US2779220A - Universal drilling machine - Google Patents

Description

Jan. 29, 1957 R. J. DUNN, JR., ETAL UNIVERSAL DRILLING MACHINE 8 sheets-sheet 1 Filed May 11. 1953 INVENTORS v RAYMOND ou/v/v, up. I B OSCAP L WR/GHCJP AT ORNEYJ Jan. 29, 1957 R. J. DUNN, JR; EIAL 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11, 1953 8 Sheets-Sheet 2 INVENTORS RAYMOND a. DUNN, JR By OSCAR L. WR/GHZJR.

94M and p/YAOZ fiM? AT ORNEYS 1957 \R. J. DUNN, JR, E AL 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11. 1953 8 Sheets-Sheet 3 FIG. 3

INVENTORS RAYMOND a. ou/v JR By OSCAR L. IMP/6H7, JR

A TORNEYS Jan.'29, 1957 R. J. DUNN, JR., ETAL 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11, 1953 8 Sheets-Sheet 4 F/GS IN VEN TORS RAYMOND d. DU/VA/,(/R- BY OSCAP L. WR/GH7; JP.

' A TORNEYJ Jan. 29, 1957 R. J. DUNN, JR., ETAL 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11, 1953 8 Sheets-Sheet 5 AJ/ I y g i f E. p v i a I 4? 1 ,e/ I, a 23 INVENTORS RAYMOND a. DUNN, L/R.

BY OSCAR L. WR/GHT JP.

A TORNEYJ' Jan. 29, 1957 J, DUNN, JRHTETAL 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11, 1953 8 Sheets-Sheet 6 F/QB Z4 INVENTOR RAYMOND 1 DUNN, JR. OSCAR L. wR/eHT, JR.

j M f TORNEYS Jan. 29, 1957 Filed May 11. 1953 R. J. DUNN, JR., ETAL 2,779,220

UNIVERSAL DRILLING MACHINE 8 Sheets-Sheet 7 INVENTORS PA YMOND a. DUNMJR.

0.3mm L. WP/GHZJRV 1957' R- J. DUNN, JR., ET AL 7 2,779,220

UNIVERSAL DRILLING MACHINE Filed May 11, 1953 8 sp gts-sheet 8 Z: Mf/ 4 k-mmfl wl I 2 We? INVENTORS RAYMOND DUN/V, JR y OSCAR L. WR/GHZ'JR M W Y I ATTORNEYS United States Patent UNIVERSAL DRILLING MACHINE Raymond J. Dunn, Jr., West Hartford, and Oscar L. Wright, Jr., West Granby, Conn., assignors to The Hartford Special Machinery Co., Hartford, Conn, a corporation of Connecticut Application May 11, 1953, Serial No. 354,166

22 Claims. (Cl. 77-64) This invention relates in general to drilling machines and pertains more particularly to an automatic drilling machine of a universal type in that it can be easily and quickly arranged for automatic operation on workpieces of widely different shape and hole pattern.

in order to attain high volume production in the drill"- ing of workpieces it is the usual practice to design and construct a special drilling machine for the particular workpiece contemplated. Normally, this entails a long time delay and considerable expense, much of which cannot be precisely estimated when the new machine is under consideration. After the specially designed machine is constructed and installed, if it is decided to discontinue the manufacture of the particular workpiece for which the machine is designed or if the workpiece or hole pattern is modified, then it becomes necessary to rebuild the machine or else let it stand by in an unproductive manner. There are some versatile drilling machines available but they are usually small single operation machines of a semiautomatic nature requiring highly skilled operators and are not suitable for high volume or rapid production.

Accordingly, it is an object of the present invention to provide a multi-head drilling machine suitable for high volume production composed of a combination of units, which units individually may be in a standardized form and which are quickly and easily interchanged or relocated so that the machine can be readily modified for use on a wide variety of workpieces. Included in this aim is to provide a novel and easily accessible control system for the various components which can be similarly replaced or varied to adapt the machine for different operations.

Also included in the above object is the provision of a drilling machine having a worktable which can be utilized for revolving a large workpiece for successive operations or for moving a small workpiece from station to station, and which is indexable in uniform or non-uniform increments in accordance with a desired plan or pattern, the control of the worktable and the drilling operations being correlated so that any desired scheduling of drilling operations can be performed.

A further object of the invention is to provide a drilling machine of the universal type referred to which despite its versatility will be suitable for rapid large volume production, which will be fully automatic in operation, which will operate with precision and accuracy over long periods of time without failure or breakdown, and which can be economically produced so as to be competitive in cost with conventional machines.

Other objects will be in part obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

in the drawings:

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Figure l is a front elevational view of the drilling machine which has been selected for illustration;

Figure 2 is a plan view of the drilling machine;

Figure 3 is a plan view of the dial assembly and its associated driving mechanism with portions thereof removed in order to expose members which would otherwise be concealed.

Figures 4, 5, and 6 are sectional views taken in the respective directions of. the several indicated lines of Figure 3;

Figure 7 is an end view of the control cam assembly, a part of one cam being removed to show the different construction of the next adjacent cam;

Figure 8 is a plan view corresponding to Figure 7;

Figure 9 is an enlarged view taken in the direction of line 99' of Figure 8;

Figure 10 is a sectional view taken in the direction of line 1010 of Figure 9; and

Figure 11 is a diagrammatic representation of the electrical circuity utilized in controlling the machine.

As a preliminary to better understanding the invention, reference should first be had to Figures 1 and 2 where the drilling machine forming the subject matter of the instant invention is pictured in its more general aspects. Later on certain features will be dealt with more comprehensively in order to present a fuller description of the exemplified drilling machine. However, from these first two figures, it will be observed that the illustrated machine includes a stationary base B having rotatably mounted thereon a dial assembly D driven by a motor DM. Extending radially from the base B and disposed in adjusted angular positions with respect to each other is a plurality of knees K which support upright columns C in the embodiment selected for description. In the present instance, the knees K are rendered angularly adjustable by means of a pair of arcuate bosses 8, spaced one above the other and extending circumferentially around the greater part of the base B. Each boss 2 contains an arcuate slot 3 of T-shaped cross section in which similarly shaped bolt members, carried by the knees, are slidably supported to permit adjustment of each knee around the base. In-order to position the knees K, each knee is equipped with a worm 4 cooperable with a Worm rack 5 affixed to the base B intermediate the arcuate bosses 2. While not visible in the drawings, the upper part of the base B has disposed therearound a T-shaped groove, there being at least one lug 7 on each knee K overlapping this groove so that a nut 8 on a correspondingly shaped bolt engaged in the groove can be tightened to assure the retention of the knees in whatever angular positions they have been moved.

While the number and type of drilling operations to be performed will dictate the number of heads to be utilized, for the purpose of illustration four heads are believed to be ample, and these heads bear the designations 1H, 2H, 3H and 4H, respectively, each head being carried for vertical reciprocation by one of the columns C. Although the heads have all been pictured as being vertically reciprocable, quite obviously they might be reciprocable in a horizontal plane, at some intermediate angle or at different angles relative to each other depending upon the Work pattern to be followed. Therefore, it will be appreciated that the columns C need not be vertical and that adapters may be substituted therefor to cause the heads to traverse a horizontal or angular path. Also visible is a pump motor PM used in the supplying of a suitable coolant to the tools and to assist in flushing the fixture and work clear of chips.

Describing now the rotatable dial assembly D more fully, it will be seen that this assembly includes an uppermost fixture or work table 10, a subjacent index plate 11 an intermediate spool or dial turret member 12 and a worm wheel 13 beneath the member 12, as best shown in Figure 6. The turret member 12 is firmly supported for rotation subjacent its periphery by reason of a relative large diameter bearing 18 (thereby enabling the dial assembly to withstand concentrated pressures unevenly applied during the Work cycle and to obviate any tendency for the Work table to tilt or cock. In mesh with the worm wheel 13 is a worm 14 afiixed to a shaft 15 which itself has at one end a worm wheel 16, as shown in Figure 3, the worm wheel 16 in turn being meshed with a worm 17 driven directly by the motor DM through a combination positive running-slip clutch 19 which is positive running in a forward direction, but is capable of slipping when driven in a reverse direction and subjected to excessive torque loads. By reason of the foregoing arrangement the dial assembly D may be rotated in either a forward or reverse direction by the motor DM. For the sake of clarity it should be explained that the fixture 10 may be seen in only Figures 1, 2 and 6, it having been removed in Figure 3 to expose the subjacent parts. In Figures 3 and 6, it will be noted that a dowel pin 20 is utilized which angularly positions the index plate 11 relative to the wheel member 12 and also the fixture 10 relative to these members, the pin 20 extending upwardly into but not through the fixture, as shown in Figure 6. It might be mentioned at this time that the index plate 11 is subject to replacement by other index plates, depending upon the hole design required in the work; hence the need for the dowel pin 20 which will angularly position each index plate accurately upon the dial assembly.

Carried at the lower end of the turret member 12 is a spiral gear 21 in mesh with a spiral gear 22, the gear 21 driving the gear 22 and thus a shaft 23 to which said gear is attached in a 1:1 ratio or correspondence with the dial D. A coupling 24 serves to connect detachably the shaft 23 to a control or cam shaft 25.

The shaft 25 is part of what will be referred to as a mechanical control MC which, in addition to the shaft 25, includes a programming or index cam IC, a full index cam FIC, and four head control cams 1HC, ZHC, 3HC and 4HC, one for each independent head in this specific embodiment selected to illustrate the invention. More will be said about each of the aforenoted six cams presently, the details of which are depicted in Figures 7, 8, 9, and 10.

