US3215191A

US3215191A - Hatch cover assembly

Info

Publication number: US3215191A
Application number: US264307A
Authority: US
Inventors: Richter Philip; Meade H Detweiler
Original assignee: Fuller Co
Current assignee: Fuller Co
Priority date: 1963-03-11
Filing date: 1963-03-11
Publication date: 1965-11-02
Anticipated expiration: 1982-11-02

Description

Nov. 2, 1965 Filed March 1l, 1963 P. RICHTER ETAL HATCH COVER ASSEMBLY 4 Sheets-Sheet 1 l l I l Nov. 2, 1965 P. RICHTER ETAL HATCH covER ASSEMBLY 4 Sheets-Sheet 2 Filed March 11, 1965 S a 5 Ref Mv, mi im mi. :A Vp/A a P i A Z Z f, Y B s U fx Ill/HU @@lr Q n N .v m w wm, mw mw wm wm mm* mw N N /m o Jr o mm, A n mmv w \N mmf@ mm Q mlm WARN m \,wmm mm WN Nm.

Nov. 2, 1965 P. RICHTER ETAL HATCH COVER vASSEMBLY F'ild March 1l. 1963 4 Sheets-SheetI 3 ATTORNEYS' P. RICHTER ETAL 4 Sheets-Sheet 4 HATCH COVER ASSEMBLY Nov. 2, 1965 Filed March l1,- 1963 M, MM n M United States Patent O 3,215,191 HATCH COVER ASSEMBLY Philip Richter, Bethlehem, and Meade H. Detweiler,

Catasauqua, Pa., assignors to Fuller Company, a corporation of Delaware Filed Mar. 11, 1963, Ser. No. 264,307 2 Claims. (Cl. 1150-206) This invenion relates to the art of hatch covers, and more particularly to a hatch cover which, when closed will be substantially llush with the level of the deck through which the hatchway extends.

As conducive to an understanding of the invention it is noted that where marine hatch covers comprise a plurality of substantially rectangular panels which are mounted on a coamingextending above the deck level around the periphery of the hatchway, such arrangement would interfere with free movement of personnel as well as that of tractors or fork lifts required to shift cargo, which is especially undesirable where the hatch cover is on a deck below the top or weather deck of a ship not readily accessible to the ships boom for movement of cargo.

Where the hatch cover when in closed, substantially horizontal position is ush with the deck and there are spaces or gaps of excessive width between the periphery of the hatchway and the periphery of the hatch cover, the spaces or gaps may cause tripping of the crew members or jamming of the wheels of tractors or fork lifts required to move cargo.

Where the hatchway is closed by means of a cover assembly of the flush deck type, comprising at least three substantially rectangular panels which are hinged together and which extend across the hatchway with one end of the assembly being pivotally mounted at one end of the hatchway on a support fixed thereto and with the pair of panels adjacent the pivotal support folding together about a common hinge and the additional panel adjacent said pair folding on a common hinge toward said pair of panels, if upon initial folding movement of the pair of panels from their original horizontal closed position, the additional panel should move away from the pivotal mount of the assembly, unless suicient clear ance is afforded between such additional panel and the adjacent edge of the deck opening, they would abut with resultant deformation thereof and possible misalignment of said panels with resultant jamming thereof `and if suliicient clearance is provided, it may result in a gap of excessive width with the difficulties above pointed out.

It is accordingly among the objects of the invention to provide a hatch cover installation having at least three pivotally connected panels, that is relatively simple to install and which, when in closed position will have the top surface of the panels in substantially horizontal position substantially flush with the deck of the ship and with no excessive clearance between the periphery of the cover and the periphery of the hatchway in the deck which might cause tripping of crew members or jamming of the wheels of a tractor or fork lift, which hatch cover may readily and rapidly be moved from closed to open position and vice versa without undue effort on the part of the crew by folding two of the panels toward each other and the additional panel toward the other panels and without jamming of the hatch cover panels against the edge of the `deck opening.

According to the invention these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claims.

