|Publication number||US3680970 A|
|Publication date||Aug 1, 1972|
|Filing date||Dec 14, 1970|
|Priority date||Dec 14, 1970|
|Publication number||US 3680970 A, US 3680970A, US-A-3680970, US3680970 A, US3680970A|
|Inventors||Deschner Richard E|
|Original Assignee||Deschner Richard E|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (13), Classifications (8)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Unnted States Patent 1151 3,680,970
Deschner Aug. 1, 1972  FEED CONTROL 2,852,965 9/1958 Wallace ..408/17 2,977 826 4/1961 Radford ..408/17 X 72 I t. Rlh dE.Desh 555OH 1 men f z 3;? 3,286,555 11/1966 Klancnik.....'. "408/17 x  Filed: 1970 I Primary Examiner-Andrew R. Juhasz 2 APP] 97 7 Assistant Examiner-Z. R. Bilinsky 57 ABSTRACT [52 U.S. c1 ..408/17, 267/125 1  Int. Cl. ..B23b 47/22 This s sure describes an invention which is effi-  Field of Search ..408/17; 267/125 Cient for ing in rmi n tool feeding operations.
f t d [5 6] Re e 15 Claims, 15 Drawing Figures UNITED STATES PATENTS 2,579,459 12/1951 Allen ..408/17 X PATENTEDAUB 1 m2 SHEET U 0F 5 ILN'VENTOR. M
mammal m2 3.680.970
SHEEI 5 0F 5 Y F76. l5
FEED CONTROL CROSS REFERENCE TO RELATED PATENT The type of hydraulic checking device described in U.S. Pat. No. 3,027,152 is preferably used in the combination described herein because it is leakproof and reliable. Its hydraulic fluid is hermetically sealed within the unit by a flexible diaphragm plunger seal that is absolutely leakproof. The self-extending plunger is much more precise in movement than that of a conventional check for two reasons: first, the vicosity of the silicone hydraulic fluid used is less affected by temperature variations than the hydraulic oil used in conventional checks where sliding seals must be lubricated; second, the silicone fluid is installed in a super-clean condition and no dirt or lint can ever contaminate it because of 1 the hermetic seal and an internal filter. The internal flow aperture can not clog and cause variations in plunger speed as it does in checks refilled periodically with non-too-clean fluid.
BACKGROUND OF THE INVENTION 1. Field of the Invention .The invention finds special usefulness while attached to a machine having a reciprocative mechanism for feeding a tool into workpiece in advancing steps interspaced with retractions of the tool to remove cuttings. The present invention will be described as used in conjunction with an automatic drilling machine although its field of usefulness is not limited to such machines.
2. Description of the Prior Art Automatic drilling machines are used extensively in present day machine shops for mass production work. Such machines, when triggered to operate, rotate a drill-bit and feed it into a workpiece to produce a hole.
The common type of automatic drilling machine comprises a rotative spindle supporting a chuck for gripping drill-bits. The spindle is reciprocated by a pneumatic cylinder which is charged with compressed air at one end to advance the spindle and feed the drillbit into a workpiece, and charged on the other end to retract the drill-bit from the completed hole. However, compressed air provides a force which is very resilient, and if uncontrolled, tends to feed a drill irregularly and to advance the drill spindle so rapidly at the beginning of its stroke that it causes the drill-bit to strike the workpiece with heavy impact. The impact is great enough to break small drill-bits, and therefore, most, if not all, pneumatic drilling machines are arranged to be equipped with optional hydraulic checking means of some kind which can be adjusted to resist the force of the pneumatic cylinder to control the speed of advance of the drill-bit.
Drilling to a depth of more than three drill diameters in most metals requires that each time the drill-bit has been fed through a short cutting stroke, the drill-bit must be pulled out of the hole to lift out the waste cuttings, otherwise the cuttings tend to bind the drill-bit in the hole and may cause it to break. During the drilling of a very deep hole, where the depth of hole is as much as for example times the drill diameter, the drill-bit must be fed into and out of the hole several times before the hole is completed. A drilling machine which automatically reciprocates a drill-bit to feed it in advancing steps interspaced with retractions to remove cuttings is said to be doing Woodpecker drilling or simply peck drilling.
An automatic drilling machine is ordinarily equipped with a control system operative to provide motive power pulses to rotate and reciprocate the spindle and to operate accessory equipment. The control system may be mechanical, electrical, or pneumatic. A slave air valve actuated by the said motive power pulses feeds compressed air to the pneumatic cylinder and causes the spindle to advance and retract while an electric or compressed air motor rotates the spindle. The present invention is adapted to be attached to such an automatic drilling machine and to be operated by the control system.
A hydraulic checking device that provides checking only for a shallow type of drilling operation can be relatively simple, because in this type of operation it is desirable for the checking device to extend back to its own starting position whenever the drill spindle rises.
