US2998281A

US2998281A - Adjustable chair locking device

Info

Publication number: US2998281A
Application number: US741519A
Authority: US
Inventors: Stoner Arthur Merrick; Girard S Haviland
Original assignee: Jacobs Manufacturing Co
Current assignee: Jacobs Vehicle Systems Inc
Priority date: 1958-06-12
Filing date: 1958-06-12
Publication date: 1961-08-29
Anticipated expiration: 1978-08-29

Description

Aug. 29, 1961 Filed June 12, 1958 A. M. STONER ET AL 2,998,281

ADJUSTABLE CHAIR LOCKING DEVICE 3 Sheets-Sheet 1 HEIQHIZI w 11/ w ATTORNEY g- 1961 A. M. STONER ETAL ADJUSTABLE CHAIR LOCKING DEVICE 3 Sheets-Sheet 2 Filed June 12, 1958 ATTORNEY 0 m W M M m 6 Y B m M 57 d 0 c T/ w mM W W 4 T! 4% Q m t Aug. 29, 1961 A. M. STONER ETAL 2,998,281

ADJUSTABLE CHAIR LOCKING DEVICE Filed June 12, 1958 3 Sheets-Sheet 3 TLLCZJE. 37

INVENTO RS AIfK/dKMAI/CA ro/vze ATTORNEY IIAIIID'I/I United States Patent 2,998,281 ADJUSTABLE CHAIR LOCKING DEVICE Arthur Merrick Stoner, Madison, and Girard S. Haviland,

Wethers'field, Coun., assignors to The Jacobs Manufactoring Company, West Hartford, Conn., a corporation of New Jersey Filed June 12, 1958, Ser. No. 741,519 11 Claims. (Cl. 297-374) This invention relates to locking devices for adjustable structures and particularly for chair structures having a back rest adjustable to a plurality of selected inclined positions. Chairs of this type are commonly used in airplanes, trains and busses.

An object of the invention is the provision of a position adjusting mechanism adapted to release the back rest for movement toward a reclined or lowered position; or selectively to act as a positive lock against such reclining movement. The positive locking action is needed, for example, in a rearwardly facing airplane chair because in the event of a collision the entire decelerating force due to the weight of the passenger is absorbed by the back rest and consequently this force is transmitted through the adjusting mechanism.

Another object is to provide a locking device for a position adjusting mechanism as described, which develops an exceedingly high locking force when needed but which releases on application of a relatively light pressure or pull on a release handle, arranged to be moved only for a short stroke. In accordance with this object, the locking device as well as the disabling means therefor are designed to possess a high degree of mechanical efficiency or a minimum of friction.

A further object is the provision of a position adjusting mechanism of the character described having means for positively locking the mechanism against movement in one direction and for yieldingly locking it against movement in the opposite direction.

A feature of this invention is a yieldable locking device arranged to hold the back rest in adjusted position with a braking force which is sufiicient to inhibit the action of a spring tending to raise the back rest but which is overcome by the application of a slight manual pressure added to the force of the spring. With this arrangement, the stewardess or any passenger may raise the seat without releasing the yieldable locking device. Alternatively, the occupant of the chair may release the lock completely to permit the spring to raise the back rest without the application of manual pressure.

A still further object is the provision of a back rest adjusting mechanism which is smooth in operation, free from jerkiness and adapted to be fixed selectively in any intermediate position.

Still another object is the provision of a locking device for a position adjusting mechanism which is reliable in operation, simple in construction, inexpensive to manufacture, and which avoids excessive wear or breakage of moving parts. I

Other objects and features of this invention will appear from the description which follows.

