US1697990A - Surfacing machine - Google Patents

Description

Jan. "8, 1929. 1,697,990

A. E. MAYNARD SURFACING MACHINE Filed Dec. 4, 1925 2 Sheets-Sheet l Jan. 8, 1929; 1,697,990.

A. E. MAYNARD SURFACING MACHINE Filed Dec. 4, 1926 2 Sheets-$heet 2 $2? 4 I gmtox i inmagnardy Patented Jan. 8, 1929.

ALBERT E. MAYNARD, OF SOUTHBRIDGE, MASSACHUSETTS, ASSIGNOR TO AMERICAN OPTICAL COMPANY, OF SOUTI-IBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOGIA- TION OF MASSACHUSETTS.

svnrn'cme MACHINE.

Application filed December 4, 1926. Serial No. 152,555.

This invention relates to surfacing machines and has particular reference to a lap form of surfacing machine in which a plurality of pieces of work are maintained against the lap under approximately equaL ized surfacing pressures during the surfacing operation.

The principal object of the invention is to provide improved means for approximately equalizing the surfacing pressure of a plurality of pieces of work against the lap for all positions of the work on the lap during the surfacing operation.

Another object of the invention is to provide improved means for holding the work against the surfacing lap so that it will be surfaced equally throughout the surfacing operation, that is to say, the work will not be thicker or thinner on one side but the surfacing will be maintained equally from the first contact until the finished surface has been made.

. Another object of the invention is to provide improved means for regulating the surfacing pressure on the work during the surfacing operation.

Another object of the invention is to provide improved means for regulating'the path the work will take on the lap during the surfacing operation. a

Another object of the invention is to pro vide simple, ecomomical and efficient means for substantially equalizing and regulating the surfacing pressure on a plurality of pieces ofwork during the surfacing operations.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings andmany changes may be made in the details of construction and arrangement of parts without departing from the spirit of the invention as set forth in the accompanying claims. I, therefore, do not wish to be limited to theexactdetails of construction and arrangement shown, the preferred forms of the invention only having been shown by way. of illustration.

Referring to the accompanying drawings: Figure l is a partlal elevation of a sur often cause the work to be facing machine to. which the invention is applied; 1

Figure 2 is a top or plan view of Figure 1 with parts removed for clearness;

Figure 3 is a cross section on line 3-3 of Figure 1; p a

Figure 4 is a partial elevation similar to Figure 1 showing the'invention applied to a concave lapinstead of to a convex lap. Prior to my invention it has been customary to hold the workagainst the surfacing lap by means of spring pressure applied on the central spindle of the machine. Itwill be seen,'therefore, that when the work is at the bottom portion of the lap the spring pressure is much weaker than when it is at the top portion of'the lap and thatthe spring pressure varies greatly in between these two portions of the lap. Therefore, there is a tendency for the work to be ground unequally, grinding faster atone place than at another, which tendency has been found from practice and from experience to very.

