Abstract:
A mechanical seat recline lock mechanism that employs a lead screw device to backdrive a nut and disk. The disk is held in place by a spring-loaded friction pin when motion needs to be constrained. The rotating disk can be oiled or greased to provide damping action.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       COPYRIGHTED MATERIAL  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a lock mechanism for controlling seat recline function for passenger comfort. More specifically, the invention relates to a lock mechanism for controlling seat recline function that provides nearly infinite position options and incorporates integrated damping.  
         [0005]     2. Related Art  
         [0006]     The recline function for seat backs in the aircraft and automotive industry has been a standard for many years. The two industries have approached the solution from different perspectives. The automotive industry has traditionally used a mechanical locking device that positively locks the seat back into a position by means of a spring and gear type engagement. This arrangement is adequate for the normal automotive application where the seat back is not adjusted very many times over the life of the product. However, it does not allow for positive engagement until the teeth are properly aligned, and therefore, results in substantial wear due to the high forces encountered when the teeth are forced to engage.  
         [0007]     The aircraft industry has a different need due to a different use profile. An aircraft seat recline function is activated at least twice per flight (take-off and landing) and potentially several times in flight with meals, reading, sleeping, etc. The solution implemented approximately 40 years ago was a hydraulic cylinder with a bypass port controlled by a lever. The cylinder piston separates two oil-filled chambers connected by a valve that allows oil to pass when activated, thereby allowing motion of the piston shaft. This arrangement has many attractive features, including nearly infinite hold power, motion damping, and a small package. However, it also has disadvantages such as a propensity for leaks (internal and external), relatively heavy weight, and high cost. Aircraft-type hydraulic systems tend to leak because they are based on pressurized hydraulic fluid with tight tolerances (typical of hydraulic systems) on the internal dimensions to operate properly. Once these tolerances begin to wear, the performance of the device deteriorates rapidly.  
         [0008]     It is to the solution of these and other problems that the present invention is directed.  
       SUMMARY OF THE INVENTION  
       [0009]     It is accordingly a primary object of the present invention to provide a seat recline lock mechanism that is mechanical and has infinite adjustability.  
         [0010]     It is another object of the present invention to provide a seat recline lock mechanism that is mechanical and has integral damping.  
         [0011]     It is another object of the present invention to provide a seat recline lock mechanism that is mechanical and has a long life.  
         [0012]     It is still another object of the present invention to provide a seat recline lock mechanism is mechanical and that does not leak.  
         [0013]     It is still another object of the present invention to provide a seat recline lock mechanism is mechanical and light in weight.  
         [0014]     These and other objects are achieved by a mechanical seat recline lock mechanism that employs a lead screw device to backdrive a nut and disk. The disk is held in place by a spring-loaded friction pin when motion needs to be constrained. The rotating disk can be oiled or greased to provide damping action.  
         [0015]     Unlike prior art mechanical devices, the mechanical seat recline lock mechanism in accordance with the present invention is its infinite adjustability, integral damping, and longer life. In contrast to prior art hydraulic systems, the mechanical seat recline lock mechanism in accordance with the present invention does not leak and has a lighter weight.  
         [0016]     Other objects, features, and advantages of the present invention will be apparent to those skilled in the art upon a reading of this specification including the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which:  
         [0018]      FIG. 1  is a perspective view of a seat recline lock mechanism in accordance with the present invention.  
         [0019]      FIG. 2  is a side elevational view of the seat recline lock mechanism of  FIG. 1 .  
         [0020]      FIG. 2A  is a partial side elevational view of an alternative head configuration of the lead screw as shown in  FIG. 2 .  
         [0021]      FIG. 3  is a cross-sectional view of the seat recline lock mechanism as shown in  FIG. 2 .  
         [0022]      FIG. 4  is an exploded perspective view of the seat recline lock mechanism of  FIG. 1 .  
         [0023]      FIG. 5  is a front view of the seat recline lock mechanism of  FIG. 1 .  
         [0024]      FIG. 6  is a back view of the seat recline lock mechanism of  FIG. 1 .  
         [0025]      FIG. 7  is a perspective view of a first type of seat in which the mechanical seat recline lock mechanism of the present invention is mounted, with the seat back in the upright position.  
