US3889820A

US3889820A - Method and apparatus for suspendedly supporting a platform

Info

Publication number: US3889820A
Application number: US384659A
Authority: US
Inventors: Eugene Ranger
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1973-08-01
Filing date: 1973-08-01
Publication date: 1975-06-17
Anticipated expiration: 1992-06-17

Abstract

A method and apparatus for lifting a platform dependently supported from a member by support arms supportingly connected to the platform and independently reciprocable relative thereto between raised and lowered positions. A force is applied between support arms in engagement with the member and the platform, acting relatively downward on the support arms and upward on the platform. The force is of sufficient magnitude to lift the platform and will move it from a position spaced below the member to a position in contact therewith. The lifting force is preferably provided by a pressurized fluid, such as air. The lifting operation may be utilized to recover vertical slippage between the platform support arms and the member with which they are engaged.

Description

United States Patent Ranger 1 1 June 17, 1975 METHOD AND APPARATUS FOR SUSPENDEDLY SUPPORTING A PLATFORM Inventor: Eugene Ranger, East Ridge, Tenn.

Assignee: Combustion Engineering, Inc.,

Windsor, Conn.

Filed: Aug. 1, 1973 Appl. No.: 384,659

U.S. Cl 214/1 BB; 74/22 R; 165/76;

214/1 CM; 214/152; 294/85 Int. Cl. F28g 15/02 Field of Search 214/1 B, 1 BB, 1 CM, 152;

{56] References Cited UNITED STATES PATENTS 2,136,255 11/1938 Scanlon 294/85 X 3,643,701 2/1972 Wadiak .t 165/76 Primary Examiner-Robert J. Spar Assislanl Examiner-George F. Abraham 5 7 ABSTRACT A method and apparatus for lifting a platform depen dently supported from a member by support arms supportingly connected to the platform and independently reciprocable relative thereto between raised and lowered positions. A force is applied between support arms in engagement with the member and the platform, acting relatively downward on the support arms and upward on the platform. The force is of sufficient magnitude to lift the platform and will move it from a position spaced below the member to a position in contact therewith. The lifting force is preferably provided by a pressurized fluid, such as air. The lifting operation may be utilized to recover vertical slippage between the platform support arms and the member with which they are engaged,

22 Claims, 10 Drawing Figures SEEEEI PATENTEUJUN 1 7 I975 IIOa IIOb

FIG.

FIG. 2

Ad GU OD CC PATENTEUJUN z 7 ms SHEET FIG. 3

FIG. 4

1 METHOD AND APPARATUS FOR SUSPENDEDLY SUPPORTING A PLATFORM BACKGROUND OF THE INVENTION The invention relates generally to means for supporting a platform from and beneath a member having holes in the undersurface. More particularly, the invention pertains to a supporting means adapted to grippingly engage said member while inserted in said holes. More particularly still, the invention pertains to a method and apparatus for recovering any slippage of the platform and its support means relative to the member from which it is suspended.

In a variety of environments it may be necessary to provide a platform or carriage from which various types of work can be remotely conducted. Further, it may be necessary to movably suspend the platform from another member. It may be further necessary to permit the platform to be remotely moved parallel the member from which it is suspended. An example of this situation arises in nuclear steam generators where it may be necessary to inspect and/or repair some of the tubes contained therein.

A remotely operated moving platform may allow remote operations to be conducted therefrom without requiring continued or frequent presence of a human in the steam generator which may be radioactive. Two such platforms, capable of remote operation and locomotion are described respectively in US. Pat. application Ser. No. 384,658 for REMOTELY MOVABLE PLATFORM by C. T. Ward, D. L. Mathis, F. T. Radcliff and R. Vorwerk filed Aug. 1, I973 and US. Pat. application Ser. No. 384,657 for REMOTELY MOV- ABLE PLATFORM by C. T. Ward, D. L. Mathis, F. T. Radcliff and E. Ranger filed Aug. 1, 1973. Each of these remotely moved platforms may be suspendedly supported beneath the undersurface of a tube sheet by support means extending upwardly therefrom and grippingly engaging the tube sheet or some member affixed thereto. In the preferred embodiments of the platforms of the above two patent applications, selectively expandable anchors are extensibly connected to the platform. These anchors include a finger and a gripper thereabout and moving therewith. The anchors are extended relative to the platform base into the openings formed by the tubes in the tube sheet. The gripper is then expanded into gripping engagement with the wall of the tube to bear a portion of the weight of the platform base connected thereto. A sufficient number of anchors are used to always support the platform. Further, the anchors may be translated relative to the base in a direction which substantially parallels the plane of the base and the tube sheet in order to move the platform base substantially parallel the undersurface of the tube sheet. By selective extension, expansion, retraction and translation of various of the anchors, it is possible to walk the platform across the undersurface of the tube sheet to align it, or a work station portion, with a tube or tubes to be inspected and/or repaired.

The supported positioning of platform base relative to the tube sheet should be such as to maintain a constant spacing between the base and the tube sheet, and this would be possible if gravity forced the platform toward the tube sheet, or if the grippers of the anchors were always uniformly inserted in the tubes and gripped sufficiently to prevent any slippage, regardless of weight or work loading. However, in practice, the

platform will generally be used where it depends below the tube sheet, such that gravity acts against the anchor grippers. Further, the work operations may include forcing a plug into the tube end which would further downwardly load the platform. Further still, it may be necessary for the platform to be "stepped" hundreds or even thousands of times and small slippage with each step could accumulate to a significant extent. If, in any of these instances, the extent of slippage accumulated sufficiently to remove the grippers from gripping engagement with the tube walls, the platform would fall face free of the tubes and tube sheet, possibly damaging it and requiring human presence for reinstallation.

SUMMARY OF THE INVENTION According to the invention there is provided a method and apparatus for remotely lifting a platform, or at least the base portion thereof, when it is supported beneath a tube sheet by anchor means extensibly connected thereto for insertion into gripping engagement with walls of openings in the undersurface of the tube sheet.

Broadly, the invention includes means and a method of operating the means which prevent a dependently suspended platform from falling out of suspended engagement with the member from which it is suspended. Further, the invention provides a method and apparatus for lifting a platform base relative to a member from which it is suspended to maintain it in close proximity therewith therebelow. More specifically, the invention provides means and a method of operation thereof which recovers relative slippage between the platform support and the member with which it is grippingly engaged, this function being accomplished either when the platform remains fixedly positioned laterally of the tube sheet or when it walks" or steps" laterally thereof. Further, the invention may be utilized to maintain the base portion of the platform proximate or in contact with the tube sheet undersurface, particularly when all of the support means grippingly engage the tube sheet.

The platform includes a base portion and at least two, and preferably four or more, anchor or support means of the finger and gripper type for selective insertion into gripping engagement with the walls of holes in the tube sheet undersurface, A support means typically comprises an upwardly extending finger mounted on a finger piston reciprocable in an upwardly extending cylinder carried by the platform base, a resilient sleeve about the finger, and sleeve expanding means including a compression jaw surface and second piston about the finger below the sleeve and above the finger piston and vertically movable relative to the finger and sleeve to longitudinally compress and radially expand the sleeve. The sleeve, when inserted in a hole in the tube sheet and expanded, will grippingly engage a wall of the hole.

