Abstract:
A value engineered latch system for latching and unlatching closures in plurality of stages namely fully open, partially open and fully closed comprising: a spring comprising of a metal rod with plurality of wound segments, bent segments and free ends; a metal striker comprising of profiled edges and slots that interact with said spring; a self presenting secondary release system actuated by the movement of the said spring; a base plate that supports the said spring and the said self presenting secondary release system.

Description:
BACKGROUND 
       [0001]    This invention uses the transmission of my provisional patent application 61/124,103 at the USPTO filed on Apr. 13, 2008. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to automotive latch system for closures such as hood, doors, deck lids, etc. 
       DISCUSSION OF PRIOR ART 
       [0003]    Today&#39;s automobile latch systems can be identified as, based on their basic principles of operation, ratchet, pawl, and striker rod type system and pin and catch system. These systems of latches pertaining to doors and hoods are capable of operating or required to operate in two stages. For example a hood latch operates in two stages where at the first stage the latch is released from the inside of the vehicle and at the second stage the latch is released from the outside. Generally there are two systems namely primary latch and secondary latch. These two systems may be completely independent of each other or they may share a few parts but still operate independently. 
         [0004]      FIG. 1  shows a typical ratchet pawl system where a striker  104  is attached to an automobile hood  107 . The ratchet  100  and pawl  101  are held in biased positions by ratchet spring  108  and the pawl spring  109 . The picture also shows a secondary latch  103 . The primary and the secondary latches are assembled together and installed over a cross member in front of the vehicle. The ratchet pawl system works on the basis that a striker rod gets trapped by a ratchet that is held in place by pawl. Both the ratchet and pawl are attached to springs. The spring attached to the ratchet, sometimes referred to as primary spring, provides the force required to lift the hood from its fully closed position. The ratchet pawl type primary latch has certain short comings. When the hood is being closed the striker rod first comes in contact with the ratchet and it has to overcome the high force exerted by the spring attached to the ratchet to actuate the ratchet to its final position. This excessive impact force exerted by the striker on the primary latch assembly makes the support system for the primary latch to be very robust. Such robustness can only be achieved by adding more components to the primary latch system. The hood inner that supports the striker needs to be reinforced with additional components. Yet another short coming of the ratchet pawl system is that the primary latch assembly, sometimes, is interfering with the hood inner and therefore a pocket has to be created in the hood inner. The pocket has to be reinforced with additional material. The other short coming of the ratchet pawl type that it requires the primary latch to be installed only a vertical surface. The vehicle components such as the radiator cross member needs to modified to create a vertical wall. If the modification is not feasible a new support structure is added to provide the support. In either case, making the support structure robust has cost and weight penalties. Yet another setback of the ratchet pawl system is the failure of the system when the ratchet becomes inoperable due to rusting or high friction due to surface quality deterioration of the sliding components. So the system needs lubrication and rust prevention. It has been established that the primary latch failure has been one of the major warranty recalls of many automakers in the past. A stuck pawl will prevent latching while a stuck ratchet will prevent opening. Yet another setback is that the striker rod and the ratchet have to align precisely for the proper operation. Misalignment at the assembly plant is one of the big problems in the automotive assembly lines. Special teams are deployed to fight misalignment in the primary latch system which adds cost. Yet another disadvantage of the ratchet pawl system is hood fluttering. Once the ratchet is locked in place by the pawl the striker rod can move within the ratchet. This causes the hood, which supports the striker, to flutter. Additional spring and components are added to overcome the hood fluttering. The main advantage of the ratchet pawl system that is aligned properly ensures positive engagement between the striker rod and ratchet provided the pawl is not stuck in open position. Yet another disadvantage when the primary and the secondary latches share components is that the combined system has to be very close to the edge of the hood so that the secondary system can be opened by manual operation. If the system cannot be packaged close to the front edge of the hood a self presenting secondary release lever has to be added to the system, which increases cost, weight and complexity. Yet another disadvantage of the ratchet, pawl and striker type latch relates to its ability to allow the hood to move down or displace during a collision with a pedestrian whose head impacts the hood&#39;s front zone. 
