Abstract:
A computer display includes a pivotally mounted upper housing having a display screen, a brake used to retard pivoting motion of this upper housing, and a release mechanism for releasing the brake so that the upper housing can be freely moved. The display screen is preferably a touchscreen, which is touched to indicate a selection made by the user, with the brake resisting a tilting movement of the screen as it is touched. In a first version, two brakes are used to retard motion in both directions, with a single release wheel being turned in one direction to allow rearward motion of the upper housing and in another direction to allow forward motion of the upper housing. In a second version, a single brake is released by stopping motion of a release mandrel to unwrap a clutch spring. In a third version, two brakes, operating near opposite edges of the upper housing to stop downward movement of the upper housing, provide a particularly stiff mechanism for mounting the upper housing, and are simultaneously released by turning a knob to pivot a shaft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a means controlling the tilt of a display unit screen, and, more particularly, for releasably locking a screen of a touchscreen display unit at an adjustable tilt angle. 
     2. Description of the Related Art 
     In the patent art, a number of examples are found of mechanisms for controlling the tilt of a computer display through the use of one or more spring clutches or brakes arranged to resist a downward tilting movement of the display while releasing the display to be tilted upward. These mechanisms do not include means for releasing the clutch or brake to allow free downward tilting movement of the display; the clutches or brakes must be overpowered in order to tilt the display downward. 
     An example of such a mechanism is found in U.S. Pat. No. 5,771,152, which describes a tilt adjustment mechanism having an upper housing, a lower housing, and a shaft assembly. The shaft assembly receives gears which are pressed on either end of the shaft, which fits through locating slots in the lower housing. Each of the gears is activated by internal gears located on each side of the upper housing and integrally formed with the upper housing. The upper housing is hinged on the lower housing and can rotate 20 degrees. The shaft assembly mechanism provides a torsion bar function to insure that the upper housing moves evenly with respect to the lower housing. The shaft assembly mechanism decouples the frictional load in the two different rotational directions about its shaft, permitting adjustment of the forces to optimal levels in both directions. This mechanism includes a one-way clutch, in the form of a spring clutch or a bearing clutch, operating between the shaft and a bushing held within a clamp. When the upper housing is raised, the clutch releases to permit rotation of the shaft. When the upper housing is lowered, the clutch locks the shaft to the bushing, which then rotates within the clamp, with friction between the bushing and the clamp significantly increasing the force required to lower the upper housing. 
     Another example of such a mechanism is found in U.S. Pat. No. 5,206,790, which describes a laptop computer in which a display is connected to the lower housing by a pivot mechanism and a swivel mechanism. In the pivot mechanism, a pivot connects the display to a pivot plate, and a second pivot connects the pivot plate to the lower housing. The pivot consists of a pivot pin on each end of the pivot plate. The second pivot consists of split pivot pins at each end of the pivot plate. Each of the split pivot pins includes a pivot pin connected to the pivot plate and to an extension shaft having a sleeve portion extending over the end of the pivot pin and a shaft portion extending, and turning within a sleeve attached to the lower housing. A clutch spring extending over the sleeve and the sleeve portion of the extension shaft is arranged to unwind, releasing its connection between the sleeve and the extension shaft, as the display is opened, but to wind tighter, establishing a friction connection between the sleeve and the extension shaft, as the display is closed. 
     U.S. Pat. No. 5,197,704 also describes the use of spring clutches in a tilt adjusting mechanism for a display device. The angle adjusting device has a stationary bracket to be attached to a base and a rotating bracket to be attached to the display device. Each of these brackets is attached to a sleeve extending inward from the bracket. A shaft, having ends extending within the sleeves, also has an enlarged central portion extending between these sleeves. At each end of this enlarged central portion, a clutch spring extending over a part of the enlarged central portion and over the adjacent sleeve resists relative rotation between the shaft and the adjacent sleeve. 
     U.S. Pat. No. 5,173,837 describes the use of a clutch spring, through which a hinge pin for a laptop computer display extends, within a bracket in which the pin is pivotally mounted. The opposite ends of the clutch spring extend over a portion of the bracket to hold the spring in place. This arrangement produces approximately the same drag torque when the display is opened as when it is closed. 
