US3870289A

US3870289A - Back support mechanism for medical examination table

Info

Publication number: US3870289A
Application number: US376456A
Authority: US
Inventors: Clarence J Aulik
Original assignee: American Hospital Supply Corp
Current assignee: MDT DIAGNOSTIC Co
Priority date: 1973-07-05
Filing date: 1973-07-05
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11
Also published as: CA1010486A

Abstract

An improved back support mechanism is provided for a medical examination table having a base, a subtop supported by the base, and a top supported by the subtop. The top includes a tiltable back section which is movable between a generally horizontal lowered position and an inclined raised position. The back support mechanism includes an elongated curved rod which is pivotally mounted on the top of the subtop for pivotal movement in a plane parallel to the direction of movement of the back section. A latch plate is pivotally mounted on the back section for pivotal movement in the same direction, and the rod extends through an opening in the latch plate. The rod includes a first end portion which is pivotally secured to the subtop, an intermediate arcuate portion which curves upwardly and rearwardly from the first end portion, and a substantially straight second end portion. As the back section is raised, the rod pivots upwardly and is drawn through the opening of the latch plate. However, when a downward force is exerted on the back section, the periphery of the opening in the latch plate frictionally engages the rod and prevents the latch plate from moving downwardly along the rod to maintain the back section in a desired inclined position. The latch plate is mounted on a shaft which is rotatable by lever means, and when the back section is to be lowered, the shaft can be rotated by the lever means to move the latch plate into a substantially perpendicular relationship with the rod to permit the latch plate to move downwardly along the rod as the rod pivots to a lowered position.

Description

United States Patent 1191 Aulik 1 1 Mar. 11, 19.75

[ BACK SUPPORT MECHANISM FOR MEDICAL EXAMINATION TABLE [75] Inventor: Clarence J. Aulik, Manitowoc, Wis.

[73] Assignee: American Hospital Supply Corporation, Evanston, Ill.

[22] Filed: July 5, 1973 [21] Appl. No.: 376,456

52 U.S.Cl. ..269/324,5/75 51] Int. Cl ..A6lg13/00 581 Field ofSearch ..5/68,75,77,78; 108/3,

Primary Examiner-Roy Lake Assistant Examiner-Mark S. Bicks [57] ABSTRACT An improved back support mechanism is provided for a medical examination table having a base, a subtop supported by the base, and a top supported by the subtop. The top includes a tiltable back section which is movable between a generally horizontal lowered position and an inclined raised position. The back support mechanism includes an elongated curved rod which is pivotally mounted on the top of the subtop for pivotal movement in a plane parallel to the direction of movement of the back section. A latch plate is pivotally mounted on the back section for pivotal movement in the same direction, and the rod extends through an opening in the latch plate. The rod includes a first end portion which is pivotally secured to the subtop, an intermediate arcuate portion which curves upwardly and rearwardly from the first end portion, and a substantially straight second end portion. As the back section is raised, the rod pivots upwardly and is drawn through the opening of the latch plate, However, when a downward force is exerted on the back section, the periphery of the opening in the latch plate frictionally engages the rod and prevents the latch plate from moving downwardly along the rod to maintain the back section in a desired inclined position. The latch plate is mounted on a shaft which is rotatable by lever means, and when the back section is to be lowered, the shaft can be rotated by the lever means to move the latch plate into a substantially perpendicular relationship with the rod to permit the latch plate to move downwardly along the rod as the rod pivots to a lowered position.

15 Claims, 12 Drawing Figures PATENTED NARI I 1975 sum 1 or 3 FIG! FIGZ

FIG?) Pmminmmms 3.870.289 I SHEU 3 UP 3 BACKGROUND This invention relates to a back support mechanism for a medical examination table, and, more particularly, to a back support mechanism in which the support rod is pivotally mounted on the subtop below the back section of the top.

