Gripper for plastic film automatic wrapping machine

Abstract: Gripper for plastic film grasping, particularly suitable for automatic wrapping machines with turntable, provided with plates sliding into mobile guides, whose convergence is allowed, during closing phase, by a device fitting between the guides.

Description: The present model relates to a gripper particularly suitable for the grasping of plastic film for automatic wrapping machines, the kind with turn-table, where the load to be wrapped is placed on a rotating table. It is known from earlier European Patent Application 9083 0504.8, published as EP-A-0 430 902 on 05.06.91, that, for an automatic plastic film wrapping machine, particularly suitable for suitcases, a gripper for plastic film grasping was designed, wherein two plates sliding into guides fastened to a support were provided. Gripper opening and closing is operated by the plate sliding into guides whose longitudinal axes converge into the closing point of the gripper; plate sliding is operated through leverages connected to upsaid plates by means of pin pairs perpendicularly fastened to them. This kind of gripper has the disadvantage of a very marrow field of operation where the film grasping is allowed through the convergence of the mobile elements into the fixed guides. This means that, if the gripper/film relative position is out of a few millimeters field, the grasping can fail and put the machine out of order, thus compromising its automatic functioning conception. The present invention aims at preventing this disadvantage by designing a gripper according to claim 1 with plates sliding in two guides oscillating in a common plane, the convergency of said plates being allowed: during the closing phase, by a device fitting between the guides. Other aims and advantages will be better disclosed by the following description and the accompanying drawings, which show a possible embodiment of the finding in an only schematic and explicative way. With reference to the drawings: Figure 1 is a frontal view of the gripper in its closing position; Figure 2 is a frontal view of the gripper in its opening position; Figure 3 is a right lateral view of the gripper in its closing position: with a dashed partial detail of the open gripper; Figure 4 is a frontal view of one of the plate-holder guides; Figure 5 is a top view of on of upsaid guides. The gripper is made by a support 1 on which guides 2a and 2b are fastened in an osciilatory way; between upsaid guides plates 3a and 3b, provided with the pairs of pins 4a/4b and 5a/5b, respectively, are sliding. Between said pin pairs, bar 6 is positioned, connected through arm 7 to bar 8, whose rotation within a prdetermined circle arc, causes gripper opening/closing, the first bar 6 being rotatably and slidably, transversely to the direction of it's dispacement, in operative engagement with both plates. Arm 7 is provided with element 10 at whose end device 9 is fastened; upsaid device is appropriately shaped (e.g. wedge-shaped) as to fit, during closing, between guides 2a and 2b. These guides, whose schematic shape is represented in Figures 4 and 5, are provided with a hole 11 to allow the passage of an appropriate screw for fastening the guides themselves to support 1, in an oscillatory way. Support 1 is provided with element 1a having a through -hole and acting as a guide for bar 8, and dowel 12 as locating element for the oscillating guides 2a and 2b during gripper closing. The finding operation is very simple and is described hereunder. When the gripper is closed (Fig. 1), the downward displacement of bar 6, thanks to bar 8 rotation, causes plates 3a/3b, sliding into guides 2a/2b, to go down. As these guides oscillate in their upper part, they will get parallel as soon as device 9 releases from them. When the gripper is open (Fig. 2), the plates will be parallel, positioned downwards at the end-of-stroke, with their ends wide apart. During closing, for plastic film 13 grasping, bar 6 coming up will cause plates 3a/3b come upwards; upsaid plates will be parallel for a long stretch, until device 9 fits between guides 2a/2b, thus helping their convergency in consequence of the specular rotation around their respective oscillation axes 14a/14b. When bar 8 completes its rotation within its working arc, device 9 will be completely fitted between guides 2a/2b, plates 3a/3b will be upwards, at the end-of-stroke and joined; in this way plastic film 13 grasping will be carried out by upsaid gripper. Thanks to its design, the gripper allows film grasping even if the film is not strictly into the narrow field passing through the vertical axis of the gripper itself. As a matter of fact, plates, before closing, will cover a long stretch being wide apart, thus allowing the gripper to grasp the film also if it is misaligned. This special characteristic is particularly suitable for automatic machines operated by unskilled operators, as they must guarantee the highest degree of duty continuity. The present finding, schematically described above in an explicative way, according to a possible but not restrictive embodiment, can be extended to all alternatives falling within the scope. Practically, in fact, sizes and materials can be whatever, according to needs, and the technical details can be replaced by other equivalent ones, without departing from the scope of the invention as defined in the claims forth below.

Claims: GRIPPER FOR PLASTIC FILM AUTOMATIC WRAPPING MACHINE , wherein a support is provided, to which two guides (2a , 2b) oscillating in a common plane are fastened , in which guides (2a , 2b) respective plates (3a , 3b) slide, this sliding being determined by the displacement of a first bar (6) operated by the rotation of another bar (8) coupled to the first bar (6) , said first bar (6) being rotatebly and slidably , transversely to the direction of it's displacement , in operative engagement with both plates (3a , 3b), wherein plates closing is determined by the fact that a device (9) gets between the oscillating guides (2a , 2b), thus causing the progressive specular rotation of the guides (2a , 2b) around their respective oscillation axes (14a , 14b) , and the consequent convergency of said plates (3a , 3b). GRIPPER , according to claim 1, wherein at least one locating dowel (12) for the oscillating guides (2a , 2b) is provided.

Inventors: ERRANI FRANCA, MISSIRINI MARINO, ERRANI, FRANCA, MISSIRINI, MARINO
Applicants: DERIFAN SPA, DERIFAN S.P.A.
Application year: 1991
Main classification: B65B11
IPC codes: B65B41, B65B11