US3538958A - Piano stringing apparatus - Google Patents

Description

United States Patent Inventors Clifford W. Andersen;

William A. Wahl, De Kalb, lll.

Appl. No. 758,902

Filed Sept. 10, 1968 Patented Nov. 10, 1970 Assignee The Wurlitzer Company Chicago, Illinois a corporation of Delaware PIANO STRINGING APPARATUS 15 Claims, 23 Drawing Figs.

US. Cl 140/1, 84/197; 140/921, 140/93 Int. Cl. B2lf 45/00, G 1 0c 9/00 Field of Search l40/l 7 l References Cited Primary Examiner-Lowell A. Larsen Att0rney0lson, Trexler, Wolters and Bushnell ABSTRACT: Apparatus for use in stringing pianos and like musical instruments combines at a single work station a string forming unit, a work table arrangement and tuning pin driving means. The string forming unit includes a winder for coiling piano wire on tuning pins to produce string assemblies and a loop kinker for permanently deforming a midportion of the wire of the string'assembly into a hitch pin loop. The work table arrangement includes platens for supporting a piano plate in fixed position during installation of the string assemblies, and the pin driving unit is arranged for setting the pins of the string assemblies in a piano plate supported by the platens.

Patented Nov. 10,1970 I 7 3,538,958

Patented Nov. 10, 1970 I Sheet of7 0 y w w U fi Q. 14% M4 flaaizzwg Patented Nov. 10, 1970 3,538,958

J90 J54 @019 mflram Patented Nov. 10,1910 3,538,958

Sheet 6 of? dzzffard [/1 Quiz/Jew d. Mafi v PIANO srmuonvc APPARATUS This invention relates generally to the manufacture of stringed musical instruments such as pianos and more particularly to the installation of strings in these instruments.

The strings of a piano are held in place on the plate by a system of fixed hitch pins and rotatable tuning pins; and for many years, the cutting, winding and installation of the strings and the setting and leveling of the tuning pins has been laboriously performed by hand. Since one man has traditionally strung the entire instrument, considerable skill, dexterity and physical strength have been required for the task.

In the past, attempts have been made to simplify the job of piano stringing by precutting the strings, forming the hitch pin loop and winding the ends of the precut strings onto tuning pins using machines. However, a piano requires strings of many different lengths; and the handling and inventorying of the prefabricated string assemblies proved complicated and impractical.

Therefore, a general object of the present invention is to provide new and improved apparatus for installing piano strings.

Another object of the invention is to provide piano stringing apparatus that eliminates the need for inventorying prefabricated string assemblies.

Still another object of the invention is to provide piano stringing apparatus that combines equipment for fabricating string assemblies and equipment for driving tuning pins at a single work station.

These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.

The invention, both as to its construction and its mode of operation, will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FIG. 1 is a plan view of a metal piano plate of the type to be strung using the apparatus of the invention;

FIG. 2 is a perspective view of stringing apparatus in accord with the invention;

FIG. 3 is a vertical sectional view taken through the work table unit of the apparatus of FIG. 2 and showing the means for raising and lowering the conveyor carriage that is used in transporting piano plate assemblies to and from the work station defined by the piano stringing apparatus of FIG. 2;

FIG. 4 is an enlarged, plan view of the wire magazine employed in the piano stringing apparatus;

FIG. 5 is a vertical sectional view taken substantially along the line 5-5 of FIG. 4;

FIG. 6 is an enlarged, perspective view showing extraction of a length of piano wire from one of the compartments of the wire magazine;

FIG. 7 is an enlarged plan view of the rotary drive for the wire magazine taken substantially along the line 7-7 of FIG. 5;

FIG. 8 is an enlarged perspective view of the winding arrangement used in the apparatus of FIG. 2, a pair of tuning pins being situated in the winding chucks and the cup supports being shown retracted for insertion of the pins in the chucks;

FIG. 8a is fragmentary perspective view of a coil guide for use with a winding chuck;

FIG. 9 is a fragmentary, plan view showing the construction of one of the cup supports;