Before describing the particular roles played by each cam mentioned in the preceding paragraph, it should be stated that the various head control cams lHC, 2HC, 3HC and 4HC freely circumscribe the shaft 25 as shown in Figure 8 and at times are selectively held so that the shaft 25 rotates relative thereto, but when not restrained are driven by the shaft. To accomplish this result, as best viewed in Figure 10, a series of friction rings 33 are keyed to the shaft 25, the rings being at either end of and interposed between the several head control cams. Motion is transmitted to the first ring 33 by means of a collar 34, also keyed to the shaft 25, and which collar is in turn connected to a thrust member 35. The purpose of the thrust member 35 is to apply pressure to the head control cams lHC, 2HC, 3HC, 4HC and the friction rings 33 in order that the head control cams will rotate in unison with the shaft 25 when the cams are not restrained, and to effect this the thrust member 35 is biased toward the head control cams as shown in Figure 10 by a spring assembly 36 including a rod 37 threaded at one end 39 and having a piston 40 at its other end received in a hollow cylindrical portion of shaft 25. Encircling the rod 37 and retained between piston 40 and a plug 42 threaded into the shaft 25 is a compression spring 41 which urges piston 40 and thrust member 35 inwardly to squeeze the head control cams and friction rings 33 together. By means of a nut 43 the extent the spring 41 is compressed may be adjusted for an optimum degree. of friction against the various faces of the head control cams-the more the compres sion, the greater the friction. In this way, it will be understood that each head control cam is rendered independently rotatable relative to the shaft 25 as well as rotatable with respect to each other, depending upon circumstances yet to be discussed. In brief, though, as the name of these several head control cams implies, the head cams exercise a pilot or supervisory control over the movements of their respective heads 1H, 2H, 3H and 4H, there being a separate cam for each head as hereinbefore indicated. In the exemplary model, each head operates independently of the others and hence there are four heads with a control cam for each.

As with the head control cams IHC, 2HC, 3HC and I 4HC, the index or programming cam IC is in 1:1 correspondence with the rotatable dial assembly D, but in order to insure that each head 1H, 2H, 3H and 4H will have had a chance to perform its particular operation upon the work placed on the fixture 10, it being within the purview of the invention to have heads 2H, 3H and 4H act sequentially upon the same points of the work as does head 1H, it becomes obvious that where holes are to be distributed throughout a complete revolution of the Work, i. e. 360 degrees, it is necessary to rotate the dial assembly D and the work supported thereon more than one revolution. Thus the purpose of the full index cam FIC is believed manifest, for its office is to make certain that each head has had the opportunity to operate through all its work cycles, and to do this the full index cam is made to rotate only one revolution for two revolutions of the dial assembly D. To provide this desired 2:1 correspondence, the cam FIC carries at one side thereof a gear section 44, preferably formed integral with the cam, which is equipped with internal gear teeth 45. Provided with gear teeth 46 of similar pitch is the collar 34, and by reason of an intermediate gear 49 rotatably carried on an angularly adjustable ring 50 by means of a pin 51, the gear section 44 is driven in a planetary fashion relative to the collar 34 which, as already described, is keyed to the shaft 25.

To permit appropriate angular alignment of the full index cam FIC with the index cam IC, the need for which will soon become more apparent, the ring 50 has a bar or arm 52 anchored thereto, the bar extending radially with respect to the ring so that the ring may be shifted relative to the collar 34. In order to effect this shifting and also to retain the ring 50 in its shifted or adjusted position, a pair of threaded studs 53 is in engagement with either side of the bar 52. The studs 53 are in turn threadedly supported, respectively, by the legs of a U-shaped bracket 54 attached to a yoke 55 which also carries a number of switches yet to be described.

From the preceding description, it is believed readily apparent thatany of the cams IC, FIC, lHC, 2H0, 3HC or 4HC may be easily replaced with another cam whenever the work schedule is to be altered. To do this, the nut 43 is first removed from the rod 37, thereby permitting withdrawal of the thrust member 35, as best understood by referring to Figure 10. In many instances, the only cam which will need changing is the programming or index cam IC, which is fastened to collar 34 by a flange of thrust member 35. If this is the situation, then quite obviously removal of the thrust member is all that is required. On the other hand, assuming the modified work schedule is so vastly different as to necessitate a changing of the cam IHC, this can being the innermost one, then all preceding cams may be quickly pulled from the shaft 25, together with the various friction rings 33, since both the intervening cams and rings only loosely encircle the shaft and may be removed without interference after the thrust member 35 has been detached. As may be seen from an inspection of Figures 1 and 2, the control MC is situated in a very convenient location, a location facilitating the above described substitutions.

Another mechanical feature playingan important part in the positioning of the dial assembly D at various. angular locations is a latch assembly L, best. viewed in Figures 3 and 4. The latch L comprises an arm 56 pivotally mounted at one end to the base B by means of a pin 56a and carrying an integral tooth 56b at its other end which is engageable with any of a series of ratchet teeth 60 disposed circumferentially around the periphery of the index plate 11. By spacing the ratchet teeth 60 at preferred increments, for example, five degrees, it will be easily understood that with a single latch L the spacing of holes in the work may be made in multiples of five degrees. Of course, any increments may be utilized, and if the hole spacing is not always to be in multiples, then additional latches L can be used which are angularly displaced so as to produce whatever spacing is desired. For instance, if a hole layout consisting of a hole at the zero or loading position of the dial assembly D is desired, one at five degrees, one at twelve and onehalf degrees, one at twenty-two and one-half degrees, etc., the second latch (not shown) would be located at some point angularly displaced from the latch L (the one shown) by an angular amount involving a two and one-half degree diiterence. As depicted, the latch L is biased into engagement with the ratchet teeth 60 by means of a spring 61 and wheneverthe dial assembly D is reversed from its forward clockwise rotation, the tooth 56b acts as a pawl to arrest at the proper point any further reverse or counter-clockwise motion. If two or more latches are utilized, provision would then be made for at times overcoming the bias of any such spring 61 so that only the particular latch which is to arrest the reverse direction of the dial assembly D at that time will do so.

Having described the salient mechanical features rather broadly, it now becomes important to correlate these mechanical features with each other so that they will perform their respective functions in the proper order. In the exemplified embodiment this is accomplished by means of auxiliary apparatus taking the form of various electrical components and associated circuitry which have been diagrammatically presented in Figure 11. As the description progresses, it will be seen that some of the electrical switches mentioned in describing the above alluded to enabling apparatus are shown in figures other than the electrical diagram, thereby better highlighting the ofiice of the mechanical devices withwhich such switches serve.

To facilitate an understanding of Figure 11, this figure will be divided into what is a three-phase power supply section PS and a single-phase electrical control section EC. The power supply PS is quite conventional and it only need be said at this time that it supplies electric power to the various motors employed in operating the drilling machine, such as the pump motor PM, the dial motor DM and those to be mentioned hereinafter. The electrical control EC is more involved, requiring a detailed description, which includes a pair of bus lines 57 supplied with voltage of a suitable value by means of a stepdown transformer 58 which has connection with the power supply PS. The bus lines 57, it will be seen, furnish electrical control power to the numerous relays and switches constituting the control circuit EC.

Before any of the motors can receive power, a relay MR must be energized and to this end there are normally open contacts 62 actuated by a start button 58 and normally closed contacts 63 actuated by a stop button in series with said relay MR, the relay MR in turn operating a first set of line contacts MR1 connecting the power supply to the various motors and a second set of contacts MR2, which second set is used in maintaining energization of the relay after release of the start button. As a condition precedent to the maintenance of the relay MR energized by contacts MR2, either a relay lCR or ZCR must be energized, these relays having contacts 1CR1 and 2CR1 in parallel with each other.

The encrgization of the relay ICR, however, is dependent upon, a latch limit switch LLS (Figures 3 and 11) being closed which can only occur when one of the ratchet teeth 60 is against the tooth 56b of the latch L. Provision is made for such closing of the latch limit switch LLS by a switch actuator 65 (Figures 3 and 4) reciprocably carried by the arm 56. Actuator 65 is biased by a spring 66 in the forward direction of rotation of the dial assembly D i. e. clockwise as viewed in Figure 3, and carries a tooth 67, shaped similarly to the tooth 5612, which is usually in extended position with the consequent result that the latch limit switch is normally open but closed when the tooth 67 is urged rearwardly by the same ratchet tooth 60 that abuts the latch tooth 56b. This position of a tooth 60, at which latch limit switch LLS is closed, defines a work performing location for dial D.

leading up to an explanation of how the relay 2CR is energized, it will be first stated that this condition can be established only when all of the heads 1H, 2H, 3H and 4H are in a fully retracted position. Accordingly, there is conventionally provided a plurality of head limit switches lHLSl, 2HLS1, 3HLS1 and 4HLSI, these switches being .so located that they will be closed only when the heads are completely retracted or fully raised in the arrangement selected for illustration.

Since, in addition to the contacts 1CR1, the relay 1CR is equipped with contacts 1CR2 in circuit with a number of solenoids, later to be referred to, instrumental in moving the heads 1H, 2H, 3H and 4H toward and from the dial assembly D, it will be appreciated when the contacts 1CR2 are open, then the solenoids cannot be energized to effect movement of the heads, and the relay ICR in. this way serves as an interlock for the entire head group inasmuch as the latch limit switch LLS must first be closed before the heads can be moved.