However, the save time in the peck drilling type of operation, hydraulic checking of the feed must take place substantially only while the drill is cutting, not while the drill is away from the workpiece. It follows that no matter what type checking device is used, it must remain substantially stationary during each retraction and reinsertion of the drill-bit, resuming movement each time only after the drill-bit reaches the position where it is again cutting. Yet, after the hole is completed and the drill retracts all the way to its starting position to begin a new hole, the checking device must then move immediately to its own starting position so it will provide checking action during the next working stroke of the drill.
To date, manufacturers of automatic drilling machines have been approaching the problem of furnishing checking for peck drilling in at least two ways. One manufacturer provides a conventional type of hydraulic check having sliding frictional seals. This checking device remains stationary when not loaded but requires an auxiliary air cylinder operated by an auxiliary air valve to return the hydraulic check to starting position whenever the drill-bit returns to its own starting position to begin a new hole. There are several disadvantages to this arrangement. It is bulky due to the air cylinder required, and it requires periodic servicing because the checking device has two sliding seals which leak fluid. In addition, the checking action is not constant. It varies when the fluid level gets low and it varies due to microscopic particles of dirt and lint which are gradually strained out of the fluid to collect around the flow aperture. As the aperture becomes clogged, it slows down the feed rate of the drilling machine. When the operator notices the feed rate has slowed down, he readjusts the flow aperture to give a larger opening, but his action temporarily frees the collected dirt and lint back into the fluid and he usually concludes his adjustment with substantially the same setting he had made originally. Subsequently accumulation of the dirt and lint begin again to slow the feed rate, and so on indefinitely.
A second manufacturer uses a constant action leakproof checking device such as is described in U.S. Pat. No. 3,027,152, and provides an auxiliary air cylinder operated by an auxiliary air valve with special pressure regulating device which is intended to hold the springretumed check plunger stationary when not loaded, and to release the said plunger whenever the drill-bit returns to its starting position to begin a new hole.
There are several disadvantages to this second arrangement also. It is costly and bulky due to the air cylinder and regulator required, and additionally, the pressure in the air cylinder cannot hold the spring-returned check plunger actually stationary during peck drilling while the drill-bit lifts and returns, because the plunger return force varies throughout its stroke and the said regulator is not capable of varying air pressure correspondingly.
SUMMARY OF THE INVENTION The present invention needs no auxiliary air cylinder. It provides unfailing, leakproof, constant action feed control for automatic drilling machines and eliminates the need for periodic servicing. It reduces breakage of small drill-bits and transforms the entire drilling machine into a more reliable tool. Preferred features of the present invention are the leakproof hydraulic checking device which has an automatically self-extending plunger, and a clutch which acts as a brake to hold the said plunger from extending until released by the control system of the drilling machine each time a new hold is to be started. The clutch permits said plunger to retract through a working stroke whenever the spindle mechanism of the drilling machine advances and contacts said plunger. The preferred embodiment of the invention, as described herein, exhibits the following characteristics when attached to an automatic drilling machine:
I. Permits peck checking for deep holes, simple checking for shallow holes, or drilling without any checking.
2. Reduces drill-bit breakage by repressing impact of the drill-bit against the workpiece, see Supplement for explanation.
3. Needs no periodic fluid replenishment.
4. Has diminutive size--mounts in restricted space.
5. Needs no lubrication.
6. Has handy adjustment features.
7. Operates through a wearing life of millions of cycles without requiring repairs or maintenance.
In the drawings,
FIG. 1 is a side elevational view of a control device for an automatic drilling machine comprising a hydraulic check unit (such as described in US. Pat. No. 3,027,152) combined with a clutching device embodying the principles of this invention,
FIG. 2 is a front elevational view of FIG. 1,
FIG. 3 is a fragmentary front elevational sectional view of the clutching device positioned as shown in FIG. 2,
FIG. 4 is a transverse section taken at 44 of FIG. 3,
FIG. 5 is a fragmentary plan view of FIG. 3 with a portion of the frame cover plate 34 shown broken away to expose the top of base block 30, the top of rocker member 42, and the top of retainer 44,
FIG. 6 is a perspective view of the switching shaft per se of FIG. 5,
FIG. 7 is a fragmentary transverse section of the piston 48 and rocker member 42 of FIG. 3 at 7-7,
FIG. 8 is a diagrammatic representation of the reciprocative action of a first type of automatic drilling machine,
FIG. 9 is a diagrammatic representation of the reciprocative action of a second type of automatic drilling machine,
FIG. 10 is a cut away front elevational sectional view of a second species of clutching device similar to that of FIG. 3 but with a modified form of construction,
FIG. 11 is a plan view of the device shown in FIG. 10 with the frame cover plate 209 removed,
FIG. 12 is a cut away front elevational sectional view of a third species of clutching device,
FIG. 13 is a plan view of the device of FIG. 12 partially broken away to show a section taken at 1313, and,
FIG. 14 is a side elevational sectional view of the device of FIG. 12 taken at 14-14,
FIG. 15 is a diagrammatic view of an automatic drilling machine equipped with a feed control embodying the principles of this invention in accordance with the following paragraph.