FIG. 10 is a view similar to the showing of FIG. 8 but illustrating the cup supports engaging the tuning pins;

FIG. 11 is a further enlarged, vertical sectional view taken along the line 11-11 of FIG. 10 and showing the means for positioning the cup supports;

FIG. 12 is a top plan view of the winder with the housing removed to show details of the winding mechanism;

FIG. 13 is a vertical sectional view taken substantially along the line 13-13 of FIG. 12 and showing the ejector mechanism;

FIG. 14 is a vertical sectional view taken substantially along the line 14-14 of FIG. 12 and showing further details of the winder drive and the control means therefor;

FIG. 15 is a perspective view of the winder and loop kinker in relaxed condition for assembly of the piano wire;

FIG. 16 is an enlarged, fragmentary perspective view of the kinker, shown tensioning the piano wire for forming the hitch pin loop;

FIG. 16a is a central, longitudinal sectional view taken, on a reduced scale, through the loop kinking arrangement;

FIG. 17 is an enlarged, fragmentary, perspective view of a tuning pin and wire coil as formed by the apparatus of the invention;

FIG. 18 is an enlarged perspective view of the pin driving unit of the apparatus of FIG. 2, shown in position for setting a tuningpin in the piano plate;

FIG. 19 is a vertical sectional view taken through the piano plate and showing further details of the pin setting operation;

FIG. 20 is a perspective view of the piano plate with two string assemblies mounted thereon; and

FIG. 21 is a schematic diagram of the control circuit for the disclosed apparatus.

Referring now in detail to the drawings, specifically to FIG. 1, a metal piano plate 30 is shown to be of the general type intended to have string assemblies installed therein in compliance with the present invention. According to conventional practices, the piano plate 30 includes a bass section 32, a treble section 34 and,middle section 36. A comparatively small number of wire-wrapped bass strings are intended to be installed in the bass section 32, each note in this section being represented by a single string. A comparatively larger number of doubled treble strings are intended to be installed in the treble section 34, each note being represented by three individual strings. The middle section 36 comprises an intermediate number of single strand strings, two such strings representing each note in this section. A suitable number of hitch pins 38 are integrally cast in the plate 30, and tuning pin mounting sites are provided in the plate 30 by means of tubu-. lar bushings 40 which are secured in suitable bores formed in the piano plate. A number of additional'bores 42 are provided at various locations about the piano plate for use in fastening the piano plate to a wooden back plate or sounding board 44, as is shown in FIG. 2 whereby to define a piano plate assembly 46.

Continuing with reference to FIG. 2, piano manufacturing apparatus indicated generally by the reference numeral 33 is arranged, in compliance with the principles of the present invention, for use in stringing the plate assembly 46. Apparatus 48 combines a string forming unit 50, a work table arrangement 52, a wire magazine unit 54 and a pin driving unit 56. The work table arrangement 52 includes a bed or stationary platform 58 that is elevated above the factory floor by legs 60; and in order to support the piano plate assembly 46 in fixed position during installation of various string assemblies, a suitable number of felt covered platens 62 are mounted on the stationary platform 58 and spaced thereabove by means of brackets 64 as is shown in FIG. 3. For facility in transporting piano plate assemblies to and from the fixed position established by platens 62, the work table arrangement 52 includes a conveyor carriage 66 that is arranged to be raised and lowered by a suitable number of fluid-actuated jacks 68 whose action is controlled by an operating lever 70. As is shown in FIG. 3, the jacks 68 include cylinder bodies 72 that are mounted on horizontal frame members 74 by means of brackets 76. The jacks 68 also include extensible and retractable piston rods 78 that are connected to the conveyor carriage 66 by means of suitable fixtures 80, and each of the jacks 68 is served by a pump 82 shown in FIG. 2. Antifriction conveyance of the piano assemblies is accomplished by means of a suitable number of horizontal rollers 84 which are journaled on the conveyor carriage 66. The rollers 84 are conveniently arranged in two rows as is shown in FIG. 2.

