Abstract:
A compliant follower cam system includes a cam rotatable about a cam rotational axis continuously aligned with a cam displacement axis. The cam has a body center spaced from the rotational axis. A compliant follower has an elastically deformable first contact wall positioned proximate to a cavity. The first contact wall is directly contacted by the cam body outer surface. A compliant follower non-deflected condition occurs when a first contact wall outer surface directly contacts the cam body outer surface prior to deflection of the first contact wall, with the cam body center out of alignment with the displacement axis. Rotating the cam moves the body center toward the compliant follower into alignment with the displacement axis. The cam thereby deflects the first contact wall into the cavity defining a compliant follower deflected condition and creates a biasing force releasably frictionally engaging the first contact wall and cam.

Description:
FIELD 
       [0001]    The present disclosure relates to cam and follower systems used to create an over-center locking position for component retention. 
       BACKGROUND 
       [0002]    Cam and follower designs are known wherein the cam is an incompressible member which when rotated brings one or more lobes of the cam into contact with the follower to displace and/or retain the position of a member. Cams can be used to create top-dead center, bottom-dead-center and over-center contact positions and to create locking positions of components and/or fastening designs. Disadvantages of known cam and follower systems result from the use of a solid cam and cam lobes that commonly require a deflection system, for example in the form of biasing springs or biasing devices separate from the cam and follower that are required to allow cam lobe displacement to occur in reaching a cam locked position. Deflection systems increase system complexity. The disadvantages are further manifested in multiple part system increased cost, and alignment/tolerance issues that must be accommodated. Cam, follower and component wear also result from the frictional contact of the cam which requires subsequent adjustment of the cam and/or follower positioning. 
       SUMMARY 
       [0003]    According to several embodiments, a compliant follower cam system includes a substantially incompressible cam having a cam body outer surface. A compliant follower has an elastically deformable first contact wall in direct contact with at least a portion of the cam body outer surface. The first contact wall is deflected to a deflected condition by rotation of the cam. 
         [0004]    According to other embodiments, a compliant follower cam system includes a cam rotatable with respect to a cam rotational axis, the cam rotational axis continuously aligned with a cam displacement axis. The cam has a cam body center spaced from the cam rotational axis. A compliant follower has a first contact wall of an elastically compressible material positioned proximate to a cavity. The first contact wall is aligned to be directly contacted by the cam body outer surface. A non-deflected condition of the compliant follower is defined when an outer surface of the first contact wall is in direct contact with the cam body outer surface prior to deflection of the elastically deformable material, with the cam body center out of alignment with the cam displacement axis. The cam when thereafter rotated with respect to the cam rotational axis moves the cam body center toward the compliant follower and into alignment with the cam displacement axis. The cam thereby deflects the first contact wall into the cavity and defines a deflected condition of the compliant follower and creates a biasing force releasably frictionally engaging the first contact wall with the cam. 
         [0005]    According to further embodiments, a compliant follower cam system includes a cam rotatable with respect to a cam rotational axis. The cam rotational axis is continuously aligned with a cam displacement axis. The cam has a cam body center spaced from the cam rotational axis. A compliant follower has a first contact wall of an elastically deformable material positioned proximate to a cavity, the first contact wall aligned to be directly contacted by the cam body outer surface. A second contact wall of the compliant follower is aligned to directly contact a workpiece. A non-deflected condition of the compliant follower is defined when an outer surface of the first contact wall is in direct contact with the cam body outer surface prior to deflection of the elastically deformable material, with the cam body center out of alignment with the cam displacement axis. The cam when thereafter rotated with respect to the cam rotational axis acts to move the cam body center toward the compliant follower and into alignment with the cam displacement axis. The cam thereby deflects the first contact wall into the cavity defining a deflected condition of the compliant follower, and creates a biasing force releasably frictionally engaging the first contact wall with the cam. 
         [0006]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0007]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0008]      FIG. 1  is a front elevational view of a cam and compliant follower system in a bottom-dead-center position prior to deflection of the compliant follower according to the present disclosure; 
           [0009]      FIG. 2  is a front elevational view similar to  FIG. 1  further showing a direct contact position of the compliant follower with a workpiece prior to deflection of the compliant follower; 
           [0010]      FIG. 3  is a front elevational view of the compliant follower system of Claim  1  in a top-dead-center position, compliant follower deflected condition; 
           [0011]      FIG. 4  is a front elevational view similar to  FIG. 3 , showing a further embodiment of a compliant follower; and 
           [0012]      FIG. 5  is a front elevational view similar to  FIG. 4 , showing a further embodiment of a compliant follower. 
