Abstract:
A driver element is provided for an endless saddle chain in a saddle line, wherein the saddle chain includes saddle segments and receiver segments, with the saddle segments defining a substantially saddle-shaped roof of the saddle chain. The driver element is arranged to be detachably fastened without tools to a respective one of the receiver segments. The driver element includes two driving flaps that are pre-tensioned against each other.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a driving element for an endless saddle chain, especially in the processing of printed matter, and a corresponding endless saddle chain. 
   2. Description of the Related Art 
   Saddle chains and drivers are found in saddle stitchers, where signatures are placed on and along the saddle chain by feeders and transported by the drivers to a stitching station. There, the signatures lying one on top of the other are stitched and then cut at three sides in a trimmer so as to produce a finished print product. The signatures used in saddle stitchers are folded sheets, having a single or several folds, that are placed on the saddle-shaped chain along the at least one fold. 
   Such saddle stitchers with corresponding saddle chains and driver components are marketed, e.g., by Heidelberger Druckmaschinen AG, under the type designation ST300, ST350 or ST400. Other configurations are known, e.g., European Patent EP 0 881 180 B1. Here, the driving elements are fixed to the ridge of the saddle chain, so that the saddle chain has a particularly narrow configuration. However, this has a drawback in that bearing blades arranged above the ridge must have a proper spacing from the feeders. Another known saddle stitcher is disclosed in European Patent Application EP 1 074 495 A1. Here, the driver elements are movably secured to the saddle chain so that they can swivel from a substantially vertical mounting position to a substantially horizontal mounting position. 
   As in other machines, the productivity of the machine does not depend primarily on the operating speed, but rather, on how many products can be processed with the machine in a specific amount of time. For saddle stitchers, one of the upper limits is the speed at which the saddle chain is driven, which is also associated with aerodynamic factors that make it difficult to transport the signatures lying loosely one on top of another on the saddle chain at higher speeds. In order to increase the number of products per unit of time and, thus, the productivity of the saddle stitcher without increasing the speed of the saddle chain, the chain pitch, i.e., the distance between the drivers on the saddle chain, is adjusted to the product size. Since a shorter spacing between the drivers on the saddle chain is sufficient for smaller products, by appropriately reducing this spacing, more products can be placed on the saddle chain per unit of time which increases the productivity. The problem with this in the prior art is that changing the chain pitch, if possible, is a costly operation, which in turn requires lengthy down time between jobs, which again reduces the productivity. Therefore, in some saddle stitchers, the saddle chain has saddle segments and receiver segments, and driver elements can be inserted in the receiver segments. The driver elements are polyurethane components which, due to their elasticity, remain form-fitted in the receiver segments and can be removed without the use of tools in order to change the pitch of the saddle chain. In practice, however, it has not always been possible to remove the driver elements from the receiver segments easily without the use of tools, since the driver elements often get jammed because of their configuration, and their removal can also result in damage to the driver elements and the saddle chain. 
   SUMMARY OF THE INVENTION 
   To solve the problems described above, preferred embodiments of the present invention provide driver elements and a corresponding saddle chain which enable a quick, easy, and low-damage method of changing the chain pitch, and thereby increasing the productivity of a saddle stitcher having such a saddle chain with corresponding driver elements. 
   According to a preferred embodiment, drivers include a driver element for an endless saddle chain in a saddle line. The saddle chain includes saddle segments and receiver segments, wherein the saddle segments have a substantially saddle-shaped roof of the saddle chain and the driver element is detachably fastened without tools to a respective receiver segment. The driver element includes two driving flaps, with the driving flaps being pre-tensioned against each other. The pre-tensioning between the driving flaps provides a snap action, resulting in secure and reproducible locking of the driver element in the receiver segment. In this manner, the installing and removing of the driver elements from the saddle chain to change its pitch is performed without the use of tools. Due to this, the refitting time for different chain pitches is drastically reduced and, thus, the productivity is increased. Furthermore, such a toolless refitting is typically rather easy and can be performed by a less talented operator quickly, easily, and without the risk of damaging the device. 
   In one preferred embodiment of the driver element, the two driving flaps protrude at the side from the roof of the saddle chain, and in particular, the two driving flaps extend beyond the ridge of the roof. In this manner, more space remains directly above the ridge of the saddle chain, so that bearing blades arranged above the ridge have a corresponding small spacing from the feeders, and thus, the signatures are more reliably transferred to the saddle chain. Advantageously, the drivers can directly push the signatures from the bearing blade, which is not possible when the drivers are arranged directly on the ridge of the saddle chain. 
