Abstract:
A hydraulic synchronizer for a plurality of hydraulic actuators has at least a pair of hydraulic fluid-holding chambers of variable fluid-holding volume. The synchronizer has a number of separate preferred features, each of which is optional depending upon the intended application of the synchronizer. These optional preferred features include an improved fluid passageway arrangement, a pneumatic pressure source, separate relief valves associated with each chamber, the capability to accommodate hydraulic fluid-holding chambers of different fluid-holding volumes concurrently, and the capability to detachably interconnect multiple synchronizer modules.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates to improvements in a hydraulic synchronizer for a plurality of hydraulic actuators, wherein the synchronizer has at least a pair of hydraulic fluid-holding chambers, each with a variable fluid-holding volume for supplying fluid to a respective hydraulic actuator.  
           [0002]    Hydraulic synchronizers of this general type have existed in the past, as evidenced by the synchronizers shown in U.S. Pat. Nos. 3,643,725, 3,776,300, 3,783,620, 4,351,153, and 4,624,126. All of these prior synchronizers have hydraulically powered displacement members each movably mounted in a respective chamber and interconnected by a mechanical connecting assembly so as to expel hydraulic fluid to the respective hydraulic actuators in predetermined relationship to each other despite differences in resistances imposed on the respective actuators. However these prior synchronizers have different drawbacks, depending upon their applications.  
           [0003]    For example, the fluid conduits which connect each displacement member of these prior synchronizers to a hydraulic power source are exposed, and could be easily damaged if portability of the synchronizer is required. The need for portability, for example, is encountered in such applications as house-moving, vehicle-transporting, and lifting of loads of all types at variable locations for display, repair, installation, construction, etc.  
           [0004]    Where portability of the synchronizer&#39;s power source is also required, the size and weight of the prior systems would also be a drawback, particularly since they rely on a hydraulic power source requiring a hydraulic reservoir.  
           [0005]    In addition, if the hydraulic actuators of the prior systems become unsynchronized, serious resulting pressure imbalances could damage the synchronizer or the actuators.  
           [0006]    Moreover, if the hydraulic actuators are not all of the same fluid cross-section, or if the number of actuators varies significantly from application to application, the prior synchronizers are not readily adaptable to such variations.  
           [0007]    Accordingly the present invention is an improved hydraulic synchronizer capable of alleviating one or more of the aforementioned problems, depending on the application.  
           [0008]    The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of an exemplary embodiment of a synchronizer module in accordance with the present invention.  
         [0010]    [0010]FIG. 2 is an enlarged sectional view of the synchronizer module of FIG. 1.  
         [0011]    [0011]FIG. 3 is a further enlarged, partially diagrammatic detail view of a portion of the synchronizer module of FIG. 2.  
         [0012]    [0012]FIG. 4 is an exemplary diagrammatic view illustrating the synchronizer module of FIGS.  1 - 3  with a hydraulic pressure source.  
         [0013]    [0013]FIG. 5 is an exemplary diagrammatic view illustrating the synchronizer module of FIGS.  1 - 3  with a pneumatic pressure source.  
         [0014]    [0014]FIG. 6 is an exemplary diagrammatic view illustrating the interconnection of a pair of synchronizer modules to accommodate an increased number of hydraulic actuators.  
         [0015]    [0015]FIG. 7 is an exemplary diagrammatic view illustrating a synchronizer module modified to accommodate actuators of differing fluid cross-sections. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]    As shown in FIGS.  1 - 3 , an exemplary embodiment of a synchronizer module  10  includes a pair of end flanges  12  and  12   a  interconnected by respective tension rods  14 . Between the end flanges  12  and  12   a  respective cylindrical housings  16  separated by partitions  18  define respective fluid-holding chambers  20 . Each chamber  20  has a respective displacement member  22   a,    22   b,    22   c  and  22   d,  which can be a piston as shown or some other type of displacement member, movably mounted in the respective chamber  20  so as to variably change the fluid-holding volume of the chamber, which is located on the right-hand side of each piston in FIG. 2. The respective displacement members are interconnected by a connecting assembly  24  so as to cause respective movements of the displacement members to be in predetermined relationship to each other despite differences in resistances to their respective movements. In the exemplary embodiment of FIGS.  1 - 3 , the connecting assembly  24  is in the form of a piston rod composed of rod segments  24   a,    24   b,    24   c,    24   d  threadably coupled together within respective ones of the displacement members  22  so as to rigidly interconnect the displacement members. A fluid passageway  26  is formed within the connecting assembly  24  and receives pressurized fluid from a pressure source  28  through an inlet port  30  formed in the adjacent end flange  12 . The opposite end of the fluid passageway  26  is closed by a threaded cap  32 . In response to fluid from the pressure source  28 , pressurized fluid is directed against the left-hand side of each displacement member  22 , directly from the inlet port  30  in the case of the displacement member  22   a,  and from respective ports  34  in the passageway  26  through annular recesses such as  35  (FIG. 3) in the case of the other displacement members. The fluid pressure thus exerted on the left-hand sides of the respective displacement members forces them to the right in FIG. 2, thereby expelling hydraulic fluid from their respective fluid-holding chambers  20  through respective outlet ports  36  and conduits  37  to respective hydraulic actuators  38 , as shown in FIGS.  4 - 7 , to lift a load  40 . In most applications, hydraulic fluid is expelled at a uniform volumetric rate from identically-sized chambers  20  due to the interconnection of identically-sized displacement members  22  through the connecting assembly  24 , causing hydraulic actuators  38  having identical piston diameters to extend uniformly to lift the load  40 . Leakage in the module  10  is minimized by the use of O-rings such as  42  (FIG. 3) between adjacent parts of the module.  
