CA1217751A - Ergonomic equipment arm - Google Patents

Abstract

ABSTRACT
A mounting arm is disclosed on one end of which a piece of electronic or other equipment is mounted and the other end of which is detachably fastened to the edge of a supporting surface. The arm has three moving joints that permit the equipment fastened thereto to be moved with multiple degrees of freedom for desired positioning of the equipment. One joint utilizes a friction washer assembly and a preloaded torsion spring counterbalancing the weight of the equipment. The torsion spring tension is adjustable to compensate for differing weight equipment on the one end of the arm. Another joint utilizes a friction ball joint arrangement having double concentric friction ball surfaces in an assembly that permits multiple degrees of freedom of motion and is easily removed from the remainder of the arm without disassembling the ball joint.

Description

12~1.7~Sl This application is a division of our Canadian patent application Serial No. 434,703 filed August 16, 1983.
The present invention relates to movable arms on which equipment is mounted and supported while being easily moved.
Movable arms on which equipment may be mounted are known in the art such as seen in United States Patent 3,030,128 issued April 17, 1962 to K. Versen. The movable arm shown in this patent utilizes three rotating and swivel joints in conjunction with friction couplings and a torsion spring to counterbalance the weight of a lamp at the end of the arm. The interaction of all these joints and elements permits the lamp at the end of the movable arm to be easily positioned in a large number of positions within the reach of the arm, and the lamp will stay in the position in which it is placed.
There are however, problems with such prior art movable arms. Each movable joint only has two degrees of freedom and when it is desired to orient the lamp or other equipment in a specific position there is often difficulty in that the three movable joints do not cooperatively move as easily as desired when the lamp or other equipment at the end of the arm is moved.
In addition, in some applications it is sometimes desired to change the type of equipment mounted on the end of the movable arm. In the prior art the weight of the new equipment must be the same as the weight of the original equipment being replaced. If heavier or lighter equipment is , i~.

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placed on the end of the arm the counter balancing forces within the arm are not optimum for the new weight and the equipment sometimes will not stay in a position in which it is placed. For example, with a heavier piece of equipment the arm will sag when the equipment is manually positioned and then released. To compensate for this type of problem in the prior art the pressure on friction coupling elements in one or more of the movable joints is increased or decreased. However, when the pressure is increased it is correspondingly harder to position the heavier equipment on the end of the arm due to jerky arm movement with the result being difficulty in positioning the equipment in a precise position. This is caused by greater forces being required to overcome the increased friction and therefore increased tendency to overshoot.
Thus, changing pressure on friction couplings accommodate for differing weight loads on the end of a movable arm is impractical. Accordingly, in the prior art a movable arm is usually only designed for a given weight load on the end of the arm. This has been acceptable in the prior art as there has not been much demand for movable arms that can accommodate differing weight loads.
In recent times there has developed a need for a movable arm that can accommodate differeing weight loads without experiencing the detrimental operation described in the last paragraph. For example, in the computer field including the word processing and office equipment fields in which television type videa displays are used, some systems place the . ~

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video display on a movable arm permitting the equipment user to place the display in whatever position they desire for greater ease in viewing the monitor. Movable arms have been designed for these applications. However, in different system configurations the displays are of different weights due to differing amounts of electronic equipment being in the enclosure on the movable arm, due to larger or smaller cathode ray tubes being used for the display, and due to cathode ray tubes being from different manufacturers and thereby being of differing weights although they have the same size display areas.
This has required that a number of different movable arms be utilized, or that the problems in the prior art be lived with.
To create the different arm the torsion springs are typically changed. Often there is a compromise between these two solutions which lesse~ the problem but doesn't minimize or eliminate it. When a number of movable arms must be utilized there are increased costs for manufacturing and keeping records.
Thus, there is a need in the art for a movable arm that can be used with differing weight loads at the end of the arm without any change in the force required to move the load, and without requiring different parts.
There is also a need in the art for a movable arm that cen be moved more easily than in the prior art.
The above described problems with prior art movable arms are solved by our novel movable arm. Our novel arm utilizes three movable joints two of which are pivoting joints each having two degrees of freedom and the third joint is a unique ~Z~7~75~

