US 3811717 A
This specification discloses a fire door lock set incorporating a latch bolt having a latch bolt stop lever which is normally maintained in an ineffective position by a fusible pin, but which drops into a position holding the head of the latch bolt in door closing position when the pin melts at a predetermined temperature caused by a fire condition.
Description (OCR text may contain errors)
United States Patent [191 Floyd et al.
[451 May21, 1974 LATCH BOLT STOP LEVER FOR FIRE DOOR LOCK SETS  Inventors: Alfred E. Floyd, North Guilford;
Lars E. Erickson, Clinton, both of Conn.
 Assignee: Sargent and Company, Division of Walter Kidde & Co. Inc., New
 Filed: Mar. 1, 1973  Appl. No.: 336,932
' [5 2] US. Cl 292/92, 292/153, 292/D1G. 66,
 Int. Cl E05f 15/20 [.58] Field of Search 292/92, 153, DIG. 66; f 70/D1G. 10; 49/1, 7, 8; 16/48.5
 References Cited UNITED STATES PATENTS 1,086,126 2/1914 Berry.- 49/8 8/1941 Adams 292/153 X 12/1972 Adler..... 292/92 Primary Examiner-Robert L. Wolfe Attorney, Agent, or FirmEric P. Schellin; Martin P.
Hoffman 5 7] ABSTRACT This specification discloses a fire door lock set incorporating a latch bolt having a latch bolt stop lever which is normally maintained in an ineffective position by a fusible pin, but which drops into a position holding the head of the latch bolt in door closing position when the pin melts at a predetermined temperature caused by a fire condition.
The present invention relates to the lock set incorporating a latch bolt and associated mechanism in a fire door and is concerned primarily with a latch bolt stop lever which is under the control of a fusible 6 Claims, 6 Drawing Figures :PATENTEDMAYZI I974 I v 3,811.71?
' 5 sum 1 0F 2 Fla. 3.
FATENTEDMAY 21 I974 23, 8 1 1,717
sum 2 0F 2 BACKGROUND OF THE INVENTION At the present time, fire doors are included in many structures and are provided for the purpose of maintaining an exit closed during a fire for the purpose of preventing the spread of the fire. Lock sets incorporating latch bolts are employed to maintain the fire doors in closed position and it is, of course, necessary to provide a mechanism to retract the latch bolt when the door is to be opened. One type of lock set incorporating a latch bolt for fire doors which is now meeting with widespread usage includes springs which bias the head of the latch bolt into the door closing position. They also include a horizontally disposed handle which is depressed and through mechanical connections retracts the bolt head from closing position. It has been found that in the event ofa fire, temperatures reach the point where the springs are annealed and thus lose their holding power. Under these conditions, the weight of the handle will retract the bolt head because the latter is no longer held in door closing position by the springs. The present invention is founded on the concept of providing a lock set incorporating a latch bolt stop lever which is maintained inineffective position under normal conditions by a fusible pin, but which will drop into 6. To provide, in'a fire door lock set of the character aforesaid, an abutment pin which is secured to the housing below the latch bolt stop lever to limit its downward swinging movement.
Various other more detailed objects and advantages of the invention, such as arise in connection with carrying out the above ideas in a practical embodiment, will, in part, become apparent and, in part, be hereafter stated as the description of the invention proceeds.
SUMMARY OF THE INVENTION The foregoing objects are achieved by two embodiments. In one embodiment, a latch bolt stop lever is pivotally mounted at one end to a wall of the housing which encases the latch bolt mechanism. The other end of this lever is formed with a notch and a tab extending therefrom on the upper side thereof. The notch receives the fusible pin which is secured to the housing wall and when this pin melts the lever drops until the tab engages the upper surface of the bolt head. In this position, the end portion of the lever below the notch engages the inner surface of the bolt head to securely hold it in door closing position.
In a second embodiment, a latch bolt stop lever is pivotally mounted at one end of the housing wall and its other end is formed with a notch that receives the effective position maintaining the bolt head in door closing position when the pin melts.
OBJECT OF THE INVENTION With the foregoing conditions in mind, the present invention has in view the following objectives:
1. To provide a lock set incorporating a latch bolt mechanism for a fire door which includes a latch bolt having a bolt head, spring means normally biasing the bolt head into door closing position and apivotally mounted handle which assumes an upraised horizontal position when the bolt head is in door closing position, with a latch bolt stop lever that is held in ineffective position by a fusible pin under normal conditions, but which falls into effective position engaging the bolt head to maintain the latter in door closing position when the pin melts.
2. To provide, in a fire door a lock set incorporating a latch bolt mechanism of the type noted, a latch bolt stop lever which falls into effective position solely by gravity action and which includes an abutment for limiting its falling movement to assure of its proper engagement with the bolt head. a 3. To provide, in*a fire door a lock set incorporating a latch bolt mechanism of the character aforesaid, a latch bolt stop lever which is moved into effective position engaging the bolthead'by gravity action and as may be supplemented by a spring together with an abutment element for limiting such movement.
