BACKGROUND OF THE INVENTION

The present invention relates to a wave-spring element for a loader-apparatus for loading bars which must be fed to a machine tool, for example a single or multi spindle lathe. In particular, the wave-spring element serves to contain and guide a bar during its rotation and advancement towards the machine tool and acts to dampen the flexural vibrations to which the bar is subjected during its rotation.

STATE OF THE ART

In the field of bar machining on machine tools, for example lathes, loading apparatuses are used for automatic bar feeding.

These loading apparatuses have a support drum and special containment and guide devices for the bars themselves.

The bars that are fed to the lathe, during processing, are rotated around their longitudinal axis.

During the rotation, the bars, especially if slender, that is thin, i.e. having a very small cross-section in relation to their longitudinal length, are subject to intense stresses and flexural vibrations due to the centrifugal effect.

It is important to reduce these flexural vibrations as much as possible, so that the processing can take place correctly without danger and a qualitatively acceptable product can be obtained.

The aforementioned containment and guide devices can have helical springs which receive the bar to be worked inside to contain and guide it so as to damp its flexural vibrations. Such springs are composed by a plurality of turns which can have different diameters in different areas, and which follow one another so as to give the spring itself a side profile, with narrow-diameter zones - intended to come into contact directly with the bar received inside them - and areas of greater diameter, intended to be separated and not in contact with the surface of the bar.

A drawback of these springs is that unfortunately the direct contact, and the relative sliding, between the smaller diameter turns and the bar, during the latter's translation movement, causes damage to the surface of the bar itself.

In fact, on the bar the innermost surfaces of the metal wire are in contact which constitutes the turns themselves and very localized contact zones are established with rather high pressures.

This problem is the cause of frequent surface damage to the machined bars, and often the final product processed does not reach the required quality levels.

In the light of the aforementioned limits, therefore, there is ample room for improvement for the containment and guide devices for the bars within the loading apparatuses for machine tools.

A spring element for guiding pipes is known from SU617172.

OBJECTS OF THE INVENTION

An object of the present invention is to improve the devices for guiding and damping the flexural vibrations of the bars within bar loading apparatuses for lathes or other machine tools.

Another object is to provide a structurally and functionally simplified solution for damping the flexural vibrations of the bars within the loading apparatus for machine tools. Another object is to provide an affordable wave-spring element but highly capable of preserving the bars from any type of damage.

BRIEF DESCRIPTION OF THE INVENTION

The above is achievable by means of a wave-spring element as defined in claim 1.

A method is also provided for producing the aforementioned wave- spring element as specified in claim 11.

Owing to the invention, the aforementioned drawbacks are overcome.

In particular, the wave- spring element according to the invention, with an advantageously simplified structure, is able to effectively carry out its function as a damper-element of flexural vibrations while preserving the surface of the bars from undesired damage caused by relative sliding with the turns that make up the wave spring element itself.

Further characteristics and advantages will become apparent from the description, from the claims and from the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood and implemented with reference to the attached drawings, which illustrate an exemplifying and non-limiting embodiment, in which:

Figure 1 is a schematic longitudinal section view of the wave- spring element according to the invention inside which a bar is housed;

Figure 2 is another view of the wave-spring element;

Figure 3 shows a part of Figure 1;

Figure 4 is an enlarged detail of Figure 3;

Figure 5 shows a first version of the bush or sleeve means of the wave-spring element according to the invention;

Figure 6 shows a second version of bush means included in the wave-spring element according to the invention;

Figure 7 is an enlarged view of the bush means of Figure 6;

Figures 8 and 9 are interrupted views showing other possible versions of bush means provided with housing seats for the turns of the wave-spring element.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the attached figures, a wave-spring element 1 according to the invention is described below, suitable for a bar loader apparatus arranged to feed the bars themselves to a machine tool, such as for example a mono or multi- spindle- lathe.

The wave- spring element 1 comprises a plurality of turn elements 2 arranged one adjacent to the other. The turn elements 2 have different diameters and are grouped in first groups Gl of turn elements with a larger diameter Dl and second groups G2 of turn elements with a smaller diameter D2.

The turn elements 2 are made of curved metal wire according to the desired helical path.

Intermediate turns 2’ placed between each first group Gl and the second adjacent group G2 are also provided, these intermediate turns 2' having a variable diameter ranging from the aforementioned diameter Dl to the diameter D2. Substantially, the intermediate turns 2’ act as a gradual connection between the groups Gl and the groups G2 and contribute to give the wave-spring element 1 the sinusoidal or wavy shape.

In other words, the first groups Gl and the second groups G2 alternate one after the other along a longitudinal axis AL and between each first Gl and each second group G2 the aforesaid intermediate turns 2’ with variable diameter are interposed. The first groups Gl and the second groups G2, together with the intermediate turns 2’ alternate so as to define, for the wave-spring element 1, a surface S having a sinusoidal profile, i.e. wavy. For this reason, it can be assumed that the wave-spring element 1 develops with a "sea wave" shape.

The wave-spring element 1 thus defined is suitable to contain and guide a bar B, so as to damp the flexural vibrations to which the same bar B is subjected during its rotation.

The wave- spring element 1 according to the invention is also provided with one or more bush or sleeve means, each one arranged inside a respective second group G2 of turns with a smaller diameter D2.

