Note: Descriptions are shown in the official language in which they were submitted.
WO 95123050 PCT/SE95/00210
2184~6~
Pneumatic impact breaker
This invention relates to a pneumatic impact breaker of
the type comprising a housing which at its rear end is
provided with one or two handles and which is formed with
a longitudinal cylinder bore, a hammer piston
reciprocably guided in the cylinder bore, a front portion
of the housing which includes a socket means for
receiving the rear impact receiving end of a working
implement, an air distributing valve located in the rear
part of the cylinder bore and arranged to direct motive
pressure air alternatingly to the opposite ends of the
hammer pistons to make the latter reciprocate in the
cylinder bore, and a rear cylinder head forming a closure
of the cylinder bore as well as an axial support for the
air distributing valve.
Pneumatic impact breakers of the above type provide an
effective breaking by a high impact energy but generate
at the same time external vibrations and internal blows
which have a detrimental influence on the operator as
well as on the mechanical parts. By using vibration
damped handles it has been aimed to improve the
protection for the operator, whereas the breaker itself
has to have a very rugged design to withstand the risk
for damage at operation. This normally means an increased
weight of the breaker as a result of the heavy steel
components and also a need for strong side bolts or space
demanding screw joints to keep the parts together.
Examples thereof are shown in the following patent
publications: US 3,446,294, US 4,303,133, and US
4,673,042. The two latters also show an aspiration to
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exchange the steel components by parts of a plastic material
for bringing down the total weight of the breaker,
vibrations and noise. Also in the British patent
GB 2,018,904 it is understood that conventional screw joints
are used to keep the parts together, and the specific valve
arrangement shown in this patent is used in the actual case
and for the purposes described below.
The object of the invention is to redesign the
rear part of this type of pneumatic breaker such that heavy
side bolts and screw joints are eliminated, the weight and
size of the cylinder head is substantially reduced, more
components of plastic material are used for keeping down the
weight and manufacturing costs, and ergonomically improved
vibration damped handles are fitted to the rear part of the
machine. These purposes are reached by the invention as it
is recited in the following claims.
A broad aspect of the invention provides a
pneumatic impact breaker comprising: a housing provided at a
rear end thereof with at least one handle; a longitudinal
cylinder bore formed in said housing; a hammer piston
reciprocally guided in said cylinder bore; a socket formed
in a front portion of said housing for receiving a rear
impact receiving end of a working implement; an air
distributing valve located in a rear portion of said
cylinder bore and arranged to direct motive pressure air
alternatingly to opposite ends of said hammer piston to make
said hammer piston reciprocate in said cylinder bore; and a
cylinder head forming a closure for said cylinder bore as
well as an axial support for said air distributing valve;
wherein said cylinder head at least partly extends into said
rear portion of said cylinder bore; wherein said housing is
formed at said rear end thereof with two parallel wall
portions both extending rearwardly beyond said cylinder
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head; wherein said at least one handle extends in between
said two parallel wall portions; and wherein a wedge bolt is
mounted between said two parallel wall portions and extends
perpendicularly to said two parallel wall portions as well
as to said cylinder bore to form an axial lock for said
cylinder head and a mounting member for said at least one
handle.
Preferred embodiments of the invention are
described below with reference to the accompanying drawings.
On the drawings,
Fig lA and 1B show longitudinal sections, divided
by a transverse line A-B, through the pneumatic breaker
according to the invention.
Fig 2 shows on a larger scale a longitudinal
section of the rear part of the breaker according to Fig 1A.
Fig 3 shows a section on a somewhat smaller scale
along line 3-3 in Fig 2.
WO 95/23050 PCT/SE95/00210
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Fig 4 shows on a larger scale a fractional view of Fig 3.
Fig 5 shows a detail view similar to Fig 4, but
illustrates an alternative embodiment.
Fig 6 shows a view similar to Fig 3, but illustrates an
alternative handle design.
