LATCHING ASSEMBLY

Abstract: A latching assembly comprising first and second mechanically engageable latch members (14, 24), biasing means (60, 62) for causing the latch members (14, 24) to assume a disengaged position, a permanent magnet (50) for overcoming the force of the biasing means, the permanent magnet (50) being isolated from the latch members (14, 24) when the latch members (14, 24) are in an engaged position, and an electromagnet (46) having a polarity when energized opposing the permanent magnet (50) for overcoming the force thereof and thereby permitting the biasing means (60, 62) to cause the latch members (14, 24) to assume the disengaged, unlatched position. The assembly is also designed so that the biasing means (60, 62) and the electromagnet (46) are isolated from the latch members (14, 24) when the latch members (14, 24) are in an engaged position.

Description: Latching Assembly Technical Field The invention relates to the field of latching assembli and, in particular, to latching assemblies utilizing permanent magnets and electromagnets in the operation thereof. Background Art Latching assemblies, and in particular magnetic latchin assemblies, are in widespread use in modern aircraft for latching doors or closure panels on compartments containin oxygen equipment and masks and other emergency supplies fo the passengers. In such magnetic latching assemblies, a permanent magnet is employed in maintaining the door in a closed or latched position and an electromagnet is used to cause the door to open or become in an unlatched position. Normally, the unlatching is accomplished by actuation of t electromagnet by the pilot of the aircraft. It has been found, however, that due to certain loading forces on the doors, the latching assemblies will either refuse to open when they are commanded to do so or will open automaticall when they are not supposed to. These loading forces consi of flight loads due to twists of the airplane, vibration frequencies of different resonances between two mating parts, handling forces due to human causes, and gravitational loads caused by rapid aircraft acceleration deceleration. A latching assembly designed to overcome the above problems is shown in U.S. Patent No. 3,635,511, entitled "Latching Assembly with Magnetic Latching", issued to H. A Waller. In Waller, a first latching subassembly, includin an electromagnet, is fastened to the inside surface of a compartment doorjamb and a second latching subassembly, including a latch lever and a permanent magnet latch bar ' mounted on the latch lever, is mounted adjacent the upper edge of the inside surface of the compartment door. When the latching assembly is closed, the permanent magnet mechanically engages the pole pieces of the first latchin assembly and stays in position due to the magnetic attraction between itself and the metallic first latching assembly. Upon actuation of the electromagnet, the magne and the latch to which it is coupled is repelled from the mechanical engagement and pivots out of latching position assisted by a spring. Thus, the permanent magnet both maintains or holds the latched position and acts as the mechanical latching engagement, until repelled by the electromagnet. Another latching assembly is shown in U.S. Patent No. 3,860,277, entitled "Latching Assembly with Magnet Locking", issued to W. S. Wang. In a first embodiment of Wang, an electromagnet is positioned on the inside surface of a compartment top wall. A first latchi lever, having a permanent magnet thereon, is pivotally mounted adjacent the electromagnet and coupled to the top wall. A second latch lever is mounted on a door and is biased open by a spring. The latch levers are held in mechanical engagement by the permanent magnet against the force of the bias spring. Upon activation of the electromagnet, the permanent magnet is repelled, causing latch levers to unlatch. In a second embodiment, a spherical latch member or ball is held in mechanical engagement by a circumferentially spaced array of latch balls which are operable to engage the spherical latch member. A latch plunger which causes the latch balls to engage the spherical latch member is biased to a rearward unlatched position by a coil spring. The plunger is normally maintained in a forward latched position by mean of a permanent magnet mounted on the plunger which attrac the poles of an electromagnet and overcomes the bias of t coil spring and a C-shaped spring which normally causes th latch balls to be in an expanded state. When the ' electromagnet is actuated, the force of the permanent magn is overcome and the bias spring allows the latching