Abstract:
An improved, compact and efficient arrangement of axial piston hydraulic pump and hydraulic cylinder into a single self-contained compression or actuating device. A combination of back-flow volume-acting pump pistons and a hollow main piston rod that serves as both a working fluid container and a head-creating organ is introduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Patent Application No. 60/565,344, filed on Apr. 26, 2004, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention primarily relates to a field of portable self-contained hydraulic tools for such applications as cutting rods, cables and like, crimping, perforating and otherwise deforming various stiff materials, as well as spreading and lifting heavy objects to relatively short distance. But far broader use of the present invention is available, for instance, in compact and light-weighted actuating devices applying linear force to various working members. These include robotic arms, bulldozer blades and forklift claws, retractable supports (plane chassis, for one), actuators that open and close valves and so on. The present invention is being especially helpful in the situations where each working member incorporates independent, portable and autonomous hydraulic circuit and power source thus notably adding survivability to the machine in the event of main hydraulic system breakdown. In fact, it provides for elimination of the main system altogether, if necessary.  
         [0003]     Conventional devices present various approaches to the creation of self-contained hydraulic tools. The invention of U.S. Pat. No. 4,998,351 to Hartmeister, Mar. 12, 1991 offers efficient way to solve the problem. But it features pressurized reservoir that is being located in its own designated portion of the tool&#39;s body, thus making the latter larger and heavier then the present invention permits.  
         [0004]     The invention of U.S. Pat. No. 6,446,482 to Heskey, et al., Sep. 10, 2002 as well as many other tools available on the market (Ridgid Pro Press, for one) uses collapsible container that serves the same purpose. But such approach, while being cost-effective and requiring less accurate calculation on design stage, does necessitate serious means to protect the soft material of which the container is made. Also, for the fact that collapsible container surrounds the tool&#39;s body, size factor remains not being adequately addressed.  
         [0005]     The invention of JP02001179530A to Kawamata, Jul. 3, 2001 also features the fluid container located at a distance from other parts of the mechanism. Besides aforementioned disadvantages, all three inventions utilize rather conventional way of pumping, where both suction and pressurized discharge of fluid by pump pistons do occur in front of the latter. This causes greater length of passageways (and therefore greater loss of energy due to fluid friction, plus design complexity) and overall tool&#39;s size then the present invention affords.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention relates to a closed circuit hydraulic compression device that substantially obviates one or more of the disadvantages of the related art.  
         [0007]     Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
         [0008]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:  
         [0010]      FIG. 1  shows a conventional self-contained compression tool of U.S. Pat. No. 6,446,482 to Heskey, et al., Sep. 10, 2002.  
         [0011]      FIG. 2  shows a plane view of longitudinal vertical cross-section of the device of the present invention.  
         [0012]      FIG. 3  shows a plane view of longitudinal diagonal cross-section of the device of the present invention.  
         [0013]      FIG. 4  shows a plane view of transverse cross-section of the device of the present invention.  
         [0014]      FIG. 5  shows an isometric view of a back-flow volume acting grooved piston of the device of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0016]     The present invention, in a broad sense, is a substantial improvement over conventional methods of arranging an axial piston hydraulic pump and a hydraulic cylinder into single closed circuit unit. In one embodiment, it introduces the following elements: 
        (a) the entire volume of working fluid necessary for the operation of the tool or implement is contained within main cylinder&#39;s bore and rod,     (b) pump pistons displace working fluid from their cylinders during forward stroke in the same direction as that of suction, i. e., working fluid circulates from the volume in front of the main piston (and within the rod) via pump pistons into the volume behind the main piston in the same direction at any given moment throughout the entire duty cycle.        
 
         [0019]     A primary object of the present invention is to arrange all elements necessary for achieving above described results in a most space-efficient fashion, yet for no loss to any benefits conventional possesses.  
         [0020]     This invention described herein can be used for:  
         [0021]     1. Reducing overall size of the tool or other implement by utilizing volumes not only in front of the main piston, but also within hollow piston rod for working fluid storage, thus eliminating any remotely located fluid reservoirs.  
         [0022]     2. Reducing length of fluid passageways by placing suction check valves in front of pump pistons (adjacent to fluid stowage volume in front of the main piston within its cylinder bore) and pressurized discharge check valves behind pump pistons (adjacent to main piston&#39;s cylinder bore).  
         [0023]     3. Reducing precision and material requirements, simplifying design and adding reliability to the tool or implement by having pump piston&#39;s length-by-diameter ratio notably greater then it is in cases of most conventional devices, for no sacrifice to the length of the tool or implement.  