The present disclosure particularly describes and illustrates the present invention in connection with its application to checking the feed of an automatic drilling machine, but the invention is adaptable for use on other machines also.
DESCRIPTION AND OPERATION OF PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the numeral 2 indicates a hydraulic check unit of the type described in US. Pat. No. 3,027,152, having a housing 4, a speed adjustment knob 6, and a braking member comprising a reciprocative plunger 8 provided with internal resilient means which automatically moves the plunger outward to its full exposed length whenever it is free of external forces. The said check unit carries a positioning snap ring 5 and is shown supported by a mounting block 10 and clamp block 11, said blocks, for the purpose of describing the present invention, will be assumed to be attached to an automatic drilling machine having a bracket 12 secured to a reciprocative spindle mechanism which reciprocates a drill-bit into or out of a workpiece. FIG. 15 shows the features of one type of automatic drilling machine spindle having a reciprocative 400 with an attached bracket 12. The reciprocative mechanism is operated by an attached piston 402 moving within a pneumatic cylinder 404 and includes a splined rotative spindle 406 axially slidable within splines 408 attached to pulley 410. A chuck 412 on said spindle holds a drill-bit 414. The spindle is rotated by an electric motor 416 provided with pulley 418, belt 420, and manually operated electric switch 422.
Referring back to FIG. 1 of the present disclosure, during the feed-in stroke, which is in the direction indicated by numeral 14, the movement of bracket 12, and, therefore, of the drill-bit, is resisted and regulated in speed by plunger 8 bearing against bracket 12 as said plunger moves downward from an extended position.
An automatic drill spindle may have a total available stroke such as shown by the 3 inch dimension in FIG. 1, but the operator will often set the drilling machine to travel only a portion of the stroke to accommodate a certain workpiece. As an example, bracket 12 might then travel through a stroke of only 2 inch as shown by the 2 inch dimension in FIG. 1. In addition to adjusting the stroke, the operator will at times set the automatic drill for peck drillingpreviously described in this disclosure.
In one mode of peck drilling as accomplished by some control systems and diagrammed in FIG. 8, the
bracket 12 would reciprocate several times during the drilling of each hole, advancing in steps 17 to a lower position during each successive downward movement and retracting through short distances 16 until the hole was completed, then it would retract distance 18 to return to starting position. It will be understood that bracket 12 actually would reciprocate in a straight line, but FIG. 8 illustrates the movement by a staggered line reading left to right to facilitate explanation.
In another mode of peck drilling diagrammed in FIG. 9, bracket 12 is retracted through varying distance 19, 19, etc. to pull the drill-bit all the way out of the hole (as far as its starting position) after each downward movement.
For efficient peck drilling by either of the methods illustrated in FIGS. 8 and 9, hydraulic checking of the feed must take place substantially only while the drill is cutting, because much time would be wasted if the feed were checked while the drill was merely advancing toward the workpiece. Therefore plunger 8 of FIG. 1 must remain substantially stationary during the correlated retractions 16 and reinsertions 17 of the drill-bit. However, after the hole is completed and the drill retracts upward for the last time as at 18 (before beginning a new hole), plunger 8 must rise immediately to its own starting position so it will provide checking action during the next working stroke of the drill.
The control of plunger 8 necessary for peck drilling as described, is accomplished by the self-energizing clutch of the invention shown at 24 in FIG. 1. Shown in further detail in FIGS. 3, 4, and 5, numeral 30 indicates a frame base block which is split at 31, thus adapted to be clamped to hydraulic check housing 4 by a clamp screw 32. FIGS. 3-5 also show a frame cover plate 34, a clamping plate 36, a fulcrum pin 40 which pivotally supports a rocker member 42, mechanically associating the retainer 44, which supports detent balls 46, with a power pulse receptive element comprising reciprocative piston 48. FIG. shows rocker member 42 to be provided with primary lugs 50 and 52 and secondary lugs 54 and 56, these being arranged to transmit movement of piston 48 to retainer 44 via said rocker member 42. The enlarged hole 43 in member 42 is necessary to permit assembly of said member over retainer 44. FIG. 3 shows a plunger 62 urged against rocker member 42 by resilient spring means 64, so that rocker member 42 is normally held in its full line position designated by numeral 42, and retainer 44 is normally urged upward, movable detent balls 46 being thereby wedged between plunger 8 and a tapered annulus 66 secured to the frame and provided to guide balls 46 into a frictional contacting condition with plunger 8.
