(12) Patent Application Publication (10) Pub. No.: US 2011/ A1

Transcription

1 (19) United State US A1 (12) Patent Application Publication (10) Pub. No.: US 2011/ A1 NG (43) Pub. Date: Jan. 13, 2011 (54) ADJUSTABLE SPRING ASSIST FOR WINDOW (52) U.S. Cl /311; 160/313; 160/315 COVERINGS AND AWNNGS (57) ABSTRACT (76) Inventor: PHILIPNG, THORNHILL (CA) There i provided a pring aited electric motor driven lifting mechanim for lifting and lowering a blind which Correpondence Addre: permit the quick and eay matching of the pring ait ELLAS BORGES pre-rotation to the torque output of the electric motor. The 56 Aberfoyle Crecent, Suite 840 device include an elongated cylinder coupled to the blind Canada, ON M8X2W4 (CA) uch that rotating the cylinder about it axi lift and lower the blind. Coupled to the elongated cylinder i an electric (21) Appl. No.: 12A498,433 motor which i configured to rotate the elongated cylinder 9 about it axi. A torion pring i coupled to the cylinder for 1-1. biaing the elongated cylinder to at leat partially neutralize (22) Filed: Jul. 7, 2009 the weight of the blind. The torion pring i in turn coupled O O to a pring preload adjuter which i configured to adjut the Publication Claification tenion on the torion pring by moving an adjutment mem (51) Int. Cl. ber. The pring preload adjuter i further configured Such E6B 9/68 ( ) that the adjutment member extend perpendicularly away E6B 9/60 ( ) from the axi of the elongated cylinder.

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11 US 2011/ A1 Jan. 13, 2011 ADJUSTABLE SPRING ASSIST FOR WINDOW COVERINGS AND AWNNGS FIELD OF THE INVENTION The invention relate generally to adjutable pring ait mechanim which are ued in window covering and awning to partially neutralize the weight of the blind or awning. BACKGROUND OF THE INVENTION 0002 Motorized blind incorporate an electric motor to raie and lower the blind. Thee motorized blind uually incorporate an elongated roller tube upon which either the blind (in the cae of a rollerblind) or the upport chord (in the cae of a roman, pleated, cellular or other blind) are wound. The electric motor i placed within the roller tube and, upon activation, caue the roller tube to rotate about it axi, either lifting or lowering the blind. The electric motor mut be ufficiently large to apply ufficient torque to the roller tube to overcome the weight of the blind when the blind i fully lowered (in the cae of a rollerblind) or when the blind i fully raied (in the cae of a roman, pleated or cellular blind). For a tandard ized blind typically ued for reidential applica tion, a relatively mall electric motori Sufficient. In the cae of a large blind which i everal meter in length, then a much larger electric motor i required ince the blind would be correpondingly much heavier. Larger electric motor have everal drawback. Firtly, they are generally larger and therefore require larger roller tube. Alo, they tend to be more expenive, and mot ignificantly, they require more electric energy to operate. Since large electric motor require more electric energy to operate, they tend to require higher voltage wiring, uually 110 V or 220 V. Thi mean that intalling thee larger electric blind generally require a licened electrician Spring aited roller blind have been in operation for many year. Thee roller blind ue an elongated torion pring to partially or completely neutralize the weight of the blind, making the blind eaier to open and cloe. The tenion of the torion pring in the pring ait i preet o that the pring ait neutralize the weight of the blind. The tenion of the torion pring i preet by pre-rotating the pring ait through everal revolution before the blind i fully aembled and intalled. Combining an electric motor with a pring ait i not practical becaue it i very difficult to match the required pre-rotation of the pring ait when the pring ait i coupled to both the roller tube and the electric motor. If not enough pre-rotation i applied to the pring ait, then the electric motor will either not be able to operate the blind or the motor will draw too much current and poten tially burn out. However, if too much pre-rotation i applied to the pring ait, then the electric motor will not be able to fully lower a raied roller blind, or in the cae of roman, pleated or cellular blind, the electric motor will not be able to fully raie the blind. A a reult, correctly matching the pre rotation of the pring ait to the electric motor i vital. Unfortunately, the only way to correctly preet the pre-rota tion of the pring ait to match with the electric motor would be to repeatedly preet the pring ait pre-rotation, then aemble and mount the blind, then tet the pre-rotation of the pring ait, then take down the blind again, diaemble it and reet the pre-rotation of the pring ait. Thi operation would have to be repeated over and over again until the correct pre-rotation for the pring ait i found. Further more, over time the tenion of the torion pring in