US3610058A - Extensible foldable manipulator - Google Patents

Abstract

A MANIPULATOR FOR EXTENDING A TOOL, PERSON OR OTHER LOAD OUT FROM A BASE IN A CONTROLLED DIRECTION AND TO A CONTROLLED EXTENT, COMPRISING ELONGATED SPACERS AND A MULTIPLE-LEVER CONNECTOR, OPPOSITELY HINGEABLE, BETWEEN EACH PAIR OF THE SPACERS. EACH VARYING-ANGLE CONNECTOR HAS A CONTROLLED MOTOR AND AN INTERACTING SYSTEM OF LEVERS, THE OUTERMOT EXTENT OF WHICH FALLS WITHIN A CIRCLE OF APPROXIMATELY THE SAME SIZE AS THE MAXIMUM DIAMETER OF THE SPACERS. OPTIONALLY, THE LEVERS MAY BE OF THE BELLCRANK TYPE OR THEY MAY HAVE SEGMENTAL GEARS AT THEIE ENDS. EACH LINK OF THE MANIPULATOR MAY BE SEPARATELY ANGLED BY ITS CONNECTOR IN EITHER OF TWO OPPOSITE DIRECTIONS AND THEN LOCKED IN ITS ADJUSTED POSITION. IN FOLDING THE MANIPULATOR FOR STORAGE EACH ADJOINING PAIR OF THE LINKS ARE COMPACTLY FOLDED IN OPPOSITE DIRECTIONS.

Description

Oct. 5, 1971 MUELLER ETAL 3,610,058

EXTENS IBLE FOLDABLE MAN IPULATOR Filed July 14, 1969 7 Sheets-Sheet 2 FIG. 2

L V i 7 A Omit/MW) IIIHHWJJJJLL IIIIMIIIII FIG. 3

FRITZ K. MUELLER,

ROBERT C. MARTIN,

AND,

J. ROLAND LOYD,

INVENTORSI AT TORNEY.

Oct. 5, 1971 MUELLER ETAL 3,610,058

EXTENSIBLE FOLDABLE MANIPULATOR 7 Sheets-Sheet 5 Filed July 14, 1969 R E D L Y L 0 E L U M .D TA Z N 0 W8 R o CIR IU INVENTORS,

FIG. 5

ATTORNEY Oct. 5, 1971 MUELLER ETAL 3,610,058

EXTENSIBLE FOLDABLE MANIPULATOR Filed July 14, 1969 7 Sheets-Sheet I.

' FRITZ K. MUELLER, ROBERT c. MARTIN,

AND,

J. ROLAND LOYD,

INVENTORS,

ATTORNEY.

INPUT ANGLE Oct. 5, 1971 F. K. MUELLER r-rr AL 3,610,058

EXTENSIBLE FOLDABLE MANIPULATOR Filed July 14 1969 O 20 4O 6O 80 FIG. 9

7 Sheets-Sheet 8 I 0 UT PUT ANGLE I I I I 200 FRITZ K. MUE LLER,

ROBERT C. MARTIN,

AND Jv ROLAND LOYD,

INVENTORE,

ATTORNEY,

Oct. 5, 1971 MUELLER ETAL 3,610,058

EXTENS IBLE FOLDABLE MAN IPULATOR Filed July 14 1969 v 7 Sheets-Sheet 7 FRITZ K. MUELLER,

FIG. l2 ROBERT c. MARTIN,

AND J.ROLAND LOYD,

INVENTORS,

BY M M ia p2.

TTORNEY.

United States Patent 01 Patented Oct. 5, 1971 ice 3,610,058 EXTENSIBLE FOLDABLE MANIPULATOR Fritz Kurt Mueller, Robert Cherry Martin, and John Roland Loyd Ill, Huntsville, Ala, assignors to Astra-Space Laboratories, Inc., Huntsville, Ala.

