GB2162146A - Equipment for handling loads - Google Patents

Abstract

Load handling equipment comprises an overhead structure 1 movable along a beam 20, and a load support 2 which is suspended underneath the structure 1 by cables 9 and 10. The cables 9 and 10 are wound around a winding drum 6 powered by an electric motor 7. The cables 9 and 10 pass over respective pulleys 11 and 12 on the structure 1 and then downwardly under respective pulleys 15 and 17 on the load support 2 before passing around a common control drum 19. The cables 9 and 10 then pass under respective pulleys 16 and 18 on the load support 2 and then upwardly to be anchored at 13 and 14 with respect to the overhead structure 1. The provision of the common control drum 19 prevents swinging of the load support relative to the structure 1 in the forward and backward directions because of the tendency of the cables 9 and 10 to rotate the control drum 19 in opposite directions at the same time when the load support 2 is displaced out of a predetermined position relative to the overhead structure 1. <IMAGE>

Description

SPECIFICATION Equipment for handling loads This invention relates to equipment used for handling loads, particularly, although not exclusively, loads that are handled by overhead cranes.

One of the difficulties of handling loads suspended from an overhead crane or other overhead handling equipment (hereinafter referred to simply as a crane) by means of a system of cables, ropes, chains or the like (hereinafter referred to simply as cables), is the limited ability of the crane to transmit forces in certain directions, in particular, the forces that are required to maintain the load in, or close to, a given relationship with the crane. One particular problem is the tendency for a load or a support used to engage the load, suspended by a system of cables to swing relative to the crane, especially when the crane is set into motion, or when such motion is arrested.

According to the present invention, there is provided equipment for handling a load, said equipment including a load support which is suspended from an overhead structure by a plurality of lengths of cable (as defined herein), a pair of said cable lengths engaging with said load support at locations which are spaced apart in a first dimension, means for varying the effective lengths of the cables so as to enable the load support to be raised and lowered relative to the overhead structure, and means for opposing swinging movement of the load support in said first dimension, said opposing means including rotary member with which said pair of cable lengths is operatively connected such that displacement of the load support in said first dimension out of a predetermined position relative to the overhead structure is opposed by the tendency of said pair of cable lengths to rotate said rotary member respectively in opposite directions at the same time.

Preferably, said load support is suspended from said overhead structure also by a further pair of cable lengths which engage with the load support at locations which are spaced apart in a second dimension, said second dimension being inclined (e.g. substantially perpendicularly) with respect to said first dimension, and there is provided further opposing means operating in a like manner to the first-mentioned opposing means but to oppose swinging movement of the load support in said second dimension.

Said rotary member may take the form of a drum around which both of said pair of cable lengths are wound so as to act thereon in mutually opposite directions. Alternatively, said rotary member may be a rotary part of a system including a first drum around which only one of said pair of cable lengths is wound and a second drum around which only the other of said pair of cable lengths is wound, said first and second drums being operatively connected together so that rotation of either drum causes rotation of the other.

The opposing means may be mounted on the load support or on the overhead structure.

The present invention is particularly applicable to equipment wherein the overhead structure includes a carriage which is movable in said first dimension on a supporting structure.

Preferably, each of said pair of cable lengths passes around a respective pair of pulleys mounted on the load support and a portion of said cable length which is between the portions passing over the respective pulleys is operably connected with said rotary member.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of one embodiment of load handling equipment according to the present invention, Figure 2 is a diagrammatic illustration of an alternative manner of opposing unwanted swinging, also according to the present invention, Figure 3 is a schematic plan view of part of another embodiment of load handling equipment also according to the present invention, Figure 4 is a schematic section of the equipment on the line A-A of Fig. 3, and Figure 5 is a schematic plan view of another part of the equipment of Figs. 3 and 4.

Referring now to Fig. 1, the load handling equipment illustrated therein takes the form of an overhead crane and comprises an overhead structure including an upper framework 1, and a lower framework defining a load support. The upper framework 1 includes brackets 3 upon which supporting wheels 4 are mounted, The wheels 4 allow the said upper framework 1 to travel along or be driven along a suitable overhead beam 20, said beam having flanges 21 that act as rails for said supporting wheels 4. The upper framework 1 and wheels 4 together define an overhead carriage.

The lower framework 2 has a number of load attaching points 5.

Mounted rotatably on the upper framework 1 is a winding drum 6 which is under the control of a motor 7 and brake apparatus 8. Preferably, the winding drum is grooved in the normal manner.

Wound in the same sense on the winding drum 6 are two lengths of cable 9 and 10 which extend from opposite sides of the drum so that clockwise rotation (as viewed in Fig. 1) of the winding drum 6 winds both cables 9 and 10 onto the winding drum 6.

A pulley 11 is rotatably mounted close to one end of the upper framework 1. In a similar manner, a pulley 12 is mounted close to the other end of the upper framework 1.

Cable anchors 13 and 14 are pivotally attached at locations part way along the upper framework 1.

