Abstract:
A brake for a gas spring rod includes a lock base having an axially extending central aperture and a pair of associated conical surfaces surrounding the aperture. It also includes a pair of clamping members positioned on opposite sides of the lock base, each of the members including a center aperture and a conical surface having an axis offset from the axis of said center aperture. The clamping members are coupled to the lock base by a coupling including a bias spring for moving the clamping members into engagement with the lock base with the respective conical surfaces in contact such that the center apertures are offset from said central aperture of said lock base.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) and the benefit of U.S. Provisional Application No. 61/647,571 entitled SAFETY RELEASE filed May 16, 2012, by Wilkinson et al.; U.S. Provisional Application No. 61/672,925 entitled SAFETY RELEASE filed Jul. 18, 2012, by Wilkinson et al.; U.S. Provisional Application No. 61/647,566 entitled DOUBLE ACTING FLUID CYLINDER LOCK filed May 16, 2012, by Wilkinson et al.; U.S. Provisional Application No. 61/672,920 entitled DOUBLE ACTING FLUID CYLINDER LOCK filed on Jul. 18, 2012, by Wilkinson et al.; and U.S. Provisional Application No. 61/758,997 entitled SELF-ALIGNING AXIAL BEARING, filed on Jan. 31, 2013, by Wilkinson et al., the entire disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a double acting lock for fluid cylinders and particularly gas cylinders employed for raising and lowering adjustable tables. 
         [0003]    Use of pressurized gas cylinders frequently referred to as gas springs is commonplace in the furniture industry in which chairs and table heights are desired to be easily adjusted. Typically, the gas spring force is selected to counterbalance the normal weight load expected and its stroke selected for the desired amount of movement. To control the telescopic support tubes in which the gas spring is employed, a variety of locking mechanisms have been employed, as well as controlling the flow of fluid on either side of the piston of a gas spring. Some of the mechanisms employed for locking an adjustable table in place require relatively complicated mechanisms which are both expensive and somewhat prone to failure. There exists a need, therefore, for a relatively robust system which minimizes the number of components to reduce costs and yet provides positive locking of an extendable rod of a gas cylinder in a selected extended or retracted direction. 
       SUMMARY OF THE INVENTION 
       [0004]    A brake for a gas spring rod includes a lock base having an axially extending central aperture and a pair of conical cam plates with outwardly projecting opposed conical surfaces also having apertures surrounding and aligned with the central aperture of the lock base. It also includes a pair of clamping members positioned on opposite sides of the plates, each of the members including a center aperture and a conical surface having an axis offset from the axis of said apertures of said plates and lock base. The clamping members are coupled to the lock base by a coupling for moving the clamping members into engagement with the lock base and the respective conical surfaces in contact such that the center apertures are offset from said apertures of said plates. In a preferred embodiment the coupling includes a pivot pin extending from the lock base and a pivot lever pivotally coupled to the pivot phi and having opposite ends coupled to the clamping members such that, as the pivot lever is rotated, the clamping members synchronously move toward or away from the lock base. Also in a preferred embodiment a bias spring is coupled between the clamping members to urge them into contact with the plates and lock base. When mounted to an extendable rod of a gas spring by mounting the lock base to one of the telescopic tubes of an adjustable member, the axially offset releasable clamping members, when in a locked position, engage the rod to hold it in a fixed position, thereby holding the telescopic tubes in a selected position. 
