Abstract: This rescue tool includes a body, providing a cylinder and a piston extending outwardly of the cylinder, and a pair of jaw members pivotally connected to the body by link members and the piston. The jaw members include cooperating outer prying portions, inner cutting portions and intermediate shearing portions. The cutting and shearing portions include arcuate edges defining overlapping points and the prying portions are thickened to facilitate wedge action. The tool can be powered by a bi-directional motor, reservoir and battery system or can be powered directly from a wrecker motor vehicle system.

Abstract: A combination tool comprises an elongated lever having a handle at one end, two divergent fingers at the other end, and an aperture between the two ends adapted for engagement with a nut. One of the fingers includes a distal end and claw in spaced relationship thereto which cooperate to provide a fulcrum for movement of the lever, thereby to facilitate the removal and replacement of nuts which are locked on a threaded shaft by a locking member having bendable tabs projecting outwardly therefrom.

Abstract: The method involves treating a cellulose fiber-containing structure with an alkaline agent, coating the structure with an acid chloride having the following formula: ##STR1## (wherein X is --H, --NO.sub.2, --CH.sub.3 or --SO.sub.2 Cl) and subjecting the resultant structure to heat treatment to cause chemical modification. The acid chloride is employed in the form of an emulsion in water. The emulsion may also contain a thickener such as a natural sizing agent or a dye. The method provides a more dyeable cellulose fiber-containing structure.

Abstract: A spring-type shank for a shoe sole is formed on the bottom of a shoe assembly during manufacture of the shoe. The heel end of the shank is formed so that it is raised slightly from the heel seat region of the insole to provide a "spring shank". The shank is formed directly on the bottom of the shoe insole from a strip of initially flexible, uncured thermosetting material which may be fiber reinforced. The spring portion at the heel end of the shank is formed by placing a wedge between the shoe insole and the heel end of the shank strip during the curing process thereby to cause the heel end of the shank strip to cure in a raised, inclined attitude, spaced from the bottom of the insole, while the more forward, remaining portions of the shank strip cure in secure attachment to the insole bottom.

Abstract: An apparatus for continuously pickling the outer surfaces of hermetically plugged tubular members is described. The apparatus includes a plurality of liquid tanks which separately contain different pickling liquids and define through-holes in their respective front and rear walls on at least one common longitudinal line to permit the successive passage of the tubular members therethrough while rotating them around their respective longitudinal axes. The apparatus includes a cleaning tank and cleaning brush unit provided sequentially before the liquid tanks. The cleaning tank includes at least one ultrasonic cleaning oscillator and defines through-holes in the front and rear walls thereof for allowing said tubular members to pass through the cleaning tank and the brush unit. Since any oil, grease or dust can be completely removed by the cleaning tank and brush unit prior to pickling, it is possible to obtain tubular members having excellent outer surface quality.

Abstract: A chalkboard eraser cleaner including a completely closeable, box-like housing containing an electrically driven, rotatable beater. At the top of the container is a side, slot-like opening with a door for the insertion of the eraser to be cleaned. Right below the area in which the eraser is inserted, there is an eraser support surface of somewhat slack, mesh netting material supported between the walls of the container for supporting the eraser during beating, with the mesh netting located directly above the rotatable beater whose arms impact the bottom of the eraser through the mesh netting to clean the eraser. Below the beater and the mesh is a removable drawer located at the bottom of the container which can be removed for the disposal of the eraser dust, which generally will fall into the drawer during use of the cleaner. An electrical contact switch is positioned in the container adjacent to the forward end of the area in which the eraser to be cleaned is inserted.

Abstract: A mop carrier is provided for mounting a mop and/or a brush to a mop handle. The mop carrier includes an elongated, continuous resilient blade having a first portion which extends downward at an acute angle, a second portion which curves around on itself and a third, straight portion which is horizontal and longer than the first portion. An upwardly open hollow cylindrical boss and connector are provided on the first portion near its outer end for mounting the mop carrier to the lower end of a mop handle. A hook is provided on the outside of the second portion for detachably retaining the loop of a mop that is sleeved on the third portion. And a set of flanges is provided on the third portion to permit a brush to be slidingly mounted on the third portion.