In one particular medical examination table heretofore manufactured, the hinged back section of the top is supported by an elongated straight rod which is pivotally secured to the back section and which extends downwardly through an opening in the subtop. A locking means mounted on the subtop is resiliently biased to frictionally engage the rod and to lock the rod in a desired extended position.

This support mechanism has not proved entirely satisfactory for a number of reasons. The support rod extends into the base of the examining table through an opening in the subtop, and dirt may enter this opening and accumulate inside the base. Preferably, a protected area for the rod must be provided inside the table base, and this restricts drawer and storage space within the base. If the support rod is located near one side of the table in order to conserve storage space, the back section of the top must be strengthened because the patients weight would not be centered on the support mechanism, thereby resulting in increased costs. If this support mmechansim were used on a pedestal style examination table in which the subtop is supported by legs, the support rod would extend below the subtop when the back section is lowered, creating an unsightly appearance. Further, the lock mechanism for the support rod is located within the subtop adjacent the support rod, and the doctor must bend to reach and release the lock mechanism when the top is to be lowered.

U.S. Pat. No. 3,499,529 illustrates another type of.

examination table in which the back section is raised and lowered by power means which pivot a pair of lever arms to raise and lower the back section. The use of power means to raise and lower the back section increases the cost of the examination table, however, and many doctors prefer a manually operated support mechanism.

U.S. Pat. No. 2,924,299 illustrates a braking mechanism for a drafting table which utilizes a curved rod. However, not only is the shape of the rod different, but the function and the securement of the rod are entirely different from that of the support rod utilizedin the present invention.

SUMMARY The inventive back support mechanism includes a support rod which is pivotally secured to the subtop rather than to the back section, and the unsightly and unsanitary hole through the subtop for the support rod is eliminated. The rod extends slidably through an opening in a latch plate pivotally mounted on the back section and is movably from a generally rearwardly extending position when the back section is lowered to a generally upright position when the back section is fully raised. The curvature of the rod permits the rod to follow the latch plate as the latch plate is raised with the back section to permit the latch plate to move smoothly upwardly along the rod. When a downwardly force is exerted on the latch plate, either by gravity or by a pa tient reclining on the back section, the latch plate is forced into an angular position relative to a line perpendicular to the axis of the rod, and the periphery of the latch plate opening frictionally engages the rod to prevent downward movement of the latch plate along the rod. The back section is thereby maintained in the desired inclined position. The latch plate is mounted on a shaft which extends laterally outwardly in both directions toward the sides of the back section, and the shaft terminates in a pair of lever arms which can be manipulated by the doctor while maintaining an erect position. When the doctor wishes to lower the back section, the lever arm is moved to rotate the shaft to move the latch plate into a perpendicular relationship with the rod to permit movement of the latch plate downwardly along the rod. The contour of the rod permits the rod to be maintained below the back section as the back section pivots downwardly. Since the rod does not extend through the subtop, the entire space below the subtop can be used for storage, and in cabinet style examination tables full with drawers can be used.

DESCRIPTION OF THE DRAWING The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing, in which:

FIG. 1 is a fragmentary perspective view of the back of a pedestal type examination table equipped with a back support mechanism formed in accordance with the invention; v

FIG. 2 is a fragmentary side elevation view of the table of FIG. 1 showing the back section in an inclined position;

FIG. 3 is a side elevational view of the examination table showing the back section in the lowered position;

FIG. 4 is a plan view of the latch plate and the mounting shaft therefore;

FIG. 5 is a top plan view of FIG. 4;

FIG. 6 is an enlarged sectional view taken along the line 66 of FIG. 4;

FIG. 7 is a sectional view taken along the line 7--7 ofFlG. 4;

FIG. 8 is a side view of one of the mounting brackets for the latch plate support shaft taken along the line 8-8 ofFIGulO;

FIG. 9 is a side view of the mounting bracket taken along the line 99 of FIG. 10;