Naturally, if each of the heads 1H, 2H, 3H and 4H is not fully retracted, the dial assembly D should not be put in rotation, for one of the tools gripped by the heads might still be engaged with the work. To prevent this occurrence, the relay 2CR acts as an interlock for the dial D circuit, there being a second set of normally open contacts 2CR2 carried by this relay which are in circuit with a dial forward relay DFR. In addition to closing a first set of contacts DFRI, which cause the dial motor DM to rotate in a forward direction to drive the dial D in a clockwise manner as viewed in Figure 2, the DFR relay also has two other sets of contacts DFRZ and DFR3, the DFRZ contacts serving to maintain the DFR relay and the DFR3 contacts being opened when relay DFR is energized to open the reversing circuit of dial motor DM and interlock the dial motor DM against reverse rotation at this time.

Focusing attention now on the part played by the index cam IC, the contour of this cam can be seen from an inspection of Figure 7 where it will be noted that the periphery is provided with a number (eight in this instance) of small lobes or bumps 69 equal in number to the number of work stations desired. As best shown in Figure 8, the cam IC is engageable with a dial limit switch DLS which is actually a single pole double throw switch but which for convenience is shown in Figure 11 as two sets of switch elements DLSl and DLS2, switch DLS being spring biased so that DLS1 is normally closed and DLSZ is normally open. As seen from Figure 8, the switch DLS is attached to a small base plate 68, which is in turn adjustably mounted on the yoke 55 to permit positioning of this switch so that its elements DLSl and DLS2 will be properly actuated. When the switch DLS is engaged by any of the lobes 69, the elements DLS1 will be opened and the other elements DLSZ will be closed. This stops the dial mot-or DM, since the contacts DLSI are in series relation with the dial forward relay DFR, the energization of which the motor DM is dependent upon for running forwardly. In the exemplified embodiment, as stated above, it is desired to stop the dial assembly D eight times during the course of one complete revolution; in

7 7 other words, there will be eight illustrative work positions or angularly spaced points at which the heads will perform machining operations.

Still another set of contacts 2CR3, normally closed, is associated with the relay 2CR, these contacts being in series with the dial limit switch contacts DLS2 and a relay 30R, the purpose of which is to insure a single index at each position into which the dial assembly D is indexed. Owing to this desideratum the relay 3CR is equipped with a first set of contacts 3CR1 in circuit with the contacts 2CR2, and because of the presence of the contacts 3CR1 the relay SCR must be energized by the closure of the dial limit switch contacts DLSZas is the situation when one of the lobes 69 is in contact with the switch DLS.

There is a run switch 70 possessing four sets of contacts 71, 72, 73, and 74 which also must be moved to on position before the relay DFR can be energixed, for the contacts 71 are in series therewith. When the run switch is in off position, the contacts 72 are closed and then by virtue of a jog forward switch 75 the dial assembly D may be manually inched into any desired angle of rotation.

As already stated, while the dial assembly D is to be moved bi-directionally, only one such direction is possible at a time-hence the normally closed contacts DFR3 which are in series with a dial reverse starter DRR equipped with contacts DRRl for reversing the dial motor DM and normally closed contacts DRRZ for interlocking this starter with the forward side of the starter DFR. Also included in series with the relay DRR is a set of contacts 76 actuated into open position whenever the start button 53 is depressed to close the contacts 62. Normally closed contacts 3CR2 belonging to the relay SCR are also included in this branch of the circuit as are contacts ITRI belonging to a time delay relay ITR which is in circuit with the contacts ZCRZ and SCRI. The purpose of the time delay relay ITR, it may be pointed out, is to deenergize the dial reverse relay DRR after the dial assembly D has engaged the latch L (Figure 3). While the relay lTR ceases to be energized upon the opening of the dial limit switch contacts DLSI, nevertheless it will be appreciated that its contacts l'l'Rl remain closed for a sufiicient length of time to assure that the index plate 11 has engaged the latch L. Finally, as

far as the relay DRR is concerned, the contacts 73 of the run switch 7d are included in circuit therewith and by means of a jog reverse switch 77 the dial motor DM may be equally well inched in a reverse direction to rotate the dial assembly D in a counterclockwise direction when viewed in Figure 2.

As is evident from Figures 9 and 10, taken together with the electrical diagram of Figure 11, a group of limit switches IHCS, ZHCS, EHCS and i-HCS is arranged so that each switch is actuated by one of the head control cams TtHC, 2HC, 3HC or 4H0 These switches are all. biased to open position, the cams permitting the switches to open whenever a notch, such as the notch 79 which is visible only on the head control cam SHC (Figure 9), comes into registry therewith. The purpose of the various switches IHC-S, 2HCS, 3HCS and 4HCS is to immobilize or render inactive any of the heads 1H, 2H, 3H, or 4H by means of circuitry now to be described. It might be mentioned at this time, though, that in some instances it will be desirable to inactivate a head at some of the work performing positions of the dial assembly but not others, and in such situations more than one notch would be relied upon, the number on each cam depending upon the particular hole pattern. To facilitate the present discussion, it will be assumed, for the sake of simplicity, that each of the head control cams lHC, ZHC, 3HC and 4HC is constructed with only one notch each, Serially connected in circuit with each switch IHCS, ZHCS, 3HCS and 4HCS is an equal number of relays IHCR, ZHCR, SHCR and 4HCR, these relays each having two smash 8 sets of contacts, one normally closed and the other normally open, which have been given the character designations 1HCR1, 1HCR2; 'ZHCRI, ZHCRZ; 3I-ICR1, 3HCR2 and 4HCR1, 4HCR2, respectively.

A double throw limit switch FIS (Figures 7 and 11) actuated by the full index cam FiC is in circuit with the four switches 1HCR1, ZHCRl, 3HCR1 and 4HCR1. As may be seen in Figures 7, there is provided a notch 80 on the periphery of the cam FIC which permits the switch FIS to be in the normal position (the lower position shown in Figure 11), closing the circuit connecting contacts 127 and 124 only when the cam is in the position pictured in Figure 7, which position, because of the 2:1 ratio of this cam with the dial D, occurs only once every other revolution of the dial. In this switch position a circuit is possible through contacts 81 of a cycle switch 82 and a stop block limit switch 83 which by virtue of a block 78 located on the cam lI-IC closes said stop block limit switch at the zero position of this cam and thereby energizes a relay 40R, the primary purpose of which relay is to close a set of contacts 4CR1. By closing the contacts 4CR1 a solenoid 84 becomes energized to retract a latch 85, mounted on the yoke 55, from obstructive engagement with a keeper portion 86 of the block 78 affixed to one side of the head control cam THC (Figure 10). This releases the first head control cam IHC for rotation with shaft 25. A second set of contacts 4CR2 serves to maintain the relay 4CR. On the other hand, when the full index limit switch FIS is moved into its other position, i. e. the upper position in Figure 11, by the cam PIC, 21 different electrical path is established, this being through a full index relay FIR, assuming that a set of contacts 86 carried by a selector switch member 87 is closed. More will be said shortly about this selector switch. The relay FIR has a first set of contacts FIRE. in shunt with the dial limit switch contacts DLSZ and a second set of contacts FIR2, these latter contacts being normally closed and in series with the contacts 4CR2.

Before proceeding with a detailed discussion of the circuit components which are instrumental in activating the heads 1H, 2H, 3H and 4H, it should be explained that these heads may be powered by any suitable means, such as an electric motor or by pneumatic means. In this connection, it is to be observed from Figures 1 and 2 that a motor lHM, ZHM, 3I-IM and 4HM is supported atop each head and is drivingly connected with a collet spindle 89 for rotating a tool (not shown) held at its lower end. Accordingly, the heads might be also reciprocated by these same motors, if desired, through the medium of appropriate lead screws, but for the purpose of descriptive simplicity it will be assumed that pneumatic means effect the requisite reciprocation for the drilling operations to be performed. Therefore, as seen in Figure 11, a series of solenoids IHD, IHU; ZI-ID, ZHU; 3HD, SHU and 4HD, 4I-IU, the HD or down group of solenoids controlling an undisclosed air valve to lower independently the various heads and the HU or up group of solenoids effecting at raising thereof It electric motors are used, then the above identified solenoids would control reversing switches instead of the pneumatic means alluded to. Since both types of head powering means are conventional, it is thought unnecessary to enlarge further upon either.

By reason of a relay SCR and a plurality of contact sets SCRl, 5CR2, 5CR3 and 5CR4 each of the solenoids IHD, 2I-ID, SHD and 4H1) may be conditioned for energization, but before energization can happen a relay 6CR must be first energized inasmuch as the relay 6CR is equipped with a first set of normally open contacts 6CR1 in series therewith and the latch limit switch LLS. To energize the relay 60R, however, a set of con tacts 2TR1 must be closed, these contacts being controlled by a time delay relay ZTR in circuit with the head limit switches 1HLS1, ZHLSI, 3HLS1 and 4HLS1. The need for the contacts 2TR1, which stay closed for a prescribed time after de-energization of the relay 2TR, will soon be better understood, for without this time delay some of the heads which are supposed to cycle might not have started on their downward journey and could not if the opening of the contacts 2TR1 were premature.

The relay GCR is maintained by a set of its own contacts 6CR2, but initially these contacts are by-passed by a set of contacts 90 carried by the cycle switch 82, the contacts 90 in turn having in circuit a set of normally closed contacts 3CR3 on the relay 3CR. Also, in parallel with the contacts 6CR2 is a set of normally open contacts DRR3. To complete the circuit in which the solenoid 1I-ID is in, there is included contacts 4CR3 associated with the relay 4CR, and shunting these contacts is a set of contacts 1HCR2, which contacts will be closed whenever the head control switch lHCS is closed, such :a condition happening only when the notch in the head control cam lHC has passed out of registry with said switch IHCS.

The head 1H is retracted automatically owing to the presence of additional limit switches 1HLS2, 2HLS2, 3HLS2 and 4HLS2 which are mounted near the lower end of the head stroke. A time delay relay TRA, controlling contacts TRAl, is in circuit with the head limit switch 1HLS2 and postpones the energization of the solenoid IHU until the head 1H has abutted against a full travel stop, thereby permitting the hole, being drilled to be thoroughly cleaned out.