friction ball joint having more than two degrees of freedom which thereby allows the arm to be moved more easily. In addition, we provide means for quickly and easily adjusting the tension of a torsion spring within one of the joints of our arm to properly counterbalance differing weights on the end of the arm.
This permits different weights on the end of the movable arm to all be moved with equal ease. Furthermore, we provide a clamp means on the end of our movable arm opposite the end of which the equipment is fastened which permits our movable arm to be mounted on other than a dedicated support base table.
This permits greater flexibility and portability. For example, with a small computer system or word processor terminal the video display can be mounted on the edge of an existing desk or table.
In accordance with a broad aspect of this invention, there is provided a computer video monitor and support arm for installation on a desk or table, comprising a computer video monitor, a movable arm ~or supporting said monitor above the surface of said desk or table to allow it to be moved into different orientations, said arm comprising a base adapted to be detachably secured to said desk or table, a first rotatable joint at said base for permitting rotation of said arm with respect to said desk or table, and a second rotatable joint at the monitor end of said arm for permitting rotation of said monitor with respect to said arm.

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Our invention will be better understood on reading the following detailed description in conjunction with the drawing in which:
Figure l shows the assembly attached tc the top of a table and flexibly supporting a television type monitor;
Figure 2 is an exploded assembly drawing showing the individual elements making up our novel arm;
Figure 3 is a bottom view of the base of our arm to show the manner in which it controls the maximum swing of the arm;
Figure 4 is a side view of the base of our arm showing the torsion spring adjustment; and Figure 5 is a cross section view of the assembled friction ball joint at the end of our arm supporting a piece of equipment such as a video display.
In Figure 1 is shown an assembled arm in accordance with the teaching of our invention. Our novel arm is quickly and easily mounted to table 10 which is shown in phantom view by means of a clamp 12. The other end of our arm is fastened to a piece of equipment 11 also shown in phantom view and, which for the present application is a video display. Our arm is made up of clamp 12 which is used to fasten our arm to the edge of a desk or table 10 or to any other mounting surface having an edge to which the clamp can be fastened. A base 13 is connected to clamp 12 such that base 13 can rotate in ~, .