In order to provide precut and straightened wires of appropriate lengths, the magazine unit 54 is included in the apparatus 48 spaced a suitable distance apart from the work table arrangement 52 and generally in juxtaposition with the string forming unit 50, as is shown in FIG. 2. Turning to FIGS. 4 and 5, the magazine unit 54 comprises a hollow rectangular base 86, a back plate 88, a rotary drum 90 and a swinguble cover 92 that is mounted to the back plate 88 by means of a hinge 94. Continuing with particular reference to FIG. 5, the drum 90 has an open top 96 and a bottom that is closed with an imperforate panel 98. A shaft 100 is secured to the bottom panel 98 by means of a flange 102 and is journalled in a bearing 104 that is mounted on the base 86. The bottom panel 98 is secured across the drum 90 spaced above the bottom edge of the drum in order that a ring gear 106 may be exposed to mesh with a pinion gear 108 of a rotary drive arrangement 110.

The drum 90 houses a number of tubular compartments 112 that have open top ends and closed bottom ends, compartments 112 being situated around the inner periphery of the drum 90, as is shown in FIG. 4. The open top ends of the tubular compartments 112 are arranged substantially coplanarly with top of drum 90. So positioned, the tubular compartments may be stepped successively into alignement with a lateral slot 114 fashioned in cover 92 and constituting the cover a selector plate. The compartments 112 take different lengths to accommodate the different lengths of piano wire required in stringing the instruments; and in compliance with the present invention, the cover 92 is normally disposed closer to the plane of the top ends of the compartments 112 than the smallest difference between the different lengths of piano wire in order to prevent loading of wires of too great a length. It will be appreciated that the cover 92 cannot be closed into its normal, horizontal condition if overlength wires are accidentally loaded into one of the compartments 112. Of course, it will be both visually and tactily apparent should wires shorter than the specified lengths be loaded into any of the compartments 112.

The drive 110 is arranged to cause incremental rotation of drum 90 for successive display of the top ends of compartments 112 at the slot 114. More specifically and with reference to FIG. 7, the drive 110 includes a ratchet wheel 116 that is fastened coaxially to the pinion 108 by means of a common shaft 118. The ratchet wheel 116 and thereby the gear 108 is driven through a suitable arc of movement by means of a pawl 120 which is swingably mounted on a gear 122 eccentrically thereof by means of a pivot pin 124, pawl 120 being biased into engagement with the teeth of ratchet Wheel 1116 by means ofa lcufspring 126. The gear 122 meshes with a companion gear 128 that is affixed on on output shaft 1.10 ol'un electric motor 132, motor 132 being secured in turn to the base 86 by means of a mounting bracket 134. The motor 132 is preferably ofa type which, when energized, turns shaft 130 through a specific rotational increment, such as one revolution. whereby to step the drum 90 in a uniform manner. Other types of incremental driven may be employed. M will be described more fully hereinafter, the motor 1321s energized in coordination with the operation of the string forming unit 50; and for this purpose, the motor 132 is connected to a control console 136 by means of an electrical cable 138 as is shown in FIG. 2.

Continuing with reference to FIG. 2, the string forming unit 50 includes a winding arrangement 140 for coiling piano wire on tuning pins to produce string assemblies and one or more loop kinking arrangements 142 for permanently deforming a mid-portion of the wire of such a string assembly into a hitch pin loop. The winding arrangement 140 and the loop kinking arrangements 142 are mounted on a horizontal platform 144 which, in turn, is supported on a vertical post 146. The control console 136 is cantilevered from the post 146 by a bracket 148, and the post 146 is connected to the stationary portion of the work table arrangement 52 by means of a horizontal arm 150. In addition, the platform 144 is provided with a lateral extension 152 which may be used in storing boxes 154 that contain a supply oftuning pins.

