CA1056667A - Percussive tool - Google Patents
Percussive toolInfo
- Publication number
- CA1056667A CA1056667A CA263,043A CA263043A CA1056667A CA 1056667 A CA1056667 A CA 1056667A CA 263043 A CA263043 A CA 263043A CA 1056667 A CA1056667 A CA 1056667A
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- CA
- Canada
- Prior art keywords
- bore
- fluid
- tool
- restrictor
- bores
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Percussive Tools And Related Accessories (AREA)
Abstract
ABSTRACT
An operation varying facility is provided for a percussive tool having a reciprocable piston driven on an impacting stroke of the tool by compressible fluid and, on a return stroke to compress that medium, by pressure fluid supplied via control valve gear responsive to low and/or high predetermined pressures of the compressible fluid. This facility is operative for the control valve gear relative to actual attainment of such control pressures, or one of them, by presetting to give a nominal tool operating rate and variation to increase or decrease the actual tool operating rate.
An operation varying facility is provided for a percussive tool having a reciprocable piston driven on an impacting stroke of the tool by compressible fluid and, on a return stroke to compress that medium, by pressure fluid supplied via control valve gear responsive to low and/or high predetermined pressures of the compressible fluid. This facility is operative for the control valve gear relative to actual attainment of such control pressures, or one of them, by presetting to give a nominal tool operating rate and variation to increase or decrease the actual tool operating rate.
Description
The invention rela-tes to percussive tools ancl has particular, but not e~clusive, reference to impact-type mineral mining machine heads.
Our Canadian Patent 937~835 (Dobson Park Industries limited, issued December 4, 1973) discloses a mining head or other impact tool with control valve gear, and in which an impact chisel or otller tool bit is driven on its impact stroke by a compressible fluid that is compressed successively by a pressure-fluid, preferably hydraulically, drive piston serving as, or driving, a hammer for the impact chisel or other tool on working strokes driven by expansion of the compressible fluid. It is an object of this invention to make provision for a variable impacting rate for such a percussive tool either to cope with desired working conditions or to compensate for the effects of temperature on the compressible fluid.
Normally, the control valve gear is made responsive to relatively low and high pressures, herein referred to as "control pressures", of the compressible fluid in order to control the application and release, respect-ively, of piston operating pressure-fluid.
According to the present invention, there is provided, in a percus-sive *ool having a reciprocable piston driven on an impacting stroke of *he tool by compressible fluid and, on a return stroke to compress that medium, by pressure fluid supplied via control valve gear responsive at least to high predetermined pressures of the compressible fluid, apparatus comprising means for varying the operation of the control valve gear relative to actual attain-ment of such predetermined pressures and presetting means operative to establish a nominal tool operating rate and variable to change the actual tool operating rate.
Our Canadian Patent 937~835 (Dobson Park Industries limited, issued December 4, 1973) discloses a mining head or other impact tool with control valve gear, and in which an impact chisel or otller tool bit is driven on its impact stroke by a compressible fluid that is compressed successively by a pressure-fluid, preferably hydraulically, drive piston serving as, or driving, a hammer for the impact chisel or other tool on working strokes driven by expansion of the compressible fluid. It is an object of this invention to make provision for a variable impacting rate for such a percussive tool either to cope with desired working conditions or to compensate for the effects of temperature on the compressible fluid.
Normally, the control valve gear is made responsive to relatively low and high pressures, herein referred to as "control pressures", of the compressible fluid in order to control the application and release, respect-ively, of piston operating pressure-fluid.
According to the present invention, there is provided, in a percus-sive *ool having a reciprocable piston driven on an impacting stroke of *he tool by compressible fluid and, on a return stroke to compress that medium, by pressure fluid supplied via control valve gear responsive at least to high predetermined pressures of the compressible fluid, apparatus comprising means for varying the operation of the control valve gear relative to actual attain-ment of such predetermined pressures and presetting means operative to establish a nominal tool operating rate and variable to change the actual tool operating rate.
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1(~5~;66'7 This could be implemented using electrically triggered control valve gear with electro-mechanical or electronic determination of a desired time lag between achievement of either or both of the predetermined high and low control pressures in the compressible fluid. However, i-t is preferred, particularly to meet intrinsic safety standards required for mining equipment, to have the control valve gear directly responsive -to compressible fluid pressures.
