This invention relates to a rotary transfer mechanism for extracting a flat article from the discharge opening of a magazine and depositing it at a receiving station.
Such mechanisms are known to comprise a support member, a drive shaft rotatably mounted on and extending from the support member, means for rotatably driving the drive shaft, carrier means rotatable with the drive shaft, at least one support shaft rotatable on the carrier means substantially parallel to the drive shaft, whereby the support shaft can orbit round the drive shaft, means for controlling the rotational disposition of the support shaft with respect to the carrier mean, at least one suction cup attached to the support shaft, means for producing a vacuum, means alternatively connecting the suction cup with the vacuum-producing means and the atmosphere, the means for controlling the support shaft including means causing the suction cup while connected with the vacuum-producing mean to contact an article at the discharge opening of the magazine, extract the article from the magazine, and transfer the article to the receiving station, whereupon the suction up is connected with the atmosphere to release the article to the receiving station.
In one such mechanism (U.S. Pat. No. 2 915 308) three support shafts with suction cups are spaced from and around the drive shaft on radial arms rotatable with and by the drive shaft, and the means for controlling the rotational disposition of the support shafts with respect to the carrier means consists of drive gears secured one to each support shaft, idler gears rotatably carried one by each of the arms and meshing one with each drive shaft, the idler gears also meshing with a stationary gear coaxial with the drive shaft, whereby the suport shafts rotate continuously in the opposite direction to the drive shaft, and the gear ratios of the planetary gearing comprised of the stationary gear (i.e. the sun gear), an idler gear, and the respective drive gear (i.e., a planet gear) being such that for each revolution of the drive shaft each suction cup moves along a hypotrochoidal path having three node points 120.degree. apart, with one node point at the discharge opening of the magazine and another node point at the receiving station.
Another example is to be found in U.S. Pat. No. 3 302 946 in which the mechanism is similar to that of U.S. Pat. No. 2 915 308 with the exception that it employs a chain drive in place of the idler gears.
In another such mechanism (U.S. Pat. No. 4 350 466) four support arms with suction cups are spaced from and around the drive shaft on radial arms rotatable with and by the drive shaft, and the means for controlling the rotational disposition of the support shafts with respect to the carrier means consists of sprockets secured one to each support shaft and a plurality of pins attached to the support member and extending substantially parallel to the support shafts in a circle concentric with the drive shaft, the sprockets engaging the pins for rolling along the interior of the circle of pins, whereby the support shafts rotate continuously in the opposite direction to the drive shaft, the gear ratios of the planetary gearing comprised of the circle of pins and the sprockets being such that for each revolution of the drive shaft each suction cup moves along a hypotrochoidal path having three node points 120.degree. apart, with one node point at the discharge opening of the magazine and another node point at the receiving station.
Similar mechanisms each with a single support shaft but with diametrically oppositely directed suction cups each following a hypotrochoidal path are to be found in U.S. Pat. No. 3 937 458 and U.S. Pat. No. 4 537 587 (EP-PS 0 134 628) transferring cartons from a magazine to a receiving station on a conveyor. A difficulty encountered by the mechanism of U.S. Pat. No. 3 937 458 is that opening of a flat sleeve carton during extraction from the magazine is resisted by the vacuum generated within the carton as the inner surfaces of the carton are being pulled apart. Therefore, in U.S. Pat. No. 4 537 587 the third node point is disposed adjacent a stationary suction cup for cooperation with each moving suction cup to open a flat sleeve carton carried thereon ready for deposit between flights on the conveyor, which flights may hold the sleeve carton open for end loading with a product at a subsequent station along the conveyor.
All these known mechanisms depend on a strict drive ratio, whether via planetary gears or chains, or sprockets nd pins, e.g., 3:1 giving three node points 120.degree. apart, which in turn determines that the discharge opening of the magazine shall be at substantially 120.degree. to the receiving station. Any departure from this ratio must be either to 2:1 or to 4:1, resulting in an inconvenient disposition of the discharge opening parallel to and above the receiving station, or perpendicular to the receiving station and thereby imposing severe limitation on the length of article that can be transferred.
Furthermore, when the receiving station is on a conveyor, as in U.S. Pat. No. 3 937 458 in which a single support shaft carries diametrically oppositely directed suction cups following a hypotrochoidal path, the suction cup depositing an article has substantially no component of movement in the direction of movement of the conveyor, so the instant of release of the article from the suction cup (by connection of that suction cup with the atmosphere) must be very precisely timed.
Moreover, when the article is a flat sleeve carton to be deposited open between flights on the conveyor there is a tendency for the carton to be re-flattened and/or damaged and/or rotationally displaced between the flights of the conveyor, especially if the carton is of the type having a substantially square cross-section.
In an alternative form of mechanism (U.S. Pat. No. 3 575 409) the problem of strict drive ratios, and consequentially restricted article length and angular disposition of the discharge opening of the magazine, is avoided by mounting each of three suction cups on a radially guided arm the radial and angular disposition of which is controlled by a continuous cam surface and a pair of cam followers, the cam surface being concentric with the drive shaft except over the extent of a pair of outwardly protruding segments which create a "node point" in the path of each suction cup at the magazine location while the remainder of the path of each suction cup is a circular sweep including past the receiving station. This mechanism has not been applied in any attempt to overcome to the difficulties encountered in opening a sleeve carton and maintaining its integrity of shape and correct disposition between flights on a conveyor. Object and Summary of the Invention
An object of the present invention is to provide an improved, yet simple, rotary transfer mechanism for extracting a flat article from the discharge opening of a magazine and depositing it with accurate placement at a receiving station on a conveyor.
