baber/WOPTO huggingface dataset:
Patent WO-0174142-A1 (WO)
Title: Verfahren und vorrichtung zur aufbereitung von fruchtständen und restpflanze als silagefutter
Inventor: GAERTNER FALK
IPC: A01D45/02
Filed: 2001-03-28
Abstract: Erntemaschin,e die neben einem üblichen Mäh- und Pflückvorsatzgerät (1) eine Transporteinrichtung bestehend aus Elevator (9) und Transportschnecke (10) mit Entliescher (11), ein nachgeschaltetes Mahlwerk (22) für die Früchte (Kolben, nämlich Spindel und Körner) und ein Häckselwerk (17) für Lieschen und separat dazu ein Häckselwerk (8) für Restpflanzen umfasst, wobei alle diese Zerkleinerungsaggregate an einem zentralen Auswurfschacht (26) mit Auswurfbeschleuniger (27) angeschlossen sind und dass der Förderschacht (24) des Mahlwerkes (22) eine Sperklappe (25), der Auswurfkanal (18) des Häckselwerkes (17) für die Lieschen und parallel zum Auswurfkanal (18) der Auswurfschacht (26) einen Sperrschieber (19, 29) aufweist und das vor den Vorpresswalzen (16) zum Häckselwerk (17) für die Lieschen ein gegenüber dem Lieschenschacht (12) verschliessbarer Auswurftunnel (13) mit Lieschenverteiler (15) angeordnet ist.
Patent WO-0179688-A1 (WO)
Title: Kraftstoffeinspritzventil fur brennkraftmaschinen
Inventor: KUNZI ULRICH
IPC: F02M61/10
Filed: 2001-04-10
Abstract: Kraftstoffeinspritzventil mit einem Ventilkörper (1), der gegen einen Ventilhaltekörper (3) axial verspannt ist und in dem eine Bohrung (5) ausgebildet ist, die am brennraumseitigen Ende verschlossen ist und dort einen Ventilsitz (32) und wenigstens eine Einspritzöffnung (34) aufweist. In der Bohrung (5) ist ein kolbenförmiges Ventilglied (10) angeordnet, das mit einer ersten (110) und einer zweiten radialen Erweiterung (210) in der Bohrung (5) geführt ist. Das Ventilglied (10) umgibt ein mit Kraftstoff befüllbarer Druckraum (23), der sich dem Ventilsitz (32) zu als ein das Ventilglied (10) umgebender Ringkanal fortsetzh. Brennraumabgewandt zum Ventilglied (10) ist in der Bohrung (5) ein Ventilkolben (2) angeordnet, der den Druckraum (23) abdichtet und am Ventilglied (10) anliegt. Die erste radiale Erweiterung (110) weist in der Bohrung (5) ein größeres Spiel auf als die zweite radiale Erweiterung (210), so daß die Reibung des Ventilglieds (10) bei der Längsbewegung vermindert ist. Die erste radiale Erweiterung (110) dient nur noch der Führung, während die Abdichtung des Druckraums (23) durch den Ventilkolben (12) erfolgt und somit durch ein vom Ventilglied (10) getrenntes Bauteil.
Patent WO-0176802-A1 (WO)
Title: Bolzenschweissverfahren und bolzenschweissvorrichtung, insbesondere für das bolzenschweissen ohne stützfuss
Inventor: CITRICH ULRICH
IPC: B23K9/20
Filed: 2001-04-12
Abstract: In einer ersten Ausgestaltung des Verfahrens wird hierzu zunächst der Bolzenhalter ohne ein zu verschweißendes Teil in einem vorbestimmten Abstand zur Werkstückoberfläche positioniert. Anschließend wird ein zu verschweißendes Teil zugeführt. Bei einer Bewegung der Schweißachse in Richtung auf das Werkstück wird diejenige Wegstrecke erfasst, die zurückgelegt werden muss, bis ein Kontakt zwischen dem zu verschweißenden Teil und dem Werkstück detektiert wird. Aus dem zuvor abgestellten Abstand zwischen Bolzenhalter und Werkstück und der zurückgelegten Wegstrecke lassen sich Rückschlüsse auf das Vorhandensein bzw. Nichtvorhandensein eines zu verschweißenden Teils ziehen. In einer anderen Ausgestaltung wird der Bolzenhalter zusammen mit einem zu verschweißenden Teil auf das Werkstück zubewegt, bis ein Kontakt detektiert wird. Ist nach dem Detektieren des Kontaktes eine weitere Bewegung der Schweißachse infolge eines Verschiebens des zu verschweißenden Teils in den Bolzenhalter hinein möglich, so wird dies als Indiz für das Vorhandensein eines zu verschweißenden Teils interpretiert.