In the accompanying drawings which illustrate one embodiment of this invention:

FIG. 1 is a side view of the structural parts of an airplane chair incorporating the position adjusting mechanism of this invention, with the back rest in raised position;

FIG. 2 is a fragmentary view similar to FIG. 1 with the back rest in the reclined or lowered position;

FIG. 3 is an enlarged cross-section taken on line 33 of FIG. 1;

FIG. 4 is a further enlarged view in rear elevation of the cover plate and release rod with the latter in its normal or locking position and showing also the associated spring and a fragmentary part of the cable for operating the rod;

FIG. 5 is a view similar to FIG. 4 but with the release rod pulled to the operated or released position;

FIG. 6 is an end elevational view of the cover plate looking from the right of FIG. 5;

FIG. 7 is a rear elevational view of the position adjusting mechanism of this invention partly broken away and showing fragmentary portions of the associated chair support and chair back;

FIG. 8 is a longitudinal section of the position adjust.- ing mechanism looking forward as in FIG. 7 but on a larger scale;

FIG. 9 is a cross-section taken along the line 99 of FIG. 8;

FIG. 10 is a cross-section taken on the line 10-10 of FIG. 8;

FIG. 11 is a longitudinal section of the lock housing taken along the line 11-11 of FIG. 10;

FIG. 12 is an enlarged elevational view partly in section of the left side of the lock housing;

FIG. 13 is an elevational view of the rear of the lock housing;

FIG. 14 is a fragmentary cross-section of the lock taken on the line 14--14 of FIG. 8, with the release rod in the normal or locking position of FIG. 4;

FIG. 15 is a fragmentary section similar to FIG. 14 but with the release rod adjusted to the release position of FIG. 5;

FIG. 16 is a rear view in elevation of the lock with the cover plate omitted and with parts in section, the release rod being in the locking position of FIG. 14;

FIG. 17 is a rear elevational view of the release rod, roller retainer, roller, spring, spring retainer and jack screw, with the parts in the released position as in FIGS. 5 and 15;

FIG. 18 is a longitudinal section of the lower thrust race, showing also a portion of the associated nut and one of the ball bearings; and

FIG. 19 is a longitudinal section of the lock housing, taken on the line 19-19 of FIG. 10.

For the convenience of description the terms front and forward will refer to the direction in which the occupant of the chair is facing, which may be astern with relation to the cabin of the airplane in which the chair is mounted.

Referring to FIGS. 1, 2 and 3, the position adjusting mechanism 20 of this invention is shown as applied to a conventional chair structure 21 having a base portion 22 adapted to be secured to the floor of an airplane cabin and having a back rest 23. The base and back rest sup port respectively a seat cushion 24 and a back cushion 25. The back rest is connected in any suitable manner to the base portion for adjustment to the upright position of FIG. 1 or the reclined position of FIG. 2 or to any selected intermediate position. In the form shown, the adjustable connection comprises a pair of spaced vertically extending angle irons 26 secured by screws 27 (FIG. 3) to the rear face of the back rest 23, a pair of stationary angle brackets 28 (FIG. 7) secured in adjacent relation to the base portion 22, and a pivot pin 29 extending horizontally through registering holes in the angle irons and angle brackets. A pair of spacer washers 30, encircling the pin 29, are interposed between the angle irons and angle brackets.

The position adjusting mechanism 20 is interposed between a pivot pin 31 extending horizontally through the stationary angle brackets 28, and a pivot pin 32 extending horizontally through the spaced angle irons 26. The axes of

pivot pins

29 and 31 are fixed while the pivot pin 32 has a motion of translation along an arc concentric with the first pin 29. Preferably, the pin 31 is offset rearwardly with respect to the pin 29, whereby the position adjusting mechanism 20 is extended as the back rest 23 is raised and contracted as the back rest is tilted back. In applying this invention to various kinds of chair structures, the position adjusting mechanism may be connected to any two pivot points which move further apart as the back rest is raised forwardly and closer together as it is tilted back, or vice versa.

Referring particularly to FIGS. 7 and 8, the position adjusting mechanism 20 comprises a clevis 3 3, having a pair of holes 34 to receive the rear pivot pin 31, a sleeve 35 supported at its lower end on the clevis and secured thereto by cap screw 36, a lock housing 37 supported at the upper end of the sleeve, an elongated helical cam member or rod 38 extending through the housing and supported for relative axial movement therein, and an extension rod 39 secured to the upper end of the helical cam member, the upper end of the extension rod being apertured to receive the movable pivot pin 32. Referring to FIGS. 7 and 8, the upper portion of the helical cam member has a threaded connection 41 with the extension rod, permitting these two parts to be assembled, disassembled and adjusted, the threads having a relatively slight inclination or lead angle, within the angle of friction, whereby application of axial force between the helical cam member and extension rod will not cause relative motion. The lower portion of the helical cam member is provided with helical splines 42 engaging complementary helical splines in a nut 43, the helical splines having a relatively great inclination or lead angle exceeding the angle of friction, whereby the application of relative axial force between the helical cam member and nut is effective to cause relative helical movement therebetween whenever the nut is released for rotary movement. As shown in FIG. 18, the nut 43 has a fast multiple thread 432 which may be formed in an insert 43p moulded of plastic material within the main body of the nut which is a hardened steel piece. The nut is recessed at its upper and lower ends to provide raceways for rows of

