Abstract:
A linear motion device ( 10 ) associated to a worm ( 14 ) including a body ( 12 ) internally provided with a housing seat for partially receiving a worm having a plurality of grooves, a mobile device ( 52 ) for temporary engagement in an exposed portion of at least one of the grooves ( 54 ) of the worm, and a pressure device ( 40 ) including a pneumatic piston for moving the mobile device in contact with at least one of the grooves of the worm.

Description:
FIELD OF THE INVENTION 
   The present invention refers to a linear motion device associated to a worm. More particularly, the present invention refers to a linear motion device fit to engage with a worm only when the traverse with linear or straight-line motion of mechanical components of machine tools or the like is required. 
   BACKGROUND OF THE DISCLOSURE 
   Examples of mechanical components wherein the motion device of the present invention can be applied comprise the trolleys with working tools temporarily sliding along guides. This condition can be found, for example, on machines cutting the foil material into films that require a plurality of aligned trolleys bearing blade and/or counter-blade holders. In these machines the trolleys are spaced among them in a proper and variable way in order to obtain, by continuous cutting, some strips of material having different widths. 
   It is known that for many machine tools of different kinds the linear motion of the equipments or the relevant supports with the working tools along guides or sliding tracks is required. This motion is usually carried out through a lead screw to which a nut is coupled, being in its turn engaged with the trolley or support to traverse. 
   Each of the trolleys or supports needs the presence of one nut associated to the lead screw that it is rotated by hand or by an engine. Even though this known solution is currently used, it is not free of from drawbacks. 
   These drawbacks are due to the fact that the equipment comprises building difficulties and implies high costs that are also connected to the periodic maintenance. The presence of a plurality of nuts associated to the lead screws, one for each trolley or supports to be moved is also cumbersome. The same nuts being constantly coupled with the lead screws can suffer from the stresses caused by the operation of the machine wherein they are applied with subsequent blacklashes due to the mechanical wears and frictions. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to remedy the above-mentioned drawbacks. 
   More particularly, an object of the present invention is the provision of a linear motion device associated with a worm that is easily manufactured and at low cost, and is not bulky and does not need a continuous and difficult maintenance. 
   A further object of the present invention is the provision of a device as defined above that temporarily engages with the lead screw, and therefore, does not suffer from possible stresses induced by the machine while applied during the operation. 
   A further object of the present invention is the provision of a linear motion device being able to assure a high level of resistance and reliability in time, as well as being easily manufactured. 
   According to the present invention, these and other purposes are achieved by the linear motion device that is associated with a worm provided with grooves and is mainly characterised in that it comprises a box-shaped body having a housing seat defined internally in the shaped body and forming a partial delimitation of said worm, a mobile device ( 52 ) which temporary engages within at least one of the grooves of the same worm, and pressure means ( 40 ) for moving the mobile device ( 52 ) in contact with at least one of the grooves ( 54 ), said pressure means comprising a pneumatic piston. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The building and functional features of the linear motion device of the present invention can be better understood from the following description wherein reference is made to the attached tables of drawings representing a preferred embodiment which is given only by way of non-limitative example wherein: 
       FIG. 1  is a schematic view of a longitudinal section of the linear motion device of the present invention in non-operative conditions; 
       FIG. 2  is a schematic view of a section along the A-A line of the same device of  FIG. 1 ; 
       FIG. 3  is a schematic view of a longitudinal section of the linear motion device of the present invention in operation; 
       FIG. 4  is a schematic view of a section along the C-C line of the device of  FIG. 3 ; 
       FIG. 5  is a partial schematic view of a cross section of the same device of the previous Figures without the upper closing element; 
       FIG. 6  is a further schematic view of a longitudinal section of a linear motion device of the present invention according to an embodiment variant; and 
       FIG. 7  is a front schematic view of the device of the present invention that is, for example, associated to a sliding guide to move a tool holder trolley. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1 and 2 , the linear motion device of the present invention, marked in its whole with  10  in  FIG. 1 , comprises a box-shaped body  12 , for example a regular prism body provided with opposite sidewalls  24 ,  26  and with an upper edge or mouthpiece  20 . Inside the box-shaped body  12 , a housing seat of a worm  14  being able to rotate with any suitable means is formed. The seat is advantageously obtained in a central position inside the body  12  wherein it is crosswise extended and delimited and in its lower part by the internal side of the base of the same body and, sideways, by opposite shoulders  16 ,  18 . 
   The shoulders,  16 ,  18  develop in height for a limited portion while remaining remarkably spaced with their upper end from the edge or mouthpiece  20  of the box-shaped body  12 . Therefore, the worm  14  is partially exposed in its part facing the mouthpiece  20  with a sector  22  that preferably corresponds to one fifth of the periphery. Between the shoulders  16 ,  18  and the opposite sidewalls  24 ,  26  of the box-shaped body  12  relevant recesses  28 ,  30  preferably of regular geometric shape extending in depth for a portion that it is lower than the bottom limit of the worm  14  abutted within the base of the same body are obtained. The recesses  28 ,  30  are fit to house elastic contrast means described here below. 
