US2892224A - Heating of dies by internal combustion - Google Patents

Description

' INVENTORA A lfred F. Bauer BY ma/ k A ORNEY June 30, 1959 u INVENTOR Alfred F. Bauer 7 BY m=&

ATTORNEY United States Patent C HEATING F DIES BY INTERNAL COMBUSTION Alfred F. Bauer, Toledo, Ohio, assignorfto National Lead Company, New York, N.YZ,' a corporation of New'Jersey Application May 9, 1957, Serial No. 658,2081' 2 Claims. cl. 22-74) This invention relates toa method of heating die casting dies.- More specifically itrelates to a method of heating die casting dies in which the heat-l-is applied to the interior of the die blo'cks 'bymeans of co'mbustionmf gas and air. I

In the production of castingsby thepressure die'casting method, molten metal is introduceddnto tlie cavityt at a high speed and under high-pressure. Preheating of the dies, therefore, is necessaryto prevent cracking of the die blocks when molten metal is shot into the die" and-to' bring the temperature of 'the die blocksclose to the operating range.

The customary method of preheating die castingdies is to direct a torchflame to the face of the'die casting die mainly along thepartin'g line of the die.- This isa very inefficient and unsatisfactorymethod of 'heating because only a small portion of the B.t.u.-s of the combustion gases is transferred into the die whilemostof theiheat escapes into the air. In directing the openflamev of the torch towards the cavity: areas, salient points; 'of the cavity, especially thin cores'and pins'may'overheatand anneal whilethe maindie blocks are hardly warming (up. Even though these shortcomings are wellknoWntheoperi torch method of heating dies has been the accepted heating method.

On large dies the deficiencies of thisopen torch heating method become much more ronounced: Heat transferredinto large die-blocks byoped-torches "dissipates into the air almost" asfastas if it ean be absor'bed bythe blocks and, therefore, increases'tre'meridously the-heating time of the dies.- -Withextremely-largedies the opentorch method never will bring the die steel up to the proper preheating temperature. In addition, the danger of overheating salient po'ints'an'd thin-sections of the die cavity and the problem of oxidation arid corrosion :of the die steel by subjecting. these. areas to the open an'd co'r'r'osive flame of the torch over a lengthy period has an adverse affect on the lifetime of the dies.

When the die blocks of large dies take on the Weight of several tons, the open torch heating method, therefore, becomes absolutely unsatisfactory. Therefore, a new heating method had to be found which is more effective and protects the steel more than the method with an open torch.

By employing an internal combustion system as herein described, through drilled or cast-in channels in the die blocks a much more efficient heating system has been developed. The heat of the combustion gases is penetrating into the die blocks through long channels and cannot escape into the air resulting in an extremely etficient heat exchange and in a relatively fast heating up of the largest die blocks.

Through additional holes along the passage Way of the combustion gases secondary air can be injected (or sucked in) to create a soft flame and to lengthen the combustion area of a reduced gas mixture. This will guarantee uniform combustion and internal heating over any area of the die. Since the combustion gases are contained within ice 2 the I internal chanhels' 'off-the' diblocks} the" gases do not corne in contact with the die' cavity and, therefore,-do*not createbverhieating and ahnealing-of the steel nor an oxidation of: the-steel in the cavity.

The internal heating system of this invention can be applied to the die blocks during-the starting period in orde'r to preheat 'the dieyb'ut also during the operating cycle to heat outer s'e'c'tion's'of the die block. On large dies the inner sections which come in direct contactwith the moltenmetal have to'bewater cooled-to prevent overheating while the heat passing through the steel does not flow fastenough to give the" outer sections of the" die the desired operating temperature Inthese cases of extremely large die's where the outer sections of the die' h'av'e to be heated during the die casting cycle,-'-the inv'ention offers id'eal conditionsin that thehe'at can be' applied 1 continuously or intermittently during the die casting cycle while atthe same time other and predominantly'innersections of the die are heavily-water cooledrthus creating ideal temperature control conditions within large dies.

With-thermocouplesbuilt-in large die blocks the internal combustionsystem inconjunction-with the water cooling of the dies lends itself-to a very efficient and practical method of temperature-control of die blocks especially on large dies: 4

It is, therefore, an object of this invention to p'rovide meansforeflici'ently heating large die blocks tothe proper preheating'teniperaturei Anotherobject of this invention is I to provide a means for heating large 'die'" blocks which is not accompanied by the usual problems of overheating salient points and thin sections 'o'fthe cavity and'oxidation and corrosion of the die steel.

A further object of this invention is-toprovide means for heatingdie casting dies from' theinteribr'of the die blocks outwardly by the combustion of gas and air.

Another object of this invention is to'provide means by which sections of large diesmore'r'emotefromthe gate area may'be-heatedthrough lo'cal heating channels While other sections of the dieare being cooled under operating conditions;

Yet another object of this-invention is to provide means by which he'at'may be applied' to 'th'e die blocks during the casting cycle.