Downward movement of plunger 8 is always unimpeded because contact pressure of balls 46 is diminished during such movement, but whenever the said plunger is free of external forces, it moves to extend upward under the action of its own resilient means, moving detent balls 46 until the contact pressure of said detent balls against plunger 8 is intensified to a value which completely stops movement of the plunger. Therefore a slight amount of extensional movement of the plunger is permitted precedent to each stopping thereof. This effects overlapping working strokes of the feed control and is effective in repressing drill-bit breakage as will be explained under Supplement, herein.
Piston 48 is surrounded by leakproof rolling diaphragm seal 72 which is in turn surrounded by a cylinder 74 which anchors and seals the diaphragm bead flange 76 to base block 30. Shown in FIGS. 3 and 4, a passageway 78 for compressed air to actuate the diaphragm and piston is provided with a threaded port 80 which supports a connector 82 providing a means of communicatively connecting said piston 48 to a conductor tube 84, the said tube providing a means of transmitting motive power pulses of compressed air from a valve 432 in the drill press control system as shown by FIG. 15.
Referring back to FIG. 3, when piston 48 is actuated by a pulse of compressed air, rocker member 42 is moved to its phantom line position designated 42 so that retainer 44 pulls balls 46 out of the aforesaid frictional contacting condition with plunger 8 and the said plunger is then free to extend under actuation of its own resilient means. When air pressure is exhausted under piston 48, plunger 68 is actuated by its spring to return piston 48 downward so that rocker member 42 again wedges detent balls 46 against plunger 8.
FIG. 7 shows a space 79 between the shoulder 49 of piston 48 and the lugs 50 and 52 resulting in lost motion between the piston 48 and the rocker member 42. Such a space permits piston 48 to travel a portion of its stroke before rocker member 42 is actuated, thereby producing a hammer blow to assist in releasing the detent balls 46 of FIG. 3 at times when the air pressure is low and the motive power pulses weak.
It may occur to those skilled in the art that the above clutching mechanism could be arranged in reverse so air pressure actuating the piston would wedge the detent balls around the plunger and the resilient means would release the said balls. In that case however, the above described hammer blow effect could not be obtained. Furthermore, the arrangement shown keeps the contact pressure of the detent balls against plunger 8 independent of the operating air pressure. Otherwise varying air pressure-could cause repeated heavy contact pressure of the balls and result in excessive wear of the plunger.
FIG. 3 illustrates a dust seal 86 held in place by a washer 88. The dust seal is preferably made of felt and serves to keep foreign material from entering the mechanism.
One type of automatic drilling machine with pneumatically reciprocated spindle mechanism equipped for peck drilling, and operating as described in lines 1-8, page 4 of this disclosure, is provided with a control system including a primary air valve 430 and a secondary auxiliary air valve 432 as shown in FIG. 15. The primary valve furnishes compressed air to reciprocate the spindle mechanism, the secondary auxiliary valve furnishes compressed air to return the hydraulic check to starting position.
Both valves shown in FIG. 15 are solenoid operated power pulse transmitters, primary valve 430 being normally closed and secondary valve 432 normally open. A compressed air supply line 434 furnishes a constant supply of low pressure air to cylinder 404 via regulator 436 and tube 438, thus constantly urging piston 402 upward. A supply of higher pressure air is furnished to valves 430 and 432, a regulator 440 giving a means of controlling the downward force exerted by the air on piston 482.
Electric power from an external source 441 is supplied to operate the valves and the motor. The valves are triggered to furnish power pulses of air pressure by means of momentary contact operators switch 443, normally open latching relay 444, normally closed timer switch 446, and a normally closed limit switch 448 which is operated by an adjustable screw 450 carried by bracket 12 when said screw advances downward as shown by the arrow.
When the present invention is installed on the drilling machine instead of the conventional type of air returned hydraulic check described, the said secondary valve 432 is utilized for operating the clutching device 24 of the present invention, the said control system operating in its usual manner so that air pressure to the clutching device is held released during pecking reciprocations of the bracket 12 of FIGS. 1 and 15. Plunger 8 does not rise substantially during the correlated pecking retractions and reinsertions of the drillbit but after the hole being drilled is completed, pressure is provided to the clutching device by the control system through conductor tube 84, forcing the detent structure out of the aforesaid frictional contacting condition with the plunger so the plunger follows bracket 12all the way back to its starting position. Then the control system again holds the air pressure released during the subsequent peck drilling operation, etc.
An operator who wishes to drill an ordinary hole, closes motor switch 422 to rotate the spindle, then closes momentary contact switch 443. This causes relay 444'to latch closed, thereby holding valve 430 open, holding valve 432 closed, and holding tube 84 open to exhaust; Piston 402 and the rotating drill-bit now advance downward until screw 450 opens switch 448 at which time relay 444 unlatches and drill-bit 414 returns upward where it remains ready for the next drilling operation. During ordinary drilling as just described, the lack of air pressure in tube 84 permits clutching device 24 to grip plunger 8, but this action has no effect. because the plunger is traveling downward.
