Abstract:
A support mechanism for raising and lowering a terminal monitor comprising an upper assembly and a lower assembly and a plurality of pivotable arms interconnecting the upper assembly and lower assembly. The upper assembly includes an upper plate, which supports the monitor, and an upper slidable plate slidably coupled to it, and the lower assembly includes a base plate and a lower slidable plate slidably coupled to it. Due to the way the pivotable arms are coupled to the various plates, when the upper slidable plate is driven with respect to its associated upper plate, the arms pivot either to raise or lower the upper assembly and its monitor load with respect to the lower assembly.

Description:
BACKGROUND OF THE INVENTION 
     Electronic data processing terminals have come into wide use in recent years. In general, such terminals include a cabinet containing a cathode ray tube and a keyboard and other associated electronic apparatus. 
     Operator comfort has become an important consideration, and, toward this end, it has been considered desirable to be able to adjust the height of the cabinet containing the cathode ray tube. 
     The requirement is to be able to raise and lower a relatively heavy cabinet with ease, with minimum manipulation by the user, and, when lowered, the lifting mechanism should have minimum height. The present invention satisfies these requirements in a height adjustment mechanism for a terminal display cabinet. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the invention; 
     FIG. 2 is a sectional view generally along the lines 2--2 in FIG. 1; 
     FIG. 3 is a sectional view generally along the lines 3--3 in FIG. 1; 
     FIG. 4 is another sectional view similar to the view of FIG. 3; 
     FIG. 5 is a perspective view of a portion of the upper assembly of the invention; 
     FIG. 6 is a perspective exploded view of the upper assembly of the invention; and 
     FIG. 7 is a perspective exploded view of the lower assembly of the invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     The height adjustment mechanism of the invention 10 is made up of a lower assembly and an upper assembly which are interconnected by pivotable connecting arms. Referring first to the lower assembly, this portion of the apparatus 10 includes a base plate or lower tray 20 having left and right upstanding end walls 22 and 23 and rear and front upstanding walls 24 and 25. Slotted horizontal nylon card guide members 26 and 27, seen in FIGS. 1, 3, and 7, are secured along the inside surfaces of the rear and front walls 24, 25, respectively, so that the rear guide member 26 is aligned with and faces the front guide member 27. 
     A lower sliding plate 30 is mounted adjacent to and above the base plate 20. The sliding plate 30 has rear and front edges 33 and 34 which are supported in, and slide in, the rear and front guide members 26 and 27, respectively. The lower sliding plate 30 has four relatively large, spaced-apart cutout areas 36 for a purpose to be described. 
     The upper assembly of apparatus 10 includes an upper plate 40, which supports a terminal monitor (FIG. 1), or the like, and an upper sliding plate 50 which are coupled to the lower plates 20 and 30 in a manner described below. The upper plate 40, generally in the form of a tray disposed upside down, has left and right depending end walls 41 and 42 and rear and front depending walls 43 and 44. Slotted nylon guide members 45 and 46 (FIGS. 3, 4, and 6) are secured along the inside surfaces of the rear and front walls 43 and 44 so that the rear guide member 45 faces the front guide member 46. 
     The upper sliding plate 50 is mounted adjacent to and just beneath the lower surface of the upper plate 40. The sliding plate 50 has left and right depending end walls 51 and 52 (FIG. 2) and rear and front edges 53 and 54 which are supported in, and slide in, the rear and front guide members 45, 46, respectively. The upper sliding plate has two relatively large cutout areas 47 disposed along its longitudinal axis for a purpose to be described. 
     Four identical lifter arms 90, 91, 92, 93, generally in the form of thin flat rectangular plates, have their lower ends pivotably coupled on pivot pins 100 seated in brackets 102 secured to the base plate. The arms 90, 91, 92, 93 slope generally upwardly to the left, along a negative slope, as seen in FIGS. 1 and 7. The upper ends (FIG. 2) are pivotably coupled to the upper sliding plate 50 on pivot pins 103 seated in brackets 104 secured to plate 50. The lower ends of arms 90-91 and arms 92-93 are aligned on parallel, vertical axes which are spaced from each other, and the upper ends of arms 90-91 and arms 92-93 are aligned on parallel, vertical axes which are spaced from each other. 
