Technical Field This invention relates to door frames for elevator systems. More particularly, this invention relates to an adjustable door frame. Description of the Related Art Elevator systems typically require an intricate installation process that is very time consuming. Each floor ,in a building has a least one elevator landing entrance way. The overall dimensions and location of each entrance way in relation to the elevator shaft or hoistway, varies with the tolerances inherent to the building trade. Each door frame, which includes a sill support, a set of side jambs or uprights and a headjamb, is anchored to fixing angles which are mounted to the hoistway walls. The orientation of each door frame is critical to provide proper alignment of the door frames with the elevator car. To accommodate for building alignment variances, the installation of the individual entrance ways require that each door frame be installed only after the guide rails have been installed to ensure the alignment required for elevator system performance. Once the door frame is properly aligned and secured, the elevator entrance way is then installed to the door frame. The serial fashion in which these installations must occur contributes significantly to the total elevator installation time. In addition, current practice requires a platform in the hoistway near each landing so that each door frame can be installed from the hoistway side of the opening. This invention provides an alternative that permits installing door frames and guide rails in a variety of orders. This invention also allows the entrances to be installed from the landing side (i.e., not in the hoistway), thus significantly reducing the total elevator installation time. SUMMARY OF THE INVENTION

In general terms, this invention is an adjustable door frame for an elevator entrance way that can be installed from the landing. In one example, the inventive frame has a sill that is mounted to a landing surface. In this embodiment, the sill is attached to the base floor at the landing and is adjustable to accommodate varying floor height. By attaching the sill to the landing surface, the entrance can now be installed from the landing, eliminating any need for an installation platform in the hoistway. In addition, plumb lines can be utilized for alignment purposes, thus eliminating the need for the guide rails to have been installed prior to installing the entrance. The guide rails can be installed subsequent to, in parallel with, or before the elevator entrances, significantly enhancing opportunities for reducing the total time required for elevator system installation. In another example, the sill is mounted directly to the frame uprights. The uprights in this example are secured to the landing surface. This can be done from the building floor side (i.e., not from the hoistway side). By attaching the sill to the uprights, the entrance is now installed from the landing surface as opposed to from a platform located in the hoistway. This configuration also provides for synchronized adjustment of the sill and header to ensure proper alignment during installation. The adjustability of the door frame assembly provides for selective manipulation of the door frame assembly after it is secure. This adjustability, in conjunction with the landing-based entrance installation, significantly reduces the total complexity and time required for elevator system installation. The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a general perspective view of selected portions of an elevator hoistway. Figure 2 is a schematic view of an example door frame assembly designed according to this invention. Figure 3 is a schematic view of a second example door frame assembly designed according to this invention. Figure 4 is a closer view of the portion of Figure 2 encircled at 4. Figure 5 is an exploded front view of the embodiment of Figure 4. Figure 6 is a schematic view of an adjustable header member. Figure 7 schematically illustrates the inventive method of installation utilizing plumb lines.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 is a general perspective view of an elevator hoistway 10. An elevator car 12 travels along guide rails 20 in a conventional manner. As known, the elevator car has doors 14, that cooperate with landing doors (not shown) supported at entrance ways 16 at each landing 18. The landing doors and the finish doorway surfaces 21 are supported by a door frame assembly 22 (Figure 2). The door frame assembly 22 includes a head jamb member 24, a sill support member 26 and a plurality of side jamb members 28 extending between the header member 24 and the sill member 26. The illustrated door frame assembly 22 is supported on the landing surface 18 A. In the illustrated example, the sill member 26 is attached to the landing surface 18 by adjusters 30. The door frame assembly 22 in its entirety is mounted in an entrance way of the building structure. In another example shown in Figure 3, the door frame assembly 22 is supported on the landing surface 18 with the side members 28 mounted directly to the landing surface 18 using anchors 29. In this example, the sill member 26 is adjustably mounted relative to side members 28 using connections 31. Referring