' FIG. 10 is a front view of the mounting bracket;

FIG. 11 is a side view of the support rod;

FIG. 12 is an enlarged fragmentary view of a portion of FIG. 3 showing the support rod and latch platein solid outline.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to FIGS. l-3, the numeral 10 designates generally a conventional medical examination table having a top 11 supported by a subtop 12. The particular examination table illustrated is a pedestal type in which the subtop 12 is supported by a base 13 comprised of a pair of

support legs

14 and 15 and a cross brace 16. The invention may also be used with cabinet type examination tables in which the subtop is supported by a cabinet style base which may be provided with storage drawers.

The top 11 includes front and

rear portions

17 and 18 which are hingedly connected at 19 in the conventional manner. The front portion 17 extends generally 12. The back section 18 is movable between a generally horizontally extending position shown in FIG. 3 in which it is supported by the subtop and an inclined or raised position shown in FIGS. 1 and 2 in which it is supported by the back support assembly 20. The particular back section illustrated is provided with a back support wall 21 which is inclined slightly relative to the horizontal when the back section is in the lowered position and a pair of side wall 22 which depend from the top surface and which space the back support wall from the top surface 23 of the subtop when the back section is in the lowered position.

The support assembly includes an elongated curved rod which is pivotally secured to the subtop by a bracket 25. The bracket 25 is secured to the subtop by screws and includes a pair of upstanding spacedapart lugs 26. The rod is pivotally secured between the lugs 26 by a pivot pin 27 which extends between the lugs through an opening 28 (FIG. 11) adjacent the end of the rod.

The support assembly also includes a generally rectangular planar latch plate 29 which is pivotally mounted on the bottom surface of the back section by an elongated shaft or rod 30. The shaft is rotatably supported by a pair of L-shaped support brackets 31 (FIGS. 8-l0), each of which includes a first leg 32 which is secured to the under surface of the back section by screws and a second leg 33 which is provided with a central opening 34 through which the shaft extends.

The brackets 31 are secured adjacent the longitudinal center line of the examination table, and the rod extends laterally outwardly from the brackets toward both sides of the back section. Each end of the shaft terminates in a lever arm portion 35 which extends perpendicularly to the remainder of the shaft and generally parallel to the latch plate 29. Each of the lever arm portions 35 is positioned adjacent one of the sides of the back section, and movement of one of the lever arms about the axis of the central portion of the shaft causes rotation of the shaft and pivoting of the latch plate in a direction perpendicular to the axis of the shaft. If desired, the end of each of the lever arms can be equipped with finger grips 36 formed of rubber or the like.

The latch plate is provided with an opening 38 adjacent the end of the latch plate which is not secured to the shaft. Referring to FIG. 6, the opening 38 has an hour-glass configuration in cross-section formed by chamfered or crusto-conical entry portions 39 which are inclined at an angle of about from the axis of the opening and a cylindrical intermediate or central portion 40.

Referring now to FIG. 11, the support rod 24 includes a relatively short end portion 42 through which the opening 28 is provided, a curved intermediate portion 43, and a long substantially straight end portion 44. The end portion 44 extends in a substantially straight line for the dimension A, and the intermediate portion 43 curves away from the straight end portion 44 along an arc extending through an angleB. The first end portion 42 includes a curved portion 45 and substantially straight end portion 46. The curved portion 45 curves in the opposite direction as the arcuate portion 43 and curves smoothly from the arcuate portion 43 along an are having a radius R and an angle C. The end portion 46 extends substantially straight for the dimension D, and the end portion is inclined an angle E from a line xx which extends parallel to the straight end portion 44. The intermediate portion of the rod curves upwardly and rearwardly relative to a line extending between the two ends of the rod.