As stated earlier, the head control cams 1HC, 2HC, 3HC may be selectively restrained from rotation in unison with the shaft 25. It has already been explained, in this connection, how the first cam 1HC is released. Rotation of the second cam 2HC is inaugurated by the first cam after said first cam has traveled a predetermined rotative amount, there being a block 91 on the cam lHC which engages a block limit switch 92 in circuit with a relay 7CR which by virtue of a set of contacts 7CR1 causes energization of a solenoid 93. The solenoid 93 is in turn mechanically connected to a latch 94, ordinarily in obstructive engagement with a keeper 95 on the head control cam 2HC, retraction of the latch effecting release of the cam. The relay 7CR is capable of maintaining itself through a set of its own contacts 7CR2 and is additionally provided with contacts 7CR3 in circuit with solenoid ZHD. The contacts 7CR3 may be by-passed, however, by contacts 2HCR2 on the relay 2HCR.

The release of the head control cam 3HC is similarly effected, since a block 96 is carried at a preferred location on the cam 2HC, the cam being capable of engaging a limit switch 97 in circuit with a relay SCR which by virtue of a set of contacts 8CR1 causes energization of a solenoid 99. The solenoid 99 is in turn mechanically connected to a latch 100 biased into obstructive engagement with a keeper 101 on the head control cam 3HC, the cam to be released. For the purpose of maintaining the relay SCR energized there is a set of its own contacts 8CR2, and further contacts 8CR3 on this relay are in the same circuit with the solenoid 3HD. Shunting the contacts 8CR3 are contacts 3HCR2 on the relay 3HCR.

The release of the fourth cam 4HC is likewise accomplished in the above described manner, there being a block 102 carried at a particular location on the cam 3HC. In the path of the block 102 is a limit switch 103 containing in circuit therewith a relay 9CR which by reason of a set of contacts 9CR1 produces energization of a solenoid 104 mechanically connected to a latch 105. The latch 105 is spring urged into obstructive engagement with a keeper 106 mounted on the head control cam 4HC, but which latch is disengageable from said keeper when the solenoid 104 is energized. For maintaining the relay 9CR is a set-of contacts 9CR2, and

further contacts 9CR3are in circuit with the solenoid 4HD. Paralleling the contacts 9CR3 are contacts 4HCR2 on the relay 4HCR. While the several relays 7CR, 8CR and 9CR are capable of maintaining themselves through their respective contacts 7CR2, 8CR2 and 9CR2, provision is made for the initial energization of the above alluded to relays in the form of a relay R in circuit with the latch limit switch LLS, this relay operating when energized to close its three sets of contacts 10CR1, 10CR2 and 10CR3.

By. referring specifically to Figure 9, it will be seen how the various blocks 91, 96 and 102, as well as the keepers 86, 95, 101 and 106, are retained in a preferentially adjusted angular position on their respective cams. To this end, there is an annular rib 88 of tapered cross section on either side of each cam lHC, 2HC, 3HC and 4HC, and by providing a complemental groove in each block and keeper the several blocks and keepers are circumferentially tracked during any adjustment thereof. After adjustment, tightening of suitable setscrews 98 against the outer arcuate face of the ribs 88 secures the blocks 91, 96, 102 and keepers 86, 95, 101 and 106 firmly in place so that the cams controlled thereby will be properly released.

Because of the use of four heads 1H, 2H, 3H and 4H, the specific control for raising the heads 2H, 3H and 4H duplicates that of the head 1H. Accordingly, it will be appreciated without further explanation that the limit switches 2HLS2, 3HLS2 and 4HLS2 correspond in function to the limit switch 1HLS2, whereas the time delay relays TRB, TRC and TRD are analogous to the relay TRA, these relays having normally open contacts TRBI, TRCl and TRDl, respectively.

Included as a part of the selector switch 87 is a set of switch elements or contacts 107 which are in a serial relation with a relay 11CR for returning all of the heads to raised or out position, and for this reason the relay is equipped with a series of contacts 11CR1, 11CR2, 11CR3 and 11CR4 each in circuit with a respective solenoid lHU, ZHU, 3HU and 4HU which, when energized, operate to raise the heads. Theswitch 87 supports another set of contacts 108 which are moved to open position when the contacts 107 are closed, thereby to de-energize the relay 3CR. Also, it is possible to lower the heads manually by means of a switch generally designated by the reference numeral 109 if the heads are otherwise conditioned or primed with the exception of the contacts 5CR1, 5CR2, 5CR3, 5CR4, which latter are merely shunted owing to a group of contacts 110, 111, 112, 113, 114, 115, 116 and 117, each in series with one of the head solenoids.

Since the purpose of the selector switch 87 is an emergency one, returning the heads 1H, 2H, 3H and 4H immediately to their retracted location when the selector switch is turned to its off position, it of necessity carries a number of switch elements besides those already referred to. These further elements include contacts 119 in series with the limit switch contacts DLS2 and the relay 3CR, contacts 120 paralleling the contacts 119 and having in circuit therewith a set of normally open contacts 3CR4 which shunt the normally closed contacts 2CR3 and contacts'121, these last contacts being capable of placing the relay 3CR in series with the latch limit switch LLS thus circumventing the dial switch contacts DLS2. However, before this latter condition can occur a dial positioner switch 122 must be closed, since the switch 122 has a set of contacts 123 in series with the contacts 121 as well as contacts 124 in circuit with still further contacts 125 carried on the selector switch 87. To insure against the solenoids lHD, 2HD, 3HD or 4HD ever being energized simultaneously with the solenoids lHU, 2HU, 3HU and 4HU, these being the solenoids which raise the heads, when the selector switch is turned to off position a relay 12CR is connected so as to be 11 energized due to the fact that the contacts 107 of the selector switch are thus closed. To this end the relay is provided with normally closed contacts 12CR1 which interrupt the circuit to the relay SCR. During this event the dial is prevented from indexing inasmuch as the contacts 119 de-energize relays 3CR with the concomitant opening of the contacts 3CR1 in the dial forward circuit.

Sometimes, after drilling a partial number of holes, it becomes expedient to bring the dial assembly D and together therewith the various cams IC, PIC, lHC, ZHC, 3HC and 4HC, back to zero or loading position. An occasion for such action might stem from the ruining of a work piece, necessitating the replacement thereof with a new one. Naturally, a waste of time would ensue if the heads went through their respective work cycles, so in order to accomplish directly this aim, the machine is equipped with a cam reset" switch 126 which is provided with contacts 127 in series with the various contacts lHCRl, 2HCR1, 3HCR1 and 4HCR1 and contacts 129 in series with contacts 12CR2 of the relay 12CR. Also included as a part of this switch 126 is a set of contacts 130 for shunting the contact 86 of the selector switch 87.

On the other hand, perhaps upon inspection the work piece is found to still be usable, requiring only the extraction of a broken drill or possibly a weld, so under these circumstances when the trouble has been remedied, the work must be returned to the angular position at which the mishap occurred. To return the dial D to the particular rotated work position at which the cam reset switch was actuated in bringing the dial assembly to its zero or loading position, the cam reset switch 126 is returned to its automatic position and the dial positioner switch 122 is depressed until the required number of indexes or work positions have been passed. Release of the dial posi'tioner switch button and the return of the selector switch 87 back to run position conditions the circuit for actuation of the cycle switch 82 which will then cause the heads to operate through one cycle and the machine to then continue on automatically as before the cam reset switch 126 was originally moved.

Up to this point nothing specific has been said about the control of the head motors lI-IM, ZHM, 3HM and 4HM. However, it will be pointed out that this control is quite conventional and it is thought only necessary to state that the various contacts hi and lo are operated by relays capable of selective energization so as to produce either a high or slow speed rotation of the collet spindles 89 which hold the drilling tools.

Operation As a basis for understanding the operation of the aforedescribed drilling machine, an exemplary hole layout will first be assumed. In the course of the preceding description, four heads 1H, 2H, 3H and 4H have been referred to. Obviously, there are a number of machining operations that could be carried out through the use of these heads, for the purpose of illustration, it will be assumed that the head 1H carries a drilling tool of a relatively small diameter, the head 2H carrying a larger drill for counterboring the holes produced by the first head 1H, the head 3H having a reamer mounted thereon corresponding in size to the drilling tool supported by the head 2H, and the head A H supporting a rearner of the proper size for finishing the small holes drilled by the first head 1H. Further, it should be clearly understood that the heads need not be arranged vertically as pictured in Figure 1 for in some applications one or more of the heads could be in the same general plane of the work supported for rotation atop the dial assembly D. In this latter situation, the heads in the plane or the work would be for the purpose of drilling holes radially into said work. However, it is thought that the description is somewhat simplified by having all of the heads arrayed vertically rather than both vertically and horizontally.

Proceeding now to the description of the operation possible with the particular number of heads shown, after the main switch in the power source circuit PS has been closed, the first procedural step consists in pressing the start button 58 thereby closing the contacts 62 and opening the contacts 76, since these two sets of contacts are mechanically interlocked together. If the dial assembly D is at its zero or loading position, in which position the index plate 11 has been so positioned that one of its teeth 60 will be hard against the ratchet tooth 56b of the latch L, then, of course, the latch limiting switch LLS will be closed and the relay 1CR will have been picked up to close the contacts lCRl. Also, if each of the heads 1H, 2H, 3H and 4H is fully retracted, then the limit switches lHLSl, ZHLSl, 3HLS1, 4HLS1 will be closed energizing the relay ZCR thereby closing the contacts 2CR1. The closure of either the contacts 1CR1 or 2CR1 establishes a circuit through the contacts MR2 when the relay MR is energized by the pressing of the start button 58 as above mentioned. The contacts MR2 are instrumental in maintaining the relay MR in energized condition, the relay MR also closing the main line contacts MR1 which supply power to the pump motor PM and also to the other motors if their individual contacts are closed.