     Other examples of the patent literature describe ways to provide friction at the pivot of a computer display through the use of friction braking without spring clutches. For example, U.S. Pat. No. 5,913,351 describes the use of friction plates held together on a pivot screw by means of a spring washer. U.S. Pat. No. 5,638,579 describes the use of a pair of bronze bearing blocks, one of which is responsive to precisely applied compressive force to produce user-controllable amounts of static and rotational friction to the tilt axis. U.S. Pat. No. 5,924,665 describes a multi-jointed and pivoted ceiling system for mounting a flat panel video display, employing elevational pivot assemblies including plastic friction washers and gas springs. 
     A problem common to these prior-art devices is that they fail to provide a release mechanism for disengaging the clutch or brake applying the friction torque. Thus, to move the display at least in one direction, a force sufficient to overcome the friction torque must be applied. In many applications, this friction torque must be substantial because it must be sufficient to hold the display in place when it is located so that gravity applies a maximum torque trying to lower the display. Having to overcome this friction torque makes it difficult to move the display and to position it precisely at a desired angle. As the display is manually moved against the friction torque, various parts within the display and within the mechanism through which it is mounted deflect elastically. When the torque moving the display is released, these elastic deflections are removed, so that the display does not remain where it has been positioned. 
     Thus, what is needed is a mechanism applying a drag torque to a computer display as it is tilted, with the mechanism including releasing means operable to cause the drag torque to be removed so that the display can be freely tilted in both directions. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is a first objective of the present invention to provide a braking mechanism, for restraining the tilting of a display housing, including a mechanism for releasing the braking mechanism to allow free movement of the display housing. 
     It is a second objective of the present invention to provide a braking mechanism which restrains the tilting of a display housing in both directions. 
     It is a third objective of the present invention to provide a braking mechanism, for restraining the tilting of a display housing, through which the display housing is rigidly held. 
     According to a first aspect of the present invention, there is provided a display unit including a base, an upper housing having a display screen, a pivot shaft, a first brake, and manually operated release means. The pivot shaft pivotally mounts the upper housing on the base. Pivoting the upper housing about the pivot shaft changes an angle of tilt of the display screen relative to the base. The first brake restrains pivoting of the upper housing in a first direction. The manually operated release means causes the first brake to release, allowing pivoting of the upper housing in the upper direction. 
     According to a second aspect of the present invention, there is provided apparatus for pivotally mounting an upper housing, including a display screen, on a base within a display unit. Pivoting the upper housing within the apparatus changes an angle of tilt of the display screen relative to the base. The apparatus includes first and second brakes. The first brake includes a first stator rigidly attached to a first end of the base and a first rotor rigidly attached to a first end of the upper housing, wherein the first rotor is pivotally mounted on the first stator, being restrained from rotation when the first brake is engaged, and being free to rotate when the first break is released. The second brake includes a second stator rigidly attached to a second end of the base, opposite the first end of the base, and a second rotor rigidly attached to a second end of the upper housing, opposite the first end of the upper housing, wherein the second rotor is pivotally mounted on the second stator, being restrained from rotation when the second brake is engaged, and being free to rotate when the second break is released, and wherein the first and second rotors are aligned along a common axis of rotation. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is an isometric view of a computer display built in accordance with a first embodiment of the present invention; 
     FIG. 2 is a front elevation of a brake mechanism within the computer display of FIG. 1 for releasably holding the display screen at a chosen angle of tilt; 
     FIG. 3 is a longitudinal cross-sectional view of the brake mechanism of FIG. 2, taken as indicated by section lines III—III in FIG. 1; 
     FIG. 4 is a fragmentary transverse cross-sectional view of a computer display built in accordance with a second embodiment of the present invention; 
     FIG. 5 is a front elevation of a brake mechanism within the computer display of FIG. 4; 
     FIG. 6 is a longitudinal cross-sectional view of a brake mechanism within the computer display of FIG. 4, taken as indicated by section lines VI—VI in FIG. 4; 
