the figures are provided only for purposes of illustrating preferred embodiments of invention , the scope of which includes other arrangements or designs of both the tube , the nets and the protection sheets and / or hollow support cylinders . fig1 - 4 illustrate embodiments of the invention that are shown comprising a support tube 1 made of a stiff material having an attachment mechanism 2 securing it to the stuffing horn , on which is placed a suitably shirred tube 3 with this assembly being coated with a separation sheet 4 and finally with a tubular net 5 , also suitably compressed or shirred , and that together with the inner tube 3 extends beyond the support tube 1 and is strangled against it by a clip , knot or staple 7 . the support tube 1 is a stiff tube made of any material , preferably one suitable for being in contact with food products . its length , inner diameter and wall thickness can vary according to the width of the tube , the characteristics of the net , the length of the stuffing horn of the machine used to fill it , the total length of the tube and net to be shirred and compressed , etc . the stuffing horn on which the system is placed will determine the minimum inner diameter of the hollow support cylinder , so that the former will fit inside the latter . the same is true of its length , as the stuffing horn must always be longer than the hollow support cylinder for the tube . the thickness of the wall of the hollow support cylinder will mainly depend on its strength , and should be enough to withstand , without deformation , the pressure transmitted by the net , particularly when the net is elastic . the hollow support cylinder can have any attachment mechanism to the stuffing horn and can be perforated to allow wetting the inner shirred tube before it is used whenever this is necessary . the tube 3 can be made of an edible or inedible material , preferably one suitable for being in contact with food products , shirred in an accordion - like manner to form folds perpendicular only to its longitudinal axis , or also parallel to said axis , in order to contain the greatest possible length in a minimal space . in order to allow the air that is trapped when stuffing the product to exit during the heat treatment , the tube can be previously perforated . the size and distribution of the orifices can be variable and should allow air to exit , yet ensure retention of fluids and the mechanical strength of the tube . the separation sheet 4 for the shirred tube 3 and the net 6 that is later placed can be made of any material , preferably one suited to come in contact with food products ; its purpose is to separate the shirred tube from the compressed net so that when the two are simultaneously deployed , the friction and drag of the film by the net is prevented , so that the deployment is uniform and the tube is not damaged by the net . it can consist of an enveloping sheet with the edges glued to form a tube , or can be formed as a tube directly , or can be a simple enveloping sheet suitably overlapped . this sheet is attached to the hollow support cylinder on the rear to prevent the sheet from being carried away by the net when the latter is extended . it can be attached to the tube by an adhesive or by any other suitable method . finally , the net 5 comprises a sock or tube - shaped weave with walls made of threads , fibers or string of vegetable - origin materials such as cotton and / or latex , synthetic materials or a mixture thereof , suitably intertwined to form a characteristic weave . the most common nets comprise an elastic thread coated with a cotton or synthetic fiber , arranged in a spiral along the entire length of the sock or tube , with adjacent coils attached to each other by threads knotted at regular intervals forming a grid closed onto itself in which the transverse fibers are elastic and the longitudinal ones are not . there are also semi - elastic nets in which the weave has a certain degree of elasticity , as well as non - elastic nets . in the latter case the threads can determine a great variety of weaves , forming diamonds , hexagons , etc . the net 5 is compressed similarly to the shirring of the inner tube 3 for non - elastic and semi - elastic nets ; however , for elastic nets , the elastic coils of the spiral that form the transverse rings of the net are arranged concentrically as shown in fig4 , remaining by their elasticity such that unshirring can take place smoothly , so that the net that is still compressed or shirred will not press against the net that is being deployed at any time , as at all times and because of the manner in which the double casing is prepared , which is also part of the scope of the invention and that will be described further below , the order of compression or shirring of the net is opposite to that of decompression or unshirring , that is , the last portion of net deployed is the first to be compressed . this system allows compressing or shirring a great length of tubular net in a small space . the assembly formed by the compressed net , which comprises a length of net substantially equal to that of the shirred tube , is placed a few centimeters behind 6 the assembly of the shirred tube ( fig3 ). the reason for this is so that the front of the film is never pressed on by the net and is thus free to be unshirred during the stuffing operation . as the assembly is extended both fronts , that of the shirred tube and that of the compressed net , are retracted in parallel and keep this safety distance 6 at all times . the assembly can incorporate a clip , knot or staple on its open end , as a closure , so that it is not necessary to perform this operation at the start of the stuffing operation . in order to manufacture the described product , in its most developed version , a commercially available cylindrical hollow stick of flexible shirred tube 3 made by any known method is used , inside which is