the pring ait would change, requiring removal, diaembly and then further adjutment followed by further teting, removal and adjutment. A a reult, pring aited electrically driven blind have not been available in the market. An improved pring ait mechanim in combination with an electric motor which make it poible to accurately, preciely and quickly match the pre-rotation of the pring ait to the electric motor i therefore deired. SUMMARY OF THE INVENTION In accordance with one apect of the preent inven tion, there i provided a pring aited lifting mechanim for lifting and lowering a blind which permit the quick and eay matching of the pring ait pre-rotation to the drive mecha nim for lifting and lowering the blind. The device include an elongated cylinder coupled to the blind Such that rotating the cylinder about it axi lift and lower the blind. Coupled to the elongated cylinder i a cylinder drive which i configured to rotate the elongated cylinder about it axi. A torion pring i coupled to the cylinder for biaing the elongated cylinder to at leat partially neutralize the weight of the blind. The torion pring i in turn coupled to a pring preload adjuter which i configured to adjut the tenion on the torion pring by moving an adjutment member. The pring preload adjuteri further configured uch that the adjutment member extend perpendicularly away from the axi of the elongated cylinder With the foregoing in view, and other advantage a will become apparent to thoe killed in the art to which thi invention relate a thi pecification proceed, the invention i herein decribed by reference to the accompanying draw ing forming aparthereof, which include a decription of the preferred typical embodiment of the principle of the preent invention. DESCRIPTION OF THE DRAWINGS 0006 FIG. 1 i a long ectional view of a roller blind incorporating a motorized and pring aited blind lifting device made in accordance with the preent invention FIG. 2 i a blown up portion of FIG. 1 howing the pring ait portion of the preent invention FIG.3 i a cro ectional view of the pring preload adjutment portion of the preent invention FIG. 4 i a front view of a portion of a roller blind incorporating a motorized and pring aited blind lifting device made in accordance with the preent invention and howing detail of the tenion adjutment portion of the preent invention. (0010 FIG. 5 i a long ectional view of a roller blind incorporating a hand operated blind lifting drive and pring ait made in accordance with the preent invention FIG. 6 i an exploded view of the lip clutch portion of the roller blind hown in FIG FIG. 7 i a perpective view of a preload rotation counter for ue with the pring ait mechanim made in accordance with the preent invention FIG. 8 i a top view of the preload rotation counter hown in FIG FIG. 9 i a ide view of the preload rotation counter hown in FIG. 8.

12 US 2011/ A1 Jan. 13, FIG. 10 i a front view, partly in cro ection, of the preload rotation counter hown in FIG. 8 being ued in com bination with pring preload adjutment portion of the preent invention In the drawing like character of reference indicate correponding part in the different figure. DETAILED DESCRIPTION OF THE INVENTION 0017 Referring firtly to FIG. 1, a blind incorporating an adjutable pring aited blind lifting device made in accor dance with the preent invention i hown generally a item 10 and include blind 12 having lower end 14 and upper end 16. Upper end 16 i attached to drive mechanim 11 which include elongated cylinder 18 having oppoite end 20 and 22 and axi 23. Elongated cylinder 18 i preferably an elon gated tube of the type generally ued to contruct rollerblind (often called roller tube). Attached to end 20 of elongated cylinder (roller tube) 18 i pring ait mechanim 24 which conit of an elongated torion pring 25 having oppoite end 26 and 28. Spring ait mechanim 24 i configured to apply a biaing torque to elongated cylinder (roller tube) 18 to at leat partially neutralize the weight of blind 12. End 26 of torion pring 26 i attached to coupling 30 which i in turn rotatably coupled to yoke 32 which i coupled to end 20 of roller tube 18. Oppoite end 28 of torion pring 25 i attached to coupling 34 which i attached to roller tube 18. Coupling 30 and 34 are dimenioned and configured uch that torion pring 25 i coaxially aligned with axi 23 or roller tube 18. A roller tube 18 i rotated about axi 23, blind 12 i lowered or lifted (depending on the direction of rotation) and torion pring 25 i loaded or unloaded, repectively. Torion pring 25 act to partially neutralize the weight of blind 12. A blind 12 i lowered, roller tube 18 rotate and torion pring 25 i loaded. Ideally, tenion pring 25 i preloaded (i.e. pre-ten Sioned) ufficiently uch that the torion pring counteract the torion applied by blind 12 when the blind i fully low ered. Torion pring 25 i coupled to pring preload adjuter 36 via end 38 of coupling 30. Spring preload adjuter 36 ha an adjutment member 40 which when moved (i.e. rotated) change the tenion in tenion pring 25 by rotating the ten ion pring about axi 23. Hence, torion pring 25 can be pre-tenioned by imply rotating adjutment member (worm gear) 40. Spring preload adjuter 36 i attached to bracket member 42 which i in turn fixed to a wall or window frame (not hown) Drive mechanim 41 i coupled to the oppoite end 22 of roller tube 18 via yoke 43. Drive mechanim 4.1 may comprie any type of electrically operated or hand operated drive configured to raie or lower blind 12 by rotating roller tube 18. Drive mechanim 41 i configured to apply a drive torque to roller tube 18 which, when combined with the biaing torque generated by pring ait 24, i ufficient to raie and lower blind 12. In the embodiment of the preent invention hown in FIG.1, drive mechanim 41 conit of an electric motor 44 having an end 46 which pae through yoke 43 and which i coupled to coupling 48. Yoke 43 i mounted to roller tube 18 and i rotatably mounted to electric motor 44 to permit the roller tube to rotate relative to the electric motor. Coupling 48 i rigidly coupled to bracket 50 which i in turn fixed to a wall or window frame (not hown). Electric motor 44 ha haft 66 which i coupled to lip clutch 54, which i in turn coupled to roller tube 18. Electric motor 44 i coaxially aligned with roller tube 18 and activation of electric motor 44 caue haft 66 to rotate which in turn caue roller tube 18 to rotate about axi 23. When electric motor 44 i de-activated, haft 66 doe not rotate, thereby keeping roller tube 18 from rotating. A explained further below, lip clutch 54 permit roller tube 18 to rotate relative to haft 66 when ufficient downward force i applied to blind Referring now to FIG. 2, pring preload adjuter 36 conit of a houing 37 which contain a circular gear 56 which i coupled to and coaxially aligned with end 38 of coupling 30. Rotation of circular gear 56 caue a correpond ing rotation intorion pring 25, which in turneither increae or decreae the tenion on the pring depending on which direction the circular gear i rotated. Adjutment member 40 i preferably a worm gear which i rotatably mounted within houing 37 and oriented perpendicularly to circular gear 56 and axi 23. Circular gear 56 ha a peripheral edge 58 with teeth which are configured to intermeh with worm gear (adjutment member) 40 uch that rotation of the worm gear caue a correponding rotation in circular gear 56. A bet een in FIG.3 adjutment member 40 conit of an elongated haft having worm gear portion 62 which i configured to intermeh with teeth 60 of circular gear 58. Adjutment mem ber 40 ha axi 66 which i perpendicular to axi 23. End 70 of adjutment member 40 i poitioned immediately adjacent opening 68 in houing 37. End 70 i alo configured uch that it can be engaged by crew driver 72 (or by an allen key or imilar tool). Opening 68 i dimenioned ufficiently to per mit the end of crew drive 72 to engage end 70 of adjutment member 40 in order to allow the uer (not hown) to rotate adjutment member ufficiently to rotate circular gear 56 and in turn adjut the tenion of the torion pring of the pring ait (ee item 25 of FIG. 2) Referring now to FIG.4, orienting adjutment mem ber 40 uch that it extend perpendicular to axi 23 of roller tube 18 make the drive mechanim of the preent invention practical. By orienting adjutment member 40 perpendicular to axi 23, the pring ait mechanim 24 can be pre-ten ioned after blind 10 ha been intalled to wall 5. It will be appreciated that if adjutment member 40 wa coaxial to axi 23, it would be impoible to adjut the pre-tenion of the pring ait while the blind wa mounted to wall 5 ince the adjutment member would not be acceible. The preent arrangement make it poible to mount blind 10 to wall 5 (or immediately adjacent wall 5) and then adjut pring ait 24 to neutralize the weight of blind 12. Since the blind i already mounted, preciely adjuting the pring ait to completely neutralize the weight of blind 12 i much eaier. Thi remove the gue work aociated with pre-tenioning the pring ait and peed up the intallation of the blind Referring now to FIG. 5, the adjutable pring ait mechanim of the preent invention can be coupled for ue with a hand operated drive mechanim for lifting and lower ing the blind. Roller blind 100 i virtually identical to the previouly dicued rollerblind and include a roller tube 18 coupled to the pring ait mechanim 24 a dicued in the previou example. Blind 12 i coupled to roller tube 18. Drive mechanim 110 conit of a roller clutch 114 which i coupled to roller tube 18 and to chain 112. Pulling on chain 112 caue roller clutch 114 to apply a torque to roller tube 18 which, with the aitance of the torque applied by pring ait 24, caue roller tube 18 to rotate in repone and blind 12 to either lift or lower depending on how the chain i pulled. Roller clutch 114 i a tandard roller clutch a commonly available in the market. Spring preload adjuter 36 i coupled to pring ait 24 a in the previou roller blind example.