ground thinner on one side than on the other. i

Y It is, therefore, the prime object 'of'this invention to substantially overcome these disadvantages of the prior art'and to provide pressure equalizing means that will insure that a plurality of pieces of work have ap-' proximately the same surfacing pressure Whether grinding at the bottom or the top 'or at points in between on the lap, and also due to this reduction inunequalized pressure the work will have a tendency to 'besurfaced equally so that the finished product will be of uniform thickness instead of being thinner on one side than the other. 1 This is. of particular importance in the surfacing of ophthalmic lenses which are ground from fragile optical glass which is an expensive material and in which the wastage has been large in the prior art surfacing machines due to the tendency of the glass material to i I become broken when shifting from the lower to the higher side of the lap, particularly where thespring pressurewas not properly adjusted. r "g Referrlng to the drawings 1n;wh1 chsirnllar characters of reference denotecorrespending parts throughout, the work or ophthalmic lens 1 is secured to a work holder 2 by means of an adhesive such as pitch or cement 3. The holder 2 has a conical centering pointAl into which is fitted the coni cal point 5 ofathe "positioning pin" 6. "The positioning pin 6 is carried on an equalizer member 7 which is pivoted at 8 to the shank 9-which is secured to the spindle" 10 of the surfacing machine by means of the-stud 11 held in place by the set screw 12. The positioning pin6 has a. shoulder 18, se('Fi'g.'3,"on which rests the spiralxspringil l. The positioning pin 6 is carried in the borcof a clamp ."member 15; into -which is escre w threaded the regulator cap 34 for regulating ,thesspring pressure-- by screwing down r the cap onther-springrll. ,The clampunember 15'2fitstinto clamps? 1'6 and. 17 which-secure it to the equalizer member 7, the clampi17-being screw threaded on to. the. end of the. clamp member15andi the clamp portion-16 having the annular-borelfitting over thegmember 15. The. equalizer member' 7 i is engaged between the jaWI18-Jofi the. member 16- andnthe jaw 19 oilthe memben 1.7 K andheldinplace thereon-.by-' the lock: nut. 20iwhichis-threaded on thetclam-p member 15,- the equalizer member -7i.hav-ing-.a dove-tail 21 to prevent separation otthe parts I The pivot 8 is; eccentric mate to one: side or, the center-I line of the spindle 10. of the surfacing machine "The spindle '10 is driven bythe, pulley. 22. aiidf the belt 23: and the spindle 10L raised fronin themlapl24: or idepressed towards. vitlvhy.aneansuolfthe lever L25, having. theIQhaIidle 26, the lever. '25 being pivoted1atl27i to theiframe. 28 ofg'the surfacing machine, iThe lap. 24isdriven by the spindle J29: by means. of theQphlley' 30 r and .the'belt3l; I iThe'equalizer member' 7iisspivotd at'S-tO the shankig, whichhasa stud ll entering the spindle. 10. "The stu'd11 is related to the. shank'9 "in'suc-h awayethat' if the set sCrewilZisf loosened arid theshank 9 turned about'lthe stud 11 the center of the pivot 8 may. be positioned at; points v varying from thecenterlline" of the spindle 10 to the point "Show? -l et-is to say; it be -.positioned at any-point between the position on ithecenterf line of. the spindle 10 and the extreme distance: therefrom by rotation of {the -.sh a.i1k member on the stud ll'ain its fitting in'the spindle 10.

' The positioning pin. 6' in 'the clamp member15 isfpo'sitiond on the dove-tail. 21 of the" equalizer member 7 by means of the clamp members 16Land 17 andth'e lock, nut 20 j in such a way L that the pin 6:1nay be angled as"d'esiredto a point normal to the work onfthe lap in d'esired position. "After it has thus been positioned the clamps 16; and

1 igs 17 are tightenedby means'of the look nut 20 to hold'fthe 'pins in the desired related position to the work. It will, of course, be understood that the angles .at which these pins 6 are approximately pointed towards the lap would be radial to the center of curvature of the lap, that is, the center of curvature to whit-lithe lap is to'be surfaced. I On the equalizer member v7 adjacent the points where the positioning pins 6 are located is a scale"32 and a registering nark 33 onithe clam-p jaw 18 by which the amount of inclination of the spindle may :be determined,

'lhec'enter of the spindle 10 is also eccentric to. the center of. the spindle 29 of the lap as shown in" Fig' 1.

.The operation of the invention is as folloWs: A lapiQ,ofpdesired curvature, either convex as-showninzFig. 1, or concave shownrinlhig. 4c, isplaced on the spindle 29. i The WVOLlK. secured to the" holder"? is placed on.thel:lap,the pin '6 is entered into the recess 1' at the holder 2, and the pint set to. the required angle with respectto the lap, that. is. to say, radially to'the center of the lap, and locked in position by means of the lock nut 20; The equalizer 7 being pivoted on the pivot 8 is free to adjust itself so that the pins'6 bearing on the workpieces hold each of the work pieces in itstrue: rc- I spective posltlon on the lap, the spring sur facing. pressure being exerted along the pins Gby: means-of the spirai spring 14 inthe clamp member 15, the spring pressure hav- 7 I ing beenadjusted by the adjusting screw i The machine t 1en set in operation, the lap being rotated: and the V spindle 1O rotated. The spindle 10 being eccentric to thespindle 29 and the pivot point 8 of the equalizer 7 being eccentric to the center "line of the pmaa 10 w'illcause thework tounove up anddown on the" lap, that isffrom' the'lower point towards the center and vice veisa'as the=equalizer 7 isbeing rotated by the spindle 10. "The positioning pins 6 being carriedby the equalizer? andunoving' therewith will always exert the same pressure on the "work. 1 regardless; of whether the workasxat the bottom of the lap, at'thetop o1 theglap or zatpositlons 111' between. As has' been stated,

the amount-of eccentr city of the pivot 8'.