assemb to unlatch. Severe difficulties exist, however, with the latching assemblies of the above configurations. The door lever in Waller is directly loaded by the permanent magnet engaging the detent of the pole piece, causing a critical interface where the latch members meet with difficult tolerance controls. The inner latch members of Wang are also direct loaded by the permanent magnet, particularly in the first embodiment, again causing a critical interface where the latch members meet with difficult tolerance controls. It apparent that poor quality control of the interfaces would inevitably lead to premature unlatching due to forces on t magnet or to lock-up due to excessive friction. In addition, in the second embodiment of Wang, any door loadi would cause the spherical latch member to jam up against t latch balls and the latch plunger and prevent the electromagnet from unlatching the door since the bias spri is not strong enough to overcome the frictional forces between the spherical latch member, the latch balls and th latch plunger. Furthermore, any other types of loads on t door are directly transmitted to the permanent magnet, thereby increasing the probability of premature unlatching Accordingly, it is a general object of the present invention to provide an improved latching assembly. It is another object of the present invention to provid a latching assembly employing a permanent magnet which is not susceptible to premature unlatching or to lock-ups. CMP! ^*£? 1 It is a further object of the present invention to 2 provide a latching assembly which does not have critical 3 interfaces. 4 5 It is still another object of the present invention to 6 provide a latching assembly employing a permanent magnet i ^ which the permanent magnet is disassociated from the ° latch members. 9 ■ L Q Disclosure of Invention 11 12 A latching assembly is provided. The latching assembl 13 comprises first and second mechanically engageable latch 1 members, biasing means for causing the latch members to 15 assume a disengaged position, a permanent magnet for 16 overcoming the force of the biasing means, the permanent 17 magnet being isolated from the latch members when the lat 18 members are in an engaged position, and an electromagnet 19 having a polarity when energized opposing the permanent 0 magnet for overcoming the force thereof and thereby 2 1 permitting the biasing means to cause the latch members t 2 assume the disengaged, unlatched position. The assembly also designed so that the biasing means and the 24 electromagnet are isolated from the latch members when th 2 5 latch members are in an engaged position. 26 7 The novel features which are believed to be 2 8 characteristic of the invention, both as to its organizat 29 and its method of operation, together with further object 30 and advantages thereof, will be better understood from th 31 following description in connection with the accompanying 32 drawings in which a presently preferred embodiment of the 33 invention is illustrated by way of example. It is to be 34 expressly understood, however, that the drawings are for 35 purposes of illustration and description only and are not 36 intended as a definition of the limits of the invention. ^i llE OMPI /fa WIPO Brief Description of Drawings * Fig. 1 is a cut-away view of a compartment showing the latching assembly of the present invention; Fig. 2 is an perspective view of the latching assembly of the present invention; Fig. 3 is an exploded view of the latching assembly of Fig. 2; Fig. 4 is a cross-sectional view take along the lines 4-4 of Fig. 2; and Fig. 5 is a perspective view of a second embodiment of the latching assembly of th present invention. Best Mode for Carrying Out the Invention In Fig. 1 a cut-away view of a compartment showing the latching assembly of the present invention is illustrated. The compartment 10 has a door 12 that has mounted on it a latch lever 14. The door 12 pivots around point 16 and is spring loaded to a open position by spring 18. The compartment 10 has a doorjamb 20 upon which is mounted a latch assembly 22 containing a latch lever 24 which engage latch lever 14 to maintain the door 12 in a closed positio Referring now to Figs. 2, 3 and 4, a perspective, exploded and cross-sectional view of the latch assembly 22 is illustrated. The latch assembly 22 has a housing 26 which surrounds the latch assembly 22 except in a portion thereof through which the latch lever 24 extends. The lat lever 24 is pivotally mounted on hinge points 25, 27 on an armature shaft 28 and is assisted in engaging the latch lever 14 by a bias spring 30 also mounted on the armature