This may be achieved by providing a single unit in a compressible fluid line and incorporating both a variable flow restrictor and a reservoir or accumulator. If desired such a unit could, of course, be mounted directly to a compressible fluid port at the tool, or be mounted -to or incorporated in the con-trol valve gear preferably at a pressure responsive pilot valve means thereof. If it is desired to control the impacting rate with reference only -to one piston stroke, and thus with reference to one only of the predetermined pressures, the restrictor/
reservoir unit may further include a one-way valve capable of by passing the restrictor. ~he direction of permitted flow through -the one-way valve will determine which of the control pressure levels is modified in its application to the pressure responsive control valve means~ ~ormally, it is preferred to operate relative to initiating the return stroke and the low con-trol pressure level in order not to reduce impacting power, and make each working cycle of subs-tantially constant length irrespective of the actual rate of impacting. ~
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''' Preferably, in a combined restrictor, one-way valve and reservoir or accumula-tor device, the one-way valve selectively obstruc-ts a first branch passageway from a compressible fluid supply passage -to a reservoir or accumulator feed passage, and the restrictor is operative on flow via a second branch passageway from -the compressible fluid passage to -the reservoir or accumulator feed passage via a clearance past or a port through the one-way valve at least when the latter is in its flow obstructing condition. This allows a particularly convenient construction where the compressible fluid flow passageway and reservoir or accumula-tor feed passageway comprise parallel bores in a valve body, when the two branch passageways may be formed as transverse bores intersecting both of the first mentioned parallel bores, preferably at different spacings therealong from the positio~ of a bore of the reservoir or accumulator.
The nearest branch passageway to reservoir is preferably counterbored to house and provide a sealing sea-t for a spring biassed one way valve and being oversize relative thereto at leas-t at its intersection with the reservoir or accumulator feed passagee to allow communication via the restrictorO Clearly, the other transverse bore could house the restrictor to be operative relative to that branch passageway at its intersection with the reservoir or accumulator feed passage. Alternatively~ the restrictor could be housed in a continua-tion of the reservoir or ~
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-accumulator feed passage and be operative relative to an orifice or step at or near the junction of that passageway. A typical restrictor would comprise a tapered member adjustable relative to a stepped seat to define a variable annular flow cross-sectionA
In an alternative arrangement a variable flow restrictor may be mounted to act relative to a bore directly communicating with the compressible medium chamber of a percussive tool of the type r~ferred to, and a communicating passageway, usually a bore, to the main valve gear, usually a pilot operating valve thereof. It is particularly convenient for that communicating passageway to have at least a part thereof of su~ficient cross-section to serve as a reservoir. A one-way valve is conveniently mounted in a similar bore directly communicating with the compressible medium chamber with an interconnecting bore to the restrictor bore. Both ends of such an interconnecting bore will usually have a said communicating passageway to the main valve gear, specifically a pilot valve. Conveniently, restrictor and one-way valves have similar bodies and are interchangeably mountable, say after the fashion of spark plugs f`or internal combustion engines. Such embodiments of the invention have particular advan-tage by way of being integrally embodyable within a tool body or rear part thereof`.
Embodiments of the invention will now be described, ,. .
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i 7 by way of example, witll referellce to the accompanying drawings, in which:-Figure l is a diagrammatic repr0sentation of valve gear xlnd pressure-fluid circwitry associated with an impact type mineral winning head shown in simplified section;
Figure 2 is a section through a preerred unilary compressible fluid pressure controlled device; and Figure 3 is a diagrammatic generally sectional view of an arrange-ment embodying the invention and integral with the rear tool body.
The mining head shown in Figure 1 is preferably of modular construc-tion. In general terms, the head comprises a body 1~ housing, in a cylinderthereof, a drive piston 14 that is retractable from left to right of the drawing by hydraulic pressure-fluid from a main valve 11 via annular passage 15 in order to compress a gaseous pressure-fluid in an end chamber 23. At its forward end, the drive piston 14 has a hammer 28 for impact engagement with a chisel tool bit 26 retained but slidable in the body 10 and shown only partly in the drawing. The basic operation cycle requires piston drive pressure fluid alternately to be applied to drive the piston to compress the pressure-fluid in the chamber 14 until a predetermined high pressure is achieved and to be released via the passage 15 so that the piston will be driven to impact the tool by the energy stored in the compressed pressure-fluid, reversal of piston driving pressure-fluid connections being made for a further compression stroke on achievement of a predetermined low pres-sure in the gaseous medium chamber 14.
