Abstract: A pick-proof lock of the cylinder type primarily intended for use in doors, which includes a locking collar or sleeve slidably mounted around a portion of the cylinder plug and which contains a notch to receive a spring pressed pin which is contained in the cylindrical shell of the lock. The collar or sleeve is slidably and rotatively received in the shell and spring pressed for engagement of its notch with the pin, whereby rotation of the plug within the shell can only be accomplished to effect unlocking of the lock when the spring urged locking collar has been displaced rearwardly of the lock from a projected locking position to a retracted unlocking position. Since the locking collar and the pin which locks said collar to the shell do not communicate with the keyway of the plug, tools and other instruments normally used for picking locks are ineffective in picking the lock.

Abstract: A corrugated elliptical waveguide comprises a unitary, fluid-impervious, corrugated metallic tube with a substantially elliptical cross section. The corrugated tube is permanently twisted about its longitudinal axis for connecting two terminals having their E planes out of register with each other. The twist is uniformly distributed along a predetermined length of the corrugated tube. The twist is formed by twisting a corrugated circular waveguide about its longitudinal axis and simultaneously converting the circular cross section to an elliptical cross section, thereby causing the twist to be set in the elliptical waveguide.

Abstract: A device for the cold rolling of narrow flat lands on the cylindrical surface of heat exchanger tubing, just prior to the winding onto the tubing of one or more metal strips for the production of finned tubing, the device having pressure rollers on pressure levers carried by a journalled supporting spindle which rotates with the tubing, and a control sleeve inside the hollow spindle which, under the action of a linear actuator, interrupts the rolling action as desired, while the winding operation continues.

Abstract: A rolling mill comprises a pair of upper and lower work rolls, upper and lower backup rolls respectively backing those work rolls, upper and lower intermediate rolls interposed respectively between the upper work roll and upper backup roll and between the lower work roll and lower backup roll, and benders connected to the upper and lower intermediate rolls, respectively. This arrangement enables the surfaces of the upper and lower work rolls in contact with a material to be rolled to be made substantially rectilinear.

Abstract: A modular linear transducer assembly is mounted between relatively displaceable piston and cylinder members of a hydraulic roll gap control arrangement in a four-high rolling mill stand. The piston and cylinder members have coaxial openings centrally therethrough which receive the modular transducer assembly. The transducer assembly includes axially displaceable sleeve and plunger members, one of which is attached to the piston member and the other to the cylinder member for displacement therewith. The plunger supports a low voltage differential transformer coil having an axial passageway therethrough, and the sleeve member supports a core rod which extends into the coil passageway. Relative displacement between the piston and cylinder members imparts corresponding relative displacement between the coil and core rod to produce a signal indicative of roll gap change.

Abstract: A method of manufacturing a heat-transfer wall for vapor condensation comprising the step of forming on the heat-transfer surface, a number of shallow grooves substantially in parallel at a fine pitch, and then forming, on the heat-transfer surface and in the direction across said shallow grooves, a number of grooves deeper than the shallow grooves at a fine pitch by cutting and turning up the heat-transfer surface in the plowing manner. Said method may further comprise a subsequent step of curling the edges of the ridges formed in the above-mentioned step into said deep grooves.

Abstract: A method of calibrating a densitometer to meter two gases of different molecular structures by empirically deriving a hole size function of the indicated error for one gas in the density equation of the other and performing tailored reboring of the hole in a production unit in accordance with the hole size derived from the function by determining the full scale error thereof.

Abstract: A variable area metering tube is described having a non-linear graduated measuring scale wherein the scale compensates for non-standard variations in the cross-sectional flow area of the metering tube.

Abstract: A testing apparatus for testing the sliding characteristics of the soles of ski boots. The testing apparatus includes a lever arm for applying a downwardly directed force onto an upwardly facing boot sole adjacent structure engaging either the toe or heel of the ski boot. A drive mechanism is utilized to draw the member which is applying the downwardly directed force laterally of the ski boot. A measuring device is provided for detecting the sliding characteristic of the member which applies the downwardly directed force onto the upwardly facing boot sole.

Abstract: The instant invention relates to a device for testing the end buckling strength of a can body wherein a uniquely disposed compressible ring- or doughnut-like member of appropriate elastic material is adapted to be compressed against the inside surface of a metal or container for the purpose of sealing the interior of the metal can from the atmosphere. The sealed interior of the can is then subjected to appropriate fluid or air pressure to determine the buckling characteristics of the can's closed end structure, after which the can body can be released from the testing device in an improved fashion.

