Abstract:
An infinitely positionable linear friction lock assembly utilizes a single friction spring coaxially disposed about a translating rod within an elongated housing. A bias bushing is provided for slidably supporting the rod. The bushing defines a sloped shoulder against which the friction spring hears, with the angle of the shoulder calibrated to provide an increased holding force up to a predetermined axial force on the rod, and permitting the rod to slip at greater axial forces without disturbing the integrity of the spring or its coils. The assembly includes a release or actuation lever having a cap bushing integrated therein to support the rod and keep the actuation lever in alignment.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention concerns positionable linear mechanical locking devices most particularly of the type used for vehicle seating. Specifically, the invention relates to a type of device in which a friction brake is used to restrict axial translation of a positionable rod. In the case of this invention, the friction brake is a coiled spring having an inside diameter smaller than the coaxially located rod, allowing the spring to grip the rod, thereby preventing axial translation of the rod relative to the spring and the housing containing it.  
           [0002]    Infinitely positionable linear friction lock assembly are known in the art. This type of lock generally has an elongated cylindrical rod extending through a housing that contains a pair of coiled springs. The rod can be locked with respect to the housing so that axial translation of the rod is prevented. In certain friction lock this is accomplished by a pair of coiled springs wrapped around the rod each having an free state inside diameter that is smaller than the outside diameter of the rod. To allow translation of the rod, an actuator is connected to an end of each spring. The actuator partially unwinds each springs by expanding their diameters, thereby reducing their gripping force of the springs and freeing the rod to slide through the springs.  
           [0003]    A locking device of this type is included in the seat lock of U.S. Pat. No. 6,164,419, issued Dec. 26, 2000, to Tribbett. As shown in FIG. 2 of the Tribbett patent, the positioning rod passes through an actuating release lever. The lock provides adjustable movement of a seat back relative to a seat frame by actuating the lever to release the coil springs from the rod. In such an application, a very large holding force is required in both directions of rod translation. The resulting housing and its multiple springs and bushings generally exceed 50 millimeters in length. Consequently, a long rod is necessary even if the required range of translation is small.  
           [0004]    Another similar locking device is the friction lock assembly of U.S. Pat. No. 4,457,406, issued Jul. 3, 1984. Although this friction lock assembly, as shown in FIG. 2, requires only one coil spring, the device still requires numerous components, including a pair of carefully machined spring end bushings at each end of the coil spring. Thus, the component count and length of this prior locking device continues to be larger than is desirable for certain applications.  
           [0005]    There are instances in which it is desirable to have a linear friction lock assembling device in which a large holding force is only required in one direction. In addition, it is sometimes desirable that the components of the lock be contained in a relatively small package or envelope. These features are particularly desirable for the adjustment and locking of various positionable members of automotive seating other than the seat itself, such as armrests, headrests and lumbar supports.  
           [0006]    It is desirable in some applications that the positionable locking devices be small in size and have a small component count. It is further desirable for the device to be inexpensive, simple to assemble, and maintenance-free. In many applications, a low unlocking force is all that is needed, allowing the device to be adaptable to many different types of mounting and unlocking systems. It is also desirable that if the holding force is exceeded, the device releases the positionable member without damage to the device.  
         SUMMARY OF THE INVENTION  
         [0007]    Briefly describing one aspect of the invention, an infinitely positionable linear friction lock assembly includes a positioning rod and a lock assembly that houses a mechanical brake. The housing assembly can include a mounting bracket, and the positioning member can include a flange mounting end. The mounting bracket can be used to mount the housing assembly so the lock can provide adjustment of a member of a vehicle seat or some other device by disengagement of the mechanical brake and translation of the rod.  
           [0008]    The difficulties with prior positionable linear friction lock are overcome in one aspect of the current invention, namely by features of the lock assembly. The lock assembly can accomplish sufficient axial load bearing with a small number of components and a small size. A coil spring contained in a housing can be coaxially wrapped around the positioning rod. The spring has an inner diameter less than the diameter of the rod, allowing the spring to resist sliding on the rod. The spring can be sandwiched between a bias bushing at one end and a spring release mechanism at its other end. A cap bushing can be located at an end of the release lever opposite the spring and mounted in an end of the housing opposite the bias bushing. The cap bushing receives and aligns the release mechanism, retaining it in the housing. Both the bias bushing and the cap bushing can have an inner cylindrical surface acting as a bearing surface for the rod.  
