Abstract: A means for lessening the entanglement of a tubular extent of fabric by inserting a hoop into a collapsed stack of that fabric prior to its being subjected to processing steps which heretofore have resulted in the entanglement and knotting of the fabric. In its preferred form, the means and method employed in the hoop emplacement include the delivery of an extent of tubular fabric to a hoop inserter; inserting a flexible length within the tubular fabric so that it extends outward from the two ends thereof; securing the distal ends of the flexible length outward of the tubular fabric extent so as to form a hoop; processing the tubular extent with the hoop in place; preferably in a porous bag; opening the hoop and securing one end to an anchor; and reorienting the tubular extent to a substantially planar flattened extent, employing the now opened hoop as a guide, and finally removing the opened hoop from the tubular fabric.

Abstract: The specification describes a procedure for the washing of clothes in a washing machine with a horizontal, perforated, driven tub arranged inside a housing, in which during the washing and rinsing cycles the clothes are repeatedly lifted up, and then fall in a trajectory onto the lower portion of the tub, and are then distributed and pressed against the tub wall, largely without unbalance, as the tub velocity is gradually increased, and are then centrifuged as the velocity is increased further.

Abstract: A device for stiffening portions of sheets of flexible material including a reciprocable and rotatable nozzle disposed upon an extruder, the nozzle having a generally V-shaped nose section and a pair of wings disposed therebehind.

Abstract: A brake system for an aircraft passenger loading bridge monitors the operation of a drive system which raises and lowers the bridge. In the event of a malfunction of the drive system, the brake system interrupts power to the drive system and actuates a brake to prevent further operation of the drive system.

Abstract: A cleaning apparatus includes a mop with a rotatable wiper, a pail having a reservoir for cleaning liquid, and a motor-driven wringer mounted upon the pail for receiving and rotating the wiper of the mop at relatively high speed to extract cleaning liquid together with entrained dirt and other matter from the wiper and return the extracted liquid to the reservoir.

Abstract: This electric toothbrush is of the type in which the brush is rotated about its longitudinal shaft; this shaft is extended forwards by a tip able to be introduced into the interdental space for massaging the papilla and cleaning the mesial and distal faces of the teeth; the brush is enveloped over about a third of its periphery by a coaxial gutter and this coaxial gutter terminates in a raised fork-shaped end which serves as a free guide for the end of the longitudinal shaft of the brush; the rotational movement of this shaft imparts thereto a simultaneous reciprocal movement which is transmitted to its tip.

Abstract: A portable golf ball washer comprising a vertical cylindrical container closed at the bottom and open at the top and lined with a piece of stiff bristled carpet having the bristles to extend inwardly and the tips defining a core hole of less diameter than that of a golf ball to be scrubbed, a plunger having one end comprising a handle extending beyond the open end of said container when fully inserted, and the other end of said plunger having a U-shaped bail-like ball-retaining member of wire formed into a circular portion extending around a ball when contained therein for more than 180 degrees of the circumference and the legs of said member being parallel and terminating in inwardly projecting ends inserted into the sides of the other end of said plunger.

Abstract: A door frame cleaner for coke ovens in which a supporting frame is mounted on a main frame, which is movable toward or away from a door frame, in such a way that the supporting frame can be moved laterally relative to the main frame in parallel therewith; a vertically reciprocable frame is mounted on the supporting frame at the front side thereof remote from the main frame; at least one pair of L-shaped levers are horizontally pivotably mounted on the vertically reciprocable frame; a front surface scraper is mounted on an outwardly extended arm of each L-shaped lever while an inner surface scraper, on the forwardly extended arm thereof; and a bias spring is so loaded that the forwardly extended arms of the L-shaped levers are normally moved toward each other, whereby even when there exist some misalignments between the scrapers on the one hand and the door frame on the other hand as the main frame is advanced, the supporting frame is so moved that the scrapers are automatically aligned with the door frame and

Abstract: A cable bushing including a frame portion, and a filler portion connected to the frame portion, the filler portion being movable between a first position in which the filler portion is remote from the interior of the frame portion and a second position in which the filler portion is disposed substantially within the frame portion, the frame portion being adapted to occupy an opening in a partition structure and being further adapted to receive a cable therethrough.

