US2324727A - Power transmission - Google Patents

Description

July 20, 1943 R. A. sHARTLE POWER TRANSMISSION 'Filed Jan. 1o, 1941 2 sheets-sheet 1 /f//wwwwww INVENTOR SHARTLE ROBERT A. BY

ATTORNEY K VIII.

4July 20, 1943. R. A. sHARTLE POWER TRANSMISSION 2 Sheets-Sheet 2 Filed Jan. l0, 1941 ix m E INV EN TOR ROBERT A SHARTLE ATTORNEY Patented July 20, 1943 POWER TRANSIVHSSION Robert A. Shartle, Rockford, Ill., assigner to Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application January 10,1941, serial No. 373,867 z Claimaj (ci. eso- 52) This invention relates to power transmissions, particularly to those of the type comprising, two

or more fluid pressure energy translating devices,

n retract the drill for the purpose of clearing the chips and cooling the drill tipand to then return the drill to its work. There have beennu merous systems devised for controlling a hydrauthe parts in various positions at different `stages `of a complete cycle.

Referring now to Figure 1, a fixed displacement pump I `is adapted to be driven by an electric lically actuated drill to produce step drilling, but Y heretofore all such systems have required specially designed control apparatus making use of very `few, if any, of the standard hydraulic components now available on the market.

It is an object of the present invention to provide an improved control system for step drilling which incorporates one ofthe standard hydraulic control mechanisms which are used on a wide variety of machine tools for producing a cycle of rapid advance, feed and rapid return movee ment and which, because of their wide eld of apof the drill a predetermined time interval after` the feed movement begins.

A further object is to provide an improved control system of this character wherein the frictional dog is automatically reset during the final return movement of the drill carriage.

Further` objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a diagrammatic view of a power transmission system incorporating a preferred form "of the present invention.

Figures 2, 3 and 4 are schematic views of the hydraulic circuit and trip dog system showing motor i2 and has a suction conduit i4 connected with a tank i6. The delivery conduit I8 of the pump has the usual pressure responsive relief valve 20 therein for bypassing oil to-tank through a conduit 22 whenever a predetermined pressure is exceeded in the conduit I8.`

The conduit i8 extends tothe pressure port of a control panel 24, the tank connection of which communicates with the conduit 22. The panel 24 may be of well-known standard construction such, for example, as that illustrated in the application of` Kenneth R. Herman et al., Serial No. 155,652, filed July 26, 1937, for a Hydraulic feed control panel, nowIPatent No. 2,274,603.`

Briefly, such a panel .comprises a main control stem 28 having a plurality of lands thereon vfor controlling communication between the various passages within the panel to provide i'lve different ow conditions; namely, a rapid advance, a coarse feed, a fine feed, a stop and a rapid reverse, as the stem is moved from right to left betweenthe various positions illustrated.

`The stem'may be moved from the stop to the rapid advance position by a solenoid 28 acting. through a bell crank 30 to shift the stem to the l right whenever the solenoidis energized. Similarly, a solenoid 32 may act through the ,bell crank 30 to shift the stem 26 completely to theleftto the rapid reverse position. l i

The panel also may include a pair of manually adjustable throttles 3l and 33, one of which controls the fine feed and the otherof which controls the coarse feed. A hydrostatic flow control valve 35` is arranged in series with the throttlesrto maintain a predetermined pressure drop-"across them irrespective of variations inwork resistance. l 'I'he entire arrangement is such that,-in the rapid advance position of stem 26, the delivery conduit I8 is connected `directly with a conduit 34 communicating with theupper end of a cylinder 36 the piston 38 of which is connectedto actuate the drill carriage 40. In this position of the stem, the tank conduit `22 is also directly connected with a conduit l2 leading to the lower end of cylinder 36. I n

When the stem is shifted to coarse feed position, the pump delivery remains connected to first throttle 3| is established between conduits 42 and 22.

In the next position of the stem for producing fine feed, this path is made to include the throttle 33 in addition to the throttle 3i, while in the stop position the pressure and tank conduits I8 and 22. are connected together to bypass the pump delivery. With the stem 26 shifted to rapid return position, conduit I 8 is directly connected with conduit 42, and conduit 34 is directly connected with conduit 22.

'Ihe conduit 42 may include a foot valve 39 of known construction such as illustrated in the Herman Patent No. 2,200,824 including a selfcontained check valve 4I for free now from the panel to the cylinder and a pressure-responsive, back-pressure valve 43 arranged to prevent backow from the cylinder except at a pressure above that produced by the gravity load on piston 38.