The finger and its piston may be moved upward relative to the cylinder and base carrying the resilient sleeve for insertion in a hole by a first force applied between the piston and cylinder. The sleeve may be expanded by a second, repulsive force applied between the finger piston and the second piston. The second piston, and accordingly the finger piston, may be moved downwardly relative to the cylinder and base, even when said second force exists between the pistons and the sleeve is engaging a hole wall, when a third force of greater magnitude and opposite direction to the first force is applied between the second piston and the cylinder. This effects a lifting or cinching of the base relative to the tube sheet if the third force is of suffcient magnitude. In each instance, the force may be provided by a pressurized fluid, such as air.

The third force may be continuously applied during the time that all support means are in gripping engagement with the tube sheet to maintain the platform base in close proximity or in contact with the tube sheet undersurface. Further, the third force may be applied to one or more support means in gripping engagement with the tube sheet during such time as other support means are being extended and inserted into holes and expanded into gripping engagement. This operation insures maximum insertion of the newly implanted support means and provides means for recovering slippage of the support means. This latter function may be accomplished while the platform remains laterally stationary relative to the tube sheet or it may be accomplished as part of a stepping operation if the support means have a stepping capability. If attendant to a step ping operation, it may be desirable for certain platform constructions to avoid or remove application of said third force during the lateral movement of the platform to prevent sliding contact between the relatively mov ing platform and tube sheet.

In one embodiment, a spacer between the finger piston and second piston of each support means defines a minimum chamber length therebetween which approximates the distance between the platform base and the upper gripping surface of the resilient sleeve when it is at its upwardly extended limit. A fluid admitting port for applying the sleeve expanding force between the finger piston and second piston is located in the cylinder wall closely above the finger piston when it is fully extended such that it will remain in registry with the chamber between the pistons even when they are partially withdrawn by the cinching operation.

In another embodiment, the spacer between the pistons may be greatly reduced in length, or eliminated, by introducing the sleeve expanding fluid to the region between the pistons from a port and conduit which move with one of the pistons.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cutaway perspective view of a steam generator showing the platform incorporating the novel support system operatively positioned therein.

FIG. 2 is a transverse section of the steam generator taken along line 2-2 of FIG. 1 to show the pattern of tube ends.

FIG. 3 is a plan view of the mobile platform incorporating the novel support system.

FIG. 4 is an elevationai view of the mobile platform depicted in FIG. 3.

FIG. 5 is a sectional view ofa typical support member of FIG. 3 taken along line 55 therein.

FIG. 6a is a view of a support member, showing it inserted in a tube prior to expansion.

FIG. 6b is a view, similar to 60, however showing the support member following expansion into gripping engagement with the tube wall.

FIG. 7a is a view similar to FIG. 6b, however showing an increased vertical spacing between the tube sheet and the base portion of the platform.

FIG. 7b is a view similar to FIG. 7a, however showing reduction of the vertical spacing through operation of the invention.

FIG. 8 is a view similar to FIG. 7b, however showing an alternate means for delivering air to the region between the two pistons of the support system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I, there is depicted a typical nuclear steam generator 10 including a vessel 12 having a large number of tubes 14 supported therein and terminating at one or both ends in a tube sheet l6. In the steam generator 10 depicted, the vessel 12 and tubes 14 are generally vertically oriented with the tubes being of an inverted U shape with both ends of the tubes terminating in or slightly below the generally horizontally extending tube sheet 16. The tubes 14 are hollow and circular in cross section and extend through generally cylindrical passages extending vertically through the tube sheet 16 and are snugly and securely affixed therewithin. Tubes 14 have an inside diameter of 0.75 inch. The tubes 14 terminate at or slightly below the lower surface of tube sheet 16 creating circular, vertically extending openings extending upwardly in the tube sheet.

Tube sheet 16 is supported within vessel 12 in spaced relationship with the bottom of the vessel. The tube sheet may be 10 to 15 feet in diameter and receives both the hot and cold ends of as many as 9,000 primary coolant U tubes 14. The region below tube sheet 16 may be divided into halves by a vertical divider 20 and a manway 24 in vessel 12 on each side of divider 20 permits human access to the steam generator below tube sheet 16. A manway 24 may have a diameter of about 16 inches.

The tubes 14, and accordingly the ends thereof, are positioned such that openings 18 are in a particular pattern which is fairly uniform and repetitive. A carriage, or platform 32 has been developed which is suspended from and thus supported by, the tube sheet 16 or tubes 14 and is remotely actuable for movement parallel the tube sheet. This movement is utilized to move a work station contained with the platform into alignment with various, and preferably all, of the openings 18.

Remotely movable carriages or platforms of the type generally described above are described in greater detail in U.S. Pat. application Ser. No. 384,658 for RE- MOTELY MOVABLE PLATFORM to C. T. Ward, D. L. Mathis, F. T. Radcliff and R. Vorwerk filed Aug. 1, 1973 and Ser. No. 384,657 for REMOTELY MOV- ABLE PLATFORM to C. T. Ward, D. L. Mathis, F. T. Radcliff and E. Ranger filed Aug. 1, 1973 mentioned earlier herein. The platforms described in the abovementioned applications generally utilized two or more anchor or support means which could be remotely engaged and disengaged from the tube sheet to support the platform. Further, one or more of the anchors or support means is translatable relative to the platform base in a direction parallel said base to effect locomotion of the platform. The invention will be described as embodied in one of the platforms described in the aforementioned applications, however, it will be appreciated that it will also be similarly applicable to the other platform described therein.

One typical pattern in which the ends of the tubes 14 are arranged in tube sheet 16 is seen in FIG. 2. This pattern of tube 14 ends, or similarly, of openings I8, has a triangular pitch. By triangular pitch it is meant that the straight rows of openings 18 which intersect one another and share a common hole do so at an angle other than 90. In the steam generator here described, this angle of intersection is l20 (or its supplement 60). as defined by

directional arrows

28 and 30 in FIG. 2. This arrangement comprises a continuous series of equilateral triangles adjacent rows or offset from one another to create this pattern. In another pattern, not shown here, the openings 18 may have a square or rectangular pitch in which rows of holes which intersect one another and share a common hole do so at an angle of 90.

Typically, the internal diameter of the tube 14 which generally defines opening 18 is about three quarters of an inch. The distance between centers of adjacent tubes 14 having the above-mentioned uniform spacing is one inch. This distance may be referred to later herein as the unit distance,

The invention is associated with a platform or carriage 32 capable of being remotely moved laterally sub stantially parallel to the lower surface of tube sheet 16 and which is dependently supported from and by the tube sheet. Carriage 32 in this embodiment is intended for use as a work platform from which various remotely controlled operations may be performed. As an example, carriage 32 may serve as a platform or support for nondestructive testing equipment such as an eddy current probe. Alternatively or additionally it may be used as a platform from which repair procedures on a partic ular tube 14 may be remotely performed. Additional explanation of such capabilities will follow a description of the carriage 32.

A preferred embodiment of carriage 32 is depicted in FIGS. 3 and 4 and comprises essentially a base portion 34 and a supporting mechanism 36 according to the invention, connected to said base 34. Mechanism 36 includes means for supporting the carriage below the undersurface of tube sheet 16. A stepping mechanism forming part of base portion 34 and to which support mechanism 36 is connected may provide means for propelling base 34 and accordingly carriage 32 parallel the undersurface of tube sheet 16.

