Patent Application
20050188645
The present invention relates to method and apparatus for producing cast concrete members and the like and more particularly to a method and apparatus for producing cast members which are provided with step inserts to facilitate insertion and firm gripping of steps in cast members. One embodiment of step inserts is designed to prevent undesirable seepage of the cast material and thereby retain the cast material within the mold assembly. Novel one-piece or two-pieces insert assemblies are provided to retain the insert in proper position during casting. The two-piece step inserts are designed to adapt to a variety of installation applications. Templates are provided for easily and accurately locating step inserts employed in cast members at least one flat wall.
It is well known in the art to provide manhole assemblies with steps to facilitate a descent into and ascent from the manhole assembly through a top opening thereof.
One of the preferred techniques is described, for example, in U.S. Pat. No. 3,974,615 issued Aug. 17, 1976, assigned to the assignee of the present invention, which patent teaches the use of hollow plastic manhole step inserts releasably mounted to an inner mold member of a mold assembly. The cast
Known inserts are preferably made of polypropylene which has a life expectancy exceeding concrete itself and further exhibits excellent chemical resistance and serve as a protective shield against dissimilar material reaction such as an electrolysis of aluminum and concrete. The insert meets requirements of all ASTM C-478 § 12 and Performance Test Procedures of ASTM C-497.
A number of conventional step members utilized in manhole assemblies and the like have been provided with substantially rectangular and in most cases square-shaped, cross-sectional shapes. Other step members adapted for insertion into the step inserts are designed to have circular cross-sections. In addition, as can be seen from
The steps of circular cross-section thus require a step insert of a design and shape which conforms with and cooperates with the design and shape of the steps whose legs are adapted to be inserted therein.
Manhole assemblies are typically produced through either a drycast or a wetcast method, both of which methods are well known in the art.
Utilizing one conventional drycast method, the granulated casting material is placed into the mold assembly which is vibrated and packed down to assure that the dry casting material is evenly and densely packed within the mold assembly. When the casting material has been filled to the appropriate level within the mold assembly and appropriately compacted, the core portion of the mold extends a pair of reciprocating pins, which are operated by either hydraulic or pneumatic means, into the casting material to form openings within the cast material of a size appropriate for receiving the legs of a step. In the conventional technique, the tremendous pressures developed within the casting material cause these openings to “sag” or become “off-round” when the pins are removed and the openings often accumulate some of the cast material when the cast member is removed from the mold assembly which necessitates that the operators employ a drill or other device to reopen or “reround” the openings to enable the legs of a step to be inserted therein.
The pneumatically or hydraulically-operated pins which create the step openings in cylindrical-shaped case members typically extend from a core mold member which has a curved, convex outer periphery. The casting material entering into the openings in the region between the pins and the opening in the core member through which the pins extend, often renders the pins inoperative and possibly even causing damage to the mechanism. At the minimum, the entry of fines into the mechanism require regular maintenance to maintain the mechanism in operating condition, which disadvantages are to be avoided.
In the employment of the wetcast method, there has heretofore been no step insert available which is inserted into the casting material by hydraulically or pneumatically operated pins.
The present invention, in one embodiment, is characterized by comprising a step insert design for use with manhole steps having circular-shaped insertion portions, said insert having a substantially circular cross-section and being provided with an open end and closed end. The closed end has a conical-shaped outer surface. The insert is designed to fit over a free end of a circular-shaped, reciprocating pin and is provided with inwardly directed projections which are parallel to the longitudinal central axis of the insert and are located near the closed end of the insert so as not to interfere with the continuous, annular projections arranged along the interior surface of the insert and provided for firmly gripping the leg of a step inserted into the insert.
The insert is mounted upon the pin and, when properly positioned, has a diagonally aligned flange at its open end which is substantially flush with the convex surface of the mold assembly core member, which flange has an outer diameter that is just slightly less than the inner diameter of the opening in the core mold which it substantially seals, to prevent seepage of fines into the mold assembly mechanism.
The outer periphery of the insert is provided with a plurality of radially outwardly extending annular flanges therealong which serve to significantly enhance the holding power of the dry cast concrete upon the insert.
The closed end of the insert may, if desired, be increased in thickness as compared with the remainder of the insert to significantly enhance the structural strength of the insert as it is pushed into the drycast material.
