Patent Grant
10054139
The present subject matter relates to hydraulic tools with a rapid ram advance feature. The subject matter also relates to hydraulic systems equipped with the rapid ram advance feature, and related methods using such systems.
Hydraulic tools generally include a hydraulic ram or piston that can be extended to perform work such as crimping of workpieces or other functions. Ram extension is performed by pumping hydraulic fluid, under pressure, behind the ram thereby causing displacement of the ram. For hydraulic tools that include a manually operated pump such as a handle pump, performing a large number of repeated crimpings or other operations requires a corresponding large number of pumping operations by a user. This can become burdensome and significantly reduce the rate of operations performed by the user.
Hydraulic systems are known which provide rapid ram extension during no load conditions or prior to a ram position at which work is to be performed. A variety of strategies have been devised to increase the speed of ram extension. However, many if not all strategies involve complex hydraulic assemblies, and intricate hydraulic systems of valving and seals. As will be appreciated, such assemblies increase manufacturing costs and can be difficult to maintain. Accordingly, a need remains for new hydraulic systems, related methods, and tools using such hydraulic systems which are reliable and easy to maintain and which do not increase manufacturing costs.
The difficulties and drawbacks associated with previously known hydraulic tools and systems are addressed in the present subject matter as follows.
In one aspect, the present subject matter provides a hydraulic system comprising a reservoir adapted to contain hydraulic fluid. The system also comprises a hydraulic cylinder defining a hollow interior and including a ram disposed therein. The ram defines a first face and an oppositely directed second working face. The interior of the cylinder and the first face of the ram define a primary chamber. The ram is positionable through a first phase of ram extension and a second phase of ram extension. The system also comprises a pushrod assembly including a housing defining a hollow interior and a pushrod positionably disposed therein. The pushrod defines a first end and an oppositely directed second end. The interior of the housing and the first end of the pushrod define a secondary chamber. The pushrod and the ram are in at least periodic operable engagement such that extension of the pushrod causes extension of the ram. The pushrod and housing include provisions to preclude fluid flow between the primary chamber and the secondary chamber when the pushrod is within a range of positions corresponding to the first phase of ram extension, and permit fluid flow between the primary chamber and the secondary chamber when the pushrod is within a range of positions corresponding to the second phase of ram extension.
In another aspect, the present subject matter provides a method of extending a hydraulic ram in which the ram is extended at a first rate of extension and then at a second rate of extension. The first rate of extension is greater than the second rate of extension. The method comprises providing a hydraulic system including (i) a reservoir containing hydraulic fluid, (ii) a hydraulic cylinder and ram positionably disposed therein, the cylinder and ram defining a primary chamber, (iii) a pushrod assembly having a housing and a pushrod positionably disposed therein, the housing and pushrod defining secondary chamber, the pushrod and the ram being in at least periodic operable engagement such that extension of the pushrod causes extension of the ram, and (iv) provisions for precluding fluid flow between the primary chamber and the secondary chamber at a first range of positions of the pushrod and permitting fluid flow between the primary chamber and the secondary chamber at a second range of positions of the pushrod relative to the housing. The method also comprises directing hydraulic fluid into the secondary chamber to thereby extend the pushrod and cause extension of the ram, whereby ram extension occurs at a first rate of extension. The method additionally comprises directing hydraulic fluid into the primary chamber to thereby extend the ram at a second rate of extension. The first rate of extension is greater than the second rate of extension.
In yet another aspect, the present subject matter provides a hydraulic tool comprising a tool body, and a tool head secured to the tool body. The tool head includes a positionable work member for performing at least one operation on a workpiece. The tool also comprises a hydraulic system generally disposed within the tool body. The hydraulic system includes (i) a reservoir adapted to contain hydraulic fluid, (ii) a hydraulic cylinder defining a hollow interior and including a ram disposed therein, the ram defining a first face and an oppositely directed second working face, the interior of the cylinder and the first face of the ram defining a primary chamber, the ram positionable through a first phase of ram extension and a second phase of ram extension, and (iii) a pushrod assembly including a housing defining a hollow interior and a pushrod positionably disposed therein. The pushrod defines a first end and an oppositely directed second end. The interior of the housing and the first end of the pushrod define a secondary chamber. The pushrod and the ram are in at least periodic operable engagement such that extension of the pushrod causes extension of the ram. The pushrod and housing include provisions to preclude fluid flow between the primary chamber and the secondary chamber when the pushrod is within a range of positions corresponding to the first phase of ram extension, and permit fluid flow between the primary chamber and the secondary chamber when the pushrod is within a range of positions corresponding to the second phase of ram extension. The ram is engageable with the work member of the tool head.