Filed July 14, 1969, Ser. No. 841,324 Int. Cl. F16h 27/02; B0511 US. Cl. 74--89.17 8 Claims ABSTRACT OF THE DISCLOSURE A manipulator for extending a tool, person or other load out from a base in a controlled direction and to a controlled extent, comprising elongated spacers and a multiple-lever connector, oppositely hingeable, between each pair of the spacers. Each varying-angle connector has a controlled motor and an interacting system of levers, the outermost extent of which falls within a circle of approximately the same size as the maximum diameter of the spacers. Optionally, the levers may be of the bellcrank type or they may have segmental gears at their ends. Each link of the manipulator may be separately angled by its connector in either of two opposite directions and then locked in its adjusted position. In folding the manipulator for storage each adjoining pair of the links are compactly folded in opposite directions.

In maneuvers outside or on the interior of space vehicles or submarines and in rescue of persons from upper floors of buildings on fire and from other high places such as mountain peaks and damaged towers, there is a need for an efiicient extensible carrier or manipulator, controllable from its base or tip, having straight spacers with jointed connectors that may be controllably operated either to extend the spacers into a variety of manipulator shapes and positions, or to fold them into a compact mass on or near the vehicle or other base. The most compact mass of their folded position and the largest variety of their extended positions in a plane are achieved when the connecting means between each pair of the straight spacers permits the pair to be folded from a fully extended, straight-line position thru various angles up to 180 degrees, in each of two opposite directions, and also permits separate motor-control of each connector so that its pair of spacers may be extended or folded thru angles that vary from the angles between other pairs of spacers. With such [flexibility of the connectors: (1) the spacers may be folded in the manner of compacting the sections of a common carpenters rule, with one pair of the spacers folded in one direction against each other and the next spacer of the series to be folded against that pair in the opposite direction; and (2) a support for a tool, person or other load at the outer tip of the connected spacers may be moved to any desired position.

'In view of these facts, an object of this invention is to provide an extensible and foldable manipulator having: a plurality of elongated spacers; a connector between each pair of spacers comprising a plurality of pivoted levers (optionally having geared ends) that are hinged for angular motion in each of two opposite directions; a motor; means, connecting the motor and an adjacent pivoted lever and connecting the said adjacent lever to other levers, for adding the angles of motion of the several members into the angle of movement between the pair of spacers; and means for separately controlling and locking the motors.

Another purpose is to devise a mechanical movement having a pair of hinged elements, and a connector between them that comprises: a motor on one of the said elements and means to control said motor; a linearly arranged series of pivoted members between the elements, each pair of these members being mounted for pivoted movement in each of two opposite directions; means connecting the motor and an adjacent pivoted member for hinging the adjacent member thru a predetermined angle; means connecting the said adjacent member to a second pivoted member of the series for hinging it thru a pre determined angle; means connecting the said second memher to a third member of the series for pivoting it thru a predetermined angle that is equal to the sum of the first-mentioned angles; and means connecting the said third member to a second one of the said pair of hinged elements, for pivoting it thru a predetermined angle that is equal to the sum of all said predetermined angles. Optionally, there may be any number of the said pivoted members as parts of the connector between thepair of hinged elements.

A further objective of the invention is to provide such a mechanical movement having the said pair of hinged elements and also having at least one other, a third, hinged element, connected to the said second hinged element by a second series of the pivoted members; whereby the second hinged element may be compactly folded against the first one in one direction and the third hinged element may be compactly folded against the second element in the opposite direction.

These and other objectives of the invention will become more fully apparent from the following detailed description and the accompanying drawings.

FIG. 1 is a side view, partly broken away and in section from a plane thru the axis of hinged spacers, showing a pair of the spacers as having been compactly folded against each other by the motor and the geared levers of the connectors that are between the spacers.

FIG. 2 is a side view, partly broken away, of a pair of the spacers, connected by geared levers with the axes of the spacers in a straight line; in this figure the tubular spacers and the bellows 30 are shown as cut in halves along a vertical plane to expose the connector levers in elevation.

FIG. 3 is a bottom view from the plane 3-3 of FIG. 2, partly broken away and with the bellows removed, of the spacers and pivoted connecting members of FIG. 2.

