Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
This invention relales to a method of starting a hydraulic reciprocating
machine such as a rock drill of the type disclosed in American Patent No.
5,222,452 and to a drill start/stop valve for carrying out the method.
BACKGROUND TO THE INVENTION
Drills of the above type generally include three pressure chambers which
in this specification will be re~er,e.l to as the supply chamber, the return
chamber and the drive chamber, and a linearly acting piston which is
diametrically stepped and reciprocal in all three of the chambers.
The diametrical dimension of the steps in the piston obviously determine
the reacti~/e force imposed on the piston by hydraulic fluid acting on that
step in the drill chamber in which the step is laca~e~. In the supply
chamber the piston is weakly hydraulically biased to..~rds the return
chamber in the drive stroke direction of the piston. The bias on the piston
in the return chamber is more firmly in the revor-~e direction towards the
supply chamber and the piston bias in the drive chamber is
overwhelmingly in the first direction of piston travel towards the return
chamber.
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During normal cyclic operation of the drill hydraulic fluid at supply
pressure is continuously fed to the supply and return chambers and to
and from the drive chamber by poppet valves. The op~rali~e positions of
the valves are primarily dependent on the position of the drill piston
during the piston cycle.
A problem with these drills is that when the hydraulic fluid supply to the
drill is terminated the piston and drive chamber valves are stopped at any
arbitrary position of the piston cycle which, in the worst case, can prove. ,l
restarting of the drill or may cause the drill not to be started pGsiti~/ely
enough to maintain the piston cycle.
SUMMARY OF THE INVENTION
A ~ hGd of starting and stopping a hydraulic reciprocating machine of
the type which includes a piston, a fluid supply chamber and a piston
return chamber according to the invention includes the steps of supplying
hydraulic fluid at supply pressure to the fluid supply chamber to move the
piston towards the return chamber and then only to the return chamber
to start the reciprocation cycle of the machine piston and stopping
reciprocation of the piston by terminating the supply of hydraulic fluid to
the machine.
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Conveniently the method includes the step of venting the return chamber
prior to starting the machine.
In one form of the invention the method includes the step of venting the
return chamber to al~--os~h~re on termi. Ialin~ the supply of hydraulic fluid
to the machine to stop the reciprocation of its piston.
In another form of the invention the method includes the step of ve.llill ~
the return chamber to the fluid supply chamber on terminating the supply
of hydraulic fluid to the running machine to stop the reciprocation of its
piston.
Further according to the invention the machine includes a piston drive
chamber and the method includes the step, during or prior to starting, of
filling the piston drive chamber with hydraulic fluid at a relatively lower
pressure than the supply pressure prior to supplying hydraulic fluid at
supply pressure to the return chamber.
A start/stop valve for a hydraulic reciprocating machine of the type which
includes a piston, a fluid supply chamber and a piston return chamber
according to the invention includes a housing having an inlet port for
hydraulic fluid at supply pressure; first and second supply fluid outlet
ports which are connected, in use, respectively to the machine fluid
supply chamber and the return clla~ r, a valve arrangement in the
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housing, an actuator on the outside of the housing for moving the valve
arrangement b~ ee.l a first position in which the first outlet port is open
to the inlet port to supply hydraulic fluid at supply pressure to the
machine's supply chamber and the second outlet port is closed and a
second position in which both outlet ports are open to supply fluid at
supply pressure to both machine chambers from the inlet port to start
reciprocation of the machine piston.
Further according to the invention the machine has a piston drive
chamber and the valve includes a third outlet port, which in use, is
connected to the machine piston drive chamber with the valve
arrangement being adapted to close the port in its second position of
movement in the valve housing and to open the port to supply hydraulic
fluid to the machine drive chamber only momentarily when the valve
arrangement is moved b_hr~ee., its first and second positions on starting
the machine.
Still further according to the i"-~e.,lion the valve includes means for
venting the return chamber prior to starting the machine.
Yet further according to the invention the valve includes means for
relieving excr~sive pressure which may be genorale~l in the return
chamber during the stopping of the drill.
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_ Page 5
In one form of the invention the valve is a rotary valve. In another form the
valve arrangement is linearly movable in the housing bctwee.l its first and
second positions.
A hydraulic rock drill according to the ;.~le.~lion includes the start/stop
valve as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of the i.,~e.,lion is now described by way of example
only with reference to the drawings in which:
FIGURE 1 is a sectioned side elevation of a rock drill.
