CA1220014A

CA1220014A - Method and apparatus for making foundry molds

Info

Publication number: CA1220014A
Application number: CA000433530A
Authority: CA
Inventors: Albert Musschoot
Original assignee: General Kinematics Corp
Current assignee: General Kinematics Corp
Priority date: 1982-11-12
Filing date: 1983-07-29
Publication date: 1987-04-07
Also published as: DE3329585A1; DE3329585C2; JPS5987956A; IT8368181A0; GB2130511A; BE898179A; FR2535988A1; CH662523A5; AU1737683A; IT1201926B; AU567107B2; FR2535988B3; GB8322322D0

Abstract

Abstract A foundry mold making apparatus and method.
The apparatus includes a base with a flask receiving station. A vibrator is employed to vibrate the foundry flask disposed in the station in at least a vertical direction and there are provided a plurality of movable compacting heads of substantial mass. The heads are mounted for movement into and out of the station and for movement relative to each other in a generally vertical direction. The apparatus is free of any de-vices for applying a downward force to the compacting heads such that the sole downward force applied there-to is that supplied by gravity. An inexpensive, but highly effective foundry mold making apparatus results.
Also disclosed is a method of forming a mold for metal casting.

Description

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METHOD AND APPARATUS FOR
M~KING FOUNDRY MOLDS

Field of the Invention ~ . . ~
This invention relates to an apparatus for making foundry molds by compacting foundry sand about a pattern.
The invention additionally relates to a method of forming such molds through the compaction of foundry sand about a pattern.

Bac~s~Kd of~ the Invention Over the years, many different methods and appa-ratus have been adopted in the age old process of forming metal in a desired shape by melting and casting the metal in a mold. In a usual case, the mold is formed using patterns about which sand and a binder .re packed.~ The packing may be performed in a variety of ways and various techniques have evolved.
For example,ino~e currently available foundry mold forming apparatus known as a Herman Moldmaster, provision is made for lining up a flask containing foundry sand and binder as well as a pattern with a pIatenhaving a plurality of downwardly projecting squeeze or compacting heads which are advanced under the influence of fluid under pressure into the flask for pressing the sand and binder around the pattern. After the desired compaction is achieved, the compacting heads are withdrawn and the flask moved to the next sta~e in the foundry process. Al-though such a machine is very efficient and generally ac-ceptable, there are certain patterns that have shapes and/
or configurations that are not fully susceptible to com-plete ramming due to the squeeze or compressing effectwith the result that less than fully rammed flasks are produced. Frequently, such flasks may be rejected, or . . ~ , . .

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if the flas~c is used in the process, an inferior casting may result. Furthermore, the need for pressurized fluid and operators responsive thereto for driving the compacting heads results in a relatively complex, and thus, expensive, apparatus.

In my Canadian application Serial No. 380,611 now Canadian patent No. 1,177,221 and entitled "Vibratory Method for Packiny Foundry Sand into a Pattern Prior to the Pouring of Molten Metal", there is described methods and apparatus which may be employed to obviate the problems encountered in prior art methods and apparatus in causing sand and binder to enter and compact within the unusual shapes of complex patterns to avoid the difficulties encountered with non-fully rammed flasks. While the method and apparatus disclosed in my Canadian patent is considered to work well for its intended purpose, occasionally there arises a need for greater compaction than can be provided by the vibratory system therein disclosed alone~

Consequently, there has been proposed apparatus which provides for compaction of foundry sand about a pattern contained in a flask utilizing both vibratory motion and fluid pressurized compacting. Again, such system works extremely well for its intended purpose but the naed for compacting head operators and a relatively large source of pressure fluid for such operators increases the complexity of the apparatus and again, the expense thereof.

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The present invention is directed to overcoming one or more of the above problems.

Summary of the Invention It is the principai object o~ the invention to 5 provide a new and improved method and apparatus for making foundry molds. More speci~ically, it is an object of the invention to provide a simple apparatus that provides for compaction of sand in a foundry ~lask containing a pattern through the use of vibratory motion and a non-vibratory compacting force that is inexpensive in cost. It is also an object o~ the invention to pro-vide a simple and inexpensive method o~ compacting sand in a flask containin~ a pattern throug~ the use of vibra-tory motion and a non-vibratory force.
~n exemplary embodiment o~ an apparatus made ac-cording to the invention achieves the foregoin~ objects in a structure including a base having means de~ining a flask receiving station. Means are disposed on the base for vibrating a flask disposed in the station in at least a vertical direction. There are provided a plurality o~ vertically moving compacting heads of substantial mass and means for lowering the heads into the station and allowing relative vertical movement between the heads while they are in the station without applying a downward-ly directed force other than gravity thereto.
Consequently, the vibratory ~orce provides compaction as does the force of gravity actin~ through the heads.
A pressure source, and the cost o~ providing the same along with operators responsive thereto are eliminated.
In a preferred embodiment, the lowerin~ means include a means mounting the heads for movement into and out of the station and ~or movement relati~e to each other in a generally vertical direction with the sole .

