Soft Support System For Hulls And The Like

Abstract

A "soft" support system, preferrably utilizing pneumatic bellows, capable of supporting a ship hull in a relatively level condition on its building foundations or ways during construction and during moving operations; the system uses either a dynamic or a static "soft" support insert between the basic "hard" foundation supports and the vessel shell; in addition to the preferred pneumatic bellows the "soft" support insert could be inter alia a hydraulic, steel or rubber/elastomeric "spring"; the system in its dynamic mode is capable of raising, lowering or leveling the ship hull, or in minutely positioning hull sections to be joined together during construction operations; the system effectively distributes all loads and reactions between the hull and the foundation or ways thereby tending to eliminate unequal elevations of the foundation or way support locations and tending to nullify hull movement effects due to welding stresses and/or temperature changes, thereby tending to provide a constant support system; during moving operations across the foundations or ways, the constant support system will more nearly allow the horizontal pushing force requirements at each support location to equalize; the preferred embodiment of the "soft" support element includes a series of pneumatic bellows units, each unit including a set of three rubber bellows fastened between two opposing plates, the pneumatic pressure in the bellows being variable, system control for the pneumatic pressure can be a simple manual operation or can be highly sophisticated.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a "soft" or resilient support system for load leveling, positioning, cushioning and equalizing stresses for ship hulls and other extremely heavy structures and the like, which system can be either dynamic or static.

In the particular application described, the present invention provides a unique system for supporting ship hulls during construction or during hull movement or positioning of the hull horizontally and/or vertically. The system of the present invention gives continuous, resilient support to ship hulls during construction similar to or approaching natural flotation, thereby eliminating any high localized stresses at support locations. The invention also permits horizontal movement over irregular building surfaces or ways without causing high, localized stresses on hull or foundations and further allows linear and differential vertical movement for positioning hulls or parts of hulls and for transfer of a hull from longitudinal to transverse ways or vice-versa. Either a dynamic system, using external means such as air or hydraulic pressure, may be used, or a static resilient system (elastic material) may be used, use of either system being dependent upon application. Any degree of manual or automatic controls may be employed to regulate or position the supported loads of a dynamic system.

The technique of the prior art now being used for building ship hulls and the like are remnants of ancient ship building practices of starting with a member leveled with wedges and building thereon. The resultant variations in foundation elevations as the loads were increased during building were considered a part of the building process and usually ignored. Also, heretofore a ship was usually built in one location and launced directly from that location. Now, however, competition in the industry forced other methods to be tried and used, and an assembly-line type of construction of ship hulls began where portions of hulls were constructed in various locations and brought together to be joined into a single jull. The assembled hull was then brought to a launch position.

The usual methods of hull support that evolved through the years were employed over new horizontal land structures installed to support the hull and hull sections in building and moving. Particular difficulties were encountered in moving the heavy masses horizontally and in positioning the various hull sections to be joined. Unless the land structures over which the loads traveled were perfectly even and did not deflect or change position in relation to one another, and unless the hull was in perfect alignment and not distorted due to temperature differential or welding stresses, high, localized stresses occurred on hull support components and land structures at their high points and highly uneven horizontal push forces, resulting in numerous problems including lost time and component failures. Also, in joining the portions of hulls, the exact positioning of the section was an arduous task of jacking, straining, and wedging, requiring much time and skill.

The present invention provides a "soft", resilient support element located between the "hard" hull support members and the "hard" land structures, thereby providing an element to cushion and to tend to equalize the loads and reactions which occur in a building position or during moving operations, providing more nearly equalized horizontal push-load requirements at each push location during moving operations. In its dynamic mode, the present invention can also provide leveling and positioning of loads in elevation, pitch, and roll, this being especially useful in joining sections of hulls or changing direction of horizontal hull movements. The control of the elevation, pitch and roll of a dynamic system utilizing compressed air or hydraulics can be simply manual or combined with automatic components.

The support system of the present invention for hulls and the like can be divided into two basic modes of operation, static and dynamic; and each of these again divided into two basic divisions, one position building and multi-position building requiring movement.

a. The static system, single building position mode would use steel or elastomeric springs of suitable deflection characteristics to cushion and equalize the loads and reactions between hull and land structures due to inequities in alignment, or to hull movement and/or deflection, thereby assuring protection to the hull, support components, and support structure.

b. The static system, multi-position building mode would use steel or elastomeric springs as in (a) above and would provide the above features in addition to equalizing the loads over emmense land structures during moving operations.

c. The dynamic system, single building position mode would use pneumatic or hydraulic devices to provide results as above in (a) in addition to better equalization of reactions due to hull or land structure movements or inequalities.

d. The dynamic system, multi-position building mode would use pneumatic or hydraulic devices as in (c) above and would provide all the above features in (a), (b), and (c) in addition to positioning capabilities.

