US3161159A

US3161159A - Counterbalanced tiltable table

Info

Publication number: US3161159A
Application number: US331865A
Authority: US
Inventors: Victor J Kritske
Original assignee: Mayline Co
Current assignee: Mayline Co Inc; Mayline Co
Priority date: 1963-12-19
Filing date: 1963-12-19
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15

Description

1964 v. J. KRITSKE 3,161,159

COUNTERBALANCED TIL-TABLE TABLE Filed Dec. 19, 1963 VII 5554 25 225775.5727? United States Patent Office Zi,lfil,l 9 Patented Dec. 15, 1064 This invention relates to tables of the type having a tiltable top board and particularly to improvements in counterbalanced tiltable tables of the type disclosed in the copending application of Elwood H. May and Victor J. Kritske, Serial No. 237,021, filed November 13, 1962, now US. Patent 3,131,654 for Counterbalanced Tiltable Table.

An important object of this invention is to provide a tiltable table having a novel arrangement for counterbalancing the tiltable top board and any apparatus mounted thereon in the various different angular positions of the top board.

Another object of this invention is to provide a tiltable table having an improved arrangement for mounting the counterbalancing springs to provide smooth and easy adjustment and operation of the tiltable table.

A more particular object of this invention is to provide a tiltable table having a torsion spring for counterbalancing the tiltable top board, wherein the spring is located within a tube attached to the tiltable top board, and is so constructed and arranged that it operates to yieldably oppose movement of the board to its upright position to prevent overbalancing of the board as it approaches the vertical, and to also yieldably oppose movement of the board to its horizontal position.

Still another object of this invention is to provide a table having a tiltable top board wherein the counterbalancing springs are located within a tube attached to the tiltable top board and which has an improved arrangement for adjustably anchoring the ends of the springs to facilitate adjusting the torsion in the springs to counterbalance the board in its different operative positions. 7

A further object of this invention is to provide a table of the type having a tiltable top and which has an improved arrangement for supporting the board intermediate its ends to prevent sagging or warping of the board.

These, together with other objects and advantages of this invention will be more readily appreciated as the invention becomes better understood by reference to the following detailed description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a table employing the improved table top mounting and counterbalancing arrangement;

FIG. 2 is a fragmentary longitudinal sectional view through the table top mounting and counterbalancing assembly;

FIG. 3 is a fragmentary end elevational view taken on the plane 3-3 of FIG. 2; and

FIG. 4 is a diagrammatic view illustrating the table top at different angular adjusted positions therefor.

The table top mounting and counterbalancing assembly of the present invention is particularly adapted for use in a drafting table and is herein shown and described in that application. As shown in FIG. 1, the table in general includes a base having end frame sections 11 and, preferably, a desk level top 12 that is attached to and extends between the end frame sections. The table also includes spaced support members designated 13 and 13a which are mounted on the base 10. The support members are preferably mounted for vertical movement with respect to the base to enable adjustment of the height of the table top and may, for example, be

adjustably supported in the manner shown in the patent to May, No. 2,982,050. A drafting table top or board 15 is mounted on the

support members

13 and 13a for vertical adjustment therewith, and alsofor tilting movement relative thereto between a generally horizontal and an upright position. As diagrammatically shown in the drawings, the pivot axis P for the table top is located relatively closer to the edge 15' than to the edge 15" of the board 15, and is also laterally olfset from the underside of the board. With this arrangement, the board is balanced only when the center of mass of the board and any apparatus such as drafting machines D mounted thereon, is disposed vertically above the tilt axis designated P of the board. For example, a board constructed as shown in the drawings wherein the pivot axis is offset from the underside of the board, would balance in a preselected range designated B, for example between eight and twelve degrees from a vertical or upright position as shown in FIG. 4. As the board moves downwardly from this balance B, the unbalance on the board increases and reaches a maximum when the board is in a horizontal position H. Conversely, as the board moves upwardly from the balance B position, the unbalance also increases but in a relatively opposite direction until the board reaches an upright or vertical position V. The counterbalancing apparatus of the present invention is arranged to counteract or counterbalance the weight of the board and any apparatus such as a drafting machine thereon as the board moves from the aforementioned balance position toward a horizontal position, H, and also to counteractor counterbalance the, board and the instruments thereon as it moves from the aforementioned balance position toward an upright position V, to prevent rapid movement of the board to either horizontal or upright position and to facilitate angular adjustment of the board.

