Load change safety system

A load change safety system in which a sheet stacker having a stacking deck formed with a discharge end discharges sheet material onto and builds a sheet stack on a conveying sheet stack removal system formed with a receiving means. A variable pinch point gap is formed by relative motion between the discharge end of the stacking deck and the receiving means of the conveying sheet material removal system. The safety system includes redundant means selectively preventing a decrease in the variable pinch point gap. The redundant means of the safety system preferably includes an electro-optical light guard means operably connected to the redundant means with one or more redirections of light beams to create a light guard perimeter guarding portions of the stacker and sheet removal system to guard against access to the pinch point.

This invention relates to a system designed to keep the operator30and/or other individuals safe from the hazardous condition of a lowering stacking deck3,3′ of a sheet stacker2,2′. The hazardous condition is the variable pinch point gap9,9′ created between the discharge end4,4′ of the stacking deck3,3′ and a conveying sheet material removal system7,7′ typically located under the discharge end4,4′ of the sheet stacker2,2′. The conveyor system provides means for transporting material away from the sheet stacker2,2′. The need for the load change safety system1–1″″ is amplified by the fact that the operator30and/or other individuals are required to frequently go near the hazardous area of the variable pinch point gap9,9′ during normal production operation to place protective sheets, referred to as dunnage50and/or pallets51on the conveying sheet material removal system7,7′ before each sheet stack6is created at the discharge end4,4′ of the sheet stacker2,2′.

The term operator30used throughout this patent shall be interpreted to include not only the person operating the sheet stacker2,2′ but also any and all other people that come near or in contact with the sheet stacker.

The term LCS system is used in this patent to refer to the Load Change Safety System.

BACKGROUND OF THE INVENTION

It is common to stack cardboard/corrugated sheet stacks6into full stacks52, which are then conveyed in a straight line by a floor conveyor (typically top of conveyor rollers approximately 12 inches above the floor) to another machine. These full stacks52are often created by first placing down a pallet51and/or a protective sheet on said sheet material removal system7,7′. These protective sheets are often referred to as dunnage50in the industry. The pallet51and/or dunnage50provides protection, for the bottom sheets of the full stacks52and/or allow machinery down stream (typically fork lift trucks) to be able to handle the full stacks52.

One form of sheet stacker2found in U.S. Pat. No. 2,901,250 granted to Martin on Aug. 25, 1959. The sheet stacker is typical of a class of stackers referred to as “upstackers” in the industry since they create a full stack52by using a stacking deck3which articulates in such a way that the receiving end has little or no vertical motion and the discharge end4has adequate motion to create full stacks52while moving in a generally upward motion. The cardboard/corrugated is transported on a plurality of conveyor belts built into the stacking deck3from the receiving end of the stacking deck3to the discharge end4of the stacking deck3.

A second form of sheet stacker is found in U.S. Pat. No. 5,026,249 granted to TEI on Jun. 25, 1991. The sheet stacker is typical of a class of stackers referred to as a “downstackers” in the industry since they create a full stack52by elevating and lowering the sheet material removal system7′ under a fixed stacking deck in such a way that the receiving end and discharge end of a stacking deck has no motion but the elevating conveyor lowers as the sheet stack6is created in order to create full stacks52.

A third form of sheet stacker is a hybrid where both the stacking deck2and sheet material removal system7′ can move in their prescribed motion in order to create the sheet stacks6.

It is also common to stack cardboard/corrugated sheets into short sheet stacks6referred to as bundles in the industry. The bundles are typically created at the discharge end4,4′ of the sheet stacker2,2′ on some sort of conveyor roller or conveyor belt system, which is typically referred to as a bundle takeaway system. Typical bundle takeaway systems are waist high in order to allow the operator to manually manipulate the bundles down stream.

In both situations where full stacks52or bundles are being created, the sheets are stacked during the motion by which the variable pinch point gap9,9′ between the discharge end4,4′ of the stacking deck3,3′ is increasing. Once a full stack52or bundle has been created, it must be transported from under the discharge end4,4′ of the sheet stacker2,2′. While the full stack(s)52or bundle(s) is being transported, an accumulation device54is often employed to collect sheetmaterial5so as to allow material to continue to fall off the end of the stacking deck3,3′ while waiting for the full stack52or bundle to be transported and allowing the stacking deck3,3′ and/or sheet material removal system7,7′ to move towards each other, thus decreasing the variable pinch point gap9,9′. One form of accumulation device54is found in U.S. Pat. No. 6,042,108, Morgan et al, granted Mar. 28, 2000. The variable pinch point gap must decrease in a relatively fast motion approximately 4–5 seconds on full stacks52and 1–2 seconds on bundles in order to keep the material collecting in the accumulator area55from exceeding the designed capacity of the accumulation device54. The ejecting of a sheet stack and reduction of variable pinch point gap9,9′ so next sheet stack can be built is commonly referred to as the load change cycle56in the industry.

