US2859499A

US2859499A - Molding press head control system

Info

Publication number: US2859499A
Authority: US
Publication date: 1958-11-11
Anticipated expiration: 1975-11-11

Description

NOV. 11, 1958 w FLOEHR 2,859,49Q

MOLDING PRESS HEAD CONTROL SYSTEM Filed Sept. 5, 1957 PEESSUEE SOURCE I 44 I I 34 42 1 r 40 48 I 32 i 38 f I x 1 4 36 I l 46 4 g 0 4 i INVENTOR 54 x, i o I '6 ilalferblloelw ATTORNEY Ice Patented Nov. 11, 1958 MOLDING PRESS HEAD CONTROL SYSTEM Walter L. Floehr, Toledo, Ohio, assiguor to Unitcast Corporation, Toledo, Ohio, a corporation of 01110 Application September 5, 1957, Serial No. 682,239

6 Claims. (Cl. 22-42) This invention relates to molding press head control systems wherein a flexible diaphragm is expanded by applying fluid pressure behind diaphragm to pack sand within a mold flask, and more particularly to an improved control apparatus for retracting the diaphragm away from the sand after the sand has been packed within the flask.

The usual arrangement in systems of this type is to employ a hollow, boxlike mold press head, the lower wall of which is defined by a flexible rubber diaphragm. The press head is mounted in a fixed position, and molding flasks which have been filled with sand are brought into position beneath the mold head by a conveyor systern (not shown). By supplying fluid under pressure to the interior of the press head, the flexible diaphragm is expanded into contact with the sand in the flask and further application of pressure to the interior of the press head causes the diaphragm to firmly compact the sand within the flask. When the sand has been compacted, the pressure source is disconnected from the press head and a vacuum source is connected to exhaust the fluid from the interior of the head, thus retracting the diaphragm away from the sand within the flask to permit the flask to be moved away from the mold head.

In the usual case, the vacuum source takes the form of a pump which, because of the relatively rapid rate at which flasks are presented to the press head, is continuously operated or driven. Because of the relatively high pressures employed in compacting the sand within the mold flask, it has been found that when the vacuum pump is first connected to the press head, the capacity of the pump is insuflicient to handle the amount of pressurized air flowing from the press head and thus actually impedes the initial flow of high pressure air from the press head. Since molding apparatus of this general type is usually operated at a full capacity basis, the cumulative delays occasioned by the inability of the vacuum pump to handle the necessary flow of air from the pressure head become quite substantial.

The primary object of my invention is to provide a means for increasing the productive capacity of molding apparatus of the type described above.

Another object of my invention is to provide a molding press head control system in which the speed of retraction of the flexible diaphragm may be increased without increasing the capacity of the vacuum pump employed to retract the diaphragm.

Still another object of my invention is to provide means for improving the efliciency of the vacuum pump employed in a molding apparatus of the type described above which may be easily installed on existing equip ment.

Other objects and advantages of my invention will become readily apparent by reference to the following specification taken in conjunction with the accompanying drawings.

In the drawings: Figure l is a partially schematic view of a molding press head, shown in cross-section, embodying my invention;

Figure 2 is an end view of the vacuum pump and as sociated ducts of Fig. 1;

Figure 3 is a plan view of the valve of Fig. 2;

Figure 4 is a partial cross-sectional view taken on the line of 44 of Fig. 2. Y

Referring first to Fig. l, a mold press head designated generally 10 includes a boxlike metallic frame 12 having a flexible rubber diaphragm 14 sealingly secured across the open lower side of the frame. While the press head assembly 10 is shown only in cross-section, it is believed apparent that the flexible diaphragm 14 defines the lower wall of a closed chamber within the head 10.

A duct 16 is connected to openings through the frame 12 as at 18 and 20 and connects the interior of the chamber 15 to one port of a schematically illustrated valve 22; A pressure source 24 is connected to the valve 22 by' means of a'duct 26 to supply pressure through the duct 16 to the chamber 15 when the movable member of the.

valve 22 is in the position shown in Fig. l.

A vacuum pump 28 is connected to the valve 22 through a duct 30. It is believed apparent that the movable member of valve 22 may be rotated through a ninetydegree angle from the position shown in Fig. 1 to con-i nect the duct 30 to the duct 16 thereby connecting" the chamber 15 to the vacuum pump 28.

.Pump 28 is of conventional construction, and may conveniently be of the centrifugal type in which the impeller is driven by means of a shaft 32 driven by a conventional motor (not shown). The normalinlet open ing 34 of the pump 28 is covered by a plate 36 having a reduced diameter inlet opening 38. An inlet duct assembly 40 includes a flange 42 which overlies the plate 36 and is secured to the frame of the pump 28 by means' of bolts 44 which clamp the plate 36 into sealing engage ment with the pump casing. As best seen in Fig. 2, the inlet duct assembly 40 includes coaxially arranged outer 46 and inner 48 ducts. At its lower end, the outer duct,

46 is connected as by welding to a duct section 50 which is provided with a flange 52 for connection to a corresponding flange on the endof the duct 30. The inner duct 48 extends across the interior of the duct section 50 and is mounted withinthe outer duct 46 by welding the lower end of the duct-48 to the interior of the duct section 50. Duct 48 is so dimensioned that when the duct assembly 40 is mounted on the pump frame, the upper end of the inner duct 48 surrounds the opening 38 in plate 36 and effectively seals this end of the duct- 48 to the plate 36. At its lower end, the inner duct' 48 is provided with a pair of relatively small orre-- stricted inlet openings 54 placing the duct 48 in com munication with the

ducts

46 and 50.