The pivot axis for the board 15 is advantageously rearwardly offset from the

support posts

13, 13a to provide additional knee room and as best shown in FIG. 3, spaced support plates or

brackets

16, 16a are attached to the outer faces of the

support posts

13, 13a

and similar brackets 17, 17a are attached to the inner faces of the posts and project rearwardly therefrom. A tubular shaft 19 has opposite end portions thereof extending through aligned

openings

21, 22 in the plates 16, Tea and 17, 17a respectively, and is rotatably supported thereby on the end brackets. Collars 23, 23:: are attached to the shaft 19 asby set screws 24 and engage respective ones of the brackets 17, 17a to retain the shaft against axial movement. A brace rod 20 is preferably provided to extend between the end brackets at opposite ends of the table to maintain the same in proper spaced relation and, as shown in FIG. 3, is conveniently attached by fasteners 20' to the

outer brackets

16 and 16a. Table

top support brackets

25, 25a are non-rotatably mounted on the shaft adjacent opposite ends and, as shown, the brackets each include spaced plates 27 and 28 which are secured to the shaft as by welding, as indicated at 29. The

brackets

25 and 25a are advantageously positioned closely adjacent the plate 17, 17a of the support brackets and a thin washer 30 drafting board increases as the board moves downwardly from its balance position B toward a horizontal position and also increases as the board moves upwardly from the balance position to an upright position. However, the effective weight of the board and any instruments mounted thereon which must be counterbalanced as the board approaches its horizontal position, is substantially greater than the weight that must be counterbalanced when the board approaches its upright position. In the present embodiment of the invention, a pair of counterbalancing' springs 33 and 33a are disposed within the tube 19' and are advantageously so' aranged that both springs cooperate to yieldably oppose downward movement of the board as the board approaches its horizontal position, and at least one spring is arranged to also yieldably oppose upward movement of the board as it approaches its upright position; In this manner, both springs are employed when maximum lifting force is required and at' least one spring remains effective to'yieldably oppose movement of the board in the opposite direction as it approaches its upright position. The springs 33 and 33a are of the coil type and have an outer diameter slightly smaller than the inner diameter of the shaft or tube 19, so as to permit free movement of the springs within the tube. The springs are advantageously formed with longitudinally extending

inner end portions

34 and 34a and are similarly formed with longitudinally extending outerend portions 35 and 35a. These end'portions, as best shown in FIG. 2, extend lengthwise of the tube and are radially offset from the axisof the tube. Inner anchor members 37 arid 37a are disposed in tube and are non-slidably and non-rotatably attached thereto as by

bolts

38 and 38 The inner anchor members have longitudinally extending

sockets

39 and 39a which slidably and non -rotatably receive the

inner end portions

34 and 34a of the springs. A guide pin of

rod

40, 40a is preferably provided on the

anchor members

37 and 37a and eit'tends into the end of the respective coil spring to guide the same and maintain the springs out of rubbing engagement with the tube.

Outer anchor members

41 and 41a are rotatably disposed in the ends of the tube 19 and have longitudinally extending eccentrically positioned sockets 42 and 42a that slidably and non-rot'atably receive the outer end portions 35 and 35a on the springs. The outer anchor members are also advantageously formed with axially projecting pins 43 and 43a that extend into the outer ends of the coil springs to radially support and center the same in the tube. The outer anchor members 41' and 41a are angularly adjustable to adjust the torsion in the respective springs and, in order to facilitate angular adjustment, provision is made for inhibiting axial movement of the outer anchor members while permitting free angular adjustment thereof. For this purpose, the outer anchor members are formed with peripheral grooves or

recesses

44 and 44a and a key such as a set screw 45 is attached to the shaft adjacent each end and arranged to project into the recess or groove in the outer anchor members to prevent axial movement of the anchor members while permitting free turning of the same. The outer ends of the anchor members are formed with multi-sided head 46 for receiving a wrench or the like to facilitate angular adjustment of the anchor members and the torsion in the springs, and an improved lock is provided for securing the anchor members in their adjusted position. As best shown in FIG. 3, the anchor members are provided with peripherally notched

disks

48, 48a which are welded or otherwise non-rotatably secured to the respective anchor member. The disks are formed with preferably square notches 49 in their outer periphery and a locking member 51 is attached to the respective support bracket to cooperate with the notches andsecure the anchor members in adjusted position. The clocking member is conveniently slidably supported on a bracket 52 for movement toward and away from the notched disk, and a means the horizontal positions.