     FIG. 7 is a right elevation of a computer display built in accordance with a third embodiment of the present invention; 
     FIG. 8 is a rear elevation of the computer display in FIG. 7; and 
     FIG. 9 is a fragmentary longitudinal cross-sectional view of a brake mechanism within the computer display of FIG. 7, taken as indicated by section lines XI—XI in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an isometric view of a computer display  10  built in accordance with a first embodiment of the present invention. The display  10  includes a base  12  and an upper housing  14 , in which a display screen  16  is mounted. The display screen  16  may be, for example, a liquid crystal display. The upper housing  14  is rigidly mounted to a pivot shaft  18  by means of a pair of mounting structures  20  extending downward from the upper housing  14 . The pivot shaft  18  is in turn pivotally mounted within a pair of outer bearing structures  22  extending upward from the base  12 . The shaft  18  is held in position by means of a brake mechanism  24 , which is attached to the base  12 , being held within a cover  26 . The brake mechanism  24  holds the shaft  18  in position until a thumbwheel  28  is rotated in the direction of arrow  30 . Thus, the upper housing  14  is held in the angular (tilt) orientation in which it is set until the thumbwheel  28  is manually rotated in the direction of arrow  30 . (As described herein, an angle of tilt is the angle between the display screen of a display unit and a vertical plane. The upper housing of a display unit is tilted to change the angle of tilt.) When the thumbwheel  28  is rotated in the direction of arrow  30 , the brake mechanism  24  releases the shaft  18  so that the upper housing  14  can be manually tilted opposite the direction of arrow  30 . When the thumbwheel  28  is rotated opposite the direction of arrow  30 , the brake mechanism  24  releases the shaft  18  so that the upper housing  14  can be manually tilted in the direction of arrow  30 . When the upper housing  13  has been pivoted to the desired angle of tilt, the thumbwheel  28  is released to lock the upper housing  13  in place. 
     A preferred version of the display  10  is a touchscreen display in which the display screen  16  provides an indication of where it is touched, so that it can be touched to make a selection. Methods for providing such a capability are well known to those skilled in the art. In such an application, the brake mechanism is used to prevent movement of the upper housing  14  as the screen  16  is physically touched. 
     FIGS. 2 and 3 show the brake mechanism  24  with the cover  26  removed. FIG. 2 is a front elevation, while FIG. 3 is a longitudinal cross-sectional view. A pair of pivoting mandrels  32 ,  33  are attached to this pivot shaft  18 , by means of pins  34 , where the shaft  18  extends through this mechanism  24 . The shaft  18  is also pivotally mounted within a pair of inner bearing structures  36 , each of which also includes an inward-extending hub forming a stationary mandrel  38 . A clutch spring  40 ,  42  is wrapped around the pivoting mandrel  32 ,  33  and the stationary mandrel  38  on each side of the thumbwheel  28 , with the two clutch springs  40 ,  42  being wound in the same direction. An inner end  44  of each clutch spring  46  extends into an aperture  46  within the thumbwheel  28 . 
     When the thumbwheel  28  is released, the clutch springs  40 , 42  are wrapped tightly enough around the pivoting mandrels  32  and the stationary mandrels  38  to hold the shaft  18  in place. If an attempt is made to pivot the upper housing  14  in the forward direction of arrow  30  without manually rotating the thumbwheel  28 , the friction torque generated between the first clutch spring  40  and the pivoting mandrel  32 , around which it is wrapped, loosens the engagement between this clutch spring  40  and this pivoting mandrel  32  so that slipping could occur, while the friction torque generated between the second clutch spring  42  and the pivoting mandrel  33 , around which it is wrapped, tightens the engagement between the second clutch spring  42  and the mandrels  33 ,  38  around which this clutch spring  42  is wrapped, so that slipping cannot occur. Similarly, if an attempt is made to pivot the upper housing  14  in the backward direction opposite the direction of arrow  30  without manually rotating the thumbwheel  28 , the friction torque generated between the second clutch spring  42  and the pivoting mandrel  33  around which it is wrapped loosens the engagement between this clutch spring  42  and this pivoting mandrel  33  so that slipping could occur, while the friction torque generated between the clutch spring  40  and the pivoting mandrel  32  around which this clutch spring  40  is wrapped tightens the engagement between the first clutch spring  40  and the mandrels  32 ,  38  around which this clutch spring  40  is wrapped, so that slipping cannot occur. Thus, when the thumbwheel  28  is not manually rotated, the second clutch spring  42  prevents pivoting the upper housing  14  in the direction of arrow  30 , while the clutch spring  40  prevents pivoting the upper housing  14  opposite the direction of arrow  30 . 