         [0005]    A pin type primary latch is shown in  FIG. 2 . A pin encased in a shell is held down by a spring. When the pin assembly  201  descends into the receiving chamber  202  a sliding plate with a spring assembly  203  traps the pin. The pin is release from the sliding plate when it is pulled away from the pin with a cable. As far as the pin or bolt type primary latch is concerned it does not encounter the excessive force faced by the ratchet pawl type latch. But the main set back in this system is that it fails to engage if the parts start binding either due to lack of lubrication or surface deterioration of sliding members. The other setback is that the alignment between the bolt and the receiving unit has limited tolerance for variation. The bolt may break or damage the latch if there is misalignment. The other setback is that the primary and secondary systems cannot be combined as effectively as ratchet pawl type since there are no common parts between the two. 
         [0006]    A type of latch that is close to the present invention is shown in  FIG. 3 . A spring  301  whose leg engages in to a slot in striker  302  retains it. But the feature of positive engagement is lacking. 
       OBJECTS AND ADVANTAGES 
       [0007]    Accordingly, several objects and advantages of my invention are: 
         [0008]    a. to reduce the number of components, especially the moving components in the primary and secondary latch system and self presenting secondary release arm; 
         [0009]    b. to reduce the impact load that would normally be experienced by a comparable ratchet pawl latch system; 
         [0010]    c. to minimize or eliminate the need for lubrication and increase life cycle durability of the primary and secondary latches; 
         [0011]    d. to improve packaging capability when compared to the ratchet and pawl type primary latch that can only be mounted on a vertical wall; 
         [0012]    e. to ensure positive latching when compared to the ratchet type and bolt type; 
         [0013]    f. to improve assembly process; 
         [0014]    g. to reduce the cost of the complete system; 
         [0015]    h. to reduce the weight of the complete system to improve fuel efficiency; 
         [0016]    i. to reduce the possibility of the hood opening due to latch failure during a collision; 
         [0017]    j. to comply with collision requirement for pedestrian head impact requirements; 
         [0018]    k. to have the ability to commonize the same system to fit into various vehicles by making slight adjustment to the latch system; 
         [0019]    l. to eliminate fluttering of the hood; 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a perspective view of a ratchet pawl type latch system 
           [0021]      FIG. 2  shows the components of a pin type latch. 
           [0022]      FIG. 3  shows a striker spring type latch. 
           [0023]      FIG. 4  shows multiple isometric views of value engineered latch system. 
           [0024]      FIG. 5  shows open and closed view of the hood operated by the system. 
           [0025]      FIG. 6  shows various views of the latch system 
           [0026]      FIG. 7  shows the action of spring 
           [0027]      FIG. 8  shows perspective view of striker 
           [0028]      FIG. 9  is a perspective view of self presenting secondary release system 
           [0029]      FIG. 10  shows the steps of closing operation 
           [0030]      FIG. 11  shows the steps of opening operation 
           [0031]      FIG. 12  shows the stages when secondary system is stuck 
           [0032]      FIG. 13  shows the stages when primary system is stuck 
           [0033]      FIG. 14  shows view of complete assembly 
           [0034]      FIG. 15  shows front view of safety striker 
           [0035]      FIG. 16  shows iso view of spring 
           [0036]      FIG. 17  shows the top view of a typical door and proximate where the striker is attached to the door outer and the spring assembly is attached to the proximate. 
           [0037]      FIG. 18  shows the primary pass through pivot pin and secondary pass through pivots pin supporting their respective arms and augmenting springs connecting primary and secondary arms 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Description of Figures 
       [0038]    A typical embodiment of the present invention is illustrated in  FIG. 4 . Various perspective views of a hood  10  of an automobile, a hood inner  11  a latch support structure  12  such as a radiator cross member, a value engineered latch system  13  and striker  14 . 
         [0039]      FIG. 5  shows a hood inner  11  that is the inner part of the hood  10 . The latch system comprises of a striker  14  that is rigidly attached to the hood inner  11  either by welding or by fasteners. The rest of the latch system  13  is attached to the latch support structure. The latch system comprises of a base plate  15  over which a spring  16  is located in such a manner that the parts of the spring is able to move about in a limited constrained environment. 
