|1.||A rotary hammering machine comprising a support structure (1) defining a circular seat (2) a shaft (20) mounted coaxially in the seat (2) and having radial passages (21) in which at least two hammering tools (22, 23) are slidable, the tools having respective shaped ends (22a) for deforming plastically a body interposed between them, and • an annular cage (3) mounted in the seat (2) around the shaft (20) and carrying a plurality of rotatable, rolling members (17) which project radially from the inner surface of the cage (3) ; the rolling members (17) being arranged to impart a radial hammering movement to the hammering tools (22, 23) as a result of relative rotation of the shaft (2) and the cage; characterised in that the rolling members (17) each have two conical surfaces (18, 19) which taper in opposite directions, and the ends (23) of the hammering tools (22, 23) which cooperate with the rolling members (17) have corresponding contact surfaces (24, 25) with respective longitudinal profiles which are inclined like the generatrices of the conical surfaces (18, 19), and in that at least two thrust members (3, 4) are provided which cooperate with the radially outermost portions of the rolling members (17, 18, 19) and which are movable simultaneously and axially in opposite directions so as to exert a radial thrust on the rolling members (17) towards the shaft (20) .|
|2.||A machine according to Claim 1, characterised in that the two conical surfaces (18, 19) defined by the rolling members (17) have the same taper.|
|3.||A machine according to Claim 2, characterised in that the rolling members (1719) are biconical rollers.|
|4.||A machine according to Claim 1, characterised in that the thrust members (3, 4) are in the form of rings and have respective inner conical surfaces (3, 4a) in contact with the radially outermost portions of the rolling members (1719) .|
|5.||A machine according to Claim 4, characterised in that it further includes drive means (815) for causing the controlled sliding of the annular thrust members (3, 4) in opposite directions.|
|6.||A machine according to Claim 5, characterised in that it includes first and second pluralities of threaded rods (8, 9) which engage correspondingly threaded axial holes (5) in the annular thrust members (3, 4); the rods (8, 9) carrying respective end sprockets (10, 11) rotatable by means of gear transmission devices (1215) .|
|7.||A machine according to any one of Claims 1 to 5, characterised in that the drive means include hydraulic or pneumatic devices.|
The present invention relates to a rotary hammering machine comprising a support structure defining a circular seat, a shaft mounted coaxially in the seat and in which there are formed at least two radial passages in which respective hammering tools are slidable, the tools having respective shaped ends for deforming plastically a body interposed between them? and an annular cage mounted in the seat around the shaft and carrying a plurality of rotatable rolling members which project radially from the inner surface of the cage; the rolling members being arranged to impart a radial hammering movement to the hammering tools as a result of relative rotation of the shaft and the cage.
It is known that rotary hammering is a mechanical operation which enables the section of bars and tubes to be reduced by plastic, deformation of such bodies, at substantially constant volume, without the removal of shavings.
Conventional rotary hammering machines allow substantially two different types of operation.
A first method enables the production of progressively tapered pieces, with successive cylindrical portions of gradually reduced diameters, which portions are connected by intermediate frusto-coniσal portions. In this method of operation, the piece being worked is inserted between the hammering tools and is advanced progressively, axially.
In a second, method of operation it is possible to form cuts- or annular grooves and, in general, profiles with undercut parts. In this second method of operation, the piece to be worked is clamped between the hammers and held axially stationary during the rotation of the hammers.
In rotary hammering machines,, the hammering tools usually include two parts: a first part (or hammer proper) cooperates with the rolling, members o£ the cage and a second part (or "die") receives the thrust from the first and is shaped according to the form wϊiich is to be imparted to thepieces being worked.
In use, the hammering dies are subject to wear which is compensated for by the insertion and successive addition of spacers between each hammer and the associated die. This operation for recovering the wear of the dies does not lend itself to being carried out automatically so that it is necessary to stop " the operation frequently.
For machines intended to form cuts or grooves. without the advance of the piece, it has been proposed "to recover the wear of the dies by inserting wedges, which are movable axially in directions parallel to the axis of the shaft, between the hammers and the dies instead of the usual intermediate spaces. ' These wedges, with their flat inclined faces, cause each hammer and its associated die to be move apart progressively and, specifically, cause the die to move radially towards the shaft to compensate for the wear.
This system is not, however, satisfactory: the wedges
inserted between the hammers and the dies tend to exert an axial thrust (even more considerable) as well as a radial thrust, with all the harmful effects that this involves.
Moreover, it has also been found rather difficult to achieve the progressive insertion of the wedges between the hammers and the dies in a controlled manner.
A consequence of these disadvantages is that rotary hammering machines for working without advancement of the piece and with progressive and controlled take-up of the wear of the dies have not yet been put on the market.
This has meant that up to now it has been necessary to use turning machines to work such pieces, such machines operating with tools which remove shavings with -a consequent reduction in the structural strength of the pieces worked and the consequent loss of material due to the waste.
The object of the present invention is, therefore, to provide a rotary hammering machine which effectively enables the dies to be advanced automatically, in a progressive and controlled manner, while avoiding, in particular, the disadvantages of the prior-art wedge solutions described above.