shaft 28. The latch lever 24 also includes a roller, shaf 32 which supports a roller 34 which engages the latch lev 14. The armature shaft 28 is supported by a pair of electromagnet pole pieces 36, 38 which also support a iron core 40 and a coil 42 surrounding the iron core 40. The pole pieces 36, 38 are fastened through holes 44 to the doo jamb 20. The combination of pole pieces 36, 38, core and coil 42 comprise the electromagnet, designated by 3 ' numeral 46, which causes the latch levers 14, 24 to become 4 disengaged. An armature support 48 is also pivotally 5 mounted on hinge points 45, 47 on the armature shaft 28 e which supports a permanent magnet 50 and a pair of pole " 7 pieces 52, 54. A nut strip 56 is used in conjunction with 8 screws 58 and armature support 48 to contain the permanent 9 magnet 50 and the pole pieces 52, 54 in an intimate 0 supported relationship. Finally, a pair of bias springs 6 1 62 are mounted on the armature shaft 28 and are coupled t 2 the armature support 48 to urge it toward the latch lever 3 24. 4 5 in operation, when the door 12 is in the open position, 6 the latch lever 24 is manually depressed in the direction 7 the pole pieces 36, 38 and consequently urges the armatur 8 support 48 towards the pole pieces 36, 38 until the pole 9 pieces 52, 54 of the permanent magnet 50 come into contac 0 with the pole pieces 36, 38 and magnetically hold the 1 armature support 48 in position against the opposing forc 2 of the springs 60, 62. The door 12 is then closed, with 3 bias spring 30 assisting the latch lever 24 to engage the 4 latch lever 14. It should be noted that the bias spring 5 does not keep the door 12 closed or the latch levers 14, 6 together but only facilitates their engagement. The latc 7 levers 14, 24 are kept in engagement mainly by the weight 8 the door 12, the force of the door spring 18, the weight 9 the contents pressing on the door 12, and the weight of t 30 latch lever 14 on the door 12. The bias spring 30 is, 31 however, useful for maintaining the engagement of the lat 32 levers 14, 24 in the event of negative G forces. When it 33 desired to unlatch the door 12, the electromagnet 46 is • 34 actuated through wires 64 and, being of an opposing polar 35 to the permanent magnet 50, causes the pole pieces 36, 38 36 overcome the attractive force of the pole pieces 52, 54 caused by the permanent magnet 50. Since the magnetic attractive force is substantially nullified, the bias ' springs 60, 62 cause the armature support 48 to pivot against the latch lever 24 and disengage it from the latch lever 14. In a particular embodiment, the magnet 50 was designed to assert 7-10 pounds of attractive force, the bi springs 60, 62 were designed to assert 2-3 pounds of opposing force, while the electromagnet 46 was designed to reduce the attractive force of the magnet 50 to approximately .2 pounds. Thus even before the electromagn 46 substantially nullified the force of the magnet 50, the bias springs 60, 62 would cause the armature support 48 to pivot towards the latch lever 24 and disengage the latch levers 14, 24. If desired, the electromagnet 46 could be designed to generate a net repulsive force on the pole pieces 52, 54 of the permanent magnet 50. In the particul embodiment, the magnet 50 consisted of samarium-cobalt and the minimum voltage applied to the coil 42 needed to cause the armature support 48 to rotate was 15.3 volts, with 23 volts being generally available in airplane circuitry. Th bias spring 30 was designed to provided .25 pounds of retu force for the latch lever 24. It is thus seen that in the present invention, although the latching assembly is extremely compact, the permanent magnet is totally disassociated from the latch members and that the latching engagement is provided merely by the interaction of the latch levers 14, 24, with some assist being provided, when desired, from bias spring 30. Thus t actual mechanical engagement of the latch levers 14, 24 ca be optimized independently of the electromagnetic circuit used for disengaging the latch assembly. In a like manner the permanent magnet 50 and its associated pole pieces 52, 54 can be designed in conjunction with the electromagnet 4 and its associated pole pieces 36, 38 and the bias springs 60, 62 to optimize the holding force of the permanent magnet 50 so that the door 12 will not become unlatched until the combination of the opposing forces of the electromagnet 46 and the bias springs 60, 62 actually causes the door 12 to become unlatched and rotate into the open position. This total disassociation of the magnet 50 from the latch levers 14, 24 reduces significantly the