In one specific embodiment of the support rod, the dimension A of the straight end portion 44 was 5-5/ l 6 inches, and the dimension D of the short end portion 46 was 1% inches. The radius R was 7-5/16 inches, and the arcuate portion 43 extended through an angle B of 53V2. The radius R of the curved portion 45 was 2-l/l6 inches, and the angle C was 43. The angle E was 9 /2", and the included angle between the

straight end portions

44 and 46 was therefore l7O This is illustrated in FIG. 12 in which the

end portions

44 and 46 form an included angle F of which opens downwardly or toward the subtop.

The diameter of the central cylindrical portion 40 of the opening in the latch plate 29 is sized relative to the diameter of the rod so that the rod can slide freely through the opening when the latch plate extends generally perpendicularly to the portion of the rod within the opening. In the specific embodiment described, the diameter of the rod was five-eights inch, and the diameter of the cylindrical central portion 40 of the latch plate opening was 0.640 inch. The latch plate was formed from bar stock having a thickness F (FIG. 6) of three-eighths inch.

When the back section 18 is in the lowered position illustrated in FIG. 3, the straight end portion 46 of the rod extends generally horizontally from the pivot pin 27, the arcuate intermediate portion 43 curves upwardly and rearwardly, and the straight end portion 44 extends rearwardly and slightly downwardly. The portion of the rod which is positioned within the opening of the latch plate is adjacent the juncture between the straight end portion 46 and the curved portion 45 of the first end portion. The back section and the rod pivot about parallel axes, and as the back section is raised, the latch plate pulls the rod upwardly about its pivot point. The

arcuate portions

45 and 43 of the rod slide freely through the opening of the latch plate, and the curvature of the rod permits the latch plate to be raised freely along'the rod without binding.

When the back section has been raisedto the desired inclination, the doctor merely releases the back section, and the weight of the back section will cause the latch plate to pivot on the shaft 30 relative to the rod into an angular relationship with a lineextending perpendicularly to the rod axis as illustrated in FIG. 2. In this position the edges of the cylindrical central portion 40 of the latch plate opening will frictionally engage the surface of the rod and prevent downward movement of the latch plate along the rod. Since the rod and the back section pivot about different pivot points, the back section cannot pivot downwardly unless the latch plate slides downwardly along the rod. The rod therefore maintains the back section in the desired inclined position. When a patient reclines on the back section, a greater force is applied to the latch plate tending to pivot it away from a perpendicular relationship to the rod, and this increases the locking action of the latch plate on the rod.

If it is desired to further raise the back section from the locked position illustrated in FIG. 2, the doctor need merely lift the back section, and the rod will continue to slide freely through the latch plate opening.

If it is desired to lower the back section from an inclined, locked position, the doctor need merely move one of the lever arms 35 which are conveniently located adjacent the side walls 22 of the back section to rotate the shaft and pivot the latch 29 into a generally perpendicular relationship with respect to the rod.

As the rod slides upwardly through the latch plate, the

latch plate can be maintained perpendicular to the rod by means of the lever arms. Since the lever arms are lo-- cated adjacent the sides of the back section, the doctor can lower the back section from either side of the table without bending or stooping.

As the back section is lowered and the rod pivots downwardly, the upper end of the rod pivots away from the back surface of the back section to permit the back section to be lowered completely into the horizontal position illustrated in FIG. 3.

In the preferred embodiment, a flat strip of spring metal 48 (FIG. 7) is used to insure locking action of the latch plate against the rod. The free end of the spring engages the back section and resiliently urges the shaft to rotate clockwise as viewed in FIG. 2 to urge the latch plate to pivot upwardly from a perpendicular relationship to the rod. The upward biasing of the latch plate by the spring does not interfere with the raising of the back section, but it does insure that the latch plate will frictionally engage the rod when the back section is brought to the desired position. The spring 48 is secured to the latch plate by rivet 49, and the outer end of the Spring is curved at 50 so that the spring does not dig into the rear surface of the back section.

Other types of springs can be used. For example,'l have had good results with a spirally wound torsion spring which was ensleeved on the shaft 30 with one end of the spring engaging the latch plate and the other end engaging the back section.

