Abstract:
A suction table which, in a machine converting sheets into package, transfers the last, lowermost sheet of a batch to a subsequent processing station. The table is provided with numerous blowing and sucking nozzles and is fitted on a hollow frame movable with regard to a fixed distributory housing which provides sucking and blowing action. The housing comprises a distributory shaft and tubes movable with respect to the table and thereby sliding within corresponding guides formed in the frame. The shaft and tubes are provided with cooperating ducts which will allow the nozzles to suck or blow as required by the angular position of the distributory shaft and the position of the table.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a transfer device for a machine converting plate or sheetlike matter into package, whereby the lowermost sheet is transferred from a sheet batch to the subsequent processing station. 
     The patent CH-A-440337, and corresponding U.S. Pat. No. 3,510,126, describes a transfer table provided with telescope-type suction cups, suction being achieved owing to the difference of pressure between two chambers of a body of every suction cup, both chambers being connected to a vacuum pump. In line with this arrangement, it has appeared appropriate to have every suction cup connected at the end of the sheet transfer to a source of pressure for quicker separation of the sheet with regard to the suction table, the quicker response to accelerate production. However, because of present production speeds which are likely to soon reach 10,000 sheets per hour, the present means for having each nozzle alternately blow or such, made of fixed valves connected through flexible air suction or pressure ducts to a movable table and actuated by control means themselves kinematically connected to the shift of the suction table, are no longer able to ensure their function on account of their slow response with regard to the time available for the accomplishment of the various control cycles. Besides that, the air contained in the flexible ducts represents a considerable inert mass retarding pressure and suction to a great extent. Moreover, such flexible ducts have a tendency to develop fatigue fissures. 
     In the patent U.S. Pat. No. 3,202,420 every suction cup of the movable table is connected through flexible ducts to a fixed valve with a rotary distribution flap switching the nozzle to the atmosphere or to suction. 
     The patent U.S. Pat. No. 3,226,108 describes a suction table provided with several suction holes. The movable table is connected to a lengthwise distributory housing by means of a cylindrical tube fitted to the table frame, and not by a flexible duct, the tube communicating with all suction holes and being able to slide within the corresponding bore of the distributory housing in the course of the sheet transfer. The bore is provided with two apertures longitudinally separated by an appropriate distance and arranged to connect alternately the suction holes to a source or aspiration or to the atmosphere. If this system has the advantage of discarding the drawbacks of the flexible ducts, it has nonetheless the disadvantage of providing only a limited number of possibilities for regulating the alteration of suction or pressure required for the control of the table. The sucking and blowing nozzles are divided up into several assemblies each of which require its own control cycle. 
     SUMMARY OF THE INVENTION 
     The objects of the present invention are to eliminate the aforementioned drawbacks on a sheet transfer table. 
     In a transfer device for a machine for converting plate or sheet-like matter into package, and acting to transfer the last, lowermost, sheet of a batch to a subsequent processing station. The invention provides a transfer table provided with two assemblies of nozzles of which the nozzles of the same assembly can be connected together through a control means alternately to either a source of aspiration to operate suction cups on the nozzles or to a source of pressure allowing the nozzles to blowingly detach the sheet from the table. 
     The invention provides a frame to support the table and means for guiding the table during the transfer stroke. 
     The control means comprise a fixed housing provided with inlet and outlet chambers for suction and pressure, the housing including a built-in distributory shaft arranged axially perpendicular to the sheet transfer stroke direction. The radial periphery of the distributory shaft has several groove-shaped conduits designed for connecting the inlet chambers to the outlet chambers as determined by the angular position of the distributory shaft. 
     The housing is extended on one of its sides by several conduits arranged in the transfer direction and connected to the outlet chambers. 
     Several guiding bores are formed in the frame of the table, each bore allowing inside free, but tight fitting, sliding of one of the conduits so as to enable the shifting of the table with regard to the fixed housing during the transfer stroke. 
     Apertures are formed on each conduit and arranged, as determined by the lengthwise position of each conduit, to move in alignment with corresponding apertures formed on each guiding bore in order to connect either the pressurized or vacuum conduits to the passages formed inside the frame connected to the various nozzles. 
     In a development of the invention, a first assembly of large nozzles is situated in the rear area of the table, and a second assembly of small nozzles is situated in the front area of the table, wherein &#34;rear&#34; is closer to the fixed housing and &#34;front&#34; is further away from the fixed housing. 
     In another development of the invention the frame comprises three guiding bores and three corresponding conduits of which the first one of each grouping is arranged to direct compressed air to the small and the large nozzles, the second grouping is arranged to provide suction to the large nozzles, and the third grouping is to provide suction to the small nozzles. 
