The present invention relates as indicated to concrete blocks and hollow insulating inserts therefor, with the inserts when used in combination with the concrete blocks providing an important insulating function, as well as other advantages.
The concept of insulating concrete block wall construction is of course well known in the art. The art has long recognized certain inherent disadvantages in the normal block wall, perphaps the most important of which are the moisture and thermal conductivity through the webs of the block, with the webs normally extending the full vertical height of the block. The voids in the block between the webs provide little insulating effect since air in the voids is constantly circulated from the warm side to the cold side of the adjoining walls. This is contrasted to absolutely still air which has substantially insulating value. Moreover, voids in the block can be accommodated only to a certain extend without diminishing the load carrying characteristics of the block.
It is also known in the art to provide plastic inserts in the block, and examples of these are disclosed in my U.S. Pat. Nos. 3,204,381, granted Sept. 7, 1965, and 3,546,833, granted Dec. 15, 1970. The concrete blocks illustrated in both of my earlier patents are provided with interconnecting web portions of reduced height, and separate insulating inserts are provided which extend over the reduced height web portions thereby reducing the moisture and thermal transmission through the block. My earlier insulating inserts are further characterized by the provision of external tongues and grooves so that adjacent and superimposed blocks can be accurately located and spaced to provide uniform horizontal and vertical mortar joints. In addition to the desirable uniform spacing of the blocks, the tongue and groove arrangement additionally provides a continuous insulating plane intermediate the side wall of the block.
Although the insulating inserts disclosed in my earlier patents have proved highly satisfactory in use, and fully accomplish the intended objectives, some degree of difficulty has been encountered with regard to maintaining the proper dimensional tolerances for a snug fitting of the inserts in the blocks. In the manufacture of the plastic inserts, which can be satisfactorily formed of polystyrene, for example, post-expansion occurs during and after molding thereby making it very difficult to uniformly adhere to the desired insert thickness, for example, 3". Where post-expansion increases the thickness even a small portion beyond the desired thickness, it is difficult to correctly position the insert in the block over and in engagement with the interconnecting web portions of the block. Since it is not desired to decrease the thickness of the inserts, which would correspondingly decrease the insulating values of the inserts, an attempt was made to correct the problem by modifying the molds for the concrete blocks. Although the modified dimensions proved initially satisfactory, the uncontrollable wearing of the molds resulted in the interconnecting or cross webs of the block increasing in thickness as the mold wore at that location. In view of the obvious cost of continually modifying the mold so as to be able to hold the proper dimension, and the noted desire of not decreasing the thickness of the insert, the problem of proper insert fit was not solved until the present invention.