Abstract:
A ram ( 10 ) with a hydraulic cylinder ( 22 ) and piston ( 52 ) has an electronics enclosure compartment ( 54 ) integrated within it at one end. The compartment ( 54 ) is formed by two clam shells ( 70, 72 ) which are bolted to the end of the cylinder ( 22 ) so as to create a chamber for housing the electronics ( 66 ). The outer clam shell ( 72 ) has an axially aligned ram mounting attachment ( 74 ) integrally formed on it, and the inner clam shell ( 70 ) has an axial opening to which is sealed a hollow tube ( 56 ) which extends axially within the ram ( 10 ) so as to enclose a sensor ( 60 ) which is associated with the electronics ( 66 ) in the compartment ( 54 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of International Application No. PCT/US98/21236 filed Oct. 8, 1998 designating the United States, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/061,773 filed Oct. 10, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a ram cylinder and piston construction which includes an electronics enclosure compartment. 
     2. Discussion of the Prior Art 
     Hydro-pneumatic vehicle suspension systems are well known. Typically, one or more single or double acting hydraulic rams are provided at each wheel to support the vehicle, with hydraulic circuits interconnecting the rams. A gas-charged accumulator is typically used to pressurize the hydraulic circuits and therefore, provide resilient displacement of the rams and consequently springing of the vehicle. 
     One hydro-pneumatic vehicle suspension system has come to be known as the “X” type. In such a system, the rams of diagonally opposite wheels of a vehicle are connected with discrete hydraulic circuits, each circuit connecting the bore side of one of the rams with the rod side of the diagonally opposite ram. Such an X-system is known, for example, from patents such as French Patent No. 1,535,641 and U.S. Pat. Nos. 4,270,771; 5,447,332; 5,562,305; 5,601,306; and 5,601,307. 
     Central to the design are the rams which support the vehicle body on the wheels and react to the hydraulic system. Another important aspect of the design are hydraulic accumulators which essentially act as springs to pressurize the rams so as to desirably support the body over the wheels. 
     Each ram may mount an accumulator assembly, which poses special problems not normally associated with shock absorbers, struts or common hydraulic cylinders. The wheel suspension rams must not only mount the accumulator assembly, but must also do so in a small and certain space or “envelope”, being closely adjacent to the body, the wheel, and other suspension components, while permitting electrical and hydraulic connections to be made to the cylinder/accumulator assembly. Each ram must fit within the permitted envelope and be lightweight and strong, since it is pressurized to an extent to bear the weight of the vehicle and dynamic loading. 
     In addition, each ram may also include electronics, for example for an internal linear displacement transducer, to provide an input of the displacement of the cylinder to an onboard computer so that the controller has that information to determine adjustments that should be made to the system to deliver the desired ride characteristics. The present invention relates to such a ram, which has an electronics enclosure integrated into it. 
     SUMMARY OF THE INVENTION 
     The invention provides a fluid power ram in which the electronic components of the ram are contained within a chamber of a compartment which is positioned at an end of the ram. The compartment is intersected by the longitudinal axis of the ram and includes a ram mounting attachment outside of the chamber for mounting the end of the ram. Thereby, electronics of the ram are protected within a structurally sound, clean and dry compartment within the ram, without increasing the radial envelope required by the ram, and in a manner which facilitates service access to the ram. 
     In a preferred form, the compartment includes first and second clam shells with a parting line between them which is generally perpendicular to the longitudinal axis of the cylinder. In this form, the first and second clam shells are preferably bolted together with bolts that have their axes parallel to the longitudinal axis of the ram. The bolts may also usefully fix the first and second clam shells to the end of the cylinder. The ram mounting attachment can be formed as part of an outer one of the clam shells. In this manner, service access to the ram is provided by unbolting the clam shells. 