In the particular embodiment illustrated, the support rod 24 was pivotally mounted on the subtop l2, and the latch plate 29 was pivotally mounted on the back section 18. However, the position of these parts can be reversed, i.e., the rod can be pivotally attached to the back section and the latch plate can be pivotally mounted on the subtop.

While in the foregoing specification a detailed description ofa specific embodiment of the invention was set forth for the purpose of illustration, it is to be understood that many of the details hereingiven may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In an examination table having a base, a subtop supported by the base, and a top supported by the subtop, the top having a tiltable back section pivotable about a horizontal axis between a substantially horizontal lowered position in which the back section is spaced slightly from the subtop and a raised position, an improved support assembly for the back section of the top comprising an elongated curved rod having first and second end portions, the rod being pivotally secured adjacent its first end portion to one of the subtop and back section for pivotal movement about a horizontal axis spaced from the pivot axis of the back section, the rod having a first curved portion adjacent the first end portion and a second curved portion extending from the first curved portion to the second end portion, the first and second curved portions having opposite curvatures to provide the'rod with a generally S-shaped intermediate portion, the second curved portion flowing smoothly from the first curved portion and being longer than the first curved portion, the first curved'portion curving away from its pivotal securement to one of the subtop and back section toward the other of the subtop and back section and the second curved portion curving away from said other of the subtop and back section toward said one of the subtop and back section when the back section is in its lowered position, the length of the second curved portion being such that the first and second end portions form an included angle opening toward said one of the subtop and back section of less than 180, the rod being enclosed completely within the space between the subtop and the back section when the back section is in the lowered position, a latch plate mounted on the other of the subtop and the back section for pivotal movement about a horizontal axis, the latch plate having an opening therethrough slightly greater than the thickness of the rod, the rod extending through the opening in the latch plate and the periphery of the opening in the latch plate being engageable with the rod when the latch plate is moved away from a perpendicular relationship with the rod whereby the latch plate can be frictionally locked against the rod at selected positions along the first and second curved portions of the rod to support the back section at a desired-inclination, the rod being pivotable between the subtop and the back section as the back section is moved between the lowered and raised positions without interfering with the subtop or the back.

2. The structure of claim 1 in which the rod is pivotally mounted on the subtop and the latch plate is pivotally mounted on the back section, the rod and the latch plate being positioned generally along the longitudinal center line of the table, the latch plate being connected to shaft means extending laterally outwardly from the latch plate in at least one direction and terminating adjace'nt one of the sides of the back section, the shaft means being 'rotatably mounted on the back section, lever means on the shaft means adjacent saidone side for rotating the shaft means whereby the latch plate may be rotated into a substantially perpendicular relationship with the rod to release the frictional engagement betweenthe latch plate and the rod to permit movement of the rod through the opening in the latch plate.

3. The structure of claim 2 including spring means associated with the latch plate for resiliently urging the latch plate into frictional engagement with the rod.

4. The structure of claim 1 in which the first and second end portions are substantially straight.

5. The structure of claim l'in which the first and second end portions form an included anglev of about l.

6. The structure of claim 1 in which the first curved portion extends along an are having a radius of about 2-1/16 inches and an angle of about 43 and the second curved portion extends along an are having a radius of about 7-5/16 inches and an angle of about 53%.

7. The structure of claim 6 in which the first end portion is substantially straight and has a length of about 1% inch and the second end portion is substantially straight and has a length of about 5-5/16 inches.

