Note: Descriptions are shown in the official language in which they were submitted.
7æs
The invention relates to an hydraulic percussion device
having a working piston displaceable in a working cylinder and a
control part displaceable in a control cylinder, which said con-
trol part has at least one control face on which acts thepressure
of a control line connected with the working cylinder, and having
also a pressure reservoir connected to the pressure line, and a
pump device delivering liqu~d under pressurei~tothepressure line.
Hydraulic percuss~on devices are known (Swiss Specifi-
cation No. 534,567, Atlas Copco, April 30, 1973), wherein control
of the working piston is effected by a smaller control piston dis-
placeable in a control cylinder. Displacement of the con~rol
cylinder ~ 5 effected hydraulically via one or more control lines
extending out of the working cylinder. The percussion devices
have a hydro-pneumatic pressure reservo~r connected to the pressure
line or to the outward-flow line, which said pressure reservoir is
:
charged with pressure liquid during prédeterminsd phases of the
working cycle o~ the working pis~on and gives up the said working
;:
quid again during other phase~ at which a higher degree of
pressure energy is required. In the known devices, reversal of -
20 ~ ~ the control piston takes place exclusively as a function of the
position of the working piston. The working piston may have al- ;
ready reached the appropriate li~t position although the required
quantity of liquid is no~ yet ~vailable in the pressure reservoir.
This is in~par~icular the case when the percussion device is em-
ployed in combination with pump devices the de~ivery rateof which
is relatively low,~i.e. such as deliver under the required pres-
sure an inadequate quantity of liquid per unit time. In such
cases, the known percussion devices operate with an ~lmost unre-
duced number of blows, but the percussion strength decreasec con-
siderably because there is not available in the pressure reser-
voir su~ficient pressure li~uid to supply the piston from above
with adequate percussion energy.
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7~25
Prequ~ntl~, the user o~ a percussion device has avail--
a~le only specific pressure pumps~ It may ~appen that the
delivexy capacity o~ the pressure pump is inadequate ~or impar-
ting to t~e work~ng piStOII, during a blow, the degree o~ pex-
cuss~on ~orce ~striking ~orce) which is required.
It is the object o~ the invent~on to provide a per~ -
cussion device ~hic~ can ~e operated with constant percussion ~-~
~orce independently o~ t~e delivery capacity o~ the pressure
pump connected thereto. For the solution o~ this problem, it
is proposed according to t~e invention to provide a~ a percus-
sion device`of the type mentioned at the outset a device which
: ,
subsequent to or dur~ng li~ting o~ the working piston permits
reversal o$ t~e control part into t~e position corresponding to
the percussion movement o~ t~e ~orking piston only when pressure~
and quantity i~ the pressure rese:rvoir have exceeded a threshold
value.
; The basic princ~ple of~the invention consists in that
t i.5 guaranteed that the impact or the downward movement of the
~orking pi~ton does not take pIace until the necessary pressure~
~ ~has been generated by the pump in the pressure reservoir. The
; advantage of~this mode o~ operation conslsts in that the per~
cussîon ~orce required în each particular înstance îs obtained
: : :ndependently o~ the deli~ery capacity o~ the pump employed and
that it is necessary to operate only with a low percussion num~er
when the delivery capacity of the pump îs inadequate.
There are various poss~ble modes o~ delaying the diis- ~-
placement movement o~ the control piston. For example, there may
be provîded in the contxol line e~tending to the control cylinder
a valve operating as a function of pressure. In the control
lîne, there obtained, towards the end of the return stroke of the
~orking piston, a pressure cor~esponding-to that of the pressure
-- 3 --
Z5
line and ~exewith also to the pressure o~ t~e pressure reser~oir.