FIG. 4 is a side view, partly in section and partly broken away, of a plurality of spacers and pivoted spacer connecting members that comprise bellcrank levers, with the second spacer of the set shown as having been angled clockwise degrees by motor and bellcrank levers from its position in alignment with the base spacer 50, and with the third spacer shown as having been folded 180 degrees in the opposite, counterclockwise direction.

FIG. 5 is a top plan view, partly broken away, showing a pair of spacers with their axes in a straight line, hinged by the bellcrank-lever type of connectors.

FIG. 6 is a side view of the bellcrank-lever form of link shown in FIG. 5, showing a pair of spacers as having aligned axes.

FIG. 7 is a side view of the link, with the bellows in place, showing the right-hand spacer to have been moved by the link motor 30 degrees in a clockwise direction from its position in FIG. 6. In this figure the bellows and one of the spacers are shown as cut in halves along a vertical plane.

FIG. 8 is a side view of the link, with sectioning similar to that of FIG. 6, showing the right-hand spacer as moved 60 degrees in a counter-clockwise direction from its position in FIG. 6.

FIG. 9 is a graph showing curves for the clockwise and counter-clockwise movement of the spacers in a link having the bellcrank-lever type of connector.

FIG. 10 is a block diagram, indicating the electrical control system of the invention.

FIG. 11 is a block diagram, indicating the link-motor control panel.

FIG. 12 is a side view of the invention shown as in a firefighting apparatus in use at a fire, with parts of a building and truck shown as broken away.

Hereafter in this spacification the term link is used to refer to the combination of connected parts of two of the tubular spacers of the manipulator and a connector, comprising levers, between the spacers.

Basically, the manipulator comprises: a plurality of movable connected pairs of spacers; a connector having at least three angularly movable elements (shown as gears in FIGS. 1 to 3, and as levers in FIGS. 4 to 8); a linkdriving, reversible motor (shown at 1 in FIG. 1 and at 32 in FIG. 4); a link-holding brake, shown as electro-magnetic in FIG. 4 at 34; a relatively fixed support at a base of operationsfor example, the wall 3 of FIG. 4; means for attaching the innermost or base link to the relatively fixed support (which may provide controllable angular motion and locking of the base spacer at the support or it may be a stationary fastening means, for example, the bolts of FIG. 4); and a power supply and control means, as indicated in FIG. 10.

In FIGS. 1 to 3, the controllable motor 1, turns the elongated nut 4 (fixed to a shaft, 5, shown in FIG. 1) which helically reciprocates on the screw 6 and thus advances or retracts the rack 7. This rack is fastened to the screw by the pin 8, and moves between the closely fitting sides of a groove in the slide bearing 9.

The rack rotates the pinion 10 which is mounted on axle 11, and this pinion turns the gear segment 12A. This segment is at one end of the double-geared lever 12; and at its other end the gear segment 12B is located. This segment 12B, together with the central part 12C, rotates about the axle 14, which, like the motor 1, is fixed to the tubular spacer 16. Also fixed to the spacer there is a segmental gear, 18, that meshes with the gear segment A of the single-geared lever 20.

The floating axle 22 pivots with the lever 12 about the fixed axle 14 and forces the gear 20A (mounted on the floating axle) to rotate clockwise (as shown in FIG. 1) about the fixed gear 18. The lever 20 forces the axle 24 to pivot about the axle 22; and on this axle the segmental gear 26 is rotated. Since it is fixed to the second tubular spacer 28 of the link and is in mesh with the gear segment 12B, it pivots the spacer 28 about the axle 24, which is fixed to this spacer.

