US2023662A - Size determining mechanism for automatic machines - Google Patents

Description

SIZ'E DETERMINING MECHANISM FOR AUTOMATIC MACHINES H. L. BLOOD Dec. 10, 1935.

Filed Feb. 23, 1953 3 Sheets-Sheet l gwuentoz Harold. LiBxood fibto mug Dec. 10, 1935. H. L. BLOOD 2,023,662

SIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Filed Feb. 23, 1 53 s Sheets-Shet 2 grwm H cnold 14.310001 a Ho mou Dec. 10, 1935. H. L. BLOOD SIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Filed Feb. 23, 1953 nqets sheet 5 80 :lWC'H M 79 Z Harold L. Blood Patented Dec. 10, 1935 SIZE DETERDIINING MECHANISM FOR AUTOMATIC MACHINES Harold L. Blood, Worcester, Mass, assignor to The Heald Machine Company, Worcester, Mass, a corporation of Massachusetts Application February 23, 1933, Serial No. 658,028

19 Claims. (01. 51-165) In prior constructions'of automatic machines made in order thatsuccessive workpieces shall 10 of this character, the size of the workpiece, beall be reduced to the same desired size. 1 ing operated upon is'determined either by a gage The principal object of the present invention is mechanism of the type shown in the McDonough to provide a novel arran'gementfor determining Reissue Patent No. 16,141, issued August 11, 1925, the size of a workpiece, which incorporates the 1 a later construction of the same type being shown advantages of the abovedescribed constructions, 15

in the Kempton 8i Gallimore Patent No. 1,731,719, without incorporating any of the disadvantagesissued October 15, 1929, or by the movement of the thereof. According to the present invention, the crossfeecl mechanism which causes the cutting size of the workpiece'is automatically determined tool to cut progressively deeper and deeper into by utilizing variations in thepotential of an elec the surface of the workpiece,- as shown in the trica-l circuit to control the-grindingoperations, 20

Guild Patent No. 1,682,672, granted August 28, such variationsof potential resulting from'either 1928. removal of material from the workpiece, or the" In the McDonough and Kempton & Gallimore appr a f a grinding wheel to a predetermined grinding machine constructions, the gage memp a In carrying u v t o the use 15 her is reciprocated relative to the workpiece, and of sizing gages that fi the w p the the grinding operation is interrupted when the utilization of the actual flow of current through workpiece is ground to such a size that the gage the workpiece is avoided, the invention utilizing may enter the bore therein. While a. gaging instead small variations of voltage in an electromechanism of the above indicated character is re p siv vi re in from onta t wi h 0 entirely satisfactory in operation, it has been either the workpiece the inding Wheel, all

The present invention relates to automatic machines for the reduction of workpieces to a predetermined size, and although in certain of its aspects it is applicable to various types of automatic machines, its particular utility, as will hereinafter appear, is in connection with machines for treating, as by a cutting operation, the internal surfaces of sleeves, gears, bushings and like articles.

found that the continued hammering action of a gage against the end of successive workpieces before a given workpiece reaches the predetermined size, in addition to the wear on a gage as'it enters within the bore of the workpiece, will impair the accuracy of the gage, necessitating inspection and replacement thereof in order to procure successive workpieces which are reduced consistently'to a predetermined size.

In a grinding machine construction of the type disclosed in the Guild patent, the size of the workpieces is controlled by the movement of the crossfeed mechanism whichoperates'to terminate the-grinding operation when the cutting surface of thegrinding wheel reaches a predetermined vertical plane during the crossfeed movement.-

The locationof this plane; is determined by a dressing tool which operates during each grind-' tential obtained from theganparatus of Fig; 2

to cause said wheel, during successive grinding operations, to move into the above-noted predetermined vertical plane before the grinding operation is terminated. Although machines of this construction are also entirely satisfactory 5 in operation, the inequalities inherent in grinding wheels and the necessarily involved construction and operation of the-machine are such-that 1 frequent inspections and adjustments must be" as will hereinafter appear from the following detailed description taken in connection with the accompanying drawings, in which:-- I Fig. 1 is a view in front elevation of an internal grinding machine embodying the invention. Fig. 2 is a fragmentary plan view of a portion of the parts of Fig. 1, on an enlarged scale.

Fig. 3 is a view in front elevation, showing a portion of the parts of Fig. 2 in a different position. a

Fig. 4 is a plan view similar to Fig, 2, showing a modification of the invention.

Fig. 5 is an enlarged transverse sectionalview along the line 5--5 of Fig. 4, looking in thedire'c tionof the arrows.

Fig. 6 is a wiring dia'gr'am illustrating automatic control of the machine through,v'ariationsofpo Fig. fLis a wiringdiagrarn'similar t Fig.6, 111 trating the part s id'difierent positionsl ,7

is a ir e d e e i lvstret nsautoef matic control of the machinethrough variations' of potential obtained'fronithe app r uses Fig. 9 is a fragmentaryview, similar to "Fig showing a further modificationoftheinv" Fig. 10 is a wiring diagram illustrating automatic control of the machine through variations of potential obtained from the apparatus of Fig. 9.