placed a hollow support cylinder 1 . after this assembly is coated with the separation sheet 4 the net is placed and shirred , by a machine as that shown in fig5 . specifically , in this machine , a coil of net 8 is placed in the coil - bearing system 9 of the machine and a certain length of net is unwound , making it pass through a tensioning roller 10 and then threading it in the rear end of a floating spindle 12 until it is placed under the carrier wheels 13 of the net . then the stick of the shirred cylindrical tube 3 is mounted on the hollow cylindrical support 1 and is placed after it is coated with the separation sheet 4 on the support 14 for the stick retraction system 15 , and the latter is placed inside the hollow floating spindle 12 until the end of the shirred film is inserted a few centimeters in the spindle . afterwards the carrier wheels 13 and the stick retraction system 15 are set in motion so that the net falls on the stick as the latter retracts , coating it with an amount of net equivalent in length to that of the previously shirred film . the density of the net shirred in this manner will be determined by the speeds of the carrier wheels 15 and the retraction system 15 . in order to define the scope and characteristics of the invention , the following examples are provided as illustrating preferred embodiments , and not to limit the scope of the invention . two sticks with a double tube and net casing were manufactured , one according to the system described in the description of the preferred embodiments , which is referred to as the “ independent coaxial arrangement ” of the tube and net sticks , and the other by shirring jointly and simultaneously the tube and the net to form a single stick . the relevant data of the materials used and the dimensions of the sticks produced are shown below in the following table : table 1 shows that the stick manufactured according to the system described a preferred embodiment has 30 meters of double casing as compared to the 6 meters contained in the one manufactured with the joint shirring method , both on 430 mm of stick , that is , 5 times more . the shirring ratios are respectively 69 . 76 and 13 . 95 meters of double casing per meter of stick . two sticks with a double tube and net casing were manufactured , one according to the system described in the description of the preferred embodiments , which is referred to as the “ independent coaxial arrangement ” of the tube and net sticks , and the other by shirring jointly and simultaneously the tube and the net to form a single stick . the relevant data of the materials used and the dimensions of the sticks produced are shown below in the following table : table 2 shows that the stick manufactured according to the system described in the invention has 25 meters of double casing as compared to the 7 . 12 meters contained in the one manufactured with the joint shirring method , both on 500 mm of stick , that is , 3 . 5 times more . the shirring ratios are respectively 50 and 14 . 24 meters of double casing per meter of stick . two sticks with a double tube and net casing were manufactured , one according to the system described in the description of the preferred embodiments , which is referred to as the “ independent coaxial arrangement ” of the tube and net sticks , and the other by shirring jointly and simultaneously the tube and the net to form a single stick . the relevant data of the materials used and the dimensions of the sticks produced are shown below in the following table : the table shows that the stick manufactured according to the system described in the description of the preferred embodiments has 16 meters of double casing as compared to the 6 . 6 meters contained in the one manufactured with the joint shirring method , the first on 270 mm of stick and the second on 430 mm of stick , that is , almost 4 times more double casing per unit length of stick in the independent coaxial arrangement . the shirring ratios are respectively 69 . 76 meters and 13 . 95 meters of double casing per meter of stick . for the purposes of promoting an understanding of the principles of the invention , reference has been made to the preferred embodiments illustrated in the drawings , and specific language has been used to describe these embodiments . however , no limitation of the scope of the invention is intended by this specific language , and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art . the particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way . for the sake of brevity , conventional aspects of the systems ( and components of the individual operating components of the systems ) may not be described in detail . furthermore , the connecting lines , or connectors shown in the various figures presented are intended to represent exemplary functional relationships and / or physical or logical couplings between the various elements . it should be noted that many alternative or additional functional relationships , physical connections or logical connections may be present in a practical device . moreover , no item or component is essential to the practice of the invention unless the element is specifically described as “ essential ” or “ critical ”. numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention .
a casing is embodied as a hollow stiff cylindrical support provided with an attachment mechanism in its coupling to the stuffing horn , on which is placed a suitably shirred tube which in turn is coated with a separation sheet and finally by a tubular net , also compressed or shirred , and which together with the inner tube extends beyond the support tube and is clamped against the tube by a clip , staple or knot such that during the stuffing operation the shirred tube and the equally shirred net are axially extended , with a simultaneous yet independent extension of the two elements favored with the aid of the intermediate separation sheet .