Although the standard control panel includes provision for both coarse and fine feed rates, only one of the feed rates is necessary for step drilling so that the other feed position of stem 26 is not utilized in the mechanism hereafter described.

For the purpose of controlling the position of stem 26, the drill carriage 40 carries an upstanding bar 44 on which various trip dogs are mounted for actuating the stem 26 directly and for actuating certain limit switches which control the energization of solenoids 28 and 32. 46, rigidly but adjustably secured to the bar 44, is arranged to actuate a limit switch 48 at the lower end of the stroke of carriage 40. The switch 48 has two normally open circuits and one normally closed circuit.

A dog 50. rigidly but adjustably secured to the bar 44, has a portion 52 arranged to contact a single-circuit, normally-open, limit switch 54 just before the carriage 40 reaches the upper limit of its stroke. A second portion 56 forms a hook cam for pulling the stem 26 to the right. from its rapid return position to its stop position as the carriagel reaches the upper end of its stroke.

A cam bar 58 is also carried by the bar 44 for the purpose of resetting a sop pin 60 which is arranged to be projected to the right by a solenoid 62 whenever the latter is energized for a purpose later to be described.

Finally, the bar 44 carries a dog 64 which is slidably mounted on the bar with frlctional engagement sufiicient to prevent relative movement between the dog 64 and the bar 44 when the dog passes the stem 26 but insuiiicient to stop movement of the carriage when the dog strikes a positive stop. Such a stop is formed by a limit switch 66 of the single-circuit, normally-open type which is arranged to be contacted by an adjustable screw 68 carried by the dog 64 just after the latter shifts the stem 26 from rapid advance position to feed position.

For the purpose of controlling the energization of solenoids 28 and 32, an electric circuit is provided which includes a two-circuit, normallyopen, manual starting switch 10, the upper circuit of which, when closed, connec-ts between one side of a suitable power line indicated by L1 and through a conductor 14 to the actuating coil of a holding relay 12. The other side of the coil is connected to the other side of the line indicated at L2. The lower circuit of switchI is arranged, when closed, to connect line L1 to a conductor 16 leading to the solenoid 28, the other side of which is connected to line L2. A branch conductor 18 extends through the normally-open controlled contacts of relay 12 and through limit vswitch 54 Thus, a dog to line L1, thus forming, when closed, a shunt around the lower circuit of switch 10.

The holding circuit of relay 12 extends from one side of the coil thereof through the holding contacts and through a conductor to the normally-closed contacts of a two-circuit, emergency-return switch 82. This holding circuit continues through a conductor 84 and through the normally-closed contacts of limit switch 48 to the line L1. The leftmost normally-open contacts of limit switch 48 are adapted to close a circuit extending from line L1 through a conductor 86 -to the solenoid 32, the other side of which is connected to line L2. A branch 88 extends from the normally-open contacts of reverse switch 82 to the conductor 86 and is in parallel with the limit switch 48. The middle contacts of limit switch 46 close a circuit from line Ll through conductor 90 to the solenoid 62, the other side of which is connected to line L.

'I'he limit switch 66 controls a circuit extending between line L2 and the initiating coil of a time delay relay 92 by a conductor 94. The output circuit of relay 92 connects by a conductor 86 with the conductor 86. A connection 98 provides a common return for both circuits 94 and 98 at the relay 92.

In operation, with the pump I8 running and with the parts in the stopped position illustrated in Figure l, the pump delivery is bypassed through the panel 24, and the drill .carriage 48 is supported on the column of oil beneath piston 38 which is prevented from escaping by means of the foot valve 39.

When it is desired to start a cycle of step drilling, the starting switch 18 may be depressed which energizes the holding relay 12, the holding circuit of which is then completed through conductor 80, switch 82, cqpductor 84 and switch 48 to form a shunt around the upper contacts of switch 10. The lower contacts of switch 18 energize the solenoid 26 through conductor 16, thus shifting the stem 26 into rapid advance position. The pump delivery is now directed from conduit I8 through panel 24 directly to conduit 34 and the head end of cylinder 36. Pressure immediately builds up suiiicient to overcome the setting of foot valve 38, permitting oil to discharge from the lower end of cylinder 36 through conduit 42 which is in direct communication through the panel 24 with conduit 22.

