Abstract:
An articulated modular mounting arm for mounting electronic peripheral devices in a statically balanced adjustable position is disclosed. This mounting arm differs from the prior art in that several of its components are constructed from lengths of stock materials that are cut down to a user specified length within preset limits. This enables the manufacture to reduce inventory of the various components because one stock component may serve the need for several length arms. In addition, molds for each of the various lengths are not required, further lowering the production costs.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to an apparatus for mounting devices, and more specifically, to a modular articulating extension arm for mounting electronic peripheral devices in a statically balanced adjustable position. 
     Articulated extension arms for mounting electronic peripheral devices, such as computer monitors, notebook computers, internet computers, video cassette recorders, cameras, computer keyboards, televisions, and the like are well known in prior art. For example, there is known from O&#39;Neill, U.S. Pat. No. 4,852,842; Greene, U.S. Pat. No. 5,584,596; and Voeller et al., U.S. Pat. No. 5,743,503 various mechanical support arms. 
     Due to recent advances in flat-screen technology, there is a demand for adjustable extension arms particularly suited for use with flat-screen devices, such as flat-screen computer monitors and televisions. One such example is described in Applicant&#39;s U.S. patent application Ser. No. 09/405,628 filed Sep. 24, 1999 entitled “Arm Apparatus For Mounting Electronic Devices.” Another example is described in Applicant&#39;s U.S. patent application Ser. No. 09/406,006 filed Sep. 24, 1999 entitled “Arm Apparatus for Mounting Electronic Devices with Cable Management System.” The disclosures of these applications are incorporated herein by reference. 
     FIGS. 1 through 7, including their respective sub-figures, disclose an extension arm for mounting an electronic peripheral device in accordance with Applicant&#39;s prior extension arms. The main elements of the extension arm are a first endcap  100 , upper channel  200 , lower channel  300 , suspension device  400 , second endcap  500  and forearm extension  600 . The extension arm is capable of supporting an electronic device attached to a mounting device, such as a tilter  700 , and also provides an internal cable management system for a cable  900 . 
     The first endcap  100  has an endcap shaft  101  that may contain a plurality of concentric circumferential grooves  114 . The endcap shaft  101  may be pivotably attached to a rigid support mount (not shown), such as an orifice sized to accept the endcap shaft  101  or a track configured and sized to slidably engage the grooves  114  provided, or both. 
     The first endcap  100  contains two pairs of holes  113  (see FIG. 2) therethrough such that pins  102  may pivotally couple the upper channel  200  and lower channel  300  to the first endcap  100 . Similarly, the second endcap  500  contains two pair of holes  513  (see FIG. 2) disposed therethrough such that pins  550  pivotally couple the opposite ends of the upper channel  200  and the lower channel  300  to the second endcap. 
     The combination of the upper and lower channels  200 ,  300  and the first and second endcaps  100 ,  500  form an adjustable parallelogram that permits a device coupled to the forearm extension  600  to be raised and lowered to a desirable height. The parallelogram retains its position by employing a suspension device  400 , which is pivotally and adjustably attached to the first endcap  100  and the upper channel  200 , as will be further described below. Generally, the suspension device  400  is sized so as to have a fixed length until an upward or downward force is exerted at the second endcap  500  that exceeds the suspension device&#39;s designed resistance. One suitable suspension device  400  is a gas filled piston known for this purpose and commercially available from a variety of manufacturers. Typically, such a gas filled piston will have an adjustable resistance with a range suitable for use in accordance with the weight of the electronic peripheral device specified. Thus, the suspension device  400  causes the parallelogram to retain its position when the only force exerted at the second endcap  500  is the weight of the device, but permits the parallelogram to be adjusted when a user pushes the electronic peripheral device up or down. 
     A first female coupling  602  couples the second endcap  500  to the forearm extension  600  while a second female coupling  603  couples the opposite end of the forearm extension  600  to the mounting device, such as the tilter  700 . Thereafter, the mounting device may be coupled to the electrical peripheral device. The electrical peripheral device may in turn have a cable  900  of sufficient length and diameter as to permit its placement through the forearm extension  600 , second endcap  500 , and lower channel  300 , so as not to be visible in those areas. 
     FIGS. 3A through 3E illustrate the first endcap  100 , having the endcap shaft  101  disposed on a first end  103  of the first endcap  100 . In accordance with one embodiment as shown in FIG. 3A, the endcap shaft  101  has an endwall  181  with a hole  104  formed at its first end  103 . The first endcap  100  also has a second end  105  with an endwall  151  having a hole  106  disposed therethrough. Within the holes  104 ,  106  and between a pair of trough walls  158 , is a threaded rod  107 . A first end  108  of the threaded rod  107  is inserted into the hole  104  at the base of the endcap shaft  101 . A second end  109  of the threaded rod  107  is aligned with the hole  106  and held in place with a clip  110 . The clip  110  is fastened to an inner surface of the first endcap  100  by screws  111 . 
     In accordance with the preferred embodiment as shown in FIG. 3B, the first endcap  100  further includes a sidewall  152  between the endwalls  151  forming a partially enclosed housing  150 . The endcap shaft  101  is typically integrally molded to the endwall  151  of the first endcap  100 . Preferably, the entire first endcap  100  (the partially enclosed housing  150  and the endcap shaft  101 ) is molded from zinc. Within the partially enclosed housing  150  and integrally molded on the sidewall  152  are a plurality of stops  153  disposed in proximity to the endwalls  151 . Also within the partially enclosed housing  150  are the trough walls  158 , disposed longitudinally along the inner surface of the sidewall  152  between the endwalls  151  so as to define a trough  159  therebetween. 
