Closed circuit hydraulic compression device with stroke-consistent pump intake

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

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

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.

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's body, thus making the latter larger and heavier then the present invention permits.

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's body, size factor remains not being adequately addressed.

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's size then the present invention affords.

SUMMARY OF THE INVENTION

The present invention relates to a closed circuit hydraulic compression device that substantially obviates one or more of the disadvantages of the related art.

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.

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

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:

FIG. 1 shows a conventional self-contained compression tool of U.S. Pat. No. 6,446,482 to Heskey, et al., Sep. 10, 2002.

FIG. 2 shows a plane view of longitudinal vertical cross-section of the device of the present invention.

FIG. 3 shows a plane view of longitudinal diagonal cross-section of the device of the present invention.

FIG. 4 shows a plane view of transverse cross-section of the device of the present invention.

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

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

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'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.

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.

This invention described herein can be used for:

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.

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's cylinder bore).

3. Reducing precision and material requirements, simplifying design and adding reliability to the tool or implement by having pump piston'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.

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

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.

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 9a (in front of piston 10) and volume 9b (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.

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.

Passageways 18 are arranged within cylinder piston 10 so that internal space of hollow rod 7 is openly connected to volume 9a of chamber 9. At the front end of volume 9a 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.

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 9b of chamber 9.

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 9a and volume 9b 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.

FIG. 3 further shows relief passageway 32 and relief valve 33. These are also arranged between volumes 9a and 9b 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 9a 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.

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

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 9b 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.

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 9a and 9b. When trigger is depressed all the way, rotary motion source activates swash plate 36 and pump pistons 22 begin reciprocating within their cylinders.

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 9b of chamber 9, urging cylinder piston 10 to move forward against resistance of a work load and/or return spring 11.

At least one of pump pistons 22 makes backward (intake) movement at any given moment when swash plate rotates. Cylinder piston's 10 forward movement causes fluid in volume 9a 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 9a of chamber 9 and thus compensating a negative difference between volumes 9a and 9b.

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 9a. 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 9b to volume 9a, and the device is idling under high pressure.

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 9b back to volume 9a and into hollow piston rod 7, forcing compensator piston 15 to move towards end cap 13 and to compress compensator spring 17.

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 9a can occur in one direction only. Once hoses are submerged into fluid in the jar, operator depresses the trigger and holds it for awhile.

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 9a 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 9b 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.

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 9b is driven into volume 9a 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

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.

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.

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'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's 27 design or routing them through pump drive area.

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.

Claims

1. A closed circuit hydraulic compression device comprising:

a housing;

a main hydraulic cylinder within the housing and comprising a hollow rod, a main piston, a bore, a piston seal, means for returning the main piston to a predetermined position within the bore after commencing a stroke to any distance, and means for preventing a loss of a working fluid,

wherein the hollow rod includes means for containing the working fluid under a predetermined pressure,

wherein the main piston allows a free passage of the working fluid in both directions between a space within the hollow rod and a space within the bore in front of the main piston,

wherein the bore in front of the main piston permits an unobstructed outward flow of the working fluid from the space within the bore in front of the main piston while preventing a reverse flow;

a group of pump cylinders located within the housing and oriented approximately parallel to a longitudinal axis of the main cylinder, wherein a front portion of each pump cylinder is openly connected to the means of preventing the reverse flow of the working fluid into the space within the bore of the main cylinder in front of the main piston and a rear portion of each cylinder has means to allow unobstructed flow of working fluid into a space within the bore behind the main piston while preventing the reverse flow,

wherein the means to allow for unobstructed unidirectional flow of working fluid from the bore in front of the main piston via the pump cylinders into the bore behind the main piston remain functional throughout a full predetermined stroke of the main piston,

each pump cylinder further incorporating a pump piston and a fluid-tight seal between a rear portion of the pump piston and a rear portion of the pump cylinder, wherein the rear portion of each pump piston extends beyond the fluid-tight seal so that a predetermined reciprocal movement of the pump piston is allowed,

each pump cylinder further incorporating means to return pump piston to a predetermined position after commencing a stroke to any distance,

each pump piston further comprising means to allow for unobstructed flow of the working fluid in a direction approximately parallel to a longitudinal axis of the pump piston,

means to allow for a return of the working fluid from the bore behind the main piston into the bore in front of the main piston throughout a duty cycle of the closed circuit hydraulic compression device;

means to impart reciprocal movement to the pump pistons; and

means to allow for charging the closed circuit compression device with the working fluid and for subsequent elimination of gas bubbles from the working fluid.

2. The closed circuit hydraulic compression device of claim 1, further comprising manual means to control means to allow for the return of the working fluid.

3. The closed circuit hydraulic compression device of claim 1, further comprising automatic means to control means to allow for the return of the working fluid.

4. The closed circuit hydraulic compression device of claim 1, further comprising means to prevent an increase in pressure of the working fluid above a predetermined value.