CRT Monitor tilt mechanism

A mechanism for tilting a display screen of a CRT housed in a cabinet includes a projection extending from the bottom surface of the cabinet for supporting one end of the cabinet and providing a pivot point for tilting the cabinet. A foot slidably mounted at the other end of the cabinet supports that end at a selectable height; the foot having a ratchet rack on one of its surfaces is normally engaged by a detent lever locking the foot in position.

TECHNICAL FIELD 
This invention relates to a display screen of a cathode ray tube and more 
particularly to a mechanism for adjusting the angle of viewing of such a 
screen. 
BACKGROUND OF THE INVENTION 
Use of cathode ray tubes (CRTs) in connection with business machines for 
production of displays on their display screens in response to 
operator-controlled keyboards has become commonplace. Time loss resulting 
from error correction in production of printed machine output has been 
minimized by such use. However, variation in operator height, or ambient 
conditions of tube use can result in glare from the display screen, 
thereby reducing operator efficiency. To prevent or minimize glare, a 
display screen should be tiltable for changing the angularity or pitch of 
viewing the screen. 
Unitl now, a number of various mechanisms have been developed for tilting 
display screens of CRTs. One of these comprises a rockable platform on 
which a CRT is mounted within a cabinet. Another mechanism includes a 
yoke-shaped bracket which is driven linearly in response to manual 
rotation of a knob, the bracket being coupled to a CRT relatively remote 
from its display screen. Yet another mechanism comprises a driven worm 
gear meshed with a gear secured to a shaft which in turn is fastened to 
the neck of a CRT. 
Each of the heretofore known mechanisms, while efficient for changing tube 
angularity or pitch, is relatively expensive, because each requires a 
plurality of parts some of which require accurate machining; and 
additionally, usually most parts are located within a cabinet enclosing 
the CRT and associated electronics making the assembly of the mechanisms 
difficult and time-consuming. 
DISCLOSURE OF THE INVENTION 
In accordance with the present invention, we provide a mechanism for 
tilting a display screen of a CRT disposed within a cabinet. The cabinet 
has extending from its bottom surface a projection which supports one end 
of the cabinet and provides a pivot point about which the cabinet may be 
tilted. A foot, slidably mounted at the other end of the cabinet, supports 
that end at a selected height. A detent lever slidably attached to the 
bottom surface of the cabinet is arranged to normally be in engagement 
with a ratchet rack located on a surface of the foot locking the foot in 
position.