     When the thumbwheel  28  is manually rotated opposite the direction of arrow  30 , the movement imparted by the thumbwheel  28  to the inner extension  44  of the second clutch spring  42  causes this clutch spring  42  to begin to unwrap, disengaging from the pivoting mandrel  33  around which the second clutch spring  42  is wrapped, so that the upper housing  14  can be rotated in the direction of arrow  30 . While this rotation of the thumbwheel  28  opposite the direction of arrow  30  also causes the first clutch spring  40  to tighten, by means of the movement imparted by the thumbwheel  28  to the inner extension  44  of the clutch spring  40 , the upper housing  14  can still be rotated in the direction of arrow  30 , since such rotation of the upper housing  14  causes the first clutch spring  40  to disengage by unwrapping. Since rotating the thumbwheel  28  opposite the direction of arrow  30  tightens the clutch spring  40 , the upper housing is not released to pivot opposite the direction of arrow  30 . 
     On the other hand, when the thumbwheel  28  is manually rotated in the direction of arrow  30 , the movement imparted by the thumbwheel  28  to the inner extension  44  of the clutch spring  40  causes this clutch spring  40  to begin to unwrap, disengaging from the pivoting mandrel  32  around which the clutch spring  40  is wrapped, so that the upper housing  14  can be rotated opposite the direction of arrow  30 . While this rotation of the thumbwheel  28  in the direction of arrow  30  also causes the second clutch spring  42  to tighten, by means of the movement imparted by the thumbwheel  28  to the inner extension  44  of the second clutch spring  42 , the upper housing  14  can still be rotated opposite the direction of arrow  30 , since such rotation of the housing  14  causes the second clutch spring  42  to disengage. Since rotating the thumbwheel  28  opposite the direction of arrow  30  tightens the second clutch spring  42 , the upper housing is not released to pivot in the direction of arrow  30 . 
     Thus, to pivot the upper housing  14  forward, in the direction of arrow  30 , the thumbwheel  28  is pivoted opposite the direction of arrow  30 , as the upper housing  14  is moved as desired. To pivot the upper housing  14  to the rear, opposite the direction of arrow  30 , the thumbwheel  28  is pivoted in the direction of arrow  30  as the upper housing  14  is moved as desired. When the thumbwheel  28  is released, the upper housing  14  is locked in place. 
     This type of operation is particularly desirable to adjust the position of a display unit having a center of gravity nearly aligned, in a vertical direction, with the axis about which the display unit is pivoted, with the center of gravity being either above or below the pivot axis. In such a display unit, gravity cannot be relied upon to keep the display unit tilted at a desired angle against stop formed by a brake which restrains movement only in a single direction. 
     FIG. 4 is a fragmentary transverse cross-sectional view of a computer display  50  built in accordance with a second embodiment of the present invention. The computer display  50  includes an upper housing  52  having a display screen  54  visible through an aperture  56 . The upper housing  52  is rigidly attached to a pivot shaft  58  by means of a pair of housing attachment structures  60  descending from the housing  52 . The pivot shaft  58  is pivotally mounted on a base  62  by means of two or more upstanding bearing structures  64 . A central bearing structure  64  also includes a pin  66 , which limits the pivoting movement of shaft  58  by contacting stop surfaces  68  of a travel limiting plate  70 . This limitation on pivoting motion is imposed so that the upper housing  52  is always in an orientation in which gravity provides a torque on the upper housing  52  in the direction of arrow  72 . With this limitation, the upper housing  52  is held in place with a brake  74  preventing rotation in the downward direction of arrow  72  while allowing rotation opposite the direction of arrow  72 . 