This rapid motion of the stacking deck3and/or sheet material removal system7′ to within close proximity results in a hazardous condition where the variable pinch point gap9,9′ is formed between the bottom side of the discharge end4,4′ of the stacking deck3,3′ and the sheet material removal system floor conveyor or bundle takeaway system. Due to the weight and strength of the machinery, a person caught in this variable pinch point gap9,9′ may have the result of serious injuries or death.

The open design of the stacking deck3,3′ is a major productivity advantage of the sheet stacker2,2′. During normal production it is important that the operator50have easy access to the discharge end4,4′ of the stacking deck3,3′. This invention targets the production operations performed by the operator. The production operations includes setting up the order, running the order, adjusting the order, checking for quality control purposes, placing dunnage50and/or pallets51, clearing jams and placing stack identification tags into full stacks52. While executing production operations the operator must be able to have access to the discharge end4,4′ of the stacking deck3,3′ without completely de-energizing and re-energizing the machinery since this would have a substantial impact on production.

The maintenance/clean up operations performed by the operator30and other employees is a different type of operation. Unlike the production operation where one individual is responsible for the area around the discharge end4,4′ of the stacking deck3,3′, the maintenance/clean up operations may involve one or more people sometimes working on key systems including the hydraulic, pneumatic and electrical systems. Most companies owning sheet stacking machinery have already established procedures, commonly referred to as Zero Energy State and/or Lock-Out-Tag-Out. These procedures require too much recovery time to use as a safety solution during production operations.

The ability of the stacking deck3and/or sheet material removal system7′ to be able to execute a load change cycle56fully automatically without the assistance of the operator is often a required productivity feature of a sheet stacker2,2′. Prior to this invention, some sheet stacker2,2′ owners have elected to eliminate the ability of the operator to execute a load change cycle56fully automatically. These sheet stackers2,2′ may require the operator to manually initiate the stacking deck3,3′ down motion or to depress some sort of push button during the entire time the variable pinch point gap9,9′ is decreasing. Even if this does not hinder the productivity due to the configuration of the sheet stacker2,2′ production line, this solution still may not meet the guidelines of the International Safety Standards which include redundancy and self-testing.

A light guard system for this type of sheet stacker2,2′ has been available since 1990 as provided by the Geo. M. Martin Co., seeFIG. 1–4. However, this system has many short comings including 1) lack of a failsafe mode should a single component fail, 2) no self testing, 3) difficult installation and maintenance due to stringent mirror alignment requirements, 4) lack of flexibility when needing multiple mirrors to reflect the light, 5) no fault detection of cross talk from external optical sources, 6) interference due to light stand locations and 7) not able to run fully automatic cycling of full stacks52when the sheet stacker2,2′ is equipped with an automatic dunnage50and/or pallet51system.

SUMMARY OF THE INVENTION

The Load Change Safety System1–1″″ of the present invention is a safety system to keep the operator30a safe distance from the variable pinch point gap9,9′ while the sheet stacker2,2′ is performing the load change cycle56, hence achieving the very important objective of keeping the operator30from accidentally getting near or in the variable pinch point gap9,9′ while decreasing.

Another objective of the present invention is to provide hydraulic redundancy by including a rigid stacking deck3with dual cylinders11,12, dual hydraulic lock valves13,14so that a single component failure in the hydraulic system will not allow the stacking deck3to initiate or continue the deck down cycle.

A further objective of the present invention is to provide the ability to perform self-testing on the hydraulic system by adding feedback sensors18,19to allow detection of a hydraulic leak and/or failure.

A further objective of the present invention is to provide a robust light guard system27by using a series of optical repeating nodes24instead of mirrors to reduce the requirements for precise alignment and the accumulation of accuracy error when needing to create a light guard perimeter21in which the beam(s) of light must be redirected multiple times. This light guard system27may be operatively connected to the LCS system control means15″,15′″ and the hydraulic lock valves13,14to place both valves in a state which does not allow the variable pinch point gap9,9′ to decrease.

A further objective of the present invention is to define a configuration of a light guard system27by which the optical repeating node24′ on the operator side of the sheet stacker2,2′ near the discharge end4,4′ of the stacking deck3,3′ is part of a movable remote control mean35in order to reduce the interference that would be caused if a floor mounted optical repeating node24was located in the same general proximity.

A further objective of the present invention is to modulate optical signals on the light beams20,20′ of the light guard system27in order to substantially increase the likelihood that any failure in the electrical and/or optical circuit is interpreted as a light guard system27intrusion and results in a fail-safe mode.

A further objective of the present invention is to configure the relationship between the sheet stacker2,2′, sheet material removal system7,7′ and the location where the light guard perimeter21crosses over the sheet material removal system7,7′ in such a manner to allow synchronized discharge of the full stacks52and fully automatic completion of the load change cycle56.