Abstract: This bracket and track assembly can be used for sliding door assemblies and facilitates the alignment and installation of such doors. The track includes a pair of spaced, inwardly facing channel-shaped track members, supported by a plurality of longitudinally spaced, U-shaped bracket members embracingly disposed about said track members. The upper portion of each bracket member includes a rotatably mounted locking clip and a pair of arcuate slots receiving opposed legs of the clip. The arcuate slots overlap the upper, inner edges of each track member so that the clip legs exert an outward force against the track members when the clip is rotated, tending to urge said track members into engagement with said bracket members.

Abstract: An apparatus is disclosed for transferring fish processed or presented in a vertical attitude with their tail downwards into a longitudinally aligned position with regard to their head-tail attitude. The apparatus has a pair of horizontally guided conveyor belts which engage the flanks of the fish and below which a flap is arranged to be pivotable against the force of a spring about a transverse pivotal axis. The conveyor belts are resiliently supported by means of pressure rollers in the vicinity of the flap and extend parallel to one another up to these rollers, but diverge after these. A conveying surface is provided below the divergent section of the conveyor belts.

Abstract: A needle rod for use in needle bar drawing devices, also termed and known as gill boxes is proposed to comprise needle plate segments (7) which are releasably connectable to a carrier bar (2) and which have a profile of T, Z or Y shaped cross-section. The needles (12) are bent approximately at right angles in the region of their shafts (13) and are securely connected to the carrier plate (8) not only with the free ends (14) of the same but also with the parts of the shafts (13) directed towards the needle tip (15).

Abstract: A clipper seam for use with a pintle or lacing unit to join adjacent ends of a papermakers belt or the like. The clipper seam comprises two seam webbings, each of which is woven as a one-piece unit to form a pocket for receiving one of the ends of the papermakers belt. As woven, the pocket is defined by first and second flaps, each of the flaps having an inner surface and an outer surface, the inner surfaces being in a spaced relationship to define the pocket, which is adapted to receive one of the ends of the papermakers belt. Each of the outer surfaces define a stepped, tapered construction. A tongue portion also forms part of the seam webbing. Recessed margins are provided on both the top and bottom surfaces of the tongue, near the distal end or selvage of the tongue. A plurality of clipper hooks adapted to receive one or more pintles are secured to the tongue within the recessed margin.

Abstract: An adjustable drapery support assembly comprises a first elongated plate member adapted to be inserted into the top of a pleat or fold in a drapery, and a second plate member hinged at its top to the top of the first member, with the edges of the members in substantial alignment. At a point spaced from the hinge, the plates are provided with interlocking means to secure the assembly to the drapery. The aligned edges of the plates are provided with suitable gripping means which supports the top of the drapery and prevents downward sagging. Along a side edge of the second plate opposite that aligned with the first plate, there is provided an adjustable attaching means including a hook assembly which can be attached at any desired point along the length of the plate.

Abstract: Apparatus and method for high pressure sizing, including sizing squeeze apparatus which effectively utilizes high pressure squeeze loading to remove excess sizing from the warp yarns, and thus to reduce the water evaporation requirement of the yarn. The high pressure sizing squeeze apparatus includes positive drive of the rubber-surface roll as well as the steel roll to prevent slippage which could strain the warp, and maintains a substantially invariant squeeze loading irrespective of variable tension in the roll drive. The surface speed of the rubber-covered squeeze roll may be slightly less than the surface speed of the steel roll, to reduce the torque required to drive the rubber-covered roll at relatively high squeeze pressures where substantial slippage is encountered. A torque limiter controls maximum axial drive torque supplied to the rubber-surface roll, in response to the magnitude of squeeze loading.

Abstract: The valve includes an input port and two output ports and an arrangement to cause fluid pulses to appear at the output ports as a result of the appearance of fluid pulses alternately at the inlet port. The fluid pulses fed to the inlet port directly appears at the outlet ports and directly causes the valve to pass at least through three successive positions for every two successive pulses at the inlet port. This valve controls the operation of a pneumatic control circuit of a wire cutting, skinning and wrapping tool which is mounted in the handgrip of the tool.

Abstract: Fasteners, such as rivets, are held and guided by a moveable guide block mounted over a plurality belt fasteners for driving through openings in the belt fasteners and into the underlying belt. The belt fasteners are held onto the base means by a clamping bar. The preferred guide block has a groove to receive the clamping bar and the guide block also has a pair of lateral ears to engage belt clamp bars for the purpose of aligning the block relative to the openings in the belt fasteners. A driving pin from a hammer or the like drives the fasteners from the guide block and into and through the openings in the belt fasteners.

