Patent Publication Number: US-4057275-A

Title: Door jamb reinforcing plate

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to breaking in locked doors, and more particularly to a metal reinforcing plate for wooden door jambs for strengthening a structurally weakened part thereof. 
     A door jamb provides a hollow space in which a latch bolt of a door can be engaged to lock the door against opening. The hollow space is close to an edge of a jamb leaving only a thin layer of wood to break away in order to force entry. A striker plate mounted around the hollow and fastened by screws adjacent thereto further weakens the jamb. A shoulder thrust or a hard kick is usually sufficient to break the jamb and open the door. 
     The prior art teaches reinforcing the door jamb with a metal plate fastened to the front of the jamb and usually including a striker plate. More screw fastenings and screw holes adjacent the jamb hollow for a latch bolt add little to the strength of the jamb, and finished surfaces have to be recessed for their installation. See E. R. Lamphere, U.S. Pat. No. 3,815,945; F. M. Sushan, U.S. Pat. No. 3,405,962 and 3,290,081; A Barone U.S. Pat. No. 3,279,840. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a reinforcing plate for application to the back of a door jamb for strengthening it at its weakest part and for the distribution of forces applied thereto to stronger and more extensive portions of the door jamb. 
     Another object of the invention is to provide a plurality of various types of fastenings that are staggered both longitudinally and transversely to prevent splitting the wooden door jambs. 
     A further object of the invention is to provide an internally mountable reinforcing metal plate that is tamper proof and requires no recessing of finished surfaces to install. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of the door jamb showing a plan view of the reinforcing metal plate mounted behind the jamb; 
     FIG. 2 is a view in three dimensions of the reinforcing metal plate; and 
     FIG. 3 is a cross sectional view taken along section lins 3--3 of FIG. 1, and including a similarly sections opposing jamb and a door between the sectioned jambs. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-3, the invenion comprises a metal plate 10 shaped to have a narrow continuous side 12 of constant width and normal along a common longitudinal edge to a second wider side 14 of variable width that defines a plurality of transversely staggered and longitudinally spaced fastening holes 15 for fixing said metal plate 10 to the back of a wood jamb 16 by fastening 17. A third discontinuous side comprises a plurality of triangular points 20 parallel to side 12 and transversely staggered as shown in FIGS. 1 and 2 for preventing the jamb from splitting when driven therein. The latch bolt side 21 of jamb 16 is longitudinally recessed from its back 22 to provide a recess 23 for receiving side 12 for the full length of metal plate 10 that extends above and below a hollow space 24 provided in said jamb 16 for receiving a latch bolt 26 operably mounted in a door 28 adapted to engage with jamb 16. A striker plate 30 is mounted across hollow space 24 and around it to engage latch bolt 26 and is positioned as shown in FIG. 3 normal to side 12 which extends outboard of latch bolt 26. 
     In use, the metal plate 10 is fastened by means of the transversely staggered triangular points 20 and fastenings 17 to the back 22 of door jamb 16 with side 12 being received in recess 23 and side 14 against the back of said jamb 16 and fitting into a complementary recess 32 in blocking 34 supporting said jamb, plate 10 being fastened to the jamb and the jamb to blocking 34.