     The stops  153  serve to provide limits of upward or downward movement of the upper channel  200  and lower channel  300  when the ends of the upper channel  200  and lower channel  300 , respectively, meet the stops  153  when one moves the electronic peripheral device in extended or contracted positions. The trough  159  disposed between the trough walls  158  allows a clevis  120  to be moved therein. As discussed in more detail later, the clevis provides connection and adjustment means for one end of the suspension device  400 . 
     FIG. 3C illustrates a variation of the first endcap  100  in accordance with the preferred embodiment, wherein shelves  160  define co-planar faces separated by a groove  161 . The shelves  160  have a connection means, such as self-tapping screw holes  162  disposed therein. The co-planar faces of the shelves  160  are configured to engage a retainer clip  163 , which is fastened in place, for example, by a pair of screws  164 . When the retainer clip is fastened in place, the groove  161  defines a space for accepting one end  108  of the threaded rod  107 . 
     The threaded rod  107  is employed within the first endcap  100  so as to adjustably support the clevis  120 . FIG. 3D illustrates the threaded rod  107 , the second end  109  of which has a circular cross-section within which is axially disposed a shaped opening  165 , for example, a hex-shaped opening for accepting a shaped key (not shown), such as a hex-shaped key. The cross-sectional diameter of the second end  109  is smaller than a cross-sectional diameter of the hole  106 , so as to be inserted therein. Adjacent the second end  109  is a shoulder  166 . The shoulder  166  has a circular cross-section of a diameter larger than the cross-sectional diameter of the hole  106 . Thus, the shoulder  166  abuts an inner surface of the endwall  151  and retains the second end  109  within the hole  106 . 
     The first end  108  of the threaded rod  107  is disposed in the groove  161  located between the shelves  160  of the first endcap  100  (see FIG. 3B) or the hole  104  of the endcap shaft  101  (see FIG. 3A) The first end  108  of the threaded rod  107  has a circular cross-section having a diameter that is smaller than the size of the groove  161  or the hole  104 , such that the first end  108  is supported between the shelves  160  but is free to rotate therein. 
     Between the first end  108  and the second end  109  of the threaded rod  107  is a threaded section  167 . Threadably mounted on the threaded section  167  is the clevis  120 . The clevis  120  as illustrated in FIG. 3E, has a tapped hole  121  formed therein for receiving the threaded rod  107 . The clevis  120  also has a pair of fastening members  123  at a first end  122  to which are fastened a first end of the suspension device  400 . The second end  124  of the clevis is configured so as to slidably engage the trough  159 . 
     The second end  109  of the threaded rod  107  can be engaged by a shaped key to rotate the threaded rod  107  around its axial centerline. When the threaded rod  107  is rotated around this axis of rotation, the clevis  120  travels along the length of the threaded rod  107  in a direction corresponding to the direction which the shaped key is turned. This movement of the clevis  120  adjusts the length of the suspension device  400  thereby altering its resistance. 
     FIGS. 4A through 4D illustrate several views of the upper channel  200  according to the prior art. The upper channel  200  includes a U-shaped body  201  and integrally cast rollers  202  disposed at opposite ends of the U-shaped body  201 . The rollers  202  can also be separately constructed and subsequently welded onto the ends of the U-shaped body  201  as disclosed in Applicant&#39;s aforementioned patent applications. The U-shaped body  201  comprises a channel bottom  203  from which extend two channel sidewalls  204 . For heavy weight electronic peripheral devices, the channel bottom  203  and the sidewalls  204  are typically stamped from heavy gauge steel with the rollers  202  being welded thereto. For lightweight electronic peripheral devices, the channel bottom  203 , the sidewalls  204  and the rollers  202  of the upper channel  200  are typically integrally cast from zinc, giving the upper channel a lesser weight and degree of rigidity more appropriate for the lighter weight application. 
     Cast molded upper channels  200  permit the angle between the channel bottom  203  and the channel sidewalls  204  to be exactly the same for each manufactured upper channel  200 . Moreover, cast molding permits the sidewalls  204  to be tapered. As illustrated in FIGS.  4 ( c ) and  4 ( d ), both an outer surface and an inner surface of the sidewalls  204  may taper in, for example, by approximately 1 degree. The taper allows for clearance between the upper and lower channels  200 ,  300  when the upper and lower channels  200 ,  300  are brought together during usage. That is, the inner surface of the sidewalls  204  being displaced by 1 degree means that there is additional clearance for the lower channel  300  to fit there within. The addition clearance ensures that the upper channel  200  and lower channel  300  will not scrape together during usage. 
     The rollers  202  have a hole  205  therethrough (either cast in or subsequently drilled) for receiving a connection mechanism, such as pins  102 ,  550 . Additionally, the channel bottom  203  includes an integrally cast threaded hole configured and sized to receive a threaded end ball stud  207 . The ball stud is configured and sized to receive a second end of the suspension device  400 . 
