US1201209A - Instrument for drawing circles. - Google Patents

Description

1. H. McMURRAY.

INSTRUMENT FOR DRAWING CIRCLES.

APPLICATION FILED OCT- 22, 1914.

1,201,209. Patented Oct. 10, 1916.

2 SHEETS-SHEET I.

Due/1751' I. H. McMURRAY.

INSTRUMENT FOR DRAWING CIRCLES.

APPLICATION FILED OCT- 22, 19M.

Patented Oct; 10, 1916.

2 SHEETS-SHEET 2.

barren s'rarns PATENT orrrlcn. 4'

JOHN H. MOMURRAY, OF SOHENECTADY, NEW YORK, ASSIGNOR OF ONE-HALF 'IO JOHN T. GORMAN, OF COI-IOES, NEW YORK.

INSTRUMENT FOR DRAWING CIRCLES.

Application filed October 22,

To all whom it may concern:

Be it known that I, JOHN H. MGMURRAY, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented new and useful Improvements in Instruments for Drawing Circles, of which the following is a specification.

My present invention relates to instruments for drawing circles or arcs and is an improvement upon instruments of the class shown and described in my prior Patents 951,255 and 1,005,992, granted March 8, 1910, and October 17, 1911 respectively.

I The primary objects of the invention are, to provide simple and improved means for operating the scribing point, to provide improved means whereby the scribing point is caused to bear upon the surface during the scribing operation and to lift or disengage therefrom when the scribing of the circle or a desired arc thereof has been completed, to provide means whereby the pressure of the scribing pointupon the surface may be regulated, and to provide means whereby the scribing point will operate with uniform pressure although the'operating means may be out of perpendicular to the surface upon which the circle or an arc thereof is to be drawn.

To these and other ends, the invention consists in certain improvements, combinations and arrangements of parts, all as will be hereinafter more fully described, the features of novelty being pointed out particularly in the claims at the end of the specification.

In the accompanying drawings, Figure 1 is a perspective view of an instrument constructed in accordance with the present invention. Fig. 2 represents a central, longitudinal section of the instrument with the parts in readiness for the scribing operation. Fig. 3 represents a central, longitudinal section through the instrument in a plane perpendicular to the section represented by Fig. 2 and showing the parts in the positions they occupy after the scribing operation has been completed. Fig. 4; represents a transverse section on the line 44: of Fig. 2. Figs. 5 and 6 are detail perspective views of the socket and the beam holding-f-raine respectively. Fig; 7 represents a Specification of Letters Patent.

Patented Oct. 10, 1916. 1914. Serial No. 868,086.

transverse section on an enlarged scale and takeno-n the line 77 of Fig. 2. Fig. 8 represents a section on the line 8-8 of Fig. 2; and Fig. 9 represents a section on the line 99 of Fig. 2.

Similar parts are designated by the same reference characters in the several views.

The present invention. is particularly applicable to instruments for drawing circles of the type shown and described fully in my prior patents above mentioned, and the im-v provements are shown and will be hereinafter described as applied to an instrument of that type. It will be understood, however, that the invention is not restricted to instruments of that particular type and also that the invention is not restricted to the particular construction shown, as equivalent constructions within the scope of the claims are contemplated.

In the present instance, the device embodies a base 1 adapted to bear upon the surface on which the circle or an are thereof is to be drawn. As shown, it embodies a rim 2 having a ring .3 of rubber secured thereto and adapted to bear frictionally upon the surface on which the circle is to be scribed. As the base of the instrument is to be placed at the center of the circle or are to be drawn, it'is preferable to provide an index or pointer i which is in alinement with the center of the instrument and is adapted to be placed at the center of the circle or arc. On the base is mounted a socket member 5 which receives the member or beam which carries the scribing point. In the present instance, this socket member istubular, it having a bottom 6 which is pivotally connected to the base 1. struction shown, the indeX or pointer 4 is utilized as a pivot connecting the base to the socket. A pair of pivot arms 6 project from one side of the socket member and the latter is formed with openings 7 and 8 in diametrically opposite sides thereof to receive a beam carrying member 9. The latter is pivoted at one end to the laterally projecting arms 6 which are located at one side of the center of the instrument. In order to enable the pivotal center of the member In the con-' 9 to be set at different distances from the centerofthe instrument and thereby vary the pressure of the scribing point as Will hereafter appear, the arms 6 are formed with a plurality of spaced apertures 10 to receive the pivot pins 11. The member 9 has a generally rectangular cross section and is hollow.