The above listed four exemplary basic modes of course do not preclude other modes or combinations of these modes.

The static system requires no outside power or system controls; the dynamic systems do require some outside source of pressure and at least a basic control system for control.

The preferred embodiment of this invention uses the mode of operation listed in (d) above, using a pneumatic device to provide for ease of control and use of a usually ready source of plant compressed air. The pneumatic device considered here is a commercially available reinforced rubber bellows or pillow capable of the pressures necessary to support the required loads.

As noted above, the present invention has particular value as applied to a method or system to aid in evenly distributing the load of a ship onto its building foundations or ways and of leveling or changing the position of sections of vessels to be joined together during construction. Such methods have become increasingly important to the shipbuilding industry as larger and larger vessels have been constructed, and as existing building foundations or ways have become more uneven because of these heavier loadings, thereby causing difficulties in moving hulls from one building position to another and where hull loads transmitted to the foundations must be maintained not to exceed a certain limit.

The magnitude of the situation can be better understood with the realization that whole ship hulls, shell structures or sections thereof, weighing thousands of tons, must be moved horizontally across extensive land structures (building ways) to various building positions or locations, particularly in the assembly-line method of ship construction which is now being practiced in the industry.

Heretofore, the basic system for distributing and leveling the load in any given building position that has been used in the industry has been a series of wedges between the fixed timber or steel supports or cradles upon which the vessel rides. However, each such support or cradle constituted individually a "hard" support, i.e. one which had little or no resiliency or variability to it. Thus a support was either in full contact with the load and hence carried its full load, or it was out of contact and carried no-load, there being little or no flexibility to it.

Because of the "hard" support nature of the prior art systems, many difficulties have arisen. Particularly when the vessel shell structure or portions thereof are attempted to be moved horizontally across the land structures or building ways in the assembly-line method of construction, alternate light and severe push loads were often encountered at support locations because of varying reaction forces. Although it would be physically possible to overdesign the pushing jacks moving the structure horizontally to be able to overcome the heavy loads, an arrangement to provide for such a wide load fluctuation is highly undesirable.

It has been determined by observation and by elevation readings before and when the load was applied that this condition is caused by differential loading along a building way and between adjacent ways, stemming apparently from the following primary causes:

1. Differential elevation and/or subsidence along and between ways; and

2. Inability of the hull to conform to the inequalities of the foundation elevations; and

3. Certain hull movements and distortions due to welding stresses and to differential temperatures changes in the hull structure.

This unequal distribution of loads results in bearing pressures on some ways far above the way design loads, causing structural failure of the way members in some instances and increasing friction loads on those ways which are carrying all or part of the load intended to be borne by an adjacent way, which is then in a sense taking a "free ride".

In addition to the above-mentioned undesirable conditions, the slide timber on the lightened way has in some instances been pushed by the jacks in relation to the cradles, leaving a portion of the ship without support and requiring repositioning of the shifted members. Attempts have been made to remedy this condition in some applications by installing struts from the jacking head of the slide timber to a bearing plate on the hull. While this has been successful in preventing differential timber movement, there are undesirable side effects such as overloading the hull shell on a relatively small area and the vertical component of the reaction from the strut forcing the jacking head down against the surface plate on the ways, causing gouging and increasing resistance to pushing.

While these side effects may be eliminated or reduced by modification of the strut ends, it becomes apparent that a system of maintaining uniform unit loads over the entire area of ways under the load would completely eliminate the entire problem.

In addition to uneven building ways, the hull structure wants to assume a different shape longitudinally as temperature differentials may affect the top and bottom and as welding stresses are introduced into the structure, making it bend slightly in one direction or another. The deflections due to temperature is temporary and variable; the deflections due to welding stresses are permanent. These movements affect the reaction forces and cause localized stress on supports effected.

Systems of supplemental support jacks and/or wedges have also been proposed to help level out the inequalities of the building ways, but these would require constant attention as the hull moves across the uneven ways, a perhaps workable system, but ardous in control. Moreover, each of the systems of jacks or wedges again involve individually "hard" supports.

