Abstract:
A conveyor for conveying piece goods and the like through a helical path in a vertical direction has a frame and an endless conveyor belt supported by the frame having a conveying part guided in the helical path and a return path. The conveyor belt includes substantially rigid slats movably coupled near their axis and having an upper transport face. The slats are relatively pivotable around both of two axes. The frame has a helical support face for slidably supporting the slats in the conveying part and a radially directed guide face for guiding these slats substantially radially in the conveying part. At least a number of slats are provided with at least a guide roller rotatable about a substantially vertical axis of rotation and adapted to roll along the radially directed guide face.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a conveyor for conveying piece goods and the like through a helical path in an upright direction, comprising a frame, an endless conveyor belt supported by the frame and driven by driving means and having a conveying part guided in the helical path and a return path. The conveyor belt includes substantially rigid slats movably coupled near their axis and has an upper transport face, the slats being relatively pivotable both around a first axis parallel to the transport face and perpendicularly to the conveying direction and around a second axis perpendicularly to the transport face and perpendicularly to the conveying direction, the frame comprises a helical support face for slidably supporting the slats in the conveying part, and the frame further comprises a radially directed guide face for guiding these slats substantially radially in the conveying part. 
     2. Description of the Related Art 
     Such conveyors are known from practice in various embodiments. For bridging a relatively large height without an overly large pitch of the windings of the helix, it is necessary to use a great number of windings This causes drive problems, however, since the pull forces necessary for moving the belt increase exponentially with the increase of the arc of the belt around the axis of the helix. The resistance experienced by the slat in the conveying direction is, first of all, the result of the frictional forces between the slat and the support face. Secondly, the resistance is caused by the frictional force created by the force with which the slat is urged against the radially directed guide face. This latter force increases exponentially with the length of the arc and thus with the number of windings, and this is the so-called “noose effect” in which the belt is jamming when driven in a pulling fashion. 
     In practice this problem has tried to be solved by building in auxiliary drives in several positions along the helix. Of course, this results in a substantial increase of the cost price of the conveyor, whereas the reliability and the noise and vibration level are also affected. Another solution for the problem has been sought in using a roller car under each relatively wide slat. These roller cars are equipped with three or four rollers directed radially with respect to a guide tube, the rollers guiding the slats both vertically and horizontally. The disadvantage of this solution is the complexity and the creation of large spaces between the slats at the position of the end pulleys, since the bending center of the conveyor belt (at the point of engagement of the chain) is at a large distance from the transport face of the slats. This makes the conveyor useless for conveying smaller and/or weaker products. It is also impossible to build this prior art conveyor in a compact manner, and the stability of the slats is defective as a result of the roller cars, whereas the chain tension is necessary for the stability. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a conveyor with which the above problems are removed in an effective way. 
     For this purpose, the conveyor according to the invention is characterized in that at least a number of slats are provided with at least a guide roller rotatable about an axis of rotation parallel to the second axis and adapted to roll along the radially directed guide face. 
     Due to this feature, the “noose effect” as mentioned before is substantially reduced because the frictional forces against the radially directed guide face are at a much lower level due to the rolling friction instead of sliding friction in the prior art. This enables the conveyor belt to be transported through a great number of windings without really necessitating auxiliary drives. Furthermore, the structure can remain simple since only a roller is used for guiding along the regularly directed guide face, whereas the support of the slats by the support face remains a sliding support. If a chain is used as connecting element between the slats, it may engage closely under the transport face of the slat, resulting in a small distance of the bending center of the conveyor belt under it, which causes hardly any spacings between the slats at the end pulleys. 
     Due to the simple structure the invention may be combined with narrow slats enabling the use of a compact end pulley, which facilitates the incorporation of the conveyor and creates a better transfer to connecting conveyors. The narrow slats also lead to a smaller spacing at the end pulley, whereas also a smaller spacing is created between the slats when they are pivoted relatively in the helical section. Smaller slats are also less inclined to form steps as a result of the inner inclination being steeper than the outer inclination of the helical path. 
     If a cylindrical guide roller and a vertical smooth guide face are used, no axial loads and no force increases due to resolved forces in the axial direction are created. 
     The invention will hereafter be further explained with reference to the drawings, showing embodiments of the conveyor according to the invention by way of example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a very schematic and general side-view of an embodiment of a conveyor according to the invention. 
     FIG. 2 is a plan-view of the frame of the conveyor of FIG.  1 . 
     FIG. 3 is a larger-scale plan-view of the slats of a small portion of the conveyor belt of the conveyor of FIG. 1 and 2 in the helical path. 
     FIG. 4 is a larger-scale sectional view along the IV—IV in FIG.  3 . 
     FIG. 5 is a sectional view corresponding to that of FIG.  4  and showing a modified embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drawing shows a conveyor adapted to convey articles, in particular piece goods, through a helical path in the vertical direction. In practice such conveyors are known as spiral conveyors or winding conveyors. This conveyors are able to transport articles in a continuous flow. This product flow may be intended for vertical transport or for buffering in a process section. Areas of utilization are for example the food processing industry, distribution centers, the graphics industry and the like. 
     The conveyor as shown comprises a frame  1 , in this case including a central column  2  having feet  3  and a helical guide chute  4  extending around the column  2  and fixed thereto. Of course various kinds of other frame structures are also conceivable. An end pulley  5 ,  6  is provided at the upper and lower ends of the guide chute  4 , and between these ends of the helical guide chute  4  extends a return chute  7  of the frame  1 . In this case a conveyor belt  8 , which is supported by the frame  1 , is guided through another path in the conveying part and the return part. However, embodiments are conceivable in which the conveying part is guided back at the lower side of the guide chute  4 . 