Fig. 11 is a wiring diagram, similar to Fig. 10, illustrating the parts in different positions.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. 1, the machine provides the usual reciprocatory table I provided in an internal grinding machine; either the grinding wheel or the work to be ground may be carried on said table, the reciprocations of the latter operating in either case to produce a relative movement between said grinding wheel and workpiece. In the construction shown, the table I supports and carries a wheelhead 2, and the work to be operated upon is held in a workhead 3, the latter being carried by a bridge 4 which spans the s lideways, not shown, provided by the machine frame, for the back and forth movement of the table I. A grinding wheel 5 is mounted on a spindle 6 journaled in the wheelhead 2 and a workpiece a is mounted in a suitable workholding chuck or other clamping device 'I journaled in the workhead.

The back and forth movement of the table I to cause the wheel 5 to make the required traverse of the workpiece a. may be procured in any well known manner, as by the use of the fluid pressure controlling and reversing mechanism, forming the subject matter of the Heald 8: Guild Patent No. 1,582,468, granted April 27, 1926. Such mechanism forms nopart of the present invention; it is sufiicient to note that the driving means employed procures the reversal of the table at each end of its normal grinding stroke by the use of spaced adjustable dogs 8 and 9 carried by the table I and adapted alternately to engage and to move a reversing member ID. The latter during the grinding operation, when the grinding wheel 5 is moving back and forth within the workpiece a is situated between said dogs 8 and 9 in position to be alternately struck by said dogs and, by its consequent movement, effects the reversals of the table I. The grinding wheel 5 is rotated at a high speed in any suitable manner and the workholding member 1 is also rotated at a somewhat slower speed by a belt drive, as will hereinafter appear.

The wheel head 2 of the machine is mounted on a cross-slide II which is arranged to have a transverse movement on suitable ways, not shown,

on the reciprocatory table, movement of said cross-slide being procured by rotation of a threaded crossfeed shaft I2, the latter engaging an internally threaded member, n66 shown, which is secured in any suitable way to the cross-slide. The crossfeed shaft I2 is rotated in a step-bystep movement by mechanism of the type disclosed in the above noted Guild Patent No. 1,682,672 to procure a feeding movement of the grinding wheel 5 to cause said wheel to cut progressively deeper and deeper into the workpiece a; for the purpose of the present invention, it is sufficient to note that a ratchet wheel, not shown, is engaged by a pawl I3 which is actuated in response to the reciprocations of the carriage I, thereby procuring rotation of said crossfeed shaft I2 carrying the grinding wheel transversely against the surface of the workpiece.

In the previous operation of grinding machines of the type shown and described in the aforesaid Patent No. 1,682,672, the grinding operation is interrupted before the workpiece reaches prede termined finished size, the interruption occurring in response to the movement of the crossfeed mechanism to procure separation of the grinding wheel from the workpiece, in order that a dressing operation may be performed on the wheel. After the dressing operation has been performed on the wheel, the grinding operation is resumed until the workpiece is ground to a predetermined finished size, whereupon the grinding operation is brought to a close by a second separation of the grinding wheel from the work in response to the crossfeed mechanism. And since the present invention also contemplates both an initial separation of the grinding wheel from the workpiece for truing, followed by resumption of the grinding to complete the work, there is shown in Fig. 1 as an illustrative embodiment of the invention, certain of the same wheel controlling mechanism described in the aforesaid Patent No. 1,682,672, to which mechanism automatic control through variations of electrical potential has been applied.

As previously pointed out, in normal operation of the machine, back and forth movement is imparted to the table I by the cooperation of the spaced dogs 8 and 9 with the reversing member I0, and for the purpose of automatically interrupting the grinding operation on the workpiece and separating the wheel for the dressing operation, the machine provides a lever I4 pivotally mounted on a shaft I5, as shown in the broken away portion of Fig. 1. The lever I4 has integral therewith a magnetic armature I6 disposed in operative relation with respect to the core of an electromagnet II, the unbalanced weight of the lever I4 tending to maintain the armature I 6 spaced from the end of the electromagnet core as long as the electromagnet I'I remains in a deenergized condition. Upon energization of the electromagnet I1 in a manner hereinafter described, attraction of the armature I6 imparts upward movement to the lever I4 and causes the latter to .lift a latch I8, assuming that the grinding wheelconditions, the block I9 is held in spaced relation to the stationary block 20 by the latch I8, but when the lever I4 is elevated as described above, the latch I8 releases the block I9 and subsequent right hand travel of the table I involves relative sliding movement between the table and the block I9, owing to the obstruction which the reversing member ID imposes against the left hand table dog 8. Continued travel of the table I finally brings the stationary block 20 up against the then slidable block I9, whereupon the dog 8 becomes immovably supported for shifting the reversing member I 0 to procure reversal of the table. The above described sliding movement of the block I9 on the table I, when released by the latch I8, results in an amplified right hand stroke of the table to withdraw the wheel 5 from the workpiece a and the disposal in the temporarily amplified path of movement of the wheel 5 of a dressing device 22, in the manner fully described in the above noted Patent No. 1,682,672. P

