Abstract:
An automatic lathe bar magazine comprises a feed channel ( 11 ) for a bar to the lathe chuck and a powered bar pusher ( 15 ) grasping with a head collet ( 17 ) the tail of a bar in the channel to cause it to run therein. The bar pusher ( 15 ) is made telescopic to have an outermost part ( 18 ) running with reduced side play in the channel ( 11 ) acting as a guide therefor and an internal part ( 16 ) with smaller diameter bearing at its head said collet ( 17 ) and growing longer on command from the outermost part to protrude from the magazine and enter the lathe. In this manner the bar being machined does not touch the channel and this greatly reduces vibrations and noise produced by the high speed rotation of the bar.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a magazine for feeding bars to automatic lathes.  
           [0002]    Bar magazines comprising a channel aligned with the inlet of the chuck of a lathe and in which the bar to be machined is made to run by means of a suitable thrust member are known. Since in general the bars being machined are very long in relation to their thickness and rotation speeds are relatively high, to seek to reduce the vibrations caused by bending of the bar being machined it is sought to support the bar continuously along its entire length. To achieve this, in the prior art there have been proposed running channels with diameter close to that of the bar and with various contrivances for damping the vibrations produced by the striking of the bar against the walls of the channel and to reduce the effects of the rubbing.  
           [0003]    In addition, to guide the bar tail and prevent its wavering, the bar pusher which gasps the bar by the tail to move it in the channel is realized with a diameter practically equal to that of the channel. Since the bar pusher must be able to enter the chuck of the lathe, the diameter of the bar pusher and consequently of the channel is near the internal diameter of the chuck.  
           [0004]    But in practice it is learnt that the vibrations are still there and especially with bars having a non-round cross section it is not possible to reach those rotation speeds which would be preferable for best utilization of the productivity of modern automatic lathes. In addition, with the variation in the diameter of the bars to be machined it is necessary to replace the guide channel and the bar pusher to keep play reduced.  
           [0005]    The general purpose of the present invention is to remedy the above mentioned shortcomings by making available a magazine allowing feeding of bars of various cross sections and forms even with high rotation speeds and virtually without vibrations.  
         SUMMARY OF THE INVENTION  
         [0006]    In view of this purpose it was sought to provide in accordance with the present invention an automatic lathe bar-magazine comprising a feed channel for a bar to the lathe chuck and a powered bar pusher grasping with a head collet the tail of a bar in the channel to cause it to run therein characterized in that the bar pusher is made telescopic to have an outermost part running with reduced side play in the channel acting as a guide therefor and an internal part with smaller diameter bearing at its head said collet and growing longer on command from the outermost part to protrude from the magazine and enter the lathe. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    To clarify the explanation of the innovative principles of the present invention and its advantages compared with the prior art there is described below with the aid of the annexed drawings a possible embodiment thereof by way of non-limiting example applying said principles. In the drawings:  
         [0008]    FIGS.  1  to  4  show diagrammatic side elevation views of a magazine in accordance with the present invention in various operating steps,  
         [0009]    [0009]FIG. 5 shows a diagrammatic perspective view of part of a channel of the magazine,  
         [0010]    [0010]FIG. 6 shows a diagrammatic perspective view of a part of the magazine bar pusher,  
         [0011]    [0011]FIGS. 7 and 8 show side views taken across the magazine channel and showing part of the channel respectively in closed and open positions,  
         [0012]    [0012]FIG. 9 shows a partial diagrammatic perspective view of a detail of the channel part of FIG. 5, and  
         [0013]    [0013]FIG. 10 shows from another angle an enlarged cross section view of a detail of FIG. 9. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    With reference to the figures, as may be seen diagrammatically in FIG. 1 the basic structure of the magazine indicated as a whole by reference number  10  comprises a channel  11  made up of an aligned series of elastic members shaped generally like the letter C and facing in pairs in such a manner as to be able to raise the upper part of the channel and introduce the bar  13  to be fed to a known automatic lathe  14 .  
