Modern drawing tables, beside a support structure (base, shelfs'
frame, etc.) and different adjustment devices (pedals, counterweigths, locking
and unlocking mechanisms, etc.), comprise, as shown in Fig. 1, a drawing board
1, on the top side of which is usually present a guide 2 for a carriage 3 carrying
a vertical guide 4 provided with a lower rest wheel (not visible in the figure)
and along which a vertical carriage 5 carrying a goniometer and the couplings
for the rulers runs.
The work at a drawing table is often characterized by frequent interruptions:
from daily stops of working hours and/or for attending to other priority functions,
such as receiving clients, to longer interruptions for vacation and holidays, etc..
During these interruptions and generally in proportion to the length of the interruption,
swelling and other deformations of the drawing sheet left on the drawing board
due to temperature and humidity changes may be observed together with an accumulation
of dust and dirt on the sheet which is often attracted by electrostatic charging
induced by the rubbing of the drawing paper. Moreover in design offices in general
the visit of extraneous personnel is often inevitable and therefore important projects
may remain incautiously exposed on the drawing table for too long periods of time.
An objective of the present invention is to provide a practical roller
blind for a drawing table, which blind may effectively protect the drawings from
dust and dirt during the periods when they are left on the drawing table as well
as to discreetely block the view of projects being elaborated to unauthorized
persons which may be passing by or standing for considerable time in view of the
These and other objectives and advantages of the device object of
the present invention will become evident through the following detailed description
of several preferred embodiments, shown for purely illustrative and nonlimitative
purpose in the attached drawings, wherein:
- Fig. 1 is a partial, perspective, schematic view of a modern drawing
- Fig. 2 is a partial schematic perspective view of a drawing table embodying
a roller blind in accordance with the present invention;
- Fig. 3 is a partial, cross sectional view along the section plane III-III
of Fig. 2;
- Fig. 4 is a partial, schematic, partially exploded view of a roll-up
mechanism of the roller blind of the present invention;
- Fig. 5 is a partial, cross sectional view of a drawing table having
a roller blind in accordance with an alternative embodiment of the invention; and
- Fig. 6 is a partial, schematic view of a modified embodiment of the
device depicted in Fig. 5.
For simplicity's sake, the same or equivalent parts are indicated
by the same number in all the figures.
According to a first embodiment of the invention, shown in Figures
2 and 3, the horizontal top guide 2 of a normal drafting machine (shown in Fig.
1) is replaced by a guide-blind roll housing 2a, provided with a longitudinal slot
17 through which a blind 7 disappears inside the housing 18 of the special guide
body 2a, upon winding on a roller 6 which is contained therein. Such a horizontal
guide body 2a may be easily fabricated by extrusion with aluminum or similar material,
thus providing to form a guide profile which may be at least partially similar
to the guide profile of a top horizontal guide 2 of a conventional drafting machine,
i.e. capable of receiving the wheels 3a and 3b of the top carriage 3 of the drafting
machine. The extruded body may also be conveniently provided with a "T" section
channel 2b capable of receiving a mating "T" projection of brackets 19 for assembling
the guide body 2a on the top edge of the drawing board 1 of the table. The slot
17 of the guide body 2a has a spacing ridge 2c over which the blind screen 7 runs
when it is pulled unwound from the roller 6 and this ridge 2c is set so as to
facilitate the pulling of the screen 7 over the drawing board at a certain distance
from the surface of the board in order to avoid the rubbing of the screen on the
surface of the drawing paper. The free extremity of the blind screen 7 is conveniently
provided with a reinforcing rod or with a rigid metal bar 8, preferably having
an "L" shaped profile so as to form a grip for making easier the pulling of the
blind 7 over the drawing board, unwinding it from the roller 6 in opposition to
the force exerted by a rewind spring.