Patent WO-2004017497-A1 (WO)
Title: Generator für den einsatz bei windkraftanlagen oder wasserkrafträdern
Inventor: HAHN UWE
IPC: H02K21/24
Filed: 2003-05-21
Abstract: Die Erfindung betrifft einen Generator (1), insbesondere für den Einsatz bei Windkraftanlagen oder Wasserkrafträdern mit niedriger Drehzahl. Zur Verbesserung des Wirkungsgrades und Leistungssteigerung wird erfindungs­gemäß ein Scheibenläufergenerator vorgeschlagen, bei dem die korrespondierenden Magnete (7) und bewickelten Ringkerne (4) in Axialrichtung auf jeweils einen Kreisring liegend angeordnet sind, deren mittlerer Radius annähernd gleichgehalten ist. Hierdurch kann die effektiv nutzbare Fläche für einen Magnetfluss bei einem Generator (1) wesentlich vergrößert und damit die Leistung bei niedrigen Drehzahlen erhöht werden. Der Aufbau des Generators (1) erfolgt zudem in einer Modulbauweise, die sehr montagefreundlich ist und einen erleichterten Austausch von defekten einzelnen Kreisringsegment (23) mit Wicklungen (13, 14, 15) jederzeit ermöglicht. Darüber hinaus kann durch Anpassung der Ringkerngröße und die der verwendeten Permanentmagnete eine weitere Leistungssteigerung erzielt werden, weil bevorzugt die Radialflä­chen der Magnete (7) und Ringkernwicklungen mit einer magnetischen Flussrichtung in Axialrichtung eingesetzt werden.
Patent WO-2004003363-A1 (WO)
Title: Elektromagnetischer direktantrieb für eine drosselklappenwelle in einem drosselklappenstutzen
Inventor: BORNMANN GERD
IPC: F02D9/02
Filed: 2003-05-28
Abstract: Der Direktantrieb für eine Drosselklappenwelle (7) in einem Drosselklappenstutzen (8) besteht aus einer Spule (1) und einem direkt neben der Spule (1) angeordneten Rotor (2). Der Rotor (2) besteht aus einem Stahlring (3), in dem innen eine erste innere Magnetschale (5a) und eine zweite innere Magnetschale (5b) zueinander gegenüberliegend anliegen. Auf seiner Außenseite weist der Stahlring (3) eine erste äußere Magnetschale (4a) und eine zweite äußere Magnetschale (4b), die zueinander gegenüberliegend anliegen, auf. An seinem der Drosselklappe (9) zugewandten Ende (3') ist der Stahlring (3) mit der Drosselklappenwelle (7) verbunden. Im Bereich (6) des von der Drosselklappe (9) abgewandten Endes (3'') des Stahlringes (3) ist mittig ein Sensor (10) zur Positionserkennung der Drosselklappe (9) angeordnet.
Patent WO-2004051083-A1 (WO)
Inventor: SCHNEIDER GUENTER
IPC: F04B1/04
Filed: 2003-08-11
Abstract: L'invention concerne une pompe haute pression comportant un arbre d'entraînement (12) et au moins un élément de pompage (14) qui est pourvu d'un piston de pompage (20) qui est entraîné, pour effectuer sa course, par l'arbre d'entraînement (12). Une bague (18) est montée, de façon à pouvoir tourner, sur une partie (16) de l'arbre d'entraînement (12) excentrée par rapport à l'axe de rotation (13) dudit arbre, le piston de pompage (20) reposant sur ladite bague par l'intermédiaire d'un élément d'appui (24). La bague (18) et/ou l'élément d'appui (24) sont, au moins dans leur zone de contact, pourvus d'une revêtement (40) constitué d'un carbone amorphe à coordination tétraédrique.