such as a screw 53 is provided to secure the locking member in its locking position as shown in FIG. 3. As will be seen, the locking member 51 cooperates with the generally square notches 49 in the disk to lock the anchor members against turning movement in either direction relative to the respective support bracket.

From the foregoing, it will be seen that the

inner ends

34 and 34a of the springs are non-rotatably connected to the tube in such a manner as to inhibit relative turning between the springs and tube in either direction. Similarly, the other ends of the springs 35 and 35a are nonrotatably attached by the anchors 41', 41a to the end supports in such a manner as to prevent turning of the outer ends of the springs in either direction relative to the supports. The springs can thus be twisted in both directions from null or undistended condition so as to both counteract the weight of the board as it approaches the horizontal and as it approaches the vertical. The springs are made relatively stiff and sufficient to counterbalance the weight of the board and any instruments thereon when the springs are turned through a relatively small angle and the positions of the outer ends of the spring are adjustable to accommodate boards of different weight and also boards having different drafting instruments and other apparatus mounted thereon. While both springs 33 and 3311 could be used to counterbalance the board both at the horizontal and vertical positions, it is more convenient and preferable to angul'arly adjust one of the springs such as 33 to provide the main lifting force for counteracting the Weight of the board When the latter is in its horizontal position, and to adjust the other spring such as 33a to assist in counteracting the weight of the board when the latter is in its horizontal position and to reverse and yieldably oppose upward movement of the board as the board approaches itsvertical position. For example, spring 33 can be adjusted when the board is in its vertical position so that it has substantially no distention or twist. As the board moves downwardly from its vertical position, the twist in the spring 33 increases and yieldably opposes downward movement of the board. The other spring 33a is then adjusted so that is has no distention or twist when the board is in a position intermediate the upright and For example, the anchor 41a for the spring 33a may be initially adjusted to a position such that the spring 33a has no distention or twist when the board is at a position approximately 45 from the horizontal and indicated by the 45 line in FIG. 4. As the board moves downwardly from the 45 position, the twist in the spring 33a increases in a direction to oppose downward movement of the board so that the spring 33a aids in counteracting the weight of the board as it approaches its horizontal position. Conversely, when the board is moved above the 45 position, the spring. 33a: is twisted in a relatively opposite direction and applies a progressively increasing resistance to upward movement of the board. The springs 33 and 33a thus combine to apply a relatively larger force to aid in counteracting the weight of the board and drafting instruments when the board is in its horizontal position and, when the board.

reaches an intermediate position at which the spring 33a: reverses, the torsion in the spring 33a builds up in an op posite direction and opposes the torsion in spring 33 so that, when the board is in its upright position, the torsion,

33a is made such that even with the maximum weight board and auxiliary apparatus on the board, the spring 33 does not have to be adjusted to a large angle and The,

preferably not through an angle of more than anchor 41a for the spring 33a is always adjusted so that the spring 33a reaches its null or zero distention position at a point intermediate the horizontal and upright positions of the board and is, accordingly, twisted through an angle of substantially less than 90 when the board is in either a horizontal or upright position.

Problems have been encountered in relatively large drafting boards due to sagging or bulging of the drafting board intermediate the end supports 31 and 31a. An improved support is provided to overcome this problem and, as best shown in FIG. 2, an intermediate support bracket 51 is attached to the tube 19 intermediate its ends, and to the underside of the board 15. As shown, the intermediate support includes a rail 52 attached to the underside of the board and a post attached to the rail and secured to the tube 19. The post is preferably adjustably secured to the tube to permit accurate compensation for sag or bulging of the board and, for this purpose, is externally threaded and extends through aligned openings 53 in the tube.

