Patent Publication Number: US-5292163-A

Title: Hook apparatus for lifting a heavy object

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hook apparatus which is used to lift a heavy object, e.g., an iron plate, a block member, etc., at a construction site or the like. 
     More particularly, the present invention relates to a hook apparatus specially used for lifting a heavy object, which is capable of being hooked. 
     2. Description of the Prior Art 
     Hitherto, heavy iron plates (e.g., several tons) have been used at many construction sites where they are laid out on the ground to form curing scaffolding for soft ground. It is frequently to move such plates, depending upon the type of work at the construction site. To move the plates, a lifting operation is conducted with a crane or the like. 
     More specifically, the operation of lifting and moving an iron plate used as the above-described scaffolding is carried out with a wire passed through a lifting hole that is provided in a desired portion of the iron plate. The wire is engaged with a hook to pull the wire, thereby lifting and moving the iron plate. 
     Conventional hooks generally used for the above operation of lifting iron plates (also known as sole plates) are of different types such as: 
     (i) In one conventional hook structure, a fall preventing plate is disposed on the hook body in such a manner that the plate is biased by resilient force to abut against the distal end portion of the hook, and the width of the opening at the distal end portion of the hook is set at an extremely small value. 
     Needless to say, the reason why the opening width at the distal end portion of the hook is made small is to prevent disengagement of the wire from the hook as much as possible. (ii) In another conventional hook structure; a hook comprises a hook support and a hook member, which are two separate members capable of pivoting relative to each other. It should be noted that when a heavy object is lifted, the respective distal end portions of the hook support and the hook member abut against each other to function as a fall preventing mechanism. 
     However, this type of conventional hook structure is also used in such a way that a wire that is attached to an iron plate which is then engaged with the hook; therefore, the width of the opening which is defined at the hook distal end portion between the hook support and the hook member when pivoted relative to each other is extremely small for the same reason as above. 
     In field work, however, heavy labor is required for the operation of engaging a wire with an iron plate laid out, which is as heavy as several tons. Therefore, the worker is apt to insert the engagement portion of the hook (i.e., the hook distal end portion) directly into a hole provided in the iron plate to lift it. In such a case, however, it is extremely difficult to engage the hook with the iron plate because the opening width at the hook distal end portion is extremely small, as described above. In other words, when an object, e.g., an iron plate, which is laid out on the ground is to be lifted up by engaging the hook directly with the iron plate, the hook cannot readily be engaged with the iron plate because the opening width of the conventional hook is extremely small. Even if the hook is successfully engaged with the iron plate, it is still difficult to disengage the hook from the iron plate after the iron plate has been relocated. 
     Properly speaking, hooks having no fall preventing device must not be used for the operation of the type described above, but in many work sites hooks which are equipped with no fall preventing device and which have a large opening width are used in the present state of art. 
     However, it is considerably dangerous to use a hook which is equipped with no fall preventing device and which has a wide opening for such an operation. 
     More specifically, when an iron plate (as a heavy object) is being lifted with a hook having no fall preventing device, there is substantially no possibility of the hook disengaging from the iron plate, but when the iron plate is lowered onto the ground so as to be installed thereon, a play is likely to be produced between the hook and the hole for lifting due to slacking of the lifting wire. Thus, undesired disengagement of the hook from the hole frequently occurs. Once the hook disengages from the hole, the iron plate will fall down, inviting danger of people being crushed to death under the iron plate. In actuality, there have, been many fatal accidents caused by falling iron plates at work sites of the kind described above. 
     The present inventor conducted exhaustive studies in order to solve the above-described problems of the prior art. 
     As a result, the present inventor has found that if a hook apparatus has such a structure that a hook that is pivotably attached to a hook support is capable of pivoting approximately 180° reversely from a locked position (in which the distal end portion of the hook is held in united relation to a fall preventing portion of the hook support to maintain a lock state) when it is unlocked, that is, if the distal end portion of the hook and the fall preventing portion of the hook support can be opened relative to each other much wider than in the prior art, it is possible to facilitate insertion of the distal end portion of the hook into an engagement hole provided in a heavy object, e.g., an iron plate or the like laid out on the ground, when the hook is to be engaged with such a heavy object to lift it, and there is no likelihood that the fall preventing portion will abut on or be buried in the ground during the operation of disengaging the hook from the heavy object, thus enabling the hook to be disengaged from the heavy object extremely smoothly without meeting with any obstacle. The present invention has been accomplished on the basis of this finding. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hook apparatus which is attached to the distal end of a wire of a lifting machine to lift a heavy object, comprising: a hook support having a fall preventing portion at a distal end thereof and a wire securing portion at the proximal end thereof; a hook whose proximal end portion has a bifurcated structure comprising two branched end portions and, the hook being pivotably attached to the hook support through a connecting pin which extends between the branched end portions, piercing through an approximately central portion of the hook support which is disposed in the space defined between the branched end portions; a lock adapted to lock the hook support and the hook to each other when the fall preventing portion of the hook support and the distal end portion of the hook are placed substantially in contact with each other, the lock being disposed in the space defined between the branched end portions; and the hook being pivotable through approximately 180° reversely relative to the hook support so that a back portion of the hook can abut on a side of the hook support when the hook support and the hook are unlocked from each other by disengaging the lock. 
     More specifically, the hook also has a shank portion which is formed opposite the distal end portion to define a throat therebetween. The hook also has a proximal end portion which has a bifurcated structure to define the branched end portions. When the hook is reversely pivoted so that a back surface of the hook abuts on a side of the hook support, an inner surface of the fall preventing portion and the inner surface of the proximal end portion extend generally within a plane which intersects a plane in which the inner surface of the shank portion generally extends so that the two planes form an obtuse angle with each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings, in which like reference numerals denote like elements, and of which: 
     FIG. 1 is a front view of a hook apparatus according to one embodiment of the present invention; 
     FIG. 2 shows a first stage of a lifting operation carried out using the hook apparatus of the present invention; 
     FIG. 3 shows a stage of the lifting operation carried out using the hook apparatus of the present invention, in which the opening width is enlarged; 
     FIG. 4 shows a stage of the lifting operation carried out using the hook apparatus of the present invention, in which a hook is engaged with a hole in an iron plate; 
     FIG. 5 shows the initial stage of the operation of lifting the iron plate using the hook apparatus of the present invention; and 
     FIG. 6 shows the final stage of the lifting operation in which the iron plate has been completely lifted up using 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The technical construction of the present invention will be described below in detail by way of one embodiment and with reference to the accompanying drawings. It should be noted that the present invention is not limited to the illustrated embodiment. 
     FIG. 1 is a front view illustrating the structure of a hook apparatus according to one embodiment of the present invention. 
     As illustrated, the hook apparatus F principally comprises hook support 1, a hook 3, and a lock 4. 
     It should be noted that since the proximal end portion of the hook 3 has a bifurcated structure, as described later, in FIG. 1 the structure of the bifurcate portion is shown with a part thereof cut out and, FIG. 1 shows the hook 3, which is in a locked position (phantom line) and also an unlocked (solid line) when the hook 3 has been pivoted approximately 180° reversely from the locked position. 
     The hook support 1 in the present invention has a fall preventing portion 11 at the distal end thereof and a wire securing portion 12 at the proximal end thereof for securing a wire rope R that is connected to a take-up mechanism provided on a crane C. The hook support 1 in the illustrated example comprises a single plate made of steel. 
     In addition, an approximately central portion 13 of the hook support 1 from which the fall preventing portion 11 projects is rotatably fitted in the space defined between two branched end portions 32 and 32&#39; constituting the bifurcated proximal end portion of the hook 3, and it is pivotably supported by a connecting pin 2 which extends between the branched end portions 32 and 32&#39; of the hook 3. 
     Further, the approximately central portion 13 of the hook support 1 is provided with a recess 14 which cooperates with the lock 4, which is disposed in the space defined between the branched end portions 32 and 32&#39; of the hook 3, as described later, to lock the hook support 1 and the hook 3 together and unlock them from each other. It is preferable for the approximately central portion 13 to have a configuration with a circular projection, as illustrated, for the cooperation with the lock 4, as a matter of course. 
     The hook 3 in the present invention comprises a hook distal end portion 31 which cooperates with the fall preventing portion 11 of the hook support 1 to prevent a heavy object, e.g., an iron plate, from falling when the hook apparatus F is in a locked state, a back portion 33, and a bifurcated proximal end portion comprising two branched end portions 32 and 32&#39; which define a space adequate to rotatably receive the approximately central portion 13 of the hook support 1 and to accommodate the lock 4 (described later) As illustrated, the hook 3 is shaped so that the branched end portions 32 and 32&#39;, the back portion 33 and the distal end portion 31 define in combination the desired hook configuration. 
     The lock 4 in the present invention is disposed in the space defined between the branched end portions 32 and 32&#39; of the hook 3 such that the lock 4 abuts against the approximately central portion 13 of the hook support 1, as illustrated. 
     The lock 4 is arranged to maintain a locked state of the hook apparatus F. That is, when the fall preventing portion 11 of the hook support 1 and the distal end portion 31 of the hook 3 are placed substantially in contact with each other, the lock 4 maintains the contacting relation between the two portions 11 and 31. For example, the locked state is attained by the following structure of the lock 4. However, the present invention is not limited thereto. 
     The distal end portion 41 of the lock 4 is shaped to be engageable with the recess 14 provided in the approximately central portion 13 of the hook support 1. The lock 4 is disposed in the space defined between the branched end portions 32 and 32&#39; of the hook 3, and the lock 4 is biased to abut against the approximately central portion 13 of the hook support 1 by resilient force from a spring 5, as illustrated. More specifically, the end portion 41 of the lock 4 is engaged with the recess 14 provided in the approximately central portion 13 of the hook support 1 by the resilient force from the spring 5, thereby maintaining the locked state stably by the cooperation of the fall preventing portion 11 of the hook support 1 and the distal end portion 31 of the hook 3. It should be noted that the lock 4 is pivotably supported by a pin 43 (not, shown in FIG. 1) which extends between the branched end portions 32 and 32&#39; of the hook 3 so that the lock 4 is accommodated stably in the space between the branched end portions 32 and 32&#39;. Further, the spring 5 is disposed by using the pin 43 so that it is always possible to obtain resilient force with which the end portion 41 of the lock 4 is kept in contact with the approximately central portion 13 of the hook support 1. 
     The most significant feature of the hook apparatus F according to the present invention resides in that when the hook apparatus F is unlocked, the opening defined between the distal end portion 31 of the hook 3 and the fall preventing portion 11 of the hook support 1 can be set to an extremely large width, i.e., approximately 180° . 
     FIG. 1 also shows a state wherein the hook 3 has been pivoted approximately 180° reversely from the locked position with the lock 4 disengaged from the recess 14 to unlock the hook apparatus F. Such a state can be attained easily in the present invention. That is, when the lock 4 is disengaged from the recess 14 to unlock the hook apparatus F, for example, by turning the operating lever 42 of the lock 4 in a direction counter to its own gravity, the hook 3 can be reversely pivoted approximately 180° , as illustrated. At this time, as the angle of pivoting of the hook 3 increases, the operating lever 42 of the lock 4 is gradually received into the space defined between the branched end portions 32 and 32&#39; of the hook 3 by virtue of the peripheral configuration (i.e., circular configuration) of the approximately central portion 13 of the hook support 1. In the present invention, it is preferable for the back portion 33 of the hook 3 to be capable of abutting on the side 15 of the hook support 1 with a view to maximizing the opening width. Accordingly, any structural element of the hook support 1 which may interfere with the reverse pivoting of the hook 3 should be avoided. For example, it is preferable to contrive optimal disposition of the connecting pin 2 about which the hook 3 pivots, or to receive the operating lever 42 of the lock 4, which projects from the branched end portions 32 and 32&#39;, of the hook 3, into the space defined between the branched end portions 32 and 32&#39;, as described above. Further, it is preferable to provide the side 15 of the hook support 1 at a position asymmetric with respect to the wire securing portion 12, as shown in FIG. 1. 
     FIGS. 2 to 6 are views illustrating the method of using the hook apparatus F having the structure shown in FIG. 1. In these figures, the spring 5 and other elements are omitted for simplification of the illustration. 
     FIG. 2 shows a state wherein the distal end of the wire rope R of the crane C is attached to the wire securing portion 12 of the hook apparatus F. 
     FIG. 3 shows a state wherein the operating lever 42 of the lock 4 is moved upwardly (in the direction of the arrow in FIG. 2) to unlock the hook apparatus F in order to lift up an iron plate I, thereby allowing the fall preventing portion 11 and the distal end portion 31 to open wide. FIG. 3 also shows the operating lever 42 of the lock 4 which is conveniently received in the space defined between the branched end portions 32 and 32&#39; of the hook 3. 
     FIG. 4 shows a state wherein the distal end portion 31 of the hook 3 is inserted into the area between a hole H provided in the iron plate I and the ground E without the fall preventing portion 11 of the hook support 1 abutting against the ground E. FIG. 4 also shows the operating lever 42 of the lock 4 which has already; been, received in the space defined between the branched end portions 32 and 32&#39; of the hook 3. 
     FIG. 5 shows a state where as the iron plate I is gradually lifted up by the lifting operation of the crane C, the hook support 1 erects and rises, thus causing the hook 3 to pivot in the closing direction and hence bite into the hole H in the iron plate I. At this time, as the iron plate I is lifted up, the fall preventing portion 11 of the hook support 1 and the distal end portion 31 of the hook 3 move toward each other, as shown by the arrows, thereby gradually approaching the locked position. 
     FIG. 6 shows a state wherein the iron plate I has been completely lifted up from the ground E by the lifting operation of the crane C. At this time, the end portion 41 of the lock 4 is completely engaged with the recess 14 in the approximately central portion 13 of the hook support 1, so that the distal end portion 31 of the hook 3 and the fall preventing portion 11 of the hook support 1 reach a complete lock state. 
     The operation that is carried out thereafter to lay out the iron plate I can be performed safely by virtue of the hook apparatus F of the present invention. In particular, the distal end portion 31 of the hook 3 can be readily disengaged from the hole H in the iron plate I without the fall preventing portion 11 coming into contact with the ground E or another iron plate which has already been laid out adjacently to the iron plate I concerned by pivoting the lock 4 upwardly after the iron plate I has been laid out on the ground E to thereby unlock the hook apparatus F, and then enlarging the opening width between the fall preventing portion 11 and the distal end portion 31, as shown in FIG. 4. 
     Although in the foregoing the operation of lifting a heavy iron plate has been explained as an applied example of the hook apparatus F according to the present invention, it should be noted that the present invention can also effectively be applied to operations of lifting various kinds of heavy structural members, e.g., heavy block members, as a matter of course. 
     According to the hook apparatus of the present invention, it is possible to lift, convey and release various kinds of heavy structural members, e.g., iron plates, extremely safely and efficiently. 
     More specifically, the hook apparatus of the present invention is arranged so that the fall preventing portion and the hook distal end portion can be opened relative to each other much wider than in the prior art, and it is therefore possible to engage the hook with a hole (engagement opening) provided in a heavy structural member, e.g., an iron plate, extremely easily and reliably. In addition, since the hook distal end portion and the fall preventing portion are locked to each other as one unit, there is no danger of such a heavy structural member disengaging from the hook during the operation of lifting, conveying and lowering the heavy structural member. Further, the hook can be disengaged from the structural member extremely easily because the fall preventing portion and the hook distal end portion can be opened relative to each other satisfactorily wide. 
     Thus, the hook apparatus of the present invention can prevent occurrence of an accident caused by the fall of a heavy structural member, e.g., an iron plate, due to disengagement of the hook during the operation of lifting such a heavy structural member. Accordingly, it is possible to improve the safety in operations at work sites, which is a significant feature of the present invention. 
     Although the present invention has been described through specific terms, it should be noted here that the described embodiment is not necessarily exclusive and that various changes and modifications may be imparted thereto without departing from the scope of the invention which is limited solely by the appended claims.