problems of critical interfaces, frictional lock-up engagements and premature unlatching. in Fig. 5, a second embodiment of the latching assembly of the present invention is illustrated. In this embodi- ment, the armature 48' is shown having one center hinge point 66 instead of two outer hinge points 45, 47 as shown in Fig. 2. The attachment of the armature support 48' to the armature shaft 28 by a single center hinge point 66 allows the armature 48' to flex and thus allows the pole pieces 52, 54 to better align with the pole pieces 36, 38, thereby reducing the size of the permanent magnet 50 neede to overcome the force of the bias springs 60, 62. As show in Fig. 5, latch lever 24' has been reconfigured to have i hinge points 25', 27* astride the center hinge point 66 of armature 48' and to have two bias springs 30', 30". Having thus described the invention, it is obvious that numerous modifications and departures may by made by those skilled in the art; thus, the invention is to be construed to be limited only by the spirit and scope of the appended claims. Industrial Applicability The latching assembly is useful for latching doors or closure panels on aircraft compartments. "gJRE O P /fa WIP &NA

Claims: Claims 1. A latching assembly comprising: ' first and second mechanically engageable latch membe biasing means adapted to cause said latch members to assume a disengaged position; permanent magnet means adapted to overcome the force said biasing means, said permanent magnet means being isolated from said latch members when sai latch members are in an engaged position; and electromagnet means having a polarity when energized opposing said permanent magnet means for overcoming the force thereof and thereby permitting said biasing means to cause said latc members to assume said disengaged, unlatched position. 2. The latching assembly of Claim 1 wherein said biasing means is isolated from said latch members when said latch members are in an engaged position. 3. The latching assembly of Claim 1 wherein said electromagnet means is isolated from said latch membe when said ' latch members are in an engaged position. 4. The latching assembly of Claim 1 further comprising second biasing means for assisting said latch members to assume said engaged position. 5. The latching assembly of Claim 1 wherein said first latch member is fixedly coupled to a door member. 6. The latching assembly of Claim 1 wherein said first latch member is coupled to a door member and said second latch member is rotatably coupled to a doorjamb member 1 7. The latching assembly of Claim 6 wherein said permane 2 magnet means is rotatably coupled to said doorjamb 3 * member and said biasing means rotatably urges said 4 permanent magnet means toward said second latch membe 5 to cause said latch members to assume said disengaged 6 position. * 7 8 8. The latching assembly of Claim 7 wherein said 9 electromagnet means includes spaced pole piece means 0 coupled to said doorjamb means. 1 2 9. The latching assembly of Claim 8 wherein said permane 3 magnet means includes pole piece means coupling said 4 permanent magnet means therebetween, said pole piece 5 means being configured to engage said pole piece mean 6 of said electromagnet means. 7 8 10. The latching assembly of Claim 7 further comprising 9 shaft means coupled to said doorjamb means and 0 rotatably supporting said second latch member and sai 1 permanent magnet means. 2 3 11. The latching assembly of Claim 10 wherein said shaft 4 means supports said biasing means in engagement with 5 said permanent magnet means. 6 7 12. The latching assembly of Claim 10 wherein said 8 electromagnet means includes spaced pole piece means 29 coupled to said doorjamb means, said pole piece means 30 being adapted to support said shaft means. 31 32 13. The latching assemble of Claim 12 wherein said spaced 33 pole piece means contains therebetween elongated core 34 means and annular coil means mounted thereon. 35 36 _ 5fE OMP 14. The latching assembly of Claim 10 wherein said shaft means supports a second biasing means for assisting ' said latch members to assume said engaged position, said second biasing means being supported in engagem with said second latch member. 15. The latching assembly of Claim 1 wherein said second latch member includes roller means adapted to engage said first latch member. 16. The latching assembly of Claim 1 wherein said electromagnet means is configured to repel said permanent magnet means.

Inventors: LEVINE HAROLD HENRY, LEVINE, HAROLD, HENRY
Applicants: LOCKHEED CORP, LOCKHEED CORPORATION
Application year: 1982
Main classification: E05B47
IPC codes: E05B47