Abstract:
A conveyor for transferring products has a belt looped about two pulleys; a first and a second conveying branch extending between the pulleys in a given direction; and an actuating device for activating the pulleys and defined by gear trains to impart to the pulleys a concordant reciprocating motion in the aforementioned direction according to a first law of motion; the belt being fed about the pulleys according to a second law of motion; and the first and second law of motion being so determined that the first branch is operated intermittently, and the second branch is operated continuously and uniformly.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a conveyor. 
     In particular, the present invention relates to a conveyor comprising a flexible member looped about at least two pulleys and having at least two conveying branches, a first of which may be operated, for example, continuously and uniformly, and a second of which may be operated, for example, intermittently. 
     BACKGROUND OF THE INVENTION 
     Conveyors of the above type are used on automatic machines, and in particular on product packing machines to transfer products between an intermittently-operated and a continuously-operated portion of the machine. 
     U.S. Pat. No, 4,735,032 relates to a conveyor of the above type, wherein a chain is looped about a number of pulleys, comprises equally spaced seats for receiving groups of cigarettes, and is powered by a drive pulley. The conveyor comprises one branch extending between two pulleys and operated intermittently, and a series of further branches extending between said two pulleys and operated continuously and uniformly. The two pulleys, which separate the intermittent branch from the continuous further branches, are fitted to respective slides engaging respective guides parallel to the intermittent branch, and are moved reciprocatingly in the same direction along the slides by means of a reciprocating connecting rod. 
     The laws of motion governing operation of the drive pulley and the connecting rod are so determined that said one branch is operated intermittently, i.e. has a succession of instants in which the branch is stopped, and the further branches are operated continuously and uniformly. 
     While theoretically ensuring correct operation of both the intermittent branch and the further continuous branches, the above conveyor, in actual use, has several drawbacks on account of the type of mechanism used to transmit reciprocating motion to the pulleys. That is, on the one hand, using slides and guides to guide the pulleys along respective straight courses generates considerable friction, thus resulting in wear and inaccuracy; and, on the other, seeing as most of the members for transmitting said reciprocating motion are themselves reciprocating members, the conveyor is subject to severe vibration. 
     Such drawbacks make the conveyor practically unusable. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a conveyor of the above type, designed to eliminate the aforementioned drawbacks. 
     According to the present invention, there is provided a conveyor for transferring products and comprising a flexible member looped about at least a first and a second pulley and in turn having at least a first and a second conveying branch, said first branch extending between said first and said second pulley in a given direction; and an actuating device for activating said first and said second pulley to impart to the first and the second pulley a concordant reciprocating motion in said direction according to a first law of motion; said flexible member being fed about said first and said second pulley according to a second law of motion; and said conveyor being characterized in that said actuating device comprises balance masses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
     FIG. 1 shows a schematic front view of a preferred embodiment of the conveyor according to the present invention; 
     FIG. 2 shows a partially sectioned side view of the FIG. 1 conveyor; 
     FIG. 3 shows a schematic view of the FIG. 1 conveyor; 
     FIG. 4 shows a detail of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Number  1  in FIG. 1 indicates a conveyor comprising a belt  2 , which is looped about a drive pulley  3  fitted to a shaft  4   a  and rotating about a respective axis  4 , and about a driven pulley  5  fitted to a shaft  6   a  and rotating about a respective axis  6 . 
     Conveyor  1  defines a path P, and comprises two straight conveying branches  7  and  8  extending between pulleys  3  and  5  in a vertical direction D. Belt  2  comprises a succession of equally spaced pockets  9  for transferring articles A between a loading station  10  for loading articles A and located along branch  7 , and an unloading station  11  located along branch  8 . 
     Axes  4  and  6  of respective pulleys  3  and  5  are movable, according to a given law of motion LM 1 , reciprocatingly in the same direction along respective straight courses T 1  and T 2  parallel to direction D, and drive pulley  3  is rotated about respective axis  4  according to a law of motion LM 2 . 
