Automatic lathe for the machining of bar material

Details Automatic lathe for the machining of bar material Automatic lathe for the machining of bar material

1980-10-01

1983-01-04

Vlachos, Leonidas

Turning

Process of turning

B23B 1302

Patent

active

043667341

DESCRIPTION:

BRIEF SUMMARY
The invention concerns an automatic lathe machining bar material, fitted with a fixed steady with material guide-bush assembled on the machine-bed, provided on its front side with radially guided tools and on the back side a headstock guided in the length direction, the spindle in the headstock being motor driven and fitted with a collet and means to open and to close it, means being provided to coordinate the control and execution of tool movements, headstock and collet motions, permitting to produce automatically workpieces out of the material bar to be machined in successive and similar sequences of operations.
Such automatic lathes are used since many years in very different designs. From the fact that all of them are fitted only with a single headstock, through which the bar to machine is passing, important disadvantages can be deduced. The first disadvantage, mainly when rather longer workpieces are manufactured, consists in the necessity to reserve a last part of the machining cycle, during which no tool is working and during which the material bar must be kept axially stopped, for the return of headstock from its most forward position to its most backward position. The required dead-time for this purpose may easily take 25% of the total machining cycle.
A second important disadvantage consists in the necessity to provide a costly bar feeding system, which must also be able to extract or take back the bar end-bit. This system requires moreover some special design of the material guide behind the headstock and of the main spindle itself, which influences negatively the correct radial seat of the material bar, resulting in the impossibility to run the machine at the high spindle speeds or cutting feeds which otherwise could be possible thanks to the high quality of the tools available today.
The invention intends to provide a design for automatic lathes of the above mentioned type, permitting to overcome these disadvantages. The solution of this problem, according to the invention, has been found by the presence on the machine-bed, behind said first headstock (12A) of a second headstock (12B), which can also be moved lengthwise and the spindle of which is revolving around the same axis as that of the first headstock and is also fitted with a collet and means to open and to close same, and that said device influences also the second headstock and its means to open and to close its collet, so that whilst a first workpiece is machined or partially machined from the material bar in the spindle of the first headstock thanks to the gradual advance of that headstock from its starting position, the second headstock is being returned to its start position and that now a second workpiece is being machined or partially machined out of the material bar in the spindle of the second headstock while it advances gradually and whilst the first headstock is returned to its starting position, whereas during the transition phases the material bar is clamped in the first and also in the second headstock spindle.
It is obvious that with such a design the first disadvantage mentioned above is eliminated, because one of the two headstocks (with opened proper collet) can always be returned to its start position while the other headstock and its collet are working. The effective work of the two headstocks can be conjugated practically without gasp.
During the whole machining time, the material bar is never released by both collets at the same time. The result is that the combination of the two headstocks and collets can assume the feeding of the material bar in lieu of the bar feeding system that was indispensable till now, including the ejection of the bar end-bit, pushed by the following material bar. If the bar feeding system is suppressed, the bar guide at the rear end of the machine can be designed in an optimal but considerably simplified manner to cope with its function. This again makes possible to reduce considerably the noise and to increase notably the number of revolutions. As to this last point, the possibility is

REFERENCES:
patent: 2376476 (1945-05-01), Chatelain
patent: 2389556 (1945-11-01), Siegerist

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