Patent Publication Number: US-6990772-B2

Title: Automatic door closure for double-acting doors

Description:
This invention relates to a mechanical door closure for double-acting doors and more particularly to a door in combination with a mechanical door closure. 
     BACKGROUND OF THE INVENTION 
     Mechanical door closure devices that automatically return a double-acting door to a preferred center position are well known and are exemplified by the mechanisms illustrated and described in U.S. Pat. No. 4,951,351, issued Aug. 28, 1990 to A. Eckel; U.S. Pat. No. 4,945,606, issued Aug. 7, 1990 to A. Eckel; U.S. Pat. No. 4,124,955, issued Nov. 14, 1978 to A. J. Kochis; and U.S. Pat. No. 3,263,365, issued Aug. 2, 1966 to O. C. Eckel. Such devices are generally satisfactory, but have limitations. For one thing, they are lacking aesthetically. For another thing they comprise a cam and cam follower, and the latter requires a roller in engagement with the cam in order to allow the door to pivot freely between open and closed positions. The roller is subject to breakdown. A further limitation of the foregoing type of closure device is that return motion to center position tends to be uneven due to the contour of the cam. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The primary object of the invention is to provide a new and improved cam/cam follower type mechanical door closure device. 
     A further object is to provide new cam-type door-closing hardware that is strong, durable, and reliable. 
     Another object is to provide a cam/cam follower type of door closure that is adjustable to assure that the attached door will close automatically to a determinate position. 
     Another object is to provide a gravitationally-operated door-closing mechanism that has simplicity of construction, can be installed with minimum skill, and can be substituted for other prior art cam/cam follower door closure devices. 
     The foregoing objects are achieved by providing a door closing system that comprises first and second members each having a central axially-extending bore for receiving a door post and a helical end surface extending transversely of its center axis. The first member is adapted to be secured in spaced relation to a side of a door frame with its central bore extending parallel to that door frame side. The second member is adapted to be mounted on and secured to a door post that extends through and is rotatable in the central bore of the first member, with the helical end surface of the second member facing and engaging the helical end surface of the first member. The helical end surfaces coact with one another to gravitationally return a door attached to the door post to a closed position automatically after the door has been pushed opened and then released. Other features and advantages of the invention are described in or rendered obvious by the following detailed description of a preferred embodiment of the invention and the accompanying drawings. 
    
    
     
       THE DRAWINGS 
         FIG. 1  is a full face view in elevation of a door mounted with cam-type hardware constructed according to the present invention; 
         FIG. 2  is an enlarged fragmentary view in elevation of the cam-type hardware taken from the same viewpoint as  FIG. 1 ; 
         FIG. 3  is a fragmentary sectional view taken along line  3 — 3  of  FIG. 2 ; 
         FIG. 4  is an enlarged fragmentary view in elevation taken from a viewpoint 90 degrees removed from that of  FIG. 1  showing the cam-type hardware with the door in a fully open position; 
         FIG. 5  is a view in elevation of one of the cam members of the cam-type hardware taken from the same viewpoint as that of  FIG. 4 ; 
         FIG. 6  is a view in elevation of one of the cam members taken from a viewpoint displaced 90 degrees from that of  FIG. 5 ; 
         FIG. 7  is an enlarged fragmentary view of the upper cam member showing how it is secured in place; 
         FIG. 8  is a fragmentary view in elevation illustrating a preferred bottom hinge connection for a door that is coupled to the new cam hardware; 
         FIG. 9  is a fragmentary view in elevation like  FIG. 8  but with the door in a fully open position; 
         FIG. 10  is a sectional view taken along line  10 — 10  of  FIG. 8 ; and 
         FIG. 11  is a sectional view of one of the support brackets for the cam hardware. 
     
    
    
