US2566678A - Heat-treating apparatus - Google Patents

Description

Sept. 4, 1951 G. c. RIEGEL ETAL HEAT-TREATING APPARATUS 3 Sheets-Sheet 1 Filed Sept. 26, 1949 I Sept. 4, 1951 G. c. RIEGEL ETAL v 2,566,678

HEAT-TREATING APPARATUS Filed Sept. 26, 1949 3 Sheets-Sheet 2 6 w .INVENTORS.

we/d M 5,

ATTORNE A Sept. 4, 1951 G. c. RIEGEL EI'AL 2,566,673

HEAT-TREATING APPARATUS Filed Sept. 26, 1949 3 Sheets-Sheet 3 E. EQE- F [e 2 INVENTORS.

ATTORNEY Patented Sept. 4, 1951 HEAT-TREATING APPARATUS Glen C.

assignors Riegel and Dale J. Wright, Peoria, 111., to Caterpillar Tractor 00., Peoria, 111.,

a corporation of California Application September 26, 1949, Serial No. 117,869 2 Claims. (01. 266-4) This invention relates to apparatus for controlling the hardness pattern of an irregularly shaped part during the heat treatment thereof.

In the heat treatment of irregularly shaped parts having relatively thin sections adjacent a larger section, one of the principal problems encountered is that during quenching the thin sections cool more rapidly and harden before the larger masses. As a result, cooling and hardening of the larger masses causes cracking of the already hardened thin sections due to the larger volume of the hardened material. This difficulty is particularly aggravated in automatic equipment for heating and quenching parts of this type in that it has been impractical to achieve selective quenching of the various sections of a single part.

It is, therefore, an object of this invention to provide apparatus for automatically controlling the cooling rate of various sections of an irregularly shaped part. It is another object of this invention to provide apparatus for automatically carrying an irregularly shaped part through is provided adjacent each end of the link for the reception of hinge pins (not shown) connecting the link with similar links to form an endless chain mechanism having a continuous rail sura heating cycle and a controlled quenching cycle V to produce a selected hardness pattern in the part. Other objects and advantages of this invention will be made apparent in the following specification wherein reference is made to the accompanying drawings.

For purposes of illustration, the invention is shown in its application to the heat treatment of a track link of the type commonly employed in the endless track mechanism of a track-type tractor, however, it will be readily apparent that it may be adapted for use with other parts.

In the drawings:

Fig, 1 is an isometric view of a typical track link;

Fig. 2 is an isometric view of the general arrangement of automatic heat treating apparatus embodying the present invention; and

Fig. 3 is a schematic diagram of a preferred arrangement of the electrical, air, and coolant circuits to accomplish automatic control of the heat treating cycle.

In Fig. 1, a typical track link of the type commonly employed in the endless chain mechanism of a track-type tractor is illustrated generally at Ill. One face of the track link is provided with suitable apertures II for the reception of bolts (not shown) for securing track shoes to the link while the opposite face is provided with a rail surface comprising a central portion l2, of full rail width, and end portions I3 and ll of 195$ than full rail width. A transverse bore 15 rail surface in a conventional manner.

face upon which the weight bearing rollers of. the vehicle may roll. The end portions l3 and I4 terminate in generally convex surfaces, l'l' and I8 respectively, which are adapted to cooperate with concave surfaces l9 and 20 underlying the full width rail portion l2 to form a self cleaning rail joint.