Abstract: The invention is a remotely thermally activatable device for delivering a payload to a pre-determined location within a pipe comprising a carrier means for supporting the payload, a driver means to axially move the carrier means, and a thermally activatable trigger means connected to the driver means to actuate the driver means. In operation, the device and payload may be placed in a location within a pipe, for example, near the end of a pipe to be welded to an adjoining pipe. Subsequent to such welding, the instant invention may be remotely activated by outside heating of the pipeline in the vicinity of the device, thereby causing the device to move the payload to the pipe weld.

Abstract: A tool for use by pipefitters in joining a length of pipe to a fitting in which one end of the pipe is accommodated with a predetermined spacing between the end of the pipe and an internal shoulder within the fitting. The tool comprises a pair of jaws which may be clamped on the pipe when the end of the latter abuts the shoulder and includes shims movable from a position spaced from the pipe toward the latter to occupy a position between the jaws and the adjacent free end of the fitting, thereby providing for a predetermined spacing between the free end of the pipe and the shoulder of the fitting. One of the clamping jaws is capable of substantial adjustment relative to the other to enable the tool to be used on pipes and fittings of considerably different size.

Abstract: Apparatus and method for tightening assemblies held together by threaded fasteners. The desired tightened condition is achieved by turning the threaded fastener through a precise tightening angle required to induce a predetermined preload in the threaded fastener and calculated from input parameters characteristic of the assembly being tightened and the predetermined preload. The tightening angle is measured from the onset of linearity of the preload-rotation curve for the assembly by sensing the onset of the substantially linear tightening portion of the torque-rotation curve through which the assembly is taken as it is being tightened.

Abstract: A machine is provided for cutting to length and joining two lengths of strand material at their ends to produce a band. A method of producing a band from two lengths of strand material is also provided.

Abstract: An idler roll cylinder is secured to roll heads mounted within the ends thereof by forming an annular, outwardly opening groove in and around the outer periphery of each roll head facing the inner surface of the roll cylinder. A forming pressure is applied adjacent each end of the roll cylinder to form an inwardly extending annular lock member which is pressed into the annular groove. Angularly spaced, outwardly opening recesses are provided in the outer periphery of each roll head facing the inner surface of the roll cylinder and receive inwardly projecting lock elements formed in the roll cylinder by the forming pressure applied thereto.

Abstract: An apparatus for arranging a plurality of different electric parts in a predetermined order for insertion into the substrate of a printed circuit board is disclosed. The apparatus has a plurality of cutter mechanisms arranged to receive respective tapes carrying respective electric parts. The cutter mechanism cuts the tape successively upon receipt of a control signal to sever the electrical parts one by one successively. The apparatus also has a plurality of carrier mechanisms arrayed on the periphery of a turn table which is arranged to be driven intermittently. When a carrier mechanism is positioned in front of the cutter mechanism having the desired electric part, the cutter mechanism is activated to sever the electric part and transfer the same to the carrier mechanism. Thus, the carrier mechanisms on the periphery of the turn table are loaded with respective electric parts.

Abstract: An improved tool exchange apparatus for milling machines with sliding carriages comprising a magazine and a pincer-arm for conveyance.The magazine is disposed so that the tools are presented with horizontal axis at an exchange station, the pincer-arm is rotatably mounted on one of the horizontal axes of a crank having two parallel horizontal axes. The crank itself is rotatably and slidably mounted along the other horizontal axis to a rotary head which is rotatable about a vertical axis which is fixed relative to the magazine.

Abstract: A tool feeder for transferring a tool to a tool receiving device includes a base plate fixedly mounted adjacent to the receiving device and a carriage mounted on the base plate for selective alignment with the receiving device. The carriage is coupled and positionable relative to the base plate.

Abstract: A bipolar compatible electrically alterable read-only memory device and process are disclosed based upon the formation of an aluminum gate structure on the surface of a thin oxide layer in an FET precursor device, wherein the aluminum gate structure serves both as an ion-implantation blocking mask for forming self-aligned source and drain regions and, in addition, a source of aluminum for the solid state reaction between the silicon dioxide layer and aluminum, forming an aluminum oxide/silicon dioxide composite charge storage region. The process is wholly compatible with existing bipolar processing technologies so that high speed bipolar support circuitry can be utilized on the same semiconductor chip with the programmable device disclosed. The programmable device disclosed has the unique advantages of having a programming voltage which can be tailored to substantially match the signal voltages on the rest of the chip by controlling the solid state reaction for the aluminum oxide formation step.

