Patent GB-726905-A (GB)
Title: Improvements in or relating to drafting mechanisms for textile fibres
IPC: D01H5/56
Filed: 1952-01-30
Abstract: 726,905. Drafting mechanism. CASABLANCAS HIGH DRAFT CO., Ltd. Dec. 9, 1952 [Jan. 30, 1952], No. 2547/52. Class 120 (2). Drafting mechanism of the kind having the top rollers carried and weighted by an arm which incorporates weighting means and is pivotally mounted on a fixture at the rear of the mechanism is characterised by the provision of a pawl which co-operates with a catch member for holding down the arm in a weighting position, spring means for automatically interengaging said pawl and catch member when the arm is depressed from an inoperative position and further spring means rendered operative by the reaction of the roller weighting pressure through the inter-engaged pawl and catch member for automatically disengaging said pawl and catch member when the latter are relieved of said weighting pressure reaction. As shown, the arm consists of side plates 1 and a cover portion 1a and is pivoted at the rear between upstanding bracket plates 6 clamped on a bar 7. The catch means includes a catch member 15 pivoted on a pin 16 secured between the plates 6 and influenced by a spring 17 such that a tail part 15a of the catch member normally butts against a fixed stop 18c also secured between the plates 6. For co-operation with the catch member a dependent pawl 18 is mounted to pivot on a pin 19 secured between the arm side plates 1 the lower end of this pawl being hooked as at 18a for engagement with the catch member 15. The upper end of the pawl is provided with a slot for the reception of a lever 20 also mounted to pivot on pin 19 and arranged to abut the underside of an extension 18b of the pawl. The other end 20b of the lever is arranged for co-operation with the stepped portion 15c of the catch member 15. The pawl is influenced by a spring 21 which tends to move the hooked portion 18a into engagement with the catch member 15 and the lever 20 is influenced by a spring 22 which is stronger than the spring 21 and tends to rotate the lever so that its end 20a by bearing on the pawl extension 18b tends to press the pawl hooked portion 18a in a direction away from the catch member 15. In operation, assuming the arm raised, when it is lowered the lever end 20b engages the catch member 15 which is held against the stop member 18c by the spring 17. This engagement of the lever 20 and catch member 15 tilts the lever end 20a away from the pawl extension 18b thus permitting the spring 21 to urge the pawl 18 into engagement with the catch member 15. The reaction of the springs 14 locks the pawl 18 and catch member 15 together and the pawl 18 tilts the catch member 15 away from the stop thus disengaging the end 15c of the catch member from the lever 20. When the arm is again depressed slightly, the lever 20 under the action of the spring 22 urges the pawl 18 out of engagement with the catch member thus permitting the arm to be raised. In an alternative embodiment the catch means consists of a depending pawl which engages a catch member comprising two similar circular plates joined together by a series of axially extending pins with which the pawl engages.