As will be realized, the subject matter described herein is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the claimed subject matter. Accordingly, the drawings and description are to be regarded as illustrative and not restrictive.
The present subject matter relates to systems for rapidly advancing a hydraulic piston. The systems include a primary chamber, a hydraulic ram or piston positionable therein, a secondary chamber typically smaller and disposed along a face of the hydraulic ram, a pushrod disposed within the secondary chamber, and two hydraulic fluid lines each with flow valves that deliver hydraulic fluid from a pump to one or both chambers to thereby advance or extend the ram.
More specifically, in certain embodiments of the present subject matter, the pushrod and the ram are configured and arranged such that extension of the pushrod causes extension of the ram. In an initial or first phase of ram extension, hydraulic fluid is directed into the secondary chamber thereby causing extension of the pushrod. Due to the configuration of the secondary chamber, the rate of pushrod extension is relatively high. Linear displacement of the pushrod causes linear displacement and thus extension of the ram, which also occurs at this relatively high rate.
Extension of the pushrod and ram continues until at a particular position of the pushrod relative to the secondary chamber, hydraulic fluid is permitted to flow from the secondary chamber to the primary chamber. This begins a second phase of ram extension characterized by a lower rate of extension as compared to that of the first phase of ram extension. During the second phase of ram extension, relatively large forces can be delivered by the ram as described in greater detail herein.
In particular embodiments of the present subject matter, the pushrod is configured such that when the pushrod is within a range of positions corresponding to the first phase of ram extension, fluid communication between the primary and secondary chambers is precluded or at least substantially so as described in greater detail herein. And, when the pushrod is within a range of positions corresponding to the second phase of ram extension, fluid communication between the primary and secondary chambers is permitted. As noted, in particular embodiments the pushrod is configured to preclude or substantially preclude fluid flow between the chambers. Although a very small amount of fluid may potentially pass between the pushrod and an inner wall of the secondary chamber, the amount of fluid and/or extent of flow is insufficient to result in a significant pressure loss in the secondary chamber, thereby permitting the rapid advance of the pushrod as described herein. Thus, the terms “preclude fluid flow” and “precluding fluid flow” as used herein refer to either no fluid flow or a relatively minor fluid flow between the primary and secondary chambers in which the maximum volume of fluid passing between the pushrod and the inner wall of the secondary chamber is less than 16% of the total volume of fluid displaced by a single pumping action, i.e., one full extension of the ram. In many embodiments, the maximum volume of fluid is less than 10%, more particularly less than 5%, and in certain embodiments is only about 1.5% of the total volume of fluid displaced by a single pumping action.
In one embodiment, the pushrod has a “free flow” configuration along a portion of its length that permits such fluid communication when the pushrod is within the range of positions corresponding to the second phase of ram extension. The free flow configuration includes a flat surface region that extends from one end of the pushrod toward the other end, but which terminates at a location on the pushrod that generally constitutes the transition between the first and second phases of ram extension. The flat region enables hydraulic fluid to pass alongside the flat region of the pushrod when the pushrod is in the range of positions corresponding to the second phase of ram extension.
The free flow configuration may also include a recessed channel extending around at least a majority of the circumference of the pushrod at the noted transition location. This recessed channel can be in the form of a recessed circumferential band. The recessed band extends around at least a portion of the circumference of the pushrod. In certain embodiments of the present subject matter, the recessed band extends entirely around the circumference or outer perimeter of the pushrod. The flat region defined along a portion of the length of the pushrod extends between an end of the pushrod and the band or circumferential channel. The recessed circumferential channel promotes positioning of the pushrod and in particular, maintaining the pushrod in a centered position within its housing and/or the secondary chamber as described in greater detail herein. As a result of the recessed channel, hydraulic fluid under pressure, is directed into that channel, and around the circumference of the pushrod thereby centering the pushrod within its housing and/or the secondary chamber.
