Patent Publication Number: US-11661741-B2

Title: Non-corroding stripping lifting inserts for precast insulated panels

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/981,677 filed on Feb. 26, 2020, entitled “NON-CORRODING STRIPPING LIFTING INSERTS FOR PRECAST CONCRETE”, the entire disclosure of which incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     This invention was made with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to precast insulated panels, and more particularly to an apparatus for removing precast insulated panels from molds and formwork. 
     BACKGROUND OF THE INVENTION 
     Precast insulated panels have become popular in construction for variability of design and efficiency of manufacture. Precast insulated panels are typically constructed in molds or formwork by pouring a first concrete panel or wythe, positioning an insulating panel on top of the wythe, and pouring a second concrete panel or wythe. Such panels must be transported to the installation site, and as the panels can be quite large, in some cases as large as 12′×60′ and weighing thousands of pounds, removing the panels from the mold can provide challenges. For this reason, stripping inserts are utilized. Cables from lifting devices such as cranes are attached to the stripping lifting inserts to provide engagement points for the cables. Such stripping lifting inserts must be quite strong, however, due to the dimensions of the panels, where the wythes may be no more than several inches thick, the stripping lifting inserts cannot be so large as to protrude and interfere with the visual aesthetics of the precast insulated panel. Such stripping lifting inserts must also preferably be corrosion resistant. 
     SUMMARY OF THE INVENTION 
     A stripping lifting insert is provided for precast insulated panels having an insulating material layer between opposing wythes. The insulating material layer, wythes, and precast insulated panel have respective widths. The stripping lifting insert includes an elongated connecting shaft having a shaft axis, and first and second spaced apart wythe engagement members connected to the connecting shaft in spaced apart relation to each other. Each wythe engagement member includes a hub and a plurality of three or more protrusions connected to and emanating from the hub. Each of the protrusions extends radially outward from the shaft axis. The wythe engagement members have a height less than the width of the wythes, whereby each wythe engagement member can be embedded in a respective wythe of the precast insulated panel. 
     The position of the wythe engagement members on the shaft is adjustable. The hubs of the wythe engagement members have a threaded interior opening, and an outside surface of the shaft is cooperatively threaded such that the wythes can be engaged to the threaded shaft. The position of the wythe engagement members on the threaded shaft can be adjusted by threading the wythe engagement members along the length of the shaft. The interior thread can be at least one selected from the group consisting of triangular or trapezoidal threads. 
     The stripping lifting insert can further include lift engagement structure secured to an end of the shaft for engaging a stripping lifting device. The lift engagement structure can be threaded and an end of the shaft is cooperatively threaded. 
     The plurality of protrusions can be four equally spaced about the circumference of the hub. The four protrusions can be arranged in a cross configuration. 
     The wythe engagement members can be made from a fiber-reinforced polymer. The fiber-reinforced polymer can include discontinuous fibers in a polymer matrix. The fiber-reinforced polymer can include, in the polymer matrix, continuous fibers and discontinuous fibers. The lengths of the discontinuous fibers can be in a range of 0.2″ to 2″. The fiber-reinforced polymer can include at least one selected from the group consisting of glass fibers, carbon fibers, aramid fibers, basalt fibers, and combinations thereof. The polymer matrix can include at least one selected from the group consisting of thermoplastic polyphenylene sulfide, polyethylene terephthalate, polyamide, polyurethane, polysulfone, polyether ketone, polyetherether ketone, thermoset epoxy, phenolic, vinyl ester and polyester. 
     The height of the stripping lifting insert along the shaft axis can be in a range of 0.75″ to 1.25″. A radial extension of each protrusion of the plurality of protrusions can be in a range of 2″ to 8″. A height of each protrusion of the plurality of protrusions along the shaft axis can be in a range of from 1/16″ to ¼″. A width of each protrusion of the plurality of protrusions orthogonal to a radial direction can be in a range of from 0.5″ to 1.5″. A diameter of the shaft can be in a range of from 0.5″ to 1.5″. 
     Each protrusion of the plurality of protrusions can include respective ribs extending radially away from the hub. Each rib can extend over 25% to 75% of the radial extension, and can have a width of 20% to 60% of the width of the corresponding protrusion. 
     A precast insulated panel can include an insulating material layer and opposing wythes on each side of the insulating material layer, the insulating material layer, wythes, and precast insulated panel having respective widths. A stripping lifting insert includes an elongated connecting shaft having a shaft axis, and first and second spaced apart wythe engagement members connected to the shaft in spaced apart relation to each other. Each wythe engagement member includes a hub and a plurality of three or more protrusions connected to and distributed around the hub. Each of the protrusions extends radially outward from the shaft axis. The wythe engagement members have a height less than the width of the wythes, whereby each wythe engagement member can be embedded in a respective wythe of the precast insulated panel. The connecting shaft can have a length greater than the width of the precast insulated panel such that a connecting end of the connect shaft will protrude from one of the wythes. 