In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention,

3,215,191 Patented Nov. 2, 1965 FIG. 1 is a plan View of a hatch cover installation of the type having four panels according to one embodiment of the invention;

FIG. 2 is a longitudinal sectional view taken along line 2-2 of FIG. 1;

FIGS. 3 to 5 inclusive are diagrammatic views illustrating the operation of the equipment;

FIGS. 6 to 8 inclusive are views showing the panels in various opening positions;

FIG. 9 is a side elevational view showing the panels in completely open position;

FIG. 10 is a top elevatorial view showing the link connector, according to the invention;

FIG. 11 is a View taken along line 11-11 of FIG. 10;

FIG. 12 is a detail sectional view taken along line 12-12 of FIG. l;

FIG. 13 is a view similar to FIG. 12 taken along line 1313 of FIG. 1;

FIG. 14 is a detail view taken along line 14-14 of FIG. l showing the depression in the track, and

FIG. 15 is a diagrammatic view showing another embodiment of the invention.

Referring now to the drawings, in the illustrative embodiment shown, the deck 21 of the ship has a substantially rectangular opening therein defining a hatchway 22, which, as shown in FIGS. 2, l2 and 13, for example, has a ledge 23 extending the length of the hatchway on each side thereof and spaced below the level of the deck. Each of the ledges 23 supports an elongated substantially rectangular track or support bar 24 clearly shown in FIGS. 2, l2 and 13. One of the ends of the hatchway has a support beam 25 extending transversely thereacross, illustratively in the same plane as the tracks 24. The ledges 23 and 25 serve to support a hatch cover assembly 26 in the manner hereinafter to be described.

The hatch cover assembly illustratively comprises two pairs of substantially rectangular panels A, B and C, D. The panels are of suicient length so that they may extend transversely across the hatchway, the length of said panels being slightly less than the width of the deck opening 22 which defines the hatchway. The panels are of such width that when in closed position they will extend from substantially one end of the deck opening 22 to the other as is clearly shown in FIG. 1 substantially to close the hatchway.

Referring to FIG. 2, it is to be noted that each of the panels has a depending skirt plate 28 located slightly inward from the outer periphery of each panel. The lower edge of each skirt is illustratively provided with a reinforcing strip 29 extending the length thereof which is designed to seat on the associated track or support bar 24 as is clearly shown in FIGS. 2 and 12, for example, thereby supporting the panels in a horizontal plane when in closed position on said support bars 24.

As is clearly shown in the drawings, the skirt plate 28 along the outer side of panel A mounts a plurality of arms 31, illustratively two in number which extend outwardly from said skirt plate 28. The free end of each of the arms 31 is pivotally connected as at 32 to the top of an associated upright standard 33, aixed to the ledge 25, the height of such standard 33 being such that the pivot connection 32 illustratively will be below the level of the deck 21 as is clearly shown in FIG. 2 and the thickness of each of the panels being such that its top surface 33 when the panels are in closed position, will be substantially ush with the deck 21.

The adjacent

inner edges

35, 35 of the panels A, B and C, D at their lower edges are connected as by means of common hinges 36 (FIG. 2), the hinges being secured to the adjacent skirt plates 28 of said panels, so that the pairs of panels A, B and C, D may be folded about such hinges 36 respectively from the closed position shown in FIG. 2 to the open position shown in FIG. 9 in the manner hereinafter to be described.

According to the invention the adjacent panels B and C are connected by means of pivoted links 4l, two of which are illustratively provided as is shown in FIG. 1.

To support the links the adjacent skirt plates 28 of panels B and C have secured thereto as shown in FIGS. 1 and 2 and l0, two pairs of spaced parallel mounting plates 44, said plates depending from the top surface 33 of said panels and being secured as by welding at their edges to the top surface and to the skirt plate 28. Desirably, a reinforcing bar 45 which extends the length of each of the panels B and C is provided to which the lower edges of the support plates 44 are secured as by welding.

As is clearly shown in FIGS. l, 2 and 10, the associated portions of the top surface of the panels B and C near their adjacent edges 46, 46' have slots Sti therein to accommodate the links 41. Each of the links 41 is positioned between associated pairs of support plates 44 of the panels B and C as is clearly shown in FIG. and is pivotally connected between the plates 44 as by

pivot pins

47, 48 which extend through

appropriate openings

49, 51 in the link 41. Desirably, each of the

openings

49, 51 is provided with a

bushing

52, 53 respectively.

The opening 49, as is clearly shown in FIG. 1l, for example, is defined by an elongated slot and the opening 51 is circular. Thus, the pin 47 and the link 41 are capable of relative movement with respect to each other. Also associated with the panel B and extending transversely between the side plates 44 is a stop pin 55, clearly shown in FIG. 1l, the purpose of said pin being hereinafter described.