Abstract: An improved apparatus for cleaning roofs and other surfaces having both coarse and fine compacted particulate matter to be cleaned. A spray of water under pressure of 1,000 to 2,000 psi is applied from the inside of an open bottommed vacuum chamber toward the surface to be cleaned along a line at an angle across the chamber, to dislodge fine and/or coarse residue from the surface. A second spray is immediately applied following the first before the residue resettles on the surface, while at the same time a vacuum is applied to the chamber to remove the deflected spray and residue.

Abstract: An electric vacuum cleaner has a generally opaque housing enclosing a bruch roller rotatable about a horizontal axis, a motor, and a belt or the like extending from the motor to a pulley on or affixed to the brush roller, for driving the brush roller. A transparent window is provided in the top of the housing and aligned with the belt, and highly contrasting markings are provided on the belt, thereby to enable an operator to determine, viewing the belt through the window, the moving condition of the belt.

Abstract: Guide means for sliding shower doors and the like includes a lower track member having a inclined upper face, an upstanding guide adjacent one edge thereof, and a guide track adjacent the other edge thereof. An outer door is guided by the upstanding guide and has a skirt which overlies it, and an inner door is coupled to and guided by the guide track, so that water impinging on the upper face of the lower track member can run off freely.

Abstract: As a series of birds are conveyed in a suspended, inverted attitude through a poultry processing plant the neck of each bird is received in a rotating helical rotor formed by a pair of helical bars arranged in overlapping, coaxial relationship and which form a helical path therebetween. The helical rotor is rotated in timed relationship with respect to the bird conveyor so as to progressively grasp and move the heads of the birds with the conveyor. The feathers at the neck of each bird are wiped across the length of the neck, and the jugular vein of each bird is severed without severing the spinal cord or trachea of the bird.

Abstract: An apparatus for pulling-off the skin of sheep carcasses in connection with slaughtering comprises an essentially horizontal drum (8) for pulling-off the skin during winding thereof on the drum (8), the drum (8) being moved upwards along the dorsal side of a sheep carcass (31) suspended from the hind legs. The drum (8) has a gradually increasing diameter from a central portion towards both ends, and is mounted at the free end of a pivotable lifting beam (3) having a means (I) for upwards directed pivoting movement of the beam during the pulling operation. A motor means provides for rotation of the drum (8) synchronously with the pivoting movement of the lifting beam (3) and with a speed which is adapted to the movement of the lifting beam.

Abstract: A bale supporting apparatus for stabilizing fiber bales during opening of the fiber bales from the top includes a support element arranged to engage a vertical end face of a bale and further arranged for stepwise, vertically downwardly oriented motion as the bale height decreases during the bale opening process. The support element is mounted on a stationary carrier structure which is situated horizontally adjacent the space occupied by the fiber bales undergoing opening.

Abstract: The device for separating individual fibers of a fiber sliver comprises sliver feed rollers, sliver opening means comprising a press roller and a separating roller adapted to carry a stack of thin disks provided with combing elements which consist of teeth or wire points for separating the fibers and with drafting elements for parallelizing the fibers, and a duct for the delivery of freed fibers. The separator can be employed for spinning slivers containing either long or short fibers or a mixture of both.

Abstract: A lock tongue for safety belts with a belt strap of the safety belt being adapted to pass through the lock tongue and be firmly attached to the belt strap so as to be safe against displacement at a certain location of the belt strap due to a loop-around friction occuring under load. The attachment is effected by repeated deflection of the belt strap by means of a component separate from the lock tab or tongue cooperating with the later. The lock tab or tongue includes two passage openings which are separated from each other by a central web, with the passage openings being adapted to accommodate the belt strap. A clamping bracket may be attached, preferably in a releasable fashion, into one of the passage openings.

Abstract: This invention relates to a one-piece push-in type of fastener having side wings or fronds on a shank and adapted to prevent withdrawal of the fastener when inserted into a hole in which the shank is of H-shape in cross-section with wings or fronds on opposite plane surfaces of the shank and with the front surface of each wing or frond curved at its inner end to lead to the inner end of the rear surface of the next adjacent wing or frond.

Abstract: A first fastener part (14) includes a flat disc (16) from which a spindle (18) extends for engagement by a hollow tubular member (24) extending from a base (22) provided with an aperture (54) through which the free end of spindle (18) is visible. A pair of resilient fingers (28, 29) are formed integrally with disc (16) and are mounted in arcuate openings (46, 48) which are of greater extent than fingers (28, 29) so that protuberances (34, 36), which extend from the free end of hollow tubular member (24), will be trapped by the free ends of fingers (28, 29) when shoulders (40, 42), on tubular member (24), and cam faces (30, 32), on spindle (18), coact to couple spindle (18) and hollow tubular member (24) together.