In certain embodiments, hydraulic systems using pushrods as described herein and particularly those that exhibit the noted free flow feature, are devoid of seals or other fluid-sealing components around the pushrod. Thus, in such versions of the present subject matter, the pushrods or pushrod assemblies are free of hydraulic seals.
The present subject matter also relates to methods of extending hydraulic rams in which the rate of extension during the noted first phase of ram extension is greater than the rate of extension during the noted second phase of ram extension. The methods involve the use of a hydraulic system as described herein and one that includes provisions for precluding fluid flow between the primary chamber and the secondary chamber at pushrod positions which correspond to the first phase of ram extension. The provisions also permit fluid flow between the primary chamber and the secondary chamber at pushrod positions which correspond to the second phase of ram extension.
The methods also involve directing hydraulic fluid into the secondary chamber from a pump or other pressure source to thereby extend the pushrod and cause extension of the ram. As noted, during this first phase of ram extension, the rate of ram extension is relatively high. Extension of the pushrod continues until a particular position of the pushrod relative to the secondary chamber is reached and the free flow feature then permits fluid communication between the secondary and primary chambers. As the pushrod is displaced from the previously noted transition position and within the range of positions corresponding to the second phase of ram extension, the rate of ram extension is less than the rate of ram extension in the first phase.
The methods also involve directing hydraulic fluid into the primary chamber from the pump or other pressure source to further extend the ram. Typically, flow of hydraulic fluid into the primary chamber is governed by one or more valves as described in greater detail herein. During this second phase of ram extension, hydraulic fluid may be, and in many instances is also being, concurrently directed into the second chamber. And, as previously noted, during the second phase of ram extension, the free flow configuration permits fluid communication between the primary chamber and the secondary chamber.
Table 1 set forth below summarizes various relationships and states associated with the first relatively rapid phase of ram extension and the slower second phase of ram extension in certain embodiments of the present subject matter.
The present subject matter also relates to tools that include the hydraulic systems described herein. Generally, the tools comprise a tool body or frame and a tool head at which one or more operations are performed upon workpiece(s). The tool head typically includes one or more work members which may be in a variety of different forms. Nonlimiting examples of such work members include dies such as crimping dies, jaws, shaping or forming members, and the like. At least one of the work members is engaged or engageable with the ram of the hydraulic systems described herein.
The system 10 additionally comprises various fluid flow lines and valves. For example, the system 10 includes a pump inlet line 24 providing flow communication between the reservoir 80 and the pump 20. One or more valves such as a one-way valve 25 can be included in the inlet line 24 precluding flow from the pump to the reservoir 80. The system 10 also includes a pump outlet line 26, a splitter or diverter 26a, a first fluid flow line 31 providing fluid communication between the pump 20 and the primary chamber 50, and a second fluid flow line 32 providing fluid communication between the pump 20 and the secondary chamber 70. In many versions of the present subject matter, the flow lines 31 and 32 are in a parallel configuration with each other. One or more valves such as a one-way valve 27 can be included in the line 31 precluding flow from the primary chamber 50 to the pump 20. And, one or more valves such as a one-way valve 28 can be included in the line 32 precluding flow from the secondary chamber 70 to the pump 20. In certain embodiments of the present subject matter, the valve 27 permits fluid flow from the pump 20 to the primary chamber 50 only at certain designated fluid pressures, or at pressures that exceed a valve biasing pressure. And, the valve 28 permits fluid flow from the pump 20 to the secondary chamber 70 only at certain designated fluid pressures, which are typically less than those associated with the valve 27.
The system 10 may also comprise a reservoir return line 82 providing fluid communication between the primary chamber 50 and the reservoir 80, and particularly from the primary chamber to the reservoir which occurs during ram retraction. And, the system 10 may also comprise a reservoir suction line 84 providing fluid communication between the primary chamber 50 and the reservoir 80. One or more valves such as a one way valve 85 can be included in the flow line 84 permitting fluid from the reservoir 80 to the primary chamber 50 of the cylinder 30, but precluding flow in the reverse direction. The hydraulic system 10 can include a wide array of additional components and/or utilize variant hydraulic circuits such as described in U.S. Pat. Nos. 4,206,603; 5,836,400; 6,718,870; and 7,124,608.