I~ a valve operat~ng as a ~unct~on ~ pressure is provided in the
control line, then "s~tch~ng-through" o~ the control line does
not take place until t~e threshold ~alue of the val~e has been
exceeded~ Onl~ then is t~e control part rerersed or changed
ovex, produc~ng the down~a.rdl~ d~xected ~lo~ of the working
piston. ~ further poss~ility ~or guaranteeing build-up o~
pressure in the pressure reservo~r consists in that a spring
~orce d~rected oppositely to t~e pressure o~ the control line is -~
caused to act on the control part~ Therewith, t~e control part
is not able to tra~el until t~e pressure acting on its control
face is greater than the spring ~ias, ~hich can be set. In the
case~o~ such an embodiment, expediently, the control part is ~;
adapted to be subjected to pressure action~at ~oth its end faces, ;
the pressure forces su~stant~ally cancelling~each other out.
This p~essure compensat~on produces the~result~that the spring
requires to be designed only to ~e su~ficientl~ strong to ensure
that ~t will exert a ~orce corresponding to the pressure
threshold - it~is not re~uired also to countera:ct an hydraulic
0 ~ bias. Additionally, the spring may also be hydraulically sup-
ported by the arrangement whereby the pressure face operative
out of the same direction as the spring is larger than the
oppositely acting pressure ~ace.
A th~rd possible method of dela~ing reversal or change-
over o~ the control piston ~s characterized in that there is
prov~ded in one of the lines through which there is a flow
during lift o~ the working piston a throttle location due to
which the liquid stream is, on workingpiston li~t taking place,
slowed down and the working piston is decelerated, and in that
the throttle location is so dimensioned tha~ the working piston
does not reach ~ lift or stroke position producing change-over
- 4 ~
~o~
o~ t~e control part ~n~il t~e pressure reser~oir has ~een
~illed ~ith a predetermined minimum ~uantity o~ liquid.
Due to tRe throttle locat~on, the return stroke of the
~orking piston is slo~ed do~n~ so that the working piston xe-
leases t~e control l~ne in delayed ~ashion ~or change-over of
the control part. Dux~ng t~e phase o~ the slow return stroke,
the pressure reservoir can ba replenished. The slowing down of
the return stroke can Be e~ected by the arrangement whereby the
throttle location is proviaad bither in the return ~low line or
in the pressure line extend~ng into t~e working cylinder. In
the second case, t~e throttle location is expediently bridged
~y a non-return val~e permeable ~or the liquid leaving the wor-
king c~linder, or the throttle element itself is permeable in
the return-~low direction.
.
~- The invention is d~scussed in detail hereinbelow~with
reference to some examples o~ em~odiment and with reference to
the figure~
FIGURE 1 shows O diagrammatically, a lonyitudinal section
t~rough ~ first em~odiment o~ the percussion device
2Q ~ ~according to the inventi~n,~having a valve, adapted
to be operated as a function of pressure, in the
control line.
FIGURE ? shows a second example of embodiment, wherein
the control sleeve is ~iased by a spring, the per-
cussion device otherwise corresponding to that shown
in Figure 1.
PIGURE 3 shows a ~urther example o~ embodiment having a
control part biased by a spring, the percussion device
corresponding other~ise to that of Figure 1.
FIGU~E 4 sh~ws an example o~ embodiment having a throttle
location located in the return ~low line, the
- 5 -
\
percuss~on dev~ce ot~exw~se correspondin~ to
t~at o~ F~ur~ 1.
PIGURE 5 sho~ an ~xample o~ em~od.~ment having a
throttle locat~on located ~n the pressu.re line,
the percussion dev~ce other~ise corresponding
to that ` o~ re.l, and
FIGURE 6 shows a modP o~ carrying into e~ect the
principle lllu~trated in ~igure 5.
Referring to ~igure 1, the working piston ll is .
arranged for longitudinal displacement in the working cylinder
: 10~ Periodically it ~mpinges on the anvil 12 which may, for . ::
example, ~e connected wit~ a drilling linkage.
rough a supply line 13, ~ydraulic medium is intro~
duced into t~e.:~de~ice.. It ~lows via a pre-tensioned:non-return
: valve 14:into t~e pressure line 15. ~The non-return llne~14~
: takes tRe~orm o~ a spring-~iased~sleeve 45. The sleeve has at
Lts lower end a ollar 46 t~e rear side of which ls connect~ed
;with the pressureless return flo~ line 21. The spring 47,~
: ~hic~ urges the sleeve downwardly, is so dimensioned that the
20~ pressure~acting.on the lower end;~.ace 48 normally drives the
sleeve 45 upwaxdly. The sleeve does not descend until the
. pxessure in the pressure line falls below for example 70 bar and ;.
is no longer able to counteract the spring 47. The normal
: : pres ure in the hydro-pneumatic pressure reservoir 43 connected :.
to the pressure li~e 15 is 5a bar.
