US3643725A

US3643725A - Method for lifting flasks and molds

Info

Publication number: US3643725A
Application number: US824777A
Authority: US
Inventors: William L Fismer
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-05-15
Filing date: 1969-05-15
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

An arrangement is disclosed for improving the handling or stripping of the flasks or molds of the type which are used to cast large items such as cast metal plates or frames. A system is provided for lifting the flask or mold vertically from the pattern with assurance that each portion or part is moved at exactly the same rate and amount as every other part.

Description

United States Patent Fismer [54] METHOD FOR LIFTING FLASKS AND MOLDS [72] Inventor: William L. Flsmer, 162 Franklin St.,

Verona, NJ. 07044 [22] Filed: May 15, 1969 [21] Appl. No.: 824,777

[52] US. Cl ..164/44, 164/213, 164/403,

254/93 L [51] Int. Cl. ..B22c 17/06 [58] Field of Search ..60/97 E, 97 L; 164/44, 131,

[56] References Cited UNITED STATES PATENTS 2,484,646 10/ l 949 Renkenberger 164/403 2,499,563 3/1950 'Bill ..60/97 P Feb. 22, 1972 FOREIGN PATENTS OR APPLICATIONS 1,210,142 2/1966 Germany ..l64/40l 451,555 9/1949 Italy ..164/227 Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney-*Curtis, Morris & Safford I ABSTRACT An arrangement is disclosed for improving the handling or stripping of the flasks or molds of the type which are used to cast large items such as cast metal plates or frames. A system is provided for lifting the flask or mold vertically from the pattern with assurance that each portion or part is moved at exactly the same rate and amount as every other part.

4 Claims, 1 Drawing Figure METHOD FOR LIFTING FLASKS AND MOLDS This invention relates to molding operations, and particularly hydraulic lifting mechanisms for raising the flask or mold upwardly from the pattern.

An object of this invention is to provide improved means for lifting molds from patterns while forming molds for copes or drags. Another object is to provide a simple and efficient arrangement for lifting with great precision any item such as a mold.,

ln casting items such as large plates or frames the top of the cavity is formed by the top mold or cope which is lifted away from the pattern at the end of the mold-forming operation. Such items and the mold assembly are so designed and constructed as to provide for the proper draw relationship between the mold and the various portions of the pattern. When the dimensions of the top flask or mold are large it is difficult to insure that it will be lifted away from the pattern without tipping or canting. It is an object of the present invention to provide for the lifting of the top mold or flask with great precision and with assurance that it is lifted at the same rate and amount throughout. These and other objects will be in part obvious and in part pointed out below.

The single FIGURE is a schematic representation of one embodiment ofthe invention.

Referring to the drawing, the flask or cope or drag ofa mold is represented at 2 and is square in horizontal section. Positioned at the four corners of the flask are four hydraulic lifting units l2, l4, l6 and 18 which are shown in alignment in the schematic drawing but actually are positioned so that their lift plates 4, 6, 8 and 10 are positioned beneath lifting ledges at the four corners of the flask. Hydraulic lift unit 12 will be described and it is understood that the others are identical with it. Unit 12 has a stationary cylinder 20, a piston 22, a piston rod 24 and a top cover 26 with a sealing boot 28 around the piston rod. Extending from the bottom of cylinder is a liquid supply line 30 which extends to the cylinder of a hydraulic operating unit 34, and similar lines extend from the cylinders of

units

14, 16 and 18 respectively to the cylinders of

operating units

36, 38 and 40 which are identical with units 34. Each line 30 for the lifting units is connected through a branch line 32 to a balancing valve 33 which will be described more fully below.

Balancing valve 33 has a stationary valve body 90 and a valve rotor 92 which may be turned by a handle 94. When the valve rotor is positioned as shown it closes the ends of branch lines 32. However, when the valve body is turned 180 a cavity 96 in the side of the valve body is positioned in alignment with branch lines 32 so as to interconnect them. Each of

units

34, 36, 38 and 40 has a piston 42 which is connected through a piston rod 44 to a plunger plate 46. Plunger plate 46 is mounted on the piston rod 48 to a main hydraulic unit 50 which has a cylinder 52-and a piston 54 positioned within the cylinder and mounted upon the piston rod.

Lines

56 and 58 are connected to the opposite ends of cylinder 52 so that piston 54 may be moved back and forth by supplying liquid alternately to the opposite ends of the piston.

