Patent Publication Number: US-6711985-B1

Title: Sealed glide adapter

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a hydraulic lift system for use in connection with adjustable work surfaces and particularly to an improvement to the support tube for preventing leakage of hydraulic fluid. 
     As the work place environment changes with technology, so too do the facilities employed by companies to provide ergonomically appropriate work stations for technical, clerical, and assembly personnel. To accommodate different job tasks, frequently it is desirable to have a work surface or table which is vertically adjustable, such that the work surface can be employed by individuals of different stature and individuals in a standing position, a sitting position on a chair, or in an intermediate position when using, for example, a stool-height seat. 
     There exists numerous adjustable table assemblies which are either mechanically controlled by screw jack mechanisms or which are electrically controlled screw jacks. Some installations employ hydraulic cylinders with a pump for pressurizing fluid from a master cylinder to slave cylinders mounted within hydraulic lifts secured to the legs of a table for controlling the vertical adjustment of the work surface. One such system is commercially sold by Suspa Incorporated under the trademark MOVOTEC®, which includes a hydraulic support tube assembly for each table leg, with each support tube assembly including an outer housing, a support tube extendable from the housing and an inner hydraulic cylinder which is coupled between the outer housing and support tube and includes a piston rod which extends and retracts for raising and lowering the support tube for extending and retracting the support tube from the housing. The support tube includes a threaded glide at its lower end which extends through a glide adapter providing an interface between the support tube and the threaded adjustable glide which is in the form of an adjustable foot which contacts the support surface for the table. In such systems, the glide adapter includes an annular outer seal extending between the inner surface of the support tube and the glide adapter to provide a sealed interface. The adjustable glide is threaded along its entire axial length to provide a maximum adjustment of the lift cylinder assembly for leveling of the table on uneven support surfaces. The piston rod from the hydraulic cylinder is typically pinned to the glide adapter, which is lockably held to the support tube by crimping. It has been discovered that with several years and thousands of cycles of use, the inner hydraulic cylinder tends to leak fluid slightly, which fluid, when exiting the hydraulic cylinder, enters the support tube area and accumulates at the lower end near the junction of the piston rod and glide adapter. With the threaded throughhole for receiving the adjustable glide, the fluid will, over a period of time, seep from the bottom of the lift, spilling over the glide and contacting the floor surface on which the table is supported. This typically only happens after several years of use, however, the result can be a hydraulic fluid stained carpet, floor, or other surface. 
     Thus, there exists a need to overcome this problem to prevent hydraulic fluid leakage from a hydraulic lift after years of use such that staining of the floor surface is prevented. Also, there exists a need for an improved lift cylinder which solves the leakage problem and allows the hydraulic cylinder to be removed for repair if necessary. 
     SUMMARY OF THE INVENTION 
     The system of the present invention solves this problem by providing a unique glide adapter which is relatively inexpensive and which includes a seal extending between the piston rod and glide adapter to prevent hydraulic fluid which may escape the hydraulic cylinder from seeping from the lift itself. In a preferred embodiment of the invention, the sealed glide adapter comprises a generally cylindrical member having an axially extending threaded aperture formed through one end for receiving a threaded adjustable glide. A cylindrical recess is formed in the glide adapter at an opposite end and includes an undercut recess for snap-receiving a resilient polymeric cylindrical seal which includes an annular groove for receiving an O-ring extending between the outer surface of the seal and the inner cylindrical surface of the glide adapter. The seal includes a blind aperture for receiving one end of the piston rod of the hydraulic cylinder. 
     With such construction, therefore, the glide adapter is sealed both on its outer periphery to the cylindrical support tube and on its inner periphery against the interior of the seal such that leakage of hydraulic fluid from the lift is prevented. 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 
     FIG. 1A is a perspective view of a work surface shown in a lowered position and including a support tube embodying the present invention attached to each of its legs; 
     FIG. 1B is a perspective view of the work surface shown in FIG. 1A, shown in an elevated position; 
     FIG. 2 is a perspective view of one of the lifts of the present invention; 
     FIG. 3 is an exploded perspective view of the components of the lift shown in FIGS. 1 and 2; 
     FIG. 4 is a vertical cross-sectional view of the lift shown in FIGS. 1-3, partly broken away; and 
     FIG. 5 is an enlarged cross-sectional view of the area V shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIGS. 1A and 1B, there is shown a table  10  having a horizontally extending work surface  12  supported by four downwardly depending legs  13 - 16 , which are stabilized by cross members  17  coupled to the legs near the lower ends thereof. Secured to each of the legs is a hydraulic lift  20  embodying the present invention. Lifts  20  are secured to the legs by conventional fasteners extending through the legs  13 - 16  and threaded into flat side  27  of the housing  22  (FIG. 2) of each of the lifts  20 . The table  10  includes a hydraulic pump unit  18  mounted to the undersurface thereof from which extends hydraulic lines  23 - 26  into each of the lifts  20  associated with the four table legs  13 - 16 . Unit  18  can include a hand crank for manual operation or, in the preferred embodiment, includes an electrically actuated pump controlled by switches on a control panel  21 . Panel  21  is mounted on the forward edge of the undersurface of work surface  12  and includes controls for selectively controlling unit  18  for raising and lowering the work surface  12  as illustrated in FIGS. 1A and 1B or to any desired intermediate position and can be preprogrammed for multiple settings. 