         [0024]     The following designations are used in the figures: 
         6 —housing      7 —piston rod      8 —elastomer seal      9 —cylindrical chamber      10 —cylinder piston      11 —return spring      12 —cylinder piston seal      13 —end cap      14 —locknut      15 —compensator piston      16 —spring guide      17 —compensator spring      18 —passageways      19 —intake passageways      20 —intake valves      21 —cylinders      22 —pump pistons      23 —intake springs      24 —pump seals      25 —discharge passageways      26 —discharge valves      27 —trigger valve      28 —valve return spring      29 —retaining seal      30 —lock seal      31 —return passageway      32 —relief passageway      33 —relief valve      34 —charging/bleeding nipples      35 —pump drive axle      36 —swash plate        
 
         [0056]     A preferred embodiment of Closed circuit hydraulic compression device with stoke-consistent pump intake comprises cylindrically shaped housing  6 . Front end of it features a circumferential opening. This opening accommodates a piston rod  7  and an elastomer seal  8  is provided for preventing fluid leakage. Housing  6  further comprises cylindrical chamber  9 , whereas a longitudinal axis of the chamber and of the housing are one and the same.  
         [0057]     Cylinder piston  10  is located within chamber  9 . It is being pressed against rear wall of the chamber by return spring  11 . Cylinder piston seal  12  is provided so that fluid can not escape from a rear portion of chamber  9  to its front portion, thus defining volume  9   a  (in front of piston  10 ) and volume  9   b  (behind piston  10 ) within chamber  9 . Piston rod  7  is hollow. Its front end accommodates threaded end cap  13  that can be turned clockwise and counterclockwise thus adjusting a length to which it extends forward. Front portion of cap  13  has an opening. Position of end cap  13  is fixed by a locknut  14 .  
         [0058]     Volume compensator piston  15  is inserted into hollow piston rod  7 . Piston  15  features a spring guide  16 . Compensator spring  17  is located around the guide between cap  13  and piston  15 , and is being partially surrounded by them. Guide  16  can protrude through the opening of cap  13 .  
         [0059]     Passageways  18  are arranged within cylinder piston  10  so that internal space of hollow rod  7  is openly connected to volume  9   a  of chamber  9 . At the front end of volume  9   a  there are intake passageways  19 , each featuring intake valve  20 . Passageways  19  further lead to (throughout intake valves  20 ) pump cylinders  21 , all of the above described is shown on  FIG. 2 . Cylinders  21  are arranged along the axis of housing  6  so that they are symmetrical with respect to it, as shown by  FIG. 4 .  FIG. 2  further shows back-flow volume acting grooved pump pistons  22  (also shown on  FIG. 5 ), each inserted into its respective pump cylinder  21 . Auxiliary intake springs  23  are placed in front of every pump piston  22 .  
         [0060]     Rear ends of cylinders  21  feature pump seals  24  to prevent fluid from escaping into drive area of the pump. Cylinders  21  further comprise high pressure discharge passageways  25 , each accommodating discharge valve  26 . Discharge passageways  25  are located so that their openings coincide with reduced diameter portions of pump pistons  22  when the latter are being at the foremost position. Passageways  25  further lead to (throughout discharge valves  26 ) volume  9   b  of chamber  9 .  
         [0061]      FIG. 3  shows another axial cross-section of housing  6 . This view demonstrates a trigger valve  27  that incorporates valve return spring  28 , fluid retaining seal  29  and trigger valve lock seal  30 . Fluid return passageway  31  is arranged between volume  9   a  and volume  9   b  of chamber  9 . It is located in bottom segment of housing  6  between and along two lower pump pistons  22  and (also see  FIG. 4 ). Trigger valve  27  protrudes through outer wall of housing  6  so that provisions for depressing and releasing of the former can be added without interference with the internal structure of the device.  
         [0062]      FIG. 3  further shows relief passageway  32  and relief valve  33 . These are also arranged between volumes  9   a  and  9   b  similarly to fluid return passageway  31 . Relief passageway  32  is shown in the top segment of housing  6 , between and along two upper pump pistons  22 . Fluid charging and bleeding nipples  34  (two required, one shown) are located between volume  9   a  and the ambient media, shown in “tightened” position. Please note that terms “bottom”, “top”, “upper” and “lower” are only relevant for the purpose of these drawings and do not necessarily imply their meaning to the actual device of the present invention.  
         [0063]     The preferred embodiment also comprises pump drive mechanism and rotary motion source that fall beyond the scope of the present invention. However, for better illustration  FIGS. 2 and 3  show pump drive axle  35  and fixed angle swash plate  36 , against which rear ends of pump pistons  22  are pressed by springs  23 . Just as well, varieties of working attachments (that can be used with the device while being demountably connected to its front end) are not shown.  
       Operation of the Preferred Embodiment  
       [0064]     When the device of the present invention is not charged with hydraulic fluid, or is not primed, compensator spring  17  keeps volume compensator piston  15  bias against the body of cylinder piston  10 , similarly to the position shown on  FIG. 3 . Cylinder piston  10  itself, however, is at this point pressed against the rear wall of volume  9   b  of chamber  9 , as shown on  FIG. 2 . Piston rod  7  is being therefore fully retracted into housing  6 . Priming and bleeding (or eliminating air from hydraulic fluid) will be discussed at the end of this description.  
         [0065]      FIG. 2  shows the device of the present invention in “ready to operate” position. Compensator spring is compressed by the fluid present in the entire system and, particularly, in front of volume compensator piston  15  within hollow piston rod  7 . When an operator depresses the trigger about half-way, valve  27  closes return passageway  31  thus separating volumes  9   a  and  9   b . When trigger is depressed all the way, rotary motion source activates swash plate  36  and pump pistons  22  begin reciprocating within their cylinders.  
