Abstract:
A mechanism for rotating about a vertical axis generally flat-bottomed objects which are moving along the working surface of a conveyor system, the mechanism including at least three rollers which are rotatable about horizontal axes and which are oriented so as to be tangent to the circumference of a circle which is concentric with the vertical axis, a support frame for moving the rollers into an active positioning above the working surface of the conveyor system and downwardly to an inactive positioning therebelow, and a belt drive system for rotating all of the rollers in the same direction with respect to the circumference of the circle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to a mechanism for rotating a generally flat-bottomed object which is located on a conveyor system over a determined angle about a vertical axis. 
     2. The Prior Art 
     Such a mechanism is known, namely in the shape of a rotating disc on which the object has to be pushed and from which it has to be pushed again after rotation. This only will occur slowly, so that this known rotating mechanism forms an obstacle for rapid conveyance. For a strapping device it is further known to provide means on either side of the strap up plane, which means are movable transversely to the conveying direction, of which means one may grip on the object near one end and the other near the other end and which are able to rotate the object a quarter of a turn. This mechanism requires a lot of space, is only suitable for objects with adapted dimensions and during rotation friction occurs. 
     The object of the invention is to provide a mechanism that is very simple in construction and requires little space while the time period necessary for performing the rotational movement is small. In particular, the invention aims at providing a mechanism for rotating an object to be strapped up in a strapping machine adapted to make straps crossing each other and in particular in such a manner that the rotation does not form an interruption in the strapping process. 
     SUMMARY OF THE INVENTION 
     The aimed objects in the first place are obtained by the fact that the mechanism comprises at least three rollers that are rotatable about a horizontal axis and that move upwardly and downwardly in concert, which rollers in inactive position are below the working face of the conveyor system and in active position extend at least partly above that working face, which rollers in the active position can be driven in the same direction which for all rollers is tangent to the circle of an arc of a circle belonging to the angular rotation that has to be performed. The rotating mechanism according to the invention can be applied in a lot of conveyor systems. If for instance an object that is supplied by a conveyor belt or roller track to a platform has to be discharged therefrom in another direction, then it is sufficient to provide this platform with a rotating mechanism according to the invention, for by moving the rollers to above the working face of the platform and driving them for a short time period the object is rotated about the desired angle and so after retracting the rollers is on the platform in another position from which it can be moved further in the desired direction. It will be clear that it is possible to effect movements in different directions dependent on the time period of the driving of the rollers. 
     The mechanism according to the invention, however, is preferably embodied in such a manner that the rollers are positioned in openings in the working table, that the conveyor system comprises a number of belts extending along each other in conveying direction, of which belts at least one extends until an opening and at least one extends along the edge of each opening. In such an embodiment practically no interruption occurs of the conveying system, that extends to and along the openings in which the upwardly and downwardly movable rollers of the rotating mechanism are present. In case rotation is not necessary the object moves simply with the aid of the conveying system over the openings and no platform is necessary to support the object. The disadvantage of a platform is that separate means are necessary to move the object from it again and to position the object on the means moving the object from the conveyor system adjoining the platform. 
     Preferably the means for driving the rollers comprise one or more belts. In this way it can be ascertained that all rollers in a simple way are driven in the same direction and with the same velocity. 
     Preferably the belts themselves form the gripping face of the rollers and the latter comprise flat discs with a groove for the belt about the outer circumference. The belt itself preferably has a circle shaped cross section so that the contact face with the flat lower side of the object to be rotated is as small as possible. 
     According to a further embodiment the rollers can be cones with the top directed to the center of the rotating circle and tangent to a horizontal face present above the rotational axes of the cones. The drive belts then are present on a diameter that may remain out of touch with the object. 
     According to the invention the drive belt or belts also may extend along belt discs of a shaft or of shafts, that forms or form a part of the drive mechanism of the conveying system in such a manner that in case the conveyor system is activated the rollers for rotating an object also are driven. Such a drive is simple and can easily be performed in such a manner that the upwardly and downwardly movement of the rollers do not influence the tension of the belts. In case the conveyor system is stopped then also the object that possibly is present thereon is stopped. 
     In case the conveyor system moves with the rollers in the retracted position then the object can be moved over the rotating mechanism. However, in case the conveyor system is driven while the rollers at the same time are moved upwardly out of the working face, then no conveying occurs but indeed rotation of the object about the vertical axis until the conveyor system is stopped again. Preferably the device is such that the movement above the working face of the rollers takes place before the conveyor system comes into action. These embodiments are significant in each conveyor system in which a rotation of the object is necessary. Therefor they are also meaningful for a strapping device that has to form straps crossing each other. In a strapping device a switch system is known with the aid of which automatically two spaced straps can be provided, in which between the first and the second strap the conveyor system moves the object to be strapped over the required distance under control of a control means. This control means may comprise an adjustable time relais, but also can be formed by abutments or light rays that can be interrupted. 
     According to the invention it is now possible that the center of the mechanism for the rotation of an object is present in or near said strapping plane and the switch diagram is completed in such a manner that in the phase for further conveyance after the first strap and before the second strap the movement upwardly of the rotating mechanism, the switching on of the conveying system and the switching off of it and also the movement downwardly of the rotating mechanism may take place. 
     In this way it is achieved that in the strapping device the phase between the first and the second strap is used for rotating the object in such a manner that the second strap is directed perpendicularly to the first strap. In this case no time is lost and the time relais can easily be adjusted in such a manner that the time period present between the first and the second strap corresponds with the time period necessary for a rotation about 90°. 
    
    
     The invention now will be elucidated with the aid of the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a strapping device in perspective provided with the mechanism according to the invention. 