Nuts

54 and 55 are threaded on the post and engage opposite sides of the tube to secure the post in an adjusted position.

Any suitable apparatus may be provided for locking the board in different angularly adjusted positions. In the embodiment illustrated, the locking apparatus is of the type disclosed'in my copending application, Serial No. 274,553 filed April 22, 1963. In general, this adjustable locking apparatus includes a sector plate 61 having a plurality of angularly spaced openings 62 disposed concentric with the tube 19 and a reciprocable dog 63 carried by the drafting board and movable into the. openings 62 to lock the drafting board in adjusted position. The dog is slidably mounted in a guide 64 carried by the bracket plates 27, 28 and a bell crank 65 is pivotally mounted at 66 on the bracket plates and operatively connected through a pin and slot arrangement 67 to the reciprocable locking dog. The bell crank 55 is, in turn, connected through a link 69 to an actuating shaft 71, at a point eccentrically of the latter. The actuating shaft 71 is conveniently rotatably mounted in the support brackets 27 and 28 and has an operating handle 72 to enable manual release of the locking dog. A spring (not shown) is provided for yieldably urging the dog into its locking position. Only one locking mechanism need be provided for locking the board in its angularly adjusted position. As best shown in FIGS. 2 and 3, one of the support plates such as 27a is provided with a sector plate 72 and an arcuate slot 73 disposed concentric with the shaft. A stationary follower pin 74 is attached to one of the support brackets and projects into the slot 73. While a particular board locking mechanism is herein illustrated and described for locking the board in its angularly adjusted positions, it is obvious that other locking mechanisms could be provided, if desired, without departing from the scope of the present invention.

From the foregoing, it is thought that the construction and operation of the device will be readily understood. The springs 33 and 33a are each terminally anchored to the tube and to the stationary support in such a manner that the springs can be twisted in relatively opposite directions. The torsion in the springs 33 and 33a can be independently adjusted by adjustment of the

respective anchors

41 and 41a. In the preferred form, one spring such as 33 is adjusted so as to provide the major portion of the lifting force necessary to counterbalance the board as it moves to a horizontal position, and the other spring such as 33 is adjusted so that its null point is intermediate the horizontal and upright positions. With this arrangement, the spring 33a will assist in counterbalancing the board as it approaches its horizontal positions and will also be twisted in a relatively opposite direction as the board approaches its vertical position to inhibit rapid movement of the board to its upright position.

I claim:

1. A drafting table comprising;

a base having first and second spaced supports;

a drafting board having mounting brackets adjacent opposite ends extending laterally from the underside of the board;

a tube rotatably mounted in said first and second spaced supports and extending horizontally therebetween;

said tube being non-rotatably secured to each of said mounting brackets to substantially equalize the torque applied to the mounting brackets and thereby minimize twisting of said board, said tube being spaced laterally from the underside of the board to pivotally support said board for movement about the axisrof said tube between a generally horizontal position and a generally upright position, said tube being located relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is normally overbalanced as it approaches said horizontal position, the offset between the board and the tube axis causing the board to be normally overbalanced as it approaches said upright position; i

a torque applying spring disposed inside said tube;

means non-rotatably attaching one end of said spring to the tube intermediate the ends of the latter to apply the torsion in the spring to the tube;

spring anchor means attached to the other end of the spring for angularly adjustably anchoring the other end of the spring on one of said supports;

said spring anchor means being attached to said support in a position to apply a twist in said spring, when the board is in said horizontal position, which twist is on one direction to yieldably urge the board up from its horizontal position and is less than one-quarter turn from the normal undistorted position of the spring whereby the twist in the spring decreases as the board is raised and reaches zero twist when the board reaches a position intermediate said horizontal and upri ht positions and the twist then increases in .the other direction .to yieldably oppose movement of the board toward its upright position;

and selectively operable means for locking said board in different angularly adjusted positions between said horizontal and upright positions.