         [0040]      FIG. 6  that shows the orientation of the spring  16  over the base plate  15 . The base plate  15  is generally a flat plate with a curved end that encloses the spiral portion of the spring  16  and a sharply bent end with slots that allow the leg portion of the spring  16  to pass through. The movement of the spring  16  is restricted by a number of pins rigidly attached to the base namely primary pivot  19 P, secondary pivot  19 S, primary limit pin inner  20 P, secondary limit pin inner  20 S, primary limit pin outer  52 P, secondary limit pin outer  52 S, primary partition  18 P, secondary partition  18 S and top plate  21 . The top plate  21  mounts over the pins and or partitions and is held rigidly in place by screws  28  and  29  passing through holes in the top plate  21  and base plate  15 . The heights of the pins and partitions are the same and are slightly more than the thickness of the spring members passing between the top plate  21  and the base plate  15  thereby allowing the free movement of the spring  16 . The primary partition  18 P and the secondary partition  18 S are tabs that are rigidly fixed into the base plate by welding or by other means to the base plate  15 . The number of effective coils on the primary spiral  17 P and secondary spiral  17 S, zero and above that will affect the force exerted by the respective arms on the striker is decided by the location of the respective partitions. The forces are governed by the number of effective coils, the spring rate, the diameter of the coil, the spring wire diameter and the elasticity of the coil material. The number of effective coils zero and above is defined by the number of coils between the partitions and the respective arms. For a given number of effective coils the other factor that affects the forces is the elongation on the coil created between the partition and the pivots. 
         [0041]    The primary pivot  19 P, the secondary pivot  19 S, the primary limit pin outer  52 P and the secondary limit pin  52 S are pins rigidly attached to the base plate  15  and the pins constrain the primary arm  16 P and the secondary arm  16 S respectively. The primary limit pin inner  20 P and the secondary limit pin  20 S are rigidly attached to the base plate and make contact to the primary arm  16 P and secondary arm  16 S respectively. The main objective of the pins and partitions is to keep the primary arm  16 P and secondary arm  16 S in a bias that keep the arms always move towards the center. Spring  16  works on the principle of tension and torsional forces of the spiral section of the spring  16 . The torsional forces of the spiral section keeps lift arm  16 L in an inclined angle Q as shown in  FIG. 6 . Decreasing the angle by the downward movement of the striker is opposed by the spiral segment of the spring  16  and lift arm  16 L is forced to move upwards. More the deviation from the angle Q more will be the opposing force that will tend to bring the lift arm  16 L to its neutral position that is angle Q. The torsional force is determined by the coil diameter, coil wire diameter and the elasticity of the material of the coil. 
         [0042]    The primary arm  16 P and the secondary arm  16 S are biased towards the centerline, that is towards each other at the free ends. This is caused by the tension in the spiral section of the spring  16 . The magnitude of the force exerted by the primary arm  16 P and secondary arm  16 S against the sliding surfaces of the striker  14  is determined by the location of the primary partition  18 P, secondary partition  18 S, primary pivot  19 P and secondary pivot  19 S. When the partitions are moved away from the center line and or the pivots move forward the forces increase. The forces exerted by the primary arm  16 P and the secondary arm  16 S hence can be different and can be customized as required. 
         [0043]    A shock absorbing material such as a rubber bumper  30  is attached to the screw  28  either by molding the bumper to the screw head  28  or installed rigidly with an interference fit or attached or by threaded means so that bumper  30  can be raised or lowered to adjust the height to account for assembly variations or for the variation in force exerted by the striker  14 . 
         [0044]    At one end of the front plate  22  is located the primary release cable slot  25 . A primary release cable outer  27  emerging from inside the vehicle is rigidly attached to the primary release cable slot  25 . A primary release cable inner  26 , which slides coaxially inside the primary release cable outer  27  extends through the primary cable release slot  25  attaches to the free end of primary arm  16 P through a crimp. The primary release cable inner moves the primary arm  16 P when actuated from inside the vehicle but also allows the primary arm  16 P to move independently during operation.  FIG. 7  shows the components of the spring  16 . The spring  16  is essentially a double torsion spring comprising of a primary arm  16 P, a secondary arm  16 S, a primary spiral  17 P, a secondary spiral  17 S and a lift arm  16 L. The extents to which the arms and spirals move are shown in phantom lines in  FIG. 7 . 
