Patent Publication Number: US-2009217815-A1

Title: Pneumatic or Hydraulic Cylinder

Description:
TECHNICAL FIELD 
     The present invention relates to hydraulic and pneumatic cylinders and more particularly but not exclusively to hydraulic cylinders as described in International Patent Application PCT/AU2004/001677. 
     BACKGROUND OF THE INVENTION 
     Hydraulic cylinders include a cylinder (barrel) with a bore that slidably receives a piston. The piston moves longitudinally of the bore. The cylinder of the abovementioned patent application has a mechanism that locks the piston with the piston rod in a retracted position. 
     The abovementioned hydraulic cylinder was initially designed for use in raising and lowering the load receiving tray of a vehicle. However it also found application in another arrangement, that is, a vehicle seat that is moved laterally out of a vehicle door for the purposes of making it easier for disabled passengers to use the vehicle. This arrangement is described in Australian Provisional Applications 2004905651 and 2004903272. 
     The abovementioned hydraulic and pneumatic cylinders have the disadvantage that they only provide for movement longitudinally of the longitudinal axis of the cylinder. 
     OBJECT OF THE INVENTION 
     It is the object of the present invention to overcome or substantially ameliorate the above disadvantage. 
     SUMMARY OF THE INVENTION 
     There is disclosed herein a pneumatic or hydraulic cylinder having a longitudinal axis to be activated by fluid under pressure, the cylinder including:
     a barrel having a bore surrounding a longitudinally extending chamber;   a piston slidably located in the bore for longitudinal movement thereof, the piston cooperating with said bore to divide said chamber into a first sub-chamber and a second sub-chamber, the sub-chambers being separated by the piston, with the volume of the sub-chambers being varied by longitudinal movement of the piston, with hydraulic fluid under pressure being delivered to the sub-chambers to cause longitudinal movement of the piston;   a first surface, said surface extending longitudinally and angularly with respect to said longitudinal axis; and   a second surface, said second surface being engagable with said first surface, with the surfaces being operatively associated with said bore and piston so that longitudinal movement of said piston with respect to said bore causes relative movement between the surfaces which in turn causes angular movement of the piston relative to the bore about said axis.   

     Preferably, said first surface is provided by a groove extending longitudinally and angularly about said axis, and said second surface is provided by a spherical element at least partly projecting into said groove. 
     Preferably, said groove is in said piston and said spherical element is maintained substantially fixed in location with respect to said bore so that engagement of said spherical element in said groove causes said angular movement. 
     Preferably, said piston has a plurality of grooves, and said cylinder includes a plurality of spherical elements, the spherical elements being retained in recesses in said bore, with each groove being operatively associated with a respective one of the elements. 
     Preferably, the elements are angularly spaced about said axis at equally angular intervals. 
     Preferably, in said cylinder, said barrel is a first barrel, said bore is a first bore and said chamber is a first chamber, with said cylinder further including:
     a second barrel, said second barrel having a second bore;   a piston rod, said piston rod being slidably located in said second bore and cooperating therewith to provide a variable volume second chamber into which fluid under pressure is delivered to move the piston rod to change the volume of said second chamber;   a port in communication with said second chamber and via which fluid is allowed to pass;   a lock assembly mounted on the piston rod, the assembly including:   at least one locking member movable relative to said axis between a radially inner position permitting movement of the piston rod, and a radially outer position engaging the second barrel to prevent movement of the piston rod in a predetermined direction beyond a predetermined longitudinal position;   a retaining member mounted on the piston rod and movable longitudinally relative thereto between a first position retaining a locking member in a radially outer position, and a second position providing for movement of the locking member to the radially inner position;   means to urge the retaining member to the first position thereof to thereby urge the locking member to the radially outer position; and   wherein said retaining member when in the first position and exposed to the fluid under pressure is moved to the second position thereof to allow movement of the locking member to the radially inner position to free set piston rod for movement in said direction.   

