FIELD OF THE INVENTION
This invention relates to manhole lift inserts and devices for positioning such inserts in concrete molds used to form manholes and other pre-cast concrete products.
BACKGROUND OF THE INVENTION
Pre-cast concrete manholes are widely used throughout the world to provide access to storm and sanitary sewer systems and a variety of other below-ground installations of piping, cables and the like. Manhole lifts are eye bolt-like devices 10 illustrated in FIGS. 1 and 2 that are positioned within a lift insert 12 imbedded in concrete 50 that forms a manhole or other precast concrete product. Manhole lift 10 permits the attachment of chains and other devices to lift a pre-cast concrete product in order to transport it and ultimately position it where it is to be used. Two lifts and corresponding lift inserts are typically used per manhole, for example. The lift inserts are placed at the same height at opposite positions on the outer surface of the manhole.
Lift inserts 12 can have a bayonet-type socket, and lifts 10 can have bayonet-type bases formed by two opposed ears 16 on the lift shaft 18 that are received in opposed grooves 20 in insert 12. After lift 10 is fully inserted in insert 12, it is rotated one quarter turn, as shown in FIG. 2, to lock it in place so that it will not withdraw from insert 12.
Prior devices for holding insert 12 in position within a manhole form or other pre-cast concrete product form have utilized expensive, relatively complex devices with a spring loaded shaft having a bayonet base that locks within the bayonet socket in an insert. A rubber molding assembly that fits within the lift insert and has a nut and bolt inside the assembly as described in U.S. Pat. No. 6,109,587 has also been used. The expense, complexity and other problems associated with such devices make it desirable to have a simpler, easier to use device for holding a lift insert 12 in position during the concrete casting process.
SUMMARY OF THE INVENTION
Embodiments of the present invention include a lift insert with a socket portion and a frangible portion that is inserted in a pre-positioned bushing associated with the outer wall of a manhole form. A key on the frangible portion may be received in a keyway in the bushing so that the insert is properly oriented in the form. Concrete is then poured into the form, enveloping and affixing the socket portion within the manhole wall.
The lift insert is manufactured of plastic or other suitable materials. A weakened, frangible region is provided on the frangible portion in a position immediately adjacent to the form wall so that after the concrete is cured, the manhole and form can simply be separated, causing the socket portion, which is embedded in the concrete, to separate from the frangible portion in the bushing. Nothing needs to be removed before separating the form and cured manhole, with a consequent diminution in necessary labor by simplification of the lift insert insertion process and elimination of the need to remove a hole-forming component or a separate positioning component before separating the cured manhole and the form.
Accordingly, it is an object of various embodiments of the present invention to provide a lift insert for a manhole form or other pre-cast concrete product form that is capable of being positioned and held in place in a relatively inexpensive manner.
Another object of various embodiments of the present invention is to provide a lift insert for a manhole form or other pre-cast concrete product form having a frangible portion used to position the insert in the form in which the frangible portion automatically separates from a socket portion of the lift insert when the form is separated from the concrete product.
Other objects, features, and advantages of the present invention will become apparent with reference to the remainder of the written portion and the drawings of this application, which are intended to exemplify and not to limit the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of a manhole and a lift insert positioned in concrete.
FIG. 2 is a perspective view showing the externally visible portion of the lift insert imbedded in concrete with a lift locked within the insert.
FIG. 3 is an exploded perspective view of a fragment of the outer form wall of a pre-cast concrete manhole form with the bushing and lift insert according to an embodiment of the present invention.
FIG. 4 is a top plan view of the frangible insert according to another embodiment of the present invention shown positioned in a portion of a manhole wall surrounded by a manhole form and insert-receiving bushing, with the form, bushing and wall shown in section.
FIG. 5 is a section view taken along line 5-5 in FIG. 4.
FIG. 6 is an axial view taken from the open end of a lift insert according to another embodiment of the present invention with the insert receiving bushing shown in broken lines.
FIG. 7 is an enlarged view of the portion of FIG. 5 in circle 7.
FIG. 8 is a top schematic view of a handle useable with a frangible insert according to certain aspects and embodiments of the present invention.
FIG. 9 is a side schematic view of the handle of FIG. 8.
FIG. 10 is a perspective view of the handle of FIG. 8.
FIG. 11 is a perspective view of a lift insert according to another embodiment of the present invention.
FIG. 12 is a schematic view of a frangible joiner according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 3 illustrates a lift insert 110 in accordance with the present invention. Insert 110 is shown prior to insertion in bushing 112 located on outside surface 114 of outer wall 116 of concrete form 117. Concrete form 117 also has inner form wall 118 (shown in FIG. 4).
Insert 110 has two principle portions, socket 12 and frangible member 130. Socket 12 forms hole 38 (shown in FIGS. 4 and 5) in which a lift is received. Frangible member 130 is received within bushing 112 of form 117. Socket 12 is attached to frangible member 130 along a frangible region 132 that may be best understood by reference to FIG. 7. FIG. 7 illustrates that frangible region 132 is a portion of insert 110 having a very thin wall created by an annular v-shaped groove defined by a collar 134 attached to socket 12 and an adjacent thin region 136 of frangible member 130. Socket 12 may be separated from frangible member 130 at frangible region 132 by applying a shearing stress to the frangible region.