           [0009]    The housing is preferably mounted to a vehicle seat and the flange end of the rod is attached to an adjustable component. The lock prevents adjustment of the component because the coil spring normally prevents the rod from translating in the housing. The component can be released for adjustment by actuating the release mechanism. Actuation of the release mechanism unwinds one end of the spring, releasing the spring from the rod surface and allowing the rod to translate axially through the housing, and thereby releasing the component attached to the rod.  
           [0010]    In one embodiment of the invention, the lock assembly includes a bias bushing having an inner bearing surface for receiving the rod therethrough. In one aspect, the bushing defines a counterbore having an obliquely sloped shoulder at the base of the counterbore for receiving and contacting an end of the coil spring. The shoulder is sloped at a predetermined angle relative to the longitudinal axis of the bore in the bias bushing (and therefore, the axis of the rod). The incline of the sloped shoulder is calibrated to accomplish a maximum axial load that can be held by the lock assembly as the rod presses the coil spring against the spring seat. Specifically, an incline can be specified that opens the spring slightly and allows the rod to slip through the spring at an axial load above a predetermined level without risk of dislodgment of the spring or overlapping of the spring coils.  
           [0011]    In another aspect of the invention, each end of the coil spring has a tang formed by bending a short portion of the spring end radially outward. The tang at one spring end extends into a slot defined by the bias bushing, securing the spring relative to the housing. The other spring end is engaged by the release mechanism that slightly, rotationally unwinds the spring relative to the housing and rod.  
           [0012]    In one embodiment, the release mechanism can include a C-shaped tube portion for receiving an end of a coil spring and a lever portion for actuating the tube portion. The tube portion can further define a slotted notch for compressing the spring against the bias bushing located at the opposite spring end. The tube portion can also have a second slotted notch for engaging a tang located at the rotatable spring end.  
           [0013]    In an additional aspect of the invention, the lock assembly includes a cap bushing attached to one end of the housing. The cap bushing can have an inner lip at one end for receiving the tube portion of the release lever. The inner lip also preferably positions the release mechanism within the housing. The cap bushing can also have an inner bearing surface for receiving the rod therethrough and for aligning the rod with the bias bushing.  
           [0014]    In the preferred embodiment, a housing containing a bias bushing, a cap bushing, a coil spring and a release means, preferably measures less than 31 millimeters in length. An in-line, offset, or other mounting bracket can be fixedly attached to the housing to secure it to a seat member, frame, or other device having an adjustable component. Although in the preferred embodiment the components are constructed from steel, the invention also contemplates use of materials such as aluminum, plastic, or other similarly rigid and durable materials.  
           [0015]    In another aspect of the invention, a number of actuating means are contemplated by the invention. These include a cable and cable bracket attached to the housing, the cable connected to and actuating the release lever; a pushbutton that when depressed actuates the release lever; a pinch actuator that pulls the release lever against another bracket or lever mounted to the lock assembly housing; and a rotatable sleeve that rotates about the housing and is attached to the lever so as to actuate it.  
           [0016]    In an additional aspect of the invention, the canting or biasing of the coil spring by the bias bushing sloped spring seat causes the coil spring to have a large holding force in one axial direction of translation of the rod. Furthermore, the incline of the sloped spring seat can be selected to allow slippage of the coil spring on the rod at a predetermined axial slip force, thus preventing damage of the locking assembly and providing continued functioning of the lock assembly under subsequent loads.  
           [0017]    One object of the invention is to provide an infinitely positionable linear friction lock assembly that features a small length along the axis of the positioning rod, yet provides a large enough load capacity for a variety of applications requiring adjustability. Another object of the invention is to eliminate the need for two or more coil springs and two or more spring bias bushings. A further object of the invention is to provide an adjustable chuck/friction feature at assembly that allows the axial bushing alignment to determine the amount of drag applied to the translating rod when the lock is released.  
           [0018]    One benefit of the invention is that the release lever functions as both a spring release mechanism and an end bushing for the coil spring. Another benefit is that the bias bushing can accomplish an override load limit that will allow the rod to translate and provide subsequent functioning of the friction lock assembly. A further benefit of the invention is that the linear friction lock assembly components can be constructed of a variety of inexpensive materials including steel, aluminum, and plastic. The linear friction lock assembly is also capable of accommodating a number of different mounting configurations and a number of different release actuator systems.  