         [0005]    These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of two adjustable tables incorporating the system of the present invention; 
           [0007]      FIG. 2  is a side elevational view of a telescopic leg of the table supports shown in  FIG. 1 ; 
           [0008]      FIG. 3  is a vertical cross-sectional view of an adjustable table support embodying the locking mechanism of the present invention; 
           [0009]      FIG. 4  is an enlarged fragmentary cross-sectional view of the locking mechanism shown in  FIG. 3 ; 
           [0010]      FIG. 5  is a fragmentary cross-sectional view, partly cutaway, of the locking mechanism and inner and outer tubes seen in  FIG. 4 ; 
           [0011]      FIG. 6  is a perspective view of the locking mechanism, shown removed from the telescopic tubes; 
           [0012]      FIG. 7  is an enlarged perspective view of the lock base; 
           [0013]      FIG. 8  is a top plan view of the lock base; 
           [0014]      FIG. 9  is a right-side elevational view of the base shown in  FIG. 8 ; 
           [0015]      FIG. 10  is a fragmentary perspective view of the area X of  FIG. 8 ; 
           [0016]      FIG. 11  is a perspective view of one of the identical conical plates; 
           [0017]      FIG. 12  is a top view of the plate shown in  FIG. 11 ; 
           [0018]      FIG. 13  is a front elevational view of the plate shown in  FIGS. 11 and 12 ; 
           [0019]      FIG. 14  is an enlarged perspective view of one of the identical clamping members; 
           [0020]      FIG. 15  is a bottom plan view of the clamping member shown in  FIG. 14 ; 
           [0021]      FIG. 16  is a rear elevational view of the clamping member shown in  FIG. 15 ; 
           [0022]      FIG. 17  is a vertical cross-sectional view of the clamping member taken along section lines XVII-XVII of  FIG. 15 ; 
           [0023]      FIG. 18  is a detailed view of the circled area in  FIG. 15 ; 
           [0024]      FIG. 19  is a perspective view of one of the pivoted locking levers; 
           [0025]      FIG. 20  is a side elevational view of the lever shown in  FIG. 19 ; 
           [0026]      FIG. 21  is a top plan view of the lever shown in  FIG. 20 ; 
           [0027]      FIG. 22  is a cross-sectional view taken along section lines XXII-XXII of  FIG. 20 ; 
           [0028]      FIG. 23  is a side elevational view of one of the springs employed in the locking assembly; 
           [0029]      FIG. 24  is a right-side elevational view of the spring shown in  FIG. 23 ; 
           [0030]      FIG. 25  is a top plan view of one of the clamping members showing the offset between the axis of the center aperture and the axis of the conical surface; 
           [0031]      FIG. 26  is a fragmentary perspective view showing the lock base positioned on the end of the inner telescopic tube; and 
           [0032]      FIG. 27  is a fragmentary perspective view showing a clamping member resting on the upper conical cam plate and on the lock base as positioned in  FIG. 26 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]      FIG. 1  shows adjustable tables  30  which include a height adjustment assembly including telescopic tubes  32  and  34  extending between a floor support  36  and a table surface  38 .  FIG. 2  shows one of the table legs  15  with a support flange  35  at the upper end of telescopic tube  34  and a fitting  33  which extends into a socket in the floor support  36  of  FIG. 1 . The telescopic tube  34  slideably extends within outer tube  32  with polymeric bearings  20  ( FIGS. 2) and 23  ( FIG. 5 ) providing smoothly guided movement between the tubes  32 ,  34 . The general construction of leg  15  is disclosed in the above-identified application Ser. No. 61/758,997, entitled SELF-ALIGNING AXIAL BEARING. Within the telescopic tubes, there is a fluid spring, such as gas spring  10  shown in  FIG. 3 , which controls a cylinder rod  12  to raise and lower the extruded inner table support tube  34 . For such purpose, the opposite ends of spring  10  are conventionally coupled to each of the tubes  32 ,  34  so that extension of rod  12  causes the overall length of the tubes forming the pedestal table leg  15  to extend and retract for raising and lowering the table surface  38 . Fixedly coupled to the lower end of extruded tube  34  is the locking mechanism  40  of the present invention. The outer tube  32  is mounted to support a member, such as  33  in  FIG. 2  or  18  in  FIG. 3 . The orientation of the telescopic tubes can be reversed depending upon a particular application. 
         [0034]    The leg assembly  15  so-formed also includes a safety release  100  which includes a 
         [0035]    Bowden cable release  120  ( FIG. 3 ) which is coupled to a control handle (not shown) and is limited in its movement, as shown by arrow A, to a few millimeters. A link  102  couples the cable release  120  to a release rod  26 , which, when raised in the direction of arrow B in  FIG. 4 , releases the locking mechanism  40 . The safety release  100  is described in greater detail in copending U.S. patent application Ser. No. (Attorney Docket No. SUS001 P344) filed on the even date herewith and entitled SAFETY RELEASE, the disclosure of which is incorporated herein by reference. 
