GB2084937A

GB2084937A - Drawing instrument

Info

Publication number: GB2084937A
Application number: GB8032682A
Authority: GB
Original assignee: Helix International Ltd
Current assignee: Helix International Ltd
Priority date: 1980-10-09
Filing date: 1980-10-09
Publication date: 1982-04-21
Also published as: GB2084937B

Abstract

A drawing instrument has a leg 1 provided at its lower end 1 a with a pointed element 2 fixed in a hole 11 extending obliquely of the leg between an upper rear mouth 12 in a laterally offset shouldered face 10 and a lower front mouth 13 in the lower end face 14 of the leg 1. The pointed element 2 is fitted by inserting it point-first into the rear mouth 12 and forcibly driving it through the hole 11 with a tool until the tip of its pointed end 2b projects through front mouth 13 and beyond lower end face 14. In this final position the pointed element 2 is held in place frictionally. Part of the pointed end 2b may remain shielded within the hole 11 and the extent of projection of the point can be readily controlled. The point-first insertion facilitates assembly and guidance of the pointed element 2 during production. <IMAGE>

Description

SPECIFICATION Drawing instrument This invention relates to a drawing instrument of that kind (hereinafter called "the kind referred to") having at least one leg having at one end an inserted fixed pointed element, one of opposite ends of said element being pointed and the other being unpointed. The invention may be applied, for example, to a drawing compass comprising a leg having an inserted fixed pointed element at one end and pivoted at its other end to one end of an arm carrying at its other end means for holding, for example, a pencil or a pencil lead. The invention may also be applied, for example, to dividers comprising a leg having an inserted fixed pointed element at one end and pivoted at its other end to one end of a second leg having at its other end a second inserted fixed pointed element.

In a conventional known method of manufacturing drawing instruments of the kind referred to there is provided in outer end of the or each leg of the instrument a blind hole into which the unpointed end of the, or the respective, pointed element is inserted.

According to the invention, in a method of producing a drawing instrument of the kind referred to the or each leg which is to be provided with the, or the respective, pointed element is provided at its outer end with a through hole having a rear mouth (which is upwardly presented when the leg is in an upstanding position of use) and a front mouth (which is downwardly presented when the leg is in an upstanding position of use), said hole extending from said rear mouth to said front mouth, and the, or the respective, pointed element is inserted point-first into the said rear mouth of said hole and is forced through said hole until the pointed end of said element projects out beyond the front mouth of the hole.Advantages of this method compared with the aforesaid conventional method are: (1) the method in accordance with the invention can give much improved guidance for the pointed element during assembly and the pointed element can require far less pressure to insert; (2) in the method in accordance with the invention the extent to which the pointed end projects beyond the leg can be fully controllable; (3) in the method in accordance with the invention the extent to which the pointed element projects beyond the leg can be arranged to be considerably less than in the case of instruments produced in accordance with the conventional method, and thereby can provide an advantage from a safety aspect, especially when the instrument is to be used by children.A method in accordance with the invention can enable there to be produced an instrument in which part of the point itself of the pointed element remains within the hole so that only the tip of the point projects beyond the front mouth of said hole. The or each leg which is to be provided with the, or the respective, pointed element may be formed with a widened outer end, with the through hole for receiving the pointed element arranged to extend through said widened portion in a direction oblique to the longitudinal direction of a main intermediate portion of the leg.

The invention also includes in its scope a drawing instrument when produced by the aforesaid method according to the invention.

