US2923101A - Pneumatic expander for honing machines - Google Patents

Description

Feb. 2, 1960 A. M. JOHNSON PNEUMATIC EXPANDER FOR HONING MACHINES Filed Jan. 22, 1957 P HYD. PIES. SOURCE 2 Spheets-Sheet l Oqpbert/ mkokvuram Mpx?. www

Feb. 2, 1960 A. M. JOHNSON PNEUMATIC EXPANDER FOR HONING MACHINES Filed Jan. 22. 14957 2 Sheets-Sheetl 2 ICO Chauvel-:5 ser: Alla Vuntil the bore is enlarged to a desired diameter.

UnitedStates Patent O PNEUMATIC EXPANDER Fon HONING MACHINES Albertv M.. Johnson, Rockford, Ill., assignor to Barnes Drill Co., Rockford, lll., a corporation of Illinois Application January 22, 1957, Serial No. 635,404

2 Claims. (Cl. 51-34) This invention relates to honing machines in which one or more abrasive elements or Vsticks carried by a rotary tool are, after entry of the tool in a rough bore, expanded rapidly into Contact with the bore wall and then held against the latter under proper pressurefor efficient cutting as the tool is reciprocated back and forth until the bore has been Aenlarged to the desired size. Thereupon, the elements are collapsed rapidly and withdrawn from the bore.

The primary object of the present invention is to provide an expanding mechanism which is extremely simple and inexpensive in construction, which permits the working faces of the abrasive sticks, although being expanded rapidly, to engage, the bore wall under a controllable pressure lighter than has been possible heretofore, and which enables the cutting action of the abrasive to start immediately after such contact. Another object is to utilize the elastic character of a compressed gaseous medium to achieve the foregoing cycle While cushioning the contact of the abrasive sticks and the bore wall at the end of the rapid expansion without at the same time interfering with rapidity of the collapse at the end of the cycle.

A more detailed object is to expand the hone by a pneumatic actuator to which the flow of compressed air is restricted in a novel manner such as to achieve rapid expansion but contact with the bore wall under a light selectively adjustable pressure.

A further object is to sense the failure of the abrasive surfaces to cut properly due to glazing or other causes and to correct such condition by automatically increasing the expanding pressure.

- Another object is to utilize an automatic sizing device to perform the additional function of sensing such cutting failure.

The invention also resides in the novel manner of achieving the desired rapid expansion without interfering with the rapid collapse of the hone.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings in which Figure 1 is a schematic view and circuit diagram of ia honing machine equipped with an expanding mechanism embodying the novel features of the present invention.

Fig. 2 is a similar fragmentary view showing a modified circuit arrangement.

In the drawing, the invention is shown for purposes of v moves back and forth in the bore.

illustration incorporated in an automatic honing machine for entering an expandable honing tool axially 10 .into the bore 11 of-a workpiece 12 clamped on a suitable fixture and reciprocating the expanded tool back and forth The tool is carried on the end of a rotary spindle 14 driven by av motor 15 and journaled in a head 16 which is moved back and forth valong guideways 16a by a lhydraulic actuator 17 to which pressure fluid from a source 18 is admitted under the control of a relay valve 19.

ice

The honing tool shown is of conventional design comprising a body 20 fixed to the lower end of the spindle 14 and having slots angularly spaced around its periphery to receive and guide abrasive elements or sticks 22. The latter are backed by the followers 23 of conical cams 24 spaced along a push rod 25 which extends up through the hollow spindle. When the rod is forced downwardly, the sticks are expanded and held against the bore wall under a pressure corresponding to the magnitude of the force applied to the push rod. As the latter is retracted or drawn upwardly, the abrasive sticks are retracted as by garter springs 26, encircling the ends of the abrading elements, the collapsed hone then being adapted to enter the usual guide ring (not shown). Expansion and collapse of the hone is effected by a uid pressure actuator comprising a piston 27 coupled to the push rod above the upper end of the spindle and slidable in a cylinder 28 mounted on the reciprocable head 16.

Operation of the valve 19 to define a conventional hon ing cycle is governed by well known mechanism such as that disclosed in Patent No. 2,381,572; In this control, a disk 31 carrying spaced dogs 32 and 33 is oscillated about its axis through a chain connection 34 with the honing head 16 and has loose thereon an arm 36 engageable by the dogs and carrying a cam 37 which acts on a follower lever 38 fulcrumed at 39. Through connections 40 and 41, the lever is joined to the armature of the solenoid R4 and to the operating arm of the pilot valve 43. The latter directs the ow of pressure uid from the source 18 to the actuators of the valve 19. The outer end of the arm 36 operates as a cam on a follower 44 to actuate a switch S2. Through the connection 41, the lever 38 also actuates a switch S3.

