US2710782A

US2710782A - Pull out typewriter supports

Info

Publication number: US2710782A
Application number: US243268A
Authority: US
Inventors: Marc E Chaft
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-08-23
Filing date: 1951-08-23
Publication date: 1955-06-14
Anticipated expiration: 1972-06-14

Description

June 14, 1955 I M. E. CHAFT 2,710,732

PULL OUT TYPEWRITER SUPPORTS 3 Sheets-Sheet 1 Filed Aug. 25, 1951 INVENTOR. MARC E CHA FT ATTORNEY M. E. CHAFT "2,710,782 r I :5 Sheets-Sheet 2 IN V EN TOR.

ATTORNEY PULL ou'r TYPEWRITER SUPPORTS June 14, 1955 Filed'Aug; as 1951 United States atent Patented dune 14, 1955 liee This invention relates to pull out typewriter supports. It is particularly directed to a desk having means to support a typewriter within the desk, at a relatively lower level, and means to permit the typewriter support to be pulled out in front of the desk and raised to a higher level and maintained at such level, so that the typist may use the typewriter.

An object of this invention is to provide a highly improved device of the character described, including common spring means for both raising and lowering the typewriter support, and for yieldably retaining the support in raised or lowered position.

A further object of this invention is to provide in a device of the character described, highly improved locking means for preventing raising of the typewriter support until it is pulled forwardly to a predetermined position, said means being releasable when the typewriter support or table is pulled forward to such position, thereby permitting raising of the typewriter support or table to its higher level in front of the desk.

Still another object of the present invention is to provide in a device of the character described, a pair of aligned horizontal rails, a carriage supported on the rails by means of rollers for forward and backward movement, a horizontal typewriter table fixed at its rear end to the carriage and extending forwardly thereof, means to permit swinging of the rails from a lower to a higher position, means to lock said rails in its lower position, said means being releasable by moving the carriage and table forwardly to a predetermined position to release the locking means to permit swinging of the rails upwardly, and means on the carriage to retain the typewriter table in its forwardly pulled position, and to prevent side sway of the typewriter table while it is being swung upwardly.

Yet another object of this invention is to provide in a device of the character described releasable catch means to lock the typewriter table in its raised position and to prevent side sway of the typewrite table while it is being used in its raised position.

Still a further object of this invention is to provide a device of the character described which shall be relatively inexpensive to manufacture, easy to manipulate, smooth and positive in operation, and yet practical and eflicient to a high degree in use.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts, which will be exemplified in the construction hereinafter described, and of which the scope of invention will be indicated in the following claims.

In the accompanying drawings in which are shown various illustrative embodiments of this invention,

Fig. l is a vertical cross-sectional view of a desk provided with a pull out typewriter support embodying the invention, and showing the support in lowered position;

Fig. 2 is a partial view of Fig. l with the support pulled forwardly but not fully;

Fig. 3 is a view similar to Fig. l, but showing the support in raised position;

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 1;

Fig. 5 is a cross-sectional view taken on line 5-5 of Fig. 1;

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 1;

Fig. 7 is a cross-sectional view taken on line 7-7 of Fig. 1;

Fig. 8 is a cross-sectional view taken on line 88 of Fig. 1;

9 is a cross-sectional view taken on line 9-9 of Fig. 1;

Fig. 10 is a of Fig. 1;

Fig. 11 is an enlarged sectional View illustrating the table catch;

cross-sectional view taken on line 1il10 Fig. 12 is a cross-sectional view taken on line 1212 of Fig. 11;

Fig. 13 is a front elevational view of the catch guide; and

Fig. 14 is an elevational view of the catch retainer.

Referring now in detail to the drawing, 10 designates a device embodying the invention. The same comprises a typewriter desk 11 which may be provided with front corner posts 12 and rear corner posts 13. The front corner posts 123 have legs 12a at their lower ends and the rear corner posts 13 have legs 13a at their lower ends. At the upper ends of the legs 12a, 13a is a bottom, horizontal wall 14. The corner posts 12. and 13 are interconnected by side walls 15. The rear corner posts 13 are interconnected by a rear wall 16. The upper ends of the front corner posts 12 are interconnected by a horizontal cross bar 18.

