The present invention relates to improved locking mechanism facilitating the use in the instruments, drawing compasses, dividers and the like in drawing or scribing circles.

Back ground and prior art of the invention

Various drawing compasses are available in the market, but they are not convenient for quick use and user friendly by means of the mechanisms or methods involved thereof, during the axial adjustment of the arms of the drawing compass for fixing exact desired radius and for drawing circle and curve thereof, precisely and finely. The features of the drawing compass that involve in the mechanisms as so mentioned earlier not being user friendly and precise due to their constructional and working technique involved thereof. However intense care is also to be maintained while said drawing compasses have been used.

US Patent No. 2557500 describes an invention relates to drawing compass of the general type having a yieldably mounted spring-urged pivot point for facilitating use of the instrument in drawing or scribing small circles and dotted circles by means of allowing scribing point to rise periodically by reducing the downward manual pressure on the compass handle, the spring urged pivot point remaining in firm contact with the paper. As the scribing point wears, the tube section (22) moves down a little farther over the spring urged pivot point, thus compensating for the wear, making it unnecessary to tilt the compass and avoiding excessive penetration of the pivot point into the paper. However it does not claims about locking and unlocking mechanism to lock and unlock the arms of the compass after fixing the radius by means of axial adjustment of its arms for drawing circle or curve thereof. While the instant invention discloses a drawing compass with novel integrated axial locking system provided for the purpose, as so mentioned ahead.

US Patent No. 3313028 describes an invention relates to improvements in drawing compass, divider and the like which may be readily adjusted to draw circles or arcs of different radii or make measurement by means of an improved finger actuated wheel having tooth like projections that are oriented so as to make it easy to determine the direction of rotation of said wheel for enlarging or reducing adjustments of the compass, divider or the like. For enlarging the radius in this compass, the wheel (22) is rotated by pressing against the abrupt side member (19) or (21), as desired by the user, with the help of thumb and forefinger. And while, one leaves the pressure against said side member, the threaded holes of the member (19) or (21) receive the threaded parts (18) and (20) of the compass adjusting member and thereby the further rotational movement of the wheel (22) is prevented and this results into locking the corresponding arm for further axial movement thereof. However this cited invention still leave the scope for improvement to provide a comfort and user friendly drawing compass with integrated locking system capable of easily and precisely scribe circle reliably for long term use thereof and while the present novel axial locking system provided in the drawing compass in the instant invention fulfils said requirements and overcomes all the aforesaid drawbacks and disadvantages.

Object of the invention

The main object of this invention is to provide an improved locking mechanism for drawing compass. Accordingly, the drawing compass is facilitated with such locking mechanism which is reliable to use for long time purpose. Another object of this instant invention is to provide an improved drawing compass which may be readily adjusted to draw circles or arcs of different radii or make measurement. Accordingly the mechanisms of features embedded in the instrument is adjusted or operated in a delicate manner.

Yet another object of the invention is to provide easy operable, inexpensive, robust and user friendly drawing compass, embedded with improved locking mechanism. Accordingly the features and different integral parts used therein are made up of suitable materials and advanced mechanism engaged with thereof.

Summary of the Invention

The present invention discloses a novel locking and unlocking mechanism for drawing compass by means of axial locking system. Said axial locking system mainly consists of locking assemblies located on both the end of threaded rod and multi start screws, provided in said locking assemblies, enables to lock the arms of drawing compass after fixing the radius and also enables to unlock the arms after the radius of the compass being fixed through the lateral arms of the compass. Detailed description of the drawings

Fig. 1 is a side elevation view of a drawing compass with axial locking system. Fig. 2 illustrates cross sectional view of locking assemblies on right and left hand side of axial locking system.

Fig. 3 illustrates the enlarged cross sectional and perspective view of right side locking assembly during unlocked position.

Fig. 3(a) is a perspective zoomed view of proximal midsection indicated in the fig. 3.

Fig. 3(b) is a perspective zoomed view of distal top section indicated in the fig. 3. Fig. 4 illustrates the enlarged cross sectional and perspective view of right side locking assembly during locked position.

Fig. 4(a) is a perspective zoomed view of proximal midsection indicated in the fig. 4.

Fig. 4(b) is a perspective zoomed view of distal top section indicated in the fig. 4.