Abstract: External pipe testing apparatus is disclosed as comprising semi-cylindrical housing sections hingedly connected for swinging between an open position to permit the housing to be moved into and out of a position about a section of the pipe to be tested. When the pipe sections are locked to one another, seal strips mounted on the inside of each housing section are caused to sealably engage with one another and the ends of the pipe section to form an annular test chamber about the pipe section.

Abstract: A method of ascertaining the state of aggregation of a medium, whereby the flow of the medium is directed to a first of a series of two or more coaxially arranged nozzle means, further the initial pressure of said medium ahead of said series of nozzle means is compared with a further pressure, said pressure generated when following nozzles are flowed at directly through a respective preceding nozzle via a closed space arranged between two or more nozzles or following the final nozzle, and the correspondingly generated differential pressure is utilized as measurement value for indication of the state of aggregation and if necessary directly or indirectly for controlling the flow of said medium.

Abstract: Apparatus and method for determining the settling rate of solids or particulate bearing liquids in a continuous process or flowing stream in which a sample of the material is periodically selected and placed in a chamber which is transparent or has a transparent portion through which a light beam can pass such that a detector detects the amount of light passing through the chamber and the material and wherein the light transmissivity at various times is recorded and used to calculate the partial settling rate, the full settling rate and the percentage of solids or parts per million in the sample.

Abstract: A process for measuring the adhesive power of pressure-sensitive adhesives, especially adhesive tapes or sheets; it is also related to a device for implementing this process. This process consists in causing a ball to fall freely onto the adhesive surface of the tape or sheet and exerting a vertical upwardly directed separating force upon the ball, the measurement of the adhesive power of the adhesive being a function of the time comprised between the instant when the separating force is initially exerted upon the ball and the instant when the ball returns to its initial starting point.

Abstract: A well driving and monitoring system for a well of the reciprocating rod type utilizes a right angle drive transmission with a load cell therein arranged to monitor torque loads and thus continuously monitor the loads on the reciprocating rod of the pumping unit. The monitoring system utilizes a first set point warning to create a signal which may be transmitted to a central station if exceeded and a second higher set point to shut down the pump if exceeded. A plug in strip chart recorder is employed to permit the operator visually to see the loads during a pump cycle so that analysis, adjustments or corrections can quickly be made. The system is secured against vandalism. In addition, a simplified adjustable counterweight is provided which can readily be altered in capacity and field adjusted as to position. An improved and simplified crank connection on the output shaft of the right angle drive facilitates assembly and disassembly while providing a narrower, cleaner, more compact drive.

Abstract: A flow meter comprises a housing defining a fluid inlet passage and a fluid outlet passage; a piston defining a jacket surface and a base surface is arranged in the housing for reciprocating movement between the two passages; a biasing spring urges the piston into a zero flow position in which the piston interrupts the communication between the two passages; the base surface of the piston faces the inlet passage so that the fluid flow displaces the piston into a flow position; flow distributing means in the form of a partition arranged in the outlet passage has a plurality of slots shaped for adjusting the flow rate between the two passages according to the variation of the spring bias of the moving piston; and an electrical position detector coupled to the piston to generate an electrical signal proportional to the displacement of the piston.

Abstract: A capacitive liquid level sensor for sensing the height of liquid in a liquid storage tank at a plurality of locations. The liquid level sensor includes a cylindrical housing which extends along a line perpendicular to a predetermined reference level which is approximately parallel to the expected level of liquid in the storage tank. Several capacitors are included within the housing, each employing an air/liquid dielectric, whereby the capacitance values of the capacitors are individually variable due to any variations in the liquid height at each location. Several alternative cross-sectional structures are shown whereby the cylindrical housings are employed as a common plate to the several capacitors located within each housing.

Abstract: An automobile fuel gauge system comprises a main sensor unit for a main indicating system being provided in a fuel tank, a small chamber with top open fixedly provided at the bottom of the fuel tank and having at its lower side a hole for fuel passage, and an auxiliary sensor unit for an auxiliary indicating system provided in said chamber. The system includes a main dial section and an auxiliary dial section for performing indications according to electric signals transmitted from said main and auxiliary sensor units, respectively, and said auxiliary sensor unit is adapted to operate only when fuel in the fuel tank is running short.

