CA1064339A

CA1064339A - Pneumatically operated oscillator

Info

Publication number: CA1064339A
Application number: CA250,884A
Authority: CA
Inventors: Nils A. Aagren; Josef Lewkowicz
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1975-04-24
Filing date: 1976-04-23
Publication date: 1979-10-16
Also published as: ZA762427B; FR2308781B1; FI60916C; FI60916B; DE2617670A1; FI761110A; FR2308781A1; DE2617670C3; DE2617670B2; SE395850B

Abstract

T I T L E

PNEUMATICALLY OPERATED OSCILLATOR

ABSTRACT OF THE DISCLOSURE

A pneumatically operated oscillator is used as a linear motor to operate a single or a plurality of linear positive displacement pumps having plunges. The oscillator has a single acting pneumatic piston that works against a spring to force the plunges in their pressure strokes. The spring effects the return stroke which is damped by a hydraulic circuit that has an adjustable restriction.
The work stroke is undamped and fast compared with the spring actuated return stroke. Variations in the pressure of the operating air affects the work strokes, but since the work strokes are many times faster than the return strokes, variations in the air pressure have little effect on the frequency .

Description

SPECIFICATION
-This invention relates to an oscillator. In the prior art, a piston pump for delivering a lubricant to a rock drill has been directly mechanically coupled to an oscillating compressed air operat-~ ed piston motor that is operated by compressed air from the supplyconduit of the rock drill. The oscillating motor therefore startsautomatically when the rock drill is started. The frequency of the oscillating motor is controlled in this prior art lubricating device by a variable restriction in the conduit for supplying operating air to the oscillating motor. Since the pressure in the supply con-duit of a rock drill mounted on a rock drilling rig usually varies `, substantially, the drive air pressure of the oscillating motor will . also vary substantially thereby varying the frequency of the oscilla-~`~ ting motor.
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~.Oti433g This invention may be generally defined as a lubricant furnishing system for a plurality of compressed air operated devices that are indepen-dently supplied with compressed air through air supply lines controlled by air supply valves, comprising: a lubricant supply line coupled to each air operated device; positive displacement pumps for supplying predetermined flows of lubricant to the lubricant supply lines; a common actuating means coupled to and actuating said pumps; and a compressed air operated oscil-lator having an adjustable frequency, coupled to said actuating means for controlling the frequency of said actuating means, the oscillator comprising a reciprocating piston and an hydraulic damping circuit for controlling the speed of the reciprocating piston.
Figure 1 is a diagr } a~ic representation of a system for lubrica-ting various air consumers, for instance the air consumers of a rock drilling rig.
Figure 2 is a section taken along the line 2-2 in Figure 1 through a positive displacement lubricant-pump and its actuating motor.
Figure 3 shows enlarged some details of Figure 2.
; Figure 4 is a section through one of a plurality of valves that are schematically shown in Figure 1.
Figure 5 shows an alternative design of an oscillating motor that is built together with a positive displacement pump.
In the system shown in Figure 1, various air consumers 11-16 are shown in symbols. They are supplied with compressed air through supply con-- duits 17-22 that are controlled by supply valves 23-28. The air consumers 11-16 may symbolize the various air consumers on a rock drilling rig. The ~, motors for moving the drilling rig can be symbolized by 11, the feed motor for a rock drill by 12, the impact motor of the rock drill by 13, the rotation motor of the rock drill by 14, an air motor for driving a generator unit by 15 and an air motor for driYing an hydraulic pump by 16. FiYe piston pumps ~, 30 29~33 for lubricating oil are driven in synchronism with one another by ~ means of a common actuator device 34 and they deliver oil to oil conduits -' 35-39. Each oil conduit 36-39 leads to a respective one of the air supply `'~ )Q~

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conduits 19-22 whereas the oil conduit 35 is branched into branches 40,41 that lead to the air supply conduits 17 and 18 respectively. In each of the conduits 36-39 and 40 and 41 there is a valve 42-47 that senses the pressure in the respective air supply conduit 17-22 and opens to permit passage of oil to the air supply conduit only ... .