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downward force acting upon the heads being that ofgravity. Preferably, each of the heads has a lost motion connection to the mounting means. A powered actuatox for raising and lowering the mounting means may also be provided. The powered actuator, the mounting means and the lost motion connections are constructed and arranged so as to be incapable of exerting a downward force on the heads.
A preferred embodiment of a method made according to the invention includes the steps of placing a pattern in a mold 1ask, filling the flask with foundry sand to a desired level, placing a plurality of weights on the upper surface of the sand and vibrating the flask and its contents including the weights in the absence of a down-wardly directed force on the weights other than that ofgravity. Preferably, the method includes the step of guiding the weights for substantially solely vertical movement during at least a portion of the step of vibrating.
Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings.

Descri~tion of the Drawinas Fig. 1 is a side elevation of an apparatus made according to the invention~ with parts broken away for clarity, atan lnitial stage in the operation of the ap-paratus;
Fig. 2 is a view similar to Fig. 1 but showing a subsequent stage in the operation of the apparatus;
Fiy. 3 is a view similar to Figs. 1 and 2 but showing still a later stage in the operation of the apparatus; and Fig. 4 is a view similar to the prece~ing views illustrating a final stage in the operation of!the ap-paratus.

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~escription of the Preferred Embodiment pparatus An exemplary embodiment of an apparatus made according to the invention is illustrated in the various figures of drawin~ and is seen to include a base 10 which may be disposed on an underlying sur-face 12 such as a floor or the like. Extending up wardly from the base 10 is an inverted, U-shaped frame 14. ' Within the frame 14 and above the base 10 there is disposed a table 16 having an upper surface 18 defining a flask receiving station for receipt of a flask 20. As illustrated, the flask 20 has a pattexn 22 disposed therein and has been fllled to a desired level with a mixture of foundry sand and binder 24.
, While not shown herein, it is considered that the table 16 may be provided with suitable conveyin~ means to assist in the movement of the flask 20 to and from the station.
The table 16 is mounted~above the base on a series of coil springs'26. Secured to the undersurface 28 of the table 16 are a plurality of electric motors 30 each haviny rotary output shafts 32 to which eccentric weights

3~ are affixed.
As a result of the foregoing structure, when the motors 30 are energized, a vert'ical vibratory force will be applied to the table lG, and thus to the flask 20 thereon in the manner described in my previously identified patent. ' Suspended from the upper end of the frame 14 is a pair of''fluid cylinders 40 of the double acting variety.
Each cylinder 40 includes an extendable rod 42 and a cross .. . . . . .
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member 44 is secured to both of the rods 42 as b~v nuts 46 such that it overlies the flask receiving station.
The cross member 44 is provided with one or more rows of vertically extending bores or apertures 48 through which rods 50 slidably extend. Preferably, the fit is relatively close so that movement of the rods 50 within the apertures 48 is principally limited to the vertical direction. In other words, the apertures 48 guide the rods 50 for movement in the vertical direc-tion.
The upper end of each of the rods 50 terminatesin a cap 52 of larger diameter than the corresponding bore 48. The caps 52 serve as stops to limit downward movement of the rods 50 relative to the cross member 44.
Each of t~ie rods 50, at its lower end, mounts a - compacting head 54. The compacting heads 54 are disposed in close adjacency and yet are relatively movable with respect to each other by reason of the lost motion con~
nection to the cross member 44 provided by the rods 50, the bores 48, and the stops 52.~ Each compacting head 54 has a lower surface 56 which is adapted to abut the - sand 24 contained in the flask to compact the same. To assure uniform compaction by each of the heads 54, it is preferable that the ratio of the weight of all of the individual headsand their associated rods 50 and caps 52 to the area of their surfaces 56 be equal. Generally, but not always, this will mean that each assembly of a head 54, rod 50 and cap 52 be of identical mass and con-figuration.