           [0019]    These and other objects and benefits of the invention can be discerned from the following written description taken together with the accompanying figures.  
       
    
    
     DESCRIPTION OF THE FIGURES  
       [0020]    [0020]FIG. 1 is a perspective view of an infinitely positionable linear friction lock assembly according to one embodiment of the invention.  
         [0021]    [0021]FIG. 2 is a partially cut away perspective view of the lock housing portion of the assembly shown in FIG. 1.  
         [0022]    [0022]FIG. 3 is a side cross-section view of the assembly shown in FIG. 1.  
         [0023]    [0023]FIG. 4 is an end view of the assembly shown in FIG. 1, shown from the end with the cap bushing and having the cap bushing removed to better illustrate the details of the spring and lever on the interior of the housing.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates.  
         [0025]    The present invention relates to positionable linear friction lock assembling devices and is particularly suited for use in vehicle seating applications. Although the preferred embodiment is envisioned for use in adjusting various members of automotive seating, the principles of the invention can be employed in a variety of applications in which an infinitely positionable friction lock assembly can be utilized.  
         [0026]    In general terms, the invention provides for positioning and locking of a rod that extends through a lock assembly. By mounting one of the rod or lock assembly to a member of a seat, and attaching the other component to another member of the seat, the two seat members can be positioned and locked relative to each other by the inventive friction lock assembly. By simply releasing the locking means contained within the lock assembly, the members can be adjusted relative to each other and then relocked when the lock assembly is re-engaged. With this general background, further details of the invention will be disclosed with specific references to feature numbers and to figures.  
         [0027]    Referring first to FIG. 1, a preferred embodiment of the positionable friction lock assembly includes a lock assembly  50  and a positioning rod  30 . The lock assembly  50  can include a housing  51 , a bias bushing  70 , a coil spring  80 , a release mechanism  90 , and a mounting bracket  40 . The lock assembly  50  can also include an end cap bushing  60  and a cable actuator bracket  100 .  
         [0028]    The rod  30  is preferably an elongated cylindrical steel rod having a mounting flange  32  at one end. The bracket  40  and flange  32  can be respectively engaged to seat members that are intended to be adjustably relatively positioned. The housing  51  is preferably cylindrical in shape and can have a window  55  along the length of the housing through which a portion of the release mechanism  90  extends.  
         [0029]    Referring now to FIGS. 2 and 3, the bias bushing  70  is preferably mounted on attached to the inside of one end of the housing  54 . The bias bushing  70  defines a bore  75  therethrough that is sized for slidably receiving the positioning rod  30 . One end the bias bushing  74  also defines a counterbored spring seat  72 , shown most clearly in FIG. 3. The base of the counterbored spring seat  72  forms a sloped shoulder  76  that inclines the spring seat  72  from a shallow end at the bushing top  74  to a deep end at the bushing bottom  73 . The shoulder  75  is sloped at a predetermined angle relative to the longitudinal axis of the bore  75 .  
         [0030]    The spring seat  72  is sized to receive a first end  81  of the coil spring  80 . The coil spring body  83  is positioned around and coaxial with the positioning rod  30 . The spring  80  preferably has a normal or free-state inside diameter that is smaller than the outside diameter of the rod  30 . With the relative diameters sized in this way, each coil of the spring  80  normally grips the rod  30  and resists translation of the rod relative to the spring.  
         [0031]    When an axial load is applied on the rod  30  in one direction, the first end of the spring  81  is compressed against the sloped shoulder  76  of the bias bushing  70 . The sloped shoulder  76  asymmetrically compresses the spring  80  against the rod  30  creating an increased gripping force of the spring upon the rod. The gripping force of the spring  80  on the rod  30  and the first spring end  81  compressing against the bias bushing  70  will inhibit translation of the rod relative to the lock assembly  50 .  
         [0032]    One inventive feature of the friction lock  50  is that the lock can have a predetermined axial slip force calibrated by the angle of incline of the shoulder  76 . This angle can be selected to be high enough relative to the first spring end  81  so that the lock assembly  50  will inhibit translation of the rod  30  upon application of an axial load on the rod in a first direction up to the predetermined axial slip force. However, the same selected incline of the sloped shoulder  76  will limit the asymmetrical compression of the first spring end  81  by the sloped shoulder  76 , so that the rod  30  will slip through the spring body  83  upon application of an axial force on the rod in the first direction that exceeds the predetermined axial slip force. Moreover, the calibrated angle will allow the rod to overcome the frictional holding force of the spring coils without dislodging or damaging the spring, and without dislodging or damaging the spring, and without allowing successive coils to overlap, thereby destroying the lock assembly.  