         [0026]      FIG. 8  is an enlarged, partial perspective view of the mounting of the mechanical seat recline lock mechanism as shown in  FIG. 7 .  
         [0027]      FIG. 9  is a side elevational view of a second type of seat in which the mechanical seat recline lock mechanism of the present invention is mounted, with the seat back in the upright position.  
         [0028]      FIG. 10  is a side elevational view of the seat and mechanical seat recline lock mechanism of  FIG. 9 , with the seat back in a reclining position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.  
         [0030]     Referring now to  FIGS. 1-6 , the mechanical seat recline lock mechanism  100  in accordance with the present invention comprises an externally-threaded lead screw  10  having a shaft  10   a  and a head  10   b , an internally-threaded lead screw nut  20  threadably engaging the lead screw  10 , and an annular brake disk  30  concentric with and matingly engaging the perimeter of the lead screw nut  20 . The head  10   b  provides an interface to the seat. The specific configuration of the head  10   b  depends upon the specifics of the interface, and is not considered to be a novel feature of the present invention. An alternative configuration of the head  10   b  is shown in  FIG. 2A .  
         [0031]     An annular bearing  40  comprising an annular race  40   a  with a plurality of ball bearings  40   b  is positioned on either side of the brake disk  30 . A housing  50  is configured with a housing inner cavity that encases the lead screw nut  20 , the brake disk  30 , and the bearings  40 , the housing inner cavity being sized to provide a small clearance between the brake disk  30  and the housing  50 , into which oil is introduced during the assembly process, for a purpose to be described hereinafter. In order to prevent leakage of the oil from between the two parts  50   a  and  50   b , a gasket or O-ring  60  can be provided between the two parts  50   a  and  50   b.    
         [0032]     The bearings  40  perform two functions, (1) constraining the lead screw nut  20  to the housing  50  against axial forces applied to the lead screw  10 , and (2) providing low friction radial support of the lead screw nut  20  to the housing  50 .  
         [0033]     The housing  50  can be formed in two parts, a first part  50   a  and a second part  50   b , for ease in manufacture and assembly. The first and second parts  50   a  and  50   b  define the housing inner cavity that receives the lead screw nut  20 , the brake disk  30 , and the bearing races. In order to reduce the weight of the housing  50 , grooves  52  can be formed in the outer face of the first part  50   a . Strengthening ribs  54  are formed on the outer face of the second part  50   b . Because the housing  50  is formed of a lightweight material (examples of which include, but are not limited to aluminum, titanium, magnesium, and plastic), the ribs  54  strengthen the housing  50  when the mechanism  100  is locked and constraining linear forces. As will be appreciated by those of skill in the art, other means besides the ribs  54  can be used to address mechanical loads.  
         [0034]     An actuation lever  70  is pivotably mounted to the outer face of the first part  50   a  of the housing  50  (via, for example, a pin  72 ) so as to define a fulcrum  70   a  (which is coincident with the longitudinal axis of the pin  72 ), an effort arm  70   b , and a resistance arm  70   c . A spring  80  is connected at one of its ends to the effort arm  70   b  of the actuation lever  70  and at the other of its ends is seated in an aperture  56  in the outer face of the first part  50   a  of the housing  50  to bias the effort arm  70   b  away from the housing  50 , and thus to bias the resistance arm  70   c  towards the housing  50  and the brake disk  30 . A resistance pin  90  is inserted into and extends through an aperture  58  in the first part  50   a  of the housing  50  between the resistance arm  70   c  of the actuation lever  70  and the brake disk  30 , so as to contact the brake disk  30  at its outer circumference.  
         [0035]     The primary mechanical support is concentrated in the shaft  10   b  and highly concentrated in the housing  50 . The lead screw  10  is used to back drive the nut  20 , which in turn rotates the disk  30 . The disk  30  is captured between the two halves of the housing  50  with a small clearance. The oil in the clearance between the housing  50  and the disk  30  acts on the disk  30  in shear to provide a damping action. The pin  90 , which has force from the spring  80  applied through the actuation lever  70 , contacts the brake disk  30  so as to prevent its rotation, providing the locking action. When the effort arm  70   b  of the actuation lever  70  is moved towards the housing  50 , either directly or through a cable, the force is removed from the pin  90 , which allows the disk  30  to rotate, and therefore, allows the shaft  10   b  of the lead screw  10  to move linearly through the seat recline lock mechanism  100 , and more particularly, through the lead screw nut  20 .  
