US2646607A

US2646607A - Means for preventing collapse of molded concrete products when core is withdrawn

Info

Publication number: US2646607A
Application number: US35348A
Authority: US
Inventors: Robert O Davis; Noel B Osborne
Original assignee: STEARNS Manufacturing Co
Current assignee: STEARNS Manufacturing Co
Priority date: 1948-06-26
Filing date: 1948-06-26
Publication date: 1953-07-28
Anticipated expiration: 1970-07-28

Description

July 28, 1953 R. o. DAVIS ETAL 2,646,607

MEANS FOR PREVENTING COLLAPSE OF MOLDED CONCRETE PRODUCTS WHEN CORE IS WITHDRAWN Filed June 26, 1948 IN VEN TORS Poberzfi C2 Dov/s 3.- fl/oe/ 5. Osborne.

ATTO NEYS.

ing the mold and block.

Patented July 28, 1953 MEANS FOR PREVENTING COLLAPSE OF MOLDED CONCRETE PRODUCTS WHEN CORE IS WITHDRAWN Robert 0. Davis and Noel B. Osborne, Adrian, Mich., assignors to Stearns Manufacturing Company, Adrian, Mich., a corporation of Michigan Application June 26, 1948, Serial No. 35,348

8 Claims. 1 This invention relates to molding concrete blocks or similar materials. In fact, it has broad application to all mold operations.

Concrete blocks are today made largely on automatically operated concrete block machines. These operate very rapidly and the result is that some of the shifting including the withdrawal of the mold and the cores is done very rapidly. This is especially true in a machine such as described in the copending application of Walter G. Schutt,

filed January 14, 1948, on Machine and Method has been recognized, and vents have been provided for the purpose of allowing atmospheric air to enter the space left by the core as it is withdrawn. However, these openings very often get clogged with some of the molding material. Furthermore, these openings have to be small in order to prevent the material which drops out of I the feed drawer from falling into the vent open-,

ings. When the core is rapidly'withdrawn the air cannot pass through the openings rapidly enough to keep the pressure on the inside and outside of the block equal. In fact, if the mold and cores are stripped from the block too rapidly they will leave a sufiicient rarified vacuum in the evacuated space to allow the atmospheric pres- [sure on the outside of the block to collapse the block. We have accordingly provided a new way of equalizing the pressure on the outside and" inside of the block as the mold and cores are stripped from the block. This provides adequate internal air pressure to prevent the collapse of the box, no matter how fast the stripping action is, and also makes sure that the air passages;

through the cores are never plugged or narrowed by some of the cementitious material getting in the passageways.

Referring to the drawings:

Fig. 1 is a side elevation of a part of a con- 'crete block machine showing our invention installed.

Fig. 2 is a vertical section of the block showthe core removed from the Fig. 3 is a vertical cross section through the mold box and the cores showing the air system installed.

Fig. 4 is a section on the line 4-4 of Fig. 3.

I designates the customary pallet used in a concrete block machine. 2 shows the mold box which has at the top an upwardly extending flange that is sometimes called a fence 3. This mold box usually consists of several molds to form three or more blocks. Three molds and three cores 4 are shown in the drawings. These cores have a slight draft, as is clearly shown in Figs. 2 and 3, to enable the core to be withdrawn from the molded block without disturbing the molded surface. The outwardly-turned flange 5 of mold box 2 supports a core bar 6, the top of which is recessed at I to form a groove. The top of this groove is closed by a strip 8 that is welded thereto. This forms an air passageway across the top of the core bar. Passageways 9 lead to vent openings I0 in each of the cores 4. A passageway. H at the endv of the core bar connects with the T [2 in the air main I3. It will be seen that there are 2 Ts and one elbow that connect the main with the three core bar grooves .(see Fig. 1). A flexible hose I4 connects the valve I5 with the air main. I6 is a pipe that leads to a source of compressed air.

In molding concrete blocks there is first a shifting of the empty pallet under the mold box, and pushing the pallet bearing the molded block out from under the mold box. Next, the mold box is lowered onto the pallet; then the feed or strike-off drawer moves upward from the material magazine to a position over the mold box where the contents of the drawer empty into the mold box to go over the top of the cores and core bars, then there is a vibrating action, then a packer head is lowered onto the mold head with the packer head feet engaging the contents of the molds, then a vibration of the packer head follows, then the packer head is lifted and the mold box and cores are stripped from the block by means of an arm I! engaging an angle member H) on the side of the mold box as shown in Fig. 2. This strips only the core box and the cores from the block. It will be obvious that if the cores are lifted out of the block that little or no air can get to the interior of the block except what little can sift under the wet blocks standing on the pallet or passed down on the side of the core between the core and the inside of the block. Little or no air can get into the interior of theblock in this way, consequently, as the core is rapidly lifted in an automatic maa chine operation the air in the hollow interior of the core and in the hollow interior of the block, as the core is lifted, becomes much rarified and there is a substantial difference of pressure on the outside and the inside of the block, which will ordinarily collapse the wet walls of the said block. This diificulty has been recognized and vent holes have been put in the top of the core to endeavor to remedy this situation, but ob.vi-. ously these vent holes cannot supply air, at atmospheric pressure, fast enough to eliminate the difierential in air pressure on the outside and inside when the core is rapidly lifted out of the block.

We have designed means for overcoming this difficulty by supplying compressed air through a conduit on the top of the core bar. This conduit guards tops of the vent openings 9 in the core bar and prevents them from catching and filling up with some of the aggregate falling out of the strike-elf drawer. At the same time, air under pressure afforded by this conduit can equalize the pressure on the inside and outside of the blocl; no matter how rapidly core is stripped out of the block.