The drill carriage accordingly approaches at full speed until a point is reached where the drills are about to engage the work. When this point is reached, dog 64 contacts stem 26, shifting it to the left into feed position, thus throwing the hydrostatic valve and throttle into the outlet cir- .cuit between conduit 42 and tank conduit 22. The carriage 40 is accordingly slowed down to the feed rate, and the excess pump delivery is bypassed to tank through the relief valve 28.

Immediately after shifting the stem 26 to feed position, the stop screw 68 contacts limit switch 66, and, after closing the same, the dog 64 can no longer descend with the carriage. Accordingly, the bar 44 is pulled through the dog 64 overcoming the frictional engagement therebetween. At the same time the closure of switch 66 initiated operation of the time delay relay 82, and, after thepredetermined time interval for which the relay is set, it closes the circuit between line connection 98 and conductor 96 which accordingly energizes solenoid 32 through conductor 86. When this occurs, the stem 26 is shifted completely to the left into the rapid returnposition, causing the slide 40 to be retracted at full speed. It will be noted that. when this rapid return movement starts, the dog 64 has taken up a new position on the rod 44 indicated by dotted lines at 64a.

Just before the slide reaches the upper limit of its travel, cam portion 52 of dog 50 closes limit switch 54 to energize solenoid 28 through conductor 18, relay 12 and conductor 16. Accordingly, the stem 26 is again shifted completely to the right to rapid advance position, and the carriage again advances at full speed. This time it advances further than it did on the rst rapid advance stroke or, in other words, until dog 64 in its new position engages stem 26 to shift the same to its feed position. From this point on, the same actions which have been described above occur, and, after a, predetermined interval,

`.At this time the dog 64 has taken up a third position on the bar 44 indicated in dotted lines at 64b.

This cycle of advancing and returning movement is continuous until the hole is drilled to its full depth at which time the dog 46 engages the limit switch 48 which simultaneously accomplishes three functions. First, it opens the holding circuit 80-82--84 of relay 12, permitting 'the latter to drop and form a break in the conductor 18, thus disabling limit switch 54 so that dog 52 will not start an advance stroke as the carriage 46 returns to its uppermost position. The second thing which limit switch 48 accomplishes is to energize solenoid 62 through conductor 90. thus projecting the stop pin 60 into the path of dog 64. as shown in Figure 4. Thirdly, the limit switch 48 energizes solenoid 32 through conductor 86, thus shifting stem 26 to rapid return position and causing the carriage 46 to be retracted.

During the upward travel of carriage 40, dog

` i 64 will engage stop pin 66 and be prevented thereby from returning upwardly with the bar 44. In this way the dog 64 is reset to its original position on the bar. When it has reached this position, the cam 58 engages a transverse pin on the stop pin 66 and gradually cams the latter back to the left so that the dog 64 can thereafter pass the pin 60 until the parts have returned to their i form, it is to be understood that other forms might be adopted. all coming within the scope standardized construction normally used for operating a drill carriage through a cycle of rapid advance, feed, rapid return and stop-movements, and having a single control member constituting the sole selecting means for said movements, of a dog for shifting the control member to change from rapid advance to feed carried by the carriage in yielding frictional relation thereto, means forming a positive stop to prevent further movement of the dog while the carriage advances in feeding movement, time delay means initiated in operation when the dog is stopped for shifting the controller to cause rapid return after a predetermined time interval, means controlled by the carriage at a predetermined point in its return movement for shifting the controller to cause rapid advance until the dog in its new position relative to the carriage shifts the controller to again cause feeding movement, and means controlled by the carriage after advancing to a predetermined point for immediately causing rapid return independently of the time delay means.

2. In a hydraulic power transmission system for step drilling the combination with a pressure source, a fluid motor and a flow controller of standardized construction normally used for operating a drill carriage through a cycle of rapid advance, feed, rapid return and stop movements, and having a single control member constituting the sole selecting means for said movements, of a dog for shifting the control member to change from rapid advance to feed carried by the carriage in yielding frictional relation thereto, means forming a positive stop to prevent further movement of the dog while the carriage advances in feeding movement, time delay means initiated in operation when the dog is stopped for shifting the controller to cause rapid return after a predetermined time interval, means controlled by the carriage at a predetermined point in its return movement for shifting the controller to cause rapid advance until the dog in its new position relative to the can'iage shifts the controller to again cause feeding movement, and means controlled by the carriage after advancing to a predetermined point for immediately causing rapid return independently of the time delay means and being arranged to disable the carriage-controlled means whereby the carriage is prevented from readvancing.

ROBERT A. SHAR'ILE.

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