As described above, the interior periphery of the insert, in one embodiment, is provided, in one embodiment, with closely spaced projections forming annular serrations of a “one way” type in that the tapered, annular projections are preferably diagonally aligned along one surface thereof so as to make it easier to insert the leg portion of a step while the opposite surface is substantially perpendicular to the longitudinal axis of the insert, thereby significantly increasing the frictional fit between the leg portion and the insert to act against forces working in the direction of removal of a leg of a step out of the insert. The interior surface adjacent to the inner most end is also provided with a plurality of inwardly, directed projections to provide a good friction grip with the reciprocating mounting pin extending through the mold member to retain the insert in its proper position during casting of the cast member.
Another step insert utilized in the fabrication of the cast members has an open end and a closed end. The open end lies in a plane which diagonal to a longitudinal axis of the insert and is provided with a flange adapted to rest against an opening in the mold assembly core member. A plurality of flexible, hook-like ears or projections extend away from the diagonally aligned flange and are arranged, preferably at equiangularly spaced intervals about the insert so as to make a snap-fit with a marginal portion of the opening to hold the insert in position preparatory to filling of the mold assembly with cast material. The flange surrounding the open end substantially seals the opening to prevent fines from entering into the mold assembly mechanism.
The ears are designed to snap off due to a shearing force applied thereto as the cast member, after having been set, is separated from the mold form.
Heretofore, inserts utilized in the wetcast method for providing inserts for circular-shaped step members employ a pin which is inserted into the mold assembly during casting. The pin is then removed from the cast member after it has set and is removed from the form. This technique requires an undesirable additional manufacturing step and further fails to provide an opening for the leg of the step which has the supporting strength and holding force of the insert of the present invention.
Another preferred insert embodiment for use in the wetcast method is comprised of an assembly of first and second hollow, cylindrical-shaped, molded plastic members. A first member, which serves as a tube holder, has a diagonally aligned flange intermediate its open end and has axially aligned slots on opposite sides of the flange. A bead provided on one end of the first member slides into a step tube welded to a mold core member and is aligned with an opening in the core. The slots allow the first member one end to be pressed inwardly by the tube, providing a good press-fit between the step tube and the first member. Alternatively, the slot on the opposite sides of the member may be omitted while still providing a suitable force-fit into both the second member and the step tube.
The second member serves as the insert and generally resembles one of the embodiments described above and has a open end and a closed end. The open end lies in a plane which forms a right-angle with a longitudinal axis of the insert and is provided with a flange adapted to rest against an opening in the mold assembly core member. The end of the first member extending away from the step tube is force-fitted into the open end of the second member. The diagonally-aligned flange on the first member, engages a marginal portion of the core surrounding the opening in the core to hold the insert assembly in the proper position and to further seal the opening in the core mold member as the casting material is poured into the mold assembly.
The first member is scored at least in the region of the diagonally-aligned flange on the side of the first member extending into the cast member, enabling the portion of the first member embedded in the cast member to easily break away from both the second member and the insert embedded in the cast member when the cast member, after having set, is separated from the mold assembly. The portion of the first member remaining in the step tube is removed from the step tube in readiness for receipt of a first member of another insert assembly in preparation for molding another cast member. The portion of the first member remaining in the second member is pushed toward the closed end of the second member when a leg of a step is inserted or may be removed prior to insertion of the leg of a step.
Another embodiment of the present invention is to provide method and apparatus for imbedding inserts within a box-like cast member having an interior typically comprised of a plurality of walls each having planar surfaces. Steps can be placed at different areas along the flat surfaces of such box-like structures to suit the particular application. One present day technique is to drill holes in the finished product at a location where steps are required. This technique is very time consuming and labor intensive. In order to greatly simplify the precise location of inserts for steps, a unique method and apparatus of the present invention comprises the provision of a pair of substantially rigid elongated plates having pairs of holder pins arranged at spaced intervals along each plate. Two additional plates employed as spacing templates are arranged between the first and second elongated plates and preferably near upper and lower ends thereof so as to provide the proper spacing between the elongated plates and hence between the holder pins. The elongated plates and templates are, in one preferred embodiment, comprised of a rigid metallic strip and a sheet of plastic material affixed to the metal plate and homogeneously impregnated with magnetized particles, said impregnated sheet being affixed to one major surface of each of the elongated strips opposite the surface carrying the holding pins. In another alternative embodiment, recesses may be formed in the surface of the rigid metal strip opposite the surface along which the pins are mounted. Permanent magnets are placed in the recesses and an epoxy is applied to the surface carrying the permanent magnets to retain them in place. The strips and templates are affixed to the wall of an interior or “core” mold member of a mold assembly which core is formed of a ferromagnetic material attractive to the magnetized sheet (or permanent magnet members). When the elongated strips and templates are properly positioned with longitudinal sides of said strips abutting opposing side edges of the templates, the templates may then be removed. Inserts are press fitted onto the holding pins and the cast material is poured into the mold assembly.
