This invention relates in general to folding apparatus for paper products, and more specifically to a high speed folder which can fold the product along two parallel lines (a "C" or "delta" fold) with the capability of adjusting the distance between the fold lines.
Automatic folding machines are used both in binderies to produce printed publications and in industries where it is necessary to fold cardboard. In cardboard folding, it is common to use blanks that are pre-creased along the intended fold line. Also, there is usually no concern with whether the folding operation smears printed ink on the cardboard. With paper folding, there is normally no pre-crease, the paper may be recently printed so that the ink has not set, and because of the flexibility of the paper, it is much more difficult to control, particularly at high speeds, than cardboard.
An important use for paper folding machines is in the production of envelope "inserts" for direct mail marketing. Common paper folding machines that operate on or off press, however, operating at speeds that are relatively slow compared to the line speed of the printing press. The folding process is therefore often a limiting factor on the efficiency of the entire printing and finishing process. Currently off press finishing of inserts is most common. Typical speeds for such off press folding machines are 5,000-7,000 pieces per hour.
Usually in known folding machines, folds are made by mechanical means and twisted belts that engage the paper. In other paper folding machines, and in many cardboard folding machines, the fold is made by driving the paper against a stationary forming member. In either case, significant problems heretofore have been that these machines are relatively slow, and there is sliding contacts between the paper and components of the machine that engage the paper. This sliding contact is very undesirable for printed paper products because it tends to mark the printed surface. This is a particularly difficult problem if the printed matter is fed directly from a printing press and the ink may not have fully dried. Thus, known folding machines are not suited for integration with the printing apparatus so that the folding can be accomplished as the material is printed and leaves the press.
Besides having a high throughput rate and an avoidance of smearing the printed material, a commercially acceptable folding machine should fold a product either in half or, for letter size inserts, in thirds (a C or delta fold) If it folds the product twice ideally it should do so without using two machines or running the same product through the same machine twice. In known folding machines, for example, it is usually necessary to double run a letter size product. A commercially acceptable folding machine should also operate reliably, maintain a proper alignment of the paper product during the folding, and accept a variety of product sizes and thicknesses, including multiple ply papers that have already been folded at least once.
Applicants' U.S. Pat. No. 4,588,393 describes an apparatus and method for the high-speed folding off freshly printed paper products that are not pre-creased. However, in the '393 apparatus the folding occurs at fixed locations. The apparatus therefore cannot vary the locations of the fold for products of the same size or accommodate significant variations in the size of the paper products being folded. To date, applicants are not aware of any paper folding machine which can produce a double running C-fold and can vary the spacing between the fold lines.
Because the inherent susceptibility of such an apparatus to paper jams due, at least in part, to misalignments of the paper products being processed, it is important to align the paper while it traverses the apparatus to produce a fold or folds that are "square", that is, where the edges of the folded paper align with one another. To control alignment, the '393 apparatus also discloses an arrangement for adjusting the skew of the product as it is fed, a pair of manually adjustable rip rollers located at the sides of the product as it enters the apparatus. In practice, however, It has proven difficult to make and maintain the correct degree of adjustment during operation. Also, the '393 apparatus is organized about a continuous central frame that acts as a primary guide for the alignment of the various assemblies of the apparatus, and therefore the alignment of the high speed (up to 50,000-60,000 pieces per hour) stream of products in the apparatus. As noted above, While this construction produces a Workable level of alignment, it does so With the restriction that the location of the folds is fixed
It is therefore a principal object of the invention to provide a folding apparatus for paper products, including folded paper sheet products ("signatures"), particularly a high speed folder for printed products, which can C-fold the products at two parallel fold lines with a variable spacing between the fold lines.
Another principal object is to provide a folding apparatus with the foregoing advantages that can readily and reliably adjust the angular orientation of the fold line with respect to the product.
A further object is to provide a folding apparatus formed of a line of several self-contained units to provide interchangeability of components, and flexibility in sequencing of operations.
Yet another object is to provide a folding apparatus with the foregoing advantages which is comparatively mechanically simple, is readily adjusted, and has a favorable cost of manufacture as compared to conventional paper folding machines.