Turning to FIG. 8, the winding arrangement 140 includes a housing 156 which contains the drive for a pair of rotatable chucks 158'. Each of the chucks 158 is fashioned with a square central aperture 160 that is sized to receive the correspondingly shaped end of a tuning pin 16?. in nonrotntable relationship. In order to locate the tuning pins 162 axially of the chucks 158, a pair of cup supports 164 are rotatably mounted in a swingable fixture 166 by means of ball bearings 168, as is shown in FIG. 9. As is also shown in FIG. 9, each of the cup supports 164 is fashioned with a conical recess 170 which confronts the corresponding chuck 158 for use in locating a tuning'pin 162 axially. The fixture 166 is arranged to be pivoted in the general direction of the chucks 158 to urge the cup supports, first, into aligning engagement with the tuning pins held in the chucks and, second, in the direction generally away from the chucks 158 to release the tuning pins for extraction from the chucks. For this purpose, the platform 14 i is perforated with an aperture 172, shown in FIGS. 11 and 11; and the fixture 166 is mounted on a bracket 174 by a bolt 176,

' bracket 174 being swingably mounted on a horizontal pin 178.

In addition, the bolt 176 serves as a vertical pivot so that fixture 166 may accommodate slight irregularities in the fitting of the tuning pins into the chuck apertures. The positioning means for advancing and retracting the cup supports 1.6 1 includes a fluid-actuated jack 180 which is suitably mounted beneath the platform 1% as is shown in FIG. 11. The jack 160 comprises a cylinder 182 that contains a piston, not shown, which is rigidly attached to an extensible and retractible rod 184. The end of piston rod 184i is secured to a pendant tail portion 186 of the bracket 174 by means of a nut 1118, the piston rod 184 passing through a diploconical opening 190 in the tail portion 186. The shape of opening 190 accommodates the rocking motion of bracket 174. The jack 180 is operated in coordination with other elements of the apparatus as will be described more fully hereinafter.

Each of the tuning pins 162 is fashioned with a transverse bore 192, as is shown in FIG. 8 for example; and as is also suggested in the latter FIG, these transverse bores are intended to be disposed. generally vertically in order to receive the cut ends of a piano wire 19.4, as is shown in FIG. 15, preparatory to the winding of abbreviated coils about each of the tuning pins.

Abbreviated coils of wire are conventionally wound on each of the tuning pins to facilitate both the tensioning of the corresponding string and the tuning thereof, and one of the general objectives in stringed instrument manufacture is the provision of uniform, relatively tightly wrapped coils. in order to direct the piano wire into n desirably cylindrical coil upon rotation of the chucks 151i and the tuning pins held therein, the winding arrangement 1 10 advantageously includes a lateral coil guide 196 as is shown in FIG. 8. The coil guide itself includes a reciprocablc foot 198 having upright guide surfaces 200 associated with horizontal wear blocks 201. A guide surface and corrmipomllng weur block are arranged with such of the chucks 153, and the guide surface is disposed generally parallel with the axis of the chuck between the chuck and the corresponding cup support. In compliance with a feature of the present invention, each of the wear blocks 201 is fashioned with a longitudinal, upwardly opening slot or groove 202, as is shown in FIG. 8a, in order that the cut ends of the piano wire 194 may pass completely through the tuning pin bores 192 and present a tip portion beyond the end of the bore. Such a tip portion will be bent over into a hook, as indicated at 203 in FIG. 17, upon rotation of the tuning pins. The bent over tip portions or hooks 203 have been found to promote the formation of tightly wrapped coils on the tuning pins.

In order to direct horizontally reciprocal movements of the foot 198, a bed member 204 is mounted on the platform 1% and includes a way 206 which slidably receives the foot 198. Horizontally reciprocal movements of the foot 198 are developed by means of a fluid-actuated jack 208 that includes an extensible and retractable piston rod 210, shown in FIG. 15, which is attached at its end to the foot 198. The foot is reciprocated between two extreme positions shown in FIGS. 11

and respectively. In FIG. 8, the foot is shown retracted with the guide surfaces 200 spaced laterally from the pins 162 in order to accommodate insertion of the tuning pins 162 into the chucks 158, for example. In FIG. 11), the foot 198 is shown in its extended position where the guide surfaces 200 are spaced relatively closely to the tuning pins 162 in order to direct the piano wire into a cylindrical coil about the tuning pins upon rotation of the chucks 158.

