US2948029A - Safety control for molding machines - Google Patents

Description

Aug. 9, 1960 B. c. FERRIS SAFETY CONTROL FOR MOLDING MACHINES Filed July 29, .1957

United States Patent SAFETY CONTROL FOR MOLDING MACHINES Burton C. Ferris, Detroit, Mich., assignor to Kelsey-Hayes Company, Detroit, Micln, a corporation of Delaware Filed July 29, 1957, Ser. No. 674,823 4 Claims. (122-35) injury to the machine due to operation with insuflicient sand in the mold flask.

The invention has for still another object to provide molding apparatus including a molding machine for packing sand in a mold flask, a sand hopper for containing a supplyof sand for the flask, and means dependent upon the quantity of sand in the hopperfor rendering the molding machine operative and inoperative.

Patented Aug. 9, 1960 sand in the flask after it has been packed around the patterns 16.

The flask is adapted to be mounted on the pattern plate 17 which in turn is mounted on the carrier 18. The carrier 18 is supported on a track 19 for movement from the solid line position beneath the molding machine to the dotted line position beneath the sand hopper 20. Any suitable means may be provided for moving the carrier-back and forth. The hopper 20 is in the form of an open top container adapted to contain a supply of sand for the molding machine. A batch hopper 21 is secured to the bottom 22 of the hopper 20 and is provided to fill the mold flask with a measured quantity of sand for the molding operation. The batch hopper may be of any suitable construction and may, for example, have a shutter at the top for admitting sand from the hopper 20 into the batch hopper 2.1 and a shutter at the bottom for discharging the sand admitted to the batch hopper. The capacity of the batch hopper will determine the quantity. of sand in each batch.

Air under pressure is supplied to the chamber 3 of the molding machine head through pipe 7 by a valve 23 and a pipe 24 connected to a suitable source of fluid under pressure. The valve '23 is a 3 way 2-position valve adapted to connect the pipe 7 selectively with the air pressure pipe 24 and the pipe 25 which leads from the The invention has for a still further object to provide molding. apparatus including a. molding machine of the diaphragm type for packing sand in a mold flask, a sand hopper, means for fillingthe flask with a predetermined quantity of sand from the hopper, and means responsive-todepletion of the sand in the hopper to a pre determined minimum level for rendering the molding machine inoperative.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating a preferred embodiment of the invention, wherein:

Fig. 1 is a semi-diagrammatic side elevational view, partly in section, of molding apparatus embodying the invention.

Fig. 2 is a diagram of an electrical circuit for the molding apparatus.

Referring now more particularly to the drawing, the molding machine 1 comprises a fixed head 2 formed with a chamber 3. The under side of the head has a concave substantially hemispherical surface 4 which communicates with the chamber 3 by ports 5. The chamber 3 is evacuated or supplied with air under pressure through port 6 by the pipe 7. The chamber 3 is a closed chamber except for the ports 5 and 6.

An annular clamping ring 8 is secured to the annular flange 9 encircling the head by bolts 10, and the entire periphery of a flexible diaphragm 11, of rubber or like material, is clamped between the ring 8 and flange 9.

The space defined between the diaphragm at the bottom of the head is closed except for ports 5 which provide communication with chamber 3.

The diaphragm 1-1 is provided for packing sand in a flask 12. The flask 12 has an annular side wall 13 and is open at the top and bottom. A plurality of sand retaining ribs 14 are secured to the wall 13 of the flask and project radially inwardly of the flask in circumferentially spaced relation to each other. The radially inner ends of the ribs are permanently secured to a ring 15. The ribs 14 and ring 15 are provided to hold the vacuum pump 26. The valve '23 has a normal position connecting chamber 3 to the vacuum pump. A solenoid 27 is associated with the valve and, when energized, shifts the valve to its other position connecting the chamber with the source of air under pressure.

In operation, the carrier 18 with the pattern plate and flask and patterns mounted thereon is moved to the dotted line position of Fig. l and the batch hopper 21 is operated to fill the flask with a measured quantity of sand. The carricris then moved to the solid line position. At this time, the valve 23 is in its normal position connecting the chamber '3 to the vacuum pump 26 to evacuate the chamber and draw the diaphragm up to the dotted line position of Fig. 1. The solenoid 27 of the valve 23 is then energized by the manually operated control button 28 (or limit switch in case of automatic operation) to shift the valve 23 to a position admitting air under pres sure to chamber 3 from the pipe 24 and pressing the diaphragm down against the sand in the flask. The pressure of the diaphragm on the sand in the flask is suflicient to pack or squeeze the sand tightly around the patterns to produce a satisfactory mold. Thereafter, the button 28 is opened to again evacuate chamber 3 and draw up the diaphragm for removal of the flask.