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when the latter is pressurized. A one-way check valve 48-52 is con-nected to ea-ch oil conduit 35-39 and these check valves are connect-ed to a common, conventional, atjustable, ~pring loaded pressure relief valve 53. ~hus, the check valves 48-52 operate as back pressure controlled pressure relief valves, the back pressure bein8 defined by the common pressure relief valve 53.
One of the identicsl valves 42-47, the valve 47, is shown in detail in Fig. 4. It has an elastic membrane 54, for instance a rubber membrane, that is forced against a seat 56 by means of a spring load-ed piston 55. The circular edge of the membrane 54 is sealingly clamp-et againct the valve body by means of a sleeve 61. The spring has been given the reference numeral 57. The oil conduit 39 ends with a passage 58 into the seat 56. The passage 58 ends with such a ~mall area in the seat 56 that the oil pressure in the conduit 39 (this lS oil pressure being definet by the pre~sure relief valve 53 and being ^~ substantially higher than the airline pressure) is not able to over-come the spring 57. Thus, the oil pressure cannot lift the membrane 54 off the seat 56. Around the ~eat 56, there is formed an annular ~' chamber 59 that is in connection with the air supply conduit 22 by-~ 20 means ~f a passage 60. The membrane 54 has 80 lar~e an annular sur-face towardc this chamber 60 that the air pre~sure lifts the membrane off the seat 56 ~hen the supply conduit 22 is pressurized so that oil can freely flow from the oil conduit 39 to the air supply conduit 22.
The valve 47 is again closed when the supply valve 24 is closed and the ¢onduit 22 is vented through the air motor 16. The membrane ~hould be off its seat at an air pressure of about 1 bar above atmos-pheric pressure in order to provide proper lubrication of a free-run~
i, nDng air motor. It is an advantage as to the reliabi~ity that the shut-off valve 47 operateq in response to the presCure and not in response to the f 1GW.
In Fig. 2, the pump 31 and its actuating davice 34 are shown in longitudinal section. The pump has a housing 92 forming a cylinder 63 and a plunge 64. It is supplied with oil through a feed conduit 65 and it forces oil out through the conduit 37 via a check valve 66.
The housing of the actuator 34 is divided by a partition 67 into a cylindrical air portion 68 and a cylindrical hydraulic portion 69.

The piston rod 70 has a piston head 71 in the air portaon and a piston head 72 in the hydraulic portion. The piston head 72 has through pasjages 73 provided with a common check valve in the form of a plate 74. The two cylinder chambers 75, 76 formed in the hydraulic cylinder S are in communication via a conduit that is provided with a variable restriction 62 and forms a damping circuit.
Th~ piston head 71 in the air portion separates a cylinder chamber 77 to the left thereof in figure 2 from a cylinder chamber 78 to:the right thereof, and the cylinder cha~ber 77 iq supplied with compressed air through a supply conduit 79. As is best shown in Fig.
3, the piston head 71 has three axial bores through which three rods - 80 slidably extend. The rods 80 unite two end plates 81, 82. The rods have axial recesses 83. The piston head 71 has three passages 84 that lead to a passage 85 that extends out through the piston rod ~ -70 to the atmosphere.
The device that is formed by the end plates 81, 82 and the ~
rods 80 are limitedly axially slidable relative to the piston head -71 as a rigid unit. It forms a ~alve that makes the piston head 71 and the piston rod 70 reciprocate. The piston head 71 is biased to the left in Pigs. 2 and 3 by means of a spring 86. Assuming that ~- the pi3ton head 71, and with it the piston rod 70 and the piston `~ head 72, has been moved to its left position as indicated in Figs.

2 and 3 by the action of the spring 86, the end position is defined ,, by a rubber element 87 against which the end plate 81 rests. Then , 25 sealing rings 88 around the rods 80 block the passages 83 between J the cylinder chambers 77, 78 at the same time as the cylinder cham-~' ber 78 is vented through the passages 84, 85. Thus , the piston 71 moves to the right in the figures and this movement is transmitted to the plunges 64 by means of a lever 89. This movement of the piston 71 to the right in the figure is not damped since the check valve ~, 74 in the hydraulic portion i8 open. Then, when the other end plate 82 abu~8 against an annular rubber element 90, sealing elements 91 block the passages 84 at the same time as the passages 83 is opened so that the cylinder cha~ber 78 becomes pressurized. The cylinder 35 chamber 77 is constantly pressurized. Then the spring 86 returns the piston head 71 to its left end p sition shown in the figures and an-,. .

