1. Field of the Invention
The present invention relates generally to hinges and similar attachments. More specifically, the present hinge is configured particularly for use with a “drop down” oven door (although it is adaptable to other structures), and acts to release the door suddenly and rapidly from its fully open horizontal position in the event that an excessive load is placed upon the door. This function prevents tipping of the oven due to the door acting as a lever, and/or the use of the door as a step by a child to access the top of the stove.
2. Description of the Related Art
Most household ovens are constructed with a “drop down” oven door, i.e., the door is hinged along its lower edge or at the ends thereof. This allows articles, such as large pans, oven racks, etc., to be placed on the inner surface of the oven door when the door is fully lowered to its horizontal position as the article is moved into or from the oven proper, as in normal use of the oven. However, ovens and oven doors are also subject to abnormal use, i.e., an excessively high load being placed on the oven door. This may occur in the event of one or more toddlers or small children using the oven door as a step to reach for something on the range top of the stove. While this is by no means a proper use of the oven and door, it nevertheless may happen from time to time. A number of tragedies in which one or more small children have spilled hot liquids, oils, etc., on themselves from the range top of a stove have been documented in the past. Free-standing range/oven appliances are designed to be firmly anchored to the adjacent building structure, but anchors are often not installed, perhaps in the majority of oven installations. As a result, even if the door structure remains intact structurally, with no deformation or breakage, the entire oven may tip, causing articles atop the stove to slide forward.
As a result, ANSI (American National Standards Institute) and UL (Underwriters Laboratories) have developed standards for oven doors for both normal and abnormal use. The ANSI standard is Z21.1, directed to gas ranges, while UL standard 858 covers electric ovens and ranges. The normal test requires that the oven door support, without the oven tipping, a 75-pound load applied mid-span of an open oven door with a maximum of one-half inch deflection of the door at six inches from the hinge line of the door. This normal requirement assures that the door will support a normal load thereon, e.g., a large turkey or roast, etc., without the door or hinge structure bending and deflecting sufficiently to allow the load to slide off and drop to the floor. The loading for this test is well below that required by safety standards to prevent tipping of the oven or damage to the door structure, and in fact the normal use test requires that the door survive the test without breakage or damage.
The abnormal use test is intended to assure that the oven will remain upright when a load of up to 250 pounds is placed on the door, as when one or more toddlers or small children may open the door and use it as a step to access the top of the stove. In the abnormal use test, deformation, deflection, and breakage of the door, door hinge structure, attachment structure, etc., is permissible, so long as the door has passed the 75-pound load test for normal use. The primary concern here is that an article placed upon the cook top of the stove should not slide off the top of the stove due to tilting of the stove or oven during this test. The oven is, of course, firmly anchored to the underlying structure during the abnormal use test, with this test serving to check the anchoring system and overall rigidity of the oven structure.
However, it is recognized that a large number of ovens, likely the majority, are not properly anchored to the floor during installation, even where such anchoring is required by building codes. As a result, it is possible for an oven that passes the abnormal use test with the door and hinge structure intact to tip if a large load is placed upon the door. The tragedy that may result from this if small children climb upon the door and spill hot oil or other liquids upon themselves, or if the entire oven tips forward toward them to allow hot liquids to be dumped onto them from the range top surface, has been noted further above.
A number of different oven door hinge configurations have been developed in the past as a response to the above problem. In some cases, a supplemental spring(s) is used to allow the door to open past the horizontal when an excessive load is placed upon the door. However, due to the spring constant, the door will lower only slightly beyond the horizontal when a weight only slightly exceeding the predetermined maximum for the horizontal door, is placed thereon. Thus, no substantial deflection of the door from the horizontal is provided with such a configuration until a weight substantially greater than the predetermined maximum for the horizontal door is placed thereon. It is difficult to design a door using such a supplemental spring configuration which will remain undeflected from the horizontal while supporting a load of 75 pounds, and yet will allow the door to drop down significantly when a load only slightly greater, i.e., a toddler or small child, places his or her weight upon the door. Some oven doors are designed with a spherical fitting that pulls through a slot extending from a socket in order to widen the slot and spread the jaws when excessive load is placed upon the assembly. In this structure, the deformation of the slot permits a slow deflection of the door assembly well before the point is reached where the fitting separates from its attachment point.