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a plane parallel to the surface of table 10. Base 13 is connected to an arm mcmbèr li viL an adjustable torsion spring (not shown~ and a friction coupling ~not shown) and arm member 14 can rotate in a plane perpendicular to the plane of the top of table 10. At the outer end of arm member 14 is connected a friction ball joint assembly 15 which is in turn fastened to the base of video displa~ ll. Friction ball joint assembly lS enables video display ll to be tilted forwar~ and backward and from side to side. With friction ball joint assembly 15 video display 11 may be moved to any position and it will remain in that position without tilting further due to its own weight. Thus the combination of the different joints in our movable arm coupled with an adjust-able torsion spring and friction coupling provide for multiple degrees of freedom of movement of our novel movable arm and video display 11.
In ~igure 2 is shown an exploded view of our novel movable arm shol~ing the individual components making up the arm. Clamp 12 is partially C shaped as shown to go around the edge of a desk table or any othe~ mounting surface, whether that mounting surface be horizontal or other than horizontal. Screw means 20 is uscd to move plate 21 in a vertical direction to securely fasten clamp 12 onto the edge of a table in a manner well known in the art. The top of plate 21 and its opposing surface on clamp 12 may have a piece of pkLstic or othcr material fastencd thereto to provide friction in contact with the mounting surface and to prevent marring tne mounting surface. Plate 21 has two conical protruberations 50 and 51 which may be created with conical set screws in threaded holes. These protruberations 50 and 51 imbed in the underside of table 10 so the clamp will not slip. I`he top surface of clamp 12 has a circular recess 22 having a diameter only slightly larger than circular bottom 26 of base 13. Within recess 22 are located three holes 24 in only one of which is placed a peg 25. The particular one of holes 24 in which peg 25 is placed determines the rotational travel of base 13 on the top of lZ1775i cl.lmp 12 as ~ill be better understood in the description for Figure 3 further in this specification. Holes 2~ may also be threaded and a set screw turned partiallv therein to accomplish the same result as peg 25.
Recess ,2 in clamp 12 also has a pivo~ member 23 mounted thereon which has a groove 19 around its periphery as shown. Groove 19 is used to fasten base 13 to clamp 12 as is described hereinafter. Base 13 has a hole 18 vertically therethrough having substantially the same diameter as pivot member 23. Hole 1~ may also be oversi~ed with a brass bushing press fit therein ~ith the inside diameter of the bushing being substantially the same diameter as pivot Inember 23. Base 13 is mounted down on clamp 12 with its bottom portion 26 sitting within recess 22 of clamp 12 and with pivot member 23 coming up through hole 18 of base 13. I~hen in this position a recessed screw (not shown) is turned inward in threaded hole 30 through base 13 until tlle tip of the screw e~tends into groove 19 around pivot member 23. There is not an interference fit between the screw and pivot member 23. A drop of thread lock sealant may be added to the thread of a screw to retain it in hole 30 without loosening.
I~ith the screw mounted in hole 30 as just described, base 13 cannot be removed from clamp 12 but can rotate about pivot member 23. A nyler piece (not shown) may be placed in recess 22 before base 13 is assembled to clamp 12 to aid in ~0 movemcnt of base 13.
Base 13 also has a pivot member 27 which is coaxial with and mounts within hole 36 through arm member 14 when arm member 14 is assembled to base 13.
- ~le diameter of hole 36 and pivot member 27 are substantially the sa,ne. Again, a brass bushing may be used in hole 36. In assembly torsion spring 28 is partially ~ound to provide tension, is mounted over the outside of pivot , member 27 and arm member 14 is then mounted up against base 13 on pivot member j 27. I~'hen arm member 14 is mounted up against base 13, wound torsion spring 28 is captivated between these two members. ~look end 49 of torsion spring 28 is , .~ .
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captivated by a boss (not shown) witllin the back side of arm member 14. ~loo~
end ~S of torsio~ sPring 2g crosses the axis of thread~d hole 29 through base 1 t and is captivated by a boss 53 (not shown in Figure 2, but shown in ~igure 4) on base l~t to prev~nt torsion spring 28 from unwinding. A recessed screw 54 (not shown in ~igure 2, but shown in Figure ~) within threaded hole 2~ has the tip of the scre~ hitting hook end 48 of torsion spring 28. As the screw (not shown) is screwed further within hole 29 it pushes against hook end 48 of spring 2~ to increase the torsion loading of spring 28 and thereby provides an effectual means to adjust the torsion loading of spring 28 to compensate ~or di~ferent weight loads attached to the outer end of arm member 14 via friction ball joint assembly 15. Initially, screw 54 in hole 29 is set to push hook end 48 away from lip 53 ~shown in Figure 4) and thereafter the torsion of spring 2S may be increased or decreased by turning screw 54.
t~rm mernber 14 is held assembled to base 13 in the following manner.
A friction screw 17 has a broad head 32 and a threaded shaft 34 which passes through friction washer 31, wave washer 16, cork washer 50 and then through hole a6 at the bottom end of arm member 14. Threaded shaft 34 then passes throug}l torsion spring 28 and into threaded hole 35 in the end of pivot member -27 on base 13. Head 32 of friction screw 17 has a diamcter only slightly smaller than the diameter of a recess 37 in the bottom end of arm member 14.
On assemb1y the screw captivates wasllers 16, 50 and 31 within recess 37 and fastens arm member 14 onto base 13. Ilead 32 of friction screw 17 has two edge rccesses 33 and a spanner wrench is utilized to tighten screw 17. As screw 17 is tiglltened against washers 16, 50 and al friction is created against the mo-vement of arm member 14 about pivot member 27 due to the function of the washers. The outer end of arm member 14 has a hole ~7 therethrougll and a plurality of mounting holes 41 as sllown. On assembly, screws coming up througll threaded holes 41 from the bottom of arm member 1l will be turned ~Z~ 5~
into rcspective ones of threaded holes 40 through the flange of middle friction meinber 39 of our novel friction ball joint 15. This is shown in greater detail in Figure 5. ~n this manner middle friction member 39 is attached to ~he outer end of arm member 14. The rest of our novel f iction ball joint 15 comprises an upper friction member 38 a fastening screw 45 a lower friction member 42 a spring 43 a flat washer 44 and a nut 46. The diameter of hole 47 through the outer end of arm member 14 is greater than the diameter of lower friction member 42 spring 43 flat washer 44 and nut 46. The holes tllrough upper friction member 3S and lower friction member 42 each have a diameter only slightly larger than the diameter of the shaft of screw 45.
Ilowever, the hole 51 through middle friction member 39 is significantly larger than the diameter of the threaded shaft of screw 45. The concave bottom of u~per friction member 38 is spherical and has the same radius and center point of curvature as the convex spherical top of middle friction member 39. The concave bottom side of middle friction member 39 is also spherical, has a radius of curvature equal to that of the convex spherical top of lower friction member 42 and has a common center point of radius as all the spherical surfaces.
On final assembly the spherical top of lower friction member 42 is mounted up inside the spherical surface in the bottom of middle friction member 39 and the spherical top surface of member 39 is mounted up inside the spherical surface in the bottom of upper friction member 38 such that all spherical surfaces are free to move about the common center point. On assembly nut 46 is screl~ed onto the threaded end of screw 45 and is screwed down to apply pressure via washer 44 and spring 43 to hold members 3S 39 and 4~ against each other as is shown in greater detail in Figure 5. Depending upon how tight bolt 46 is screwed on to the sllaft of screw 45 the degree of friction created between the spherical mating surfaces of elements 3S 39 and 42 may be varied to crrate our novel double surface friction ball joint 15. Upper _~_ 1~1775~
}riction mcmber 39 is attached to video display 11 or may be an integral part of the base of video display 11. As video display 11 is tilted forliard, backward or to either side elements 38, 45, 42, 43, 44, and 46 pivot about while member ~9 remains in a fixed position attached to outer end of arm memDer 14. The friction between the assembled elements 38, 39 and 42 permit the video display 11 to be moved into a position and remain in that position.
Turning now to Figure 3 therein is shown a bottom view of base 13.
In the bottom of base 13 are located three grooves 50, 51, 52 which lie along the periphery of circles having different radii. When base 13 is assembled to clamp 12 each of grooves 50, 51 and 52 sits directly over one of the three holes 24 in rccess 22. As previously mentioned, peg 25 is inserted into one of holes 24 and extends upward out of the hole as shown in Figure 2. The portion of peg 25 protruding up from a hole 24 extends into on0 of grooves S0, 51 and 52. In particular, when peg 25 is located in the one of holes 24 closest to pivot member 23 of clamp 12, the top of peg 25 protrudes into groove 52. Rotation of base 13 is thereby limited to ninety degrees in one quadrant. I~hen peg 25 is mounted in the middle one of holes 24 of base 12 its protruding end extends into groove 51 to restrict rotation to 90 degrees in a different quadrant. With peg 25 being located in the outer one of the tllree l-oles 24 it extends into groove 50 which allows for 180 degrees rotation of base 13 about pivot member 23 of clamp 12. It would be obvious to one skilled in the art that the position and length of these grooves may be varied to suit particular applications or may be eliminated allowing a full 360 degrees rotation.
~igure 4 is a side view of base 13 showing the aforementioned lip or boss 53 against which hook end 48 of partially wound torsion spring 28 sits when spring 28 is assembled between base 13 and arm 14 on assembly of the arm.

