US2869237A

US2869237A - Trammel bar compass

Info

Publication number: US2869237A
Application number: US610311A
Authority: US
Inventors: Joseph M Berge
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-09-17
Filing date: 1956-09-17
Publication date: 1959-01-20
Anticipated expiration: 1976-01-20

Description

Jan. 20, 1959 J. M. BERGE TRAMMEL BAR COMPASS Filed Spt. 17, 1956 AAAA- IN VEN TOR. J0551 1! l7. Bazae United States Patent TRAMMEL BAR COMPASS Joseph M. Berge, San Clemente, Calif. Application September 17, 1956, Serial No. 610,311

1 Claim. (Cl. 33-27) This invention relates to drafting instruments and in particular to compasses of the trammel bar type, wherein center point and lead holders respectively are attached to respective ends of a trammel bar in a manner to be adjustable longitudinally thereof for setting the radius of a circle to be scribed.

The invention has as its primary object to provide improvements in this type of compass. In particular, the invention contemplates an improved slider and chuck unit embodying parts having improved gripping qualities. More particularly, the invention contemplates a slider embodying a collet, fabricated from a soft plastic material such as a nylon resin, providing improved gripping attachment to the trammel bar when the collet is tightened, and also embodying improved wearing qualities to avoid the development of looseness over an extended period of use.

Another object is to provide a chuck for a center point or lead, embodying an improved collet of a plastic material such as that indicated above, having improved gripping qualities in securing a center point or lead in such collet.

A further object is to provide an improved arrangement of spring loaded slider with vernier adjustment for fine adjustment of the spacing between center point and lead.

Another object is to provide an improved slider and collet unit embodying storage space for extra lead and center points.

Other objects will become apparent in the ensuing specifications and appended drawings in which:

Fig. l is a side view, partially broken away and in section, showing one end of a compass embodying my invention;

Fig. 2 is a view of the same side of the compass, partially broken away and in section, showing the other end of the compass;

Fig. 3- is a front sectional view of the slider collet, taken on the line 33 of Fig. 1;

Fig. 4 is an end view of the same, partially in section, taken on the line 44 of Fig. 1;

Fig. 5 is an enlarged detail exploded view of the slider collet, with parts broken away and shown in section;

Fig. 6 is an enlarged detail view, partially in section, of the slider collet and an associated section of the trammel bar;

Fig. 7 is an enlarged fragmentary detail side view of the spring loading portions of the vernier-adjusted slider unit;

Fig. 8 is a cross-sectional view of the same;

Fig. 9 is a detail enlarged sectional view of the vernier portion thereof;

Fig. 10 is an exploded side view partially in section, of one of the point holding collets;

Fig. 11 is a detail axial sectional view of the assembled point holding collet; and

Fig. 12 is a cross sectional view thereof taken on the line 12-12 of Fig. 11.

Referring now to the drawing in detail, I have shown, as an example of one form in which the invention may be embodied, a trammel bar type of compass embodying, in general, a trammel bar 12, a manually adjustable slider and collet unit 13 on one end of bar 12, and a vernier adjustment slider unit 14 on the other end of the bar 12. Unit 13 is adapted to be loosened, slid bodily to any selected position along the length of bar 12 short of the unit 14, and locked to the bar in the selected position. Fine adjustment of the spacing between the two units is then obtained by adjusting the vernier unit 14.

Each of the

end units

13 and 14 includes identical sub units as follows: a sliderblock 16 is slidably mounted on the tramrnel bar 12 and is provided with a collet unit 17 for locking it to the bar 12. Similar slider block and collet parts are indicated at 16 and 17' in the unit 14. A point holding chuck unit 18' is attached to slider block 16.

Slider blocks

16, 16 are fabricated of a very tough, durable, long wearing plastic material of the group including the nylon (polyamide) and Teflon (tetrafluoroethylene) resins and since the nylon resin is the less expensive of the two, it is preferred. Such a resin provides smooth, slick surfaces within the passage 19, of

cross section corresponding to that of trammel bar 12,'

which extends lengthwise through the central body 20 of slider block 15, 16 through a collet neck 21 which is formed integrally with one end of body Ed, and through collet jaws 22 which are formed integrally with the end or neck 21 and project therebeyond in coaxial relation thereto. laws 22 are circumferentially separated by slots 23 so that the jaws can be deflected inwardly into gripping engagement with the faces of bar 12 by the wedging action of a conventional collet nut 24- which is threaded onto an external thread 25 on neck 21. To this end, the nut 2% has the conventional frusto-conical throat 26 for engagement with jaws 22.