To facilitate movement of the panels A, B and C, D from closed to open position and vice versa, in the manner hereinafter to be described, the panel B at each end 56 adjacent its outer edge 46 mounts a flanged roller 57, rotatably mounted on a shaft 58 extending laterally outwardly from the side plate 59 (FIG. 1) and the panel C at each end 62 mounts a flanged roller 63 rotatably mounted on a shaft 64 extending laterally outwardly from a depending plate 65 as is clearly shown in FIGS. 1 and 13. As is clearly shown in FIGS. 1 and 13, the

flanged rollers

57 and 63 are mounted on the outside of plate 59 and the inside of plate 65 respectively and ride 'on the track 24. Similarly, a anged roller 57 is provided on the end 66 of panel D adjacent the outer edge 67 thereof, the rollers 57 being rotatably mounted on the outer side of depending plate 65 and longitudinally aligned with the rollers 57.

In the closed position of the hatch cover panels as is shown in FIGS. 1, 2, 12 and 13, for example, the rollers 63, and 57' will be positioned in

depressions

68 and 69 respectively. The

depressions

68 and 69 are of such length and depth that when the

rollers

63 and 57 are aligned therewith, the lower portion of the rollers will be spaced from the bottom as well as the sides of said depressions as is clearly shown in FIG. 14. In rthis position the weight of the hatch cover will be supported on the rails 24 by means of the reinforcing strips 29 secured to the lower edges of the skirt panels 28 of the panels C and D as is clearly shown in FIG. 2, for example. With this construction there will be no severe load on the

shafts

58, 64 which support the

rollers

63, 57 so that heavy cargo may be placed on the hatch cover panels when they are in closed position. As far as the panels A and B are concerned, when they are in closed horizontal position, although the roller 57 of panel B will rest on the associated rail 24 as is clearly shown in FIG. 13, when in closed position the bars 29 will rest on the rails 24 to take the load off the shafts of the rollers 57.

Although the panels A, B and C, D may be moved in any suitable manner from the closed position shown in FIG. 1 in which they lie in side by side relationship in a horizontal plane, to the open position shown in FIG. 9 in which they extend parallel to each other in a vertical 4 plane, in the embodiment shown in FIGS. 1 to 14, hydraulic means are preferably employed which may be of the type shown in reissue No. 24,238 dated November 13, 1956.

To this end, referring to FIG. 2, a reaction member, preferably a plate 71, is provided which may be substantially triangular in shape and has an

opening

72, 73, 74 at each of its corners and is desirably positioned in a vertical plane with a pin 75 which defines the axis of hinge 36 extending freely through the bottom opening 74.

Reacting against each of the plates 71 is a pair of opposed

hydraulic units

77, 78 mounted respectively in panels A, B and C, D. The rear ends of each of the

units

77, 78 is preferably piv-otally mounted as at 79 to an associated beam 81. The outer ends of the reciprocable plungers 82, 83 of the

units

77, 78 respectively are pivotally connected to `an associated reaction plate 7l by means of pins extending through the outer ends of the plunger and the

openings

72, 73 respectively. The

hydraulic units

77, 78 are illustratively of the double acting type and each has a

control port

86, 87 at its respective end on each side of the piston (not shown) slidably mounted thereon.

It is to be noted as diagrammatically shown in FIG. 3, for example, and also in FIG. 2, that when the panels are in closed horizontal position over the hatchway, lines drawn between pivot 32, hinge 36 and axle of the roller 57 will form a triangle having its base line uppermost and its vertex, which illustratively defines an obtuse angle pointed downwardly. In addition, the hinge 36 will be below the base line of the triangle above described.

To open the hatchway, suitable valves controlling a source of fluid under pressure may be actuated so that such tluid under pressure will beapplied to the ports 87 of the

hydraulic units

77, 78 of panels A, B in the first instance in direction to move the pistons thereof toward each other. As a result, an upward component of force will be exerted against the hinge pin 7 S and the two panels A, B will move upwardly from their normal horizontal position.