         [0015]    To move the bar there is a bar pusher  15  which grasps the tail of the bar and is powered to slide within the channel. Differently from known magazines, the diameter of the magazine channel is larger than the diameter of the bar in an amount such as to reduce as much as possible and if possible entirely avoid contact between the bar and the channel. The channel is consequently greater than the internal diameter of the chuck  19  of the lathe; for example, if the lathe chuck diameter is 40 mm the channel may have a diameter of 60 mm.  
         [0016]    To be able to enter the lathe chuck and push the bar to the bottom of the chuck the bar pusher must of course have a diameter slightly smaller than that of the lathe chuck. To prevent the bar pusher from oscillating in the magazine channel it is made in two parts, to wit the innermost part or central rod  16  equipped with the coupling or collet  17  for the bar tail and an external tubular part  18  advantageously of plastic material, for example Vulkolan, in which the rod  16  can run with minimal play. The tubular part  18  has an outside diameter equal to that of the channel  11  and length equal to the rod  16 . In this manner a telescopic bar pusher is obtained. The head chuck rotates freely with respect to the rest of the bar pusher to avoid transmitting to the bar pusher the rotation movement of the bar.  
         [0017]    In this manner, from the beginning of feeding of the bar (FIG. 1) to the end of the channel (FIG. 2) the bar pusher has its central rod  16  retracted into the outer tubular part  18  and the gripping head  17  is in this manner perfectly guided in the channel. This prevents oscillation of the bar tail. When the channel ends, the tube  18  stops and only the internal rod  16  which has a diameter suitable for entering the lathe chuck  14  continues its travel as shown in FIG. 2. In the travel inside the channel of access to the lathe chuck the rod  16  of the pusher can be advantageously guided by an elastic reduction bush  20  appropriately shaped to receive the head  17  of the pusher and be moved by the pusher to the end of the path and return hooked to the head  17  to the starting position as may be seen by comparing FIGS.  1 - 3 . When the bar is used up the bar-pusher backs to the starting position and the crop end remaining in the collet  17  is extracted by a purposeful extractor, the upper part of the channel opens raising the entire bar pusher also and a new bar is inserted in the channel for a new feed cycle.  
         [0018]    To take the bar into the initial position of FIG. 1 there is provided in accordance with the prior art a powered pre-positioner  21  which pushes the bar into the channel up to a predetermined amount after which it returns, the channel closes, the extractor inserts the bar in the collet  17  and the new machining cycle begins.  
         [0019]    [0019]FIG. 4 shows a variant for thin bars for which the support of the collet  17  alone at one end, the elastic bush  20  in an intermediate position and the chuck  19  at the other end is judged insufficient.  
         [0020]    In accordance with this variant, when necessary the bars may be kept in axis by one or more lower portions of channel, for example three elastic sectors  22  in FIG. 4, which rise to then be withdrawn when the bar pusher arrives. These supporting members also facilitate entry of the bar into the elastic reduction bush. The hoisting mechanism for the segments is readily imaginable to those skilled in the art and not further shown nor described.  
         [0021]    [0021]FIG. 5 shows in greater detail a possible advantageous embodiment of the guide channel. As may be seen in the figure, the channel made up of lower and upper C members connected laterally by a known opening mechanism  25  is divided in two parts  11   a  and  11   b  to allow insertion of a known tong extractor  23  and falling of the bar crop end to be evacuated at cycle end. The entire channel is advantageously mounted on a frame with the interposition of pairs of vibration-proof members  24 .  
         [0022]    A chain  26  moved by a motor  27  runs along the entire channel to move the bar pusher.  
         [0023]    Advantageously as clarified below, in the first half of the channel there is a device  28  for locking of the bar pusher in the retracted position and in the second half there is a device  29  for disengagement of the internal rod  16  from the outer tube  28  to allow telescopic lengthening within the lathe spindle.  
         [0024]    As may be seen in FIG. 6, to transmit the movement of the motor  27  to the bar pusher the chain  26  drags a small block  31  having seats  32 ,  33  in which are engaged respective tongues  34 ,  35  which project radially respectively from the pre-positioner  21 , which is not constrained to the bar pusher, and from the bar pusher  15 .  
         [0025]    In particular the tongue  35  is connected to the tail of the rod  16  and projects from the tube  18  to pass through a milling  36  made in the side of the tube and extending for the entire desired travel of the rod  16  in the tube  18 . The extracted position of the rod  16  is shown in broken lines.  