When the cast material has set, the cast member is removed from the mold assembly. The embedded inserts and holding pins are lifted together with the cast member, the lifting forces overcoming the magnetic attraction of the magnetized sheets (or permanent magnets) to the surface of the mold core so that the elongated strips and magnetized sheets are stripped from the inner mold member.
The elongated strips carrying the pins are then peeled away from the interior wall of the cast member, leaving the inserts embedded within the cast member. The steps are then pushed into the inserts thereby completing the procedure.
The templates and elongated strips bearing the positioning pins are reusable and in fact have a long useful operating life.
In an alternative embodiment wherein the mold assembly is formed of a material which is neither ferromagnetic nor metallic such as wood, aluminum or plastic, the elongated strips and templates are magnetically attracted to a planar wall of the mold form upon which inserts are to be provided by placing a magnet or magnets on or beneath an interior surface of the hollow interior mold member opposite the surface receiving the elongated strips carrying the holding pins and the templates. This embodiment enables the use of metallic forms formed of non-magnetic material as well as wooden or plastic forms.
As another alternative, an adhesive may be placed upon the rear surface of the elongated plates bearing the positioning pins and the templates, which adhesive has sufficient strength to hold the elongated plates and templates in position against the interior mold member during the positioning and pouring phases of the casting operation but which has a limited holding power, enabling the elongated strips to break away from the interior mold member when the completed cast member is lifted away from the mold core.
It is therefore one object of the present invention to provide a novel insert for cast members and which is adapted to receive the insertable leg of a step having a circular cross-section.
Still another object of the present invention is to provide a novel insert for use in a casting method and which is designed to prevent seepage of the cast material into the mechanism of the mold assembly.
Still another object of the present invention is to provide a novel step insert for use in a casting method wherein the insert has an alignment slot which is keyed to a insertion pin to assure proper mounting and alignment thereof.
Still another object of the present invention is to provide a novel insert for step members produced in either a wetcast or drycast method and having an internal serrated design which provides increased frictional holding forces acting against forces which may be applied in a direction to pull the step out of the insert.
It is still another object of the present invention to provide a novel two-piece insert for cast members produced employing the wetcast method and which is adapted to receive the insertable leg of a step having a circular cross-section.
It is still another object of the present invention to provide a novel two-piece insert for cast members produced during a casting method and which is adapted to seal the opening in the core mold member during casting of a mold member.
Still another object of the invention is to provide novel method and apparatus for casting step inserts into cast members having a flat wall for receiving the step members.
The above as well as other objects of the present invention will become apparent from a consideration of the specification and drawings of the present invention, in which:
Any suitable drycast method capable of utilizing hydraulically operated insert pins may be employed with the present invention.
Making reference to
The core member 50 is provided with circular-shaped openings 50a, 50b which are precisely arranged so as to provide the proper relationship between openings formed in the cast member and the legs of a step, such as legs 22a′ of the step 20′, for example.
When the cast material reaches an appropriate level and has been sufficiently vibrated, tamped down and the like, a pin 54 is operated by suitable hydraulic or pneumatic means (not shown for purposes of simplicity) to project out of core 50 and into the casting material.
The pin assembly 54 has a cylindrical shape and is comprised of a first portion 54a of a first diameter integrally joined to a second cylindrical portion 54b having a diameter larger than portion 54a so as to form a shoulder 54c there between. At least one projection 54d is arranged at one point along shoulder 54c and extends in an axial direction along the smaller diameter portion 54a.
It should be understood that the pin assembly 54 shown is modified from conventional pins to provide the design shown incorporating the smaller diameter portion 54a, larger diameter portion 54b, ledge 54c and projection 54d.
