Abstract:
A bar guiding device in a feeder for feeding a machine tool, composed of two elements that have respective slots and can move with respect to each other between an open position, which allows insertion of a bar between them, and a mutually adjacent position, at which the slots form a longitudinal channel for advancement of a bar to be fed to the machine tool by way of a bar pusher connected to an actuation chain that is external to the channel by means of a bridge that is guided through regions where the elements mate, the regions being in mutual contact, so as to close the channel, and undergoing elastic deformation in order to allow passage of the bridge between them.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a bar guiding device in a feeder for feeding machine tools. 
     Devices having various structures are known which, in feeders for feeding bars in machine tools, allow to keep the bars guided during the intended machining operations. The most common devices consist of a pair of longitudinally superimposed half-shells that are articulated one another and comprise mutually opposite semicylindrical cavities. By means of suitable actuators, the half-shells are actuated between an open position, in order to allow to insert a bar in the cavity of one half-shell, and a closed position, in which the cavities of the two half-shells are mutually integrated so as to form a channel along which the bar is pushed toward the machine tool. In some embodiments, each half-shell is constituted by a plurality of longitudinally aligned sections. 
     In particular, Italian patent No. 1,266,350 discloses a guiding device composed of a plurality of pairs of sprockets that mesh together and are provided with polygonal peripheral slots that decrease in depth and form passage and guiding openings for a bar that is driven through them. 
     In known devices of the described type, the advancement of the bars along the guiding channel is provided by means of an appropriately provided pusher (known as bar pusher), which is connected by means of a bridge to an actuation chain, which lies outside the channel. The bridge is constituted by a plate which, during the advancement of the bar pusher, moves between the contiguous edges that delimit the bar guiding channel on the longitudinal opening side. 
     In order to allow passage of the bridge, the contiguous edges of the channel must be spaced at least by an extent equal to the thickness of the bridge. In this manner, the guiding channel is open longitudinally through a slit that produces internal edges, against which the bar makes sliding contact during machining. However, if the bar has a polygonal cross-section, during its rotation the edges of the bar collide against the inner edges of the cap, causing damaging vibration and intolerable noise. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a guiding device for bars that allows to obviate these shortcomings suffered by known devices. 
     Within this aim, an object of the present invention is to provide a device that is flexible in use and is suitable to be used in feeders of various design. 
     This aim and this and other objects that will become better apparent hereinafter are achieved by a bar guiding device in a feeder for feeding a machine tool, composed of two elements that have respective slots and can move with respect to each other between an open position, which allows insertion of a bar between them, and a mutually adjacent position, at which said slots form a longitudinal channel for the advancement of a bar to be fed to the machine tool by means of a bar pusher connected to an actuation chain that is external to said channel by means of a bridge that is guided through regions where said two elements mate, characterized in that said regions are in mutual contact, so as to close said channel, and can undergo elastic deformation in order to allow the passage of said bridge between them. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become better apparent from the following detailed description of some preferred but not exclusive embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a sectional view of a guiding device according to a first embodiment and in the closed position; 
     FIG. 2 is a sectional view of the device of FIG. 1 in the open position; 
     FIG. 3 is a perspective view of the elements that provide the guiding channel of the device of FIGS. 1 and 2; 
     FIG. 4 is a perspective view, similar to FIG. 3, of a second embodiment; 
     FIG. 5 is a transverse sectional view of the elements that provide the guiding channel according to a third embodiment; 
     FIG. 6 is a transverse sectional view of the elements that provide the guiding channel of FIG. 5 during the passage of the bridge that entrains the bar pusher; 
     FIG. 7 is a transverse sectional view of the elements that provide the guiding channel according to a fourth embodiment; 
     FIG. 8 is a transverse sectional view of the elements that provide the guiding channel of FIG. 7 during the passage of the bridge that entrains the bar pusher; 
     FIG. 9 is a view of the elements according to a fifth embodiment; 
     FIG. 10 is a side view of the elements of FIG. 9; and 
     FIG. 11 is a view that is similar to FIG. 10 but is taken during the passage of the bridge. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, the reference numeral  1  generally designates a bar guiding device in a feeder for feeding a machine tool. The device  1  is composed of a beam  2  that has a rectangular tubular cross-section and lies between two side walls  3  that are rigidly coupled to the beam at its opposite ends. 
