Abstract:
A triple piston fluid pressure cylinder is disclosed with a parallel arrangement of the pistons that allows a combination of the first two stages of the cylinder into one stage so that the first two stages of the cylinder are working into the same common space. 
     As the result of that arrangement the overall length of the triple pistons cylinder is reduced by a significant amount. 
     The saved length may be used to increase the stroke of the cylinder. 
     The piston body assembly is built around the piston arrangement, and is composed of a cylinder tube with one head end cover and one rod end cover and one middle fixed pistons. 
     The middle fixed piston is extended through an extension tube to an extension fixed piston.

Description:
BACKGROUND 
     Field of the Invention 
     The present invention relates to a fluid pressure cylinder that uses fluid pressure to displace a piston assembly in an axial direction relative to a cylinder body assembly. 
     Description of the Related Art 
     In many applications there is a need for higher forces developed by the actuator, or cylinder. 
     The solutions existent so far is to stack multiple cylinders inline and that led to invention of the multiple piston cylinders that is practically a series of two or more pistons secured on a common rod, inside a cylinder body divided into multiple chambers. 
     The pistons under pressure exert an axial force on the rod and all the forces are summed and applied at the rod end of the cylinder. 
     The earliest patent regarding the multiple pistons cylinders are the U.S. Pat. No. 825,866 granted Jul. 10, 1906 to L. H. Rogers, U.S. Pat. No. 1,565,767 granted Dec. 1, 1922 to C. R. Westbrook, and U.S. Pat. No. 2,956,549 granted Jul. 5, 1955. 
     The multiple pistons cylinder has limitations regarding stroke, due to the overall length of such a cylinder. 
     Usually triple pistons cylinders go up to 3 or 4 inches of stroke as standard and higher strokes are custom build, and are usually extremely long, implying higher cost in building the cylinder and building longer and heavier support frames. 
     For example, every inch of extra stroke of the triple pistons cylinder generates three extra inches of length of the cylinder body. 
     OBJECT OF THE INVENTION 
     The principal object of the present invention is to reduce the overall length of the triple piston cylinders. 
     Considering actual limits accepted by the industry that reduction of overall length will allow for an increased stroke of the cylinder. 
     SUMMARY OF THE INVENTION 
     By definition the work volume of a piston in the multiple piston cylinders is called a stage. So the triple pistons cylinders have three stages. 
     The present invention is based on the inventor&#39;s observation, that the front two stages of a triple piston cylinder may be combined to use practically the same volume of work. 
     The present invention provides a solution that generates a reduction of one third of the overall length of a triple piston cylinder, compared with triple piston cylinders invented so far. 
     The piston assembly has a parallel arrangement of the pistons and not an inline arrangement like existing triple pistons cylinders. 
     The front piston is connected in parallel with the second and third piston. 
     The outside diameter of the front piston is connected to the internal dual piston through a piston tube and the inside diameter of the front piston is connected to the end piston through a piston rod. 
     The pistons arrangement generates the structure of the cylinder body assembly. 
     Similar to any other cylinders the body of such a cylinder is made of a cylinder tube that has a head end cover at one end and a rod end cover at the other end. 
     The difference consists of an additional middle fixed piston, attached inside on the cylinder tube and extended to an extension fixed piston through an extension tubular shaft. 
     The second piston of the piston assembly is a dual piston, meaning that the outside diameter of the dual piston is sliding on the inside surface of the cylinder tube and the inside diameter of the dual piston is sliding on the exterior surface of the extension tubular shaft. 
     The above and other objects, features and advantages of the present invention will become clearer through the following detailed description when taken together with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the overall cross sectional view of the preferred embodiment of a triple pistons fluid pressure cylinder with reduced overall length. 
         FIG. 2  shows the overall cross sectional view of the piston assembly of the preferred embodiment of a triple pistons fluid pressure cylinder with reduced overall length. 
         FIG. 3  shows the cross sectional view of the body assembly of the preferred embodiment of a triple pistons fluid pressure cylinder with reduced overall length. 
         FIG. 4  shows the overall cross sectional view of the second embodiment of a triple pistons fluid pressure cylinder with reduced overall length. 
         FIG. 5  shows the rod end view of the rod end cover with flats. 
         FIG. 6  shows the rod end view of the rod end cover without flats 
     
    
    
     DETAILED DESCRIPTION 
     Targeted Space of the Cylinder for Present Invention 
     The focus of the present invention was to combine the first two stages or the triple pistons cylinder into one common dual stage. 
     This endeavor led to a parallel arrangement of the three pistons of the cylinder. 