4. To provide, in afire door a lock set incorporating a latch bolt mechanism of the kind described, a latch bolt stop lever which is pivotally mounted at one end on the housing which encases the lock set and which has a notch at the other end which receives the fusible pin which is also secured to the housing.
5. To provide,- in a fire door lock set of the type noted, a pivotally mounted latch bolt stop lever having a tab projecting from the notched end which functions as an abutment that engages the bolt head when the latch bolt stop lever falls into effective position.
fusible pin. When this pin melts, the lever will exhibit a tendency to fall under gravity action, but this tendency may be supplemented and the required movement'furth er assured by a spring that is coiled about the pivotal pin on which the lever is mounted. An abutment for limiting downward movement of the lever is provided as an element separate from the lever and takes the form of a pin secured to the housing wall.
For a full and more complete understanding of the invention, reference may be had to the following description and the accompanying drawings wherein:
FIG. 1 is a vertical section through the housing for a fire door lock set incorporating a latch bolt mechanism with door closing position of the latch bolt being illustrated in full lines and a retracted position by broken lines;
FIG. 2 is a detailed view depicting the latch bolt stop lever in effective position;
FIG. 3 is a detailed perspective illustrating the effective position of the latch bolt stop lever in full lines and the ineffective position in broken lines;
FIG. 4 is a side view of a modifiedform of the fire door lock set and the latch bolt stop lever with the latter in ineffective position;
FIG. 5 is a detailed view inside elevation of the latch bolt stop lever in effective position, and
FIG. 6 is a detailed perspective of the latch bolt sto lever in effective position.
DESCRIPTION OF THE FIRST EMBODIMENT Referring now to the drawings, wherein like reference characters denotev corresponding elements throughout the several views, and more particularly to FIGS. 1, 2 and 3, afire door is represented at 9 and the outer plate 10 and the inner plate 14 of the lock set are formed with an opening at 11 through which a bolt head 12 extends when the fire door is closed. It will be understood that the bolt head 12 is received in a strike in the door jamb or frame to maintain the door closed.
Lock bolt mechanism housing is represented generally at 13. It comprises an outer decorative plate and an inner plate 14 which is secured to the outer plate 10 in any preferred manner and from which tabs 15 are struck. The housing proper comprises an upper wall 16 secured to one of the tabs 15 by screws 17 and a lower wall 18 secured to the other tab 15 by a screw or pin (not illustrated which passes through openings 19. Housing 13 also includes a rear wall 20 remote from plate 14 and a pair of side walls, one of which is shown at 21.
A latch bolt tail 22 has one end secured to bolt head 12 and its other end is formed with a tail-piece 23. It passes through a guide 24 secured to the wall structure. A light expansion coil spring 25 is coiled about latch bolt tail 22 and biases the bolt head 12 into door closing position.
A handle 26 is drivably connected to shaft 27 rotatably supported in the wall structure 21. It projects from the surface of the fire door and is pivotally movable by hand and is supported in a bearing mounted on the surface of the fire door (not illustrated). The inner end of handle 26 is attached to a hub which is formed with an upstanding tongue 28 which engages a stop 29 secured to wall structure 21 to limit upward swinging movement of handle 26. The hub which engages the inner end of handle 26 is also formed with a downwardly extending tongue 30 which is engaged by a plunger 31 which is biased by an expansion coil spring 32 mounted on wall structure 21 to rotate the handle upwardly.
A latch bolt actuating member 33 is swingably mounted on a pivot pin 34 mounted on wall structure 21. Member 33 has an upper end portion 35 which engages latch bolt tail-piece 23.
Under normal conditions, springs 25 and 32 bias the bolt head 12 into door closing position. However, handle 22 may be depressed against the influence of these springs to cause tongue 28 to engage member 33 and retract the bolt head 12 under the influence of the pressure exerted by end portion 35 against tail-piece 23.
The influence of spring 32 may be supplemented or replaced by a torsion spring 36 coiled about a pin 37 secured to wall structure 21 and having one end 38 secured to an anchorage 39 on the wall structure 21 and a second end 40 which is received in a recess in end portion 35 of member 33.
The structure above described is more or less conventional and well known in fire door lock set mechanisms. In accordance with the present invention, a latch bolt stop lever 41 is pivotally mounted at one end on a pin 42 secured to wall structure 21. Lever 41 is formed with a notch 43 at the end remote from pivot pin 42 and received in notch 43 is a fusible pin 44. Pin 44 is of a metal which will melt at a predetermined required temperature. Zinc is one example of such a metal. Midway its extremities, lever 41 carries a spring abutment 45 against which may be engaged by the end of a torsion spring 46 which is coiled about pivot pin 42. The other end of spring 46 may be engaged against pin 39 mounted on wall structure 21. At an appropriate point below lever 41 -is an abutment element 47 mounted on wall structure 21. It will be noted that lever 41 has a tab 48 which projects beyond the lower side of notch 43.