Under these particular operating conditions, the dial limit switch DLS is engaged by the first lobe or bump 69 on the index cam IC thereby opening the contacts DLSl and closing the contacts DLS2, as shown in the electrical diagram. The opening of the contacts DLS precludes the energizing of the relay DFR and therefore the dial D is immobilized.

However, by pressing the cycle button 82, the relay 6CR is picked up through the contacts 90 and the normally closed contacts 3CR3 which are in circuit with the contacts 2TR1 of the relay 2TR. Since the relay 6CR is equipped with normally open contacts 6CR1, the energization of this relay will cause the contacts to close whereby a circuit is established through the relay 5CR having in series therewith the latch limit switch LLS. The latch limit switch LLS being closed by the index plate 11 of the dial assembly D abutting against the latch L, through the medium of the relay 5CR the various contacts SCRl, 5CR2, 5CR3, 5CR4 become closed, which contacts are in circuit with the solenoids IHD, ZHD, 3HD, 4HD. As thus described, the various solenoids which cause the heads 1H, 2H, 3H, and 41-1 to move toward the dial assembly D are only partially conditioned for energization, energization not yet taking place. Since the contacts 1CR2 are closed when the latch limit switch LLS is closed by virtue of the relay 1CR being in circuit with this limit switch, then all that has to be accomplished to produce an energization of the first solenoid lHD is to have the contact 4CR3 closed.

Coming now to the energization of the relay 4CR which carries the contacts 4CR3, which, as stated in the paragraph above, must be closed in order to complete the circuit in which the solenoid lHD is included, it will be observed that the stop block limit switch 83 is closed by virtue of the fact that the block 78, which is mounted on the head control cam IHC, is angularly positioned so that when this head control cam is in its zero position corresponding to the loading position of the dial assembly D, then the stop block limit switch is urged into closed position. It is thought quite apparent that the circuit through the relay 4CR is then by way of the limit switch 83, the contacts 81, the full index limit switch PIS, the contacts 127, and the various contacts IHCRI, ZHCRI, SHCRI, 4HCR1. At this time, it should be pointed out that the full index switch P15 is in its lower position due to the fact that the full index cam PIC is in its zero position, which position brings the notch in registry with said switch FIS, as shown in Figure 7, the notch permitting the switch to assume the particular position in which it is pictured in the electrical control circuit EC. The energization of the relay 4CR in addition to closing the contacts 4CR3 also closes the contacts 4CR1 which are in series with the solenoid 84, this solenoid retracting the latch 85 and disengaging it from the keeper 66 to thereby permit the cam IHC to be rotated with the shaft 25' when the shaft 25 is later rotated by the dial assembly D through the associated gearing 21 and 22.

The function of the relay 4CR with which we are most concerned at the moment is the closing of the contacts 4CR3. Having closed these particular contacts, the solenoid IHD is energized and causes the head 1H to be propelled toward the work held in place on the fixture which is part of the dial assembly D. It will be assumed, of course, that the head motor 1HM, as well as the head motors ZHM, 3HM, 4HM, is in rotation at this time, although only the head IE is lowered into engagement with the work to perform the first machining operation. .As previously stated, this first machining operation in the exemplified arrangement consists in drilling a hole of a relatively small diameter. After the head has reached the lower limit switch 1HLS2, the head 1H is permitted to continue in its work performing direction even though the limit switch 1HLS2 has been closed. The reason for this centers around the desirability of having the head reach a solid stop in order to assure that a clean hole will be produced. Owing to this desideratum, as previously brought out, a time delay relay TRA is incorporated into the circuit with the limit switch 1HLS2, and while the relay TRA is immediately energized upon the closing of this limit switch, nonetheless its contacts TRAl remain open for a predetermined time before they close, causing the solenoid IHU to be energized and thereby retract the head 1H. It will be recalled that pneumatic means were decided upon as the particular actuating mechanism for the various heads 1H, 2H, 3H, 4H, and, therefore, the solenoid 1HU is utilized to actuate an air valve in a direction opposite to that which the solenoid 1HD moves this undisclosed air valve. The head 1H upon completing its cycle closes its upper limit switch 1HLS1 and since the other heads have not as yet been put through their respective cycles, the limit switches 2HLS1, 3HLS1 and 4HLS1 associated therewith have remained closed so that only the closing of the switch lHLSl is necessary to energize both the relay 2CR and the relay ZTR. While the function of the relay ZTR has already been referred to in the general description preceding the operational description, even more will be said about this relay in conjunction with the operation of the subsequent heads.

During the first work cycle of the head 1H, the relay ZCR was of course de-energized by the opening of the limit switch lHLSl and through its set of normally closed contacts 2CR3 caused the immediate energization of the relay 3CR inasmuch as the switch contacts DLS2 of the dial limit switch DLS were closed by the dial assembly D being against the latch L. Once the relay 3CR was energized in this manner, it maintained itself through its contacts 3CR4.

With the relay ZCR again energized, the machine is now ready for a forward indexing movement of the dial assembly D and to effect this, the relay DFR, which is responsible for precipitating a forward rotation of the dial becomes energized through the medium of the contacts 2CR2 and the contacts 3CR1. In this way, the dial assembly D is put into rotation and the particular tooth 69 which has been in abutting engagement with the pawl tooth 56b of the latch L moves away from said tooth 56b thereby permitting the latch limit switch LLS to open. This action causes the relays ICR and SCR to be (file-energized promptly and concurrently therewith the relay 3CR is de-energized, since the dial limit switch contacts DLS2 are open by the passing of the first lobe 69 on the index cam 1C from registry with the dial limit switch DLS.

Since the contacts DLS1 of the limit switch DLS are closed by the movement of the first lobe 69 out of registry with the dial limit switch DLS, these contacts are closed to cause a continued energization of the dial forward relay DFR even though the contacts 3CR1 open due to the de-energization of the relay 3CR. In the exemplified embodiment, the index cam IC has been provided with eight lobes or bumps 69 and thus we are desirous of effecting the drilling of eight holes at spaced intervals of fortyfive degrees. Accordingly, no more holes will be drilled by the head 1H until the dial assembly D has been rotated this angular amount. However, when the second lobe 69 comes into registry with the dial limit switch DLS, the dial assembly D will once again be stopped for the drilling of a second hole by the first head 1H for at this moment the circuit to the dial forward relay DF will be opened by reason of the switch contacts DLS1 having been opened by the second lobe 69.

Before continuing with the detailed description of how the dial assembly D is stopped and simultaneously reversed, it should be made apparent that the block 91 on the side of the head control cam lHC has been angularly disposed so that this block will have closed the block limit switch 92 to condition the relay 7CR for energization when the latch limit switch LLS is again closed and the closure thereof produces an energization of the relay NOR and its contacts 10CR1. The block 91 which effects the closing of the block limit switch 92 need be only arranged so that the block limit switch 92 is closed just prior to the stoppage of the dial assembly D, the head control cam IHC being rotated in unison, that is, in a 1:1 correspondence with said dial.

Returning now to the stoppage of the dial assembly D, owing to the opening of the switch contacts DLS1, it will be observed that the normally closed contacts DFR3 are again closed when the relay DFR is energized, and, since the contacts DFR3 are in circuit with the dial reverse rotation relay DRR, this reverse rotation relay is energized by the completion of a circuit through the contacts 1TR1 and the contacts 3CR2 together with the normally closed contacts 76 of the start button 58 and the contacts 73 of the run switch 70. Also, it is to be noted that the opening of switch contacts DLS1 are instrumental in causing the tie-energization of the time delay relay ITR, this time delay relay controlling the contacts 1TR1 in such a manner as to have the opening of the contacts 1TR1 delayed sufficiently so that the motor DM will drive the dial assembly D far enough in a reverse direction so that the proper tooth on the index plate 11 will have abutted against the pawl tooth 56b positioned on the latch L. By virtue of the slipping of clutch 19, the running of the dial motor DM for a short time after the engagement of the index plate 11 with the latch L will not be injurious to any of the parts, the time delay of the contacts 1TR1 opening the circuits to the relay DRR shortly after the index plate 11 has been arrested in its backward or reverse movement.

As was the status of the parts when the descriptive operation was started, the latch limit switch LLS is again closed by a particular tooth 60 coming into contact with the latch L, in this Way completing a circuit to the relay SCR which in turn closes all of the contacts SCRI, SCRZ, 5CR3 and 5CR4. Although the stop block limit switch 83 is not closed at this time as was the situation when the head control cam IHC was in its zero position, it being remembered that this cam was released for rotation with the shaft 25, nevertheless it is not necessary at this time to energize the relay 4CR, since the head control switch lHC has been closed by the rotation of the head control cam 11-10 to energize the relay IHCR, thus causing the contacts ll-ICRZ to be closed. In this manner, on the second cycle of the head 1H, the solenoid 1HD which produces travel of the first head toward the work is energized through the contacts SCRI and the contacts 1HCR2, the contacts 1CR2 having again been closed by reason of the relay 1CR being energized through the latch limit switch LLS. In this connection, it might be emphasized at this point that the witch IHCS is only open when the notch in the head control cam IHC is in registry therewith which only happens when this particular head control cam is at its zero position. At all rotated positions of the exemplified cam lHC, the switch lHCS will be closed and thus the contact llI-ICRZ will likewise be closed since they are controlled by the relay lI-ICR.

