WO1991015372A1

WO1991015372A1 - Compass with its drawing means maintained automatically perpendicular

Info

Publication number: WO1991015372A1
Application number: PCT/IT1991/000028
Authority: WO
Inventors: Rolando Poeta
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-09
Filing date: 1991-04-08
Publication date: 1991-10-17
Anticipated expiration: 1992-10-09
Also published as: IT9002921A0; IT1244231B; IT9002921A1

Abstract

A characteristic of this compass is that its centering (45, 51, 27, 43) and/or drawing means (53, 13, 61, 38) are automatically maintained perpendicular to the drawing plane (29) notwithstanding any size variations (S1, S2) in the drawn circumferences (7, 10, 11). Said drawing means can be located either on an eccentric adjustment member (22, 21, 37) orbitally movable about an axis (3, 31, 14, 39) parallel to the compas centering axis (40, 35, 401), or on a slider (48) disposed perpendicular to a pivoting (45) bar (44) and made to advance horizontally by screw (50, 48) movements.

Description

Description COMPASS WITH ITS DRAWING MEANS MAINTAINED AUTOMATICALLY PERPENDICULAR

Technical Field

This invention relates to< the field of compasses. As is well known, urrent compasses, with the exception of bean compasses (used for large diameters), consist of two legs hinged together at 5 their upper end by which they are operated, one of their lower ends being used for central pivoting by means of a needle and their other end being used for drawing circumferences by usual means (scribers, pencil leads, pens). As these legs are oblique, the pivoting leg by virtue of rotating

^"10 with its needle oblique tends to dig into the drawing surface and form an inverted conical cavity which besides ruining the drawing sheet results in a loss of accuracy of any further circumferences drawn on that centre, which becomes increasingly deep and large. This obliqueness also creates problems for the drawing leg, these

\5 relating mainly to irregularity of the drawn lines. For example, modern Indian ink pens (rapidograph type) do not write at all if insufficiently perpendicular to the sheet. Even simple leads tend to draw lines which are thicker the greater their inclination. Background Art 0 This is what would happen theoretically. In practice, however, most compasses are able to "counter-incline" both the pivot needle and the support for the drawing member. This facility does not however overcome the problem of having -to (at least theoretically) arrange both the pivot part and drawing part perpendicular to the 5 drawing surface, ie to make two different adjustments for each different circumference to be drawn.

A further drawback of usual compasses is that as the two legs are oblique, the necessary drawing pressure can cause them to diverge, 2 so changing the drawing radius and hence drawing an imperfect circle. An attempt has been made to remedy this drawback by joining the two legs together by means of screw connections to form bow compasses, which can be of small precision size or as large as normal compasses. These bow compasses have however only partly solved the problem, firstly because the complexity of the engaging adjustment members results in a degree of slack which reduces the compass precision, and secondly because the small diameters of the engaging screws make their threads liable to damage because of their inadequacy to resist the stresses caused by the opening and closure of the legs each time a different degree of opening of the compass has to be set. To overcome this latter drawback, use is currently made of reversible long-pitch screws. This however results in ^" considerable component wear because of the large forces resolved by the thread inclination, and which precisely because of this greater inclination leads to greater adjustment slack, unless high-precision machining and high-quality materials are used, with obviously proportional costs. All normal oblique-leg compasses also require a vertical summit pivot for their operation, by which the compass is rotated. This pivot must obviously be maintained symmetrically vertical with respect to the changing inclination of the two legs, the means provided to attain this being always of considerable constructional commitment and cost. The object of the present invention is to overcome the aforesaid Disclosure of Invention This object is attained by a compass of which the centering and/or drawing means, such as scribers or pencil leads or pens, are automatically maintained perpendicular to the drawing plane notwithstanding any variations in the drawn circumferences. Said drawing means can be located either on an eccentric adjustment body orbitally movable about a central compass axis, or on a slider disposed perpendicular to a pivoting bar advanced horizontally by screw movements.