Abstract: An apparatus for indicating the level of a surface of a fluid in a tank including a vertically disposed non-magnetic column provided on the tank and coupled to the tank such that the fluid in the tank flows into the column, a non-magnetic level indicator housing provided on the column, a plurality of horizontally disposed magnetic rotors rotatably coupled to the housing, a float provided in the column and a magnetic member provided in the float.

Abstract: A sight glass and sampling system for the output of a liquid processing device. The system includes a sight glass connected to the outlet of a liquid processing device. A first three-way valve controls the flow from the outlet of the liquid processing device to the inlet of the sight glass. A second three-way valve controls the outlet from the sight glass. A valve controlled sample conduit is connected between the first and second three-way valves. A bypass conduit connects the first and second three-way valves and is controlled by these valves.

Abstract: A wheel balancing tool having a support cable that partially extends into a hollow shaft to a suspension point coincident with the tube axis, two wheel adapters threaded onto the tube, and an annular magnifying indicator attached to the cable juxtaposed an indicator plate attached to the tube, the suspension point adjustable within the tube by means of a rod having an end portion extending into the tube to define the suspension point and a stop means attached to the rod for adjusting entry of the rod into the tube.

Abstract: The inspection of a portion of an internal member of an assembled article, unavailable for direct line inspection, for example portions of the rotor of a gas turbine engine, is accomplished through the use of an ultrasonic probe inserted through an access port of the article toward a surface of the member to be inspected. As a result of predetermined positioning of a transducer in the operating head of the probe to bounce an ultrasonic signal from an internal boundary toward the portion to be inspected and the comparison between predetermined and received signals, along with an analysis of the comparison, determines whether a defect is present in the member.

Abstract: A transducer for measuring the internal pressure in pipes, preferably injection pipes of diesel engines by determination of pipe deformations, comprises a rigid housing enclosing the pipe in which the pressure is to be measured, and at least one elastic sensor element arranged inside the housing and adjacent to at least a part of the circumference of the pipe. The sensor element and the housing are detachably mounted on the pipe and between the housing and the sensor element there is arranged an endorsing element elastically forcing the sensor element against the pipe whereby deformations of the pipe are transmitted frictionally to the sensor element.

Abstract: A grip for a materials testing machine comprises a housing, first and second wedge members within the housing, the first wedge member having a gripping surface defining a test-specimen-receiving aperture and the second wedge member having an aperture for receiving the first wedge member, the wedge members being movable with respect to each other, and each of the wedge members having an inclined portion directed oppositely to the inclined portion of the other wedge member, and means for preloading the wedge members to cause them to move with respect to each other, whereby the wedge members interact to exert a gripping force on a test specimen through the first wedge member's gripping surface.

Abstract: A push-button controlled device is provided for storing a number of preselected positions of a control member controlling the variable condition of a second device such as an electrical circuit.A plurality of push button units are operable both for storing a position of the control member and for selecting the stored position.

Abstract: A crank assembly for coupling a plurality of connecting rods to a common crank pin of a crankshaft includes an articulation member journaled on the crank pin. The articulation member carries a plurality of knuckle pins arranged in a radial array about the crank pin. Auxiliary cranks interconnect the articulation member and the body of the machine to limit freedom of movement of the articulation member and to assure that it does not rotate in space as it moves with the crank pin in a circular path around the axis of the crankshaft. The described assembly is particularly useful with reciprocating piston machines of the type having a radial array of cylinders with pistons movable in the cylinders, and permits the use of identical connecting rods, each drivingly connecting a separate one of the knuckle pins and a separate one of the pistons. Moreover, each of the auxiliary cranks can be used either as an additional power transmission input or output for the system.

Abstract: Vibrator devices, of the type which produce a vibratory effect as a result of rotation of an out-of-balance mass, comprise a casing and a rotor which has a fluid-containing cavity with the contained body of fluid contacting a swept annular surface of the casing. A piston movable radially in the rotor and/or the body of fluid provides the out-of-balance mass and the vibratory force is transmitted to the casing directly by the fluid pressure on the swept annular surface thereof. The rotor structure is mechanically balanced so that substantially no vibratory force is transmitted through the rotor shaft and bearings.