     Each of the lifts  20  are identical so only one such lift is now described in connection with FIGS. 3-5. Lifts  20  incorporate a few structural elements, the understanding of which will become apparent upon a description of the details of the lift construction, however, a brief description of the overall system is first presented. As best seen in FIG. 4, each lift  20  includes a connecting head  30  which is lockably secured to the upper end of housing  22 . Connecting head  30  is sealably coupled to the upper end of a hydraulic cylinder  40  having a piston  50  which is in sealed communication with a fluid channel  35  in connecting head  30 . Thus, hydraulic fluid pressure applied through a suitable hydraulic connection to one of the lines  23 - 26  shown in FIG. 1 applies pressure to a piston  50 , which is coupled by piston rod  60  to the sealed glide adapter assembly  70  which, in turn, is lockably coupled to the support tube  90 . Support tube  90  is slidably positioned and supported within housing  22 , in part, by a support tube sleeve bushing  100 . A threaded adjustable glide  110  is inserted into a glide adapter  80  included in assembly  70  such that, as fluid pressure is applied to the upper end of piston  50 , piston rod  60  extends and retracts from the cylinder  40  extending and retracting the support tube  90  from the lift, as seen in FIGS. 1A and 1B. 
     As will become apparent from the following description, the annular space  120  (FIG. 4) between the piston rod  60  external to hydraulic cylinder  40  and the inner surface  92  of support tube  90  is sealed at its lower end such that any loss of hydraulic fluid from cylinder  40  over a period of use will not be capable of seeping through the lower end of lift  20  due to the unique design of the sealed glide assembly  70 . Having briefly described the overall components of the lift  20 , a detailed description now follows in conjunction with FIGS. 3-5. 
     As seen in FIGS. 3 and 4, the housing  22  for lift  20  includes a generally cylindrical, longitudinally extending opening  29  extending along its length for receiving the components of the lift including the hydraulic cylinder  40 , support tube sleeve bushing  100 , support tube  90 , piston rod  60 , and the sealed glide adapter assembly  70 . The exterior of housing  22  includes at least one flat surface  27  (FIGS.  2  and  3 ), which is positioned against one of the flat table legs  13 - 16  and which includes threaded apertures (not shown) for receiving threaded fasteners extending through the table legs and securing a housing  22  to each of the table legs as seen in FIGS. 1A and 1B. The lift  20  includes a connecting head  30  which is secured to housing  22  by means of an annular groove  33  formed in the connecting head and which is held against axial movement by a pair of locking pins  32  extending through apertures  34  in housing  22  (FIG.  3 ). The connecting head  30  includes a central threaded, axially extending aperture  35  for receiving a fitting sealably coupling one of the hydraulic lines  23 - 26  which extends through aperture  37  in a closure cap  36  snap-fitted to the open upper end of housing  22 . 
     The connecting head  30  is sealably coupled to the inner cylindrical wall of the elongated hydraulic cylinder  40  by means of an O-ring  38  (FIG. 4) positioned in an annular groove  39 . The metallic cylindrical wall  44  of hydraulic cylinder  40  is crimped around its periphery at  41  to seal the upper end of cylinder  40  to the reduced diameter downwardly depending cylindrical end  42  of connecting head  30 , which thereby sealably extends into the top of cylinder  40 . Sealably coupled to the inner cylindrical surface  43  of cylinder  40  is a hydraulic piston  50  comprising a polymeric member which has a piston head  52  in fluid communication with the passageway  35  through connecting head  30  to receive the pressurized hydraulic fluid applied thereto. Piston  50  includes an annular groove  52  which holds an O-ring seal  54  for sealing the piston to inner wall  43  of hydraulic cylinder  40 . An axial aperture  56  extends upwardly from the lower end of piston  50  and receives, in a force-fitting manner, the serrated upper end  62  of the piston rod  60  which is force-fit within aperture  56  to hold the end  62  of piston rod  60  to the piston  50 . The lower end of the hydraulic cylinder  40  engages the outer cylindrical surface  64  of piston rod  60  by means of a bushing  65  which allows the piston rod to extend and retract from cylinder  40  for extending and retracting the support tube  90  as described below. 
     Over a period of years of use, the piston seal  54  will allow some leakage of hydraulic fluid into the annular space  66  between piston rod and inner surface  43  of cylinder  40  which can seep through the sliding bushing  65  and into the annular space  120  between the piston rod  60 , cylinder  40 , and inner wall  92  of support tube  90 . Leaked hydraulic fluid, under the force of gravity, flows to the lower end of lift  20 . The sealed glide assembly  70  of the present invention prevents leakage of such fluid from the lower end of the lift. 