13 US 2011/ A1 Jan. 13, 2011 Roller clutch 114 may incorporate a lip clutch (not hown) there in to permit a uer (not hown) to lower blind 12 by imply pulling on the blind with a force greater than the torque applied by pring ait Referring now to FIG. 6, lip clutch 54 conit of a hub member 62, lip pring 64 mounted onto hub member 62, and coupling 60. Hub member 62 i configured to fit onto haft 66 which extend from electric motor 44 o that the hub and haft move together. Slip pring 64 ha end 68 and 70 which are paced apart ufficiently uch that protruion 72 of coupling 60 fit between end 68 and 70 when coupling 60 i coaxially mounted over hub 62. Slip pring 64 i configured uch that when hub 62 i rotated relative to coupling 60, one of end 68 and 70 of the lip pring are engaged by end 76 and 74 of protruion 72, repectively, cauing lip pring 64 to contrict more tightly onto hub 62. Slip pring 64 and hub 62 are further configured uch that when coupling 60 i rotated relative to hub 62 with a torion force (lip torque) exceeding a predetermined level, lip Spring 64 will rotate along with coupling 60 relative to hub 62 without damaging hub 62. A mentioned above with reference to FIG. 1, electric motor 44 i configured to apply a motor torque to roller tube 18 and pring ait 24 i configured to apply a biaing torque to roller tube 18 ufficient to rotate the roller tube and lift blind 12. Slip pring 64 and hub 62 are configured uch that the predetermined level of the lip torque exceed the combined motor and biaing torque to permit the uer, not hown, to lower blind 12 imply by pulling down on the blind Referring back to FIG. 2, it will be appreciated that accurately adjuting the biaing torque applied by the pring ait mechanim 36 i important to enure that the pring ait mechanim neutralize the weight of the blind 12. A mentioned above, in order to enure that the pring ait mechanim 36 neutralize the weight of blind 12, the pring ait mechanim mut be preloaded by pre-rotating the elon gated torion (biaing) pring 25 through one or more rota tion via everal rotation of worm gear 40. However, accu rately pre-rotating the biaing pring may involve gue work, particularly if there i a large ration between worm gear 40 and circular gear 56. Hence, if the uer wihed to rotate elongated biaing pring 25 by 4 rotation, and if the ratio between circular gear 56 and worm gear 40 wa 9:1, then the uer would have to rotate the crew by 36 rotation. Rotating worm gear 4036 time i trivial if an electric crewdriver or drill i ued; however, keeping track of the number of rota tion through which worm gear 40 i rotated may be quite difficult. Therefore, preciely adjuting the pre-rotation of elongated biaing pring 25 to a pecific number of pre rotation may be difficult Referring now to FIGS. 7,8 and 9, a preload rotation counter, hown generally a item 200, may be ued to help preciely adjut the tenion (i.e. pre-rotation) of elongated torion pring 25 (ee FIG. 1). Preload rotation counter 200 conit of an elongated haft 210 rotatably mounted to hou ing 212 and having oppoite end 214 and 216. Elongated haft 210 ha threaded portion 220 with nut 222 threaded thereon. Houing 212 ha protruding end 218 and face 215 with elongated lot 217 and indicia 226 formed thereon. But 222 i coupled to indicator 224 which project through lot 217. Nut 222 i configured uch that a haft 210 i rotated, nut 222 move along threaded portion 220 and indicator 224 move along face Referring now to FIG. 10, end 214 of haft 210 