block I9, and as the table moves to the left,

offers enough resistance to movement of the block IS with the table to detain the block until the latch I8 is restored to its normal position in which it positively holds the block l9 separated from the block 20. On the above noted amplified right hand dressing stroke of the table I, in order to prevent a repetition of the dressing stroke, an arm 24 mounted on the latch pivot 2| strikes a lug 25 of a switch member 26 pivotally mounted above the lever I4, thereby turning the switch member 26 into the position shown to break the circuit through the electromagnet l1 and re lease the lever l4, as will be hereinafter more fully described. Upon the resumption of the grinding operation after dressing of the wheel as described above, the normal back and forth movement of the table continues until the work is reduced to a predetermined finished size, whereupon the grinding operation is brought to a close by a second separation of the grinding wheel from the work in response to the electric potential control of the present invention. For the purpose of obtaining a final run out of the table I into the position shown in Fig. 1, there is provided a second lever 2'! mounted on the same shaft l5 as the lever l4, the lever 21 having integral therewith an armature 28 responsive to an electromagnet 29, as shown in Fig. 6. Normally, the unbalanced weight of the lever 21 maintains the armature 28 away from the core of the electromagnet 29 while the latter is in a deenergized condition, and such is the condition of affairs during the grinding operation. Upon energization of the electromagnet 29 in the manner hereinafter described, the lever 21 is raised to move its upper end into the path of the left hand table dog 8, while the table is in its left hand position. Since the table dog 8 is pivotally mounted on its block l9, right hand movement of the table after elevation of the lever 21 results in lifting of the dog 8 so that it is carried clear of the reversing member l0. Therefore, the table I is not reversed but continues its movement to the right carrying the grinding wheel 5 out of the workpiece a, the table being brought to a full stop by any suitable means, such as is shown in the aforesaid Heald & Guild Patent No. 1,582,468. The return of the table I to the working position from the fully withdrawn position of Fig. 1 is effected by the shifting of a hand lever 38 operatively connected to the reversing member l0, and on the left hand movement of the table an arm 3! also mounted on the pivot 2i strikes a second lug 32 on the movable switch member 26, thereby turning the switch member in a position to disconnect the electromagnet 29 from its source. This turning movement of the switch member 26 upon the initiation of another grinding cycle restores the switch member to the position shown in Fig. 6 in readiness for the energization, at the proper time in the grinding of the next workpiece,'of the electromagnet l1 controlling the wheel dressing operation.

The above described mechanism for mechanically controlling the movements of the table I carrying the grinding wheel is more fully described in the above mentioned Guild Patent No.

1,682,672, and therefore forms no part of the present invention per se; the present invention,

electrical circuit resulting from either removal of material from the workpiece, or the approach of the grinding wheel to a predetermined plane. In other words, the table'controlllng mechanism described above with reference to Fig. 1' is merely 5 an illustrative embodiment of the manner in which any one of the several forms of potential control, next to be described, can be applied to a grinding machine of the character shown.

As best shown in Figs. 2 and 3, one form of the 0 potential control contemplated by the present invention embodies the use of a gaging finger 33, one end of which provides a head 34 mounted on a block 35 of piezo-electric material of such character that an electro-motive force will be generated therein, in response to twisting of the block. A Rochelle salt crystal is a well known example of such material of which the block 35 may be composed, the base of the block 35 being insulated at 36 from a bracket 31 carried by and movable with the lower portion of the table i.

As indicated in Fig. 2, the base 31a of the bracket 31 is laterally adjustable on the table through the provision of slots 38 receiving the table bolts 39, so that the free end of the gaging finger 33 may be set so as to cause an inset 33a, preferably a diamond or other hard material, to engage the periphery of the unreduced workpiece substantially coincidentally with the engagement of the grinding wheel 5 at the initiation of the grinding operation. As the finger 33 enters the workpiece it, its initial engagement with the inner periphery thereof will result in a turning moment being exerted on the finger in a clockwise direction about the axis of the crystal block 35. This turning moment will result in actual twisting of the crystal block 35 with the generation of an electro-motive force across leads ll] extending from the base of the block and the head 34, respectively. Obviously, removal of material from 40 the workpiece a by the grinding wheel 5 from successive working strokes of the wheel will result in a decrease of the turning moment exerted on the gaging finger 33 as the internal diameter of the workpiece increases. Therefore, the potential generated within the crystal block 35 will vary with each cut of the wheel, and the invention contemplates the utilization of such variations of the crystal block potential to automatically control the grinding operation, as will next be described.

Since the electro-motive force impressed across the leads 40 by twisting of the crystal 35 is relatively small and the range of variation of potential is limited, the invention provides means for amplifying the effect of potential variations of the crystal block so as to better control the energization of the electromagnets I1; and .29 respectively. One means of readily amplifying the potential of the crystal block is through theuse of a grid glow tube designated by the reference character 4| in Fig. 6. The glow tube 4| comprises a filament 42, plate 43 and grid 44, with the filament 42 energized from a portion 45a of the secondary winding of a transformer T, thees primary Winding 46 of which is connected across a suitable source of alternating current indicated at 41. One terminal of another portion 45b of the transformer secondary is connected to the grid 44 through a resistor 48 so as to give the grid 44 a negative bias with respect to the anode or filament 42 of the tube. The plate 43'is connected in series with the energizing coils 49 and 50 of relays that are adapted to control energization of the electromagnets l1 and 29 respectively, '5

in a manner hereinafter described, with one terminal of coil 5|) connected to one side of the primary winding 49. Therefore, with the connections shown, the coils 49 and 59 will be energize-d when the glow tube 4| passes suflicient current, as determined by the characteristics of the coils.