This multiple-lever type of connector between the spacers permits a plurality of the manipulator links to be compactly folded, thru 180 degrees, alternately in opposite directions, as indicated in FIG. 4. This folding is possible because of the structure of the linkage, eliminating jamming together of the spacer ends before they are folded thru the desired 180-degree angle. This invented structure also permits use of a foldable bellows that has a cross-sectional circle of approximately the maximum diameter of the spacers. The length of each pair of spacers is determined by the specific use of the manipulator and the power of the link motor between the spacers. All of the various spacers may have the same length; or they may have varying lengths. Their lengths and numbers are de termined by the maximum desired reach of the outer tip of the manipulator.

For clarity and convenience of illustration no bellows is shown in FIGS. 1, 3 to 6, and 8. But optionally and preferably a waterproof bellows of the type shown at 30 in FIGS. 2 and 7 is used to flexibly protect each of the illustrated connectors. In some specific uses-for example in space or under watersuch a bellows is especially desirable. It may be made of stainless steel, Phosphor bronze or other resilient metal, rubber or other resilient plastic, or fabric that is impregnated and coated with resilient plastic.

A bellows having a maximum diameter that is only slightly larger than that of the tubular spacers is used. This small diameter, permitting the desired compact folding of the manipulator when it is storedfor example in a small auxiliary housing or other space adjacent to the wall of a vehicle, is made possible by the fact that the levers of the invented connector are sufficiently short and numerous for their ends, in all the pivotal positions of the levers, to lie within a circle that has a diameter equal to or only slightly exceeding that of the tubular spacers. When this circle of the levers ends slightly exceeds that of the spacers, small metallic shoes optionally may be placed on each of the lever ends that lie within the bellows-in positions that prevent hanging of the bellows on the segmental gears.

Optionally also-and especially for underwater usethe bellows may be filled with compressed air.

An alternative and currently preferred form of the connector between spacers, shown in FIGS. 4 to 8, has bellcrank levers instead of the geared levers of FIGS. 1 to 3. Three connectors of this bellcrank-lever type are illustrated in FIG. 4 as connecting tubular spacers that have been compactly folded, alternately in opposite directions, 180 degrees from their position in which the axes of the spacers are in a straight line.

In this figure, the reversible motor 32, the reduction gear 33 and the controllable magnetic brake 34 (which holds the link in any adjusted position) are similar to the motor, gear and brake of the structure indicated in FIGS. 1 to 3. The motor 32 rotates the screwthreaded shaft 36; and this screw reciprocates the nut 38. In the compactly folded position of the manipulator as shown in FIG. 4 this nut has reached the right-hand limit of its travel; and since the push-pull bars 40 are pivoted on the nut at 42 and on the bellcrank lever 44 at 46, the nut has forced lever 44 to the limit of its clockwise pivoting about its pivot bearing. This bearing has an axle 48 that is fixed at each end to the tubular spacer 50.

The lever 44 comprises a pair of spaced, parallel, similarly shaped elements that are held properly spaced apart *by the axle 46 and bars 40. Each of these elements comprises: a central portion 44A; a motorward, bellcrank portion 44B; and a second bellcrank portion 44C.

FIG. 6 shows two of the spacers, 50 and 52, and a connector between them, in position in which the axes of the spacers are in a straight line; and FIG. 7 shows the same set of spacers and connector with spacer 52 having angularly moved in clockwise direction 30 degrees from its position of FIG. 6. In this motion the plane containing the axes of 46 and 48 has moved thru 4.6 degrees from its vertical position, shown in FIG. 6, to its position in FIG. 7. As shown in FIG. 7, this pivotal angle has been amplified into the angle of 30 degrees between the axes of the spacers. This amplification is made possible, within the desired small compass of the spacers, by the invented bellcrank-lever system.

As the bellcrank lever 44 pivots clockwise it moves the axle 54 downward, together with a portion of the bellcrank lever 56. This lever is forced to pivot on the axle 54 because its left-hand bellcrank arm 56A is pivoted with respect to the push-pull bar 58, and this bar is pivoted on the fixed axis at 60 with respect to the spacer 50.