         [0017]    Alternative arrangements of the synchronizer system may feature different shapes of the housings  16 , different types of displacement members, parallel rather than serial arrangement of the chambers  20  and connecting assembly  24 , different fluid passageway arrangements, different types of linear or rotary hydraulic actuators  38 , etc.  
         [0018]    In some instances, the hydraulic actuators  38  may not be properly synchronized prior to the application of power to the synchronizer module from the pressure source  28 . This could be due to incomplete previous retraction of an actuator  38 , previous leakage of fluid within the actuator, or placement of the actuators with respect to the load so that different degrees of extension are needed to lift the load. Another possible source of such initial lack of synchronization might be previous leakage within the synchronizer module. In any case, under such circumstances it is possible that one of the actuators  38  will experience excessive resistance to extension, thereby causing excessive pressure in one of the chambers  20  of the synchronizer module. Since such excessive hydraulic pressure could damage the synchronizer module or the hydraulic actuator, it is preferable to provide a respective pressure-relief valve separately for each chamber  20  to enable hydraulic fluid in the chamber to escape through the valve if the pressure in the chamber exceeds a predetermined maximum pressure. Although such a relief valve could be positioned in numerous alternative locations, it is preferably mounted on a respective displacement member  22   a,    22   b,    22   c  and  22   d  as exemplified by relief valve  44  in FIG. 3, so that the escaping fluid is conducted to the opposite side of the displacement member to avoid damage. A replenishment port  46  is preferably provided for each chamber  20  to enable the later introduction of hydraulic fluid into the chamber to replace the fluid which has previously escaped through the relief valve, after the excessive pressure problem has been corrected.  
         [0019]    [0019]FIG. 4 is a simplified diagrammatic drawing illustrating a typical use of the synchronizer module.  10  in a situation where the module  10  is portably inserted into an existing hydraulic lifting system, such as that used by house movers. In such case the synchronizer module, preferably supported on some suitable type of wheeled transporter  48 , is transported to and operably connected between the hydraulic pressure source  50  and the hydraulic actuators  38  of an existing hydraulic system, and operated as described previously. The hydraulic pressure source  50  is conventional, and is shown in simplified form as a hydraulic pump  52  receiving hydraulic fluid from a reservoir  54  and conducting it to the module  10  through a manual control valve  56 .  
         [0020]    [0020]FIG. 5 is a simplified diagrammatic drawing illustrating the use of the module  10  in a portable lift  56  supported on a wheeled transporter  58 , where the hydraulic actuators  38  and a pneumatic pressure source  60  are likewise supported on a wheeled transporter  61  as parts of a complete portable synchronizer system. The pneumatic pressure source  60  is conventional, and is shown in simplified form as an air compressor  62  supplying pressurized air to an accumulator  64  and to the synchronizer module  10  through a manual control valve  65 .  
         [0021]    [0021]FIG. 6 is a simplified diagrammatic drawing illustrating an exemplary detachable interconnection between a pair of synchronizer modules  10  and  10 ′ to accommodate more hydraulic actuators  38  than the maximum number which can be synchronized by the module  10  alone. The end flanges  12   a  and  12   b  of the two modules are interconnected by threaded spacers  66  passing through holes such as  67  (FIG. 1) to provide a separation of the end flanges of approximately the same length as one of the housings  16 . The ends of the respective connecting assemblies  24  and  24 ′ are threadably interconnected by a suitable collar or flange such as  68  to synchronize the movements of the displacement members of both modules  10  and  10 ′. The interconnecting collar or flange  68  likewise interconnects the respective fluid passageways  26  of the respective connecting assemblies  24  and  24 ′.  
         [0022]    [0022]FIG. 7 is a simplified diagrammatic drawing illustrating the adaptation of a module  10  so as to have fluid-holding chambers  20 ,  20 ′ of different fluid-holding volumes, thus enabling the module to synchronize the movements of differently-sized hydraulic actuators  38  and  38 ′. A smaller chamber  20 ′, having a fluid-holding cylindrical cross-sectional area less than that of the other chambers  20 , is provided in the module  10  for connection to a fluid actuator  38 ′ of proportionately lesser fluid-holding cylindrical cross-section than the other actuators  38 . This is accomplished by removing the tension rods  14 , and substituting a smaller housing  16 ′ and appropriately-modified partition  18 ′ and end flange  12   c  accommodating the substitute housing  16 ′, together with a substitute displacement member  22 ′ matching the internal dimensions of the housing  16 ′.  
         [0023]    The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.