         [0045]    The striker  14  is generally a plate that has unique profile at the lateral edges as shown in  FIG. 8 . The contours and profiles namely primary sliding surface  42 , primary pull in ramp  43 , primary strike surface  44 , primary over slam slot  45 , primary ramp  46 , primary slot  47 , secondary sliding surface  48 , secondary ramp  49 , secondary pull in ramp  50  and secondary upper spot  51  are named essentially on their function during the operation of the latch. The striker  14  rigidly attached to the hood inner  11  by fasteners or by spot welding traverses through the primary arm  16 P and secondary arm  16 S during operation. The primary arm  16 P engages with the primary sliding surface  42 , primary pull in ramp  43 , primary strike surface  44 , primary over slam slot  45 , primary ramp  46 , primary slot  47  while the secondary arm  16 S engages with the secondary sliding surface  48 , secondary ramp  49 , secondary pull in ramp  50  and secondary upper spot  51 . 
         [0046]      FIG. 9  shows the components of a self presenting secondary release arm system  31 S. The function of the self presenting secondary release arm system  31 S is to bring forward the self presenting arm from its retracted position when the hood  10  is released from its fully closed position and is ready to be opened from outside by releasing the secondary latch. The self presenting arm makes it easy for the operator to locate the secondary latch release mechanism without having to search for the same. The components of the self presenting secondary release arm as shown in  FIG. 9  are self presenting arm  31 , self presenting arm support  32 , self presenting arm pulley  34 , self presenting arm actuator chord  35 , self presenting arm actuator chord guide  36 , self presenting arm actuator chord clamp  37 , self presenting arm retraction spring  38 , self presenting arm retraction spring support  39  and secondary arm actuator link  40 . One end of the self presenting arm actuator chord  35 , made from a semi elastic material, is attached to the self presenting arm actuator chord guide  36 , and is looped through the hole in the self presenting arm actuator chord guide  36  which is crimped or welded to the lift arm  16 L. The chord is run through the self presenting arm pulley  34  that is mounted on the self presenting arm support  32 . The chord passes through the support and then is crimped to the end of the self presenting arm  31 . The self presenting arm  31  passes through the self presenting arm support  32  and front slot  24  moves in a reciprocating fashion when operated. The free end of the self presenting arm  31  is provided with a thumb  31 T which when manually pushed activates the secondary arm  16 S to release the secondary latch. The self presenting arm is constantly pulled backwards, towards the vehicle, by a self presenting arm retraction spring  38  one end of which is attached to the self presenting arm retraction spring support  39 . The self presenting arm  31  is actuated back and forth by the raising and lowering of the lift arm  16 L. The self presenting arm support block is pivotally attached to the base plate through self presenting arm support hole  33 . The self presenting arm and the secondary arm  16 S are connected through a secondary arm actuator link  40  which is rigidly attached to the self presenting arm and loops around the secondary arm  16 S but allows it to move freely during the latch operation. 
         [0047]    Operation— FIGS. 10 ,  11 ,  12 ,  13   
         [0048]    The primary and secondary latch functionalities are accomplished by the interaction of the spring  16  and the striker  14 . The striker  14  is attached to the hood inner and it moves up and down with the hood while the spring  16  is entrapped into the base plate  15  and top plate  21  and the base plate  15  attached to the top of the support structure such as radiator cross member. The interaction of the striker  14  and spring  16  is best explained in a sequence of figures that show the location of various components of the primary and secondary latch system. The figures, for simplicity sake, only shows the cross section of the arms and not the background information. When the hood  10  is being closed the striker  14  approaches the spring  14  between the primary arm  16 P and secondary arm  16 S. 
         [0049]    Closing Operation: 
         [0050]    It is easier to show the closing operation in stages. For a better understanding of the positions of various components  FIG. 10  shows the incremental steps, in sequence, the closing operation. To clarity sake the numbers are provided only once per picture. 
         [0051]    Stage  1  ( FIG. 10-1 ) 
         [0052]    The striker  14  is descending towards the primary arm  16 P and the secondary arm  16 S which are now resting against their respective pivot pins and limit pin inners (not shown). 