to Figure 4, the example sill member 26 of the embodiment of Figure 2 is mounted to the landing surface 18 by at least one adjuster 30. In this example, each adjuster 30 comprises a bracket 32 having an anchor 34. The anchor 34 is secured to the landing surface 18 in a conventional manner appropriate for the sub-floor construction of the landing surface 18. A slot 35 in the bracket 32 facilitates horizontally adjusting a position of the bracket 32 to align the sill member 26 as needed. Alternatively, multiple holes may be used in place of slots. In this example, the sill member 26 is attached to the adjuster 30 by a threaded member 36, which is a carriage bolt in one example. Figure 5 shows a slot 38 through one example sill member 26 that allows access to the threaded member 36 for adjustably securing the sill member 26 in place. The example bracket 32 includes a cutout 40. The threaded member 36 is received through a hole 42 and secured in place with a nut 44. At least one threaded member 36 received at least partially through the slot 38, hole 42 and the cutout 40 secures the sill support member 26 to each bracket 32 and provides for vertically adjusting of the position of the sill member 26 relative to the bracket 32 and the landing surface 18 as may be needed. A threaded member 37 is received by the bracket 32 with one end abutting the landing surface 18. The adjuster 30 is vertically adjustable in relation to the landing surface by rotating the threaded member 37. Coordinating the position of the anchor 34 and the height of the member 37 allows for setting the adjuster 30 to facilitate leveling the sill 26 and aligning it with an elevator car position or the finish floor height at the landing 18 as needed. Figure 6 shows selected details of an example header member 50. The header 50 bolted to a plurality of vertical fixing angles 52 which are anchored to the underside of the floor 18B above the landing 18 A. This attachment provides selective adjustability of the header member 50 in relation to the sill member 26 to readily square off the opening provided by the frame and to accommodate various floor heights. The head jamb 24 may be secured to the header 50 in a variety of ways. The adjustability of the header allows for easier sill placement and adjustment. One example method of mounting the illustrated door frame assembly 22 (as shown in Figure 2) includes first assembling the head jamb 24, header 50, side jambs 28 and the sill member 26 together. The fixing angles 52 are secured in place. The brackets 32 of the adjusters 30 are also set. The assembled frame, which can be laying flat on the floor 18, can be rotated upward so that the bolts 36 slide into the cutouts 40. The fixing angles 52 act as stops at the top of the frame and engage the header 50 to prevent the frame from tipping over into the hoistway. The sill member 26 and the frame are installed from a position on the landing surface 18 (i.e., not from the hoistway side of the entrance 16). The other frame members may be pre-attached to the sill, subsequently attached or a combination of the two options. Plumb lines 60, as illustrated in Figure 7, are positioned in the hoistway 10 to provide a reference for placement of the adjustors 30. The position of the sill member 26 is adjusted to align the side members 28 and to level the sill 26 by disengaging or further engaging the threaded members of the adjusters 30. The position of the header member 50 may also be adjusted as needed. The frame installation process advantageously is conducted entirely from the landing surface 18. Aligning the door frame assembly 22 with the plumb lines 60 ensures proper orientation of the doorways relative to elevator car travel without having to rely on previously mounted guide rails for support during installation or for accurate sill placement. After the car assembly is in place on the guide rails, further adjustment of the door assembly is possible to achieve precise alignment. In a second example method of mounting the example door frame assembly 22 (as shown in Figure 3), the side members 28 are first mounted to the landing surface 18 using known anchors 29. The plumb lines 60 provide a reference for side member alignment. The sill member 26 and the header member 24 are subsequently adjusted relative to the side members 28. The sill member 26 and the header member 50 are selectively adjustable in relation to one another and the side members as needed. These example methods provide for adjustment of the door frame assembly 22 and any one or all of its sub-components; the sill member 26, the plurality of side members 28 and the header member 50, after installation. They provide for plumb lines 60 to be used for alignment purposes in place of guide rails 20 and, in addition, these methods also provide for the door frame assembly 22 to be installed from the landing surface 18 and eliminate the requirement for a platform in the hoistway. The present invention eliminates the need for the guide rails 20 to be installed prior to entrance way installation, providing now for the two installations to be conducted in parallel or any order, greatly reducing the total elevator system installation time. The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.