The invention is illustrated by way of non-limiting example on the accompanying drawings, in which: Figure 1 is a schematic representation of the operating principle of an orbital adjustment version;

Figure 2 is a perspective view of an embodiment of a compass of free orbital adjustment;

Figure 3 is a sectional side view of an embodiment of a compass with orbital adjustment effected by a worm;

Figure 4 is a side view of an embodiment of a compass with free orbital adjustment relative to different vertical axes;

Figure 5 is a side view of an embodiment of a compass with transverse linear adjustment; Figure 6 is a plan view of an embodiment of a compass with transverse linear adjustment.

With reference to said Figure 1, a first element 1, extending in a vertical plane, is shown in plan view associated with a second element 2 to which it is pivoted about a vertical axis 3. The first element is provided with a usual knurled top pivot 4 for conventional compass operation. Below the pivot 4, in a coaxial position (and therefore not visible), there is a usual compass centering needle 5. At a point 6 below one end 2A of the second element, there is provided a drawing element spaced by a distance r from the centre represented by the needle 5.

By rotating the two elements 1 and 2, if rigidly joined to each

^~ other, about the centre 5 a circumference 7 of radius r can be drawn. By swivelling the second element 2 relative to the first element 1 about the axis 3 on which they are pivoted, said second element can be positioned aligned with the element 1 as shown by the dashed outline 8. In this manner the point of drawing becomes

10 located from the centre 5 at a distance Rmax, representing the maximum opening of the compass and determining a maximum circumference 9.

This type of adjustment, effected by orbitally moving the drawing element 6 about a pivotal axis 3, enables both the centering axis, 5 identified as the needle 5, and the axis of the drawing element 6, identified as a scriber or a pencil lead or a pen, to be maintained vertical and mutually parallel. This orbital movement results in greater accuracy than conventional adjustment methods as it enables a given radius variation to be obtained by a greater O adjustment movement.

This is shown by the scheme of Figure 1. It will be assumed that the drawing scriber 6 of the element 2 is arranged in a position

6A representing the minimum distance SI from the centre 5 and therefore drawing a circumference 10, and that a traditional

¥> compass is also available and opened to the distance SI. Then to pass from this degree of opening to a degree of opening S2 in order to draw a circumference 11, the traditional compass has to

^" increase its opening between its points by a distance S4, whereas the orbital adjustment compass has to undergo an angular widening such that its drawing element moves through the distance S3, this being clearly greater than S4. Thus if a series of minimum movement forces are applied to both types of compasses for the purpose of widening them, the type with said orbital adjustment is able to more easily attain the desired position because a greater number of such minimum movements are necessary to traverse the greater space involved in orbital adjustment than in normal radial or linear adjustment. This clarification given with reference to Figure 1 is more easily apparent from Figure 2. The compass illustrated is indicated by numerals corresponding to those of Figure 1, and comprises a first element 1', a second element 2', a needle 5', a top pivot 4', a drawing scriber 6', and a pivotal axis 3'. The pivot 4' and the needle 5' have a common axis 40'. Said Figure 2 shows that the elements 1' and 2' are hinged on an axis 3' by a pivot 2B rigid with the second element 2' and a head 1A comprising a hole made elastic by a through cut IB. A usual transverse screw operated by a knob 12 enables the hole to be tightened around the pivot 2B, and thus create friction between these parts until they are completely clamped together. The second element 2' is associated with a graduated disc 2C by which the radius of the circle to be drawn can be exactly set by means of a reference pointer lC. This presupposes that a needle 5' and a drawing element 6', or rather its axis, are in fixed positions on their respective structures.. By way of example, the element 2' is provided to this