Patent WO-2004031622-A1 (WO)
Title: Umlaufgetreibe mit sicherheitslaufbahn
Inventor: ROHS ULRICH
IPC: F16H15/42
Filed: 2003-09-29
Abstract: Bei einem Getriebe mit zwei umlaufenden Getriebegliedern, die jeweils zumindest eine Lauffläche für ein umlaufendes Koppleglied aufweisen, umfassen die Verstellmittel eine Sicherheitseinrichtung, die bei Ausfall einer ansteuerbaren Verstelleinrichtung das Koppelglied in eine Sicherheitslaufbahn verstellt.
Patent DE-1801441-A1 (DE)
Title: Back washing multichamber filter
Inventor: SCHWARZ HANS-LUDWIG
IPC: B01D29/00
Filed: 1968-10-05
Abstract: The filter has a number of chambers connected in series or in parallel which can be selectively cut off on their inlet and outlet ends from the flow of medium to be filtered and subsequently connected to a pressure source of air or other cleaning fluid for backwashing, and in which the valve plug in its enclosing housing is supported rotatably and preferably also is capable of a small oscillating movement. It is sealed to the cylindrical wall by a seal member; the housing for the valve plug and the plug in combination with this is provided with filter chamber feed inlet and discharge outlet separated by partition, with the seal between the valve-plug and housing lying in a region between the inlet and outlet on the bottom end of the filter chamber or chambers.
Patent DE-1805178-A1 (DE)
Title: Vulcanising mould for tyres
Inventor: FRITZ PIRINGER ING
IPC: B29D30/06
Filed: 1968-10-25
Abstract: Mould comprises upper and lower side wall moulds, and several tread segments which are moved to closed position by sliding on inclined conical inner face of a closure ring, spring-connected with upper side wall mould. These segments are attached to slides running on a base-plate supporting the lower side mould. When the mould opens, slides move radially outwards under a spring force as far as a stop.
Patent DE-1805558-A1 (DE)
Title: Synthesis of urea
Inventor: KARL MAYER DIPL-ING
IPC: C07C273/02
Filed: 1968-10-26
Abstract: Urea is produced by the reaction of NHo gas with carbon monoxide instead of the usual carbon dioxide. The former is a single stage reaction viz. 2 NH3 + CO right arrow NH2CONH2 + H2 whereas the former is a 2-stage reaction viz. (a) 2 NH3 + CO2 right arrow NH2COONH4 (b) NH2COONH4 right arrow NH2CONH2 + H2O The mole ratio of NH3:CO in the present process is pref. 1-6:1 and the reaction may take place at 1-100 atm. pref. 10-30 atm. The temp. is so chosen that the urea is formed as a melt and is withdrawn in fluid form above the m.p. of 132 degrees. It may be converted into crystals, granules or prills for fertilising or other purposes. The liberated H with small amts. of unreacted NH3 and CO is purified and used in NH3 synthesis.
Patent DE-1812061-A1 (DE)
Title: Crystalline 7-nitro-8-hydroxyquinoline to - combat pests (weeds)
Inventor: HEELMUT PARNEMANN DIPL-CHEM DR
IPC: C07D215/28
Filed: 1968-12-02
Abstract: The compds. (I) useful as acaricide or herbicide can be obtained as a by-product from prepn. of 5-nitro isomer or 5,7-dinitro compd. The main product is precipitated from strongly acid solution and, after separation, alkali is added to adjust pH of mother liquor to 3 to 4.5. The crude product (i.e. 7-nitro isomer) is obtained by extraction with a water-immiscible organic solvent followed by separation of the solvent by precipitation.
Patent DE-1817104-A1 (DE)
Title: Phosphate fertilisers low in nitrogen
Inventor: WILHELM BOOS DR PHIL
IPC: C05B11/06
Filed: 1968-12-27
Abstract: Phosphate fertilisers low in nitrogen Are manufactured by:- (i) dissolving natural phosphate in mineral acid (e.g HNO3), (ii) neutralising with discalcium phosphate, (iii) adding to further soln. (i), (iv) filtering, and (v) neutralising liquors.