DETAILED DESCRIPTION 
FIG. 1 shows a partial side elevation of a cabinet 11 having a front 12, 
with an opening 13 (not shown), a top 14 and a bottom 15 joined by sides 
16 and 17 and a back 18. The cabinet 11 is adapted to house a CRT 19, 
which is positioned within the cabinet 11 so that the image display screen 
23 of the CRT 19 is visible through the opening 13. The cabinet 11 has 
extending from its bottom surface 20 two projections 21, shown in FIG. 2, 
which terminate in knifelike edges 22. The projections 21 are located near 
the front 12 and sides 16 and 17, respectively, and have their edges 22 
aligned so that they are substantially parallel to the image display 
screen 23. When the cabinet 11 is placed on a flat supporting surface 29, 
such as the top of a deck (not shown), the projections 21 support the 
front portion of the cabinet 11 and the edges 22 provide a pivot line 
about which the cabinet 11 may be tilted to change an operator's angle of 
viewing the display screen 23. 
The back portion of the cabinet 11 is supported by a foot 24 which is 
slidably mounted on the back 18 of the cabinet 11. The foot 24 has a 
rectangular shape and is mounted inside the cabinet 11 by insertion into a 
channel guide 27 located on the back 18 of the cabinet 11. The guide 27 
has its longitudinal axis parallel to the vertical axis of the cabinet 11 
and has a slot 40 extending the length of the guide 27 and opening into 
the cabinet 11. The dimensions of the channel 27 are such that the foot 24 
is free to slide within the channel 27. One end of the channel 27 is 
connected to an aperture 28 (FIG. 5) located in the bottom 15 of the 
cabinet 11. Aperture 28 permits an end 37 of the foot 24 to exit outside 
the cabinet 11 and contact the supporting surface 29. A two row ratchet 
rack 25 having a plurality of teeth 39 is located on one longitudinal 
surface of the foot 24. The foot 24 is oriented in the guide 27 so as to 
align and place the teeth 39 across from the slot 40. 
A detent lever 30 is slidably mounted on the bottom surface 20 of the 
cabinet 11 by having mounting posts 31 extending from the lever 30 engage 
slots 32 located in the bottom 15 of the cabinet 11. The detent lever 30, 
the foot 24 and the cabinet 11 may all be molded from a thermoforming type 
of plastic material. One end of the detent lever 30 is shaped in the form 
of a pawl 33 and is adapted to mesh with the teeth 39 of the ratchet rack 
25. 
A compression spring 34 located in one of the slots 32 between the bottom 
15 of the cabinet 11 and one of the mounting posts 31 develops a force 
which pushes the detent lever 30 towards the back 18 and the foot 24 
keeping the pawl 33 in engagement with the ratchet rack 25. The shapes of 
the teeth 39 and the pawl 33, as shown in FIG. 5, are such that when the 
pawl 33 is in engagement with the rack 25, the foot 24 is movable in only 
one direction, downwards and out of the cabinet 11. 
Normally, a portion of the weight of the cabinet 11 is transmitted via the 
detent lever 30 and the pawl 33 to the teeth 39 of the ratchet rack 35 
locking the foot 24 in place. To release the foot 24, the other end of the 
detent lever 30 has a finger or a hand grip area 35 for application of a 
force on the detent lever 30 to overcome the force developed by the 
compression spring 34 and thus to disengage the pawl 33 from the ratchet 
rack 25. 
A hook 36 is located on a portion of the foot 24 located opposite the end 
37. An extension spring 38 has one end attached to the hook 36 and the 
other end attached to a tab 41 of the detent lever 30. The tab 41 slides 
in a channel 42 located between the two rows of the ratchet rack 25. The 
extension spring 38 exerts a force on the foot 24 pushing the foot 24 down 
and out of the cabinet 11 thus enabling the end 37 to maintain contact 
with the supporting surface 29. The force exerted by the extension spring 
28 is less than the force exerted on the foot 24 through the detent lever 
and the pawl 33 by the weight of the cabinet 11. Downward travel of the 
foot 24 is limited by portions 43 which extend from the sides of the foot 
24 more than the width of the channel guide 27. 
The operation of the tilt mechanism may be best understood by describing 
how the change in the angle of viewing of the display screen 23 is 
effected by the raising or lowering of the back end of the cabinet 11 
thereby pivoting the cabinet 11 about the edges 22. To raise the back of 
the cabinet 11, a force "A" is applied to the top 14 of the cabinet 11 in 
a direction as shown in FIG. 1. An operator can normally accomplish this 
by placing one hand on the top 14 of the cabinet 11 and pulling the 
cabinet towards himself. This action takes the weight of the cabinet 11 
off the foot 24, and the force exerted by the extension spring 28 is now 
able to move the foot 24 downward enabling the end 37 to maintain contact 
with the supporting surface 29 as the back of the cabinet 11 is elevated. 
Once the desired angle of viewing is reached, the force "A" is relaxed 
shifting the weight of the cabinet 11 back through the detent lever 30 and 
pawl 33 to the foot 24. When a sufficient amount of weight of the cabinet 
11 is shifted back to the foot 24 to overcome the force developed by the 
extension spring 28, the foot 24 is locked in place by the detent lever 30 
ratchet rack 25 combination. 
To tilt the cabinet 11 the opposite way, a force "B" is exerted on the 
detent lever 23 disengaging the pawl 33 from the ratchet rack 25. When the 
detent lever 33 disengages from the ratchet rack 25, the weight of the 
cabinet 11 overcomes the force developed by the extension spring 28 and 
forces the foot 24 up into the cabinet 11. The cabinet 11 pivots about the 
edges 22, and the back end of the cabinet 11 moves towards the supporting 
surface 29. Keeping the detent lever 23 disengaged from the ratchet rack 
25 will allow the back end of the cabinet 11 to eventually settle on the 
supporting surface 29.