^' end with a hole 2D for connecting usual rapidograph pens. With reference to the compass of Figure 3, the orbital adjustment of its drawing means 13 about the axis 14 is achieved by an angular movement deriving from a usual preferably irreversible reduction gear of the worm type, consisting for example of a usual worm 15 (which on the drawing is nearly hidden and is indicated only by four small rectangles representing its ends) engaging a ring gear 16 of perpendicular axis. The worm 15 is rotated by wheels 17 and/or 17A, to cause a certain angular movement of the ring gear 16 fixed on a cylindrical tubular pivot 18 which has flat parallel faces and is rotationally guided by a seat provided in a region 19 eccentric to the compass centering axis 40. Said cylindrical tubular pivot 18 with the outer fixing surface is provided with a foot 18A which enables a radial screw 20 to press against and thus clamp a solid shaft 21 contained coaxially within it. In this manner, each rotation of the ring gear 16 determines an equal rotation of the shaft 21. The degree of friction between these is however adjustable, so that the compass adjustment can be made directly on the shaft 21 itself by moving the eccentric parts rigid with it (rather than moving the wheel 17). These parts can for example consist of a holed plate 22 for mounting rapidograph pens 23. This plate could also be disc-shaped and be graduated in the manner of the disc 20 of Figure 2, to show the drawn radii, using a fixed pointer 24C. The worm 15 is locked axially with precision by two support shoulders 24A and 24B integral with the main body 24 of the compass. The worm is mounted by inserting through it a cylindrical pivot 25 integral with the wheel and comprising flat fixing faces 25. A stem 17A' of the wheel 17A, which is fixed on the pivot 25 and is retained on it by a screw 26, maintains the pivot 25 in its seat. To enable even very small circles to be drawn without having to incline the "points" of the compass (as is currently done), the compass according to the invention uses a needle 27 mounted on a low bracket support 28, close to the drawing surface 29. The bracket 28, especially if metal, can be provided with a needle welded to it such that it just skims the drawing means 13.

The axis 40 of the top pivot 41 passes through the position of said needle. Said bracket is mounted by a usual male-female insertion joint on a portion 24' forming a centering bar. The joint can be formed in various ways, for example by simple parallel side shoulders shown schematically by the dashed line 28' in Figure 3, by which rotation about a screw 30 is impossible. In all cases this joint is effected between sections which prevent any relative rotation between the two parts, and which also allow the bracket 28 to be mounted in the opposite position 28A, to increase the maximum circumference drawable by the compass. The screw 30 helps to fix the two parts securely together. With reference to the sectional view of Figure 4, an orbital adjustment compass is provided with a plurality of holes 31, 32, 33 at different distances from a centering axis 35, and in which there can freely rotate a through pivot 34 provided with a base shoulder 34A or the like, and a projecting threaded head 34B for engagement-by a ring nut 36. By tightening the ring nut 36 the through pivot 34 can be locked not only axially in any one of the possible holes 31, 32, 33, but also locked torsionally to fix it in a certain required angular position. In this respect, as the pivot 34 is fixed to a projecting plate for supporting a drawing element 38, each angular position of the pivot 34 corresponds to a certain set drawing radius on the compass. Using a plate 37 of only small eccentricity, the embodiment of Figure 4 enables large diameter circles to be drawn by inserting its pivot 34 into the most peripheral hole 33. If even larger circles are to be drawn, the plate 37 has merely to be replaced by a longer plate, which therefore allows a greater distance or eccentricity between the drawing element 38 and the axis of the most peripheral hole 33.

It should be noted that again in this version of Figure 4 the centering axis 35 coincides with the axis of a top pivot 42 and passes through the centre point of the circle to be drawn, as defined by a centering needle 43.

The pivot 42, as in the case of the equivalent pivots 4', 41, 46, is integral with the compass body and requires no device for its symmetrical positioning as it is always aligned with the centering or centre needle of the compass.

With reference to Figures 5 and 6, a centering bar structure 44 provided with a needle 45 is associated with a usual top pivot 46. Said structure is also provided with two cheeks 47A and 47B each provided with a horizontal hole of antirotation cross-section conjugate with the cross-section of a threaded shaft 48 which must be able tα slide along an axis 49 but must not be able to rotate about this axis. A preferred section for this function is cylindrical with flat faces in parallel planes. The cylindrical surface of the pivot is threaded with possibly square threads and is engaged by a nut screw 50 in the form of a knurled roller, 5 prevented from moving axially along the axis 49 by the shoulders formed by the flat inner surfaces of the cheeks 47A and 47B, In this manner, on rotating the nut screw 50 the shaft 48 is moved axially in an irreversible manner. On then tightening a ring nut 51 on the threaded end of the shaft 48 the fixed cheek 47A is