Patent DE-1909564-A1 (DE)
Title: Dust-free, non-caking alkali chlorides
Inventor: BUDAN GERHARD
IPC: C01D3/26
Filed: 1969-02-26
Abstract: Decreasing of caking tendency of and removal of dust from alkali chloride is achieved by treating NaCl or KCl with concentrated CaCl2 (pref. 2-101/t of a 30-40% solution) then with ether:- (a) soluble organic acids or their salts, particularly CH3COOH, tartaric, citric or ascorbic acids or (preferably 50-150g/t) (b) H3PO4 or its salts, partic. Ca(H2PO4)2 (pref. 40-200 g/t). Pref. the solution is then separated and rapidly dried at ca 100 degrees C to 0.2-0.5% H2O. In an example table salt had a shattering pressure of 0.7 kg/cm2 untreated and 0.13 kg/cm2 after treatment with 30% CaCl2 solution and CH3CO2H.
Patent DE-1936853-A1 (DE)
Title: Multi layer printed circuits
Inventor: GEORG GRUENDIG HEINZ
IPC: H05K1/14
Filed: 1969-07-19
Abstract: Inter layer connections between the conductive inlays on the insulating foils are made by electrically conductive pins passed through holes in the foils. The conductor patterns are in the form of sets of parallel stripes in the conventional way and the holes in the matrix pattern are off centre of the stripes. The pins are force fitted through the holes and soldered to the stripes which consist of a Cu layer which is tinned and fluxed. The insulating foils are of woven fibre glass impregnated with epoxy resin.
Patent DE-1954893-A1 (DE)
Title: Air blast removal of lubricant prior to - flow pressing
Inventor: BARTHELMESS KURT
IPC: B21C23/32
Filed: 1969-10-31
Abstract: Removal of excess solid lubricant used in flow pressing of aluminium tubing from cylindrical blanks. especially with axial holes, by means of a blast of compressed air prior to the deformation treatment. This ensures unblemished surface of the finished tubing after the recrystallisation treatment, permitting further processing particularly for food container applications.
Patent DE-1956288-A1 (DE)
Title: Heat curing acrylic epoxide based colourant - compn
Inventor: D HERVEY JOHN
IPC: C08L63/02
Filed: 1969-11-08
Abstract: Compn. contains 12-45% by wt. of a carboxyl active heat-curin acrylic resin with an acid equiv. wt. of 500-900 gm resin per gm. mol acid, 3-40% by wt. of curing epoxide resin which is a condensation polymer of bisphenol A + epichlorohydrin with an epoxide equiv. wt. of less than 695, and 15-65% by wt. of an organic solvent having a m.p. of 49 degrees - 93 degrees C and a b.p. below 320 degrees C.
Patent DE-2001241-A1 (DE)
Title: Printing pile fabric, particularly towelling
Inventor: REUTER GERHARD
IPC: D06P1/22
Filed: 1970-01-13
Abstract: Pigment print is applied first to determine the pattern outlines on the pile fabric. The standard binder amt. in the pigment dye is at least doubled, and pref. increased tenfold. The surfaces are subsequently provided with a vat print, particularly an indanthrene print. Pref. the pattern contours applied by the pigment print and which cover and glue the fibres together, are 1-2 mm. wide, and 200-300 g. binder are used per kg. dye. Both pigment- and vat print are pref. applied by screen-printing.
Patent DE-2017522-A1 (DE)
Title: Toothed strip - for slide fastener with gauze strip to aid extraction from profiling roller
IPC: B29D5/00
Filed: 1970-04-13
Abstract: As the hard polyamide strip emerges from the extruder, it is fed into the space between a pressure and a profiling roller together with a textile gauze strip, placed on the plain side which will not be profiled. The warm and still malleable plastic is moulded into the toothed profile for one side of a slide clasp fastener, with the gauze embedded allowing easy extraction from the profiling roller, and increasing process speeds.
Patent DE-2018940-A1 (DE)
Title: Two stage cryogenic expansion machine with one piston and cylinder
IPC: F25B9/06
Filed: 1970-04-20
Abstract: Piston-type gas expansion machine, esp for cryogenic temps, with top-dead-centre inlet controlled by an annulus in the piston and bottom-dead-centre outlet controlled by the piston end, has a piston of two diameters, joined by a stepped portion so that the stepped portion forms an additional, high-pressure cylinder, the circular low pressure cylinder being at the opposite end of the piston. Additional high pressure inlets and outlets are operated by additional annular grooves on the large diameter portion of the piston so that the piston and cylinder operate as a two stage system.