' 2. A drafting table comprising;

a base having first and second spaced supports;

a tube rotatably mounted in said first and second supports and extending horizontally therebetween;

said tube being non-rotatably attached to each mounting brackets to substantially equalize the torque applied to the mounting brackets at opposite ends of the board and thereby minimize twisting of the board, said tube being spaced laterally from the underside of the board and supporting the board for movement between a generally horizontal and a generally upright position, said tube being located intermediate the edges of the board but relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is overbalanced as it approaches said horizontal position, the offset between the board and the tube axis causing the board to be normally overbalanced as it approaches said upright posit-ion;

at least one torque applying spring inside said tube;

a first anchor means non-rotatably connecting one end of said spring to said tube to prevent relative turning between said one end of the spring and the tube in either direction;

a second anchor means at one end of the tube non-rotatably connected to the other end of said spring to prevent relative turning between said other end of the spring and said second anchor means; 7

means for locking said second anchor means to one of said supports in different angularly adjusted positions to prevent turning of the second anchor means from its adjusted position in either direction relative to that support;

said second anchor means being angularly adjusted relative to said support to a position in which said second spring is in an undistended condition when the board is in a position intermediate said horizontal and upright positions;

said spring being twisted when the board is in a horizontal position through an angle of less than 90 degrees from an undistended condition and in one direction to yieldably urge the board in an upwardly direction away from said horizontal position and said spring being twisted when the board is in an upright position through an angle of less than 90 degrees from said undistended condition in the other direction to yieldably urge the board in a downwardly direction away from said upright position;

and selectively operable means for locking said board in different angularly adjusted positions between said horizontal and said upright positions.

3. A drafting table comprising;

a base having first and second spaced supports;

said tube being non-rotatably attached to each mounting bracket to substantially equalize the torque applied to the mounting brackets at opposite ends of the board and thereby minimize twisting of the board, said tube being spaced laterally from the unders-ide of the board and supporting the board for movement between a generally horizontal and a generally upright position, said tube being located intermediate the edges of the board but relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is overbalanced as it approaches said horizontal position, the offset between the board and the tube axis causing the board to be normally overbalanc'ed as it approaches said upright position;

first and second torque applying springs inside said tube;

first and second anchor means non-rotatably connecting one end of said first and second springs to said tube at points located intermediate the ends of the tube to prevent turning between said one end of said springs and the tube in either direction;

a third anchor means at one end of the tube non-rotatably connected to the other end of said first spring and engaging said first support and providing an angularly adjustable anchor for said first spring;

a fourth anchor means at the other end of the tube nonrotatably connected to the other end of said second spring and engaging said second support and providing an angularly adjustable anchor for the other end of said second spring;

said third and fourth anchor means being independently adjustable to enable individual adjustment of the torsion in each spring for counterbalancing said board;

said first spring being twisted when the board is in its horizontal position in a direction to yieldably urge the board in an upwardly direction away from said horizontal position;

said fourth anchor means being adjusted relative to said second support to a position such that said second spring is in an undistended condition when the board is in a position intermediate said horizontal and upright positions;

said second spring being twisted when the board is in its horizontal position through an angle of less than degrees from said undistended condition in a first direction to aid in yieldably urging the board in an upwardly direction away from said horizontal position and being twisted when the board is in its upright position through an angle of less than 90 degrees from' said undistended condition in a direction opposite said first direction to yieldably urge said board in a downwardly direction away from said upright position;

4. A drafting table comprising;

a base having first and second spaced supports;

said tube b'eing non-rotatably attached to each mounting bracket to substantially equalize the torque applied to the mounting brackets at opposite ends of the board and thereby minimize twisting of the board, said tube being spaced laterally from the underside of the board and supporting the board for movement between a generally horizontal and a generally' upright position, said tube being located intermediate the edges of the board but relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is overbalanced as it approaches said horizontal position, the offset between the board and the tube axis causing the board to be normally overbalanced as it approaches said upright position;

first and second helical torque applying springs in said tube eachhaving end projections on opposite ends thereof extending generally parallel to the axis of the springs and radially offset from the center thereof;

first and second anchor members in said tube intermediate the ends thereof and non-rotatably attached to said tube, said first and second anchor members each having a socket therein generally parallel to the axis of the tube and radially offset from the center thereof and slidably and non-rotatably receiving one end projection on" the first and second springs respectively;

third and fourth anchor members rotatably disposed in said tube at opposite ends thereof, said second and third anchor members each having a socket therein generally parallel to the axis of the tube and radially offset from the center thereof and slidably and nonr'otat'ably receiving the other end projections on the first and second springs, respectively;

said third and fourth anchor members each having a eripheral recess therein, keys on said tube extending into said recesses to constrain the third and fourth anchor member against axial slid-ing in the tube while permitting rotation thereof;

first and second locking means for selectively locking said third and fourth anchor members to said first and second supports in a selected angularly adjusted position thereof to independently adjust the torsion in each spring for counterbalancing the board;

and selectively operable means for locking the board in different angularly adjusted positions between said horizontal and said upright positions.