Abstract: A lever mechanism including a lever which is pivotally mounted between its ends on a pivot shaft forming two lever arms. One of the lever arms is arranged to receive a force applied thereto and the other of the lever arms has an end portion arranged to transmit movement and force to a working element. The end portion has part-cylindrical surfaces which cooperate with part-cylindrical surfaces on oppositely located slide blocks. Each slide block has a planar slide surface which is parallel to a shaft of the part-cylindrical surfaces of the end portion. The planar surface of each slide block is arranged to slidably abut a planar surface on the working element. The slide blocks are non-rotatably connected to each other via their planar slide surfaces in parallel planes by means of dogging elements which are pivotally mounted on the shaft of the part-cylindrical surfaces of the end portion.

Abstract: The variable speed transmission includes a power input drive shaft and a variable throw crank having a zero throw position aligned with the input shaft. The variable throw crank is coupled to the input shaft for rotation therewith and its eccentricity with respect to the axis of rotation of the input shaft can be varied. A control plate, also referred to as a master link, is rotatably mounted on the crank and a plurality of clutches having input and output shafts are operatively connected to the control plate through a plurality of pitman type links, whereby the control plate oscillates the input shafts of the clutches upon rotation of the power input shaft and variable throw crank of the transmission. The outputs of the clutches are connected to an output shaft for the transmission.

Abstract: A bicycle transmission with one or two driving sprockets on a pedal shaft, selectively connectable with any one of several driven sprockets of progressively varying diameters on a rear-wheel axle, is controlled by a gear-shifting lever rigid with one or two cam disks each coacting with a cam follower on an associated rocker arm. Each rocker arm is tied to a flexible link, such as a Bowden cable, serving for the relative axial shifting of the chains and a respective sprocket set to let the chain jump from one driven (or driving) sprocket to an adjoining one. Each cam disk has a plurality of peripheral lands whose distances from the disk axis determine the engagement of the chain with one of the sprockets of the associated group.

Abstract: A front derailleur for a bicycle pivotally couples a base member fixed to the frame of the bicycle, two linkage members, and a movable member having a chain guide mounted thereon which together constitute a four-connected component linkage mechanism. When a bicycle speed change is made, the movable member moves relative to the base member such that the chain guide component swingingly moves with the amount of movement of the chain guiding portion of the chain guide being larger than the amount of movement of the movable member.

Abstract: An improved, blocked, change gear transmission having an input shaft driven by a prime mover through a normally engaged, selectively disengageable, master friction clutch is provided with means for decelerating and positively reverse rotating the transmission input shaft. The means for decelerating and positively reverse rotating the transmission input shaft may be selectively operator actuated and/or automatically actuated. The means for decelerating and positively reverse rotating the transmission input shaft is preferably only actuatable upon disengagement of the master clutch and may be selectively or automatically actuated by the master clutch control.

Abstract: A support member joined to a steering column to hold the column from below has planar opposite side portions formed in their rear ends closer to the steering handle with elongated grooves for passing bolts for anchoring the support member to the vehicle body. A frame-shaped energy absorbing member having a deformation promoting aperture punched therein to form zigzag substantial portions in parallel to the axis of the column is provided between the support member and the vehicle body. The absorbing member is partially formed with weak portions and is secured at its front end to the front portion of the support member and anchored to the vehicle body by the bolts.

Abstract: A mechanism is described for selectively engaging a handwheel with a shaft to manually rotate the shaft with the handwheel. The mechanism automatically disengages the handwheel from the shaft when the shaft is rotated by a power source above a predetermined speed. Further, when the shaft is thusly rotated by a power source, the mechanism does not allow an operator to engage the handwheel with the shaft. The mechanism includes a complementary groove system and a cam, one being on the shaft and the other on the handwheel. The groove system comprises at least two laterally-spaced grooves encircling the axis of the shaft, and a third groove spiralling about the axis between the first and second grooves. In one embodiment, the cam is mounted on the handwheel and rides in the grooves in the shaft. When the handwheel is axially depressed, to engage the shaft, the cam rides in the innermost encircling groove.

Abstract: The present invention relates to a chain guard for a chain which is conventionally used as a means for transmitting power and typically includes individual roller link pairs coupled together by pin links, said guard consisting of an elongated flexible elastic member with its ends secured together forming a loop and provided with a chamber which opens inwardly of the loop and elongated slots provided in the chamber wall and disposed to accept the pin links and provided with lubricant storing means within the chamber.