Abstract: A high strength safety belt buckle characterized by a clevis attached to one belt end, a connector attached to another belt end releasably held within the clevis by a latch passing through the connector and engaging both sides of the clevis. A first embodiment is suitable for use as a safety release buckle in a passive restraint system which need be disconnected only under emergency conditions. A second embodiment is suitable for normal safety belt buckle use where maximum convenience of connection and disconnection is essential.

Abstract: A releasable, hook-type fastener of the kind intended to secure pieces of equipment or structural members together, the fastener including a casing, a drive shaft turnable in the casing, an eccentric bushing carried by the casing and turnable with the shaft, and a pair of separate and distinct, similarly-shaped spring hooks that are disposed side by side and substantially in broadside contact with each other. At one end, the hooks have looped bearing portions which are frictionally engaged with the eccentric bushing, and at the other end they have registered bill portions. A pin is provided, separate from the hooks and adjacent to the eccentric bushing, for engagement with the hooks so as to maintain them in registration with one another. The arrangement is such that an unusually strong and sturdy construction results, without the need for heavy gauge springs and without the use of odd-shaped springs which would require special metal stock and bending fixtures or jigs for their fabrication.

Abstract: Lock for a safety belt having a belt lock and a plug-in tongue which can be locked in position by a latch movable by a manual pressure element transversely to the plug-in tongue direction to the opening position. The latch is retained by a force, preferably a spring-loaded ejector, in the opening position. When a pulling force exceeding a predetermined value acts on the plug-in tongue, an insertion lock in the belt lock permits withdrawal of the tongue but prevents a renewed insertion of the tongue.

Abstract: A grommet clip, particularly useful for suspending air conditioning ducts, formed of a flat body having opposite portions snapped together along a fold line with means which penetrate a web on the duct and which define an eyelet to receive hangers for supporting the duct.

Abstract: A resilient capturing bead of silicone rubber is deposited and cured inside a tubular watch band endpiece and functions to frictionally engage a spring bar connector inserted in the endpiece, retaining the spring bar connector in proper position during assembly of the band and endpiece to a watchhead. The endpiece typically includes an access opening through which the capturing bead material is introduced into the endpiece.

Abstract: An apparatus for commingling yarn. The apparatus has an inner body having a yarn passageway with a diameter of about 1/4 inch to 5/16 inch. There are orifices through which a high pressure fluid such as air pass to the yarn passageway. The orifices have a diameter of about 0.060 to 0.80 inches.

Abstract: A method of taking up a bundle of filaments is disclosed wherein the bundle of filaments is ejected together with a compressed fluid toward a container and coils of the bundle of filaments are formed when the bundle of filaments is received in the container. Before arriving at the container, the above-mentioned compressed fluid is deviated from a passage of the bundle of filaments having a spiral shape. The apparatus for effectively carrying out this method comprises a rotary member rotating around the central line of the upstream portion of a guide passage for feeding the bundle of filaments toward the container and means, which ejects the bundle of filaments being conveyed into the rotary member in the above-mentioned upstream portion by means of a compressed fluid. The rotary member has a guide passage that expands gradually toward the outlet end of the guide passage.

Abstract: Disclosed is a single chamber ultra-high vacuum processing system for the oduction of hermetically sealed quartz resonators wherein electrode metallization and sealing are carried out along with cleaning and bake-out without any air exposure between the processing steps. The system includes a common vacuum chamber in which is located a rotatable wheel-like member which is adapted to move a plurality of individual component sets of a flat pack resonator unit past discretely located processing stations in said chamber whereupon electrode deposition takes place followed by the placement of ceramic covers over a frame containing a resonator element and then to a sealing stage where a pair of hydraulic rams including heating elements effect a metallized bonding of the covers to the frame.

