| United States Patent | 3,920,273 |
| Scholtze | November 18, 1975 |
Keyless chain lock
Abstract
A keyless chain lock providing a multiposition latching of a hinged door, the lock including an anchor plate secured to a door jamb, a flexible chain secured at one end to the anchor plate and fastened at the other free end to a chain knob, and a locking plate coupled to a spacer plate secured to the surface of a door, the locking plate having a main longitudinal slot directed generally away from said anchor plate with an enlarged opening at the distal end of the slot for insertion of the chain knob into the slot, and, having two radial side slots connected to the main slot into which said chain knob may be alternately tracked, thereby forming three alternate positions that the hinged door may be oriented, a substantially closed position when the chain knob is in the radial side slot most distant from the anchor plate, a partially opened or intermediate position when the chain knob is in the radial side slot closer to the anchor plate, and a substantially opened position when the chain knob is at the end of the main slot adjacent the anchor plate.
| Inventors: | Scholtze; Herman J. (Berkeley, CA) |
| Appl. No.: | 05/461,248 |
| Filed: | April 15, 1974 |
| Current U.S. Class: | 292/264 |
| Current International Class: | E05C 17/00 (20060101); E05C 17/36 (20060101); E05C 017/36 () |
| Field of Search: | 292/264,268 |
| 257986 | May 1882 | Skerrett |
| 747866 | December 1903 | Diehl |
| 68,300 | Apr., 1893 | DD | |||
Assistant Examiner: Pietruszka; Carl F.
Attorney, Agent or Firm:
What is claimed is:
1. A chain lock comprising: an anchor member adapted to be secured to a door jamb structure; a locking plate member adapted to be secured to a door structure substantially adjacent said anchor member, said locking plate member having a longitudinal slot with a first end and a second end, and having further a first curved side slot substantially normal to the longitudinal slot intersecting said slot at the first end and a second curved side slot substantially normal to the longitudinal slot, intersecting said slot between said first end and said second end, said longitudinal slot being sloped to the horizontal with said first end above said second end, said second end being substantially adjacent said anchor member and said first end being displaced from said anchor anchor member with said curved side slots each having a radius of curvature taken from a point substantially at said second end and with said side slots depending from said longitudinal slot when said plate member is secured to said door structure; and a chain member having a first end secured to said anchor member and a second end with connecting means for engaging and tracking in said slots, said chain member being substantially taut when said connecting means engages said first side slot and when said connecting means engages said first side slot and when said anchor member and said plate member are secured to said structures wherein said chain member becomes increasingly taut as said connecting means tracks in said first side slot.
2. The chain lock of claim 1 wherein said connecting means at said second end of said chain member comprises a knob with an end having a first flange and a second larger flange, and said longitudinal slot has an aperture at the intersection of said longitudinal slot and said first side slot, said first flange being insertable into said aperture and said knob being generally movable in said slots and retained by said plate member between said first flange and said second flange.
3. The chain lock of claim 1 comprising further a filler bracket adapted to be secured to said door structure immediately adjacent said anchor member and between said anchor member and said locking plate member.
BACKGROUND OF THE INVENTION
Keyless chain locks are commonly used on doors in addition to other conventional key locks both to provide an additional protection from unauthorized entry by a device that reduces tampering from the outside and to allow a party to partially open a door to receive small packages or identify callers without total loss of security. Conventional chain locks customarily include an anchor plate on a door jamb with a chain attached at one end to the anchor plate. The free end of the chain is attached to a chain knob or stud that is inserted into the distal end of an elongated slot in a locking plate fixed to the open door. In such arrangements, the chain knob is positioned in the elongated slot closest to the anchor plate. In such single-position chain latches, a substantial slack is provided in the chain. While this slack allows the door to be partially opened for the desirable purpose of receiving small packages or mail, it has the undesirable aspect of being subjected to tampering.
For example, the knowledgeable burglar can easily eliminate a conventional cylinder key lock by drilling the cylinder or pulling the locking mechanism. A door protected by the conventional chain lock can then be partially opened exposing the chain. The chain can be quickly severed by bolt cutters and entry gained.
