29/141,175,29/141,189 & 29/141, 174, each filed May 1,2001, each of my above-identified prior applications is hereby incorporated by reference.

BACKGROUND OF THE INVENTION This invention relates to spring counterbalanced arm assemblies, and more in particular to such assemblies incorporated in lamps.

An object of this invention is to provide an improved spring counterbalanced arm assembly. A further object is to provide a lamp incorporating such an assembly that overcomes the difficulties heretofore associated with spring counterbalanced arm assemblies. A still further object of the present invention is to provide a spring counterbalanced arm assembly that is superior to those heretofore available in that the inventive assembly is more attractive and does not have exposed springs. These and other objects will be obvious, in part, and pointed out, in part, below.

Spring counterbalanced arm assemblies have been used to support various components and objects. A common application of a spring counterbalanced arm assembly has been in lamps. Some such assemblies heretofore have been provided which are free of external springs, but such assemblies have had serious deficiencies in use. For example, some have had limited adjustment while others have been too complicated or costly or have had limited useful life.

Nonetheless, counterbalanced arm assemblies with external extension springs have been provided and have proven very satisfactory. However, the external springs tend to collect dust and other dirt, although that objection has been somewhat reduced by providing sleeves over the springs. Nevertheless, the mounting structures for the springs cause certain difficulties.

The best known type of lamps having the external springs are provided with two parallelogram arm assemblies, the lower of which is swingably mounted at its bottom end upon a swivel pivot, and which is hinged at its other end to one end of the upper arm. The lamp assembly or lamp head is mounted upon the other end of the upper arm, and is provided with a universal joint mounting. Each of the parallel arm assemblies is formed by two tubular arms which are of equal length and pivoted separately at their ends upon brackets so as to form a parallelogram relationship. Each arm assembly is provided with two or more springs mounted along the sides of the arms so as to provide counterbalancing forces. Those forces support the lamp assembly so that it can be moved throughout the wide range of the swinging movement of the arm assemblies both vertically and horizontally.

Counterbalanced arm assemblies have also been provided for objects such as television sets where each arm is formed by mating channels which enclose the counterbalancing springs. It is a still further object of the present invention to provide arm assemblies for lamps and other objects wherein counterbalanced springs are totally enclosed within the arm assemblies. It is a yet further object to provide for the above with constructions wherein extension springs exert forces longitudinally of the arms and those forces are exerted in an improved manner to provide the desired counterbalancing effects.

BRIEF SUMMARY OF THE INVENTION One embodiment of the present invention provides a lamp assembly. Typically, the lamp assembly has a base which can be placed on a work surface or mounted, for instance to either the work surface or to a nearby vertical surface such as a wall or a wall of a work cubical.

Desirably, a first pair of tubular arms are pivotally mounted to said lamp base.

Also in a typical embodiment of the present invention, pivotally mounted to the distal end of said first pair of tubular arms is a floating bracket. A second pair of tubular arms is pivotally mounted to the distal end of said floating bracket. A lamp head bracket is then pivotally mounted to the distal end of said second pair of tubular arms.

A typical embodiment of the present invention might also include a first anchor mounted on said lamp base and secured to a first spring mounting wire. The first spring mounting wire is, in turn, attached to a first extension spring, which in turn is pivotally mounted to a floating bracket within said first tubular arm. A second anchor mounted on said floating bracket can be secured to a second spring mounting wire, which in turn, is secured to a second extension spring. In some embodiments of the present invention, the second extension spring is attached to a third extension spring. In such an embodiment, the second extension spring generally is anchored, albeit pivotally, to the lamp head bracket and said anchor is within said third tubular arm.

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a perspective view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 2 is a rear view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 3 is a first side view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 4 is a front view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 5 is a second side view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 6 is a top view of a lamp showing an embodiment of a lamp using a shade of the present invention; Fig. 7 is partial cut-away view of an embodiment in which the mechanism is in the substantially neutral position according to the present invention; Fig. 8 is an enlarged partial cut-away view of an embodiment in which the mechanism is in a slightly raised position according to the present invention; Fig. 9 is a partial cut away view of an embodiment in which the mechanism is in a lowered position according to the present invention; Fig. 10 is an enlarged partial cut-away view the lower portion of an embodiment according to the present invention; and Fig. 11 is a view of the springs and wires of a preferred embodiment according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION Figs. 1-6 generally illustrate a lamp incorporating an embodiment of the counterbalancing mechanism of the present invention.

Fig. 7 illustrates an embodiment of a counterbalanced lamp mechanism of the current invention. In this embodiment, post 701 is inserted into a lamp base (not shown).

Mounted on the top of post 701 is mounting bracket 705. First arm 707 of mounting bracket 705 extends to pivot axis 709. Second arm 702 of mounting bracket 705 extends to pivot axis 703.

