US3643729A

US3643729A - Squeeze head assembly for molding machines

Info

Publication number: US3643729A
Application number: US876882A
Authority: US
Inventors: Russell J Smith; William H Froman
Original assignee: Midland Ross Corp
Current assignee: Smith Corona Corp; Midland Ross Corp
Priority date: 1969-11-14
Filing date: 1969-11-14
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

A molding machine for making metal casting sand molds having for compacting the sand a squeeze head presenting to the sand a diaphragm backed by a liquid-filled pressure chamber open to the liquid side of an accumulator which adds liquid to the chamber for an initial compacting of the sand under low pressure and receives liquid therefrom during projection of the head in a final high-pressure compacting stage.

Description

United States Patent Smith et al.

[ 1 Feb. 22, 1972 [54] SQUEEZE HEAD ASSEMBLY FOR MOLDING MACHINES [72] Inventors: Russell J. Smith, Toledo; William H.

Froman, Luckey, both of Ohio Midland-Ross Corporation, Ohio [22] Filed: Nov. 14, 1969 [21] Appl.No.: 876,882

[73] Assignee: Cleveland,

[52] US. Cl ..l64/l70, 164/207 [51] Int. Cl. ..B22c 15/08 [58] FieldofSearch ..l64/l69, 170, 171, 172, 37,

[56] References Cited UNITED STATES PATENTS 2,956,317 10/1960 Peasley ..l64/l70 3,041,685 7/1962 Taccone ..164/170 X 3,089,206 5/ 1963 Abraham l 64/ 1 70 3,168,764 2/1965 Miller ..l64/38 X Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown AuomeyWilmer Mechlin [s11 ABSTRACT.

6 Claims, 4 Drawing Figures PATENTEDFEBZZ m2 SHEET 1 BF 3 FIG. 1,

FIG. 2

lnvenfora Russel J. Smith William H. Froman their Attorney PAIENTEDFB22 m2 3.643 .729

SHEET 3 0F 3 FIG. 4

SQUEEZE HEAD ASSEMBLY FOR MOLDING MACHINES BACKGROUND OF THE INVENTION A sand mold for casting steel and other metals generally has two parts, known as the cope and the drag, and it is customary to make each part by compacting molding sand in a flask about a pattern inserted in one end of the flask. Depending on the molding machine, the mold parts may be made either separately or together, the latter by inserting between a pair of flasks a mold plate mounting on opposite faces the patterns for both parts. In any case, it is desirable that the sand in a flask be compacted uniformly, regardless of the intricacy of the pattern, and for this purpose it is now common practice to apply pressure to the sand through a rubber or like flexible or elastic diaphragm, which, at least in the initial compacting, is bulged or distended by fluid under pressure applied to its back. If, as in our copending application Ser. No. 684,765, new U.S. Pat. No. 3,528,480, issued Sept. 15, 1970, the pressurized fluid is air or another gas, it also is not unusual to perform the compacting in two stages, the first or initial stage at low pressure and the second or final stage at high pressure, with the compressibility of the gas enabling the diaphragm to yield as necessary for uniform compacting in the second stage.

To minimize the volume of the fluid required, Peasley US. Pat. No. 2,956,317 backs the diaphragm by a pressure chamber containing a liquid and bulges the diaphragm by adding liquid under pressure to the chamber, but only against the weight of the sand, and locks the added liquid in the pressure chamber before applying compacting pressure. The liquid being incompressible, the practical effect is to limit the compacting to a single stage. It is with the adaptation of a liquidbacked diaphragm to plural stage compacting that the present invention is primarily concerned.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide an improved molding machine squeeze head assembly which not only applies pressure through a liquid-backed diaphragm but also enables the diaphragm to compensate for otherwise nonuniform compacting in both lowand high-pressure compacting stages.

Another object of the invention is to provide a molding machine squeeze head assembly applying pressure to molding sand through a liquid-backed diaphragm wherein the diaphragm is pressurized for initial low-pressure compacting and enabled to continue compensating for depth irregularities in the sand or other particulate material being compacted during a succeeding high-pressure stage, by an accumulator having a liquid side open to a liquid pressure chamber in back of the diaphragm.

Designed for incorporation in a molding machine for making metal casting molds of sand or other particulate material, as a dynamic or static head or both, the improved squeeze head assembly presents for compacting the material a rubber or like flexible or elastic diaphragm backed by a pressure chamber containing oil or other suitable liquid and open to the liquid side of a positive displacement accumulator, the chamber at all times containing sufficient liquid to fully back the diaphragm. Applying a predetermined pressure to the diaphragm through the liquid in the pressure chamber by compressed air or another suitable compressible medium for an initial low-pressure compacting stage, the accumulator, during a final compacting stage at otherwise applied relatively high pressure, enables the diaphragm to yield as necessary by displacing liquid from the pressure chamber into the accumulator's liquid side.