balls

44 and 45. The rows of balls engage respectively an upper and a lower thrust race 46 (FIGS. 8 and 18) to restrain the nut against axial movement relative to housing 37, while permitting free rotary movement except when such movement is prevented by means to be described later. The upper thrust race 46 seats against the end wall of a counterbore 47 (FIG. 11) in the housing while the lower thrust race seats on a flange (FIG. 8) on the sleeve 35 which is threaded into the lower end of the counterbore. After the race 46,

balls

44 and 45 and nut 43 have been assembled in the counterbore 47, the

sleeve

35, 35 is screwed into the lower end of the counterbore by an amount suflicient to take up all lost motion above and below the sets of balls while still permitting them to rotate freely. To retain or lock the sleeve in the selected position of adjustment, there is provided an arcuate slot 48a (FIGS. 10 and 19) extending upward for a short distance from the bottom of the lock housing 37 to leave a crescent shaped segment 48 connected to the main body of housing 37 only at the top of the segment. The inner face of the segment is formed with threads movable into locking engagement with the threads on flange 357. The outer face of the segment abuts against a set screw 49 for forcing the segment inwardly to elfect and maintain the locking engagement aforesaid. For a further description of the locking arrangement, reference is made to Stoner U.S. Patent 2,280,270 granted April 21, 1942.

The helical cam member 38 and extension 39 are urged upward relative to the lock housing '37 by means of a helical compression spring 50 which encircles the helical cam member and extension rod and is separated therefrom by a thin sleeve 51. The sleeve serves as a shield to keep dirt away from the threads 42. The lower end of the spring rests on an annular flange 52 at the lower end of the sleeve 51 which flange is seated on an annular shoulder at the upper end of the housing 37. The upper end of the spring extends into and supports an inverted cup shape washer 53, the upper face of which presses against a pin 54 carried by the extension rod 39 and extending through a selected hole 55. As shown in FIG. 7, the rod 39 is provided with a series of holes 55 each snugly fitting the pin to retain the latter by friction engagement, the holes being uniformly and closely spaced to permit the washer to be seated at any desired position along the length of the rod and thus regulate the degree of compression of the spring 50 and the force exerted thereby to support the back rest 23. Preferably, the holes extend perpendicular to the back rest to permit the pins to be inserted and removed without obstruction by the angle irons 26, as will appear from FIG. 3.

The operation of the portion of the mechanism described up to this point is as follows: The back rest 23 is normally supported in the upright position of FIG. 1 by means of the front pivot pin 29 at its lower end and the movable pivot pin 32 near the middle portion of the back rest. The spring 50 urges the back rest upward into a position as nearly vertical as possible, wherein further forward movement is arrested by any suitable limiting means such as a stop washer 56 (FIG. 8) at the bottom of helical cam member 38 engaging the lower thrust race 46. The stop washer is secured to the helical cam member 38 by a cap screw 57. The spring 50 and position adjusting mechanism 20 are fully extended in the limit stop position of FIG. 1 but the spring, being pre-compressed, has sufficient force to keep the back rest in the upright or forward position in opposition to the weight imposed on the back rest as long as the occupant is merely resting in the chair.

' lock housing 37. As the helical cam member 38 descends,

it causes the helical splines 42 to ride over the complementary helical splines in the nut 43 to turn the latter in a counterclockwise direction (looking downward). As soon as the occupant relieves the thrust on the back rest 23, the spring 50 and position adjusting mechanism 26 expand to overcome the weight of the back rest and return it to the upright position of FIG. 1, and during this return movement the nut rotates clockwise.