FIGURE 2 is a sectioned side elevation of the start valve of the invention
shown schematically con"ccte.l to the drill of Figure 1,
FIGURES 3 and 4 are sectioned side elevations of the Figure 2 start valve
illustrating the valve members in ~lifrere~l positions of operation, and
FIGURES 5 to 7 are sectioned side elevations of a second embodiment of
the start valve of the ;.,~e.,lion.
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DETAILED DESCRIPTION OF THE DRAWINGS
The drill of Figure 1 is substantially identical to that described in American
Patent No.5,222,452 with the differences betwee., the two being explained
below.
The drill is shown in the drawing to include a housing 10, a piston 12, and
a valve arrangement indicated generally at 14.
The housing 10 includes a supply chamber 16, a return chamber 18, a
drive chamber 20, an inlet port 22 into the supply chamber, a fluid
passage 24 extending l.~twee., the inlet port 22 and a fluid passage 26
which exle. ,~s from the passage 24 towards the drive chamber, an annular
exhaust port 28 in the drive chamber and a fluid passage 30 connecting
the exhaust port 28 to atmosphere on the outside of the housing.
The piston 12 includes four portions 32, 34, 36 and 38 which are
downwardly stepped in diametrical measurement from the portion 32 to
the portion 38 as shown in the ~Iraw;.~g. The stepped portions of the
piston provide lands or hydraulically P~,uo6e~ piston areas 40, 42 and 44
on the piston. The piston portion 38 includes a fluid passage 46 which
extends from the outer surface of the piston adjacent the land 44 to the
free end of the piston as shown in the drawing.
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The valve arrangement 14 includes an exhaust valve member 48, an inlet
valve 50 and a pick-up member 52 for the inlet valve 50.
The valve arranye...~.,l 14 is associated with a housing insert 51 which is
fixed to the housing wall in any suitable manner. The purpose of the
insert is for ease of assembly and maintenance of the drill but need not
necessarily be a separate component and could equally well be ;.,ley,al
with the remainder of the housing.
The exhaust valve member 48 is annular with its inner surface radially
spaced from the outer surface of the piston portion 36. The outer surface
of the valve member is stepped into a complc."e.ltal step in the chamber
20, as shown in the dlaw;"~, to provide a hydraulically exposed land on
the exhaust member which is permanently in communication with the fluid
supply passage 26. The forward end of the exhaust valve, at its limit of
travel to the right in the drawing, seats on the insert 51 against a reduced
diameter portion of the insert to close the exhaust port 28. The rear face
of the exhaust valve, on the left in the drawing, ca..i~s radially extending
fluid passage grooves.
The inlet valve is slidable on the portion 36 of the piston on a seal
bearing, as shown in the drawing and includes a radially disposed head
which seats on the rear face of the insert 51, to close the chamber 20 to
fluid at supply pressure in the chamber 16, and a boss which is spaced
from the inner surface of the insert.
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The pick-up member 52is slidable on the piston portions 36 and 38 on
seal bearings as shown in the drawing. The pick-up member includes an
annular groove which defines a chamber 54 in the member which,
throughout the cyclic operation of the drill, is open to atmosphere through
the passage 46 in the piston. The front face of the pick-up member
carries fluid passage grooves similar to those in the rear face of the
exhaust valve.
The piston is guided for reciprocal m~ve,..c.,l in the housing in seal
bearings 58 and the exhaust valve member 48is similarly guided in seal
bearings in the insert 51 which are spaced from each other in the axial
direction of the piston on either side of the step in the outer surface of the
valve member.
The supply chamber 16 of the Figure 1 drill typically includes a pressure
accumulator which conventionally is in the form of a gas pressurised
diaphragm (not shown in the drawing). This accumulator substantially
maintains the supply pressure in the supply chamber 16 irrespective of
abrupt changes in fluid flow caused by the piston operation and valve
actions in the drill.
Although only the body of the rock drill is shown in the drawing it does in
practise include a front end which carries a conventional chuck and rotor
for the drill steel 56.
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As mentioned above the drill of Figure 1 is s ~hstantially identical to the
drill described with relere..ce to Figure 1 of American Patent No.5,222,452
with the only differences between the two drills being that in the previous
drill the fluid passage 24 is connected from the supply inlet 22 to the
return chamber while the inlet 60 of the present drill is a separate inlet
and the earlier drill does not include a fluid passage 62 which is in
communication with the exhaust port 28 in the drive chamber 20.