     The distributory shaft can be fashioned to be hollow and equipped with a first assembly of suction grooves and with a second assembly of pressure grooves opposite the first assembly of suction grooves. Some of the grooves can be connected inside the hollow distributory shaft by radial orifices in such a way that with a revolution of 360° of the distributory shaft corresponding to the complete reciprocation cycle of the table in the course of a transfer of a sheet, and when the table is in its forward section of its stroke, the pressure chamber will be connected to the common conduits of the small and large nozzles by at least an aperture formed at the front end of the first grouping with a view to directing compressed air to both the small and large nozzles. 
     As a further development of the invention a mechanism can be provided for retarding the beginning of suction of a transverse cycle by angular positioning of the distributory shaft as required by the length of the sheets of a given batch. 
     The nozzles of the exemplary embodiment are advantageously fashioned having a first, fixed tube, a second tube making up a first tight chamber with the first tube, and a third, movable tube topped by a suction cup and thus making up a second tight chamber with the second tube. The two described chambers are interconnected by inside conduits of the first tube so that when the second chamber contains a vacuum, a difference in pressure being produced between the two chambers, results in a shift of the third tube. 
     The present invention provides a reliable transfer machine having the ability for quick response with regard to the time available for the accomplishment of the various control cycles and resulting fast production speeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a table according to the invention; 
     FIG. 2 is a rear view in a direction of II--II of FIG. 1; 
     FIG. 3 is a sectional view taken generally along III--III of FIG. 1; 
     FIG. 4 is a sectional view taken generally along IV--IV of FIG. 1; 
     FIG. 5 is a sectional view taken generally along V--V of FIG. 1; 
     FIG. 6 is a sectional view taken generally along VI--VI of FIG. 3; 
     FIG. 7 is a sectional view taken generally along VII--VII of FIG. 6. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows transfer device Z which includes a movable table 1 and a rear, fixed housing 2 for providing alternate blowing and sucking. 
     An upper portion 1a of the table 1 holds a first assembly of five large nozzles 3 situated in a rear area 3a with regard to the direction of the table transfer motion, as well as a plurality of small nozzles 4 situated in a front area 4a. In the exemplary embodiment 28 small nozzles are employed. 
     As shown in FIGS. 3-5, the table consists of a hollow frame B whose upper portion 1a is shut by a plate P and whose surface is perforated to expose the small and large nozzles 3, 4. 
     The body of a typical large nozzle 3 consists essentially of: a first tube 30 screwed onto an inner rib 30a of the hollow frame B, a second, fixed, tube 31 surrounding the first tube 30, and a third tube 32 surrounding the second tube 31 along which it is able to slide. A first tight chamber 33 is formed between the first tube 30 and the second tube 31. A second tight chamber 34 is formed between the second tube 31 and the third tube 32. The top of the third tube 32 is provided with an elastic suction cup 37. The first tube 30 is connected, at one end 30b, to a main duct 10 for alternate blowing and sucking produced within the frame B and involving all large nozzles 3; and the first tube 30 is connected at another end, through a radial orifice 35 to the first tight chamber 33. The first tight chamber 33 is connected to the second tight chamber 34 through a radial orifice 36 on the second tube 31. 
     When the main duct 10 is under suction, a difference of pressure will arise between the two chambers 33 and 34 causing an upward shift of the third tube 32 and thereby of the elastic suction cup 37 which can thus be shifted from the position shown in full lines in FIG. 4 where it is flush with a top surface P&#39; of the plate P to the position shown in dashed lines situated above the level line N related to a lower end of a sheet batch plate used as a gauge (not represented) in the front area of the sheet batch. More details about the telescope-type suction cups are contained in the above-mentioned patent CH-A-440337 and corresponding U.S. Pat. No. 3,510,126 incorporated herein by reference. 
     The large nozzles 3 have for purpose to fetch the lowermost sheet of the batch and to pull it down flat onto the table 1. In the course of the movement of the table 1, the large nozzles 3 remain behind the sheet batch gauge. 
     The small nozzles 4 are designed, and operate, in almost the same, though simplified, way as the large nozzles 3. FIG. 4 shows that the small nozzles 4 have also a telescope-type tube 40 topped by an elastic suction cup 41 which can occupy a first position flush with the upper surface P&#39; of the plate P, and a second position, represented in dashed lines, situated underneath the level N since the small nozzles 4 are to move beyond the batch gauge. The body of every small nozzle 4 also includes a tight chamber 42 contained between the telescope-type tube 40 and a fixed tube 45 fitted inside the hollow frame B. Both tubes 40, 45 as well as the chamber 42 are connected through appropriate passages 44, 43 to a main blowing or sucking duct 11 common to all the small nozzles 4. The small nozzles, or telescope-type suction cups 4 are arranged to be applied in a bent area of the sheet which, at an earlier stage, has been separated from the batch and flattened onto plate P by the large suction cups 3. 
     Inside the frame B and underneath the plate P arranged on a parallel horizontal plane, three guiding bores G 1 , G 2 , G 3  with the shape of cylindrical hollow tubes are arranged along the sheet transfer direction. A front end Ga of the bores is closed and a rear end Gb is open. 