Abstract: A method of fabricating a thin film semiconductor hybrid circuit is disclosed. After processing of the integrated circuit in the semiconductor wafer up to the point of establishing ohmic contacts (14) to devices (13), a thin film RC circuit is fabricated on an insulating layer (11,12) overlying the wafer. This is accomplished by first forming the capacitor anodes (15') on the insulator by depositing and etching a layer such as alpha tantalum. Resistors (16) are then formed by depositing and etching a layer such as tantalum nitride. Portions of the capacitor anodes are then anodized using an appropriate mask (17) to form the capacitor dielectric. Capacitor counterelectrodes (20') and interconnect conductors (20'") are formed by depositing and etching successive layers of metal such as nickel-chromium and gold. After all thin film components are formed, the resistors and capacitors are stabilized by heating the circuit in an atmosphere comprising high pressure steam.

Abstract: A switch assembly including a base member having a contact receiving cavity open at the top and defined by a floor that is laterally enclosed by side wall means, first terminal means in the cavity adapted for electrically connection to outside circuitry, second terminal means in the cavity adapted for electrical connection to outside circuitry having a resilient contact blade portion with an end above the first terminal means. The contact blade portion is moveable between a normally open position wherein the end is spaced from the first terminal means in a closed position wherein the end contacts the first terminal means. A thin, stretchable, resilient, impermeable sealing gasket is provided on the base member which overlies the cavity. A cover engages the periphery of the gasket and includes interengaging means cooperating with the base member to lock the covering gasket to the base member to form a hermetic seal over the cavity.

Abstract: An apparatus is disclosed for pre-assembling a connector housing, which is pre-loaded with a plurality of terminals, with a respective connector cover and subsequently applying the pre-assembled connector to terminate a multi-conductor flat cable. The pre-loaded connector housings and the covers are separately fed to the apparatus by magazines. Each cover is positioned with respect to a housing and applied thereto with the assembly thereafter being rotated and moved to a termination station where a multi-conductor flat cable is terminated by the connector. The feed arrangement assures that only a single cover and connector will be fed from the respective magazines for each pre-assembly operation thereby obviating the possibility of jamming.

Abstract: A disposable razor has a body of synthetic plastic material. The front portion of the body has a slot in which a single-edge blade is mounted. A bladeguard is either a separate element and detachably connected to the body, or is of one piece with the body and can be broken off and removed.

Abstract: An improved twin blade razor system having a unitary member positioned between the pair of blades for both spacing the blades and ejecting shaving debris from that space. The unitary member, which may conveniently be of injection molded plastic, includes a spacer portion, an ejector portion, and biasing apparatus connecting the ejector portion and the spacer portion for biasing the ejector portion to a normally retracted position relative to the blades and spacer. The ejector portion is manually displaceable to an advanced ejecting position. The biasing portion may be one or more beam springs connected and configured to reduce distortion and/or stressing of the relatively moving portions of the member during actuation.

Abstract: There is provided a shaving apparatus comprising an external cutting element and an internal cutting element cooperating with and drivable relative to the external cutting element with a reciprocating movement. The internal cutting element is secured to the external cutting element by means of a connecting element which is flexible in the direction of driving and is rigid in directions extending substantially transversely of the direction of driving. The external cutting element is formed as a U-shaped part from a sheet material. The internal cutting element together with the connecting element constitutes a strip also made of a sheet material and positioned between the legs of the U-shaped part. The internal cutting element is situated at the end of the strip near the transverse portion of the U-shaped part; and the other end of the strip is connected to the legs of the U-shaped part.

Abstract: This invention pertains to apparatus for trimming branches of trees and particularly branches high above the ground, without a pole saw, climbing the tree or using a ladder. The apparatus include spaced cutting links with sharp teeth at one end fastened upon a flexible chain. Each end of the chain is connected to a length of rope. A metal weight, sand bag, etc. attached to one of the ropes carries the flexible chain into position over the branch desired to be cut. A counter weight is also provided on one end of the flexible chain to automatically position the cutting side of the spaced cutting links in a downward facing, cutting position as the chain is pulled up onto and over the branch.