As the panel A is pivotally mounted as at 32 in fixed position with respect to the deck of the ship, the initial upward movement of the panels will cause the hinge 36 to rise in an arcuate path as shown in FIG. 3 and at first such hinge will move to the right away from the pivot connection 32, and such movement will cause the panel B to move slightly lto the right. Without the presence of the pivoted link 41, this movement would be transmitted to the panels C and D causing them to move to the right also and consequently, the edge 67 of the panel D would jam against the adjacent edge 88 of the hatch opening in the deck, causing injury or damage to both the edge of the deck and the adjacent edge 67 of the panel D. In addition, due to the restriction of movement of panel D, the pair of panels C, D would tend to fold and this could cause the rollers thereof to be dislodged from the tracks 24. These problems are eliminated by the presence of the slotted links 41.

Thus, referring to FIGS. 3, 4 and 11, for example, as the panel A starts its initial folding movement and the panel B is moved slightly to the right, by reason of the slot 49 in link 41, the pin 47 will be free to move to the right without imparting any movement to the panels C and D. The spacing between the adjacent edges 46, 46' of panels B and C is sufficient to permit the necessary movement of the panel B without causing abutment of the

edges

46, 46 and of course the slot 49 is of length sufiicient to accommodate such movement. When the panels: A and B have been pivoted upwardly a slight amount, the: hinge 36 will rise in an .arcuate path away from the pivot: connection 32 until it is aligned with the base line of the triangle as shown in FIG. 4. From this point on with continued folding movement of the panels A. and B, the hinge 36 will continue its arcuate path, but now '[.QWJJdl the hinge point 32 as shown in FIG. 5.

As the panels A and B are folded from the position shown in FIGS. 3 and 6 to the position shown in FIGS. 5 and 8, for example, the stop pin 55 which is iixed with respect to the panel B, will also move in an arcuate path from its position beneath the link 41 as shown in FIG. 3 to a position where it is immediately in front (to the left) of the link and abutting there against as shown in FIG. 5. Similarly, at the position shown in FIGS. 4 and 7, the panel B will have reached its maximum position of movement to the right so that the pivot pin 47 will be at the right end of the slot 49 in the link 41 and when it has reached the position shown in FIGS. 5 and 8, i.e., when the panel B has gone past the position shown in FIGS. 4 and 7, the pin 47 will be at the left end of the slot 49.

At this time with further folding movement of the panel-s A and YB, the force exerted by the pins 47 on the ends of link 41 will move panels C and D, which are still in horizontal position, to the left. This will cause the rollers `63, 57 of panels C and D to ride out of the associated

depressions

68, 69.

When the rollers of panels C and D reach the top of the sloped side of the depressions, the force required to move the panels C and D will immediately be greatly reduced. Due ot the force exerted on panels C and D through the link connection to panel B, the panels C and D would tend to move to the left taking up the lost motion in the slot and jar and possibly damage the panels.

However, by reason of the fact that when the rollers of panels C and D rise out of

Athe depressions

68, 69 and are free, the stop pin 55 will be, at this time, in front of and against the associated link 41 so that the link will be -restrained from movement, consequently, even though the force required to move the panels C and D is reduced, there will be no sudden movement of such panels to the left.

With continued -force applied to the panels A and B through

actuators

77, 78, the panels A and B will reach their booked or completely folded position. When panels A and B reach their booked position, panels C and D are still in the horizontal position, and due to momentum, panels C and D tend to continue moving toward panels A and B. Without stop pin 55 being present, when panels A and B were stopped, panels C and D could continue movement until all of the slack in slot 49, of link 41 were taken up. In this position, were panels C and D being booked, the edge 46 of panel C would gouge into and damage the upper surface of panel B as well as interfere with the booking of panels C and D. However, stop pin 55 prevents the slack in slot 49 from being taken up since pin 55 engages link 41 and limits the movement of panels C and D to keep the necessary spacing between panels B and C so that there will be clearance between these panels to allow booking of panels C and D without interference and without damage to any of the panels. At the time panels A and B reach their booked or completely folded position, valves are actuated so that the hydraulic actuation of panels C and D will be energized. Thus, the panels C and D will start to yfold to closed position until all four panels are fully folded at the left end of the hatchway as is shown in IFIG. 9.

It is to be noted that the

rollers

57, 63 as well as the rollers 57 are of such dimensions that their edges extend slightly beyond the edges of the associated panel to permit the requisite folding action so that the lower edges of the skirt plates will be moved clear of the rails on which they ride.

