Method to forge with a swaging machine, and a swaging machine suitable to carry out the method

Abstract: Method to forge metallic pieces with a swaging machine, whereby during the rough-shaping step the hammers carry out a long stroke with a low number of hammer blows, whereas during the finishing step the hammers carry out a short stroke with a great number of hammer blows. Swaging machines suitable to perform the above method.

Description: The invention concerns a hydraulic swaging machine. To be more exact, the invention concerns a device which makes it possible to obtain a differentiated frequency of hammering during the forging step with a hydraulic swaging machine for metals. Hydraulic swaging machines of the type to which the invention is applied are disclosed and illustrated, for instance, in EP-A-0.297.312, US-A-4,745,793 or US-A-3,707, 866. In this invention the word "forging" includes also "swaging". To carry out a complete swaging process, swaging machines are required which can work firstly for the roughing and then for the finishing. DE-A-2.306.566 is known and discloses a swaging machine with a pump having two displacements and driven by a motor the speed of which can be adjusted according to the desired frequency. This system makes necessary power commutation valves, power switching assemblies and other power devices. This involves great investments, wastage of energy, an increase in maintenance costs, more personnel, longer times, etc., and all of this is no longer acceptable under present competitive conditions and in the ecological situation which has become evident for some time now. The present applicants have therefore tackled a problem which has been felt for some time now, and have studied, tested and achieved this invention. The hydraulic swaging machine according to the invention is defined in the claim. According to the invention the hammers of the swaging machine can perform at least two different strokes, a long stroke and a short stroke; the short stroke is associated with a greater frequency of hammer blows; this frequency may be four times or more greater than the slow frequency. The drive motor may be an electric D.C. motor or an electric motor with a sliding connection or any other system which enables the speed of the drive shaft to be varied. Each pump assembly of the hydraulic swaging machine, the pump assembly operating with a specific hammer, is equipped with means suitable to modify its displacement. This modification in its simplest form provides for the obtaining of two different displacements for each piston of the pump. Modification of the displacement alters the quantity of oil aspirated by and pumped into the actuation chamber of the piston that bears the hammer in question. Alteration of the quantity of oil changes the stroke of the piston and therefore of the hammer in question. The achievement of a differentiated displacement is obtained with an auxiliary piston that has an inactive position (greatest displacement) and a working position (smallest displacement). According to a variant the auxiliary piston may be formed with concentric elements, each of which can take up both the inactive and the working positions. These concentric elements, being one or more in number, can be set to work as required so as to obtain as many different displacements. As we said above, alteration of the displacement alters also the quantity of hydraulic oil displaced and thus modifies the stroke of the specific piston that bears the hammer in question. If the displacement is reduced, the quantities of the movements in question are reduced and the displaced mass of oil is much more reduced. It is then possible to change more easily and quickly the number of revolutions by increasing them. With the invention it is therefore possible to bring about at least two conditions of actuation of the swaging machine and to enable the machine to work either as a rough-shaping forging machine (long stroke, low frequency) or as a finishing swaging machine ((short stroke, high frequency). The attached figures, which are given as a non-restrictive example, show the invention applied to hydraulic swaging machines. Fig.1 shows an embodiment according to the invention; Fig.2 shows a variant of the embodiment of Fig.1. Fig.1 shows a diagram of a vertical section of a pump 10 corresponding to a main piston 11. A chamber 13 in which the main piston 11 plunges is connected to the specific piston of the hydraulic swaging machine (not shown in the figures) through a pipe 12. The hydraulic swaging machine may be of the type disclosed in EP-A-0.297.312 or in US-A-4,745,793 or be of another known type. The main piston 11 is displaced axially by a connecting rod 14 actuated by a crankshaft 15 set in rotation by a motor 16. So long as the main piston 11 is free to slide in the chamber 13, the displacement stays constant, as also does the stroke of the hammer. The number of strokes per unit of time can be varied by speeding up or slowing down the rotation of the crankshaft 15, namely by acting on the motor 16 and crankshaft 15. If an auxiliary piston 18 is rested on the main piston 11 and is solidly fixed thereto, the displacement is reduced by the volume correspondingly taken up by the auxiliary piston 18. In its working position the auxiliary piston 18 has to move together with the main piston 11. When the auxiliary piston 18 is in its inactive position, the displacement will be the maximum available. In the example of Fig.1 the auxiliary piston 18 is positioned by an actuation piston 19 actuated by fluid under pressure coming from the pipe of a reservoir 17. When the auxiliary piston 18 is in its working position, that is to say, rendered solidly fixed continuously to the main piston 11, the actuation piston 19 thrusts the auxiliary piston 18 always against the main piston 11 so that both pistons 11, 18 travel concordantly with each other. In this way two different displacements are obtained with two different strokes of the specific pistons that bear the hammers of the swaging machine. In fact, if the displacement of the specific pistons that bear the hammers remains constant, a variation of displacement of the pump changes the stroke of those specific pistons. A variant of the invention, shown diagrammatically in Fig.2 for instance, provides for two or more auxiliary pistons cooperating with the upper surface of the main piston 11. These auxiliary pistons may be independent and be positioned, for instance, along a circumference, or may be coaxial. Fig.2 shows an example of coaxial auxiliary pistons. In the embodiment shown in Fig.2 each auxiliary piston 18 has a positioner assembly 20 comprising, for instance, a gear wheel-rack coupling 22, which in this case includes springs 21 to enable the auxiliary piston 18 to follow the stroke of the main piston 11.

Claims: Hydraulic swaging machine with a plurality of chamber/piston units (13-11) connected from time to time with the respective specific hammers, the stroke of the individual hammers being varied by acting on the volume of the respective chamber/piston units (13-11), the actuation motor having at least two rotation speeds, the pistons (11) travelling axially in a chamber (13) comprising the hydraulic connection (12) with the respective hammer, characterised in that substantially coaxial to the chamber (13) and opposite the main piston (11) there is at least one auxiliary piston (18) with a first retracted position and a second position where it is in continuous contact with the main piston (11).

Inventors: DURI ANTONINO, DURI', ANTONINO
Applicants: DANIELI OFF MECC, DANIELI & C. OFFICINE MECCANICHE S.P.A.
Application year: 1991
Main classification: B21J11
IPC codes: B21J7, B21J1, B21J11