     With reference to FIG. 2, conveyor  1  comprises an actuating device  12  for transmitting to pulleys  3  and  5  the reciprocating motion according to law of motion LM 1 ; an actuating device  13  for transmitting to pulley  3  the rotary movement about axis  4  according to law of motion Lm 2 ; and a supporting frame  14 . 
     As a consequence of the above movements of pulleys  3  and  5 , branch  7  is preferably operated intermittently, and branch  8  continuously and uniformly. 
     Device  12  is defined by a number of gear trains, and comprises a motor  15  for powering a belt transmission  16 ; an epicyclic gear train  17  connected to pulley  3 ; and an epicyclic gear train  18  connected to pulley  5 . Transmission  16  transmits motion from motor  15  to gear trains  17  and  18 , and comprises a belt  19  looped about two pulleys  20  and  21  rotating about respective axes  22  and  23  parallel to axes  4  and  6  of pulleys  3  and  5 . Epicyclic gear trains  17  and  18  comprise respective sun gears  24  and  25  rotating about respective axes  26  and  27 ; respective fixed ring gears  28  and  29 ; and respective planetary gears  30  and  31  rotating about respective axes  32  and  33 . 
     Pulley  20  of transmission  16  is integral with a gear  34 , which is coaxial with pulley  20  and meshes with sun gear  24  with a gear ratio of one; and pulley  21  is integral and coaxial with sun gear  25 , which therefore rotates with the same law of motion as, but in the opposite direction to, sun gear  24 . 
     Pulley  3  is connected to gear train  17  by means of a coupling between shaft  4 a of pulley  3  and planetary gear  30 , and wherein axis  4  is eccentric with respect to axis  32  of planetary gear  30 , with an eccentricity value “e” equal to the distance between axis  26  of sun gear  24  and axis  32  of respective planetary gear  30 . Similarly, pulley  5  is connected to gear train  18  by means of a coupling between shaft  6   a  of pulley  5  and planetary gear  31 , and wherein axis  6  is eccentric with respect to axis  33  of planetary gear  31 , with an eccentricity value “e” equal to the distance between axis  27  of sun gear  25  and axis  33  of respective planetary gear  31 . In other words, and as shown more clearly in FIG. 3, each epicyclic gear train  17 ,  18 , together with respective pulley  3 ,  5 , forms a respective crank mechanism  35 ,  36 , wherein the distance between the axis  26 ,  27  of respective sun gear  24 ,  25  and the axis  32 ,  33  of respective planetary gear  30 ,  31  represents a respective virtual crank  37 ,  38  of a length equal to eccentricity “e”; and the distance between the axis  32 ,  33  of planetary gear  30 ,  31  and respective axis  4 ,  6  of pulley  3 ,  5  represents a respective virtual connecting rod  39 ,  40  of a length equal to eccentricity “e”. 
     Crank mechanisms  35  and  36  impart to axes  4  and  6  of respective pulleys  3  and  4  the reciprocating motion along respective courses T 1  and T 2 , which assume a value equal to four times the value of eccentricity “e”. Mechanically, axes  4  and  6  are maintained along straight courses T 1  and T 2  by sun gears  24  and  25 , which, while effecting a given rotation, produce respective movements of cranks  37  and  38  and, at the same time, roll respective planetary gears  30  and  31  along respective fixed ring gears  28  and  29 . Rotating about respective axes  32  and  33 , planetary gears  30  and  31  rotate respective virtual connecting rods  39  and  40  about axes  32  and  33  by the same amount as and in the opposite direction to the rotation of respective virtual cranks  37  and  38 . 
     With reference to FIG. 2, constructionwise, gear trains  17  and  18  are housed inside frame  14 , are rotated by belt transmission  16  located on one side of frame  14 , and transmit reciprocating motion to pulleys  3  and  5  located on the opposite side of frame  14  to belt transmission  16 . Whereas fixed ring gears  28  and  29  are fitted rigidly to frame  14 , sun gears  24  and  25  are connected rigidly to respective hollow drums  41  and  42  coaxial with respective sun gears  24  and  25  and fitted in rotary manner to frame  14 . The cavities of drums  41  and  42  are eccentric with respect to axes  26  and  27  of respective sun gears  24  and  25 , and comprise respective small portions facing belt transmission  16 , and respective larger portions facing the respective pulleys. The cavities of drums  41  and  42  act as respective seats  43  and  44  for supporting respective planetary gears  30  and  31  in rotary manner. 
