US3613769A - Shell-molding machine with pivotable investment bin - Google Patents

Abstract

A machine for making shell molds has an investment bin for holding shell-molding material, the bin having openings in its sidewalls against which a pivotally mounted pattern plate can be locked. Once a pattern plate is in position, the plate and the bin are rocked about the pivotal axis of the pattern plate to invest the pattern plate after which the invested plate is swung away from the pin to a position in which curing of the investment is completed.

Description

United States Patent [72] Inventor Kenneth William Cowlam Pembury, near Tunbridge Wells, England [21] Appl. No. 827,719 [22] Filed May 26, 1969 [45] Patented Oct. 19, 1971 [73] Assignee Polygram Casting Company Limited Frant, Tunhridge Wells, Kent, England [32] Priority June 19, 1968 [33] South Africa [31] 68/3919 [54] SHELL-MOLDING MACHINE WITH PIVO'IABLE INVESTMENT BIN 6 Claims, 5 Drawing Figs.

[52] 11.8. CI 164/166, 118/425, 118/421,164/l8, 164/24 [51] Int. Cl 1322c 13/08 [50] Field of Search 164/18, 19,

[56] References Cited UNITED STATES PATENTS 2,905,987 9/1959 l-Ioekstra et a1 164/165 3,307,232 3/1967 De Fasselle et a1. 164/21 3,326,142 6/1967 Town 118/24 X 3,429,358 2/1969 Tingquist et a1. 164/26 3,503,435 3/1970 Dunlop 164/26 X FOREIGN PATENTS 703,749 2/1954 Great Britain 164/21 831,228 3/1960 Great Britain 164/21 Primary Examiner.l. Spencer Overholser Assistant Examiner-John E. Roethel Attorney Holcombe, Wetherill & Brisebois ABSTRACT: A machine for making shell molds has an investment bin for holding shell-molding material, the bin having openings in its sidewalls against which a pivotally mounted pattern plate can be locked. Once a pattern plate is in position, the plate and the bin are rocked about the pivotal axis of the pattern plate to invest the pattern plate after which the invested plate is swung away from the pin to a position in which curing of the investment is completed.

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SHEET t [1F 5 SHELL-MOLDING MACHINE WI'III PIVOTABLE INVESTMENT BIN This invention relates to molding machines and has particular reference to machines for making shell molds.

Shell molds are made by a process in which a heated pattern plate is invested with a layer of a shell molding material which may comprise a refractory granular material and a thermosetting binder. After investment, the layer is cured and then removed from the pattern plate.

It is an object of the present invention to provide a molding machine able to produce superior molds.

SUMMARY OF THE INVENTION According to the present invention, a shell-molding machine comprises an investment bin for holding shell-molding material, the bin having a base and at least two opposite sidewalls extending upwardly from the base and being inclined towards one another, at least one aperture in each inclined sidewall, at least two pattern plate carriers, pattern plate carrier-locking means on the investment bin for locking a pattern plate against an aperture, and means for swinging a pattern plate carrier about its pivotal mounting from a rest position to a position covering an aperture in a sidewall and then to rotate both pin and pattern to and from a position in which the sidewall against which the pattern plate is located is substantially horizontal and then to return the pattern plate to its rest position.

Where a sidewall as an aperture or apertures which are not required for the production of molds, such aperture or apertures are blanked off. A sidewall may have apertures of different sizes.

One or more or all of the sidewalls is or are in the form of masks each of which is detachable from the investment bin. A user may then hold a number of masks having a variety of apertures, the most appropriate of which is selected for the production of a particular mold.

The pattern plate may include means, for example ejector pins, for ejecting the molds from the pattern plate after the mold has been cured. Curing may be accelerated by means of gas burners or electric heaters contained in a hood which is movable to a suitable position over the invested pattern plate.

In one embodiment of the invention, there are the additional heating units for heating the or each pattern plate when on the mounting. The heating unit may comprise gas burners which may be accommodated in a mechanism for operating the ejector means.

Because of the limited rotational movement of the mounting, spring-loading of the ejector pins, when used, is not essential, all that is required is some means, for example a split pin, through the shank of the ejector pin to stop the latter being removed from the pattern plate after curing.