To promote winding of the desired type of coil on the tuning pins 162, the winding arrangement 140 additionally includes a reciprocable winding blade 212 with each of the chucks 158. The winding blades 212 are arranged to advance parallel with the axis between the associated chuck and its cup support upon rotation of the chuck in order to cooperate in directing the piano wire into a cylindrical coil. For this latter purpose, each of the winding blades 212 is mounted on a horizontal rod 214 by suitable means such as a fastener 216, in compliance with the showing of FIG. 13. Continuing with reference to FlG. 13 and with additional reference to FIGS. 12 and 14, the rod 214 is affixed to a square shaped nut 218 by an annular fillet weld or other suitable means, the rod 214 passing slidably through a bore formed in a cover plate 220 and a mounting block 222. The chuck 158 comprises an extension of a screw 224 which threadedly engages the nut 218 whereas both the chuck 158 and the screw 224 are driven from a spur gear 226 having a bearing hub 228. A pair of bearing blocks, fore block 230 and aft block 232 are mounted on the platform 144 in spaced relationship to admit the gears 226 therebetween. The bearing block 232 is appropriately apertured and lined with bearing material to define journals for the bearing hubs 228 and the bearing block 230 is provided with square ways 234 for receiving and guiding the nuts 218. One or more tubular spacers 236 maintain the relative position of the bearing blocks 231) and 232, and the end face of bearing block 232 is closed by a pair of cover plates 238.

In order to rotate the chucks 158 in a counterclockwise direction as viewed from the cup supports, that is, as viewed in FIG. 8, the spur gears 226 are meshed with a common drive gear 240, shown in FIGS. 13 and 14. To provide reversible driving motion to the spur gears 226, the common drive gear 240 is meshed, in turn, with a rack 242, rack 242 being mounted on an extensible and retractable piston rod 244 of a fluid-actuated jack 246 as is shown in FIG. 14. The jack 246 is mounted beneath the platform 144 by suitable brackets, not shown; and the actuation of jack 246 is coordinated with the energization of the other drive elements in the apparatus as will be described more fully hereinafter.

In compliance with the features of the present invention, means are advantageously provided for expelling the tuning pins 162 from the chucks 158 at a suitable moment in the cycle of fabricating the string assemblies. More specifically and with reference to FIGS. 12 and 13, an ejector rod 248 is reciprocally arranged and coaxially disposed with each of the chucks 158. In order to pass the ejector rod 248 into expelling relationship with the corresponding tuning pin 162, a common bore 250 is formed successively in the chuck 158, the screw 224, the gear 226, the bearing hub 228 and the cover plate 238, as is best shown in FIG. 13. A radial thrust bearing 252 encircles the ejector rod 248 beyond the cover plate 238 to be held in place by a retainer 254.

Reciproeable drive for the ejector rods 248 is provided by fluid-actuated jack 256. Conveniently, the jack 256 is mounted on platform 144 by means of a bracket 258; and the jack includes an extensible and retractable piston rod 260 which slidably penetrates a suitably sized bore, not shown, in the bracket 258. So that both the ejector rods 248 may be actuated in unison from the jack 256, the piston rod 260 is secured to a yoke 262, and the ejector rods 248 are, in turn, secured to the yoke by suitable means such as the nuts 264.

Turning to FIGS. 15, 16 and 16a for a description ofa loop kinking arrangement 142, such a unit comprises, in compliance with the features of the present invention, stringstretching means in combination with string-bending means.

More specifically, the arrangement 142 includes a track or way member 266, a stretching unit 268, and crimping means 270. The way member 266 is affixed to a support bracket 272 which is mounted on the platform 144 by means of screws 274 in general alignment with the winding arrangement 14%. The way member 266 is canted from the vertical in order that the hitch pin loop which is kinked into the piano wire 194 will be offset from the midpoint of the wire in accordance with the requirements. of the construction of the string plate. Structurally, the way member 266 comprises spaced parallel rails 276 and 278 and a backplate 280 to which the rails are secured. The rails 276 and 278 are grooved adjacent their juncture with the backplate 2811 to define an inverted T- shaped track or way; and the stretching unit 268 includes a slide 282 which has a cooperatively shaped tongue, not shown, which fits in the T-shaped way to preserve assembly of the slide and the track member.