OPERATION OF FIRST EMBODIMENT Under normal conditions of usage of the fire door lock set above described, the latch bolt stop lever 41 assumes the horizontal ineffective position illustrated in FIG. 1 in which the tab 48 is disposed above bolt head 12 and in no way interferes with the operation either of retracting bolt head 12 into door opening position or of having it move into door closing position under the influence of the springs above described. Should a fire occur, any of the springs 25, 32 or 36 may become annealed, in which event they lose their holding power and the weight of handle 26 would cause the bolt head 12 to be retracted. However, when the temperature generated by the fire is sufficiently great, the fusible pin 44 melts and the lever 41 falls downwardly under gravity action and as may be supplemented by spring 46 until it engages abutment element 47. In this position, tab 48 on the end of lever 41 engages the rear face of bolt head 12 and thus prevents its retraction.
SECOND EMBODIMENT This embodiment which is illustrated in FIGS. 4, 5 and 6, is shown as mounted on door 9 the outer plate 10 and the inner plate of the lock set both of which have an opening for a bolt head 49 which is generally similar to bolt head 12. The plate 50 is secured to outer plate 10 in any preferred manner and secured to plate 50 and is a housing designated generally 51 comprising top wall 52, bottom wall 53 and side walls, one of which is shown at 54. Secured to bolt head 49 is a tail 55 formed with a slot 56 which receives a guide pin 57 mounted on wall structure 54. Tail 55 is formed with an end flange 58 which is engaged by one end of an expansion coil spring 59, the other end of which engages a spring abutment 60 mounted on wall structure 54. A handle 61 is drivably mounted on a shaft 62 which is pivoted on wall structure 54 and to which is also drivably connected an actuator 63, the upper end portion of which engages flange 58 on tail 55. Actuating member 63 is also formed with a projection 64 which is engaged by one end of a coil spring 65, the other end of which is secured to an anchor 66 secured to wall structure 54. The tendency of the springs 59 and is to bias the bolt head 49 into door closing position. As in the case of the embodiment of FIGS. 1, 2 and 3, the lock set mechanism above described is another type which is meeting with widespread use.
In accordance with the present invention, a latch bolt stop lever 67 is pivotally mounted on a pin 68 secured to wall structure 54. At the end remote from pivotal mounting 68, lever 67 is formed with a notch 69, a tab 70 on the upper side of the notch and an end portion 71 on the lower side. A fusible pin 72 is received in notch 69 and is secured to wall structure 54.
OPERATION OF SECOND EMBODIMENT Under normal conditions, latch bolt stop lever 67 assumes the horizontal position depicted in FIG. 4 in which end portion 71 is above and clear of bolt head 49 and does not interfere with movement thereof. Thus, handle 61 may be depressed to retract bolt head 49 against the influence of springs 59 and 65 or pennit it to be moved into door closing position by these springs.
Should a fire occur, the springs 59 and 65 might become annealed as above pointed out and lose their holding power. When the temperature generated by the fire becomes sufficiently high, pin 72 melts and latch bolt stop lever 67 swings downwardly under gravity action. This downward swinging movement is continued until tab 70 engages the upper surface of bolt head 49 in which position end portion 71 engages the rear face of bolt head 49 to positively inhibit retraction of the bolt head and maintain it in door closing position.
While preferred specific embodiments are herein disclosed, it is to be clearly understood that the invention is not to be limited to the exact constructions, mechanisms and materials illustrated and described because various modifications of these details may be provided in putting the invention into practice.
What is claimed is:
1. In a tire door lock set including a housing presenting a wall structure, a latch bolt having a bolt head presenting a top face and a rear face, spring means normally biasing said bolt head into door closing position and a handle pivotally mounted on the wall structure and operatively connected to the latch bolt to retract the same against the influence of said spring means, the improvement consisting of a lock set comprising:
a. a latch bolt stop lever pivotally mounted at one end on said vwall structure and having a notch atits 0. means for limiting downward swinging movement of said lever when said fusible pin melts.
2. The lock set of claim 1 in which the means for limiting downward swinging movement of the latch bolt stop lever consists of a tab formed on said lever and extending beyond said notch and which engages the upper face of the bolt head when the lever swings downwardly, and an end portion below said notch which engages the rear face of the bolt head after the lever has swung downwardly and reaches its lowermost position as determined by said tab.
3. The lock set of claim 1 in which the means for limiting downward swinging movement of the latch bolt stop lever consists of an abutment element mounted on the wall structure below the lever.
4. The lock set of claim 3 together with an optional torsion spring associated with the pivotal mounting of the latch bolt stop lever which biases the lever downwardly.
5. The lock set of claim 3 in which the latch bolt stop lever is formed with a tab below the notch which engages the rear face of the bolt head when the lever is in its lowermost position.
6. The lock set of claim 1 in which the fusible pin is of zinc or other suitable element or alloy of suitably low temperature melting characteristics.