The impact breaker 10 shown in Figs lA, 1B comprises an
elongate housing 11 with a cylinder bore 20 and provided
with a cylinder head 12, handles 18, 19, and a front
portion 13. These parts are interconnected and
symmetrically oriented relative to the longitudinal axis
24 of the cylinder bore 20. The cylinder bore 20 is
extended rearwardly from an annular shoulder 21 through
an enlarged bore 23. The cylinder bore 20 is also
extended forwardly from an inner annular shoulder 25
through a forward bore 45. In front of the bore 45 the
housing 11 is formed with a clamping portion 46 including
an axial slot 47. The clamping portion 46 defines a
further enlarged bore 48 which extends coaxially with the
bore 45 and the cylinder bore 20.
In the bore 45 there is received a sleeve shaped
intermediate member 17 which has an outer shoulder for
abutting cooperation with the annular shoulder 25 and
which extends sealingly into the cylinder bore 20. The
intermediate member 17 has an annular end surface 49
which faces the cylinder bore 20. The intermediate member
17 is a part of the front section of the breaker housing
11 and serves as a guide sleeve for the impact receiving
parts of the tool. The intermediate member 17 has a
WO 95/23050 PCT/SE95/00210
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central coaxial first bore 50 and an enlarged coaxial
second bore 51 separated from the first bore 50 by an
annular forwardly facing shoulder 52. The front portion
13 of the housing is a separate part which is formed with '
a tubular neck 55 to be inserted in the enlarged bore 48
of the clamping portion 46, thereby being axially located
by the intermediate member 17 which defines the axial
position of the front portion 13 relative to the housing
11 via the annular shoulder 25.
A clamping bolt 56 extends transversely through a bore 57
in the clamping portion 46 and engages a tangential
groove 58 in the neck portion 55 to lock positively the
latter axially relative to the housig 11. By means of a
nut (not shown) the clamping bolt 56 locks frictionally
the neck 55 to the clamping portion 46 such that the
front portion 13 and the intermediate member 17 are
rigidly secured to the housing 11.
In the bore 50 in the intermediate member 17 there is
sealingly guided an impact transferring anvil 14. The
anvil 14 is formed with an impact receiving end surface
62 facing the cylinder bore 20 and an annular flange 53
which is guided in the enlarged second bore 51. The anvil
14 is rewardly displaceable by the neck portion 15 of the
working implement 16, and the interengagement of the
flange 53 and the annular shoulder 52 defines the rear
working position of the anvil 14 relative to the housing
11. See Fig 1B. In the working position of the anvil 14, '
the rear impact receiving end surfaces 62 is located
substantially in level with or slightly below the rear
end shoulder 49 of the intermediate.member 17. In a
WO 95/23050
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conventional way, the front portion 13 carries a
releasable working implement retainer 60 which is
engagable with the collar 61 of the working implement 16
while allowing a limited axial movement of the latter
with the neck 15 guided in the neck portion 55 of the
front portion 13. In its forwardmost position, the
working implement 16 is blocked against further movement
by the retainer 16 engaging the collar 61, which means
that the anvil 14 remains in its extended position in
which it abuts against the neck portion 55 of the front
portion 13. The anvil 14 and the neck 15 forms the impact
transferring means of the working implement 16.
At its rear end, the housing 11 is formed with two side
walls 29, 30, Fig 2, which extend rearwardly beyond the
cylinder head 12 and the central portions of the handles
18, 19. In opposite coaxial bores 67, 68 in the side
walls 29, 30 there is inserted a wedge bolt 32 which
comprises a cylindrical steel tube having an axially
extending zigzag shaped slot 33 for obtaining radial
compressability. Thanks to the zigzag shaped slot 33, the
wedge bolt 32 gets a smoother outer surface without any
straight cutting edges which could damage the bores 67,
68 at mounting. The wedge bolt 32 forms a mounting pivot
for the central parts of the handles 18, 19, Fig 3,
thereby connecting the handles 18, 19 to the housing 11.
Vibration damping pretensioned springs 35 are located
between the housing 11 and each of the handles 18, 19 to
bias the handles toward a rear end cover 31. This end
cover 31 is formed of a plastic material and is secured
in opposite grooves 74 in the side walls 29, 30.
