DEVICE FOR CONTROLLING BAR FACING ON AUTOMATIC LATHES FOR MACHINING BARS

Abstract: The device for controlling the facing of a bar on an automatic lathe for machining bars, comprises a bar-pusher (1) actuated by a traction element (6) to cause the advancement of a bar towards the lathe (3), a carriage (13, 14) slideable on a guide (15) parallel to the traction element (16), a hook (20) for intercepting the carriage (13, 14) in a bar loading position, a clutch (7) adapted to keep the bar-pusher (1) rigidly associated with the carriage (13, 14) when the carriage (13, 14) is free to slide on the guide (15) and to allow the bar-pusher (1) to move with respect to the carriage (13, 14) when the carriage (13, 14) is intercepted. The hook (20) is controlled by a sensor (21) adapted to detect the end of a bar to be machined at the entry point of the lathe (3) and to control the hook (20) during free sliding of the carriage (13, 14). A further sensor (23) is provided to actuate the bar-pusher (1) in the bar facing position.

Description: The present invention relates to a device for controlling bar facing on automatic lathes for machining bars. Since the initial portion of a bar to be machined usually has irregularities, said initial portion is removed by means of an operation called "facing" before the bar is machined. A device for facing bars on an automatic lathe, showing features as recited in the precharacterizing part of claim 1, is described in the document DE-A-2 024 032. Such a device is provided with a bar-pusher actuated so as to cause advancement of the bar into a lathe. Further means are also provided to allow, when necessary, the positioning of bars with variable length. The technical aim of the present invention is to provide a device to be applied to a bar loader, by means of which it is possible to determine exactly the point at which the bar must be stopped to allow the facing by the tool of the lathe. Within this aim, an object of the present invention is to provide a device which allows to recover any variations in length occurring among the various bars. This aim and this object are achieved by a device with the features disclosed in the characterizing part of claim 1 Further characteristics and advantages of the invention will become apparent from the following description of a preferred embodiment, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a partially schematic view of a control device in an initial position; figures 2 and 3 are perspective views of the device in two successive operating positions corresponding to the position for eliminating variations in the length of the bar and respectively, the position for facing the bar. With reference to the above described figures, the reference numeral 1 indicates a bar-pusher of a bar loader 2, which individually pushes bars along a guide and then through the tubular chuck of a lathe 3, where they are gripped by a collet 4. The guide, which is not illustrated in the drawings since it is conventional in structure, is constituted for example by a pair of longitudinal and opposite shells which define a channel in which the bar slides axially, and a longitudinal slot through which there moves the bracket 5 for the coupling of the bar-pusher 1 to a chain 6 constituting the bar-pusher advancement element. The chain 6 extends parallel to the bar 2 around a pair of toothed wheels and is actuated with advancement motion in a direction F from an initial position (coinciding with the one in which the bar-pusher 1 is shifted to the left in figure 1) towards the lathe 3. The bracket 5 has a clutch mechanism, generally indicated by the reference numeral 7, which is capable of sliding with friction on a rod 8 parallel to the advancement chain 6. The mechanism 7 is constituted by a jaw 9, fixed to the bracket 5, and by a movable jaw 10 which is guided with respect to the fixed jaw by bolts 11 and is biased towards the fixed jaw by springs 12 which interact between the heads of the bolts 11 and the movable jaw 10. The jaws 9, 10 have opposite semicircular grooves which cooperate to form an engagement channel for the rod 8. Naturally between the adjacent faces of the jaws an interspace is defined to ensure that the rod 8 is clamped therebetween consequent to the action of the springs 12. The rod 8 has its opposite ends fixed to two shoes constituted by plates 13, 14 which are slideably coupled to a guide or rail 15, extending parallel to the chain 6. In practice therefore the rod 8 and the plates 13, 14 form a carriage, which slides along the rail 15. The movement of the carriage 13, 14 on the rail 15 is interceptable by means of a ratchet device 16 composed of a lever 17, pivoted at an axis 18 to fixed parts of the frame of the device and comprising two arms arranged mutually orthogonally. One of said arms is connected to an actuator 19, e.g. of the electromechanical type, while the other arm is shaped to define a hook 20 adapted to engage, in one position of the lever 17, against the plate 14 to intercept the carriage. The actuator 19 is controlled by a sensor 21 located proximate to the entry of the lathe 3 to actuate the hook 20 in the free stroke position of the carriage 13, 14. The operation of the described device