With the connections shown in Fig. 6, in the absence of any potential across the crystal block 35, that is to say with the crystal in an untwisted condition, the negative bias of the grid 44 by the winding portion 45b is such as to effectively prevent the passage of current by the tube 4 I. However, when the crystal block 35 is twisted, as a result of the engagement of the finger 33 with the workpiece a, the lead 49 from the crystal block 35 to the grid 44 gives the grid 44 a positive bias sufficient to overcome the basic negative bias and cause the glow tube 4| to pass enough current to energize the relay- coils 49 and 59. Obviously, the amount of current passed by the tube will depend upon the degree of positive bias by the crystal block 35, which in turn will be dependent upon the degree of engagement of the finger 33 with the workpiece to twist the crystal block. The

' amount of twisting is at a maximum at the beginning of the grinding operation and decreases I progressively as the material is removed, and the manner in which the resulting variations in the degree of energization of the relay coils 49 and 59 to first cause withdrawal of the wheel from the workpiece, for truing, and then the final run out of the wheel when the workpiece is reduced to finished size will now be described.

To this end, one terminal of the electromagnet H is connected to the movable contact 5| under the control of the relay coil 49, the contact 5| being biased in the direction of a stationary contact 52 by a spring. 53. This stationary contact 52 is adapted to be connected to ground, as indicated at 54 by relatively movable contacts 55 and 56, the contact 55 being mounted on the table so as to engage the stationary contact 55 just as the finger 33 carried by the crystal block 35 enters or leaves the workpiece a. The other terminal of electromagnet I7 is connected to a stationary contact 51 engaged by the movable switch member 25 in the position shown in Fig. 6, the switch member 26 being in turn connected to the supply generator 58 shown as being grounded at 54a; With the circuit connections just described, it is obvious that the electromagnet I! will remain in a deenergized condition as long as'the glow tube 4| passes enough current to hold the movable contact'5l out of engagement with the stationary contact 52 at the time when the finger 33 is engaging the workpiece, and the table controlled contacts 55 and 56 are in engagement, as,shown in Fig. 6.

The terminals of electromagnet 29 are similarly connected to the movable contact 59 under the control of relay coil 50 and to a stationary contact 65 adapted to be engaged by the pivoted switch member 26, when the latter is moved into the position shown in dotted lines in Fig; 7. The movable relay contact 59 is normally biased in the direction of a stationary contac 6| by a spring 62, so that the circuit of the electromagnet 29'is adapted to be completed through the table controlled contacts 55 and 55 only when'the current passed by the glow tube 4| is reduced to a value in which the relay coil 59 no longer maintains its movable contact 59 out of engagement with the stationary contact 6| As previously pointed out, each left hand movementof the grinding wheel 5 into contact with the workpiece a is accompanied by entrance of the finger 33 into the workpiece, and at the beginning of the grinding operation with the diameter of the workpiece substantially unreduced as indicated in Fig. 6, the twisting of the crystal block 35 is at a maximum. Thereafter during the early stages of the grinding operation, the crystal block 35 is twisted each time the finger 33 enters the workpiece to such an extent that the potential across its leads 40 is more than sufficient to overcome the basic negative grid bias and cause the glow tube 4| to pass enough current to fully energize the relay coils' 49 and 50 and hold the movable contacts 5| and 59 out of engagement with thecorresponding stationary contacts 52 and 6|, as shown in Fig. 6. ment of the contacts 55 and 56, during this phase of the grinding operation has no effect upon the electromagnets IT and 29.

As the grinding operation proceeds and the diameter of the workpiece a increases, the amount of twisting of the crystal block 35 gradually decreases, with a corresponding decrease in the amount of current passed by the glow tube 4|. Therefore, after a number of reciprocations of the grinding wheel 5, sufficient to reduce the workpiece a to roughing size, the amount of twisting of the crystal block 35 will be reduced to such an extent that not enough current will be passed by the tube 4| t5 energize the relay coil 49 and hold the movable contact 5| away from stationary contact 52 as the finger 3-3 is about to leave the workpiece on the right hand stroke of the wheelhead. Therefore, the movable contact 5| will engage the stationary contact 52 at this moment, and since as previously pointed out, the table contact 55 is then in engagement with the stationary contact 55, the electromagnet 'i will be energized as indicated in Fig. '7, thereby raising the lever 4. Since the lever is raised by energization of the electromagnet after the grinding wheel 5 has started on its right hand movement, the resulting lifting of the latch I8 releases the block I9 and renders the table dog 8 ineffective to turn the reversing member ID until after the table has run out far enough to withdraw the grinding wheel 5 from the work for truing by the dressing tool 22, as previously described. The circuit of the electromagnet I1 is broken as the grinding wheel 5 is withdrawn, due to the engagement of the lug 25 on the movable switch member 26 by the arm 24, thereby disconnecting contact 51 from the generator 58, see Fig. 1.

With the switch member 26 in engagement with the contact 69 leading to the electromagnet 29, as indicated in dotted lines in Fig. 7, the circuit of the electromagnet 29 is then in condition to be completed upon engagement of the movable contact 59 with the stationary contact 6 I, as will next be described. Upon resumption of the grinding operation following truing of the wheel 5 as just described, the re-entry of the finger 33 into the workpiece a, then reduced to roughing size, is accompanied by just enough twisting of the crystal block 35 to cause the tube 4| to pass sufiicient current to energize therelay coil 50, although not enough to energize coil 49 as previously described. Therefore, the relay coil 59 still holds its movable contact 59 out of engagement with stationary contact 6! as the wheel enters the workpiece for the final cut, or cuts. The finger 33 carried by the Therefore, the engagecrystal black 35 is so set that removal of additionaoeaecc substantially no contact between the finger 33 and the workpiece, so that there is no appreciable l the left hand table dog BI Consequently, on the succeeding right hand movement of the table, the dog 8 clears the reversing member it and the right hand movement of the table continues to the Cal extreme run-out position shown in Fig. 1, following which the completed workpiece is removed. Upon initiation of the grinding operation upon a new workpiece, the left hand movement of the table from the run-out position causes the arm iii to engage the lug 32 on the movable switch member 26, thereby breaking the circuit through the 'electroet 29, when the switch member moves from the dotted to the full line position of Fig. 7 to reengage the contact El. This partially restores the circuit of the electromagnet ll, and