       
    
    
       [0013]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a cam system  10  includes a substantially incompressible cam  12  which is positioned in contact with a sliding compliant follower  14 . Compliant follower  14  slides within a guide member  16  until a first contact surface  18  of compliant follower  14  contacts an outer surface  20  of a work-piece  22 . Compliant cam  12  rotates to slidably displace follower  14  in a first direction “A” until contact is made between follower  14  and work-piece  22 . Work-piece  22  is held or fixed in position by or at a fixed member  24 . 
         [0015]    Guide member  16  can include opposite first and second guide walls  26 ,  28 , which between them define a guide member bore  29  within which at least a portion of cam  12  can be positioned and within which compliant follower  14  is slidably displaced. To promote a controlled sliding motion of compliant follower  14 , first and second bearing members  30 ,  32  are oppositely positioned about compliant follower  14 , having first bearing member  30  in sliding contact with first guide wall  26  and second bearing member  32  in sliding contact with second guide wall  28 . 
         [0016]    Cam  12  includes a cam body  34  which, according to several embodiments, is one-piece, homogeneous and substantially solid, and can be made from a polymeric or a metal material. According to other embodiments, cam body  34  can be created from a composite of materials. The term “homogeneous” as used herein refers to a component such as cam  12  wherein a material of the component is the same throughout its volume, and any connections between portions of the component are provided during the manufacturing process such that mechanical, welded, bonded, or similar connection methods for the portions are not used. According to several embodiments, cam body  34  defines a geometric shape, e.g., a circular shape as shown, or an oval, obround, or other geometric shape having a cam body outer surface  36  defining an outer perimeter of cam body  34 . 
         [0017]    In a first or bottom-dead-center position of cam  12  shown, a cam body center  38  defining a geometric center of cam  12  is axially aligned with a cam rotational axis  40 . A cam mount aperture  42  is co-axially aligned with cam rotational axis  40  and both are spatially separated from cam body center  38  by a fixed center-to-axis spacing “X”. The cam rotational axis  40  is fixedly spaced from the closest point of contact with outer surface  20  of work-piece  22  by an axis-to-surface spacing “Y”. Cam mount aperture  42  is provided to rotatably connect cam  12  to a rotating component (not shown) such as a shaft of a motor using a rotational fastener (not shown). In the first or bottom-dead-center position of cam  12  both cam body center  38  and cam rotational axis  40  are axially aligned on a cam displacement axis  44 , with cam rotational axis  40  positioned between cam body center  38  and compliant follower  14  as viewed in  FIG. 1 . Cam displacement axis  44  in the bottom-dead-center position of cam  12  according to several embodiments is centrally aligned between first and second guide walls  26 ,  28 , although central alignment is not required. 
         [0018]    According to additional embodiments, in the bottom-dead-center position of cam  12  cam displacement axis  44  is coaxially aligned with a bore axial centerline  46  of guide member bore  29  such that opposed portions of cam body outer surface  36  are substantially equally spaced with respect to each of first and second guide walls  26 ,  28 . Compliant follower  14  is displaced in the first direction “A” by rotation of cam  12  and, conversely, can also return in an opposite second direction “B” by an opposite rotation of cam  12  to provide either direct contact between first contact surface  18  and outer surface  20  of work-piece  22 , or to provide a clearance space or distance between first contact surface  18  and outer surface  20 . 
         [0019]    According to several embodiments, compliant follower  14  is entirely made of an elastically deformable material and includes opposed first and second contact walls  48 ,  50  and opposed first and second follower side walls  52 ,  54 . A follower void space or cavity  56  is created and bounded between first and second contact walls  48 ,  50  and first and second follower side walls  52 ,  54 . The cam body outer surface  36  of cam  12  contacts and when cam  12  is rotated slides against a follower second contact surface  58  facing outwardly of first contact wall  48 . To induce inward deflection of first contact wall  48  and minimize or prevent inward deflection of second contact wall  50 , first contact wall  48  has a first contact wall thickness “C” which is less than a second contact wall thickness “D” of second contact wall  50 . According to additional embodiments, only the first contact wall  48  of compliant follower  14  is made of an elastically deformable material. The deflection of first contact wall  48  is better described in reference to  FIG. 3 . 