The base 34 of carriage 32 includes a member 38 which is preferably of a strong light material such as aluminum or magnesium and is in plan view in the form of a pair of E's back-to-back and having a short crossarm at the outer end of the middle arm of each E. The lateral extent of base member 38 may be some eight to ten inches in each direction and it may be an inch or more in thickness. A pair of rollers 40 are mounted in each diagonally opposite laterally outer corner of base member 38 for rotation about a vertical axis. The rollers 40 are horizontally disposed for rotation about a vertical axis provided by mounting bolts or pins 42. Each pin 42 is captively retained on or in base member 38 against substantial vertical or lateral motion relative thereto and a roller 40 is retained on each pin against substantial vertical or lateral motion relative thereto. A limited amount of vertical freedom of roller 40 relative to base member 38 may be desirable to permit limited vertical movement between base member 38 and sliders 46a and 46b. Each roller 40 is free to rotate relative to base member 38, as mounting pins 42 may also. Rollers 40 are generally above base member 38. A pin 42 and associated roller 40 is positioned near the extremity of each arm of the back-to-back E5 of base 34 and at the extremities of the crossarms on the middle arms of the ES. These portions of the base 34 and accordingly the rollers 40 are positioned and spaced such that a pair of rollers are in laterally spaced opposition at each corner of the base.

The stepping mechanism on base 34, and accordingly carriage 32, includes a pair of sliders 46a and 46b, which house supporting mechanisms 36 which include fingers 48a and 48b respectively and gripping sleeves 50a and 50b respectively. The sliders 46a and 46b each comprise a pair of laterally spaced parallel vertically extending housing members 52 connected at or near their upper ends by a transversely extending rigid connecting arm 54. Arm 54 and housing members 52 may be integrally formed of aluminum or magnesium or the like. Each housing member 52 includes an upwardly or vertically extending cylinder therein which is closed at its bottom and opens upwardly to be used in a manner described hereinafter. The cylinders 56 in slider 460 will be designated cylinders 56a and correspondingly those in slider 46b will be designated cylinders 56b. Work stations or locations such as cylindrical bores or tubes 58 may extend through or be affixed to each slider 46a and 46b at or near laterally opposite ends thereof preferably outward of cylinders 56. Tubes 58 might additionally or alternately be positioned on or within base member 38 along its outer perimeter. However certain advantages obtain if tubes 58 may be variably positioned relative to the base, as by movement of the sliders 46.

Sliders 46a and 46b are movably connected with base member 38, or more accurately, are connected in a manner to movably support the base by means of rolling contact with the rollers 40. Each slider 46 is of such length laterally that it concurrently extends between a pair of rollers 40 at diagonally opposite ends of base member 38 and is of such lateral width that it is in supported or supporting contact with the pair of rollers. Preferably each slider 46 is wider than the space between a pair of rollers 40 and includes a pair of horizontally extending grooves or guides 60 along opposite sides thereof parallel the longitudinal extent of the slider at or near each end thereof. Guide grooves 60 each receive a portion of the outer periphery ofa roller 40 therewithin and are in rolling and supported contact therewith. In this manner sliders 46a and 46b may be translated or reciprocated in a direction which substantially parallels the plane of base member 38 and base 34.

The connecting arm 54 of one slider 46 extends or crosses over the arm of the other slider in noninterfering relationship, both above base member 38. The sliders 46a and 46b cross one another at an angle which corresponds to the angle made between intersecting rows of holes 18 in the tube sheet 16. For the tube sheet shown this angle is conveniently 120 (with a supplementary angle of 60) in accordance with the angle revealed by the

intersectional arrows

28 and 30 in FIG. 2. It might be for tubes having a square or rectangular pitch. In the rows of holes 18 paralleling the

directional arrows

28 and 30 each hole in the rows in both directions is uniformly spaced from the immediately adjacent hole in that row in the spacing is the same in both intersecting directions and corresponds to the unit distance earlier mentioned. This uniformity of spacing of holes 18 pennits a uniformity of spacing of the support means which include fingers 48 and gripping sleeves 50 to be described later. Further, this uniformity of spacing of holes l8 permits uniformity in the length of lateral thrust of each slider relative to base 34. The fingers 48 and gripping sleeves 50 at opposite ends of each slider 46 are spaced from one another by some integer number times the unit distance between centers of adjacent pairs of holes 18. Typically this spacing might be five to ten times the unit distance. Further, the probe tubes 58 are also spaced from fingers 48 and gripping sleeves 50 by an integer multiple of the unit distance, usually one. Tubes 58in the depicted embodiment are centered in the same plane that extends vertically through the centerline of the fingers 48 in cylinders 56 of a slider. Each slider 46 is of sufficient length that it may be reciprocated longitudinally an extent corresponding to one, or possibly two, times the unit distance between an adjacent pair of holes 18 while in supported or supporting engagement with rollers 40. This reciprocation or translation of each slider 46a and 46b is effected by means of respective motors, preferably linear motors, such as fluid actuated piston and

cylinder combinations

62a and 62b respectively. It will be appreciated that such linear motion might also be obtained by converting the rotary motion of a motor to linear motion, as with a rack and pinion. Each piston and

cylinder combination

62a and 62b is horizontally disposed and the cylinder portion thereof is affixed to the base 34 as by being rigidly joined to base member 38.

Cylinders

62a and 62b are oriented to parallel the respective sliders 46 with which they are associated. A piston rod 64 extends from each of the pistons associated with the

combination

62a and 62b and is nonyieldingly secured at its outer end to a

flange

66a or 66b respectively associated with slider 460 or 46b. Flange 66a is fixedly secured to slider 460 near one end thereof and flange 66b is fixedly secured to slider 46b near one end thereof. Actuation of the piston and cylinder combination 620 and/or 62b thus serve to reciprocate or translate the respective sliders in an obvious and well known manner. Each slider 46 may have two discrete lateral positions relative to base 34, or possibly three such positions, as disclosed in either of the aforementioned patent applications. if only two positions are to be used piston and cylinders 62 will be conventional double acting pistons requiring two

air conduits

68a or 68b and 700 or 70b shown in FIG. 4 connected respectively through

control valves

69a or 69b and control valves 71a or 7117 to air supply 73. If the piston and cylinder combination is to have a two stroke capability (three positions), then a third conduit to each combination will be required. A two stroke, three position piston and cylinder combination is described in the aforementioned patent applications to which reference may be made for any further details. Each stroke length of the piston and cylinder combination 62 is made equal to the unit distance" between centers of an adjacent pair of holes 18.

A description of the novel supporting mechanism 36 for the carriage 32 and the operation thereof will now be undertaken. Referring to FIG. the housing member portion 52 of a slider 460 or 46b is shown with a vertical section taken through the center of cylinder 56 therein. Each cylinder 56 may be formed by a cylindrical vertical bore in a housing member 52. This bore may be made from the underside of the housing member and extend upwardly part way therethrough. A smaller bore concentric with cylinder 56 may extend the remainder of the way upward from the cylinder through housing member 52. The bottom end of the bore forming cylinder 56 will be sealingly closed, as by a cover plate 74. A cylinder 56 might typically be three or more inches in length with the smaller diameter concentric bore extending upwardly therefrom being nearly the same length, or somewhat less.