         [0053]    Stage  2  ( FIG. 10-2 ) 
         [0054]    The primary arm  16 P and secondary arm  16 S are beginning to slide on primary sliding surface  42  and secondary sliding surface  48  respectively. 
         [0055]    Stage  3  ( FIG. 10-3 ) 
         [0056]    The secondary arm  16 S reaches the end of the secondary sliding surface  48 . 
         [0057]    Stage  4  ( FIG. 10-4 ) 
         [0058]    The secondary arm  16 S engages over the secondary ramp 
         [0059]    Stage  5  ( FIG. 10-5 ) 
         [0060]    The primary arm  16 P slides over the primary sliding surface  42 . 
         [0061]    Stage  6  ( FIG. 10-6 ) 
         [0062]    The primary arm  16 P strikes the primary strike surface  43  and the striker bottoms on the bumper  30  and over slammed. 
         [0063]    Stage  7  ( FIG. 10-7 ) 
         [0064]    The primary arm  16 P settles in the primary slot  47  after the striker gets lifted up by the lift arm  16 L. The latch system  13  is now in closed position. 
         [0065]    It is easier to show the opening operation in stages. For a better understanding of the positions of various components  FIG. 11  shows the incremental steps, in sequence, the opening operation. To clarity sake the numbers are provided only once per picture. 
         [0066]    Stage  1  ( FIG. 11-1 ) 
         [0067]    The striker  14  is in fully closed position. Now the primary arm  16 P is pulled away from the primary slot  47  by the effort of the release cable inner  26  (not shown) 
         [0068]    Stage  2  ( FIG. 11-2 ) 
         [0069]    The primary arm  16 P comes completely out of the primary ramp  46  and the lift arm  16 L starts lifting the striker  14  up. 
         [0070]    Stage  3  ( FIG. 11-3 ) 
         [0071]    The striker continues to get raised by the lift arm  16 L. 
         [0072]    Stage  4  ( FIG. 11-4 ) 
         [0073]    The secondary arm  16 S stops over the secondary ramp  49  preventing the striker from moving further. 
         [0074]    Stage  5  ( FIG. 11-5 ) 
         [0075]    The secondary arm  16 S is pulled away from the secondary ramp  49  and the lift arm  16 L continues to lift the striker upwards. 
         [0076]    Stage  6  ( FIG. 11-6 ) 
         [0077]    The striker  14  is completely released from the primary arm  16 P and secondary arm  16 S and is free to be lifted up. 
         [0078]    Positive Latching of Primary Arm  16 P 
         [0079]    It is possible the primary arm  16 P could remain stuck open i.e away from the striker  14 . The primary limit pin outer  20 P will prevent the primary arm  16 P from moving outboard extensively. The following passages explain the positive latching feature of the invention. The primary pull in ramp  43  extends beyond the farthest point that the primary arm  16 P can go. During the downward movement of the striker  14  the primary pull in ramp  43  pulls the stuck open primary arm  16 P towards the striker. The movement of various components is shown below in stages for better understanding. 
         [0080]    Again for the sake of convenience the movements of the striker  14  and the primary arm  16 P and the secondary arm  16 S are shown in stages in  FIG. 13 . For clarity sake the back ground information and the numbering of repeating components in the figure are omitted. 
         [0081]    Stage  1  ( FIG. 13-1 ) 
         [0082]    The primary arm  16 P is stuck in open position that is away from the striker  14 . It is necessary to draw the primary arm  16 P inboard so that the latch will be engaged. 
         [0083]    Stage  2  ( FIG. 13-2 ) 
         [0084]    The striker  14  continues to come down and the primary pull in ramp  43  encounters the primary arm  16 P and the angle of the primary pull in ramp  43  starts to pull the primary arm  16 P inboard. 
         [0085]    Stage  3  ( FIG. 13-3 ) 
         [0086]    The striker  14  or hood bottoms out over the bumper  40  (not shown) and comes to a stop. 
         [0087]    Stage  4  ( FIG. 13-4 ) 
         [0088]    The downward pressure on the striker is released and the lift arm  16 L begins to lift the striker  14  and the primary arm  16 P comes in contact with the primary ramp  46 . 