Due to the abrasive environment in which the track mechanism must operate, it is desirable that the rail surface of the track link be, hardened to increase its life. been accomplished by heating the rail surface above the critical temperature of the material and then quenching the part to producea rail surface of substantially uniform hardness. .-.'In a track link hardened in this manner, the thin edges indicated at 2| and 22 formed by themtersection of the concave surfaces. I9 and 20 with the full width rail portion l2 become too hard and brittle and are subject to early breakage in service due to impact of the track rollers crossing the rail joint. In addition, during quenching, the thin edges frequently crack due to differences in the cooling rate between the thin sections and the adjacent thicker sections,

This difliculty has been overcome by the apparatus illustrated in Fig. 2 which comprises an endless belt 23 which is carried for rotation on a pair of power driven drums 24. The belt is adapted to carry a plurality of track links ill at a predetermined rate between a pair of guide bars 25 which are provided to insure that the links are properly aligned with respect to the side edges of the belt. The track links are carried first through the induced heating field produced by an induction heating block 26, which is adapted to produce localized heating of the After heating, the track links are carried past a pair of fog nozzles 21 and 28 adapted to spray a mixture of air and liquid coolant on the area of the rail surface immediately adjacent the thin edges 2| and 22 only. The nozzles are calibrated to discharge coolant and air in the proper proportions to cool the area adjacent the thin edges to a predetermined temperature below the critical temperature of the material. After passing the fog nozzles, the track links pass under a quench block 30, connected by a pipe ill to a suitable source of liquid coolant (not shown) which is sprayed on the links, quenching the entire part.

In the past, this'fhas The quench block is spaced from the fog nozzles a distance suilicient to permit the pre-quenched thin edges to be reheated, by residual heat in the remainder of the link, to a drawing temperature. After quenching, the major part of the rail surface is hardened, however, the areas immediately adjacent the thin edges 2| and 22 are relatively soft due to quenching by the fog spray and subsequent reheating to a drawing temperature prior to the final quenching of the entire part. The hardness of the thin edges may be controlled by variation of their quenching temperature and amount of reheating prior to the final quench to produce the desired hardness pattern in the rail surface. In addition, by providing a softer more ductile material at the thin edges, cracking in this area is eliminated.

The fog nozzles 21 and 26 are connected by pipes 32 and 33 to a suitable source of compressed air (not shown) and also connected by pipes 34 and 35 to a tank 36 adapted to collect a part of the coolant discharged from the quench block 36. The fiow of air through the nozzles withdraws coolant from the tank by aspiration which intermixes with the air stream and is discharged as a fog-like spray. The flow of air through the nozzles is controlled by normally closed poppet type valves 31 and 38 interposed in the pipes 32 and 33 respectively. The valves 31 and 38 are adapted to be opened and closed by electrically actuated solenoids 40 and 4|, one of which is associated with each of the valves. The operation of the solenoids is controlled by an automatic electrically actuated timing mechanism indicated generally at 42 which is connected by electrical conductors 43 and 44 to a suitable electrical source, and to the solenoid 48 by conductors 45 and 46, and to solenoid 4| by conductors 41 and 48. The timing mechanism is adapted to be energized by a switch 58 connected therewith by conductors and 52. The switch 58 is adapted to be actuated by an arm 53 extending from a shaft 54 supported for rocking movement in a pair of bearings indicated at 55. A second arm 56 is rigidly secured to the opposite end of the shaft 54 and at its extending end carries aroller 51 adapted to be engaged by a boss 58 extending from each of the track links. As the track link passes along the belt, the boss 58 engages the roller 51, depressing the arm 56 and rocking shaft 54 which closes the switch 50, energizing the electrical timing mechanism 42. After the timing mechanism has been energized, it automatically controls the operation of the valves 31 and 38 so that spray from the nozzle 21 is directed on the thin edge 22 and the spray from the nozzle 28 is directed on the thin ed e 2| only. As the timing mechanism is energized by each track link as it reaches a predetermined position and operates for one cycle only, the spray from the fog nozzles may be accurately timed to occur as the thin edges reach the proper position regardless of the spacing of the track links on the belt.