Close to one end of the lower framework 1, two pulleys 15 and 16 are rotatably mounted. Close to the opposite end of the lower framework 2, two pulleys 17 and 18 are rotatably mounted.

A rotary control drum 19 is rotatably mounted at a location approximately midway along the lower framework 2. preferably, the control drum 19 is grooved in the normal manner. The rotary control drum comprises a means for opposing swinging of the lower framework 2.

From the winding drum 6, cable 9 is passed over pulley 11 down to and under pulley 15 and thence to control drum 19. The cable 9 is wound around the control drum 19 for a part turn or a part turn plus a number of whole turns (in this embodiment one additional whole turn). The cable 9 is then led to and around pulley 16 and thence up to the anchor 13 to which the cable 9 is attached.

The cable 9 is wound around the control drum 19 in such a direction, that when the winding drum 6 is rotated in a clockwise direction, in order to wind in cable 9 and so raise the lower framework 2, the control drum 19 is caused to rotate in an anticlockwise direction (as viewed in Fig. 1).

From the winding drum 6, the cable 10 is passed over pulley 12 and is then led down and under pulley 17 and thence to control drum 19. The cable 10 is wound around the control drum 19 for a part turn or a part turn plus a number of whole turns (in this embodiment one whole turn). The cable 10 is then around pulley 18 and up to the anchor 14 to which the cable 10 is attached.

The cable 10 is wound around the control drum 19 in such a direction that, when the winding drum 6 is rotated in a clockwise direction, in order to wind in cable 10 and so raise the lower framework 2, the control drum 19 is caused to rotate in an anticlockwise direction (as viewed in Fig. 1).

Thus, during the raising of the lower framework 2, and, if any, the load, both the action of cable 9 and the action of cable 10 cause the control drum 19 to rotate in the same direction, in the case illustrated, this is in an anticlockwise direction (as viewed in Fig. 1). Hence the presence of the control drum 19 does not significantly affect the raising lowering operation ultimately controlled by the winding drum 6 and motor 7.

It should be noted that the rotational axes of he various drums and pulleys described above are all substantially parallel to each other but substantially perpendicular to the "first dimension" referred to hereinafter. Minor variations may be introduced in order to ease the path of certain portions of the cables 9 and 10. The cable carrying pulleys are mounted as close to the central plane of the system as is practicable. It is preferable that the portions of the cables 9 and 10 passing between the upper framework 1 and the lower framework 2 are so arranged as to be symmetrical and be inclined to the vertical by substantially the same angle. In this embodiment, the angle is about 15 to the vertical.However, it is possible for this angle to be 4 to 40 , and is preferably 10 -20 , depending upon the circumstances of use. It is also possible for the angles to be mutually different. For example, the portion of the cable 9 between pulleys 11 and 15 and the portion of the cable 10 between the pulleys 12 and 17 may be inclined at an angle of 0 to the vertical whilst the portion of the cable 9 between the pulley 16 and the anchor 13 and the portion of cable 10 between the pulley 18 and the anchor 14 may be inclined at an angle of 30' to the vertical. The above angles are the intended angles of inclination when the lower framwork 2 is in its lowermost position of use.Such angles are adopted when the lower framework 2 is in the desired position in the horizontal plane relative to the upper framework 1.

In operation the upper framework 1 may need to move along the rail 20. In order to maintain the lower framework 2 in a fixed relative position to the upper framework 1, during such movements, accelerating and decelerating forces will need to be applied in the directions marked "forwards" and "backward" in Fig. 1. Such directions are in what is referred to herein as a first dimension. This is the dimension in which the longitudinal directions of extent of the upper and lower frameworks exist and in which the upper framework moves along the beam 20.

If a disturbing force is applied to the lower framework 2 in the "forwards" direction, the cable system associated with cable 9 would tend to rotate the control drum 19 in an anticlockwise direction, whereas, the cable system associated with cable 10 would tend to rotate the control drum 19 in a clockwise direction. Thus equal, or near equal, but opposed rotational forces are applied to the control drum 19 at the same time. Since the control drum 19 is, in this example, one rigid unit, relative rotation cannot occur and in effect, the cable systems associated with cables 9 and 10 are locked together by the control drum 19. A similar situation arises if a disturbing force is applied in the "backward" direction. This feature prevents any significant relative movement in the first dimension between the lower framework 2 and the upper framework 1.

In the event of a massive sway (e.g. due to collision of the load with some object) the cables 9 and 10 may slip. Even after such a slip, however, the lower framework 2 still remains substantially horizontal, but its centre line is horizontally displaced from its previous centre line and requires re-setting.

Both cables are wound around the control drum 19 such that they are substantially locked together.

During raising and lowering, the cables 9 and 10 precess along the control drum 10. In cases where the height of lift is great, this precession would require a long control drum 19 which might be difficult to accommodate on the lower framework 2. In such cases, the arrangement of Fig. 2 may be preferred.