     FIGS. 5A through 5E illustrate several views of the lower channel according to the prior art. The lower channel  300  includes a U-shaped body  301  and integrally cast rollers  302  disposed at opposite ends of the U-shaped body  301 . The U-shaped body of the lower channel  300  includes a channel bottom  303  from which extend two channel sidewalls  304 . As with the upper channel  200  components, for heavy weight electronic peripheral devices, the channel bottom  303  and the sidewalls  304  of the lower channel  300  are typically stamped from heavy gauge steel, the rollers  302  being welded thereto. For lightweight electronic peripheral devices, the channel bottom  303 , the sidewalls  304  and the rollers  302  of the lower channel  300  are typically integrally cast from zinc, giving the lower channel a lesser weight and degree of rigidity more appropriate for the lighter weight application. The rollers  302  have a hole  305  therethrough (either cast or subsequently drilled) for receiving a connection mechanism, such as the pins  102 ,  550 . 
     The channel bottom  303  additionally includes a cable channel  306  running longitudinally there along. Typically, a first end  307  of the cable channel  306  starts near the end of the channel bottom  303  that pivotably connects to the first endcap  100 . The cable channel  306  then runs along the entire length of the channel bottom  303  to the end of the channel bottom that pivotably connects to the second endcap  500 . The second end  308  of the cable channel  306  provides an opening between the rollers  302 . The first end  307  may be, for example, rounded to improve the rigidity of the lower channel  300 . The cable channel  306  is configured to receive a cable cover  325  (illustrated in FIG. 5E) which is configured to removably fit within the cable channel. Thus, cables  900  of the mounted device may be substantially retained within the lower channel  300  so as to hide them from view and protect them from harm. The cable channel  306  and the cable cover  325  enable cables to be accessed when desired, while securing them within the lower channel  300 . 
     As illustrated in FIGS. 5C and 5D the sidewalls  304  of the lower channel  300  are also tapered. For example, an outer surface of the sidewalls  304  may be tapered approximately ½ degree while an inner surface may be tapered approximately 1 degree. It should be noted that the taper is not limited to a particular angle, and that the taper of the inner surface and the outer surface may be the same. The taper is possible because the lower channel  300  is typically cast molded. As noted above with respect to the upper channel  200 , the taper provides more clearance between the upper channel  200  and the lower channel  300  so as to reduce or eliminate the chance of the upper and the lower channels  200 ,  300  scraping. 
     As illustrated in FIG. 5E, the cable cover  325  includes a top cover  326  with two sidewalls  327  extending therefrom. A far end of each sidewall  327  has a catch  328  formed thereon so as to engage with the cable channel  306 . Typically, the cable cover  325  is molded from plastic and is sufficiently flexible so that the stops  328  may be engaged and disengaged from the cable channel  306  as necessary. The cover is not, however, so flexible that the stops  328  naturally flex such that the cable cover  325  fails to engage with the cable channel  306 . 
     As illustrated in FIGS. 6A through 6I the second endcap  500  includes a partially enclosed housing  501  and a shaft assembly  502 . The partially enclosed housing  501  has a first endwall  503  and a second endwall  504  oppositely disposed from each other and fixedly connected by a sidewall  505 . The sidewall  505  extends partially around the partially enclosed housing  501  so as to permit manipulation of components, such as cables, which may be contained there within. The first endwall  503  has a hole  506  disposed therethrough and threaded holes  507  disposed therein that are in communication with the hole  506 . Typically, the diameter of the hole  506  is large enough to allow a plug end of a cable to fit therethrough. Disposed within the threaded holes  507  are set screws  508 . 
     As illustrated in FIGS. 6E through 6G, the shaft assembly  502  typically includes two symmetrical endcap adapters  509  which when assembled provide the boundaries for a hollow shaft  510 . The endcap adapters  509  have a mounting end  511  and a shaft end  512  that is thinner than the mounting end  511 . As illustrated in FIG. 6D, the mounting ends  511  of both of the endcap adapters  509  are inserted into the hole  506  and are coupled together and to the partially enclosed housing  501 , to form the second endcap  500 , by tightening the set screws  508 . 
     As stated earlier, the upper and the lower channels  200 ,  300  and the first and the second endcaps  100 ,  500  are configured so as to form an adjustable parallelogram. When configured, the shaft  101  of the first endcap  100  and the hollow shaft  510  of the second endcap  500  point in opposite directions. For example, as illustrated in FIG. 2, the shaft  101  of the first endcap  100  extends vertically downward while the hollow shaft  510  of the second endcap  500  extends vertically upward. The shape of the parallelogram is retained by the suspension device  400 . As previously mentioned, the first end of the suspension device  400  is adjustably mounted to the clevis  120  within the first endcap  100  and the second end is attached to the ball stud  207  mounted within the upper channel  200 . 
     Generally, the suspension device  400  is sized so as to have a fixed length until an upward or downward force is exerted at the second endcap  500  that exceeds the suspension device&#39;s designed resistance. Thus, the suspension device  400  retains the parallelogram shape when the only force exerted at the second endcap  500  is the weight of the electronic peripheral device. However, the suspension device  400  permits the parallelogram shape to be adjusted when a user pushes the electronic peripheral device coupled to the forearm extension  600  up or down. 