While some prior art devices attempt to eliminate this effect by swinging multiposition shield plates which cooperate with the tracking slot in the locking plate, or tortuous tracking slots, these devices are cumbersome and difficult to operate, particularly in time of stress or nervousness. The keyless chain lock of the present invention eliminates the undesirable feature of the conventional locks by providing the locking mechanism with an operating position in which the door cannot even be partially opened and accomplishing this feature in a simple and efficient manner which has not been considered by prior devices.
SUMMARY OF THE INVENTION
The keyless chain lock of this invention is constructed to allow the user alternatives in its use and operation. The chain lock has a uniquely arranged locking plate which allows the chain knob at the free end of the chain to be positioned in one of three positions. A first closed position in which the chain is taut preventing any opening of the door. In this position, the user can rest assured that even if his additional key lock is picked or pulled, he will still be protected and the chain of his secondary chain lock will not be exposed and severed. A second intermediary position in which the chain is partially slack allows the door to be opened a crack. In this position, conversation can be engaged and identifications made without fear that a partial entry by arm or foot be attempted. A third part open position in which the chain is in its greatest slack condition approximates the single position of the conventional chain lock. In this position, the door can be opened to a sufficient degree that small packages can be exchanged and a full view of a caller made.
It is clear that the two positions which will be most used are the closed position and the part open position. For convenience of operation, the locking plate is specifically and uniquely designed to allow the chain knob to be moved from the closed position to the part open position merely by a flip of the finger on the chain knob. Such action permits the chain knob to self-track to the part open position. Where caution is the guide, the chain knob can alternately be released from the closed position and deliberately positioned in the intermediate position.
The novel construction and arrangement of the keyless chain lock of this invention, which operates in this simple and convenient manner, is described in greater detail in the following detailed description of the preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view, partially fragmented, of the keyless chain lock mounted on a door and associated structure.
FIG. 2 is a cross-sectional view, partially in phantom, of the arrangement in FIG. 1, taken on the lines 2--2 in FIG. 1.
FIG. 3 is a cross-sectional view, partially fragmented, taken on the lines 3--3 in FIG. 1.
FIG. 4 is a front view detailing the locking plate in the keyless chain lock of FIG. 1.
FIG. 5 is a front view detailing the spacer plate which accompanies the locking plate in the keyless chain lock of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the keyless chain lock designated generally by reference numeral 10 is illustrated mounted on a door 12 and accompanying door-jamb structure 14. The chain lock 10 has an anchor plate 16 secured to the door-jamb structure 14 by two wood screws 18. The anchor plate 16 has an anchor bracket 20 fixed to the plate to which an end link 22 of a flexible chain is attached. The flexible chain 24 has a stud or chain knob 26 attached to the distal or free end link 28 of the chain 24. The anchor plate includes an aperture 30 into which the chain knob 26 may be inserted for retaining the flexible chain when the lock is not in use.
Attached to the door 12 is a locking plate 32 and a spacer plate 34, the latter shown in phantom in FIG. 1 and visible in the cross-sectional view of FIG. 2. The locking plate 32 and spacer plate 34 are fastened to the door by a plurality of wood screws 36.
Additionally, a filler bracket 38 is attached to the door 12 adjacent the anchor plate. While the filler bracket is not essential to a properly installed chain lock, it is preferred for two important reason. First, the filler bracket protects the door from damage from the flexible chain during ordinary use. Second, and perhaps more importantly, the filler bracket provides for a final adjustment of the chain 24 when the chain is extended to the taut position shown in FIG. 1. After the locking plate 32 and spacer plate 34 are installed and the chain 24 is arranged as shown in FIG. 1, the filler bracket 38 can be installed to provide a taut condition to the chain. Adjustment can be made by the installation of one or more shim plates 40 as shown in FIG. 2. The filler bracket is secured to the door by wood screws 42 in the same manner as the anchor plate 16.