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I!oo~ CnL~ extcllds downward and is in line Wit]l the axis of hole 29 through l)aae 13 and screw 5~ therein the tip of ~hicll contacts hook end ~l8. The tcnsion of torsion spring 28 is increased by turning screw 5~ into threaded holc~ 29 tllrough base 13. Screw ~4 is scre~ed into push hook end 48 of spring 2S away from lip 53 to set an in-itial tension in torsion spring 28.
~s dir'ferent weight loads are attached to the outer end of our novel arnn, screw 54 is screwed in or out to change the tension of torsion spring 28 to compensate for the different weight load. ~or lighter weight loads on the end of our novel arm screw 54 is unscrewed to decrease the tension of torsion spring 28. ~or heavier weights on the end of our arm, scre~ 54 is screwed into holc 29 to further ~ind tension spring 28 and thereby increase the torsion to compellsate for the increased ~eight load.
~igure 5 shows the above described details of our novel friction ball joint 15 with the ball joint being in an assembled state. The outer end of arm mellll)er l4 l~aving hole 47 therethrough is only partially s}lown with its mounting holes 41 being aligned with the holes 40 through the flange of middle friction member 39 and which is fastened to arm 14 via scre~s through each pair of holes 40 and 41. 'I'hus, mernber 39 is affixed to arm member 14.
Upper friction member 38 is an integral part of or is attachcd to video display ll (not shown). It can be seen how the spherical inncr surfacc of uppcr'friction melllber 38 matches the convex spherical surfacc of middle friction melllber ~'3. ~t can also be seen how thc concave spheric.ll surface of membcr 39 mates Wit}l thc convex spherical surface of lower friction member 42 and all spherical surfaces have a common center point of radii. In assembly nut 46 is fastened to bolt 45 as shown and applies pressure via wasllcr 14 and spring 43 against lower friction member 42. This spring action forces membcrs 3~, 39 and 42 togetller so that there is a friction couplin~ as l~ell as a ball joint function being accomplishe.i betlieen members 38, 39 and 42 as shown in ~Z~775~ ~