The bellcrank lever 56 has a middle part 56B, having a lever arm of axis extending between axle 54 and an axle, 62, that is connected to lever 56. In its pivoting, this line between 54 and 62 moves thru a greater angle with respect to the original horizontal plane containing the aligned axes of spacers 50 and 52 (as shown in FIG. 6) than the angle moved by the line between axles 48 and 54 with respect to the said original horizontal plane. This amplification of angle is due to the following functions of an interacting system of the levers, axles and pushpull bars: the axle 54, as shown in FIGS. 6 and 7, is forced by lever 44 to move clockwise and to the left in reaching its lower position. This leftward motion causes the angle between the axes of elements 56A and 58 in FIG. 7 to be less than it was in FIG. 6. In consequence, the axle 64 is moved clockwise and the axis line hetween axles 54 and 62 is moved clockwise, increasing its angle with the horizontal plane. This amplification of angle is in addition to the increase in this angle that is due to the pivoting of the lever 44 about 48.

The axle 62 is the fulcrum of a third bellcrank lever, 66. In FIG. 7 this fulcrum has moved clockwise and downward a greater distance from its position in FIG. 6 than the distance thru which axle 54 has moved from its position in FIG. 6. This amplification of distance is due to the difference in the lengths of the arms of lever 56. Because of this lowering or advancement of axle 62 the line between it and the axle 65 on the third bellcrank lever 66 (also pivoting clockwise about its axison axle 62) begins its pivotal movement at a considerably lower or further advanced position than the axle 54.

Due to the fact that the angle between the line 54-62 and the horizontal plane is greater than that between 48-54 and the horizontal and the further fact that the axle 68 is res-trained by its attachment to lever 44 at 70, the angle between the line 62-65 and the horizontal is still greater than the similar angle made by the line 54-62.

In like manner, the angle made with the horizontal by the axis of the tubular spacer 52 is amplified with respect to the angle made by the line 62-65. This output angle of the second spacer 52 is shown as degrees in FIG. 7, whereas the input angle between the line 46-48 and a vertical plane in a preferred engineering design is only 4.6 degrees.

Similar progressive increases of angular movement in the geared-lever structure of FIGS. 1 to 3 are also made; but in this form of the invention each of these increases is the same as every other. Whereas, in the preferred, bellcranklever invention form of FIGS. 4 to 8, the progressive increases are not exactly equal. In the preferred design of this form three bellcrank levers are used in the connector and their lengths are such that the said increases in angle occur according to the graph of FIG. 9.

An important result of the invention is the operators ability to pivot a selected link in either clockwise or counterclockwise direction thru any angle (up to the 180- degree angle used in folding the manipulator), and to hold that link in its adjusted position. This pivoting in either of two opposite directions is achieved with either the geared-lever or the bellcrank-lever inventive form. In the bellcrank-lever form the increases of angle in the steps of the angle-adjusting motions of the connector are the same in either clockwise or counterclockwise direction, but in the preferred, bellcrank-lever form there is a small difference in the above-described amplification of angles in the two opposite directions. This difference is indicated in the curves of the graph of FIG. 9.

According to this graph, and as indicated in FIG. 8, in the preferred design a counterclockwise input angle of 10.3 degrees achieves a resultant counterclockwise output angle of degrees between the axes of the two connected spacers. The principles involved in the motions of the connector parts of FIG. 8 are the same as those described above in connection with FIG. 7.

After a link has been moved into its desired angular position the reversible motor is stopped and the link is locked in position by the automatic or operator-controlled magnetic brake 34. In the usual operation of the manipulator the angles of the lower links are first adjusted to provide for its extension out from its base until its tip (carrying a tool, a hose, a housing, a person or the like) is near its desired final location, and then the tip link (or pair of outer links) is actuated until the tip is in its proper position.

After a particular operation is finished the manipulator is folded in the manner indicated in FIG. 1 or FIG. 4. In FIG. 4, the base spacer 50 of the manipulator is shown as fixed to the wall 3, but (as indicated in FIG. 12), it optionally may be pivotally and lockably mounted on the wall. This element 3 optionally may be an outer wall of a vehicle, a housing on a vehicle, or a platform. In folding the manipulator against element 3: the tubular spacer 52 has been folded degrees in one direction; the tubular spacer 74 has been folded 180 degrees in the opposite direction; and a fourth spacer (not shown) has been folded (by its connector which is shown as partly broken away) 180 degrees in the same direction as was the spacer 52.

