US1816774A - Means for packing sand in foundry molds and cores - Google Patents

Description

July28, 1931. MGRINDAL vVIEANSAFR PACKING SAND IN FOUNDRY MOLDS AND CORES Filed Sept.

Patented July 28, 1931 l f PATENT OFFICE j MOETEN GRINDAL, OF MTALA VERKSTAD, SWEDEN' MEANS non yrnoxnxa SAND .1N FOUNDRY MoLDsAND 00ans Application filed September 10, 1929, Serial No. 391,658, and in Germany October 5, 1928.

The present invention refers to an improved method of making` foundry molds and cores, more particularly to the method and means ywhereby the sandf is packed mechani- 5 cally in-lasks'and coreboXes.A 1 y The ymethods now commonly used in packing the sand in the molds may be divided into three sections. F or flat work with low flasks n the sand is condensed by exertion of pressure 0 only, mainly in vertical direction. lf the pressure comes from above, the sand at the top of the flask is packed Vharder than at the bottom, and should the pressure comefrom below, the sand is hardest at the bottom of 5 the mold, around the pattern. It is practically always necessaryto do some of the packing by hand, when a plain: squeezing machine is used. f

For high molds "the sand is generally D packed. by means of jolting. The mold carrier is raised a certain height and given a free drop, which is" suddenly interrupted. The kinetic energy gathered in the sand during the fall is thusutilized to do the work. The 5 sand at the bottom of the mold is hardest packed, as this materialis also acted upon by the descending weight of thesand above. l yThe sand at the top of a mold which has been jolted is never hard enough for cast-ing l purposes, and the third method commonly resorted to is therefore-first to jolt the mold and afterwards subject it to a hard squeeze from above. It is sometimes practised to place a heavy plate on top otthe mold during jolting, whereby an eXtra gravity 'force' acts on the sand. v

' Jolt machines are generally built for pneumatic power.` Electricor belt driven machines have been patented, and the j olting has been eected by means ofan eXcentric body which lifts the mold carrier a` short distancel at rapid intervals. However, these machines have never been'a success in foundries, because of the particular intermittent conditions under which molding machines have to work: MaXimum Vetl'ect must be'obtained i-nstaiitaneouslyand instantaneously cut off.

This can generally only be doneby meansofthe u@v tluid pressure.

'ihre 32o-rentner: prey for con# struction whereby the molds can be completed in one single operation without any manual work whatsoever, and with the density of the sand entirely even from top to bottom even in comparatively deep molds.

The invention which is illustrated in Fig. l, 2 and 8, utilizes a hitherto new principle in the design of molding machines. The mold carrier is acted upon by a mechanically operated hammer. The hammer may preferably be pneumatically or electrically operated, and may be of known standard design. ri'lhe number of blows per second which the hammer gives against the mold carrier may be varied withinany desirable limits.

The sand is packed by means of the kinetic energy ofthe hammer piston, which is transmitted through the mold carrier to the sand. The result is ythe same as when the joltingy method is used, but vthe principles involved in thetwo cases are quite dilerent. When the mold is jolted the sand at the bottom is packed hardest, because of the dynamic effect of the sand higher up in the mold. When themold carrier'is hammered, the sand grains at the bottom of the mold will jump up andvmeet the 'static inertia. of the masses above, and is thereby squeezed in between the grains of the ascending particles. Due to gravity the entire molding material is, after each blow, returnedA to the lowest possible position where it will immediately receive a new impulse. It is necessaryin jolting not only to lift the molding material, but even the pattern, the flask and the very heavy mold carrier for each blow. y Thus much power is used. kIt will be seen that in the case of the hammering method a very small body, the piston of the hammer, is at work, producing the desired result with' but a small fraction of the power required by a joltingfmachine.

In orderto pack the sand at the top of the mold other means than the hammering must be resorted to. In the case of the jolting machines it isas statedl'previously, possible to jolt the mold firstand then squeeze. Withv the hammering method, however, it is pos-` sible tu ieeze the mold and subject the malen materiel t@ the i aaien @annilamcusly. The resina Si? very squeeze is used, the sand will bridge beterial.

tween deep parts ofthe pattern, or between v Vthe pattern and thewalls of the flask, with the result that the sand lying below the bridge will not be packed. Theresult is that manual workfor packing sand is partly used, when ordinary squeeze ymachines are used. Machines built after the present invention, however, have the great advantage that any tendency tobridge1, willi at' once be broken' up by the hammering action against the ma- The intensive hammering will dislodge each gra-injof sand from its position in relation to the neighboring grain, and" they .will under theV force of the-pressure settle after'each blow in direction of the least resistance. The result `is anabsolute uniform mold Vfrom 'bottom to top.` Practice has shown, that the4 sand can, by meansof the present invention, be packedin average sized Y molds -in 2 to` 3 seconds.

inthe illustration.