Typically a cylinder 56 might be about one inch in diameter with the smaller bore thereabove being about one-half an inch in diameter.

A finger piston 76 is radially sized for sliding relationship within cylinder 56 axially thereof. A rigid rod or finger 48 is affixed to and extends upwardly from finger piston 76. Each piston 76 includes an O-ring there about for sliding sealing contact between the piston and the wall of cylinder 56. Piston 76 is movable within cylinder 56 between a lowered position in which it contacts the bottom end of the cylinder and a raised position thereabove but below the upper end of the cylinder. The length of finger 48 is such that it extends more than an inch, and preferably two inches or more, above the upper surface of housing member 52 of a slider 46 when the piston 76 is in its raised position. Further, this length is such that the upper end of finger 48 is flush with or below the upper surface of the housing member when the piston 76 is in its lowered position. Finger 48 includes a downwardly facing jaw 80 at or near its upper end. Jaw 80 may be formed as an integral part of finger 48 or by means of an enlarged nut threadedly secured thereto.

Means for grippingly engaging the inner wall or walls of openings 18 defined by tubes 14 are associated with and carried by the finger 48. In this embodiment these engaging means comprise a deformable gripping sleeve 50 disposed about an axially extending portion of finger 48 and of somewhat smaller outer diameter than the diameter of the small bore above cylinder 56. A gripping sleeve 50 may be tubular and comprised of a flexi ble or deformable material or elastomer, such as gum rubber, a polyurethane or the like. The material of sleeve 50 is preferably one having a relatively high coefficient of friction.

A rigid tubular sleeve 82 slidably encircles each finger 48 along its lower extent below the deformable gripping sleeve 50 and also extends radially outward beyond the inner diameter of the gripping sleeve, thus forming an upwardly facing lip or jaw against the undersurface of the gripping sleeve 50. A piston 84 is affixed to rigid sleeve 82 near its lower end and slidably encircles finger 48. Each piston 84 is of essentially the same diameter as the piston 76 associated with the finger 48 and includes an O-ring thereabout for sliding fluid sealing contact between the piston and the wall of cylinder 56. In this arrangement piston 84 is positioned intermediate piston 76 and the upper end of cylinder 56 and, accordingly, will contact the upper end of the cylinder when the finger piston 76 is driven upwardly to its raised position. The underside of piston 84 may serve as a stop limit for finger piston 76 to define the raised limit position of the latter piston. it may be desirable for reasons to be described hereinafter to prevent the entire upper surface of piston 76 from contacting the lower surface of piston 84 in order to maintain a fluid receiving chamber therebetween, therefore spacer means such as the raised land 86 on the upper side of piston 76 is provided. The spacer, in this instance land 86, is significantly smaller in diameter than the diameter of either of

pistons

76 or 84. The spacer might also have been a free standing shim or washer encircling finger 48 below piston 84 or it might have been a downwardly extending land affixed to the bottom side of piston 84. Land 86, in one embodiment, is of an axial length equal to or somewhat less than the distance from the upper surface of housing member 52 to the upper extent of the active gripping portion of sleeve 50 when

pistons

76 and 84 are in their raised limit positions.

A small land might also be provided on the upper surface of piston 84 to maintain it slightly spaced below the upper end of cylinder 56 when it and piston 76 are in their raised limit positions to facilitate introduction of driving fluid thereabove.

Finger 48 and gripping sleeve 50 are shown in the lowered position in FIG. 5. In order for sleeve 50 to grippingly engage the wall of an opening 18 it is necessary that the finger 48 and sleeve 50 be upwardly extended to the raised limit position determined by piston 76 and that the sleeve 50 then be radially expanded by axially separating

pistons

76 and 84 relative to one another. By axially moving

pistons

76 and 84 away from one another the upper surface of rigid sleeve 82 and the downward facing surface of jaw 80 are moved relatively toward one another axially compressing sleeve 50 therebetween. Sleeve 50 may not move radially inward because of the presence of finger 48 thereat and accordingly expands radially outward. lf carriage 32 has been previously placed, possibly manually, closely below the undersurface of tube sheet 16, with fingers 48 aligned with openings 18, the upward extension of finger 48 and sleeve 50 and the subsequent expansion of the latter member will result in the sleeve grippingly engaging the wall of a tube 14 into which it was inserted.

FlG. 6a depicts carriage 32 closely below and preferably with base portion 34 in contact with the undersurface of tube sheet 16 and shows the finger 48 and its gripping sleeve 50 in its raised limit position and fully inserted within an opening 18 defined by tube 14. FIG. 6b depicts the gripping sleeve 50 in its radially expanded configuration and shows it in gripping engagement with the interior wall ofa tube 14. The outside diameter of sleeve 50 in its relaxed state is enough smaller than the inside diameter of tube 14 to permit its easy insertion therewithin but is sufficiently large to provide good radial expansion into gripping contact with the tube when axially compressed and shortened by [-20 percent ofits length. Typically the outside diameter of gripping sleeve 50, when relaxed, is 0.56 inch.

The means for actuating

pistons

76 and 84 preferably include pressurized driving fluid, and more particularly, a pressurized gas such as air. It will be appreciated however that other means such as springs might be used in combination with pressurized air. Raising of the

pistons

76 and 84 to the raised limit positions is effected by admitting air to cylinder 56 below piston 76 when it is in its lowered limit position. This is accomplished by connecting one end of a conduit 88 to port 90 in the lower end of cylinder 56 and connecting the other end to a relatively low pressure source of air 92 through a control valve 94.

In order to effect axial compression of sleeve 50 and to obtain the necessary radial expansion, pressurized air is admitted to the region or chamber between

pistons

76 and 84 when they are in their raised limit positions. This is accomplished in one embodiment by connecting a relatively high pressure source of air through control valve 102 in conduit 96 to port 98 in cylinder 56. Port 98 is located just above the upper surface of piston 76 when it is in its raised limit position.

The pressures involved will of course depend on the quality and geometry of sleeve 50, the active surface areas of the piston, and the weight and friction of the elements to be moved, however in the embodiment described a pressure of about 25 pounds per square inch at source 92 has been found adequate to extend finger 48 and insert it within a tube 14 and a pressure of some 100-150 pounds per square inch has been required of source 100 to effect the necessary separating force between the two pistons to expand the sleeve 50 into snug gripping engagement with the tube.

The several control valves discussed and to be discussed herein are conventional three-way valves which utilize only two operative positions, one being that which admits air from the source to the cylinder and the other being that which vents air from the cylinder to the atmosphere. These valves may be manually or automatically operated, as is well known. To release sleeve 50 from gripping engagement with tube 14 it is only necessary that valve 102 be vented to the atmosphere removing the separating force between

piston

76 and 84. Finger 48 might descend to its lower limit position when control valve 94 is vented to the atmosphere following venting of control valve 102, however, friction between the pistons and cylinder may require that an additional downwardly applied force be applied. This additional downward force would normally be applied to piston 84 and would not normally be of great magnitude. This may be accomplished by admitting air to cylinder 56 above piston 84 through a conduit 104 connected at one end to a port 106 in cylinder 56 above sleeve 84 in its raised limit position and connected at its other end to a source of air 108 through valve 110. Air source 108 would normally have to be at a pressure no greater than l0-25 pounds, however, according to the invention, a greater pressure may be desirable to accomplish the lifting of carriage 32 in the manner to be hereinafter described.

