[0001] The invention concerns an asphalt cutting pneumatic hammer holder powered hydropneumatically,
based on the increased pressure achieved by pairing joined coaxial pistons of different
surfaces.
[0002] The asphalt cutting machines were and realized to replace the tiring operation of
manually cutting the asphalt covering on roads and the like, for the construction
of cuttings, for laying electrical and telephone cables, and gas installations, previously
done with pneumatic hammers equipped with spade tools, designed for digging.
[0003] Said machines of known type may be subdivided according to the type of power and
feed in:
- completely hydraulically powered ashpalt shearer (in- eluding the demolition hammer)
with no compressed air used.
[0004] These are autonomous, powered by a Diesel engine and must be driven by an operator;
they are the most sold and the most expensive; however, they have the disadvantage
of a very heavy ammortization iwth regard to their occasional use. Moreover, the operator
sits on the machine itself and so is subjected to the excessive vibrations of the
hydraulic demolition hammer.
[0005] - Completely pneumatically powered asphalt cutter, with automatic feed, with no operator.
[0006] This has not been met with enthusiasm given its extremely complex mechanism and the
unsuitable application of two penumatic pistons in direct contact with the pneumatic
hammer which subject it to continuous breakdown; moreover their complex mechanism
requires greater air consumption than simpler machines.
[0007] - Pneumatically operated asphalt cutter, with manual feed.
[0008] These present the disadvantage that only with great difficulty, if at all, is the
demolition tool extracted from the asphalt once fixed in it. This problem is caused
by the inadequate dimensions of the rising piston, which is not powerful enough to
extract it; on the other hand, if the diameter were adequate, after the initial resistance
were overcome, the extraction would occur so fast that it would be dangerous and uncontrollable,
to the point of jerking the machine and putting it out of alignment on each cut.
[0009] Another problem is that a hammer heavy enough to achieve reasonable results cannot
be mounted on the machine, since a heavier hammer would allow the tool to enter the
asphalt faster but would make extracting it difficult. Moreover, the pneumatic hammer
bearing piston is simple in effect, that is it can only extract and not push the hammer.
Said pneumatic hammer thus operates only by falling, with no possibility of regulating
the advancement.
[0010] The aim of this invention is to eliminate all the inconveniences of the machines
described.
[0011] This aim is achieved with an asphalt cutting machine of the pneumatic type equipped
with a pressure multiplier which transforms the pneumatic pressure to hydraulic pressure
increasing it from the 7 atmospheres supplied by the penumatic compressor to the approximately
50 atmospheres present in the hydraulic piston; said 50 atmosphere pressure obtained
with the pressure multiplier is then fed into the hydraulic piston cylinder on which
the pneumatic hammer is mounted, achieving the following advantages in succession:
1) possibility of mounting a 40Kg pneumatic hanrner on the still light structure of
the machine, since the extraction. power obtained with the pressure multiplier allows
it;
2) fast driving rates of the tool, obtained by increasing the hammer weight and by
regulating the descent by adjusting the air pressure;
3) the vibrations of the pneumatic hammer are absorbed by the hydraulic piston and
transmitted to the pneumatic one which in this case acts as shock absorber as well,
thus preventing the vibrations from being absorbed by the carriage and so by the operator's
arms;
4) certainty of extracting the tool using the hydraulic pressure in the pneumatic
hamner bearing piston; possibility of adjusting both pressure and stroke, with the
flow regulator, to adjust the hammer to the hardness and thickness of the asphalt
to be cut;
5) elimination of mechanisms (levers, stroke stops, mechanical devices, etc.) subject
by the vibrations present to wear and continuous breakdown, and presence in the automation
system of pneumatic and hydraulic components only;
6) use of a small capacity air compressor (m3/2.4min) since the pneumatic components
absorb a modest quantity of air.
[0012] The invention is shown in a preferred embodiment in the attached drawings, which
show:
- figure 1, a schematization of a cross section of the machine;
- figure 2, a top view;
- figure 3, a side view;
- figures 4 and 5, a variant of the device for automatic step by step feed;
- figure 6, a possible hydropneumatic operating circuit.