         [0026]    A slot  37  is made both in the tube  18  and in the rod  16  so that by operating the locking device  28  a locking insert  38  is inserted in the slot  37  to prevent running of the tube and the rod.  
         [0027]    [0027]FIGS. 7 and 8 show the rear part of the channel respectively in closed and open positions. As may be seen by comparing the two figures, two cams  40 ,  41  connected to the mechanism which opens the channel cause the tongue  34  and consequently the pre-positioner  21  to rotate. In the closed channel position (FIG. 7) the tongue  34  is in a position disengaged from the insert  31  while the tongue  35  is engaged. When the channel is open (FIG. 8) the tongue  35  is disengaged thanks to the rising of the upper part of the guide and the bar pusher while the tongue  34  is engaged with the insert by the movement of the cams  40 ,  41 .  
         [0028]    In this manner when the Channel is open the motor  27  moves the pre-positioner  21  while when the channel is closed the motor  27  moves the bar pusher  15 .  
         [0029]    During the entire channel opening step and also when the extractor  23  operates, the locking, device  28  is operated to hold the bar pusher in position.  
         [0030]    [0030]FIGS. 9 and 10 show in greater detail the disengagement device  29 . As may be seen in the section plane of FIG. 10 the tail of the rod  16  is engaged with the rear end  30  of the outer tube  18  by means of a quick connector similar to those used in hydraulics and comprising a shaped pin  42  projecting axially from the rod  16  to be snapped into a coupling sleeve  43  fastened to the tube. During travel of the bar pusher in the magazine channel the coupling connects the rod  16  to the tube  18 . When both have reached the end of the channel the tail  30  is opposite the disengagement mechanism  29  which operates through a lever  44  a pawl  45  which enters a purposeful slot  46  in the tube  18  and moves a ringnut  47  which operates the quick connect to disconnect the pin  42 . At the same time the pawl  45  locks the movement of the tube in the guide.  
         [0031]    The bar-pusher rod can then continue its travel in the lathe spindle alone as explained above. Upon its return, the pin  42  again hooks the coupling  43  and the tube and rod of the bar pusher return to the retracted rest position.  
         [0032]    It is now clear that the predetermined purposes have been achieved by making available an innovative magazine having a telescopic bar-pusher which can be guided with minimal play in a wide bar-feeding guide though having one end with smaller diameter emerging from the magazine to be able to enter the lathe accurately.  
         [0033]    It is noted that the manner of proceeding in accordance with the present invention is radically opposite that of the prior art. In the prior art indeed the road of leaving the least possible play between the bar and the channel is followed to arrive even at introducing lathe spindle reduction tubes and using bar pushers of diameters differing depending on the bar to be machined. While this may be somewhat useful for small diameter bars because they are flexible and hence easily contained it becomes extremely counterproductive with larger diameter bars.  
         [0034]    With the magazine in accordance with the present invention the large-diameter bars which are more awkward as regards noise and vibrations are prevented from touching the magazine channel. The bars are held up by the lathe collet, the elastic bush and the magazine collet and rotate empty. This is all results in excellent vibration damping and less wear. As the magazine collet is quite far, in its rotation from the channel walls the elastic members making up the channel can be without the conventional metal insert typical of known single-spindle magazines with the resulting further reduction of noise. Stress on the tongues which move the bar pusher and the pre-positioner and hence these fragile parts is considerably reduced.  
         [0035]    With the magazine in accordance with the present invention it is possible to considerably increase the number of rpms with a resulting considerable increase in production. The manufacturer&#39;s advantages are also considerable since he can produce magazines which with very few changes in the bar pusher alone can be rapidly adapted to different lathes.  
         [0036]    It was surprisingly verified experimentally that with a magazine in accordance with the present invention even with thick-profile non-round bars, for example hexagonal bars ch.  40 , no added noise is noted over that emitted by the lathe even at very high rotation speeds, for example 4000 rpm. Naturally the above description of an embodiment applying the innovative principles of the present invention is given by way of non-limiting example of said principles within the scope of the exclusive right claimed here. For example the device which loads the bar into the channel is not shown since it can be realized by any method known to those skilled in the art.