Referring to FIG. 7a, finger 48 and gripping sleeve 50 are shown respectively in their fully extended and fully expanded configurations, however, it will be noted that they are not fully inserted within tube 14 to an extent which brings the upper surface of housings 52 of a sliders 46 into contact with the undersurface of tube sheet 16. This condition may result either because carriage 32 was spaced somewhat below tube sheet 16 when finger 48 was initially extended and inserted, or because it has slipped downward relative to tube sheet 16 and tube 14. The latter-mentioned slippage may arise from excessive loading of carriage 32 as during a work operation in which an instrument or plug is inserted into a tube 14 and the carriage is used as the support platform from which this work operation is launched or a slight amount of slippage may occur during the stepping operation in walking the carriage across the undersurface of the tube sheet.

it is preferable that carriage 32, and specifically base portion 34 thereof, remain as closely adjacent the undersurface of tube sheet as possible, both to serve as a relatively constant reference point from which work operations may be conducted and additionally to avoid the problem of lateral misalignment of a test probe or the like which may be launched from base 34 into a tube 14. Further, if the spacing results from slippage of the gripping sleeve 50 and is repetitive with time then it will be necessary to recover some or all of this slippage to prevent the carriage 32 from ultimately falling free of tube sheet 16.

To eliminate this greater than minimum spacing between the tube sheet 16 and the base portion 34 of carriage 32 and/or to insure maximum insertion of finger 48 and sleeve 50 into tube 14, the invention provides means and a method for lifting base 34 relative to tube sheet 16 and/or fully inserting finger 48. Firstly, the pressure of air from source 108 admitted to cylinder 56 through port 106 is sufficiently great to force piston 84 and accordingly piston 76 downwardly relative to the cylinder 56 and base 34, or stated another way, to force the base 34 upwardly relative to piston 84. This pressure will depend principally upon the weight being supported by finger 48 and gripping sleeve 50 and the frictional forces between the pistons and the wall of cylinder 56. The greater the number of supporting means in gripping engagement with tubes 14 and tube sheet 16, the less the amount of weight supported by each individual support means. in the embodiment being described in which normally at least two supporting means are always in engagement with the tube sheet 16 a lifting force of some 20-50 pounds at each finger 48 is quite sufficient. As the effective work area of the upper surface of piston 84 is about three quarters of an inch, an air pressure greater than 30 psi, typically about 70 psi, has been found to be adequate. Such pressures may of course be adjusted to suit the particular design and weight. The pressure of air required to separate

pistons

76 and 84 might have to be increased somewhat to accommodate the increased downward force on finger 48 and sleeve 50 needed to raise and hold base portion 34. FIG. 7b shows carriage 32, or more specifically housing member 52 of slider 46 thereof, in contact or nearly in contact with the undersurface of tube sheet 16 following the above-mentioned introduction of air to cylinder 56 through conduit 104. This operation may be termed a "lifting" or cinching" operation.

By considering the extent to which the gripping sleeve 50 might extend above the uppermost surface of base 34 or housing 52 when fully raised, it will be seen as depicted in FIG. 7a, that the base 34 and housing 52 might descend to a spacing of an inch or more below the undersurface of tube sheet 16 if the gripping sleeve 50 slips somewhat. in such instance the

pistons

76 and 84 will move downward relative to cylinder 56 by an equivalent amount during a cinching operation. It is for this reason that, in one embodiment, the spacer land 86 on piston 76 is placed between the two pistons and the port 90 is positioned near the upper surface of finger piston 76 in the latters raised limit position. By making the land 86 of an axial length which approximates the distance or spacing between the upper surface of housing member 52 and the upper extent of the active gripping portion of sleeve 50 when

pistons

76 and 84 are in their raised limit positions, port 98 may move upward relative to

piston

76 and 84 by that distance during a cinching operation and still remain in fluid com munication with the chamber between spaced pistons. This is true even for the maximum amount of cinching movement. so long as the sleeve 50 was initially in gripping engagement with a tube 14. While the length of the spacer land 86 does not effect the length of the stroke of finger 78 it does require that cylinder 56 be made axially longer than would otherwise be the case for a particular stroke length without the spacer.

As an alternative to the spacer land 86, the increased length and weight of cylinder 56 and the precise positioning of port 98, there is depicted in FIG. 8 an embodiment of the carriage supporting means in which the air conduit 96 is connected to a hollow rigid tubular conduit 97 which in turn is carried by and moves with piston 76. Conduit 97 is connected at one end to conduit 96 remote from air source 100 and is securely connected at its other end to finger piston 76 at the underside thereof and is preferably concentric therewith. A passage or port 98' extends from the end of conduit 97 through piston 76 and possibly into finger 78 and opens or exits into the region or space between

pistons

76 and 84. Rigid conduit 97 slidably passes through a central opening in cover plate 74 across the lower end of cylinder 56. An O-ring seated in housing member 52 or plate 74 at the lower end of cylinder 56 fluidly isolates the cylinder 56 from the atmosphere while allowing reciprocable motion of the conduit 97 relative thereto. Conduit 97 may be of a material such as stainless steel. A downwardly extending sleeve 101 is affixed at its upper end to the undersurface of cover plate 74 and extends downwardly about conduit 97 to protect it. By delivering the driving fluid to the region between

pistons

76 and 84 in this latter described manner, port 98 will always remain in registry with the region between the pistons regardless of their positionings relative to cylinder 56. It may be desirable to retain a short axially extending spacer between the pistons to insure at least a minimum space therebetween.

The operation of carriage 32 and more specifically, of the support means including fingers 48 and gripping sleeves 50 will now be described. The description is equally applicable to the different embodiments for introducing air through port 98 or 98'. As described more thoroughly in the earlier mentioned patent applications, fingers 48 and gripping sleeves 50 are divided functionally into two independent groups with the elements of a group being controlled preferably in unison. The support means associated with one such group have been given the subscript a and those associated with the other group have been given the subscript b. Structurally the supporting means of one group are identical to those of the other group, however their sequence of operation may be varied as described below.

In the description above relative to FIGS. 68, no subscripts were assigned to the several air conduits, control valves and ports associated with the cylinder and pistons under discussion. It will be appreciated that if these elements are associated with a cylinder 56a of one functional group, they would bear the a subscript and those associated with a cylinder 56b of the other functional group would hear the b subscript. For purposes of discussing the operation of the support means in the two different functional groups, the a and b subscripts will be used. It will be appreciated that the air supplies 92, 100 and 108 may be common to both groups. Further there might only be a single one of each

control valve

94, 102, and 110 associated with the several cylinders 56 of a functional group, with distribution of the air occurring between a valve and the several cylinders for unity of control.

