US3578749A

US3578749A - Self-locking drop-door

Info

Publication number: US3578749A
Application number: US821714A
Authority: US
Inventors: Homer G Woten
Original assignee: Individual
Current assignee: Certainteed LLC
Priority date: 1969-05-05
Filing date: 1969-05-05
Publication date: 1971-05-18
Anticipated expiration: 1988-05-18

Abstract

A drop-door hinged at the bottom to an enclosure, and having support bars pivotally connected to the door and slidable through slots in the enclosure adjacent the opening closed by the door. The support bars are angular, with short arms adjacent the door to move into the slots in the enclosures, and counterweight arms to move about the bottoms of the slots in the enclosures as fulcrums to assume downwardly depending self-locking positions.

Description

United States Patent Inventor Homer G. Woten 912 Perrin Ave. N. W., Winter Haven, Fla. 33880 Appl. No. 821,714 Filed May 5, 1969 Patented May 18, 1971 SELF-LOCKING DROP-DOOR 4 Claims, 5 Drawing Figs.

U.S. Cl 49/387, 296/57 Int. Cl E05f 1/00 Field of Search 296/50, 57; 49/3 87 [56] References Cited UNITED STATES PATENTS 474,353 5/1892 Bailey 296/57 1,270,695 6/1918 Carlson 296/57 3,063,747 11/1962 Anderson 296/57 Primary Examiner-Kenneth Downey Altorney-Mason, Fenwick & Lawrence ABSTRACT: A drop-door hinged at the bottom to an enclosure, and having support bars pivotally connected to the door and slidable through slots in the enclosure adjacent the open-- ing closed by the door. The support bars are angular, with short arms adjacent the door to move into the slots in the enclosures, and counterweight arms to move about the bottoms of the slots in the enclosures as fulcrums to assume downwardly depending self-locking positions.

PATENTEU am a 197i BY Wm HOMER. G WOTEN BACKGROUND OF THE INVENTION This invention relates to self-locking, hinged closures, and particularly to self-locking drop-door supports.

The conventional drop-door construction, whether it be an access door into a building or machine housing, or a vehicle tailgate, consists of a rectangular door which is hinged at its bottom to the building, housing, etc., and has some means to hold it at an open position, usually horizontal at right angles to the opening it closes. The holding, or support, means normally consists of a chain or hinged brace secured to the wall adjacent the opening and to the door, to support the door in the open, horizontal position.

The usual support member is incapable of holding the door in its raised, closed position, and some other means must be employed for this purpose. Many types of locks, latches, hasps, etc. have been used to accomplish this. Obviously, the door must be held in its raised position while the lock, or similar device, is fastened, and the holding means must be released before the door can be lowered.

SUMMARY OF THE INVENTION The object of the present invention is to provide a dropdoor having support means which will automatically hold the door in predetermined open position when lowered and automatically hold the door in closed position when raised.

Another object of the invention is to provide such means which can be designed to hold the door closed with sufficient force to require considerable pull to open it, or so designed that a light pull is all that is necessary to open the door.

A further object is to provide a door support which can counterbalance the door to hold it in some intermediate positron.

Yet another object of the invention is to provide a dropdoor support which is extremely simple, yet can be made to withstand great loads and operate very smoothly and easily.

Other objects of the invention will become apparent from the following description of one practical embodiment thereof, when taken in conjunction with the drawings which accompany, and form part of, this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a drop-door and support means embodying the principles of the present invention, with part of a representative housing on which the door is mounted being shown;

FIG. 2 is a view similar to FIG. I, but with the door in lowered position;

FIG. 3 is a vertical section taken on the line 3-3 of FIG. 1;

FIG. 4 is a similar view to FIG. 3, but with the door in lowered position; and

FIG. Sis a perspective view of one of the new support members.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, the door I of the present invention is shown in conjunction with a housing 2, which is representative of any type of walled structure into which the door 1 is designed to provide access. The housing has an opening 3 which the door is designed to cover when in closed positron.