DESCRIPTION OF THE INVENTION

In the present invention, a load change safety system1–1′″ is provided for a sheet stacker2,2′ in which a variable pinch point gap9,9′ is created during the load change cycle56due to the motion of the stacking deck3,3′ and/or the conveying sheet material removal system7,7′. The variable pinch point gap9can be created with an “upstacker” type of sheet stacker2where the stacking deck3moves in a generally upward direction, while the conveying sheet removal system7remains fixed, as illustrated inFIGS. 5,6,7&8. Alternatively, the variable pinch point gap9′ can be created with a “downstacker” type of sheet stacker2′ where the stacking deck3′ remains fixed, while the conveying sheet removal system moves in a generally downward direction, as illustrated inFIGS. 9,10,11&12.

The sheet stacks6are first created as the sheet material5exits the discharge end4,4′ of the stacking deck3,3′ and the variable pinch point gap9,9′ increases. This increase in said variable pinch point gap keeps the relative distance between the elevation at which the sheet material5exits the discharge end4,4′ of the stacking deck3,3′ and top of the sheet stack6approximately the same while the height of the sheet stack6increases. Once the sheet stack6has been created, it is necessary to perform a load change cycle56.

The load change cycle56, illustrated inFIG. 13first requires load ejection cycle56′ in which the sheet stack6′ is transported downstream on the conveying sheet material removal system7,7′ using rollers57or belts. Often, during this period an accumulation device54is used to allow the sheet material5to continue to exit the discharge end4,4′ and the stacking deck3,3′. After the load ejection cycle56′ is the deck down cycle56″ in which the variable pinch point gap9,9′ is decreased by motion of the stacking deck3down and/or motion of the conveying sheet material removal system7′ up. Once the deck down cycle56″ is completed, the accumulation device54retracts transferring the beginning of the next sheet stack6″ from the accumulation area55to the receiving means8,8′ of the conveying sheet material removal system7,7′.

In the present invention, redundant means10including, e.g., hydraulic cylinders11,12, valves13,14and LCS system control means15as shown in FIGS.17,18, and20, are provided to selectively prevent the decrease of the variable pinch point gap9,9′ to reduce the chances of an operator30being hurt.

An upstacking sheet stacker2has a variable pinch point gap9which decreases as shown by two positions, first inFIG. 6and then inFIG. 8. This is due to gravities affect on the moveable stacking deck3.FIGS. 14 & 15show two different perspective views of a typical upstacker stacking deck3. In this preferred embodiment, you will note the rear deck58is constructed using side wall members59,59′ and cross torque tubes60,60′ such that the box frame created forms a planer surface61. Since the cross torque tubes60,60′ are able to resist torque, typically made from rectangular tubing, the rear deck58is a substantially rigid structure that attempts to keep planer surface61flat when rigidly pinned for pivoting by swing arms62,62′. The four bar linkage created by the rear deck58, swing arms62,62′, the stacker base63and lifting arms64,64′ creates a nearly straight vertical motion at the discharge end4of the stacking deck3when the lifting arms64,64′ are operably connected to support hydraulic cylinders11,12. InFIGS. 14 & 15the side casting65opposite65′ has been removed for clarity but may be seen inFIG. 18. The hydraulic cylinders11,12provide redundant support, due to the existence of the substantially rigid structure created by the rear deck58and the fact that either hydraulic cylinder11or12is capable of supporting the weight of the entire stacking deck3. Should either cylinder fail to provide support, the deck will ‘rack’ slightly as the planer surface61warps slightly, but the deck does not come down substantially.

InFIG. 16 & 17are detail side views of the sheet stacker2when viewed from line16—16ofFIG. 15. It shows the left side casting65′, left stacker lifting arm64′ and left hydraulic cylinder12connecting stacker base frame63′ to left stacker lifting arm64′. If oil flows into left hydraulic cylinder port66, the left hydraulic cylinders12rod extends94increasing the variable pinch point gap9. Likewise, due to gravity, oil is naturally pressurized at all time to flow out of left hydraulic cylinder port66. Connected to left hydraulic cylinder port66is first a left hydraulic velocity fuse68. The left hydraulic velocity fuse68has a feature of locking up and stopping oil from exiting left hydraulic cylinder port66should the flow rate exceed a certain designed threshold; typically to keep a hydraulic line blowout from causing damage. While not required for the present invention, including a hydraulic velocity fuse67,68on each cylinder is considered good practice. Then, connected to the left hydraulic velocity fuse68is hydraulic lock valve14which will let oil into hydraulic cylinders12via check valve but will only let oil out of hydraulic cylinder port66only if hydraulic lock valve solenoid70is energized. There is a separate and independent right hydraulics lock valve13connected in a redundant fashion to right hydraulic cylinders11. The result is two independent and redundant support means or systems10, with both right hydraulic lock valve solenoid69and left hydraulic lock valve solenoid70needing to be activated in order to allow a narrowing of variable pinch point gap9.