         [0036]    The locking mechanism  40 , which is secured to one of the telescopic tubes  32 ,  34 , grips the rod  12  extending from gas spring  10  in any desired position selected by the user by moving rod  26  upwardly, as indicated by arrow B, to release the grip on rod  12  by locking mechanism  40 . The table surface can then be manually raised or pushed down until the desired position of the table (or chair) is reached. 
         [0037]    The locking mechanism  40  comprises a lock base  42 , which is a generally triangular member having a central aperture  49  ( FIGS. 4 ,  7  and  8 ) surrounding piston rod  12 . It includes three lateral flanges  47  ( FIGS. 7 and 8 ) with apertures  52  through which three screws  41  extend to securely fix the lock base and hence the locking mechanism  40  to threaded extrusions  58  (partially shown in  FIG. 5 ) of the extruded hexagonal inner support tube  34  to secure the locking mechanism to the lower end of tube  34 . The outer tube  32  is fixed and is attached to the table (or chair) base, while the inner extruded tube  34  moves up and down with the rod  12  sliding through locking mechanism  40 , when in a released position, to raise and lower the table attached to the upper end of extruded tube  34 . Associated with the lock base  42  are opposed upper and lower conical cam plates  46 ,  48  with external conical surfaces  43  and  45  (FIGS.  4  and  11 - 13 ). Surfaces  43 ,  45  are engaged by interior conical mating surfaces  61  and  63  of upper and lower movable clamping members  60  and  62  ( FIGS. 4-6 ,  14 , and  15 - 18 ), respectively. The plates  46 ,  48  have central apertures  50 ,  51  ( FIGS. 4 ,  11 , and  12 ) which generally align with aperture  49  of lock base  42  and receive rod  12 , which extends through members  60 ,  46 ,  42 ,  48  and  62 , as best seen in  FIG. 4 . Lock base  42  has an upper surface  53  which is slideably engaged by the lower surface  55  ( FIGS. 4 ,  7 ,  8 , and  13 ) of conical cam plate  46 . Similarly, the lower surface  56  of lock base  42  is engaged by the upper surface  57  of conical cam plate  48 . This sliding or floating arrangement of the cam plates  46 ,  48  allows the tapered clamping members  60 ,  62  to better engage the offset cam plates to effect locking of the locking member  40  to rod  12 , as described below. 
         [0038]    Extension springs  70  ( FIGS. 5 ,  6 ,  23  and  24 ) have loop ends  71  which fit over mounting tabs  66  on opposite sides of each of the clamping members  60 ,  62 , as best seen in  FIG. 6 , to urge members  60 ,  62  in a compressed position against lock base  42 . Members  60 ,  62  have center apertures  65  ( FIGS. 15 and 17 ) which are offset a distance d ( FIG. 25 ) of about 1 mm from the axis of their conical surfaces  61 ,  63  and shift and/or tilt members  60 ,  62  under the forces of springs  70  such that, when compressed to the opposed conical surfaces  43  and  45  of conical cam plates  46 ,  48 , the inner cylindrical surfaces  68  ( FIG. 17 ) of center apertures  65  bind to the outer surface of rod  12 , thereby locking the inner extruded tube  34  in a selected adjusted position. Polymeric bearing sleeves  20 ,  23  (shown in  FIGS. 2 ,  3 , and  5 ) facilitate movement of tubes  32  and  34  when the locking mechanism is unlocked. 
         [0039]    The unlocking of mechanism  40  is controlled by rod  26 , which is coupled to the bracket  64  of upper clamping member  60 , which, along with clamping member  62 , has outwardly extending pins  67  on each side ( FIGS. 5 ,  14  and  15 ). Pins  67  extend through apertures  91  in the ends of pivoted levers  90 , which are pivotally mounted to lock base  42  by pivot axles  44  ( FIGS. 6-10 ) integrally extending from opposite sides of the lock base  42 . Lateral pressure from springs  70  hold the levers  90  in place on lock base  42 , as best seen in  FIGS. 5 and 6 . 
