[0001] The invention concerns a method to forge with a swaging machine and also a swaging
machine suitable to perform the method.
[0002] To be more exact, the invention concerns a method which provides for a differentiated
frequency of hammering during the forging step with a swaging machine for metals which
is hydraulic or mechanical.
[0003] Hydraulic swaging machines of the type to which the invention is applied are disclosed
and illustrated, for instance, in EP 88108963.5 or in US 4,745,793.
[0004] Mechanical swaging machines with hammers actuated by an eccentric are also known.
[0005] In this invention the word "forging" includes also "swaging".
[0006] Hydraulic swaging machines performing swaging work are fed at the present time by
fixed displacement pumps and their hammering frequency is unchanged. The hammering
frequency is altered by small values by varying the number of revolutions of the pump,
but this system in itself is neither enough nor advantageous in view of the masses
in movement and therefore of the waste of energy with each variation in the quantity
of movements.
[0007] The same problem is encountered with mechanical swaging machines, which have substantially
one single working speed that can be altered a little by acting on the speed of rotation.
[0008] The swaging machines, whether hydraulic or mechanical, are of two types, one with
a long stroke and the other with a short stroke. The machines with a long stroke apply
a small number of hammer blows per minute, whereas those with a short stroke carry
out a greater number of hammer blows per minute.
[0009] Swaging machines with a long stroke are used for roughing work, whereas those with
a short stroke serve for finishing work. Therefore, both machines are required to
perform a finished forging work, so that one machine can be used for the rough-shaping
and the other be used thereafter for the finishing.
[0010] This entails high investment, waste of energy, considerable employment of space,
increased maintenance costs, more personnel, longer times, machines for handling work,
etc., which are factors no longer acceptable in the present competitive conditions
and in the environmental situtation which has become more and more evident as time
goes by.
[0011] In fact, the long stroke of the hammers of one type of swaging machine is ill-suited
to the work of finishing a forged product. In other words, great investments in space,
machines, plant, manpower and a high energy consumption are necessary nowadays to
obtain a high output.
[0012] The present applicant has therefore tackled a problem which has been felt for some
time now, and has studied, tested and achieved this invention.
[0013] The method of forging with a swaging machine and the swaging machine suitable to
carry out the method according to the invention are set forth and characterized in
the respective main claims, while the dependent claims describe variants of the ideas
of the respective main solutions.
[0014] 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.
[0015] 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.
[0016] If the swaging machine is a mechanical machine, a second eccentric is placed in cooperation
with the eccentric that actuates the relative single hammer. The reciprocal positions
of the two eccentrics determine the longest stroke, shortest stroke and any intermediate
stroke.
[0017] Instead, where the swaging machine is hydraulic, each pump assembly cooperating with
a specific hammer is equipped with means able to change its displacement. Such change
in its simplest form provides for the obtaining of two different displacements for
each piston of the pump.
[0018] 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.
[0019] Alteration of the quantity of oil changes the stroke of the piston and therefore
of the hammer in question.
[0020] 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).
[0021] According to a variant the auxiliary piston may be formed with concentric elements,
each of which can take up both the two inactive and 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.
[0022] According to a further variant an independent chamber in which an auxiliary piston
works or can work at the same time as the main piston is included coaxial with the
chamber where the main piston works.
[0023] The ability to vary the displacement is achieved by inserting or not in the circuit
one or the other of the compression/aspiration chambers or both of them.
[0024] 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.
[0025] If the displacement is reduced, the quantities of movements in question are reduced
and the mass of oil the displaced is reduced much more.
[0026] It is then possible to change more easily and quickly the number of revolutions by
increasing them.
[0027] 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).
[0028] 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.3 shows another embodiment of the invention.
[0029] 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.
[0030] The hydraulic swaging machine may be of the type disclosed in EP 88108963.5 or in
US 4,745,793 or be of another known type.
[0031] The main piston 11 is displaced axially by a connecting rod 14 actuated by a crankshaft
15 set in rotation by a motor 16.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] In its working position the auxiliary piston 18 has to move together with the main
piston 11.
[0036] When the auxiliary piston 18 is in its inactive position, the displacement will be
the maximum available.
[0037] 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.
[0038] 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.
[0039] In this way two different displacements are obtained with two different strokes of
the specific pistons that bear the hammers of the swaging machine.
[0040] 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.
[0041] 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
(18-118-218 etc.)
[0042] In the embodiment shown in Fig.2 each auxiliary piston 18 has a positioner assembly
20 comprising, for instance, a grearwheel-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.
[0043] Fig.3 shows another variant, which provides for at least two coaxial chambers 13-113
independent of each other. The main piston 11 operates in one chamber 13, while the
auxiliary piston 18 solidly fixed to the main piston 11 operates in the other chamber
113.
[0044] In this way both pistons 11-18 operate in their own chambers 13-113, and the connection
or disconnection of one or both chambers 13-113 to or from the pipe 12 leading to
the specific piston of the swaging machine determines the desired displacement.
[0045] By means of the invention it is possible to link to one or the other displacement
of the pump the required speed at the axis of the crankshaft 15.
1. Method to forge metallic pieces with a swaging machine, the method being characterized
in that 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.
2. Method as claimed in Claim 1, whereby the great number of hammer blows is even more
than four times the number of hammer blows during the condition of a low number of
blows.
3. Mechanical swaging machine suitable to carry out the method of the claims hereinbefore
and characterized in that it comprises for each eccentric actuating a single hammer
a countereccentric to regulate the stroke of the hammers, the actuation motor being
able to run at least at two speeds.
4. Hydraulic swaging machine suitable to carry out the method of the claims hereinbefore
and characterized in that the stroke of the individual hammers is altered by acting
on the displacement of the relative pumps, the actuation motor being able to run at
least at two speeds.
5. Pump for a hydraulic swaging machine as claimed in Claim 4, wherein a chamber (13)
in which a main piston (11) operates is connected directly to the chamber of the specific
piston that bears the specific hammer, the pump being characterized in that the displacement
of each chamber (13)/main piston (11) assembly has at least two values.
6. Pump as claimed in Claim 5, in which a variation of displacement is obtained with
at least one auxiliary piston (18) having an inactive position and a working piston,
the auxiliary piston (18) operating in the chamber (13) and being substantially solidly
fixed to the main piston (11) when in its working position (Figs.1 and 2).
7. Pump as claimed in Claim 5, in which the variation of displacement is obtained with
at least one auxiliary chamber (113) coaxial with and independent of the main chamber
(13), an auxiliary piston (18) coaxial with and solidly fixed to the main piston (11)
operating in the auxiliary chamber (113).