H. P. SHERMAN Oct. 3, 1961 INKING PAD STRUCTURE FOR A MIMEOGRAPH DUPLICATING MACHINE Filed Dec. 24, 1958 5rerzfi ia jzkm BY M M 9%rng States Patent 3,002,449 INKING PAD STRUCTURE FOR A MIMEO- GRAPH DUPLICATING MACHINE Herbert P. Sherman, 724 W. Washington St., Chicago, Ill.
Filed Dec. 24, 1958, Ser. No. 782,740
4 Claims. (Cl. 101-119) -'.My invention relates to improvements in inking pad structures used in mimeograph duplicating machines.
Heretofore, fluid type inks have been utilized in mimeograph duplicating machines having perforated cylindrical drums over which haveb'een stretched inking pads. Such pads usuallywere formed of cotton flannels having highly napped surfaces'which were placed contiguous to the outer surfaces of the perforated drums so that the napping could protrude through the perforations into the drums containing the ink supply. The napping thus functioned as wicks drawing the ink by capillary action to the outer surface of the-pads and then to the stencils stretched over the'pads.
While the above described combination of fluid type ink and flannel pad functioned generally satisfactorily, there were certain inherent disadvantages in the use of fluid type inks. For example, the oil vehicle had a tendency to separate out from the pigment resulting in a relatively poor quality of copy, and additionally, considerable dripping of ink was experienced in the case of an excessively inked machine.
With the view to overcoming the objectionable characteristics of fluid type inks the industry has developed new types of paste and semi-paste inks having relatively high viscosities. Such inks can be used to a reasonable degree with capillary type pads as described above only if the drums of the machines are perfectly cylindrical and enough ink is placed within them to build up a centrifugal force great enough to force a flow of ink through the capillary pad. Even this method does not provide suflicient flow for good printing at speeds of more than 80 to 90 copies per minute. All this, of course, is due to the high viscosities of the inks which retard materially the capillary flow in the regular cotton pad.
Accordingly, it is an object of my invention to provide an improved inking pad for use on duplicating machines of the type described which may be used satisfactorily with inks of high viscosities.
Another object of my invention is the provision of an inking pad of the foregoing type which produces a high quality of printed copy at greater operating speed than is possible with machines now using semi-paste inks in single perforated cylinders with conventional cotton capillary type pads.
A further object of my invention is the provision of an inking pad of the foregoing type which eliminates the impressions of the drum perforations on the printed copy, a disadvantage characteristic of the inking pads heretofore used, particularly in conjunction with electronically perforated stencils.
A still further object of my invention is the provision of an improved pad of the type described which is simple in construction, efficient in operation and economical to manufacture.
Other and further objects will become apparent from the following description when considered in connection with the accompanying drawing in which;
FIGURE 1 is a plan view of my invention with portions cut away to illustrate the construction.
FIGURE 2 is a side elevational view partly in vertical section.
FIGURE 3 is an end view partly in section showing the inking pad applied to the drum of a mimeographing machine, and
Patented Oct. 3, 1961 ice- FIGURE 4 is a perspective view showing my inven tion applied to the perforated drum with portions cut away to show structural details. Referring to the drawings, the numeral 10 designates the'drum or cylinder of a mimeographing machine, which drum is perforated substantially throughout its entire surface area. The drum is provided with suitable means 12 for securing an inking pad tightly against the outer surface of-the drum. The foregoing is of conventional construction and forms no part of the present invention which relates specifically to my novel inking pad.
Thepad of my invention, generally designated at 14, comprises a plurality of contiguous layers of fabric in superimposed relation, as will be presently described. The lowermost layer 16 arranged to be disposed immediately adjacent the outer surface of the drum 10 consists of a finely woven relatively stiff nylon taffeta having a thread count of approximately 124 x 84 threads per square inch. Superimposed over layer 16 is a second layer of nylon leno woven fabric 18 which is relatively stiff in relation to all of the other layers and has a thread count of 23 x 20 threads per square inch. The third layer 20 consists of an open mesh nylon fabric which is substantially more flexible and finer than layer 18 and has a thread count of approximately 28 x 33 threads per square inch. The fourth layer 22 consists of a sheer plainly woven fabric of somewhat softer and finer texture than layer 20 and has a thread count of 106 x 86 threads per square inch. The uppermost layer 24 is identical to layer 16.