The tool body and associated valve gear is preferably of modular construction where a central body portion accommodates the drive piston proper and provides the fluid access passage 14 from a main valve 11 that is integral therewith or secured thereto. A gas chamber body part securable :.
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to the central part to complete the overall configuration of l~igure 1.
Pilot valve ~mcl accumulator units will then be securable to the main valve bocly forwardly and rearwardly thereof, respectively but preferably inter-changeably. Preferred accumulators operate directly on the main flow ancl return for the piston drive pressure-fluid.
A diagra~matic representation of the control valve gear and pres-sure-fluid circuitry associated with the mineral winning head for operating purposes is also given in Figure 1. It will be seen that individual high and low pressure pilot valve parts are shown separately at 32A and 32B
with both connected by gas lines 51 to the gas chamber 231 to respond7 differentially, to high and low pressures of the gas so as to constitute high and :::: ~ . - . , -:: ~ ' : ~ : -- : .::
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low pressure gas opera-ted switches of predeter~i~ed or preset characteristics say according to variable sprin~
ratings or settings. A hydraulic pilot start line 52 is shown connected to one port of the low pressure pilot valve ~2B which has other ports connected to the cylinder of one of the pilo-t pistons of the main valve ll via line 53 and to a hydraulic drain pipe 56, respectively.
Drain connections 60, 61 are also shown -together with intercoupling bored paths 62.
Hydraulic flow and return mains are shown at 30A
and 30B, respectively, connected to corresponding ports of -the main valve ll and, via branch pipes, to ports of the high pressure pilot valve 32A which has a further port connected via a spring loaded shuttle valve device 54 to the cylinder of the other pilot piston of the main valve via line 55. ~he device 54 also has a port connected i `
to a pilot reset line 57. s`
In describing operation, it is first assumed that the piston ]4 is in its forward position and there is no ~.
pressure-fluid supplied to the head. On applying hydraulic fluid pressure 9 the main valve pilo-t pistons will set to positions corresponding to the states shown in Figure l, if they are not already in such positions, due to pressurisation of the pilo-t reset line 57. Hydraulic pressure in the pilot start line 52 will act via the low pressure pilot valve part 32B and the relevant main valve pilot piston to cause the main valve to operate ,: :
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~5 ~ ~ 7 as described above to admit hydraulic fluid to retract the piston 14 and compress the gas in the chamber 23.
Rislng gas pressure will act first to cancel the low pressure pilot valve par-t 32B and lock the piston 14, and then to op0rate the o-ther pilot valve part 33~ to switch the main valve position to allow exhaustion of hydraulic fluid as -the piston 14 is driven on its impact stroke by the compressed gas. Subsequent cycles will be self-starting for as long as hydraulic pressure is applied over lines 30A and 52.
If desired, a controlled pressure non-return air line branch can be connected to the front end of the piston 14 to impose a higher than atmospheric pressure and give both an air pump action and dirt ingress pro-tection.
Connections 6~ and 64 are shown directly to accumulators for the main flow and return lines immediately adjacent to the maln valve llo ~ he compressible fluid pressure lines 51 are shown as incorporating a uni-tary or integral control devlce or means 65 incorporating a reservoir 66 and a flow restriction device 67 which is preferably bridged by a one-way valve 68 to ensure -that it is only the initiation of -the return or compression stroke of the piston 14 that is modified.
If the one-way valve was reversed, it would operate to delay initiation of the drive stroke, but that might alter the impact power characteristics. If the one-way valve is omitted, both stokes would be delayed.
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Figure 2 shows a preferred construction of the de~ice 65 where a body 70 has two parallel bores 71 æLd 72 both intersected by cross bores 73 and 7~ he bore 71 serves as a compressible fluid supply passage from the gas chamber 23, and the bore 72 serves as a supply passage to the reservoir 66 formed as a much larger bore 75 from which a fluid pressure line are taken to the pilot valve gear. Seals are shown at the ends of these bores to facilitate connections thereto.
The transverse bore 73 is disposed between the transverse bore 74 and the reserYoir 66, and is counterbored to accommodate a one-way valve device 68 having a spring loaded actuator 76 equipped with a seal 77 for closing the bore 73 against fluid flow from the supply bore 71 for low excess pressures therein compared with the pressure in the reservoir 66. ~he bore 72 is also shown as being counterbored to house a pressure-fluid flow restrictor 67 with a threaded adJuster 78 for varying the extension of a tapered end 79 through an annular step 80 and thus the annular flow section for pressure-~luid between -the compressible fluid supply bore 71 and the reservoir supply bore 72 via the transverse bore 74. ~he counterboring of the transverse bore 7~ is such as to provide a clearance chamber 81 about the actuator of the one-way valve 68, and so provide clear passage for fluid between the restrictor and the reservoir.