Abstract: A multistage speed reducer for high speed rotation including a planetary roller friction reducer for the first stage reducer and a geared reducer for the second stage reducer, the planetary roller friction reducer having its output shaft also used as the input shaft of the geared reducer. Such an arrangement permits transmission of a very high speed and large horsepower rotation at a relatively high reduction ratio with low noise while at the same time consuming less space. The speed reducer may preferably be equipped with safety means for excessive torques.

Abstract: A motion transmitting device including four basic elements, namely, eccentric means, meshing means formed from a number of meshing elements which are linked but movable independently with respect to each other, wheel means formed with portions adapted to engage said meshing elements, and movement limiting means, including a datum member, wherein said eccentric means is disposed to cause each of said meshing elements to become engaged with, and subsequently to become dissociated from, said portions, while said meshing elements are individually guided by said movement-limiting means within specific limits of movement relative to said datum member, such that always a plurality of adjacent ones of said meshing elements are simultaneously in driving engagement with, and stationary relative to, a corresponding number of said portions, and that the total movement relative to said datum member of each of said meshing elements, while it is drivingly engaged with one of said portions, follows a substantially ovoidal pa

Abstract: When the engine runs on all cylinders thereof, a diaphragm device for a hydraulic pressure regulating valve will operate in response to a pressure difference between the atmospheric pressure and intake vacuum within an intake manifold of the engine. A control system includes a solenoid valve which, when the engine runs on selected cylinders of all, will apply vacuum within a source of a predetermined vacuum to the diaphragm device. According to one preferred embodiment, the diaphragm device has a single chamber and the solenoid valve is adapted to selectively apply the induction vacuum and the predetermined vacuum to the single chamber. According to another preferred embodiment, the diaphragm device has a first chamber in communication with the intake manifold and a second chamber and the solenoid valve is adapted to selectively apply the atmospheric pressure and the predetermined vacuum to the second chamber.

Abstract: Fuel economy of a multi-cylinder internal combustion engine has been improved by allowing, when a vehicle is at a standstill, the engine to run on selected cylinders of all. The idling operation of the engine on the selected cylinders has been made smooth by the provision of a switch valve in a control circuit of the transmission. With the switch valve, as soon as an accelerator pedal is released when the vehicle is at a standstill, hydraulic fluid will be drained from the control circuit to render a gearing of the transmission in a neutral condition even if a manually selector valve in the control circuit is held in a drive range position. This prevents transmission of load to the engine through the hydrokinetic unit which otherwise would occur when the manually selector valve is in the drive range position.

Abstract: There is disclosed an electronic circuit arrangement for the regulation of the transmission stages of an automatic gear changer employed, for example, in a vehicle. The circuit includes a monostable circuit comprising an input transistor and an output transistor, the circuit being released by a pick-up device which is responsive to the speed of the vehicle. The circuit is substantially independent of variations of ambient temperatures and is of simple design.

Abstract: A drill pipe handling mechanism for a drilling rig includes spaced apart upper and lower arms mounted on a shaft which is mounted for pivotal and limited axial movement with respect to an axis which is spaced from and parallel to the drilling axis. The lower arm includes a receptacle for the lower end of a drill pipe section. The upper arm includes a drill pipe holder having a power actuated movable gate section. A drill pipe retainer is pivotally mounted on the shaft above the pipe holder and is operated by a separate power actuator. Opposed power actuated pipe gripping and holding wrenches are disposed on the lower part of the rig mast for gripping and holding a drill pipe section while threaded joints are broken loose by a rotary head connected to the upper end of the drill string. A power actuated wrench is mounted for pivotal movement into pipe gripping position for breaking loose threaded joints which cannot be loosened by the rotary head.

Abstract: The apparatus has a loading drum 3 with rod guide tubes 31, a rod magazine 4, and a rod separator apparatus 5. In order to permit the rod stock of the openable guide tubes 31 to be fed in more than one spindle position, there are provided arms 9 and bails 11 for the rod magazine 4, the separator 5, and the motor 6 of a rod feeding apparatus. The arms 9 and bails 11 are pivotable about a common longitudinal traverse 10 and can be locked in various chosen positions A, B by means of a rod 13 passing through all the arms 9, the bails 11 and through in each case one of a plurality of bores 12', 12", 12"'.