Also, according to the invention, there is provided a drawing instrument which is of the kind referred to and which is a drawing compass comprising a leg having a pointed element at its outer end and pivoted at its other end to one end of an arm comprising a shank provided at its other end with a stub or barrel which is provided with a socket hole for receiving a pencil or the like and which is provided with an external screw thread engaged by a clamping nut or ring for clamping the pencil or the like in place in the socket, characterised in that said outer end of the leg is provided with a through hole having a rear mouth (which is upwardly-presented when the leg is in an upstanding position of use) and a front mouth (which is downwardly presented when the leg is in an upstanding position of use), in that said pointed element is fixed in said hole so that its pointed end projects out beyond the said front mouth of the hole, and in that the arrangement is such as to enable the pointed element to be installed by inserting it point-first into the rear mouth of said hole and then forcing said element through the hole until the pointed end of the element projects out beyond the front mouth of the hole.

In the accompanying drawings, which illustrate, by way of example, an embodiment constructed in accordance with the invention: Figure 1 shows a drawing compass constructed in accordance with the invention; Figure 2 is a cross-section on the line ll-ll, Fig. 1; and Figures 3 and 4 are fragmentary views illustrating diagrammatically two stages in a method of installing a pointed element of the compass shown in Fig. 1.

Referring to the drawings, a drawing compass comprises a die-cast leg 1 carrying a circular-sectioned pointed element 2 at its outer end and pivoted at its other end, by a pivot screw 3, to one end of a shank 4 of an arm 5, said shank 4 carrying at its other end an integral laterally-projecting stub or barrel 6 provided with a socket hole 7 for receiving a pencil or the like and also provided with an external screw thread 8 engaged by a clamping ring 9 for clamping the pencil or the like in place in the socket hole.

The outer end of the leg 1 is shown at 1 a and is of widened form whereby to provide the leg 1 with a portion which is laterallyoffset from the main portion of the leg and which has an upwardly-presented face 10 forming a shoulder. Said outer end 1 a of the leg is provided with a circular-sectioned through hole 11 having a rear mouth 12, at said shoulder 10, and a front mouth 1 3 in an end terminal face 14 of the leg, said hole 11 extending, obliquely to a main intermediate portion 1 b of the leg, through the widened portion I a of the leg from said mouth 1 2 to said mouth 1 3. The pointed element 2 is fixed in the hole 11 by friction created by a calculated push fit, and said element has an unpointed rear end 2a which, in the embodi ment shown, terminates flush with the shoulder 10, and a conically-tapering pointed front end 2b projecting out beyond the terminal face 14 of the leg.

The pointed element 2 is installed in the leg 1 by inserting said element 2 point-first into the rear mouth 1 2 of the hole 11 so that the pointed end 2b of the element 2 locates within the rear portion of the hole 11 as shown in Fig. 3, and then by a punch 15, or other suitable tool, applied as shown in Fig. 4 to the rear end 2a of the element 2, forcing the element 2 through the hole 11 until the pointed end 2b of the element 2 projects out beyond the face 14 of the leg. This installation can be carried out by a bench machine under the control of an operator, or can be suitably automated.In the arrangement shown the forcing operation ceases when the punch 1 5 strikes against the shoulder 10 and the rear extremity of the unpointed rear end 2a of the element 2 is flush with the said shoulder 10, in which position the rearmost portion of the conically-tapering front end 2b of the pointed element 2 is still inside the hole 11, only the foremost or tip portion of said conically-tapering end 2b projecting out beyond the leg 1. Thus only a short portion, for example 3.5 mm long, of the element 2 projects out beyond the leg 1, the shortness of this projecting portion being advantageous from the safety aspect.

The shoulder 10 in effect constitutes a control abutment for controlling the extent to which the element 2 projects out beyond the leg 1. In the embodiment shown, the forcing operation ceases, as mentioned, when the rear extremity of the rear end 2a of the element 2 is flush with the shoulder 10, but if desired the punch 1 5 can be of such form (for example be provided with a spigot which can enter the hole 11) that it does not strike the shoulder 10 until the said rear extremity of the end 2a is some distance inside the hole 11, or can be of such form (for example provided with a socket for loosely fitting over the rear end 2a) that it strikes the shoulder 10 whilst the extremity of the rear end 2a is still projecting rearwards from the rear mouth of the hoe 11.