     Two other lifter arms 120 and 122 have one end pivotably secured to upper sliding plate 40 on pins 123 (FIGS. 2 and 6) seated in brackets 124. and they slant downwardly to the left, along a positive slope, where their lower ends are pivotably coupled by pins 130 to brackets 135 on lower slide plate 30. Arm 120 is located between the two arms 90 and 91 and is secured to plate 30 rearwardly of them. Arms 90, 91, and 120 form an operating unit. Arm 122 is secured to plate 30 between arms 92 and 93 and rearwardly of them, and these three arms form an operating unit. A pin 140 is inserted through the center of the three arms 90, 91, and 120, seen at the left in FIG. 1, and another pin 140 is inserted through the centers of the three arms 92, 93, and 122, seen at the right in FIG. 1. 
     In addition to having the nylon guides 45 and 46 reduce the friction of movement of the sliding plates, the movement of the lifter arms may be enhanced by providing bronze rollers 141 (FIG. 6) on the pivot pins at the upper and lower ends of the lifter arms. 
     It is noted that, as to arms 90, 91, 92, and 93, each extends through one of the apertures 36 in lower sliding plate 30, and, as to arms 120 and 122, each extends through one of the apertures 47 in upper sliding plate 50. 
     In the apparatus described, the tray 20 is the ground link for the lifter arms 90 and 92 which form a set of parallel links of a four-bar mechanism. The top sliding plate 50 is the coupler. The same applies to the lifter arms 91 and 93. Additional guidance control and improved stability are achieved by the four link mechanism made up of the top tray 40 as the ground link and arms 120 and 122 as the parallel links. The bottom slide plate 30 forms the coupler link. 
     A plurality of vertical helical compression springs 144 are provided between the upper and lower portions of the lifting apparatus 10 to assist in operation of the apparatus. The number and location of these springs depends on the application, and, in one embodiment of the invention, four such springs were provided, two spaced apart at about the center of the apparatus and two spaced apart near the front end of the apparatus. The upper ends of the springs are secured to the upper sliding plate by means of brackets 145 or in any suitable manner, and they extend part way to the bottom plate when the apparatus is elevated, generally as illustrated in FIG. 2. 
     Four horizontal extension springs 146 are also provided to assist the operation of the apparatus 10. The springs are disposed in pairs and are secured, at one end, to the channel 168 which is fixed to the top plate 40 and, at the other end, to brackets 148. 
     The drive mechanism for the apparatus 10, which is self-locking, includes a knob 150 having a shaft 152 which extends through a hole in depending wall 42 of upper tray 40 (FIGS. 1, 2, and 6). The inner end 156 of the knob shaft 152 is seated on a bearing retainer 158. The bearing retainer 158, the channel 168, and the bearing block 164 are all secured to the depending wall 42. The inner end 156 of the knob shaft is coupled to and is adapted to rotate a lead screw 160 which extends through a thrust bearing block 164 and a nut 166. The nut 166 is fixed to the lower surface of the top sliding plate 50 at end wall 52. The channel 168 is secured to the top plate 40. The channel 168 houses the thrust bearing block 164. 
     In operation of apparatus 10, as the lead screw 160 is turned by the knob 150, its axial motion is prevented by the thrust bearing block 164, but it moves the nut 166 and thus the top slide plate 50. The nylon guides 45 and 46 reduce the friction of the movement of the parts, and, if desired, bronze rollers may be provided at the upper and lower ends of the lifter arms to further reduce friction. When the top slide plate 50 moves, it drives and pivots the lifter arms 90, 91, 92, and 93 at their lower ends since they are connected to the top slide plate, and these interact with arms 120 and 122 to cause the bottom slide plate to move with respect to the bottom tray 20, and either it goes up or down and either raises or lowers the terminal 38 carried on the top tray 40. The four lifter arms 90, 91, 92, and 93 are partially held in position by the extension springs 146, and the unbalanced load is distributed in the lead screw nut assembly and in the thrust bearing 164. 
     When the apparatus 10 is at its lowest position, the effort required to raise the CRT terminal 38 placed on top of the tray 40 is high. In order to overcome the weight, the four compression springs 144 are used. These compression springs are inactive when the mechanism is in the upper range of its motion. 
     The complete mechanism described above is hidden inside a bellows 35 (FIGS. 2 and 3) which contracts and expands, depending upon whether the motion is downward or upward. The top edges of the bellows are attached to plate 170 secured to the edges of the bottom tray 20. 
     The apparatus 10 has many advantages and favorable features. For one thing, in its lowered state, the apparatus measures only about one inch in height. When elevated, the apparatus has great stability, even with the weight of the terminal, and, in addition, a relatively heavy terminal can be raised easily by manipulation of a small knob which is self locking. The various operations are assisted by the springs which are provided &#34;L-shaped brackets (28, 29) are secured to the front and rear edges of the upper and base plates to form a channel for securing the guide members&#34;.