The insert 60 shown in
The open end 60b is provided with two diametrically aligned alignment slots 60g, each of which is designed to receive the projection 54d of pin assembly 54 thereby assuring that the insert is aligned with proper orientation upon pin assembly 54 as will be understood from the description set forth below.
Noting the right-hand insert 60 shown in
When the cast material has been duly and properly vibrated and compacted, the hydraulic (or pneumatic) mechanism (not shown) operating pin 54, moves the pin assembly 54 in the direction shown by arrow A1, urging the pin and the insert 60 mounted thereon into the cast material so as to ultimately occupy the final position shown by the left hand-insert 60′. The pin assembly 54 is designed so as to cause the ledge 54c to partially enter into the cast material, whereby the open end of the insert 60′ is slightly recessed into the cast member so that when the pin assembly 54 is withdrawn from the cast member into the mold core 50 there is no wiping action of the insert 60′ against the core, thereby preventing both the core 50 and the cast member (together with the insert) from being damaged and to prevent the cast material from swept into the core 50.
The insert 60 is provided with slots 60g at two (2) diametrically opposed positions in order to provide an insert of universal design. The manner of use is such that the slot 60g which receives projection 54d aligns the insert 60 so that the diagonally aligned end 60f is flush with the concave surface of the core. By rotating the second insert 60′, 180° relative to the first insert 60 and placing this insert 60′ on the left-hand pin assembly and so that the opposite slot 60g receives pin 54d, this assures that the diagonally aligned closed end 60f′ is flush with the curved surface surrounding the left-hand opening 50a when initially positioned on the left-hand pin 54.
As can be seen from the embodiment shown in
In equipment used for the drycast method wherein the interior region containing the hydraulically operated pins 54 is easily accessible, the inserts may be placed upon the pins when they are in a retracted position such as the left-hand pin 54 shown in
In some applications, wherein the openings 50a, 50b in the core member 50 is at least slightly greater that the outer diameter of the flanges 60d, the pins 54, together with the inserts 60, 60′ mounted thereon my be retracted from the region 51 between the outer jacket 52 and inner core 50 during the casting operation. Nevertheless, the pins 54 and inserts 60, 60′ may be employed using either of these two (2) techniques.
The open end of insert 60″ is further modified so that the flange 60d″ immediately adjacent the open end lies in a plane which is diagonally aligned relative to center line CL. A plurality of ears 60h are integrally joined to the insert adjacent to the flange 60d″ and project away from the opening and are substantially parallel to the longitudinal axis CL. Each ear 60h has a substantially hooked-shaped configuration and each ear is sufficiently flexible so that, as the ears are pushed into opening 56a, the inclined surfaces 60h-1 slidingly engage the edge of the opening and cause the ears to be flexed substantially radially inwardly until the inclined surfaces 60h-1 clear the interior side of the opening, at which time the locking surface 60h-2 of each ear 60h grips a marginal portion of the inner mold member 56 surrounding opening 56a on the interior side of core 56 as the flexed ears return to their normal unflexed position, whereby the insert 60″ is locked into position with the ears engaging marginal portions along the interior concave surface of core 56 while flange 60d″ rests against a marginal portion surrounding the exterior convex portion of the core 56 surrounding opening 56a. Flange 60d″ prevents fines from entering into the interior of the mold member 56.
The insert 60″ utilized for both the left and right-hand positions, i.e., for insertion into the left and right-hand openings 56a, 56b, are identical in design to one another. The proper orientation of the inserts relative to the mold member 56 is obtained by rotating each insert so that the flange 60d″ rests against the external, curved convex surface of core 56. Thus, the insert inserted into the right-hand opening 56b is rotated 180° about its center line relative to the insert inserted into opening 56a so that the inserts are aligned with their longitudinal axes CL substantially parallel to one another to assure proper alignment with the insertion portions of step 20′ (see
After the inserts are snapped into position, the cast material is poured into the mold. When the cast material has been set, the cast member is pulled out of the form, whereupon the ears 60h shear off as the cast member is removed from the mold. The ears 60a are of a strength sufficient to retain the inserts in position during the casting operation and yet adapted to be easily sheared away from the main body of the insert when the cast member has been set and is pulled away from the mold.
