This invention relates to a bar feeder for machine tools, in particular for latches and similar machines, of the type in which the bars are supported in a rotating manner and are guided towards the machine tool by carriages moving along longitudinal guides.
In feeders of the aforementioned type there is the problem of reducing the high level of noise caused by the carriages jolting against the guides due to the vibrations generated by the bars when rotating rapidly.
In the past, attempts have been made to at least partially eliminate this inconvenience by fixing the guides rigidly with a material suitable for partially damping or absorbing the vibrations, and providing the sliding runners of the carriages with a similar material.
Nevertheless the results achieved, even if they did enable the noise of the bar feeders of the aforementioned type to be reduced in part, are not completely satisfactory since the vibrations generated by the rotation of offset parts of the bars are in any case transmitted by the carriages to the slide guides and by the latter to the support structure, still causing a considerable amount of noise.
An object of this invention is to provide a bar feeder, of the aforementioned type, by means of which it is possible to substantially reduce the noise caused by the vibrations generated by the bars during rapid rotation, at the same time enabling the bars to be guided gently and safely to the mandrel of the machine tool.
A further object of this invention is to provide a bar feeder as stated above, having auxiliary bar guide means for an additional push member and/or for lengths of rods, or for elongated parts having relatively small longitudinal dimensions, for example for shafts or the like which have to undergo head machining, for which guiding in the end section of the feeder may be less critical compared to bars of greater dimensions.
From tests carried out it was found that a considerable reduction in noise of the feeder is obtained by allowing the carriage and support guide assembly to freely oscillate, at the same time maintaining the guides parallel to one another and uniformly spaced apart by means of the carriages themselves. In this way the vibrations caused by the eccentric rotation of the bars are absorbed by the free oscillations of the guides without causing excessive jolting and noise.