Handling: hand and hoist-line implements – Hook – hoistline – or grab type – Load releasing means
Reexamination Certificate
1999-08-18
2001-06-05
Cherry, Johnny D. (Department: 3652)
Handling: hand and hoist-line implements
Hook, hoistline, or grab type
Load releasing means
C294S082300, C294S082230, C294S905000
Reexamination Certificate
active
06241298
ABSTRACT:
The present invention relates to a release mechanism suitable for use with lift or crane hooks but not exclusively. The invention relates also to a hook for use with the release mechanism and to a control system for use therewith.
Release mechanisms for use with crane hooks and the like are generally well known. There are essentially two different types of release mechanism for use with hooks—the self-releasing type arranged for automatically releasing the load on a hook upon deposition of the load on the ground and manually operable release mechanisms which release a load only upon being activated by an operator. The former automatically releasing mechanisms have the disadvantage that they release a load as soon as it is placed on the ground and thus for example, if the load is in the wrong place, it has to be placed back onto the crane hook before it can be moved. This is time consuming and in certain conditions, for example off-shore drilling operations, potentially very dangerous to operators. Such automatically releasing mechanisms are known from DE Patent No. 2757321, FR Patent No. 2411795, SU Patent No. 578257, International Publication No. WO 86/07582 and U.S. Pat. No. 5,178,427.
The latter type of release mechanism which are frequently arranged for remote operation have the advantage over automatically releasing mechanisms that they will only release a load when instructed to do so by an operator and thereby avoid unintentional disconnection. UK Patent Publication No. 2293407A discloses a crane hook having a remotely controlled ejection lever. A particular disadvantage of the release mechanism disclosed therein is that there is required a more or less large shank housing to house a motor; an hydraulic pump driven by said motor; a power supply for said motor; an hydraulic cylinder/ram driven by the hydraulic pump and the various control circuitry for the remote operation of the ejection lever portion of the hook. Both types of release mechanism might typically be approximately 1 m in length and lm in diameter and weigh 565 kg and do not lend themselves to use in off-shore oil and gas exploration applications as it will be appreciated that such a large and heavy hook may swing about and result in damage under adverse weather and other operating conditions to installations and personnel securing a load to be carried by the hook.
Furthermore, conventional known hooks are generally in the form of more or less large cast or forged one-piece bodies containing an ejection lever. One disadvantage of such one-piece bodies is that they are not possible to repair insofar as they cannot be disassembled. Furthermore, the arrangement by which the ejector lever is operated, i.e. a hydraulic ram together with the one-piece construction, means that such hooks are generally large with the hydraulic ram mounted externally as in GB 2293407A.
Additionally, such one-piece hooks which have a centrally mounted ejection lever cannot meet increasingly stringent national, regional and international standards in, for example, the United Kingdom and De Norsk Veritas rules relating to offset loading. Offset loading is where one may have different loadings on the hook on each side of the centrally mounted ejection lever due to a load not being lifted centrally or by the load swinging as may happen in use on off-shore application.
It is an object of the present invention to avoid or minimise one or more of the foregoing disadvantages.
In a first respect the present invention provides a release mechanism suitable for use in releasing remotely a load supported on a hook or the like which mechanism comprises a discrete load supporting means provided with ejector means formed and arranged for selectively ejecting a said load supported thereby and discrete control means formed and arranged for controlling said ejector means on said load supporting means; characterised in that said load supporting means is substantially spaced apart and depends from said control means by an elongate support link and said control means and said ejector means are connected together by a communication means whereby in use a load may be secured to said load supporting means by an operator with said control means of the release mechanism substantially remote from said operator.
Thus, with a release mechanism according to the present invention a load may be secured thereto in a substantially safer way than previous designs of automatic and remotely releasable mechanisms have allowed.
Preferably, said control means is provided in a control means housing which includes power supply means for driving said ejector means. Preferably, said power supply means is in the form of compressed pressurised hydraulic fluid contained within an accumulator bladder and said ejector is in the form of hydraulic ram in spaced apart communication with said control means whereby said control means can control the flow of pressurised hydraulic fluid from said accumulator to said spaced apart ejector means. Preferably said control means is in the form of valve means formed and arranged in a first open position to permit pressurised fluid to pass from said accumulator to said ejector means for operation thereof and in a second closed position to prevent pressurised fluid passing to said ejector means and thereby operating said ejector means for ejecting a load supported on said load supporting means. Preferably, said communication means in the form of an elongate flexible hydraulic pipe of generally known type and construction.
In its simplest form, the volume of hydraulic fluid being transferred from said accumulator to said ejector is a generally fixed volume. Preferably though, and so as to provide for a standby or redundancy eventuality in the situation where for example there is a partial loss of hydraulic fluid, the accumulator bladder is so formed and arranged with a capacity to store a plurality of charges of pressurised fluid, in the range of from two to ten charges for example five charges, each charge being sufficient to operate the ejector means once. Preferably, the charging of the accumulator is effected by a self generating power lift cylinder formed and arranged within the control means whereupon upward movement of the control means by, for example a crane, in use of the release mechanism, and lifting a load loaded onto said load supporting means causes said cylinder to stroke within the control unit and to pressurize fluid into said accumulator. Preferably, said cylinder has a full stroke in the range of from 175 mm to 230 mm and one full stroke of the cylinder is sufficient to provide a plurality of charges, for example five to seven charges, each charge being sufficient to operate said ejection means once. Desirably, a partial stroke of the cylinder, for example a stroke of 35 mm, is sufficient to provide one to two charges, each charge being sufficient to operate the ejection means once.
Preferably, there is provided a hydraulic fluid reservoir to supply fluid to be pressurised in said cylinder. Preferably, said reservoir is in the form of an annular tank surrounding said accumulator so as to reduce the overall length of the control means of the release mechanism according to the invention.
Preferably, said valve means is actuated by a solenoid type switch which is switched on and/or off by a hand held remote control transmitter using infra-red acoustic (for underwater applications) or radio signals to transmit a control signal to said control means for operation of said solenoid valve. The remote control transmitted may be of the three channel, two switch high security radio transmitter type and includes a receiver/decoder so that the receiver will decode received signals and operate only if the received signals are correct. The transmitter/receiver may be pre-set to any one of a multiplicity of separate radio frequencies and signal codes according to a user's requirements. This feature is particularly useful where several release mechanisms according to the invention are in use and it is required to operate them selectively an
Hamilton David Stewart
Whyte Ronald Norris
Cherry Johnny D.
Easylift Limited
Kelemen Gabor J.
Venabler
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