     With reference to FIGS. 7A and 7B, the forearm extension of the prior art includes a body  601  having a first female coupling  602  located on a first end and a second female coupling  603  located on a second end. The first female coupling  601  has an inner diameter  604  that is sized to rotatably engage the hollow shaft  510  of the second endcap  500 . The first female coupling  602  is also configured to receive a cable through the hollow shaft  510 . That is, the first female coupling  602  has a cable slot  605  formed therein, for example by milling the cable slot  605  into the first female coupling  602 , or by casting the first female coupling  602  with the cable slot  605  integrally formed therein. 
     The first female coupling  602  generally has a set screw  606  formed within a wall  607  thereof. The set screw  606  can be tightened to prevent the first female coupling  602  from rotating about the hollow shaft  510 . Advantageously, the first female coupling  602  has a plurality of voids  608  formed in the wall  607 , which saves on material costs and weight and permits the forearm extension  600 , when cast, to be cooled more quickly. 
     A bushing  609  (see FIG. 2) is preferably used to engage the first female coupling  602  and the hollow shaft  510 . That is, the bushing  609  is placed over the hollow shaft  510  and within the first female coupling  602 . The bushing  609  is preferably made of a smooth material, such as plastic, in order to reduce friction and prevent metal to metal contact. As illustrated in FIGS. 6H and 6I, the bushing  609  also has a cable slot  610  formed therein. The cable slots  605 ,  610  are aligned so that a cable can pass therethrough. When the set screw  606  is tightened it causes the bushing  609  to flex inward and frictionally engage the hollow shaft  510  and thus prevent the forearm extension  600  from rotating about the hollow shaft  510 . The hollow shaft  510  and the first female coupling  602  are held together by utilizing a screw  611  and a washer  612  (see FIG.  2 ). 
     The body  601  preferably has an inverted U-shape with a topwall  613  and two sidewalls  614  so that a cable can be hidden therein. Advantageously attached within the U-shaped body  601 , and preferably on the topwall  613 , is a cable holder  615  (see FIG.  2 ). The cable holder  615  secures a cable within the U-shaped body so that it can be hidden from view as it travels the length of the forearm extension  600 . 
     The second female coupling  603  is for attachment to a device mounting, such as a tilter  700  described in Applicant&#39;s co-pending patent application Ser. No. 09/406,530 filed on Sep. 27, 1999 which is incorporated herein by reference in its entirety. Thus, the second female coupling  603  has an inner diameter  616  that is sized to rotatably engage a shaft of the device mount. A bushing  621  (see FIG.  2 ), preferably made of a smooth material such as plastic, is placed over the shaft and within the second female coupling  603 . The second female coupling  603  preferably has a set screw  617  formed within a wall  618  of the second female coupling  603 . When the set screw  617  is tightened it causes the bushing  617  to flex inward and frictionally engage the shaft and thus prevent the device mount from rotating around the second female coupling  603 . Advantageously, the second female coupling  603  also has a plurality of voids  619  formed in the wall  618 . 
     The forearm extension  600  illustrated in FIGS. 7A and 7B, has the topwall  620  flush with an upper edge of the female couplings  602 ,  603 . Since the first female coupling  602  is larger than the second female coupling  603 , the center of the first female coupling  602  is not aligned with the center of the second female coupling  603  or an axial centerline of the body  601 . It should be noted that an alternative embodiment is to have the center of the female couplings  602 ,  603  and the axial centerline  621  of the body  601  all aligned, so that the topwall  620  would not be aligned with an upper edge of the first female coupling  602 . 
     Referring back to FIG. 1, an electronic device such as a flat-screen monitor is attached to a device mounting, such as tilter which is rotatably coupled to the second female coupling  603 . A cable, such as a power cable, proceeds from the electronic peripheral device to the underside of the body  601  of the forearm extension  600 . The cable is held in place within the body  601  by the cable holder  615 . The cable proceeds from the body through the cable slots  605 ,  610 , in the bushing  609  and the first female coupling  602 . The cable then proceeds through the hollow shaft  510  of the second endcap  500 . The cable exits the second endcap  500  through the open end of the partially enclosed housing  501 . The cable proceeds down the length of the lower channel  300  and exits at the first end  307  of the cable channel  306 , while being hidden from view and substantially protected by the cable cover  325 . 
     Typically, the cable is inserted into the lower channel  300  as portions of the lower channel  300  and upper channel  200  are being assembled. That is, the cable is placed under the body  601  of the forearm extension  600  and is held in place by the cable holder  615 . The cable is then passed through the cable slots  605 ,  610 . The cable including the plug is then fed through the hole  506  in the second endcap  500 . The second endcap  500  is now assembled by inserting the mounting end  511  of each endcap adapter  509  into the hole  506 , thus surrounding the cable. The endcap adapters  509  are held together and within the hole  506  by tightening the set screws  508 . The hollow shaft  510  is then placed within the first female coupling  602 . The cable is placed within the lower channel  300 , prior to the lower channel  300  and the second endcap being secured together. This ensures that the cable is above the roller  302  and is contained within the hollow bar formed by the upper channel  200  and the lower channel  300 . 
     Referring back to FIG. 2, several additional components of the extension arm  100  are typical. For aesthetic purposes, a bumper  650  may be placed on the second endwall  504  of the second endcap  500  and a plug  651  is generally placed over the first female coupling  602 . A washer  652  is typically placed over the two endcap adapters  509  to help secure them together. 