the gaging finger 38 associated with the crystal bloclr 535 resumes control of the grinding cycle in the manner previously described, so as to autotically cause the tool to be withdrawn for tru= ing when the wo'rlr reaches predetermined roughing size and to cause the tool to be finally run out from the work when the predetermined 1i 1 size is reached.

In the automatic control of the grinding cycle just described, variations of voltage indirectly resulting from removal of material from the workpiece have been utilized, but as previously pointed out, the invention also contemplates utilization oi the actual approach'oi the periphery oi the grinding wheel to a predeteed plane by the cross feed movement to obtain the desired variations of voltage values. In Figs. and 5, a crystal block 35' is shown carried by a holder that is mounted on a bracket (it by a resilient member The resilient'meniber be is shown as a leaf spring, with one end received in the bracket 65, so that the member 35 tends to maintain the holder dB in a substantially. horizontal position. The crystal block 35 extends in the directian of the grinding wheel 5 and terminates in a head carrying a ieeler bl oi wear-resistant material adapted to be engaged by the periphery of the grinding wheel when the latter has been fed a predetermined amount withrespect to the workpiece c. The end or? the holder ltd opposite to the head (ll carries a child (38' that-is adapted to limit movement of the right hand end of the holder inresponse to a horizontal thrust exerted on ithe opposite end by reason oi engagement of the ieeler bl by the periphery of the grinding wheel 6. The onnot position of the ieeler bl with respect to the wheel 5 is adjustable through the provision of bolts cooperating with slots lb provided in the bracket h t, as shown in Fig. 1.

At the beginning of a cycle or grinding opera tions on a workpiece a, it is obvious from Fig; 5 that the holder bi extends substantially horizontally with the end of the feeler bl spacedan appreciable'distance from the periphery of the grinding wheel 5. As the grinding proceeds, each operation of the cross feed mechanism brings the periphery of the grinding wheel nearer the the workpiece has been reduced to roughing size, the next succeeding cross feed of the wheel head will cause the periphery of the wheel 5 to engage the feeler tl. When this occurs, a substantially horizontal thrust is exerted on the holder such 5 as to tend to move the head 66 away from the wheel 5, but the setting of the stud $8 is such that any shifting of the holder 53 is prevented, and there results an axial compression of the, crystal block 35' sufilcient to generate anelectro- 1o motive force therein. Obviously, the voltage generated within the crystal block 35' will vary with the pressure exerted by the wheel 5, and the mam ner in which such voltage variations may be employed to control energization of the electromagnets ill and 2% will next be described.

Referring to Fig. 8, a lead do from the crystal block 35' is shown as connected to the grid 44 of a glow tube ill that is adapted to be energized from a source dl in exactly the same manner as 20 described with reference to Fig. 6. Furthermore, the relay coils it and 5t are'connected in series with the plate (it, as shown in Fig. 6, so that the flow of current through these coils is directly controlled by the output of the tube ii.

The electromagnets ill and 2d are connected to the stationary contacts bl and 6d under the control of the movable switch member 26 in the manner previously described with reference to Fig. 6-, while the other terminals of the electro- 30 magnets are connected to movable contacts ii and 62 under the control of the relay coils it :and 50, respectively. With the coils ld and 5d in a deenergized condition as shown in Fig. 8,

,the'niovable contacts ll and it are held against 35.

' grinding wheel isoperating with its periphery at an appreciable distance from the end of the feeler til. Consequently, there being no voltage generated in the crystal block 35, the basic negative grid bias prevents the passage of current by the tube ll, and the coils iii and till remain completely deenergized. During thisstage of the grinding cycle engagement between the table controlled contacts and has no efiect on the circuits of the electromagnets iii and 29, in view of the fact that the movable contacts ll and T12 are maintained out of engagement with the cor responding " stationary contacts 52 and 69, as shown in Fig. 8.

its the grinding proceeds and the diameter of the workpiece increases, the wheel 5 comes closer 9 and closer to the feeler bl, and the bracket bit is so set that when the workpiece has been re- .-duced to roughing size, the feeler til is engaged by the wheel 5 and the crystal block 35' axially cause the tube ll to pass enough current to energize the coil til, the coil 39 being'designed to pull up its armature carrying the movable contact member it on considerably less current than is required for the coil 50 to pull up its armature. When the movable relay contact ll engages its stationary contact 52, the resulting energization of the electromagnet ll raises the lever I l4 and automatically causes separation of the grinding wheel from the workpiece, for truing. in the manner previously described with reference to Fig. 7.

