Patent GB-506168-A (GB)
Title: Improvements in or relating to respirators
IPC: A62B23/02
Filed: 1937-11-23
Abstract: 506,168. Respiratory appliances. McDONALD CO., B. F. Nov. 23, 1937, No. 32223. Convention date, Nov. 23, 1936. [Class 81 (ii)] A respirator for use in dust or smoke-laden atmosphere, comprises n mask adapted to cover the mouth and nostrils of the wearer, a valved outlet in the mask an inlet opening in the mask and filter means covering the said opening and comprising a cover having perforations therein, a filter element both sides of which are engaged by substantially rigid spreading members to space the different portions of the filter element apart and prevent it from collapsing, one of said spreading members having substantially rigid reversely bent end portions co-operating with similar portions of the cover which comprises the other spreading member for sealing by engaging the opposite surfaces of the ends of said filter element and holding it in reversely bent form, said end portions of the former spreading member being connected by cross-pieces extending across the inner surface of the filter element and around which the element is bent. The mask 12, with face mould 13 and valve is connected to the filtering means 14 by a cap 45 which has a pair of openings 53 having upwardly extending flanges 54 which extend through openings in the floor of the mask and are swaged over. The filter spreading member 48 which may be pressed from a single sheet of metal has an overhanging flange 63 over which a dependant flange 65 of the cap is rolled oxcept at the ends where the dependant flange is turned inwards to form the ledge 66. The spreading member is provided with two legs 61 and 62, the ends of which are closed and together form a W-shape. The outer lateral surfaces of the legs are largely cut away leaving but a marginal suface adjacent the ends, at the apices of the W and at the upper parts of the member and also a centrally disposed spacing strip 77. The inner walls are similarly cut away but have no strip 77. The cover 46 comprises a perforated rectangular shell having two resilient latch members 94 at either end co-operating with the ledges 66 to attach the cover to the cap. The ends of the side walls taper down at the same angle as the walls of the legs 61 and 62 and in co-operation with two inverted U-shaped members 100 attached to the inside of the end walls of the cover form a complementary surface to the end walls of the spreading member but spaced therefrom, when the cover is attached to the cap, by the thickness of the filter element. This'is gripped at the ends by the complementary surfaces and made to conform to a W-shape while the lateral edges are gripped by the upper edges of the spreading member and the cover. The apices of legs 61 and 62 and member 100 are arcuate. Except where it grips the filter element, the cover is spaced from it in order to allow air to circulate over the surface of the element after passing through the perforations. The filter element may be of heavy felt. The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 505,414. This subject - matter does not appear in the Specification as accepted.