Optimizing Window Patchers Performance

With the growing demand for transparent features in packaging, window patchers in folding carton companies are busier than ever. To optimize every factor in operations, converters turn to intelligent window patching machines that help them reduce material waste (both carton blanks and transparent substrate and glue), energy usage, labor costs, changeover time and downtime due to repairs.

WP Master Window Patcher from Heiber + SchröderWindow patchers are capable of gluing:

  • regular film windows
  • folding boxes with liner
  • shaped, perforated, full or intermittently cut windows
  • lengthwise perforated windows
  • folding boxes with liner
  • pre-sealed inner tubes
  • creased windows (length wise)
  • shaped die cuts
  • pre-cut shaped windows feeding from a pile.

Typical folding cartons that take advantage of window patchers are donut boxes, paper tissue boxes, high-end cosmetics, candy boxes, pasta boxes and toy boxes, just to name a few.

Window Substrates

The windows are made of plastic films, like cellulose acetate, PP, PVC or PET. Should the film need to extend to two panels, a crease line helps it bend appropriately. The window is cut in the previous step (cutting and creasing) and the window patcher applies the glue in the reverse side of the carton. The blanks move towards the film cutting section, that transfers it to the exact place where the glued window borders are. Vacuum suction helps keep all pieces in place and alignment during the process.


Folding cartons with windows have the opportunity to offer direct view of the contents, promoting impulse purchases. Consistent with the trend to make "healthy" and "fresh" appearance evident, windows are ideal to help the consumer judge the product's quality. As the packaging will be structurally weakened by the openings, the material must be evaluated to withstand them without deforming.

Smart Window Patchers in Action

The first stage in the process is feeding the carton blanks. They come in different sizes and the H+S timed-belt feeder can fit an enormous variety of carton blank styles, working in 3 standard and one optional modes. To reduce changeover time, make-ready can be done through the teach-in function, that learns from the carton lengths and is subsequently controlled electronically. No need for cams or dimensions! It can be done in under a minute.

Heiber + Schröder window patchers also have a digital panel where blank length, blank width, window length, and position can be input. The system is fully guided, step by step, to minimize errors. Then all components are automatically set in the running direction, as well as all sensors.

WPS 1100 Window Patcher from Heiber + SchröderFriction level in the blank stack varies from beginning to end. Therefore these window patchers feature automatic friction control at every speed level. As a result, cartons are not fed out of sync, skewed or two at a time. This reduces waste and make-ready time. Conveyor chains can be adjusted by quick change driver blocks for precise positioning and spindles in the cross direction. To facilitate setup, top guide bars can be raised pneumatically by a simple push-button. The side bars can also be positioned by spindles.

From here, rubber rollers transfer the blanks to the mono-belt, which keeps consistent positioning using vacuum suction. Heiber + Schröder window patchers have a built-in maintenance-free vacuum system (produced by special fans), with the advantage that there is no need for vacuum channels, vacuum tubes or additional filters. It is the most precise positioning system in the market.

Window Gluing Station

Moving to the gluing station, the system works by fixed doctor blades with movable side scrapers. They are fully splash guarded and laterally limited. A stencil cylinder with precise height control applies the glue. As it functions with a separate drive mechanism, it is independent of the window patcher and can continue working during machine standstill. It can be adjusted during operation, modifying the position relative to the carton blanks: in the running direction, by a stepless motorized mechanism, and in the cross direction, via hand wheel spindles. It is automatically lowered at startup and lifted when the system is stopped.

Likewise, if during operation, one or more blanks are missing, the suction belt is automatically lowered from the stencil cylinder to prevent the glue from soling the anvil disks.

To save time, the gluing stencils can be set up on a special table outside of the window patcher. Then they are glued onto a stencil blanket. When in production, it is mounted on the gluing cylinder, and when not in used, it can be removed and stored for future runs.

For quick changeovers, Heiber + Schröder window patchers include a cleaning system that removes any glue residue under 3 minutes. The gluing unit can be extracted from the machine by lateral, easy-running guides.

WP 600 Speedliner Window Patcher from Heiber + Schröder

Foil and Lining Material Station

The substrate material is placed on an unwind shaft with clamping cones. After passing through the web infeed, they are cut with a rotary cross cutter on the application cylinder. Both of them have suction and air blower controls that allow the window or lining material to remain perfectly positioned along the way. The cut-off length can even be digitally adjusted during operation.