The LCS system control means15shown inFIG. 20allows the operator30to press a deck down enabled button71in order to electrically activate redundant hydraulic lock valve solenoids69,70. Said deck down enabled button71has redundant right and left deck down enabled contacts72,73that will conduct electrical power down redundant paths to self testing means74,75which then may conduct to fault detection means76,77. The order of these paths are not important. In the simplest form, the redundant LCS system control means15would not have self-testing means74,75nor fault detection means76,77. However, in the preferred embodiment, these elements are added to even further reduce the likelihood of an unsafe condition.

In the simplest form, the operator30would press the deck down enabled button71which is positioned such that the operator30is a safe distance from the variable pinch point gap9. If the operator releases the deck down enabled button71both redundant paths would provide support to the stacking deck. However, should a single component fail on either redundant path, the variable pinch point gap9would still stop decreasing.

A downstacking sheet stacker2′ has a variable pinch point gap9′ which decreases as shown by two positions; first inFIG. 10and then inFIG. 12. This is due to the raising of the conveying sheet material removal system7′. Unlike an upstacker, seeFIG. 6, in which gravity naturally tries to decrease the variable pinch point gap9, with a downstacking sheet stacker2′, gravity is naturally trying to increase the variable pinch point gap9′, seeFIG. 10. As a result, redundancy can be achieved by using only one hydraulic cylinder11′ or more than one hydraulic cylinders11′,12′. A mechanical failure of the hydraulic cylinder11′ can not cause the variable pinch point gap9′ to decrease. In typical embodiments, there are a plurality of cylinders due to mechanical engineering requirements.

This invention could be applied to the variable point point gap (101′) that may exist between the bottom side of the conveying sheet material removal system (7′) and the floor. However, in the interest of brevity, this will not be described in detail

The redundancy means10′ involves using a plurality of hydraulic lock valves13′,14′ in a redundant LCS system control means15′ shown inFIG. 21. By placing the hydraulic lock valves13′,14′ in series, they both must be actuated and functioning normally in order to allow pressurized oil to flow into one or more than one hydraulic cylinders11′,12′, which in turn decreases the variable pinch point gap9′.

The LCS system control means15′ shown inFIG. 21allows the operator30to press a deck down enabled button71in order to electrically activate redundant hydraulic lock valve solenoids69′,70′. Said deck down enabled button71has redundant right and left deck down enabled contacts72,73that will conduct electrical power down redundant right and left paths to self testing means74′,75′ which then may conduct to redundant right and left fault detection means76′,77′. The order of these paths are not important. In the simplest form, the redundant LCS system control means15′ would not have self testing means74′,75′ nor fault detection means76′,77′. However, in the preferred embodiment, these elements are added to even further reduce the likelihood of an unsafe condition.

In the simplest form, the operator30would press the deck down enabled button71which is positioned such that the operator30is a safe distance from the variable pinch point gap9′. If the operator releases the deck down enabled button71both redundant paths would provide support to the stacking deck. However, should a single component fail on either redundant path, the variable pinch point gap9′ would still stop decreasing.

Both LCS system control means15,15′ use feedback from various sensor means17,17′ in order to detect if a condition exists that requires making sure no power flows to redundant hydraulic lock valve solenoids69,70,69′,70′. Some of these conditions are classified as self-testing in nature while others are considered to be faults.

Sensor means17,17′ include hydraulic position sensor18,18′, which is activated in one state at a predefined raised position of an associated hydraulic cylinder11,12. Should a failure of support occur in one of the hydraulic cylinders, the associated hydraulic position sensor18,18′ will activate to a different state.

Sensor means17may also include the deck down enabled button71, which can be monitored to determine if redundant contacts are synchronized and how long they have been in either state.

Sensor means17may also include the operator in position sensor47, which can be monitored to determine if its output changes and how long it has been in either state. The operator in position sensor47is mounted on remote control means35operably connected to said sheet stacker2or2′. The LCS system control means15,15′ monitors said operator in position sensor47to make sure the operator is a safe distance from the variable pinch point gap9,9′ while decreasing.

Sensor means17may also include the boom in position sensor48, which can be monitored to determine if its output changes. Since the remote control means35is swivelly attached to or adjacent to said sheet stacker2,2′, in the preferred embodiment, the boom in position sensor48makes sure the boom is in the position shown inFIG. 35as opposed to the location shown inFIG. 36. This assures that the operator30has a good sightline to the area near the variable pinch point gap9,9′.