Th.e pressuxe line 15 is continuously connected to the
,
lo~ex cham~er 16 o~ t~e cylinder 10, so that the hydraulic
pressure always acts on t~e small annular ~ace 17 of the working
pi~ton 11 and endeavours to drive t~e latter upwardly.
72S
The upper cham~er 18 o~ t~a c~lindex is connected ~ia
a line 19 ~ith t~e control Yal~e 20~ The latter connects the
line 19 alternat~n~l~ w~t~ the pressure line 15 and with the
return ~lo~ line 21. The upper cham~er 18 is delimited by the
large annular ~ace 22 o~ t~e working piston. When, therefore,
the ~ull p~essure acts ~ot~ on the lower annular face 17 and
alsQ on thQ upper annular ~ace 22, the working piston is driven
do~nwardly. ~hen, on the other hand, the pressure medium acts
only on the smaller annular face 17 and the line l9 is connected
with the pressureless return-flo~ line 21, the working piston
e~fec~s i~s return stroke, during which it travels upwardly.
The hollo~ control sleeve 55 arranged in the control
valve 20 is;formed externally,~in its rearward zone~ ~ith a wide
annular groo~e 29 capable of connecting with each other the ;
bores, offset relati~e~to each other in the longitudinal direc~
; ~ t~on, of the lines l~ and 21. In the other end position shown
in the draw~ngs, the connection to the return flow line 21 is
shut off by the control sleeve, whereas the bore to the line l9
s free and is thus ccnnected with the interior of the continuous
20~ cllo~ ccntroI sleeve and with t~e pressure line 15. The inner
~; ~idth of the control sleeve is continuously constant. The rear
end face~30~is, together vith the effective control~face 58~,
largex~than the front end face 57 - alone, however, it is
smaller than~the front end face 57. ;~
Control of the control sleeve 55 i5 ef~ected via the
co~trol line 24 the pressure of which acts on the control face 58
o~ the annulax collar 56. The front delimiting face 59 of the
annular collar îs continuously connected with the return flow
l~ne 21. The control line 24 ~ranches, in the case of the
present example of em~odiment, into t~ree first branch lines, 65,
66, 67, and ~our second branc~ lines 25, 26, 27, 28, each of
~LID3~7;æ5 :
which debouches into an annular ~roove ~ormed ~n the ~orking
cylinder.
In the zone of the annular grooves connected with the ~;~
branch lines, the ~orking p~ston 11 has a luwer, thickened
piston element 62 the d~ameter o~ whic~ is adapted to the ~-
c~linder d~eter. The piston element 62 ~s able to close in
sealing manner the ~ranc~ l~nes ~ith associated annular grooves.
Underneath, it is delimited ~y the annular face 17 and above by
: :.
the annular ~ace 61~ Adjacent the annular face 61 is the wide ~;
; 10~ annular groove 69 and t~erea~ove is disposed a further thickened
piston element 64 ha~ing t~e same diameter as the piston element
:
62.~
In the zone of khe annu:lar~ ~roove 69 formed in the
piston, a return-~flo~ line 52 extends out of the working cylinder.
The annular groove~69 o~ the work.ing piston is so dimensioned
t~at Ln eac~ position o~ the ~orking~piston it engages the;return-
lo~ line 52. ~When, there~ore, t~e workin~ piston has descended
to s~uch aD extent that t~e upper annular face 61 o~ the plston
part or element~62 passes into~position below the first opened
20~ ~ranah line 65 to 67, the associated branch line 65 to~67 is
connected via~the annular groove 69 with the return-flow llne 52,
~hereby the control line 24 becomes pressureless.
