US3618922A

US3618922A - Method and machine for heat treating metal balls

Info

Publication number: US3618922A
Application number: US882814A
Authority: US
Inventors: Roland C Crans
Original assignee: Holcroft and Co
Current assignee: Holcroft and Co
Priority date: 1969-12-08
Filing date: 1969-12-08
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

Apparatus for hardening metal balls consisting of a spiral track within a quenching medium through which the heated balls move downwardly by gravitation thereby subjecting them to uniform quenching action. The speed of quenching is varied by rotating the spiral track and by moving the quenching medium relative to the track by a pump.

Description

United States Patent Inventor Roland C. Crans Detroit, Mich.

Appl. No. 882,814

Filed Dec. 8,1969

Patented Nov. 9, 1971 Assignee Hoicroh 81 Company Livonia, Mich.

METHOD AND MACHINE FOR HEAT TREATING METAL BALLS 10 Claims, 2 Drawing Figs.

0.8. CI 266/6 R, 266/4 A, l48/l43, 148/153 Int. Cl C2ld 1/62 Field of Search 266/4, 4 A

6,6PC, 8,5; 148/124, I3l, I43, I46, I52, I53

[56] Reierences Cited UNITED STATES PATENTS 2,007,009 7/l935 Staples 266/5 2,063,784 l2/l936 Bechtel et al. 266/4 2,918,070 12/1959 Carrier 266/5 3,201 ,289 8/i965 Stewart 266/4 Primary Examiner-Gerald A, Dost Attorney-Whittemore, Hulbert & Belknap ABSTRACT: Apparatus for hardening metal balls consisting of a spiral track within a quenching medium through which the heated balls move downwardly by gravitation thereby sub jecting them to uniform quenching action. The speed of quenching is varied by rotating the spiral track and by moving the quenching medium relative to the track by a pump.

PATENTEDHUV 9 lgn INVENTOR AOZA/VQ c. GPA/v ATTORNEYS BALLS BACKGROUND OF THE INVENTION In the heat treatment of metallic articles to harden the same, it is usual to beat them above the critical transformation range and then dump the heated articles into a quenching tank.

One of the problems encountered in quenching any piece of any shape is that the surface of the piece must be continuously in contact with the quenching media in order to rapidly remove the heat. If the piece being quenched is allowed to come to rest before the quenching is complete, a condition occurs at and adjacent to the point of contact between the piece and the surface on which it rests such that there is a partial stagnation of the quenching media. This results in retarded heat removal, and an incomplete hardening of the piece in this area.

SUMMARY OF THE INVENTION The object of the present invention is to provide improved means for heat treating meta] balls to obtain uniformity of hardness. To this end the heated balls are compelled to continually roll while in contact with the quenching medium until the temperature of the metal has been sumciently reduced to complete the hardening action. This is accomplished by providing a spiral track extending downwardly into the quench tank with guide rails to prevent escape from the track until the work has completed the'spiral path of travel. The track is of sufficient length to assure complete quenching before coming to rest. The rolling action assures that no point on the surface of the work is in contact with the track for sufficient time to retard the quenching action. Means are provided for rotating the spiral track and for forcing the quenching media countercurrent to the direction of travel of the work on the spiral track.

DRAWINGS FIG. 1 is a transverse section through an apparatus embodying the invention.

FIG. 2 is a plan view.

PREFERRED EMBODIMENT A heating furnace is provided with a conveyor belt 11 from which the heated metal balls 12 tumble over the edge of the belt into a delivery chute 13 which projects outwardly and downwardly through the furnace wall 14. Fifieen (15) is a vertical cylindrical tubular casing provided with a helical screw 16 attached to a central hollow shaft 17. The casing 15 is closing by an upper end 18 and lower end 19, each having

bearings

20 and 21 respectively through which the shaft 17 projects. At the bottom of the casing a discharge spout 22 inclines downwardly to conduct the work into a suitable receiving device. As shown, the receiving device is a conventional inclined endless belt conveyor 23. A quench tank 24 surrounds the casing 15 and contains a sufficient volume of quench media for the type of heat treating operation. Since the casing 15 is immersed in the quench media, the casing is filled with the media. In order'to increase the rate of contact of the media with the heated work, a pump 25 is provided which circulates additional media through the hollow shaft. A series of perforations 26 in the shaft permit discharge of the additional media into the casing 15. The helical screw 16 can be rotated at the desired speed in either direction by a suitable device mounted outside the quench tank. As shown there is an electric motor 27 with a belt connection 28 to a variable speed and reverse mechanism 29 which in turn has its driven shaft 30 connected to a pulley or sprocket wheel 31 on the upper end of shaft 17.

In the operation of the invention, heated balls 12 from the conveyor 11 are discharged either one at a time or in small quantities, and pass by gravity through the delivery chute 13.

From the chute they enter into contact with the helical screw thread 16 and continue to roll downwardly by gravity for the full length of the spiral path. During this rolling movement, the heated balls, pass through the quenching media and finally are discharged through the spout 22 onto the conveyor 23 which delivers the quenched balls from the tank.

