Automated destacking device and method

An automated destacking device is used to remove a single flat item or sheet from the top of a stack, and to then transport the item from the stack so that it may be used in an assembly line, manufacturing process, or the like. The stacked items are placed into a hopper, and an elevator drives the hopper upwardly until the top item in the stack contacts the underside of a horizontally movable carriage. The underside of the carriage includes an adhesive element, which engages the top item, and then the carriage moves in a horizontal direction away from the stack, carrying the top item from the stack to a position separately from the stack.

BACKGROUND OF THE INVENTION

The present invention relates generally to devices used to individually remove a flat item from a stack during a manufacturing process. More specifically, the present invention is directed to a robotic device that is capable of receiving a stack of flat items, removing each item individually from the stack, and feeding the individual item into a manufacturing process in a continuous cyclical manner.

Heretofore, a number of different types of devices have been developed for the purpose of removing a single flat sheet of material from a stack, and feeding each individual sheet into a manufacturing or printing process, or an assembly line. Most commonly, such destacking sheet feeders may be found in printers and copiers, where a stack of paper is loaded into a hopper, and the printer or copier feeds a single sheet at a time into the printing process, typically using mechanized rollers to remove the top sheet from the stack for printing.

Other types of destackers and sheet feeders have been developed, as well. U.S. Pat. No. 4,345,752 is directed to a sheet transport apparatus that picks up and transports a topmost sheet of a stack of sheets in a one-by-one manner by using a rotating suction drum to pick up the sheets. U.S. Pat. No. 5,494,398 discloses a device for unstacking tortillas and conveying them to a moving belt by using a rotating cylinder having holes in its surface through which suction acts on the tortillas. Other devices, similarly to printers and copiers, simply use rollers to frictionally engage one sheet or flat item at a time and slide it from the top of the stack.

One problem associated with various destacking devices is that it is difficult for the device to consistently move a single sheet, and sometimes multiple sheets are moved together, when the intent is to move one sheet at a time. Another problem is that rollers used to frictionally engage the stacked items sometimes wear down, creating a lower coefficient of friction, which causes the rollers to simply rotate against the item without forcing any movement thereof. Additionally, the use of suction drums and other suction devices requires the use of a vacuum system, which is a costly component and uses significant amounts of electricity to run. Thus, it would be desirable to provide a destacking device that overcomes these problems associated with the prior art, is inexpensive to manufacture, and consistently transports a single sheet or item at a time in a reliable manner.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a destacking device includes a hopper for receiving a stack of flat items, a servo-driven elevator attached to the hopper for raising and lowering the stack of items, a rotary actuator with a pivoting arm that is used to transport a single sheet at a time from the top of the stack, a laser photosensor, and a programmable logic control (PLC). The PLC is programmed to actuate the movement of the various components. An operator manually loads a stack of items into the hopper. The pivoting arm is attached to a shuttle or carriage that moves horizontally between a first position and a second position along a pair of guide rods. The carriage includes, in a preferred embodiment, a pair of needle rings that rotate in a single direction only, for engaging the stacked items, as well as several contact plates having a tacky adhesive such as double sided adhesive tape, on an underside thereof. When the destacking device begins its cycle, the elevator is raised to an upper position until the top of the stack is sensed by the photosensor. In one embodiment, when the photosensor detects the top of the stack, then the elevator raises the stack to a slightly higher, predetermined level, and then the rotary actuator moves the pivoting arm so that the underside of the contact plates comes into contact with the top sheet. The tacky adhesive on the underside of the contact plates engages the top sheet, and the bottom of the needle rings also engages the sheet, and the elevator drops downwardly, leaving the top sheet attached to the contact plates. The pivoting arm then moves the carriage laterally, and the needle rings rotate in the same lateral direction as the motion of the carriage in order to remove the sheet from the underside of the contact plates, thus making the single sheet available to be transported to the next phase of the assembly line, manufacturing process, or the like. Then, the pivoting arm moves the carriage back to the first position, so that it is ready to receive the next top sheet from the stack, thus completing the cycle.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes, in a first embodiment, an automated destacking device10that is used to remove a single flat item or sheet from the top of a stack, and to then transport the item from the stack so that it may be used in an assembly line, manufacturing process, or the like. Specifically, the automated destacking device10may be used in the automotive industry for the small, rectangular textile sheets that are used to connect an airbag panel to the airbag unit within the dashboard of an automobile. It should be understood, however, that this automated destacking device may be employed for any such operation where a stack of flat articles must be destacked so that the individual items may be removed from the stack for further processing or manufacturing activities.