In the foregoing description, it is assumed that the nut 43 is free to turn in the housing 37 except for the friction offered by the helical splines 42 which is not sufiicient in itself to offer much opposition to the rotation of the nut or to the axial movement of the helical cam member. The present invention enables the occupant, by selective operation of a control device, either to release the nut for free rotation as described, or to impose a restraint thereon. The restraining or locking mechanism of this invention is novel in that it provides a yieldable lock against clockwise (elevating). movement of the nut and a positive lock against counterclockwise (lowering) movement.

The locking and restraining device comprises a roller or pawl 58 engageable in epi-cyclic relation with the cylindrical periphery of the nut 43. Referring to FIGS. l4-17, the roller is supported for rotation about a vertical axis in a retainer 59 consisting of a plate having a rectangular aperture 59a which receives and loosely fits the roller, the plate lying in the plane of the axis of the roller. The roller and retainer plate are mounted for reciprocation in unison in a horizontally extending slot 60 in the housing 37 of the locking device. The horizontal slot is of suflicient depth to provide an Opening 61 (FIGS. 11, 13 and 15) in the wall of counterbore 47 through which the roller 58 may project when it comes into contact with the nut 43. The upper and lower walls of the horizontal slot 60 are provided with grooves 62 (FIGS. 12 and 13) which fit over the edges of the plate 59 and support the latter for sliding movement in a vertical plane. During the assembly of the parts of the locking device, and after the plate 59 has been inserted from the open end of the slot 60, the latter is closed by the insertion of a biasing device com prising a spring retainer 63 frictionally fitting within the slot 60 and projecting beyond the end thereof. The retainer may be provided with additional means for securing it in assembled relation with the housing 37 such as a. set screw 64 (FIG. 16). The biasing means also comprises a spring 65 partially enclosed within the retainer 63, the outer end of the spring abutting against the ret'ainer, and the inner end of the spring abutting against the outer edge of the Sliding plate 59 in surrounding relation to a pilot portion or lug 66 on the plate which assists in centralizing the spring. The set screw 64 permits adjustinent of the position of the retainer 63, thus regulating the force of the spring 65 and therefore the degree of restraint against raising of the back rest as will be described later.

The inner end of the plate 59 normally extends into a vertical slot 67 provided in the housing 37 and normally is held in such an extended position under the biasing action of the spring 65. The plate at times may be forced out of the vertical slot 67 by means of a release rod 68 slidably mounted in the vertical slot 67 and having an inclined edge 69 engaging a complementary inclined edge on the plate 59 to actuate the latter with a camming action. In a physical embodiment of the invention, the edge 69 is inclined at an angle of 15 degrees to the vertical and is efi'cctive to impart the necessary force for shifting the plate 59 even though the release rod 68 is given only a limited amount of applied force over a limited distance. This arrangement facilitates operation by a remote control device having a short stroke. The mechanical efliciency of the release rod arrangement is also due in part to the means for supporting the rod 6*3,for sliding movement with little friction. Referring to FIG. 15, the upper portion of rod 68, above the inclined edge 69, is of rectangular cross-section and has a sliding fit within the rectangular opening provided between three walls of the vertical slot 67 and by'the inner face of a cover plate 71. The cover plate is attached to the back face of the seat lock housing 37 by cap screws 72 extending respectively into four threaded holes 73 in the housing. The plane of the inner face of the cover plate 71 is spaced from the cylindrical periphery of nut 43 by a distance somewhat less than the diameter of the roller 58 with the result that the retainer plate 59 can move to the right only as far as permitted by the roller 58 when it becomes wedged between the nut 43 and cover plate 71 as shown in FIG. 14. When the release rod 68 is pulled down from the normal position shown in FIGS. 14 and 16 to the locking posit-ion of FIGS. 15 and 17, whereupon the retainer plate 59 moves to the left in opposition to spring 65 to lift the roller 58 out of contact with the nut 43.

