed position. In the closed position, the dipper door  86  closes the material discharge opening  82  (FIG. 5) as shown, for example, in FIG.  4 . While the door  86  is closed, the valve  166  is closed to prevent the flow of hydraulic fluid between chambers  126  and  130  so that the hydraulic assembly  98  prevents the dipper door  86  from pivoting about the dipper door axis  90 . 
     As the digging cycle continues, the dipper handle  26  is pivoted counterclockwise so that the dipper  38  contacts the ground or bank of material being excavated. As the dipper handle  26  is pivoted further counterclockwise, the dipper handle  26  is extended (crowded) as necessary for the dipper  38  to excavate more of the load as ground material passes into the dipper body  62  through the material receiving opening  78  (FIG.  4 ). Finally, the dipper handle  26  reaches the horizontal position as shown in FIG.  1 . Once the dipper  38  has collected the load of material and has been moved to a proper location, the valve  166  is opened so that the hydraulic fluid is allowed to flow between the chambers  126  and  130 , thereby allowing the dipper door to open, whereby the load of material is discharged through the material discharging opening  82 . 
     After the material has been discharged, the dipper  38  is swung downward which causes the dipper door  86  to move by inertia towards its closed position. As gravity closes the dipper door  86 , the movement of the door  86  causes the hydraulic assembly  98  to contract, which causes the hydraulic fluid in the chamber  126  to shift back or flow back to the chamber  130  via conduit  158 . Once the dipper door is closed, the valve  166  is closed to prevent the dipper door  86  from opening until such time as the power shovel operator chooses to open the door  86  by opening the valve  166 . 
     Throughout the digging cycle, when the dipper door  86  is allowed to pivot about the dipper door axis  90  thereby opening or closing, the restricted flow conduit  158  prevents the hydraulic fluid from transferring too quickly between the chambers  126  and  130 . Thus, the hydraulic assembly of the present invention effectively dampens the opening and closing of the dipper door. 
     Variations and modifications of the foregoing are within the scope of the present invention. For example, although the hydraulic assembly according to the present invention eliminates the need for the mechanical latch mechanisms of the prior art, it is envisioned that the hydraulic assembly of the present invention may act only as a snubber device as described herein whereby conventional latch mechanisms may be employed to latch a dipper door of a power shovel. Furthermore, the hydraulic assembly of the present invention may act only as a closure device as described herein whereby other known snubber devices may be employed to dampen the effect of opening and closing a dipper door of a power shovel. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.