- Upon return of thegrinding wheel to theworkpiece for completion of the grinding operation, it is evident that the'feeler 61 will be engaged by the grinding wheel with a greater pressure than before, so that sufficient voltage will be generated in. the crystal block 35' to cause the tube to pass enough current to energize the coil 50. That is to say, the coil 50 is so designed that when the periphery of the "grinding wheel reaches a vertical plane corresponding to the position it occupies when the workpiece has been reduced to predetermined finished size, compression of the crystal block 35' is such as to cause energization of the coil 50. The resulting engagement of the movable contact 12 with the stationary contact 8| serves to energize the electromagnet 29- and lift the lever 21. When this occurs, the succeeding righ hand movement of the table is continued until the tool reaches the full run-out position shown in Fig. 1, following which the completed workpiece is removed. Upon initiation of the grinding operation upon a new workpiece, the circuit through the electromagnet 29 is broken by the switch member 26, as previously described, thereby partially restoring the circuit of the electromagnet I1, whereupon the feeler 61 associated with the crystal block 35' resumes control of the grinding cycle.

Referring now to Figs. 9 and 10, there is illustrated a further modification of the invention, whereby variations in the voltage impressed on the grid of a glow tube may be obtained in a manner different from that previously described with reference to Figs. 6 and 8, for the purpose of automatically controlling the grinding cycle. In Fig. 9, an arm 11 is shown as being yieldingly supported on a bracket 18 by a resilient member 19, the arm 11 normally extending in a substantially vertical direction. The bracket 18 is adjustably mounted on a portion of the machine base, a screw 80 serving to shift the bracket 18 and its arm 17 with respect to the axis of the grinding wheel 5. The lower end of the arm 'II carries an inset Ila of wear resistant material,

and feeding movement of the grinding wheel 5 with respect to the workpiece a will cause the" periphery of the wheel to engage the inset "a. p and to shift the arm Tlon its flexible support I8 in such a direction as to swing the upper end of the arm away from an upward extension 18a of the bracket 18.

With the grinding wheel 5 spaced from the lower end of the arm 11, as at the beginning of the grinding cycle, the upper end of the arm 11 is in engagement with a contact 8.| adjustable within an insulating bushing 8|a on the bracket extension 18a (while a flexible contact finger 82 also can'ied by the arm 11 but insulated therefrom is in engagement with a contact 83 carried by the bracket extension 18a and insulated therefrom, as by a bushing 83a. With the parts in the position shown in Fig. 9, the contact finger 82 is under a slight initial compression, so that when the grinding wheel 5, due to its feeding movement, engages the arm: I1 as shown in Fig.

11, the end of the arm 11 will be disengaged from the upper contact 8|, while the contact finger 82 remains in engagement with the contact 83. The contact 83 is so adjusted with respect to the finger 82 that a very slight further movement of the arm." from the position shown in Fig. 11

will cause the finger 82- to leave the contact 83. With the above described arrangement, it is apparent then that the arm 11 will leave the contact 8| when the periphery of the grinding wheel 5 reaches a predetermined plane, and that the 5 contact finger 82 will leave the contact 83 when the periphery of the wheel 5 reaches another plane parallel to but slightly removed from the first plane.

Referring now to Fig. 10, the plate 43' of a 10 grid glow tube 4| is connected directly to one terminal of the electromagnet H, the other terminal of the electromagnet I! being connected to one side of the primary winding 46'-of a transformer T, so that the electromagnet I! will be is energized when the tube 4 I passes sufiicient current. The filament 42 of the tube 4| is energized from a portion 84 of the secondary of transformer T, and with the parts in the position of Fig. 10, a negative bias is maintained on the grid 20 44 by a secondary winding portion 85 having one terminal thereof connected through the engaged arm Tl and contact 8|- to one end of the grid 44 through the usual resistor 48. The secondary winding of transformer T also provides a third portion 88, the function of which is to place a positive bias on the grid 44 through an adjustable potentiometer connection at 86a, so set that normally the negative bias from winding 85, through the contact 8|, is more than sufiicient to overcome the positive bias and prevent the tube 4| from passing any appreciable current. This condition of aifairs is maintained during the first part of the grinding cycle and as long as the arm 11 engages contact 8|. The electromagnet 29 controlling the lever 21 has one terminal thereof connected to a plate 43" of a second grid glow tube 4|", the other terminal of the electromagnet being connected to one side of the primary winding 48" of a second transformer T". The filament 42" of this tube 4|" is energized from a secondary winding portion 81 in substantially the same manner as is the filament 42' of tube 4| energized from winding 84. With the parts in the position of Fig. 45 10,'the tube 4|" is prevented from passing any appreciable current by reason of the fact that a negative bias is placed on the grid 44" by means of a secondary winding portion 88 connected to one end of the grid 44" through the then closed contact finger 82 and contact 83. It is to be vnoted that one terminal of the negative bias winding 88 is connected directly to thecontact. finger 82, and that the latter is insulated from the, arm 'II, so that the circuits for controlling the negative bias of grids 44' and 44" are mainthat the positive bias is less than the negative bias, and the tube 4 therefore passes no current at the beginning of the grinding cycle. With the 7 parts arranged as described with reference to Fig. 10, it is apparent that while the electromagnets l1 and 29 are directly under the control of the glow tubes 4| and 4|", these tubes are both maintained in such a condition that they will'not pass sufflcient current to energize either the electromagnet H or the electromagnet 29 during the first part of the grinding cycle.