Inthe casel o f large molds it is sometimes desirable to use the hammer for a` second or two'. before pressure is applied. rllhe hammer may eveniwork'while the sand is 'shovelled into the mold.k It is'also possible to stop the hammerany time during the squeezing Aaction. A highly flexible method isf thus pro-- vided, makingV the system perfectly eiiicient under allvarying'practical conditions.

y Theinventon'has the great advantage that it can be easily built into knownstandardv types of squeeze moldingmachines, as shown InFig. 1 theh'ammer located at the Y bottom ofthe squeezing'pistonl. Thev piston which is, worked by lluidjpressure `rsubmitted and exhaustedl through pipe 3, travelslinthe ycylinder 2. Abeam e" is in known manner hinged to a shaft rigidly connected` tol the cylinder. 1 The beam carries a squeeze plateV 5 with the adjustable spindle 6. The hammer receives fluid pressurethrough the pipe 0.A

The hammer is operated independently ofthe squeeze piston and the density ofthe pressure applied may Veven be different-forinstance 8O lbsfper square yinch for the ham mer and say 50lbs.per in'chzfor the squeeze.A By regulating the squeezingpewer it is possible to use different dimensions-of'flaskson thevsame machine and work with the samer .amountfof squeezingpower per square unit ineach case, whileppreferably. the hammer should always work at maximum capacity.

'The squeeze plate is adjustable,ibecause it is desirablek to work with the smallest possible distance between the flask and thepl-ate, ,and- ,di'lferentjlheight of flasks may be used. The hammer" and the squeezing'pi'ston act simultaneously or partly so', atthe will =of` the operator.

In Flg a machme Wlth a Statlonary mold fier, an inner cylinder enclosing the Yextenb 'is illustrated. kA flask f with sand gare shownin working position. The .hammer 7i.

1,816,774 p n u Y j rests'in the stationary frame 7 of the machine. The squeezing platev 5 with the spindle 6 is connected to the squeeze Vcylinder 8 located on the beam 4. The cylinder can be actuated by means of fluid pressure in known manner.

chines, in such a way thatA the hammer is opy erated mechanically while the pressure 'is eX- ertedby manualpower.V Fig. 3 shows the same machine as Fig. 1,. substantially, but' with lthe pressurefplate 5 movable in relation to beam t by means ofthe handle 9.

A hammer' device of'` particularly simple construction is shown. The moldcarrier Z2 is-.ttedrwith an extension lOwhich acts as a p-iston inside cylinder- 1l. Y rllhe fluidpressurefto the cylinder l1 is supplied in known manner through-pipe o. Thecylinder is supportedby a spring l2=restingon the' bottom ofpiston l. The strengthof this spring is so adjusted that it holds the piston against-the mold carrier but without. lifting same.

The method of `operating vthev hammering construction in'this machine-is as follows: The fluid pressure submitted to the cylinder pressesy VcylinderV ll downwards, while Vthe table b with flask f andA sandY gremains stationary. VWhen the exhaust position is reached, the spring 1`2`throws the cylinder l1 againstthe.mold-carrier b, and-thus produces the desired hammering effect. It will be seen that even the cylinder, and not only the piston,` maybe utilised ink carrying the invention into; practice. Y' VThe moldV may be squeezed by handpower while the hammer is in action.k Y p 1 y 'Ehe type machines,v described are not the only onesto which the'inventgion is limited, while they may be considered as preferred constructions.- 'lllie inventionis claimed to cover any type-ofr machines .where pressureV other t-hanzgravity iseXented onthevmoldor core simultaneously with the action of the hammer. Y f.

Having new.v describedf'my inventiomwhat I claimas new and'desire to secure'by Letters Patent is: f

. l. In a 'molding-machine, ya supporting frame, a mold carrier adjacent thereto, a piston-like extension mounted-on the mold carsion, a spring supporting said inner cylinder, fluid means for operating thespring and inner cylinder to produce a jolting action on the mold carrier and mold, a squeeze-plate and yoperating means therefor mounted on the supporting frame.

2. In a molding machine, a supporting frame, an outer stationary cylinder attached to the frame, a squeeze-piston reciprocating in the outer cylinder, a mold carrier above the squeeze-piston, an inner hammer cylinder' operating Within the squeeze-piston, a pistonlike extension on the mold carrier operating in the hammer-cylinder, a spring Within the squeeze-piston in alinement With the hammer cylinder of proper length to normally permit the inner hammer cylinder to rest against the bottom of the mold carrier, and means for compressing, and releasing the spring, and lowering the hammer cylinder, in order to deliver a jolting blow on the mold carrier, a

movable squeeze-plate mounted in the frame, and means for operating the squeeze-piston in order to exert pressure on the mold and mold carrier when the mold is in contact With the squeeze-plate.

3. In a molding machine, a supporting frame, a mold carrier adjacent to said frame, an integral attached piston-like extension on the mold carrier, an inner hammer cylinder enclosing the said extension, av resilient actuating means beneath the inner cylinder, fluid means for operating the inner cylinder, and resilient means to produce a j olting action lon the mold carrier and mold, an adjustably operated squeeze-plate mounted on the supporting frame, in contact With said mold and designed to resist the jolting motion of the mold, When the latter is acted upon by the resilient actuating means.

4. In ya molding machine, al supporting frame, an outer squeeze-cylinder attached to the frame, a hollow squeeze-piston operating Within the outer cylinder, a mold carrier in contact with said cylinder, an inner and movable cylinder positioned and operating Within the squeeze-piston, a piston-like extension integral with the mold carrier reciprocating Within the movable cylinder, a resilient jolting means Within the squeeze-piston for jolting the piston-like extension and mold carrier, of suitable length when quiescent to permit the mold carrier to rest on the top of the squeeze-piston, fluid means for actuating the j olting means and movable cylinder, for delivering a series of hammer-like blows on the mold carrier, and adjustable pressure resisting means'for resisting the action of the jolting means and the squeeze-piston, when the mold is in proximate relation with the pressure resisting means.

In Witness whereof I have hereunto signed my name.

MOETEN GRINDAL.

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