Method The inventive method, contemplates as a first step,the placing of a pattern in a mold flask. For example, ' ~ ~z~

this step can be accomplished by placing a pattern such as the pattern 22 in a mold flask such as the mold flask 20.
The next step of the method involves filling the flasX with foundry sand, and usually a binder, to a desired level. ~s illustrated in the drawings, this may be accomplished by filling the flask 20 with a foundry sand and binder mix 24 to a level well abo~e the uppermost end of the pattern 22.
The next step of the method involves the placing of a plurality of weights on the upper surface of the sand. This can be accomplished using the above described apparatus as ~ollows. Through suitable conventional con-trols, the cylinders 40 are caused to extend their rods 42 as illustrated in Fig. 2. This in turn lowers the cross member 44 until the rods 42 are fully extended.
In the usual case, this will bring the cross member 42 to a level just slightly above the upper edge of the flask 20 but not suficiently low as to engage the up~er surface of the heads 54.
During the lowering proc'ess thus described, at some point in time, the compacting surfaces 56 o~ the vari,ous heads 54 will engage the upper surface of the sand and bear against the same. - ` , The next step of the method involves the vibrating of the flask and its contents including the weights in the absence of a downwardly directed force on the weights other than that of gravity. This is accomplished ~y ener-~izing the motors 30 as illustrated in Fig. 3. Where a generally purely vertical oscillation is desired, the motor shafts 32 are caused to rotate in opposite direc-~ions. Conversely, if a sideways force along with a vertical force is desired, the motor shats 32 are caused ~o rotate in the same direction.

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As a result of this step, the sand 24 will flow into crevices or passages, no matter how intri-cate, in the pattern 22 in the manner described in my co-pending application. At the same time, the force of gravity will be continuously operatiny on the com pacting heads 54 to cause the same to move downwardly.
Additionally, when.-the table 16 is moving upwardly, inertial forces will tend to cause compaction of the sand and binder mix 24.
10When the desired degree of compaction is achieved, the moto.rs 30 may be deenergiz.ed at which time oscilla-tion of the flask 20 will cease. The cylinders 40 may then be caused to retract their rods 42 as illustrated in Fig. 4. As the rods 42 retract, at some point in time, the cross member 42 will be brought against the under-side of the caps 52, though not necessariiy simultaneously, and continued retraction of the rods 42 w~ill cause the heads 54 to be moved outwardly to a location above the - flask receiving station as seen in Fig. 4. At this point, the flask 20 may be removed from the apparatus and moved to any desired location for further processing.
It will also be observed that during the fore-going method, a step of guiding the heads 54 for sub-stantially solely vertical movement occurs during at least a portion of the step of vibrating. This step is performed in the above apparatus by the relationship of the bores 48 to the rod 50 as described previously and assures uniform compaction of the sand and binder mix 24 within the flask 20. Finally, it will be ob-served tha.t at no time is there a downwardly directedforce on the heads 54 other than that of gravity. Thus, the force of gravity is utilized to avoid the need for operators to force the heads 54 downwardly and any source 2~

g --of energy therefore, Consequently, the apparatus is greatly simplified over prior art apparatus and is considerably less expensive to build. Nonethless, the advantages of combined vibratory and non-vibratory compaction of the sand and binder mix 24 are retained.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A foundry mold making apparatus comprising:
a base including means defining a flask receiving station;
means on said base for vibrating a flask disposed in said station in at least a vertical direction;
a plurality of vertically movable compacting heads of substantial mass, and means mounting said heads for (a) movement into and out of said station and (b) movement relative to each other in a generally vertical direction;
said apparatus being free of motor means for urging said heads downwardly when in said station such that gravity is the sole downward force acting upon said heads.

2. The foundry mold making apparatus of claim 1 wherein each of said heads has a lost motion connection to said mounting means.

3. The foundry mold making apparatus of claim 2 further including a powered actuator for raising and lowering said mounting means, said powered actuator, said mounting means and said lost motion connection being constructed and arranged so as to be incapable of exerting a downward force on said heads when said heads are in said station and yet move said heads into and out of said station.

4. The foundry mold making apparatus of claim 2 wherein each said lost motion connection includes a stop for limiting downward movement of the corresponding head relative to said mounting means.

5. A foundry mold making apparatus comprising:
a base including means defining a flask receiving station;
means on said base for vibrating a flask disposed in said station in at least a vertical direction;
a plurality of vertically movable compacting heads of substantial mass, and means for lowering said heads into said station and allowing relative vertical movement between said heads while in said station without applying a downwardly directed force thereto.

6. The foundry mold making apparatus of claim 5 wherein said lowering means is further operable to lift said heads out of said station.

7. The foundry mold making apparatus of claim 5 including means for guiding said heads for substantially solely vertical relative movement.

8. In a method of forming a mold for metal casting, the steps of:
placing a pattern in a mold flask;
filling the flask with foundry sand to a desired level;
placing a plurality of weights on the upper sur-face of the sand; and vibrating the flask and its contents including the weights in the absence of a downwardly directed force on the weights other than that of gravity.

9. The method of claim 8 further including the step of guiding the weights for substantially solely vertical movement during at least a portion of the step of vibrating.