regtilated'by the shanlij9moving on its stud 11 on thespindle 1O,v this being capable of beingset either an the center of 'the spiiidle in' all positions of the work on the'lapfnr tendencyto grind on the lower side, it having been found in the prior art machines 10hr at positions therefrom up tothe naxr V mum amount. The spring pressure exerted on thework through the pinst being'equal' that there was a"tendencyfor the' -len's t grind thick :on the lower side and to stop 7 turningas'it was brought towards thec'enter of the lap. The arrangement of this invention is such as to practically eliminate these disadvantages. The positioning pins 6 are advanced towards the work, are retreated therefrom at the termination of the surfacing operations by means of the lever and handle 26, the lever 25 having locking arrangements for securing the spindle 10 in the proper adjusted position for grinding.

Y'Vhile I have shown my invention as applied to one particular form of surfacing machine it may be applied to many different kinds of surfacing machines, and while I have shown my device as applied to the surfacing of ophthalmic lenses other forms of lenses and other forms of surfacing may be I equally Well done with this apparatus.

It will be seen that the pressure exerted by the springs 14 on the pins 6 is equalized by the equalizer member 7 operating about the pivot 8 because as one piece of the work is on a low portion of the lap another piece of the work is on the higher portion of the lap and as these two pieces change their positions on the lap the equalizer 7 rocks on the pivot point 8. Therefore, they act as a couple and the pressure exerted by the spring 14 on the pins 6 is equal in all positions of the work on the lap. It is clear that the two pins 6 are so located with respect to the lap that in the movement of the work over the lap there is an effect to neutralize each other, that is, as one spring is tightened the other is loosened b' an equal amount so the pressure exerted y the couple is always equalled.

From the foregoing description it will be seen that I have provided simple, efficient and economical means for carrying out all the objects of the invention, particularly equalizing the pressure on the work during the operation and overcoming the difliculties encountered in prior art machines, especially the unequal surfacing and unequal speed of surfacing as well as insuring a uniform and constant wear on the surfaces of the laps themselves.

Having described my invention, I claim:

1. In a surfacing machine in combination with a tool and spindle, an equalizer member movably connected with the spindle having a pair of arcuate portions thereon, yielding positioning pins slidably carried by the arcuate portions and means to lock the positioning pins on the arcuate portions at the desired angle with respect to the tool.

2. In a surfacing machine in combination with a tool and a spindle, a member movably secured to the spindle so that it may be 3. In a surfacing machine in combination with a tool and spindle, an equalizer member movably connected with the spindle having a pair of arcuate portions with slide means thereon, members having internal recesses adapted to'slide on the arcuate portions, reciprocal pins in the recessed member, yieldin means in the recessed members adapted to yieldingly urge the reciprocal pins out- Wardly from the recessed members against work holders which are adapted to present the work to the tool,'and means to lock the recessed members on the arcuate portions of the equalizer member to position the positioning pins at the desired angle with re spect to the tool.

4C. In a surfacing machine in combination with a tool and. spindle, an equalizer member movably connected with the spindle having a pair of arcuate portions with slide means thereon, members having internal recesses adapted to slide on the arcuate portions, reciprocal pins in the recessed members, yielding means in the recessed members adapted to yieldingly urge the reciprocal pins out wardly from the recessedmembers against work holders which are adapted to present the work to the tool, means to lock the recessed members on the arcuate portions of the equalizer member to position the positioning pins at the desired angle with respect to the tool, and means to regulate the yielding pres sure of the yielding means in the recessed members. i V

5. In a surfacing machine in combination with a tool and spindle, a supporting member movably connected in eccentric relation to the end of the spindle, an equalizer member movably connected with the support ng member and having a pair of arcuate portions thereon, said arcuate portions hav-' ing slide means, yielding positioning means slida-bly carried by the arcuate portions of the equalizer member and adapted to engage the work holding means for urging the same toward the tool, and means to lock the po-' sitioning'pins on the arcuate portions at the desired angle with respect to the tool.

. ALBERT E;- MAYNARD. g

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