The stretching unit 268 includes a wire-holding hook 284 and a circular cam 286, and these two elements are mounted on the slide 282 in axially spaced relation. An overplate 288 is secured to the way member 266 by a pair of spaced screws 290 which threadedly engage the tracks 276 and 278 respectively, the overplate 288 being appropriately grooved confronting the way defined between the tracks for passing the slide 282 therebeneath. Furthermore, the overplate 288 is fashioned with an axial slot 292 that exposes the wire-holding hook 284 for draping of the piano wire 194 thereover; and as is well shown in FIG. 15, the heads of the screws 290 serve as locators for the piano wire prior to the kinking of a hitch pin loop therein. In order to provide reciprocable motion in the slide 282, a fluid-actuated jack 294 is provided with a traveling cylinder 296 which is fastened to the slide 282 by means of a mounting block 298. The jack 294 also includes a stationary piston rod 301) which has an outer end that threadedly engages a stop plate 302, a lock nut 3114 securing this threaded engagement. The stop plate 302 is itself secured to the overplate 288 by means of allen head screws 306, and pressurized fluid is supplied to an appropriate chamber in the cylinder 296 of jack 294 from suitable lines, not shown. The piston rod 300 passes through the upper end of the cylinder 296 to be held in a mounting fitting 308, shown in FIG. 15.

The crimping means 270 comprises a pair of cam arms 3111 and 312 which are pivoted on the shanks of screws 314, screws 314 threadedly engaging the overplate 288. At their upper ends, the arms 3111 and 312 are provided with confronting cam surfaces 316 which coact with the circular cam 286 in providing the motion for kinking a hitch pin loop in the piano wire 194. The arms 310 and 312 are fashioned, at their lower ends, with confronting kinking ears 318 which accomplish the actual kinking of the wire. Between the cam surfaces 316 and the kinking ears 318, the cam arms 310 and 312 have relieved edges 320 which define an enlarged slot for freely passing the cam 286. The cars 318 are biased apart and the cam surfaces 316 are biased generally toward each other by a tension spring 322, spring 322 being mounted between posts 324 which are affixed to the respective cam arms 310 and 312.

Returning to FIG. 2 to initiate a description of the pin driving unit 56, that assemblage includes impact means comprising a conventional, hand-operated pneumatic hammer 326 which is supplied with operating air from a line 328 and which is suspended from an articulated boom 3311. The boom 330 includes a fixed boom section 332 and a swingable boom section 334 which is pivoted to the fixed section by a pin 336. A compression spring 338 is connected at its respective ends to the fixed and swingable sections in order to bias the swingable section in a generally upward direction for retracting the hammer 326. The air line 328 is suspended from the boom 330 by suitable hangers 3411.

Turning to FIGS. 18 and 19, the pneumatic hammer 326 includes an oscillating impact tool 342 that is fashioned with a tip recess 344, the recess 344 having a square cross section for fitted engagement with the square end of a typical tuning pin 162, as is shown in FIG. 19. In compliance with a feature of the present invention, the pneumatic hammer 326 is provided with controls including a switch 346, shown in FIG. 18, that is actuatable to deenergize the pneumatic hammer 326. The switch 346 is mounted to the body of hammer 326 by a bracket 348 that also supports the upper end of a position responsive rod 350, rod 350 serving as a depth gauge. A collar 352 is affixed to the rod 350 by a set screw 354, and a compression spring 356 is confined between the collar 354 and a guide block 358 in order to bias the rod 350 in a generally downward direction. The guide block 358 is secured in place by the bracket 348 and is apertured to pass the upper end of rod 350 into actuating engagement with a swingable roller element 360 that operates switch 346. A tubular sleeve or bushing 362 is welded to the body of hammer 326 to serve as both a guide for the rod 350 and a downstop for the collar 354. As will be appreciated, suitable adjustment in the position of the collar 354 will position the tip of rod 350 beyond the tip of tool 342 and downward movement of the hammer 326 will cause the tip of rod 350 to engage a support surface, such as the string plate 30, further downward movement urging. the rod 350 upward against the action of spring 356 until the upper end of the rod engages the switch-actuating element 360. Thus, the positioning of rod 350 may serve to deenergize the hammer 326 when the tool 342 has driven a tuning pin 162 to a selected depth in the piano plate.