The hydraulic ram 40 is engaged or otherwise engageable with the work member 140 such that extension or retraction of the ram 40 can result in extension and/or retraction of the work member 140. The tool 110 is shown in a state of retraction of the ram 40 and the work member 140.
Various methods of using the hydraulic system 10 and/or the tool 110 are as follows. Referring to
Continued operation of the pump 20 results in additional fluid directed into the secondary chamber 70 thereby causing extension of the pushrod 64. Referring to
Pumping of the handle 122 continues and hydraulic fluid is continued to be directed through the inlet line 32 into the secondary chamber 70 thereby causing extension of the pushrod 64 and the ram 40. Linear displacement of the pushrod 64 continues through a range of positions relative to the housing 62 which correspond to the first phase of ram extension. As previously noted, the rate of extension of the pushrod and ram is relatively fast. While the pushrod 64 is within this range of positions corresponding to the first phase, fluid communication between the first and secondary chambers 50 and 70 is precluded. This is achieved by the flat region 72 of the pushrod 64 being sufficiently spaced from an end of the housing 62 at which the primary chamber 50 is accessible. Thus, the position of the pushrod is such that the interface 71 does not extend to the end of the housing. For versions of pushrods 64 having the recessed bands 72, the band is spaced from the end of the housing 62 at which the primary chamber 50 is accessible.
Continued pumping causes additional hydraulic fluid to enter the secondary chamber 70, and extend the pushrod 64 until fluid communication can occur between the secondary chamber 70 and the primary chamber 50. This typically occurs at a location of the ram relatively close to a fully extended position such as at least 80% of ram full extension, in certain embodiments at least 90% of ram full extension and in still other embodiments at least 95% of ram full extension. For applications in which no or minimal loads are placed upon the ram, as the pushrod reaches this transition location, i.e., the pushrod position between the first and second phases of ram extension, an operator may experience a reduction in pumping pressure at the handle 122. This is due to hydraulic fluid entering the primary chamber 50 instead of causing ram extension.
Eventually as pumping continues, the ram advances until resistance is encountered, i.e., a work or crimping operation is begun. Continued pumping results in an increase in fluid pressure until eventually the pressure at valve 27 exceeds the bias pressure to open that valve and allow fluid flow into the primary chamber 50 via the inlet line 31. Additional fluid is directed into the primary chamber 50 and as a result of the relatively large surface area of the face 42 of the ram 40, relatively high compressive forces can be delivered by the ram 40 with continued extension. Fluid flow through the inlet line 32 may continue into the secondary chamber 70. Work such as crimping can be performed during this second phase of ram extension.
The present subject matter hydraulic systems are particularly well suited for incorporation in handheld hydraulic tools such as for example manually powered hydraulic tools such as the tool 210 depicted in
It will be understood that the tool 210 can be used in conjunction with a variety of different work heads. For example, the tool 210 can potentially be used with works heads adapted for performing crimping, pressing, forming, cutting, or other operations. A nonlimiting example of a specific type of work head that could be engaged at the head end 215 of the tool 210 is a press frame such as described in U.S. Pat. No. 7,979,980.
Many other benefits will no doubt become apparent from future application and development of this technology.
All patents, published applications, standards and articles noted herein are hereby incorporated by reference in their entirety.
It will be understood that any one or more feature or component of one embodiment described herein can be combined with one or more other features or components of another embodiment. Thus, the present invention includes any and all combinations of components or features of the embodiments described herein.
As described hereinabove, the present subject matter solves many problems associated with previous strategies, systems and/or devices. However, it will be appreciated that various changes in the details, materials and arrangements of components, which have been herein described and illustrated in order to explain the nature of the present subject matter, may be made by those skilled in the art without departing from the principle and scope of the claimed subject matter, as expressed in the appended claims.
The present application claims priority upon U.S. provisional application Ser. No. 62/024,011 filed Jul. 14, 2014.
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