During peck drilling, clutching device 24 prevents plunger 8 from rising until valve 432 opens. To peck drill a hole, the operator uses a timer or other means to open timer switch 446 several times before screw 450 reaches switch 448. At each opening of switch 446, valve 430 operates but 432 does not, so that the drillbit rises, but air pressure is not admitted to tube 84 so plunger 8 is kept from rising by clutching device 24. Each time switch 446 is closed, the drill-bit advances again. When screw 450 finally opens switch 448, both valves 430 and 432 operate, causing drill-bit 414 to return upward where it remains ready for the next drilling operation, and causing clutching device 24 to release plunger 8 so that it too rises and remains ready for the next drilling operation.
SWITCHING MEANS FIGS. 2 and 6 show a mechanical switching means comprising a rotatable switching shaft 100 provided with a screwdriver slot 102 and impressed arrow 104, and in FIG. 6, it is seen that the central portion is cut 7 away to leave a 90 segment 106. As indicated by lettering on the nameplate 105 in FIG. 2, switching shaft 100 may be rotated into On and Off positions.
segment 106 positioned as shown by the solid lines in I FIG. 3, rocker member 42 is free to move between its two positions 42 and 42; but when shaft is in the Off position with said segment positioned as shown by phantom lines l06' in FIG. 3, then segment 106 acts as a cam locking the rocker member into position 42' thereby holding balls 46 out of contact with plunger 8 so that the said plunger is free to extend under actuation of its own resilient means. Switching shaft 100, therefore, permits the operator of a drilling machine, to which the present invention is attached, to set the clutching device to provide proper hydraulic checking for ordinary drilling or for peck drilling.
FIG. 6 shows that switching shaft 100 is provided with a circumferential groove l08 to permit a rubber O ring 110 to be installed as shown in FIG. 5. Such an O ring provides friction to keep shaft 100 in position after it has been adjusted.
STROKE LIMITER As explained for FIG. 1, the operator of an automatic drilling machine will often set the spindle mechanism to travel only a portion of its stroke. In addition to this, the operator will often wish to limit the stroke of the plunger of the hydraulic check so that the check will retard the drill feed for only the final portion of the stroke of the drill press, thus to permit fast advance of the of the drill-bit yet prevent the drill-bit from snagging when it breaks through the workpiece. The present invention provides the operator with means for limiting the stroke of said plunger. In FIG. 1, a plunger extension limiting device 1 16 is shown having a columnar portion 118 and stop lug portion 120. The columnar portion is supported between frame cover plate 34 and clamping plate 36. FIG. 5 shows that a slot 37 is provided in the clamping plate for the accommodation of the columnar portion, the said slot being shallower than the thickness of the said columnar portion so that screw 122 can be used to clamp the limiting device at any position desired. Light clamping means is sufficient because the type of hydraulic check shown has a light weight, nearly frictionless plunger, and a very light plunger return force. With the stroke limiter in the position shown by the solid lines in FIG. 1, plunger 8 can rise only as far as the position indicated by numeral 124 no matter how high bracket 12 moves. Fully extended positions of the stroke limiter and plunger are shown at and 124'.
FLOW RESTRICTING CHECK VALVE If the drilling machine were only required to peek drill as diagrammed in FIG. 8, wherein the spindle reaches the highest possible point in its stroke only after a hole is completed, then a mechanically operated valve could be used to operate the clutching device of the present invention whenever the drilling machine spindle reached the top of its stroke. However, if the said spindle were reciprocating so rapidly that it made only momentary contact with such a valve, then the said clutching device might be released for too brief an interval to permit plunger 8 of FIG. 1 to extend fully. To make the present invention perform properly under this possible condition, a flow restricting check valve such as shown in FIG. 4 may be provided by a ball 130, a spring 131, a seat 132 and a metering passageway 133 which permits leakage of air past the ball. Such a valve, designed to permit an ample flow of compressed air toward piston 48 but to retard the flow of air away from said piston, will prolong the time during which balls 46 are held out of contact with plunger 8, thereby giving plunger 8 ample time to extend.
SECOND SPECIES A simpler species of self-energizing clutch is shown in FIGS. 10-11 wherein the balls are omitted and rocker member 200 is provided with an opening 202 which fits the plunger 204 with a barely free fit. The rocker member itself acts as a detent means and binds the plunger to prevent it from extending whenever the said rocker lifts to its full line position designated by numeral 200. When air piston 201 moves member 200 into its phantom line position designated by numeral 200' (wherein it rests against shoulder 205 provided in the frame and is disposed substantially at right angles to the axis of plunger 204) plunger 204 is released and is then free to extend.
The device of FIG. 10 has a frame consisting of base block 207, cover plate 209, and clamping plate 211. It contains a dust seal 206 held in place by an internal type retaining ring 208. Spring plungers 210 and 212 perform the same function as plungers 68 and 62 of FIG. 3.