This folding operation may be begun at or near the tip of the manipulator or at its base. If a person or spillable liquid or an unfastened device is supported by the tip the tip link is preferably the last to be folded.

ELECTRICAL CONTROL SYSTEM Base-power console The base-power console, located at the support of the manipulator, is shown schematically at 76 in FIG. 10. It is on the vehicle or other base of operations, provides for the input power connection, which, for example, may be of 28 volts DC. It also contains the on-off power switch, circuitry for protection against overloads and short circuits, the voltage amplifier for the actuator motors, and a power supply for the operators proportional control of the voltage amplifier input. This console is connected to the base of the manipulator by an electrical cable.

Link motive power Basically, the motive power of the connector between each pair of the spacers comprises a driving motor and a locking brake; and optionally it may also comprise the switches to limit the motion of mechanical parts of the connector by control of the motor.

The driving motor, energized by current from the amplifier in the base console, is under the command of an operator who optionally may be at the console, or the base-attachment link, or outer, tip link. This motor is preferably a DC. torquer, which exhibits linear speedtorque characteristics, provides torque at low speeds, and can be indefinitely stalled without damage.

The brake for each of the connectors iselectromagnetic. It is on the same shaft as the motor and is used to lock a link of the manipulator when angular motion of this particular link is not desired. It thus holds the link so that its pair of spacers are at any angle desired by the operator. The other link-angle controls-namely, the optional mechanical stop and the limit switches-limit extreme travel of the connector. Preferably the brake is automatically actuated when the motor is stopped.

OPERATOR-CONTROL CONSOLE The operator-control console, which is in a separate box, may be plugged in and mechanically mounted at either end of the manipulator, or it may be attached to some suitable holder on the operator, such as a belt or bracket.

As indicated in detail in FIG. 11, the console has a control switch on each link; it allows the operator to select the link to be operated and the direction of its angular motion. The switch lever for a particular linkfor example, 78, may be pivoted up, toward the plus sign, to provide motion of the outer spacer of the link in one direction, or down, toward the minus sign, to provide motion of this spacer in the opposite direction. At about the same time the operator controls the speed of the link motor by the potentiometer 80. This potentiometer determines the output voltage of the amplifier.

The operator-control box is sealed, for protection of the controls in underwater use or in rain, and all the controls are waterproofed by means of rubber boots, and are adapted for operation by an astronaut with space-suit gloves or a diver with diving-suit gloves. Optionally, a cable of any chosen length may be provided for connecting the box to the actuator.

The invented, compactly foldable and variously extendable device may be used in various applications-for example on space vehicles, satellites, submarines, and in firefighting. One example of these uses is shown in FIG. 12 as on a fire truck at a building of which an upper story is on fire. The motors of the connectors between spacers of the manipulator have been controllably actuated and locked until the tip spacer 82 is adjacent to the upper room in which the fire is located, with its point 84 close to the window, the frame of which is indicated at 86. The motor of the tip link then has been actuated to force the steel tip thru the window-breaking it if not openuntil, as indicated in FIG. 12, the point is sufficiently far in the room to spray and fill it with fireextinguishing chemicals. This spraying is controllably done by a pump on the truck, sending the chemicals thru the hose 88. This hose is attached to the sides of each spacer by the bands or loops 90; and at the hole 92 in the tip spacer the hose enters the hollow interior of the spacer, and so is flow-connected with the hollow, fluid-supplying point 84. After the firefighting operation is complete the manipulator is compactly and efiiciently folded, by means of the motors and the invented system of connector levers, on or into the rear part of the truck body.