Abstract: Shank and knife portions of a cutting tool having particular known utility in the leather tooling art are permitted to swivel within a sleeve member that is held in the chuck of a conventional electrical vibrating tool holder. An angular extension of the shank portion is bevelled to provide the knife portion of the cutting tool for contacting a leather work piece. The ease with which the shank and knife portions of the cutting tool are permitted to swivel is controlled at the time the cutting tool is inserted into the chuck of the tool holder by urging the sleeve against a spring that is coaxially positioned over the shank portion of the cutting tool between the sleeve member and a shoulder that serves to terminate the shank portion.

Abstract: Apparatus for mapping the outline of a surface area, such as a golf green, including a board having depending legs for placement on the green and a centrally mounted pivot peg extending upwardly from the top of the board. A sheet of paper is attached to the top of the board and typically surrounds the pivot peg. A dual segment measuring element includes an inner, rigid, proportional measuring segment and an outer, flexible, full-scale measuring segment. The inner measuring segment has a pivot hole for engagement around the pivot peg. The inner and outer measuring segments both have their respective zero-points of their scales coincident with the pivot hole. Full-scale measurements are transferred to the paper at corresponding points along the inner, proportional measuring segment.

Abstract: Strand-like apparatus for measuring roll position, i.e., roll gap and/or roll alignment, is moved through a caster between roll faces of a series of oppositely spaced pairs of conveyor rolls which define either a straight or curved strand travel path. Apparatus includes carrier means having resiliently deformable parallel sensing surfaces with an elastomeric core, and plural lateral and plural diagonal inductive distance measuring means pivotally linked to the sensing surfaces for generating roll gap and alignment signals. These signals are recorded. Single and multiple harness means attach single and multiple measuring apparatus to a powered starter bar at one or more lateral strand axes, thereby to make lateral roll position measurements during multiple or single passes, respectively.

Abstract: An apparatus including two gauging heads, each having a feeler adapted to cooperate with a cylindrical surface of a part to be checked, and control devices for moving the feelers into contact with the cylindrical surface and for obtaining a scanning motion of the feelers as a relative displacement of the measurement axis passing through the feelers with respect to the geometrical axis of the cylindrical surface.The apparatus is particularly adapted for controlling small diameters, in a static as well as in a dynamic condition.

Abstract: An electronic aligner head is mounted on one rear wheel of a vehicle. The aligner head projects a light beam toward the front wheel on the same side of the vehicle. A centering gage is adapted to contact lower points on the inner flanges of each of the rear wheel rims. A lateral arm is connected to a housing on the centering gage. The lateral arm extends past the one rear wheel and carries a centering gage head on the free end. The arm is adjustable in length to place the centering gage head at the same lateral distance from the chassis centerline as the light beam projector. The centering gage is removed from the position between the rear wheel rims and placed in a similar position between the front wheel rims. The centering gage head is configured to either reflect the beam back to a light beam detector on the aligner head or alternatively to direct the beam to a detector in the gage head. The detector provides a signal indicative of the toe of the one rear wheel.

Abstract: The circuitry and structure of a levitated ball inclinometer are disclosed. A ferromagnetic ball is centerized between pairs of electromagnets by electromagnetic forces of magnitudes sufficient to offset the gravitational forces imposed on the ball. The electric currents required are therefore proportional to the forces and can be used as measurements to determine inclination.

Abstract: A drying apparatus for drying a moving web of textile fabric material as it passes over a series of closely adjacent rotating cylinders. Each cylinder has a pair of end portions and an intermediate portion. A heat insulating cap is mounted on each end portion to restrict the flow of heat energy therefrom.

Abstract: This invention relates to a kiln for drying timber comprising:an elongated housing having a base, two side walls and a top wall and two end walls defining a timber treatment zone;a gas circulation passageway having a top passageway portion extending over said timber treatment zone, a side passageway portion extending down one side of said timber treatment zone, a treatment passageway portion extending through said timber treatment zone, and a side passageway portion extending up the other side of said timber treatment zone merging with said top passageway portion, each said side wall being sloped whereby each of said side passageway portions is broad at the top of the kiln and narrower at the bottom of the kiln thereby to provide a substantially even rate of flow of gases at various levels within said treatment zone; and,reversible gas circulation means within said top passageway for maintaining the circulation of treatment gas in said other direction through said gas passageway thereby the direction of gas f

Abstract: An improved light weight crampon for ready attachment to shoes and boots as an ice creeper or the like having rugged construction and versatility of adjustment.