Any suitable means may be provided for adjusting the vertical position of the release rod 68. In the form shown, the release rod is provided at its lower end with a threaded stud 74 (FIG. 16) projecting through a washer 75 into a threaded opening at the upper end of an extension 76 which is slidably supported in a bearing provided by a horiiontal flange 77 (FIGS. 4, 5, 6) integral with the cover plate 71. A compression spring 78 interposed between flange 77 and the washer 75 normally retaining the release rod 68 in the raised position. The release rod may be lowered by the action of a hook 79 formed at the end of a flexible cable 81 slidably mounted in a sheath 82 extending forward along the chair structure 21 to a bracket 83 mounted at the side of the base portion 22 of the chair structure. The front end of the flexible cable 81 terminates in a knob or handle 84 conveniently accessible to the occupant of the chair. The force required for pull-ing the cable 81 may be regulated by selecting a spring 78 of suitable weight.

In operation, let it be assumed that the chair structure 21 is unoccupied and the back rest 23 is inclined back as far as it will go, in the position of FIG. 2. In this posi-' tion, the movable pivot 32 is so located with respect to the fixed pivots 29 and '31 that the position adjusting mechanism 20 is contracted to minimum size, and the helical cam member 38 is in its lowest position with the head of the screw 57 seated on top of the cap screw 36. To vary the range of the mechanism 20, or the stroke of the helical cam member 38, the screw 36 may be replaced by another screw of diiferent length. The compression spring 50 tends to raise the helical cam member 3'8 and pivot 32, but this tendency is opposed by the weight of the back rest 23. The upward force on the helical cam member 38 is also opposed by the action of the helical splines 42 upon the nut 43 which tends to turn the helical cam member in the direction of the arrow ES (elevation by spring pressure) in FIG. 15. The spring force would be sufiicient to raise the back rest and turn the nut 43 if the latter were completely free to turn as in FIG. 15. Assuming, however, that the locking device is not released and the roller 58 is spring engaged with the nut 43 and cover plate 71 as shown in FIG. 14, the roller rubs against the surface of the cover plate and drags along the periphery of the nut. This braking action prevents the nut from turning and the spring 56 is not effective by itself to raise the back rest. If, however, the spring pressure is supplemented by a manual force, the braking action is overcome and the nut 43 turns in the direction of the arrow ESM (elevation by spring and manual pressure) in FIG. 14. During this time the roller 58, being overcome by the combined forces, turns in an epicyclic movement as indicated by the arrow ESM in FIG. 14 and the helical cam member rises as indicated by the arrow ESM in FIG. 16. The manual pressure required for this elevating action may be applied by a passenger or by the stewardess directly to the back rest 23 without the necessity of releasing the locking device. If the manual pressure is discontinued the raising movement of the helical cam member and the turning movement of the nut 43 are arrested immediately by the braking action of the spring pressed roller 58. Assuming that the manual pressure is continued, the back rest 23 is elevated to the FIG. 1 position, in which further movement is arrested by any suitable limiting means, or by the engagement of the washer 56 against the lower thrust race 46 in FIG. 8.

In order to lower the back rest 23 from the FIG. 1 to the FIG. 2 position, it is necessary for the occupant to grasp the knob or handle 84 and pull the release rod 68 to the release position shown in FIGS. 15 and 17. With the parts in that position, the roller 58 is completely disengaged from the nut 43 and permits the latter to move freely in either direction. The occupant of the chair may then lower the back rest by leaning back or by pushing 7 against the upper part of the back rest, or alternatively,

the latter could be grasped by the hand and pulled from the rear. During such manual application of force,

against the pressure of the spring 50, the helical cam member descends as indicated by the arrow LM (lowered manually in FIG. 17 and the nut 43 turns in the direction of the arrow LM in FIG. 15. If the manual pressure is discontinued while the locking device is still released, the spring 50 will raise the helical cam member to cause the nut 43 to be turned in the direction of the arrow BS in FIG, 15. Thus with the release rod 68 operated, the back rest 23 may be moved conveniently back and forward (by manual and spring means respectively) and held in any selected position away from the one shown in FIG. 1 until the occupant lets go of the knob 84 to cause the release rod 68 to rise and the roller 58 to lock, whereupon the back rest is held in adjusted position. If the selected position happens to be intermediate the extreme positions shown in FIGS. 1 and 2, the roller 57 yieldingly locks the back rest 23 against forward movement but obstinately locks it against rearward movement. The obstinate lock against rearward movement, which is effective in any selected position of adjustment and which forms an important feature of this invention, will now be described in further detail.