     In the case as shown, the helical guide chute  4  includes four windings, but this number may be increased or decreased depending on the particular case. Due to the invention it is now possible to drive the conveyor belt  8  through a great number of windings without any drive problems. In the embodiment shown the drive motor may engage the end pulley at the end of the path of the conveyor, that is the end pulley  5  or  6 , and if desired it is possible to use also auxiliary drives at other positions in the transport path. A linear drive for the conveyor belt  8  is also conceivable. The conveyor may join to other conveyors at the upper and lower end pulleys  5 ,  6 . 
     With reference to FIG. 3, the conveyor belt  8  comprises a plurality of slats  9  coupled to each other, either directly or through an endless connecting member. Each slat  9  has an upper flat transport face and the slats are joined to each other so closely in the transport path that articles may be supported by a number of adjacent slats  9 . As mentioned before, the slats  9  are pivotally interconnected directly or in this case through an endless connecting member to be described hereafter, such that the slats  9  are relatively pivotable both around a first axis parallel to their transport face and perpendicularly to the direction of conveyance, and around a second axis perpendicularly to the transport face and perpendicularly to the direction of conveyance. This latter pivotal movement allows the formation of the spiral path, whereas the first mentioned pivotal movement enables the bending of the conveyor belt  8  around the end pulleys  5  and  6 . Since the slats  9  are slightly tapered from their central axis to the ends, the slats  9  do not interfere in curves. Other configurations, such as a rhomb shape, V-shape, and fork shape and also overlapping configurations or a combination thereof, are conceivable. In a particular case the slats  9  may be segment-shaped, but in this case the conveyor belt may only run through a completely curved path, but then there is created a completely closed surface of the conveyor belt  8 . 
     With reference to FIGS. 2 and 4, the guide chute  4  of the frame  1  includes helical sections  10  ( 10 ′, 10 ″) having an upper support face  11  on which the slats  9  rest with their lower side so that the slats  9  are slidingly supported by the support face  11  when they move. By a proper selection of the materials of the sections  10  and the (plastic) slats it is possible to keep the friction and wear at a low level. 
     FIG. 4 also shows that the slats  9  are interconnected by a chain  12 , preferably a steel chain, for example a so-called “side-bow” chain or space chain allowing a bending into directions and allowing torsion so that the chain  12  may run through the helical path. In a known manner the main links  13  of the chain  12  are provided with extended pins  14  snapped into holes of vertical flanges  15  of the slats  9  on either side of the chain  12 . Preferably, each main link is attached to a slat  9  so that it is impossible for the chain  12  to sag between adjacent slats  9  and this allows for a small radius of the helical path without overloading the chain. The vertical flanges  15  at the lower side of each slat  9  comprise at the lower side outwardly pointing, horizontal feet  16  which may be used to engage under the sections  10  to prevent the slats  9  from moving upwardly away from their support faces  11 . 
     FIG. 4 further shows that there is arranged a guide roller  17 , in this case inwardly of the central axis of the shown slat  9  and consequently inwardly of the inner flange  15  (as seen in relation to the helical path). The guide roller  17  is rotatable around a rotary shaft  18  extending parallel to the second axis, perpendicularly to the transport face of the slat, and perpendicularly to the direction of conveyance. The guide roller  17  is journalled on the rotary shaft, preferably by means of a rolling bearing to obtain smooth running of the guide roller  17 . The rotary shaft  18  of the guide roller  17  extends through a reinforcing member  19  having a tilted substantially U-like shape, whereas the rotary shaft may also serve as fixing means to fix the rotary shaft  18  and guide roller  17  to the slat  9  as shown in FIG.  4 . Of course various other manners of fixation are conceivable. 
     The guide roller  17  co-operates with the radially outwardly turned guide face  20  of the inward guide section  10 ′ so that the conveyor belt is guided by a rolling support in the radial direction. The guide roller  17  preferably has a cylindrical running surface co-operating with the smooth and vertical guide face  20  so that no forces are created in vertical direction. The reinforcing member  19  is provided with a horizontal foot  21  taking over the function of the foot  16  of the vertical flange  15  since the foot  16  of the inward vertical flange  15  is now used for confining the reinforcing member  19 . 
     The embodiment shown has the advantage that a standard slat is utilized and, with respect to a conveyor without guide rollers  17 , is only necessary to displace the inward section  10  inwardly to be able to support a conveyor belt  8  having guide rollers  17 . 
     The guide rollers  17  may be provided on all slats  9 , but it is also possible to equip only a limited number of slats with the guide roller  17 . Furthermore it is possible to provide two guide rollers on a slat, for example if the conveyor belt should run through both left and right curves. 
     FIG. 5 shows a modified embodiment in which the guide roller  17  is positioned outwardly of the central axis of the respective slat, as seen in relation to the spiral-shaped path. The reinforcing member is now positioned between the support face  11  of the outer section  10 ″ and the lower side of the slat  9  so that the reinforcing member  19  now also serves for guiding the slat on the support face  11 . The section  10 ″ is now shaped in a different way also because the reinforcing member  19 ′ should also prevent movements in vertical direction. This embodiment has the advantage of a more stable guidance of the slats  9  since the guide roller  17  is positioned outwardly of the point of engagement of the chain  12 . 
     From the foregoing it will be clear that, by making use of simple and reliable means, the invention allows for driving a conveyor belt, which is guided through a helical path, through a great number of windings, without drive problems and without affecting the structure of the slats. It is not necessary to tension the belt. 
     The invention is not restricted to the embodiments shown in the drawing and described herein before by way of example, which may be varied in different manners within the scope of invention. For example, the slats may also be interconnected directly in a pivotable manner near their central axis by special connecting parts. A separate chain or the like is then rendered superfluous.