     It has become increasingly apparent that additional innovations are necessary to make extension arms for electronic peripheral devices more cost effective. Extension arms according to the prior art have been manufactured utilizing members individual to specified stock lengths. Thus, if an end-user required an extension arm of a particular length different from that manufactured, it was either unavailable, or more costly because an entirely new arm assembly of the correct length would have to be manufactured. Additionally, if a manufacturer wished to provide arms of various lengths, he would be required to maintain an inventory of several different length components at a significant cost. 
     SUMMARY OF THE INVENTION 
     It is broadly an object of the present invention to provide an effective modular mounting arm for electronic peripheral devices such that the end user may specify a customized finished length. 
     In order to address this objective, this invention is directed to a support apparatus with arm members capable of being cut from a length of stock material to user specified dimensions. The benefit of this design is that the manufacturer is required only to keep one stock length of components on hand, rather than maintaining inventory of various length components. From those stock components, arms may then be cut and assembled to various lengths as specified by the end user. 
     In one embodiment of the present invention, the extension arm comprises modular upper and lower channels capable of being cut down from stock pieces to a user specified length. 
     Another embodiment of the present invention contemplates a modular forearm extension capable of being cut down from stock pieces to a user specified length. 
     In accordance with one embodiment of the present invention there is described an adjustable extension arm for mounting an electronic device thereto, the extension arm comprising a forearm extension having a first end and a second end for attachment of an electronic device thereto; a first endcap having a first end attachable to a support structure; a second endcap having a first end rotationally attached to the first end of the forearm extension; and elongated first and second channel members having first and second ends, the first and second channel members being nested together to form a channel therebetween, the first channel member comprising an elongated hollow member providing a first cavity extending therethrough, a first reinforcing member received within the first cavity and having first and second ends, and first and second roller units, the first roller unit including a first end coupled to the first end of the first reinforcing member and a second end pivotably coupled to the first end cap, the second roller unit including a first end coupled to the second end of the first reinforcing member and a second end pivotably coupled to the second end cap; the second channel member comprising an elongated hollow member providing a second cavity extending therethrough, a second reinforcing member received within the second cavity and having first and second ends, and third and fourth roller units, the third roller unit including a first end coupled to the first end of the second reinforcing member and a second end pivotably coupled to the first end cap, the fourth roller unit including a first end coupled to the second end of the second reinforcing member and a second end pivotably coupled to the second end cap. 
     In accordance with another embodiment of the present invention there is described an adjustable extension arm for mounting an electronic device thereto, the extension arm comprising a forearm extension including a hollow elongated body having a first end and a second end for attachment of an electronic device thereto; a first endcap having a first end attachable to a support structure; a second endcap having a first end rotationally attached to the first end of the forearm extension; and elongated first and second channel members having first and second ends, the first and second channel members being nested together to form a channel therebetween, the first channel member comprising an elongated hollow member providing a first cavity extending therethrough, a first reinforcing member received within the first cavity, and having first and second ends, and first and second roller units, the first roller unit including a first end coupled to the first end of the first reinforcing member and a second end pivotably coupled to the first end cap, the second roller unit including a first end coupled to the second end of the first reinforcing member and a second end pivotably coupled to the second end cap; the second channel member comprising an elongated hollow member providing a second cavity extending therethrough, a second reinforcing member received within the second cavity, and having first and second ends, and third and fourth roller units, the third roller unit including a first end coupled to the first end of the second reinforcing member and a second end pivotably coupled to the first end cap, the fourth roller unit including a first end coupled to the second end of the second reinforcing member and a second end pivotably coupled to the second end cap; the reinforcing members comprising hollow members having open ends, the first ends of the roller units comprising a projecting member received within a respective end of one of the reinforcing members, and the second ends of the roller units comprising a cylindrical member; the forearm extension including a first coupling attached to the first end of the body and a second coupling attached to the second end of the body, the first coupling including a first end having a bore therein adapted for pivotably mounting the forearm extension to the second end cap, and a second end attached within the first end of the body, the second coupling including a first end having a bore therein adapted for coupling an electronic device thereto, and a second end attached within the second end of the body. 
     In accordance with another embodiment of the present invention there is described a channel member for an adjustable extension arm, the channel member comprising an elongated hollow member providing a cavity extending therethrough, a reinforcing member having first and second ends received within the cavity, and first and second roller units, the first roller unit including a first end coupled to the first end of the reinforcing member and a second end adapted for coupling to a first end cap of an adjustable extension arm, the second roller unit including a first end coupled to the second end of the first reinforcing member and a second end adapted for coupling to a second end cap of an adjustable extension arm. 
     In accordance with another embodiment of the present invention there is described a forearm extension for an adjustable extension arm, the forearm extension comprising an elongated hollow body having first and second ends, a first coupling attached to the first end of the body and a second coupling attached to the second end of the body, the first coupling including a first end having a bore therein adapted for pivotably mounting the forearm extension to a second end cap of an adjustable extension arm and a second end attached within the first end of the body, the second coupling including a first end having a bore therein adapted for coupling an electronic device thereto and a second end attached within the second end of the body. 
     In accordance with another embodiment of the present invention there is described a method of making a channel member for an adjustable extension arm, the method comprising forming an elongated hollow member having a cavity extending therethrough, inserting a reinforcing member having first and second ends into the cavity, coupling one end of a first roller unit to the first end of the reinforcing member, and coupling one end of a second roller unit to the second end of the reinforcing member. 