The present invention, on the other hand, contemplates instead the use of a series of "soft" supports, i.e., ones which can carry any variation or degree of the load as desired. The present invention in the preferred embodiment achieves this by in effect inserting a series of pneumatic "spring" units, whose tensions preferably can easily, completely and individually be varied, between the load and each support.

The system of the present invention distributes the load of the ship onto the building foundation or ways more evenly and eliminates hard spots that would tend to bind and retard motion during moving operations, or prevent the overload of support members and their possible failure.

A basic advantage of the present invention over the prior art is the provision of a soft, resilient, spring-like structure support system that naturally tends to offer some measure of support irrespective of variations in way elevation, hull distortion, or air pressure.

The present invention achieves this "soft" or "spring" support by several types of systems among which are:

a. direct acting pneumatic bellows manifolded to a source of air pressure through regulators (the preferred embodiment);

b. direct acting hydraulic jacks or hydraulic jack operated wedges manifolded to multiple central hydraulic systems with accumulators;

c. actual, large heavy duty steel springs; and

d. large, heavy duty rubber or elastomeric "springs".

Of the systems of the present invention, the direct acting pneumatic bellows system using standard plant air pressure as a power source is the most workable and easily controllable system, is considered the preferred embodiment and hence will be described in detail.

The usual availability of plant air pressure and ease of control through regulating air supply pressures to the bellows greatly enhances the great value of the preferred embodiment. The pneumatic system compares favorably with the advantages of the other systems of the present invention but in addition has the advantages of simplicity, practically frictionless operation, ready power source (plant air), ability to measure actual loads, and ease of control.

The present system unlike the prior art gives continuous resilient support to ship hulls and sections during construction thereof similar to natural buoyancy or flotation. It allows horizontal movement over irregular building surfaces or ways without causing high, localized stresses on the hulls, support components, or the support members. It further allows linear and differential vertical movement for position hulls or sections and for easy transfer of a hull from one set of ways to the other. It also allows distortional movements of the hull shell without overloading the foundations or the shell itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an assembly-line type shipbuilding facility wherein the present invention can be applied to particular advantage;

FIG. 2 is a perspective view of the support system of the present invention as applied to a ship being moved across ways;

FIGS. 3 and 4 are side and top, plan views, respectively, of a support unit of the present invention.

FIGS. 5 and 6 are side, cross-sectional and top, plan views, respectively of a pneumatic bellow which can be used in the present invention;

FIG. 7 is a schematic diagram of a pneumatic, manually operated control system which can be used in the present invention; and

FIGS. 8A - 8D are generalized representations of alternative types of "soft" or resilient "spring" or support elements which can be used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Because of the need to economize in shipbuilding, the shipbuilding industry has been adopting the technique of continuous, assembly-line fabrication of ships. An example of the adoption of this technique is found in the Ingalls shipbuilding facility of Litton Industries in Pascagoula, Mississippi, a portion of which is generally illustrated in FIG. 1.

In this technique preliminary preparation of the materials and subassembly work is done in a continuous process (note arrows). As shown in FIG. 1, the sub-assemblies are welded together into complete sections or modules 1 of the ship being built. Each module 1, in this instance weighing 1,500 to 2,100 tons, is moved down the longitudinal building ways or tracks 2 as it is being completed. Upon completion of each module - section 1, the modules 1 are brought into the lateral building ways or tracks 3 to the integration area and mated together to form the completed ship 4. To launch the ship 4, now approximately 92 percent complete, it is moved on lateral and longitudinal building ways or tracks onto the launch pontoon 5. After replacing the wingwalls 6, the launch pontoon 5 is moved into the ship channel and submerged, launching the ship 4.

As is apparent, a great deal of moving and positioning of extremely heavy (hundreds and thousands of tons) objects is involved in this technique. It is in this moving and positioning of these extremely heavy objects (ships, module sections and the like) that the support system of the present invention is applied.

As is well known in the art, horizontal movement of these heavy loads can be accomplished by sliding action (a slide member on a lubricated way member) or by some force of rolling action (roller bearings or wheeled members). Horizontal push forces are applied to each transverse or longitudinal support member to effect the horizontal movement; the nature and application of these forces are dependent on the user's choice.