One end 12 of the member has an aperture 13, and the opposite end of said member 1s provided with a socket 14c whlch contains an aperture 15 corresponding to the aperture 13. The beam 16 or arm which carries the scribing point is adapted to be inserted in the apertures 15 and 13 and is slidable long1- tudinally in these apertures, in order that the distance of the scribing point from the center of the instrument may be varied in accordance with variations in the radii of the circles or arcs to be drawn. In the construction shown, the beam 16 is substantially round in cross section, and in order to avoid turning of the beam in the socket 141:, the latter is provided with a key 17 which is adapted to slide longitudinally in a keyway 18 formed in the beam. Preferably, the socket 1a is swiveled on the frame of the member 9 in order that the beam 16 may be swung into a position at one side or in parallelism with the body of the instrument when the same is not in use. In the construction shown, the socket is mounted on a frame 9 by the pivot 17 at one side and a screw 18 at the opposite side, the screw 18 also serving as a clamp to secure the beam 16 in different adjusted positions. The outer end of the beam is provided with means for holding an appropriate scribing point. In

the construction shown, it is provided with,

a clip or holder for a stick of chalk, the clip or holder embodying a pair of segmental jaws 19 and 20 which are adapted to receive the chalk between them, and these jaws are carried by the resilient or springy arms 21 and 22 which proceed from the outer end to the beam. A ring 23 is movable longitudinally along the arms 21 and 22 and thereby operates to force the jaws together to clamp the chalk or to release the jaws and permit opening thereof. The opposite end of the beam which can be a hollow metal tube is preferably filled with suitable material to form a counterbalance 24 to compensate for the weight of the chalk and its holder.

A tubular casing or sleeve 25 is fitted in the upper end of the socket member 5 in such a manner that it may have a limited and axial movement relatively to the socket member and may also have a tilting motion relatively thereto. In the construction shown, the socket member is formed with longitudinal slots 26, and the lower end of the casing or sleeve 25 carries pins and screws 27 arranged to operate in the slots 26 to permit the movements just described. The lower end of the casing or sleeve 25 is also surrounded by a sleeve 28 which expanded outwardly from the sleeve or casing 25 and fit into an interior annular groove 30 in the sleeve 28. The interior of the sleeve 28 is preferably formed with an incline 31 which will operate to contract the tongues 29 as the sleeve 28 is moved into position, these tongues thereupon expanding within the groove 30 and thus retaining the sleeve .in proper position. The casing or sleeve 25 contains a spiral member 32 which constitutes part of the means for operating the scribing point. I referably, this spiral member is composed of a strip of metal which is fiat in cross section and is twisted on its longitudinal axis. As shown, the lower end of the spiral member is fixed to the casing or sleeve 25 by a stem 33 on the lower end thereof which is threaded or otherwise secured to a part 34: which latter is secured immovably to the bottom of the casing or sleeve 25. The upper end of the spiral member 32 is secured to a follower 35 which latter is adapted to slide freely within a hollow or tubular plunger 36, the latter telescoping or moving longitudinally within the casing or sleeve 25. The plunger 36 has a handle or knob 37 at its outer or upper end for operating it and is provided at its lower or inner end with a clutch which operatively connects the plunger 36 to the casing or sleeve 25 and its related parts when the plunger is forced inwardly and which permits withdrawal of the plunger without causing relative rotation between the casing or sleeve 25 and the plunger. In the construction shown, a clutch member 38 is fixed l within the plunger 36 and has ratchet teeth 37 thereon adapted to cooperate with companion ratchet teeth formed on the cooperating clutch member 38, the latter being revolubly mounted within the plunger 36 and is yieldingly held in cooperative relation with the clutch member 38 by a compression spring 39. The movable clutch member 38 is provided with a pair of rollers 40 which are adapted to travel along the fiat sides of the spiral member 32 as the plunger is operated, the ratchet teeth of the clutch members being then engaged and as the handle 37 is held from turning during the working stroke of the plunger, the rollers 40 will maintain their aXes in a fixed direction, and the spiral member 32 passing be tween them to be rotated, and the rotation of the spiral member will be transmitted to the socket member 5 and thence through the frame 9 to the beam causing the scribing point to rotate about the pointer 4' as an aXis.

