Drawing table

Abstract

A drawing table having a stand and a board linked to the stand in such a manner as to allow the board to be adjusted in position whereby the weight of the board creates a second moment about the axis opposing the first moment. A compensating means varies the second moment to compensate for variations in the first moment due to changes in the position of the board so that the board is balanced in any position.

We claim: 
     
       1. A drawing table including a stand, a board, a horizontal spindle constituting an axis rotatably mounted in the stand, a first arm mounted on the spindle adjacent each end thereof, a second arm pivotally mounted on the spindle adjacent each end thereof, each of said first arms being pivotally attached to said board, a link arm pivotally attached to each of said second arms and to said board, a compensating member having a peripheral spiral groove rotatably mounted adjacent each end of said spindle, a cable having first and second ends, said cable being attached at the first end to the compensating member and located in the spiral groove, a counterbalancing means adjustably connected to the stand, and the second end of the cable being attached to the counterbalancing means, the attachment of the cable to the compensating member in the spiral groove enabling the point of action of the counterbalancing means to vary with respect to the pivot axis during rotation of the compensating member with respect to the pivot axis, the arrangement being such that the first and second arms and the link arms connecting the board to the horizontal spindle allow the board to be adjusted in position and in which the weight of the board creates a first moment about the axis and the counterbalancing means creates a second moment about the axis, with said compensating member varying the second moment to compensate for variations in the first moment due to changes in the position of the board whereby the board is balanced in any position thereof. 
     
     
       2. The drawing table as claimed in claim 1 in which the counterbalancing means is a helical spring. 
     
     
       3. The drawing table as claimed in claim 2 in which the adjustable connection of the counterbalancing means to the stand includes an eyebolt to which the helical spring is attached, a bracket on the stand receiving the eyebolt, and an adjustment nut for the eyebolt for adjusting the position of the eyebolt on the bracket for varying the tension of the helical spring. 
     
     
       4. The drawing table of claim 1 further comprising a receiving disc fixed to said first arm and rotatable about said axis, the receiving disc being linked to the compensating member having a peripheral spiral groove for varying said point of application. 
     
     
       5. The drawing table of claim 4 wherein the compensating member is a partial disc sector. 
     
     
       6. The drawing table of claim 5 wherein the compensating member has a pivotably secured screwbolt carrying a thrust element which is adjustable by means of a nut on the screwbolt and rotatably secured in a transversely directed recess of the receiving disc. 
     
     
       7. The drawing table of claim 6 wherein the compensating member has a recess situated in the sides of the spiral helical groove of the corrector member and extending transversely to the spiral helical groove adjacent the screwbolt, a securing element for the cable of the helical spring being rotatably secured in said recess. 
     
     
       8. The drawing table of claim 7 wherein the link arm is connected to an adjustable lever acted upon by a second spring which is secured on a spring mounting of the stand, the spring mounting being adjustable in vertical and horizontal directions. 
     
     
       9. The drawing table of claim 8 wherein the helical spring, cable, and compensating member are housed within the stand. 
     
     
       10. The drawing table of claim 9 wherein the drawing board is displaceably arranged on a securing bar which is pivotably fixed to said first arm and said link arm.