A venting duct 56 is secured, as by welding, to the outer duct 46 and is in open communication with the, interior of the outer duct. At its upper end, the venting" duct is provided with a flap valve assembly 57 which includes a flap 58 which is supported upon a pivot pin 60 journaled into a lug 62 fixed to the upper end of duct 56. a The lower surface of the plate-58 is provided with a rubber face 64 to improve the sealing characthe valve 22 is actuated to the position shown in Fig. 1 to .connect the pressure source 24 to the chamber 15. Fluid under pressure enters the chamber and expands the flexible diaphragm into engagement with the sand, and as further pressure is supplied to the chamber 15, the flexible diaphragm 14 compacts the sand within the flask F about the pattern P.

After a predetermined pressure has been achieved Within the chamber 15, the valve 22 is actuated to disconnect pressure source 24 from the chamber 15 and connect the chamber 15 to the duct Fluid under pressure passes from chamber 15 into the duct 30 and into the interior of the duct section 50. From the duct section 50, the fluid under pressure may flow into the interior of both

ducts

46 and 48. When the pressure within the duct 46 begins to rise due to the flow of pressurized air from the press head, plate 58 of the flap valve is moved upwardly into the dotted line position of Fig. 2, thereby opening the interior of the duct 46 to the atmosphere through the duct 56. In this manner, the pressure within chamber 15 is rapidly reduced to atmospheric pressure.

As disclosed in the drawings, plate 58 is gravitationally biased toward its closed position, and when the pressure within the chamber 15, and hence

ducts

30, 50, and 46 approaches atmospheric pressure, the flap valve automatically closes by the fall of plate 58 to its full line position in Fig. 2. In certain applications, it may be desirable to use a spring biased valve closure member. After the valve 57 closes, the constantly driven vacuum pump 28 continues to reduce the pressure within chamber 15 to below atmospheric pressure and thereby retracts the flexible diaphragm 14 upwardly away from the sand within the flask F. When the diaphragm is retracted, the traverse car T- containing the compacted mold flask is removed and a fresh traverse car T is moved into position beneath the press head 10 fora repetition of the foregoing operation.

Since the vacuum pump 28is constantly driven, it can be appreciated that the foregoing operation may be rapidly repeated. The rapid lowering of the pressure within chamber 15 by venting this chamber to the atmosphere through the outer duct 46, duct 56 and the flap valve permits-the pressure within chamber 15 to be rapidly reduced below atmospheric without: requiring a substantial increase in the capacity of the vacuum pump 28.

While I have described butone embodiment of my invention,'itwill be apparent-to those skilled in the art that the disclosed embodimentis capable of modification. Therefore, the foregoing description is to be considered exemplary rather than limiting and the true scope ofmy invention is that defined in the following claims.

I claim:

1. In combination with a mold press head having pressure responsive means for compacting sand within a mold flask; a pressure source for moving said pressure responsive means to a sand compacting position and including a first duct means, a vacuum source for retracting said pressure responsive means from said sand compacting position and including a second duct means, valve means for selectively connecting either said first or said second duct means to said press head, and means for venting said second duct means to atmospheric pressure when the pressure in said second duct exceeds a predetermined pressure.

2. In combination with a mold press head having pressure responsive means for compacting sand within a-mold flask; a pressure source for moving said pressure responsive means to a sand compacting position and including a first duct means, a vacuum source for retracting said pressure responsive means from said sand compacting position and including a second duct means, valve means for selectively connecting either said first or said second duct means to said press head, a valve in said second duct means for venting said second duct means to atmospheric pressure, and means for closing said valve when the pressure in said second duct means approaches atmospheric pressure.

3. The combination recited in claim 2 wherein said second duct means includes an inner duct connected to said vacuum source, an outer duct in communication with said inner duct, and means connecting said valve to said outer duct.

4. In combination with a mold press head having pressure responsive means for compacting sand within a mold flask; a pressure source for moving said pressure rcsponsive means to a sand compacting position and including a first duct means, a constantly driven vacuum pump for retracting said pressure responsive means from said sand compacting position, second duct means connected to the inlet of said vacuum pump, valve means for selectively connecting either of said first and said second duct means to said press head to operate said pressure responsive means, and means for venting said second duct means to atmospheric pressure when the pressure in said second duct exceeds a selected pressure.

5. In combination with a mold press head having pressure responsive means for compacting sand Within a mold flask; a pressure source for moving said pressure responsive means to a sand compacting position and including a first duct means, a constantly driven vacuum pump for retracting said pressure responsive means from said sand compacting position, second duct means connected to the inlet of said vacuum pump, valve means for selectively connecting either of said first and said 'second duct means to said press head to operate said pressure responsive means, a valve in said second duct means for venting said second duct means to atmospheric pressure, and means for closing said valve when the pressure in said second duct means approaches atmospheric pressure.

6. In combination with a mold press head having pressure responsive means for compacting sand within a mold flask; a pressure source for moving said pressure responsive means to a sand compacting position and including a first duct means, a constantly driven vacuum pump for retracting said pressure responsive means from said 'sandcompacting position, an inner duct connected to the inlet of said vacuum pump, an outer duct surrounding said inner duct and in communication there with, a normally closed valve mounted on said outer duct for venting said outer duct to atmospheric pressure, and means for opening said valve when the pressure Within said outer duct is above a predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,715,758 Taccone Aug. 23, 1955 2,767,445 Taccone Oct. 23, 1956 2,805,455 Whitesell Sept. 10, 1957 FOREIGN PATENTS 682,295 France Feb. 11, 1930 788,955 France Aug. 5, 1935