     Each planetary gear  30 ,  31  is in the form of a hollow drum, which comprises a relatively small-diameter portion  45 ,  46  facing belt transmission  16  and having outer teeth formed on the end facing respective fixed ring gear  28 ,  29  and which mesh with fixed ring gear  28 ,  29 ; and a larger-diameter portion  47 ,  48  facing respective pulley  3 ,  5  and connected integrally to a respective further hollow, coaxial drum  49 ,  50 . 
     The cavities of drums  49  and  50  are substantially eccentric cylindrical holes, and act as respective seats  51  and  52  for respective shafts  4   a  and  6   a  of pulleys  3  and  5 . 
     To transmit to pulley  3  the rotary movement about axis  4  according to law of motion LM 2 , actuating device  13  comprises a motor  53  connected to a constant-velocity universal joint  54 , which comprises a shaft  55  fitted to frame  14  and connected to motor  53 , and a shaft  56 , which is fitted inside the cavity of the first portion  45  of planetary gear  30 , is connected by a connecting rod  57  to shaft  55 , and is connected by a connecting rod  58  to shaft  4   a  of pulley  3 . 
     Shaft  6   a  of pulley  5  is connected by a connecting rod  59  to a shaft  60  housed inside the cavity of the first portion  46  of planetary gear  31 , so that both the gear trains have the same rotary components, even though pulley  5  is driven by pulley  3  via belt  2 . 
     In actual use, motor  15  drives device  12 , which transmits to pulleys  3  and  5  the reciprocating motion along respective straight courses T 1  and T 2  according to law of motion LM 1 ; and motor  53  drives device  13 , which, via constant-velocity universal joint  54 , rotates pulley  3  and belt  2  according to law of motion LM 2 . 
     During operation, conveyor  1  subjects to reciprocating motion in direction D a mass M, which substantially corresponds to the sum of the masses of pulleys  3  and  5  and the respective shafts  4   a  and  6   a.    
     With reference to FIG. 3, mass M is considered as being applied equally, i.e. M/2, to axes  4  and  6  of pulleys  3  and  5 ; and the reciprocating motion of axes  4  and  6  generates forces of inertia F 1  oriented in direction D and applied to axes  4  and  6 , as shown more clearly in FIG.  4 . 
     Drums  49  and  50  integral with respective planetary gears  30  and  31  are so sized that their own masses correspond to the masses M/2 applied at respective points  61  and  62 , which are located at a distance equal to “e” from axes  32  and  33 , and are diametrically opposite axes  4  and  6  with respect to axes  32  and  33 . 
     Drums  41  and  42  integral with respective sun gears  24  and  25  are so sized as to be equal to respective eccentric masses M rotating about respective axes  26  and  27 . 
     With reference to FIG. 4, mass M/2 of drum  49  generates a force of inertia F 2  applied to axis  26  and perpendicular to force F 1 . The composition of forces parallelogram determines the resultant force F 3 , which is applied to axis  26 , substantially rotates about axis  26 , and is balanced by the applied mass M, which generates a rotary force F 4  equal to and opposite force F 3  and applied to axis  26 . Such balancing is made possible by both sun gear  24  and the respective planetary gear rotating about respective axes  26  and  32  with the same law of motion LM 1 . 
     Epicyclic gear trains  17  and  18  rotate in opposite directions, so as to balance the torques generated by the variations in speed of law of motion LM 1 . 
     Conveyor  1  described affords various advantages. transmitting reciprocating motion to pulleys  3  and  5  by means of gearing  16 ,  17 ,  18 ,  34  provides, on the one hand, for precise transmission with no need for guides, and, on the other, for achieving a balanced conveyor as regards both moments of inertia and the forces of inertia in direction d.