     The cylinder body was built around the pistons parallel arrangement. 
     Preferred Embodiment 
       FIGS. 1, 2 and 3  disclose such a cylinder. 
     The cylinder  100  is composed of a cylinder body assembly  201  and a piston assembly  101 . 
     The cylinder piston assembly  101  is composed of a triple force ram  1 , an internal dual piston  3 , a tubular piston rod  4 , and an end piston  5 ; altogether they constitute a rigid assembly. 
     The piston tube  2  has one or more orifices  60  in the close vicinity of one of its ends. 
     The triple force ram  1  is rigidly attached to the end of the piston tube  2  that has no orifices, the attachment being also air tight, not allowing any fluid leak. 
     Different devices may be attached on the exterior face of the triple force ram  1 , like brackets, flanges, rod ends, studs, pivoting eyes, etc. that are well known in the art without departing from the scope of the present invention. 
     The internal dual piston  3  has a stepped outside diameter and a bore through its center, it is rigidly attached to the end of the piston tube  2  that has the orifices  60 , and it has a seal  21  on its larger outside diameter and a seal  22  on its internal diameter. 
     The tubular piston rod  4  has a central hole  54  through and is rigidly attached at one end to the triple force ram  1 . 
     There are one or more orifices  55  in either the piston rod  4  or the triple force ram  1 , to allow fluid flow between the central hole  54  and the chamber  45 . 
     The opposite end of the piston rod  4  is rigidly attached to the end piston  5 . 
     The engagement of the piston rod  4  and the end piston  5  is sealed by the seal  24 . 
     The end piston  5  has a seal  23  on the outside diameter and a central hole  53  to allow fluid flow between the chamber  41  and the central hole  54 . 
     The cylinder body assembly  201  is composed of a cylinder tube  6 , head cover  7 , a rod end cover  8 , an intermediate header guide  9 , an extension tubular shaft  10 , an extension fixed piston  11  and a spacer  12 ; altogether they form a rigid assembly. 
     The cylinder tube  6  is the exterior tube of the cylinder and has one or more orifices  62  at one of its ends. 
     The inside diameter of the cylinder tube  6  is larger than the outside diameter of the piston tube  2  in such a way that a chamber  61  is created in between. 
     The rod end cover  8  is rigidly attached at the end of the cylinder tube  6  that has the orifices  62  and is configured as a guiding ring for the piston assembly  101 . 
     The head cover  7  has one or more inlet ports  51  and is rigidly attached to the opposite end of the cylinder tube  6  and the attachment is air tight not allowing any fluid leak. 
     There are one or more orifices  55  in either the piston rod  4  or the triple force ram  1 , to allow fluid flow between the central hole  54  and the chamber  45 . 
     The intermediate header guide  9  is rigidly attached inside the cylinder tube  6  in a position that will allow for an equal travel of both the end piston  5  and the internal dual piston  3 . 
     Intermediate header guide  9  has one or more inlet ports  58  with seals  31  on both sides of the inlet ports  58 . 
     The intermediate header guide  9  has a guiding bore through its center holding seal  32 , an extension hole and a stepped outside diameter holding a seal  59 . 
     The guiding bore of the intermediate header guide  9  is guiding the tubular piston rod  4 . 
     The spacer  12  is attached with one end to the intermediate header guide  9  and the opposite end engages the head cover  7 . 
     Alternatively the engagement between the head cover  7  and the spacer  12  may be sealed. 
     The extension tubular shaft  10  is rigidly attached to the extension hole of the intermediate header guide  9 , the engagement being air tight. 
     The exterior diameter of the extension tubular shaft has a sealed engagement with the internal dual piston  3  by the seal  22 . 
     The inside diameter of the extension tubular shaft  10  is larger than the exterior diameter of the tubular piston rod  4 , in such a way that the space between is defining a chamber  56 . 
     The extension tubular shaft  10  has one or more orifices  57  in the close vicinity of its attachment to the intermediate header guide  9 . 
     Alternatively the orifices  57  can be made in the intermediate header guide  9 . 
     The extension fixed piston  11  is rigidly attached at the opposite end of the extension tubular shaft  10 , and has a sealed engagement with the piston tube  2  by seal  33 . 
     The engagement between the extension fixed piston  11  and the extension tubular shaft  10  is sealed by seal  34 . 
     The two cylinder assemblies  101  and  201  are moving relatively to each other guided by the seals  21 ,  22 ,  23 ,  32 ,  33  and the rod end cover  8 . 
