Static molds – Container-type molding device
Reexamination Certificate
2000-10-19
2002-10-15
Mackey, James P. (Department: 1722)
Static molds
Container-type molding device
C249S140000, C425S443000
Reexamination Certificate
active
06464199
ABSTRACT:
BACKGROUND OF THE INVENTION
Concrete masonry units are available in a wide range of sizes and shapes, and are used for a variety of applications ranging from concrete blocks and bricks to segmental retaining wall blocks (the latter are sometimes called “SRW” blocks).
Depending on the intended end-use application of the concrete masonry units being produced, the surface appearance of the units may be important and the marketplace has come to expect various decorative or cosmetic surface finishes for many masonry units. Such surface finishes include those commonly described as broken or split, striped, striated, simulated broken, and smooth (alone or in combination with one of the other surface finishes). One such surface finish is a texture that resembles the appearance of a “split” rock. A “split” surface finish on a concrete masonry unit may be achieved by mechanically splitting away a portion of a face of the masonry unit. This is typically achieved with a mechanical splitting blade similar to a guillotine and the splitting is performed on the masonry units after they have been cured or hardened. To avoid waste, this is often done by first forming the masonry units as “Siamese” twins and then splitting them apart. The resulting fractured surface on the front face of both blocks is generally thought to be pleasing to look at and is sought after.
The mechanical splitting of masonry units is an added cost of processing since one must invest in the splitting equipment, and transport the masonry units from their place of curing to the splitter, and then to a suitable collection station for palletizing or the like. When the applicable capital, labor and other costs (e.g. utilities and floor space) are added together, this added cost is significant. This cost provides a substantial incentive to develop new methods of roughening the surface of masonry units to create a desirable surface finish without the need to mechanically split the masonry units. Although some approaches have involved processing steps to be performed on the green or uncured masonry units immediately after they are discharged from the mold, the most common approach has been to modify the mold in some fashion so that a roughened surface is produced on the concrete masonry units as they are ejected from the mold (i.e. the masonry units are roughened in the mold cavity).
For example, U.S. Pat. No. 3,940,229 describes a mold for making concrete masonry units with a roughened texture on at least one face. The mold has a wall with a lip on the lower edge of the wall, that projects inwardly into the mold cavity. The lip is rectangular in profile, and it may be smooth or it may be serrated to provide sawtooth-like projections. As the shaped but uncured concrete masonry unit is forced out of the bottom of the mold, the patent says that the protruding lip produces a scraping or tearing action on the adjacent face of the concrete masonry unit so as to roughen the surface of the masonry unit. Although a small amount of fill material will loosely rest on or adhere to the mold wall above the lip after use, the mold of U.S. Pat. No. 3,940,229 is self-cleaning since the small amount of material that remains loosely adhered to the mold wall after the mold is stripped is knocked clear of the wall when the next machine pallet is placed against the mold bottom and the mold is vibrated. Experiments with this type of mold demonstrate that it produces a roughened surface on the concrete unit, but that the face sometimes has a slight “shingled” appearance. Further, the lip is relatively small, and wear is a problem with the passage of time due to the abrasive nature of the moldable fill material from which the concrete masonry unit is formed. The lip is also susceptible to damage if the head of the block machine is not properly aligned. Replacing the lip is time consuming. Sometimes a new lip is welded to the mold and at other times a new mold wall is made.
A modified form of the lip design of U.S. Pat. No. 3,940,229 has been developed and that modified lip design is the subject of U.S. Pat. No. 6,209,848 entitled “MOLD FOR PRODUCING MASONRY BLOCK WITH ROUGHENED SURFACE”. According to that patent (which is incorporated herein by reference), a satisfactory roughened surface is produced by forming grooves in a wedge shaped lower lip with the grooves at an angle to the direction of travel that the material moves through the mold. Masonry units made with this improved mold seem to have less shingling than units made with a solid or serrated lower lip. The mold remains self-cleaning. However, the grooves in the lower lip are subject to the same wear and damage as the lower lip of U.S. Pat. No. 3,940,229.
U.S. Pat. Nos. 5,078,940 and 5,217,630 describe a somewhat different type of mold for making concrete masonry units with a roughened surface. Although the molds described in these patents also employ a protruding lip on the lower edge of at least one wall of the mold, the lip is wedge-shaped in profile. In addition, the mold includes a plurality of projections above the lip on the same wall and these multiple projections also intrude into the mold cavity. In addition, an optional mesh extends upwardly from the lip generally close to and parallel to the wall and associated projections. In use, concrete fill material is introduced into the mold and compressed to a size slightly “oversize” of the desired masonry unit. The projections and the mesh are designed to retain a meaningful portion of the concrete fill material in place against the wall of the mold as the formed concrete masonry unit is forced out of the bottom of the mold. As described in these patents, the concrete fill material held against the mold wall by the projections and the mesh is sheared from the concrete masonry unit that is being forced out of the mold, thus forming a roughened surface on the concrete masonry unit as it is ejected from the mold. These patents teach that the mold is then re-used one or more times to make additional masonry units and the concrete fill material retained in the mold remains in place and reportedly assists in roughening the surface of the masonry units that are successively formed in the same mold. Molds of this type are not self-cleaning, but are designed to retain fill material on the projections and against a wall of the mold during successive machine cycles. It is believed that molds of this design, although without the mesh, have been commercialized under the trademark “Softsplit”. Others familiar with the use of this process on a commercial scale have reported that the process must occasionally be interrupted to clean out the fill material that agglomerates around the projections since the fill material eventually becomes too hard for this process to be effective. This is not necessarily an easy cleaning process. It depends upon how accessible the mold face is to the machine operator. In many of the commonly used concrete block machines, the mold faces are relatively difficult to get at, and safety dictates that precautions such as machine lockouts and the like be used when the cleaning process is undertaken. The cleaning process is not easy, and is costly since production is interrupted for cleaning to take place.
U.S. Pat. No. 5,879,603 describes an improvement to the '229 style mold. The '603 patent describes a mold with a wedge-shaped lower lip and an upper lip spaced apart from the lower lip by the distance defining the height of the concrete unit to be produced. Both lips protrude into the mold cavity. The mold acts in a similar fashion to the molds of U.S. Pat. No. 3,940,229, but produces less “shingling” effect on the roughened face, and is also self-cleaning in the same fashion, i.e. the concrete fill material that loosely adheres to the lower lip and to the mold wall above the lower lip is knocked off the wall when the next pallet is brought into place beneath the mold and the mold is vibrated.
U.S. Pat. No. 6,113,379 describes another style of mold for roughening the surface of a masonry unit as it is ejected from th
Anchor Wall Systems Inc.
Mackey James P.
Merchant & Gould P.C.
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