As is best illustrated in Fig. 3, the timing device comprises a continuously operating synchronous motor 68, a drive shaft 6|, a clutch 62, a solenoid 63 for actuating the clutch, and a drive gear 64. The gear 64 is in driving engagement with a rack bar 65 which is adapted for sliding movement in the housing enclosing the mechanism. Movement of the rack bar actuates normally open switches 66 and 61 associated with solenoids 48 and 4| respectively. Switches 66 and 61 are provided with a pair of pivotally supported lever arms identified as 63a, 66b, 61a and 61b respectively, disposed in the path of the rack bar to eflect closing and then opening of the switches in sequence. A switch 68. adapted to be closed by the solenoid 63, is disposed between conductors Stand 52 oi switch 58 to keep the solenoid energized after switch 56 is opened by the boss 58 passing beyond roller 51. A normally closed switch 1| is connected by a conductor 12 to solenoid 63 and a conductor 13 with conductor 44 to maintain an energizing current in the solenoid. The switch 1| is adapted to be opened by the rack bar at the end of the cycle, deenergizing the solenoids 63, permitting the rack bar to be returned to its starting position by a return spring 1 In operating, closing he switch 58 energizes solenoid 63 by way 01' conduits '43, 5|, 52, 12, 13, and 44 which in turn engages the clutch 62 and closes switch 69. Upon engagement of the clutch, the rack bar 65 is moved downwardly by gear 64 until it engages lever 66a closing switch 66. Closing of switch 66 energizes solenoid 40, by way of conduits 43, 45, 46, switch 66, and conduit 44, which in turn opens valve 31, spraying air and coolant from nozzle 21 on the thin edge section 22 of the track link. Valve 31 remains open until the rack bar 65 engages lever 66b, opening switch 66 and deenergizing solenoid 48.

Further movement of the rack bar downwardly actuates lever 61a, closing switch 61, which energizes the solenoid 4| by way of conductors 43, 41, 48, switch 61', conductors 13 and 44. Energizing solenoid 4| opens valve 38, spraying air and coolant from the nozzle 28 on the rail surface of the track link adjacent the thin edge section 2|. The valve 38 remains open until the rack bar 65 engages lever 61b, opening the switch and deenergizing the solenoid 4|. The rack bar 65 will continue to travel downwardly until it opens switch 1| at which time, the solenoid 63 is deenergized, disengaging the clutch 62 and the rack bar is returned to its starting position by the spring 14. The timing mechanism is conventionally adjustable to permit variation of the timing and sequence of the operation of the switches 66 and 61 to insure that the desired operation of the fog nozzles is obtained.

We claim:

1. In an apparatus for controlling the hardness pattern in an irregularly shaped article during the heat treatment thereof with localized heatingand quenching means, means to advance a plurality of articles one at a time past the heating and quenching means, a plurality of fog nozzles intermediate the heating and quenching means, automatic timed control means actuated by contact of an advancing article for directing a fog-like spray through said nozzles on selected parts intermediate the leading and trailing end of the article in timed relation to its advancement, and means to discontinue said fog-like spray after treatment of said selected parts.

2. In an apparatus for controlling the hardness pattern in an irregularly shaped article during the heat treatment thereof with localized heating and q enching means, means to advance a plurality of articles one at a time past the heating and quenching means, a fog nozzle intermediate the heating and quenching means, automatic timed control means actuated by contact of an advancing article for directing a fog-like spray through said nozzles on selected parts intermediate the leading and trailing end of the article in timed relation to its advancement, and

means to discontinue said fog-like spray after Number Name Date treatment of said selected part. 2,178,281 Judge Oct. 31, 1939 GLEN C. RIEGEL. 2,202,758 Denneen et a1 May 28, 1940 DALE J. WRIGHT. 2,202,759 Denneen et a1 May 28, 1940 6 2,282,942 Crowe May 12, 1942 REFERENCES CITED 2,294,161 Crowe Aug. 25, 1942 The following references are of record in the 2,312,339 Kullman fl- 1943 file of this t t; 2,321,645 Bishop et a1 June 15, 1943 Y UNITED STATES PATENTS m 'FOREIGN PATENTS Number Name Date Number Country Date 1,277,262 Sandberg Aug. 27, 1918 497,422 Great Britain Dec. 12, 1938-

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