Power shovel with dipper door snubber and/or closure assembly

Excavating – Scoop or excavating and transporting container – Scoop or bucket structure – per se

Reexamination Certificate

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Details

C037S444000, C414S726000, C188S312000

Reexamination Certificate

active

06219946

ABSTRACT:

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 provi

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