Patent DE-2027009-A1 (DE)
Title: Heat-treatment of pigmentation of textiles
IPC: D06B5/00
Filed: 1970-06-02
Abstract: The textile are loaded into drum mounted in the housing of the apparatus. Treatment liquor is then fed into the housing. The drum is slowly rotated at a speed suitable for the textiles being treated. The liquor is heated until the inner pressure is considerably higher than the ambient atmospheric pressure. Excess liquor is then tapped off and the drum is centrifugally accelerated to drive the liquor from the textiles. The speed of revolution is adjusted to suit the textiles being processed.
Patent DE-2050380-A1 (DE)
Title: Regulation of the boron concentration - in a reactor coolant
IPC: G21C7/22
Filed: 1970-10-14
Abstract: A proportion of the coolant is circulated through temperature sensitive adsorbers such as Zr, Th, W, or Si providing control of excess reactivity. The plant comprises a recuperative heat exchanger, cooler, particulate filters, and adsorbers with valve arrangements enabling three basic circulation circuits to be achieved according to whether reaction conditions require boron enriched coolant, boron depleted coolant or maintenance of the existing boron concentration. The size of the plant units is variable and lends itself to automatic control.
Patent DE-2065745-A1 (DE)
Title: Assembled lattice-frame scaffolding support - with two wedge blocks on coupling sockets fitting cutouts in corner bar ends
Inventor: WITSCHEL KLAUS
IPC: E04G7/30
Filed: 1970-09-03
Abstract: The lattice scaffolding support, for assembly from components, comprises horizontal and vertical frames, with vertical coupling sockets at the corners of the bar frames of the horizontal frames accommodating the ends of the corner post of the vertical frames (as in 1957913). These sockets are provided with two wedge blocks, and the corners posts of the vertical frames have cutouts for the blocks at their upper and lower ends. The sockets may have an annular inner projection in the centre between the two wedge blocks. The cutouts may be in the form of an annular groove. Improved rigidity is combined with simplified assembly.
Patent DE-2105403-A1 (DE)
Title: Sound absorbing panel - with at least one polystyrene damping panel bonded in disconnected zones
IPC: E04B1/84
Filed: 1971-02-05
Abstract: At least one soft fibre or polystyrene damping panel is bonded to a cover panel of wood, plastic or chip board etc. in which the bonding agent is applied as a multitude of individual disconnected adhesive zones rather than a solid layer to improve the sound absorbing qualities. Pref. a perforated sheet of paper, plastic or metal is arranged between the panels to limit the adhesive zones.
Patent DE-2121449-A1 (DE)
Title: Synthetic plastics sheet scoring apparatus
IPC: B31B50/25
Filed: 1971-04-30
Abstract: Plastics sheet e.g. a semi rigid polyolefin sheet is interposed between a platen member, having a slot, and a male die member having a scoring rule surrounded by resilient material. As the platen and male die move together the resilient material engages and immobilises the plastics sheet about the slot while the scoring rule stretches the sheet material into the slot to form a score line along which the sheet may be folded.
Patent DE-2126397-A1 (DE)
Title: Acyloxyalkyl-oligopeptides - useful as textile softening agents
IPC: C07K1/00
Filed: 1971-05-27
Abstract: Long-chain oligopeptides contg. alkylol and acyl gps are prepd. by reacting protein aminolysates prepd from protein and aliphatic 2-10 C di- and/or polyamines with epoxides of the formula: R-O-CH2-CH CH2 (where R is 7-21 C alkyl) and acylating the reaction prod. so as to introduce 10-24 C acyl gps. The products have textile-softening props. In the form of their aq. dispersions they display very good softening action towards cotton cloths, esp. those hardened by repeated washing.
Patent DE-2127886-A1 (DE)
Title: Mechanical ladle - for transferring molten metal from a smelting or heating furnace to a pressure-casting machine
IPC: B22D39/02
Filed: 1971-06-04
Abstract: Mechanically operated casting ladle is for transferring molten metal from a smelting or heating furnace to the pressure-chamber of a cold-chamber pressure-casting machine. THe ladle is first lowered to the melt keeping its edge opening above the melt, and is then tipped forwards so that the rear is still above the melt while the front is submerged. The ladle is then moved backwards to remove oxide skin from the front ladle section, and is then straightened out into the horizontal and raised. This ensures that ladled metal is free from surface contaminants, partic, slag.