Figure 5. ~s video display 11 (not sllo~n in ~igure 5) is tilted forward, bac~ ard or from side to side the ball joint friction members 38, 39 and 42 rotate ~gainst each other with a friction coupling. This friction coupling permits the video display 11 to be tilted to a certain position and then to stay in that position. The degree of friction coupling in our novel friction ball joint depends upon the nature of the materials and the amount of force transmitted through spring 43 to elements 38, 39 and 42 when turning nut 46 onto bolt 45.
I~'hile what has been described above is the preferred embodiment of our invention, it would be obvious to those skilled in the art that numerous variations may be made therein without departing from the spirit and scope of our invention. For instance hole 51 through middle friction member 39 may be oval or any other shape and limit the degree to which video display 11 (not shown in Figure 5) may be tilted. In addition, spring 43 in our friction ball joint 15 may be eliminated and pressure applied directly by nut 46.
Further, it should be realized that friction ball joint lS may be modified to eliminate one of the spherical friction surfaces.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A computer video monitor and support arm for installation on a desk or table, comprising a computer video monitor, a movable arm for supporting said monitor above the surface of said desk or table to allow it to be moved into different orientations, said arm comprising a base adapted to be detachably secured to said desk or table, a first rotatable joint at said base for permitting rotation of said arm with respect to said desk or table, and a second rotatable joint at the monitor end of said arm for permitting rotation of said monitor with respect to said arm.

2. The apparatus of claim 1 wherein said base comprises a clamp for detachably securing said base to the edge of said desk or table, said clamp having a first horizontal surface for resting on the upper surface of said desk or table, and a second horizontal surface adapted to be clamped against the undersurface of the edge of said desk or table.

3. The apparatus of claim 1 wherein said first rotatable joint is adapted to permit rotation about vertical and horizontal axes.

4. The apparatus of claim 1 further comprising a spring built into said arm for supporting the weight of said monitor.

5. The apparatus of claim 1 wherein said arm and second rotatable joint are adapted to be located entirely beneath said monitor.

6. The apparatus of claim 1 wherein said base comprises a clamp for detachably securing said base to the edge of said desk or table, said clamp having a first horizontal surface for resting on the upper surface of said desk or table, and a second horizontal surface adapted to be clamped against the undersurface of the edge of said desk or table, said first rotatable joint is adapted to permit rotation about vertical and horizontal axes, said apparatus further comprises a spring built into said arm for supporting the weight of said monitor, and said arm and second rotatable joint are adapted to be located entirely beneath said monitor.

7. The apparatus of claim 6 wherein said spring comprises a torsion spring installed within said first rotatable joint between two housings adapted for relative rotation with respect to one another.

8. The apparatus of claim 7 wherein adjustment means are provided for moving one end of said torsion spring while holding the other end fixed to adjust the torque of said torsion spring to compensate for variation in the weight of said monitor.

9. The apparatus of claim 8 wherein said spring is helical and wherein said adjustment means comprises a screw means extending through one said housing with one end of said screw means touching said one end of said spring, said screw means being adapted so that as it is wound it moves said one end of said torsion spring so as to either increase or decrease the torque of said spring.

10. The apparatus of claim 6 wherein said second rotatable joint comprises a frictional ball joint permitting rotation in two degrees of freedom.

11. The apparatus of claim 10 wherein said frictional ball joint comprises mating convex and concave spherical surfaces squeezed together by a fastening means.

12. The apparatus of claim 11 wherein said mating spherical surfaces are provided by clamping three elements together, a spherically-shaped middle shell positioned between inner and outer elements providing mating convex and concave surfaces, respectively.

13. The apparatus of claim 12 wherein said three elements are clamped together by a bolt passing between said inner and outer elements and through an aperture in said middle shell.

14. The apparatus of claim 6 wherein said second horizontal surface of said clamp has proturbances adapted to engage and grip the edge of said desk or table.