The plugs 68 adapted to be inserted into the branch
lines 65 to 67 so as to selectively seal of~ the latter, have the
ta k o~ determining that piskon position in which the control
line 24 is, during the piston movement, rendered pressureless for
the ~irst time in the manner described, so that the pressure
~orce acting on the control ~ace 58 of the control sleeve ceases. ;
The second branch lines 25 to 28 are disposed below
3~ the ~irst branch lines and determine durin~ which piston stroke
the pressure of the pressure line 15, which o~ta~ns continuously
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3~72~i
in the lo~er c~am~er 16 of t~e ~orkin~ c~linder~ is intxoduced
into t~e control line 24.
Inserted into t~e control line 24 is a ~alve 34 which
operates as a funct~on o~ pressure and wh~ch permits through-
~low o~ the li~u~d stream in the direct~on towards the control
slee~e 55 onl~ ~hen t~e pressure i5 a~ove a predekermined -
CQpt~onally presetta~lel m~nimum ~alue. In the counter-airec-
t~on, ~.e. ~rom the control sleeve to ~he working cylinder, the
control line 34 is completel~ permeable, this ~ing illustrated
~; 10 b~ the non-return val~e 38 connected anti-parallel to the valve
~; ~ 34.
hen the pressure of the control line 24 exceeds the -
minimum value set at t~e valve 34, it acts on the control face
5~8 of the control slee~e.
.
For~explanat'on of the~mode~o~ operatlon of~the per-
; cussion tool, the discussion ~~ commence from~t~e position of
the elements~s~ho~n in the dra~ings,~wherein the control sleeve
5~ connects the~;line l9 with~the~pressure line 15 and shuts-off
~ , , ,
;th~ connectlon to~t~e return-~lo~ line 2l.~ ~Since the full ~ ~ ;
~ ~pressure~obtains both at~the upper,~large~annular~face 22 and
also at~the lo~exl small;annular face 17, the working piston~ll -
accelerated~downwardl~. As th~s takes place, the piston ~`
: . ~ :
part 62 first of~all continuousIy closes off the branch lines
28, 27, 26 and 25, and then fxees the~first branch lines 65, 66
and 67, provided that the~ are not sealed with a plug 68. On ~;
sealing the ~ixst branch line 2S, the control line 24 ls cut off
from the high pressure and on ~reeing the uppermost branch line
65 it is connected with the pressureless return_flow line 52.
Thexeby~ liquid flows bac~ t~rou~h the valve 38, which in this
position is permea~le, and the ~orce acting at the control ~ace
58 o~ the control slee~e i~ xeduced. Under the pressure of the
_ g _
-
~0~7~
~orce actin~ on t~e lar~er ~nd ~ace 57, the control p~ston 55
is displaced up~ardl~.
Dur~ng the do~n~ard ~ovement o~ the working piston,
the pressure reservoix 43 has ~een discharged to a considerable
degree, ~ecause t~e upper e~d ~ace 22 is relatively large and
dux~ng impact a large quantit~ o~ liqu~d must ~e driven within
a s~ort time into the wor~ing cylinder so as to achieve a high
degree o~ impact energ~. Dur~ng the return stroke, following
thereof, of the ~rking piston, the pressure liquid engages only
the relatively small ~ace 17. Whilst the working piston -
ascends, the pressure reservo~r 43 is simultaneously refilled.
Thereby1 the pressure ascends in the pressure line 15. This
pxessure is routed via the control line 24 to the valve 34 oper-
ating as a function o~ pressure~and, initially, the said valve ~ :
; ~ sti~ locks" for as lony~as t~e pressure has not yet reached
the mlnimum value set. ~I~ t~e pressure pump ~not shown) con-~
:: nected to khe arrangement has::~ Led the pressure xeservoir 43
~: to such an e~tent that the pressure threshold has been reached in
the control line 24, then the valve 34 "switches through" and the
; pressure liquid ~lowing into the control cylinder 23 pushes: the
control sleeve S5 ~ack:into the position shown in Figure l.