As illustrated in FIG. 10, the power pulse receptive element 201 is shown to be an air operated piston with an air diaphragm, which would be communicatively connected to the control system of the drill press the same as the corresponding element 48 of FIGS. 3-5.
The clutch of FIGS. 10-11 acts similarly to that of FIGS. 3-5, permitting slight extensional movement of the check plunger precedent to each positive stopping thereof. This action effects overlapping working strokes of the feed control and is a desirable feature of this invention as explained in the Supplement. However, the amount of stroke overlap is less predictable than that of the first species because it depends to a large degree on manufacturing variations in the diameter of plunger 204, and opening 202 in.the rocker member.
THIRD SPECIES A third species of clutch that is simple and inexpensive and which proves adjustment means permitting an operator to pre-set the amount of overlap in the working strokes of the feed control, is shown in FIGS. 12-14 wherein a one piece frame block 300 is split at 302, thus adapted to be clamped to hydraulic check housing 304. A movable cylindrical detent member 306 which serves both as a piston and as a detent is supported by drilling machine, a pneumatic pressure pulse sent to the diaphragm 308 moves detent member 306 to contact plunger 314 to prevent .said plunger from extending. Release of the pneumatic pressure releases detent 306 permitting it to float free and permit plunger 314 to extend. For the FIG. 12 third species, the drilling machine control system would be equipped with a normally open valve instead of a normally closed valve as required for the FIG. 3 species, or vice versa, depending on the basic principle of operation of the said control system.
Springs 328 and 330 are designed to hold detents 306 and 320 in their full line positions shown in FIG. 12 whenever there is no pneumatic pressure applied to port 324, the said springs being weaker than the resilient means which causes automatic extension of plunger 314. When a pneumatic pressure pulse is applied to port 324, plunger 314 is immediately gripped between said detents, but the said plunger, if subsequently freed of external load, will move to extend upward under action of its own resilient means causing said detents to rock upward against the action of springs 328 and 330 to their phantom line positions 306 and 320', this action providing overlapping working strokes of the feed control as described for the first and second species.
The rocking action of detent 306 is permitted by its recessed surfaces 334 and 336, and that of detent 320 by corresponding surfaces 340 and 342, the amount of recession of said surfaces determining the amount of extensional movement of said plunger permitted between the gripping and stopping thereof. The amount of overlap of the feed control may therefore be adjusted by proportioning the shapes of the detents to give the amount of overlap desired.
When an external load is applied to plunger 314 and it is forced to move downward through a working stroke, detents 306 and 320 rock downward to their full line positions, the plunger subsequently being forced to slide through said detents while their full frictional force is being exerted. For this reason the third species has less wearing life than the preferred species of FIG. 3.
If a roller instead of detent 320 were provided to bear against plunger 314, then detent 306 acting alone, would accomplish the same action as described for both detents, but it would require twice the force applied by the pneumatic pressure pulse to hold plunger- 314 from extending.
SUPPLEMENT Drilling machines are normally operated with the spindle vertical. During peck drilling the ordinary hydraulic check permits repeated impact of the drill-bit on the workpiece because the check remains stationary or drops slightly while the drill-bit lifts and returns. On the downward feeding stroke the drill-bit is permitted to strike the workpiece before the ordinary check can act to restrain it and impact occurs for one or all of the following reasons:
1. The returning drill-bit strikes a high spot it left in the bottom of the hole.
2. The workpiece is not supported rigidly and it springs upward slightly each time the drill-bit is lifted.
there is a new coaction of elements between said feed control and said bearing housing which represses drillbit breakage during peck drilling. The said coaction is due to the combined action of any of the clutches described for FIGS. 3-5, -11 or 12-14, and the selfextending hydraulic check described for FIGS. 1 and 2, the said clutch effecting overlapping working strokes of the feed control by permitting slight extensional movement of the plunger of the hydraulic check precedent to each extensional stopping of said plunger. Before each downward feeding stroke of the spindle, the hydraulic check is'permitted by the clutch to pre-position itself to retard advance of the bearing housing slightly above the point where said bearing housing stopped during its previous downward feeding stroke. Therefore, during peck drilling, the drill-bit is retarded a little earlier in each movement toward the workpiece than it would be if a conventional feed control were being used. The production time lost by the slightly overlappingworking strokes is negligible.
In the combination of a clutching device with a hydraulic check, wherein the clutch acts by applying frictional pressure perpendicular to the axis of the plunger of said check, the use of a check having a leakproof diaphragm fluid seal on the plunger (such as shown in US. Pat. No. 3,027,152) provides an important advantage for the control device in that the plunger stays absolutely dry and free of hydraulic fluid and thereby enables the clutching device to act with a non-varying dependability that would not be attainable if a hydraulic check with sliding seals were used. Sliding seals always leaka certain amount of fluid, the amount varying with the age of the seal, and the lubricity of the fluid would affect the gripping characteristics of any frictional clutching device if it had to utilize an oily hydraulic plunger for one of its working parts.