The door is shown as a rectangular member 4 of such proportions as to fit within the opening 3 in the housing. Plates 5 are mounted along the sides of the main door portion 4, and project outwardly beyond the sides to provide flanges 6 to abut the wall of the housing about the opening 3 and limit the inward movement of the door. Plates 5 terminate short of the bottom of the door, so that when the door is open they will not conflict with an outwardly projecting ledge 7 along the bottom of the opening 3. The ledge fonns a mounting surface for hinges 8 which connect the door to the housing, and also as a rear support means when the door is lowered to relieve the hinges of the weight of the door and any load which may be supported upon it. Two or more hinges may be used, as

required, and the hinges are attached to the bottom portion of the door and to the ledge 7.

Each side flange 6 has an elongated slot 9 near its top, the slot extending longitudinally of the flange, and there is a mounting bearing 10 secured upon the outer faces of the flanges 6 overlying the slots 9. Each bearing plate has a pair of spaced, upstanding ears l1, and there is a slot 12 in each bearing, similar to the slots 9 in the flanges 6 and overlying the slot 9 of its respective flange.

One end of a support bar 13 extends through each pair of aligned

slots

9 and 12, and pins 14 project transversely from the end and are journaled in the ears ll of the bearing plate. This provides for pivotal mounting of the bars 13 relative to the door. The opposite ends of the bars 13 pass slidably through slots 15 in those portions of the sidewall of the housing 2 overlapped by the flanges 6 when the door is in closed position. Slots 15 will be in underlying alignment with the

slots

9 and 12 when the door is in its raised, closed position. Transversely extending pins 16 at the rear ends of the bars abut the inner surface of the housing wall at the sides of the slots 15 when the door is in its lowered, open position, and form stops to limit the downward movement of the door.

It will be noted from the drawings that the support bars 13 are elongated, straight members for the major portion of their lengths, to provide counterweight arms 17, and there are short, angularly offset locking arms adjacent the pins 14 and movable within the

slots

9 and 12, and also in the slots 15 when the door is in closed position. The lengths of the locking arms 18 relative to the thickness of the various parts at the door area determine the downward angle of the arms 17 when the door is in raised position, and this angle, together with the weight of arms 17, detennines the closure force exerted by the arms 17 to maintain the door in closed position.

When the door is in use, and in its open position as shown in FIG. 2, the support bars will be fully drawn through the slots 15 in the housing, and the pins 16 at the rear ends of the slides will be in abutment with the backface of the housing wall. In this position, the bars act as diagonal braces to support the door from points well above the hinge line of the door. This will provide the same support as would conventional chains or hinge braces. When the door is raised, however, the bars begin to slide through the slots 15, with the front ends of the bars freely pivoting in the bearing plates 10. When the door is approximately half raised, the counterweight arms 17 of the bars will occupy the position shown in dotted lines in FIG. 4. Continued movement of the door in an upward direction will first I bring the arms 17 to a horizontal position, and then the arms will begin to assume a slightly downward tilt. After the arms 17 have reached the horizontal position, the weight of the arms will serve to counterweight the door, and the door may be stopped in some intermediate positions. As the door approaches its closed position, however, the bars move inwardly to the point where the inner angle 19 between the

arms

17 and 18, reaches the slot 15 and counterweight arms 17 of the bars begin to move rapidly downward. When this position is reached, the weight of the arms 17 will draw the door to its completely closed position and will be sufficient to hold the door closed.

The closure force exerted by the support bars can be varied to suit specific means. This can be done in either of two ways, or by means of a combination of the two. The first manner in which the force can be increased is by increasing the weight of the counterweight arms 17 of the support bars. The greater the weight of the arms, the more pull on the door in an opening direction will be required to cause the arms to swing upwardly, while moving about the bottom edges of the slots 15 as fulcrums. The heavier the weight of the arms, the greater the force which will be applied to automatically bring the door to its closed position and the support bars into their locking positions. The second manner of increasing the locking force is by changing the lengths of the locking arms 18 so as to allow the arms 17 to assume positions more nearly vertical when the door is in closed position. The closer the arms 17 approach the vertical, the more force will be required to swing them upward about their fulcrums on the lower edges of the slots 15. The lighter the weight of the arms 17 and the greater their angle from the vertical when in final locked position, the easier the door will be to move from its closed position.