Referring now to Fig. 2, the arrangement illustrated therein operates in a similar manner to that of Fig. 1 and similar parts are accorded the same reference numerals. However, in this embodiment, control drum 19, instead of being mounted on the lower framework 2 (not shown in Fig. 2) is mounted on the upper framework 1 (also not shown in Fig. 2). This increases the number of portions of each cable 9 and 10 which extends between the upper and lower frameworks and requires the provision of a respective additional pulley 31, 32 for each cable 9, 10. Such an arrangement however, reduces the load per cable portion extending between the upper and lower frameworks. If desired the relative positions of the pul leys 15 and 16 may be exchanged, as may the relative positions of the pulleys 17 and 18.

Referring now to Figs. 3 to 5, the equipment illustrated therein operates in a similar manner to that of Fig. 1 except that it is designed to oppose swinging of the lower framework 2 in a second dimension (line Y-Y in Fig. 3) in addition to the first dimension (line X-X in Fig. 3), said second dimension being perpendicular to the first dimension. In Figs. 3 to 5, parts similar to those of Fig. 1 are accorded the same reference numerals. The components of the system for opposing swinging of the lower framework 2 in the second dimension (Y-Y) which are similar to the components of the first dimension anti-swing system are accorded the same reference numerals succeeded by the letter "a".In this embodiment, motor 7 drives a pair of winding drums 6' and 6" via a gear box 35 and coaxial drive shafts 36, 37 which extend diagonally relative to the upper framework 1 which is square in plan view. Cables 9 and 9a (not shown) are wound on and anchored to winding drum 6' and whilst cables 10 and 10a are wound on and anchored to winding drum 6" so that operation of the motor 7 in one direction causes all the cables 9, 9a, 10 and 10a to be wound equally onto their respective drums 6' and 6" to raise the lower framework 1 whilst operation of the motor 7 in the opposite direction lowers the lower framework 1.As can be seen from Fig. 5, the pulleys 11, 12 and 12a are appropriately positioned and inclined at 45" relative to the first and second dimensions X-X and Y-Y to ensure proper alignment of the cables 9, 10 and 10a with the respective pulleys 15, 17 and 17a. (This applies also to the pulley 11a and cable 9a which are not shown).

The lower framework 2 is square in plan view as shown in Fig. 3. The pairs of pulleys 15 and 16, 17 and 18, 15a (not shown) and 16a (also not shown), 17a and 18a are mounted midway along the respective sides of the lower framework 2.

As stiffness of the resistance to sway of the system is a function of the included angle between the two parts of each rope 9, 10 it is necessary for this included angle to be significant when the lower framework 2 is in the lowest load carrying position. However when the height of lift becomes great, the overall length of the upper framework 2 also becomes great and thus to conserve space, the arrangement of Figs. 3 to 5, with one rope portion vertical and the other rope portion angled, may be advantageous.

Claims (9)

1. Equipment for handling a load, said equipment including a load support which is suspended from an overhead structure by a plurality of lengths of cable (as defined herein), a pair of said cable lengths engaging with said load support at locations which are spaced apart in a first dimension, means for varying the effective lengths of the cables so as to enable the load support to be raised and lowered relative to the overhead structure, and means for opposing swinging movement of the load support in said first dimension, said opposing means including a rotary member with which said pair of cable lengths is operatively connected such that displacement of the load support in said first dimension out of a predetermined position relative to the overhead structure is opposed by the tendency of said pair of cable lengths to rotate said rotary member respectively in opposite directions at the same time.

2. Equipment as claimed in claim 1, wherein said rotary member is a drum around which both of said pair of cable lengths are wound so as to act thereon in mutually opposite directions.

3. Equipment as claimed in claim 1, wherein said rotary member is a rotary part of a system including a first drum around which one of said pair of cable lengths is wound and a second drum around which the other of said pair of cable lengths is wound, said first and second drums being operatively connected together so that rotation of either drum causes rotation of the other.

4. Equipment as claimed in any preceding claim, wherein the opposing means is mounted on the load support.

5. Equipment as claimed in any one of claims 1 to 3, wherein the opposing means is mounted on the overhead structure.

6. Equipment as claimed in any preceding claim, wherein the overhead structure includes a carriage which is movable in said first dimension on a supporting structure.

7. Equipment as claimed in any preceding claim, wherein each of said pair of cable lengths passes around a respective pair of pulleys mounted on the load support and a portion of said cable length which is between the portions passing over the respective pulleys is operably connected with said rotary member.

8. Equipment as claimed in any preceding claim, wherein said load support is suspended from said overhead structure also by a further pair of cable lengths which engage with the load support at locations which are spaced apart in a second dimension, said second dimension being inclined with respect to said first dimension, and there is provided further opposing means operating in a like manner to the first-mentioned opposing means but to oppose swinging movement of the load support in said second dimension.

9. Equipment for handling loads substantially as hereinbefore described with reference to Fig. 1, Fig. 2 or Figs. 3 to 5 of the accompanying drawings.