These and other objects of the present invention will become apparent frointhe following more complete description andthe drawings in which:

. Figure l is a face-view, partially'sectioned;-of-atypical holding block for one die-half, and

Figure 2 is a similar view of a second embodiment of the present invention.

Figure 1 shows impression block cavity 20 in the die holding block 10. The specific embodiment of the invention illustrated has two combustion chambers 11 and 11a extending laterally through said holding block from side 14 to the opposite side 15. The heating source is burner 30 which burns a mixture of a combustible gas and a combustion supporting gas which, because of the economics involved, will usually be natural gas and air and are available from a source of supply by means of supply lines 41 and 42 through control valves 43 and 44 into mixing chamber 40. The premixed gas from said mixing chamber is supplied through fuel line 35, which may or may not have shut-oif valves for the separate burners, to burner 30 which includes torch 31 provided with air ports 33, aspirator shell 32 and fuel tube 34. In the form of the invention illustrated in Fig. 1, flame 16 may, by proper adjustment of the length of said fuel tube and the relative amounts of combustible gas and air, be made to burn the full length of combustion chamber 11 beginning at entrance port 12 and continuing through the die block to exit port 13.

The burners are held in place adjacent to the entrance ports of said combustionchambers by means of burner supports or other suitable means in such a way that when the die halves are opened to permit removal of the casting, the burner assembly is moved and is held in the same position relative to the combustion chamber of the die block to which it is attached.

Prior to starting the operation of the die casting machine, during the warm-up period, the burners are turned on and the premixed gas and air mixture is ignited. In the apparatus of Fig. 1, the total quantity of air needed for complete combustion of the gas is not pre-mixed. A portion of the necessary air is introduced into the combustion chamber through aspirator shell 32 and air ports 33 of burner 30 by the aspirator action of the gas stream being fed into the combustion chamber. Additional air is drawn into the combustion chamber through the space between the burner and entrance port 12. By proper adjustment of gas valve 43 and air valve 44, a flame is produced which will extend the full length of the combustion chamber.

A modified form of combustion chamber 11b is shown in Fig. 2 employing only one torch 30. In this modification, the combustion chamber is cast into the die block by means of a pipe or tube and a portion or all of the chamber may follow the irregular path shown at 22 so as to apply heat more directly to desired portions of the die block.

Flame from torch 30 enters the combustion chamber at entrance port 12a and passes through the chamber to exit port 13a. Additional air to support combustion may be drawn in through air inlets 50 by the aspirator action of the gases and flame passing through the combustion chamber. By proper adjustment of the gas and air, it is possible to maintain a soft flame the full length of the combustion chamber.

By casting the combustion chamber in the die block, it can be given any desired configuration so as to apply more heat where desired and to avoid coolant lines, dowels and fastening bolts.

It is understood that the combustion chambers shown are for illustrative purpose only and are susceptible to considerable modification according to the specific needs of the application. Therefore, the form of the invention described is not intended to limit the scope of the following claims.

I claim:

1. A die casting die assembly including a holding block of substantially solid ferrous metal having a recess in one face thereof for holding an impression block in intimate contact therewith, said holding block containing at least one combustion channel extending laterally through said holding block with its entrance and exit ports in opposite side faces of said block and at least one passage extending from an end face thereof and intersecting said combustion channel, the angle formed at the intersection of said passage and said combustion channel being such that air will be drawn in through said passage by the aspiratory action of gases passing through the combustion channel; a gas burner positioned on the side face of said holding block adjacent the entrance port of said channel; sources of combustible gas and air, respectively, connected to said burner; said burner including a mixing chamber wherein said gas and air are intermixed prior to combustion; and means for igniting said gas mixture; said gas and air sources having control means whereby each may be adjusted such that the flame produced by combustion of the gas mixture is contained generally within the confines of said combustion channel.

2. A die casting die assembly including a holding block of substantially solid ferrous metal having a recess in one face thereof for holding an impression block in intimate contact therewith, said holding block containing a combustion channel generally encircling said recess in the holding block with its entrance and exit ports in one side face of said block and at least one passage extending from an end face thereof and intersecting said combustion channel, the angle formed at the intersection of said passage and said combustion channel being such that air will be drawn in through said passage by the aspiratory action of gases passing through the combustion channel; a gas burner positioned on the side face of said holding block adjacent the entrance port to said channel; sources of combustible gas and air, respectively, connected to said burner; said burner including a mixing chamber wherein said gas and air are intermixed prior to combustion; and means for igniting said gas mixture; said gas and air sources having control means whereby each may be adjusted such that the flame produced by combustion of the gas mixture is contained generally within the confines of said combustion channel.

References Cited in the file of this patent UNITED STATES PATENTS 639,130 Allen Dec. 12, 1899 1,296,588 Bamberg Mar. 4, 1919 1,336,234 Jamison Apr. 6, 1920 2,173,618 Ahlert Sept. 19, 1939 2,536,692 Miller Jan. 2, 1951 FOREIGN PATENTS 260,390 Great Britain Nov. 4, 1926 881,775 France May 7, 1943

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