Abstract:
A device for transporting printed sheets includes a first traction element and a support attached to the first traction element for movement therewith in a transport direction. The printed sheets are deposited in adjacent stacks on the support. Windshield elements are arranged respectively between adjacent stacks of sheets deposited on the support for holding down the deposited printed sheets with a use of environmental air.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a device for transporting printed sheets, in particular in a gathering and stitching machine or an assembling machine having a traction element to which there is connected a saddle-shaped support or an approximately level support on which the printed sheets are successively deposited in adjacent stacks, either straddling the saddle-shaped support or forming a piles of sheets on the level support, and particularly to such a device having a mechanism for holding down the deposited printed sheets. 
     Gathering and stitching, as well as assembling machines, are well known. European application EP-A-0 681 923, for example, shows a gathering and stitching machine with a device of the generic type, wherein a traction element is provided with a saddle-shaped support which transports the printed sheets that are successively deposited thereon in a straddling manner by distributors. In assembling machines the support is level and moves in a horizontal conveying direction. The traction element in this case can be an endlessly circulating belt. In order to increase the capacity of gathering and stitching machines and assembling machines, it has long been a desire to transport the printed sheets in the aforementioned device at higher speeds than has been possible so far. The difficulty here is that, in particular, thin and light weight printed sheets will lift off, fly away or the edges will be folded over, which leads to interruptions in the continued processing of the printed sheets. It is a known practice to exert control over the printed sheets during the transport by aiming a blast of air at them, weighing them down with brake springs or holding them down, for example with brushes. However, blast air is hard to control and can have disadvantageous effects in addition to being expensive. Hold-down devices have the essential disadvantage that access to the printed sheets is limited during transport and the known hold-down devices in each case must be adjusted exactly to the respective products. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a device for transporting printed sheets that avoids the above-mentioned difficulties, including interruptions due to printed sheets flying away and thus permits operation at higher speed. 
     The above and other objects are accomplished according to the invention by the provision of a device for transporting printed sheets, comprising: a first traction element arranged for being driven in a transport direction; a support attached to the first traction element for movement with the first traction element in the transport direction and on which the printed sheets are deposited in adjacent stacks; and windshield elements arranged respectively between adjacent stacks of sheets deposited on the support for holding down the deposited printed sheets with a use of environmental air. 
     For a device of the generic type, the solution according to the invention is that the aforementioned mechanism for holding down the printed sheets comprises windshield elements that move along with the printed sheets and are designed to keep away or carry along environmental air in the region of the printed sheets. These windshield elements are preferably arranged such that one element is arranged between each pair of adjacent printed sheet stacks or piles. 
     Such windshield elements permit a start-up with a higher acceleration since a start-up whirl or eddy develops through the windshield elements, which press the sheets against their support and thus also hold down the sheets. Such windshield elements restrict access to the printed sheets only insignificantly and are easily maintained. 
     The windshield elements can be fastened directly to the traction element. For a modification of the invention, the windshield elements are attached to another traction element. The other traction element may be, for example, an endlessly circulating belt. According to another modification of the invention, the windshield elements have, at least in part, a flexible or elastic design, that can yield in case of blockages. 
     According to another modification based of the invention, the windshield elements are fastened so that they can be removed or adjusted, in particular, folded down or swiveled, which permits an optimum adaptation of these elements to the printed product format. This is achieved in that the windshield elements are attached to the traction element such that they can be lowered and/or moved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two exemplary embodiments of the invention are explained in more detail in the following with the aid of the drawing. 
     FIG. 1 is a perspective view of a diagram of a segment of the inventive device which is intended for a gathering and stitching machine. 
     FIG. 2 is a perspective view of a diagram of a segment of another embodiment of the device for use with an assembling machine. 
     FIG. 3 is a side elevation of a diagram of a segment of the device according to FIG. 2 for explaining the principles of the invention. 
     FIG. 4 is a perspective view of a segment of the invention device as shown in FIG. 1 and depicting an alternative location for attachment of the windshield elements. 