   In another preferred embodiment of the driver element, the driving flaps have a common swivel axis, and, in the installed position in the saddle chain, the driving flaps are tensioned against the inner sides of the saddle chain. Furthermore, the driving flaps include an extension that extends the interior of the roof of the saddle chain, and a connection element provided on the extension, with which the driver elements can be detachably connected to the saddle chain. Thus, the driver elements can be easily pressed together at the flaps for inserting into the saddle chain. Due to the common swivel axis, the extension of the flaps extending inside the roof is compressed, e.g., against a spring in a similar to scissors. If the compressed driver element is then relieved of tension in the position inside the roof of the saddle chain, the spring pre-tensions the extensions of the flaps against the inside of the saddle chain. Advantageously, corresponding detent bolts or similar detachable fasteners are engaged at these positions, so that the driver element is securely installed in the saddle chain. A removal of the driver element from the saddle chain is performed by simply pressing the driver flaps together, whereby the locking is released. The corresponding detent elements can either be a portion of the receiver segments provided on the saddle chain or a portion of the driver elements, or a combination of both, as is generally known from the prior art for such detent systems. Furthermore, a clamping mechanism may be used as an alternative to a spring, whether active or passive, such as various other elastic materials. Advantageously, however, these elements are especially simple and user-friendly, low-maintenance, and economical, such as the aforementioned spring, for example. 
   Another preferred embodiment of the present invention provides an endless saddle chain in a saddle line, wherein the saddle chain includes saddle segments and receiver segments. The saddle segments define a substantially saddle-shaped roof of the saddle chain, and on at least one receiver element, a driver element is fastened and removed without the use of tools. 
   In another preferred embodiment of the endless saddle chain, a cover element on at least one receiver segment is fastened and removed without the use of tools, and the cover element is substantially flush with the saddle-shaped roof of the saddle chain. This enables completely covering the saddle chain for different chain pitches in order to reduce the danger of injury and to avoid dirtying the signatures and the saddle chain. Preferably, all receiver segments in which no driver element is installed are covered with such a cover element. The cover piece can be an injection molded component, which can move in the nature of a hinge, i.e., the cover piece has a desired elasticity. 
   Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view through the saddle chain in a side view of a driver element according to a preferred embodiment of the present invention. 
       FIG. 2  is an isometric view of a segment of the saddle chain according to a preferred embodiment of the present invention. 
       FIG. 3  is a chain piece with two different chain pitches. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The endless saddle chain  10  and the driver elements according to a preferred embodiment of the present invention, shown in  FIGS. 1 to 3 , are shown schematically. Additional elements necessary for the operation, such as bearings, drive units, controls, and other elements, which are not relevant to the present invention, are shown only schematically or not at all, since they are known and would hamper an understanding of the present invention. 
   An endless saddle chain  10 , which can be used in a saddle stitcher of the prior art (not shown), includes saddle segments  12  and receiver segments  16 . Chain segments are disposed between the saddle segments  12  and the receiver segments  16 , which are conventional for saddle chains of this kind. The number of chain piece  30  of the endless saddle chain  10  depends primarily on the number of feeders, which place signatures  1  on the saddle chain  10 . 
   As shown in  FIG. 3 , the saddle chain  10  includes identical chain pieces  30  of a length L 3 , where the length L 1  is, for example, 120 cm. The chain piece  30  extends from a chain piece beginning designated by the letter A to a chain piece end designated by the letter E. To clarify the relationship between the chain length L 3  and the lengths L 1 , L 2  of the chain pitch, a reference line with the letter R is indicated, which shows the position of the next driver element  40  along the saddle chain  10 . 
   At desired locations, the chain piece  30  has receiver segments  16 , instead of saddle segments  12 . These are spaced, as shown in  FIG. 3 , such that a first chain pitch length L 1  or a second chain pitch length L 2  is provided, substantially corresponding to an equidistant distance of drivers  40  along the chain piece  30 . In the case of the first chain pitch length L 1 , this provides a chain pitch of four, i.e., a distance between the driver elements  40  of about 30 cm. Thus, with this chain piece  30 , four stacks of signatures  1  can be transported at the same time. With the second chain pitch length L 2 , a chain pitch of three is provided, i.e., a distance between the driver elements  40  of about 40 cm. With this chain piece  30 , three stacks of signatures  1  can be transported at the same time. In addition, a chain pitch of two may be provided, whereby every second driver  40  of the first chain pitch is provided with a cover element  20 , i.e., a distance between the driver elements  40  is about 60 cm, or a chain pitch of one, if only a single driver element is mounted on the chain piece and the other receiver segments  16  are covered with cover elements  20 , so that a distance of around 120 cm is provided between the driver elements  40 . Accordingly, the chain piece shown has, e.g., six receiver segments  16 , being occupied by a driver element  40  or a cover element  20 , depending on the chain pitch. 