Tramrnel bar 12 is of non-circular cross section, and is preferably square although it may be hexagonal or other prismatic cross section. The passage 19 is of corresponding cross section and fitted fairly closely to the bar 12. When jaws 22 are tightened against the bar 12, all such looseness is completely eliminated by the engagement of the flat inner faces of jaws 22 with the correspondingly llat faces of the bar 12.

When the collet nut 24 is loosened, the smooth internal surfaces of the sliders 16, is allow them to be freely slide along the bar 12 to new positions.

Referring now to the

point chucking units

18 and 18, each of these units includes a coupler nut 27 which is threaded onto a threaded coupler neck 28 formed as an integral portion of the slider body 211 and projecting at right angles to the neck 21. Coupler nut 27 includes an internally threaded skirt portion 29 which received the neck 23, a reduced tip portion 33 which has a cylindrical bore 31 therein, and a frusto-conical throat 32 extending between the bore 31 and the internally threaded bore of skirt portion 2%. Received in neck 27 is a chuck sleeve 33 including a cylindrical intermediate body portion, an enlarged head 34 received in throat 32 and having a frusto-conical shoulder fitted thereto, and a tapered collet tip 35 at its opposite end, projecting beyond the end of nut 319 and having a reduced bore 36 to receive a lead point 37 (unit 1'3) or a center point 38 (unit 14). A look nut 39 is threaded onto collet tip 35 and engages with collet jaws at the end thereof to tighten the same against the

point

37 or 38 in accordance with conventional sub-structure in drawing instruments.

Tubular body 33 has an enlarged bore 40 which registers with a bore 41 of the same diameter in neck 28. The bores 40 and 41 cooperatively define a storage chamber for extra lead points and center points in the

respective chuck units

18, 18.

The chuck sleeve 33 is of a nylon or Teflon material adapted to provide improved gripping of the lead point 37 and center point 33. Head 54- has a fiat end which abuts a squared end on neck 23 and is tightened thereagainst when nut 27 is drawn tight on neck 28. Additional locking efiect is attained by the frictional engagement of throat 32 against the conforming shoulder on head 34, plus the engagement between collar and neck 28. The locking of sleeve 33 to body is necessary before collet nut 39 can be rotated upon sleeve 33. Improved gripping of the chuck body 33 to the neck 28 is provided by engagement of the two like plastic surfaces under pressure.

Nuts

27 and 24 are of metal for facilitating the rotation of the threaded parts relative to one another. Nut 39 on the other hand is of the plastic material, and is inexpensively produced by a molding operation.

Referring now to the Vernier unit 14, this unit is interposed between a vernier nut 42 which is threaded onto a threaded end portion 43 of bar 12, and a coil spring 44 which abuts against a washer 45 in the form of a snap ring (Fig. 8) inserted into a slot 46 extending around the bar 12. Spring 44 is engaged under compression between washer 45 and the nut 24 of collet unit 17'.

It will now be apparent that by rotating nut 42 on threaded shank 43 in an advancing direction, the slider unit 16' will be advanced toward the unit 13, compressing spring 44, and upon rotating nut 42 in a retracting direction, spring 44 will move the unit 14 back toward the threaded end 43 of the bar 12.

4 I claim: In a scribing compass of the trammel bar type: a trammel bar; and a pair of point carrying units attached torespective ends of said bar; at least one of said point carrying units including a slider body of polyamide material siidably mounted on said bar and having externally threaded collet jaws for clamping it to the bar in any selected position of adjustment thereon, and a metallic collet nut threaded onto said jaws for constricting the nto said clamping engagement; and a point holdin chuck unit attached to said slider body, said chuck unit including a coupler neck integral with said slider body and projecting at right angles to the axis of said collet iaws, a metallic coupler nut threaded onto said coupler neck; a chuck body of polyamide material received in said coupler nut and having an inner end in the form of a head in abutting relation to the end of said coupler neck and adapted to be locked thereto by tightening said coupler nut, and a point holding chuck on the outer end of said chuck unit.

References Cited in the file of this patent UNITED STATES PATENTS 522,053 Gates June 26, 1894 534,152 Henkel Feb. 12, 1895 695,661 Theibault Mar. 18, 1902 1,236,069 Duryea Aug. 7, 1917 2,046,508 Friess July 7, 1936 2,246,086 Austin June 17, 1941 2,419,752 Zumbuhl Apr. 29, 1947 2,755,110 Jacobs July 17, 1956