     When the two cylinder assemblies  101  and  201  are put together they form pressure chambers  41 ,  42 ,  43 ,  44  and  45 . 
     The pressure chamber  41  is defined in between the head cover  7  and the end piston  5  inside the spacer  12 . 
     The pressure chamber  42  is defined in between the end piston  5  and the intermediate header guide  9  inside the spacer  12 . 
     The pressure chamber  43  is defined in between the intermediate header guide  9  and the internal dual piston  3 . 
     The pressure chamber  44  is defined in between the internal dual piston  3  and the extension fixed piston  11  inside the piston tube  2 . 
     The pressure chamber  45  is defined in between the extension fixed piston  11  and the triple force ram inside the piston tube  2 . 
     When pressurized fluid is applied to the inlet port  51 , the pressure is built in the chamber  41  and in the chamber  45  through the central hole  53  and the orifices  55  and in the chamber  43  through the chamber  56  and the orifices  57 . 
     Extending forces are developed on the back of the end piston  5 , the internal dual piston  3  and the triple force ram  1 , and the cylinder  100  extends. 
     The force built on the back of the end piston  5  is transferred to the triple force ram  1  through the tubular piston rod  4 . 
     The force built on the back of the internal dual piston  3  is transferred to the triple force ram  1  through the piston tube  2 . 
     The triple force ram cumulates the three forces and applies them to the device attached on its exterior face. 
     When pressurized fluid is applied to the inlet port  58 , a force builds on the front face of the end piston  5  and the cylinder  100  retracts. 
     The exterior diameter of the extension tubular shaft has a sealed engagement with the internal dual piston  3  by the seal  22 . 
     The inside diameter of the extension tubular shaft  10  is larger than the exterior diameter of the tubular piston rod  4 , in such a way that the space between is defining a chamber  56 . 
     The cylinder is identical with the cylinder described as the preferred embodiment and has an additional liner  13  between the intermediate header guide  9  and rod end cover  8 . 
     The intermediate header guide  9  has an additional stepped diameter to engage the additional liner  13 , and an additional seal  59  seals the engagement between the two. 
     The engagement between the extension fixed piston  11  and the extension tubular shaft  10  is sealed by seal  34 . 
     The two cylinder assemblies  101  and  201  are moving relatively to each other guided by the seals  21 ,  22 ,  23 ,  32 ,  33  and the rod end cover  8 . 
     When the two cylinder assemblies  101  and  201  are put together they form pressure chambers  41 ,  42 ,  43 ,  44  and  45 . 
     The pressure chamber  41  is defined in between the head cover  7  and the end piston  5  inside the spacer  12 . 
     The pressure chamber  42  is defined in between the end piston  5  and the intermediate header guide  9  inside the spacer  12 . 
     The pressure chamber  43  is defined in between the intermediate header guide  9  and the internal dual piston  3 . 
     The pressure chamber  44  is defined in between the internal dual piston  3  and the extension fixed piston  11  inside the piston tube  2 . 
     The pressure chamber  45  is defined in between the extension fixed piston  11  and the triple force ram inside the piston tube  2 . 
     When pressurized fluid is applied to the inlet port  51 , the pressure is built in the chamber  41  and in the chamber  45  through the central hole  53  and the orifices  55  and in the chamber  43  through the chamber  56  and the orifices  57 . 
     Extending forces are developed on the back of the end piston  5 , the internal dual piston  3  and the triple force ram  1  and the cylinder  100  extends. 
     The force built on the back of the end piston  5  is transferred to the triple force ram  1  through the tubular piston rod  4 . 
     The force built on the back of the internal dual piston  3  is transferred to the triple force ram  1  through the piston tube  2 . 
     The triple force ram cumulates the three forces and applies them to the device attached on its exterior face. 
     When pressurized fluid is applied to the inlet port  58 , a force builds on the front face of the end piston  5  and the cylinder  100  retracts. 
     Second Possible Embodiment 
     The  FIG. 4  discloses a second possible embodiment of the present invention. 
     The cylinder is identical with the cylinder described as the preferred embodiment and has an additional liner  13  between the intermediate header guide  9  and rod end cover  8 . 
     The intermediate header guide  9  has an additional stepped diameter to engage the additional liner  13 , and an additional seal  59  seals the engagement between the two. 
     INTENDED USE 
     The present invention may be used for applications that require an increased thrust force within limited spaces and related length restrictions accepted by the industry, like: a) clamping parts in fixtures for production processes in confined spaces, b) resistance welding cylinders that require high clamping force to produce a welding nugget, or c) processes that require the use of presses and stamping machines.