First, platform 32 will be considered as remaining laterally stationary at a particular location below tube sheet 16. As mentioned earlier, it is preferable that the carriage 32 and particularly the base portion 34 thereof be positioned vertically closely below or in contact with the undersurface of tube sheet 16 to provide a constant and reliable reference from which to launch or conduct work operations. In this configuration some, and probably all, of the support means which include fingers 48a and 48b in gripping sleeves 50a and 50b, will be in gripping engagement with tubes 14. This will mean that air is being provided to the region between

pistons

76 and 84 from source 100. Concurrently therewith, air will be admitted to cylinder 56 from source 108 through conduit 104 and ultimately port 106. This air is of sufficient pressure as mentioned earlier to effect relative longitudinal motion between the pistons and cylinders housed in member 52, with members 52a and/or 52b rising until they contact the undersurface of tube sheet 16. At this point control valves 110a and 11011 and 102 a and remain open to retain the supporting means in gripping engagement within the tubes 14 and to cinch the carriage up closely against the undersurface of the tube sheet while any work functions are performed.

As a modification of the above-described procedure some, but not all, of the gripping sleeves 50 may be released from gripping engagement with their associated tubes 14. For instance, it will be assumed that the gripping sleeves 50 of the b subscripted functional group are released. This is effected by operation of valves 10211 to disconnect source 100 from cylinders 56b and vent that region of the cylinder to the atmosphere. This is accomplished prior to the introduction of air through port 106b. Source 108 is subsequently connected with cylinders 560 through conduits 104a and ports 106a to lift the base 34 relative to those fingers 48a in gripping sleeves 50a which remained in gripping engagement with tubes 14. The support means bearing the disengaged gripping sleeves 50b will be raised to their upper limit through admission of air to cylinders 56!; via ports 90b and are subsequently reexpanded into gripping engagement with the tubes 14 by application of air from source 100 through ports 9812. In this manner those support means which were released from gripping engagement will have been reinserted to the maximum depth within their particular tubes 14. Those support means which originally remained in supporting engagement with tubes 14 may now be released from gripping engagement with the tubes by venting through ports 98a and valve 1020. These support means may now also be extended to their raised limit position and reexpanded such that all support means will now be fully extended and fully inserted within the various tubes 14 and gripping engagement therewithin.

A somewhat similar procedure is followed in stepping the platform 32 laterally of the tube sheet 16 and is described hereinafter. The operation will be assumed to begin from a condition in which all sleeves 50 are expanded and the carriage base 34 is cinched up against the tube sheet undersurface by means of air pressure from source 108 admitted to the cylinders 56 through ports 106.

While maintaining expansion pressure on the pistons of cylinders 56a through ports 98a, the expansion pres sure is released from the pistons of cylinders 56b by venting through ports 98b and control valves l02b. If

the cinching pressure has been maintained in all cylinders 56 through ports 106 during this operation, both pistons 76b and 84b in cylinders 56b will be moved to their lower limit positions. Then the cinching pressure may be removed from some or all cylinders 56 by venting through ports 106 and control valves 110. This release of cinching pressure might have been occurred prior to or concurrent with the above-mentioned release of the expansion pressure. In either event, the gripping sleeves 500 will now remain in gripping en gagement, fingers 48b are in their lowered positions, and the platform 32 will be released from its cinched position, for easy lateral movement relative to tube sheet 19. At this point, the platform is ready to be stepped laterally of tube sheet 19. It should be noted that the aforementioned release of the cinching pressure from cylinders 56 a will be necessary only if there will be some sliding contact or interference between the sliders 460 or 46b and the underside of tube sheet 16 during the stepping operation. If, as noted earlier, some degree of vertical freedom exists between base member 38 and sliders 46a and 46b, it will not generally be necessary to release the cinching pressure or force from that group of cylinders (560 above) which are to remain in gripping engagement with the tube sheet 16 during the stepping operation. Rather. the slider (46b above) which will move laterally relative to tube sheet 16 drops away from the tube sheet by the amount of limited vertical freedom provided between it and base member 38. This allows a clearance between the slider which moves relative to the tube sheet during the stepping operation.

Because sleeves 50a remain inserted and expanded in tube sheet 16, their slider 460 must remain fixed relative to the tube sheet. However, slider 46b may be moved relative to slider 46a and tube sheet 16 by actuating piston and cylinder 62a to move the base 34 and slider 46b in a direction parallel the extent of slider 46a. Alternatively, if the step is to be parallel the extent of slider 46!), piston and cylinder 62b will be actuated moving slider 46b relative to base 34 and tube sheet 16. This latter mentioned operation might be considered a half-step as it moves only the slider and not the base and carriage. ln either event, the fingers 48b of slider 46b will now be aligned with a new" pair of tube openings 18. Air will be reintroduced to cylinders 560 via ports 106a by control of valve 1100 to cinch" the base 34 up into contact with the tube sheet 16. This step is of course unnecessary if the cinching pressure was not previously released from cylinders 56a. Fingers 48b with sleeves 50b are then fully raised by introducing air to cylinders 56b through ports b. Because base portion 34 was cinched up into contact with the tube sheet, fingers 48b will be inserted to the maximum extent in tubes 14. At this point, sleeves 50b will be expanded into gripping engagement with tubes 14 by admitting air to cylinders 56b through ports 98b (or 98'b) by control of valve l02b. Thus, fingers 48b and sleeves 50b are fully inserted in and are gripping tubes 14 of tube sheet 16, thereby recovering any slippage or spacing previously accruing between base 34 and the tube sheet. It will be appreciated that fingers 48b might have been raised or extended prior to, or concurrent with, the "cinching" operation with fingers 48a.

Sleeves 50a might now be relaxed, fingers 48a raised to their limit and sleeves 50a reexpanded into gripping engagement to obtain a fully inserted configuration for all fingers 4S and sleeves 50. Alternatively, this repositioning of fingers 4811 might wait until those fingers are moved to a new set of openings 18 during a stepping operation.

The earlier-mentioned half step operation, in which slider 46b was moved relative to base 34, may be com pleted now by moving the base in the same direction relative to slider 46b. This is accomplished by freeing and retracting fingers 48a and sleeves 50a and actuating piston cylinder combination 621) as was described for movement of fingers 48b.

One complete step of a slider 46 and base 34 relative to tube sheet 16, both parallel slider 46a and parallel slider 46b, has been described including the cinching" operation. From this discussion, the interrelationship of the cinching operation with the stepping operation should be evident.

It will be understood that the embodiment shown and described herein is merely illustrative and that changes may be made without departing from the scope of the invention as claimed.

What is claimed is:

l. A platform for support below a member comprising:

a. a base portion;

b.. at least two upwardly extending support means supportingly connected to said base portion and independently reciprocable relative thereto between raised and lowered positions and including remotely actuable means therewith for grippingly engaging said member to support a portion of the weight of said platform therefrom when in said engagement; and

c. remotely controllable means for selectively applying a force to said support means relative to said base portion of a magnitude and direction to selectively move said support means either toward said raised position or said lowered position, even when said portion of platform weight is supported thereby.

2. The apparatus of claim I wherein said member includes openings in the undersurface thereof and said means for grippingly engaging said member are sized for insertion in said openings and are expandable into frictional engagement with a wall of openings.