     A plurality of brackets  4  are fixed to the beam  2 , are provided with supports  5  and rise at right angles to the beam; a longitudinal profiled element is articulated in supports  5  by means of a shaft  6 , and the profiled element acts as a cover  7  of the guiding device  1 . 
     An element  10  is fixed to the brackets  4 , with the interposition of a strip  8  that is fixed by means of screws  9 , and is constituted by a longitudinal body that has a rectangular cross-section and is made of a wear-resistant and elastically deformable material. The element  10  can be monolithic or can be constituted by a plurality of mutually aligned segments. 
     The element  10  is fixed to the strip by means of screws  11  driven through bushes  12  that are shaped so as to remain locked between the head of the screws  11  and the strip  8 . 
     The portion of the bushes  12  in which the head of the screws  11  is recessed is wider than the remaining portion so as to form a step  13 , which abuts against an annular shoulder formed in holes  14 , through which the bushes and the screws are inserted in the element  10 . 
     The cover  7  has a substantially U-shaped cross-section, with a protrusion  15  that is welded to eyes  16  whereby the cover is hinged to the shaft  6 . 
     An element  17 , having a cross-section that is substantially mirror-symmetrical with respect to the element  10  and made of the same wear-resistant flexible material, is fixed to the inner face of the cover  7 , which is directed toward the beam  2 . Like the element  10 , the element  17  also is fixed by means of screws  11  and bushes  12 . 
     The mutually opposite faces  18  and  19  of the elements  10  and  17  are flat and are suitable to mate on a mating plane P (see FIG. 1) when the elements are placed in mutual contact. Two respective semicircular slots  20  and  21  are formed in the mutually opposite faces  18  and  19  of the elements and are equidistant from the rotation axis of the shaft  6 , so as to form a channel having a circular cross-section along which the bar to be machined is accommodated. 
     By way of actuation means, not shown, the cover  7  is actuated between an open position and a closed position. In the open position (see FIG.  2 ), edges  22  and  23  of the elements  10  and  17  are spaced one another so as to allow a bar B, which rests on an inclined plane  24 , to roll downward and enter the lower slot  20 . In the closed position, the edges  22 ,  23  are in contact on the plane P and close the bar guiding channel perfectly. 
     The elements  10  and  17  are completed by two longitudinal slits  25  and  26  that are formed in the elements  10  and  17  respectively so as to be co-planar to the faces  18  and  19 . The slits are open on the opposite side with respect to the side on which the cover  7  is pivoted, and by way of the flexibility of the material of which the elements  10  and  17  are made they allow the edges  22  and  23  to be flexible with respect to a longitudinal axis located proximate to the bottom of the slits  25  and  26 . 
     The bar B is pushed along the channel  20 ,  21  by a bar pusher  27 , which by means of a bridge  28  is connected to the upper portion of a driving chain  29  that lies outside the guiding device  1 . The bridge  28  is constituted by a relatively thin plate that rests on the face  18  of the element  10  and is capable of sliding thereon. 
     The upper and lower portions of the chain  29  slide in a housing  30  that has two parallel slots  31  and  32  closed by a metal plate  33  that is rigidly coupled to the beam  2 . 
     The metal plate  33  has a lip  34  that is folded toward the element  10  and forms a sort of extension of the surface  24  on which the bars B roll toward the slot  20 . Moreover, the lip  34  acts as an abutment for a protrusion  35  of the element  17  that is capable of cushioning the resting of the cover  7  when it is actuated into the closed position. 