5. The combination of claim 4 wherein said first and second locking means includes a notched disk attached to each said third and fourth anchor members, and a latch secured to each of said first and second supports and engageable with a respective one of said notched disks to 6. A drafting table comprising;

a base having first and second spaced supports;

said tube being non-rotatably attached to each mounting bracket to substantially equalize the torque applied to the mounting brackets at opposite ends of the board and thereby minimize twisting of the board, said tube being spaced laterally from the underside of the board and supporting the board for movement between a generally horizontal and a generally upright position, said tube being located intermediate the edges of the board but relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is overbalanced as it approaches said horizontal position, the offset between the board and the tube axis causing the board to be normally overbalanced as it approaches said upright position;

first and second anchor members in said tube intermediate the ends thereof and non-rotatably attached to said tube, said first and second anchor members each having a socket therein generally parallel to the axis of the tube and radially offset from the center thereof and slidably and non-rotatably receiving one end projection on the first and second springs respectively;

third and fourth anchor members rotatably disposed in said tube at opposite ends thereof, said second and third anchor members each having a socket therein generally parallel to the axis of the tube and radially offset from the center thereof and slidably and nonrotatably receiving the other end projections on the first and second springs, respectively;

said third and fourth anchor members each having a peripheral recess therein, keys on said tube extending into said recesses to constrain the third and fourth anchor members against axial sliding in the tube while permitting rotation thereof;

7. A drafting table comprising;

a base having first and second spaced supports;

said tube being non-rotatably attached to each mounting bracket to substantially equalize the torque applied to the mounting brackets at opposite ends of the board and thereby minimize twisting of the board, said tube being spaced laterally from the underside of the board and supporting the board for movement between a generally horizontal and a generally upright position, said tube being located intermediate the edges of the board but relatively closer to the side edge of said board that is lowermost when the board is upright whereby the board is overbalanced as it approaches said horizontal position, the olfset between the board and the tube axis causing the board to be normally overbalanced as it approaches said upright position;

first and second torque applying springs inside the tube;

first and second anchor means connecting one end of each spring to said tube at points located intermediate the ends of the tube to apply the torsion in the springs to the tube;

a third anchor means at one end of the tube nonrotatably connected to the other end of said first spring and engaging said first support providing an angularly adjustable anchor for said other end of said first spring;

a fourth anchor means at the other end of the tube connected to the other end of said second spring and engaging said second support providing an angularly adjustable anchor for said other end of said second p said third and fourth anchor means being independently adjustable to enable individual adjustment of the torsion in each spring for counterbalancing the board;

an intermediate board support attached to said board and to said tube at a point intermediate the ends of the latter for supporting the board intermediate said board mounting brackets to inhibit sagging of the board;

8. The combination of claim 7 wherein said intermedisaid fourth anchor means being adjusted relative to said second support to a position such that said second spring is in an undistended condition when the board is in a position intermediate said horizontal and upright positions;

said second spring being twisted in one direction when ate support bracket is adjustable to vary the spring between the board and the tube at the point of attachment of the intermediate bracket.

References Cited by the Examiner UNITED STATES PATENTS the board is in its horizontal position through an 1,759,878 5/30 Cizzo 108--134 X angle of less than 90 degrees from said undistend 1,856,297 5/32 Marie et a1. 297-426 condition to aid in yieldably urging the b ard i a l 1,859,456 5/32 Nestler 108-2 upwardly direction away from said horizontal posi- 1,956,546 4/34 Froelich 108--2 tion and being twisted in the opposite direction wh n 3,078,613 2/63 Morcheles 108-2 the board is in its upright position through an angle 3 039 275 5 3 Alabor 10 2 of less than 90 degrees from said un istended condi- 54 5 4 May 1 T: og-z tion to yieldably urge said board in a downwardly direction y from said upright position; FRANK B. SHERRY, Primary Examiner.