Supported by the desk 11 is the pull out typewriter table mechanism 20. The mechanism comprises a pair of parallel, horizontally aligned, similar, symmetrically disposed bars 21 attached at their front ends to the front corner posts 12 as by screws 22, and attached at their rear ends as by screws 23 to the rear corner posts 13. The bars 21 are located substantially midway between the bottom wall 14 and the upper end of the desk. The desk may be provided with any suitable top wall (not shown). It will be understood furthermore that the mechanism 2! may be incorporated into any suitable desk or support, and the only attachment of the mechanism 20 to the desk or support is by means of the parallel bars 21.

The bars 21 are formed with outwardly pressed portions 23a located closer to their rear ends than to their front ends. The portions 23a are parallel to the main portions of the bars and are connected to said main portions by offset shoulder portions 24. Pivoted to the bars 21 as on pivot pins 25, located forwardly of portions 23a, are front bell cranks 26. The bell cranks 26 are similar and symmetrically disposed to one another. They are located on the inside of the bars 21.

Each bell crank 26 has a portion 27 formed with a through opening 23 through which a pivot pin passes. Each pivot pin 25 has a central spacer portion 29 to space portion 27 of the bell crank 26 from the bar 21. It has a reduced outer end 30 received in the opening 28 in said portion 27, and an opposite reduced end 31 passing through an opening in the bar 21. Said reduced ends 30 and 31 are riveted over to keep bell crank 26 assembled with the bar 21.

It will now be observed that the portion 27 is in a plane disposed inside of the plane of bar 21. Extending from portion 27 is an arm 32 in the plane of said portion 2'7. Said arm 32 is formed with a pivot opening 33 for the purpose hereinafter appearing. It will be noted that the arms 32 of the bell cranks 26 project forwardly when the typewriter table is in its lower position, as will be ex plained hereinafter.

The portions 27, 32 of each bell crank are in a vertical plane. Extending outwardly from each portion 27 is an offset portion 34 from which extends downwardly and forwardly an inclined portion 35, likewise disposed in a vertical plane just inside of the plane of the bar 21. Offset inwardly from the lower end of the portion 35 is a portion 36 from which extends downwardly a portion 37, likewise disposed in a vertical plane. Portion 3'7 is disposed substantially in the plane of the portion 27. Fixed to the inner surface of each portion 37 is a locking cam 40 disposed in a vertical plane. The portion 37 and the locking cam 49 are formed with registering through openings 41 through which extends portion 42 of a pivot pin 43. Portion 37 may be provided with an extruded pin portion 44 extending through openings in the cam 40 for locating said cam.

The cam 40 has a circular outer peripheral edge 45. The peripheral edge 45 extends through an angle of about 180 beginning at its forward end from a point 46 (Fig. 1) above the level of the pivot pin 43 and extending downwardly and rearwardly around to a point 47 below and in back of the pivot pin 43. Extending from the point 47 upwardly is an inwardly curved peripheral edge 48. The peripheral edge 45 has a radius about the axis of pivot pin 43. The cam 40 is preferably hardened and hence is made separately from the bell crank 26 and is fixed thereto as by welding. The extruded pins 44 serve as locating pins for locating the locking cam 4% relative to the bell crank.

Each pivot pin 43 is formed with a spacer portion 59 at the inner side of the locking cam 49 and extending therefrom is a reduced portion 50a passing through an opening in a horizontal rail 51. It will now be understood that the front portions of the rails 51 are suspended from the bars 21 by means of the bell cranks 26. It will now be further understood that the rails 51 are spaced inwardly of the locking earns 40 by means of the spacers 50.

Said rails 51 are also suspended from the bars 21 by means of rear bell cranks 55. It will be noted that there are two rear bell cranks 55 and that they are similar and symmetrically disposed with respect to one another. Each bell crank 55 comprises a portion 56 disposed in a vertical plane and inclined forwardly and downwardly at substantially the same angle as portions 35 of bell cranks 26. At the lower end of portion 56 is an outwardly offset portion 57 from which extends downwardly a portion 53 disposed in the plane of portion 56. Portion 58 is formed with through opening 59 to receive one riveted end 66) of a pivot pin 61. The pivot pin 61 comprises an intermediate spacer portion 62 and an opposite riveted end 63 passing through an opening in the rail 51.

Portion 56 of each bell crank 55 is formed with a through opening 63a near its upper end through which extends a horizontal round bar 64. Bar 64 is formed with a spacer collar portion 65 contacting the outer surface of said portion 56. Extending beyond the collar 65, bar 64 has a portion 66. Pivoted on said portion 66 is the lower end of a brace bar 68 formed with an opening through which said portion 66 passes. Said portion 66 also passes through an opening 69 in the fixed bar 21. The outer end of portion 66 is riveted over as at 79.

