Twist finger apparatus for wrapping candies and the like
BACKGROUND OF THE INVENTION 
     The present invention relates to the devices known as twist finger assemblies mounted on machines for wrapping candies or similar products in what is known as the `single end` (`side bow`) or the `double end` twist style and, to be more precise, has as its subject a device for opening and closing the twist fingers on the said assemblies. 
     DESCRIPTION OF THE PRIOR ART 
     With machines for wrapping candies or similar products, the method is already used of creating a tubular wrap around the product to be wrapped and of having folding mechanism at the opposite ends of the said wrap with which to fashion it into the desired style: for example, the `point wrap` style, the `soap/diamond` style, the `single end twist` (`side bow`) style, the `double end twist` style and in other styles too. 
     In the particular case of what are called the `single end twist` (`side bow`) and the `double end twist` styles of wrap, the use is known of what are called twist finger assemblies positioned along the wrapping track of the wrapping machine which, when brought into operation, grasp the opposite end/s of the tubular wrap, rotate around their axis which generally coincides with that of the tubular wrap and simultaneously move closer to the product because of the wrap having got shorter as a result of the twist/s given to the end/s to suit the desired wrapping style. 
     On all the devices of this type known to date, the twist finger assemblies are made to open their fingers, to grasp the end/s of the tubular wrap, rotate, progressively move closer to the product, and return to their initial position. This is done either by means of cams keyed onto one single drive shaft and levers associated thereto, or through toggle lever systems which operate the various parts, see for example, British Pat. Nos. 442,803 and 699,422, German Pat. Nos. 650,533 and 885,227 and Italian Pat. No. 466,665, l or, according to Patent Application Ser. No. 528,663 filed on the same day herewith by; the same applicant as herein, it is done directly by disk means rotatable and slidable on a sleeve and rod. 
     The twist fingers have been opened and closed by means of a rod, resiliently reciprocated in the sleeve, which has been provided at one end with a rack meshing with a gear segment on each of the fingers concentrically with a pivot pin for the closing and opening operations. 
     With this rack operating mechanism meshing with the annular toothing of the twist fingers, what happens in actual practice is that when twist finger assemblies of this nature are used on high unit output speed wrapping machines, for example, of the type described in British Pat. No. 1,259,912 and in Italian Pat. No. 862,104, the fingers frequently get broken and the breakage generally occurs in the area of the annular toothing where the pressure reacting to the grip applied by the fingers to the part of the wrap to be twisted, is the greatest. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to overcome the aforementioned problem by providing a device for opening and closing the fingers on twist finger assemblies which can be used even on high speed wrapping machines without any kind of breakage being caused. 
     This and other objects too have been attained with the device according to the invention the fingers on the twist finger assemblies, mounted on machines for wrapping candies or similar products, particularly high speed wrapping machines, in order to fashion a tubular wrap in what is known as the `single end` (`side bow`) or the `double end` twist style of wrap, are symmetrically pivoted to one end of an axially guided sliding sleeve and there is a rod that also slides and is guided in an axial direction in the inside of the sleeve, one end of which extends adjacent to the point where the pivot pins of the fingers are located. Means are provided for causing the sleeve and rod to rotate in unison.  The fingers are each provided with a protrusion radial with respect to their pivot pin and there are two links, each of which is articulated at one end to a common pivot pin at the one end of the aforementioned rod, and at the other, to the extremity of the radial protrusion of one of the twist fingers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages will emerge more clearly from the following detailed description of a preferred but not the sole form of embodiment for the device according to the invention, illustrated purely as an example in the accompanying drawings in which: 
     FIG. 1 shows, in a perspective view, a twist finger assembly provided with the new mechanism, with the fingers open; 
     FIGS. 2 and 3 show the same device with the fingers closed and open, respectively, in side elevation with certain parts in sectional form and still others removed so that others can be seen better. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As can be seen from the above mentioned figures, the device for opening and closing the twist finger assemblies comprises a sleeve 1, provided with a fork shaped head 2, and wherein two fingers 3 and 4 are symmetrically pivoted by means of pins 5 and 6, respectively. Each finger, as best shown in FIG. 1, is integral with a hub 3&#39;, 4&#39; rotatable on the respective pivot pin 5,6 and slidably supported in between parallel sidewalls 2a, 2b, 2a&#39;, 2b&#39;; of the fork of head 2. 
     The part comprising the gripping area 3b, 4b of the said fingers 3 and 4 is shaped in a conventional manner but instead of the customary gear segments or annular toothings concentric to the pivot pins 5 and 6, respectively, the invention provides the hub of each finger with a radial protrusion 3a and 4a, respectively, shown as an integral part of the hub extending from the respective pivot pin in a direction opposite to that of the finger. 
     Inside the sleeve 1, coaxially with respect to it, is mounted a rod 7 and this slides in a bush 8 which is also housed in the inside of sleeve 1. 
     The rod 7, as shown, has a forked outer or forward end 7a adjacent the pivot pins 5 and 6 of the fingers 3 and 4 are located. The rod has an inner or rearward end, which protrudes from the sleeve, and terminates at a mechanism with which it is operated. This mechanism forms part of the subject matter of the aforementioned application of the same applicant as herein, and the under mentioned parts of it are shown on the accompanying drawing. Two more bushes 9 and 10 are provided for guiding the rod and, coaxially mounted on the two bushes respectively, there are two thrust bearings 11 and 12. A gear disk 13 rides on bush 9 and is inclined relative to it, this disk being structured in its plane in the form of a cam. A return spring 14 acts on disk 13, tending to shift it and thereby thrust bearing 11, bush 9, and rod 7 forwardly. Also provided are a cap 15 for the said spring 14, a lock nut 16, another bearing 17, a circular slide guide 18, and guide members 19 engaging the cam type gear disk 13 for reacting to rotary movement of the latter by axially shifting it. The gear and cam disk 13, having teeth 13&#39;, is rotated by suitable drive means, not shown. As already mentioned, the sleeve 1 and rod 7 are rotated in unison. This is done by suitable rotating means M. 
     The free end of each of the aforementioned radial protrusions 3a and 4a of the fingers 3 and 4 has articulated to it, through a pin 20 and 21, respectively, the end of a link 22 and 23, respectively, the other end of which is articulated, through a common pin 24, to the aforementioned extremity 7a of the rod 7. 
     The coordination of the parts 3a-4a, 22-23 and 7a of the rod is such that the angles formed between the pins 5-6 and the pins 20-21 and between the latter and the common pin 24 are always acute, and preferably vary in magnitude from around 54° when the fingers are closed, to around 73° when they are open. 
     The way in which the parts are arranged is, furthermore, such that, when the fingers are in their closed position, the axes of pins or trunnions 20-21 between the radial protrusions 3-4 and the respective links 22-23 lie, with respect to the plane of symmetry of the fingers, on the outside of the  planes parallel with the axis of the rod 7 passing through the axes of pins 5-6 that serve for the rotation of the said fingers.