Preferably, means are provided for fluidizing the molding material in the investment bin during periods between investing pattern plates.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevation of the embodiment,

FIG. 2 is a front elevation of a component of the embodiment on a larger scale,

FIG. 3 is a plan view of the component shown in FIG. 2,

FIG. 4 is a front view on a larger scale of part of the embodiment with certain components removed, and

FIG. 5 is an end view on a larger scale of the embodiment with certain components removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT The machine has a rigid base of generally rectangular form when seen in plan. The base comprises two end portions 1, 2 of open-frame construction with vertical members and cross supports, the end portions being joined by front and back crossmembers. FIGS. 4 and 5 show one end portion I, two front vertical members 3, 4, rear vertical member 5 and cross supports 6, 7, 8 and 9. FIG. 4 also shows two, I0, II, of the crossmembers joining end portion 1 to end portion 2. The end portions have levelling feet 12 adjustable to level the machine.

Both end portions 1, 2 have spaced bearing brackets 13 in which axles 14 are mounted, theaxles extending from front to back of the machine as is indicated in FIG. 3. Each axle I4 has an arm I5, fixed to it, one end of the arm being bolted to a pattern plate carrier I7 which is simply a rectangular frame in which a pattern plate is releasably secured. The arms 15 are in different positions on their respective axles, that arm I5 adjacent end portion I being located towards the front of the machine whilst the arm 15 adjacent end portion 2 is located towards the rear of the machine. In addition, each arm 15 extends beyond its associated axle, each extension being connected by a clevis 18 to the piston of an individual pneumatically operated, double-acting piston-cylinder unit I9 located between the end portions I, 2 as seen in FIG. 4.

Counterweighting of the weight of the pattern carrier I7 is provided by masses 20 each pivotally secured between an arm 15 and a further arm 21 extending from the axle I4.

Mounted upon each of the end portions 1, 2 are two brackets 22 between which an axle 23 is rotatably mounted. Fixed to the axle between the brackets 22 is a link 24 attached to the piston of a double-acting, pneumatically operated, piston-cylinder unit 25. Anns 26 are fixed to the ends of the axle as shown in FIG. 5. One arm 26 extends beyond its point of attachment to the axle and carries a counterweight 27 at its end. The other end of the arms 26 are pivotally connected to the sidewalls 28 of a hood 29. Also pivotally connected to the sidewalls 28 are the ends of further arms 30 whose other ends are pivotally connected to the brackets 22 so forming, as is shown in FIG. 5, a parallel linkage with the arms 26. The hoods have gas burners mounted in their roofs 31, part 32 of the burners being seen in FIG. I. The burners which heat radiant panels located inside the hoods are fed with gaseous fuel via supply lines 33, a section of which (not shown) is flexible to accommodate movement of the hoods as will be described later. The positions of the radiant panels as well as the thermal outputs may be variable to suit the particular pattern plate.

In FIG. I, an investment bin 34 is shown in a rest position between the end portions I, 2 and is shown in more detail and on an enlarged scale in FIGS. 2 and 3. The bin has a base of rectangular shape from which extend vertically end walls 36 of truncated triangular shape when seen in elevation as in FIGS. 1 and 2. The apex angle between the inclined edges of the end walls is about 50. The sides of the bin are formed by two bin masks 35 which are plates of rectangular form detachably secured between the end walls. Each bin mask has one or more apertures in it, those shown in the drawings each having a single central rectangular aperture 37. Round each aperture is an upstanding flange 38 which extends away from the bin 34. The flanges 38 are or incorporate seals of resilient material with heat insulating properties, for example a silicone rubber. The flanges 38 match a mating edge round a pattern plate as will be made clearer later.

The bin is mounted between spaced arms 39, 40 by means of short extension brackets 41 carrying eccentric bushes 44. The bushes 44 are mounted in slightly elongated holes 45 in the arms 39, 40. Rotation of stub shafts passing through the bushes 42, provides adjustment of the vertical position of the bin with respect to the arms as will be described later. The bin is also'supported on further stub shafts 46 disposed centrally with respect to the bin and which carry eccentric bushes 47 located in apertures in the arms 39, 40. Rotation of the shafts 46 provides adjustment of the horizontal position of the bin with respect to the anus 39, 40.

The outer ends of the arms 39, 40 are hook-shaped as shown in FIG. 2 and they rest on the axles I4.

Inside the bin and adjacent its base is a floor 43 which is pe rvious to air but impervious to molding material. Beneath the floor 43 is an air box 430 flexibly coupled to compressed air supply lines 48.