Enlargement of the bore to the desired size is determined by a suitable gaging device 50 which in the present instance is of the type disclosed in Patent No. 2,777,257. Briey, this device comprises a plurality of nozzles 51 mounted ou a laterally floating carrier 52 on the tool body 20 and adapted to direct jets of uid such as liquid coolant from a pressure source 53 against the wall 11 as the tool The coolant is delivered to the nozzles through a conduit 54, a 'transfer ring 55 surrounding the spindle, and a passage 56 extending down to a chamber with the nozzle carrier. Branching-from the conduit 54 is a .conduit 54a terminating in'a master orifice 57 which cooperates with the nozzle orifices and restrictions 58 and 59 to form a hydraulic bridge the balance of which is sensed by bellows 60 and 61 whose opposed movable ends are coupled to the arm of a switch 62. The arrangement is such that when the bore being felt of by the fluid jets is undersize, the relatively high backpressure in the passage 56 will hold the switch open. The control pressure decreases progressively as the bore is enlarged and finally, at the desired size determined by the setting of the master orifice 57, the switch 62 will be closed thus giving the up-to-size signal.

In the operation of production honing machines Vof the above charactenit is desirable, after the 'collapsed hone has entered theV rough work bore, to expand the hone rapidly until the active surfaces of the sticks approach or Contact the bore wall and then press the sticks against the walliunder'the required working pressure by continuing the expansion of the sticks. Finally, when the bore is up-to-size, -the tool is collapsed rapidly and withdrawn from the bore. v Y 'A 'i In accordance with the present invention, suchrapid expansion followed by slow expansion under increased pressure is effected pneumantically by so controlling the admission of compressed air to the cylinder 28 that the sticks 22`ar'e expanded rapidly against the bore wall but come into contact with the latter under extremely Patented Feb. 2, 1960 i tion. More particularly, the invention contemplates admitting air to the cylinder at a supply pressure of sufficient magnitude-to provide-the1iinal working force'but at arate correlated withthedisplacement ofthe piston'2'7 required toproduce contact with thebore wall,such `rate being adjusted to so restrict theiniiow ofthe air that there is no substantial build -up of pressure -in =the rcylinder until after the sticks have come against Vthe 'bore-wall. Thus, although the sticks may-be moved quite rapidly to the bore wall, the pressure of the engagement isso low `and so cushioned by the compressibility of the ypropelling air that there is lno danger of damaging the Arelatively 'brittle abrasive sticks. This desirable action is achieved without in anyway interfering Vwith the rapid'co'llapse-of fthe hone to terminate the -cycle with a -minimum `time delay.

To the foregoing ends, -air compressed to rthe proper regulated pressure, for example 50 p.s.i., is delivered -to the expanding actuator from a source 64 through a valve 65 and a suitable pressure regulator66a. Herein the latter comprises an orifice varied -in Varea by -movement of a plunger 67 which is loaded by a-spring .68 adjustable by a screw 69 to provide the desired supply pressure, for example 30 p.s.i. A 'plunger 70 ofthe valve 65 is actuated by a lsolenoid R2 and disposed, when the solenoid is energized, ina position to admit air to the regulator 66a and into a conduit 66 leading to ,the head end of the cylinder 28. interposed in the conduit 66 is a restriction 71 adjustable -by a needle which -may be turned by a screw 72 to limit the flow of the air -into the cylinder to a rate which is only a small fractionof the flow capacity of the conduit 66.

At the time of admission of the air through the restriction 71, the hone is collapsed and offers very 'little resistance to the movement of the piston 27. Thus, as the air enters, the piston vstarts to move causing the pressure in the cylinder to drop to a low value because of the restriction of the continuing air supply. Even at this reduced pressure, the piston continues to move and expand the hone rapidly until the working faces of the sticks 22 come into actual contact with the bore wall 11. Then, the pressure starts to build up in the cylinder and soon attains the full value, 30 p.s.i., of the supply pressure. Under this working pressure abrading of the bore wall continues at the proper rate.

When the bore attains the desired size as evidenced by closure of the switch 62, the solenoid R2 is deenergized by means to be described later and the plunger 70 is returned to the position shown in the drawing. As a result, high pressure air from the source 64 is admitted to a conduit 75 having a exible portion 76 leading to the rod end of the cylinder 28. Under this pressure, the piston 27 and the expanding cams 24 are retracted rapidly by virtue of a by-pass 76eL around the restriction 71 including a spring loaded check valve 77 which opens automatically and permits the free ow of air out of the head end of the cylinder 28 and through the valve 65 to an escape outlet 98a. The hone is thus collapsed rapidly without interference by virtue of the location of the restriction 71 in the conduit through which air is passed to the head end of the cylinder 28 for rapidly expanding the hone and bringing the stones into coutact with the bore wall under light pressure.