     A method of making a precast insulated panel having an insulating material layer between opposing wythes can include the steps of providing a stripping lifting insert comprising an elongated connecting shaft having a shaft axis, and first and second spaced apart wythe engagement members connected to the shaft in spaced apart relation to each other. Each wythe engagement member includes a hub and a plurality of three or more protrusions connected to and distributed around the hub. Each of the protrusions extends radially outward from the shaft axis, wherein the wythe engagement members have a height less than the width of the wythes. Each wythe engagement member can be embedded in a respective wythe of the precast insulated panel, and the connecting shaft can have a length greater than the width of the precast insulated panel such that a connecting end of the connect shaft will protrude from one of the wythes. 
     A mold is provided for the precast insulated panel. A first wythe engagement member is placed into the mold. Concrete constituting a portion of a first wythe is poured into the mold such that the wythe engagement member is embedded within the concrete of the first wythe and the connecting shaft protrudes from the wythe. An insulation material layer is placed over the wythe with the connecting shaft protruding from the insulation material layer. A second wythe engagement member is positioned onto the connecting shaft. Concrete constituting a second wythe is poured over the insulation material layer, with a second wythe engagement member embedded within the second wythe, and the connecting shaft protruding from the second wythe, to form a precast insulated panel. A lifting device is connected to the elongated connecting shaft protruding from the second wythe, and the precast insulated panel is lifted from the mold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There are shown in the drawings embodiments that are presently preferred it being understood that the invention is not limited to the arrangements and instrumentalities shown, wherein: 
         FIG.  1    is a perspective view of a precast insulated panel in a first stage of construction. 
         FIG.  1 A  is an expanded view of area  1 A in  FIG.  1   . 
         FIG.  2    is a perspective view of a precast insulated panel in a 2 nd  stage of construction. 
         FIG.  3    is a perspective view of a precast insulated panel in a 3 rd  stage of construction. 
         FIG.  4    is a perspective view of a precast insulated panel in a 4 th  stage of construction. 
         FIG.  5    is a perspective view of a precast insulated panel in a 5 th  stage of construction. 
         FIG.  6    is a perspective view of a precast insulated panel in a 6 th  stage of construction. 
         FIG.  7    is a perspective view of a precast insulated panel in a 7 th  stage of construction. 
         FIG.  8    is a perspective view of a precast insulated panel in an 8th stage of construction. 
         FIG.  8    A is an enlargement of area  8 A in  FIG.  8   . 
         FIG.  9    is a perspective view of a precast insulated panel in a 9 th  stage of construction. 
         FIG.  10    is a cross-section of a precast insulated panel. 
         FIG.  10    A is an enlargement of area  10  A in  FIG.  10   . 
         FIG.  11    is a perspective view of a first wythe engagement member the first mode of operation. 
         FIG.  11    A is a cross-section of the first wythe engagement member in the first mode of operation. 
         FIG.  12    is a perspective view of a first wythe engagement member in a 2 nd  mode of operation. 
         FIG.  12    A is a cross-section of a first wythe engagement member in a 2 nd  mode of operation. 
         FIG.  13    is a plan view of discontinuous fibers in a polymer matrix. 
         FIG.  14    is a plan view of woven fibers in a polymer matrix. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A stripping lifting insert is provided for precast insulated panels having an insulating material layer between opposing wythes, the insulating material layer, wythes, and precast insulated panel having respective widths. The stripping lifting insert includes an elongated connecting shaft having a shaft axis. First and second spaced apart wythe engagement members are connected to the connecting shaft in spaced apart relation to each other. Each wythe engagement member includes a hub and a plurality of three or more protrusions connected to and emanating from the hub. The wythe engagement members have a height less than the width of the wythes, whereby each wythe engagement member can be embedded in a respective wythe of the precast insulated panel. 
     The position of the wythe engagement members on the shaft is adjustable. The hubs of the wythe engagement members can have a threaded interior opening, and an outside surface of the shaft is cooperatively threaded such that the wythes can be engaged to the threaded shaft, and the position of the wythe engagement members on the threaded shaft can be adjusted by threading the wythe engagement members along the length of the shaft. The interior thread can be at least one selected from the group consisting of triangular or trapezoidal threads. 