     A preferred version of the display  50  is a touchscreen display in which the display screen  54  provides an indication of where it is touched, so that it can be touched to make a selection. In such an application, touching the screen places a torque on the display screen in the downward direction of arrow  72 , with the brake mechanism being used to prevent movement of the upper housing  52  as the screen  54  is physically touched. 
     FIGS. 5 and 6 show the brake  74  used to hold the upper housing  52  at a preset angle within the computer display  50  of FIG. 4, with FIG. 5 being a front elevation of the brake  74 , and with being a longitudinal cross-sectional view, taken as indicated by section lines VI—VI in FIG.  4 . The brake  74  includes a stationary mandrel  76 , a pivoting mandrel  78 , a release mandrel  80 , and a clutch spring  81 . The stationary mandrel  76  is formed as a hub extending from the central bearing structure  64 . The limiting plate  70  and the pivoting mandrel  78  are each fastened to the pivot shaft  58  by means of a pin  82 . The release mandrel  80  is pivotally mounted on the pivot shaft  58 , being held in place on the shaft  58  by means of a retaining clip  84 . The clutch spring  81  is wound to extend over the three mandrels  76 ,  78 ,  80 . The release mandrel  80  includes a ridge  86 , which is contacted by an inner end  88  of a pushbutton  90  when the pushbutton  90  is depressed to the rear, in the direction of arrow  92 . The pushbutton  90  slides within a button holder  94 , extending within a cover  96 . The pushbutton  90  is then returned opposite the direction of arrow  92  by a compression spring  97 , to be held in place by a retaining clip  98 . Thus, the pushbutton  90  is used as a brake to stop rotation of the release mandrel  80 . 
     When a torque is applied to the upper housing  52  in the direction of arrow  72  with the release mandrel  80  being allowed to turn, friction between the pivoting mandrel  78  and the clutch spring  81  causes the clutch spring  81  to wind more tightly on the pivoting mandrel  78  and the stationary mandrel  76 , so that movement of the upper housing  52  is restrained. On the other hand, when torque is applied to the upper housing in the direction of arrow  72  as the release mandrel  80  is held through the depression of pushbutton  90 , the friction between the stationary mandrel  80  and the clutch spring  81 , which begins to turn in the direction of arrow  72  with the pivoting mandrel  78 , causes the clutch spring  81  to unwrap from the pivoting mandrel, releasing the brake  74  so that the upper housing  52  can be freely moved in the direction of arrow  72 . 
     When a torque is applied to the upper housing  52  opposite the direction of arrow  72 , friction between the pivoting mandrel  78  and the clutch spring  81  causes the clutch spring  81  to unwind on the pivoting mandrel  78  and the stationary mandrel  76 . Thus, the upper housing  52  is raised, opposite the direction of arrow  72 , without depressing the pushbutton  90 . Because of the travel limitations imposed through the use of pin  62  and travel limiting plate.  70 , gravity holds the upper housing downward, in the direction of arrow  72 . 
     FIG. 7 is a right elevation of display unit  100 , built in accordance with a third embodiment of the present invention, which includes an upper housing  102 , mounted to pivot about a shaft  104  extending between a pair of bearing brackets  106  extending upward as part of a base  108 . The upper housing  102  includes a display screen  110  visible through an aperture  112 . The display unit  100  is configured so gravity places a torque on the upper housing  102  in the direction of arrow  114  about the shaft  104 . 
     A preferred version of the display  100  is a touchscreen display in which the display screen  110  provides an indication of where it is touched, so that it can be touched to make a selection. In such an application, touching the screen places a torque on the display screen opposite the direction of arrow  114 , with the brake mechanism being used to prevent movement of the upper housing  102  as the screen  110  is physically touched 
     FIG. 8 is a rear elevation of the display unit  100 , showing a first brake  116  and a second brake  118 , which are used together to pivotally mount the upper housing  102  on the base  108  and to restrain a pivoting movement of the upper housing  102  in the direction of arrow  114 . Each brake  116 ,  118  extends between a bearing bracket  106  forming part of the base  108  and support bracket  120  extending along the upper housing  102 . 
