US2876669A - Micrometer stops for machine tools - Google Patents

Description

March l0, 1959 D. D. PETTIGREW 2,876,669

y MICROMETER STOPS F 0R MACHINE TOOLS Filed Sept. 28, 1955 lll-I+ j INVENTOR DAV/a Rrr/fee# fmya ATTORNEY/5 United States Patent O MICROMETER STOPS FOR MACHINE TOOLS David D. Pettigrew, Pittsburgh, Pa., assiguor to Rockwell Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Application September 28, 1955, Serial No. 537,249

2 Claims. (Cl. 82--21) This invention relates to stop devices for limiting movement of the tool carriage of a machine tool and more particularly to micrometer stops for use with metal working lathes and the like.

It is the principal purpose and object of the invention to provide improved micrometer stops of simple, rugged construction which maintain a high degree of accuracy under use for extended periods. v

It is a further object to provide novel micrometer stops which may be manufactured at a cost well below units of comparable accuracy and durability.

It is also an object of the present invention to provide novel micrometer stops having a micrometer dial for positioning the stop element in which the effects of backlash normally present in such devices are eliminated whereby the dial may be rotated in either direction without loss of accuracy. p

It is a further object to provide micrometer stops of novel construction which are held in adjusted position without the use of the usual separate locking mechanisms.

It is an additional object of the present invention to provide micrometer stops of novel construction which are reversible to permit their installation to control the movement of the tool carriage at either end of its stroke.

It is a further object to provide novel micrometer stops in which a spring is utilized in a unique manner to perform the dual functions of eliminating backlash and locking the unit in adjusted position.

It is an additional object to provide novel micrometer stop units having an elongated stop member threaded into a rotatable micrometer dial in which a relatively inexpensive construction including easily fabricated cooperating ats on the stop rod and a bushing prevent rotation of the stop whereby rotation of said dial produces axial movement of the stop rod.

Additional objects and advantages will become apparent as the description proceeds in connection with the drawings in which:

Figure l is a top plan view of a micrometer stop assembly constructed in accordance with the present invention;

Figure 2 is a vertical section taken along line 2-2 of Figure 1;

Figure 3 is an end view looking from the left in Figure l; and j Figure 4 is a fragmentary section taken along line 4-4 of Figure 2 and showing details of construction.

Referring now more particularly to the drawing, 10 indicates generally a relatively heavy body member, preferably of cast iron. The body member has a central section 12 integrally joined to a pair of aligned arms 14 and 16 formed at the opposite sides of a central recess 18 having a sloping bottom wall 20 and vertical side walls 22 and 24. The under surface of the central section 12 is provided with a downwardly opening groove 26 having inclined side wall portions 28 and 30 adapted to receive the mating surfaces of the front prismatic way' 32 of a standard lathe bed. The body 10 is adjustably 2,876,669 Patented Mar. l0, 1959 ice clamped to the prismatic way 32 by a plate 34 which engages a portion of the undersurface of the way 32 and is secured to a downwardly projecting portion 36 of the body by a square head collar screw 38 threaded into a tapped opening 40 in the body section 36. The lower surface of the body section 36 is cut away as at 42 to permit the desired clamping action.

The arms 14 and 16 are provided with aligned bores 44 and 46 which are of the same diameter and substantially the same length. The bores terminate at their inner ends in the recess 18 and are provided at their outer ends with identical tapped portions 48 and 50, respectively. Threaded into the tapped portion 50 of the arm 16 is a nut bushing 52 having a central reamed bore 54 which slidably receives the cylindrical end portion 56 of the stop rod indicated generally at 58. A cylindrical portion 60 formed at the opposite end of the stop rod 58 is received in a reamed central bore 62 formed in a nut bushing 64 threaded into the tapped portion 48 of the arm 14. The end 65 of the rod `58 is carefully nished to provide a precision stop surface.

The nut bushing 64 is provided with a smooth cylindrical shank 66 which is split by the opposed slots 68 and 70 and received within bore 44. A relatively shallow slot 72 is formed across the inner end of the nut bushing 64, the opposite parallel sides of which slidably engage flats 74 formed in an enlarged section 75 of the stop rod 58. The central portion of the nut bushing 64 is undercut to a diameter substantially larger than the diameter of the section 75 of the stop rod. Accordingly, only the relatively short bore 62 and the relatively shallow slot 72 need be .carefully machined to achieve the desired support of the stop rod 58. By virtue of this construction the respective bores 62 and 54 in the nut bushings 64 and 52 support the stop rod 58 for axial movement in exact parallelism with the prisrnatic way 32 and the cooperating surfaces of the slot 72 and the ats 74 x the stop rod y58 against rotation. The cylindrical shank portion 66 of the nut bushing 64 lits within the bore 44 of the arm 14 with a relatively large clearance to obviate the necessity for close tolerances in the manufacture of the slot 72 and the flats 74. If the dimension between the latter is slightly oversize the slots 68 and 70 will permit limited expansion of the shank of the nut to accommodate the iiats 74 with a free sliding fit.