     In the several views like components are designated by like numerals. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is illustrated a door frame  10  comprising an outer jamb  12 , and inner jamb  14 , a lintel  16  and a sill  18 . Hung in the door frame is a door  20 . The door is attached by an upper door mount identified generally by the numeral  22  and a lower door mount identified generally by the numeral  24 . The portion of the door adjacent to jamb  14  is notched as shown at  26  and  28  to accommodate the upper and lower door mounts. 
     Referring to  FIGS. 2–4  and  11 , the upper door mount comprises a metal door bracket  30  of U-shaped cross-section that straddles a portion of the door in the region of notch  26  and comprises a top plate  32  that sits on a top edge of the notched section of the door and two side plates  34 A and  34 B that extend down along opposite sides of the door. Bracket  30  is secured to the door by suitable fastening means, e.g., by bolts  36  and nuts  38  that extend through the side plates  34 A and  34 B. Welded to top plate  32  is a round door post  40 . The latter may be a hollow tube or a solid rod and is made of a metal such as ordinary steel or stainless steel. 
     The upper door mount also includes new cam-type door closure hardware comprising a first U-shaped metal bracket  42  and a second L-shaped metal bracket  44 . The first bracket  42  fits in the upper corner formed by inner jamb  14  and lintel  16  and is fixed to those members by screw bolts  46 . The second bracket is fixed to inner jamb  14  by additional screw bolts  50  and its horizontal arm  54  is spot welded to the horizontal arm  52  of bracket  42 . Brackets  42  and  44  have holes, e.g., as shown at  43  in  FIG. 11 , to accommodate screw bolts  46  and  50 . Referring to  FIG. 4 , the lower arm  52  of bracket  42  and arm  54  of bracket  44  are notched as shown at  56  and  58  to accommodate door post  40  without interfering with its rotation. Additionally, as shown in  FIG. 11 , arm  52  has two holes  53  and a slot  55  centered between holes  53  at the inner end of notch  56 . Although not shown, it is to be understood that arm  54  of bracket  44  has like holes  53  and a like slot  55  disposed for alignment with the like elements of bracket  42 . 
     Seated on lower arm  52  of bracket  42  is a first cam member  60 A having at one end a flat surface  62  and at its other end an inclined helical cam surface  64  as hereinafter described in greater detail. The outer surface of cam member  60 A is cylindrical. Cam member  60 A is secured to bracket  42  by means of three screw bolts  66  that pass through aligned holes  53  and slots  55  in arms  52  and  54  and are screwed into tapped holes formed in the bottom end of the cam member. Cam member  60 A has an axial bore  68  and a coaxial counterbore  70 . The outer diameter of door member  40  is sized so that it makes a close but rotatable fit in bore  68 . Counterbore  70  and the outer diameter of cam member  60 A are sized so that the radial dimension of cam surface  64 , measured between its inner and outer edges, is sufficient to assure a bearing surface that is adequate for supporting the weight of the door. By way of example but not limitation, cam member  60 A has an outer diameter of about 2.375 inch, a diameter for bore  68  of about 1.250 to about 1.321 inch, a diameter for counterbore  70  of 1.500 inch, and a height of 2.500 inch measured between bottom surface  62  and the highest point of surface  64 . 
     The upper door mount also includes a second cam member  60 B that is mounted on the upper end of door post  40  and functions as a cam follower. Except as otherwise described hereinafter, cam member  60 B is identical to cam member  60 A, but is oriented so that its helically curved end face  64  faces counterpart surface  64  of cam member  60 A. The upper end of door post  40  is formed with an exterior screw thread  41  and the surface defining the axial bore  68  of cam member  60 B has a slightly smaller diameter than axial bore  68  of cam member  60 A, but is formed with a screw thread whereby it can be screwed onto the upper end of the door post. The rotational orientation of cam member  60 B on door post  40  is fixed by means of a set screw  78  that is screwed into a tapped, radially-extending hole in the cam member. The set screw may engage the door post thread directly. However, that entails the risk that the set screw will deform the thread and make it difficult thereafter to unscrew the cam member of to alter its rotational position on the door post. Therefore, a preferred practice is to lock the cam member  60 B to the door post by the combination of a set screw  78  and a brass plug  79  ( FIG. 7 ) that is disposed between the inner end of the set screw and the door post thread. This preferred arrangement offers the advantage that the brass plug rather than the screw thread will deform under the pressure exerted by the set screw. 
     Referring to FIGS.  2  and  4 – 6 , the surfaces  64  of cam members  60 A and  60 B have a helical curvature and are flat between their inner and outer edges, with all co-radius points between those edges being equidistant from the corresponding flat end surfaces  62 . As used herein with reference to surfaces  64 , the term “helical curvature” denotes a helical curvature in relation to the longitudinal axis of the corresponding cam member, similar to the relationship of a screw thread to the axis of the shaft on which it is formed. As seen in  FIGS. 4 and 5 , the helically curved end surface  64  is effectively subdivided into two mirror halves  64 A and  64 B by a high point or top terminus  64 C and a low point or bottom terminus  64 D. The two surface portions  64 A and  64 B of each cam member are helically curved with the same pitch. The top terminus is a narrow flat surface area. The bottom terminus is also a narrow flat surface area. More specifically as illustrated in  FIGS. 4 and 5 , the two mirror halves of surface  64  come together to form a valley or dwell at the bottom terminus  65 D. By way of example but not limitation, if cam members  60 A and  60 B each have an overall length of 2.500 inches, their helical surfaces  64  may be cut so that the axial distance between their top terminus and their bottom terminus is about 1.50 inches. 