         [0089]    Stage  5  ( FIG. 13-5 ) 
         [0090]    Further upward movement of the striker  14  pushes the primary arm  16 P completely into the primary slot  47 . The latch system  13  is now closed. 
         [0091]    Positive Latching of Secondary Arm  16 S 
         [0092]    The secondary arm  16 S operates between top plate  21  and the base plate  15 . It is possible the secondary arm  16 S could remain stuck open that is away from the striker  14 . The secondary limit pin outer  20 S will prevent the secondary arm  16 S from moving outboard excessively. The following passages explain the positive latching feature of the invention. The secondary pull in ramp  50  extends beyond the farthest point that the secondary arm  16 S can go away from the striker. During the downward movement of the striker  14  the secondary pull in ramp  50  pulls the stuck open secondary arm  16 S towards the striker. The movement of various components is shown below in stages for better understanding. 
         [0093]    The following passages explain the positive latching feature of the invention. Again for the sake of convenience the movements of the striker  14  and the primary arm  16 P and the secondary arm  16 S are shown in stages in  FIG. 12 . 
         [0094]    Stage  1  ( FIG. 12-1 ) 
         [0095]    The secondary arm  16 S is stuck in open position that is away from the striker  14 . It is necessary to draw the secondary arm  16 S inwards so that the latch will be engaged. 
         [0096]    Stage  2  ( FIG. 12-2 ) 
         [0097]    The striker  14  continues to come down and the secondary pull in ramp  50  encounters the secondary arm  16 S and the angle of the secondary pull in ramp  50  starts to pull the secondary arm  16 S inwards. 
         [0098]    Stage  3  ( FIG. 12-3 ) 
         [0099]    The striker  14  bottoms out over the bumper  40  (not shown) and comes to a stop. The secondary arm  16 S is completely pulled into the secondary upper spot  51 . 
         [0100]      FIG. 14  shows an exploded view of the value engineered latch system  13  with the components of the system labeled. 
         [0101]      FIG. 15  shows a safety striker  14 A that is similar to the striker  14  in all aspects except for the change shown in a safety ramp  70 . The primary arm  16 P is located in primary slot  47 . If an external object, such as a human head or body, comes in contact with the hood  10  at a high speed the hood needs to move towards closing direction to reduce the impact. The safety ramp  70 , will allow the safety striker  14 A to move down to the over slam position thus reducing the severity of the impact to the human. 
         [0102]      FIG. 16  shows an alternative of the secondary arm  16 C that has a thumb  16 T so that there is no need for the self presenting secondary release arm. When the secondary latch needs to be released the thumb  16 T is directly pushed outboard thus releasing the secondary arm  16   c  from restraining the striker  14  or  14 A. 
         [0103]      FIG. 17  shows the latch system adapted to an automobile door where the striker plate is fastened or welded to the door outer  200  while the base plate and spring assembly is attached to the proximate body structure including B pillar or C pillar  201 . The interaction between the striker plate  14  and the spring  16  are very similar to the narrative above. There are difference in the modes in which the primary arm  16 P and secondary arm  16 S are operated and will depend on vehicles body structure and mode of actuation such as electrical and or mechanical actuation through complex linkages. It is only possible to show a schematic representation of how the components of the latch system would interact. 
         [0104]      FIG. 18  shows the primary arm  16 P and secondary arm  16 S pass through a primary pass through pivot  80 P and a secondary pass through pivot  80 S respectively. The pins are pivotally or rigidly attached to the base plate. The arms are secured rigidly to the pins by means of screws or weld. This provides for the primary arm or secondary arm to be completely independent of the respective spirals where by the primary arm  16 P and secondary arm  16 S can function in a standalone manner. 
         [0105]      FIG. 18  also shows augmenting springs  90  and  91  connecting the primary arm  16 P and the secondary arm  16 S. Augmenting springs  90  and  91  bias the primary arm and the secondary arm towards the striker and enhance the force applied by the primary arm  16 P and secondary arm  16 S on the striker. This arrangement allows for further customization of the forces in the latch system. The augmenting springs  90  and  91  attach to the primary arm  16 P and the secondary arm  16 S by any means including wind or hook around the primary and secondary arm  16 S. The forces on the primary arm  16 P and secondary arm  16 S are influenced by the spring rate of augmenting springs  90  and  91 .