   The saddle segments  12  of the saddle chain  10  have a roof  14 , and the saddle segments  12  of the saddle chain  10  in their entirety form a substantially continuous saddle. The signatures  1  are placed on the saddle so that, as the saddle chain  10  moves in the transport direction indicated by the reference symbol T in  FIG. 2 , stacks of signatures  1  are gradually accumulated on the saddle chain  10 . The signatures  1  on the saddle chain  10  are pushed by driver elements  30  at a rear edge. Many feeders have a support blade arranged underneath the opener drums, on which the opened signature  1  is placed, so that the open sides of the signature hang down on either side of the saddle chain  10 . The driving flaps  41 ,  41 ′ then push the stack of signatures from the support blade. A hold-back element may also be provided, which ensures that the signature  1  is pushed by the driving flaps  41 ,  41 ′ from the support blade, and not by friction alone. This is important to the formation of proper print products to the extent that, as a rule, no pushing of the signatures  1  occurs on the saddle chain  10  before the wire stitches are driven in. In this manner, with the driving flaps  41 ,  41 ′ protruding at the side beyond the ridge  11 , while leaving the ridge itself free for a support blade, a very secure transfer from feeder to saddle chain  10  is provided. 
   As shown in  FIG. 1 , the driver element  30  includes two driving flaps  41 ,  41 ′ which have a common swivel point  42  and are mounted so as to pivot. The driving flaps  41 ,  41 ′ project at the sides beyond the roof  14  of the saddle chain  10  and extend above the ridge  11  of the saddle chain  10 . Each driving flap  41 ,  41 ′ includes an extension  43 ,  43 ′ beneath the swivel point, which extends into the receiver segment  16 . A spring  47  is provided between the two legs of the extension  43 ,  43 ′ which clamps the driving flaps  41 ,  41 ′ against each other and furthermore clamps the driving flaps  41 ,  41 ′ against the side wall  17  of the receiver segment  16  when the driver element  40  is inserted into the receiver segment  16 . Openings  18  are provided in the side wall  17  of the receiver segment  16  for installing the driver element  40  into the receiver segment  16 . The driver element  40  includes detent bolts  45 ,  45 ′ which correspond to the openings  18 , and which engage these openings  18  when the driver element  40  is installed. 
   Detents are provided in a cover element  20  which correspond to the openings  18  in the side wall  17  of the receiver segment  16 , and which can be inserted in place of the driver element  40  into the receiver segment  16  in order to create a continuous roof  14  for signatures  1  on the saddle chain  10 . The cover element  20  is, for example, a plastic injection molded piece, having enough elasticity to produce a hinge action, so that it can be easily removed from the receiver segment  16 . 
   The chain pitch is changed as described below. First, the desired chain pitch is determined, e.g., as a function of the dimensions of the signatures  1 . Then, in the appropriate locations, the cover element  20  is removed by pressing together and lifting the cover element  20  out from the corresponding receiver segments  16 . Next, the driving flaps  41 ,  41 ′ of a driver element  40  are pressed together, whereby the extensions  43 ,  43 ′ are pressed together against the spring  47 , such that the driver element  40  is inserted between the side walls  17  of a receiver segment  16  and positioned with the detent bolts  45 ,  45 ′ in front of the openings  18  of the side wall  17 . Now, as soon as the driving flaps  41 ,  41 ′ are released, the detent bolts  45 ,  45 ′ lock in the openings  18  of the side wall  17  and the driver element  40  is secured to the receiver segment  16 . Loosening of the driver element  40  from the receiver segment  16  of the saddle chain  10  is performed in the reverse sequence. 
   Advantageously, the receiver segments  16  are marked externally in such a manner, by their shape, an inscription, or a color code, for example, that it is easy to determine which of the receiver segments  16  of the saddle chain  10  need to be replaced to achieve a certain chain pitch. 
   Other chain pitches are also possible by appropriate arrangement of receiver segments  16  between the saddle segments  12  of the saddle chain. 
   The present invention has been explained with respect to a saddle stitcher with saddle-shaped support. However, other saddle lines, such as a saddle canal, in which not only folded sheets, but also unfolded sheets can be accommodated, may be outfitted with a saddle chain according to preferred embodiments of the present invention, and this saddle chain  10  will then include regular segments  12  and receiver segments  16  with optional cover elements  20  or driving elements  40 . 
   While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.