If desired, the panels may be moved to open position by means of the reeving arrangement shown in FIG. and the hydraulic actuators may be eliminated. To this end, a cable 91 is provided which is operatively driven by the Winch of a ship. The cable 91 extends around a pulley 92 and then around a pulley 93 connected to a lift pad 94 pivotally mounted on panel A. The cable 91 after passing around pulley 93 is then passed around a pulley 95 located adjacent pulley 92 and connected at its free end to a lift tab 96 pivotally connected to panel C. When the winch is energized, since the force acting on panel A is twice that acting on panel C, the panels A and B will first be folded before panels C and D are folded.

Pin 51 is also important in the FIG. l5 arrangement. In this arrangement, since a continuous external force is exerted on panel C through tab 96 tending to move panels C and D toward panels A and B immediately upon removal of the rollers from their recesses panels C and D would move quickly toward panels A and B, taking up the lost motion in the slot, and knock into panel B with great force with possible derailment of the rollers, were pin 51 not present. In addition, pin 51 is effective in preventing interference with the booking of panels C and D and damage to the panels after panels A and B are stopped in the completely booked position.

With the constructions above described, there is no need to have the pivotal connection 32 of the panel A at a suiiicient depth below the level of the deck so that with initial folding movement, the hinge connection 36 will immediately move to the left rather than to the right. Such arrangement is undesirable as it would require that the thickness of the panels be increased thereby requiring not only a relatively deep opening to accommodate the pivotal connection 32, but the space between the edge of the panel A and the connection 32 would also have to be increased resulting in a gap of excessive width in the deck.

In addition, with such a thicker panel, when the panels are pivoted to vertical position since there would be considerable Weight on each side of the pivotal connection 32, the vertical panels could tilt forwardly over the hinge connection thereby disabling the hatch cover assembly.

With the slotted hinge arrangement herein described the hinge connection can be located adjacent the deck level thereby avoiding the problems above noted.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A cover assembly for a hatchway in the deck of a ship, comprising a pair of panels, adapted to extend over said hatchway, said panels lying in side by side relation in substantially a horizontal plane when in closed position, means pivotally mounting an edge of one of said panels, said pivotal mount being located at one end of the hatchway, means pivotally connecting the adjacent edges of said panels for folding movement thereof between closed and open position, a roller mounted on said other panel at each end of the opposite edge of the other panel, a track positioned on each side of the hatchway on which said rollers ride to guide the opposite edge of the other of said panels in substantially a horizontal plane, additional panel means adapted to lie in side by side relation with said pair of panels when in closed position over the hatchway, all of said panels when in closed position having their outer peripheries adjacent the periphery of the hatch opening in the deck, means pivotally connecting said additional panel means to the adjacent panel of said pair, said connecting means comprising a link having an elongated opening at one end and a substantially circular opening at the other, a pair of pivot pins fixed with respect to and carried respectively by said additional panel means and said adjacent panel, and extending respectively through said circular opening and said elongated opening, said elongated opening defining a lost motion slot to permit a predetermined movement of said pair of panels independently of said .additional panel means, said pivotal connection between adjacent edges of said pair of panels lying below a plane extending between said pivotal mount and the centers of said rollers when said panels are in closed position, and a rigid stop member carried by said adjacent panel and extending outwardly thereof beneath and in juxtaposition to said link when said panels are in horizontal position, said stop member being clear of said link when the pair of panels are in substantially horizontal position and being moved in alignment with said link and adjacent the end thereof having an elongated opening for abutment of such end thereagainst to restrain relative movement between the link and the pin extending through such elongated opening after said pair of panels have folded toward each other by an amount such that the pivotal connection between the adjacent edges of said pair of panels lies above a plane extending between said pivotal mount and the centers of said rollers.

2. The combination set forth in claim 1 in which said additional panel means comprises a second pair of panels, means pivotally connecting adjacent edges of said second pair of panels, a roller at each end of the edge of the panel of said second pair pivotally connected to the iirst pair of panels, and a -roller at each end of the edge of the other panel of said second pair adjacent the other end of the hatchway, said rollers of said second pair of panels riding on said tracks, each of said tracks having a depression in which said rollers of said second pair of panels are positioned when said two pairs of panels are in closed horizontal position over said hatchway, and means to support said panels with the peripheries of said rollers of said second pair spaced from the Walls of said depressions when said two pairs of panels are in closed horizontal position.

References Cited by the Examiner UNITED STATES PATENTS 2,484,286 10/49 Groppell 160l88 X 2,770,297 ll/ 56 Mercier et al. 160-188 2,943,675 7/60 Ford 1GO-4206 3,043,257 7/ 62 Appleton et al 114-202 3,114,346 12/63 Dahlin 160-188 XR FOREIGN PATENTS 168,626 9/59 Sweden.

