US2282915A - Heat control system for pressure casting machines - Google Patents

Description

y 1942- D. D. WHYTE HEAT CONTROL SYSTEM FOR PRESSURE CASTING MACHINES Filed Sept. 19, 1939- n. J 2 u M L I "&M M

S A l INVENTOR.

ATTORNE Patented May 12, 1942 HEAT CONTROL SYSTEM FOR PRESSURE CASTING MACHDVES Daniel D. Whyte, New York, N. Y., assignor to Lester Engineering Company, Cleveland, Ohio, a corporation of Ohio Application September 19, 1939, Serial No. 295,613

2 Claims. (Cl. 219-20) This invention relates, as indicated, to a heat.

control system for pressure casting machines and more particularly to a method whereby the temperature to which the material to be cast is related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting heated may be automatically regulated. forth'in detail certain means and one mode of In machines for the pressure casting of macarrying out the invention, such disclosedmeans terials generally known as plastics,- such as and mode illustrating, however, but one of varithe machine disclosed in the application for U. S. ous ways in which the principle of the invention Patent of Nathan Lester, Ser. No. 174,175 filed may be used. 7 November 12, 1937, some difliculty is often ex- In said annexed drawing, Fig. 1 is a fragmenperienced in maintaining the temperature to tary elevational view, partly in cross-section, of which the finely divided or powdered material is an improv d pressure casting ma hine; and Fi heated at a designated level. It will be under- 2 is a diagrammatic layout of the electric cirstood that in the operation of machines of the cuits of the temperature control means.v type referred to the dry plastic is introduced 5 Referring now more particularly to said drawto the pressure casting cylinder, there rendered ing, the machine illustrated comprises a hydrauplastic by heat from an electric heating jack et,, lic'cylinder 1 in which a piston and piston rod and then forced through an injection nozzle into are adapted to reciprocate. A material feedthe die. There is, of course, an ideal temperahopper 2 feeds measured charges into the presture to which each material should be heated to S e a g Cylinder v3 Where u h material is secure precisely the proper degree of plasticity. heated by the electric heating jacket 3 and However, since the machine is operated with con ejected through the nozzle 5 by action of an siderable rapidity, a practical dificulty arises in annular plunger 6 in turn actuated by said hythat there occurs a lag in the rate of applica draulic cylinder. Also shown are die plates i tion of heat with respect to its rate of withdrawal 5 and 8 and knock-out paddle 9. For a comcaused by the introduction and discharge of map e description of the machine reference may terial to be cast. As a result, although the tembe had to the specification of the above menperature of the casting cylinder might be at the tioned application Serial No. 174,175. ideal when material is first introduced, controlled AS Ordinarily op d, the ea C l is reguheating systems heretofore known are not capaa e by m ans of a thermostat adjacent said ble of anticipating this temperature drop, and cylinder 3. Whenever the temperature d p when they do not operate to compensate for it, below an appointed minimum the circuit is autoit is too late because the material has left the matically closed until the proper temperature is cylinder. Hence, a contrary condition occurs regained. Of course the thermostat is unable tending to produce. a temperature rise above the to anticipate what the heat requirement will be ideal. Such fluctuation in the temperature of for each step in the casting cycle and as a result the material is of course strictly to be avoided considerable fluctuation arises. since too low a temperature will not cause the A typ ca Casting y le may be as follows: A proper degree of plasticity and too high a temmeasuredcharge of the dry material is fed into perature may result in streaks or burns in the 40 the cas ing ylinder 3, the plunger 6 descends, finished article. For most "plastics there is a plasticizing and injecting the material into the well known temperature at which the material dies. Then the dies are opened and the casting should be maintained. ejected while said plunger returns to its starting It is, therefore, a primary object of this invenposition and another charge of dry material is tion to provide a heat control system for presfed. After a dwell interval which is usually sure casting machines and the like whereby the somewhat, variable the cycle is repe d. temperature to which the material to be cast is I is pparent that considerable heat will be heated may be maintained substantially uniform required in the first stages to raise the temperaand at any desired point. ture of the dry material but that less heat will A further object is to obtain the above result automatically, the means provided being adjustable depending on the material employed.