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''' ',' ''' . ~, `' , , ~', , ' , ~n~ 7 The transverse bore 74 is also shown as being counterbored and plugged at 82, though it will be appreciated that the restrictor could be mounted in such a counterbore and be operative relative to an orifice or stepped seat of that transverse bore 74.
In operation, the illustrated device will allow unrestricted built-up of pressure through the device via the one-way valve until the pressure on the reservoir side rises to within a prede-termined amount of the pressure in the feed bore 71 related to the bias of the one-way valve. ~his will normally be at or above the high pressure control valve operation level at which the piston drive stroke is initiated by switching from pressure fluid supply to pressure fluid return for the passage 15.
~he drive stroke will produce a rapid drop of pressure in the gas chamber 23 and thus the feed bore 71, and release of -the previously built-up pressure on the reservoir side of the one-way valve will be necessaril~
via the restrictor, and will take a substantially constant time to drop to the low pressure control level at which a compression or return s-troke of -the piston 1~ is initiated.
It will be appreciated -that the unit illustrated in Flgure 2 could be attached -to or even formed integral with the gas chamber or the pilot control valve gear.
Figure 3 shows a control arrangement wherein a rear tool body part 87 defining the compressible medium chamber 23 is drilled at 88 and 89 to mount restrictor , .
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and one-way valves 67 and 68 having similar external body configurations. A communicating bore 90 extends between the bores 88 and 89 and the valve~; control compressible medium access to that bore 90 from the chamber 23. Interconnecting bores 91 and 92 to a .
pilot valve of the main valve gear are shown extending through the body part 87 generally at right angles to -the interconnecting bore 90 and connected at opposite ends thereof by further bores 93 and 94, respectively, that are preferably inclined into the plane of the drawing to aid flow. ~he interconnecting bores 91 and 92 are larger than the bores 90, 93 and 94 at least over a substantial part of their length and so are capable of serving as the above-mentioned reservoir or accumulator 66.
The bores 88 and 89 are clearly equivalent to the branch passageways 7~ and 74 of Figure 2 and there will be a clearance about the one-way valve so that both enlarged comrnunicating passages 91 and 92 serve in providing said reservoir capability~
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, .
:; ,.,. ~ :
' ;~ '" , ' ' ' ' : ' :' .
1(~5~;66'7 This could be implemented using electrically triggered control valve gear with electro-mechanical or electronic determination of a desired time lag between achievement of either or both of the predetermined high and low control pressures in the compressible fluid. However, i-t is preferred, particularly to meet intrinsic safety standards required for mining equipment, to have the control valve gear directly responsive -to compressible fluid pressures.
This may be achieved by providing a single unit in a compressible fluid line and incorporating both a variable flow restrictor and a reservoir or accumulator. If desired such a unit could, of course, be mounted directly to a compressible fluid port at the tool, or be mounted -to or incorporated in the con-trol valve gear preferably at a pressure responsive pilot valve means thereof. If it is desired to control the impacting rate with reference only -to one piston stroke, and thus with reference to one only of the predetermined pressures, the restrictor/
reservoir unit may further include a one-way valve capable of by passing the restrictor. ~he direction of permitted flow through -the one-way valve will determine which of the control pressure levels is modified in its application to the pressure responsive control valve means~ ~ormally, it is preferred to operate relative to initiating the return stroke and the low con-trol pressure level in order not to reduce impacting power, and make each working cycle of subs-tantially constant length irrespective of the actual rate of impacting. ~
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.
.
''' Preferably, in a combined restrictor, one-way valve and reservoir or accumula-tor device, the one-way valve selectively obstruc-ts a first branch passageway from a compressible fluid supply passage -to a reservoir or accumulator feed passage, and the restrictor is operative on flow via a second branch passageway from -the compressible fluid passage to -the reservoir or accumulator feed passage via a clearance past or a port through the one-way valve at least when the latter is in its flow obstructing condition. This allows a particularly convenient construction where the compressible fluid flow passageway and reservoir or accumula-tor feed passageway comprise parallel bores in a valve body, when the two branch passageways may be formed as transverse bores intersecting both of the first mentioned parallel bores, preferably at different spacings therealong from the positio~ of a bore of the reservoir or accumulator.