3. A lifting mechanism for a platform self-supported below a member having openings in the undersurface thereof comprising in combination:

a. a generally horizontally extending carriage base portion;

b. two upwardly extending cylinders carried by said base portion in vertically fixed relationship thereto;

cv a first piston reciprocable in each said cylinder between raised and lowered positions and having a finger extending upwardly therefrom, said finger extending substantially above said base portion in said raised position and having a downwardly facing compression surface near the upper end thereof;

d. a second piston in each said cylinder concentrically disposed about said finger above said first piston and reciprocable relative thereto and to said cylinder between raised and lowered positions relative to said first piston and having an upwardly facing compression surface extending upwardly therefrom;

e. a resilient sleeve about each said finger between said upwardly and downwardly facing compression surfaces for outward expansion into gripping engagement with the wall of a said opening when inserted thereinto and said second piston is in its raised position relative to said first piston;

f. first means for admitting driving fluid to each said cylinder below said first piston at a pressure to raise said piston and finger;

g. second means for admitting driving fluid to each cylinder intermediate said first and second pistons at a pressure to move and maintain said second piston at its said raised relative position to outwardly expand said sleeve; and

h. third means for admitting driving fluid to each cylinder above said second piston at a pressure to move said second piston downward relative to said cylinder when said sleeve is in said gripping engagement, whereby said cylinder and carriage base portion are lifted towards said member.

4. The apparatus of claim 3 wherein said second means for admitting driving fluid include a fluid conduit carried by said first piston and movable relative to said cylinder in fluid sealed relationship therewith, one end of said conduit being connectable to a fluid source and the other end fluidly communicating with said cylinder intermediate said first and second pistons.

5. In a platform for suspended support below a mem her having holes in the undersurface thereof and including two support means supportingly connected to a base portion of said platform and including means for grippingly engaging said member, apparatus for lifting said base portion relative to said undersurface comprising:

a. each said support means being reciprocable between raised and lowered limits relative to said base portion;

b. said means for grippingly engaging said member moving with said support means and sized for insertion into a said hole for selective engagement with a wall thereof to support the weight of said support means and a portion of said base;

c. means for selectively actuating each said engaging means into and out of gripping engagement with said hole wall; and

(1. means for selectively applying a force to each said supporting means relative to said base of a magnitude and direction to reciprocate said supporting means toward said raised and said lowered limits, said force applied for said downward relative reciprocation of said support means being sufficient to overcome the portion of weight of said base supported by said support means, whereby to lift said base relative to said member.

6. The apparatus of claim 5 wherein at least one of said support means is translated relative to said base in a direction parallel to said base for moving said platform parallel said member undersurface.

7. The apparatus of claim 5 wherein said base includes two cylinders joined thereto against upward and downward motion relative thereto; each said support means comprises a finger extending upwardly from a piston, said piston being reciprocably mounted within a said cylinder; and said force applying means comprise means for applying a first force between said piston and cylinder to move said piston in one direction relative to said cylinder and base and a source of driving fluid admitted to said cylinder for moving said piston in the other direction.

8. The apparatus of claim wherein said base includes two cylinders joined thereto against substantial upward and downward motion relative thereto; each said support means comprise a finger extending upwardly from a piston, said piston being reciprocably mounted within a said cylinder; and said force applying means comprise a first source of driving fluid admitted to said cylinder above said piston in its raised position for moving said piston relatively downward and a second source of driving fluid admitted to said cylinder below said piston in its lower position for moving said piston relatively upward.

9. The apparatus of claim 8 wherein each said finger includes an upper jaw near its upper end; said hole engaging means comprise a resilient sleeve about said fin ger below said finger jaw said sleeve being normally diametrically smaller than a said hole and expandable into gripping engagement therewith; said actuating means for each said engaging means comprise a lower jaw carried by a second piston slidably disposed in a said cylinder about said finger above said finger piston and below said resilient sleeve for reciprocation between a raised and lowered position relative to said finger piston to respectively expand and relax said sleeve; and a third source of driving fluid admitted to said cylinder between said finger piston and said second piston for relatively moving said second piston to its raised position', and said first source is admitted to said cylinder above said second piston in said raised position of said finger piston.

10. The apparatus of claim 9 wherein the uppermost gripping surface of each said resilient sleeve is a certain distance above said carriage base in said raised limit position of said support means; spacer means posi' tioned to coact between said finger piston and said second piston establish a minimum spacing therebetween, said minimum spacing being substantially that of said certain distance of said resilient sleeve uppermost gripping surface above said base; and said third source of driving fluid is admitted to said cylinder proximate the upper surface of said finger piston in its said raised position.

11. The apparatus of claim 10 wherein at least one of said cylinders in translatable relative to said base in a direction parallel to said base, whereby to translate said support means relative to said base for moving said platform parallel to said member undersurface.

12. The apparatus of claim 9 wherein spacer means are positioned to coact between said finger piston and said second piston to establish a minimum spacing therebetween and said third source of driving fluid is admitted to said cylinder proximate the upper surface of said finger piston in its said raised limit position.

13. A method for supporting a platform closely adjacent the undersurface of a member having an opening in said undersurface, said platform having a base portion and support means supportingly connected to said base and movable relative thereto between raised and lowered positions respectively in response to raising and lowering forces applied therebetween and actuable into gripping engagement with a wall of said opening when inserted therein, comprising the steps of;

a. positioning said platform near said member undersurface such that said support means are inserted in said opening when in said raised position;

b. applying a raising force to move said support means to said raised position;

c. actuating said support means into gripping engagement with a wall of said opening; and

d. applying a lowering force to said support means while maintaining said gripping engagement, said lowering force being of sufficient magnitude to move said platform base portion upward to a limit closely adjacent said member undersurface.

14. The method of claim 13 wherein said limit is established by contact of said base with said member.

15. The method of claim 13 including the step of maintaining said support means lowering force follow ing arrival of said base at said limit.

16. The method of claim 13 wherein said member included a plurality of openings and said platform includes two support means independently raisable and lowerable and actuable into gripping engagement with different of said openings and further comprising the steps of:

a. actuating one of said support means out of gripping engagement with a said opening wall while maintaining the other in engagement;

b. applying a raising force to said one said support means while applying said lowering force to said other support means; and

c. actuating said one support means into gripping engagement with the wall of a said opening.

17. The method of claim 16 wherein a particular said support means is translatable relative to said base in a direction substantially parallel to said base to align a support means with a different one of said openings, and further comprising the steps of:

a. applying a said lowering force to said one support means to move it to its lowered position following its said actuation out of gripping engagement; and

b. translating said particular support means relative to said base to align said one lowered support means with a different one of said openings prior to applying said raising force thereto.

18. The method of claim 17 including the step of maintaining said support means lowering force, following arrival of said base at said limit.

19. A method for lifting a platform dependently supported from a member having openings in the under surface thereof. said platform including a base and two upwardly extending supporting means supportingly connected thereto and independently movable relative thereto between raised and lowered positions for insertion in said raised position into said opening and actuable into and out of gripping engagement with the wall of said opening when inserted thereinto to support said platform, both said supporting means normally in grip ping engagement with said member, said method comprising the steps of:

a. actuating one of said supporting means out of gripping engagement with said member;

b. moving said supporting means remaining in gripping engagement downward relative to said base, whereby said base is raised relative to said member; and

c. actuating said previously removed supporting means into gripping engagement with said member.

20. The method of claim 19 wherein at least one of said supporting means is movable relative to said base in a direction substantially parallel said base to align a 21. The method of claim 19 wherein said downward movement of said supporting means relative to said base is sufficient to lift said base to a maximum elevation proximate the undersurface of said member.

