Abstract:
A bar feeder for feeding a machine tool, comprising at least one guide that forms a channel along which the bar to be fed is made to advance by way of a bar pusher connected, through a bridge, to a carriage that is guided parallel to the channel and is actuated by a linear electric motor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a bar feeder for feeding machine tools, particularly for automatic lathes.  
           [0002]    Known bar feeders for machine tools, particularly the ones having the most common structure for feeding bars to be machined in automatic lathes, consist of a pair of mutually articulated half-shells that are superimposed longitudinally and have opposite semicylindrical cavities. By way of suitable actuators, the half-shells are actuated between a spaced or open position, to allow the insertion of a bar to be machined in the cavities of a half-shell, and a mating or closed position, in which the cavities of the two half-shells integrate each other in order to form a channel along which the bar is pushed toward the machine tool.  
           [0003]    In known feeders of the above type, the advancement of the bar along the guiding channel is usually provided by means of a suitable pusher (known as bar pusher), which is connected to an actuation chain that runs outside the channel through of a bridge. 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.  
           [0004]    In order to allow the passage of the bridge, the contiguous edges of the channel must be spaced by at least the thickness of the bridge. In this manner, the guiding channel, even in the position in which the half-shells are closed, is open longitudinally through a slot.  
           [0005]    Conventional bar pusher actuation systems suffer certain drawbacks that substantially consist in excessive plays, which reduce the positioning precision of the bar and can cause considerable noise.  
         SUMMARY OF THE INVENTION  
         [0006]    The aim of the present invention is to provide a bar feeder that allows to obviate the cited shortcomings of known feeders.  
           [0007]    Within this aim, an object of the present invention is to provide a feeder that has a high dynamic performance and can allow synchronization with the lathe.  
           [0008]    This aim and this object are both achieved with a bar feeder for feeding a machine tool, comprising at least one guide that forms a channel along which the bar to be fed is made to advance by way of a bar pusher, characterized in that said bar pusher is connected, through a bridge, to a carriage that is guided parallel to said channel and is actuated by means of a linear electric motor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    Further characteristics and advantages of the invention will become better apparent from the following description of some preferred but not exclusive embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein:  
         [0010]    [0010]FIG. 1 is a perspective view, with some parts removed, of a portion of the feeder and of the bar feeding surface according to a first embodiment;  
         [0011]    [0011]FIG. 2 is a view of the feeder of FIG. 1 after removing the bar feeding surface;  
         [0012]    [0012]FIG. 3 is a view of the feeder of FIG. 1 after removing the panels of the lateral housing;  
         [0013]    [0013]FIG. 4 is an axial view of the feeder of the preceding figures;  
         [0014]    [0014]FIG. 5 is a perspective view of the feeder according to a second embodiment;  
         [0015]    [0015]FIG. 6 is an axial view of the feeder of FIG. 5;  
         [0016]    [0016]FIG. 7 is an axial view of the feeder according to a third embodiment; and finally  
         [0017]    [0017]FIG. 8 is an axial view of the feeder of FIG. 7. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    With reference to FIGS.  1  to  4 , reference numeral  1  generally designates the feeder for feeding a machine tool. The feeder  1  is composed of a frame that consists of a tubular beam  2  that has a rectangular cross-section and lies horizontally between two heads that are rigidly coupled thereto at the opposite ends.  
         [0019]    A side wall  3  is fixed to the beam  2 , and posts  4  are fixed thereto in a cantilevered fashion in order to support panels  5  that form the lateral housing of the feeder.  
         [0020]    The posts  4  are shaped so as to form a right angle and have, at their top, an inclined surface  6  that constitutes the magazine from which the bars B are taken individually to be inserted in the guide of the feeder. Pick-up is performed by a singling lever system  7 , which is not described in detail since it is fully conventional and does not relate to the present invention.  
         [0021]    The guide of the feeder can be of various kinds. In the described example, it is assumed that it is composed of two superimposed half-shells  8  and  9 ; the lower one  8  is fixed in a cantilevered fashion to the upper edge of the wall  3 , which protrudes from the beam  2 , by means of a profiled element  10 . The half-shells  8  and  9  have mutually opposite cavities that form the channel  11  for guiding a bar toward the machine tool.  
         [0022]    The upper half-shell  9  is articulated to the lower half-shell  8  so that the edges of the two half-shells that are directed toward the loading surface  6  can be spaced or open in order to allow the insertion of a bar B in the channel  11  and then moved closer one another in order to close the channel and keep the bar guided during its advancement toward the machine tool.  