In the embodiment shown in FIG. 3, collar 134 allows frangible member 130 to be positioned within bushing 112 to a desired depth, thereby ensuring that frangible portion 132 is positioned such that removal of outer wall 116 from the completed manhole will fracture insert 110 at frangible portion 132. Thus, collar 134 may be any structure which prevents insert 110 from being inserted into bushing 112 to some point beyond frangible region 132, such as a bulges, tabs, or other obstructive protuberances. In some embodiments, the lift insert 110 may be used without a bushing 112, rather the insert 110 may be positioned in the outer wall 116 by itself. In such an embodiment, collar 134 may be adapted to contact the outer wall 116 to position the insert 110 at a desired depth.
The collar can be located at other positions other than the one illustrated in FIG. 3. For example, a collar 204 can be located in a position as shown in FIG. 11. In embodiments that include a collar 204 located in the position shown in FIG. 11, lift insert 110 may be inserted into a bushing such that collar 204 contacts the bushing to locate the lift insert 110 at an appropriate depth with respect to the concrete form. In the embodiment shown in FIG. 11, socket end of the insert is inserted through the bushing until the collar 204 on the frangible member 130 contacts the bushing.
Socket 12 and frangible member 130 need not be formed in one piece, but may be manufactured separately and joined thereafter by some readily frangible, fracturable or deformable connector. For example, a frangible joiner 300, such as an inner insert or coupling may be provided. As shown in FIG. 12, the frangible joiner 300 may simply be a relatively thin, cylindrical insert. Frangible member 130 and socket 12 may be slipped over opposite ends of the joiner 300 so that they abut in a configuration similar to that shown in the figures. Such a coupling would thereby hold frangible member 130 and socket 12 in the desired orientation for the manhole forming process but could be thin enough to fracture in the same manner as frangible region 132 or deform enough to permit separation of socket 12 from frangible member 130. In another alternative, frangible member 130 could be bonded to socket 12 in a manner that will fail, permitting the socket 12 easily to separate from frangible member 130.
Appropriate rotational positioning of insert 110 is achieved by use of a keyway 138 in each bushing 112. Keyway 138 receives key 140, which is positioned on the outside of frangible member 130. Keyway 138 may be a longitudinal slot on the inside of bushing 112, or, as illustrated in the figures, a longitudinal slot remaining after removing of an entire longitudinal wall section in a tubular bushing 112.
Key 140 in sleeve 130 may be an upstanding ridge or projection. Such a key 140 may be provided, as is illustrated in the figures, by positioning on the outside of sleeve 130 two side-by-side upstanding projections 144, which may be a structure superior to a solid key because projections 144 can bend slightly towards each other to accommodate narrow keyways 138. In an alternative not shown, sleeve 130 may include a keyway that corresponds to a ridge in bushing 112. In some embodiments, such as the embodiment shown in FIG. 11, the key 140 may not extend the entire length of the frangible member 130.
Frangible member 130 is generally cylindrical, although other shapes may be selected as appropriate. For example, frangible member 130 may be oval in shape to further ensure it is properly aligned when inserted in bushing 112. The outside of sleeve 130 may also be provided with longitudinal ribs 146 that contact bushing 112. Longitudinal ribs 146 lend frangible member 130 sufficient flexibility to ensure that frangible member 130 can compress if necessary to accommodate a narrow bushing 112, while providing sufficient friction to firmly secure insert 110 in place when concrete is poured into form 117. Ends 150 of ribs 146 and key 140 may be tapered to facilitate insertion of sleeve 130 in holes 152 in wall 116 of form 117 with which holes 152 and bushings 112 are aligned.
Referring to FIG. 3, the keyway 138 of bushing 112 is oriented such that the position of the socket portion ensures that the lift can be positioned correctly. As show in FIG. 2, the lift is inserted so that its eye portion is vertical.
In the embodiment shown in FIG. 3, insert 110 is positioned by inserting frangible member 130 through a hole 152 and into bushing 112 from the interior surface 154 of wall 116. In other embodiments, such as the embodiment shown in FIG. 11, the insert may be inserted through the bushing from an outer wall of the form. Next, in the embodiments shown in FIGS. 3 and 11, the insert 110 is rotationally positioned so that its key 140 will be received in the keyway 138, and the frangible member 130 is pressed into the bushing 112 until collar 134 abuts either the wall 116 or the bushing 112 so that when concrete 50 is placed between form walls 116 and 118 and allowed to cure, frangible region 132 is positioned at about the interface between cured concrete 50 and the interior surface 154 of outer wall 116. Form walls 116 and 118 are then removed, thereby causing each insert 110 to separate along frangible region 132 without the need for removal of any hole forming sockets. Frangible member 130 will typically remain within bushing 112 and may be easily pushed out from either side as, for instance, by pressing a new insert 110 into bushing 112.
In other embodiments, such as the embodiments shown in FIGS. 8-10, a bushing 200 may be incorporated into a handle 202 to facilitate positioning an insert. Handle 202 may be attached in a removable manner to an outer surface of a concrete form prior to insertion of the insert. Curved slots 206 in the handle 202 may facilitate securing the handle in a removable manner to the outer surface of the concrete form by a pair of screws or other appropriate structures. Hand grips 208 allow the handle to be rotated such that the screws or other appropriate fasteners are engaged by the curved slots 206. Handle 202 may be disengaged from the screws or other appropriate fasteners by rotating the handle in the opposite direction.
As will be readily appreciated by those skilled in the art, frangible inserts may be advantageously manufactured by molding them of plastic, such as any of a variety of a thermoplastic resins, including polyvinyl chloride (PVC), and other suitable materials such as other plastics or steel.
As those skilled in the art will appreciate, the particular embodiment of this invention described above and illustrated in the figures is provided for explaining the invention, and various alterations may be made in the structure and materials of the illustrated embodiment without departing from the spirit and scope of the invention as described above.
Patent Application
20050002735