     FIG. 5 is a perspective view of a segment of the inventive device as shown in FIG. 1 and depicting still another alternative location for attachment of the windshield elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is shows a diagram of a segment 1 of a gathering section 2 for a gathering and stitching machine (not shown). The basic layout of such a gathering section is disclosed in the above-mentioned European patent application EP-A-0 681 923, the disclosure of which is incorporated herein by reference. The gathering section 2 has a traction element 3, which is preferably a known link roller chain, which has carriers 6 that are adjusted to the operating cycle of the gathering and stitching machine and are attached to it. These carriers 6 receive printed sheets 5 in a straddling manner from feeders, which are not shown here. Traction element 3 comprises an uninterrupted saddle-shaped support 4 with an upper edge 4a, on which printed sheets 5 that are folded along a line 5a loosely rest. Printed sheets 5 have a lower edge 5b that is parallel to folding line 5a, of which only the front lower edge is visible here. Printed sheets 5 are held in the shown position only by their own weight. Traction element 3 has a transporting direction indicated by an arrow 9 and thus moves in FIG. 1 from right to left. 
     Two windshield elements 8 are arranged on opposite sides of the saddle-shaped support 4, respectively, between adjacent sheets 5, or stacks of such printed sheets, wherein only the front windshield elements are visible in FIG. 1. Windshield elements not visible in FIG. 1 are positioned in a mirror-inverted arrangement on the here not visible rear side of gathering section 2. Windshield elements 8 are moved along synchronously in the direction of arrow 9 during the transport of printed sheets 5. The shown distances between windshield elements 8 and the neighboring printed products 5 thus are retained during transport. As depicted in FIGS. 4 and 5, windshield elements 8 may be attached to the traction element 3 and/or the carriers 6. Alternatively, windshield element 8 are moved with an additional traction element 7, comprising two endlessly circulating belts 7c and 7d that face each other. These belts 7d and 7c are preferably clocked such that they move synchronously with traction element 3. Belts 7d and 7c have openings 7a at uniform distances via which they can be driven by a drive mechanism which is not shown. Suitable drives are known per se and do not have to be discussed here in detailed. 
     Windshield elements 8 are respectively provided with a fastening component 8a, which is inserted into a vertical slot 7b of belt 7c or 7d. Windshield elements 8 are preferably fastened so that they can be lowered as well as vertically displaced. It is also possible to have a fastener that permits a folding down or swiveling of windshield elements. Windshield elements 8 preferably are composed of a flexible or elastic plastic and are plate-shaped as can be seen. Windshield elements 8 extend approximately vertically downward and project at an approximate right angle from the outside of belt 7c or 7d, respectively. On their bottom, windshield elements 8 project somewhat over the lower edge 5b of printed sheets 5, however, this is not imperative. With this, the lower frontal edge 5b of each printed sheet 5 in particular is on the leeward side of a windshield element 8. 
     FIGS. 2 and 3 show segments of an assembling section 11 for an assembling machine 10 that is known per se. Sheet piles 13 containing a plurality of printed sheets 14 are transported in the direction of arrow 16. Windshield elements 15 that correspond to windshield elements 8 are here attached to a traction element 12, which can be an endlessly circulating belt. Windshield elements 15 are respectively arranged between adjacent printed sheets piles 13. 
     The effect of windshield elements 8 shown in FIGS. 1, 4 and 5 and windshield elements 15 shown in FIGS. 2 and 3 is explained in more detail in the following, with particular reference being made to FIG. 3. As can be seen, each windshield element 15 projects somewhat over the top printed sheet 14a of a respective one of the printed sheet piles. During a start-up of traction element 12, sheet piles 13 are on principle subjected to a driving wind as a result of resting environmental air. This wind causes a whirl or eddy 17 behind each windshield element 15, which exerts a hold-down pressure in the direction of arrow 18 onto upper sheet 14a. The same hold down effect occurs with respect to sheet 5 in FIGS. 1, 4 and 5. As a result of this, the total sheet pile 13 is held down against the supporting surface 12a of traction element 12. Thus, a flying away of the sheet or the bending of an edge is avoided, even with a strong acceleration. Once a constant transporting speed is reached following start-up, windshield elements 15 or 8 cause the environmental air above the sheet pile 13 or the printed sheet 5 to be carried along. As a result of this, the printed sheets are subjected much less to the driving wind, and correspondingly higher transporting speeds can be used. 
     The invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and the invention, therefore, as defined in the appended claims is intended to cover all such changes and modifications as fall within the true spirit of the invention.