Assuming that the back rest 23 is raised as in FIG. 1 and the locking device is in the normal (locking) position of FIGS. 14 and 16; if the operator attempts to lower theback rest by applying a rearward force thereto he transmits the force through the angle irons 26, movable pivot pin 32, extension rod 39 and helical cam member 38, causing the inclined threads 42 to apply a downward compressive force on the nut 43. The downward force is resolved into two components, one of which is axial and tends to lower the nut 43. This downward component of force is sustained by the balls 45, thrust race 46, flange 35f, sleeve 35, clevis 33 and stationary pivot pin 31. The rotary component of force tends to turn the nut 43 counterclockwise to the direction of the arrow ESM in FIG. 14, and the nut starts to turn in this direction. It only moves an infinitesimal distance, however, and then becomes obstinately locked by the roller 58 in becoming wedged between the periphery of nut 43 and the hardened steel cover plate 71. As will be apparent from FIG. 14, the parts are so proportioned that it requires only a relatively slight pressure of spring 65 on roller 58 to set up a very great torque resisting turning movement of the nut 43 in the lowering direction and to set up a tremendous resistance to downward movement of the helical cam member and to rearward tiling movement of the back rest. In fact, the resistance is so great that in the event of a crash of the airplane (flying in a direction opposite to the one in which the chair occupant is facing) the decelerating force set up by the weight of the occupants body is not sufl'lcient to displace the back rest 23 from the position in which it is adjusted, and the occupant is thus held in the chair with a secure support provided for the back cushion 25 to absorb the impact.

The locking device is automatically restored from the release position of FIGS. l517 to the normal or locking position of FIGS. 14 and 16 whenever the operator releases his grasp upon the knob 84, thus protecting the operator against the consequences of inadvertence in failing to restore the mechanism to locking condition.

From the foregoing description, it will be seen that the chair back rest 23 may be adjusted to any desired position by pushing it back against the pressure of the spring 50, only while the locking device is released; or by manually pushing or pulling it forward to supplement the spring 50 and overcome the restraint of the epicyclic roller 58 while the latter is in its normal or effective position; or by permitting the spring 50 to raise the back rest While the roller 58 is disabled. Each of these three kinds of movement occurs smoothly against a relatively small amount of friction and without jerkiness. Each kind of movement progresses by infinitesimal increments as distinguished from a series of finite steps. At any one of the infinite selected positions the occupant may imrnediately fix the position of the back rest. This is accomplished, in the case of the back rest being lowered, 'by letting go of the manipulative knob 84 whereupon the 8 locking device is restored quickly to its normal position with the roller in contact with the nut. In the case of the back rest being raised against the restraining action of the roller 58, the back rest becomes fixed and yieldingly locked in its adjusted position the instant that the manual force is discontinued, the action being immediate due to the fact that the roller does not lose contact with the nut at any time during such raising movement.

The restraining and locking device of this invention is simple in construction and inexpensive to manufacture as the same physical parts perform a plurality of functions under diflerent conditions. For example, the same roller which acts as a positive lock under one set of conditions, serves as a brake or yieldable lock under other conditions. The braking force can be adjusted to a value within certain limits to cause the roller to overcome the spring 50 acting alone but to yield whenever the spring is supplemented by a rather slight manual force. Despite the necessity of keeping the braking force within limits, the adjustment of pressure on the roller does not interfere with the action of the roller as a positive lock under the first set of conditions. Due to the fact that the roller 58 and nut 43 may engage in an infinite number of selected positions, wear on these parts is evenly distributed and the life of the locking device is prolonged. Other parts are slow to wear as they do not require the application of great pressures over areas which are subjected to sliding friction.

If desired, the position adjusting mechanism 20 may be inverted to connect the clevis 33 with the movable pivot pin 32 and to connect the free end of extension rod 39, through another clevis (not shown) with the rear pivot pin 31.

