Adjustable Support Arm
An adjustable support arm utilizing a spring having a dynamic attachment point to support the weight of an attached object. The adjustable support arm can comprise a lower bracket connected to an upper bracket by a parallelogram linkage. A spring is utilized to counterbalance the weight of an attached object. The first end of the spring can be attached to the upper link of the parallelogram linkage. The second end of the spring is attached to a drag link to provide a dynamic attachment point that automatically adjusts as the support arm is moved between the upper and lower vertical positions. Either a pivot link or a slot in the lower link can be used to guide the drag link's movement as the support arm's vertical height is adjusted.
1 . An adjustable support arm comprising:
a. A lower bracket;
b. An upper bracket;
c. A parallelogram linkage attaching the upper bracket to the lower bracket, the parallelogram linkage comprising an upper link and a lower link;
d. A pivot link having a first end and a second end, the pivot link's first end pivotally attached to the lower link;
e. A drag link having a first end and a second end, wherein the drag link's first end is pivotally attached to the upper bracket and the drag link's second end is pivotally attached to the pivot link's second end; and
f. A spring attached to the drag link.
2 . The adjustable support arm of claim 1 , wherein the spring defines a first end and a second end, wherein the spring's first end is attached to the upper link and the spring's second end is attached to the drag link.
3 . The adjustable support arm of claim 2 , further comprising a means for applying a preload to the spring.
4 . The adjustable support arm of claim 3 , wherein the means for applying a preload to the spring comprises:
a. a screw cap having internal threads and external threads, the screw cap's external threads being threadingly engaged to the spring's first end; and
b. a bolt extending through an aperture in the upper link to threadingly engage the screw cap's internal threads.
5 . The adjustable support arm of claim 2 , wherein the spring is an extension spring.
6 . The adjustable support arm of claim 1 , further comprising a second pivot link having a first end and a second end, wherein the first end of the second pivot link is pivotally attached to the lower link and the second end of the second pivot link is pivotally attached to the drag link's second end.
7 . The adjustable support arm of claim 6 , wherein lower link defines a left sidewall and a right sidewall, wherein the first end of the first pivot link is pivotally attached to the left sidewall and the first end of the second pivot link is pivotally attached to the right sidewall.
8 . The adjustable support arm of claim 1 , further comprising a base assembly attached to the lower bracket and a mount assembly attached to the upper bracket.
9 . An adjustable support arm comprising:
a. A lower bracket;
b. An upper bracket;
c. A parallelogram linkage attaching the upper bracket to the lower bracket, the parallelogram linkage comprising an upper link and a lower link;
d. A drag link having a first end and a second end, the first end pivotally attached to the upper bracket, the second end engaging a slot in the lower link; and
e. A spring attached to the drag link.
10 . The adjustable support arm of claim 9 , wherein the spring defines a first end and a second end, wherein the spring's first end is attached to the drag link and the spring's second end is attached to the upper link.
11 . The adjustable support arm of claim 10 , further comprising a means for applying a preload to the spring.
12 . The adjustable support arm of claim 11 , wherein the means for applying a preload to the spring comprises:
a. a screw cap having internal threads and external threads, the screw cap's external threads being threadingly engaged to the spring; and
b. a bolt extending through an aperture in the upper link to threadingly engage the screw cap's internal threads.
13 . The adjustable support arm of claim 10 , wherein the spring is an extension spring.
14 . The adjustable support arm of claim 9 , further comprising one or more rollers attached to the drag link for engaging the slot in the lower link.
15 . The adjustable support arm of claim 14 , further comprising a base assembly attached to the lower bracket and a mount assembly attached to the upper bracket.
16 . An adjustable support arm comprising:
a. A lower bracket;
b. An upper bracket;
c. A parallelogram linkage attached the upper bracket to the lower bracket, the parallelogram linkage comprising an upper link and a lower link;
d. A drag link having a first end and a second end, the drag link's first end pivotally attached to the upper bracket;
e. A spring attached to the drag link; and
f. A means for guiding the movement of the drag link's second end as the adjustable support arm is raised and lowered.
17 . The adjustable support arm of claim 16 , wherein the means for guiding the movement of the drag link's second end comprises a pivot link, the pivot link having a first end attached to the lower link and a second end pivotally attached to the drag link.
18 . The adjustable support arm of claim 16 , wherein the means for guiding the movement of the drag link's second end comprises a slot in the lower link operatively engaged by the drag link's second end.
19 . The adjustable support arm of claim 16 , further comprising a base assembly attached to the lower bracket and a mount assembly attached to the upper bracket.
20 . The adjustable support arm of claim 16 , further comprising a means for applying a preload to the spring, wherein the means for applying a preload to the spring comprises:
a. a screw cap having internal threads and external threads, the screw cap's external threads being threadingly engaged to the spring; and
b. a bolt extending through an aperture in the upper link to threadingly engage the screw cap's internal threads.