     FIG. 2 shows the same machine as in FIG. 1 in another working position. 
     FIG. 3 shows the rotating mechanism on a larger scale and in perspective view. 
    
    
     FIGS. 1 and 2 show a strapping device with a working table 1 and a supply table 2. Both tables 1 and 2 are provided with a conveying system comprising two tracks 3 and 4, each comprising a plurality of conveyor belts extending parallel to each other and having a circle-shaped cross section. The strapping device comprises a strap guide frame 5 and to allow for the strap to be formed the working table is interrupted by a slot 6. The conveyor system is interrupted by the slot 6 with the upstream and downstream portions of the conveyor system at a short distance from each other on either side of the slot. 
     In the working table four rectangular openings 7 are provided and FIGS. 1 and 2 show that some of the belts of the conveyor system terminate their path of travel in the conveying direction toward the slot 6 at a transverse edge of each of the openings 7 whereas some of the belts terminate their path of travel in the conveying direction toward the slot 6 at a point closer to the slot 6, at least one of these latter belts extending along an outer longitudinal edge of each of the openings 7. 
     In FIG. 1 the rollers 8 of the rotating mechanism are shown in their position above the working face 1. 
     In FIG. 2 the same rollers are shown in the retracted position. In the retracted position shown in FIG. 2 an object that has to be strapped up, such as a stack of newspapers, a box or another object, can be provided on the spot of the strap up frame with a strap, if desired with a plurality of spaced straps. 
     In case a strap is made over about the middle of the object and the rotating rollers move upwardly out of the working plane, as shown in FIG. 1, then the object is rotated, after which a next strap can be provided crossing the preceding strap. The mechanism that is used for this matter is shown in detail in FIG. 3. 
     This mechanism comprises four columns 9, 10, 11 and 12, of which the columns 9 and 10 form a unity with the horizontal beam 13 and the columns 11 and 12 with the horizontal beam 14. These again are mutually coupled with the aid of downwardly-directed extensions 15 and 16 of the columns 9 and 12 and the horizontal connecting bridge 17. On latter a pressure cylinder may act with the aid of which the above described mechanism can be moved upwardly and downwardly in vertical direction of the columns 9 to 12 inclusive as a unit. 
     Each column 9, 10, 11 and 12 respectively has at its upper end a roller 8 comprising a flat disc provided with a half circle shaped groove. 
     The rollers 8 of the columns 9 and 10 are driven by a belt 18 with circle shaped cross section, which extends from a driving disc 19 on the shaft 20, seen in driving direction, over the guide wheel 21, the wheel 8 of the column 9, the guide wheel 22 and the guide wheel 23 and subsequently about the roller 8 positioned at the upper side of the column 10 and subsequently back downwardly about the guide wheel 24 to the driving wheel 19. The wheels 21 and 22, 23 and 24 are free rotatably positioned on pins that are connected to the beam 13. 
     The shaft 20 is fixedly but rotatably supported in the frame of the machine and is synchronically driven with the belt of the conveyor system shown in FIGS. 1 and 2, and preferably with the same velocity. 
     This shaft has a second drive wheel 25 with the aid of which a second belt 26 extends about the guide wheel 27 to the wheel 8 on the upper side of the column 12 subsequently downwardly about guide wheels 28 and 29 to the wheel 8 positioned at the upper side of the column 11 and then back via the guide wheel 30 to the drive wheel 25. The wheels 8 on the upper side of the columns 9 to 12 inclusive are rotatable about axes positioned in a common horizontal plane and are directed to a common center. The rollers 8 that are free rotatably supported on these shafts are formed by flat discs that are tangent to a circle. This means that the upper points of the curve of the belts extending about the rollers 8, when driven have a working direction that at the spot of all rollers is tangent to a common circle through these points 31 with the work lines all in the same circumferential direction of this circle. An object that is present on these points 31 so will be rotated while the belts are driven about the center line of the circle. 
     In the embodiment shown in FIG. 3 two belts 18 and 26 are necessary to move the rollers 8, with the common drive shaft 20 and the chosen arrangement of the guide wheels, also in the correct direction. 
     The shaft 20 is laterally next to the vertically upwardly and downwardly movable columns by which this movement is possible without disadvantageous influencing the tension in the belts 18 and 26. 
     It is of course possible to provide a drive with a single belt for all rollers or with separate belts for each roller. 
     The strapping machine shown in the FIGS. 1 and 2 is of a known type. This machine is embodied in such a manner that, in case a light ray is interrupted by a supplied object, a time relay is activated that takes care of the fact that the object will be stopped in the correct position for providing a first strap. This time relay is adjustable in such a manner that a first strap can be provided on a position in the middle plane of the object but also at positions spaced from this middle plane, in which case a second time relay after providing the first strap takes care of the fact that the object is displaced along a determined distance by the conveyor system after which the second strap is provided. 
     This second time relay now can be used in a useful way in this known machine for controlling the rotation. The first time relay then is in a position necessary for providing a first strap about in the middle plane of the object. After providing this first strap, the conveyor system controlled by the second time relay comes into action again but at the same time or preferably a little bit earlier the rotating mechanism is moved upwardly, so only the tops 31 of the belts on the rollers 8 grip the object. This then is rotated in the same time period that in another way should be used for the axially further displacement of the object. After retracting the rotating mechanism, the object again rests on the conveyor system that comes into action again as soon as the second strap is provided, that crosses the first one. 
     In this way very rapidly straps can be provided that cross each other; this is of particular importance in case strapping up of newspapers, parcels or such is involved. 
     Further, it will be clear that the mechanism according to the invention can be provided in a simple way in the existant design of a strapping machine.