The nearest branch passageway to reservoir is preferably counterbored to house and provide a sealing sea-t for a spring biassed one way valve and being oversize relative thereto at leas-t at its intersection with the reservoir or accumulator feed passagee to allow communication via the restrictorO Clearly, the other transverse bore could house the restrictor to be operative relative to that branch passageway at its intersection with the reservoir or accumulator feed passage. Alternatively~ the restrictor could be housed in a continua-tion of the reservoir or ~
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-accumulator feed passage and be operative relative to an orifice or step at or near the junction of that passageway. A typical restrictor would comprise a tapered member adjustable relative to a stepped seat to define a variable annular flow cross-sectionA
In an alternative arrangement a variable flow restrictor may be mounted to act relative to a bore directly communicating with the compressible medium chamber of a percussive tool of the type r~ferred to, and a communicating passageway, usually a bore, to the main valve gear, usually a pilot operating valve thereof. It is particularly convenient for that communicating passageway to have at least a part thereof of su~ficient cross-section to serve as a reservoir. A one-way valve is conveniently mounted in a similar bore directly communicating with the compressible medium chamber with an interconnecting bore to the restrictor bore. Both ends of such an interconnecting bore will usually have a said communicating passageway to the main valve gear, specifically a pilot valve. Conveniently, restrictor and one-way valves have similar bodies and are interchangeably mountable, say after the fashion of spark plugs f`or internal combustion engines. Such embodiments of the invention have particular advan-tage by way of being integrally embodyable within a tool body or rear part thereof`.
Embodiments of the invention will now be described, ,. .
~: . . .
: . : .
i 7 by way of example, witll referellce to the accompanying drawings, in which:-Figure l is a diagrammatic repr0sentation of valve gear xlnd pressure-fluid circwitry associated with an impact type mineral winning head shown in simplified section;
Figure 2 is a section through a preerred unilary compressible fluid pressure controlled device; and Figure 3 is a diagrammatic generally sectional view of an arrange-ment embodying the invention and integral with the rear tool body.
The mining head shown in Figure 1 is preferably of modular construc-tion. In general terms, the head comprises a body 1~ housing, in a cylinderthereof, a drive piston 14 that is retractable from left to right of the drawing by hydraulic pressure-fluid from a main valve 11 via annular passage 15 in order to compress a gaseous pressure-fluid in an end chamber 23. At its forward end, the drive piston 14 has a hammer 28 for impact engagement with a chisel tool bit 26 retained but slidable in the body 10 and shown only partly in the drawing. The basic operation cycle requires piston drive pressure fluid alternately to be applied to drive the piston to compress the pressure-fluid in the chamber 14 until a predetermined high pressure is achieved and to be released via the passage 15 so that the piston will be driven to impact the tool by the energy stored in the compressed pressure-fluid, reversal of piston driving pressure-fluid connections being made for a further compression stroke on achievement of a predetermined low pres-sure in the gaseous medium chamber 14.
The tool body and associated valve gear is preferably of modular construction where a central body portion accommodates the drive piston proper and provides the fluid access passage 14 from a main valve 11 that is integral therewith or secured thereto. A gas chamber body part securable :.
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to the central part to complete the overall configuration of l~igure 1.
Pilot valve ~mcl accumulator units will then be securable to the main valve bocly forwardly and rearwardly thereof, respectively but preferably inter-changeably. Preferred accumulators operate directly on the main flow ancl return for the piston drive pressure-fluid.
A diagra~matic representation of the control valve gear and pres-sure-fluid circuitry associated with the mineral winning head for operating purposes is also given in Figure 1. It will be seen that individual high and low pressure pilot valve parts are shown separately at 32A and 32B
with both connected by gas lines 51 to the gas chamber 231 to respond7 differentially, to high and low pressures of the gas so as to constitute high and :::: ~ . - . , -:: ~ ' : ~ : -- : .::
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low pressure gas opera-ted switches of predeter~i~ed or preset characteristics say according to variable sprin~
ratings or settings. A hydraulic pilot start line 52 is shown connected to one port of the low pressure pilot valve ~2B which has other ports connected to the cylinder of one of the pilo-t pistons of the main valve ll via line 53 and to a hydraulic drain pipe 56, respectively.