Due to the valve 34 operating in pressure-dependent
: manner, it is guaranteed that the control sleeve 55 will not be ~` :
pressed into that position which corresponds to the downward --~;
movement of the working piston until the necessary pressure has
built up in the pressure line 15, i.e, until the pressure reser-
~oir 43 has been ~illed to the required degree. Therewith,
constant percussion energy ~s made ready for each blow o~ the
working piston, independentl~ o~ the delivery capacity of the
pressure pump connected to the supply line 13.
~n the case o~ the example o~ em~odiment of Figure 2,
-- 10 --
-
~L03~7~5
there i8 provided a spr.~ng~ased slee~e 551 the two end ~aces
30 and 57 o~ w~ch are o~ suB~tantiall~ equal size. The rear
collar ~ace 58 o~ the collar 561 is, here again, subjected to
the act~on o~ the pressure o~ the control line 24, in ~hich, how-
ever, there is no Yal~e, and t~e ~ront collar ~ace 59 which is
~it~dra~n relakiYe to the end face 57 is disposed in an annular
chamber connected to t~e pressureless return--flow line 21.
~ n order to generate pre-tension at the control sleeve
551, there is arran~ed in t~e interior thereo~ a helical spring
35 bearing at one end at the control sleeve 551 and at its other
end at a set screw 36. The spring 35 imparts to the control
sleeve 551 ~ias into the upper end position corresponding to
:
o~ the working piston. The ~orce o~ the spring counter-
acts the pressure engag~ng at the~ace 58 o~ ~he control line
24, ~Only when this pressure is aBle to overcome the spring
orce is the~control sleeve displaced down~ardl~ and the path
rom~the~pressure line lS through the control sleeve to the
line~l9 freed, whereby the down~ardly directed impact mo~ement
o~ the~working pisto~ is initiated.
;;2~ The~bias o~ t~e~spring is ad~usta~le by rotating~the ~ ;
set screw 36, s~o that t~e des.~red percus~ion energy can readily
be set~hy varying the spring bias.
Refer~ring to the example of embodiment according to
Figure 3, a control cylinder 552 biased by a spring 37 is provi-
ded, The spring 37 is arranged substantially in a blind bore
formed in the control cylinder. The lower end ~ace 572 consti-
tu,tes, together with the base ~ace o~ the blind bore, the engage-
ment face for the pressure of the pressure line 15, whereas the
upper end ~ace 582 represents ~he control ~ace at which the
pressure o~ the contxol line 24 is operative. The control face
582 is larger than the two lower pressure ~aces. ~dditionally,
there is ~ormed ~n the control pi.ston an annular gxoove 2q2
which in one of the end position$ o~ the working piston connects . .
the line 19 wit~ the return-~lo~ line 21 and, in the other end
position of the ~orking piston, connects the line 19 with a
line 152 extend~ng to t~e pressure line 15.
After a ~lo~ o~ t~e ~or~ng piston, the spring 37
drives the control piston 582 into the upper end position. The
pressuxe in the pressure l~ne 15 and inthe control line 24 has
~allen to a lo~ value. During t~e su~sequent lift o~ the :
~oxking piston, this pressure increases slo~ly. Only when the ::
pres9ure has become so large that t~e dif~erence in the forces
actlng ~xom a~ove and ~elow on~the control piston 552 exceeds
the force o~ the spring.37 is the control piston driven down~
~ardly, whereupon it connects tne line l9 with the line 152
extending to the pressure line.~ Thus, only then does the next
~impact or ~lo~ take place. Since, in the case o~ this example
o$ em~odiment, the contxol ~ace 582 is only slightly larger than
~he two lo~er pressure faces of the control piston, the spring
37 may be designed to ~e relatively weak even ~f the pressure
: 20 : ~ t~xes~old at whic~ changeover or reversal is to take place is ~;.
high. ~ ~.