First tubular arm 710 and second tubular arm 712 are pivotally mounted on mounting bracket 705 at pivot axes 703 and 709 respectively. Note that first tubular arm 710 extends beyond pivot axis 703, which extension is labeled 713 for reference.

It is preferred that mounting bracket 705 is made from more than one piece. For example, mounting bracket 705 could be formed from two"halves"that mate and form the unit.

Typically, in such an embodiment, the several pieces are, once assembled, held together by one or more screws.

Inside first tubular arm 710 is first spring mounting wire 714, which at point 716 is secured to first extension spring 718, in a conventional manner, for instance first spring mounting wire 714 can have a ring connector at its end that is looped through an end of first extension spring 718. At its proximal end, first spring mounting wire 714 is anchored to mounting bracket 705 at anchor point 704 in a conventional manner. As first spring mounting wire 714 exits first tubular arm 710, it passes between two pulley rollers, 706 and 708.

The distal ends of first tubular arm 710 and second tubular arm 712 are pivotally mounted on floating bracket 724, at pivot points 720 and 722 respectively. Connected to pivot point 720 and within first tubular arm 710 is spring anchor 726, which is pivotally mounted to pivot point 720. The proximal ends of third tubular arm 750 and fourth tubular arm 760 are pivotally mounted on floating bracket 724 at pivot points 728 and 730 respectively.

Third tubular arm 750 has a projecting arm 732 on which is mounted a pulley roller 734. Shown in dotted lines is pulley roller 734 in position a (i. e., 734a), which position occurs when the third and fourth tubular arms, 750 and 760 respectively, approach an angle of about 20° with first and second tubular arms, 710 and 712 respectively. Also shown in dotted lines is pulley roller 734 in position b (i. e., 734b), which position occurs when the third and fourth tubular arms, 750 and 760 respectively, approach an angle of about 180° with first and second tubular arms, 710 and 712 respectively.

Inside third tubular arm 750 is second spring mounting wire 740, which at point 745 is secured to second extension spring 747. At its proximal end, second spring mounting wire 740 is anchored to floating bracket 724 at anchor point 742. At its distal end, in this embodiment, second extension spring 747 is attached to the proximal end of third extension spring 749.

In an alternative embodiment of the present invention, a single extension spring is used inside third tubular arm 750 instead of the second and third extension springs described above. However, whether there is one, two, or more extension springs inside the third tubular arm 750, it is preferred that the length of the extension springs inside third tubular arm 750 is about double the length of the extension spring inside first tubular arm 710.

Distal ends of third tubular arm 750 and fourth tubular arm 760 are pivotally attached to lamp head bracket 770 at pivot points 755 and 765 respectively. Third extension spring 749 is secured to spring anchor 758, which is pivotally mounted to pivot point 755.

The details of a particularly preferred lamp head bracket 770 are given in more detail in my US Patent Application No. 60/298, 519 entitled LAMP AND SHADE filed on June 14,2001, which application is hereby incorporated by reference.

It is preferred that both first spring mounting wire 714 and second spring mounting wire 740 coated with a plastic to permit the wires to easily slide over the several pulley rollers.

In a preferred embodiment of the present invention, floating bracket 724 is made of two pieces that are joined by knob 738. Tightening knob 738 increases the friction about pivot points 720,722,728,730, or a combination thereof such as 720 and 722, or 728 and 730, or all four pivot points. By increasing friction in this manner, lamp head bracket 770 tends to maintain the position into which its user puts it.

It is also desired that the friction in moving the arms is increased by using close tolerances between the pivot points on floating bracket 724 and the tubular arms. Again, by increasing friction in this manner, lamp head bracket 770 tends to maintain the position into which its user puts it. While the counter balanced force of the springs and cables maintains the lamp head in whatever position it is placed, any slight force--e. g., a brushing touch--applied to the lamp head will cause it to move. To prevent the lamp head from moving when an inadvertent force is applied, a particularly preferred embodiment of the present invention incorporates some friction between the arms to stabilize the position of the lamp head.

It is also desired that pivot points 709,722,730 and 765 are hollow so that wire 711, which provides power to lamp head bracket 770 can be hidden within the tubular structure of the lamp.

First spring mounting wire 714 and second spring mounting wire 740 can be attached to anchor point 704 and anchor point 742, respectively, by any conventional means.

Nonetheless, a preferred means of attaching the spring mounting wires to their respective anchor points is by cinching a ball with a hole onto the spring mounting wire and creating a slot and pocket in which the spring mounting wire with cinched ball sits securely.