Drain connections 60, 61 are also shown -together with intercoupling bored paths 62.
Hydraulic flow and return mains are shown at 30A
and 30B, respectively, connected to corresponding ports of -the main valve ll and, via branch pipes, to ports of the high pressure pilot valve 32A which has a further port connected via a spring loaded shuttle valve device 54 to the cylinder of the other pilot piston of the main valve via line 55. ~he device 54 also has a port connected i `
to a pilot reset line 57. s`
In describing operation, it is first assumed that the piston ]4 is in its forward position and there is no ~.
pressure-fluid supplied to the head. On applying hydraulic fluid pressure 9 the main valve pilo-t pistons will set to positions corresponding to the states shown in Figure l, if they are not already in such positions, due to pressurisation of the pilo-t reset line 57. Hydraulic pressure in the pilot start line 52 will act via the low pressure pilot valve part 32B and the relevant main valve pilot piston to cause the main valve to operate ,: :
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~5 ~ ~ 7 as described above to admit hydraulic fluid to retract the piston 14 and compress the gas in the chamber 23.
Rislng gas pressure will act first to cancel the low pressure pilot valve par-t 32B and lock the piston 14, and then to op0rate the o-ther pilot valve part 33~ to switch the main valve position to allow exhaustion of hydraulic fluid as -the piston 14 is driven on its impact stroke by the compressed gas. Subsequent cycles will be self-starting for as long as hydraulic pressure is applied over lines 30A and 52.
If desired, a controlled pressure non-return air line branch can be connected to the front end of the piston 14 to impose a higher than atmospheric pressure and give both an air pump action and dirt ingress pro-tection.
Connections 6~ and 64 are shown directly to accumulators for the main flow and return lines immediately adjacent to the maln valve llo ~ he compressible fluid pressure lines 51 are shown as incorporating a uni-tary or integral control devlce or means 65 incorporating a reservoir 66 and a flow restriction device 67 which is preferably bridged by a one-way valve 68 to ensure -that it is only the initiation of -the return or compression stroke of the piston 14 that is modified.
If the one-way valve was reversed, it would operate to delay initiation of the drive stroke, but that might alter the impact power characteristics. If the one-way valve is omitted, both stokes would be delayed.
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Figure 2 shows a preferred construction of the de~ice 65 where a body 70 has two parallel bores 71 æLd 72 both intersected by cross bores 73 and 7~ he bore 71 serves as a compressible fluid supply passage from the gas chamber 23, and the bore 72 serves as a supply passage to the reservoir 66 formed as a much larger bore 75 from which a fluid pressure line are taken to the pilot valve gear. Seals are shown at the ends of these bores to facilitate connections thereto.
The transverse bore 73 is disposed between the transverse bore 74 and the reserYoir 66, and is counterbored to accommodate a one-way valve device 68 having a spring loaded actuator 76 equipped with a seal 77 for closing the bore 73 against fluid flow from the supply bore 71 for low excess pressures therein compared with the pressure in the reservoir 66. ~he bore 72 is also shown as being counterbored to house a pressure-fluid flow restrictor 67 with a threaded adJuster 78 for varying the extension of a tapered end 79 through an annular step 80 and thus the annular flow section for pressure-~luid between -the compressible fluid supply bore 71 and the reservoir supply bore 72 via the transverse bore 74. ~he counterboring of the transverse bore 7~ is such as to provide a clearance chamber 81 about the actuator of the one-way valve 68, and so provide clear passage for fluid between the restrictor and the reservoir.
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''' ',' ''' . ~, `' , , ~', , ' , ~n~ 7 The transverse bore 74 is also shown as being counterbored and plugged at 82, though it will be appreciated that the restrictor could be mounted in such a counterbore and be operative relative to an orifice or stepped seat of that transverse bore 74.
In operation, the illustrated device will allow unrestricted built-up of pressure through the device via the one-way valve until the pressure on the reservoir side rises to within a prede-termined amount of the pressure in the feed bore 71 related to the bias of the one-way valve. ~his will normally be at or above the high pressure control valve operation level at which the piston drive stroke is initiated by switching from pressure fluid supply to pressure fluid return for the passage 15.
~he drive stroke will produce a rapid drop of pressure in the gas chamber 23 and thus the feed bore 71, and release of -the previously built-up pressure on the reservoir side of the one-way valve will be necessaril~
via the restrictor, and will take a substantially constant time to drop to the low pressure control level at which a compression or return s-troke of -the piston 1~ is initiated.