As shown in Fig. 2, near the bottom edge of the drawing board 1 of
the table, or along the two sides of the board 1, suitable hooks 9 are provided
for anchoring the two ends of the grip bar 8 in order to keep the extended blind
from rewinding back on the spring loaded roller 6. One or more pairs of hooks
9 may be fixed along the sides of the drawing board 1 for engaging the opposite
ends of the reiforcing road or grip bar 8 which purposely extend beyond the edge
of the blind screen 7 and of the drawing board 1. Of course other and/or different
retaining means will be easily contrived by a skilled technician.
As shown in Fig. 4, the rewinding mechanism of the blind screen 7
on the roller 6 preferably comprises a shaft 10, solidly connected through a nonrotatable
joint on at least an end flange or cap 13 of the guide body 2a. The roller 6,
through a coupling tooth (not shown in the figure) is rotatably coupled to a sleeve
11 which is free to rotate (together with the roller 6) about the shaft 10.
A helical torsional spring 12 is mounted over the shaft 10 and has
a first extremity 12a connected to the shaft 10 while the opposite extremity is
fixed to the sleeve 11, which is also free to move axially along the shaft 10 and
the roller 6 (the coupling tooth of which being able to run inside the longitudinal
guide 11a present on the sleeve 11).
The operation of such a rewind mechanism is well known. During the
assembly of the mechanism the torsional spring 12 will be pre-torsioned in order
to exert a certain return force also when the blind 7 is completely wound on the
Preferably, the slot 17 of the guide body 2a is provided with a small
longitudinal brush 14, which is mounted so as to be easily replaced periodically
upon wear and deformation, for detaching particles which may have adhered to the
surface of the blind screen 7 during rewinding of the latter on the roller 6.
Preferably such a brush will contain metallic whiskers for preventing induction
of static charges on the blind 7 which could attract and retain dust particles
and/or erasing rubber particles.
A further embodiment is depicted in Fig. 5. This alternative embodiment
is particularly suitable for retrofitting an existing drafting table without substituting
or modifying the horizontal top guide of the drafting machine, when such is present
or in the case of traditional, balance-type, drafting machines.
According to this alternative embodiment of the invention, the roller
guard body is fixed to the bottom edge of the drawing board 1 and the blind screen
7 is extended from the bottom to the top of the table.
The guard body 15 which contains the winding roller 6 of the blind
7 may be made by an extruded aluminum bar having a profile as depicted in Fig.
5. The profile may already be shaped so as to be easily fastened to the bottom
portion of the drawing board 1 by means of screws 19, by providing for the use
of eventual spacers over the fixing flange portion to account for different thicknesses
of the drawing board 1. the guard body 15 is preferably provided with an appendix
16 having a shape suitable to act as a shelf for drawing instruments.
In yet another modified embodiment of the invention, schematically
shown in Fig. 6, the roller guard body 15 may also be hinged at the point 18 to
the flange portion 20 in order to be able to drop down the roller guard body for
removing accumulated debris and dirt. Of course when the blind must be used, the
guard body 15 will be raised and blocked in a working position by means of hooks
or by means of a central stop mechanism fixed on the back of the board (not shown
in the figure).
In the two figures 5 and 6 the profile of the rest wheel 4a at the
bottom of the vertical guide 4 of the drafting machine may be seen.
The blind screen 7 may be a sheet or a cloth of nylon, polythene
or other flexible and opaque material such as a sheet of polyvinilchloride (PVC)
loaded with an opacizer material and/or coupled with a reinforcing fabric. Essentially
the blind screen 7 will be opaque in order to impede the vision of a drawing affixed
on the drawing board.
The roller blind of the invention may also be useful for implementing
various safety systems which, by contemplating a block of the extended blind, detect
(if not prevent) an eventual unauthorized lifting of the blind. Locks and other
blocking devices, as well as electronic alarm systems may be easily contrived
and utilized for implementing such systems.
The unwinding and the rewinding of the blind may also be motorized
by using a geared-down electric motor.
Of course the roller guard body may also be mounted along one side
of the drawing table and the blind may be extended horizontally across the board.