Without departing from the principles of the invention various changes in the specific disclosed structures may be made. For example, in the straight-line position of the spacers shown in FIG. 6 all the axes of the axles 48, 54, 62 and '65 may be exactly aligned with the coinciding axes of the spacers 50 and 52, in the manner of the lever fulcrums in FIG. 2.

We claim:

1. An extensible, foldable device having at least one pair of spacers and connecting means between the spacers for controllably angling them in either of two opposite angular directions, said connecting means comprising:

a lever, 'mounted for pivotal movement on an end portion of a base spacer of said pair, having: a fulcrum at the axis of said pivotal movement; a connection, adjacent to said base spacer and spaced from said fulcrum, for application of turning force on one end portion of the lever in either of two opposite angular directions; and an axle at another portion of the lever, spaced farther from said fulcrum than said connection, for transmittal of force to a second lever;

a second lever, mounted for pivotal motion on the said axle and receiving force thru said axle, one of its end parts having a second fulcrum and means pivotally connecting this second fulcrum to said base spacer, and another of its parts having a second axle, spaced farther from the second fulcrum than said first-named axle, for transmittal of force to a third lever;

a third lever, pivotally mounted on the said second axle, one of its end portions having a third fulcrum and means pivotally connecting the third fulcrum to the said first-named lever, said third lever having means at another end portion, connected to a second one of said pair of spacers, for angling the said second spacer; and

means, connected to the said base spacer and to the said connection, for controllably pivoting said firstnamed lever and holding it in an adjusted position;

the said interacting levers being constructed and arranged to adjust and hold the said second spacer at an angle that is considerably greater than the adjusted angle between said first lever and the axis of said base spacer. 2. A device as set forth in claim 1, in which the lengths of said levers are such that all of their parts, in all of their angular positions, are within circles, each of which has an area approximately equal to the maximum crosssectional area within peripheries of said spacers; and in which the device comprises a bellows around said levers, sealably connected at each of its ends to adjacent ends of the pair of spacers.

3. A device as set forth in claim 1, in which said second and third fulcrums comprise portions of segmental gears, and in which the said connectionand two connecting means comprise gear portions.

4. A device as set forth in claim 1, in which said levers, axles, connection and connecting means are constructed and arranged to permit folding of said second spacer, in either of said two angular directions, with its axis pivoting thru 180 degrees with respect to the axis of said base spacer.

5. A device as set forth in claim 1, in which: said means for controllably pivoting said first-named lever is a motor; said levers are bellcrank levers; said connection comprises a bellcrank arm of said first-named lever, a push-pull bar, a pintle between said push-pull bar and said bellcrank arm, and means connecting said push-pull bar to said motor; and each of said connecting means comprises a push-pull bar and means pivoting it to a lever.

6. A device as set forth in claim 5, in which the lengths of said levers are such that all of their parts, in all of their angular positions are within circles, each of which has an area approximately equal to the maximum crosssectional area within peripheries of said spacers; and in which the device comprises a bellows, around the said levers, sealably connected at each of its ends to adjacent ends of the pair of spacers.

7. A device as set forth in claim 6, in which the ends of said levers that are adjacent to the inner surface corrugations of the said bellows are rounded.

8. A device as set forth in claim 4, having at least three of said spacers, in which the said second spacer is foldable in one angular direction with its axis at 180 degrees to the axis of said base spacer, and in which a third spacer is foldable in the opposite angular direction, with its axis at 180 degrees from the axis of said second spacer.

References Cited UNITED STATES PATENTS 617,884 l/l899 Poe 7489.17 681,890 9/1901 Snow 137-615 2,390,029 11/1945 Parsons 74-8917 3,199,553 8/1965 Garrett et al l41-388 3,228,421 1/1966 Sheiry 137-35516 3,266,059 8/1966 Stelle 285223 3,399,909 9/1968 Ambrose l37-615 2,414,774 1/ 1947 Spinks 248277 3,470,981 10/ 1969 Huxley III 248277 WILLIAM F. ODEA, Primary Examiner W. S. RATLIFF, JR., Assistant Examiner U.S. Cl. X.R.

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