An advantage of the combinations of FIGS. 1-3 and 10-1 1 is in having the piston moving parallel to the axis of the plunger. This facilitates boring the frame blocks during manufacture and permits use of simple, flat plate type rocker members as the means for transmitting motion from pistons to detent members.
An important characteristic of the FIG. 1-3 combination is that of exceptionally long wearing lifemore than adequate for use in industrial mass production wherein machinery must operate efficiently for millions of cycles with minimum maintenance. It is seen in the present disclosure that the clutching device operates to grip the check plunger by direct frictional contact, therefore the plunger is forced to slide through the resulting frictional resistance during all times that the plunger is being forced to retract by the drilling machine. The continual sliding would ordinarily cause considerable wear. However, the diaphragm fluid seal in the type of hydraulic check shown in US. Pat. No.
3,027,152 is virtually frictionless and a very light plunger return force (on the order of 1 lb. for each oneeighth inch of plunger diameter) is provided and is suf-v ficient to provide fast automatic extension of the plunger. As a result the clutchingdevice need exert only light contact pressure to hold the plunger from extending. Even this light pressure is automatically diminished by the self-releasing action of FIG. 3 clutching device whenever the plunger moves the retract. The resulting light contact pressure causes no noticeable wear on the mating parts, even after 5,000,000 cycles by actual test. The species of selfenergizing clutch illustrated in FIG. 3 is exceptionally efficient too. It distributes pressure evenly around the plunger of the hydraulic check and operates effectively without deflecting the plunger8 from its normal alignment. The balls themselves rotate continually and present new areas of contact to the plunger at each engagement.
In all species in this disclosure, the preferred type of seal for the power pulse receptive element is shown to be a pneumatically operated diaphragm because most automatic drill presses are equipped with pneumatic control systems and diaphragms are leakproof and require no lubrication. However, an equivalent receptive element such as an electric solenoid or mechanical push rod could be substituted for the diaphragm to be in accord with the type of control system existing on the drill press, it being intended that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which come withinthe scope of the subject matter claimed.
What is claimed is:
1. In combination with a drilling machine having a reciprocative spindle mechanism actuated by a pneumatic cylinder, and a control system including a primary motive power pulse transmitter comprising a valve operative to control movement of said pneumatic cylinder, and a secondary motive power pulse transmitter for operating accessory equipment; a feed control for hydraulically controlling the speed of feed of said spindle mechanism, said feed control being attached to said drilling machine in position to be actuated through working strokes by said spindle mechanism and comprising: a hydraulic checking device and clutch therefore, said hydraulic checking device including a housing, a fluid damped plunger having an axis and being reciprocative axially relative to said housing, and resilient means operative to cause automatic extension of a portion of said plunger relative to said housing when said plunger portion is free of force tending to effect its retraction into said housing; said clutch comprising: a frame secured adjacent said housing, movable detent means adapted for applying frictional pressure perpendicular to the axis of said plunger for gripping and stopping said plunger from extensional movement, retaining and guiding structure for said detent means within said frame, and a power pulse receptive element supported by said frame and movable relative thereto, said element being communicatively connected to said secondary transmitter and adapted to be actuated relative to said frame by said power pulses, and correlative means associating said element and said detent means thereby actuation of said element actuates said detent means.
2. The subject matter of claim 1, said retaining and guiding structure for said detent means being constructed and arranged to retain said detent means yieldably to permit movement of said detent means a measurable distance axially of said plunger between positions where said gripping and said stopping of said plunger occur, thereby effecting overlapping working strokes of said feed control during peck drilling to repress impact of said drill-bit against said workpiece.
3. A feed control adapted for use in conjunction with that type of automatic machine having a reciprocative mechanism for feeding a tool into a workpiece in advancing steps interspaced with retractions of said tool to facilitate the work, said automatic machine being provided with a pneumatic cylinder and piston assembly for actuating said reciprocative mechanism, and a control system operative to provide motive power pulses to cause movement of a portion of said pneumatic cylinder assembly and to operate accessory equipment, said feed control comprising the combination of: a checking device and accessory clutching device, said checking device comprising; a checking member having an axis and being axially reciprocative, bearing structure attachable to said automatic machine to support said checking member in position to be moved through a working stroke relative to said bearingstructure by said reciprocative mechanism, said checking member and said bearing structure being associated by adjustable hydraulic means operative to resist movement of said checking member through a working stroke, resilient means continuously urging said checking member to move relative to said bearing structure opposite the direction of its working stroke, whereby to return said checking member automatically to starting position when it is freed of forces tending to effect a working stroke, said clutching device comprising; a frame secured adjacent said bearing structure, movable detent means adapted for applying frictional pressure perpendicular to the axis of said checking member for gripping and stopping said checking member from extensional movement, retaining and guiding structure for said detent means within said frame, a power pulse receptive element supported by said frame, power pulse conductive means communicating with said receptive element and adapted to be communicatively connected to said control system, said receptive element being constructed and arranged to be actuated relative to said frame by said motive power pulses, and correlative means associating said receptive element and said detent means whereby actuation of said element actuates said detent means.