As shown in FIGS. 1 and 4, the locking plate has a main slot 44 that is longitudinally arranged at an angle to the horizontal. While the angle may be varied somewhat, the angle in the preferred embodiment is approximately 20.degree. which provides for an efficient operation of the chain lock as described hereafter. The end of the slot most distant from the anchor plate 16 has an enlarged aperture 46 allowing insertion of the chain knob 26 as described in greater detail below. Depending from the main slot 44 is a first radial side slot 48 and a second radial side slot 50. The point from which the radii of these two side slots 48 and 50 are constructed is at the end 52 of the main slot closest the anchor plate 16. In this manner, the flexible chain 24 being pivoted from the anchor bracket 20 on the anchor plate encounters a slight additional displacement from its point of pivot, at the anchor bracket when the chain knob 26 is displaced into the side slots 48 and 50. This displacement is of particular importance when the chain knob is displaced into the first, more distant side slot 48. In this position, the chain knob encounters a slight wedging action by the additional displacement, thereby providing a leverage to increase the tautness of the chain 24 when finally positioned as shown in FIG. 1. Thus, the desired resultant tautness can be achieved without making it difficult to initially move the chain knob 26 to the first side slot 52 as would be the case were the radius of the slot centered on a point at the anchor bracket 20 rather than the end 52 of the main slot 44.
Additionally, when the chain knob is released from the first side slot 48 by a flip of the finger, the relief in tautness aids in carrying the chain knob up to the aperture 46 at the end of the main slot 44. At this point, the angle or slope in the main slot and the weight of the chain automatically cause the chain knob 16 to track down to the end of the side slot bypassing the second side slot 50.
If placement of the chain knob 26 from the first slot 48 to the second or intermediate side slot 50 is desired, the chain knob 26 is raised from the first slot 48 in the same manner as above described, but must be deliberately carried to the second slot 50 and placed therein. This operation is in keeping with the normal consciousness of an operator who, in the usual case, will want the chain lock operated from a position where the door is closed to a position where it is most open. When the operator is cautious, he will naturally take care to deliberately place the chain knob in the intermediate position.
This intermediate position is shown in FIG. 2, where the chain knob 26 is shown placed in the intermediate second side slot 50. In this position, the door 12 is only slightly open, thus allowing for only partial inspection of a caller or the receipt of only small or thin packages. The closed position, where the chain knob 26a is positioned in the distant first side slot 48a, as shown in FIG. 1, is illustrated in FIG. 2 in phantom or dotted line. In this position, the chain 24a is taut, keeping the door 12a closed. The part open position, which is not shown, is substantially the same as the intermediate position with the door opened approximately twice the displacement as that shown for the intermediate position. This position is substantially the same as that for conventional chain locks. As shown in FIG. 1, the three alternate positions for the chain knob 26 are spaced along the horizontal to the anchor bracket 20.
Referring to FIGS. 2 and 3, the configuration of the chain knob 26 is apparent. The chain knob has a head 54 for convenient finger manipulation, a neck 56 and an end with a first flange 58 displaced from a second flange 60. The end link 28 of the flexible chain 24 is attached to the neck 56 of the chain knob 26 between the head and the first flange 58. The second flange 60 is slightly smaller than the first flange 58 to permit only the second flange 60 to be inserted in the aperture 46 in the main slot 44. Both flanges are greater in diameter than the width of the slots in the locking plate enabling the knob to track in the slots without jamming. In this respect, the locking plate is displaced from the door 12 by spacer plate 34 which is skeletal in construction, as shown in FIG. 5. The locking place 32, as shown in FIG. 4, and the spacer plate, as shown in FIG. 5, have the same periphery and coincident holes 62 for the wood screws 36.
When assembled and installed, as shown in FIG. 1, the keyless chain lock is both efficient and convenient to operate in the manner herein described.
Both plates 32 and 34 can be used for left and right side installations by simply flipping them over 180.degree., individually and arranging them generally as shown in FIG. 1.
While in the foregoing specification an embodiment of the invention has been set forth in considerable detail for purposes of making a complete disclosure thereof, it will be apparent to those skilled in the art that numerous changes may be made in such details without departing from the spirit and principles of the invention.
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