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 The present invention relates to a system for constructing an insulated cast concrete wall and a tie for securing insulation to a cast concrete wall.
 Cast concrete walls are typically constructed by pouring concrete into a set of forms, curing the concrete and removing the forms. Since energy costs have risen dramatically over the past three decades, it has now become desirable to insulate cast concrete walls. Typically, insulation has been added to the wall after casting and curing of the concrete. However, this technique is very labor intensive and suffers from a lack of effective methods for securing the insulation to the wall. Other techniques have been developed whereby the insulation is placed within the set of concrete forms and the concrete poured around or beside the insulation. In some variations, the insulation may be outfitted with ties which help secure the insulation to the cured concrete. An example of this variation is disclosed in U.S. Pat. No. 6,079,176. While such techniques have increased the effectiveness of securing the insulation to the concrete, they have proven to be labor intensive and have increased the amount of insulation handling. Furthermore, insulation must often be outfitted in advance with ties, or prepared in advance to receive ties, thereby decreasing flexibility of the system and requiring undesirable off-site handling of the insulation. In addition, a system such as that disclosed in U.S. Pat. No. 6,079,176 is difficult to adapt for insulating both sides of a cast concrete wall. Thus, there still remains a need for a simple, flexible and effective method for constructing insulated cast concrete walls.
 The present invention provides a tie for securing insulation to a cast concrete wall comprising: a head; a shaft attached to the head and having a longitudinal axis, the shaft comprising a series of barbs positioned at pre-determined longitudinal positions along the longitudinal axis, each successive barb being rotated about the longitudinal axis by a predetermined rotational increment from the immediately preceding barb; and, a tip on the shaft.
 There is also provided a process for producing an insulation tie comprising providing a mold having a mold cavity having a shape complementary to the tie; introducing a plastic into the mold; and, forming the tie.
 There is further provided a system for constructing an insulated cast concrete wall comprising: a set of concrete forms comprising two opposing partitions set apart a pre-determined distance; a sheet of insulation secured between the partitions adjacent one of the partitions; and, at least one tie consisting essentially of a head, a shaft attached to the head and a pointed or wedge-shaped tip on the shaft, the tie being inserted through the sheet of insulation such that the tip elastically deforms the insulation to permit passage of the shaft through the insulation and a portion of the shaft extends beyond the insulation into a cavity defined within the forms for securing the insulation to the concrete once the concrete has been poured and cured.
 There is still further provided a method for constructing an insulated cast concrete wall comprising the steps of: providing a set of concrete forms having opposing partitions set apart a pre-determined distance; providing at least one tie consisting essentially of a head, a shaft attached to the head and a pointed or wedge-shaped tip on the shaft; inserting the at least one tie through a sheet of insulation such that the tip elastically deforms the insulation to permit passage of the shaft through the insulation until a portion of the shaft extends beyond the insulation; securing the sheet of insulation between the partitions adjacent one of the partitions such that the portion of the shaft extending beyond the insulation extends into a cavity defined within the forms; and, pouring concrete into the cavity and curing the concrete.
 The tie of the present invention is easy to use and is impaled through the sheet of insulation, obviating the need for pre-forming passages to accommodate the tie. The tie may therefore be inserted through the insulation on-site in any desired pattern, providing flexibility during construction. The system and method of the present invention use conventional concrete forming techniques to quickly erect an insulated cast concrete wall with minimal labour and without re-training of personnel. The ties may be manufactured simply and with low cost using, for example, plastic injection molding techniques. Veneer can be applied to the insulated surface of the wall by fastening the veneer to the ties. Either one or two sides of the wall can be readily insulated using the system and method of the present invention. This permits application of veneer to both sides of the wall if so desired.
 In order that the invention may be more clearly understood, preferred embodiments hereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:
 With reference to
 The head
 The shaft
 The shaft
 The shaft
 The longitudinal position of at least one of the barbs
 The tie may be manufactured of any suitable material that provides sufficient structural strength to allow the tie to be impaled through the sheet of insulation while allowing easy attachment of a fastener to the head
 The preferred process for producing the insulation tie comprises providing a mold having a mold cavity having a shape complementary to the tie. The plastic may then be introduced into the mold by suitable means, for example injected into the mold using a piston or pump. The plastic is then solidified to form the tie using conditions suitable for the plastic chosen; for example, temperature and/or pressure conditions may be selected according to the type of plastic that allow the plastic to be introduced into the mold as a liquid and then changed to solidify the plastic. Suitable plastics include but are not limited to thermoplastics, for example polyolefins, such as polyethylene or polypropylene.
 With reference to
 A tie having a head
 After insertion of at least one tie, the sheet of insulation
 The portion of the shaft
 To form the wall, concrete is poured into the cavity
 With reference to
 Other advantages which are obvious and which are inherent to the structure will be evident to one skilled in the art.
 It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.
 Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.