By expanding the hone rapidly into full contact with the bore wall and retracting the actuating piston at high speed, it will be apparent that thev duration of the honing cycle may be reduced to a minimum. At the same time, any desired working pressure may be employed as determined by the adjustment of the regulator 66. The construction of the expanding mechanism and its control are 4excgeauiingly simple thus reducing the overall cost of manlvrfaeture as compared to the structures heretofore used in arqdutiqn honing machines With a simple addition to the 'pneumatic expanding 'mechanism above described, -this mechanism vmay 'be zthe up-to-size signal to be-.given within a predetermined time `normallylsuflicientto enlarge vthe bore to the desired size.

Such an increase in the expanding pressure'ma'y be effected through a .valve .80.normally closed by a spring 81 and opened by energization of a solenoid R3. When the valve is open, air from the high pressure source 64 is admittedvto a conduit 82 leading to the conduit 66 beyond the restriction 71. In other words, 'the working pressure isincreasedffrom the normal value of 30 p.s.i. to the full supply pressure of 50 p.s.i. This is 'sufcient to break down any glaze'that may have developed 'on the faces Iof the stones 22 thus vrestoring 'the cutting 'eiciency of the abrasive and continuing the honing action at an increased rate so as to bring 'the bore up to size rapidly.

Detection of the condition of reduced cutting eciency is eiected in the present instance 'by an efectrically operating timer 84 such as is sold under the trade designation of Microflex by Eagle Signal Corporation. As is well understood in the art, such timers are activated by energization of a motor 85 whereupon, after the lapse of an interval determined by the timer setting` closes a switch 86 to complete a circuit for energizing the 'solenoid R3. Herein, the timer motor 85 is connected in parallel with the solenoid R2 and thus is energized and measuring of thetime interval started at a time substantially coincident with lthe starting of the honing action. Whenthe motor is deenergized, the timer is reset automatically and thus prepared for measuring a new time interval.

Operation With the parts positioned as shown on the drawing and assuming that the motor 15 is running and pressure uid is available at the different sources 18, 53 and 64, a complete honing cycle is executed automatically in response to the manual closure of a switch 89. This energizes a relay 90 whose switch 91 energizes a solenoid R1. The latter opens a valve 92 admitting pressure fluid fromthe source 1S to the pilot valve 43 which directs the uid to the lower end of the plunger 93 to maintain the raised position of the plunger and thus allow the uid to flow through the valve 19.to ,the rod end of the cylinder 94. Through a conduit 96, the fluid in the head end of the cylinder escapes to the return side of the pressure source 18. As the head 16 descends, the hone enters the work bore and the disk 31 turns counterclockwise. In the initial downward movement of the head 16, a switch S1 is closed as by a cam (not shown) on the head thus completing a circuit for holding the relay 90 energized during the remainder of the cycle. After ,the hone haspassed the full length of the bore and thus completed a stroke of the desired length, the dog 33 engages a lug 95 and shifts the arm 36 to actuate the follower 44 and close the switch S2. At the same time, the cam 37 rocks the lever 38 to reverse the pilot valve 43.

Closure of the switch S2 completes a circuit for energizing the solenoid R2 thus shifting the valve plunger 70 to admit air from the source 64 to the pressure regulator 66. As described above, the air flow through the restriction 71 and to the cylinder 28 moves the piston 27 causing the hone to be expanded rapidly until the stlcks v22 come into actual Ycontact with the bore wall 11. Thereafter, the pressure builds up 'to ther full Working value and continues during the ensuing up stroke of the hone.

Reversal of the pilot valve 43 directs pressure fluid to the upper end of the plunger 93 thus shiftingA the latter downwardly thereby applying pressure to the head end of the cylinder 94 and connecting the other end to the drain line 96. The head then moves upwardly and the disk 31 clockwise until the dog 32 shifts the arm 36 reversely far enough for the cam 37 to reverse the position of the pilot valve 43 but not far enough for the follower 44 to drop otf from the end of the arm. Thus, the switch S2 remains closed thereby continuing the energization of the solenoid R2 and the application of the normal working pressure behind lthe piston 27 of the pneumatic expander.