According to the present invention, the scribing point is caused to bear with the desired degree of pressure upon the surface on which the circle or are thereof is to be drawn and means is also provided for tilting or disengaging the scribing point from such surface when. the circle or the desired arc thereof has been drawn. In the construction shown, a compression spring 42 is fitted in the lower portion of the socket member 5 and bears upwardly or against the. under side of the member 9 tending to swing the same upwardly about its axis and to thereby lift or disengage the scribing point or chalk. Means is also provided for exerting a yielding pressure on the member 9 tending to lower it and thereby engage the scribing point with the surface. As shown, a spring seat l3 is placed below the part 34 and has a stem 4A which is centered in a socket 45 formed in the stem 33 and a bow spring i6 is interposed between the spring seat as and the part 3th. The spring seat 43 is adapted to bear downwardly on the beam carrying member 9. In order to vary the degree of such pressure, a movable fulcrum l7 is provided which is adapted to be ad justed in a direction toward or from the pivotal center of the beam carrying member by a screw 48 which is journaled in a pair of lugs 49 and 50 which may be struck up from the top of the beam carrying memher 9. This provides a close adjustment for the pressure of the scribing point and a greater degree of adjustment can be obtained by shifting the pivotal center of the beam carrying frame. In order to avoid squeaking or vibration of the scribing point or chalk during the scribing operation, the same is inclined as shown, whereby the chalk or scribing point has a dragging movement over the board or surface on which the circle is to be drawn.

In operation, the instrument is applied to a blackboard or other surface by placing the index or pointer 4: at the center of the circle or are and then the operator presses the sleeve 28 toward the board or surface, thus operating to force the sleeve or casing into the socket member 5 and thus pro ducing pressure between the spring seat 43 and the fulcrum l7 to a degree sufficient to overcome the effect of the spring 42 and to move the chalk or scribing point into engagement with the board or surface. The plunger 36 is then forced inwardly and the member 32 and its cooperating parts convert the longitudinal movement of the plunger into rotary motion to swing the beam and the scribing point about the pointer 4 of vthe center, thus scribing a circle or any desired arc of the circle. incident to the inward thrust of the plunger serves to maintain a pressure upon the spring seat 43 and the latter operates yieldingly and uniformly to press the chalk or scribing point upon the surface. When the circle or the .desired-- arc thereof has been Part of the force completed, the pressure of the plunger is relicved and the spring 42 will then act to lift or disengage the chalk or scribing point from the board or surface.

Having fully described my invention, I claim v 1. An instrument for drawing circles comprising a base, a beam rotatable thereon and carrying a scribing point, a member movable axially of the beam, means for converting the axial movement of said member into rotary movement to rotate the beam, and means operative by pressure incident to such axial movement of said member to press the scribing point upon the surface on which the circle is to be drawn.

2. An instrument for drawing circles comprising a base, a beam rotatable thereon and carrying a scribing point, an operating member movable in the direction of the axis of rotation of the beam, means operative by such movement of said member to rotate the beam, means also operative by such movement of said member to press the scribing point upon the surface on which the circle is to be drawn, and means for disengaging the scribing point from said surface.

3. An instrument for drawing circles comprising a base, a beam rotatable with respect thereto and carrying a scribing point, an operating member movable in the direction of the axis of rotation of said beam, means operative by said member to rotate the beam, means also operative by the axial movement of said member to press the scribing point upon the surface on which the circle is to be drawn, and means acting in opposition to the means first mentioned for disengaging the scribing point from said surface.

4. An instrument for drawing circles comprising a base, a beam rotatable thereon and carrying a scribing point, means acting yieldingly to hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, and means movable in the direction of the axis of rotation of the beam and operative by pressure applied thereto to rotate the beam and capable of overcoming the force of said yieldingly acting means to press the scribing point upon.

said surface.

5. An instrument for drawing circles, comprising a base, a beam rotatable thereon and carrying a scribing point, means acting yieldingly to hold the scribing point, in disengaged relation to the surface on which the circle is to be drawn, a member movable toward the, beam by pressure applied thereto, means operative by the pressure applied to said member to rotate the beam, and means operative by pressure applied to said member to press the scribing point upon said 'sllrfae- I r 6. An instrument for drawing circles comprising a base, a beam rotatable thereon and carrying a scribing point in disengaged relation to the surface on which the circle is to be drawn, a device for initially engaging the scribing point with said surface, and means movable toward the beam and operative by pressure appliedthereto to rotate the beam and to maintain the scribing point in engagement with said surface.

7. An instrument for drawing circles comprising a base, a beam rotatable thereon and carrying a scribing point, means acting yieldingly to hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, a member movable by the application of force thereto in a direction toward the base, means for converting such movement of said member into motion to rotate the beam, and means operative by the pressure applied to said menr her to yieldingly press the scribing point upon said surface.