22. The method of claim 20 wherein said downward movement of said supporting means relative to said base is sufficient to lift said base to a maximum elevation proximate the undersurface of said member.

l I III

Claims

1. A platform for support below a member comprising: a. a base portion; b. at least two upwardly extending support means supportingly connected to said base portion and independently reciprocable relative thereto between raised and lowered positions and including remotely actuable means therewith for grippingly engaging said member to support a portion of the weight of said platform therefrom when in said engagement; and c. remotely controllable means for selectively applying a force to said support means relative to said base portion of a magnitude and direction to selectively move said support means either toward said raised position or said lowered position, even when said portion of platform weight is supported thereby.

2. The apparatus of claim 1 wherein said member includes openings in the undersurface thereof and said means for grippingly engaging said member are sized for insertion in said openings and are expandable into frictional engagement with a wall of openings.

3. A lifting mechanism for a platform self-supported below a member having openings in the undersurface thereof comprising in combination: a. a generally horizontally extending carriage base portion; b. two upwardly extending cylinders carried by said base portion in vertically fixed relationship thereto; c. a first piston reciprocable in each said cylinder between raised and lowered positions and having a finger extending upwardly therefrom, said finger extending substantially above said base portion in said raised position and having a downwardly facing compression surface near the upper end thereof; d. a second piston in each said cylinder concentrically disposed about said finger above said first piston and reciprocable relative thereto and to said cylinder between raised and lowered positions relative to said first piston and having an upwardly facing compression surface extending upwardly therefrom; e. a resilient sleeve about each said finger between said upwardly and downwardly facing compression surfaces for outward expansion into gripping engagement with the wall of a said opening when inserted thereinto and said second piston is in its raised position relative to said first piston; f. first means for admitting driving fluid to each said cylinder below said first piston at a pressure to raise said piston and finger; g. second means for admitting driving fluid to each cylinder intermediate said first and second pistons at a pressure to move and maintain said second piston at its said raised relative position to outwardly expand said sleeve; and h. third means for admitting driving fluid to each cylinder above said second piston at a pressure to move said second piston downward relative to said cylinder when said sleeve is in said gripping engagement, whereby said cylinder and carriage base portion are lifted towards said member.

5. In a platform for suspended support below a member having holes in the undersurface thereof and including two support means supportingly connected to a base portion of said platform and including means for grippingly engaging said member, apparatus for lifting said base portion relative to said undersurface comprising: a. each said support means being recIprocable between raised and lowered limits relative to said base portion; b. said means for grippingly engaging said member moving with said support means and sized for insertion into a said hole for selective engagement with a wall thereof to support the weight of said support means and a portion of said base; c. means for selectively actuating each said engaging means into and out of gripping engagement with said hole wall; and d. means for selectively applying a force to each said supporting means relative to said base of a magnitude and direction to reciprocate said supporting means toward said raised and said lowered limits, said force applied for said downward relative reciprocation of said support means being sufficient to overcome the portion of weight of said base supported by said support means, whereby to lift said base relative to said member.

8. The apparatus of claim 5 wherein said base includes two cylinders joined thereto against substantial upward and downward motion relative thereto; each said support means comprise a finger extending upwardly from a piston, said piston being reciprocably mounted within a said cylinder; and said force applying means comprise a first source of driving fluid admitted to said cylinder above said piston in its raised position for moving said piston relatively downward and a second source of driving fluid admitted to said cylinder below said piston in its lower position for moving said piston relatively upward.

9. The apparatus of claim 8 wherein each said finger includes an upper jaw near its upper end; said hole engaging means comprise a resilient sleeve about said finger below said finger jaw, said sleeve being normally diametrically smaller than a said hole and expandable into gripping engagement therewith; said actuating means for each said engaging means comprise a lower jaw carried by a second piston slidably disposed in a said cylinder about said finger above said finger piston and below said resilient sleeve for reciprocation between a raised and lowered position relative to said finger piston to respectively expand and relax said sleeve; and a third source of driving fluid admitted to said cylinder between said finger piston and said second piston for relatively moving said second piston to its raised position; and said first source is admitted to said cylinder above said second piston in said raised position of said finger piston.

10. The apparatus of claim 9 wherein the uppermost gripping surface of each said resilient sleeve is a certain distance above said carriage base in said raised limit position of said support means; spacer means positioned to coact between said finger piston and said second piston establish a minimum spacing therebetween, said minimum spacing being substantially that of said certain distance of said resilient sleeve uppermost gripping surface above said base; and said third source of driving fluid is admitted to said cylinder proximate the upper surface of said finger piston in its said raised position.

13. A method for supporting a platform closely adjacent the undersurface of a member having an opening in said undersurface, said platform having a base portion and support means supportingly connected to said base and movable relative thereto between raised and lowered positions respectively in response to raising and lowering forces applied therebetween and actuable into gripping engagement with a wall of said opening when inserted therein, comprising the steps of: a. positioning said platform near said member undersurface such that said support means are inserted in said opening when in said raised position; b. applying a raising force to move said support means to said raised position; c. actuating said support means into gripping engagement with a wall of said opening; and d. applying a lowering force to said support means while maintaining said gripping engagement, said lowering force being of sufficient magnitude to move said platform base portion upward to a limit closely adjacent said member undersurface.

15. The method of claim 13 including the step of maintaining said support means lowering force following arrival of said base at said limit.

16. The method of claim 13 wherein said member included a plurality of openings and said platform includes two support means independently raisable and lowerable and actuable into gripping engagement with different of said openings and further comprising the steps of: a. actuating one of said support means out of gripping engagement with a said opening wall while maintaining the other in engagement; b. applying a raising force to said one said support means while applying said lowering force to said other support means; and c. actuating said one support means into gripping engagement with the wall of a said opening.

17. The method of claim 16 wherein a particular said support means is translatable relative to said base in a direction substantially parallel to said base, to align a support means with a different one of said openings, and further comprising the steps of: a. applying a said lowering force to said one support means to move it to its lowered position following its said actuation out of gripping engagement; and b. translating said particular support means relative to said base to align said one lowered support means with a different one of said openings prior to applying said raising force thereto.

19. A method for lifting a platform dependently supported from a member having openings in the undersurface thereof, said platform including a base and two upwardly extending supporting means supportingly connected thereto and independently movable relative thereto between raised and lowered positions for insertion in said raised position into said opening and actuable into and out of gripping engagement with the wall of said opening when inserted thereinto to support said platform, both said supporting means normally in gripping engagement with said member, said method comprising the steps of: a. actuating one of said supporting means out of gripping engagement with said member; b. moving said supporting means remaining in gripping engagement downward relative to said base, whereby said base is raised relative to said member; and c. actuating said previously removed supporting means into gripping engagement with said member.

20. ThE method of claim 19 wherein at least one of said supporting means is movable relative to said base in a direction substantially parallel said base to align a supporting means with a different said opening and further comprising the steps of: a. moving said one supporting means actuated out of gripping engagement to its said lowered position; b. moving said at least one supporting means relative to said base in said direction substantially parallel thereto to align said lowered supporting means with a different said opening; and c. moving said one supporting means actuated out of gripping engagement to its said raised position.

21. The method of claim 19 wherein said downward movement of said supporting means relative to said base is sufficient to lift said base to a maximum elevation proximate the undersurface of said member.