i configured to couple to an electric crew driver or drill 230 and end 216 i configured to couple to worm gear 40 of pring preload adjuter 36. Drill 230, when activated, will caue the rapid rotation of haft 210 of preload rotation counter 200, which in turn will caue the rapid rotation of worm gear 40 and a correponding lower rotation of circular gear 56. A mentioned above, rotation of circular gear 56 caue a corre ponding rotation in the elongated torion pring 25 (ee FIG. 2) and therefore preload the elongated torion pring with tenion. Alo, a haft 210 i rotated, indicator 224 move. The treading of threaded portion 220 and the pacing of indicia 226 are configured uch a haft 210 i rotated through Sufficient turn to caue circular gear to 56 to rotate through one full rotation, indicator 224 move one full indicator num ber. Hence, the number of rotation of circular gear 56 i indicated by the indicia on preload rotation counter 200. Thi provide a convenient and efficient mean for accurately pre loading the elongated torion pring 25 (ee FIG. 2) by a et number of pre-rotation. Hence, if 5 pre-rotation are required, the uer need only apply the drill to rotate haft 210 until the indicia 226 read 5. Thi take the gue work out of pre-loading the pring biaing mechanim and decreae the likelihood that the pring biaing mechanim will be either pre-loaded too much or not pre-loaded enough to neutralize the weight of the blind. Thi alo permit the rapid intallation of everal blind. The firt intalled blind will require ome level of teting before the correct pre-rotation i found to fully neutralize the weight of the blind. Once the exact number of pre-rotation i found, however, the remaining blind (aum ing they are of the ame ize and type) can imply be pre rotated to the exact level a the firt intalled blind. Minor variation to the pre-rotation can then be done by hand A pecific embodiment of the preent invention ha been dicloed; however, everal variation of the dicloed embodiment could be enviioned a within the cope of thi invention. It i to be undertood that the preent invention i not limited to the embodiment decribed above, but encom pae any and all embodiment within the cope of the fol lowing claim. Therefore, what i claimed i: 1. A lifting mechanim for lifting and lowering a blind having a weight, the lifting device compriing: a) an elongated cylinder having an axi, aid elongated cylinder being coupled to the blind uch that rotating the cylinder about the axi lift and lower the blind; b) a cylinder drive coupled to the elongated cylinder and configured to rotate the elongated cylinder about the ax1s, c) a torion pring coupled to the elongated cylinder for biaing the elongated cylinder to at leat partially neu tralize the weight of the blind, aid torion pring coupled to a pring preload adjuter for adjuting tenion on the torion pring by moving an adjutment member, the adjutment member extending perpendicularly away from the axi of the cylinder. 2. The lifting mechanim of claim 1 wherein the torion pring i coaxially mounted within the elongated cylinder and wherein the torion pring ha oppoite firt and econd end, the firt end of the torion pring being coupled to the elon gated cylinder and the econd end of the pring being coupled to a cam coaxially mounted to the pring, the cam being in turn coupled to the adjutment member, the adjutment mem ber and cam being configured uch that moving the adjut ment member caue the cam and torion pring to coaxially rotate together.

