Rotary cutting dies are used to cut and score sheets of corrugated board to produce a die cut product that can be manipulated into boxes. Rotary cutting dies typically include a curved die board that is configured to mount on a die cylinder. When used, the die cylinder and die board are mounted adjacent an anvil and a nip is defined between the cylinder and the anvil. Sheets of corrugated board are fed into and through the nip and, in the process, the sheet of corrugated board is cut and scored to form the die cut product. Die boards commonly include product and scrap cutting blades, scoring rules, trim and scrap strippers and product ejectors for separating the die cut product from the cutting die.
A common problem with rotary cutting dies that operate on corrugated board is that of controlling the pressure exerted against the corrugated board by the product ejectors. If the pressure is too great, the die cut product is damaged. That is, if the pressure is too great, the flutes are crushed. This makes the resulting boxes weaker and hence the boxes possess less stacking strength and the crushed flutes have a negative impact on the appearance of the product.
On the other hand, if the ejection force exerted by the product ejectors is too low, then this will impact the separation of the die cut product from the cutting die during the die cutting operation. That is, if the force is insufficient to dislodge or remove the cut die product from the cutting die, it follows that the product will continue with the cutting die and the die cutting operation will be seriously impacted.
One might consider seating the product ejector as deep into an opening in the die board as feasible in order to enhance control over the pressure exerted against the corrugated board by the product ejector. In the regard, one might consider gluing the entire sides of the product ejector to the wall of the opening in the die board. This, however, leads to even more problems. This can be referred to as a product ejector shear problem. When the entire product ejector (elastomer) is adhered to the die board, the repeated compressions and releasing creates shear forces and causes the product ejector to tear loose. Also, when the entire product ejector is adhered into the opening in the die board, it is possible for adhesive to wick into the main body and once in the main body the adhesive hardens and this can contribute to a cutting or tearing action that damages the product ejector.
USPTO Backgrounds
USPTO Backgrounds