     The stripping lifting insert can further include stripping lift engagement structure secured to an end of the shaft for engaging a stripping lifting device. The stripping lift engagement structure can be any suitable structure. The stripping lift engagement structure can be threaded and an end of the shaft can be cooperatively threaded to engage the stripping lift engagement structure. 
     The plurality of protrusions can have different numbers, sizes, thicknesses and widths, depending in part of the size and weight of the precast insulated panel. The plurality of protrusions can comprise four equally spaced protrusions about the circumference of the hub. The four protrusions can be arranged in a cross configuration. 
     The stripping lifting insert of the invention can be made of different materials, but preferably are corrosion resistant and possess the strength to lift the precast panel from the mold or formwork. The wythe engagement members can be made from a fiber-reinforced polymer. The fiber-reinforced polymer can comprise discontinuous fibers in a polymer matrix. The fiber-reinforced polymer can also include, in the polymer matrix, continuous fibers and discontinuous fibers. The dimensions of the discontinuous fibers can vary. In one embodiment, the lengths of the discontinuous fibers are in a range of 0.2″ to 2″. 
     The fiber-reinforced polymer comprises fibers made from a suitable material. The fibers can be at least one selected from the group consisting of glass fibers, carbon fibers, aramid fibers, basalt fibers, and combinations thereof. Other fiber materials are possible. The fibers are dispersed in a polymer matrix. The polymer matrix can be a variety of different materials. The matrix material can be at least one selected from the group consisting of thermoplastic polyphenylene sulfide, polyethylene terephthalate, polyamide, polyurethane, polysulfone, polyether ketone, polyetherether ketone, thermoset epoxy, phenolic, vinyl ester and polyester. Other matrix materials are possible. 
     The protrusions can have varying sizes and shapes, but in general will have elongated portions which become embedded in and engage the wythes. In one embodiment, the height of the hub is greater than the height of the protrusions, such that the hub can be flush with the surface of the wythe while protrusions remain embedded in the wythe, to facilitate connection of the shaft to the wythe engagement members. Each of the protrusions extends radially outwardly from the shaft axis, and can be perpendicular or within any range of ±25 degrees of perpendicular to the shaft axis. 
     Each protrusion of the plurality of protrusions comprises respective ribs extending radially away from the hub. Each rib can extend over 25% to 75% of the radial extension of the protrusion. Each rib can extend 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%, and can be within a range of any high value and low value selected from these values. The ribs can have a width of 20% to 60% of the width of the corresponding protrusion. The ribs can have a width of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60% of the width of the corresponding protrusion, and can be within a range of any high value and low value selected from these values. 
     The stripping lifting insert can have different dimensions depending on the particular installation and particularly the dimensions and weight of the precast insulated panel for which it is intended. These panels can have very significant dimensions, for example 10-12 feet in height and 20-60 feet in length. In one aspect, a height of the stripping lifting insert along the shaft axis is in a range of 0.75″ to 1.25″. A radial extension of each protrusion of the plurality of protrusions can be in a range of 2″ to 8″. A height of each protrusion of the plurality of protrusions along the shaft axis can be in a range of from 1/16″ to ¼″. A width of each protrusion of the plurality of protrusions orthogonal to a radial direction can be in a range of from 0.5″ to 1.5″. A diameter of the connecting shaft can be in a range of from 0.5″ to 1.5″. Other dimensions are possible. 
     A precast insulated panel can be provided in which one of the first and second wythe engagement members is embedded in a respective one of the first and second wythes of the precast insulated panel, and connected by the connecting shaft. The connecting shaft can have secured thereto the lift engagement structure. 
     A method of making a precast insulated panel having an insulating material layer between opposing wythes can include the step of providing a stripping lifting insert. The stripping lifting insert includes an elongated connecting shaft having a shaft axis, and first and second spaced apart wythe engagement members connected to the shaft in spaced apart relation to each other. Each wythe engagement member comprises a hub and a plurality of three or more protrusions connected to and distributed around the hub. Each of the protrusions extends radially outward from the shaft axis, wherein the wythe engagement members have a height less than the width of the wythes, whereby each wythe engagement member can be embedded in a respective wythe of the precast insulated panel. The connecting shaft has a length greater than the width of the precast insulated panel such that a connecting end of the connecting shaft will protrude from one of the wythes. 
     A mold or formwork for the precast insulated panel is provided. Concrete constituting a portion of a first wythe is placed into the mold. A first wythe engagement member is placed into the mold. A remainder of the concrete constituting the first wythe can then be poured, embedding the first wythe engagement member with the connecting shaft protruding. The protrusions are embedded within the concrete. The first wythe engagement member should have concrete underneath it. Other methods of construction are possible. 
