Shin guard and method of making
BACKGROUND OF THE INVENTION 
     The present invention relates to athletic shin guards. 
     For many years players of certain sports such as soccer, hockey, field hockey, and others, have found it advantageous to protect their shins with shin guards. The shin guards used have generally included a protective barrier shaped generally to fit the forward facing portion of the shin. These shin guards have been worn either inside the players&#39; socks or have been attached by means of straps which extend around the leg. 
     Some prior art shin guards have been constructed with a rigid outer shell backed by a softer foam rubber. However, such shin guards have not provided the maximum possible protection. In U.S. Pat. No. 4,346,205 there is described and claimed a modified, dense polyurethane of essentially linear structure containing unsatisfied hydroxyl groups, having a compression set of less than 15% and preferably less than 5%, an elongation break of at least 500%, and a recovery which is delayed after compression by at least 0.7 seconds. Further, the polyurethane disclosed in said patent has a hardness on the Shore 00 scale not exceeding 50 and preferably in the range of 0 to 10. Said patent declares that its modified dense polyurethanes may find application in sportswear such as shin pads. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new and improved shin guard which includes an outer shell made of rigid polyurethane having a contour generally conforming to the shape of the shin. A composite polyurethane backing is attached to the rigid outer shell. The backing comprises a polyurethane foam with an outer contour essentially the same as that of the rigid shell. A vertically extending and centrally located oblong recess in the foam backing is filled with a modified dense polyurethane similar to that disclosed in U.S. Pat. No. 4,346,205. 
     The invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and annexed drawing setting forth in detail an illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the present invention may be carried out. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the annexed drawing: 
     FIG. 1 illustrates an exploded view of a shin guard constructed in accordance with the present invention; 
     FIG. 2 shows a plan view of one component of the shin guard of FIG. 1; and 
     FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 with the insert included. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The shin guard 10 (FIG. 1) includes a rigid outer shell 12, a polyurethane foam backing 14, and a dense, modified polyurethane insert 16. The shin guard 10 is intended to be worn on the shin of an athlete as illustrated in FIG. 1. To this end the shin guard 10 is about 8 inches tall and 51/2 to 6 inches wide. Shin guard 10 is curved around a vertical axis to partially surround a shin and has an arcuate cut-out 18 to accommodate ankle movement. The shin guard 10 may be worn inside the socks of the athlete, or it could also be provided with straps or elastic to secure it in place. 
     The rigid outer shell 12 is formed of a rigid polyurethane material and protects the foam backing 14 and the modified, dense polyurethane insert 16 from abrasion while at the same time distributing applied forces over a wide area. The polyurethane foam backing 14 has an outer perimeter essentially the same as that of the rigid outer shell 12 and is about one eighth of an inch thick. The polyurethane foam backing 14 is glued to the shell after the insert 16 is in place. The foam backing 14 serves as a lightweight carrier for the modified, dense polyurethane insert 16, but itself provides only minor protection from impact. Preferably the foam backing 14 has a hardness on the Shore 00 scale of between 30 and 60, and preferably between 40 and 50. 
     The backing 14 is provided with an oblong recess 20 which may be approximately 61/2 inches long and one inch wide. The recess 20 extends vertically and overlays the shin bone or tibia of the shin guard user. The recess 20 extends into the foam backing approximately 0.090 inches. Thus there is a relatively thin bottom 22 (FIG. 3) to the recess 20. 
     The recess 20 may be formed by stamping or pressing the foam backing 14 with a hot die conforming to the desired shape of the recess 20. This process melts the polyurethane in the area where the recess 20 is to be formed and creates a skin over the entire interior surface of the recess 20. 
     The insert 16 is formed of a modified, dense polyurethane and is cast in place in the recess 20. In this way, the polyurethane of the insert 16 is intimately bonded with the polyurethane foam of the backing 14. 
     The insert 16 is formed of a material similar to that disclosed in U.S. Pat. No. 4,346,205, the disclosure of which is incorporated herein by reference. However, it is preferred in carrying out the present invention that the modified, dense polyurethane used to make the insert 16 have a Shore hardness of between 20 and 70 on the 00 scale. Said U.S. Patent discloses a modified, dense non-cellular polyurethane having a hardness not exceeding 50 and preferably not exceeding 20 and most preferably in the range of 0 to 10. In order to form the polyurethane of the present invention, it is necessary to decrease the percentage of unsatisfied hydroxyl groups from about 1 in 5 in the aforementioned U.S. Patent to approximately 1 in 4. 
     The resulting modified, dense non-cellular polyurethane absorbs impact approximately with the same efficiency that human tissue does. Upon impact, the modified dense polyurethane distorts laterally and does not return to its initial configuration until after a delay of at least 7/10 of a second. By this time, the impact (usually caused by another player&#39;s foot or a game ball) has terminated. Therefore, there is little energy returned to the player&#39;s shin in the form of rebound. 
     The shin guard 10 of the present invention, because of its unique three-component construction, provides an extremely lightweight and very effective shin guard. The shin guard 10 provides excellent energy dissipation immediately in front of the shin bone or tibia where it is most required. In areas where the extra protection is not required, the conventional polyurethane foam backing 14 is utilized. The rigid outer shell 12 spreads the applied impact forces widely.