Another object is to provide a rotary transfer mechanism with which the disposition of the discharge opening of a magazine in relation to a receiving station, particularly on a conveyor, can be varied infinitely.
A further object of the invention is to provide a rotary transfer mechanism adaptable to a wide range of lengths of flat articles to be transferred from a magazine to a receiving station, particularly on a conveyor.
Yet another object is to provide a rotary transfer mechanism for transferring flat sleeve cartons from the discharge opening of a magazine to a receiving station on a conveyor having flights and for facilitating opening of the cartons ready for end loading with a product at a subsequent station along the conveyor.
According to the present invention, a rotary transfer mechanism for extracting a flat article from the discharge opening of a magazine and depositing it at a receiving station on a conveyor comprises a support member, a drive shaft rotatably mounted on and extending from the support member, means for rotatably driving the drive shaft, carrier means rotatable with the drive shaft, at least one support shaft rotatable on the carrier means substantially parallel to the drive shaft, whereby the support shaft can orbit round the drive shaft, means for controlling the rotational disposition of the support shaft with respect to the carrier means, at least one suction cup attached to the support shaft, means for producing a vacuum, means alternatively connecting the suction cup with the vacuum-producing means and the atmosphere, the means for controlling the support shaft including means causing the suction cup while connected with the vacuum-producing means to contact an article at the discharge opening of the magazine, extract the article from the magazine, and transfer the article to the receiving station, whereupon the suction cup is connected with the atmosphere to release the article to the receiving station, characterised in that the means for controlling the at least one support shaft comprises: on the one hand, a pinion secured coaxially to the support shaft, and an arcuate rack secured to the support member in such a position as to act upon the pinion to create a partial path of the at least one suction cup with a "node point" at the discharge opening of the magazine; and, on the other hand, a cam follower on an arm extending laterally from the support shaft, and a cam track secured to the support member and of such an operative extent as to act upon the cam follower when the arcuate rack is not acting on the pinion, the profile of the cam track being such as to cause the suction cup to move past the receiving station in the same direction as the conveyor with the article generally parallel to the conveyor.
Thus, the suction cup "plucks" each article from the magazine, but instead of merely dropping the article at the receiving station, the suction cup imparts to the article a major component of motion in the direction of movement of the conveyor, with consequent better placement of the article on the conveyor. The flexibility of design in suction cup path afforded by the combination of the ratio of the rack-and-pinion drive, the disposition of the rack, and the profile of the operative extent of the cam track, allows for a wide choice of article length and disposition of magazine, whilst avoiding interference between the magazine on the conveyor with the article while it is being transferred. This is particularly important when the conveyor has flights for the timed positioning of the articles in relation to a subsequent operation, such as when the article is a sleeve carton presented on the conveyor in open condition ready for end loading with a product at a subsequent station.
Indeed, in accordance with a feature of special significance, a rotary transfer mechanism in accordance with the invention for transferring flat sleeve cartons from the discharge opening of a magazine to a receiving station on a conveyor having flights, facilitates opening of the cartons ready for end loading with a product at a subsequent station along the conveyor, by arranging for the combined action of the means for rotatably driving the drive shaft and the means for controlling the at least one support shaft so that at the receiving station the at least one suction cup is moving in the same direction as the conveyor relatively at a slightly greater speed, whereby the relative movement between the suction cup, holding one side of a sleeve carton, and leading flights on the conveyor, which flights are abutted by the leading corner fold of the carton, is such as to effect an opening of the carton which is substantially completed before the carton is abutted by trailing flights on the conveyor to hold the carton in its fully open condition as it passes to and through a subsequent end-loading station.
The arcuate rack may be disposed radially inwards with respect to the orbital path of the at least one support shaft, with an idler gear in permanent mesh with the pinion and adapted to mesh with the arcuate rack (during the appropriate arc of the support shaft orbit). However, the arcuate rack is preferably disposed radially outwards with respect to the orbital path of the at least one support shaft, whereby the pinion conveniently meshes directly with the arcuate rack (during the appropriate arc of the support shaft orbit), thus avoiding the need for an idler gear. The cam follower may be carried by the pinion offset from the common axis with the support shaft, whereby the pinion serves as the arm extending laterally from the support shaft, and the cam track may be continuous but be provided with an inoperative portion along which the cam follower passes with clearance when the rack is acting on the pinion.
Conveniently, three support shafts are provided with two suction cups attached to each shaft; but two, or four or more support shafts may be provided, depending on the size of the article to be transferred and/or the spacing of articles on a conveyor; and, likewise, three or more suction cups may be attached to each support shaft, depending on the size and/or weight of article to be transferred.
Further advantageous features will become evident from the following description of an embodiment of the invention, given by way of example, only with reference to the accompanying drawings, in which: