Method for manufacturing a lifting hook and a lifting hook

Abstract: A method for manufacturing a lifting hook and a lifting hook. In this method a supporting portion (7) is formed of a lifting hook billet at the end of a lifting hook shaft (6), the lower surface of the supporting portion is formed into a bearing surface (3) and correspondingly a separate uniform bearing ring (4) surrounding the shaft (6) is separated from the lifting hook billet, and a bearing surface (5) is formed into the bearing ring (4). The lifting hook comprises a supporting portion at the end of the shaft and a uniform bearing ring surrounds the shaft between the hook and the supporting portion.

Description: The invention relates to a method for manufacturing a lifting hook billet comprising a hook portion and a base portion. The invention also relates to a lifting hook comprising a hook portion, a shaft integrated to the hook portion and a supporting portion at the end of the shaft substantially coaxial with the shaft, the diameter of the supporting portion exceeding the diameter of the shaft, and the supporting portion including a first bearing surface surrounding the shaft and facing the hook portion. Lifting hooks are used in different hoisting apparatuses for supporting a load. In order to be able to turn a load as desired or to turn a hook to an appropriate position regarding the load, the hook is suspended from its upper end to a separate supporter rotatably around the vertical axis. At present the hook is frequently pivoted in order for the hook to rotate smoothly even when carrying a heavy load. Highly complicated constructions are presently used to mount the hook into a hole in the body rotatably in relation to the body. Both the hook and the body require a separate bearing surface supporting the load, which in today's heavy hoisting use is made of various separate bearing surfaces and fastening portions. Such surfaces are disclosed in publications DE 72 51 114 and DE 37 35 021, for example. US publication 3,995,822 in turn discloses a solution in which the hook is at first fabricated so that a supporting flange is placed at the upper end of the hook, whereafter a supporting portion is cast around the hook between the flange and the hook portion around the axis of the hook. This structure is intended for solutions in which the hook carries a small load. Here it is not possible either to form proper bearing surfaces, since the cast portion cannot in practice be machined around the hook on location. The problem with prior art solutions is that the constructions composed of different separate portions are expensive to manufacture. Possible mounting mistakes and the loading capacity of small components restrict the loading and may cause the construction to collapse. This, in turn, increases the accident risk. It is an object of the present invention to provide such a method for manufacturing a lifting hook and such a lifting hook that allow to avoid the problems of the prior art solutions and to provide a firm and durable hook construction. The method of the invention is characterized by comprising the steps of forming a lifting hook shaft from the base portion of the lifting hook billet, forming a first bearing surface at the end of the lifting hook shaft, where the first bearing surface faces the hook portion and is intended to support the lifting hook, and forming a uniform bearing ring around the lifting hook shaft, the bearing ring being arranged between the first bearing surface and the hook portion, by detaching it from the lifting hook billet. The lifting hook of the invention is further characterized by including between the supporting portion and the hook portion a uniform bearing ring surrounding the shaft, the bearing ring being made of a hook billet by detaching a ring-shaped portion that surrounds the hook shaft. The basic idea with the invention is that the supporting portion at the end of the lifting hook as well as both the bearing surfaces of the lifting hook are formed of the same hook billet so that, on one hand the supporting portion at the upper end of the hook supporting the load and the bearing surface on the lower surface thereof are made of the same material as the rest of the hook, and on the other hand the lower bearing ring supporting the hook and the bearing surface on the upper surface thereof are machined of the same hook billet, in which case the required bearings can be placed between these two bearing surfaces. Thus a uniform solid bearing surface is simply and easily obtained at the upper end of the hook and beneath the hook. The structure is also very reliable and endures heavy loading. Another advantage is that the supporting body does not require a bearing surface, instead the bearing ring detached from the hook by machining is unrotatably supported by the body. In the following the invention will be described in greater detail with reference to the accompanying drawings, in which Figure 1 schematically shows a hook billet, Figure 2 schematically shows the partly machined hook billet and Figure 3 schematically shows a completed lifting hook. Figure 1 schematically shows a hook billet fabricated either by casting or by forging. The hook billet comprises an actual hook portion 1 and a base portion 2. The actual hook is fabricated by machining the hook billet. Figure 2 schematically shows the partly machined and partly cut base portion of the hook billet according to Figure 1. As Figure 2 shows, an upper bearing surface 3, i.e. a first bearing surface 3, for supporting the hook and correspondingly a bearing surface 5, i.e. a second bearing surface 5, of a lower bearing ring 4 are formed to the hook billet, for example, by turning. The Figure also shows how the second edge of the lower bearing ring is machined so as to form the lower surface thereof and at the same time a portion of the lifting hook shaft 6. The Figure shows that a part at the end of the lifting hook shaft 6, or the part on the left of the Figure, still remains unmachined, and the bearing ring 4 is still attached to the lifting hook shaft 6. At this stage all these parts are made of the same material, from which a separate bearing ring 4 and correspondingly the supporting portion of the lifting hook end are fabricated. Figure 3 is a partly cut view showing the end of a completed lifting hook. As the Figure shows the lower bearing ring 4 is separated from the lifting hook billet by removing material from the space between the bearing ring and the lifting hook shaft 6, for example by turning or by using another type of machining. In this way a separate ring-shaped part functioning as a bearing ring is formed around the lifting hook shaft 6. Correspondingly the shaft 6 uniformly continues to the end of the lifting hook, where a supporting portion 7 comprising the upper bearing surface 3 is made of the same material as the lifting hook shaft 6. Thus, a separate uniform bearing ring 4 is formed between the supporting part 7 at the end of the lifting hook and the actual hook portion 1. Therefore when the lifting hook is mounted in position, bearing balls can be placed between the bearing surfaces 5 and 3, whereafter the hook can be placed to rest on the supporting body by means of the lower bearing ring 4. The invention is explained above by way of example only, but it is not restricted thereto. The different stages of the fabrication method can be performed in various ways and in a different order, as long as a supporting portion made of the same material as the lifting hook and comprising a bearing surface is formed at the end of the lifting hook billet. The lifting hook is able to rotate by means of such a supporting portion. Correspondingly a separate bearing ring is formed around the lifting hook shaft 6. The bearing ring comprises a second bearing surface facing the bearing surface connected to the lifting hook shaft so that the lifting hook can rotate by means of said bearing ring. Furthermore, various machining methods can be used for manufacturing lifting hooks, such as turning, arc machining, sawing, milling etc. as long as the end result is a construction comprising at the end of the lifting hook shaft a supporting portion which is made of the same uniform material as the lifting hook shaft, and in addition the shaft is surrounded by a separate uniform bearing ring forming together with the supporting portion at the end of the shaft a bearing pair so that the lifting hook may smoothly rotate around the bearing ring when mounted to the support thereof.