The foregoing and other objects and features of the invention will appear hereinafter in the detailed description, be particularly pointed out in the appended claims and be illustrated in the accompanying drawings, in which:

FIGURE DESCRIPTION FIG I is a side elevational view ofa molding machine incorporating a preferred embodiment of the improved squeeze head assembly of the present invention;

FIG. 2 is a horizontal sectional view on a larger scale taken along lines 2-2 of FIG. I;

- 'FIG. 3 is a fragmentary vertical sectional view on the scale of FIG. 2, taken centrally through the pressure head and accumulator and showing their condition in the initial low-pressure compacting stage; and

FIG. 4 is a view similar to FIG. 3, showing the condition of the pressure head and accumulator during the final high-pressure compacting stage.

DETAILED DESCRIPTION Referring now in detail to the drawings in which like reference characters designate like parts, the improved molding machine squeeze head assembly of the present invention, designated as l, is adapted to be applied to or incorporated in molding machines for making molds of sand or other particulate material for casting steel or other metals.

Ordinarily, sand casting molds are made in two parts, one, a cope and the other, a drag, and each part is made in one of a pair of flasks which are clamped together during casting. Among molding machines now in use, some make both parts at once, while others make them separately. In either case, the molding operation involves inserting a pattern mounted on a pattern plate in one end of a flask, which is either previously or subsequently filled with molding sand and applying pressure to compact the sand, usually by a dynamic head acting on one end of the flask against a static head on the other. For simple patterns, solid heads may suffice, but, as suited for both simple and complex or intricate patterns, diaphragm-type heads are widely used and in machines making both parts of a mold at the same time, both heads may be of this type. Depending on its type, a molding machine thus may have either one or a pair of the improved assemblies. However, for simplicity of depiction, the machine 2, illustrated as exemplary of applications of the improved assembly, has been shown with but one such assembly, even though adapted to make both parts of a mold at the same time.

The exemplary machine 2 has a frame 3 formed of uprights or columns 4 joined at the top by a crossmember or header 5. Within the frame, a stationary flask stool or table 6, having a suitably hollow platform or top frame 7 mounted at the corners on legs 8, is adapted to support one or more flasks 9 at the outset of a molding operation. In the illustrated molding machine, two superimposed flasks 9 are initially supported on the stool 6 and interposed between them is a pattern plate 10 mounting or carrying on opposite faces the patterns 11 for the two parts of the complete mold the machine is adapted to make at the same time. A sand shield or fill frame 12 surmounting the upper of the flasks 9, during filling or charging guides loose molding sand from a hopper (not shown) into the upper flask'and, between filling and compacting, holds the extra or additional loose sand required for the upper mold, the latter a function performed for the lower mold by the hollow platform or top 7 of the stool 6.

Equipped with lower dynamic or force-applying and upper static or force-receiving squeeze or

pressure heads

13 and 14, respectively, acting in compacting on opposite ends of the flasks 9, the illustrated molding machine 2 has the lower head mounted on the upper end of a vertically acting, suitably hydraulic ram or jack 15. In operating or compacting position vertically aligned with the lower head 13 and reacting against the crossmember or header 5 at the top of the frame 3, the upper head 14 conveniently so reacts through a carriage 16 mounted on the frame on rollers 17 for shifting horizontally out of the way of a sand hopper (not shown) taking its place during filling of the flasks.

Whether dynamic or static, each of the

heads

13 and 14 can be a head of one of the improved squeeze head assemblies 1 of H024 nun this invention and, as mentioned earlier, this would be the preferred arrangement, when, as illustrated, the machine 2 is adapted to make both parts of the mold at the same time.

Serving in the exemplary installation as the squeeze head of the improved assembly 1 of this invention, the lower dynamic head 13 is comprised of a rigid housing or casing 18 having an end wall 19 and sidewalls 2O integral or rigid with and upstanding or outstanding from the end wall and therewith bounding or confining sides and an end ofa cavity or recess 21 opening at its other end upwardly or outwardly toward the associated flask 9 A rubber or like flexible or elastic diaphragm 22, peripherally secured to the sidewalls 20, conveniently by a clamping ring 23 bolted thereto, forms with the cavity 21 a pressure chamber 24.