In the event that the flask is filled with an insuflicient quantity of sand, there is the possibility that the diaphragm will be damaged during the subsequent packing or squeezing operation. Thus the diaphragm may be unduly stretched when subjected to air under pressure, or it may contact sharp edges on the ribs 14, ring 15 or patterns 16 with rmultant damage to the diaphragm. In order to avoid damage to the diaphragm, a probe 29 is provided which includes a relay 30 connected into an electrical circuit by the wires 31 and 32 which extend into the hopper. The wires 31 and 32 terminate within the hopper in spaced relation to each other to provide a gap 33 in the circuit to the relay 30. With sand in the hopper above the level of the gap, the circuit across the gap is completed by the sand to energize the relay. The molding sand normally employed for this purpose has a measured amount of Water in it and the moist sand is a sufliciently good conductor of electricity for this purpose. Experiments have shown that any suitable green sand for molding will carry the current across the gap no matter what its water content.

When the level of sand in the hopper drops beneath the dotted line '34, that is beneath the level of one of the wire terminals, the circuit to the probe relay is broken. The probe relay has a normally open contact 35 in the circuit to the solenoid 27. Accordingly, when the level of sand in the hopper drops beneath the dotted line 34, the circuit to the solenoid is opened to shift the valve to its normal position evacuating the chamber 3. Under these conditions, the solenoid valve cannot be energized by the manual switch 28 to subject the diaphragm to fluid under pressure and pack or squeeze the sand into the flask.

What I claim as my invention is:

1. Molding apparatus comprising a molding machine having means including a flexible, fluid pressure operated diaphragm for packing sand in a flask,.means for subjecting said diaphragm to fluid under pres-sure to press said diaphragm against sand in the flask to pack the sand, a sand hopper, means for filling the flask with a measured quantity of sand from said hopper, and control means dependent upon the quantity of sand in said hopper for rendering said second-mentioned means operative and inoperative, said control means rendering said second-mentioned means operative when the sand in said hopper is above a predetermined level suflicient to adequately fill the flask and inoperative when the sand in said hopper falls below said predetermined level.

2. Molding apparatus comprising a molding machine having means including a flexible, fluid pressure operated diaphragm for packing sand in a flask, means for subjecting said diaphragm to fluid under pressure to press said diaphragm against sand in the flask to pack the sand, a sand hopper, means for filling the flask with a measured quantity of sand from said hopper, and means for rendering said second-mentioned means inoperative in response to depletion of the sand in said hopper to a predetermined minimum level.

3. Molding apparatus comprising a molding machine having means including a flexible, fluid pressure operated diaphragm for packing sand in a flask, means for subjecting said diaphragm to fluid under pressure to press said diaphragm against sand in the flask to pack the sand, a sand hopper, means for filling the flask with a 4 measured quantity of sand from said hopper, and control means including an electric circuit extending within said hopper and having a gap in said circuit at a predetermined minimum level within said hopper such that the quantity of sand at said level is suflicient to adequately fill the flask, said circuit across said gap being closed by sand in said hopper at or above said predetermined minimum level, and means operated by said control means when said circuit is closed for rendering said secondmentioned means operative and when said circuit is open for rendering said second mentioned means inoperative.

4. Molding apparatus comprising a molding machine including means for packing sand in a flask, a sand hopper for containing a supply of sand for the flask, and control means including an electric circuit extending within said hopper and having a gap in said circuit at a predetermined minimum level within said hopper such that the quantity of sand at said level is suflicient to adequately fill the flask, said circuit across said gap being closed by sand in said hopper at or above said predetermined minimum level, and means operated by said control means when said circuit is closed for rendering said first-mentioned means operative and when said circuit is open for rendering said first-mentioned means inoperative.

References Cited in the file of this patent UNITED STATES PATENTS Fisher May 31, 1927 OTHER REFERENCES Foundry Trade Journal, Bin Level Indicator, January 12, 1950, page 38.

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