Referring now to Fig. 11, it is evident that when the grinding cycle proceeds to the point that the workpiece a has been reduced to roughing diameter, the wheel 5 will engage the lower 76 iii) end of the arm Tl, whereupon shifting of the arm ii on its resilient supporting member 19- will cause the upper end thereof to leave the stationary contact at, as indicated. When this occurs, the basic negative bias on the grid M 'is immediately removed, so that the positive bias from the secondary winding portion 88 immediately becomes efiectiveon the grid M. The tube il thereupon passes sumcient current to energize the electromagnet ii, the resulting lifting of the lever iii, as shown, autotically causing separation of the wheel a from theworkpiece c for truing. The circuit of the electromagnet ii is broken as the grinding wheel is withdrawn, due to the engagement of the lug it on the movable switch member 26 by the arm lid, see Fig. 1, thereby disengaging a'bridging contact at on the switch member 23 from the spaced stationary contacts 92- in'the circuit of the electromagnet, as indicated in dotted lines in Fig. ll. Upon resumption of the grinding operation after truing, it is evident that further removal oi material from the workpiece to bringit to predetermined finished diameter will cause the wheel 5 to further shift the arm ill from the position of Fig. 11, so asto separate the flexible contact finger 82 from the contact at. When this occurs, removal of the negative bias from winding portion 88 on the grid dd" immediately causes the tube M" to pass current, due to the positive bias impressed on the grid M" by the secondary winding portion ta. This passage of current by the tube it" is sumcient to energize the elcctromagnet 2t and cause the grinding wheel ii to be moved to the finalrun-outposition of Fig. 1. At this time the circuit from the electromagnet 29 is maintained by a bridging contact 93 on switch member 25, which bridging contact @8 is in engagement with stationary contacts dd when the switch member 25 is in the dotted line position. Upon the initiation of the grinding operation upon a news workpiece, obviously the above described cycle of operations will be repeated.

From the foregoing, it is apparent that by the present invention there is provided a size determining mechanism of the above indicated type, characterized by the automatic control of the entire grinding cycle through variations of electrical potential resulting from either removal of material from the workpiece, or the approach of the grinding wheel to a predetermined plane. In other words, the control ofthe grinding cycle is obtained without the use of sizing gages that fit within the workpiece, or without utilization of the actual now of current through the workpiece or the grinding wheel.

I. claim: T

i. In a mechanism or the class described, the combination with a cutting tool, means for holding a workpiece, means to procure a cutting operation between said tool and workpiece by feeding movement of the tool relative to the'workpiece, and an electromagnet adapted to bring about the separation of said tool from said workpiece, of a glow tube for controlling the energization of said electromagnet, and means dependent upon variations in the internal condition of an electroresponsive material for automatically subjecting.

the grid of saidjsube to a voltage such as to cause it to pass enough current to energize said. magnet and cause separation of the tool from the workpiece when said workpiece reaches a predetermined diameter.

2. In mechanism of the class described, the combination with a cutting tool, means for holdoperation in accordance inga workpiece, means to procure a cutting operation between said tool and workpiece by feeding movement of the tool relative to the workpiece, and an electromagnet adapted to bring about the separation of said tool from said workpiece, of a glow 'tube for energizing said electromagnet, said tube having a'basic negative grid bias to restrict its passage of current, and means dependent upon variations in the internal condition of an electro-responsive material resulting from the removal of material from said workpiece for creating a voltage sufllcient to overcome the negative grid bias and cause said tube to pass 'suflicient current to energize said electromagnet.

3. In mechanism of the class described, the

' combination with a cutting tool, means for holdmovement of the tool relative to the workpiece,

and an electromagnet adapted to bring about the separation of said tool from said workpiece, of a glow tube for energizing said electromagnet, said glow tube having a basic negative grid bias to restrict its passage of current; and meansdependent upon variations in the internal condition of an electro-responsive material resulting from the approach of said tool to a predetermined plane for overcoming said negative grid bias and causingsaid tube to pass sufilcient current to energize said electromagnct.

c. In a mechanism for performing a cutting operation on a workpiece by a cutting tool, involving feeding movement of the tool relative to the workpiece, an electrical circuit, piezoelectric material in said circuit and means for automatically' controlling the progress of the cutting operation in accordance with variations of the voltage generated in said electrical circuit by said piezoelectric material, as a result of such feeding movement between tool and workpiece.

5. In a mechanism for performing a cutting operation on a workpiece by reciprocatory movernent between the workpiece and a cutting tool, accompanied by feeding of the tool relative to the workpiece, an electrical circuit, piezoelecsaid piezoelectric material when subjected to variations of its internal condition resulting directly from such reciprocatory movement.

6. In a mechanism for performing a cutting operation on a workpiece by reciprocatory movement between the workpiece and a cutting tool, accompanied ,by feeding of the tool relative to the workpiece, an electrical circuit. piezoelectric material in said circuit and means for automatically controlling the progress of the cutting operation in accordance with variations of the voltage generated in said electrical circuit by said piezoelectric material as a result of the application of force tending to deform the material due to rcci'procatory movement of the cutting tool.

7. In a mechanism for performing a cutting operation on a workpiece by reciprocatory movement between the workpiece and a cutting tool, accompanied by feeding of the tool relative to the workpiece, an electrical circuit, a piezoelectrio crystal in said circuit and means for automatically controlling the progress of the cutting with variations of'the voltage generated in said electrical circuit by the deformation of said piezo-electric crystal resulting from direct engagement of said crystal with the workpiece.