As illustrated in FIG. 2, the preferred embodiment of the support system of the present invention as applied to an extremely heavy object such as a ship 4 comprises a series of "soft" or resilient supports 7 including a row of pneumatic air bellows 8 situated between the top of each slide timber 9 of the building ways 2 - 3 and the bottom of each hull cradle 10. Although only three sets of "soft" supports 7 are illustrated for simplicity sake, in actual practice a full set of "soft" or resilient supports 7 would be used at each way or support location.

The "soft" or resilient supports 7 can be provided in basic units 11 of three bellows 8 each (note FIGS. 3 and 4), capped top and bottom with steel plates 12 and 13, respectively. As it is necessary that the faces of the bellows 8 be separated by at least 3 1/2 inches when in a closed position, 2 inch high bumper blocks 14 on the inside face of each plate are provided.

The bottom plate 13 is edge drilled for air supply to each bellow 8, while rim bolt holes 15 for attaching the bellows 8 to the plates 12 and 13 are countersunk to present a smooth outside surface. The bellows 8 are strong enough to support the weight of one plate when suspended by the other plate. The bellows are also strong enough to withstand relatively high air pressures without load or restraint, however this procedure is not recommended as the bellows 8 could be damaged and appropriate maximum pressure restraints should be provided for safety.

The flexible body 16 of the circular pneumatic bellows 8 can be of a nylon-tire-cord reinforced rubber such as neoprene, a suitable commercial bellows being sold under the trademark "Airmount" (Model No. 211-A) by the Firestone Industrial Rubber Products Co. Each bellows 8, as illustrated in FIGS. 5 and 6, includes a metal mounting or bead rim 17 with mounting bolts 18 at its top and bottom for attachment to the plates 12 and 13. In the event any bellows is damaged or otherwise made unusable, it can be removed and another inserted at any time by removing the bolts 18 holding the rim 17 to the plates 12 - 13.

Suitable dimensions of the bellows 8 for this application are approximately 9 inches in height and 28 inches in diameter when expanded to working elevation. The bellows 8 have varying load capacity with varying air pressure with high capacity at high air pressures and low capacity at low air pressures. As is true of bellows in general, external means may be employed for greater lateral stability.

The pneumatic bellows are relatively maintenance free and frictionless in operation. Minor leaks in the air system are of small consequence, particularly when air supply exceeds leak rate. Bellows life should be long (10 years service is anticipated); however, physical damage to the bellows in this environment must be considered in the total life picture.

In order to control the positioning of the load, for example ship 4, a pneumatic pressure control system can be used (note FIG. 7). Small groups of air bellows 8 on each building way, for example two to six units 11, are individually manifolded to a suitable supply of air pressure which can be manually regulated. The total support forces can be regulated on each building way or on portions of a way. The hull 4 can be lifted or lowered or tilted as required through coordinated control of the air supplies at each way or support. During moving operation, the unevenness of the ways are absorbed by the combined bending of the slide timber 2 - 3 and the flexibility of the pneumatic bellows 8, and constant support forces can be attained by manual regulation of air pressures to the bellows 8 during this operation.

When the vessel 4 is in a building position, wedges or other adjustable support devices such as jacks or other "hard" supports can be inserted to support the loads, and the bellows 8 can be deflated to a few pounds pressure to effect a soft-skin condition. This soft-skin condition will help guard against accidental puncture of the rubber material 16.

The supplemental support by wedges, etc. and reductions of air pressure to a soft-skin condition is not necessary, but is an option of the user. A continuously inflated system does have the advantage of continuously equalizing changing loads transmitted to the supports or foundations during building, e.g., those due to hull distortions caused by temperature changes or welding stresses. In this instance however the bellows 8 are inflated and pressure regulated as required for lifts or positioning and during moving operations, but during static building operations the pressure in the bellows is reduced to a few pounds to effect the soft-skin condition.

Most shipyards have air pressure systems already as part of their facilities, these systems normally being of the order of 100 - 200 psi. The bellows 8 of the present invention work well on the 100 psi in the instance described and hence usually require no additional pressure source. However, if the basic plant pressure is below or only near the bellows operating point, supplemental compressors can be used. Adequate air pressure should be provided because a pressure reserve is necessary for the system to maintain positive system control. If a lower air pressure is used, additional bellows will be required as the load capacity is a directly related foundation of the pressure. Greater lifting capacity is of course achieved by increasing the number of bellows 8, or increasing the working pressure.