First increasing and then decreasing in volume in the course of a compacting operation, the pressure chamber 24 at minimum must have sufficient volume and depth for the particular mold being made to fully back the diaphragm 22 and space it from the chambers rigid rear or inner end wall 19 over the range of pressures to which the diaphragm is subjected. To this end, the pressure chamber is filled with oil or other suitable liquid, with the preferred minimum content sufficient to fill the cavity 21 when the diaphragm is flat or undistended. Additionally, for varying its volume, the pressure chamber is connected and open to or in open communication with the liquid side of an accumulator 25, which and the head 13 are the main components of the assembly I. The accumulator 25 may either be inbuilt into the squeeze head 13, behind or below the pressure chamber 24, or be a separate member stationarily mounted on the molding machine 2, conveniently on an adjoining column 4. However, whatever its relative location, the accumulator 25 must be capable of alternately adding liquid under a predetermined pressure to the pressure chamber 24 to distend or bulge the diaphragm 22 and yieldably receiving liquid from the pressure chamber, up to the amount added, when the diaphragm is subjected to an opposing higher pressure.

Possessing the foregoing capability, the preferred accumulator is comprised ofa cylinder or cylindrical casing 26 and a floating piston or shuttle 27 in and shiftable or reciprocable axially of the cylinder. Suitably gasketed, as by peripheral rings 28, against fluid leakage between itself and the sidewall 29 of the cylinder 26, the piston 27 divides the cylinder 26 axially into two compartments of relatively variable volume. One is a liquid compartment 30, filled or fillable with the same liquid as and open to or in open communication with the pressure chamber 24 and serving as the accumulators liquid side, and the other, an actuating compartment 31, at least during compacting, containing or receiving a resilient, yieldable or compressible, actuating or force-applying means or medium, such as a coil spring or, as illustrated, a compressed gas. Most conveniently compressed air, the compressed gas may be introduced into the air chamber 31 through a suitably valved supply or feedline 32 leading thereto from a compressor or other source (not shown). An open, suitably unvalved connecting line or pipe 33, at least partly flexible, if, as in the illustrated application, the head 13 and the accumulator are relatively movable, connects the liquid compartment 30 to the pressure chamber 24 in the head.

Each of the

squeeze heads

13 and 14 must be of a size and shape to slide or fit into the adjoining end of the related flask 9 and, to suit most flasks, both the squeeze heads and the pres sure chamber 24 usually will be rectangular in horizontal cross section. However, the interfit between the heads and the flasks ordinarily will not obtain at the outset of a compacting operation. instead, in the condition depicted in FIG. 1 in which the charging or filling of the two flasks 9 with molding sand has just been completed, the

heads

13 and 14 will be withdrawn or spaced vertically from their respective flasks sufficiently to accommodate for the lower mold in the platform 7 and the upper mold in the sand shield 12 the additional loose sand required to complete the molds. In this inactive or preliminary condition, the pressure head assembly 1 has its head 13 inside the platform 7, the diaphragm 22 is flat, the piston 27 is unpressurized on its actuating side and at substantially the top of the cylinder 26 and the pressure chamber 24, the liquid compartment 30 below the piston and the connecting line 33 are all filled with the same liquid.

ln commencing the two stage compacting operation for which the improved assembly 1 is particularly designed, using compressed air as the yieldable actuating medium, the compressed air is introduced into the actuating compartment 31 in the cylinder 26 of the accumulator 25 at the desired first stage pressure, usually on the order of 3540 p.s.i., and, by shifting the piston 27 toward the liquid end of the cylinder 26 and correspondingly displacing or adding liquid to the pressure chamber 24, the same pressure is transmitted through the liquid to the diaphragm 22, causing the latter to bulge or distend upwardly or outwardly. Either during or after this pressurizing of the diaphragm 22, the lower head 13 is raised or elevated by actuation of the ram 15 to lift the flasks 9 from the stool 6 to approximately the position shown in FIG. 3 in which the upper head 14 has been brought into play as a reactance and equilibrium has been reached between the pressures applied to and reacting against the diaphragm. Since, due to the backing of the liquid in the pressure chamber 24, the pressure is uniform over the entire surface of the diaphragm, on reaching equilibrium, the pressure of 35-40 p.s.i. applied through the accumulator 25 for the initial or first low-pressure compacting stage, will be distributed through the diaphragm uniformly over the sand in the lower mold and the flexibility or elasticity of the diaphragm will enable it to yield or change contour as necessary to accommodate any height irregularities in the lower pattern.