Each of the layers is woven of nylon filament and after weaving the fabric is subjected to a treatment which renders the filaments substantially plastic. Accordingly, there is effected a bonding of the filaments constituting the warp and woof of the fabric which stabilizes the fabric and prevents ravelling.
The layers arranged in superimposed relation are stitched together at their ends which are preferably covered by reversely bent strips 26 and 28 of plasticized fabric or other suitable material, the said strips being secured to the layers as by lines of stitching 30 and 32 respectively. Suitable means are attached to the strips 26 and 28 to afford securement of the inking pad 14 to a drum 10 in taut condition. A conventional stencil is stretched tightly over the pad.
As hereinabove explained, the novel pad of my invention may be used with inks having relatively high vis cosities and does not depend for its proper functioning on capillary action or flow as is the case with flannel type pads.
According to my invention, layer 16 which is contiguous to the drum surface, when activated by the impression roller 35 functions in cooperation with the perforations to create a multiplicity of diaphragm pumps, each of which draws out from the drum the highly viscous ink which is then deposited in the intermediate layers 18 and 20, as will be hereinafter explained. It will be clear that the impression roller 35 which is formed of soft rubber and is spring biased serves to press the paper against the stencil so as to transfer the ink to the paper. This same action in effect pushes portions of the layer 16 into the perforations during the interval of contact of the roller with a particular area of paper. After passage of the roller 35 the pushed in areas of the layer 16 move outwardly in the manner of tiny diaphragms creating a pumping action. Thus, as the roller 35 traverses the area of the pad, a series of pumping operations occurs effecting a uniform distribution of ink over the entire area of layer 16. The ink thus pumped is deposited in the open mesh structure of the layers 18 and 20 which serve as reservoirs for the ink. Layers 22 and 24 similarly func- E 1 tion as diaphragm pumps in cooperation with the open spacings of the layers 18 and 20 in the same manner hereinabove described. The ink is carried to the surface of layer 24 and is caused to be uniformly distributed there over and to be deposited on a paper surface in a printing operation.
The inking pad of my invention produces clear crisp printed copy in smooth shaded tones which is superior to the kind of printed copy heretofore obtainable with prior inking pads. The texture and relative stiffness of the several layers affords a relatively hard surface layer over the drum which eliminates the impression of the drum perforations on the printed copy, a condition which is undesirable but commonly found in the operation of prior art inking pads.
1. An inking pad for a mimeograph apparatus having a perforated drum over which the pad .is adapted to be stretched, said pad comprising five superposed layers each of woven monofilament nylon fabric secured together, in contiguous relationship, each of said layers having difierent textures with the outermost layers being characterized by a fine closely woven texture and the intermediate layers being characterized by relatively open mesh texture.
2. The invention as defined in claim 1 in which the outermost layers each have a thread count of the order of 124 x 84 threads per square inch, and the intermediate layers have thread counts respectively of the .order of 6 23 x 20 threads per square inch, 28 x33 threads per square inch, and 106 x 86 threads per square inch.
3. An inking pad for a mimeograph apparatus having a perforated drum over which the pad is adapted to be stretched, said pad comprising three or more superposed layers each of woven monofilament nylon fabric secured together in contiguous relationship, with the outermost layers being characterized by a fine closely woven texture and the intermediate layer or layers being characterized by relatively open mesh texture.
4. An inking pad for a mimeograph apparatus having a perforated drum over which the pad is adapted to be stretched, said pad comprising three or more superposed layers secured together in contiguous relationship, with the outermost layers being characterized by a fine closely woven texture made of nonabsorbent material with at least one of the intermediate layers characterized by open mesh textures and serving as areservoir for the References Cited in the file of this patent UNITED STATES PATENTS 416,174 Meriman Dec. 3, 1889 1,626,323 Bendick Apr. 26, 1927 2,346,023 Gold Apr. 4, 1944 2,546,304 Huebner Mar. 27, 1951 FOREIGN PATENTS 582,693 Great Britain Nov. 25, 1946