         [0066]     At least one of pump pistons  22  makes forward (pumping) movement at any given moment when swash plate rotates. During such movement fluid in corresponding pump cylinder  21  is being displaced by invading volume of pump piston  22 . Resulting pressure acts to keep intake valve  20  closed while forcing discharge valve  26  to open. Fluid in front of pump piston  22  by-passes back via grooves and proceeds through discharge passageways  25  into volume  9   b  of chamber  9 , urging cylinder piston  10  to move forward against resistance of a work load and/or return spring  11 .  
         [0067]     At least one of pump pistons  22  makes backward (intake) movement at any given moment when swash plate rotates. Cylinder piston&#39;s  10  forward movement causes fluid in volume  9   a  of chamber  9  to flow through corresponding intake passageway  19  into its respective pump cylinder  21 . At the same time volume compensator piston  15  is moved within piston rod  7  towards cylinder piston  10  by compensator spring  17 , urging fluid in front of piston  15  to flow through passageways  18  into volume  9   a  of chamber  9  and thus compensating a negative difference between volumes  9   a  and  9   b.    
         [0068]      FIG. 3  shows the device of the present invention at the end of its useful work cycle. Cylinder piston  10  is pressed by fluid against fully compressed return spring  11  and reduced diameter area of chamber  9   a . Compensator piston  15  has traveled all its way towards cylinder piston  10 , compensator spring  17  is only slightly compressed. Assuming the operator still holds the trigger fully squeezed, trigger valve  27  is closed and rotation of swash plate  36  continues, hydraulic circuit is being active through relief valve  33  opened by fluid pressure. Relief passageway  32  returns fluid from volume  9   b  to volume  9   a , and the device is idling under high pressure.  
         [0069]     If operator partially releases trigger, rotation stops, but trigger valve is still closed, so piston rod  7  remains fully extended. When the operator lets go of the trigger, valve  27  opens, fluid under pressure created by return spring  11  escapes from volume  9   b  back to volume  9   a  and into hollow piston rod  7 , forcing compensator piston  15  to move towards end cap  13  and to compress compensator spring  17 .  
         [0070]     In order to charge the device of the present invention with fluid and bleed air from its hydraulic system, there is no need for any separate priming pump. Two flexible hoses must be placed over heads of partially unscrewed charging and bleeding nipples  34 . Opposite ends of these hoses must then be placed into a jar full of fluid of choice. One of these hoses has a foot valve, another has one-way check valve so that flow in both hoses throughout volume  9   a  can occur in one direction only. Once hoses are submerged into fluid in the jar, operator depresses the trigger and holds it for awhile.  
         [0071]     At this point auxiliary intake springs  23  play their role. They keep pump pistons  22  in contact with swash plate at any time so that suction effort materializes upon rearward movement of pistons. Fluid therefore enters volume  9   a  through the hose with foot valve and starts filling the system, thereby urging the air to escape through the hose with check valve. This shortly causes pressure buildup within volume  9   b  and cylinder piston  10  starts moving forward. Once that occurs, operator repeatedly releases and depresses the trigger until piston rod  7  extends fully forward (to the point of opening of the relief valve  33 ) and returns fully back, driving the remaining air out of the system.  
         [0072]     When no more air bubbles are observed escaping the system, operator partially releases the trigger as soon as piston rod reaches full extent forward. Without letting the trigger go operator then immediately tightens the nipple with check valve hose. Then he/she releases the trigger completely, trigger valve opens and fluid from volume  9   b  is driven into volume  9   a  and hollow piston rod  7  by return spring  11 , forcing compensator piston  15  to compress compensator spring  17 . This procedure must be repeated two-three times. Upon doing so, some more air bubbles will show escaping. When it happens no longer, both nipples must be tightened, hoses removed and stowed, the device of the present invention is charged and ready to operate.  
       Alternative Embodiments  
       [0073]     The closed circuit hydraulic compression device with stroke-consistent pump intake of the present invention is primarily intended to be used as a core element of hand-held tools for cutting, crimping, deforming and perforating of various objects made of metals and other stiff materials. However, it can also be utilized as part of any stationary equipment where compression force is required and compact design is being a matter of importance.  
         [0074]     Housing  6  may be of prismatic or other suitable shape. Axis of the housing and of cylinder piston do not necessarily have to coincide or to be precisely parallel.  
         [0075]     A highly desirable alternative embodiment presumes a replacement of compensator piston  15  and spring  17  by a collapsible elastomer compensating container. Such design change eliminates a necessity of precision machining of hollow piston rod&#39;s  15  bore. Passageways  18  can then be arranged through walls of hollow piston rod  7  instead of the body of cylinder piston  10 . Also, the opening to ambient media in end cap  13  can be done away with in order to nullify sensitivity of the device to a pressure and chemical aggressiveness of the media. Finally, both return passageway  31  and relief passageway  32  can be located wherever it is convenient and functional, including their unification by a slight change of trigger valve&#39;s  27  design or routing them through pump drive area.  
         [0076]     It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.