     In accordance with another embodiment of the present invention there is described a method of making an adjustable extension arm for mounting an electronic device thereto, the method comprising forming a first channel member having a cavity extending therethrough, inserting a first reinforcing member having first and second ends into the cavity, coupling one end of a first roller unit to the first end of the first reinforcing member and coupling one end of a second roller unit to the second end of the first reinforcing member; forming a second channel member having a cavity extending therethrough, inserting a second reinforcing member having first and second ends into the cavity, coupling one end of a third roller unit to the first end of the second reinforcing member and coupling one end of a fourth roller unit to the second end of the second reinforcing member; nesting the first and second channel members together; pivotably attaching one common end of the first and second channel members to a first end cap; pivotably attaching the other common end of the first and second channel members to a second end cap; and pivotably attaching one end of the second end cap to a forearm extension. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above description, as well as further objects, features and advantages of the present invention, will be more fully understood with reference to the following detailed description of a modular mounting arm, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is an assembly drawing in front elevation of an extension arm for mounting a computer monitor in accordance with the prior art; 
     FIG. 2 is an exploded assembly drawing in perspective view of the extension arm in accordance with the prior art; 
     FIGS. 3A through 3E illustrate various views of the first endcap and the components forming the first endcap in accordance with the prior art; 
     FIGS. 4A through 4D illustrate various views of the upper arm extension in accordance with the prior art; 
     FIGS. 5A through 5E depict various views of the lower arm extension in accordance with the prior art; 
     FIGS. 6A through 6I illustrate various views of the second endcap and the components forming the second endcap in accordance with the prior art; 
     FIGS. 7A and 7B illustrate various views of the forearm extension in accordance with the prior art; 
     FIGS. 8A through 8G illustrate various views of the upper arm extension and components therefore forming the upper arm extension constructed in accordance with one embodiment of the present invention; 
     FIGS. 9A through 9F illustrate various views of the lower arm extension and components therefore forming the lower arm extension constructed in accordance with one embodiment of the present invention; 
     FIGS. 10A through 10F illustrate various views of the forearm extension and components therefore forming the forearm extension in accordance with one embodiment of the present invention; and 
     FIG. 11 is an assembled view of an extension an constructed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     In describing the preferred embodiments of the subject matter illustrated and to be described with respect to the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and is to be understood that each specific term includes all technical equivalence which operate in a similar manner to accomplish a similar purpose. 
     Referring to FIGS. 8A through 8F, there is illustrated an upper arm extension  250  constructed in accordance with one embodiment of the present invention. The upper arm extension  250  is constructed of an upper channel exterior member  253 , a pair of roller units  251  and a reinforcing bar  252 . The upper arm extension  250  can be constructed from a variety of metals, such as extruded aluminum which has the beneficial properties of both strength and light weight. The upper channel exterior member  253  is in the nature of a U-shaped member of indeterminate length. The upper channel exterior member  253  is capable of being cut from an indeterminate length to a user specified size and will therefore include a first end  262  and a second end  263 . Accordingly, multiple upper channel exterior members  253  can be cut from a single extruded length of stock material. 
     The upper channel exterior fitting  253  includes two spaced apart sidewalls  255  and a transversally arranged top wall  254  therebetween, thus forming the U-shaped member. The sidewalls  255  may be tapered as previously described. Located on the interior surface of each sidewall  255  at positions equidistant below the top wall  254  are two projecting shelves  256 . The shelves  256  generally extend between the first and second ends  262 ,  263  of the upper channel exterior member  253 , such that they run through the entire length of the upper channel  250 . The shelves  256  are situated such that an open cavity  259  is formed between the top wall  254 , sidewalls  255  and the shelves. The cavity  259  is defined by cavity walls  261  and a cavity roof  260 . At each end of the upper channel  250 , a notch such as a circular region  264  can be cut out of the sidewalls  255  where it joins with topwall  254  to accommodate a portion of the roller units  251  in assembled relationship, as to be described hereinafter. 
     A reinforcing bar  252  of preferably tubular construction is slideably disposed or force fit within the cavity  259  along the length of the upper channel exterior member  253  between the first and second ends,  262 ,  263 . The bar is sized in height and width such that its bottom surface  257  rests upon the shelves  256  while the top surface  258  generally contacts the cavity roof  260  and its side surfaces  263  generally contact the cavity walls  261  forming a rigid structure. The bar  252  is formed with a cavity  274  extending therethrough. Typically, the reinforcing bar  252  is formed from extruded steel or other suitable material to enhance and strengthen the upper channel  250  and is cut to a length dependent on, and generally equal to, the final length of the upper channel exterior member  253 . Formed with the top and bottom surfaces  257 ,  258  of the reinforcing bar  252  at both ends are through holes  265 . The holes  265  are preferably located near both of the first and second ends  262 ,  263  of the upper channel  250 , and as illustrated, are typically elongated holes, although other shapes are contemplated. 