HARRISON R. MOSELEY, Primary Examz'ner.

Claims

1. A COVER ASSEMBLY FOR A HATCHWAY IN THE DECK OF A SHIP, COMPRISING A PAIR OF PANELS, ADAPTED TO EXTEND OVER SAID HATCHWAY, SAID PANELS LYING IN SIDE BY SIDE RELATION IN SUBSTANTIALLY A HORIZONTAL PLANE WHEN IN CLOSED POSITION, MEANS PIVOTALLY MOUNTING AN EDGE OF ONE OF SAI PANELS, SAID PIVOTAL MOUNT BEING LOCATED AT ONE END OF THE HATCHWAY, MEANS PIVOTALLY CONNECTING THE ADJACENT EDGES OF SAID PANELS FOR FOLDING MOVEMENT THEREOF BETWEEN CLOSED AND OPEN POSITION, A ROLLER MOUNTED ON SAID OTHER PANEL AT EACH END OF THE OPPOSITE EDGE OF THE OTHER PANEL, A TRACK POSITIONED ON EACH SIDE OF THE HATCHWAY ON WHICH SAID ROLLERS RIDE TO GUIDE THE OPPOSITE EDGE OF THE OTHER OF SAID PANELS IN SUBSTANTIALLY A HORIZONTAL PLANE, ADDITIONAL PANEL MEANS ADAPTED TO LIE IN SIDE BY SIDE RELATION WITH SAID PAIR OF PANELS WHEN IN CLOSED POSITION OVER THE HATCHWAY, ALL OF SAID PANELS WHEN IN CLOSED POSITION HAVING THEIR OUTER PERIPHERIES ADJACENT THE PERIPHERY OF THE HATCH OPENING IN THE DECK, MEANS PIVOTALLY CONNECTING SAID ADDITIONAL PANEL MEANS TO THE ADJACENT PANEL OF SAID PAIR, SAID CONNECTING MEANS COMPRISING A LINK HAVING AN ELONGATED OPENING AT ONE END AND A SUBSTANTIALLY CIRCULAR OPENING AT THE OTHER, A PAIR OF PIVOT PINS FIXED WITH RESPECT TO AND CARRIED RESPECTIVELY BY SAID ADDITIONAL PANEL MEANS AND SAID ADJACENT PANEL, AND EXTENDING RESPECTIVELY THROUGH SAID CIRCULAR OPENING AND SAID ELONGATED OPENING, SID ELONGATED OPENING DEFINING A LOST MOTION SLOT TO PERMIT A PREDETERMINED MOVEMENT OF SAID PAIR OF PANELS INDEPENDENTLY OF SAID ADDITIONAL PANEL MEANS, SAID PIVOTAL CONNECTION BETWEEN ADJACENT EDGES OF SAID PAIR OF PANELS LYING BELOW A PLANE EXTENDING BETWEEN SAID PIVOTAL MOUNT AND THE CENTERS OF SAID ROLLERS WHEN SAID PANELS ARE IN CLOSED POSITION, AND A RIGID STOP MEMBER CARRIED BY SAID ADJACENT PANEL AND EXTENDING OUTWARDLY THEREOF BENEATH AND IN JUXTAPOSITION TO SAID LINK WHEN SAID PANELS ARE IN HORIZONTAL POSITION, SAID STOP MEMBER BEING CLEAR OF SAID LINK WHEN THE PAIR OF PANELS ARE IN SUBSTANTIALLY HORIZONTAL POSITION AND BEING MOVED IN ALIGNMENT WITH SAID LINK AND ADJACENT THE END THEREOF HAVING AN ELONGATED OPENING FOR ABUTMENT OF SUCH END THEREAGAINST TO RESTRAIN RELATIVE MOVEMENT BETWEEN THE LINK AND THE PIN EXTENDING THROUGH SUCH ELONGATED OPENING AFTER SAID PAIR OF PANELS HAVE FOLDED TOWARD EACH OTHER BY AN AMOUNT SUCH THAT THE PIVOTAL CONNECTION BETWEEN THE ADJACENT EDGES OF SAID PAIR OF PANELS LIES ABOVE A PLANE EXTENDING BETWEEN SAID PIVOTAL MOUNT AND THE CENTERS OF SAID ROLLERS.