Extending upwardly and forwardly from said portion 56 (Fig. l) is a portion 71 formed with a through opening 72. Extending from the opening '72 is a pivot pin 73. Extending through the opening 33 in the forwardly and upwardly inclined arm 32 of the bell crank 26 is a pivot pin 75.

The forward ends of said portions 32 and 71 of the bell cranks 26 and 55 are interconnected by horizontal links 76 formed with openings through which said pivot pins 73 and 75 pass. Each link 76 has an outwardly re- 4 cessed portion 77 shorter in length than the outwardly recessed portions 23a of the fixed bars 21 and located between the ends of the latter. Recessed portions 230 allow clearance for recessed portions 77 and the latter allow clearance for pivots 61.

The upper ends of the brace bar 68 are interconnected by a horizontal transverse rod 89 at their upper ends. Brace links 81 are connected at their upper ends as by pins 82 to intermediate portions of the braces 68. The lower ends of the braces 81 are connected to the rear ends of the fixed bars 21 as by said screws 23. Braces 68 are inclined rearwardly and upwardly from their lower ends. The braces 81 are inclined forwardly and upwardly from their lower ends. Said braces 68 and 81 are fixed with relation to the fixed bars 21.

Fixed to the cross bar 64 are a pair of similar symmetrically disposed spring anchor members 88. Each comprises a short arm 89 contacting the inner surface of wall 56 of bell crank 55. The short arm 89 is formed with a through opening through which the bar 64 passes. Extending from the short arm 89 is a portion 90 parallel to bar 64 and disposed thereabove when the parts are in the position shown in Fig. l. Extending downwardly from portion 90 is a long arm 92 parallel to the arm 89. When the parts are in the position shown in Fig. 1, arm 92 is inclined downwardly and forwardly. At the lower end of each arm 92 is a through opening 93 carrying a pivot pin 94. Pivoted to each pivot pin 94 is a hooked member 95. A line connecting the axis of pivot pin 94 with the axis of the transverse rod Si is located somewhat rearwardly of the axis of the transverse rod 64 when the parts are in the position shown in Fig. l, for the purpose hereinafter appearing. The hooked members 95, in the position shown in Fig. 1 each has an arm 96 extending upwardly from the pivot pin 94 to a position above the rod 64.

Extending downwardly and rearwardly from the upper end of arm 96 is an arm 97 formed with an opening 98. Each hooked arm contacts the inner surface of the long arm 92 of one of the brackets 83. The opening 98 is interconnected to rod 89 by a coil compression spring 100. The short arms 89 of the brackets 88 are welded to portions 56 of the bell cranks 55 so as to be integral therewith and to rotate about the axis of the rod 64 together with said rear bell cranks 55.

It will be noted that in the position of Fig. l, the axis of openings 98 will be in a line connecting the axis of rivets 94 with the axis of the rod 80. The pull of the coil spring 3'09 will therefore tend to swing the rear bell cranks 55 in a counterclockwise direction, looking at Fig. 1, so as to hold the rail members 51 in their rearwardly position and against forward movement.

it will be noted that the distance between the axes of pivots 25 and rod 64 is the same as the distance between the axes of

pivots

43 and 61, and is also equivalent to the distance between the axes of pivots 73 and 75. For this reason the bell cranks 26 and 55 can rotate about their pivots 25 and 64 respectively from the position shown in Fig. l, in clockwise direction, to bring the rails SE from their lowermost position shown in Fig. 1 to their uppermost position shown in Fig. 3.

Means is provided, however, to prevent such movcment. To this end the rails 51 are each formed at points spaced rearwardly from the pivots 43, with an opening 181 through which extends one end of a pivot pin 102. The pivot pin is formed with a spacer portion 103 contacting the outer side of the rail 51, and is formed with an outwardly extending stem 184. Pivoted to the stem 164 is a locking lever 1S5. Said locking lever 105 has a straight lower edge 196. It is formed in its upper side with a rearwardly and upwardly inclined slot 107 which is open at its outer end. It is also formed with an outwardly curved peripheral edge 108 which is adapted to contact the inwardly curved edge 43 of the bell crank 26. At the lower end of outwardly curved edge 108 is an outwardly extending finger 169 which serves as a stop to contact point d7 of member 40. Extending from the upper end of the curved edge 1% is an inwardly curved peripheral edge 110 to provide clearance when operating the device. The center of curvature of peripheral edge 108 is the axis of pivot 1&2. Therefore, the center of curvature of the peripheral edge 48 is likewise the axis of pivot pin 102.