     It is evident from the above description that in the active position of the device  1 , i.e., after inserting a bar B in the lower slot  20  in front of the bar pusher  27  and after closing the cover  7 , the bridge  28  remains interposed between the edges  22  and  23  of the elements  10  and  17 . As shown more clearly in FIG. 3, the edges  22  and  23  of the elements  10  and  17 , due to the presence of the slits  25  and  26  and of the flexibility of the material of which they are made, undergo a slight deformation at the width of the bridge, i.e., at its extension in the bar advancement direction. In this manner, the guiding channel of the bar B, formed by the slots  20  and  21 , remains perfectly closed at a short distance upstream and downstream of the bridge  28 , thus ensuring perfect, vibration-free guiding of the bar over the entire advancement path toward the machine tool. During the advancement stroke, the bridge can in fact penetrate between the faces  18  and  19  in contact with the edges  22  and  23  by way of the flexibility offered by the slots  25  and  26  and by the elastic nature of the material of the elements, while the edges remain closed in front and behind the bridge, ensuring the geometric continuity of the bar guiding channel. 
     The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. 
     FIG. 4 illustrates a variation in which the elements  10  and  17 , while maintaining the features of the ones shown in the preceding figures, have a circular cross-section. 
     FIGS. 5 and 6 illustrate another version, in which the flexibility of the edges  22  and  23  is not provided by the slits  25  and  26  but by providing bevels  36  and  37  that reduce the thickness of the edges toward the mating plane, so as to reduce the advancement stress of the bridge without compromising the continuity of the guiding channel. 
     A similar solution is shown in FIGS. 7 and 8, in which the edges are rendered more flexible by means of circular channels  38  and  39 . It should be noted that the circular channels, by compressing when the bridge  28  passes, bend outward the edges  22  and  23  and therefore space apart the opposite faces in contact with the bridge. 
     The inventive concept of the present invention can also be applied to a bar guiding device of the type disclosed in U.S. Pat. No. 5,584,648, which is referenced here as background to the present description. In this known device, the bars are guided by means of a plurality of assemblies that are aligned longitudinally, each assembly being composed of a pair of sprockets that can rotate about parallel axes and have semicylindrical peripheral recesses of different depths. The sprockets of each pair have constantly meshed toothed portions. At least one of the two sprockets, moreover, has a pinion that meshes with a rack that controls the angular position of the sprockets so that the identical recesses lie mutually opposite in order to form circular openings that are aligned so as to form a channel for guiding a bar. Therefore, as is evident, the longitudinally aligned sprockets of the assemblies compose two elements that are equivalent to the two elements  10 ,  17  of the device  1  that are designed to guide the bar B. 
     FIGS. 9 to  11  illustrate an assembly according to U.S. Pat. No. 5,584,648, in which the reference numerals  40  and  41  designate the two sprockets, which on one side have mutually meshing gears  42  and  43 . The reference numeral  44  designates a pinion that meshes with a rack that controls the mutual angular position of the sprockets, and the reference numerals  45 ,  46  and  55 ,  56  designate the recesses of various depths that form the guiding channel. The sprockets  40  and  41  have, at the ends that lie opposite with respect to the gears, respective collars  47 ,  48  in mutual tangential contact. In the collars  47  and  48  there are respective annular slots  49  and  50 , which increase the flexibility of the peripheral edges so that said edges allow the passage of the bridge  28  while maintaining the contact of the collars of the sprockets that lie upstream and downstream of the bridge, ensuring the closure of the guiding channel. 
     In another variation, the cover can be opened by moving parallel to itself instead of about an articulation axis as shown in FIGS. 1 to  3 . 
     In the practical execution of the invention, the materials used may be any without altering the requirements of wear-resistance and flexibility required for guiding particularly abrasive polygonal bars. 
     The disclosures in Italian Patent Application No. BO2001A000770 from which this application claims priority are incorporated herein by reference.