The amount of compressed air passing into the core must be properly .co-ordinated with the speed of raising the cores. Of course, the faster the core is raised the more compressed air will have to be sent into the core during the raising operation. A cam 20 is timed to trip the lever II that operates a valve if: at substantially at the point of time the lifting of the core begins.

The ventilating openings 9 in the core bar meters the air. The pressure in the shop lines may be near from 80 to 120 pounds per unit area, and, consequently, the greaterthe pressure the more restriction has to be applied .to letting the air through the air line 6. This is accomplished by means of the valve and the lever arm 2|. An arrangement may be provided in this valve for adjusting the lost motion between the lever 21 and the valve stem 2d. The more the lost motion the less opening in the valve and, consequently, this will result in a pressure reduction and this will adapt the air supply to the needs of the block, depending on the speed of which the cores are lifted. This lost motion may be between the lever end and the valve actuator such as a nut 22 on the end of the valve stem.

What we claim is:

1. The method of preventing the collapse of a hollow block in molding hollow concrete blocgs or similar products when the core is withdrawn and the outer mold stripped simultaneously from the block, which comprises the supplying to the space left between the pallet and the withdrawing core, a charge of compressed air calculated to substantially equalize the pressure on the inside and outside of the block as the Gore is withdrawn.

2. The method of preventing the collapse of a i hollow block in molding hollow concrete blocks or similar products when the core is rapidly withdrawn and the outer mold stripped simultaneously from the block, which comprises using ahollow core with a vent opening the top and supplying .a .metered charge of compressed air at a determined pressure to the ho w n or of the core through the vent Ow in said charge of air under pressure calculated so as to, substantially equalize the pressure on the outside and inside of the block by correlat ng t e air charge with the speed of withdrawal of thfi core from the block.

3. A mold box containing one or more cores and means for preventing the collapse of the hollow molded block when the cores and mold are stripped from the molded block which comprises the said mold box, the said core 'or cores, and a conduit and passageways through the core or cores for supplying compressed air to the space left by the core or cores in the block as they and the mold are withdrawn.

4. A mold box containing one or more cores and means for preventing the collapse of the hollow molded block when the cores and mold box are lifted simultaneously, which comprises the said bold box,'the said core or cores, and a conduit and passageways through the core or cores for supplying compressed air to the space left by the core or cores in the block as they and the mold box are simultaneously withdrawn from the molded block, the air supplied to the space in the block being a charge co-ordinated to the speed of withdrawal of the core from the block so as to keep the pressure on the inside and outside of the block substantially equalized.

5. A mold box containing one or "more cores and means for preventing the collapse of the hollow molded block when the cores and mold box are stripped simultaneously from the block, which comprises the said mold box, the said core or cores, and a conduit and passageways through the core or cores for supplying compressed air to the space left by the core or cores in the block as they are withdrawn, the air supplied to the space n the l ck being a char e O-e u te to the speed of withdrawal of th core fr m th block so to keep the pressure on the inside and outside of the block substantially equalized, and a cam and cam-operated valve for opening the air supply to the block and cutting off the air supply to meter said air charge.

,6. A mold box containing one or more cores and means for preventing the collapse of the hollow molded block when the cores and mold box are lifted contemporaneously and rapidly leaving the block stripped, which comprises the sa d mold box, the said core or cores united to the mold box to lift therewith, and a conduit and p agew thr h e c re or cores for supplying compressed air to the space left by the core or cores in the block as they are withdraw the air supplied to the space in the block being a charge co-.-.ordinated to the speed of Withdrawal of the core from the block so as to keep the pressure on the inside and outside of the block substantially equalized, a cam and cam-controlled valve for openi g the supply of air to the space in the block and closin off the supply of air, the amount of opening of the valve being adjustable by means of lost motion between the cam and the valve, and means for actuating the valve adjustable to vary the amount of lost motion and, cons qu ntly, the ope ing o the a ve- 7, A method of preventing the collapse of molded block walls when rapidly and Simultaneously stripping the core or cores and the mold from the block in a concrete block machine, which comprises simultaneously supplying to the interior of the cores during the stripping operation a metered charge of compressed air to substantially equalize the pressure on the outsi and ins e O t e We s O the 4 dur n the stripping operation.

.8, In a concrete blocl: molding machine, a pa et a m ld n e o e a e b r temme on the top of the mold, and one or morecores supported by the core bars and each having a hollow open lower end interior and each having a slight draft to permit withdrawal from the block and its seat upon the pallet, passageways through the core bar or bars and into the core or cores, and means for supplying air under compression to the interior of the core or cores through said passageways, simultaneously with the stripping of both the mold and the cores vertically upwardly off the block on the pallet, said compressed air being coordinated to atmospheric pressure by adapting the amount of pressure and metering the air to the interior of the cores so that the pressure on the inside and outside of the block Wall will be substantially equalized 15 2,297,090

6 during the rapid stripping of both the core 01 cores and the mold from the block resting on the pallet.

ROBERT O. DAVIS.

5 NOEL B. OSBORNE.

References Cited in the file of this patent UNITED STATES PATENTS 10 Number Name Date 1,706,647 Besser Mar. 26, 1929 1,717,996 Moore, Jr. June 18, 1929 2,186,331 Flood et a1. Jan. 9, 1940 2,193,847 Strong Mar. 19, 1940 Weaver Sept. 29, 1942