As yet, the switch ZHCS associated with the head control cam ZHC has not been closed since the cam 2H has not been permitted to rotate and its notch is still in registry with the switch ZHCS. However, the relay 7CR has been conditioned for energizati-on by the closure of the block limit switch 92 and when the contacts IGCRI become closed due to the fact that the relay lflCR is again energized by the closure of the latch limit switch LLS, then the relay 7CR picks up its contacts "/CRS so that the solenoid ZHD which causes the head 21-1 to be started is effected through the contacts SCRZ and the contacts 7CR3. Thus, the head 2H starts on its journey toward the dial assembly D together with the head 1H. Obviously, since a hole spacing of forty-five degrees is desired, the sec-nd head 2H is angularly positioned relative to the first head so that there is an angular difference of the requisite forty-five degrees. Also, it will be recalled from the general description of the teeth 66 that these teeth in the exemplified embodiment are spaced at intervals of five degrees, thereby permitting the dial to be positioned precisely forty-five degrees from the position from which it assumed when the first hole was drilled, to be exact, nine teeth having passed by the latch tooth 56b during the rotation of the dial assembly D through forty-five degrees.

The heads 1H and 2H accordingly are moved toward the work placed on the dial assembly D and the head 1H drills its second hole while the head 2H performs a counterboring operation on the first hole which has been moved into juxtaposition therewith. The retraction after the counterboring operation has been performed by the second head 21-1 is identical with the retraction employed in conjunction with the first head 1H. Stated otherwise, the limit switch 2HLS2 corresponds in function with the limit switch lHLSZ and the time delay relay TRB, together with its contacts TRBl, corresponds to the time delay relay TRA and its associated contacts TRAl.

After retraction of the two heads 1H and 2H, the first from its second cycle and the second from its first work cycle, each of the limit switches 1HLS1, 2HLS1,

3HLS1 and 4HLS1 will then be closed so that the relay ZCR will again have closed its contacts ZCRZ. The contacts 3CR1, which must be closed in order to complete the circuit which energizes the dial forward relay DFR, have already been closed by virtue of the fact that the relay 3CR has been energized, holding itself in by means of the contacts 3CR4. Thus the dial assembly D runs in a forward direction to place the first hole, which has now been both drilled and counterbored, beneath the third head 3H.

As with the first two heads 1H and 2H, the dial assembly D is stopped in its forward movement by means of the third lobe 65 on the index cam IC. However, just before this occurrence, the block 96 comes into registry with the block limit switch 97 to thus condition or prime the relay 8CR for energization when the contacts 10CR2 are soon closed, as will happen when the latch limit switch LLS is closed by another reverse rotation of the dial assembly D. As in the preceding releases of the head control cams IHC and ZHC, the block 96 is positioned on the cam ZHC at such a location that the release of the third cam SHC will occur at the proper moment, that is, just prior to the stopping of the dial assembly by the third lobe 69 opening the contacts DLSl.

In addition to effecting the retraction of the latch via the energization of the solenoid 99 when the contact 8CR1 are closed, the relay 8CR further closes the contacts 8CR3 so that when the contacts 5CR3 are closed by the energization of the relay SCR the third head 3H will be started on its particular work cycle. As explained earlier, the third head is intended to perform a reaming of the counterbored holes formed by the head 2H. Since the switch ZHCS is closed by the rotation of the head control cam 2HC, this being possible due to the above alluded to release of this head control cam, the relay ZHCR becomes energized after the notch has passed out of registry with said switch ZHCS to close the contacts ZHCRZ just as the switch lHCS eflected the closing of the contacts 1HCR2. Therefore, when the third head 3H proceeds toward the dial to produce a machining operation, the heads 1H and 2H also travel downwardly to effect concomitantly the same operations previously described. The three heads 1H, 2H and 3H will be returned to their retracted positions by their repective engagements with the lower limit switches 1HLS2, 2HLS2, and 3HLS2, the time delay relay TRC functioning just as the previously described relay TRA and TRB function.

When the heads 1H, 2H, and 3H have been fully retracted, then, of course, each of the limit switches ll-ELSE, ZHLSI, 3HLS1, and 4HLS1 become closed, the latter switch not as yet having even opened, and the relay ZCR becomes energized to close its contacts ZCRZ. Due to the fact that the contacts 3CR1 have already been closed owing to the energization of the relay 3CR when the switch contacts DLSZ were closed by the third lobe 69, it will be seen that the dial forward relay DFR, is once again energized so that the dial motor DM drives the dial D through another forty-five degrees of rotation.

The block 102 carried by the third cam 31-1 is instrumental in closing the block limit switch 103 just prior to the fourth lobe 69 coming into registry with the dial limit switch DLS. This, of course, conditions the relay QCR so that when the relay 10CR is energized again by the closure of the latch limit switch LLS then the sole noid 104 will be energized through the contacts 9CR1 to retract the latch 105 from its keeper 166. Of course, as in the previous three occurrences, the latch limit switch is closed by the dial assembly D being driven in a reverse direction due to the energization of the dial reverse rotation relay DRR.

The fourth head 4H, which reams the holes drilled by the first head 11-1, is placed in operation by means of the contacts 9CR3 closed by the energization of the relays 9CR plus the closing of the contacts 5CR4 which are closed because of the energization of the relay 50R accomplished when said latch limit switch LLS is closed. Thus the fourth head 4H starts on its first work cycle, together with the other heads now on repeat work cycles. In like manner, the fourth head is retracted by the closing of the lower limit switch 4HLS2 as the fourth head approaches its lowermost position.

From the foregoing description, it is believed that the duty of the relay ZTR has been clearly manifested, but to make certain that the otlice of this relay is completely understood, it will be mentioned at this time that it is necessary to delay the opening of the contacts ZTRi after deenergization of the relay ZTR by the opening of any of the limit switches lHLSll, ZHLSI, SHLSl,

and 4HLS1 because, when, say, all four heads or at least more than one head are to start on their downward excursions, the contacts 2TR1 without some delay would immediately open when the relay 2TR becomes deenergized by the first head switch that might open, whether it be switch lHLSl, 2HLS1, 3HLS1 or 4HLS1, without the assurance that all of the heads that are supposed to have started on their downward excursions have done so. By having a time delay provided, the relay 6CR is maintained, and consequently, the relay 5CR,

since the contacts 6CR1 controlled by the relay 6C1; are in series with this latter relay SCR. This-'result'i's desired inasmuch as the limit switches IHLSI, ZHLSI, 3HLS1, 4HLS1 obviously cannot be positioned accurately enough so that they all open simultaneously, a certain amount of overtravel being involved relative to each switch. Stated briefly, the relay 6CR cannot be permitted to become de-energized immediately, for its contacts 6CR1 would cause the relay SCR to drop out, thereby opening the various contacts CR1, SCRZ, 5CR3 and 5CR4 which must be closed before any head can start on its work cycle.

Once again, after the various heads have been fully retracted, this time the retraction including all four heads, the dial assembly continues to be indexed by operating sequentially in the foregoing manner until it has made one complete revolution. More specifically, when the fifth lobe 69 reaches the dial limit switch DLS all of the four heads will be put into operation, since at this time the switch l-HCS will be closed, thereby energizafter the foregoing part of the automatic operation until it has" actually made two complete revolutions. To understand this, attention is directed to the normally closed contacts IHCR, ZHCR, 3HCR, and 4HCR which continue to maintain the ful'l'index relay FIR in an energized state until the full index limit switch PIS has been moved from its upper'angular position in Figure ll back to its lower position, an event that can happen only by means of the full index cam PIC having made one full revolution. Because of the 2:1 reduction, a full revolution of cam FTC can be completed only after two full revoluing the relay 4HCR and, of course, closing the contacts 4HCR2. Since these operations are sheer repetition of each other, there is no necessity of referring to each work cycle in detail. However, once the head cam 1I -IC has made one complete revolution, its. notch will be returned into registry with the switch IHCS, and, as previously stated, this notch permits the switch lHLS to open, thereby de-energizing the relay lHCS, for during one complete revolution of the head cam. this relay has been energized. The de-energization of the relay lI-ICR, of course, causes the contacts IHCRZ to open and since the full index limit switch P13 is still in its upper position as viewed in Figure 11, the return of the block 78 to its registered position with. the stop blocklirnit switch 83 is ineffective to again energize the relay 4CR. It will be recalled that the full index cam FIC whichis associated with the full index limit switch P18 is driven in a 2:1 correspondence with the dial assembly D and also in this same ratio withrespect to the various earns IC, IHC, ZHC, 3HC, and 4HC. 86 restrains further rotation of the head control cam lHC and it is thereby rendered inactive. Of course in this connection, it will be appreciated that the head 1H has performed all of the drilling operations thathave been expected of it since thedial assembly D has made one full revolution and the head control cam 1'HC has been driven in unison therewith due to the fact that no more drilling operations are expected of the first head 1H. It will be quite apparent that this cam should no longer rotate inasmuch as any rotated position of the cam IHC will be effective to close the contacts 1HCR2, these contacts being actuated by the relay IHCR which is in turn energized by the closing of the switch lHCS whenever the peripheral notch on the cam lHC is out of registry with said switch lHCS.

The second head control cam 2H, of course, continues to rotate until it has made one complete revolution and opens the switch ZHCS by virtue of its notch coming into registry therewith. In the same manner that the head 1H became de-activated, the headZH becomes deactivated. By this time though, the dial assembly D has rotated forty-five degrees more than a full revolution so that the head 2H has had a chance to perform acounterboring operation on the last hole drilled'by-the head .1H. Similarly, the head 3H is rendered immobile ass ve bythehead control cam 3H0 having made onerevolution-thereby permitting thehead 3H to effectra reaming operation on the-last hole counterbored by the second head 2H. Likewise, when the head control cam.,4 I lC has completed one revolution, the sWitchAHCS- opens and prevents any further cycling of this fourth head, the fourth head in this way reaming the last hole drilled by the first head-1H.