There is a need for a hinge configuration for a “drop down” oven door having a hinge axis along its lower edge, in which the hinge configuration precludes any breakage or substantial deformation of the door and hinge structure in testing according to ANSI and UL standards of normal use. Moreover, the hinge configuration should provide a sudden failure mode, allowing the door to drop completely until its distal edge contacts the underlying surface, or the door is stopped in some other manner, when a single, simple, easily replaced part (which may be considered to be a “mechanical fuse”) fails at a predetermined load in abnormal use testing. The sudden failure mode must remain completely intact with no significant deflection until sufficient force is applied to cause the sudden and complete failure of the “mechanical fuse.”
Thus, a load limiting hinge solving the aforementioned problems is desired.
The load limiting hinge is used to attach a drop down door to the fixed structure of an oven or other appliance. The hinge is assembled upon a hinge post made from a rigid, substantially inelastic structure, a hinge post being bolted, riveted, welded, or otherwise immovably attached to the fixed structure of the oven on each side of the door opening. A hinge plate is secured to each hinge post, with the hinge plate providing attachment for the door arm. The hinge plate is normally fixed in position by a bolt or the like having a necked down cross section at one point, thereby providing a “weak link” in the assembly. This hinge plate securing bolt may be considered as a “mechanical fuse,” in that it operates much like an electrical fuse by allowing normal operation so long as loads do not exceed a predetermined value, but breaks or opens when the load exceeds that predetermined level.
At this point, the hinge plate pivots about its pivotal attachment point to the hinge post, allowing the door arm to drop the distal edge of the attached door to the underlying surface or other stop. The hinge plate has an arcuate slot therein with a narrower width at the distal end of the slot, thereby frictionally gripping the shank of a fastener captured within the slot as the hinge plate pivots after breakage of the attachment bolt. This prevents the door from swinging upwardly by means of the balance spring and slider mechanism incorporated therewith.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
The present invention is a load limiting door hinge that provides essentially rigid and undeformed extension of the door to which it is attached under normal loads and use, but permits the door to break away beyond its normally fully opened position in the event of an excessive load thereon. The weak link or “mechanical fuse” used to permit the door to break away under a predetermined load is quickly, easily, and inexpensively replaced in the event that it is broken. While the hinge may be adapted to a wide range of door attachments, it is particularly useful with “drop down” type oven doors and the like.
The hinge post 12 may be formed of a length of “angle iron” stock material, i.e., having a hinge plate attachment wall 18 (more clearly shown in
A generally flat, substantially rigid hinge plate 28 is formed of a relatively thick piece of strong metal in order to preclude any significant bending or deformation thereof when high loads are placed upon the hinge assembly 10. The hinge plate 28 includes a pivot attachment hole 30 and an arcuate pivot limit slot 32 formed therethrough, with the arc of the pivot limit slot 32 being defined by the pivot attachment hole 30. The hinge plate 28 also includes a mechanical fuse attachment lug 34 extending substantially normal to the main expanse of the plate 28, with a threaded mechanical fuse attachment hole 36 formed through the lug 34.