Logic means for self testing78,78′ include but are not limited to: 1) periodic testing the load change hydraulic system49,49′ integrity, 2) proper functioning deck down enabled button71, 3) proper functioning of boom in position sensor48and 4) proper functioning of operator in position sensor47. If the self-testing conditions are not met, the self-testing contact chain80,81,80′,81′ will not allow power to flow to hydraulic lock valve solenoid(s)69,70,69′,70′.

Logic means for fault detection79,79′ include but are not limited to: 1) redundant hydraulic lock valve solenoids not being synchronized in the on or off state, 2) the deck down enabled button71being active for too long of a period and 3) the operator in position sensor47being active for too long of a period. If a fault condition is detected, the fault contact chain82,83,82′,83′ will not allow power to flow to hydraulic lock valve solenoid(s)69,70,69′,70′.

The basic form of redundant means10,10′ for keeping the operator a safe distance from the variable pinch point gap9,9′ requires that the operator30holds down the deck down enabled button71anytime the variable pinch point gap9,9′ is decreasing. However, there are production line configurations where this is not practical or economical. For instance, in a bundling application where the sheet stacks6are built short to form bundles, not shown, the cycle time of the discharge end4the stacking deck3can be so short that the operator30would end up spending nearly all his/her time holding the deck down enabled button71.

In order to solve this problem, the present invention includes an electro-optical light guard means27, seeFIG. 22, that is activated by the operator30from outside the light guard perimeter21after the operator30first visually checks to make sure the area within the light guard perimeter21is clear of other personnel and then presses a light guard activation button in order to latch the light guard control circuit85to an active state. The term latch indicates that the light guard control circuit85will remain active until another event, such as the light guard perimeter21being crossed or loss of power to sheet stacker2,2′ should occur. Thus, after activating the light guard control circuit85, the operator30may walk away from light guard activation button, leaving the redundant means10,10′ in a state allowing a decrease in variable pinch point gap9,9′. The light guard activation button is operably connected to the deck down enabled button71in the preferred embodiment. This light guard control circuit85is operably connected to the light guarded LCS system control means15″,15′″ which operably controls the redundant means10,10′ for selectively preventing a decrease in variable pinch point gap9,9′.

The light guard perimeter21is constructed by using one or more light beam (s)20,20′ that must be redirected multiple times in order to create the appropriate perimeter around portions of the sheet stacker2,2′ and portions of the conveying sheet material removal system7,7′ such that when an operator30or other person should break the light guard perimeter21, the redundant means10,10′ can prohibit a decrease in variable pinch point gap9,9′. Each light beam circuit starts with a light beam transmitter22that converts an electrical signal into an optical signal. The redirection is accomplished using an optical repeating node24,24′, as illustrated inFIG. 24. Unlike conventional mirrors used to redirect the light beam, the optical repeating node (s)24,24′ uses a repeater pair28which consist of an repeater optical receiver25which is aligned in the general direction of the incoming light beam20. The repeater optical transmitter26is electronically connected by repeater circuitry29to its associated repeater optical receiver25such that the optical signal received by the repeater pair transmitted at the new redirected angle by the repeater optical transmitter26. The repeater circuitry29needs to meet the electrical engineering requirements of the selected electro-optical components, but in the preferred embodiment, the repeater circuitry29does not include any sophisticated clock base electronics, such as micro-controllers or other crystal based components. This is to assure that an optical data signal initiated by the light beam transmitter22can only be repeated and received by light beam receiver23by properly functioning repeater pair(s).

The advantage of using the optical repeating node(s)24,24′ instead of using reflective mirrors89–89′″ is illustrated inFIGS. 25–30. InFIG. 25, a scaled version of a sheet stacker2was drawn in planned view, using AutoCAD with a light guard perimeter21″ created using a light beam transmitter22″, a series of mirrors89–89′″ at stations86,86′,86″,86′″ and a light beam receiver23″ at station86″″. A dimension of 120 inches has been added to Figure to give the drawing scale. By applying the basic physics of light where the angle of incidence equals the angle of reflection, a perfectly aligned light guard perimeter21″ was created using light guard beam87. Then, in order to show how sensitive a reflective mirror system is to misalignment, the mirror at the first station86, which is assumed to be 4 inches in size, seeFIG. 26, is misaligned by approximately 0.010 inches. This correlates to an angular misdirection of approximately 0.3 degrees. Then, assuming all the other mirrors89′–89′″ remain in perfect alignment, which is quite an assumption in heavy industry, the light beam is redrawn as misaligned light guard beam88, again using the basic law of reflection. As shown inFIG. 26, the angle of reflect is off by approximately 0.3 degrees. InFIG. 27, when the light rays arrive at station86′, the misaligned light guard beam88is off by 2⅜ inches. At station86″, inFIG. 28, the misaligned light guard beam88is off by 4 1/16 inches. At station86′″, inFIG. 29, you would now need over a20inch mirror, since the misaligned light guard beam88is over 10 inches off center line. By the time the misaligned light guard beam88gets to the light beam receiver23″ inFIG. 30, it is off by over 4 inches. In addition to this tremendous sensitivity to angular misalignment, a reflective mirror system also has the poor characteristic of accumulating misalignment error. That is, if the mirrors89′,89″ at station86′ and86″ both have a misalignment, the error would add to each other.