On the flat top 49 of the bin 34 is mounted an actuating mechanism for movable locking bars 50. The mechanism comprises two double-acting, pneumatically operated piston cylinder units 51 whose pistons are connected to the locking bars which are slidably mounted upon pairs of rods 52 extending from the bin. The locking bars 50 have apertures 53 at their ends shrouded partially by extensions 54 of the bars.

The pattern plates to be used with the machine are not shown in the drawings because they are of substantially conventional design. The plates incorporate ejector pins which are loosely mounted in holes in the plates. The pins have mushroom heads and shanks with split pins through them so that the pins can move freely in the holes without any risk of falling out.

Operation of the ejector pins is by means of ejector pin bolsters indicated as block 55, there being two such bolsters. The bolsters 55 are located in the end portions 1, 2 and each is supported by a vertical rod 56 which extends through a bearing assembly 57. The rod is reciprocated in the bearing assembly by a piston-cylinder unit 58 through a lever 59 which interconnects the rod 56 and the piston of the unit 58. As can be seen from FIG. 5, the bolster is not attached directly to the rod 56, but is carried by screw-supports 60 attached to a support plate 61 of rectangular shape when seen in plan. The plate 61 has guide members (not shown) which travel along vertical guides in the end portions and one, 62, of which can be seen in FIG. 4. The guides 62 and the guide members stop movement of the plate 61 and thus of the bolster 55 about the vertical axis of the rod 56.

The moving parts of the machine are pneumatically operated and can be cycled automatically through a given sequence by a control system not shown. A control console 63 located at the front of the machine mounts controls which can be set to allow the machine to cycle automatically or to enable an operative to determine the sequence of events. Suitable interlocks are provided to prevent damage in the event of maloperation of the controls by an operative. Timing mechanisms may be fitted to control heating times, investment times and cure times. In addition, the burners or other heaters for bringing the pattern to temperature and for curing the coatings may be thermostatically controlled and this control may provide for variation of the heating rate of the burners according to the temperature of the patterns, e.g. the heating rate may decrease as the pattern reaches the temperature at which investment is to take place.

The machine is provided with a source (not shown) of compressed air and is connected to a supply of gaseous fuel.

Prior to operation, pattern plates mounting the patterns from which shell molds are to be made are secured in position on the pattern plate carriers 17. In addition to housing the ejector pins as described above, the pattern plates have a rim which coacts with the upstanding flanges 38 in a manner shortly to be described.

The position of the bin 34 is, if necessary, adjusted by rotating the stub shafts 42 and 46 so that the flanges 38 mate correctly with the edges referred to above. Further support for the bin when set in its correct rest position is provided by adjustable supports 64 mounted upon the cross supports interconnecting the end members 1, 2.

The investment bin 34 is loaded with a desired amount of shell-molding material by pouring the latter through one of the openings 37. This can be done with the bin in the position shown in FIG. 1 but, preferably, the bin is pivoted over one or other of the end supports so that one of the openings is in a position which makes it easier to pour shell-molding material into the bin. The other opening 37 is, of course, closed by a pattern plate. After the desired quantity of material has been loaded, the bin 34 is returned to the position shown in FIG. 1 and compressed air is then admitted to the air box 47 to fluidize the shell-molding material and so level" the latter.

While loading of the investment bin has been taking place, the supply of gas to the burners in the roofs of the hoods 29 and the burners in the ejector pin bolsters has been turned on and ignited at the burners. Heating of the pattern plates now takes place, both hoods 29 being in position over the pattern plates, i.e. in the position of the left-hand hood as seen in FIG. 1.

When the pattern plates have been heated to the appropriate temperature, the production of shell molds can begin.

If the machines is to operate automatically, the controls on the console 63 are set to the appropriate positions. This brings one of the hoods, say that of end portion 1, to an elevated position over the portion as seen in FIG. 1 thus revealing the heated pattern plate which can be sprayed with a suitable parting liquid to assist removal of the shell mold at a later stage in the cycle of operation.

Movement of the hood to the position shown in FIG. 1 is effected by the piston-cylinder unit 25 acting through the link 24, axle 23 and arms 26 and 30.

The pattern plate carrier 17 and the pattern plate is then pivoted with the axle 14 in the bearing brackets 13 adjacent end portion I to the position shown in FIG. 1, this movement being effected by operation of the associated piston-cylinder unit 19 acting through the clevis 18 and the arm 15. In that position, the pattern plate is located over the aperture 37 in the sidewall 35 of the investment bin, the flange 38 cooperating with the rim round the pattern plate to seal the aperture.