The window/lining material can be modified to match the exact position of the carton blanks, without stopping the window patcher, via stepless adjustment servo motor. This saves considerable time.

Beyond unwind with clamp cones, Heiber + Schröder window patchers can use pneumatic lifters or custom semi or fully automatic unwind systems.

Delivery Table

The window patched folding cartons arrive at the delivery table via conveyor belts, which have a steplessly adjustable separate drive so that shingling can be digitally setup. The delivery table is movable, so the operator has easy access to the knife station.

Energy Efficiency and Speed

Heiber + Schröder window patchers are 100% servo-driven and maintenance-free. In line with the growing demand for energy-efficient mechanisms,  servo drives are optimized to reduce power consumption and perform 30% faster than comparable competing machines.

Food Contact Safety

Complying with all latest regulations, all parts which may be in contact with film or carton inner side conform to food packaging production standards.

Diagnostics and Support

When doubts or problems arise, it is crucial to have any necessary assistance immediately accessible. No need to explain how costly downtimes are. These window patchers have an onboard video training program that walks the operator through all standard operations. The same system is used for the operator's manual, help and troubleshooting. The regular maintenance program is also included in the support system.

An integrated diagnostics program allows H+S window patchers to adjust drives, sensors and motors. If the issue exceeds standard training and help materials, the window patchers include a camera to interact with H+S service staff. Some diagnostics and software upgrades can also be done remotely via built-in modem link to H+S servers.

To make service requests simpler, spare parts are completely visualized in 3D in the operator's panel.

Time Saving, Statistical and Error Prevention Features

To save time for repeating jobs, all setup data can be stored with the product name, even including photos and comment text.

Heiber + Schröder window patchers come with a digital speed counter, and production counters with photocells, being able to generate, store and export production statistics for later analysis.

To reduce unnecessary machine stops and material waste, there is a blank positioning control behind the feeder, so the chain conveyor unit does not get jammed. Similarly, there is another jam control in the blank delivery section.

Additional controls can be installed upon request, such as detectors for missing film or lining on the blanks, or end of reel controls.

Automatic Reel Change

The optional H+S splicers allow window patchers to continue running during reel changes, thereby eliminating standstill times. Automatic brakes and dancer rollers guarantee constant tension during production and reel changes.

Transfer Components

In a constant search for more efficient handling of carton blanks to streamline operations, H+S offers a wide variety of transfer components to deliver them to and from the window patchers.

At the beginning of the production chain, the load conveyor assists in the manual loading of piles. The transfer conveyor automatically transports the piles with the ability to buffer batches. The pile infeed automatically transports the piles into the window patcher pre-feeder. 
The pre-feeder assists in supplying even level blanks in large volume runs, reducing operator handling. Time-consuming tasks like turning cartons upside down can be done with the pile turner.

Once in the production run, additional components simplify operations, such as the ability to merge two lanes into one, or splitting one lane into two, make 90° turns or rotate carton blank piles.

Specialty Accessories for Window Patchers

Intermittently Operating Length Slitter

The intermittently operating length slitter lifts the knife holder with cam disks at specific intervals, allowing cuts measuring between 31 to 81% of the material length. The cutting length can be extended to the complete window with special configuration.

This accessory allows window patchers to continuously slit, perforate and crease the window film. It consists of a cutting knife with holder, also called blade, a counter slitting wheel made of steel, and a counter reel made of rubber for creasing.

Lifting Die Cutter for Window Cutting with Hot Creasing

Heiber + Schröder window patchers can crease the film lengthwise or crosswise, suing a lifting die cutter with hot creasing. The process is as follows: after unwinding, the film passes near heated bars and the discs crease it. Both the discs and the heating bars ad adjustable across the film web by use of spindles, even during operation. The male and female cutting die can be moved crosswise and lengthwise as well.

The whole cutting station can be removed laterally for a quick exchange or to adjust the dies. To ensure constant tension during die cutting, a pair of dance rollers are placed prior and after the station.

Automatic Stacker

After windows are patched and shingled in the delivery table, the automatic stacker can form pre-counted piles, working in two to three lanes.

Advanced Window Patchers: Liquid Proof Packing

Leak Proof Window Patcher WPH from Heiber+ SchröderWhen a window is required to display liquid level as a scale, or simply to exhibit the contents, a special window patcher is required.

Heiber + Schröder Leak Proof Window Patchers can work with carton or multi-layer substrates with sealable inner coating, delivering up to 42,000 finished pieces per hour. The sealing format is adaptable to the desired application.