The start valve, ~n the first embodiment of the invention, is shown in
Figure 2 to include a housing 64 having two chambers 65 and 66, a supply
fluid inlet port 67 which is adapted for connecting to a high pressure
hydraulic fluid hose and fluid outlet ports 68, 70 and 72. As is shown in
the composite d-a~/;.-g the outlet port 68 is con,-Ecte~l in use to the inlet
port 22 of the Figure 1 drill, the port 70 is connected to the return
chamber 18 through the fluid inlet passage 60 and the port 72 of the valve
is connected to the drive chamber 20 of the drill through the fluid p~ss~ge
62 and the exhaust port 28. The start valve further includes a composite
valve arrangement which consists of a hollow stepped body 74, a headed
valve member 78 which carries a stem 80 and an operating handle 82
which is located on a stud which is threadedly engaged with a threaded
aperture in the wall of the housing 64. The free end of the handle stud is,
for convenience of assembly, separate from and bears up against the free
end of the valve stem 80. The valve housing 64 is divided into its two
chambers 65 and 66 by a throat 84 in which the reduced diameter portion
85 of the sleeve 74 is sealingly freely slidable.
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The valve member body 74 includes one or more inlet ports 86 which
pass through its wall to permit hydraulic fluid flow between the chamber
65 and the interior of the valve member body. The free end of the reduced
diameter portion 85 of the body 74 is open. A spring 87 in the chamber 65
biases the valve body 74 to the right of the chamber 65.
The valve member 78 carries a bore 88 which p?sses through its stem 80
and which is in axial re.a;ster with a bore 90 which passes through the
threaded handle stud to atmosphere. The bore 88 is open into the
housing chamber 66 through a port 92.
In the Figure 2 position of the composite valve member components all
three of the outlet ports from the housing 64 are close~ to supply fluid
connected to the port 67 by the closed head of the valve member body
74 and the valve member 78. Prior to starting the drill of Figure 1 by
means of the valve, the handle 82 is rotaled to move the valve member 78
and the valve body 74, by the pressure of the supply fluid acting on it, to
the right from the closed isolation position shown in Figure 2 to the
starting position shown in Figure 3. In this position of the valve, fluid at
supply pressure flows through the valve inlet port 67 and from the port 68
to the fluid supply chamber 16 of the drill through the drill inlet port 22.
Fluid flow from the port 22 through the passages 24 and 26 bias the drill
exhaust valve member 48 to the left in the drawing in which position the
exhaust port 28 is open to the drive chamber 20 as shown in Figure 1. In
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Page 11
moving to the Figure 3 start position fluid at supply pressure also flows
from the valve port 72 to the fluid passage 62 and into the annular exhaust
port and the drive chamber while the exhaust port is open through the
fluid exhaust passage 30 so that the fluid in the drive chamber 20 is at a
substantially lower pressure than the fluid supply pressure in the chamber
16. The valve body 74 is, in this stage of operation of the valve, biased by
fluid pressure in the valve chamber 65, and the bias of the spring 87,
tightly onto the valve member 78 to pre\re.ll fluid flow from the open end
of the body 74 into the chamber 66 and so through the port 70 to the drill
return chamber 18. The port 92 in the valve member 78 is now open to
all.,Q-phere and the return chamber pressure is relali~ely low with the
consequence that fluid at supply pressure in the supply chamber 16
biases the piston to the right in the drawing.
Continued rolali~., of the handle 82 causes the valve member 78 to move
from the Figure 3 start position to the Figure 4 running position at which
the motion of the valve body 74 to the right in the drawing is arleste.~ by
the throat shoulder in the chamber 65, the step on the body 74 closes the
port 72 and the valve member 78 separates from the open end of the
valve me."~r body 74. When the rear face of the valve member 78 bears
up against the wall of the chalnL _r 66, as shown in Figure 4, the vent port
92 into the valve member bore 88 is closed by the chamber wall. Fluid at
supply pressure now flows through the valve body ports 86, from the
open end of the body into the chamber 66 and from the port 70 through
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the fluid passage 60 in the drill into the drill return chamber 18. The flow
of hydraulic fluid, which is now at supply pressure, into the return
chamber imposes a high pressure on the land 40 of the piston to drive the
piston in the direction of the arrow in the drawing on its return stroke to
commence cyclic operation of the piston. The piston is driven more
positively than is the case with the drill descri~e~l in the American patent
as the pressure accumulator in the supply chamber 16 is charged prior to
the drill starting through the starting valve as shown in Figures 3 and 4.