The plate 28 is secured to the hinge post 12 by a series of three fasteners, i.e., a hinge plate pivot fastener 38 which passes through a hinge plate pivot hole 40 formed through the hinge plate attachment wall 18 of the hinge post 12 and the pivot attachment hole 30 of the hinge plate 28; a hinge plate pivot limit fastener 42 which passes through the pivot limit slot 32 of the hinge plate 28 and through a hinge plate pivot limit fastener hole 44 formed through the hinge plate attachment wall 18 of the hinge post 12; and a threaded “weak link” or “mechanical fuse” 46, which passes through a hinge plate locking hole 48 formed through the hinge plate locking wall 20 of the hinge post 12 to thread into the mechanical fuse attachment hole 36 of the hinge plate 28. The pivot limit slot 32 and pivot limit fastener 42 combine to both guide and limit pivoting of the hinge plate 28 upon fracture of the fuse 46, as described below. The mechanical fuse 46 includes a head 50 positioned against the front or door arm extension side 22 of the hinge plate locking wall 20 of the hinge post 12, and a threaded shank 52 engaging the locking lug 34 of the hinge plate 28 in tension to grip the locking lug 34 securely against the hinge plate locking wall 20 of the hinge post 12 in normal operation of the hinge assembly 10.
An elongate, substantially rigid and inflexible door arm 54 has a hinge plate attachment end 56 with a hinge plate attachment hole 58 therethrough, through which a door arm pivot fastener 60 passes to secure the door arm 54 to the hinge plate 28 by means of a door arm attachment hole 62 formed through the hinge plate 28. The door arm 54 also includes a laterally offset slider bar attachment arm 64 with a slider bar attachment hole 66 therethrough. An elongate, substantially rigid and inflexible slider bar 68 includes a door arm attachment end 70 with a laterally offset door arm attachment lug 72 extending therefrom. The door arm attachment lug 72 has a door arm attachment hole 74 formed therethrough, with a door arm and slider bar connection fastener 76 passing through the slider bar attachment hole 66 of the door arm 54 and the door arm attachment hole 74 of the slider bar 68 to secure the door arm 54 to the slider bar 68.
The various fasteners used to assemble the hinge assembly 10, i.e., the hinge plate pivot fastener 38, hinge plate pivot limit fastener 42, door arm pivot fastener 60, and door arm to slider bar connection fastener 76, may comprise threaded bolts secured by corresponding conventional nuts, if so desired. However, the fasteners 38, 42, 60, and 76 are preferably rivets, as the shop heads of such rivets may be compressed to a relatively low height to provide greater clearance between the closely overlapping hinge plate 28, door arm 54, and slider bar 68, and the edges of the clearance slot 26 formed through the hinge plate locking wall 20 of the hinge post 12 and through which the hinge plate 28, door arm 54, and slider bar 68 at least partially pass.
The slider bar 68 and its tension spring 78 serve to counteract the weight of an open drop down door, weakly biasing the door to the closed position and thus facilitating lifting the door for closure. The slider bar 68 includes a laterally offset spring attachment arm 80 extending from the door arm attachment end 70, opposite the door arm attachment lug 72 thereof. The tension spring 78 includes a slider bar attachment arm hook 82 which secures about the spring attachment arm 80 of the slider bar, and an opposite hinge post attachment hook 84 which secures to the spring attachment end 16 of the hinge post 12. The spring 78 is in tension, urging the slider bar 68 toward the spring attachment end 16 of the hinge post 12, and thus drawing the slider bar attachment arm 64 of the door arm 54 downward to rotate the door arm 54 upwardly to its closed position, generally as shown in
The slider bar 68 may also include a hinge post contact end 86 having a protuberance extending therefrom, which slides upon the hinge plate attachment side or surface 24 of the hinge plate locking wall 20 of the hinge post 12 as the slider bar 68 moves when the door arm 54 swings open and closed. The protuberance also engages a detent 88 which is secured to the hinge post 12, thus lightly securing the door arm 54 (and door which is attached thereto) in a closed position. Opening the door (and thus pivoting the arm 54 away from the hinge post 12) pulls the protuberance at the hinge post contact end 86 of the slider bar 68 over the raised side of the detent 88, thereby allowing the door to open freely.