         [0020]    A depth or thickness and a geometry in cross section of cams  12  and compliant followers  14  of the present disclosure can vary. Although cams  12  and compliant followers  14  having opposed, substantially planar faces and cam body outer surface  36  and first and second contact surfaces  18 ,  58  which are substantially perpendicular to the faces can be used, additional geometries can also be used. These include but are not limited to at least one of the faces being curved, non-symmetrical, faceted, or the like. Portions of the cam body outer surface  36  and either or both of first and second contact surfaces  18 ,  58  can also be angular, irregular or locally raised. 
         [0021]    Referring to  FIG. 2  and again to  FIG. 1 , the mechanical advantage of cam  12  is used by converting a rotational motion of cam  12  into a longitudinal displacement of compliant follower  14 . Initially and as previously described, direct contact is made between cam body outer surface  36  and second contact surface  58  of compliant follower  14 . Cam rotational axis  40  is retained at the axis-to-surface spacing “Y”, therefore as cam  12  is subsequently rotated in a counter-clockwise cam direction of rotation “E” by rotation through cam rotational axis  40 , a difference in a center-to-axis spacing “Z” is created between cam rotational axis  40  and cam body center  38  which is less than the center-to-axis spacing “X”. Center-to-axis spacing “Z” can be calculated as the cosine of an angle a, given a fixed dimension for center-to-axis spacing “X”. As cam body center  38  rotates with respect to cam rotational axis  40 , a component of cam axial displacement is created parallel to first direction “A”, thereby displacing compliant follower  14  in the first direction “A”. 
         [0022]    Cam  12  is rotated in the cam direction of rotation “E” until cam body center  38  is positioned to the right of cam displacement axis  44  and bore axial centerline  46 , and above cam rotational axis  40  as shown. In this position, cam body center  38  is located closer to second contact surface  58  of compliant follower  14  than cam rotational axis  40 . This rotated position of cam  12  creates direct contact between outer surface  20  of work-piece  22  and first contact surface  18  of compliant follower  14 . When initial contact is made between first contact surface  18  of compliant follower  14  and outer surface  20  of work-piece  22 , cam rotational axis  40  is positioned at a first spacing dimension “F” with respect to second contact surface  58 . At this time, a minimal force is applied, therefore first contact wall  48  is in an initial, substantially non-deflected condition and cam body outer surface  36  makes substantially point contact at a contact location  60  with first contact wall  48 . Subsequent application of force causes deflection of first contact wall  48 , therefore, because cam  12 , work-piece  22  and fixed member  24  are substantially incompressible, any subsequent rotation of cam  12  about cam rotational axis  40  in the cam direction of rotation “E” will result in a deflection of first contact wall  48  of compliant follower  14 . 
         [0023]    Referring to  FIG. 3  and again to  FIGS. 1 and 2 , cam  12  is shown following additional rotation about cam direction of rotation “E” until cam rotational axis  40  and cam body center  38  are once again both axially aligned with cam displacement axis  44  and bore axial centerline  46 , defining a top-dead-center position of cam  12 . The top-dead-center position of cam  12  is rotated substantially 180 degrees with respect to the position of cam  12  in the bottom-dead-center position shown in  FIG. 1 . Because cam rotational axis  40  is maintained at the axis-to-surface spacing “Y”, and first spacing dimension “F”, shown and described in reference to  FIG. 2  is maintained, a deflection of a first contact wall portion  48   a  of first contact wall  48  in the first direction “A” will occur. The deflection of first contact wall  48  results in first contact wall portion  48   a  displacing at least partially into cavity  56 . A maximum extension dimension “G” of cam  12  in the first direction “A” coincides with a maximum deflected condition of first contact wall portion  48   a . The elastically displaced material of first contact wall portion  48   a  can follow the geometry of cam body outer surface  36 , and therefore in the embodiment shown defines a substantially circular geometry. This deflection of first contact wall portion  48   a  occurs elastically, thereby creating a biasing force acting from first contact wall portion  48   a  through compliant follower  14  to work-piece  22 , having a component of the biasing force “W” acting parallel to first direction “A”. 
         [0024]    As previously noted, the bottom-dead center-position is established when cam rotational axis  40  is positioned between compliant follower  14  and cam body center  38 , with both cam rotational axis  40  and cam body center  38  axially aligned with cam displacement axis  44  and bore axial centerline  46 . Conversely, the top-dead-center position is established when cam body center  38  is positioned between cam rotational axis  40  and compliant follower  14 , again having both cam rotational axis  40  and cam body center  38  axially aligned with cam displacement axis  44  and bore axial centerline  46 . 