The interior design of the insert 60″ is substantially identical to the design of insert 60 to preferably obtain the “one way” feature of the internal serrations for assuring the positive retention of the legs of the step within the inserts.
The inserts 60″ may be modified for use in core molds having flat walls by aligning flange 60d″ perpendicular with the center line CL.
Testing has indicated that the inserts 60 and 60″ are capable of withstanding as much as four (4) times the normal pulling force (1600 lbs. pulling force), the normal pulling force being of the order of 400 lbs. capability.
The two-piece insert assembly embodiment 70, shown in exploded fashion in
The major portion of member 72 extending between and 72a and flange 72c has a plurality of individual annular projections F′, similar to the projections F on the step 20, each of which has an inclined surface F1′ which is inclined at an angle to a longitudinal center-line CL, on a side of each projection and a surface F2′, which is substantially perpendicular to the center-line CL and which is on the side of each projection remote from the end 72a. Alternatively, the surface F1′ may be aligned perpendicular to the central axis CL. This design is such as to make it easier for insertion of the end 72a into insert member 74, whereas any effort or attempt to pull the insert member 74 out of insert member 72 is met with an increased frictional holding force, due to the “one way” design of the serrated or flanged portions F′.
Insert member 74 has a closed end 74a and an open end 74b. End 74a has a planar surface which is diagonally aligned relative to center line CL and terminates in an integral annular flange, similar to the embodiment 60 shown in
The interior periphery of member 74 is provided with a plurality of closely spaced, inwardly directed, annular projections F″, having an inclined surface F1″ which is inclined at an angle to the longitudinal center-line CL and a surface F2″ which is substantially perpendicular to the center-line CL and which is on the side of the projection remote from the end 74b. This design is such as to make it easier for insertion of the end 72a into insert member 74, whereas any effort or attempt to pull the insert member 74 out of insert member 72 is met with an increased frictional holding force, due to the “one way” design of the projections which form a serrated configuration. The “one way” design also more effectively holds the leg of a step when inserted into the insert 70. Nevertheless, both sides of the projections may be diagonally aligned, if desired.
The manner in which the insert assembly 70 is employed in the wetcast method will now be explained making reference to
The core mold member 76 is provided with a pair of circular-shaped openings 76a, 76b. Step tubes 77, 78 are preferably welded to the core member 76 in the manner shown. The end of each step tube joined to mold core 76 is defined by an edge which lies in a plane that is diagonally aligned to the longitudinal axis of the step tube. Each step tube is aligned with its associated opening 76a, 76b and further so that the step tubes are parallel to one another.
Member 72′ is inserted into opening 76a from the convex surface side of core 76 and enters into step tube 77. The integral bead 72f at the open end 72b has an outer diameter which is greater than the inner diameter of opening 76a and step tube 77, causing the sides of member 72a to be pressed inwardly providing a force-fit. The sides of member 72′ are yieldable due to the slots 72d. Member 72′ is pushed into tube 77 until the flange 72c′ engages the marginal portion of core 76 surrounding opening 76a. Member 74′ is then pushed onto member 72. The slots 72e′ enable the sides of member 72′ to yield while providing a good force-fit between members 72′ and 74′. The one-way projections F′ and F″ make it easier to telescope member 74′ onto member 72′ while providing a snug fit as well as making it harder to pull members 72 and 74 apart.
Flange 72c′ substantially seals opening 76a, preventing fines from entering into the opening 76a. It should be understood that an insert assembly 70″ is mounted upon opening 76b in a similar fashion to that described above with regard to assembly 70. Alternatively, member 74 may be telescopingly mounted upon member 72 before member 72 is inserted into step tube 77.
When the insert assemblies have been properly mounted upon core 76, the casting material is poured into the mold assembly. After the casting material has set, the cast member separated from the mold assembly. Member 72 is scored in two (2) places in the region of flange 72c. The two substantially annular-shaped scored regions 72g, 72h respectively located above flange 72c and just below the annular projection F′ closest to the diagonal flange 72c and just below the diagonal flange 72c, preferably are formed by reducing the thickness of the first member in these regions as shown best in
The shear line 72g is located so that the portion inside member 74 breaks into two parts, thereby simplifying its removal from member 74. The portion of the members 72 remaining in each step tube is also easily removed preparatory to the molding of the next member to be cast. The intermediate portion falls free of the core member 76 and the cast member when it is removed from the mold assembly.