10 clamped between the nut screw 50 and the ring nut 51 itself, so that these parts also become fixed or rigid with the structure 44. On the shaft 48 there is fixed a plate 52 which is bent at an angle to vertically fix the drawing means 53 and to obtain a distance 39 which enables the drawing element to reach close to

15 the needle 45, for drawing minimum circumferences. If the tip of the drawing means 53 is required to be very close to the needle 45, the plate must be fixed on the shaft 48 with a certain degree of obliqueness, as can be deduced from the perspective view and to which it is consequently subjected. The extent of this is such

20 that the tip 53A of the drawing element can skim an imaginary line 54 parallel to the axis 49 and passing through the centre point represented by the needle 45, and to slide along the line 54 until it touches the needle 45 (it should be noted that the sizes shown on the drawing are not of the correct proportions for attaining

2.5 this contact, the sizes having been chosen merely for conceptual clarity) .

Claims

Claims 1. A compass characterised by centering means (45, 5', 27, 43) and/or drawing means (53, 13, 6', 38) which are automatically maintained perpendicular to a drawing plane (29) notwithstanding any size variations (SI, S2) in the drawn circumferences (7, 10, 11), which drawing means can be located either on an eccentric adjustment member (22, 2', 37) orbitally movable about an axis (3, 3', 14, 39) parallel to the compass centering axis (40, 35, 40'), or on a slider (48) disposed perpendicular to a pivoting (45) bar (44) and made to advance horizontally by screw (50, 48) movements.

2. A compass as claimed in the preceding claim, characterised by an adjustment member (2', 22, 37) eccentric to an axis (3', 14, 39) which is itself eccentric to an axis (35, 40, 40') defined by the centering engagement of a needle (5', 27, 43).

3. A compass as claimed in the preceding claims, characterised by an adjustment member (2', 37, 22) provided with an eccentric shaft (2B, 21, 34) freely fixable in a desired angular position by friction acting between it and its containing seat, which friction can be set at different values by tightening a screw (12, 20, 36).

4. A compass as claimed in the preceding claims, characterised by an adjustment member (37, 34) housable in different holes (31, 32, 33) of different eccentricity, their axis being essentially parallel to the pivoting axis (35) of the overall compass (Figure 4).

5. A compass as claimed in the preceding claims, characterised by an adjustment member (2', 22) provided with a

^' shaft (2B, 21) which, in order to determine variations in the distance defining the radius of the circumference to be drawn, can be moved angularly by angularly moving a ring gear (16) which is rigid with said shaft and derives its movement via a reduction ~ gear.

6. ' A compass as claimed in the preceding claim, characterised by a reduction gear in the form of a usual gear pair comprising a ring gear (16) and a worm (15), the control for said screw being arranged either parallel (17, 17A) or perpendicular (12) to the 0 pivoting body (24, 1').

7. A compass as claimed in the preceding claims, characterised by a graduated disc (2C, 22) able to show by means of a reference pointer (1C, 24C) the linear distance or radius between the centering needle (5', 27, 43) and the drawing element 5 (38, 13, 6), and proportional to the relative angular movement between the two articulated adjustment parts (1', 2'; 24, 21), said disc being rigid with either the one or the other of said parts under orbital adjustment.

8. A compass as claimed in the preceding claims, 0 characterised by an orbital adjustment (22) shaft (21) rigid with toothed elements (16) for the rigid transmission of adjustment commands via friction means (18, 21; 20).

9. A compass as claimed in claim 1, characterised by a threaded (48B) slider (48) having an anti-rotation cross-section 5 preferably with at least one flat face and guided by holes of conjugate profile, these therefore having an identical flat face (47C, 47C'.) and being provided in two support cheeks (47A, 47B) rigid with the body (44) of the compass, said slider being movable axially by rotating a nut screw (50) which is axially restrained by the opposing inner faces of said cheeks (47A, 47B) and being lockable in the desired position by tightening a ring nut (51) S against the outer surface of one (47A) of said two cheeks.

10. ^"A compass as claimed in the preceding claim, characterised by a slider engaged with a bar (52) bent to such an angle as to enable a drawing element (53) to describe minimum circumferences, by reaching close to a centering needle (45).

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