Drafting machine scale locking device

Claim 2

In a drafting machine comprising a protractor head including an outwardly extending arm member adapted to receive and firmly engage the chuckplate of a drafting scale, the improvement comprising means for establishing a rigid yet readily disengageable connection between said arm member and said drafting scale chuckplate, said improvement comprising: a. a protractor head arm member having defined therein a tapered longitudinal channel; b. means rendering at least a portion of said arm member laterally yieldable whereby a lateral moment of force applied outwardly at the sidewalls of said channel results in an expansion of the normal width of said channel; and c. retainer means adapted to removably engage the lateral edges of said arm member and immobily contain the expandability of said channel against said lateral force moment, whereby during such engagement of said retainer means insertion into said tapered channel of a like-tapered drafting scale chuckplate effects a rigid wedge-fit union between said chuckplate and said arm member, and upon disengagement of said retainer means said channel expands in its lateral dimension in response to the force exerted at its sidewalls by the taper of said chuckplate, thereby effecting a release of said chuckplate from said wedge-fit union.

Claim 3

The improvement according to claim 1 wherein said arm member comprises a generally flat elongate plate having a channel therein tapering outwardly to the free end of said arm member, the body of said arm member being split intermediate the sidewalls of said channel for a substantial distance from said free end thereby rendering at least that portion of said arm member immediate its free end laterally yieldable to force applied outwardly at the sidewalls of said channel.

Claim 4

The improvement according to claim 2 wherein said arm member comprises a relatively thin rectilinear plate of substantial width between parallel side edges and wherein said retainer means comprises a rigid channel member having parallel inner sidewall portions, said channel member being dimensioned to laterally span and closely engage said arm member side edges at the respective inner surfaces of said channel member sidewall portions.

Claim 5

The improvement according to claim 3 wherein said channel member is hingedly attached to said arm member for reciprocal movement into and out of said engagement with said arm member side edges.

Claim 6

The improvement according to claim 3 wherein said retainer means comprises a body portion affixed to said arm member and wherein said channel member is hingedly attached to said body portion for reciprocal movement into and out of said engagement with said arm member side edges.

Claim 7

In a drafting machine having a protractor head, the improvement In means for detachably affixing a drafting scale to said protractor head comprising: a. an arm member attached to said head and extending therefrom, said arm member comprising a relatively thin rectilinear plate of substantial width between its side edges having defined therein at one of the wider faces thereof and intermediate said side edges an open longitudinal channel tapering outwardly to the free end of said arm member, said arm member being longitudinally divided intermediate the sidewalls of said channel for a substantial distance from said free end, thereby rendering at least that portion of said arm member immediate said free end laterally yieldable to force applied outwardly at the sidewalls of said channel; and b. retainer means adapted to reciprocally engage and disengage said arm member side edges and immobily contain said arm member against laterally yielding to said outwardly applied force, whereby during such engagement of said retainer means insertion into said tapered channel of a drafting scale chuckplate of matching taper effects a rigid wedge-fit union between said chuckplate and said arm member, and upon disengagement of said retainer means said arm member is rendered capable of laterally yielding to the force applied outwardly at the sidewalls of said channel by the taper of an inserted chuckplate, thereby allowing a lateral expansion of said channel and release of said chuckplate from said rigid wedge-fit union.

Claim 8

In a drafting machine having a protractor head, the improvement In means for detachably affixing a drafting scale to said protractor head comprising: a. an arm member attached to said head and extending therefrom, said arm member comprising a relatively thin rectilinear plate of substantial width between its side edges having defined therein at one of the wider faces thereof and intermediate said side edges an open longitudinal channel tapering outwardly to the free end of said arm member, said arm member being longitudinally divided intermediate the sidewalls of said channel for a substantial distance from said free end, thereby rendering at least that portion of said arm member immediate said free end laterally yieldable to force applied outwardly at the sidewalls of said channel; and b. retainer means adapted to reciprocally engage and disengage said arm member side edges and immobily contain said arm member against laterally yielding to said outwardly applied force, whereby during such engagement of said retainer means insertion into said tapered channel of a drafting scale chuckplate of matching taper effects a rigid wedge-fit union between said chuckplate and said arm member, and upon disengagement of said retainer means said arm member is rendered capable of laterally yielding to the force applied outwardly at the sidewalls of said channel by the taper of an inserted chuckplate, thereby allowing a lateral expansion of said channel and release of said chuckplate from said rigid wedge-fit union.

Claim 9

The improvement according to claim 6 wherein said arm member side edges are substantially parallel and said retainer means comprises a rigid channel member having substantially parallel inner sidewall portions, said channel member being dimensioned to laterally span and closely engage said arm member side edges at the respective inner surfaces of said channel member sidewall portions.