Claims: A method for manufacturing a lifting hook from a lifting hook billet comprising a hook portion (1) and a base portion (2) characterized in that the method comprises the steps of forming a lifting hook shaft (6) from the base portion (2) of the lifting hook billet forming a first bearing surface (3) at the end of the lifting hook shaft (6), where the first bearing surface (3) faces the hook portion (1) and is intended to support the lifting hook, forming a uniform bearing ring (4) around the lifting hook shaft, the bearing ring (4) being arranged between the first bearing surface (3) and the hook portion (1), by detaching material from the lifting hook billet. A method as claimed in claim 1, characterized by at first forming a second bearing surface (5) on the bearing ring (4), the second bearing surface (5) facing the first bearing surface (3) and being coaxial with it, and thereafter by detaching the bearing ring (4) from the lifting hook shaft (6) by removing material from the space between the lifting hook shaft (6) and the bearing ring (4) to be formed. A lifting hook comprising a hook portion (1), a shaft (6) integrated to the hook portion and a supporting portion (7) at the end of the shaft substantially coaxial with the shaft, the diameter of the supporting portion exceeding the diameter of the shaft, and the supporting portion including a first bearing surface (3) surrounding the shaft and facing the hook portion (1), characterized by including between the supporting portion (7) and the hook portion (1) a uniform bearing ring (4) surrounding the shaft (6), the bearing ring being made of a hook billet by detaching material from the billet to form a ring-shaped portion that surrounds the hook shaft (6). A lifting hook as claimed in claim 3, characterized in that the bearing ring (4) comprises a second bearing surface (5) facing the supporting portion (7) at the end of the hook shaft (6) so that bearing balls or the like can be placed between the bearing surface (5) of the bearing ring (4) and the bearing surface (3) of the supporting part (7).

Inventors: KIVINIITTY ARI, KIVINIITTY, ARI
Applicants: KCI KONECRANES PLC
Application year: 2000
Main classification: B66C1
IPC codes: B66C1