The time the balls will be in rolling motion will depend upon several factors:

1. The diameter the tubular casing.

2. The length of the helical screw.

3. Pitch of the helix, which is limited by the size of the balls which must fit between the threads.

4. Viscocity of the quenching media. items (I), (2) and (3) are design variables to agree with the rolling time desired for a ball of a given size.

In any quenching operation, it is necessary to provide sufficient movement of the quenching media over the surface of the piece being quenched to wash away fluid vapors, heated fluid and assure that the piece is completely in contact with fresh, cold fluid. ln this instance, the rolling action of the balls will tend toward this, depending on their velocity of travel as determined by the pitch and diameter of the helix. In order to assure an adequate movement of quench media over the surface of the balls, the cylindrical core is made tubular with perforations, and a predetermined volume of quench media directed into the tubular member emerging through the perforations.

in a device as described, of a fixed size, the length of track, and therefore the travel time, is fixed. If different size balls are to be quenched in the same device, some means must be provided to decelerate, or possibly accelerate, the rate of travel in order to permit a greater travel time for larger balls than for small balls. To accomplish this, the helical screw 16 is rotated at a rate which is adjustable. By rotating the helix counter to the direction of gravity action the effective length of the track, and travel time, can be increased; Conversely, opposite rotation will decrease the time.

The advantage of the spiral track is that a great length can be achieved in a small space. in basic concept, the track does not necessarily need to be enclosed in a casing, and can consist of two properly spaced parallel rail members formed into a helix, with side guards to retain the balls from escaping. The chief importance of the casing is to provide a member inside which the spiral track can be rotated and in which the quenching media can be injected in close proximity to the balls being quenched.

What i claim as my invention is:

1. Apparatus for hardening metal balls comprising a helical track arranged vertically and submerged in liquid quenching media, means for feeding heated metal balls into the upper end of said helical track, said track having a pitch angle causing said balls to move downwardly with a rolling action through the liquid quench media, and having a sufficient length so that said heated balls are completely quenched during downward movement thereof and means for rotating said helical track about its axis to change the travel time of said balls through the media.

2. Apparatus according to claim 1, wherein said helical track is enclosed in a cylindrical casing.

3. Apparatus according to claim 1 in which said helical track is rotatable about its longitudinal axis and means is provided to form a circumferential guide for the descending balls in their downward helical path.

4. Apparatus according to claim 2 with means for moving quenching media upwardly through said casing.

5. Apparatus according to claim 4 in which the upwardly moving media is conducted through a hollow-shaft forming the axis of said helical track and said hollow shaft has a series of outlet parts for discharging media between the convolutions of said helical track.

6. Apparatus according to claim 3 including means for upwardly moving quenching media into contact with the downwardly traveling heated articles.

7. Apparatus according to claim 1 in which said helical track is rotatably mounted on a hollow shaft within a cylindrical casing, said shaft being provided with a series of outlets between the convolutions of said spiral track, a pump for feeding quenching media through said hollow shaft and said outlets into contact with the descending heated articles, means for variably and reversibly rotating said helical track to thereby vary the time of contact of the rolling articles with said media.

8. Apparatus according to claim 7 including a delivery chute between a heating furnace and the top of said cylindrical casing, a discharge chute from the bottom of said casing below said helical track and a conveyor cooperating with said discharge chute to remove the quenched articles from the quench media.

9. Apparatus for hardening metal articles comprising a helical track arranged vertically and submerged in liquid quenching media, means for feeding heated metal articles into the upper end of said helical track, said track having a pitch angle causing said articles to move downwardly and having sufficient length so that said heated articles are completely quenched during downward movement thereof through the liquid quenched media, a cylindrical casing surrounding said helical track and means for moving liquid quenching media upwardly thru said casing to increase the rate of contact of said liquid with said downwardly moving articles.

10. Apparatus according to claim 9 in which-the upwardly moving media is conducted through a hollow shaft forming the axis of said helical track and said hollow shaft has a series of outlet parts for discharging media between the convolutions of said helical track.

i 0 t h

Claims

5. Apparatus according to claim 4 in which the upwardly moving media is conducted through a hollow shaft forming the axis of said helical track and said hollow shaft has a series of outlet parts for discharging media between the convolutions of said helical track.

9. Apparatus for hardening metal articles comprising a helical track arranged vertically and submerged in liquid quenching media, means for feeding heated metal articles into the upper end of said helical track, said track having a pitch angle causing said articles to move downwardly and having sufficient length so that said heated articles are completely quenched during downward movement thereof through the liquid quench media, a cylindrical casing surrounding said helical track and means for moving liquid quenching media upwardly thru said casing to increase the rate of contact of said liquid with said downwardly moving articles.

10. Apparatus according to claim 9 in which the upwardly moving media is conducted through a hollow shaft forming the axis of said helical track and said hollow shaft has a series of outlet parts for discharging media between the convolutions of said helical track.