Lines

56 and 58 extend to a reversing valve 60 and extending from valve 60 is a line 66 having a flow control valve 68 therein and extending to the outlet ofa pump 70. Also extending from valve 60 is a liquid discharge line 62 which extends to the top ofa liquid reservoir or sump tank 64. A branch of line 66 is also connected to a pair of discharge lines 74 and 76 extending to reservoir 64 and having pressure-control relief valves 78 and 80 therein, respectively. Valve 78 and 80 are operative to bypass liquid from pump 70 back to reservoir 64 so as to limit the maximum liquid pressure in line 66. As will be explained more fully below, valve 78 is adjusted to a lower maximum pressure than valve 80 and valve 78 is rendered inoperative during the main portion of each operating cycle. Hence, valve 80 is always operative to provide a maximum limit on the pressure in line 66; whereas valve 78 acts only when performing an operating function as is explained below.

Pump is driven by an electric motor 72 and when valve 60 is positioned as shown oil is delivered through line 66 and valve 68 to valve 60 and thence through line 56 to the head of cylinder 52. That drives piston 54 to the left and causes liquid at the left of the piston to flow through line 58, valve 60 and discharge line 62 to the liquid reservoir. When valve 60 is turned 90 from the position shown the liquid under pressure flows through valve 68 and line 66 to valve 60 and thence through line 58 into cylinder 52 to the left of piston 54. That moves piston 54 to the right and drives liquid from the head of the piston through line 56, valve 60 and discharge line 62 to the liquid reservoir.

The system includes means not shown to maintain the cylinders of

units

34, 36, 38 and 40 and all of the

lines

30 and 32 filled with liquid. Hence, with the parts positioned as shown the movement of piston 54 to the left acts through plunger plate 46 and the piston rods 44 to move pistons 42 to the left in their cylinders. With branch lines 32 closed by balancing valve 33 unit 34 forces liquid into the bottom of-the cylinder of unit 12 and raises the piston therein so as to exert a lifting force on plate 4. Similarly, each of

units

36, 38 and 40 actsto exert a lifting force through its unit (14, 16 or 18) to exert a lifting force on its lifting plate (6, 8 or 10). Hence with the operation just described the supplying of liquid under pressure to the head of cylinder 52 causes flask 2 to be raised. However, as has been pointed out above, it is important to insure that flask 2 is lifted the same amount and at the same rate at all places; in this embodiment, at each of its corners.

in practice there is play in the operation of each of the

units

12, 14, 16 and 18 and that varies from unit to unit. For example, unit 12 may take up the play and start lifting flask 2 prior to unit 14 at an adjacent corner or prior to unit 16 at the opposite corner. That mode of operation would be unsatisfactory and is avoided in accordance with the present invention. To accomplish that purpose there is an initial tightening" step which precedes the step of lifting the flask. During that tightening step each of the

units

12, 14, 16 and 18 is supplied with sufficient liquid under a controlled pressure which moves its piston 22 upwardly so as to press its pressure plate (4, 6, 8 or 10) against its lifting ledge on the flask. The liquid pressure is not great enough to produce any lifting movement on the flask so that each of

units

12, 14, 16 and 18 is moved into lifting position but it cannot move further upwardly.

That initial step is also carried on with valve rotor 92 turned to a position with its cavity 96 interconnecting all of the branch lines 32. Hence, all of the

units

34, 36, 38 and 40 act together in parallel to supply liquid at a uniform pressure to all of the

units

12, 14, 16 and 18. Any differences in the operating relationship between one or another of one operating unit and its lifting unit (e.g., 34 and 12) and another are balanced out so that all of the operating units are exerting exactly the same pressure and all of the lifting units are pressing their lifting plates against the flask with the same force. Valve body 92 is then turned to the position shown in the drawing so as to close the interconnection between lines 32 and liquid at higher pressure is supplied through line 56 to unit 50 so that plunger plate 46 moves to the left and each of the

lifting units

34, 36, 38 and 40 then supplied liquid to its

lifting unit

12, 14, 16 M18 to lift the flask. Valve 68 is adjusted to control the rate at which liquid is supplied through line 66 to line 56 and that controls the rate at which the flask is raised. However, each of the lifting units exerts the same lifting pressure at the same rate as all the others and the flask is moved precisely the same distance and at the same rate throughout.