8. The structure of claim 6 in which the first and second end portions form an included angle of about 9. In an examination table having a base, a subtop supported by the base, and a top supported by the subtop, the top having a tiltable back section pivotable about a horizontal axis between a substantially horizontal lowered position in which the back section is spaced slightly from the back section and a raised position, an improved support assembly for the back section of the top comprising a. an elongated rod having first and second ends and being pivotally attached adjacent its first end to the subtop for pivotal movement about a horizontal axis spaced from the pivot axis of the back section, the rod including i. a first substantially straight end portion extending from the first end, the first end portion extending generally rearwardly from the pivotal attachment of the rod to the subtop when the back section is in the lowered position,

ii. a first arcuate portion curving upwardly and rearwardly from the first end portion when the back is in the lowered position, the arc of the first arcuate portion having a center positioned above a line extending between the ends of the rod,

iii. a second arcuate portion curving upwardly and rearwardly from the first arcuate portion and then downwardly away from the back section when the back is in the lowered position, the curvature of the second arcuate portion being opposite to the curvature of the first arcuate portion, the arc of the second arcuate portion being longer than the arc of the first arcuate portion ahd having a center positioned below a line extending between the ends of the rod, and

iv. a substantially straight second end portion ex tending from the second arcuate portion away from the back section when the back is in the lowered position, the first and second end portions forming an included angle of less than 180, the rod being completely enclosed within the space between the subtop and the back section when the back section is in the lowered position,

b. a latch plate mounted on the back section for pivotal movement about a horizontal axis and having an opening therethrough slightly greater than the diameter of the rod, the rod extending through the opening in the latch plate and the periphery of the opening in the latch plate being engageable with the rod when the latch plate is moved away from a perpendicular relationship with the rod whereby the latch plate can be frictionally locked against the rod at selected positions along the first and second arcuate portions and the second end portion of the rod to support the back section at a desired inclination.

10. The structure of claim 4 including a shaft rotatably mounted on the back section, the latch plate being secured to the shaft so that rotation of the shaft pivots the latch plate with respect to the rod, lever means on the shaft adjacent at least one side of the back section for rotating the shaft whereby the latch plate may be rotated into a substantially perpendicular relationship with the rod to release the frictional engagement between the latch plate and the rod to permit movement of the rod through the opening in the latch plate.

11. The structure of claim 10 including spring means associated with the latch plate or resiliently urging the latch plate into frictional engagement with the rod.

12. The structure of claim 9 in which the first and second end portions form an inclined anglev of about 170.

13. The structure of claim 9 in which the first curved portion extends along an are having a radius of about 2-1/16 inches and an angle of about 43 and the second curved portion extends along an arc having a radius of about 7-5/16 inches and an angle of about 53 /2.

14. The structure of claim 13 in which the first end portion has a length of about 1% inch and the second end portion has a length of about 5-5/16 inches.

15. The structure of claim 13 in which the first and second end portions form an included angle of about 170.

Claims

1. In an examination table having a base, a subtop supported by the base, and a top supported by the subtop, the top having a tiltable back section pivotable about a horizontal axis between a substantially horizontal lowered position in which the back section is spaced slightly from the subtop and a raised position, an improved support assembly for the back section of the top comprising an elongated curved rod having first and second end portions, the rod being pivotally secured adjacent its first end portion to one of the subtop and back section for pivotal movement about a horizontal axis spaced from the pivot axis of the back section, the rod having a first curved portion adjacent the first end portion and a second curved portion extending from the first curved portion to the second end portion, the first and second curved portions having opposite curvatures to provide the rod with a generally S-shaped intermediate portion, the second curved portion flowing smoothly from the first curved portion and being longer than the first curved portion, the first curved portion curving away from its pivotal securement to one of the subtop and back section toward the other of the subtop and back section and the second curved portion curving away from said other of the subtop and back section toward said one of the subtop and back section when the back section is in its lowered position, the length of the second curved portion being such that the first and second end portions form an included angle opening toward said one of the subtop and back section of less than 180*, the rod being enclosed completely within the space between the subtop and the back section wHen the back section is in the lowered position, a latch plate mounted on the other of the subtop and the back section for pivotal movement about a horizontal axis, the latch plate having an opening therethrough slightly greater than the thickness of the rod, the rod extending through the opening in the latch plate and the periphery of the opening in the latch plate being engageable with the rod when the latch plate is moved away from a perpendicular relationship with the rod whereby the latch plate can be frictionally locked against the rod at selected positions along the first and second curved portions of the rod to support the back section at a desired inclination, the rod being pivotable between the subtop and the back section as the back section is moved between the lowered and raised positions without interfering with the subtop or the back.