   A covering element or lid  32  that is centrally provided with a projection or turret  34  of any shape and size is fastened to the upper edge or mouthpiece  20 . The lid  32  is integral to the body  12  with fastening means such as screws  36  or the like. 
   The turret  34  of the lid  32  internally defines a housing seat  38  for pressure means that are, for example, constituted by a small pneumatic piston  40  as shown in Figures from 1 to 4. 
   The small pneumatic piston  40  is conventionally fed through a fitting  42  and its relevant duct  44  for a working fluid. In the alternative embodiment of  FIG. 6 , that it is given by way of example, the pressure means is marked with  46  and it is constituted by a similar small piston that is manually moved for example by a screw  48 . In both cases, the pressure means  40  or  46  bears a temporary engagement member with the worm  14  in its lower end facing the body  12  and the worm  14  in order to cause, if necessary, the linear motion of the body  12  in its whole. 
   For example, with reference to  FIG. 7 , the body  12  constitutes the traverse vehicle along the worm  14  and a support such as a trolley  50  is connected to it with known means. A working tool to cut the materials, which is shown and sketched with a dashed line in its whole with  60 , or any other means requiring a linear or straight-line motion on a machine tools or equipment is coupled with the trolley  50 . 
   Referring now to  FIGS. 1-5 , the member engaging with the worm  14  is advantageously constituted by at least one rod or pin  52  that extends crosswise in the body  12  according to a direction that is parallel to the grooves of the worm  14  marked with  54 . The rod  52  is fit into opposite guiding slots  52 ′ ( FIG. 5 ) obtained on the internal face of the sidewalls  24 ,  26  of the body  12 . The crosswise extension of the rod or pin  52  is preferably slightly lower that the whole width of the body  12  and it is higher than the maximum distance existing between the recesses  28 ,  30 . The profile of the rod or pin  52  is complementary to the one of the grooves  54  of the worm  14 . 
   With an appropriate dimensioning, the pressure means  40  or  46  can bear two or more parallel rods or pins  52  fit to match with as many grooves  54  of the worm  14  as described here below. 
   In recesses  28 ,  30 , for example, contrast elastic means of the rod or pin  52  are constituted by helical springs  56 . 
   The springs  56  keep the rod or pin  52  separated from the grooves of the worm  14 , i.e. it is driven upwards towards the lid  32  forming the rebating plane for the same rod. The internal surface of the sidewalls  24 ,  26  of the body  12  defines, together with the mouthpiece of the recesses  28  and  30 , a step  58  that is substantially aligned to the grooves  54  of the worm  14  in its part protruding from the shoulders  16 ,  18 . The step  58  can form a stop rebate of the rod or pin  52  of the vertical excursion towards the same worm  14 . 
   As it can be noticed from the above description, the operation of the motion device  10  temporarily engages the body  12  and the support  50  connected to it by the worm  14  with the subsequent required linear traverse or motion.  FIGS. 1 ,  2  and  6  schematically show in detail the device  10  of the present invention in a non-operating condition as the rod or pin  52  is moved upwards due to the effect of the elastic means  56  with respect to the grooves  54  of the worm  14 . 
   Therefore, the possible rotation of the latter in the body or bodies  12  does not cause their traverse or linear motion effects as the rod or pin  52  is not engaged with one or the other groove  54 .  FIGS. 3 and 4  schematically show the device  10  in operation, its rod or pin  52  is abutted into one of the grooves  54  of the worm  14 . This condition occurs after the pneumatic or hand operation of the pressure means  40  or  46  by which the rod or pin  52  lowers towards the body  12  and centrally matches with one of the grooves  54  of the worm  14 . The clockwise or anti-clockwise rotation of the worm  14 , in this case, causes the traverse or linear motion of the body  12  and of all means fastened to it, i.e. of the support or trolley  50  with the relevant tool  60  or of any other kind of tool. On the contrary, once the required positioning of the body/bodies  12  is obtained, the rod or pin  52  is disengaged from the groove  54  of the worm  14  and this result is obtained removing the fluid pressure on the pressure means  40  or the mechanical one on the pressure means  46  intervening on the screw  48 . 
   As it can be noticed from the above-mentioned description, the advantages obtained by the invention are clear. 
   The linear motion device of the present invention can be easily manufactured and installed at low costs and it does not require particular maintenance. 
   The opportunity of temporarily engaging, if necessary, the device/devices,  10  with the worm  14  is particularly advantageous. 
   Even though the invention has been described with reference to some embodiments given as an illustrative and non-limitative example, many changes and variations can be carried out by a person skilled in the art according to the above-mentioned description. It is therefore understood that the present invention is meant to comprise all changes and variations falling within the spirit and the protective scope of the following claims.