The optical repeating system of the present invention essentially uses a transmitter and receiver to create each straight section of the light guard perimeter21. Since the preferred optical transmitters generates a cone of light, the preferred optical receiver has a lens to allow for rays of light to enter to a certain amount of angular misalignment, an angular misalignment of 3 degrees or more are easily achieved. In addition to the 10 times or more forgiveness to misalignment, the optical repeating system does not accumulate misalignment error. By referring toFIG. 24, it is clear that any misalignment of the rays of beam coming into repeater optical receiver25has no impact on the alignment of repeater optical transmitter26. The only disadvantage of the optical repeating system compared to the reflective mirror system is the fact that the repeating nodes typically require an external power supply.

In the preferred embodiment, the light guard means27, includes two light beam20,20′ circuits, separated vertically as shown inFIG. 23. The number of light beams, their vertical locations and the distance of the light beams from the variable pinch point gap9,9′ are based on using safety standards as a guideline and computer simulated biomechanical analysis of trip scenarios. When using two beams, it is preferred to have the top beam20and the bottom beam20′±s12v1P directed in opposite direction, to further eliminate the possibility of cross talk between the two beams.

A load change safety system1″ of the present invention for a sheet upstacker2having a stacking deck3, formed with a discharge end4, for discharging sheet material5onto and building a sheet stack(s)6on a conveying sheet material removal system7, formed with a receiving means8may consist of the following elements.

In such systems, a variable pinch point gap9is formed by relative motion between the discharge end4of the stacking deck3of the sheet stacker2and the receiving means8of the conveying sheet material removal system7. In the present invention, redundant means10is provided for selectively preventing a decrease in the variable pinch point gap9.

To guard personnel from this pinch point gap9, an electro-optical light guard means27is operably connected to the redundant means10with one or more redirections of one or more light beams20to create a light guard perimeter21for guarding portions of the sheet stacker2and portions of the conveying sheet material removal system7.

The electro-optical light guard means27includes one or more light beam transmitters22and one or more light beam receivers23. The electro-optical light guard means27further includes one or more optical repeating nodes24or24′ using an optical receiver25and an optical transmitter26for creating the redirection of the light beam(s)20.

The redundant means10also includes a plurality of hydraulic cylinders11and12for raising and lowering the stacking deck3. The hydraulic cylinders11and12must be of adequate strength such that should one cylinder11or12fail to provide a support for the stacking deck3, the remaining cylinder11or12can support the weight of the stacking deck3.

A plurality of valves13and14are provided wherein at least one valve13or14is independently connected to each of the cylinders11and12which may selectively and alternatively permit and prevent flow of fluid from those of the hydraulic cylinders11and12which are operating normally and have not failed, thereby resulting in rapidly preventing the variable pinch point gap9from narrowing.

A light guard control means15″ is operatively connected to the electro-optical light guard means27and operatively and independently connected to each of the valves13and14for alternatively permitting and preventing flow of fluid from the hydraulic cylinders11and12. The load change safety system1′″ for a down stacker system is nearly identical to the load change safety system1″ for an upstacker system as described immediately above, but with the following changes.

The redundant means10′ include one or more hydraulic cylinders11′,12′ for raising and lowering an elevating platform16′ of the conveying sheet material removal system7′ instead of being mounted on the upstacker2.

Further, while only a single cylinder is required for raising the platform16′, generally two or more cylinders are provided for other reasons. In such systems, a plurality of valves13′ and14′ are provided wherein the valves13′ and14′ are operatively connected to each other and the cylinders11′ and12′ by means such that all of the valves13′ and14′ must simultaneously be activated and operate normally for selectively and alternatively permitting and preventing flow into the hydraulic cylinders11′ and12′ which are operating normally and have not failed, thereby preventing the variable pinch point gap9′ from narrowing.

In the present invention the pinch point gap9′ is protected by a light guard control means15′″ operatively connected to the electro-optical light guard means27and operatively and independently connected to each of the valves13′ and14′ for alternatively permitting and preventing flow of fluid into the hydraulic cylinders11′,12′.