2. The structure of claim 1 in which the rod is pivotally mounted on the subtop and the latch plate is pivotally mounted on the back section, the rod and the latch plate being positioned generally along the longitudinal center line of the table, the latch plate being connected to shaft means extending laterally outwardly from the latch plate in at least one direction and terminating adjacent one of the sides of the back section, the shaft means being rotatably mounted on the back section, lever means on the shaft means adjacent said one side for rotating the shaft means whereby the latch plate may be rotated into a substantially perpendicular relationship with the rod to release the frictional engagement between the latch plate and the rod to permit movement of the rod through the opening in the latch plate.

5. The structure of claim 1 in which the first and second end portions form an included angle of about 170*.

6. The structure of claim 1 in which the first curved portion extends along an arc having a radius of about 2-1/l6 inches and an angle of about 43* and the second curved portion extends along an arc having a radius of about 7-5/16 inches and an angle of about 53 1/2 *.

7. The structure of claim 6 in which the first end portion is substantially straight and has a length of about 1 1/4 inch and the second end portion is substantially straight and has a length of about 5-5/16 inches.

8. The structure of claim 6 in which the first and second end portions form an included angle of about 170*.

9. In an examination table having a base, a subtop supported by the base, and a top supported by the subtop, the top having a tiltable back section pivotable about a horizontal axis between a substantially horizontal lowered position in which the back section is spaced slightly from the back section and a raised position, an improved support assembly for the back section of the top comprising a. an elongated rod having first and second ends and being pivotally attached adjacent its first end to the subtop for pivotal movement about a horizontal axis spaced from the pivot axis of the back section, the rod including i. a first substantially straight end portion extending from the first end, the first end portion extending generally rearwardly from the pivotal attachment of the rod to the subtop when the back section is in the lowered position, ii. a first arcuate portion curving upwardly and rearwardly from the first end portion when the back is in the lowered position, the arc of the first arcuate portion having a center positioned above a line extending between the ends of the rod, iii. a second arcuate portion curving upwardly and rearwardly from the first arcuate portion and then downwardly away from the back section when the back is in the lowered positIon, the curvature of the second arcuate portion being opposite to the curvature of the first arcuate portion, the arc of the second arcuate portion being longer than the arc of the first arcuate portion ahd having a center positioned below a line extending between the ends of the rod, and iv. a substantially straight second end portion extending from the second arcuate portion away from the back section when the back is in the lowered position, the first and second end portions forming an included angle of less than 180*, the rod being completely enclosed within the space between the subtop and the back section when the back section is in the lowered position, b. a latch plate mounted on the back section for pivotal movement about a horizontal axis and having an opening therethrough slightly greater than the diameter of the rod, the rod extending through the opening in the latch plate and the periphery of the opening in the latch plate being engageable with the rod when the latch plate is moved away from a perpendicular relationship with the rod whereby the latch plate can be frictionally locked against the rod at selected positions along the first and second arcuate portions and the second end portion of the rod to support the back section at a desired inclination.

12. The structure of claim 9 in which the first and second end portions form an inclined angle of about 170*.

13. The structure of claim 9 in which the first curved portion extends along an arc having a radius of about 2-1/16 inches and an angle of about 43* and the second curved portion extends along an arc having a radius of about 7-5/16 inches and an angle of about 53 1/2 *.

14. The structure of claim 13 in which the first end portion has a length of about 1 1/4 inch and the second end portion has a length of about 5-5/16 inches.