It will now be observed that when the parts are in the position shown in Fig. 1, the rails 51 cannot be swung forwardly because edges 16%? of the locking levers contact edges 18 of the bell cranks 26. It will be noted, furthermore, that the upper lip 112 formed above the slot 107 projects above the level of the upper edge of the rail 51, whereas, the finger 113 below the slot 107 is normally disposed below the upper edge of the rail 51, as shown in Fig. 1 of the drawing.

Fixed to the rails 51 adjacent the lock ng levers 1% are pins 114 connected by coil tension springs 115 to openings 116 in the pivoted locking levers 1 595. The openings 116 are located above the slots 1W. The springs 115 thus tend to rotate the locking levers 165 in clockwise directions looking at Fig. l. The engagement of fingers N9 with points 47 of members 4-0 serve to limit rotation of the locking levers 165 in said counterclockwise direction.

Mounted on the rails 51 are a pair of carriages 124). The carriages 120 are similar and symmetrically disposed so that only one of said carriages will be described. Each carriage 120 comprises a vertical wall 121 disposed on the inside of the rail 51. The lower edge 12?. of wall 121 is disposed below the rail when said rail is in the position shown in Fig. 1. Wall 131 has a rearwardly extending finger 123. Fixed to said finger is a horizontal pivot pin 12 i disposed below the rail 51 and extending from the inside thereof, to the outer side thereof. Rotatably mounted on the pivot pin 124; by means of ball bearings is a grooved roller or wheel 125 engaging the underedge of rail 51. Extending from the wall 121 is a horizontal wall 126 projecting inwardly of said wall 121.

Said wall 121 is formed with an upwardly extending finger 127 from which extends a horizontal wall 123 located rearwardly of and above the level of said Wall or flange 12$. interconnecting said carriages 120 and mounted thereon is a typewriter table or support 130. Said table is in a horizontal position. It rests on top of the flanges 126 and beneath the flanges 123 and is fixed thereto by suitable screws, or in any other suitable manner. The screws may pass through suitable openings in the

flanges

126, 123. low the flange 126 at the forward end of the carriage is a pivot pin 132 passing above the rail 51 from the inside to the outside thereof. Rotatably mounted on pivot pin 132 is a grooved roller or wheel 133 contacting the upper edge of the rail 51.

' It will now be understood that the carriages 1253 being interconnected by the table 13% may slide forwardly or rearwardly on the rails 51. Extending outwardly from the forward edge of wall 121 adjacent its lower end is a vertical lip 121a disposed below the lower edge of the rails. Fixed to wall 121 of each carriage and extending outwardly therefrom is a pin 135 disposed just above the upper edge of the rail 51.

A typewriter, or other instrument not shown, may be fixed or attached to the top of the table 130 in any suitable manner. While this device is described as a pull out support for a typewriter, it will be understood that any other article or oiiice machine may be attached to the table 130 and this invention is not limited to typewriter supports.

It will now be understood that the springs 1% keep the rails 51 in their rearwardly position at a level below the fixed bars 21. It will also be understood that the carriages and table may roll freely back and forth on the rails 51. Therefore, the table 130 may be pushed all the Fixed to wall 121 and disposed be- 5 way back on the rails 51 so that the typewriter or other article supported thereon will be wholly housed within the desk.

To release the locking levers 165 so as to permit the table 130 together with the rails 51 to be swung frwardly and then upwardly about the bell cranks 26, 55 it is necessary to first pull the table 130 forwardly. As that is done the pins 135 will engage within the slots 107, as shown in Fig. 6 of the drawing, to rotate the locking levers 105 in a counterclockwise direction against the tension of the springs 115. When the carriage is pulled entirely forwardly the locking levers Hi will rotate about the pivot pins 102 to positions where the fingers 113 contact the top edges of locking members 40. In such position the pins 135 will be located adjacent the edges 45 of said members 40.

The front ends of the rails 51 are interconnected by a horizontal transverse rod 51:: fixed thereto. Said rails are furthermore interconnected adjacent their rear ends by a horizontal transverse rod 51.) fixed thereto. When the carriages and table have been pulled forward to their forwardmost position the front edges 121a of the side walls 121 of the carriages will contact the front cross bar 51a to stop further movement of the table or carriages in the forward direction, and to maintain the pins 135 substantially in contact with the edges of members 46.