Since any electro-optical component can fail and the failure can result in a sensor output in the on or off state, the electro-optical light guard means27requires a modulated signal detection means34such that a failure of an electro-optical component in either state will send the same light guard output signal as if the light guard perimeter21is blocked. A modulated transmitter circuit is connected to the light beam transmitter(s)22such that the modulated signal detection means34can generate a defined modulated optical signal33in series around the light guard perimeter21via optical repeating nodes24,24′. A receiver decoding circuit31feeds back to the modulated signal detection means34the electrical equivalent of the defined modulated optical signal33. The modulated signal detection means34can determine if the modulated signal has been properly received. Since the signal must be modulated, a failure of any electro-optical component in either the on or off state can be interpreted as a blocked light guard perimeter21and the associated signal sent as the light guard output signal43. Of course, an actual blockage of the light guard perimeter will generate the proper signal sent as the light guard output signal43.

The light guard output signal43is operably connected to light guarded LCS system control means15″,15′″. When the light guard output signal43indicates a blockage of the light guard perimeter21, the associated light guard control circuit85will be deactivated which operably controls the redundant means10,10′; preventing a decrease in the variable pinch point gap9,9′.

In addition to making sure that the a failure of any electro-optical component results in a fail-safe mode, the modulated signal detection means34, in the preferred embodiment, is also connected to the fault detection mean76,77since certain failures can be detected.

In the preferred embodiment, there is an independent modulated signal detection means34for each light guard beam20,20′.

In prior art,FIGS. 1,2,3&4, the light guard perimeter was created using two way redirections of the light guard light beams and fixed post mounted to the ground as the starting and stop points for the light guard perimeter. In addition to not providing an adequate distance between the light guard perimeter and the pinch point of concern, this system results in the nuisance of having a floor mount post in the way of the operator30.

This invention teaches the idea of using a four way redirection of the light guard light beams and starting and stopping points for the light guard perimeter mounted to the machine. This allows a greater distance between the light guard perimeter and the pinch point of concern. However, while using a floor mount optical repeater node as shown inFIG. 34would provide the greater distance, it would still not solve the problem of the nuisance of having a floor mounted post96in the way of the operator.

This invention includes a solution to this problem, as shown inFIG. 35. A remote control means35is connected to the sheet stacker2and positioned so that the operator30has a good visual vantage point for observing the variable pinch point gap9,9′ and the light guard perimeter21. The remote control means35includes deck down enabled button71which in the preferred embodiment both allows basic enabling of the decreasing of variable pinch point gap9,9′ and also the activating the light guard control circuit85.

The remote control means35is connected to the movable part of the boom37which in turn is swivelly attached to or adjacent to the sheet stacker2,2′. This give the operator the ability to move the moveable part37of boom36from the boom in position location44to the boom out of position location45as shown inFIG. 36. From this illustration, we can see how the operator does not have any post in his/her way. Also, there are often ten other controls on the remote control means35that are better adjusted when the operator is in this boom out of position location45.

By mounting one of the optical repeating nodes24′ to the bottom of the remote control means35, which is operably connected to the movable part of the boom37. The resulting configuration provides a completed light guard perimeter21when the boom36is at the boom in position location44, while also effectively eliminating the possibility of the light guard control circuit85being activated when the remote control means35is swiveled to the boom out of position location45. This works well with the design intent of only letting the operator30activate the light guard control circuit85when the boom36is in the boom in position location44.

In the preferred embodiment there is also a boom in position sensor48, shown inFIG. 35, mounted near the elbow of the boom36. This allows the basic LCS system control means15,15′ to make sure the remote control means35is properly positioned before allowing the deck down enabled button to enable the variable pinch point gap9,9′ to decrease.

In the preferred embodiment there is also an operator position sensor47, shown inFIG. 35that makes sure the operator30is standing in front of the remote control means35as not to be able to activate the light guard control circuit85from within the light guard perimeter21.

The light guard means27presents the challenge when building full stacks6′ because of the need to eventually convey the completed full stacks6′ from within the light guard perimeter21to outside the light guard perimeter21on the conveying sheet removal system7,7′. A technique exists called ‘muting’ by which the light beam blockage is ‘ignored’ by the control means when the control means ‘thinks’ the material is exiting through the light beams such that the light beam then automatically becomes active after the control means ‘thinks’ the material has successfully exited. This technique is considered inadequate for the sheet stacker2application since it is possible for an operator to enter the light guard perimeter21at the same time the full stack6′ is blocking light beams20,20′ resulting in the operator being able to go undetected from the outside to the inside of the light guard perimeter21.

This!invention solves the problem of transporting the full stacks6′ from inside to outside the light guard perimeter21by configuring the light guard means27in a relative fashion to the conveying sheet removal system7,7′ such that it naturally works with the operators30work habits to minimize the impact of needing to press a light guard activation button in order to latch the light guard circuit85to an active state after the full stack6′ has reset the light guard circuit85to a deactivated state.