In
In
The mechanical fuse link 46 is configured to break at some predetermined load, as discussed in greater detail further below, but is sufficiently strong to hold the hinge plate 28 in its normal position as shown in
A 75-pound load, as used in checking for door deformation or damage in normal loading tests, is by safety standard requirements insufficient to cause even an unanchored standard size oven to tip. However, greater loads imposed upon the door may cause an unanchored oven to tip forward, or may produce sufficient stress to twist the structure and tilt the cook top of the oven and range slightly, even when the legs of the oven are anchored. The load limiting hinge 10 provides a solution to this problem by means of the mechanical fuse or weak link 46 which secures the hinge plate 28 in place on the hinge post 12, as shown in
The fastener 46 is properly termed a “mechanical fuse,” as it is analogous to a conventional electrical fuse. The mechanical fuse 46 completely transfers all normal loads thereacross, allowing the hinge assembly 10 to function normally. This is analogous to the operation of electrical fuses in electrical circuits. However, both the mechanical fuse 46 and conventional electrical fuses are specifically configured so that their respective mechanical or electrical force transmitting paths separate, or open, when the mechanical or electrical load reaches a certain predetermined limit. The electrical fuse opens by melting to protect the rest of the circuit, while the present mechanical fuse 46 breaks in tension to preclude damage to the rest of the structure.
When the moment exceeds a certain predetermined load, the mechanical fuse 46 will fracture in tension, thus allowing the hinge plate 28 to swivel or pivot about its hinge plate pivot fastener 38, generally as shown in
The configuration of the load limiting hinge 10 positions the head 50 of the frangible fastener 46 to the front surface of the oven or other structure in which the hinge 10 is installed, i.e., immediately adjacent the hinge line of the door extending from the door arm 54. Thus, the broken fastener or mechanical fuse is readily accessible and easily removed and replaced when required. One need only remove the head 50 from its position at the hinge plate locking hole (
Preferably, the shank 52 of the mechanical fuse 46 is configured to facilitate removal, as in some of the examples shown in
It will also be noted that the circumferential groove 92c of the mechanical fuse 46c has a square cross section. The intent here is to show that virtually any cross sectional shape may be used to form the circumferential groove, as desired. For that matter, virtually any head configuration may be used as desired, e.g., flat heads for use in countersunk holes, etc. The three mechanical fuse fasteners 46a through 46c illustrated in
It is envisioned that most such mechanical fuse fasteners would be formed of a high strength ferrous metal of some sort, e.g., steel. This would allow the internal wrenching socket to be formed to have a reasonable internal diameter, without unduly increasing the external diameter of the threaded shank portion of the fastener. However, softer and less durable metals may be used, so long as consideration is given for their tensile strengths and the cross-sectional areas of the material between their circumferential grooves and internal sockets (if any). For that matter, such mechanical fuses could be formed of plastic materials, if desired, so long as their sizes are adjusted in accordance with the tensile strength required. However, it is envisioned that metals, and particularly relatively brittle metals, are the preferred materials for such fasteners, due to the sudden failure mode of such materials with little or no elongation (and therefore little or no deflection of the door arm and door) prior to failure.
In conclusion, the load limiting hinge of the present invention provides a much improved means of providing safety for small children and others who may misuse an appliance, such as an oven or the like. It should be noted that the load limiting hinge is adaptable for use in a number of different environments and installations and is particularly suitable for use in appliances with drop down doors, e.g., clothes dryers and ovens. The load limiting hinge is particularly valuable in oven installations, due to: (1) the suitability of the hinge configuration for use in relatively heavy oven doors; and (2) the potential hazard of spillage of heated materials from the cook top of the oven. The load limiting hinge provides a release of the oven door from the horizontal before excessive weight may be applied thereto, thereby precluding tipping of an unanchored oven and/or access to the cook top by a small child by using the open, horizontal oven door. The hinge is economical to manufacture and install, requiring little more in the manner of parts and labor than conventional hinges. The mechanical fuse of the present hinge is also easily replaced when broken, particularly where internally wrenched fasteners are used. Thus, the load limiting hinge will prove to be an extremely valuable component in the ovens and similar appliances of most appliance manufacturers, potentially saving vast amounts when the potential liability problems of existing conventional hinges are considered.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
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