As shown inFIG. 1, the destacker10includes a frame member12to support the various components, and a hopper14for receiving a stack of flat articles, including a hinged door16that may be secured in a closed position when the stack is in position within the hopper. A servo-driven elevator18is attached to frame12and the hopper14for raising and lowering the hopper14and the stack in a vertical direction. The destacker10also includes, at a top portion of the frame12, a rotary actuator20with a pivoting arm22attached to a shuttle or carriage24, and a photosensor (not shown) for sensing when the stack is raised to a certain level. The pivoting arm22is driven by the rotary actuator20, and the carriage24is positioned on a pair of horizontally disposed guide rods28, so that the carriage24may move horizontally back and forth between a first and a second position. In one embodiment, the carriage24defines a pair of horizontal holes30, and the guide rods28slide through the holes30, allowing the carriage24to move in a horizontal direction along the guide rods28. The carriage24further includes a plurality of contact plates (not shown) on a bottom portion thereof, and each contact plate may include a tacky adhesive, such as double-sided adhesive tape on its underside surface. The contact plates are attached to the carriage24via a small compressed air cylinder34, springs, or the like, so that the contact plates may be compressed slightly toward the underside of the carriage24, and tend to spring back to the decompressed position when no pressure is applied thereto. When the top sheet from the stack comes into contact with the adhesive on the underside of the contact plates, the sheet sticks to the tape, which allows the carriage24to transport only the top sheet, rather than the top two or three sheets. The carriage24also includes a shaft36having, in a preferred embodiment, a pair of needle rings38that may freely rotate about the shaft36in a single direction, but are locked and do not spin in an opposite direction (accomplished in one embodiment by using Sprague uni-directional bearings).

A programmable logic control (PLC)40is operationally connected to the elevator18, the rotary acutator20and the motor(s)42, and may be programmed and adjusted to make the process flow in a smooth and timely manner, as desired. Additionally, the PLC40is operationally connected to the photosensor so that the photosensor provides information to the PLC40, and the PLC40processes that information by generating an output signal as a result of the triggering of the photosensor. In a preferred embodiment, the PLC40includes a display44and a keyboard, touchscreen, or some other means for data entry, such as a data jack to receive input for programming and adjustment purposes. One preferred PLC is a Siemens product, model number S7-300. The PLC serves as the brain of the unit, and may be programmed to operate the components in any desired manner.

The automated destacking device10operates in a cyclical manner. An operator manually inserts a stack of the textile sheets into the hopper14, and engages the destacker10to begin its cycle. The elevator18raises the hopper14in an upward direction until the top of the stack triggers the photosensor, which is aimed across the elevator shaft in a set position. In a preferred embodiment, when the photosensor is triggered by the top of the stack, that information is sent to the PLC40, which then sends an instruction to the elevator18to rise slightly further to a predetermined level. This predetermined level is calculated so that the top sheet of the stack comes into contact with the contact plates and the bottom portion of the needle rings38, so that the contact plates are slightly compressed toward the underside of the carriage24, thereby ensuring sufficient contact and pressure between the top sheet and the tacky adhesive to remove the top sheet from the stack. The elevator18is then lowered, together with the stack, leaving the top sheet stuck to the bottom of the contact plates and engaged with the bottom portion of the needle rings38. Then, the PLC40sends a signal to the rotary actuator20, which actuates the pivoting arm22and causes the carriage24to slide in a lateral, horizontal direction along the guide rods28from a first position to a second position. Upon reaching the second position, the carriage24stops, and the single sheet is removed from the underside of the carriage24, either manually or robotically. As the top sheet is removed, the needle rings38, which are still engaged with the top sheet, spin about the shaft36in the direction necessary for removal, but are prevented from spinning in the opposite direction, as set forth above. Then, the PLC40signals the rotary actuator20to rotate in the opposed direction, causing the pivoting arm22to rotate and the carriage24to slide back along the guide rods28from the second position to the first position, where the next cycle may begin.

It is contemplated that other components may be substituted for the components set forth herein, in order to perform the same tasks. For instance, it is contemplated that the photosensor may be replaced by another type of proximity device, and that the elevator mechanism may be driven by electric, hydraulic, or pneumatic means.

The automated destacking device10is compact and lightweight, so that it may easily be positioned as desired within an assembly line or on a factory floor. It is simple to operate and maintain, and may be manufactured at relatively low cost. The PLC40offers the ability to reprogram or adjust the unit with respect to cyclical speed, sequencing, positioning, timing and direction of the various moving components.

Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein. All features disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.