The piston-cylinder units 51 are then operated to withdraw the locking bars 50 towards the end walls 36 of the bin 34 and in so doing the apertures 53 on the locking bars 50 engage projections extending laterally outwards from the pattern plate carrier 17. In that way, the pattern plate carrier 17 is held against the sidewall 35 of the bin 34 with the pattern plate located securely in the aperture 37 in the sidewall.

At this stage, the piston-cylinder unit 19 linked to the pattern carrier of the end portion 1 is reoperated causing both the pattern plate carrier 17 and the investment bin 34 to pivot with the axle 14 in the bearing brackets 13 adjacent end por tion 1 to return the pattern plate carrier 17 to the position in which it is shown in FIGS. 4 and 5. It will, of course, be understood that during the stages of the operating cycle just described, the hood 29 of the end portion 1 is held in the position in which it is shown in FIG. 1. Before movement of the pattern plate carrier 17 and bin 34 take place, the flow of fluidizing air to the air box 47 is cut off.

The movement of the pattern plate carrier 17 and investment bin 34 just described is rapid and during the movement,

molding material in the bin 34 is thrown over the pattern plate and effectively covers the latter with a coating of the material.

After a slight pause sufficient to allow the coating to build up, the carrier 17 and the investment bin 34 are swung back to the position shown in FIG. 1 by further operation of the piston-cylinder unit 19. When the bin reaches that position, the locking bars are disengaged from the projections on the pattern plate carrier by operation of the piston-cylinder units 51 and the supply of fluidizing air is restored to the air box 47. The carrier 17 is now restored to the position it occupies in FIGS. 4 and 5 and the hood 29 of the end portion 1 is lowered down over the pattern plate to the position shown in FIGS. 4 and 5 in order to complete the curing of the coating.

When the curing is complete, the hood 29 is raised and the ejector bolster 55 moved upwardly to operate the ejector pins which left the cured coating from the pattern plate. The bolster 55 is operated by the piston-cylinder unit 58 through the lever 59. To hold the pattern plate carrier 17, and thus the pattern itself, firmly in place during operation of the ejector pins, catches 65 are provided. The catches are pivotally mounted on the end portions, FIG. 4 shows one catch 65 mounted upon the crossmember 6, and they engage pins 66 on the carriers 17 to hold the latter against movement. Normally, the catches are in the position shown in FIG. 4 in which the catch 65 is clear of the pin 66. As the bolster moves upwardly abutments thereon cause the catches to pivot and engage the pins just before the bolster itself engages the ejector pins. On the downward movement of the bolster after operation of the ejector pins, the same abutments pivot the catches back into positions clear of the pins, i.e. to the position in which catch 65 is shown in FIG. 4.

A similar cycle of event s is followed at the other end portion 2. Movement of the carrier 17 of that portion to the position against the sloping side of the investment bin 34 can take place as soon as the carrier 17 of the end portion 1 has been unlocked by operation of the piston-cylinder units 48.

Thus, the operating cycle of the machine is such that it produces investment of the pattern plate on one carrier and then on the other.

The purpose of fluidizing the molding material in the investment bin is essentially to level the surface of the material between each investment and as is clear from what has been said above that fluidizing air is applied to the molding material only between investments immediately the investment bin returns to position between the two stations. The air used for fluidization should preferably be dry as this helps the molding material to maintain its maximum dry flow properties.

The pattern plate or plates does or do not rotate through a full 180 as is the case with many conventional molding machines. Rotation occurs through about 130 and this reduces considerably the tendency of the coating with which the plate or plates is or are invested to peel-off" during rotation. The rapid rotation of the investment bin tends to throw the molding material over the pattern plate and this produces investment without the so-called shadow effects.

It will be understood that the investment bin may have more than two apertured sloping sides and the same number of pattern plate carriers, thereby increasing the number of stations and the output of molds from a single machine.

The size of the investment bin is selected to give a number of investment cycles before refilling becomes necessary.

The pattern plate carriers are able to receive a range of pattern plate sizes for each of which there is a corresponding bin mask. The apertures 37 in the bin masks 35 of the investment bin 34 can be fitted with adapter frames to accommodate the size of pattern plate used. Change of pattern plate is a simple matter effected in a very short time.