Such reciprocation of the expanded hone axially back and forth in the bore 11 continues until the bore has been enlarged to the desired size determined by the sizing device 50. When the up-to-size signal is given as evidenced by closure of the switch 62, a circuit for energizing the solenoid R4 is prepared lbut this circuit remains open until the end of the next down stroke of the hone when the cam 37 rocks the lever 38 to reverse the valve 43 and also close the switch S3. The solenoid is thus energized and through the connection 40, its armature u holds the lever 38 in its actuated position against the force of the spring 9S. As a result, upward movement of the hone is continued beyond the upper end of the normal working stroke and until the head 16 reaches its fully withdrawn position shown in the drawing at which the switch S1 is opened. This interrupts the holding circuit for the relay 90 thus deenergizing the solenoid R1 to close the valve 92 and stop the reciprocating actuator 17.

In the withdrawing movement of the hone the arm 36 is swung by the dog 32 far enough in the clockwise direction to pass the follower 44 thereby opening the switch S2. This deenergizes the solenoid R2 allowing the spring 97 to return the plunger 70 to the position shown in the drawing. Pressure fluid from the source 64 is thus admitted through the conduit 75 to the rod end of the cylinder 28 thus moving the piston 27 to permit retraction of the stones 22 by the springs 26. Such collapse of the hone at a rapid rate is permitted by the escape of air from the head end of the cylinder 28 through the automatic check valve 77 and to the outlet 98 through the valve 65.

The timer 84 is adjusted manually to measure an interval somewhat longer than that normally required for the bore 11 to be enlarged to the desired diameter as evidenced by closure of the switch 62. Since the timer motor 85 is connected in parallel with the solenoid R2, the time cycle will start with the expansion of the hone as a result of which a failure of the sizing switch 62 to close before the timer switch 86 is closed is evidence of inetlcient action by the hone. When this condition arises, the solenoid R3 will be energized by closure of the timer switch 86 and the Working pressure of the hone will be increased by the higher pressure then applied to the expanding actuators 27, 28.

Under this increased pressure, any glaze that may be present on the abrasive surface will be broken down and the cutting efficiency restored. Enlargement of the bore to the desired final sizes takes place rapidly and, as soon as the up-to-size signal is given by closure of the switch 62, the cycle is terminated as before by full withdrawal of the hone from the bore coupled with rapid collapse of the hone as above described.

A preferred arrangement of the Huid circuits i-s shown in Fig. 2 wherein the valve 65 is mounted on the reciprocating tool head and compressed air, at the different regulated pressures above described, is delivered through a single exible section in connection between the valves 65 and 80. In this instance, the valve 80 is of the fourway type adapted when the solenoid R3 is deenergized to deliver air through a check valve 101 to the connection 110 at a normal working pressure, for example, 30 p.s.i. maintained by a regulator 102. The pressure in the connection 10 is increased to the desired higher value, for example, 50 p.s.i. when the solenoid R3 is energized, this pressure value being maintained by a regulator 103 also supplied from the compressed air source 64. The air ilows to the conduit 110 through a check valve 104. The check valves prevent a back pressure from being applied to either of the two regulators 102 and 103.

I claim as my invention:

1. In a machine for honing the wall of a bore, the combination of, a rotary tool having movable abrasive elements, expanding means therefor, a piston coupled to said expanding means, a cylinder enclosing and guiding said piston, a source of fluid under a predetermined pressure, means for admitting said uid at a reduced pressure to said cylinder to expand said tool against the bore wall, a device for gaging the size of said bore and operable to interrupt the expanding pressure on said hone when the bore has been enlarged to a predetermined diameter, a timer for measuring an interval longer than that normally required for the bore to attain said predetermined diameter while said hone is under said reduced expanding pressure, and means controlled by said timer and operable upon expiration of said interval to increase the pressure of the fluid expanding said hone.

2. In a machine for honing the wall of a bore, the combination of, a rotary tool having movable abrasive elements, expanding means therefor, a piston coupled to said expanding means, a cylinder enclosing' and guiding said piston, a source of fluid under a predetermined pressure, means for admitting said fluid at a reduced pressure to said cylinder to expand said tool against the bore wall, a device for gaging the size of said bore and operable to interrupt the expanding pressure on said hone when the bore has been enlarged to a predetermined diameter, a timer for measuring an interval longer than that normally required for the bore to attain said predetermined diameter while said hone is under said reduced expanding pressure, and means controlled by said timer and operable upon expiration of said interval to connect said pressure source directly Vto said cylinder and thereby increase the expanding pressure exerted on said abrasive elements.

References Cited `in the le of this patent

Images