To permit first and second tubular arms 710 and 712 to pivot freely about their pivot points, 703 and 709 respectively, it is preferred that first arm 707 of mounting bracket 705 is arc shaped, with a radius originating at pivot point 703, slightly greater than the length of extension 713 plus any projection of pulley rollers 706 and 708 beyond extension 713. This arc shape of first arm 707 of mounting bracket 705 pennits first and second tubular arms to pivot "backwardly"about their pivot points, 703 and 709 respectively.

In a preferred embodiment of the present invention, third tubular arm 750 has more than one spring linked in series. It is further preferred that third tubular arm 750 has two springs linked in series. The use of more than one spring reduces the force the spring system imparts to the counterbalancing mechanism. In part, the reduced force is a result of increasing the amount of stretch (approximately doubling) necessary to achieve a given force. This reduced force prevents lamp head bracket 770 from moving upward when a user positions lamp head bracket 770 in a position close to mounting bracket 705.

Turning now to Fig. 8, a mechanism used in a preferred embodiment of the present invention to control the counterbalancing force applied to the third and fourth tubular arms, 750 and 760 can be seen more readily. In this Fig. 8 it can be seen that second spring mounting wire 740 travels under pulley roller 728 and bends upward to go over pulley roller 734.

In going around pulley roller 728, second spring mounting wire 740 forms an angle of about 115 to 145°, preferably the angle formed is about 130°. As noted above, after going over pulley roller 734, second spring mounting wire 740 is secured to anchor point 742 on floating bracket 724.

In a preferred embodiment of the present invention, pulley roller 734 is mounted on projecting arm 732 is between about 0.8 and 5 inches from pivot point 728. It is more preferred that pulley roller 734 is mounted on projecting arm 732 is between about 1 and 3 inches from pivot point 728. It is further preferred that pulley roller 734 is mounted on projecting arm 732 is about 2 inches from pivot point 728.

By using this mechanism, the spring force decreases as the distance between pulley roller 734 and anchor point 742 is decreased, and conversely, the spring force increases as the distance between pulley roller 734 and anchor point 742 is increased. These spring force changes occur because while the length of second spring mounting wire 740 is fixed, the distance increases when the lamp head is lowered, which stretches the springs and thereby increases the force urging the lamp head upward.

In a preferred embodiment, the device of the present invention supports a constant load. As illustrated in FIG. 7, in such a preferred embodiment, the spring force applied to support the load by the upper arms is at its maximum when the upper arms are substantially parallel to the horizon. When, in this embodiment, the load is raised (from being substantially parallel to the horizon), the spring force required to balance the cantilevered load is decreased.

As shown in phantom, when the load is raised, pulley roller 734 moves into position 734b, which is closer to anchor point 742. Bringing pulley roller 734 closer to anchor point 742 increases the length of wire 740 between pulley roller 734 and point 745. This lengthening, in turn, reduces the spring stretch, which reduces the spring force. Correspondingly, when the load is raised, the effective cantilevered load is reduced because the horizontal component of the distance between the pivot point and the load is reduced.

When the load is lowered (from being substantially parallel to the horizon), the spring force required to balance the cantilevered load is decreased. However, as shown in phantom, when the load is lowered, pulley roller 734 moves into position 734a, which is further from anchor point 742. Bringing pulley roller 734 further from anchor point 742 decreases the length of wire 740 between pulley roller 734 and anchor point 742. This reduction in the length of wire 740 between pulley roller 734 and anchor point 742 increases the spring stretch, which increases the spring force. Thus when the load is lowered, the cantilevered load is decreased while the spring force is increased, which is a combination that should destabilize the load position.

However, a preferred geometry for the present invention, compensates for the decreased cantilevered load and increased spring force by reducing the effectiveness of the increased spring force. A particularly preferred means of decreasing the effectiveness of the increased spring force is by reducing the distance from the end of tubular arm 750 and wire 740 between pulley roller 734 and anchor point 742. This reduced distance can be seen in phantom in FIG. 7.

FIG. 8 provides another illustration of the distance that is reduced to decrease the effectiveness of the spring force. Here, the distance between the end of tubular arm 750 and the intersection of wire 740 and an imaginary projection of tubular arm 750, e. g., intersection point 800 in Fig. 8, changes the effectiveness of the spring force. In the particularly preferred embodiment described above, the distance between the end of tubular arm 750 and intersection point 800 is at its maximum value when tubular arm 750 is substantially parallel to the horizon and decreases as tubular arm 750 is moved downward from being parallel to the horizon. See also the phantom illustrations of FIG. 7.

Desirably, the amount of force applied by the springs holds the lamp head in the position set by the user and does not cause the lamp head to move once the user has positioned the lamp head.

While the embodiments of the various aspects of the present invention that have been described are the preferred implementation, those skilled in the art will understand that variations thereof may also be possible. For instance, the present mechanism could be used to position, for instance, a flat screen monitor or the head of an x-ray machine. Therefore, the invention is entitled to protection within the full scope of the appended claims.