     Referring now to FIGS.  1  and  8 – 10 , the bottom mount comprises a U-shaped bracket  80  having two oppositely and outwardly extending side flanges  82  and bottom flanges  84  (only one each of flanges  82  and  84  is visible in the drawings) that are secured to inner jamb  14  and sill  18  by screw bolts  86 . Welded to the upper end of bracket  80  is a top plate  88 . Fixed in a hole in plate  88  is a tubular bearing  90  having peripheral flange  91  that engages plate  88 . The latter rotatably accommodates a door post  92  that is a fixed extension of a U-shaped metal door bracket  94  that is similar to door bracket  30 . Bracket  94  embraces opposite sides of door  20 . The bracket is attached to door  20  by means of bolts  96  that extend through the door and are secured by nuts  98 . The upper and lower door mounts are attached to the door so that door post  92  is axially aligned with door post  40 . 
     Mounting the door is facilitated by the slots  56  and  58  in bracket arms  52  and  54 . The door installation involves first attaching mounting brackets  42  and  44  and bracket  80  to the door frame as shown in the drawings. Then with brackets  30  and  94  attached to door  20 , the bottom door post  92  is inserted in bearing  90  and door post  40  is moved into the slots  56  and  58  of brackets  42  and  44  respectively. Cam member  60 A is then slipped onto upper door post  40  and attached to brackets  42  and  44  by means of screws  66 . Alternatively and preferably, the rear screw  66  (the screw to the right in  FIG. 2 ) may be attached to cam member  60 A before the latter is moved into position over arm  52  of bracket  42 , after which the cam can be shifted to the desired position and screw  66  tightened to lock the cam member to the two brackets. The two other screws  66  may be applied to secure the cam member in place. It is to be noted that the screw holes in the bottom of cam member  64 A and the matching through holes in brackets  42  and  44  are located so as to assure that the cam member will be secured with its dwell point  64 D in the 6 o&#39;clock position using the side jamb  14  as a reference 12 o&#39;clock position. Then top cam member  60 B is secured to door post  40  with its high point  64 C aligned with dwell point  64 D of cam member  60 A and its surface  64  fully engaged with the corresponding surface  64  of cam member  60 A, as shown in  FIG. 2 . Thereafter the set screw  78  is tightened to lock cam member  60 B to door post  40  via the brass plug  79 . When this has been accomplished, the door will be in closed position, extending at substantially a right angle to the plane of side jam  14 . If subsequently the door is pushed open in either direction, cam member  60 B will ride up on the surface  64 A or  64 B of cam member  60 A, causing the door to rise as it is turned. When the door is released, it will automatically return under the influence of gravity to its center at-rest or closed position. Because of the fact that the surfaces  64  of cam members  60 A and  60 B have identical helical contours, in all open positions of the door those surfaces make a least a line contact with one another for the full distance between their inner and outer edges which are identified in  FIG. 5  as  64 E and  64 F respectively. 
     If the door is not exactly in fully closed position when at rest, i.e., when the cam members are as shown in  FIG. 2 , the set screw  78  may be loosened and cam member  60 B rotated on door post  40  in the direction and by the amount required to position the door so that it extends perpendicular to side jamb  14 , after which the set screw is tightened to lock cam member  60 B to the door post. The extent to which the door may be swung open in either direction is determined by engagement of the door with a door stop (not shown) that may be a wall-mounted or floor-mounted device. Alternatively the door stop may be attached to the bottom mount bracket  80  or top mount bracket  44 . Preferably the door stop is set to allow the door to swing open more than 90 degrees from its closed position, so as to maximize the pass-through opening between the door and the opposite doorjamb  12 . 
     The two cam members may be made of various materials, e.g., a metal such as steel or aluminum or a plastic or fiber-reinforced plastic. A primary requirement of the cam members is that they be strong enough to carry the weight of the door. Preferably the bottom cam member  60 A is made of Delrin®, a product of E.I. DuPont de Nemeurs Company, while the upper cam member is made of Teflon®-impregnated hardcote anodized aluminum. The Teflon® impregnation reduces the coefficient of friction of the aluminum and the tendency of dirt or other materials to adhere to the cam member, thereby assuring satisfactory operation of the door closure hardware. As a second preference, the upper cam member is also made of Delrin®. 
     The invention is susceptible of other modifications. Thus, for example, the two short door posts may be replaced with a single door post that extends for substantially the full length of the door, e.g., in the manner disclosed in U.S. Pat. No. 4,951,351, cited supra. Also the invention may be practiced by using other means for attaching the cam hardware components to the door frame and the door post, and the number and type of screws or other fasteners used in connection with the cam hardware may be varied. The arm  54  of bracket  44  need not be spot welded to arm  52  of bracket  42 . Another modification is to replace U-shaped bracket  42  with an L-shaped bracket that is attached to the side door jamb but not to the lintel. A further modification comprises installing the door closure hardware as part of the bottom mount instead of as part of the top door mount. Alternatively two sets of the same cam hardware may be used for a single door, one set as part of the top door mount and the other set as part of the bottom door mount. Also, although the illustrated embodiment comprises a single door in a door frame, the door closure hardware provide by this invention may be used in installations comprising double doors, i.e., two swinging doors mounted side by side in a single door frame. In this connection it should be noted that an important advantage of the cam hardware described herein is that it may be used for relatively heavy duty doors, e.g., doors in a warehouse. A further advantage is that it eliminates the need for the roller that is necessary in all “V” cam door closure hardware used on double acting traffic doors, e.g., the hardware shown in U.S. Pat. Nos. 4,951,351, 4,945,606, 4,124,955, and 3,263,365, all cited supra. Still other modifications and advantages will be obvious to persons skilled in the art from the foregoing description and the related drawings.