         [0023]    For the advancement of the bar in the channel  11  there is a bar pusher  12 , which is actuated by means that are external to the guide, to which it is connected by means of a pair of bridges  13  and  14 . In order to allow the passage of the bridges  13  and  14 , the openable edges of the half-shells remain in any case spaced, in the guide closure position, by a slot  15  whose gap is wider than the bridges are thick. In FIG. 4, the slot  15  is enlarged for the sake of clarity.  
         [0024]    The ends of the bridges  13  and  14  that are external to the half-shells are rigidly coupled to a carriage, generally designated by the reference numeral  16 , which is composed of two L-shaped brackets  17  and  18 , with a first arm  19  that lies horizontally above the upper edge of the wall  3  and the profiled element  10  and a second arm  20  that runs vertically downward from the end of the first arm  19 .  
         [0025]    The horizontal arms  19  and  20  are connected by a rod  21  for coupling the bridges  13  and  14  and respectively by a plate  22  that is flat and parallel to the wall  3 .  
         [0026]    Two sliders  24  are rigidly coupled, with suitable spacer blocks  23  interposed, to the plate  22  in its upper part and are provided with grooves for slidingly engaging a horizontal rail  25  that has a dovetail cross-section and is fixed to the wall  3 .  
         [0027]    As shown more clearly by the axial view of FIG. 4, the carriage  16  is provided in a lower region with additional arms  26  that extend toward the wall  3  and support additional sliders  27  for resting slidingly on said wall  3 .  
         [0028]    The dimensions of the carriage  16  are such that it can slide in the axial compartment  28  comprised between the wall  3  and the housing  5 .  
         [0029]    The armature winding  29  (also known as stator) of a linear motor  30  for moving the carriage  16  along the rail  25  is fixed to the wall  22  under the sliders  24 .  
         [0030]    The inductor elements of the linear motor  30  that cooperate with the winding  29  are constituted by magnets forming an inductor bar  31 , distributed on a first bar  32  (also known as magnetic track), which is fixed to the wall  3  below and horizontally with respect to the rail  25  in front of said winding  29 .  
         [0031]    Operation of the described feeder is fully evident from the description given. In particular, the characteristics of the linear motor  30  ensure a uniform advancement of the carriage  16  and of the bar pusher  12  and therefore a constant and progressive thrust on the bar to be fed into the lathe.  
         [0032]    It should be noted that the guiding of the carriage  16  provided by the sliders  24  on the rail and by the sliders  27  on the wall  3  ensures a constant gap between the stator  29  and the magnets  31  distributed on the first bar  32  over the entire stroke of the carriage  16 .  
         [0033]    Furthermore, the linear motor is capable of providing a precise dynamic response that allows perfect synchronization with the operating steps of the lathe.  
         [0034]    Advantageously, in order to protect the sliding guides of the carriage and the gap region against the penetration of dirt that might compromise the efficiency of the linear motor, a barrier that closes the compartment  28  in an upward region is arranged above the sliders  24 .  
         [0035]    Said barrier is constituted by a first strip  33 , which is fixed to the top of the wall  3 , and by a second strip  34 , which is fixed to the top of the posts  4 . The two strips  33 ,  34  protrude longitudinally toward each other and support respectively, along their opposite edges, a double brush  35  and a single or double brush  36 , whose upper bristles engage between the bristles of the double brush  35 . The bristles  35  and  36 , together with the strips  33  and  34 , therefore form a seal of the compartment  28  that however allows the passage of the vertical arms  20  of the brackets  17  and  18  of the carriage  16 .  
         [0036]    The invention is susceptible of numerous modifications and variations, shown in FIGS. 5, 6,  7  and  8 , in which the elements and parts that are equal or equivalent to those of the feeder described above are designated by the same reference numerals.  
         [0037]    In particular, FIGS. 5 and 6 illustrate a feeder in which the linear motor comprises a second magnetic track, composed of a second bar  37  provided with permanent magnets. The second bar  37  is arranged opposite the first bar  32  and is rigidly coupled thereto, so as to form an interspace  38  along which the stator  29 , supported by the arms  19  of the brackets  17  and  18 , moves.  
         [0038]    [0038]FIGS. 7 and 8 illustrate a third embodiment, in which the stator  29  is of the tubular type and is crossed by a longitudinal bar  39 , which constitutes the inductor of the linear motor. The opposite ends of the bar  39  are rigidly coupled to supports  40  which are rigidly coupled to the wall  3 . In order to reduce the bending angle of the bar  39 , which due to the length of the feeder can assume significant values, so-called retractable supports, i.e., supports adapted to allow the passage of the stator  29  during the forward and return strokes of the carriage while continuing to support said carriage upstream and downstream, are used.  
         [0039]    The disclosures in Italian Patent Application No. BO2002A000134 from which this application claims priority are incorporated herein by reference.