What is claimed is:

1. In an adjustable chair structure comprising a base portion and a back rest pivotally mounted thereon for relative tilting movement and comprising a pair of connecting elements arranged to move further apart when the back rest is tilted in one direction and. to move closer together when the back rest is tilted in the opposite direction, the improvement which resides in a position adjusting mechanism interposed between the said connecting elements, said position adjusting mechanism comprising: a sleeve, an elongated helical cam member adjustably mounted within said sleeve, the remote end of the sleeve and the remote end of the elongated helical cam member each having means for attachment to one of said connecting elements, a nut follower supported by said sleeve for realtive rotation but held against axial movement relative to said sleeve and to the helical cam member, the elongated helical cam member being mounted for reciprocation relative to the sleeve but held against relative rotary movement, the helical cam member extending through the nut and having a steep helically splined mating connection with the nut so as to impart rotation to the nut upon axial movement of the helical cam member through the nut and relative to the sleeve, the nut being arranged to rotate in one direction as the back rest is tilted forwardly and the helical cam member is carried with it, locking means constantly engaging the nut for exerting a frictional drag upon the latter as it is rotated in said one direction as the back rest is tilted forwardly and for exerting an obstinate lock on the nut to restrain it from rotating in said opposite direction so as to obstinately prevent the back rest from being tilted rearwardly, and manually selective means for displacing the locking means clear of the nut to release the latter for free rotation in either direction.

2. In an adjustable chair structure, a position adjusting mechanism as defined in claim 1, in which the obstinate locking means comprises a lock housing attached to the sleeve in surrounding relation to the nut and having an opening in its wall to the outside, the nut .having a peripheral surface projecting in part into the said opening, a detachable cover plate closing over said opening and having an inner face in opposed spaged relation to the peripheral surface of the nut, a roll pawl rollable in the opening having a peripheral surface engageable with the inner face of the plate and with the peripheral surface of the nut, the diameter of the roll pawl being slightly greater than the spacing between the periphery'of the nut and the opposed face of the plate, resilient means constantly pressing the pawl so that its peripheral surface is in contact the peripheral sugface' of the nutand with th e inner face of the plate, the pawl being adapted under the load of the resilient means while in pressed engagement with the periphery of the nut to be rotated in consequence of rotation of the nut in said one direction, and to be rotated into wedged relation to the periphery of the nut and the said plate in consequence of a slight turning of the nut in the said opposite direction whereby the nut is obstinately locked against rotation in the latter direction, the detachable plate allowing ready access to the locking means for servicing and inspection thereof.

3. A position adjusting mechanism adapted to be interposed between two connecting elements to hold the latter apart by a selected distance, comprising a housing, a rod mounted for reciprocation in said housing and extending beyond one end thereof, the remote end of the rod and the remote end of the housing each having means for attachment to one of the connecting elements, a nut mounted in said housing and held against relative axial movement therein, the rod extending through the nut and having a helical splined connection therewith arranged to impart rotary movement to the nut upon relative axial movement, and restraining means for controlling the rotation of the nut and thereby controlling the extension and contraction of the rod relative to the housing, said restraining means comprising a roller engageable with the periphery of the nut with an epicyclic motion, a wall carried by the housing and spaced from the nut by a distance less than the diameter of the roller, and resilient means for holding the roller simultaneously in engagement with both the nut periphery and the wall to provide a positive wedging force locking the nut against rotation in one direction and a yieldable breaking force retarding rotation of the nut in the opposite direction, said yieldable braking force adapted to be overcome upon application of sufficient axial force to the rod to cause the roller to roll and drag over the nut periphery while frictionally rubbing against the wall, and a prestressed spring interposed between the rod and housing and urging the rod in a direction to turn the nut, the force of the spring being insufl'lcient to overcome the restraining means, but being adapted upon the addition of manual pressure to overcome said restraining means to impart the axial and rotative movements aforesaid.