It will be understood that the carriers 17 may be fitted with a single pattern plate of large size or several smaller sized pattern plates.

It will be understood that the machine may be actuated hydraulically, mechanically or electrically instead of pneumatically as described above. In addition, facilities may be provided for automatically recharging the investment bin with molding material. Recharging may be effected through the fluidizing bed of the bin.

I claim:

l. A shell-molding machine comprising a combination an investment bin for holding the shell-molding material, the bin having a base and at least two opposite sidewalls-extending upwardly from the base and being inclined towards one another, at least one aperture in each inclined sidewall, at least two pattern plate carriers, pattern plate carrier-locking means on the investment bin for locking a pattern plate against an aperture, a pivotal mounting for each pattern plate, and means for swinging a pattern plate carrier about its pivotal mounting from a rest position to a position covering an aperture in a sidewall and then to rotate both pin and pattern plate to and from a position in which the sidewall against which the pattern plate is located is substantially horizontal and then to return the pattern plate to its rest position.

2. A shell-molding machine as claimed in claim I in which each pivotal mounting includes an axle having arms to which the pattern plate carrier is detachably secured, and in which the investment bin has laterally extending supports by means of which the investment bin is supported on the axles.

3. A shell-molding machine as claimed in claim 1 in which at least one of the apertured sidewalls of the bin is detachably mounted thereon.

4. A shell-molding machine as claimed in claim I and further comprising, for each pattern plate carrier, a hood, a pattern plate heater mounted in the hood, and a mechanism connected to the hood for placing the hood in a position over the carrier and for withdrawing the hood to a position clear of the carrier. I

5. A shell-molding machine comprising in combination an investment bin for holding shell-molding material, the bin having a base and at least two opposite sidewalls extending upwardly from the base and being inclined towards one another, a floor in the investment bin, the floor being impervious to molding material but pervious to air, an air box beneath the floor, the floor forming one face of the box, inlets in the box for admitting compressed air thereto, at least one aperture in each inclined sidewall for receiving a pattern plate, and means for rotating the bin to and from positions in which one of the inclined sidewalls is substantially horizontal.

6. A shell-molding machine as claimed in claim 1 and further comprising support arms, bearing mounts on the arms, support axles secured to the bin, and cam members mounted eccentrically on the axles and located on the bearing mounts, adjustment of the position of the bin with respect to the support arms being effected by rotating the support axles.

Claims (6)

1. A shell-molding machine comprising a combination an investment bin for holding the shell-molding material, the bin having a base and at least two opposite sidewalls extending upwardly from the base and being inclined towards one another, at least one aperture in each inclined sidewall, at least two pattern plate carriers, pattern plate carrier-locking means on the investment bin for locking a pattern plate against an aperture, a pivotal mounting for each pattern plate, and means for swinging a pattern plate carrier about its pivotal mounting from a rest position to a position covering an aperture in a sidewall and then to rotate both pin and pattern plate to and from a position in which the sidewall against which the pattern plate is located is substantially horizontal and then to return the pattern plate to its rest position.

2. A shell-molding machine as claimed in claim 1 in which each pivotal mounting includes an axle having arms to which the pattern plate carrier is detachably secured, and in which the investment bin has laterally extending supports by means of which the investment bin is supported on the axles.

3. A shell-molding machine as claimed in claim 1 in which at least one of the apertured sidewalls of the bin is detachably mounted thereon.

4. A shell-molding machine as claimed in claim 1 and further comprising, for each pattern plate carrier, a hood, a pattern plate heater mounted in the hood, and a mechanism connected to the hood for placing the hood in a position over the carrier and for withdrawing the hood to a position clear of the carrier.

5. A shell-molding machine comprising in combination an investment bin for holding shell-molding material, the bin having a base and at least two opposite sidewalls extending upwardly from the base and being inclined towards one another, a floor in the investment bin, the floor being impervious to molding material but pervious to air, an air box beneath the floor, the floor forming one face of the box, inlets in the box for admitting compressed air thereto, at least one aperture in each inclined sidewall for receiving a pattern plate, and means for rotating the bin to and from positions in which one of the inclined sidewalls is substantially horizontal.

6. A shell-molding machine as claimed in claim 1 and further comprising support arms, bearing mounts on the arms, support axles secured to the bin, and cam members mounted eccentrically on the axles and located on the bearing mounts, adjustment of the position of the bin with respect to the support arms being effected by rotating the support axles.

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