         [0033]    The angle of incline of the sloped shoulder  76  can range between 10° and 30° from a line perpendicular to the axis of the bias bushing bore  75 . However, the angle of incline of the sloped shoulder  76  is preferably approximately 25° or less from the line perpendicular to the axis of the bias bushing bore  75 . By selecting an angle of incline of approximately 25° or less, an inventive override feature can be achieved. Although a peak load capacity of at least 900 pounds can be achieved in the specific illustrated embodiment, when the predetermined axial slip force for the selected sloped shoulder  76  incline angle is exceeded, the rod  30  will slip through the spring  80  and lock assembly  50  without damage to the lock assembly components or without disrupting the integrity of the spring or the spring coil. The friction lock assembly will therefore continue to function normally.  
         [0034]    In the preferred embodiment, the first spring end  81  is secured from rotating within the housing  51 . The spring  80  preferably has a first tang  81  protruding radially outward from the spring body  83  and located at the first end of the spring. The bias bushing  70  can have a first catch  77  for engaging the first spring tang  81 . In the preferred embodiment, the first catch is an axial slot  77  along an inside wall of the counterbored spring seat  72  as shown in FIGS. 2 and 3. The axial slot  77  will allow the first spring end  81  to translate axially relative to the bias bushing  75  as it is asymmetrically compressed at an angle against the sloped shoulder  76 . However, the axial slot  77  will prevent the first spring end  81  from rotating relative to the bias bushing  70 .  
         [0035]    The inventive friction lock assembly  50  comprised of at least the housing  51 , the bias bushing  70 , and the spring  80 , and can be preferably less than 31 millimeters long. Thus, the assembly is especially suited for applications in vehicle seating that require a small profile and a lower load capacity. Envisioned applications include, but are not limited to, positionable members of automotive seating, for example: armrests, headrests, and lumbar supports.  
         [0036]    In order to easily reposition the rod  30  relative to the lock assembly  50 , a release mechanism  90  can be included in the preferred embodiment. The release mechanism  90  applies an unwinding torsion on the second end  82  of the spring  80 . The release mechanism  90 , as shown in FIG. 2, preferably includes a C-shaped tube portion  93  connected to a lever portion  91 . The tube portion  93  receives the second spring end  82  and has a first slotted notch  96 , or “kick-in,” for contacting the second end of the spring  80 , as best seen in FIG. 3. The release mechanism  90  also includes a second catch  92  for engaging a second tang  82  protruding radially outward from the spring  80  at the second spring end. When the lever portion  91  of the release mechanism  90  is actuated, the tube portion  93  rotates about the axis of the spring body  83 , applying an unwinding torsion to the spring  80  via the second catch  92  and displacing the second spring tang  82 . The unwinding torsion increases the inside diameter of the spring body  83  to a diameter that is larger than the outside diameter of the rod  30 , thereby permitting axial translation of the rod. In the preferred embodiment, the first and second spring tangs are located 180° circumferentially apart.  
         [0037]    In addition to the first slotted notch  96  protruding across an interior segment of the tube portion  93  of the release mechanism  90 , the tube portion can also define slots  97  extending along a segment of the circumference of the tube portion. The second catch is preferably a slotted notch  92  punched into the release mechanism  90  at the junction of the tube portion  93  and the lever portion  91 . The lever portion  91  of the release mechanism  90  preferably protrudes from the interior of the housing  51  through the housing window  55 . The width of the housing window  55  along a portion of the circumference of the housing  51  must be wide enough to provide sufficient travel of the lever portion  91  so that the second spring tang  82  is displaced enough to allow the rod  30  to slip through the spring body  83 .  