When the locking levers 135 have been rotated fully in counterclockwise directions, they will be held in such positions because the openings 116 which are normally located above the pivots 192 will have moved below the pivot pins li 5 so that the springs 115 will retain the locking levers in their releasing positions. When said locking levers have been rotated by the carriages and released, further forward movement of the table will cause the rails 51 to move forwardly therewith, and as soon as the pivot points 94 have moved forwardly of a line interconnecting the axis 6 with the axis 80, the springs 109 will exert upward pull on the rails to raise the rails 51, carriages 12th, and table 13% together with the typewriter or other article thereon, and to cause a swinging of the bell cranks 26 and in a clockwise direction about the pivots 25 and 64, bringing the parts to the position shown in Fig. 3. During such movement the brackets 88 will likewise swing in a clockwise direction to a position shown in Fig. 3, the hooks which pivot freely about the pivots 94 will be moved to the position shown in Fig. 3 and the springs will exert an upward pull through the hooks 95 on the brackets 83 to retain the table 131' in its raised position.

Releasable catch means is provided for retaining the table 139 in raised position. To this end there is fixed to the cross bar 18 as by screw 140 a plate 141 provided with a forward and downwardly inclined lower flange 149a. Said plate 141 is formed with a V shaped notch 142 at its lower end, widening toward the bottom. Also fixed to the cross bar 18 is an angle member 144 having a top flange 1 1-5 contacting the top of the cross bar 18 and screwed thereto as by screws 146. Extending downwardly from wall 145 is a well 147 contacting member 1 11 and extending therebelow. Member 147 is formed with a vertical slot 148 aligned with the notch 142 but extending therebelow.

Fixed to the top of the table 130 is a bracket 150 having a horizontal wall 151 screwed to the top of the table. Extending upwardly from the horizontal wall 151 is a vertical wall 152 formed with a horizontal opening 153. Extending from the opening 153 is a pivot pin 154. Pivoted to the pivot pin 15 i is a lever 155. The lever 155 has a hooked head or catch 156 at its upper end. It is provided with a handle 157. On the pivot pin 15 i is a collar 160. On the collar 160 is a torsion spring 161 having one arm engaging a lip 162 on the lever and another arm contacting the horizontal wall 151 of the bracket 159. Torsion spring 161 tends 7 to rotate the lever 155 in a clockwise direction, looking at Fig. 11.

The head 156 is so located that as the table 130 comes up said head 156 will pass first through the notch 142 and then through the slot 148, engaging the lower edge of the slot, and holding the table 130 against accidentally being pushed down or vibrating or side swaying. The notch 142 being wide at its lower end serves to guide the head 156 to the slot 148.

\Vhen it is desired to lower the table 136 the lever handle 157 is depressed against the torsion spring to release the head 156, and then the table may be pulled down to its lowermost position. As that is done the table is pushed back so that the pins 135 will engage the lingers 1113 ard rotate the locking cams 105 in clockwise directions to locking position. The table can be pushed all the way back so that it is wholly housed within the desk.

It will be observed that the outwardly pressed portions 57 of the rear bell cranks 55 provide channels or spaces for the pins 135 to be moved rearwardly as the table and carriages are pushed back in their lowermost position. Furthermore, as the table is swung forwardly and raised said outwardly offset portions 57 move through the outwardly offset portions 77 of the links 76 and during the operation of the device said offset portions '77 move through the spaces afforded by the offset portions 23a of the bars 21. Thus, sufiicient clearance is provided for operating the device.

it will be observed that when the carriages and table 130 are moved forwardly sufliciently to release the locking cams 105 a slight movement forwardly against the bar 51:: is sufiicicnt to bring the axis of the pivots 94 from the back side of a plane passing through the axes of bars 64 and 80 to the front side of said plane, and such movement will immediately bring the coil springs into play to pull upwardly and to raise the typewriter desk 130 easily, even with the weight of the typewriter or other article thereon.