Abstract: The invention relates to a dragging type head (1) of a suction dredger, the head having a driven cutting device in front of the suction tube mouth, which cutting device (5) rotates about a horizontal transverse axis and has cutting blades at its outer circumference. The main part of the cutting device (5) is enclosed by a cap (6) connected to the suction tube mouth (4). The cutting blades (e.g. 15,16,17,18,19 and 16', 17', 18', 19') are arranged in the form of several V-shaped patterns (11,12) upon the circumference with a channel digging type blade (15,20,27) at the leading top of each V. All the blades are shaped such that they move the cut material laterally towards the plane of the channel digging blades (15,20,27) and all the blades may be in the shape of a plough (28).

Abstract: An identification snap for attachment to woven material such as clothing includes a first plate member bearing identifying indicia on an outer surface and a post projecting from an inner surface, and a second plate member including a centrally disposed orifice extending from an inner face to an outer face, the orifice being defined by a substantially frusto-conical wall which converges toward the inner face. The orifice is sized to receive the post of the first plate member in an interference fit so that when the first plate member is placed against the fabric of a garment with the post extending through it and the second plate member is placed on the opposite side of the fabric, the post can be received within the orifice, thereby joining the first and second plate members and clamping the fabric therebetween.

Abstract: The invention concerns the field of information display boards, and relates to an attachment plate constituted in the form of a plane body comprising:on its vertical side edges, two mutually complementary assembling tabs,and on the level of its lower edge, a bar designed to fit in one slot of the board.The present invention finds a particular application with boards designed for the display of T-shaped cards.

Abstract: A machine for the manufacture of a panel file for the storage of flat, flexible data elements is herein disclosed. A sheet of flexible resilient material is unrolled from an arbor. The material is cut into strips and rolled onto reels. The strips are substantially narrower than the depth of the pockets to be formed in the panel file. The reels are mounted on a strip aligning mechanism so that as the strips are unloaded from the reels they are in a parallel overlapping relationship. The strips are then pulled through an accumulator and placed in a heat sealing die. In the heat sealing die, the strips are joined to each other proximate the ends thereof to form a layered panel of overlapping pocket entrances. Also in the heat sealing die, a pocket forming sheet is attached to the back of the layered panel of strips.

Abstract: An animated display showing the Nativity scene. Human figures representing the Wise Men, shepherds, etc., move past the crib containing the infant Jesus. Each figure pauses, turns towards the crib, bows, turns back, and then moves away. The pausing action is created by a drive gear with some missing teeth. The turning action is created by two racks which mesh sequentially with a gear on which each figure is mounted. The bowing motion is created by a hinge mounting for each figure, and a push-rod actuation mechanism.

Abstract: A signage system includes a frame including a vertical support plate having horizontal sign mounting flanges on at least one side of the plate. Removable plate-shaped lettering inserts are mounted on the frame by mounting flanges on the back surface of the lettering inserts that mate with the mounting flanges on the support plate. The flanges are engaged by fitting the mounting flanges of the lettering insert endwise on the ends of the mounting flanges for the support plate and sliding the lettering inserts horizontally onto the frame. Removable end caps cover the ends of the frame and lettering inserts, with the end caps including at least two opposed resilient fingers that fit over and press resiliently against the opposite sides of the support plate to hold the end caps on the frame. The end caps are formed by joining together two identical halves.

Abstract: A tool for extending the barrel of a revolver crane and for checking the alignment of the crane barrel and cylinder locking aperture in a revolver frame. The crane barrel is inserted over an alignment stud and an adjustable stylus is threaded into contact with the crane barrel near its end. Rotation of the crane barrel causes a groove to be worn on the outer surface of the crane barrel and thus cause the barrel to elongate to its desired length. Additionally, the alignment stud may be used to align the crane barrel to the revolver cylinder locking aperture.

Abstract: A firing pin block for a firearm of the type having a reciprocating bolt assembly including a breech bolt and slide block, a firing pin, and a pivotal locking block. The slide block and locking block have cam means which cooperate to pivot the locking block in and out of locking engagement with a recess in the barrel as the slide block is reciprocated to close and open the bolt. The operation of these cam means is coordinated with relative longitudinal displacements between the bolt and slide block so that, at any time the locking block is not completely locked, the slide block prevents sufficient forward movement of an abutment on the firing pin to cause the firearm to discharge. This firing pin block is effective even though the firing pin spring and retaining pin may be broken, distorted, or missing.