The bush means 3 are configured to come into contact with, and receive inside, respective portions of the bar B to avoid contact with, and avoid the sliding with respect to, all the turns which are included in the wave-spring element 1. It is possible to provide any number of bush means 3 distributed along the longitudinal axis AL and spaced apart from one another by an amount appropriately chosen in relation to the diameter of the bar B to be supported and based on the thickness of the metal wire of the turns.

The bush means 3 comprises a tubular element 3A having a cylindrical portion C on which the turn elements 2 of a respective second group G2 of turns with smaller diameter D2 are wound.

As best seen in the enlarged views in fig. 4 and 5, the bush means 3 are provided with widened edge portions 8 at each of the two ends El, E2 of a tubular element 3 A.

The aforesaid widened edge portions 8 are configured to couple externally with the inner surface of intermediate turns 2’ having a larger diameter than the diameter D2 and placed at the ends of the respective second group G2.

In this way, the widened edge portions 8 constrain, by means of a shape coupling, the bush means 3 to the wave-spring element 1. In other words, the flared shape of the ends of the bush means 3 causes the latter to remain stuck stably in the plurality of turns of variable diameter which make up the wave-spring element 1.

The widened edge portions 8 have internally a truncated cone-shaped surface diverging towards the outside to favour the advancement of the bar B and to promote its insertion inside the respective bush means 3.

The turns 2 with smaller diameter D2 of each second group G2 are wound tightly, and therefore tight, on the respective tubular elements 3A. The tight winding of these turns on the tubular 3A elements makes their position stable without risk of separation.

In one version, the aforesaid turns 2 with a smaller diameter D2 of each second group G2 can be glued or welded or are connected through melting to the respective tubular elements 3 A.

During operation, the wave-spring element 1, according to the version just described, rotates together with the bar B contained therein. There is therefore no relative rotation of the bar B with respect to the bush means 3.

According to another version, shown in Figure 8, on the outer surface 20 of the tubular elements 3 A, recess housing seats 21 are obtained extending sinusoidally around the longitudinal axis AL and shaped to house the respective turns 2 and keep them in a firm position with respect to said bush means 3.

The corrugated profile, or in any case provided with housing seats of the external surface 20, which conforms to the wavy profile of the sequence of turns 2, ensures that there are no relative displacements of the bush means 3 with respect to the turns 2 themselves.

According to another version shown in Fig. 6 and 7, the bush means 3 comprise an annular element 3B located internally to the respective tubular element 3A, rotatable with respect to the latter.

With this configuration, the annular element 3B and the respective tubular element 3 A together define a bush unit 3 or sliding bearing unit 3.

According to this version, the annular element 3B is rotatable, together with the bar B, around the longitudinal axis AL and relative to the tubular element 3 A which instead, during operation, can remain in a stationary position together with the plurality of turns 2.

In a further version, in combination with the previous versions described, at least the turns 2 of the first Gl groups are made of plasticized metal wire or covered with a layer of material suitable for not scratching or damaging the bars B.

Similarly to what has already been disclosed, also for this version of the bush means 3 made in two relatively movable and coaxial pieces, it is possible to provide recess housing seats 21 on the external surface 20 of the tubular elements 3 A.

These housing seats 21 with a recess extend sinusoidally about the longitudinal axis AL and are shaped to house the respective turns 2 and keep them in a fixed position with respect to said bush means 3.

Also in this case, therefore, the corrugated profile, or in any case provided with recessed areas of the external surface 20 of the bush means 3, conforming to the corrugated profile of the sequence of turns 2 ensures that there are no relative displacements of the bush means 3 compared to the same turns 2.

The wave-spring element 1, in the various versions just described, can be made by a method that includes the following steps:

a) winding a first portion of metal wire to generate a first group Gl of mutually adjacent turns 2 and having the first diameter Dl, and

b) winding a second portion of the metal wire, subsequent to the first portion, around bush means (2) so as to generate a second group G2 of turns 2 mutually adjacent and having a second diameter D2 smaller than the first diameter Dl, in which the turns 2 of the second group G2 are tightened around the bush means 3 to hold the latter in a stable position.

The aforementioned steps a) and b) have to be repeated to obtain a wave-spring element 1 with a sinusoidal profile extending along a longitudinal axis AL until a desired length is reached for this wave- spring element 1.

From what has been described and shown, it follows that the wave-spring element 1 according to the present invention achieves the previously stated aims and advantages.

Specifically, the described wave-spring element 1, although structurally and functionally simplified and therefore also affordable and simple to implement, effectively performs its function as a damper for the flexural vibrations of the bars while at the same time preserving the bars from any type of damages (due for example due to the relative sliding with the turns), owing to the presence of the bush means 3.

In fact the bar B is in contact, on several zones distributed along the longitudinal axis AL, with the cylindrical internal surfaces of the bush means 3, which being smooth and not presenting peak and valley areas (as instead would occur with the contact direct with the turns) they do not exert localized pressures and are not able to scratch the surface of the bar B.

Therefore, thanks to the invention final finished products are obtained which are qualitatively superior to those fed by traditional feeding devices which are not immune to the frequent risk of scratching the surface of the bars destined to work on machine tools.

It is possible to configure and dimension the wave-spring element 1 in a desired manner according to the applications for which it is intended. Any component forming the wave- spring element 1 according to the invention can be replaced with other equivalents in structural and functional terms, and the materials, insofar as they are compatible with the specific use for which they are intended, can be suitably chosen according to the requirements and the available state of art.

Variants and/or additions to what has been described above and illustrated in the attached drawings are possible, without thereby departing from the scope of protection claimed.