Abstract: In a device for acting on webs of material which includes at least one roll, which comprises a revolving hollow cylinder constituting the working roll circumference, a crosshead going through the cylinder with spacing on all sides, and against which the hollow cylinder is braced by means of a fluid pressure medium contained in its interior between the crosshead and the inside of the hollow cylinder in at least one chamber, force members which operate in the action plane of the roll and engage the ends of the crosshead protruding from the hollow cylinder, or corresponding points of a counter roll, and a control for holding the forces exerted by the fluid pressure medium on the one hand and by the force members on the other hand substantially in equilibrium, force measuring cells are inserted between the force members and the ends of the crosshead or the corresponding points of a counter roll, respectively, which cells substantially transmit the entire exerted force, and means provided for feeding the signal of

Abstract: Articles of jewelry with gems set in precious metal are cast by a modified lost wax method whereby each gem is retained in position in the investment mold after removal of the wax enabling the setting of the gem to be simultaneous with the casting of the precious metal. The wax model of the article of jewelry is molded with undercut grooves in the sidewall of the gem seat located to engage portions of the girdle of the gem for retention thereof in set position in the finished article. The wax for the model is formulated to provide resiliency to permit the gem to be snapped into position in the wax model prior to embedding the model with the gem set therein in investment material in the conventional flask. Curing time is reduced to approximately one half the conventional fourteen hours by precise control of predetermined time and temperature which also prevents marring of the gems during the curing of the investment and the casting of the precious metal.

Abstract: Stacked leaded hybrid substrates and associated carrier plates are exited from a reflow solder operation into a vibrating table. Vibration of the table sequentially advances each stacked carrier and substrate until components on the latter contact an arm that is spaced above the table. Detection of the presence of a substrate and carrier adjacent the arm causes a plunger to move transversely across the table and into contact with an edge of the substrate. Further movement of the plunger pushes an edge of the carrier into contact with spring loaded pins in the table top. The shear force created on contiguous surfaces of the substrate and carrier by the plunger and pins causes the substrate to slide off of the carrier and over the pins. If this shear force exceeds a prescribed value, the pins rotate into the table top for passing a carrier and/or substrate without damaging the latter.

Abstract: Disclosed herein is method for assembling a pair of slide fastener stringers each having spaced sections in continuous rows of scoops and an apparatus for the same. The leading edge of the scoop row in the leading stringer is detected by a probe inserted into the guide groove of the binder member for the scoop row. The engagement of the leading edge and the claw of the probe retards the progress of the leading stringer thereby retarding the rotation of the feed roller for the leading stringer while increasing the speed of the rotation of the other feed roller for the trailing stringer, which is connected to the first feed roller through a differential transmission mechanism. After both of the stringers are brought into right alignment for exact engagement in the binder member, the claws disengage from the leading edges of the scoop row in the stringers and come out of the spaced sections. In this condition, the spaced sections in the stringers are detected individually by detecting lever means.

Abstract: A method and apparatus for production of couplings for joining together sections of metal tubing, the couplings being of the type comprising sockets having e.g. an annular recess carrying a filler metal, whereby the filler metal comprises a plastic composition which is applied under pressure to a selected internal area of a section of deformable tubing, thereby to form an indentation containing a deposit of plastic composition.

Abstract: A method is provided for assembling a combination shock absorber and air spring including a tubular shock absorber having an outer tube and a piston rod reciprocably projecting from one end of the outer tube, and an air spring consisting of a resilient diaphragm member having an outer wall portion connected to a cylindrical housing secured to the projecting end of the piston rod, an inner concentric wall portion secured to the outer tube, and a rolling wall portion formed between the inner and outer wall portions.

Abstract: A connector sleeve for polyolefin pipe ends for connecting butted pipe ends by a coupling. The connector sleeve is metallic and has a pair of internal circumferential ribs mated in external grooves of the pipe end which is press-fitted within the sleeve in sealing relation. The connector sleeve has a pair of external grooves registering with the ribs formed by a pressing or rolling operation. Butted pipe ends with their fitted connector sleeves are connected by a coupling engaging the connector sleeves. The connector sleeve and pipe end have registering bevelled ends and in the fitting operation the sleeve and pipe end are axially aligned and forcefully engaged whereby the bevelled end of the connector sleeve causes the pipe end to be internally deflected and compressed in mating engagement with said connector sleeve.