14 US 2011/ A1 Jan. 13, The lifting mechanim of claim 2 wherein the cam i coupled to a circular gear rotatably mounted withina houing, the circular gear being coupled to the cam Such that rotating the circular gear caue rotation of the cam, the adjutment member compriing a worm gear rotatably mounted within the houing, the worm gear being oriented perpendicular to and intermehed with the circular gear, the worm gear having an end immediately adjacent an opening in the houing Such that the worm gear can be rotated by rotating the end through the opening, the opening oriented perpendicular to the axi of the elongated cylinder, the worm gear and circular gear being configured uch that rotating the worm gear caue rotation of the circular gear. 4. The lifting mechanim of claim3 wherein the worm gear and the circular gear are configured uch that rotating the worm gear caue a correponding rotation of the circular gear while rotating the circular gear doe not caue a corre ponding rotation of the worm gear. 5. The lifting mechanim of claim 1 wherein the pring preload adjuter comprie a circular gear rotatably mounted within a houing, the circular gear being oriented parallel to the axi of the elongated cylinder, the circular gear being coupled to the torion pring uch that rotation of the circular gear caue a correponding rotation in the torion pring thereby adjuting the tenion in the torion pring, the adjut member compriing a worm gear rotatably mounted to the houing and intermehed with the circular gear, the worm gear being oriented perpendicular to the circular gear, the worm gear and circular gear being configured uch that rotat ing the worm gear caue a correponding rotation of the circular gear. 6. The lifting mechanim of claim 5 wherein the worm gear and the circular gear are configured uch that rotating the worm gear caue a correponding rotation of the circular gear while rotating the circular gear doe not caue a corre ponding rotation of the worm gear. 7. The lifting mechanim of claim 6 wherein the worm gear ha an end poitioned adjacent an opening in the houing, the opening in the houing being dimenioned Sufficiently to permit the rotation of the end of the worm gear from outide the houing. 8. The lifting mechanim of claim 7 wherein the end of the worm gear i configured to couple to an end of a crew driver. 9. The lifting mechanim of claim 1 wherein the cylinder drive comprie an electric motor. 10. The lifting mechanim of claim 9 wherein the electric motor i configured to apply a motor torque to the elongated cylinder and wherein the torion pring i configured to apply a biaing torque to the elongated cylinder to at leat partially neutralize the weight of the blind, the electric motor and torion pring being configured Such that the combined motor torque and biaing torque being ufficient to raie and lower the blind, the electric motor being coupled to the elongated cylinder by a lip clutch, the lip clutch being configured to permit the blind to be lowered by pulling the blind down with a force greater than the combined biaing torque and motor torque. 11. A roller blind compriing: a) a roller tube having an axi, aid elongated cylinder being coupled to a blind Such that rotating the cylinder about the axi lift and lower the blind; b) a drive coupled to the elongated cylinder configured to rotate the elongated cylinder about the axi; c) a torion pring coupled to the elongated cylinder for partly neutralizing the weight of the blind weight, aid torion pring having oppoite firt and econd end, the firt end being coupled to the elongated cylinder, d) a circular gear rotatably mounted in a houing, the circular gear being coupled to the econd end of the torion pring Such that rotating the circular gear caue a correponding rotation in the tenion pring and a correponding adjutment in the tenion pring' ten S1On; e) a worm gear rotatably mounted in the houing and ori ented to meh perpendicularly with the circular gear, the worm gear and circular gear being configured uch that everal rotation of the worm gear caue a ingle cor reponding rotation in the circular gear, and f) the worm gear having an end poitioned perpendicularly away from the axi of the roller tube, the houing being configured uch that the end of the worm gear can be acceed to caue the worm gear to rotate. 12. The lifting mechanim of claim 11 wherein the end of the worm gear i poitioned adjacent an opening in the hou ing, the opening in the houing being dimenioned uffi ciently to permit the rotation of the end of the worm gear from outide the houing. 13. The lifting mechanim of claim 12 wherein the end of the worm gear i configured to couple to an end of a crew driver. 14. The lifting mechanim of claim 11 wherein the cylinder drive comprie an electric motor. 15. The lifting mechanim of claim 14 wherein the electric motor i configured to apply a motor torque to the elongated cylinder and wherein the torion pring i configured to apply a biaing torque to the elongated cylinder to at leat partially neutralize the weight of the blind, the electric motor and torion pring being configured Such that the combined motor torque and biaing torque being Sufficient to rotate the elon gated cylinder to raie and lower the blind, the electric motor being coupled to the elongated cylinder by a lip clutch, the lip clutch being configured to permit the blind to be lowered by pulling the blind down with a force greater than the com bined biaing torque and motor torque. 16. The roller blind of claim 11 further compriing a pre load rotation counter for preciely meauring a preload rota tion of the torion pring, the preload rotation counter com priing an elongated haft having a firt end configured to couple to the end of the worm gear and a econd end config ured to couple to an electric drive, the elongated haft being rotatably mounted to a counterhouing having a face thereon, a threaded portion being formed on the elongated haft between the firt and econd end of the elongated haft with a nut being threaded thereon, the nut being configured Such that the nut move along the houing a the elongated haft i rotated, an indicator being coupled to the nut and houing Such that indicator move along the face of the houing a the nut move along the haft, the face having a plurality of paced apart indicia formed thereon to meaure the move ment of the indicator, the treaded portion and the indicia being configured Such that the movement of the indicator corre pond to the rotation of the circular gear. c c c c c