Patent GB-645822-A (GB)
Title: Improvements in or relating to paint brush and method of producing same
IPC: A46D1/00
Filed: 1946-01-30
Abstract: 645,822. Paint brushes and their manufacture. RUBBERSET CO. Jan. 30, 1946, No. 2969. Convention date, March 18, 1944. [Class 19] A paint brush is bristled with synthetic resin bristles, at least 5 per cent of the bristles being waved, the amplitude of the waves being not greater than a quarter of an inch. Alternatively, the brush may have a bristle body comprising an intermixture of straight and deformed synthetic resin bristles having wave-like deformations, the amplitude of the waves being between onesixty-fourth and a quarter of an inch and the period of the waves preferably being from one-sixteenth to half an inch. The waved bristles cause formation of pockets increasing the pick-up capacity of the brushes, as shown in Fig. 7. The deformed bristles desirably constitute between 5 and 80 per cent of the mixture. Generally, the deformed bristles are waved for two-thirds of their length, this portion preferably being intermediate their length. The synthetic resin bristles may be tapered. The brushes may be prepared by placing at least a portion of the bristles to be used in the bristle body between a pair of die members having completed undulated or wavy or similarly non-planer surfaces, for example, the dies 27 and 28 shown in Fig. 11 or wire screens 25 and 26 shown in Fig. 10 and subjecting the bristles to a squeezing action at an elevated temperature to impart a permanent distortion to the bristles and then assembling the bristles into a bristle body. The bristles may be inserted as a bunch in a ferrule so as to project at both ends. The butt end is dropped in a binder such as a rubber composition, the ferrule forced over the impregnated end, an additional quantity of binder poured into the open end of the ferrule and the bottom of a handle e subsequently inserted and secured, for example, by nails. The synthetic resin bristles are preferably made of nylon but casein and cellulose acetate types of bristles may also be used; the last mentioned may be treated to withstand paint solvents or carriers. The straight and waved bristles may be arranged in various ways in the bristle body; they may be uniformly interspersed, or an outer shell of straight bristles may surround an inner body of waved bristles. A composite brush body may have a shell of synthetic resin bristles around an inner body of natural bristles or a shell of natural bristles may surround a central body of straight and waved bristles. The ends of all the bristles may be ground. The brushes may be square-ended or chisel-tipped. A comparison is made of the paint pick-up capacity of brushes made of all natural bristle, natural bristle and horsehair, straight nylon, and nylon with 50 and 75 per cent respectively crimped in a wave form having an amplitude of one-sixteenth of an inch and a period of one-tenth of an inch, the pick up being 43, 68, 19, 50 and 64 grams respectively. U.S.A. Specification 2,258,361 is referred to. The Specification as open to inspection under Sect. 91 is not limited as regards the amount of deformed bristles present and the nature of the deformation giving rise to increased pick-up. This subject-matter does not appear in the Specification as accepted.