     Each roller unit  251  includes a rectangular member  266  of solid or tubular construction from extruded aluminum having a first end  269  and a second end  270 , and a cylindrical member  267  also formed from aluminum. At the second end  270  of each rectangular member  266 , an arcuate or semi-circular region  268  may be formed. The cylindrical member  267  is welded transversally to a respective rectangular member  266  along the length of the top wall  271 , bottom wall  272 , and sidewalls  273  of the rectangular member. Each cylindrical member  267  has a cast or formed hole  205  extending therethrough such that it may be pivotally attached via pins  102 ,  550  to the first endcap  100  or second endcap  500 . The roller unit  251  may also be formed as an integral one piece casting or machining and the like. 
     The rectangular member  266  is sized and shaped such that it may be snugly disposed longitudinally within the cavity  274  of the reinforcing bar  252 . Provided through the top wall  271  and bottom wall  272  of the rectangular member  266  are aligned openings, for example, elongated holes  275 . When the roller units  251  are properly slid within the reinforcing bar  252 , the holes  265 ,  275  will have at least a common overlying portion in alignment with each other. By way of example, the holes  265 ,  275  may have the same size and shape. These overlying holes  265 ,  275  enable the reinforcing bar  252  and each roller unit  251  to be fixed in assembled position. Typically, the reinforcing bar is made of steel while the roller units  251  and upper channel  250  are made of aluminum. This material divergence prevents each element from being directly welded together. 
     In one embodiment of the invention, aluminum material may be welded to the roof  260  of the top wall  254  of the upper channel exterior member  253  by filling the holes  265 ,  270  to form a rigid connection plug  280  as shown in FIG.  8 G. In another embodiment, a pre-formed aluminum plug (not shown) suitably sized to fill the space within the two elongated holes  265 ,  275  may be inserted and bonded to the upper channel exterior member  253 . In either case, the plug serves to lock the components together in assembled relationship, such that they may no longer slide relative to one another. In another embodiment, the roller units  251 , reinforcing bar  252  and upper channel exterior member  253  may be chemically bonded, for example, with epoxy adhesive. Additionally, these components may be mechanically connected with, for example, screws or rivets or the like. 
     As previously described, each roller unit  251  is engaged with the upper channel&#39;s respective first end  262  and second end  263 . At each first end  262  and second end  263 , the cylindrical member  267  of each roller unit  251  abuts the upper channel. The abutment may either be directly against the first end  262  and second end  263  or may be within the notches, such as the circular region  264  expressly provided for this purpose. For illustrative purposes, FIG. 8B depicts a first end  262  with the standard abutment against a right angle corner and a second end  263  with the notched semi-circular region  264 , see also FIG.  8 A. It is therefore contemplated that the ends of the reinforcing bar  252  will be similarly notched with a corresponding circular region to receive the cylindrical member  267 . 
     Disposed adjacent the second end  263  of the upper channel  250  is a tapped hole  277  within the reinforcing member  252 . The tapped hole is sized to accept a threaded end ball stud  278 . The ball stud is configured and sized and threaded to receive the second end of the suspension device  400 , as previously described in the prior art. 
     FIGS. 9A through 9F illustrate a lower arm extension  350  including a lower channel exterior member  363 , a pair of roller units  351  and a reinforcing bar  352  constructed in a like manner as the upper arm extension  250  detailed above. 
     Referring to FIGS. 8D and 9C, each sidewall  255 ,  355  of the upper and lower channel  250 ,  350  may be slightly tapered inwardly, for example, by approximately ½ to 1 degree. The taper allows more clearance between the upper and lower channels  250 ,  350  when the upper and lower channels  250 ,  350  are brought together during usage. That is, the inner surface of the sidewalls  276  of the upper channel exterior member  253  being tapered by approximately ½to 1 degree means that there is additional clearance for the exterior surface  376  of the lower channel exterior member  353 , which can be similarly tapered, to fit there within. The addition clearance ensures that the upper channel  250  and lower channel  350  will not scrape together during usage. 
     Referring to FIGS. 10A through 10F, there is illustrated a forearm extension  650  constructed in accordance with one embodiment of the present invention. In this embodiment, the forearm extension  650  includes a first female coupling  651 , elongated body  652  and second female coupling  653 , each formed from aluminum or similar material. In one embodiment of the present embodiment, the body  652  is formed from extruded metal of indeterminate length, preferably aluminum, and may be cut or formed to a user specified length to achieve a forearm extension  650  of the required length when connected to the first female coupling  651  and the second female coupling  653 . The first and second female couplings  651 ,  653  may be formed by casting machining and the like. 
     As shown in FIG. 10B, the first female coupling  651  includes a coupling end  654  and a shaft end  655 . The coupling end  654  has a through bore  800  having an inner diameter  656  that is sized to rotatably engage the hollow shaft  510  of the second endcap  500 . The first female coupling  651  is also configured to receive a cable through the hollow shaft  510 . That is, the first female coupling  651  has a cable slot  657  formed therein during casting which communicates with the interior of the elongated body  652 . 