Abstract: A safety system for the drive of a cross cutter for a web of material, having an electrical or mechanical synchronizing system between the drives of the feed and cutting mechanism which is adjustable for the size of the piece to be cut and which consists of an adjustable asymmetrical mechanism and has speed control associated with the drive of the feed mechanism to limit the speed of the feed means on the basis of a signal corresponding to the setting of the asymmetrical mechanism. A function generator generates a signal to be applied to the speed control which is directly dependent thereon to define the speed value for the drive of the feed mechanism and wherein the function generator is responsive to the asymmetrical mechanism for size-related, maximum permissible web velocity.

Abstract: A tubing notcher which comprises a housing having a longitudinally slidable cutter assembly attached thereto. The cutter assembly is to be manually moved through an appropriate actuation means connected to the cutter assembly. The cutter assembly includes a cutter which has an arcuate cutting edge. A tube, the open end of which is to be notched, is to be located upon a guide means which is fixedly secured to the housing. The guide means is inclined slightly less than a right angle in respect to the longitudinal axis of movement of the cutter. The cutter is to be located within the open end of the tube and upon movement of the cutter the open end of the tube is appropriately notched.

Abstract: A compact die cutting apparatus that is particularly well suited for cutting individual image sections out of a multiple image photograph of the type provided by a self-developing camera that takes identification photographs having two or more portrait pictures thereon for use on passports, I.D. credit cards, etc. The die cutting apparatus includes a base section with a punch device pivotally and slidably mounted on a lower portion thereof, an actuator assembly that pivots toward and away from the lower portion of the base section and has a cutting die, an image viewing and registration frame, and photograph support thereon, and aligning structure for automatically maintaining a punch cutting head on the punch device in operative alignment with the cutting die as the die is moved in operative relation with the punch cutting head.

Abstract: This invention relates to an apparatus for slicing cylindrically shaped columns of gels. More particularly, it relates to an apparatus for firmly holding cylindrical columns of acrylamide gel while making a longitudinal slice through the entire length of the column.

Abstract: In a key code generator which has key code generator circuits, each corresponding to one of a plurality of key switches and composed of a memory circuit for storing the status of the key switch with a master clock pulse, a circuit for detecting the status change of the key switch to its depressed or release state, means for deriving a key code from the outputs of the memory circuit and the detecting circuit, means for producing a latch pulse from the master clock pulse and the key code and means for completing the output generation with the master clock pulse, a circuit for determining priority of the key code generator circuits, and a control circuit for giving priority to key release over key depression when key switches are simultaneously released and depressed, respectively, there is provided a time-division device which comprises a key switch (m.times.

Abstract: An echo effect in a polyphonic digital tone synthesizer in which a musical tone is repeated at a controlled repetitive rate but decreasing peak amplitude when a key is depressed. The tone is repeated until the peak amplitude decays to a predetermined level regardless of when the key is released. If the key remains depressed, the peak amplitude decay recycles so that an echo effect will be repeated. The echo effect is obtained on a plurality of overlapping notes that need not be keyed in unison. The echo control includes an echo envelope register which stores a control word for each key that is depressed. The control word includes bits coded to identify the current amplitude of the echo decay envelope. The value of the control word is decremented at a control rate to provide a decaying echo amplitude. An echo delay register stores a control word for each key depressed, the control word being incremented at a controlled rate.

Abstract: An electronic tone synthesizer in which a master data list of digital values representing the amplitudes of points defining the waveform of a musical tone are transferred to a digital-to-analog converter at a rate proportional to the pitch of the tone being generated. Noise is superimposed on the musical tone by means of a random binary signal generator which controls a circuit for modifying selected ones of the digital values as they are transferred from the master data list to the converter. Modification of the selected values may be by a right shift operation, a 2's complement operation, or by selective delay.

Abstract: A keyboard musical instrument utilizes a magnetic action to strike a resonator element with a hammer in response to playing of a pivotally mounted key, the magnetic action including a pair of opposite polarity magnetic poles mounted on an actuating end of the key and a magnetic pole mounted on the hammer to be disposed in horizontal alignment with one of the poles mounted on the key of an opposite polarity when the hammer is in a rest position such that the opposite polarity magnetic poles attract one another with the hammer in the rest position and, when the playing end of the key is depressed, the similar polarity pole on the actuating end of the key is moved to repel the magnetic pole carried on the hammer to impel the hammer to strike the resonator element. A block of non-magnetic material can extend from the lower magnetic pole on th actuating end of the key under the magnetic pole of the hammer to engage the same and initiate movement of the hammer when the playing end of the key is depressed.