8. An instrument for drawing circles comprising a base, a beam rotatably and tiltably mounted thereon and carrying a scribing point, means acting yieldably to tilt the beam and hold the scribing point in disengaged relation to the surface upon which the circle is to be drawn, and means including a plunger movable toward the base and operatively connected to the beam to rotate the latter and also including means acting on the beam to maintain the scribing point in engagement with said surface in opposition to said yieldingly acting means.

9. An instrument for drawing circles comprising a base, a beam rotatably and tiltably mounted thereon and carrying a scribing point, means acting yieldably to tilt the beam and hold the scribing point in disengaged relation to the surface upon which the circle is to be drawn, and means including a plunger movable toward the base and oper-atively connected to the beam to rotate the latter and also including a pressure transmitting member acting on the beam in opposition to said yieldingly acting means to maintain the scribing point in engagement with said surface and means for adjusting said pressure transmitting member to vary the degree of pressure so exerted by the scribing point on said surface.

10. An instrument for drawing circles comprising a centering base, a socket rotatable thereon, a beam carrying a scribing point, a frame connected to the beam and tiltably mounted on said socket, a spring in the socket acting on said frame to yieldingly hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, and means including a plunger movable toward the base and operated to rotate the beam and also to bear on said frame in opposition to said spring and there- I by maintain the scribing point in engagement with said surface.

11. An instrument for drawing circles comprising a centering base, a socket rotatable thereon, a beam carrying a scribing point, a frame connected to the beam and tiltably mounted on said socket, a spring in the socket acting on said frame to yieldingly hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, and means including a plunger movable toward the base and operated to rotate the beam and also to bear on said frame in opposition to said spring and thereby maintain the scribing point in engagement with said surface and carried by and adjustable relatively to said frame for varying the effective force of pressure of the plunger on said frame.

12. An instrument for drawing circles comprising a centering base, a socket rotatable thereon, a beam carrying a scribing point, a frame connected to the beam and tiltably mounted on said socket, a spring in the socket acting on said frame to yieldingly hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, and means including a plungcr movable toward the base and operated to rotate the beam and also to bear on said frame in opposition to said spring and thereby maintain the scribing point in engage ment with said surface, the axis on which said frame tilts being adjustable to vary the pressure of the scribing point on said surface.

13. An instrument for drawing a circle comprising a centering base, a socket rotatable thereon, a. beam carrying a scribing point, a frame connected to the beam and tiltably mounted on said socket, a spring in the socket acting on said frame to yield-- ingly hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, and means including a plunger movable toward the base and operated to rotate the beam and also including a fulcrum on said frame arranged to receive pressure from said plunger in opposition to said spring and thereby maintain the scribing point in engagement with said surface, said fulcrum being shiftable relatively to said frame to vary the point of application of pressure by the plunger on said frame and to thereby vary the pressure of the scribing point on said surface.

14. An instrument for drawing circles, the combination of a centering base, a socket rotatable thereon, a beam carrying a scribing point, a frame tiltably mounted on said socket and cooperative with the beam, a spring acting on said frame to yieldingly hold the scribing point in disengaged relation to the surface on which the circle is to be drawn, a sleeve movable axially of said socket, a plunger reciprocable in said sleeve toward the base, means for transmitting the thrust of said plunger through said sleeve to said frame'to maintain the scribing point in engagement with said surface, and means for connecting the movement of said plunger into rotatable movement of the beam.

15. An instrument for drawing circles comprising a centering base, a beam rotatable thereon and carrying a scribing point, and means including a plunger movable toward the base for rotating the beam and also including means for maintaining the scribing point in engagement with the sur face on which the circle is to be drawn by pressure transmitted thereto incident to the movement of the plunger toward the base, said last mentioned means being capable of adjustment from the axis of rotation of the beam.

16. An instrument fordrawing circles comprising a centering base, a beam rotatable thereon and carrying a scribing point, and means for rotating the beam embodying a plunger movable toward the base, a spiral member flat in cross section and operatively connected to the beam, and rollers carried by the plunger and cooperative with the fiat sides of said spiral member.

In testimony whereof I have hereunto set any hand in presence of two subscribing Witnesses.

JOHN H. MQMURRAY. lVitnesses WVALTER D. GooDALE, FRANK E. GOODALE.

copies of this patent may be obtained for five cents each, by addressing the commissioner of latenti,

Washington, D. G. I

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