Detailed description of the invention

Referred to the drawing, fig. 1 illustrates a drawing compass (16), here shown by way of example, which is of conventional construction except for the locking mechanism provided through axial locking system, as directed in fig. 2 in detail. A drawing compass (16) comprises a pair of adjustable arms (7) and (15). The arm (15) is provided with a member (9) such as a pen or pencil held clamped in one end thereof. While the arm (7) is provided with a pointed member (10) which is held clamped in the corresponding end thereof. The other or inner ends of arms (7) and (15) being hinged inside the bearing member (14) by means of conventional pivoting pin, not shown in the figure. A hand grip (13), which is provided with a knurled surface, is disposed at the top centre portion of the said bearing member (14) for manipulating the compass during the use thereof. Arms (7) and (15) are held against the center wheel screw (11), a part of axial locking system, as directed in fig. 2, located axially beneath said bearing member cap (14); and the spread of the legs is adjusted by an center wheel (12) is rotatably provided on the centre part of said center wheel screw (11). There are two different hands of threading are provided on the threaded rod (11) i.e.; right side part from actuating wheel (12) is provided with a right hand thread and whereas, the other left part thereof is provided with a left hand thread. Thus, by rotating said center wheel, subject to lock and unlock conditions of the locking assembly, part of an axial locking system, and rotating direction of actuating wheel, the arms (7) and (15) are moved either toward each other or further apart, as desired by the draftsman using the compass.

The outer surface of center wheel (12) is knurled and whereas, a series of pointed tooth like projections, either clockwise or counter clockwise being furnished on the inner surface to engage with that of the outer surface of center wheel screw (11). Such an arrangement facilitates relatively fine edges with gaps there between which the draftsman may engage with a thumb and forefinger to provide small and accurate adjustments for enlarging or reducing the radius of the compass by rotation of the actuating wheel (12).

Axial locking system, as directed in fig. 2, operably connected beneath the bearing member cap (14) and said locking system comprises center wheel screw (11), furnished with actuating wheel (12) at its axially centre location, and locking assemblies (8) and (8') at the end portions of said center wheel screw (11). Axial locking system has been connected with the drawing compass through a hinge connection between the arms of the compass and locking assemblies (8) and (8') at respective end portions of the center wheel screw(ll). Locking and unlocking of arms (7) and (15) through locking assemblies (8) and (8'), during compass operation thereof for enlarging or reducing the radius can be explained with the help of fig. 3 and 4.

As directed in fig. 2, locking assembly (8) on the right side of center wheel (12) consists of multi start threaded screws such as, a substantially cylindrical with hollow interior multi start nut (17) that is located proximally from that of center wheel; centrally hollow, a cylindrical with hollow interior shaped threaded lock nut (19) which is located distally from said center wheel (12) and a multi start check nut (18) which is located axially inner side of said hollow interiors of the multi start nut (17) and multi start lock nut (19) and on the periphery of center wheel screw (11). While, constructionally in the like manner, the locking assembly (8') on the left end of threaded rod (11) consists of multi start nut (17a), multi start check nut (18a) and multi start lock nut (19a).

As directed in fig. 3, 3(a) and 3(b), during the fine and accurate adjustment of the arms (7) or (15), for free movement of or unlocking arm (7), one has to turn the threaded lock nut (19) of the locking assembly (8) in counter clockwise direction to dispel the contact or meet edges (20) and (21) of multi start nut (17) and multi start lock nut (19) respectively in mutually opposite direction to each other, and hence pushing multi start check nut (18) thereof, on right hand side, in axial direction so as to allow rotational movement of actuating wheel (12) for axially enlarging or reducing the arm (7) to scribe a circle or curve. Same is the provision applied for unlocking and free movement of arm (15) through locking assembly (8').

As directed in fig. 4, 4(a) and 4(b), subsequent to fine and accurate adjustment of the arm (7) or (15), to fix or lock the arm (7) for the desired radius, multi start lock nut (19) is rotate in clockwise direction for being caused to fully rest/touch the meet or contact edge (20) of the multi start lock nut (19) on to the meet or contact edge of the multi start nut (17), thereby pulling multi start check nut (18) on left hand side, in axial direction to prevent rotational movement of actuating wheel (12) and eventually to scribe secured circle or curve thereof by the drawing compass (16). Same provision is applied to locking the arm (15) through the locking assembly (8').

Hence by recapitulating the above process, it can be shown that, in unlocked position of the drawing compass, contact or meet edges of the threaded lock nuts (19) and (19a) of locking assembly (8) and (8') respectively, do not touch contact or meet edge or edges of multi start nuts (17) and (17a) respectively, by turning multi start lock nuts (19) and (19a) in counter clockwise directions as shown in the fig. 3(b), thereby pushing multi start check nuts (18) and (18a) respectively as directed in fig. 3(a), in axial direction so as to allow rotational movement of actuating wheel (12), subject to unlock status of the locking assembly (8) or (8'), in clockwise or anticlockwise direction and thereby axially extending or reducing the arms (7) or (15) for fine and accurate adjustment of the radius thereof.

While in locked position, said contact face or edge of the multi start lock nuts (19) and (19a) of locking assembly (8) and (8') respectively, fully rest (touch) the contact or meet edges of the multi start nuts (17) and (17a) by turning said multi start lock nuts (19) and (19a) in clockwise direction as direction in fig. 4(b), thereby pulling multi start check nuts (18) and (18a), on left and right hand side respectively as directed in fig. 4(a), in axial direction so as to prevent rotational movement of actuating wheel (12) for preventing further adjustment of the arms (7) and (15) of the drawing compass.