Abstract: A method and apparatus for forming a drum seam. A tray-like end plate having a cylindrical portion forming an indented shape and an outward extending end plate flange formed by the edge of the cylindrical portion is fitted into the end of a cylindrical drum body having a body flange extending outward from the edge thereof perpendicular to the cylindrical axis of the body with the end plate flange overlapping and extending along and beyond the body flange. A seaming chuck having a cylindrical forming face is fitted into the tray-like end plate for holding the body and end plate together with the forming face of the seaming chuck against the inner surface of said cylindrical portion and rotated for rotating the drum body and end plate. The seaming chuck has a fillet on the end adjacent the position where the end plate flange extends from the cylindrical portion and an inclined surface extending from the forming face outwardly thereof.

Abstract: In a method of joining two metal members by forming an annular groove at least on one of the two metal members to be joined and causing part of the material of the metal member to flow into the annular groove by plastic deformation to form a joint, at least one annular angled member is formed in the annular groove. The annular angled member extending the entire periphery of the annular groove is substantially triangular in axial cross-sectional shape. The joint has increased strength and can be formed with reduced pressure.

Abstract: Process of making thin film materials for high efficiency solar cells on low-cost silicon substrates. The process comprises forming a low-cost silicon substrate, forming a graded transition region on the substrate and epitaxially growing a thin gallium arsenide film on the graded transition region. The process further includes doping the thin gallium arsenide film and forming a junction therein. The graded transition region preferably is a zone refined mixture of silicon and germanium characterized by a higher percentage of germanium at the surface of the region than adjacent the substrate. The process also includes the formation of homojunctions in thin gallium arsenide films.Solar cells made from the materials manufactured according to the process are characterized by a high conversion efficiency, improved stability and relatively low unit cost.

Abstract: A method for forming electrical interconnections in an integrated circuit which involves forming an insulating layer on the silicon chip on the lower of two conductive layers to be interconnected, opening a window in the insulating layer, filling the window with a metallic plug by a lift-off technique, and then forming an interconnection pattern extending over the layer and contacting the plug.

Abstract: A method of forming low resistance silicided gates or interconnects is described wherein a refractory metal and silicon is simultaneously co-deposited to form a composite layer which is thereafter heat treated in a non-oxidizing atmosphere to form the polycrystalline state of the silicide.

Abstract: The present invention relates to an applicator tool capable of picking up loose miniature spring sockets and inserting them into holes in a printed circuit board. More particularly, the tool has dual air lines, one being connected to a compressed air supply and the other being connected to a vacuum. With the sockets laying on the work surface, vacuum pulls a socket into the tool nozzle. The tool is then placed into alignment with a hole and the trigger squeezed to activate the air supply to drive a ram which drives the socket out of the tool and into the hole in the board.

Abstract: A device for removing leads (14) of a circuit module (12) from sockets (16) mounted in a circuit board (18) includes a first assembly (51, 52 and 54) having two depending arrays of fingers which engage the socket (16) and a second assembly (34) having two arrays of pivotally mounted jaws (31 and 32) which are manipulated to grip opposite sides of the circuit module. The second assembly is movably mounted within the first assembly, and when moved upwardly away from the circuit board, acts to pull the circuit module to extract the leads from the sockets while the fingers hold the sockets from dislodgement from the board. The fingers are longitudinally grooved (61) to guide the leads during extraction from the sockets.

Abstract: A contact member for a switching device is formed by soldering a contact tip to a movable contact member. The movable member is formed from an age-hardenable copper alloy that has been subjected in series to solution treatment, half age-hardening, grinding and rust-prevention coating.

Abstract: A one-piece razor handle molded from resilient plastic has spaced-apart opposing side walls joined at an intermediate location by a neck. The walls diverge upwardly from the neck into upper portions for gripping a blade cartridge, and extend downwardly to a spacer that extends between the lower portions of the wall. The lower portions of the walls, between the neck and spacer, are resiliently squeezable. The neck acts as a fulcrum so that the upper portions pivot outwardly as the lower portions are squeezed inwardly. A base joins the bottoms of the walls extending past the spacer.

Abstract: A hand tool for use in performing manual agricultural grafting, comprises a fixed and a movable handle pivotally connected to each other and having working portions extending beyond the pivot. A coil tension spring connects the first handle to the working portion of the second handle thereby tending to spread the handles apart. The spring is connected to the same point on the working portion of the second handle as is pivotally connected to one end of an arm whose other end is pivotally connected to a positioning fork that locates the stock to be cut. The positioning device slides in a groove on the working portion of the first handle toward and away from a cutting edge carried by the working portion of the first handle.