8. In a machine of the class described, the

combination with a cutting tool, means for hold- 5 ing a workpiece, and means to procure the removal of material from the workpiece by a cutting operation resulting from relative feeding movement between said tool and workpiece, of

an electrical circuit, piezoelectric material in said 10 circuit and means for'automatically controlling the cutting operation of the machine in response to variations in the voltage of said electrical circuit, with said piezoelectric material being sub- .iect to variations of its internal condition result- 15 ing from the removal of material from said workpiece.

9. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece, and means to procure the removal of 2 material from the workpiece by a cutting operation resulting from relative feeding movement between said tool and workpiece, of an electrical circuit, piezo electric material in said circuit and means for automatically interrupting the cutting 25 operation when the workpiece reaches a predetermined size in response to a voltage generated in said electrical control circuit with said piezo electric material being subject to variations in its internal condition resulting from the removal of 30 material from said workpiece.

10. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece, and means to procure the removal of material from the workpiece by a cutj 35 ting operation resulting from relative feeding movement between said tool and workpiece, of an electric circuit, piezo electric material in said circuit and means for automatically interrupting the cutting operation in response to the genera: 4 tion of a voltage in said electrical control circuit, with said piezo electric material being subject to variations in its' internal condition by the approach of the cutting toolto a predetermined plane due to its feeding movement toward said 4.3 workpiece.

11. In a machine of the class described, the combination with a cutting tool, meansfor holding a workpiece, and means to procure the removal of material from the workpiece by a cutto ting operation resulting from relative feeding movement between said tool and workpiece, of an electric circuit, piezo electric material in said circuit ancimeans for automatically interrupting the cutting operation in resp'onseto the genera- 05 tion of a voltage in said electrical control circuit, with saidpiezo electric material being subject to variations in,its internal condition due to reduction in the size' of the workpiece.

12. In a machine of the class described, the

60 combination with a cutting tool, means for holding a workpiece, and means to procure the removal of material from the workpiece by a cutting operation resulting from. relative feeding movement between said tool and workpiece, of a 05 control circuit for said machine, and an electroresponsive material in said circuit adapted to enerate a voltage in said circuit due to deforma tion of the material by engagement with the cutting tool as the latterapproaches a predeter- 7o mined plane in its feeding movement with respect to the workpiece.

13. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece, and .means to procure the re- 75' moval of material from the workpiece by a cutting operation resulting from relative feeding movementbetween said tool and workpiece, of a control circuit for said machine and an electroresponsive material in said circuit adapted to generate a voltage in the circuit as a result of 5 deformation of the material due to its engagement with the workpiece.

14. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece, and means to procure the re- 10 moval of material from the workpiece by a cutting operation resulting from relative feeding movement between said tool and workpiece, or a gaging member supported by a block of piezoelectric crystal and an electrical circuit for controlling the operation of the machine, said circuit including said crystal and being responsive to voltages generated through the deformation of said crystal as a result of the relative feeding movement between said tool and workpiece. 2o

15. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece and means to procure the removal of material from the workpiece by, a cutting operation resulting from relative feeding movement between said tool and workpiece, of an electrical control circuit, piezo electric material in said circuit subject to variations in its internal condition due to relative feeding movement between said tool and workpiece, which variations are reflected in said control circuit,

and means under the supervision of said circuit for automatically interrupting the cutting operation when the workpiece reaches a predetermined size. I 16. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece and means to procure the removal of material from the workpiece by a cutting operation resulting from relative feeding movement between said tool and workpiece, of an electrical control circuit, piezo electric material in said circuit subject to variations in its internal condition by the approach of the cutting tool to a predetermined plane due to its feeding movement toward said workpiece, which variations are reflected in said control circuit, and means under the supervision of said circuit for automatically interrupting the cutting operation when the workpiece reaches a predetermined size. 17. In a machine of the class described, the combination with a cutting tool, means for holding a workpiece and means to procurethe removal of material from the workpiece by a cutting operation resulting from relative feeding movement between said tool and workpiece, of an electrical control circuit, piezo electric material in said circuit subject to variations in its internal condition due to reducton in size of the workpiece, which variations are reflected in said control circuit, and means under the supervision of said circuit for automatically interrupting the cutting operation when the workpiece reaches a predetermined size.

18. In a grinding machine, the combination with a workholder, a grinding wheel, and means to procure a grinding cycle on a workpiece carried by said holder, of an electric circuit, piezo electric material in said circuit subject to variations in its internal condition due to relative feeding movement between the workpiece and the grinding wheel, and means under the influence of said circuit to automatically control the progress of the grinding cycle, said cycle being characterized by temporary separation of the wheel from the workpiece for truing, when the workpiece is reduced to roughing size, and final separation of the wheel from the workpiece when'the latter reaches a predetermined finished size.

19. In a. grinding machine, the combination with a workholder, a grinding wheel, and means to procure a grinding cycle on a workpiece carried by said holder, of an electric circuit, piezo electric material in said circuit subject to deformation due to relative feeding movement between the workpiece and the grinding wheel, and means responsive to variations in the voltage of said circuit resulting from deformation of said piez'o electric material to automatically control the progress of the grinding cycle, one voltage value causing temporary separation of the wheel from the workpiece for truing, when the workpiece is reduced to roughing size, and a second voltage value causing final separation of the wheel from the workpiece when the latter is reduced to predetermined finished size.

HAROLD L. BLOOD.

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