Passive mold cooling and heating system

• US 4,680,001 A
• Filed: 02/10/1986
• Issued: 07/14/1987
• Est. Priority Date: 11/28/1984
• Status: Expired due to Fees

• Current Assignee: First National Bank of Chicago (JP Morgan Chase & Co)
• Original Assignee: Application Engineering Corporation
• Inventors: Waters, Michael A.
• Primary Examiner(s): Woo, Jay H.
• Assistant Examiner(s): Housel, James C.
• Application Number:
  US06/827,827
• Time in Patent Office: 519 Days
• Field of Search: 425/144, 425/143, 425/552, 425/526, 425/29, 425/407, 425/547, 264/40.6, 264/328.16, 165/104.21, 165/96
• US Class Current: 425/144
• CPC Class Codes: B29C 35/007 Tempering units for temperature control of moulds or cores, e.g. comprising heat exchangers, controlled valves, temperature-controlled circuits for fluids B29C35/0294 takes precedence
• CPC Class Codes: B29C 45/7306 Control circuits therefor

Abstract

A mold for molding articles of plastic or other like materials, having a plurality of vertically extending internal passages, is connected by inlet and return conduits into a closed loop that includes a heat exchanger partially filled with a liquid supply of a cooling fluid or a heating fluid. For cooling the heat exchanger is positioned with its liquid level above the top of the mold, the inlet conduit connects the lower part of the heat exchanger, below the liquid level, to the lower ends of the mold passages, and the return conduit connects the upper ends of the mold passages to the upper part of the heat exchanger; for heating these relationships are reversed. In operation the fluid changes its physical state at critical points in the mold passages, going from liquid to vapor for cooling and from vapor to liquid for heating; circulation in the closed loop is in response to the effect of gravity. Operation of the heat exchanger is controlled to maintain a controlled pressure in the closed loop.

Claims

1. A passive cooling system for cooling a mold for molding articles of plastic material without substantial pumping, the mold including a plurality of vertically extending internal passages for passing a cooling fluid through the mold, the system comprising:

a condenser heat exchanger partially filled with a supply of cooling fluid in a liquid state, the cooling fluid constituting a fluid which changes from its liquid state to its vapor state in response to temperatures occurring in critical portions of the mold passages during operation of the mold, the heat exchanger being positioned so that the upper level of liquid fluid in the heat exchanger is approximately at or above the tip of the mold;

an inlet conduit connecting the heat exchanger, from a point below the upper level of the fluid, to the lower ends of the mold passages;

a return conduit connecting the upper ends of the mold passages back to the heat exchanger;

the heat exchanger, the mold passages, and the inlet and return conduits constituting a closed loop;

and heat exchanger control means for controlling operation of the heat exchanger to maintain a controlled pressure in the loop while condensing vaporized fluid back to its liquid state as the fluid returns from the mold to the heat exchanger;

the heat exchanger control means including means to adjust the controlled pressure to establish a minimum limit temperature for cooling of the mold and means for actuating the heat exchanger to vary the loop pressure in synchronism with the molding cycle.

2. A passive mold cooling system according to claim 1 in which the cooling fluid is water.

3. A passive mold cooling system according to claim 1 in which the cooling fluid is a Freon refrigerant.

4. A passive mold cooling system according to claim 1 in which one of the inlet and return conduits includes pump means for circulating the cooling fluid through the closed loop at a slow rate, insufficient to afford substantial cooling of the mold, to assure movement of vaporized cooling fluid back to the heat exchanger.

5. A passive mold cooling system according to claim 1 in which the heat exchanger control means further comprises:

pressure sensing means for sensing the pressure in the closed loop;

first and second inlet/outlet conduits for the heat exchanger, one including a control pump and the other a control valve;

and controller means, connected to the pressure sensing means, for actuating the control pump and the control valve in response to variations in pressure in the closed loop.

6. A passive mold cooling system according to claim 1 in which the heat exchanger includes an internal coil and the heat exchanger control means further comprises:

pressure sensing means for sensing the pressure in the closed loop;

chiller apparatus for circulating a chilled heat transfer fluid through the heat exchanger coil; and

controller means, connected to the pressure sensing means, for adjusting operation of the chiller apparatus in response to variations in pressure in the closed loop to maintain a constant pressure.

7. A passive heating system for heating a mold for molding articles of plastic material without substantial pumping, the mold including a plurality of vertically extending internal passages for passing a heating fluid through the mold, the system comprising:

an evaporator heat exchanger partially filled with a supply of heating fluid in a liquid state, the heating fluid constituting a fluid which changes from its vapor state to its liquid state in response to temperatures occurring in critical portions of the mold passages during operation of the mold, the heat exchanger being positioned so that the upper level of liquid fluid in the heat exchanger is approximately at or below the bottom of the mold;

an inlet conduit connecting the heat exchanger, from a point above the upper level of the fluid, to the upper ends of the mold passages,

a return conduit connecting the lower ends of the mold passages back to the heat exchanger;

the heat exchanger, the mold passages, and the inlet and return conduits constituting a closed loop;

and heat exchanger control means for controlling operation of the heat exchanger to vaporize fluid from the liquid supply in the heat exchanger to maintain the conduits and the mold passages filled with fluid vapor at a controlled pressure;

the heat exchanger control means including means to adjust the pressure to establish a maximum limit temperature for heating of the mold and means for actuating the heat exchanger to vary the loop pressure in synchronism with the molding cycle.

8. A passive mold heating system according to claim 7 in which the heating fluid is water.

9. A passive mold heating system according to claim 7 in which the heating fluid is a Freon refrigerant.

10. A passive mold heating system according to claim 7 in which the heat exchanger control means further comprises:

pressure sensing means for sensing the pressure in the closed loop;

first and second inlet/outlet conduits for the heat exchanger, one including a control pump and the other a control valve;

and controller means, connected to the pressure sensing means, for actuating the control pump and the control valve in response to variations in pressure in the closed loop to maintain a constant pressure.

11. A passive mold heating system according to claim 7 in which the heat exchanger includes an internal coil and the heat exchanger control means further comprises:

pressure sensing means for sensing the pressure in the closed loop;

heater apparatus for circulating a heated heat transfer fluid through the heat exchanger coil; and

controller means, connected to the pressure sensing means, for adjusting operation of the heater apparatus in response to variations in pressure in the closed loop to maintain a constant pressure.