Sliding doors of a type suitable for patio and porch enclosures are well known and widely used in present-day construction. Their frames are generally fabricated from metal profiles and provided with either glass or screen, depending upon the use to which the doors are to be put. The doors are mounted on grooved wheels or rollers adapted to roll on a guide track or rail which directs the doors during their movement, rollers being located at both the top and the bottom of the doors in some instances. The doors described are usually fabricated from lightweight materials, such as aluminum, so that they will be easy to roll back and forth during the opening and closing process. In this regard, screen doors of the type described are usually relatively light, commonly weighing less than about ten pounds.
While the lightness of the doors and panels greatly facilitates their ease of use, unfortunately, their lack of weight provides certain inherent disadvantages. One of these is the tendency of the door rollers to become disengaged from their track. This tendency to derail is caused by a variety of factors including, for example, variations in clearance between the track and the door, resulting from clearance faults between the door and the opening in which it is located; from the tendency of individuals to lift up on the doors when operating them, as well as for various other reasons. Irrespective of the cause for derailment, whenever the doors are disengaged from their tracks, they immediately become inoperable and must be reinstalled, frequently a difficult task.
In the past, a number of solutions have been proposed to solve the problem described, particularly including the use of spring-loaded rollers which force the rollers into firm engagement with their tracks. Oftentimes, however, the spring-loaded rollers have been undesirably complicated and have proven to be expensive and difficult to make and install in the course of the doors' manufacture. Furthermore, the load-carrying capacity of such roller has frequently been inferior as well.
Still another problem has involved adjustment of the spring, required to provide a proper engaging force between the track and the rollers associated with it. Generally, such force has been suitably increased or decreased by means of adjusting screws forming part of the roller assembly. However, the mechanics of the assemblies have typically required that the adjusting screws be located in positions in which they are not readily accessible, making the adjustment process difficult.