     In another useful aspect of the invention, an opening is formed in the inner one of the clam shells, the opening being axially aligned with the longitudinal axis of the ram. A pressure tube is sealed to the opening and the pressure tube extends axially within the ram along the longitudinal axis. A sensor extends within the pressure tube from the compartment. Thereby, the invention can be practiced to house long, axially extending electronic components inside the ram. 
     These and other objects and advantages of the invention will be apparent from the detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal cross-sectional view of a ram according to the invention, shown together with a nitrogen charged accumulator assembly; 
     FIG. 2 is a perspective view of an inner tube of the ram of FIG. 1; 
     FIG. 3 is a perspective view of an upper clamshell of the ram of FIG. 1; and 
     FIG. 4 is a perspective view of a lower clamshell of the ram of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a ram  10  of the invention for incorporation into a vehicle suspension system of the above-described type. The ram  10  is illustrated with an accumulator assembly  12  attached to it, which establishes fluid communication between the ram  10  and a nitrogen charged accumulator  13 . The assembly  12  has a goose neck fitting  14  which is sealed and affixed to the upper outer tube  18  by welding or other suitable means. The goose neck  14  provides communication between the upper reservoir  20  inside the tube  18  and the accumulator  13 , and has a bleed fitting  15  for bleeding air from the hydraulic circuit. 
     Preferably, a disc valve pack  17  is provided in the goose neck  14  in the fluid stream between the reservoir  20  and the accumulator  13 , so as to damp the resilience provided by the accumulator  13 . An on/off or proportional solenoid operated valve may also be provided, for remotely varying the damping of fluid communication with the accumulator  13 . However, the invention need not be practiced with any type of accumulator or valve, or any particular hydraulic circuit or suspension system, and no such accumulator, valve circuit or system forms any part of the present invention. 
     The ram  10  has a cylinder  22  which includes an outer tube  24  and an inner tube  26 . The outer tube  24  includes the upper tube  18 , and a lower tube  28 . The upper tube  18 , lower tube  28 , and inner tube  26  are all welded together by seam weld  30 . In addition, the lower end of outer tube  24  is welded to the inner tube  26  by seam weld  32  at the gland end of the cylinder. The upper and lower tubes  18  and  28  are generally tubular. The inner tube  26 , on the other hand, has an outer surface which is contoured with circumferentially spaced, axially running ribs  34 , best shown in FIG.  2 . The ribs  34  define between them passageways for fluid flow between the inner tube  26  and the outer tube  24 , while permitting free flow from one passageway to another, by providing a break at  35  and at  37  in each rib. A lower port  38  is provided for supplying and exhausting fluid from the lower reservoir  40 , which is defined between the lower tube  28  and the inner tube  26 . An upper port  42  is provided for supplying and exhausting fluid from the upper reservoir  20 . Thus, port  38  provides communication with reservoir  40  and port  42  provides communication with reservoir  20 . It is noted that reservoir  20  is in communication with the bore side or upper chamber  36  (passageways not shown) and that the reservoir  40  is in communication with rod side or lower chamber  44 , via holes  46  which are formed in the inner tube  26 . 
     Chamber  44  is the volume which is at the lower, gland end  48 , below piston  52 , which is bordered on the outside by inner tube  26  and is bordered on its inner diameter by piston rod  50 . Piston  52  is secured to the top of rod  50  and establishes a sliding seal with the inner tube  26 . Bore side chamber  36  is capped off by clam shell compartment  54  and includes the volume above piston  52  and extends down inside the piston rod  50 . The inner diameter of chamber  36  is defined by pressure tube  56 . Pressure tube  56  is sealed at its lower end by a pressure tube cap  58  and at its upper end is joined and sealed, such as by welding, to the clam shell compartment  54 . A position sensor  60  extends down inside the pressure tube  56 , which keeps the sensor  60  dry, and a magnet  62  is affixed inside the piston  52  by a magnet carrier sleeve  64  so that the sensor  60  can sense the axial position of the magnet  62 . Sensor  60  may be any type of linear displacement transducer, although in the embodiment disclosed it is a magneto-strictive type of sensor. 