Control of the lifting, lowering and leveling of the load can be achieved by a manual operation with manned control locations at each cradle 10, or building way or support 2 - 3. Each control location can consist of an air piping manifold including valves, gauges, and air pressure regulators. Central control and coordination of the whole pneumatic operation can be accomplished through "walkie-talkie" communications to each cradle or support control location.

When a load is ready to be moved, the bellows 8 are pressured and the load raised from any physical support, which is then removed or lowered to provide clearance for the move across the uneven ways or supports 2 - 3.

As the move progresses, it is anticipated that each cradle or support control station be manned and the air pressures on each manifold be kept as closely as possible to the design pressure in order to best equalize the reaction forces transmitted to the slide timbers, and to maintain the load in as level a condition as possible. Although a simple manual system of control has been indicated, any degree of sophistication of control can be achieved through many presently available pneumatic instrumentation components.

As is apparent, the ease of control of the "soft" or resilient "spring" system of the present invention for moving, raising and lowering is highly desirable and advantageous. Indeed the system's ability to tilt the load in elevation, pitch or roll to match up sections being assembled together is unique.

Although the invention has been described with particular reference to the moving and positioning of ships and hull sections, its general application for lateral movement of any large masses involving loads of hundreds and thousands of tons over land structures is excellent. Moreover, although a particular air bag is described in detail, other resilient or "soft" support members might be used such as a hydraulic "spring" (FIG. 8A), a steel spring (FIG. 8B) or a rubber or elastomeric "spring" (FIG. 8C) or a different form of air "spring" (FIG. 8D).

The static embodiments of FIGS. 8B and 8C have a counter-reaction to a load (communicated through plate 12) proportional to their deflections, this being a physical property of the support material. The dynamic embodiments of FIGS. 8A and 8D can of course give support reactions similar to that of FIGS. 8B and 8C when their fluid medium is static. However, when the internal fluid pressure or volume is changed through external means, the support reactions also change as well as the support elevations.

Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiment herein detailed in accordance with the description requirements of the law, it is to be understood that the details herein are to be interpreted merely as illustrative and not in a limiting sense.

Claims

What is claimed as invention is:

1. A pneumatic support system for supporting and/or moving a heavy load, as for example a ship hull or the like, in the ambient comprising:

a series of support unit means dispersed between the heavy load and the ground for supporting at least part of said heavy load and for equalizing forces occuring in the static supporting, positioning and horizontal moving of said heavy load; each of said support unit means comprising

a hard, rigid upper load-bearing member upon which said load is, at least indirectly, partially carried, said upper member having a lower, downwardly-directed facing surface having a multiple number of facing areas thereon;

a hard, rigid, lower, load-bearing member, resting at least indirectly upon the ground, said lower member having an upper, upwardly-directed facing surface having a multiple number of facing areas thereon which are located opposite the corresponding facing areas of said upper member, said upper and said lower load-bearing members being two opposed, flat plates disposed in at least a generally parallel relationship;

a multiple number of "soft", pneumatic support elements dispersed between and fixedly attached to said upper and lower load-bearing members at and between their opposing facing areas, said support elements serving to transmit the load from said upper to said lower load-bearing member, said "soft", pneumatic support elements comprising pneumatic air bag means for variably and continuously equalizing any variations in the applied load between said support unit means and for changing the relative positioning of the upper and lower load-bearing members, said pneumatic air bags being generally cylindrical in configuration and completely open at both ends, said load-bearing members being flat at said facing areas and closing off the ends of said air bags to create a closed, inner, air-tight system with said air bags.

2. The support system of claim 1 wherein said air bags are fixedly attached to said upper and lower load-bearing members by means of a series of rim bolts placed about and through the facing periphery of said air bag and bolted securely into said upper and lower load-bearing members, whereby a defective air bag can be readily and easily removed and replaced while that support unit is still supporting the heavy load.

3. The support system of claim 1 wherein said flat plates each have disposed thereon opposing bumper plates for limiting the amount of minimum spacing between the plates to protect the air bags fixed therebetween.

4. The support system of claim 1 wherein at least one of said plates includes integrally within it an air supply line feeding into said closed, inner, air-tight system.

5. The support system of claim 1 wherein there is further included dynamic fluid means attached to said air bags for independently and individually varying the load-carrying characteristics of said series of support units, said dynamic fluid means comprising a pneumatic pressure control system.