Abstract: A coating thickness gauge employs a permanent magnet suspended on a coil spring within a pencil shaped housing; the spring being attached to a slide which encircles the housing aid is manually slidable along the length of the housing to adjust the tension of the spring exerted on the magnet. The end of the magnet projects through the end of the housing in contact with a coating deposited on a ferromagnetic base so that the thickness of the coating is measured in terms of the spring tension exerted when the side is moved to pull the magnet away from the coating and this thickness can be read on a scale mounted along the length of the housing. The slide can be provided with internal resilient friction rings or an internal expandable friction element can be placed in the housing to resist inadvertent movement of the slide and an internal stop can be employed to prevent bouncing of the magnet to displace the slide.

Abstract: A letter forming stencil for use in signwriting or the like comprises a substantially rectangular plate having two apertures formed therethrough and having a separate corner forming piece or pieces, the stencil in use being placed on the surface upon which it is desired to form letters and the outline of the letter being traced thereon, the length of various lines comprising the letter being judged against indication means and spaced around the perimeter of the plate and the corners of the letter being formed with the aid of corner forming pieces.

Abstract: An adjustable face-plate template adapted to be adjustably fitted and clamped to the longitudinal edge of a door to establish a predetermined-size recess for a face plate of a door latch or lock, wherein the template includes a first, adjustable, parallelogram structure defining a clamping device having a pair of clamping bars, and a second parallelogram structure defined by a pair of guide bars arranged to determine the width of the recess to be cut. Slidably mounted to one of the clamping bars is a pair of transverse guide bars adapted to be adjusted to establish the length of the recess to be cut. Both parallelogram structures are pivotally connected together.

Abstract: A device for use in grading operations and includes an elongated rod having front, rear and side surfaces. The endless band is formed by a first band portion of a given color and having a first set of graduations extending from zero at one end thereof to a first value at the other end thereof and a second band portion of a color clearly distinguishable from the given color and having a second set of graduations ascending from zero at one end thereof to a second value at the opposite end thereof. Attached to the one end of the first band portion is the one end of the second band portion while the opposite end of the first band portion is attached to the opposite end of the second band portion. A slide mechanism is mounted for longitudinal sliding movement on the elongated rod and includes a clamp for selectively securing the slide mechanism to the endless belt.

Abstract: A heat-treatment apparatus for a textile web comprises a gas-pervious conveyor belt having a stretch defining a treatment path having an upstream end and a downstream end, a system for feeding the web to the upstream end and for advancing the belt to advance the web toward said downstream end along the path, a plurality of upwardly directed lower slot nozzles underneath the stretch along said path, a plurality of downwardly directed upper slot nozzles above the stretch along the path and a device for feeding a hot gas alternately to the upper and lower nozzles. The lower slot nozzles are transverse to at least some of the upper slot nozzles.

Abstract: A particulate dryer is disclosed in which upwardly moving hot gases contact downwardly moving particulate matter. The particulate matter is supported by rotating trays which, due to the absence of support at their outer ends at selected loci are caused to tilt downward to effect passage of the particulate matter downwardly through the dryer.

Abstract: An overshoe is provided having improved means for facilitating its being put on or taken off, especially over bulky or unusually shaped footwear. The overshoe is provided with opposing apertures on either side of the ankle, extending from almost the heel, vertically to the top of the ankle of the overshoe. These apertures are closed by appropriate fasteners, such as slide type fasteners, which are attached to expandable flaps so that the entire ankle portion of the overshoe can adapt to bulky footwear. When the overshoe is unfastened, the rear portion of the ankle of the overshoe serves as a convenient grip to facilitate putting on or taking off of the overshoe. The overshoe is particularly adapted to be worn over orthopedic type shoes.

Abstract: A molded outsole for an athletic shoe including molded, non-metallic studs or cleats includes a plurality of first substantially identical studs and a plurality of second substantially identical studs. The first studs have a shape characterized by three partially-overlapping frustoconical shapes, blended together to present an outline which does not retain dirt, in a triangular pattern, and produce a stud shorter than a second stud. The second studs have a shape characterized by a large frustoconical portion bounded by two partially-overlapping smaller frustoconical portions, of equal height, arranged to define a generally arcuate shape presenting a concave face and a convex face, the large frustoconical portion and the two small frustoconical portions being appropriately filleted to produce a smooth surface which does not retain dirt. These second studs may be oriented to support traction primarily in a predetermined direction, and to allow pivoting.