         [0036]     Referring now to  FIGS. 7 and 8 , there is shown a first type of seat  200  in which the mechanical seat recline lock mechanism  100  of the present invention is mounted. The seat  200  comprises a seat pan  210 , a seat pan frame  212  extending from the back of the seat pan  210 , a seat back  220 , and a seat back frame  222  extending from the bottom of the seat back  220 , the seat back frame  222  being pivotably mounted to the seat pan frame  212  to permit the seat back  220  to recline relative to the seat pan  210 . The housing  50  of the mechanical seat recline lock mechanism  100  is fixedly mounted to a bracket  214  extending downwardly from the bottom of the seat pan  210 , while the head  10   b  of the lead screw  10  threadably engages a bracket  224  fixedly mounted to the seat back frame  222 . The brackets  214  and  224  are positioned along one side of the seat  200  so that the mechanical seat recline lock mechanism  100  is easily accessible to the person sitting in the seat  200 . Operation of the mechanical seat recline lock mechanism  100  results in reclining motion of the seat back  220  as indicated by the arrow A 1 .  
         [0037]     Referring now to  FIGS. 9 and 10 , there is shown a second type of seat  200 ′ in which the mechanical seat recline lock mechanism  100  of the present invention is mounted. The seat  200 ′ comprises a seat pan  210 , a seat pan frame  212 ′ extending from the back of the seat pan  210 , a seat back  220 , and a seat back frame  222 ′ extending from the bottom of the seat back  220 . The seat pan  210  is slidably mounted in fixed left and right tracks  230  via front and back rollers  240   a  and  240   b , and the seat back frame  222  is pivotably mounted to the seat pan frame  212  in alignment with the back rollers  240   b . A pair of struts  250  on either side of the seat  200 ′ are pivotably connected at one end to the seat back  220  and at the other end to the back ends of the tracks  230 . The left and right tracks  230  are themselves mounted to a fixed base  250 . The housing  50  of the mechanical seat recline lock mechanism  100  is fixedly mounted to a bracket  214  extending downwardly from the bottom of the seat pan  210 , while the head  10   b  of the lead screw  10  threadably engages a bracket  264  fixedly mounted to the base  260 . As with the first type of seat  200 , the brackets  214  and  264  are positioned along one side of the seat  200 ′ so that the mechanical seat recline lock mechanism  100  is easily accessible to the person sitting in the seat  200 ′. Operation of the mechanical seat recline lock mechanism  100  results both in reclining motion of the seat back  220  as indicated by the arrow A 1  and forward and backward motion of the seat pan  210  as indicated by the arrow A 2 .  
         [0038]     The basic principles upon which the seat recline lock mechanism  100  is constructed allow it to be designed and built with: (1) any variation of gear reduction between the lead screw  10  and the lead screw nut  20 , as long as it can be back driven; (2) any multiple of brake disks  30  and spring  80 /lever  70  combinations to provide normal forces and friction adequate to hold the brake disk  30 , and thereby hold the nut  20  to which it is matingly engaged, from rotating; (3) any viscosity of oil to vary damping characteristics; (4) a barrel type configurations for the housing  50  for lower profile construction; and (5) any means that can replace the lead screw  10 /lead screw nut  20  combination to transform motion from linear to rotational, including, but not limited to spur gears, rack and pinion gears, planetary gear set, and chain and sprockets, all of which are also capable of being back driven.  
         [0039]     Because the seat recline lock mechanism  100  is a friction-based device, there are no gear teeth to wear away, and there is no harsh “locking” action. The seat recline lock mechanism  100  also provides infinite adjustability, as well as integrated damping due to shear of the oil in the lock mechanism acting on the disk  30 .  
         [0040]     Further, the seat recline lock mechanism  100  is not under pressure or required to constrain oil under pressure, thereby preventing the occurrence of leaks. The internal tolerances are much less critical than in a hydraulic system. It weighs less than a conventional hydraulic lock system because it only requires a few drops of oil compared to approximately 100 mL in the conventional hydraulic lock system.  
         [0041]     Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.