Other objects of this invention will appear as the description proceeds.

To the accomplishment of the foregoing and be needed as the plasticized material is forced into the dies. The thermostat naturally lags somewhat and as a result the casting cylinder 3 is too cool in the first stage of the cycle and too hot thereafter.

ensure a sufiiciently high temperature in the If the thermostat be such as to' lated to supply the necessary additional heat at and for just the proper time.

These circuits and their controls are shown diagrammatically in Fig. 2. The line L1, leads to thermostat III, which when closed also causes the closing of relay-switch H, and thence out to line L2. With said relay switch closed current passes through heating coil I2 until a temperature is attained at which said thermostat again opens and said relay switch follows suit. By the closing of plunger limit switch [3 current may be passed through said heating coil even when said thermostat is open, thus anticipating a sudden increase in heating requirements. This result is obtained as follows: switch I3 is closed energizing clock motor M and clutch C whereby contacts I4 and I5 are closed. Current now passes through the following circuit, L1, heating coil l2, contacts l5, and L2. When limit switch I3 is opened contacts I4 and I5 remain closed, maintaining said motor and clutch circuits and the auxiliary heating circuit. At the end of the preset interval said clock motor trips said contacts l4 and I5 breaking said motor and clutch circuits and said auxiliary heating circuit. The cycle is then ready to repeat.

Said motor, clutch, contacts, etc. form the conventional timer which may be purchased as a ,unit and installed on the machine as is the timer l6 shown in Fig. 1.

In operation, dry'material is fed into the cylinder 3 andplunger 6 descends, arm I1 moving therewith and closing plunger limit switch l3. The current passing through coil 4 heats the material to the proper temperature'for plasticiz ing and the same is forcedjhrough nozzle' 5 into the dies. When plunger 6 with arm I'I rises, the switch I3 is opened but as above pointed out this does not affect the circuits. carrying current to coil 4 or timer l3. These are broken by said clock motor after the passage of the interval for which it was set, whether before or after the return of the plunger. If the temperature now drops below the minimum of the thermostat I0, the other heating circuit will again be closed as above described until such temperature is regained.

It will readily be seen from the foregoing deto satisfy the requirements of any particular material or quantity thereof. As a result, expensive delays and wastage are eliminated so that the production capacity and efllciency of the machine are maintained.

Certain modifications are apparent whereby the principle of this invention may be employed in connection with various types of casting machines. For example, separate heating coils may be employed for the thermostat and the timer controlled circuits. Or, especially when the machine is operated with great rapidity, the thermostat controlled circuit may occasionally be dispensed with. Furthermore, the switch l3 may be operated by other mechanism moving in connection with said plunger instead of byan arm attached directly thereto. All such modifications are clearly within the scope of the present invention.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any ofthe following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a pressure casting machine wherein successive charges of material are heated to a predetermined temperature prior to being injected into a die, a casting cylinder into which such successive charges are measured, an electric heating element for heating said cylinder, a circuit including said element, a switch in said circuit, a thermostat adjacent said cylinder operative to close said switch when the temperature of said cylinder reaches a predetermined minimum, a second circuit including said heating element, time control means for said second circuit operative to close said second circuit for a predetermined period of time, and means associated with such casting machine for automatically setting said time control means in operation.

2. In a pressure casting machine wherein successive charges of material are heated to a predetermined temperature prior to being injected into a die; the combination of a casting cylinder having a plunger operable therein; and a heat scription that the timer It may be set to anticiv pate the suddenly increased heat requirement when a charge of dry material is about to be plasticized and also to cut out when such heat is no longer required. The time may be adjusted control system for said cylinder comprising an electric heating coil about said cylinder, a circuit including said coil, a switch in said circuit, a thermostat adjacent said cylinder operative to close said switch when the temperature of said cylinder reaches a predetermined minimum, a second circuit including said coil, time control means for said second circuit operative to close said second circuit for a predetermined period of time, and means connected with such plunger for automatically setting said time control means in operation.

DANIEL D. WHYTE.

Images