         [0025]    The top-dead-center position defines a deflected condition of first contact wall  48  of compliant follower  14 . According to several embodiments, the top-dead-center position of cam  12  also provides substantially equal spacing between opposed portions of cam body outer surface  36  and each of the first and second guide walls  26 ,  28 , however equal spacing is not required. The component of the biasing force created by elastically deflecting first contact wall  48  acting in the first direction “A” in the top-dead-center position of cam  12  is directed through the center of work-piece  22  and thereby maximizes a holding force retaining compliant follower  14  in direct contact with work-piece  22 . In a maximum deflected condition first contact wall  48  contacts second contact wall  50 . From the top-dead-center position of cam  12 , cam  12  can be returned to the bottom-dead-center position by continued rotation in the cam direction of rotation “E” or by opposite rotation of cam  12  in a cam rotation of direction “E””. 
         [0026]    Referring to  FIG. 4  and again to  FIGS. 1-3 , according to further embodiments a compliant follower  62  is modified from compliant follower  14  by increasing a width of first and second follower side walls  64 ,  65 . This modification decreases a volume of a cavity  66 . In this embodiment, a first contact wall  68  is fully deflected when a first cavity wall  70  of cavity  66  is in alignment with a first contact point  72  defined between cam body outer surface  36  and a second contact surface  74  in the deflected condition of compliant follower  62 . At the same time, a second cavity wall  76  of cavity  66  is in alignment with a second contact point  78  defined between cam body outer surface  36  and second contact surface  74  in the deflected condition of compliant follower  62 . Contact between the first contact wall  68  and second contact surface  74  as first contact wall  68  elastically deflects follows the contour or shape of cam body outer surface  36  out to the first and second outward contact points  72 ,  78 . A lateral location or positioning of the first and second cavity walls  70 ,  76  where they align with the second contact surface  74  locate the first and second outward contact points  72 ,  78  between the cam body outer surface  36  and the first contact wall  68  at a maximum deflected position “H” of the first contact wall  68 . 
         [0027]    Further deflection of compliant follower  62  from the maximum deflected position of the first contact wall  68  shown in  FIG. 4  requires deflection of a second contact wall  80  oppositely positioned with respect to first contact wall  68 , in the second direction “B”, which is resisted by the greater thickness of second contact wall  80 . A second contact wall  80  thickness is equal to the second contact wall thickness “D” of second contact wall  50 , described in reference to  FIG. 1 . By adjusting the lateral positioning of first and second cavity walls  70 ,  76  in the embodiment of compliant follower  62 , an effective stiffness of compliant follower  62  can be controlled, thereby controlling a holding force of compliant cam  62  at a specific deflection. A maximum deflected position “H” of first contact wall  68  is controlled by the geometry of cam  12 , center-to-axis spacing “X”, and a thickness of first contact wall  68 . Similar to cavity  56 , the lateral position of first and second cavity walls  70 ,  76  together with the first and second contact wall thicknesses “C” and “D” define a shape and an area of cavity  66 , which according to several embodiments has a rectangular shape, but can be circular, oval, or other geometric shapes. 
         [0028]    Referring to  FIG. 5  and again to  FIGS. 1 and 4 , a curved compliant follower  82  includes a curved first contact wall  84  having a first contact wall thickness “J”, and an opposed curved second contact wall  86  having a second contact wall thickness “K” which is a greater thickness than first contact wall thickness “J” to induce first contact wall  84  to elastically deflect upon rotation of cam  12  without deflection of second contact wall  86 . First and second contact wall thicknesses “J” and “K” can also be equal to permit both first and second contact walls  84 ,  86  to equally deflect upon rotation of cam  12 . A substantially curve-shaped cavity  88  is created between first and second contact walls  84 ,  86 . A thickness or width of opposed first and second follower side walls  90 ,  92  can also be varied to provide first and second outward contact points similar to first and second outward contact points  72 ,  78 . Curved compliant follower  82  can be substituted for compliant followers  14 ,  62  for example to provide an increased initial resistance to deflection of first contact wall  84  compared to first contact wall  48 , and to provide an increased resistance to deflection by use of second contact wall  86 . The amount of curvature of curved compliant follower  82  can be increased or decreased, including providing a substantially circular compliant follower  82 . 
         [0029]    Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
         [0030]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0031]    When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0032]    Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
         [0033]    Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0034]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.