The control sleeve 553 in the case of the example of
embodiment according to Fiyure 4 corresponds exactly to that of
the example of embodiment according ta Figure 1. Whereas in
the case of the previously describ~d examples of embodiment, the
working piston ls not impeded during its return stroke, and the ;-
del~y in changeover o~ the control sleeve takes place as a func~
tion o~ the magnitude o~ tne control pressure, in the case of
the device according to Figure 4 the return stroke o~ the working
piston 11 is delayed in that a throttle element 40 is inserted
into the return-~lo~ line 21. When the working piston per~orms
- 12 -
its ret~rn stroke, liqu~d ~s pressed out o~ ~ie cham~ex 18 into
the l~ne l9. The liquid ~lows throug~ the annulax yroove 29
into the return_~lo~ line 21. Due to the throttle location 40
provided in the return-~low line 21, ~low-of~ o~ the liquid is
slo~ed_down, so that also t~e li~t o~ the working piston is !~.,''
slo~ed down. T~e work~ny piston t~us connects the line 24 in
delayed manner ~it~ t~e pressure line 15. Due to this delay,
the pressure xeservo~r 43 ~s gi~en the opportunity o~ ~ecom~ng
c~arged, T~us, the up~ard movement o~ the w~rking piston is
~ntent~onally slowed~down in order t~at the pressure reservoir
43 may in the~intermediate period ~e ohargedO
lso, ~n the case o~ the device according to Figure 5, ~ ~-
; the upward movement o~ the working~piston LS delayed by a ;~
throttle location. In th~s case-, the~throttle location ~41 is
prov~ded in that~sect~on o~ t~he~pressure line 15 which is
located betwean the contro1 s1ee~e 553 and ~the working cylinder
10.~ Connected in parallel with ~the throttle location 41 is a
ncn-return valve 42 which is opened ~cr the flow-back which,~
dur~ng~the~downward~ vement of the working piston~, flows-back
20~-~ out o~t~e working cylinder, but is closed in the opposite
direct~on. ~
During a working movement of the working piston,
liquid flow~ cut of the working cy1inder into the pressure line
15. There~y, the non-return ~alve 42 permits throughflow~ so
that the impact or blo~ is not hindexed. During the subsequent
return stroke, the non-return valve 42 is closed. Thus, the
liguid i~ required to pass through thethrottle location 41.~
Thus, working piston lift ta~es place so slowly that meanwhile
the pres~u~e reservoir 43 can ~e recharged. In differentiation
~rom Figure 4~ in the case o~ Pi~ure S the throttle location 41
i8 arranged upstrea~ oX the woxking cylinder in the ~low
direction~
- 13 -
In t~e case o~ the exa~le o~ emBod~ment accord~n~ to
Fi~ura 6, the same control sleeve 553 is emplo~ed as ~n the
embodiment accordin~ to ~igure 5, The pressure line 15 has,
s~ortly ~efore its entr~ into the working cylinder, a right
angle bend locat~on rearwardly o~ which a diaphragm 39 is inser-
ted into $he line. T~e diaphra~m 39 has a narro~ central bore
and const~tutes the t~rottle element. A ~ore 70 extending ~rom
the interior to the d~aphragm 39 is sealed with a screw plug 71.
From the innex end ~ace o~ tne screw plug projeats a spring 72 -
dri~ing the d~aphragm 39 with a small degree o~ pre-tension
, .. .. . . . .. .
against its seat. ~he diaphragm 39 is displaceable against
the action of the spring 72. In its other end position, into
which it is pressed on pressure li~uid flowing out of the
,
working~-cylinder, the liquid~flo~s through longitudinal grooves
73 formed in the outer si;de of the diaphragm and extending over
a part of the diaphragm length. ~ In the position of the dia~
phragm 39 shown in Figure 6, thé grooves 73 are clo~ed, so that
for the return stroke of the worXing piston only the passage
~oross-section o the central bore of the diaphragm 39 is avaiI-~
20~ able. During~the impact, the diaphragm is pushed back, so
that for escape o~ the pressure liquid out of the working
cylinder the larger flow cross-section of the longitudinal
grooves 73 i5 avaiIable.
Subsequent to screwing out o~ the screw plug 71,
various t~pes o~ diaphragms can be inserted through the bore 70.
The selection o~ diaphragm si~e depends in each particular
instance on the delivery capacity of the pump available and on
the impact force required.
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