[0013] The figures show in detail the wheeled carriage 1 bearing pneumatic hammer 2, with
spade tool 3, powered by means of hydraulic tubes 4 and 5 from the pressure multiplier,
consisting of cylinder 6 with pneumatically powered piston 7, coaxial and joined via
hsaft 10 with hydraulic piston 8, sliding in overlaying cylinder 9 so that the force
developed by inlet of air in cylinder 6 is transferred via shaft 10 to piston 8, smaller
in surface than piston 7, and causes a considerable increase in the pressure exerted
by piston 8 itself, which pumps the oil in its separate circuit, alternatively, by
means of tubes 4 and 5, inside and outside cylinder 11, joined to hammer 2, which
is in this way lowered and raised, while the base of shaft 13 and piston 14 remain
joined to carriage 1. The hammer can operate behind carriage 1 as shown in dotted
lines in figure 2 or may be shifted 90 , as shown by the arrow, to operate next to
it for sidewalks and the like.
[0014] At the same time the simulator shown in figure 4, by means of rotation of a wheel
of carriage 1, allows the cutting distance of hammer 2 to be adjusted automatically,
causing a step by step feed since the single, or multiple, cam A, depending on the
cutting distance, operates valve 15 which, via timer 16, which supplies the delay
necessary to block the wheel in the position of maximum elevation of cam A, switches
over valve 17 to brake the wheel by means of cylinder 18. Then when the slide of hammer
2 returns to the top position, it pushes against stroke stop 19 which, by means of
timer 20, repositions valve 17 to unlock brake 18.
[0015] The hydropneumatic circuit shown in figure 5 functions as follows: the operator presses
valve 21 to switch over valve 23, which inverts the feed to cylinder 6 of lwo penumatic
pressure, of the pressure multiplier; the oil then flows from cylinder 9, of high
hydraulic pressure, through flow regulator 25, into the rear side of cylinder 11 to
which hammer 2 is joined, thus causing the latter to begin to descend; at this point
by pressing valve 22, valve 24 is operated to send air to hammer 2 and that is, to
begin to place it in operation; once the cut is effected by the spade 3 of hammer
2, this automatically with its movement, presses stroke stop valve 26, which repositions
valves 21 and 22 and, therefore, valve 21 takes air from hammer 2, closing valve 24,
and valve 22 incerts 23, bringing the hammer back to its initial position.
[0016] Of course, while the principle of the finding remains the same, the forms of realization
and the particulars of construction may be varied widely with respect to that described
and illustrated here, without going beyond the bounds of this invention.
1. Hydropneumatically operated asphalt cutting.machine characterized by the presence
of a pressure multiplier consisting of cylinder 6 with pneumatically powered piston
7, coaxial and joined via shaft 10 with hydraulic piston 8, sliding in overlaying
cylinder 9 so that the force developed by inlet of air in cylinder 6 is transferred
via shaft 10 to piston 8, smaller in surface than piston 7, and causes a considerable
increase in the pressure exerted by piston 8 itself, which pumps the oil in its separate
circuit, alternatively, by means of tubes 4 and 5, inside and outside cylinder 11,
joined to hammer 2, which is in this way lowered and raised, while the base of shaft
13 and piston 14 remain joined to carriage 1.
2. Asphalt cutting machine as claimed in claim 1 characterized by the presence of
a hydropneumatic circuit in which pressing valve 21 switches over valve 23, which
inverts the feed to cylinder 6 of low pneumatic pressure, of the pressure multiplier;
the oil then flows from cylinder 9, of high hydraulic pressure, through flow regulator
25, into the rear side of cylinder 11 to which hammer 2 is joined, thus causing the
latter to begin to descend; at this point by pressing valve 22, valve 24 is operated
to send air to hammer 2 and that is, to begin to place it in operation; once the cut
is effected by the spade 3 of hammer 2, this automatically with its movement, presses
the stroke stop valve 26, which repositions valves valves 21 and 22 and, therefore,
valve 21 takes air from hammer 2, closing valve 24, and valve inverts 23, bringing
the hammer back to its initial position.
3. Asphalt cutting machine as claimed in the preceding claims characterized by an
automatic step by step feed of carriage 1 caused by single, or multiple, cam A, which
depending on the cutting distance, operates valve 15 which, via timer 16, which supplies
the delay necessary to block the wheel in the position of maximum elevation of cam
A, switches over valve 17 to brake the wheel by means of cylinder 18; then when the
slide of hammer 2 returns to the top position, it pushes against the stroke stop 19
which, by means of timer 20, repositions valve 17 to release brake 18.