     Preferably, said cylinder includes a piston rod in a first piston rod and said assembly includes a second piston rod, the second piston rod being attached to said piston so as to move angularly therewith, and wherein said second piston rod extends into said first piston rod, with angular movement of said second piston rod about said axis causing angular movement of said first piston rod about said axis. 
     Preferably, said second piston rod is telescopically received within said first piston rod. 
     Preferably, said locking member is spherical in configuration. 
     Preferably, said locking member is a first locking member, and said cylinder includes further locking members, all the locking members being spherical in configuration with the same diameter, the locking members being angularly spaced about said axis. 
     Preferably, the means to urge is a spring extending between said retaining member and said second piston. 
     Preferably, said cylinder includes a third chamber which is sealingly separated from the second chamber. 
     Preferably, fluid under pressure delivered to the second chamber causes movement of the second piston rod in said predetermined direction while if delivered to said third chamber causes the piston rod to move in a direction opposite to said predetermined direction. 
     Preferably, said retaining member moves in said predetermined direction relative to said piston rod when moving from the first position to the second positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings wherein: 
         FIG. 1  is a schematic sectioned side elevation of a hydraulic or pneumatic cylinder, the cylinder being in a first configuration; 
         FIG. 2  is a schematic sectioned side elevation of the cylinder of  FIG. 1  in a second configuration; 
         FIG. 3  is a schematic sectioned side elevation of the cylinder of  FIG. 1  in a third configuration; 
         FIG. 4  is a schematic sectioned end elevation of portion of the cylinder of  FIG. 1 ; and 
         FIG. 5  is a schematic isometric view of a piston employed in the cylinder of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the accompanying drawings there is schematically depicted a hydraulic or pneumatic cylinder  10 . The cylinder  10  is operated by a liquid or a gas under pressure, such as air or hydraulic fluid. In the following example the cylinder  10  is operated by hydraulic fluid. 
     The cylinder  10  includes a barrel  11  having a longitudinal axis  12  and an internal bore  13 . The bore  13  is of a cylindrical configuration and slidably receives a piston  14 . The piston  14  sealingly engages the bore  13  by means of a seal  15 . 
     The bore  13  surrounds a chamber  16  that is divided into a first sub-chamber  17  and a second sub-chamber  18  by means of a piston  14 . 
     The piston  14  has longitudinally extending generally cylindrical side surface  19  that is provided with a plurality of grooves or slots  20 , the slots  20  being arcuate in transverse cross-section. The slots  20  extend longitudinally and angularly about the longitudinal axis  12 . That is the slots  20  extend in a spiral manner about the axis  12 . 
     The barrel  11  is provided with a plurality of apertures  21 , with a spherical element  22  located in each of the apertures  21 . The elements  21  project into the slots  20 . 
     Upon hydraulic pressure being delivered to the sub-chamber  18  through the port  23 , the piston  14  is caused to move in the direction of the arrow  24 . This longitudinal movement of the piston  14  also results in angular movement of the piston  14  about the axis  12  due to engagement of the elements  22  in the slots  20 . The piston  14  is moved in the direction  24  until the sub-chamber  17  is at its minimum volume. When the piston  14  is moved in the opposite direction to the direction  24 , that is, by the delivery of hydraulic fluid under pressure to the port  24 , the piston  14  is moved longitudinally so that it moves angularly in the opposite direction. 
     Attached to the piston  14  is a piston rod  25 . The piston rod  25  is fixed to the piston  14  by means of a cap  26 . The cap  26  has a circular flange  27  fixed to the piston  14  and a cavity portion  28  that is longitudinally splined. The cavity portion  28  also has an annular recess  29 . 
     The piston rod  25  is longitudinally splined so as to matingly engage with the internal splines of the cavity portion  28 , with a clip  30  engaged within the annular recess  29  fixing the piston rod  25  within the piston  14 . Accordingly the rod  25  is fixed to the piston  14 . 
     When the piston  14  moves longitudinally and angularly, the piston rod  25  moves in unison therewith. 
     The cylinder  10  includes a second barrel  31 . The second barrel  31  being fixed to the first barrel  11  so as to be coaxial with respect thereto. 
     The barrel  31  has a bore  32  that slidably and sealingly engages a piston rod  33 . The piston rod  33  has a tubular portion  34  that telescopically receives the piston rod  25 . An extremity of the piston rod  33  has a head  35  with a cap  36 . 
     The bore  32  surrounds a chamber  37  that is divided into a first sub-chamber  38  and a second sub-chamber  39  by the head  35  sealingly engaging the bore  32 . 
     The head  35  and cap  36  provide an annular recess  46  that receives a plurality of spherical elements  40 . The elements  40  are maintained in spaced angular positions about the axis  24  by the cap  38  having projections that operate as a cage retaining the elements  40  spaced as mentioned. 
     The head  35  is slidably mounted on the tubular portion  33  so as to be movable longitudinally of the axis  12  relative to the tubular portion  33  between the position shown in  FIG. 1  and the position shown in  FIG. 2 . In the position shown in  FIG. 1 , the head  35  is located adjacent the port  23  while in the position shown in  FIG. 2 , the head  35  is displaced from the port  23 . 
     The elements  40  are movable radially relative to the axis  24  so as to be movable between a radially outer position ( FIG. 1 ) maintaining the piston rod  33  in the retracted position, and a radially inner position permitting movement of the piston rod  33  to the position shown in  FIG. 2 . 
     The head  35  is urged by a spring  41  toward the port  23 . The spring  41  bears against an annular flange  42  fixed to the tubular portion  33 . 
     The bore  31  provides an annular step  43  that is engaged by the elements  40  when adjacent the port  23 . 
     In operation of the cylinder  10 , when hydraulic fluid under pressure is delivered to the sub-chamber  18  via the port  23 , the hydraulic fluid under pressure moves the head  35  away from the cap  36 . This movement allows radially inward movement of the elements  40 . The pressure applied to the head  35  causes movement of the head to move away from the port  23  thereby compressing the spring  41 . 
     This movement of the head  35  provides for radially inward movement of the elements  40 . Due to pressure applied to the head  35  and the piston rod  33 , the piston rod  33  is urged to move in the direction of the arrow  44 . By engagement with the cap  36 , the elements  40  are moved radially inwardly thereby releasing the piston rod  33  for movement in the direction of the arrow  44 . Accordingly the piston rod  33  moves to the position shown in  FIG. 2 . 
     Movement of the piston rod  33  relative to the piston  40  can be coordinated by preventing or permitting movement of hydraulic fluid through the port  24 . For example, once the piston rod  33  has reached the limit of its travel, such as in  FIG. 2 , the port  24  can be opened. The hydraulic fluid delivered to the sub-chamber  18  will then cause movement of the piston  14  in the direction of the arrow  24 . 
     Attached to the tubular portion  13  is a splined bearing  45  that slidably engages the piston rod  25  so that angular movement of the piston rod  25  also causes angular movement of the piston rod  33  about the axis  12 .