4. The subject matter of claim 3, and said hydraulic means including a dynamic fluid seal comprising a leakproof flexible diaphragm anchored to and between said checking member and said bearing structure to insure a permanently dry friction surface on said checking member.
5. A clutching device usable as an accessory to a hydraulic check unit constituting a feed control adapted for attachment to an automatic drilling machine of the type having a pneumatically reciprocative spindle mechanism for feeding a drill-bit to a workpiece, said drilling machine having a control system operative to provide motive power pulses to cause reciprocation of said spindle mechanism and to operate accessory equipment, said hydraulic check unit being of the type having a housing and a plunger portion exposed externally of said housing, said plunger portion having an axis and said plunger portion and housing being axially reciprocable relative to each other and having a working stroke during which said plunger portion retracts relative to said housing, said check unit being provided with resilient means continuously urging said plunger and housing relatively opposite the direction of said working stroke whereby to cause automatic extension of said plunger portion relative to said housing when said check unit is freed of external forces, said check unit while attached to said drilling machine being contactable by a portion of said spindle mechanism as said spindle mechanism advances to feed a drill-bit, said check unit being capable of resisting movement of said spindle mechanism during said working stroke, said clutching device comprising: a frame adapted to be mounted adjacent said housing, movable detent means adapted for applying frictional pressure perpendicular to the axis of said plunger for gripping and stopping said plunger from extensional movement, retaining and guiding structure for said detent means within said frame, a power pulse receptive element supported by said frame and movable relative thereto, power pulse conductive means communicating with said receptive element and adapted to be communicatively connected to said control system, said element being adapted to be actuated relative to said frame by said motive power pulses, and correlative means associating said element and said detent means whereby actuation of said element adjusts said detent means.
6. The subject matter of claim 5, and mechanical switching means supported by said frame, said switching means being manually adjustable from an Off position to an On position wherein it contacts and prevents movement of a portion of said correlative means, thereby preventing said detent means from gripping said plunger portion.
7. The subject matter of claim 5, and a plunger extension limiting device supported by said frame, said limiting device having a columnar portion the length of which extends substantially parallel to the axis of said plunger portion while said frame is attached to said housing, and a laterally extending stop portion held by said columnar portion in the path of said plunger portion, the position of said stop portion being adjustable parallel to the axis of said plunger portion.
8. The subject matter of claim 5, said frame being provided with a cavity and an inlet passage for compressed air communicating therewith, said power pulse receptive element being positioned within said cavity and movable in response to pneumatic power pulses.
9. The subject matter of claim 5, said retaining and guiding structure for said detent means being constructed and arranged to retain said detent means yieldably to permit movement of said detent means a measurable distance axially of said plunger between positions where said gripping and said stopping of said plunger occur, thereby effecting overlapping working strokes of said feed control during peck drilling to repress impact of said drill-bit against said workpiece.
10. The subject matter of claim 5, said guiding structure comprising an annular internally tapered wall surface surrounding said plunger portion, said detent means comprising a plurality of balls and a reciprocative retaining member holding said balls positioned at circumferential intervals between said plunger portion and said tapered wall surface, said retaining member being arranged to move axially of said plunger portion consequent to movement of said power pulse receptive element.
11. The subject matter of claim 5, said power pulse receptive element being provided with a flexible, airtight, diaphragm type seal to permit said clutching device to be controlled by power pulses of unlubricated compressed air.
12. The subject matter of claim 5, said correlative means being constructed and arranged to have measurable lost motion between said power pulse receptive element and said detent means to permit said receptive element to travel a portion of its stroke before said detent means is actuated, thereby effecting the producsaid gripping condition, and flow restrictive means adapted to retard flow of air away from said receptive element. 1
14. The subject matter of claim 5, said frame being provided with a plurality of parallel bores adapted to enclose, at least partially, said receptive element and said check housing, said receptive element being arranged to move substantially parallel to the axis of said plunger, said correlative means including a pivotally supported rocking member for transmitting motion from said receptive element to said detent means.
16. The subject matter of claim 5, and secondary resilient means continuously urging said detent means to move substantially parallel to and opposite the direction of extensional movement of said plunger, said secondary resilient means operating to hold said detent means yieldably positioned against a portion of said retaining structure, the shapes of said retaining structure and of said detent permitting said detent to move under the influence of said receptive element substantially perpendicular to the axis of said plunger to grip said plunger, and to move thereafter along with said plunger a limited distance against said secondary resilient means to permit said plunger to extend a predetermined distance before being brought to a stop.
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|U.S. Classification||408/17, 267/125|
|International Classification||B23Q5/26, B23B47/00, B23Q5/22, B23B47/22|