With the fluid flow to the exhaust port 28 now cut off through the passage
62 by the closure of the port 72 of the start valve, fluid in the drive
chamber 20 is forced from the cha"~l;Er by the land 42 on the piston
through the open exhaust port 30. The return stroke of the piston
continues until the land 42 on the piston strikes the forward face of the
exhaust valve member 48 to move the exhaust valve to the left in the
drawing with the forward portion 32 of the piston then closing the exhaust
port. The shock of the impact of the piston land 42 on the exhaust valve
is transmitted through the valve to the inlet valve 50 to knock the inlet
valve to the left in the d~ ;.lg from its seat on the insert 51 to a pos~tion
le,-,ote from the insêrt. As the inlet valve leaves its seat pressurized fluid
from the supply chamber 16 enters the drive chamber 20 which is still
fluid flooded at no pressure because of the initial fluid flooding through
the port 72 in the valve and the p~s~. ge 62 in the valve body. In practice,
the outlet of the open exhaust port 30 is on the upper surface of the drill,
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and not in the position shown in Figure 1, to prevent fluid in the drive
chamber 20 from draining under gravity from the chamber. Being fluid
filled the small injection of fluid from the supply chamber into the drive
chamber 20 rapidly builds up pressure in the drive chamber and against
the land 42 of the piston to decelerale the piston and revo,r~e its direction
of travel into its drive stroke more efficiently than in the embodiment of
the drill described in the America.l patent to ensure very positive starting
of the drill.
In order to stop the drill, the handle 82 is rotaled in the opposite directiG.I.Initially the motion of the valve member 78 from its running position in
Figure 4 to that in Figure 3 opens the port 92 to exhaust fluid through the
bores in the valve member stem and the handle stud, so venting the
return clla,l~er. As a consequence of this venting of the return chamber
to atmosphere pressure spikes in the return chamber arising from the
forward motion of the piston are minimised.
The seco.-~ embodiment of the valve of the invention is shown in Figures
5, 6 and 7 in which like rererellce numbers are used as those in Figures
2 to 5 of the first embodiment. In this em~odiment of the valve the throat
84 is stepped to provide a seat 94 and the reduced diameter portion 85
of the valve body 74 is complementally outwardly stepped to an illcre3sed
diameter 96. The reduced diameter portion 85 of the valve body is smaller
in diameter than the portion of the throat 84 in which it is located to
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-- Page 14
permit free fluid flow between the valve chamber 66 and the port 73 when
the port 73 is open.
The start-stop valve of this embodiment of the invention operates in much
the same manner as that of the first embodiment save that while the valve
body 74 is moved from the Figure 1 isolation position to the Figure 2 start
position fluid at supply pressure is not fed from the now non-existe.ll
valve port 72 to the drill drive chamber, and in stopping the drill fluid is no
longer exhausted through the previous embodiment handle passages 88
and 90.
During starting of the drill, I,ctwoe" the valve body 74 positions of Figures
5 and 6, the port 73 is open to the valve chamber 66 and retained fluid is
pumped through the valve from the drill return chamber 18 through the
valve ports 70 and 73 to the drill drive chamber 20 to pre-charge the drive
chamber. Should the retained fluid have drained from the drill return
chamber 18 over a long period of non-use of the drill the drill is, as with
the previous valve embodiment, merely false started to pre-charge the
drive chamber during start-up of the drill.
In the event that the pressure becomes excessive in the return chamber
during stopping of the drill the pressure pulse or spike will act on the
stepped face of the valve body 74 in the bore 84 to cause the valve body
to act as a spring and hydraulically loaded relief valve which is lifted by
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the excess pressure from its seat 96 to relieve the fluid pressure through
the port 73, the drive chamber and the exhaust port 30 which is directed
away from the drill operator. Fluid may similarly be exhausted from the
drill during the commencement of the start-up of the drill if the drill
chamber 18 is fluid filled as described above, by moving the valve body
74 towards the Figure 5 isolation position to vent the drill return chamber
fluid through the valve ports 70 and 73 over the seat 94 to the drill drive
chamber and exhaust port 30.
The invention is not limited to the ~.r~cise details as herein describE~. For
example the start valve need only be operable between the Figures 3 and
4 and 6 and 7 positions as the Figures 2 and 5 shut-off positions would
in any event only be required in exce~JtiG,-al circumstances and the drive
chamber may be fluid filled by false starting the drill.