         [0038]    Although a number of actuating means are contemplated to actuate the lever portion  91 , the preferred embodiment includes a cable actuator bracket  100  for connecting a cable actuator to the lock assembly  50 . As shown in FIG. 4, the cable actuator bracket  100  can have a loop portion  106  for attaching the bracket to the housing  51  and a back portion  108  forming a first and second notch  103  and  104 , a first and second post  101  and  102 , and a tie  105  for terminating a cable housing. The bracket  100  back portion  108  is strengthened by bracket side walls  107 . The lever portion  91  also has a cable slot  95  and a bent portion forming a hook  94 , both for connecting an actuating cable. Actuating the cable will, therefore, rotate the release mechanism  90  relative to the housing  51 , unwinding the coil spring  80 , and freeing the rod  30  to translate through the lock assembly  50 .  
         [0039]    The preferred embodiment can also include an end cap bushing  60  as depicted in FIGS. 2 and 3. The cap bushing  60  is preferably attached to an interior end of the housing opposite the bias bushing  70 . The cap bushing  60  has a bore  65  defined therethrough that is sized to receive the rod  30 . At the exterior end  61  of the cap bushing  60 , the bore  65  can have a chamfer  62 .  
         [0040]    In addition to supporting the rod  30 , the end cap bushing  60  provides for alignment of the tube portion  93  of the release mechanism  90  within the lock housing  51 . The end of the cap bushing  60  opposite the exterior end  61  has a lip  64  on the interior of the bushing and a shoulder  63  defined by the exterior of the bushing. The lip  64  and shoulder  63  are sized to couple with the tube portion  93 . The tube portion  93  rotates around the outside of the lip  64 , thereby centering the tube portion within and away from the interior of the housing  51 . The end cap bushing  60  also serves to sandwich the tube portion  93  between the end cap bushing  60  and the spring  80 .  
         [0041]    Placement of the end cap bushing  60  in the housing  51  at assembly of the lock assembly  50  determines the amount of bias compression on the spring body  83  as the spring  80  is compressed between the first slotted notch  96  of the tube portion  93  and the sloped shoulder  76  of the bias bushing  70 . Axial alignment of the end cap bushing  60  with the bias bushing bore  75  also provides for smooth translation of the rod  30  when the release mechanism  90  is actuated.  
         [0042]    Another feature of the inventive friction lock assembly is the lock assembly  50  mounting bracket  40 , as depicted in FIGS. 2 and 4. The mounting bracket  40  can have a flat bracket body  43  having tab holes  46  for receiving tabs  52  extending from the housing  51 . The tabs  52  preferably pass through the tab holes  46  and are crimped around the bracket body  43 , fastening the bracket  40  to the housing  51 . Extending from the bracket body  43  can be a first and second ear  41  and  42  having mounting holes  45  for mounting the lock assembly  50  to a member of a seat. Alternatively, the mounting bracket  40  can be attached to the housing  51  by other fastening means, for example, welding. Other methods known in the art of mounting the lock assembly  50  to a member of the seat are also contemplated by the present embodiment of the invention.  
         [0043]    The positioning rod  30  can have a flange end  33  having a mounting flange  32  with a flange hole  34  defined therethrough and a neck portion  31  at the junction of the mounting flange and rod. The mounting flange  32  is for connecting the positioning rod  30  to a member of the seat. The end of the rod  35  opposite the flange end  33  can have a radius  36  or chamfer, removing the sharp outer circumference of the rod end.  
         [0044]    Although in the various components are preferably constructed from steel, the invention also contemplates use of other rigid, durable materials such as aluminum, plastic and tubular steel.  
         [0045]    Anticipated applications that require a large holding capacity in only one direction allow the inventive friction lock assembly to contain fewer components and to be smaller in size. Specifically, the preferred embodiment contains only one coil spring  80  and one machined bias bushing  70  having an inclined sloped shoulder  76 . Previous friction lock assembly required a pair of coil springs and/or a pair of matched bias bushings. In order to further overcome the problem of numerous components and excessive lock size, the release mechanism  90  feature provides an easily constructed, compact, and inexpensive method of both disengaging the lock and of supporting the second end of the coil spring  80 . These features and other inventive aspects of the invention provide distinct advantages over other linear friction lock assembly devices. For example, the sloped shoulder  76  of the bias bushing bore  75  and the first slotted notch  96  of the tube portion  93  of the release mechanism  90  provide spring biasing and a predictable load capacity for a predetermined axial slip force. Applied loads above the predetermined slip force will cause the rod  30  to slip through the spring  80 , protecting the friction lock assembly components from damage.  
         [0046]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.