Following the initial low-pressure compacting, the pressure on the molding sand will be increased to the compacting pressure of the second or final stage, usually on the order of about psi, but with the difference over the first stage that the increase to the final pressure is produced by actuating or extending the ram 15 for further advancing or raising the lower head 13 and therewith the flasks 9 to the position shown in FIG. 4, and thereby further squeeze or compact the sand in the flasks between that head and the upper head 14. During this further squeezing, up to the final compacting pressure, the valve 34 in the supply line 32 may be either open or closed, but the pressure chamber 24 will, as always, be open to the liquid compartment 30 in the accumulator 25 and the compressed air or other actuating medium, responsible for the low pressure of the first stage, will be yieldable to the opposing higher pressure applied through the diaphragm 22. Consequently, as the pressure is increased in the final compacting stage, the diaphragm, despite the incompressibility of the backing liquid, can yield by displacing or returning part or all of the quantity of liquid added in the first stage to the accumulator 25. At the same time, the diaphragm will retain both its flexibility and full backing by the liquid, the latter because of the minumum limit imposed on the liquid content of the pres sure chamber 24. Thus, as in the initial compacting stage, in the final stage the compacting pressure applied by the lower head 13 through the diaphragm to the molding sand presented thereto, will be uniform over the entire surface of the diaphragm and the diaphragm, by displacing liquid or flexing, or both, can continue to correct or compensate for any inequalities in compacting to the completion of the compacting operation.

From the above-detailed description it will be apparent that the improved squeeze head assembly of the present invention combines the economy in fluid requirements of a liquidbacked diaphragm with the increased uniformity of plural stage compacting. It should be understood that the described and disclosed embodiment is merely exemplary of the invention and that all modifications are intended to be included that do not depart from the spirit of the invention and the scope of the dependent claims.

Having now described our invention, we claim:

H074 (nu 1. in a molding machine having a squeeze member, a squeeze head assembly opposing said member for therewith hydraulically compacting particulate molding material in a plurality of stages at successively higher pressures, said assembly comprising a head, an elastic diaphragm mounted on said head for applying pressure therefrom to said material, a pressure chamber contained in said head and closed at an outer end by said diaphragm, an accumulator having a variable volume liquid compartment open to said pressure chamber throughout a molding operation, liquid filling said chamber and compartment and throughout said operation freely transferable therebetween and fully backing said diaphragm, and yieldable means acting on said compartment for transferring liquid therefrom to said pressure chamber under a predetermined pressure and applying said pressure to said material through said diaphragm in one compacting stage, and a ram acting on one of said member and head in a succeeding compacting stage for applying through said material to said diaphragm a pressure opposing and higher than the pressure applied thereto by said yieldable means, said yieldable means under said opposing higher pressure yielding thereto for enabling said compartment to receive liquid from said pressure chamber.

2. A squeeze head assembly according to claim 1, wherein the maximum limit of the capacity of the accumulator to receive liquid in the succeeding stage is the amount of liquid transferred therefrom to the pressure chamber in the one stage.

3. A squeeze head assembly according to claim 2, wherein the accumulator includes a cylinder and a floating piston axially shiftable therein, the liquid compartment is on one side of said piston, and the yieldable means acts on the other side of said piston for applying the predetermined pressure of the one stage and yielding to the higher pressure of the succeeding stage.

4. A squeeze head assembly according to claim 3, wherein the yieldable means is received during compacting in the cylinder.

5. A squeeze head assembly according to claim 4, wherein the yieldable means is compressed gas.

6. A squeeze head assembly according to claim 4, wherein only a rigid rear wall of the pressure chamber is presented for engagement with a back of the diaphragm, and the liquid in the chamber at all times spaces the diaphragm therefrom.

Claims

1. In a molding machine having a squeeze member, a squeeze head assembly opposing said member for therewith hydraulically compacting particulate molding material in a plurality of stages at successively higher pressures, said assembly comprising a head, an elastic diaphragm mounted on said head for applying pressure therefrom to said material, a pressure chamber contained in said head and closed at an outer end by said diaphragm, an accumulator having a variable volume liquid compartment open to said pressure chamber throughout a molding operation, liquid filling said chamber and compartment and throughout said operation freely transferable therebetween and fully backing said diaphragm, and yieldable means acting on said compartment for transferring liquid therefrom to said pressure chamber under a predetermined pressure and applying said pressure to said material through said diaphragm in one compacting stage, and a ram acting on one of said member and head in a succeeding compacting stage for applying through said material to said diaphragm a pressure opposing and higher than the pressure applied thereto by said yieldable means, said yieldable means under said opposing higher pressure yielding thereto for enabling said compartment to receive liquid from said pressure chamber.