4. A position adjusting mechanism adapted to be interposed between two connecting elements to hold the latter apart by a selected distance, comprisinga housing, a rod mounted for reciprocation in said housing and extending beyond one end thereof, the remote end of the rod and the remote end of the housing each having means for attachment to one of the connecting elements, a nut mounted in said housing and held against relative axial movement therein, the rod extending through the nut and having a helical splined connection therewith arranged to impart rotary movement to the nut upon relative axial movement, and restraining means for controlling the rotation of the nut and thereby controlling the extension and contraction of the rod relative to the housing, said restraining means comprising a roller engageable with the periphery of the nut with an epi-cyclic motion, a wall carried by the housing and spaced from the nut by a distance less than the diameter of the roller, and resilient means for holding the roller simultaneously in engagement with both the nut periphery and the Wall to provide a positive wedging force locking the nut again t tat s i 9 d ect on nd a ie d ble rak his on retardin o at n f h nu in e opp site dream s ldabl br ng fo a ap ed o be overcome upon application of s'ufiicient axial force to the rod to cause the roller to roll and drag over the nut Periphery while frictionally rubbing against the wall, the roller being supported for pivotal movement in a retainer plate mounted for reciprocation between the nut and the said wall in a plane parallel to the latter, said plate being arranged to carry the roller into and out of engagement with the nut.

5. A position adjusting mechanism according to claim 4, in which'the resilient means comprises a spring interposed between the housing and the retainer plate to cause the latter to carry the roller into engaging relation with the nut periphery.

6. A position adjusting mechanism according to claim 5, in which the housing has a pair of grooves guiding the retainer plate for movement toward and away from the spring.

7. A position adjusting mechanism comprising a housing, a non-rotatable elongated cam rod mounted for reciprocation in said housing, a rotatable nut mounted in said housing and held against relative axial movement therein, the rod extending through the nut and having a helical splined mating connection therewith arranged to impart rotary movement to the not upon axial movement of the rod relative to the housing, the helix angle of the splines of the splined connection being greater than the angle of friction thereof, and restraining means for controlling the rotation of the nut and thereby controlling the extension and contraction of the rod relative to the housing said restraining means comprising a pawl engageable with the nut, a wall on said housing spaced from the nut, and a spring for moving the pawl along the wall into engagement with the nut, said pawl providing a wedging force obstinately locking the nut against rotation in one direction and frictionally holding the nut against rotation in the opposite direction, and means detachably mounting said wall to the housing whereby the said wall may be readily removed for servicing and inspection of the restraining means.

8. A position adjusting mechanism according to claim 7, in which the pawl is carried by a retainer plate supported for reciprocation toward and away from the spring in a plane parallel to said wall.

9. A position adjusting mechanism comprising a housing, a rod mounted for reciprocation in said housing, a nut mounted in said housing and held against relative axial movement therein, the rod extending through the nut and having a helical splined connection therewith arranged to impart rotary movement to the nut upon relative axial movement, and restraining means for controlling the rotation of the nut and thereby controlling the extension and contraction of the rod relative to the housing, said restraining means comprising a pawl engageable with the nut, a wall on said housing spaced from the nut, and a spring for moving the pawl along the wall into engagement with the nut, said pawl pro- "viding a wedging force positively locking the nut against rotation in one direction and frictionally holding the nut against rotation in the opposite direction, the pawl being carried by a retainer plate supported for reciprocation toward and away from the spring in a plane parallel to said wall, and the housing having a groove extending transverse to the direction of movement of the retainer plate, and a release rod mounted for reciprocation along the groove, said release rod and retainer plate having interengaging inclined edges arranged to respond to movement of the release rod in a releasing direction, by forcing the retainer plate against the spring to carry the pawl out of locking engagement with respect to the nut.

10. A position adjusting mechanism according to claim 9, which includes a second spring urging the release rod toward a position out of the path of the retainer plate,

11 and manipulative means for overcoming the last mentioned spring to move the release rod and cause the latter to move the retainer plate against the first spring, thereby to disengage the pawl from the nut.

11. A position adjusting mechanism according to claim 10, in which the manipulative means comprises a handle located remotely with respect to said housing, said handle being connected by a flexible cable to the release rod to actuate the latter against the second spring.

References Cited in the file of this patent UNITED STATES PATENTS Di Renzo Dec. 29, 1936 Binus Aug. 26, 1947 Harrington Oct. 5, 1948 Cushman Dec. 18, 1951 McGregor May 6, 1958 Williams Oct. 28, 1958