     The glide adapter assembly  70  includes a seal  75 , which can be generally cup-shaped (FIG.  5 ), and a glide adapter  80 , with the seal  75  being made of a polymeric material and generally cylindrical, having a central axially downwardly depending blind aperture  72  which receives in force-fitting fashion the lower serrated end  67  of piston rod  60 . Seal or cap  75  is sealably and lockably secured to an inner cylindrical surface  82  in glide adapter  80 , as best seen in FIG. 5, by means of an outwardly projecting annular tang  74  of seal  75  having a latching shoulder  76  which engages undercut recess  84  in glide adapter  80 . Thus, edge  76  of tabs  74  engage the horizontally extending annular surface  86  formed by undercut recess  84  to lockably hold the cylindrical seal  75  to the glide adapter  80  against movement in a longitudinal direction (indicated by arrow A in FIG.  5 ). To allow the flexing of tabs  74 , an annular recess  78  is formed upwardly in the integrally machined seal  75  radially inside tabs  74 . Seal  75  further includes a peripheral annular recess  79  for receiving a sealing O-ring  77  which seals against the inner cylindrical surface  82  of adapter  80 . Thus, the seal  75  provides a physical coupling of piston rod  60  to glide adapter  80  and a sealed interconnection between glide adapter  80  and the space  120  between support tube  90  and hydraulic cylinder  40 . The seal  75  includes an annular shoulder  71  (FIG. 5) which engages the upper annular rim  81 ′ of glide adapter  80  to transmit the downward force applied by the piston rod on seal  75  to support tube  90  through glide adapter  80 . 
     The glide adapter  80  is a machined generally cylindrical steel member and includes a central threaded aperture  87  extending therethrough (FIG. 4) having a hex-shaped lower end  88  for allowing adjustment of glide  110  as described below. Glide adapter  88  further includes an annular recess  89  which receives a sealing O-ring  81  therein for sealing the outer cylindrical surface  83  of glide adapter  80  to the inner cylindrical surface  92  of support tube  90 . Support tube  90  is secured to the glide adapter  80  by means of an annular groove  85  extending around the periphery of glide adapter  80  and which receives a crimp  95  in the cylindrical wall of support tube  90 . Thus, the lower end of support tube  90  is mechanically and sealably coupled to glide adapter  80 . 
     The glide  110  includes a foot  112  and an upwardly extending threaded end  114  which is adjustably threaded into threaded aperture  87  of glide adapter  80 . Glide  110  includes a hex surface  111  which, together with hex surface  88  on glide adapter  80 , allows wrenches to adjust the glide for leveling the table on uneven surfaces and to provide a finite amount of final height adjustment if desired. The support tube  90  is guidably held within the cylindrical aperture  29  of housing  22  by means of a cylindrical guide bushing  100  having a longitudinally serrated inner surface  102 , as best seen in FIG. 3, and an enlarged annular shoulder  104  which overlies, as best seen in FIG. 4, the lower end of housing  22 . As seen in FIG. 4, the axial height of threaded section  114  of glide  110  is selected to prevent the glide from engaging seal  75 . 
     In operation, as pressure is applied to the piston  50 , rod  60  extends from cylinder  40 , pushing downwardly against the connecting cap  30  locked to the housing  22  thereby pushing against seal  75  and glide adapter  80  which is coupled to support tube  90 , thereby extending support tube  90  through bushing  100  outwardly from housing  22 , raising the work surface  12 , as illustrated in FIG.  1 B. Upon release of the hydraulic pressure in cylinder  40 , the support tube  90  can again retract within housing  22  as piston  60  retracts within cylinder  40 . By providing the sealed glide assembly  70  of the present invention, any fluid which may leak from cylinder  40  into annular space  120  of the lift  20  is captured and prevented from escaping the lower end of the lift by means of O-ring seals  77  and  81  (FIGS.  4  and  5 ). 
     If it becomes necessary to replace hydraulic lift cylinder  40 , cap  36  is removed from housing  22 , as are locking pins  32 . Glide  110  is then removed from glide adapter  80  and a tool, such as a rod, is inserted through aperture  87  to press the cap seal  75  and attached hydraulic cylinder  40  out through the open upper end of housing  22 . A new cylinder and seal can then be installed. 
     In a preferred embodiment of the invention, the seal  75  is screw machined from a polymeric material made of, for example, acetal, polybutylene teraphthalate, or other suitable material. The glide adapter  80  is machined of metal, such as steel, and support tube  90  can also be made of metal, such as polished aluminum, stainless steel, or the like to provide an aesthetically acceptable external wall surface appearance when extended from the housing  22  as seen in FIG.  1 B. Support tube sleeve bushing  100  is also made of a lubricious polymeric material, as are piston  50  and foot  112 . The remaining components typically are machined aluminum or other suitable metal for providing the desired strength and rigidity to the lift  20  so formed. The locking tab  76  on seal  75  is a continuous annular member. In some embodiments it may be desirable to provide serrations to define a plurality of arcuately spaced locking tabs. 
     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.