It has been indicated above that valves 78 and are pressure-regulating valves and they are used to maintain the desired pressure of liquid supplied through line 66. Pump 70 operates continuously and is adapted to supply liquid at the pressure necessary to lift flask 2. However, valve 78 is adapted to limit the pressure of the liquid supplied in line 66 to the value desired during the initial step of the lifting operation as described above. Hence, during that initial step when valve 33 is rendered operative and interconnects lines 32, relief valve 78 is also rendered operative. Therefore, when all of the lifting units are properly positioned during the initial step of a lifting operation, the operating units can no longer move and that prevents piston 54 from moving further in its lifting stroke. As a result, the flow through line 56 stops and the pressure rises in line 66 to the value where valve 78 opens and all of the liquid from pump 70 is returned through line 74 and valve 78 to reservoir 64.

Valve 80 is a pressure-limiting switch which is effective when valve 78 is not operating to limit the maximum oil pressure in line 66 and, therefore, the maximum pressure which is exerted at the lifting units. Hence, if for any reason flask 2 exerts abnormal resistance to the lifting movement, the pressures within the system rise and are limited by the opening of the bypass valve 80. This valve 80 can also be used to limit the lifting stroke by the arrival of the pistons 22 to the tops of their cylinders 20. Also, if there is malfunctioning in the system, valve 80 opens to prevent damage due to excessive pressures.

The return of the lifting components to their respective positions as shown is effected by returning valve 60 through 90 so that liquid under pressure is supplied from line 66 to line 58 into cylinder 52 at the left of piston 54, and line 56 is connected to line 62 so as to permit the liquid to flow from the right-hand side of the piston.

During the initial, step, as described above, with lines 32 interconnected by the cavity 96, all variations in the amount of play in units 12, l4, l6 and 18 and between their lifting plates and flask 2 are taken up and there is an equalization between the

liquid pressure units

34, 36, 38 and 40. The equalizing overcomes any variation in the amount of liquid in the various cylinders which would cause an unbalance in the subsequent lifting action. A stable condition is then reached in this initial step wherein pump 70 maintains the constant pressure determined by valve 78 and all of the lifting plates are held against their respective ledges on flask 2 with the same pressure.

Hence, when valve 33 is turned to disconnect lines 32 and valve 78 is rendered inoperative by manual or automatic means, there is an immediate increase in the pressure in line 66. That causes liquid to flow through line 56 into cylinder 52 so as to move piston 54 to the left. That rate of movement is controlled by the adjustment of valve 68. The movement of piston 54 causes a corresponding movement of each of the pistons 42 and, the liquid not being compressible, there is a corresponding lifting movement by each of the pistons 22. Hence. the lifting action is immediate and uniform and the rate of lifting may be increased or decreased by adjusting valve 68.

As indicated above, the flask is lowered into place by the reverse action, and during the lifting and lowering, valve provides control to insure against excessive pressure conditions.

It is thus seen that the operation is simple and dependable and that flask 2 is moved with great precision at all times and that the above and other desirable objects are accomplished. It is understood that modifications in the construction and mode of operation may be made within the scope of the claims.

What is claimed is:

1. In the method of separating a mold and its pattern with the aid of a plurality of hydraulic lifting units having separate liquid supplies, the steps of, performing an initial step of providing engagement with said units at a plurality of zones with a predetermined lifting force from a single source by interconnecting the supplies of liquid to said lifting units and limiting the predetermined force by controlling the liquid pressure, after said engagements are made, disconnecting the interconnection of the supplies of liquid to said lifting units and then increasing the lifting force at each of said zones with a total force sufficient to perform the separating by increasing the liquid pressure applied simultaneously and independently to said lifting units through said supplies.

2. The method as described in claim 1 wherein the fluid pressure exerted in said initial step and said force increasin step 18 created by a plurality of independent units correspon ing in number to said lifting units and connected respectively therewith and wherein said independent units are operated simultaneously.

3. The method of separating a mold part and its pattern with the aid of a plurality of hydraulic lifting units having separate liquid supplies comprising, the steps of initially interconnecting said liquid supplies, pressurizing said separate liquid supplies from a single source to engage said mold part at a plurality of locations with each of said lifting units at a predetermined lifting force, thereafter, disconnecting the interconnection between said liquid supplies and increasing the pressure in said supplies applied by said single source to apply a total lifting force at said locations through said lifting units sufficient to separate said mold part from said pattern.

4. The method as defined in claim 3 including the steps of limiting the pressure in said liquid supplies when producing said predetermined lifting force and limiting the pressure in said liquid supplies when producing said total lifting force.

Claims

2. The method as described in claim 1 wherein the fluid pressure exerted in said initial step and said force increasing step is created by a plurality of independent units corresponding in number to said lifting units and connected respectively therewith and wherein said independent units are operated simultaneously.