Because the pointed element is inserted point-first into the leg, there results a muchimproved guidance of the element during assembly, compared with the known conventional method of inserting a pointed element, because during the initial stage of the pointfirst insertion the pointed end of the element forms a lead for centralising the element before the actual forcing operation commences.

In another exemplary embodiment (not shown) in accordance with the invention, the drawing instrument is in the form of dividers having two legs pivoted together at their inner ends with each leg being constructed, and provided with a pointed element inserted point first, in exactly the same way as in the case of the leg 1, with pointed element 2, shown in the drawings.

Claims

1. A method of production of a drawing instrument of the kind referred to having at least one leg provided at its outer or lower end with an inserted fixed pointed element, said method comprising forming the outer or lower end portion of said leg with a through hole extending between a rear mouth which is upwardly presented when the leg is in an upstanding position of use and a front mouth which is downwardly presented when the leg is in said upstanding position of use, inserting said pointed element point-first into said hole through said rear mouth, and displacing said pointed element axially through said hole into an operative final position in which at least the tip of the pointed end thereof projects out beyond said front mouth.

2. A method as claimed in claim 1, wherein the extent to which said pointed element is displaced axially through the hole is such that in the operative final position a part or portion of the pointed end of said element still lies in shielded relationship within the hole adjacent said front mouth thereof.

3. A method as claimed in Claim 1 or 2, wherein the pointed element has a circular cross-section terminating in said pointed end at its lower end which has a conically tapering form.

4. A method as claimed in any of Claims 1 to 3, wherein the extent to which said pointed element is displaced axially through the hole is such that in the operative final position the upper end of said pointed element, opposite to said pointed end, lies flush with said rear mouth or within the hole adjacent said rear mouth.

5. A method as claimed in any of the preceding claims, wherein said hole for receiving the pointed element is formed so as to extend axially in an inclined or oblique direction to an adjacent main intermediate portion of the leg.

6. A method as claimed in any of the preceding claims, wherein said outer or lower end portion of the leg has a widened form providing a laterally offset part through which extends the hole for receiving the pointed element.

7. A method as claimed in any of the preceding claims, wherein the pointed element engages within the hole in close-fitting relationship and is forcibly driven by a tool into said operative final position wherein it is held frictionally.

8. A method as claimed in Claim 7, wherein the rear mouth of said hole opens through an external face of the outer or lower end portion of the leg which face lies perpendicular to the axis of said hole.

9. A method as claimed in Claim 8, wherein said face forms a shoulder which is utilised as an abutment or limit stop for engaging a tool used in forcing the pointed element through the hole thereby to control the extent to which the pointed element is displaced therein in said final operative position.

1 0. A method as claimed in any of the preceding claims, wherein the front mouth of said hole opens through an external end face of the outer or lower end portion of the leg which end face lies perpendicular to the axis of said hole.

11. A method of production of a drawing instrument substantially as herein described and illustrated with reference to the accompanying drawings.

12. A drawing instrument produced by a method as claimed in any one of the preceding claims.

1 3. A drawing compass, being a drawing instrument of the kind referred to, having a leg fitted with a pointed element at its outer end and pivoted at its other end to one end of an arm comprising a shank provided at its other end with a stub or barrel which is provided with a socket hole for receiving a pencil or the like and which is provided with an external screw thread engaged by a clamping nut or ring for clamping the pencil or the like in place in the socket, characterised in that said outer end of the leg is provided with a through hole having a rear mouth (which is upwardly-presented when the leg is in an upstanding position of use) and a front mouth (which is downwardly presented when the leg is in an upstanding position of use), in that said pointed element is fixed in said hole so that its pointed end projects out beyond the said front mouth of the hole, and in that the arrangement is such as to enable the pointed element to be installed by inserting its pointfirst into the rear mouth of said hole and then forcing said element through the hole until the pointed end of the element projects out beyond the front mouth of the hole.