     The first guiding tube G 1  which, as will be described below, has for a purpose the direction of compressed air to the small and large suction cups 3, 4. The first guiding tube G, is provided with an aperture or radial slot L 1  situated rearwardly and communicates with both main ducts 10, 11 of the small and large nozzles 3, 4. The second guiding tube G 2  directing suction to the large suction cups 3, is provided with a radial slot L 2  situated frontwardly and communicates with the main duct 10 of the large suction cups 3. The third guiding tube G 3  directing suction to the small suction cups 4, is provided with a radial slot L 3  situated frontwardly and communicates with the main duct 11 of the small suction cups 4. 
     The bore 20 formed in the fixed distributory housing 2 contains a horizontally fitted, hollow, distributory shaft D closed at both ends and arranged perpendicularly to the transfer direction. The distributory shaft D is rotated at one of its ends by a drive shaft 81. As shown in FIG. 7, the housing 2 comprises a suction inlet chamber AS connected through a duct 200 to a source of aspiration (not represented), and similarly a pressure inlet chamber PS is connected through a duct 210 to a source of pressure (not represented). As shown in FIGS. 3, 4 and 5, the housing 2 also comprises three outlet chambers S 1  to S 3  of which each is connected to a cylindrical hollow duct T 1  to T 3  respectively, said hollow ducts T 1  to T 3  emerging from the housing 2 and penetrating each into one of the three guiding tubes G 1  to G 3 . The fixed housing 2 and the movable table 1 are arranged so that the cylindrical ducts T 1  to T 3  will be able to slide freely and with effective leak tightness within the guiding tubes G 1  to G 3  along a stroke which is at least equal to the one required for a sheet transfer. For this purpose, as shown in FIG. 2, the frame B of the table 1 is provided with guiding bushings 90 able to slide along the bars 91 fitted on a support 92. 
     The radial periphery of the distributory shaft D is fashioned to have a first suction groove R a  which, depending on the angular position of the shaft D, can connect the suction inlet chamber AS to the outlet chambers S 2  and S 3 . The radial periphery also will be provided with a groove R p  which, as required by the angular position of the shaft D, is to connect the pressure inlet chamber PS to the outlet chamber S 1 . In a position diametrically opposed to the suction and pressure grooves R a  and R p  respectively, auxiliary grooves R 1 , R 2  and R 3  respectively will be connected each to the hollow shaft through radial orifices O 1  to O 3  respectively. 
     The first cylindrical duct T 1  is provided with at least one radial slot L 4  situated at its open front end and arranged with the table 1 in a forward part of the transfer stroke, to move to a position opposite the slot L 1  of the guiding tube G 1  in order to connect the duct T 1  to the common ducts 10, 11 of the large and small nozzles 3, 4. The second cylindrical duct T 2  is provided at its closed front end with a radial slot L 5  arranged, with the table 1 in a retracted part of the transfer stroke, to move to a position opposite the slot L 2  of the guiding tube G 2  in order to connect the duct T 2  to the common duct 10 of the large nozzles 3. The third cylindrical duct T 3  is provided at its closed front end with a radial slot L 6  arranged, with the table 1 in a retracted or rearward part of the transfer stroke, to move to a position opposite the slot L 3  of the third guiding tube G 3  in order to connect the duct T 3  to the common duct 11 of the small nozzles 4. 
     More information concerning the arrangement and the dimensions of the various grooves R a , R p , R 1 , R 2 , R 3  and the slots L 1  to L 6  may be gathered from the FIG. 3 to 6 which contain also the main angular positions of the various grooves starting from a 0 reference axis. As has been stated, the aforesaid distributory system is designed to, during a sheet transfer cycle corresponding to a 360° revolution of the shaft 81, apply vacuum by aspiration at a first stage, i.e., in the retracted position of the table 1, to the large nozzles 3, and, subsequently, to the small nozzles 4 before applying blowing pressure to the large and small nozzles 3, 4 towards the forward part of the stroke of table 1. 
     The above-described transfer device can be provided with a retardation mechanism (not represented) withholding the beginning of the suction as required by the size, i.e., the length of the sheet taken from the batch. In fact, considering that: 
     1. the lengthwise shift of the cylindrical duct T 1 , T 2 , T 3  with regard to the corresponding guiding tube G 1 , G 2 , G 3  commands, i.e., achieves, the switching-over from sucking to blowing at a fixed point of the stroke of the table 1, and 
     2. the rotary shaft D achieves the switching-over from blowing to sucking in the vicinity of the retracted position of the table 1, 
     it is possible, in a transfer cycle, to have the aspiration set in sooner or later as required by the sheet size. To this aim, the retardation mechanism is to detect the sheet length and to, consequently, vary the angular position of the shaft D that would correspond to the beginning of a transfer cycle. This method allows flexibility in the event of a diminishing sheet length so that the sucking nozzles will be uncovered at an earlier stage. The time-lag intervening before suction sets in will thus enhance the operational safety of the transfer device. 
     Although the present invention has been described with reference to a specific embodiment, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.