         [0040]    When rod  26  is moved upwardly in the direction of arrow B in  FIG. 6 , levers  90  rotate in a counterclockwise direction, as viewed in  FIG. 6 , to raise clamping member  60  away from lock base  42  and associated cam plate  46 , as well as pushing clamping member  62  downwardly away from the lock base  42  and associated cam plate  48 , thereby allowing the apertures  65  of clamping members to move to a coaxial position around rod  12 . This releases the locking force of members  60 ,  62  against rod  12  and permits the table-supporting extruded tube  34  to move up and down on rod  12  extending or collapsing the telescopic tubes  32 ,  34 . The actual weight of the table on members  60 ,  62  offset by the force of gas spring  10  causes the apertures  65  of members  60 ,  62  offset from the central aperture  49  of locking base  42  to increase the effect of the locking action. 
         [0041]    The weight on the table surface is transferred by lock base  42  and conical cam plates  46 ,  48  to one or the other of the clamping members  60 ,  62  of the locking mechanism. When the weight exceeds the force of spring  10 , the lower clamping member  62  locks against the rod  12  as the conical surface  45  of cam plate  48  ( FIG. 4 ) pushes against conical mating surface  63  of clamping member  62 . When the weight on the table surface is less than the force of spring  10 , lock base  42  wants to raise and conical surface  43  of cam plate  46  engages the conical mating surface  61  of upper clamping member  60  to prevent the undesired raising of the table. Thus, the table surface will remain in a selected adjusted position until such time as the safety release  100  is actuated. The heavier the weight on the table, the more locking force is applied, with the springs  70  positioning locking members  60 ,  62  into a locking position. By providing members  60  and  62  on opposite sides of the locking base  42 , the table is locked against either raising or lowering until the release rod  26  is moved upwardly in the direction of arrow B. 
         [0042]    The details of construction of the lock base  42  and cam plates  46 ,  48  are shown in  FIGS. 7-13 , while the details of construction of the metal clamping members  60 ,  62  is shown in  FIGS. 14-18 . The details of construction of the coupling levers  90  is shown in  FIGS. 19-22 , while the details of springs  70  are shown in  FIGS. 23 and 24 .  FIG. 6  shows the locking assembly  40  mounted to rod  12 . The top plan view of clamping member  62  in  FIG. 25  illustrates the 1 mm offset of the axis of the central aperture  65  and the axis of the interior conical surface  63 .  FIG. 26  illustrates the position of the lock base  42  at the end of inner tube  34 , and the drawing of  FIG. 27  illustrates the positioning of upper clamping member  60  with respect to lock base  42 . 
         [0043]    The locking mechanism  40  ( FIG. 3 ) grips the rod  12  extending from gas spring  10  in any desired position selected by the user until it is desired to change the position of the table. In which case, cable release  120  ( FIG. 3 ) is drawn inwardly (to the left in  FIG. 3 ), moving rod  26  upwardly through link  102  to release the grip on rod  12  by locking mechanism  40 . Unless overloaded or under loaded, the table can then be lowered or raised under the influence of gas spring  10 . The safety release  100  ( FIG. 3 ) prevents the release of the locking mechanism when the table is overloaded, such that it will not precipitously drop. If the weight on the table is significantly less than the force provided by the gas spring, the safety release will also prevent the release of the locking mechanism, such that the table surface will not quickly raise. The operation of the safety release assembly  100  to accomplish these features is disclosed in detail in provisional application entitled SAFETY RELEASE, Ser. No. 61/672,925, filed on Jul. 18, 2012, by Wilkinson et al, and utility application entitled SAFETY RELEASE, Ser. No. (SUS001 P344), filed on the even date herewith, the disclosures of which are incorporated by reference. 
         [0044]    It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.