- However, the dialassembly D does not stop rotating In this way, the keeper tions of the. dial assembly D. Even though the various lobes 69 on the index cam IC continue to open and close the switch contacts DLSZ of the dial limit switch DLS, nevertheless the dial fails to index as it is being returned to its original loading station because the relay FIR causes its contacts MRI to shunt or short circuit the switch contacts DLSZ. The shunting of the switch contacts DLS2 cause continued 'energization of the relay 3CR without having to have the energizing current course through the switch contacts DLS2.

Obviously, when the dial assembly D has been brought back toits starting position, having made two complete revolutions, it is in readiness for another indexing program. :If -another piece of work is thereby drilled with the'samehole layout as the first work piece just described, then-all that is necessary is for' the operator to remove the-finished workpiece and substitute in'lieu thereof a new, hlankwork piece. If some change is to be made in the hole design, either in the. spacingthereof or in the type of drilling operation performed, then, of course, the index'plate 11 might have to be changed, the index cam IG'might, or the various head control cams IHC, ZHC, 3H0 or 4HC-might have to'be replaced. However, as earlier stated, the substitution of one cam for a different canr'is rapidly accomplished, for any of the control cams may be withdrawn fromthe shaft 25 once the thrust member 35 has been removed, the detaching ofthe thrust memb'errequiring only the removal of a single nut. Also, any replacement-of cams is facilitated due to the location ofthe control MC, the control'MC being accessibly located right at the forward part of the machine where there is absolutely no interference from other machine parts. The index plate 11, when only one latch L is utilized, would have to' be changed only if the new hole pattern is to. be ofa spacing not-involving a multiple of five degrees, it being remembered that'in the illustrative embodiment the teeth 6 00f this'index plate-11 have been disposed at intervals of fivedegrees around its periphery; If more or less than the eight hole-positions are-desired, then, of course, the index cam IC would be replaced with a cam havingthe requisite-amount of; lobes 69 thereon for the number of-holes desired. Also, it is to be appreciated that more than one latch L might be employed to efiect a varied location of the holes to be made in the work,

' thus in many designs obviating any need for changing the index plate 11. Still further, in some instances, it might be desirable to have certain of the heads function at specified positions of the dial and other heads to function at-sti'll different positions of the dial. To facilitate an understanding of thispossibility, it will be assumed that the first two heads perform drilling and reaming operations at specified locations and the last two heads perform drilling-and reaming operations at-locations other than those. .atrwhich the firsttwo heads function. In such a situation, the head control cams IHC, ZHC, 3HC and 4HQwould havemore than one notch on their periphery, a'notch being located wherever the particular head controlled by the head control camv is to be inactivated. This is due to the fact that whenever a notch is in registry with pieces may be secured to the work table at desired stations, the machine functioning just as effectively as with the larger type of single work piece. Thus, it can be seen that our drilling machine is truly universal in character, being capable of accommodating many different types of work pieces and also being able to perform a multiplicity of work operations according to a large variety of prescribed plans or patterns.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim:

1. In a drilling machine, the combination comprising a rotatable dial assembly including a work supporting fixture and an index plate having a plurality of ratchet teeth distributed about its periphery at preferred locations, a pawl engageable with said ratchet teeth, drive means for rotating said dial assembly in either a forward or reverse direction, first control means for causing said drive means to rotate said dial assembly in its forward direction, a first index cam driven in 1:1 correspondence with the dial assembly for interrupting said first control means to stop said dial assembly at selected points in the forward travel of said dial assembly, second control means associated with said first control means for causing said drive means to rotate said dial assembly in its reverse direction when s id first control means is interrupted to cause the particular ratchet tooth which has just passed the pawl to be moved against said pawl whereby the work supportin fixture is accurately positioned at various angles for different work perf rming operations, respective head means angularly spaced for performing said different operations, and a second index cam driven in a 2:1 correspondence with the dial assembly for effecting two revolutions of said dial assembly for one revolution of said second index cam whereby sufiicient rotation of the dial assembly is assured to permit the completion of said different oper ti ns by the respective head means.

2. In a drilling machine, the combination comprising a rotatable dial assembly including a work supporting fixture nd an index plate having a plurality of ratchet teeth distributed about its periphery at preferred l cations, a pawl engageable with said ratchet teeth. driving means for r tating said dial assembly in either a forward or reverse direction, a plurality of successive heads angularly spaced with respect to the dial assembly for performing different work performin operations on a piece of work supported on said fixture, first control means for causing said drive means to rotate said dial assembly in its forward direction, index means for interruptin said first control means to stop said dial assembly at selected points in the forward travel of said dial assembly, second control means connected to said drive means to rotate said dial assembly in its reverse direction when said first control means is interrupted to cause the particular ratchet tooth which has just passed the pawl to be moved against said pawl whereby the work s pporting fixture is accurately positioned at various angles for the different work operations to be performed by said heads, a first control element mounted for actuation by reverse movement of the index plate into engagement with the pawl, a plurality of head control cams driven in correspondence with the dial assembly, second control elements mounted for actuation by the head control cams, and means for energizing the heads connected for operation by the first control element and second control elements.

3. In a drilling machine, the combination comprising a rotatable dial assembly including a work supporting fixture and an index plate having a plurality of ratchet teeth distributed about its periphery at preferred locations, a pawl engageable with said ratchet teeth, driving means for rotating said dial assembly in either a forward or reverse direction, a plurality of successive heads angularly spaced with respect to the dial assembly for performing different work performing operations on a piece of work supported on said fixture, first control means for causing said drive means to rotate said dial assembly in its forward direction, index means for interrupting said first control means to stop said dial assembly at selected points in the forward travel of said dial assembly, second control means associated with said drive means to rotate said dial assembly in its reverse direction when said first control means is interrupted to cause the particular ratchet tooth which has just passed the pawl to be moved against said pawl whereby the Work supporting fixture is accurately positioned at various angles for the different Work operations to be performed by said heads, means associated with said pawl for conditioning each head for performing its particular work performing operation, means for permitting actuation of the various heads other than the first head only after the work completed by said first head has reached each succeeding head, and a full index cam driven in a 2:1 correspondence with the dial assembly for effecting two revolutions of said dial assembly for one revolution of said full index cam, whereby sufiicient rotation of the dial assembly is assured to permit the completion of said different operations by the respective head means.

4. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a plurality of teeth disposed thereon at preferred locations, a latch member engageable with certain of said teeth, motor means for rotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced heads arranged for reciprocable movement toward" and from the dial assembly for the purpose of performing respective machining operations on a work piece supported on the dial, a cam shaft driven in 1:1 correspond ence with the dial assembly, an index cam and a pair of head control cams rotatably supported on the cam shaft, a first electrical circuit including a switch actuatable by said index cam at selected points in the forward travel of the dial to stop said motor means, a second electrical circuit connected to said first electrical circuit for reversing said motor means upon stoppage thereof to cause the particular tooth which has just passed the latch to abut said latch and angularly position the dial assembly for the respective machining operations to be performed by said pair of heads, individual driving means for the heads;

and individual electrical circuits for energ zing the lastnamed driving means including control elements mounted for actuation by the pair of head control cams for first initiating a work cycle of the first head at one angular position of the dial assembly and causing simultaneous work cycles of said heads after said one position of the dial assembly has been rotated into registry with said second head.

5. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a plurality of teeth disposed thereon at preferred locations, a latch member engageable with certain of said teeth, motor means for rotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced heads arranged for reciprocable movement toward and from the dial assembly for the purpose of performing respective machining operations on a work piece supported on the dial, a cam shaft driven in 1:1 correspondence with the dial assembly, an index cam and a pair of head control cams rotatably supported on the cam shaft, a first electrical circuit including a amen Switch actuatable by-said index cam at selected points in the forward travel of the dial to stop said motor" means, a second electrical circuit associatedwith said first electrical circuit fo'rreversing said motor means upon stoppage thereof to cause the particular tooth which has just passed the latch to abut said latch and angularly position the dial assembly for the respective machining'operations to be performed by said pair of heads, individual electrical circuits for energizing the heads, individual control means connected to the lastnamed circuits and mounted for actuation by the pair of head control cams for first initiating a work cycle of the first head at one angular position of the dial assembly and causing simultaneous work cycles of said heads after said one position of the dial assembly has been rotated into registry with said second head, a full index cam on the cam shaft, and electrical circuit means controlled by the full index cam for assuring sufficient rotation of said dial assembly to permit the second head to complete the work pattern.

6. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a plurality of teeth disposed thereon at preferred locations, a latch member engageable with certain of said teeth, motor means for rotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced heads arranged for reciprocable movement toward and from the dial assembly for the purpose of performing respective machining operations on a-work piece supported on the dial assembly, a cam shaft driven in 1:1 correspondence with the dial assembly, an index cam mounted on the cam shaft for rotation therewith, a pair of head control cams rotatably supported on the cam shaft, a yieldable driving connection between the cam shaft and head control cams, a first electrical circuit including a switch actuatable by said index cam at selected points in the forward travel of the dial to stop said motor means, a second electrical circuit connected to said first electrical circuit for reversing said motor means upon stoppage thereof to cause the particular tooth which has just passed the latch to abutsaid latch and angularly position the dial assembly for the respective machining operations to be performed by said pair of heads, and respective releasing means mounted for engagement with the head control cams for selectively restraining said head control cams from rotation with said cam shaft.

7. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a plurality of teeth disposed thereon at preferred locations, a latch member engageable with certain of said .teeth, motor means forrotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced heads arranged for reciprocable movement toward and from the dial assembly for the purpose of performing respective machining operations on a work piece supported on the dial assembly, a cam shaft driven .in 1:1 correspondence with the dial assembly, an index cam and a pair of head control cams rotatably supported on the cam shaft, a first electrical circuit including a switch actuatable by said index cam at selected points in the forward travel ,of the dial to stop said motor means, a second electrical circuit associated with said firstvelectrical circuit for reversing saidmotor means uponhstoppage thereof to cause the particular tooth which has just passed the latch to abut said latch and angularly position the dial assembly for the respective machining operations to be performed by said pair of heads, respective first and second latch means for restraining said head control scams from rotating with said camshaft, means associated with said first head control cam for efiecting release of its latch means to permit rotation of this camwith said camshaft, and further ,means associated with said first head control cam for effecting release of the other latch means after the I first heed ntre sam as been me d a P f d. amount to permit rotation of the seeomrcam witli s'aitlj @ms am. t v

8. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate pro: vided with a plurality of teeth disposed thereon at preferred locations, a latch member engage'able with certain of said teeth, motor means for rotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced heads. arranged for reciprocable movement toward and from the dial assembly for the purpose, of performing respective machining operations on a work piece supported on the dial assembly, a'cam shaft driven inlzl correspondence with the dial assembly, an index cam and a pair of head control cams rotatably supported on the cam shaft, a first electrical circuit including a switch actuatable by said index cam at selected points in the forward travel of the dial to stop said, motor means, a second electrical circuit associated with said first electrical circuit for reversing said motor means upon stoppage thereof to cause the particular tooth which has just passed the latch to abut said latch and angularly position the dial assembly for the respective machining operations to. be performed by said pair of heads, respective first and second latch means for restraining said head control cams from rotating with said camshaft, means associated with said first head control cam for effecting release of its latch means to permit rotation of this cam with said cam shaft, further means associated with said first head control cam for effecting release of the otherlatch means after the first head control cam has been rotated a preferred amount to permit rotation of the second cam with said cam shaft, a control circuit for the first head including a switch actuatable by said first head control cam into closed position upon initial rotation of said first cam, and a control circuit for the second head including a switch actuatable by said second head control cam into closed position upon initial rotation of said second cam.

9. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a'plurality of teeth disposed thereon at preferred locations, a latch member engageable with certain of said teeth, motor means for rotating said dial assembly in either a forward or reverse direction, a pair of angularly spaced'heads arranged for reciprocable movement toward and from the dial assembly for the purpose of performing respective machining operations on a work piece supported on the dial assembly, a cam shaft driven in 1:1 correspondence with the dial assembly, an index cam and a pair of head control cams rotatably supported onthe cam shaft, a first electrical circuit including a switch actuatable by said index cam at selected points in the forward travel of the dial to'stop said motor means, a second electrical circuit associated with said first electrical circuit for reversing said motor means upon stoppage thereof to cause the particular. tooth. which has just passed the latch to abut said latch and angularly position the dial assembly for the respective machining operations to be performed by said pair of heads, respective first and second latch means for res-training said head control cams from rotating with said cam shaft, means associated with said first head control cam for effecting release of its latch'means to permit rotation of this cam with said cam shaft, further means associated with said first head control cam for effecting release of the other latch-means after the first head control cam has been rotated a preferred amount to permit rotation of the second cam-with said cam shaft, a control circuit for the first head including a switch actuatable by said first head control cam, said first head control cam being configured to cause said first head control circuit switch to be open at the zero position of said cam, to close upon rotation of said cam and to open again after a full revolution of said cam, and acontrolcircuit for the second head including a switch actuatable by said 23 second head control cam, said second head control cam being configured to cause said second head control circuit switch to be open at the zero position of said cam, to close upon rotation of said cam and to open again after a full revolution of said cam.

10. In a drilling machine, the combination comprising a rotatable dial assembly, means for rotating said dial assembly, a cam shaft driven in correspondence with said dial assembly, an index cam fixedly carried by said cam shaft for rotation therewith and configured to stop the dial assembly at selected points in its rotative travel, a plurality of control cams frictionally mounted for rotation with said shaft to control respective machining operations, respective means for selectively restraining each control cam from rotation with said shaft, means carried by one of said control cams for effecting its release so that it will rotate with said cam shaft, and further means carried by said one control cam for effecting the release of a different control cam so that it will rotate with said cam shaft after said one cam has ben rotated a desired amount.

11. In a drilling machine, the combination comprising a rotatable dial assembly, means for rotating said dial assembly, a cam shaft driven in correspondence with said dial assembly, an index cam fixedly carried by said cam shaft for rotation therewith and configured to stop the dial assembly at selected points in its rotative travel, a plurality of control cams frictionally mounted for rotation with said shaft to control respective machining operations, respective means for selectively restraining each control cam from rotation with said shaft, means carried by one of said control cams for effecting its release so that it will rotate with said cam shaft, further means carried by said one control cam for effecting the release of a different control cam so that it will rotate with said cam shaft after said one cam has been rotated a desired a amount, and a full index cam driven in a 2:1 correspondence with said dial assembly for assuring two revolutions of said dial assembly in order that each control cam will have been permitted to make one complete revolution.

12. In a drilling machine, the combination comprising a rotatable dial assembly, means for rotating said dial assembly, a cam shaft driven in correspondence with said dial assembly, an index cam fixedly carried by said cam shaft for rotation therewith and configured to stop the dial assembly at selected points in its rotative travel, a plurality of control cams loosely circumscribing said shaft for controlling respective machining operations, friction discs interleaved between said control cams, spring means for urging said control cams and friction discs together, respective means for selectively restraining each control cam from rotation with said shaft, means carried by one of said control cams for effecting its release so that it will rotate with said cam shaft, and further means carried by said one control cam for effecting the release of a different control cam so that it will rotate with said cam shaft after said one cam has been rotated a desired amount.

13. In a drilling machine, the combination comprising a rotatable dial assembly, means for rotating said dial assembly, a cam shaft driven in correspondence with said dial assembly, an index cam fixedly carried by said cam shaft for rotation therewith and configured to stop the dial assembly at selected points in its rotative travel, a plurality of control cams loosely circumscribing said shaft for controlling respective machining operations, friction discs interleaved between said control cams, spring means for urging said control cams and friction discs together,

respective means for selectively restraining each control cam from rotation with said shaft, means carried by one of said control cams for effecting its release so that it will rotate with said cam shaft, further means carried by said one control cam for effecting the release of a different control cam so that it will rotate with said cam shaft after said one cam has been rotated a desired amount, and a full index cam driven in a 2:1 correspondence with said 'dial assembly for assuring two revolutions of said dial assembly in order that each control cam will have been permitted to make one complete revolution.

14. In a drilling machine, the combination comprising a rotatable dial assembly, a motor for rotating said dial assembly in a forward or reverse direction, means for at times stopping and reversing said motor, means adjacent said dial assembly for limiting reverse rotation thereof, a pair of reciprocable heads arranged to perform respective machining operations on work supported on said dial assembly, means restricting feed movement of said heads to only when said dial assembly is in engagement with said limiting means, a control cam associated with each head for additionally influencing the feed movement of either head even when said dial assembly is in engagement with said limiting means, said cams being rotatable in correspondence with said dial assembly, and means for delaying the rotation of one of said cams from rotation with said dial assembly until the other cam has rotated a desired amount.

15. In a drilling machine, the combination comprising a rotatable dial assembly, a motor for rotating said dial assembly in a forward or reverse direction, means for at times stopping and reversing said motor, means adjacent said dial assembly for limiting reverse rotation thereof, a pair of reciprocable heads arranged to perform respective machining operations on work supported on said dial assembly, means restricting feed movement of said heads to only when said dial assembly is in engagement with said limiting means, a control cam associated with each head for additionally influencing the feed movement of either head even when said dial assembly is in engagement with said limiting means, said cams being rotatable in correspondence with said dial assembly, means for delaying the rotation of one of said cams from rotation with said dial assembly until the other cam has rotated a desired amount, and a full index cam rotatable at a slower angular speed than said dial assembly but in a definite ratio therewith for assuring that the dial assembly will be rotated by said motor a distance sufficient to complete the desired number of work cycles of each head.

16. In a drilling machine, the combination comprising a rotatable dial assembly including an index plate provided with a plurality of ratchet teeth disposed thereon at preferred locations, a pawl member biased into engagement with said ratchet teeth, motor means for rotating said dial assembly in either a forward or reverse direction, said pawl limiting reverse rotation of said dial assembly, a pair of angularly spaced heads arranged for reciprocable movement toward and from the dial assembly for the purpose of performing respective machining operations on a work piece supported on the dial assembly, means for energizing said motor means for forward rotation of the dial assembly, means for energizing said motor means for reverse rotation of the dial assembly, said reverse energizing means becoming effective upon de-energization of said motor means by said forward energizing means, an index cam driven in 1:1 correspondence with the dial assembly for interrupting said forward energizing means at selected points in the forward travel of the dial assembly to open said forward energizing means whereupon said reverse energizing means becomes effective to rotate said dial assembly in a reverse direction until stopped by said pawl for a machining operation by at least one of said heads, head control means associated with each head for moving said heads toward and from said dial assembly, means for permitting said respective head control means to cause said heads to move toward the dial assembly only when said dial assembly is against the pawl, a full index cam driven in a 2:1 correspondence with said dial assembly, control means associated with said full index cam for assuring two revolutions of said dial assembly thereby to permit completion of the work schedules of both heads, said respective head control means each including a control cam selectively rotatable in a 1:1 correspondence with said dial assembly, means for

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