Another preferred embodiment of a two-piece insert 80 is shown in
A tube holder 82 has upper body portion 82a and a lower body portion 82b joined at an intermediate shoulder 82c. The interior of holder 82 tapers at 82d to provide an annular, diagonally aligned region of reduced thickness relative to the upper body portion 82a and lower body portion 82b of the tube holder 82 to control breakage in the region of the shoulder 82c. More particularly, the inner diameter of upper body portion 82a just above shoulder 82c is larger than the inner diameter of upper body portion 82a at shoulder 82c, forming a diagonally aligned interior surface 82d. Upper body portion 82a telescopes into the interior of insert 81, shoulder 82d resting against flange 81b radially outwardly extending from insert 81. Upper portion 82a is preferably slightly tapered, increasing in diameter moving from the top end 82a-1 to the shoulder 82c, forming a force-fit when tube holder 82 is telescoped into the open end of insert 81. It should be understood that the tapered configuration of tube holder portion 82a may be employed to replace the serrated portion F′ of the holder 72′ of
Tubes 84 and 86 have their ends, 84a, 86a welded or otherwise secured to the manhole mold core 88 which forms the inner mold member or core of a mold assembly used to cast manholes. The tubes extend inwardly into the hollow interior of the core 88 and are arranged in spaced parallel fashion. It should be noted that tubes 84 and 86 do not require slots or “keyways” since the edges 82e-2 and 82e-3 of fins 82e provide a good force-fit with interior surface of tubes 84, 86. The fin arrangement may be employed to replace the bead 72f and slots 72d in the holder 72 shown in
In use, inserts 81, 81′ are each mounted upon a tube holder 82, 82′ and the lower ends of each tube holder 82, 82′ is inserted into one of the tubes 84 and 86 with the edges 82e-2, 82e-3 of fins 82e holding the tube holders in tubes 84 and 86.
Cast material, such as concrete is poured into the mold assembly and, after the cast member is set, the cast member is separated from the mold assembly, causing the upper halves 82a of each tube holder to break away from the lower halves 82b along the score lines 82c of each tube holder, each upper end 82a being retained within insert 81, whole the lower ends 82b are retained within the steel tubes 84 and 86. The broken away ends 82b are then removed and discarded preparatory to a subsequent casting operation.
In order to insert the legs of the manhole steps, the legs are pushed into the open ends 81b of the inserts 81. The upper ends 82a of the tube holders remaining in the inserts 81 are driven toward the closed ends 81a of the inserts 81 as the legs of the steps are forced fitted into the inserts. Alternatively, the upper portion 82a may be removed from the interior of insert 81.
The tube holders 82 need not be used when other positioning means are employed. As one example, the inserts may be mounted on positioning pins employed, for example, in dry cast installations, thereby greatly increasing the versatility of the two-piece design shown in
The interior periphery of the insert 81 is preferably substantially identical to the interior of the embodiment shown in
In box-shaped enclosures employed in sewage and water handling systems, the cast members typically have four interior planar surfaces, any one of which may be selected for the embedment of inserts for manhole type steps. However, it is both expensive and wasteful to provide for embedment of a plurality of sets of inserts along each interior wall since only one set of steps is sufficient. In situations requiring a decision as to which planar wall to provide for the embedment of inserts prior to installation of the cast member, the conventional technique was to drill holes in the desired wall for each of the inserts after the cast member has been formed and then mount inserts into each drilled opening, which technique is time consuming, labor intensive and costly.
Another embodiment of the present invention is characterized by comprising method and apparatus for embedding inserts which is greatly simplified as compared with conventional techniques and which permits selection of any of the interior planar surfaces of the box like cast member to utilize as that surface or wall of the cast member which is to receive the inserts.
Making reference to
A plastic sheet 91c, 92c is affixed to each of the rearward surfaces of the metal strips 91a, 92a. The plastic sheets 91c, 92c are each impregnated with a magnetized ferro-magnetic material which is preferably homogeneously dispersed throughout the sheets 91c, 92c. Each sheet 91c, 92c is secured to the surface of the metal strips 91a, 92a opposite the surface from which the pins 91b, 92b project. The adhesive is chosen to assure a high strength adhesion of the sheets 91c, 92c to the plates 91a, 92a for a purpose to be more fully described.