This object is achieved according to the invention by means of a rotary hammering machine of the type specified at the beginning of the present description, the main characteristic of which lies in the fact that the rolling members each define two conical surfaces which taper in opposite directions and the ends of the
hammering tools which cooperate with these rolling members having corresponding surfaces with respective longitudinal profiles which are inclined like the generatrices of the conical surfaces; and in that at least two thrust members are provided which cooperate with the radially outermost portions of the rolling members and are movable simultaneously and axially in opposite directions so as to exert a radial thrust on the rolling members towards the shaft.
According to a further characteristic, the conical surfaces of the rolling members have the same taper. These rolling members are, in particular, bi-conical rollers.
In one embodiment, the thrust members are annular with inner conical surfaces in contact with the radially outermost portions of the rolling members.
Further characteristics and advantages of the invention will become apparent from the detailed description which follows, given with reference to the appended drawings, provided purely by way of non-limiting example, in which:
Figure 1 is an axial sectional view of a machine according to the invention, and
Figure 2 is a cross-section taken on the line I - I of Figure 1.
With reference to the drawings, a rotary hammering machine according to the invention includes a support structure 1 which defines a circular, cylindrical seat> 2 whose axis A-A is arranged horizontally.
Within the seat 2 are two rings 3 and 4 with frusto-coniσal inner surfaces 3a and 4a of substantially the same dimensions and, in particular, with the same taper. More particularly, these surfaces lie on cones which taper in opposite directions.
In the embodiment illustrated, each ring 3, 4 has a series of three threaded through-holes 5 which are equiangularly spaced and alternated with another three through-holes 6 with smooth walls.
Three rods (only one of which is visible in Figure 1, at the top) are indicated 8. and each has a threaded end portion 8a which extends into a correspondingly- threaded aperture 5 in the ring 3 and a smooth portion 8b guided in a smooth hole 6 in the ring 4.
Similarly, a further three rods (of which only one is visible in Figure 1, at the bottom) are indicated 9 and each has a smooth portion 9a, which extends into a smooth hole 6 in the ring 3 r and a threaded portion 9b which engages a correspondingly threaded hole 5 in the ring 4.
The corresponding ends of the rods 8 and 9 carry respective sprockets 10 and 11 (Figure 1) which mesh with a gear 12 of a transmission device 13. This device includes a further gear 14 with helical teeth which meshes with a worm screw 15. This worm screw is connected to a drive motor (not illustrated) .
In operation, the transmission 13 driven by the worm screw 15 causes the simultaneous rotation of the rods 8 and 9 in the same sense and, as a result of the threaded coupling of the rods with the rings 3 and ,
it is possible , in particular , to cause the rings to move one towards the other in a controlled and progressive manner.
Within the rings 3 and 4 is an annular cage , indicated 16 in Figure 2 , which carries a plurality of idle rollers 17. These rollers project radially from the inner surface of the cage 16 through corresponding slots 18 in the cage.
- s is seen in particular from Figure 2 , each roller 17 has two end portions 18 and 19 of frusto-conical form with the same taper, whose profiles roll on the frusto-conical inner surfaces of the rings 3 and 4 respectivel .
A rotatable shaft 20 is mounted coaxially inside the cage 17. The outer diameter of the shaft 20 is less than the inner diameter of the cage and, moreover , the outer surface of the shaft extends at a certain distance from the radially-innermost portions of the rollers 17.
In the embodiment illustrated, the shaft 20 is formed with a diametral slot 21 in which two dies 22 and associated hammers 23 , which are radially outermost, are radially slidable.
As seen in particular in Figure 1 , the facing surfaces of the dies 22 have respective shaped surfaces 22a arranged in dependence on the shape to be given to a piece to be worked.
The hammers 23 project from the outer surface of the shaft 20 and each have two surfaces 24 and 25 (see in particular Figure 1) which are inclined to the axis A-A
like the radially innermost generatrices of the conical surfaces 18 and 19 of the rollers 17.
In use, a cylindrical member to be worked, which may be solid or tubular, is inserted between the dies 22. The shaft 20 is then rotated (by means of a motor not illustrated) ♦ Each time the hammers 23 interfere with a pair of rollers 17 carried by the cage 16, the hammers apply an impulsive force to the associated dies which, correspondingly, deform radially the piece being worked. As the working proceeds, the worm screw 15 is rotated progressively by a control system (not illustrated) and this causes the rings 3 and 4 to move towards each other. Bach of these rings consequently exerts a radial thrust on the rollers 17 towards the axis A-A of rotation and an axial stress which is, however, compensated for by the equal and opposite axial stress imparted to the rollers 17 by the other ring.
It follows that the mutual approach of the rings 3 and 4 causes a force to be applied to the rollers 17 solely- in the radial sense whereby these gradually move the opposing dies together as working progresses, achieving the necessary recovery for wear.
The advance of the dies 22 may be controlled with micrometric precision through the drive system for the rings 3 and 4 described above.
Alternatively, the movement of the rings 3 and 4 may be driven by other devices, for example of hydraulic or pneumatic typ .
In the embodiment illustrated, the moving together of
the dies is achieved by means of the progressive moving together of the rings 3 and 4. It is however obvious that the machine may be arranged so that the moving together of the dies is a consequence of the moving apart of the two drive rings.
It is also clear that the invention should not be understood..as., .limited to hammering machines with only two hammering tools.
Furthermore the member to be worked may be held axially stationary or may be axially advanced.
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