It will be appreciated -that the unit illustrated in Flgure 2 could be attached -to or even formed integral with the gas chamber or the pilot control valve gear.
Figure 3 shows a control arrangement wherein a rear tool body part 87 defining the compressible medium chamber 23 is drilled at 88 and 89 to mount restrictor , .
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and one-way valves 67 and 68 having similar external body configurations. A communicating bore 90 extends between the bores 88 and 89 and the valve~; control compressible medium access to that bore 90 from the chamber 23. Interconnecting bores 91 and 92 to a .
pilot valve of the main valve gear are shown extending through the body part 87 generally at right angles to -the interconnecting bore 90 and connected at opposite ends thereof by further bores 93 and 94, respectively, that are preferably inclined into the plane of the drawing to aid flow. ~he interconnecting bores 91 and 92 are larger than the bores 90, 93 and 94 at least over a substantial part of their length and so are capable of serving as the above-mentioned reservoir or accumulator 66.
The bores 88 and 89 are clearly equivalent to the branch passageways 7~ and 74 of Figure 2 and there will be a clearance about the one-way valve so that both enlarged comrnunicating passages 91 and 92 serve in providing said reservoir capability~
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Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a percussive tool having a reciprocable piston driven on an impacting stroke of the tool by compressible fluid and, on a return stroke to compress that medium, by pressure-fluid supplied via control valve gear responsive at least to high predetermined pressures of the compressible fluid, apparatus comprising means for varying the operation of the control valve gear relative to actual attainment of such predetermined pressures and presetting means operative to establish a nominal tool operating rate and variable to change the actual tool operating rate.
2. Apparatus according to claim 1, wherein means for varying includes a variable flow restrictor in a main valve gear control line for compres-sible fluid, and fluid feed means communicating therewith.
3. Apparatus according to claim 2, wherein the means for varying is operative relative to one direction of piston travel and further includes a one-way valve connected to by-pass said restrictor.
4. Apparatus according to claim 2 or claim 3, wherein the means for varying comprising a unitary body bored and fitted with a valve or valves.
5. Apparatus according to claim 3, wherein a unitary body of the means for varying includes a bored supply passage for compressible fluid, a said one-way valve fitted to selectively obstruct a first branch passageway from said supply passage to a feed passage, and a said restrictor fitted to control flow via a second branch passageway from said supply passage to said feed passage.
6. Apparatus according to claim 5, wherein the feed passage includes a passage from one side to the other of the one-way valve.
7. Apparatus according to claim 5 wherein said supply and feed passages are parallel bores in the unitary body and the first and second branch passageways are transverse bores intersecting said parallel bores.
8. Apparatus according to claim 7, wherein feed means includes a relatively large bore in the unitary body communicating with the feed passage.
9. Apparatus according to claim 8, wherein the restrictor is housed in a continuation of said feed passage and is operative relative to an orifice or step adjacent the junction with the second branch passageway.
10. Apparatus according to claim 2 provided relative to bores in a compressible medium housing tool body part.
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11. Apparatus according to claim 10, wherein the tool body part has a first bore from its compressible medium chamber and a communicating bored passagway to the main valve gear, said restrictor being housed in an extension of said first bore.
12. Apparatus according to claim 11, wherein said tool body part has a second bore from its compressible medium chamber and an interconnecting bore between the first and second bores, said one-way valve being housed in an extension of said second bore.
13. Apparatus according to claim 12, wherein the restrictor and one-way valve have externally similar bodies for interchangeable fitment to the first and second bore extensions.
14. Apparatus according to claim 12, with two communicating bored passageways from the interconnecting bore to the main valve gear, with the first and second bores between their junctions.
15. Apparatus according to claim 14, wherein each communicating bored passageway is of relatively large section over at least part of its length to serve in providing said reservoir or accumulator means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,043A CA1056667A (en) | 1976-10-08 | 1976-10-08 | Percussive tool |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,043A CA1056667A (en) | 1976-10-08 | 1976-10-08 | Percussive tool |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056667A true CA1056667A (en) | 1979-06-19 |
Family
ID=4107026
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA263,043A Expired CA1056667A (en) | 1976-10-08 | 1976-10-08 | Percussive tool |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1056667A (en) |
-
1976
- 1976-10-08 CA CA263,043A patent/CA1056667A/en not_active Expired
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