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Inside the cover 31, the handle 19 supports a pivot lever
36 which by means of a push rod 40 is arranged to control
an air inlet valve 38. The latter is biassed by a spring
39 toward closed position. By manipulating the lever 36,
thereby activating the inlet valve 38, a connection
between a pressure air inlet 80 and an inlet passage 81
in the housing 11 and the rear bore 23 of the cylinder
bore 20 is controlled.
Resting on the axial shoulder 21 in the enlarged bore 23,
there is inserted a valve housing 27 of a distributing
valve, Fig 2, 4,. The cylinder head 12 comprises a plug
of metal or a plastic material which is introduced into
the enlarged bore 23 and abuts and locks axially the
valve housing 27 via a seal ring 82. At its rear end the
plug 12 is formed with two rearwardly extending heals 83
which are formed with indentations 79 and which are
located on.both sides of the handles 18, 19. The heals 83
rest against the wedge bolt 83 such that the plug 12 is
axially locked in the bore 23. The plug 12 has a radially
extending air distributing passage 84 which via a
longitudinally extending feed passage 86 in the housing
11 communicates with a front end of the cylinder bore 20.
The passage 84 is open toward the valve housing 27 via a
central axially extending opening.
The valve housing 27 is formed in a plastic material,
preferably acetal plastic (delrinj, and comprises a
rotationally symmetric and substantially cup-shaped main
part having an outer circumferential groove 87
communicating with the air inlet passage 81 in the
housing 11. In the valve housing 27, there is shiftably
WO 95/23050 PCT/SE95/00210
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dispose:.d a valve plate 26, also of a plastic material,
for alternative cooperation with a forward valve seat 41
which is open to the cylinder bore 20 and a rear valve
seat 42 which is open to the radial air passage 84 in'the
plug 12. The bottom 88 of the circumferential groove 87
is provided with radial openings 89 which are disposed in
axially separated rows between which the valve plate 26
is shiftable. The rear valve seat 42, also formed in a
plastic material such as acetal plastic, comprises a lid
which is inserted in the valve housing 27 and locked by a
lock ring 43.See Fig 2.
In a modified design, shown in Fig 5, the rear valve seat
42 may be formed in one piece with the cylinder head plug
12 and have the form of a ring portion 90 extending
around the central opening communicating with the radial
passage 84.
In the cylinder bore 20, between the valve housing 27 and
the end surface 49 of the intermediate member 17, there
is reciprocably guided a hammer piston 28. The latter is
formed with a piston head 63 which comprises a rear end
portion 65 and a forward end portion 66 and which are
sealingly guided in the cylinder bore 20 and a piston
neck 64 which is intended to deliver hammer blows onto
the impact receiving surface 62 of the anvil 14.
As an alternative to the above described embodiment, the
impact receiving surface may be formed by the rear end
surface of the working implement neck 15, which means
that the anvil 14 may be omitted.
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As the operator applies the impact~~.breaker 10 against the
working surface the working imp~Le,~nent 16 as well as the
anvil 14 are displaced rearwardly to their normal
operating positions. (See Fig 1B.) As the lever 36 is
pressed down, pressure air will be supplied to the valve
housing 27 from the air inlet 80, through the inlet valve
38 and the passage 81. By cooperating alternatively with
the valve seats 41, 42, the valve plate 26 will
distribute pressure air to the respective ends of
cylinder bore 20, to thereby make the hammer piston 28
reciprocate in the cylinder bore 20 and deliver
repetetive hammer blows on the anvil 14. During the
reciprocation of the hammer piston 28, the respective
parts of the cylinder chamber 20 are vented to the
atmosphere through outlet openings 70, 71 located at
different axial levels in the housing 11. The outlet
openings 70 vent the rear part of the cylinder chamber 20
behind the hammer piston 28, while the openings 71 vent
the forward part of the cylinder chamber 20 in front of
the hammer piston 28.
In Fig 6, there is shown a simpler design of the
pneumatic impact breaker 10 which comprises a cylinder
head 37 formed in a plastic material (for instance
polyeurethan ) and formed in one piece with the handles
18', 191 and the plug 121. This cylinder head and handle
design may be fitted as a replacement unit by removing
the end cover 31 and the wedge bolt 32 and inserting the
alternative parts and lock them to the housing 11 by the '
insertion of the wedge bolt 32.