The stop rod is moved axially with respect to the body 10'by means of a collar indicated generally at 80 provided with an internally threaded central section 82 threaded onto a central section 84 of the stop rod 58. The collar is received between the opposite faces 22 and 24 `of the recess 18 and the end faces 86 and 87 of the collar and the adjacent faces of the recess are accurately ground or otherwise finished to provide full surface contact therebetween. Suitable indicia 88 are provided around the end of the collar 80 adjacent the face 22 which cooperate with a scribe line 90 formed on a boss 92 on the arm 14 to determine the rotative position of the collar 80. Tofacilitate manual adjustment of the collar 80 the collar is provided with an-enlarged knurled section 94 which may be readily grasped by the operators thumb and forenger.

A coil spring 96 is compressed between the inner end surface of the nut bushing 52 and a washer 98 positioned at the shoulder formed between the end of the threaded section 84 and the cylindrical section 56 of the stop rod 58. The spring 96 has two important functions. First it takes up all backlash in the stop assembly, for example, between the threads on the stop rod 58 and the threads on the collar 80 and between sembly, respectively. Secondly, it provides a frictional lock to retain thev collar in adjusted position. The locking effect -is sufiicient yto-preventinadvertent-movement Y of the collar and yet permit yeasy rotation when desired. 1t will be understood that the end surface 65 of the stop rod 58 is the operating'istop'surface.

It is a feature of the invention that the ystop rod may be reversed end for end withrespect to the body yto permit the use of thedevice to control the travel'of Specifically the y the carriage at either end of its stroke. reversal is accomplished by removing the nut bushings 52 and 64 and the spring 96 and threading the stop rod out of the collar 80. The stop rod 58 is then reversed end for end and threaded in to collar S0, the spring 96 is positioned around the 'cylindrical portion 56' of the stop rod and the reversed nut Ibushings 52 amd64 are threaded into the respective arms 14 and `16.k Again the spring 96 will effectively removethe backlash from the systemy urging the end surface l87 of the collar 89 against the adjacent surface 24 yof the Vrecess 18. vThe surface 65 remains Vthe effective stop surface.

The'micrometer stop Iassemblyof the present invention is normally used to facilitate finishing operations. After the roughy cut is, completed` and'it'has been determined the amount of additional movement of fthe tool carriage rrequired to complete lthe finish' cut the along the way to disposethe stop surface 65 in contact with thetool carriage. After the nut 38 is tightened the collar 80 is rotated to move the stop surface-65 away from the tool carriage the exact amount required to perform the finishing operation as indicated by the scale 8S andthe lscribe line 90. stop surface .will be retainedv in this position becauseA of the frictional lock established by the lcoil spring 96.

From the foregoing it will ybe seen that the above stated vadvantages of the invention havev been attained by the provision of a novel micrometer stop assembly of simplified, rugged, construction yand high accuracy.

Theinvention maybe embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is 'therefore to be considered in all forms as illustrativeand not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within themeani ing and range of equivalency ofthe 'claims are therefore intended to be embraced therein. jWhat is claimed and desired to be secured by United States Letters Patent is:1

1,. An adjustable stop assemblyrcomprising a bodyl member adapted to be secured toa Ifixed support; a stop rod mounted for longitudinal movement in `said body member and fixed against rotation, said rod having a As indicated above, the

i central threaded portion and having a stop surface disposed externallyfof said body; an adjustment nut having threads engaging the threads of said stop rod, said adjustment nut being fixed against axial movement in said body member, and a spring surrounding a portion of said stop rod within said body member and compressed between surfaces rigid with said body member and said stop rod, respectively, to urge said rod in the direction to move said stop surface inwardly of said body to thereby eliminate backlash.

2. An adjustable' stopV assembly comprising a body member adapted to be secured to a xed support, said body member having spaced aligned bores provided with threaded end portions; a pair of bushings having aligned central bores mounted respectively in said threaded portions; a stop rod having relatively reduced cylindrical end sections mounted in said bores for sliding movement longitudinally of said body, and having a stop surface disposed externally of said body, said stop rod having an intermediate portion provided with opposed plane surfaces, one of saidbushings having plane surfaces adapted to slidablyV engage the plane surfaces on said stop rod t0 `prevent rotation of said stop rod with respect to said nut 38 isloosened and the entire stop assembly is moved body, `s'ailstop rod also having a relatively enlarged threaded central section, a collar having internal threads engaging said threaded central section of said stop rod; means-fixing said collar against longitudinal movement in said body whereby rotation of said collar moves said rod axially of said body; and a coil spring surrounding a portion of said stop rod within Said body member and compressed between the inner end surface of one of said bushings and a shoulder on said stop rod and adapted to urge said rod in a direction to move said stop surface inwardly of said body to thereby eliminate backlash between said stop rod and said collar and between said collar and said body.

References Cited in the file of this patent UNITED 'STATES PATENTS 1,446,557 Godfriaux Feb. 27, 1923 1,480,522 Fergusony Jan. 8, 1924 1,490,413 Blood Apr. 15, 1924 1,551,017 Erway Aug. 25, 1925 1,582,077 Palmer Apr. 27, 1926 1,950,491 Heald -Mar. 13, 1934 2,338,001 La Vigne Dec. 28, 1943 2,450,004 t Knox Sept. 28, 1948 2,455,793 Monkiewicz Dec. 7, 1948 2,734,394 Chauvel Feb. 14, 1956 FOREIGN PATENTS 139,481 Sweden Mar. 28, 1950 l $472,048., Italy 4 .l June 4, 1952

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