is as follows. At the beginning of the operating cycle the carriage 13, 14 is in the position of figure 1, i.e at the left end of the rail 15, retained by the hook 20. In this position the bar-pusher 1 is at a distance from the sensor 21 greater than the length L of the bar 2 to be machined, so as to allow the insertion of the bar into the guide of the loader. After inserting the bar into the guide, "A" is the distance between the left end of the bar and the bar-pusher 1, and "B" is the distance between the opposite end and the sensor 21 (see figure 1). Upon the actuation of the chain 6, as the carriage 13, 14 is retained by the hook 20, the bar-pusher 1 slides with friction on the rod 8 to move first into contact with the left end of the bar 2, thus annulling the distance A, and then pushes the bar forwards until its right end reaches the sensor 21, thus annulling the distance B. At this point (see figure 2) further advancement of the bar-pusher 1, which up to this point has traversed the total path A+B determines activation of the sensor 21 which controls release of the ratchet 16 by disengaging the hook 20 from the plate 14. In this manner the sliding of the jaws 9,10 on the rod 8 is interrupted and the movement of the carriage 13,14 along the rail 15 is started. When the carriage has traversed the distance C, which corresponds to the distance between the sensor 21 and the position in which the front end of the bar 2 is positioned in front of the tool 22 (i.e., the bar facing position of figure 3), the carriage 13, 14 activates a further sensor 23 which stops the carriage to allow the lathe to face the bar. Upon completion of the facing operation the bar is caused to advance by the bar-pusher for subsequent machining. As can be seen from the above description, the relative movement between the jaws 9, 10 and the carriage 13,14 during the first step of advancement of the carriage allows to recover the bar portion A+B regardless of the length of said portion and therefore to annul length variations of the bar being machined. This allows to simultaneously start the bar 2 and the carriage 13,14 and to stop the bar when the same has traversed a portion equal to the stroke C of the carriage which can be adjusted as required by varying the longitudinal position of the sensor 23. The described invention perfectly achieves the intended aim and object. In its practical embodiment numerous modifications and variations, all within the scope of the inventive concept, are possible. For example the actuator 19 may be constituted by an electromagnet 24 cooperating with a return spring 25 adapted to return the hook 20 to the carriage interception position as soon as the sensor 21 is deactivated. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Device for controlling the facing of a bar on an automatic lathe for machining bars, comprising a bar-pusher (1) actuated by an advancement element (6) to cause advancement of a bar towards a lathe (3), a carriage (13, 14) slideable on a guide (15) parallel to said advancement element, clutch means (7) adapted to keep said bar-pusher (1) rigidly coupled to said carriage (13, 14) when said carriage is free to slide on said guide (15) and to allow said bar-pusher (1) to move with respect to said carriage (13, 14) when said carriage is in an interception position, said device characterized in that it comprises means (20) for intercepting said carriage in a bar loading position, said interception means (20) being controlled by a sensor (21) adapted to detect an end of a bar (2) to be faced upon entry of said bar into a lathe (3) and to control said interception means (20) in the position of free sliding of the carriage (13, 14), that a further sensor (23) adapted to control said advancement element in the bar facing position is provided, that said carriage (13, 14) comprises a rod (8) being parallel to said guide(15) and being provided with shoes (13, 14) sliding on the guide (15), and in that said clutch means (7) act on said rod (8) so as to allow said bar-pusher to slide thereon when said carriage (13, 14) is in the interception position. Device according to claim 1, characterized in that said clutch means (7) comprise a pair of jaws (9, 10) pressed elastically against one another, between which said rod (8) is driven. Device according to any one of the preceding claims, characterized in that said interception means (20) comprise a ratchet (16) controlled by an actuator (19), in turn controlled by said sensor (21) for detecting an end of a bar (2) to be faced. Device according to any one of the preceding claims, characterized in that the position of said further sensor (23) is adjustable with respect to said carriage interception means (20). Device according to any one of the preceding claims, characterized in that said advancement element (6) is constituted by at least one chain (6) wound in a loop on at least one pair of toothed wheels, and in that said bar-pusher (1) is connected to said chain by means of a bracket (5) on which said clutch means (7) are mounted.

Inventors: FABBRI, VLADIMIRO
Applicants: I.E.M.C.A. S.P.A.  INDUSTRIA ELETTROMECCANICA COMPLESSI AUTOMATICI
Application year: 1988
Main classification: B23B13
IPC codes: B23B13, B23Q7