Conveyors: power-driven – Conveyor system for moving a specific load as a separate unit – System includes a load supported by a conveyor portion which...
Reexamination Certificate
1999-05-06
2001-09-25
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor system for moving a specific load as a separate unit
System includes a load supported by a conveyor portion which...
C198S530000, C104S166000
Reexamination Certificate
active
06293388
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to mixed powered and gravity feed overhead conveyers, which have a gravity rail section for accumulation, re-timing, workstation waiting, buffers and the like, and a suspended trolley step feeder on the gravity rail conveyer section.
As a specific powered overhead conveyor system and for specific trolleys that have a gravity rail engaging top wheel that are conventionally used in combination with a step feeder, reference is made to the following patents, whose disclosure is incorporated herein in their entirety by reference: U.S. Pat. No. 5,806,655 issued Sep. 15, 1998 to Tabler; U.S. Pat. No. 5,785,168 issued Jul. 28, 1998 to Beall Jr.: U.S. Pat. No. 4,203,511 issued May 20, 1980 to Uhing; U.S. Pat. No. 3,164,104 issued Jan. 5, 1965 to Hunt; and U.S. Pat. No. 3,850,280 issued Nov. 36, 1974 to Ohrnell.
Gravity rail conveyors are well known and generally much lighter in construction. Usually, a trolley is supported by a top wheel riding on a rail and suspending the load from the trolley, by a carriage. The trolleys, being light even when loaded may be manually pushed along the rail.
Being powered, conveyer systems of the above type can handle loads that commonly range to over one hundred pounds each, and the step feeder needs to have a substantial stop to hold upstream accumulated trolleys in line on a gravity section while the lead trolley is released. Transfer devices are known to automatically move a loaded trolley between the powered and gravity sections, and such transfer may be accomplished manually also.
SUMMARY OF THE INVENTION
Due to the conveyor system being a mixed system of powered and gravity conveyors, the trolleys are heavier than they would be in a dedicated gravity system and carry far heavier loads, so that the inventor has noticed a problem that the front trolley in a line of abutting trolleys in, e.g. an accumulator, will swing forward about its top wheel axis and has a tendency to abnormally actuate a release switch of a step feeder when such actuation should not occur, which can cause operational problems.
An analysis of this problem by the inventor has led to consideration of one possible solution, which was rejected and led to the present embodiment. The rejected solution necessitated relatively complicated and expensive structure (relative to the simple and inexpensive structure of a lightweight solely gravity conveyer for light loads). This rejected solution to this gravity section step feeder problem would entail two separate trolley retaining abutments on two separate step feeder arms and two separate actuators, one actuator to release the lead trolley and one actuator to hold the remaining trolleys far enough upstream in the line to prevent the following trolley from swinging into the release limit switch when the lead trolley has departed. With two actuators, controls would be needed to coordinate the operation of the actuators, thus requiring the controlled release of one following trolley by the upstream step feeder arm at a time to the downstream step feeder.
Although there would be no requirement for additional limit switches, this another step feeder arm and the necessary controls for it's integration is readily seen to greatly increase the initial expense, installation cost and complexity of controls as compared to the use of a single step feeder arm that may be all that is needed on a simple lightweight solely gravity rail conveyor system.
This gravity section step feeder operation problem is caused by the relatively large amount of backpressure caused by empty or heavily loaded trolleys that also operate on the powered section, as analyzed by the inventor and which analysis is part of the present invention.
With the weight handled by the trolleys of a powered conveyer, there can be substantial forces on the step feeder in the gravity rail section that require a substantial actuator and dog or the like for each function of 1) holding and selectively releasing of the lead trolley, and 2) holding and selectively releasing of the second and subsequent trolleys that have accumulated in line. Sensors, controls and actuators, usually electrical and fluid are needed and must be timed to synchronize and coordinate the above two functions. The second function can involve widely varying forces, depending upon the loads on the trolleys and the number of trolleys being held in line. Problems encountered by a step feeder of a gravity rail section that handles relatively large and heavily loaded trolleys of a mixed power and gravity conveyor system are far more severe than typically encountered in a relatively lightweight dedicated gravity conveyor.
By way of a specific example and as the best mode of carrying out the invention, the step feeder having the new trolley retention mechanism is in combination with a gravity accumulation buffer as one of many different types of gravity systems throughout the overall mixed conveyor system.
In the powered portions of the conveyor system, a horizontal rotating drive shaft is engaged on it's top periphery by skewed or canted driven rollers/wheels that will each track a spiral line of contact with the rotating shaft as the rollers move the trolley on which they are mounted axially along the drive shaft in a direction depending upon the direction of skew and the direction of rotation of the drive shaft.
Each trolley has an upper or top single wheel/roller that is freely mounted for rotation about an axis perpendicular to the drive shaft axis and mounted above the driven rollers. The wheel may be selectively engaged and lifted to disengage the driven rollers from the drive shaft as the wheel is moved to a gravity rail of a gravity rail conveyor section, which in the example is an accumulation buffer. Herein wheels and rollers are generally equivalent and interchangeable terms, with different terms being used merely to denote association with different uses for specific ones of the structures, namely wheels for the gravity section and rollers for the powered section.
The step feeder of the present invention is placed on (used herein broadly, because such is equivalent to operatively adjacent to) a gravity line or section. The step feeder has a retention abutment, the retention abutment has an operation as follows:
1) In a normal receiving state, a pivoted step feeder arm will be in a position to receive and hold the top gravity wheel of the lead trolley.
2) When a trolley body of the lead trolley actuates a release limit switch indicating that the lead trolley has been received by and is being held by the pivoted step feeder arm, the release limit switch provides a release signal that causes (solely or in combination with other trolley position signals, a time out signal for a delay, a command signal from a controller, or the like signals for other purposes) actuation of one side of a double solenoid valve (as a specific example of one of many types of actuators that may be used) and which in turn causes the step feeder arm to rotate to a release position to release the lead trolley. While in this release position, the abutment mounted on the accumulation side of the step feeder arm, prevents any following trolley from actuating the release limit switch.
3) The step feeder arm will remain in the release position until a second limit switch, which may be mounted on either an in-feeder non-powered rail (for a double trolley carrier) or the out-feeder side such as the powered line (for a single trolley carrier), is actuated by the trailing trolley (for a double trolley carrier) or single following trolley (for a single trolley carrier). When this happens a signal is transmitted to actuate (again by itself or in combination with other signals) the other side of the solenoid valve and thereby causing the step feeder arm to rotate to the receiving and holding position where the step feeder arm is ready to receive the next lead trolley, which was formerly the following trolley.
Two significant advantages of the abutment, which is more preferably a cam shaped
Beall, Jr. Thomas E.
Deuble Mark A.
Ellis Christopher P.
OCS - Intellitrak, Inc.
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