Patent DE-2147093-A1 (DE)
Title: Foamed substitutes for conventional foodstuffs - having low calorific value
IPC: A23L9/20
Filed: 1971-09-21
Abstract: Imitations of oil-like low-fat spreads, whipped garnishings, icecreams, etc., consist of a stable aq. foam contg. up to 55 wt. % of non-aqueous compounds including not more than 5 wt. % of a fat, 0.33-7.5 wt. % of a polyglycerol fatty ester (contg. 3-10 clycerol units and 1-2 satd. fatty acyl ester gps. comprising 16-20 C atoms each, per molecule) as an emulsifier, 0.2-3 wt. % of a hydrophilic colloid as a stabiliser, and additives such as taste improvers, body builders, dyes, dispersing agents, preservatives, etc.
Patent DE-2149755-A1 (DE)
Title: Measuring liquid conc or temp - using reference liquid coupled by onsager effect
Inventor: LA DR ROCHE ULRICH
IPC: G02B27/50
Filed: 1971-10-05
Abstract: Method of determining the temp. and/or other associated parameters or changes therein of a liquid specimen uses the temp. gradient produced between this specimen and a second liquid (reference liquid) which is thermally coupled by vapour phase osmosis to the first; the second liquid is spread in the form of a film, and either this film or a third liquid coupled to it or to the specimen liqiud by thermal conductance is used for regulating the light of an optical system; this light is then used as an indicator for the values or parameters under investigation. Pref., the thin support on which the liquid subjected to the light effect is spread is of polyester, methacrylate or epoxy resin, or alternatively, a thin low-conducting membrane e.g. of glass or ceramics.
Patent DE-2150480-A1 (DE)
Title: Botanical purifier system - for treating waste-water or water supply contaminated with inorganic and organic materials
Inventor: MAIER DIETRICH DIPL-CHEM DR-IN
IPC: C02F3/32
Filed: 1971-10-09
Abstract: The water to be treated is passed through a colony (plantation) of plat cultures in an absorption/adhesion filter bed esp. of activated charcoal, the culture being of autotrophic aquatic or marsh plants, esp. Scirpus lacustris (braiding/plating rushes). The water is purified physically, chamically, biologically and bacteriologically at the same time. Esp. contamination by org. synthetic fertilizers in water from agricultural land catchment areas is eliminated.
Patent DE-2157099-A1 (DE)
Title: Quenching of hydrocarbon gases - on cool surfaces coated with liquid films to prevent coke deposition
Inventor: FEJGIN JEWGENIJ ALEXANDROWITSC
IPC: C10G9/00
Filed: 1971-11-17
Abstract: In the quenching of hydrocarbon processing products by addn. of liquids to prevent formation of unwanted by-products, an additional liquid is added directly to the stream, which forms a mobile film on the surfaces surrounding the products. The film is continuously replenished by addn. of fresh liquid in dispersed state, being removed from the surfaces by the velocity of the gas. Pref. films are melts of metals, or their oxides or salts. Heat transfer to the cool surfaces is improved, and deposition of carbon prevented, so that the rate of quenching is increased.
Patent DE-2214914-A1 (DE)
Title: Resistance welding flat pieces together - with corrugations on one surface
Inventor: BECKER OTTO ALFRED DR
IPC: B23K11/14
Filed: 1972-03-27
Abstract: The surface of a flat metal piece is corrugated before it is resistance-welded to another piece. The corrugations are produced by planning or another machining method, and are pref. 1 mm wide and high with sharp peaks. A second set of corrugations may be machined at right angles to leave only point contact. The metals may be of any kind and thickness and the surfaces may be coated with a layer of insulating material such as plastic, or an oxide. Careful control of welding parameters leaves the coating undamaged.
Patent DE-2216366-A1 (DE)
Title: Bandage - with dry adhesive core and foam overlay - for activation by light pressure
Inventor: BUESE GEORGE
IPC: C09J7/26
Filed: 1972-04-05
Abstract: The light pressure applied such as by a spatula, during winding presses the adhesive core through into the foam to give a holding and binding effect. The core is of a thermoplastic polymerisate, polycaprolactone, trans 1.4-polyisoprene or polychloroprene with a Williams plasticity of 0.4-8.0 mm. The foam cladding is na open-cell polyurethane. The purpose is to provide a firmly-wound bandage, easy to apply and to wear, cheap to produce, and which does not develop ridges.