     The sensor  60  is supported inside the pressure tube  56  by a printed circuit board  66  which itself is encased in a protective housing  68 . The circuit board  66  and housing  68  are captured between a lower or inner clam shell  70  and an upper or outer clam shell  72 , which make up the clam shell compartment  54 . The shells  70 ,  72  define a side opening  71  (FIG. 4) at the parting line between them to permit wires (not shown) to enter the compartment created by the shells, to make electrical connections to the electronic circuitry contained therein. The lower clam shell  70  is sealed to the upper outer tube  18  and the upper clam shell  72  has upper mounting stud  74  extending from it, for connection to the vehicle chassis. The stud  74  is one type of ram mounting attachment, it being possible to practice the invention with other types of ram mounting attachments, another common type being a ball joint, for example. The upper clam shell  72  has spaced holes  76  and the lower clam shell  70  has spaced holes  78  in registration with the holes  76  so that the clam shell assembly  54  can be bolted to the upper end of the upper outer tube  18 . The printed circuit board  66  may also have a similar pattern of holes for securing it in the compartment  54  using the bolts (not shown). 
     As mentioned above, the gland  48  is formed by the lower end of the inner tube  26 . Gland  48  has formed in it an axial generally cylindrical hole through which the piston rod  50  extends and in which annular grooves are formed for containing sliding seals  49  and  51  so as to establish a fluid-tight sliding seal with the piston rod  50 . At the lower end of piston rod  50 , compression disc  78  is screwed into the piston rod  50  with a fluid-tight seal  79  between the disc  78  and the rod  50 . Mounting stud  80  extends from the disc  78  for mounting the lower end of the cylinder  10  to a wheel support wishbone, or other wheel support suspension structure. A bellows  82  has its lower end attached to the disc  78  and its upper end attached around the outer tube  24  so as to help keep the piston rod  50  clean. 
     The chamber  44  extends upwardly from the gland  48  for a distance before encountering the holes  46  which establish communication between the chamber  44  and the reservoir  40 . Thus, when the piston  52  reaches the lower limit of its stroke, its bottom corner first passes the holes  46  so as to trap a volume of hydraulic fluid between its bottom end and the gland  48 , which provides a hydraulic cushion. However, since the piston seals are provided higher up on the piston  52 , there must be a very close fit between the piston  52  and the lower end of the chamber  44 . Thus, the lower end of the chamber  44  is slightly smaller in diameter than the chamber  44  above the holes  46 , as can be seen in FIG.  1 . Because of the extremely accurate concentricity required to establish a small enough clearance between the piston  52  and the bore at the lower end of the chamber  44  to provide a hydraulic cushion, the gland  48  and the inner tube  26  which defines the bore of chamber  44  are made in one piece. 
     Also as mentioned above, the inner tube  26  has the raised ribs  34  which define between them axial and circumferential flow passages. The raised ribs  34  also serve to reinforce the inner tube  26  because of the increased thickness of material in the area of the ribs  34 . However, in addition, the outer surfaces of the ribs  34  are in close proximity to the inner surface of outer tube  24  as shown in FIG.  1 . Thus, as inner tube  26  flexes outwardly, the ribs  34  contact the outer tube  24  and outer tube  24  helps restrain the inner tube  26  from flexing further outwardly. Thus, there is structural sharing between the inner tube  26  and the outer tube  24  of the loads which are placed on the inner tube  26 . 
     Thus, at least three aspects of the cylinder  10  are believed to be unique. One is providing the clam shell compartment  54  for housing the electronics associated with the sensor  60 . Another is providing for structural sharing between the inner tube  26  and the outer tube  24 , more specifically by providing the ribs  34 , and the third is forming the gland  48  and the inner tube  26  in a single piece. 
     Many modifications and variations to the preferred embodiment described will be apparent to those skilled in the art, which will still incorporate aspects of the invention. Therefore, the invention should not be limited to the embodiment described but should be defined by the claims which follow.