Motors: expansible chamber type – Independently operated timer – delay – pattern or cyclic control – Fluid actuated valve with volume chamber delay means
Reexamination Certificate
1999-03-15
2001-10-02
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Independently operated timer, delay, pattern or cyclic control
Fluid actuated valve with volume chamber delay means
C091S00400R, C091S035000, C060S394000, C060S409000, C173S002000, C173S011000, C417S012000, C417S046000
Reexamination Certificate
active
06295913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to hydraulic pumps for providing hydraulic fluid under pressure to a hydraulic torque wrench, and in particular to such a pump which is air powered.
2. Discussion of the Prior Art
Air powered hydraulic torque wrench pumps for providing hydraulic fluid under pressure to operate a hydraulic torque wrench are known. Such a pump is connected to a source of compressed air, which is common in industry, and the compressed air drives an air motor of the pump which is mechanically coupled to drive a hydraulic pump. Operation of the hydraulic pump provides hydraulic fluid under pressure from a hydraulic fluid reservoir which is typically incorporated into the pump assembly. The air motor is typically a rotary air motor which is mechanically coupled to a rotary hydraulic pump, although linear air motors and hydraulic pumps are also possible.
In such pump assemblies, once the air motor is turned on, the pump typically continues to operate until the supply of air to the air motor is turned off by the operator. Since continuous operation of the hydraulic pump generates considerable heat in the hydraulic fluid which is being pumped, a heat exchanger has been provided as part of the pump assembly so as to provide cooling for the hydraulic fluid when the pump is operated for a long period of time. In these units, continuous operation of the pump was common, even though tightening of the fasteners using the hydraulic wrench was only intermittent. As a result, not only was the provision of the heat exchanger made necessary, but energy operating the pump during the periods that a fastener was not being tightened was wasted.
SUMMARY OF THE INVENTION
The invention provides a hydro-pneumatic control circuit for a compressed air-powered hydraulic torque wrench pump of the above-described type in which the controls continue operation of the air motor after the advance button is deactuated to drive the hydraulic pump until a post-advance period of operation has expired. If the pump assembly is used to provide power to a double acting wrench, the post-advance period provides power to retract the wrench, to make it ready for the next advance called for by the operator. If the next advance is called for by the operator (by actuating the advance actuator) during the-post-advance period, pump operation continues without interruption. When the advance actuator is once again deactuated, a new post-advance period of operation begins, at the end of which the pump will turn off unless the advance actuator is first reactuated, which will again continue operation without interruption as described above. This cycle of operation can continue so that the pump can be operated continuously if the advance actuator is reactuated before the end of the post-advance period. However, if the advance actuator is not reactuated before the end of the postadvance period, the air motor and pump will stop, thereby conserving energy and avoiding unnecessarily heating the hydraulic fluid.
In an especially useful form, the advance actuator actuates an air valve which when actuated pressurizes through a first air line a first pilot port of a first pressure actuated air valve, the actuation of which causes the air motor to come on. In this aspect, the first air line includes a flow restriction and a one-way check valve which bypasses the restriction in the flow direction toward the pilot port of the first pressure actuated valve. In the opposite flow direction, when the first pilot port is being relieved, the check valve blocks flow so it all must flow through the restriction, which acts as a timer to set the duration of the post-advance period of operation of the pump assembly.
In another preferred aspect, a second air line communicates air pressure from the first pressure actuated air valve to a pilot port of a second pressure actuated air valve. The second pressure actuated air valve shifts when the pilot port is actuated to admit pressurized air to an inlet of the air motor. This isolates the compressed air supply to the air motor so that the pressure supplied to the air motor is not affected by minor variations in the pressure drop past the first pressure actuated air valve.
In another useful aspect, an immediate off actuator is provided for turning off the pump during the post-advance period. This is useful, for example, if a leak of hydraulic fluid occurs during operation of the pump assembly, so it becomes desirable to turn the pump off immediately.
In a preferred form, actuation of the immediate off actuator admits compressed air to a second pilot port of the first pressure actuated air valve for shifting the first pressure actuated air valve so as to turn off the air motor. Thereby, this feature can be provided using air controls at a low cost. In one form, a flow restriction can be provided for timing relief of the second pilot port so that the pump does not restart if the immediate off actuator is deactuated before the end of the post-advance period.
In an especially preferred form, the second pilot port flow restriction is not provided, and instead a pilot pressure operated, spring return on/off (two way, two position) valve vents the second pilot port when the advance actuator is actuated. Thus, pressure is held on the second pilot port even after the immediate off actuator is released, until the advance actuator is actuated.
In another useful aspect, a pump assembly of the invention preferably includes a pair of hydraulic connectors for connecting to two hydraulic lines in communication with a hydraulic torque wrench. This is required for operating a double acting hydraulic torque wrench, which is where the invention provides the greatest advantages. However, the invention also provides advantages in operating a single acting wrench, and a pump assembly having two hydraulic connections can be used to operate such a wrench simply by plugging the connector which would otherwise be connected to the rod side port of a double acting wrench.
In another useful aspect, whether the invention is applied to operating a single acting or a double acting hydraulic wrench, it is preferred that the controls continue operation of the pump if the advance actuator is reactuated before the post-advance period expires. Thereby, the pump can be operated continuously if only brief pauses occur between deactuating and reactuating the advance actuator, as occur when tightening a fastener with multiple serial advances or when moving the wrench from one fastener to another. This, therefore, avoids restarting the pump, and the disadvantages associated therewith, such as increased wear of the components of the pump assembly and wrench, and major variations in the hydraulic pressure supplied by the pump assembly.
In this aspect, it is also preferred that each deactuation of the advance actuator start a new post-advance period, even if the deactuation follows an actuation which occurred during a post-advance period. This way, each post-advance period is of substantially the same duration (assuming no interruption by an actuation of the advance actuator), for consistent operation of the pump assembly.
REFERENCES:
patent: 3084674 (1963-04-01), Watson
patent: 4074612 (1978-02-01), Miller
patent: 5567886 (1996-10-01), Kettner
patent: 5782158 (1998-07-01), Rothering
patent: 0502748 A (1992-09-01), None
patent: 0625408 A (1994-11-01), None
Applicant's Exhibit A, catalog page regarding “Pegasus™” Air Hydraulic Torque Wrench Pump, Pub.#9413-364 of Enerpac, A Unit of Applied Power Inc., Butler, WI, dated 4/94, admitted prior art.
Applied Power Inc.
Lopez F. Daniel
Quarles & Brady LLP
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