It will thus be seen that there is provided a device in which the several objects of this invention are achieved and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention I claim as new and desire to secure by Letters Patent:

1. A device of the character described comprising a pair of parallel horizontally aligned fixed bars, front bell cranks pivoted to said bars and having downwardly and forwardly extending arms, and forwardly and upwardly extending arms, cam means at the lower ends of the downwardly extending arms and having outwardly curved peripheral edges and inwardly curved peripheral edges, rear bell cranks pivoted to said bars and having downwardly and forwardly inclined arms and forwardly and upwardly inclined arms, rails interconnecting the lower ends of said downwardly extending arms of said bell cranks, links interconnecting the forwardly and upwardly extending arms of said bell cranks, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam means, a supporting member mounted for sliding movement on said rails, and means on said supporting member to rotate said locking members in opposite directions to bring the outwardly curved edges of said locking levers into and out of engagement with the inwardly curved edges of said cam means.

2. A device of the character described comprising a pair of parallel horizontally aligned fixed bars, front and forwardly extending arms, and forwardly and up wardly extending arms, cam plates fixed to the lower ends of the downwardly extending arms and having outwardly curved peripheral edges and inwardly curved peripheral edges, rear bell cranks pivoted to said bars and having downwardly and forwardly inclined arms and forwardly and upwardly inclined arms, rails interconnecting the lower ends of said downwardly extending arms of said bell cranks, links interconnecting the forwardly and upwardly extending arms of said bell cranks, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, spring means to rotate the locking lovers in one direction, a supporting member mounted for sliding movement on said rails, and means on said supporting member to rotate said locking members in an opposite direction to bring the outwardly curved edges of said locking levers beyond the inwardly curved edges of said cam plates, a fixed cross bar, brackets fixed to said rear bell cranks, hooks pivoted to said brackets, and springs interconnecting said hooks with said fixed cross bar.

3. in combination, a pair of fixed parallel bars, bell cranks pivoted to said bars, links interconnecting the arms of said bell cranks to form parallelograms to permit swinging of said bell cranks together, a pair of said links constituting rails, carriages mounted on rollers on said rails, a table fixed to said carriages and interconnecting the same, a pair of said bell cranks having cam plates formed with inwardly curved edges, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, said locking levers being formed with slots opening above the rails, and pins on said carriages adapted to engage within said slots for rotating said locking levers upon moving the table and carriages forwardly, for moving the outwardly curved edges of the locking levers beyond the inwardly curved edges of the cam plates.

4. In combination, a pair of fixed parallel bars, bell cranks pivoted to said bars, links interconnecting the arms of said bell cranks to form parallelograms to permit swinging of said bell cranks together, a pair of said links constituting rails, carriages mounted on rollers on said rails, 21 table fixed to said carriages and interconnecting the same, a pair of said bell cranks having cam plates formed with inwardly curved edges, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, said locking levers being formed with slots opening above the rails, and pins on said carriages adapted to engage within said slots for rotating said locking levers upon moving the table and carriages forwardly, for moving the outwardly curved edges of the locking levers beyond the inwardly curved edges of the cam plates, said cam plates having outwardly curved part circular edges adapted to be engaged by said pins on said carriages as said rails are swung about said bell cranks from a lower to an upper position.

5. In combination, a pair of fixed parallel bars, bell cranks pivoted to said bars, links interconnecting the arms of said bell cranks to form parallelograms to permit swinging of said bell cranks together, a pair of said links constituting rails, carriages mounted on rollers on said rails, a table fixed to said carriages and interconnecting the same, a pair of said bell cranks having cam plates formed with inwardly curved edges, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, said locking levers being formed with slots opening above the rails, and pins on said carriages adapted to engage within said slots for rotating said locking levers upon moving the table and carriages forwardly, for moving the outwardly curved edges of the locking bell cranks pivoted to said bars and having downwardly 7-3 levers beyond the inwardly curved edges of the cam plates, means on said locking levers to limit rotating of the locking levers relative to said cam plates, and toggle spring means to aid in rotating said locking levers in one direction or another.

6. In combination, a pair of fixed parallel bars, bell cranks pivoted to said bars, links interconnecting the arms of said bell cranks to form parallelograms to permit swinging of said bell cranks together, a pair of said links constituting rails, carriages mounted on rollers on said rails, a table fixed to said carriages and interconnecting the same, a pair of said bell cranks having earn plates formed with inwardly curved edges, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, said locking levers being formed with slots opening above the rails, and pins on said carriages adapted to engage within said slots for rotating said locking levers upon moving the table and carriages forwardly, for moving the outwardly curved edges of the locking levers beyond the inwardly curved edges of the cam plates, and toggle spring means to lower the rails at the end of the downward movement of said rails and to raise said rails when said carriages are moved forwardly to release the locking levers.