FIG. 37shows a standard configuring of the light guard means27in a relative fashion to the conveying sheet removal system7. The important parameter is the distance D146which is the distance from the face of the discharge end4of the stacking deck3where the full stack6′ is being built to the location where the light beams20″,20′″ cross over the conveying sheet removal system7. The light beams20″,20′″ are the upper and lower beams in the preferred embodiment created by optical repeating nodes24positioned at station locations40,41shown inFIG. 35. In the configuration shown inFIG. 37, there is no pallet and/or dunnage inserting system95. As a result, the operator30is typically required to manually place the pallet51and/or dunnage50every time the full stack6′ is transported an adequate distance downstream on to the conveying sheet removal system7and before the stacking deck3makes the deck down cycle56″, referred to inFIG. 13for typical load change cycle56sequence. As a result, it is natural for the parameter D146to be somewhat longer than the length L91of the largest full stack6′ size so the light guard perimeter21is not blocked while full stack6′ is being built, however, the parameter D146should allow the full stack6′ to block and exit the light guard perimeter21in short order during the load ejection56′ allowing the operator30to also cross the light guard perimeter21and place the pallet51and/or dunnage50before the associated deck down cycle56″ begins. As a result, the operator30and the full stack6′ are both breaking the light guard perimeter at approximately the same time, and since the operator30is in the vicinity of the remote control means35, he/she can easily press a light guard activation button71in order to latch the light guard circuit85to an active state.

This invention includes a configuration of the light guard means27to allow for a common production line configuration that includes a pallets and/or dunnage inserter system95similar to the one illustrated inFIG. 38. When a pallets and/or dunnage inserter system95exist, the operator30has the luxury of not having to be present at the discharge end4or the stacking deck3during any part of the load change cycle56. This is because the pallet51and/or dunnage50can be placed on the inserter system95during the time while the full stack6′ is being built. During the load change cycle56the pallets and/or dunnage inserter system95automatically indexes the pallet51and/or dunnage50during the load ejection cycle56′ in such a way as to properly position the pallet51and/or dunnage50to receive the next full stack6″ to be created. If the light beams20″,20′″ were to cross over the conveying sheet removal system7at the distance D146, the operator30would be required at the remote control means35to press a light guard activation button71in order to latch the light guard circuit85to an active state.

FIGS. 38 and 39illustrate the solution to this problem. The light beams20″,20′″ that cross over the conveying sheet removal system7are moved downstream to the distance D246′ which is the distance from the face of the discharge end4of the stacking deck3where the full stack6′ is being built. The distance D246′ is somewhat longer than twice the longest length L91of the full stacks6′ that are planned for production on sheet stacker2. This distance D246′ allows for completed full stack6′ to be transported during the load ejection cycle56′ with its leading edge to stop at approximate location P90using conveying system control means92, which is operably connect to a travel limit control means38. Since the complete full stack6′ is still within the light guard perimeter21, the latch light guard circuit85may remain active and the deck down cycle56″ can be completed without the need for operator30attention.

Upon completion of the deck down cycle56″, the next new full stack6″ begins to be built, at which point, the operator has two options for transporting the complete full stack6′ from inside to outside the light guard perimeter21. The conveying system control means92may simply wait for the operator30to press a load release control39at which point the conveying system control means92which is operably connected to a travel limit control means38releases new full stack6′ for transport downstream. Alternatively, the conveying system control means92may be set to a mode that allows the light guarded LCS system control means15″,15′″ to operably signal the conveying system control means92when the deck down cycle56″ has been completed which then will automatically release new full stack6′ for transport downstream.

FIG. 39illustrates in schematic form the functional relationship of conveying system control means92. There are many well known ways to implement travel limit control means38such that complete full stack6′ stops at location P90. One common method is to apply a braking section to the rollers integrated into the conveying sheet removal system7. Typically, a feedback sensor, full stack at position P sensor93is connected to conveying system control means92. The two optional release signals are also shown inFIG. 39. The one coming from the manual activated load release control39and the other from light guarded LCS system control means15″,15′″, which can monitor the position of the stacking deck3. In the preferred embodiment, the conveying system control means92would include a selectable mode setting to allow the operator30to change release modes depending on the current orders being run in production.

A similar but alternate configuration of the system shown inFIG. 38is shown inFIG. 40. The light beams20″,20′″ that cross over the conveying sheet removal system7are moved downstream to the distance D346″ which is the distance from the face of the discharge end4of the stacking deck3where the full stack6′ is being built. The distance D346″ is substantially longer than the longest length L91of the full stacks6′,6″,6′″ that are planned for production on sheet stacker2. !This distance D346″ allows a plurality of completed full stack6′,6″ to be transported and stored within the light guard perimeter21making sure the leading leading edge of full stack6′!stops at approximate location P90using conveying system control means92, which is operably connected to a travel limit control means38. Since the complete full stacks6′,6″ are still within the light guard perimeter21, the latch light guard circuit85may remain active and the deck down cycle56″ can be completed multiple times without the need for operator30attention. This is advantageous in production line configurations where there are no pallets51and/or dunnage50required under full stacks6′,6″.