A door having the support means of the present invention can be opened simply by pulling the door from its closed position and moving it about its hinges. When the door reaches a horizontal position, the support bars will have reached their limit of travel and will serve as braces to maintain the door in that position and support any load which may be put upon it. When the door is raised to a position close to the fully closed position, it will automatically move to its fully closed position and the support bars will hold the door against accidental opening.

Iclaim:

l. A self-locking drop-door for a wall having an opening comprising, a door proper, hinges pivotally connecting the bottom of the door proper to the wall adjacent the bottom edge of the opening, and a support bar pivotally connected at one end to the door proper by pivot connector means at a point spaced from the bottom of the door proper, the wall having a slot through which the support bar slidably passes with the lock bar having a lower edge resting on the lower edge of the slot with the slot being adjacent the opening and at a distance from the hinges equal to the spacing from the hinges to the connection of the support bar to the door proper, the support bar being angular in shape and comprising a short locking arm having said pivot connector means on one end pivotally connected to the door proper and a long counterweight arm extending angularly from the other end of said short locking arm so that said pivot connector means is not in alignment with the axis of said counterweight arm, stop means on the end of said counterweight arm opposite said locking arm dimensioned and oriented so as to be incapable of passage through said slot, the locking arm being no longer than the distance from the pivotal connection of the locking arm to the door proper to the inside of the wall when the door proper is in raised closed position, and the angle between the locking arm and the counterweight arm being such as to position the counterweight arm at an inclined angle to said wall when the door is in its raised closed position so that the weight of said counterweight arm acts to provide a holding force on the door to hold the door in its raised closed position whereby an opposite opening force exerted on the top of the door in excess of the holding force in a door opening direction causes said counterweight arm to pivot upwardly while simultaneously sliding outwardly of said slot until said stop means engages the wall adjacent the slot to enable a full opening of movement of said door.

2. A self-locking drop-door as claimed in claim 1, wherein, there is a support bar pivotally attached to each side of the door proper and slidable through a slot at each side of the opening.

3. A self-locking drop-door as claimed in claim 2 wherein said stop means comprises transversely extending pin means on the support bars to engage the wall adjacent said slots to limit the sliding movement of the support bars and the downward swinging movement of the door proper.

4. A self-locking drop-door as claimed in claim 3 wherein, the counterweight arm is of sufiicient length to allow the door proper to open to horizontal position before said pin means engages the wall.

Claims

1. A self-locking drop-door for a wall having an opening comprising, a door proper, hinges pivotally connecting the bottom of the door proper to the wall adjacent the bottom edge of the opening, and a support bar pivotally connected at one end to the door proper by pivot connector means at a point spaced from the bottom of the door proper, the wall having a slot through which the support bar slidably passes with the lock bar having a lower edge resting on the lower edge of the slot with the slot being adjacent the opening and at a distance from the hinges equal to the spacing from the hinges to the connection of the support bar to the door proper, the support bar being angular in shape and comprising a short locking arm having said pivot connector means on one end pivotally connected to the door proper and a long counterweight arm extending angularly from the other end of said short locking arm so that said pivot connector means is not in alignment with the axis of said counterweight arm, stop means on the end of said counterweight arm opposite said locking arm dimensioned and oriented so as to be incapable of passage through said slot, the locking arm being no longer than the distance from the pivotal connection of the locking arm to the door proper to the inside of the wall when the door proper is in raised closed position, and the angle between the locking arm and the counterweight arm being such as to position the counterweight arm at an inclined angle to said wall when the door is in its raised closed position so that the weight of said counterweight arm acts to provide a holding force on the door to hold the door in its raised closed position whereby an opposite opening force exerted on the top of the door in excess of the holding force in a door opening direction causes said counterweight arm to pivot upwardly while simultaneously sliding outwardly of said slot until said stop means engages the wall adjacent the slot to enable a full opening of movement of said door.

4. A self-locking drop-door as claimed in claim 3 wherein, the counterweight arm is of sufficient length to allow the door proper to open to horizontal position before said pin means engages the wall.