7. In combination, a pair of fixed parallel bars, bell cranks pivoted to said bars, links interconnecting the arms of said bell cranks to form parallelograms to permit swinging of said bell cranks together, a pair of said links constituting rails, carriages mounted on rollers on said rails, a table fixed to said carriages and interconnecting the same, a pair of said bell cranks having cam plates formed with inwardly curved edges, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam plates, said locking levers being formed with slots operiing above the rails, and pins on said carriages adapted to engage within said slots for rotating said locking levers upon moving the table and carriages forwardly, for moving the outwardly curved edges of the locking levers beyond the inwardly curved edges of the cam plates, toggle spring means to lower the rails at the end of the downward movement of said rails and to raise said rails when said carriages are moved forwardly to release the locking levers, and means on the carriages to engage the rails to push the rails forwardly upon moving the carriages fr wardly to change the toggle spring action from pulling the rails down to an upward pull operation of said toggle springs.

8. A device of the character described comprising a frame, front links pivoted to said frame and having dOW"- wardly extending arms, cam means fixed to the lower ends of the downwardly extending arms and having inwardly curved peripheral edges, rear links pivoted to said frame and having downwardly inclined arms, rails interconnecting the lower ends of said downwardly extending arms f said links, locking levers pivoted to said rails and having outwardly curved edges conforming to the inwardly curved edges of said cam means, a supporting member mounted for sliding movement on said rails, and means on said supporting member to rotate said locking mer bers in opposite directions to bring the outwardly curved edges of said locking levers into and out of engagement with the inwardly curved edges of said cam means.

9. A device of the character described, comprising a member, a pair of bell cranks pivoted to said member at spaced points, each bell crank having a first and a second arm, link means to interconnect the first arms of said bell cranks, table support means mounted on said link means, link means to interconnect the second arms of said bell cranks, one of said bell cranks having a curved edge, a pivoted locking element having a curved edge complementary to the curved surface of said bell crank, the center of curvature of said edges being coincident with the pivotal axis of said locking element, and means to rotate said locking element to engage or disengage said curved edges thereby to lock or unlock said bell cranks against rotary movement.

10. In combination a rail member, a carriage slidable on the rail member and movable from a rear position to a front position, a supporting member associated with the carriage and movable with the carriage from said rear position to said front position, means to elevate the supporting member from a lower front position to an elevated front position, means to lock the supporting member against being elevated from its lower position as it is moved from the rear position toward the lower front position, and means to release said locking means as the supporting member reaches its lower front position, said locking means comprising a pivoted elevating member which is part of the elevating means and being formed with a curved edge, and a pivoted locking member having a complementary curved edge adapted to engage the curved edge on the pivoted elevating member when the supporting member is in its lower position rearwardly of the front position thereof to lock said supporting member against being elevated until said carriage reaches its front position, and means to rotate said locking member to disengage the curved edge thereof from the curved edge of the pivoted elevating member when the carriage reaches its front position to permit the supporting memher to be elevated by said elevating means when said supporting member reaches its lower front position.

11, In combination, a rail member, a carriage member slidable thereon, from a front position to a rear position, a support movable with the carriage from front to rear, means to elevate said support from a lower to an elevated position when said carriage is in its front position, said elevating means comprising a pivoted elevating link having a locking portion, a locking element pivoted to one of said members, and having a locking portion adapted to engage the locking portion of the pivoted link to prevent elevating of said support in a first angular position of said locking element, and to disengage from said locking portion of said link in a second angular position of said locking element, and means on the other of said members to positively engage and rotate said locking element from the first angular position thereof to the second angular position thereof, and to positively hold said locking element in said second angular position when said carriage reaches its front position, to release said pivoted lever and permit elevation of the support by said elevating means, and to positively engage and rotate said locking element in an opposite direction from its second position to its first position when said carriage is moved rearwardly from its front position to lock said lever and prevent elevation of said support as soon as said carriage moves rearwarclly away from its front position.

References Cited in the file of this patent UNITED STATES PATENTS 1,178,220 Dietz Apr. 4, 1916 1,415,909 Vaaler May 16, 1922 1,904,217 Fox Apr. 18, 1933 2,402,412 Koch June 18, 1946 2,524,386 Johnston Oct. 3, 1950 FOREIGN PATENTS 579,591 Germany June 15, 1933