As is mentioned above, pins 91b, 92b may be affixed to strip assemblies 91, 92 in any suitable fashion. However, a preferred technique is to drill holes 91d, 92d, as shown in
In order to assure the proper positioning between assemblies 91 and 92, a pair of rectangular-shaped templates 95 and 96 are provided, each having plastic sheets 95c, 96c, impregnated with magnetized particles. The templates are positioned between strips 91 and 92 as shown in
The assemblies 91 and 92 and templates 95 and 96 are aligned along surface 94a of core 94 and adhere to core 94 due to the magnetized ferro-magnetic material homogeneously dispersed throughout the sheets 91c, 92c and 95c, 96c, are magnetically attracted to the core 94 which is formed of a suitable ferro-magnetic material.
Inserts, such as, for example, inserts similar to the inserts 81 shown in
With the assemblies 91, 92, inserts I and templates 95, 96 holding the assemblies 91, 92 properly in place as shown in
More specifically, once the assemblies 91 and 92 are properly aligned and magnetically attracted to the surface 94a of core 94, templates 95 and 96 are preferably removed. The templates 95 and 96 are preferably formed in a manner similar to the assemblies 91 and 92 in that they are metallic plates each having a plastic sheet 95c, 96c, each being formed of a plastic material having a magnetized ferro-magnetic material uniformly dispersed throughout the sheets so as to be magnetically attracted to surface 94a of the mold core 94. The templates are pried away from the mold core 94 after the assemblies 91, 92 are aligned and prior to filling the mold assembly with casting material, by a suitable tool (not shown), this operation preferably being performed in such a manner so as not to disturb the desired orientations of the assemblies 91 and 92.
After the cast member has been set, either the core 94 is lifted away from the cast member or the box-like cast member is lifted away from the core member. The separating (lifting) force is sufficient to overcome the magnetic attraction of the magnetized plastic sheets 91c, 92c to the core 94, causing the inserts 81, which are now embedded in the box-like cast member, and the assemblies 91 and 92 to be retained as part of the box-like cast member.
When the box-like cast member 93 has been removed from the mold assembly, the interior surface 93a of the cast member has the appearance shown in
As a further alternative embodiment, in applications where the members making up the mold assemblies are formed of a material other than a ferro-magnetic material such as aluminum, wood, etc., the arrangement shown in
As was described hereinabove, the templates 95′, 96′ are preferably removed before the cast material is poured into the mold assembly.
When the cast material has been set, it is separated from core 94. The force exerted in separating the cast member from the core 94 is sufficient to overcome the magnetic attraction between permanent magnets 99, 100 and the assemblies 91′, 92′ whereby the inserts I and hence the assemblies 91′, 92′ are retained by the cast member and are subsequently pried away from the cast member in the same manner described above, making reference to
The assemblies 91′, 92′, templates 95′, 96′, as well as the assemblies 91, 92 and templates 95 and 96 are sufficiently sturdy so as to provide repeated use over a long useful operating life.
As a further alternative, a suitable adhesive or glue may be placed upon the rear surface of each assembly 91′, 92′, which adhesive is sufficient to hold the assemblies in place during the alignment and the molding operations. The adhesive further preferably has limited adhesive holding power so as to enable the templates 95′, 96′ to be removed rather easily prior to filling the mold assembly with cast material and to enable the assemblies 91′, 92′ to be separated from the core member 94 when the cast member is lifted out of the mold assembly, whereupon the final steps of prying the assemblies 91′, 92′ away from the wall 93a of cast member 93 and the insertion of the manhole steps S are performed in the manner described above.
A latitude of modification, change and substitution is intended in the foregoing disclosure, and in some instances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein described.
This application is a continuation-in-part of U.S. patent application Ser. No. 09/395,106, filed Sep. 14, 1999, which is incorporated by reference as if fully set forth and which claims priority from provisional application Ser. No. 60/100,234, filed Sep. 14, 1998 and which provisional application is also incorporated by reference as if fully set forth.
| Number | Date | Country | |
|---|---|---|---|
| 60100234 | Sep 1998 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09395106 | Sep 1999 | US |
| Child | 11107252 | Apr 2005 | US |