     The first female coupling  651  generally has a threaded hole  658  to receive a set screw (not shown) formed within a wall  659  thereof. The set screw can be tightened to prevent the first female coupling  651  from rotating about the hollow shaft  510 . A bushing  609  (see FIG. 2) is preferably used to engage the first female coupling  651  and the hollow shaft  510 . That is, the bushing  609  is placed over the hollow shaft  510  and within the first female coupling  651 . The bushing  609  is preferably made of a smooth material, such as plastic, in order to reduce friction and prevent metal to metal contact. As illustrated in FIG. 6H, the bushing  609  also has a cable slot  610  formed therein. The cable slots  605 ,  610  are aligned so that a cable can pass therethrough. When the set screw  658  is tightened it causes the bushing  609  to flex inward and frictionally engage the hollow shaft  510  and thus prevent the forearm extension  650  from rotating about the hollow shaft  510 . The hollow shaft  510  and the first female coupling  651  are held together by utilizing a screw  611  and a washer  612  (see FIG. 2) threadably engaging a portion of the second endcap  500 . 
     The shaft end  655  of the first female coupling  651  is constructed in a U-shaped configuration with a bottom wall  670  and two spaced apart sidewalls  671 . Each sidewall  671  extends outwardly from the coupling end  654  of the first female coupling  651 . Formed within the bottom wall is a void  674 , such as an elongated hole. 
     The shaft end  655  of the first female coupling  651  is sized and shaped such that it may be slideably engaged within the body  652  of the forearm extension  650 . The body is configured as a lipped U-shaped member forming a hollow interior which is slightly larger than the shaft end  655  of the first female coupling  651  to accept same. Specifically, the body  652  as shown in FIG. 10C includes a bottom wall  675 , spaced apart sidewalls  676  and a partially enclosed top wall  677  formed by inwardly extending lips. The body  652  and the first female coupling  651  are joined together such that the bottom wall  675  of the body slideably engages the bottom wall  670  of the shaft end  655  of the first female coupling; the inner surface of the sidewalls  676  of the body slideably engage the outer surfaces of the sidewalls  671  of the shaft end  655  of the first female coupling  651 ; and, the sidewall top surface  673  of the shaft end  655  of the first female coupling  651  slideably engages undersurface of the lips  677  of the body  652 . The shaft end  655  is permitted to penetrate the body  652  until stops  672  disposed at the junction of the coupling end  654  and the shaft end  655  prevent further movement. The stops  672  are sized and positioned such that the void  674  of the shaft end  655  will align over the bottom wall  675  of the body  652 . The first female coupling may be rigidly attached to the body  652  using similar means as that described for the upper channel exterior fittings  253  connection with the perspective roller units  251 , including by means of a welded plug, preformed plug, chemical bonding, screw or rivet. The aforementioned engagement form an essentially rigid structure. 
     Slidably engaged into the opposite end of the body  652  in a similar manner is the second female coupling  653 . The second female coupling  653  includes a shaft end  680  and a coupling end  681 . The coupling end  681  comprises two spaced apart sidewalls  682  and a circular endwall  683  directly opposite the shaft end  680 . Within the coupling end  681  is a through bore  699  having an inner diameter  684  for rotatably engaging a shaft of the tilter or similar device mount (not shown). A bushing  617  (see FIG.  2 ), preferably made of a smooth material such as plastic, is placed over the shaft and within the inner diameter  684  of the second female coupling  653 . The second female coupling  653  preferably has a threaded hole to accept a set screw  685  formed within a wall  686  created by the inner diameter  684  and the semi-circular endwall  683 . When the set screw  685  is tightened it causes the bushing  617  to flex inward and frictionally engage the shaft and thus prevent the device mount from rotating around the second female coupling  653 . 
     Formed within the coupling end  681  of the second female coupling  653  is a cable opening  684 . The opening is suitably sized such that the device cable and plug may be placed therethrough. Following placement through the cable opening, the cable and plug may then be placed through the cable slot  685 , the body  652 , and the first female coupling  651 , as previously described. 
     The shaft end  680  of the second female coupling  653  is shaped and dimensioned such that it may be slideably engaged within the opposite end of the body  652  of the forearm extension  650  as the first female coupling  651 . As such, the shaft end  680  of the second female coupling  653  is cast in a U-shaped configuration with a bottom wall  681  and two spaced apart sidewalls  682 . Each sidewall  682  extends outwardly from a stop  683  formed with the coupling end  681  of the second female coupling  653 . Formed within the bottom wall  681  is a void  687 , such as an elongated hole  686 . The void  686  is utilized in a similar manner as that of the first female coupling void  674  to form an essentially rigid structure with the body  652 . 
     A cable cover  692  is typically affixed upon the first female coupling  651 , body  652 , and second female coupling  653 . The cover is molded from plastic and contains a top cover  695  with a pair of sidewalls extending therefrom. The cable cover is shaped and sized such that the top cover  695  rests upon the first female coupling, body  652  and second female coupling  653 . As such, at the first female coupling  651 , the cover is circular in shape. Similarly, the extending sidewalls  693  are semi-circular in shape and extend into the inner diameter  656 . The sidewalls  693  are suitably flexible such that stops  694  attached thereto engage the inner diameter  656  with sufficient pressure to prevent the cover from being released without an intent to do so. The portion of the cover  692  affixed to the shaft end  655  of the first female coupling  651 , the body  652 , and the second female coupling  653  is rectangular corresponding to the shape of those elements. This portion of the cable cover  692  may be cut to a corresponding length to that of the specified forearm extension  600 . An assembled extension arm constructed in accordance with the present invention as thus far described is shown in FIG.  11 . 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that the embodiments are merely illustrative of the principles and application of the present invention. It is therefore to be understood that numerous modifications may be made to the embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the claims.