     An insulation material layer is then positioned over the wythe with the connecting shaft protruding from the insulation material layer. A second wythe engagement member is attached to the connecting shaft. Concrete constituting a second wythe is poured over the insulation material layer, with the second wythe engagement member embedded within the second wythe, and the connecting shaft protruding from the second wythe, to form a precast insulated panel. Stripping lifting engagement structure can be connected to the elongated connecting shaft protruding from the second wythe, and the precast insulated panel can be lifted from the mold by a suitable lifting device such as a crane. 
     There is shown in  FIGS.  1 - 14    a precast insulated panel assembly system  10  and method in which a stripping lifting insert according to the invention is positioned in a mold  18  used to make the precast insulated panel. A first wythe engagement member  14  can be positioned in the mold on an initial concrete portion of a first wythe  24  and optionally rebar  22  can be included. As shown in  FIG.  1 A , the first wythe engagement member  14  is comprised by a hub  26  and a plurality of radially extending protrusions  30 . 
     As shown in  FIG.  2    a connecting shaft  40  can be secured to the hub  26  by suitable structures such as cooperating threads. A remaining portion of concrete wythe  24  is then poured so as to embed the first wythe engagement member  14 , leaving a portion of the connecting shaft  40  extending from the first wythe  24  ( FIG.  3   ). 
     An insulation layer  50  is then positioned in the mold  18  onto the first wythe  24  ( FIG.  4   ). The insulation layer  50  can have a cut out portion  52 . A second wythe engagement member  44  can then be threaded onto the connecting shaft  40  and placed on the first wythe  24  within the cut out portion  52  ( FIG.  5   ). Optionally rebar  56  and  58  which can be fiber-reinforced polymer can be positioned over the second wythe engagement member  44  to provide additional engagement to a second wythe and added strength during the stripping lifting procedure ( FIG.  6   ). A second concrete wythe  60  can then be poured ( FIG.  7   ). The end portion of the connecting shaft  40  will extend out of the second concrete wythe  60 . 
     Stripping lift engagement structure  66  can be secured to the end portion of the connecting shaft  40  extending from the second concrete wythe  60 . The stripping lifting engagement structure  66  can take many forms, but in the embodiment shown in  FIG.  8 A  includes a base  67 , a connecting nut  68  for engaging the connecting shaft  40 , and a U-shaped portion for connecting to a stripping lifting device. As shown in  FIG.  9   , the first wythe engagement member  14  is embedded in the first wythe  24 , and the second wythe engagement member  44  is embedded in the second wythe  60 . As the stripping lifting device applies a lifting force to the stripping lifting engagement structure  66 , the first wythe  24  and second wythe  60  will be simultaneously acted upon by the respective first wythe engagement member  14  and second wythe engagement member  44  through the connecting shaft  40 . Rebar  56  and  58  will provide additional strength. As shown in  FIG.  10   , the stripping lifting device such as a crane is used to lift the completed precast insulated panel  100  from the mold  18 . In the embodiment shown in  FIG.  10    A, the crane includes a lifting cable  72  and hook  70  used to engage the U-shaped portion  70  of the stripping lifting engagement structure  66 . The invention can be used with other kinds of stripping lifting devices. 
     As shown in  FIGS.  11 - 11 A  and  FIGS.  12 - 12 A , the wythe engagement members such as the first wythe engagement member  14  can have additional structure for strengthening these members. Such structure can be radially extending ribs  84  on the protrusions  30 . Also, the manner of connecting the connecting shaft  42  the wythe engagement members can vary but in the embodiment shown the connecting shaft  40  has threads  42  which engage cooperating threads  82  in a threaded opening  80  in the hub  26 . In this manner, each wythe engagement member can be axially adjustable on the connecting shaft  40  by rotation of the wythe engagement member on the connecting shaft  40 . 
     The wythe engagement members are preferably made of a strong, lightweight and corrosion resistant material. Such materials include fiber reinforced polymer. As shown in  FIG.  13   , discontinuous fibers  90  can be provided in a polymer matrix  92 . As shown in  FIG.  14   , woven fibers  94  can be provided in a polymer matrix  96 . Other continuous and discontinuous fiber reinforced polymer structures are possible. 
     The invention as shown in the drawings and described in detail herein disclose arrangements of elements of particular construction and configuration for illustrating preferred embodiments of structure and method of operation of the present invention. It is to be understood however, that elements of different construction and configuration and other arrangements thereof, other than those illustrated and described may be employed in accordance with the spirit of the invention, and such changes, alternations and modifications as would occur to those skilled in the art are considered to be within the scope of this invention as broadly defined in the appended claims. In addition, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.