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- - . . . . - . -~0~4339 other work stroke starts in the way described. During the return move-~ent of the piston 71 its velocity is controlled by the hydraulic damp~
ing circuit that includes the atjustable restriction 62. The plunges 64 join the piston 71 in the return moveme~t because of the pressure in the oil supply conduit 65 acting on anaular shoulders 92.
Thus, the frequency of the pumps is defined by the easily adjustable restriction 62 of the hydraulic damping circuit. Since this restriction controls the velocity of the return stroke whereas the work stroke is effected by a spring 86, the time for a return movement will be independent of variations in the pressure of the drive air. The work stroke is undamped by the hydraulic circuit 62 and its velocity will depend on the drive pressure, but since he work stroke is normally several times as fast as the return stroke that is controLt ed by the damping circuit 62, variations in the drive pressure will only slightly affect the frequency of the actuator 34. Thus, the actuator 34 is an adjustable oscillator, the frequency of which ~9 ; only ne~ligibly influenced by the variations in the pressure of the drive air. It has been found that a frequency higher than about 10 pump strokes per minute should be used. At lower frequencies, the oil consumption must be increased in order to provide adequata lubric-ation. Preferably, the pumps are dimensioned so that the frequency can be held above 0,5 H~ when used to lubricate rock drills.
In the example rock drilling rig, the actuator 34 is advantage-ously connected to start its reciprocation as qoon as the main supply valve (not illustrated) of the rig is opened. This means that the five pump~ 29-33 reciprocate in synchronism and continously deliver oil flows to the respective conduits 35-39. These metered flows are defin-ed by the frequcncy of the oscillator and the lubricant flows out through the pressure relief valves 48-52 and through the single pressure relief valve 53 to tank if the valves 42-47 are not open.
The oil pressure defined by the pressure relief valve 53 should be ~ hiRher than the pressure of the drive air and preferably it should -j be several bars higher.
The motor 11 for moving the rig and the feed motor 12 for feed-~,~ 35 ing the rock drill along its guide can be connected to the same pump 29 without disadvantage since these motors will never bo used simul-:, -.

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~ 64339 taneously. Therefore, the pump 29 can be regarted as associated either with the motor 11 for moving the rig or with the feed motor 12, but it can never be associated with both motors simultaneously. The various pumps can have different capacity by having different cylinder diameters and different length of their plunges.
The auto-controlled oscillating actuator 34 need ~ot directly mechanically drive the pumps 29-33 as s~own but the pumps can be triven by a simple air-powered membrane actuator or air-powered cylinder that is controlled by a valve, that is controlled by the oscillator 34 which shifts the position of the valve. A combined syste~ can also be advantageous in which the actuator 34 mechanically drives for instance five pumps as shown and described but also shifts position of a valve that controls one or more air cylinders that drive a group of pumps each.
In Fig. S a lubricator unit is ~hown that comprises an oscillator 34 whose piston rod 70 serves as a plunge 64 in a posi- -tive displacement pump as w~ll. In this figure, some details that correspond to details i~ the preceding figures have been given the same reference numerals as in tho~ figures. A lubricator unit accord-20 ing to Fig. 5 is suitable for a single compressed air operated tcvice, ; e.g. a handheld pavement breaker 100. The breaker is supplied with ~ compressed air via a supply passage 101 and a supply valve 102. The -; oil i8 delivered from the positive displacement pump via a conduit ~ 103 to the air inlet of the breaker as illustrated. Alter~atively, `d~ 25 the oil conduit 103 can lead directly to the in~erior of the breaker.
In this oscillator, the cylinderri~chamber 78 i8 continously vented and the cylinder chamber 77 is alternately supplied with compressed air;~ from and vented through a valve 104 that i8 connected to the supply conduit 101. A pilot valve 105 effects pneu~atically the shift-ing o the position of the valve 104 and the piston rod 70 shifts mechanically the position of the pilot valve by means of a coupling 106, 107. One member 106 of the coupling is affixed to the piston rod and the other member 107 of the coupling is affixed to the valve 105. Between the two members 106, 107 of the coupling, there is an 35 axial play that makes the pilot valve 105 shift position when the ~- -piston rod 70 comes close to its end positions. A shut-off valve r 6 ,` - .
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in the oil conduit 103 is not needed in the embodiment according to Fig. 5 since the oscillator starts and stops simultaneously with the breaker. The valve arrangement shown in Fig. 5 can be utilized also in an oscillator used in the system shown in Fig. 1.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A lubricant furnishing system for a plurality of compressed air operated devices that are independently supplied with compressed air through air supply lines controlled by air supply valves, comprising: a lubricant supply line coupled to each air operated device; positive displacement pumps for supplying predetermined flows of lubricant to the lubricant supply lines;
a common actuating means coupled to and actuating said pumps; and a compressed air operated oscillator having an adjustable frequency, coupled to said actuating means for controlling the frequency of said actuating means, the oscillator comprising a reciprocating piston and a hydraulic damping circuit for controlling the speed of the reciprocating piston.

2. Lubricant furnishing system according to Claim 1, wherein said common actuating means comprises an actuating lever.