UNITED STATES PATENT OFFICE CE F Patent No. 3,161,159 December 15, 1964 Victor J. Kritske It is hereby certified that error appears in the above numbered patent req'iiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 61, for "member'" read members column 9, after line 24, insert:

first and second helical torque applying springs in said tube each having end projections on opposite ends thereof extending generally parallel to the axis of the springs and radially offset from the center thereof;

(SEAL) Signed and sealed this 18th day of May 1965.

Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Anvsting Officer Commissioner of Patents

Claims

1. A DRAFTING TABLE COMPRISING; A BASE HAVING FIRST AND SECOND SPACED SUPPORTS; A DRAFTING BOARD HAVING MOUNTING BRACKETS ADJACENT OPPOSITE ENDS EXTENDING LATERALLY FROM THE UNDERSIDE OF THE BOARD; A TUBE ROTATABLY MOUNTED IN SAID FIRST AND SECOND SPACED SUPPORTS AND EXTENDING HORIZONTALLY THEREBETWEEN; SAID TUBE BEING NON-ROTATABLY SECURED TO EACH OF SAID MOUNTING BRACKETS TO SUBSTANTIALLY EQUALIZE THE TORQUE APPLIED TO THE MOUNTING BRACKETS AND THEREBY MINIMIZE TWISTING OF SAID BOARD, SAID TUBE BEING SPACED LATERALLY FROM THE UNDERSIDE OF THE BOARD TO PIVOTALLY SUPPORT SAID BOARD FOR MOVEMENT ABOUT THE AXIS OF SAID TUBE BETWEEN A GENERALLY HORIZONTAL POSITION AND A GENERALLY UPRIGHT POSITION, SAID TUBE BEING LOCATED RELATIVELY CLOSER TO THE SIDE EDGE OF SAID BOARD THAT IS LOWERMOST WHEN THE BOARD IS UPRIGHT WHEREBY THE BOARD IS NORMALLY OVERBALANCED AS IT APPROACHES SAID HORIZONTAL POSITION, THE OFFSET BETWEEN THE BOARD AND THE TUBE AXIS CAUSING THE BOARD TO BE NORMALLY OVERBALANCED AS IT APPROACHES SAID UPRIGHT POSITION; A TORQUE APPLYING SPRING DISPOSED INSIDE SAID TUBE; MEANS NON-ROTATABLY ATTACHING ONE END OF SAID SPRING TO THE TUBE INTERMEDIATE THE ENDS OF THE LATTER TO APPLY THE TORSION IN THE SPRING TO THE TUBE; SPRING ANCHOR MEANS ATTACHED TO THE OTHER END OF THE SPRING FOR ANGULARLY ADJUSTABLY ANCHORING THE OTHER END OF THE SPRING ON ONE OF SAID SUPPORTS; SAID SPRING ANCHOR MEANS BEING ATTACHED TO SAID SUPPORT IN A POSITION TO APPLY A TWIST IN SAID SPRING, WHEN THE BOARD IS IN SAID HORIZONTAL POSITION, WHICH TWIST IS ON ONE DIRECTION TO YIELDABLY URGE THE BOARD UP FROM ITS HORIZONTAL POSITION AND IS LESS THAN ONE-QUARTER TURN FROM THE NORMAL UNDISTORTED POSITION OF THE SPRING WHEREBY THE TWIST IN THE SPRING DECREASES AS THE BOARD IS RAISED AND REACHES ZERO TWIST WHEN THE BOARD REACHES A POSITION INTERMEDIATE SAID HORIZONTAL AND UPRIGHT POSITIONS AND THE TWIST THEN INCREASES IN THE OTHER DIRECTION TO YIELDABLY OPPOSE MOVEMENT OF THE BOARD TOWARD ITS UPRIGHT POSITION; AND SELECTIVELY OPERABLE MEANS FOR LOCKING SAID BOARD IN DIFFERENT ANGULARLY ADJUSTED POSITIONS BETWEEN SAID HORIZONTAL AND UPRIGHT POSITIONS.