     FIG. 9 is a fragmentary longitudinal cross-sectional view of the display unit  100 , taken as indicated by section lines IX—IX in FIG. 7, to show the structure of brakes  116 ,  118 . Each brake  116 ,  118  includes a stationary mandrel  122  attached to an adjacent bearing bracket  106 , a pivoting mandrel  124  attached to an adjacent support bracket  120 , and a clutch spring  126  wound to extend along both of these mandrels  122 ,  124 . Each clutch spring  126  includes a first end  128  extending through a slot  130  in the adjacent support bracket  120  into a hole within an adjacent release knob  134 . Each clutch spring  126  also includes a second end  136  extending through a hole  138  in the adjacent bearing bracket  106 . The shaft  104  is pivotally mounted within the mandrels  122 ,  124 , being rotationally attached only to the first ends  128  of the clutch springs  126  through the release knobs  134 , which are individually fastened to the shaft  104  by means of set screws  140 . 
     Between the two brakes  116 ,  118 , the relative positioning of the mandrels is reversed. That is, the pivoting mandrel  124  extends in the direction of arrow  141  from the stationary mandrel  122  in the first clutch  116 , while, in the second clutch  118 , the pivoting mandrel  124  extends from the stationary mandrel  122  in a direction opposite that of arrow  141 . Also, the clutch springs  126  of the two brakes  116 ,  118  are wound in opposite directions. When these configurational changes are made together, the two brakes  116 ,  118  are made to operate in the same manner. Thus, as a torque is applied opposite the direction of arrow  114  to the upper housing  102  with the shaft  104  unrestrained, within each brake  116 ,  118 , the frictional torque between the pivoting mandrel  124  and the clutch spring  126  causes this spring  116  to tighten on the pivoting mandrel  124  and on the stationary mandrel  122 , so that movement of the upper housing  102  in the opposite direction of arrow  114  is resisted. On the other hand, when a torque is applied to the upper housing  102  in the direction of arrow  114 , the housing  102  is easily raised, since, in each brake  116 ,  118 , the frictional torque between the pivoting mandrel  124  and the clutch spring  126  causes this spring  126  to loosen by unwinding on the pivoting mandrel  124  and the stationary mandrel  122 . 
     To tilt the upper housing  102  upward, opposite the direction of arrow  114 , either of the knobs  134  is first pivoted in the direction of arrow  114 , causing the end  128  of the clutch spring  126  to move within a slot  130  so that the clutch spring  126  is loosened from its engagement with the adjacent pivoting mandrel  124 . The shaft  104  is thus used to transfer a pivoting motion between the two release knobs  134 . 
     A significant advantage of the display unit  100  built in accordance with the third embodiment of the present invention over the prior art arises from the attachment of the pivoting mandrels  124  directly to the support brackets  120  of the upper housing, together with the attachment of the stationary mandrels  122  directly to the stationary brackets  106  of the base  108 . The shaft  104  is not used to attach either pivoting mandrel  124  to a support bracket. This arrangement provides for a particularly rigid connection between the base  108  and the upper housing  102 , eliminating bouncing conditions which can otherwise occur following the engagement of the brakes. 
     It is understood that, while the present invention has been described with some degree of particularity in the form of three specific embodiments, this description has been given only by way of example, and that numerous changes in the details and use, including the combination and arrangement of parts may be made without departing from the spirit and scope of the invention. In particular, various features of these embodiments may be combined to obtain configurations having valuable properties. For example, the clutch springs of the third embodiment, described above in reference to FIGS. 7-9, can be wound in the same direction, as described above in reference to FIGS. 1-3 to provide a display unit in which the brakes prevent tilting movement of the upper housing in both directions. The shaft would be pivoted in one direction to allow upward movement of the upper housing and in an opposite direction to allow downward movement of the upper housing. The use of the release mandrel of the second embodiment, described above in reference to FIGS. 4-6 can be applied to the other embodiments to replace unwrapping an end of a clutch spring.