It will be appreciated that the apparatus that has been thus far described is capable of producing a string assembly comprising a pair of tuning pins and a length of piano wire which is assembled at its ends to the tuning pins by means of'abbreviated coils and which includes a medially kinked section that defines a hitch pin loop. Two such string assemblies are indicated generally in FIG. by the reference numerals 364 and 366. Each of these string assemblies comprises a pair of tuning pins 162 and a suitable length of piano wire 194. As described hereinabove, each end portion of a Wire 2194 is wrapped into an abbreviated coil 368 which surrounds one of the tuning pins. Furthermore, each of the string assemblies 364 and 366 includes a medially disposed, off-centered bight 370 permanently formed in the piano wire 194 to be looped over a hitch pin 38 as shown in the FIG.

Having described the construction of those elements in the apparatus 48 which are employed in fabricating string assemblies, such as the assemblies 364 and 366, it will be advantageous at this juncture to describe the sequence of fabrication steps and the manner of installing the fabricated string assemblies in the piano plate 30. Assuming that the apparatus 48 has been readied for operation and assuming that the wire magazine unit 54 has been suitably charged with supplies of the various lengths of piano wire, fabrication of a string assembly will be initiated by selecting a pair of tuning pins 162 from the boxes 154 shown In FIG. 2. The selected tuning pins will then be inserted in the chucks 158 with the bores 192 disposed generally vertically as is shown in FIG. 8. Thereafter, an appropriate piano wire will be withdrawn from the compartment 112 which is displayed by the slot 114 of magazine unit 54 as is suggested in FIG. 6. The selected piano wire will then be assembled with the tuning pins which were previously inserted in the chucks 158, as is shown in FIG. 15, the tip portions of the wire being passed through the tuning pin bores and into the slots 202, described hereinabove with reference to FIG. 8a. The medial portion of the piano wire 194 will be draped over the wire-holding hook 284 and generally beneath the heads of the screws 290 in accordance with the solid line showing of FIG. 15. The string assembly parts are now ready to be processed.

Functioning of the apparatus 48 is initiated by manually depressing an actuating button 372 on the control panel 136, shown in FIG. 2, whereby to close a normally open switch 374 shown in the-circuit diagram of FIG. 21. Closing of the switch 374 completes an electrical circuit to three solenoid operated, three-position valves, valves 376, 378 and 380. These three valves actuate, respectively, the jack 180 which drives the cup supports 164 into engagement with the tuning pins as is shown in FIG. 11, the jack 208 which repositions the reciprocable foot 198 into the coil guiding condition shown in FIG. 10, and

the jack 246 which drives the rack 242 for powered rotation of the chucks 158 as shown in FIGS. 1214. Advantageously, the electric power to valve 380 is passed through a time delay 382 whereby to insure actuation of the foot 198 and the cup supports in advance of the initiation of movement of the rack 242. The jacks 180, 208 and 246, as well as the jacks 256 and 294 are supplied with suitable fluid from a reservoir 384, and pressurization of the fluid may be achieved by individual compressors or pumps 386. A back pressure valve 388 may be provided in parallel fluid circuit with each of the pumps 386 if desired.

Upon actuation of the jacks 180, 208 and 246, the cup supports 164 will be urged into aligning engagement with the pins 162 and the foot 198 will be positioned to guide the coil which is to be rolled in the piano wire as the pins are rotated by the chucks 158. It should be appreciated that the initial rotation of the pins will cause the hook 203 to be bent into the tip portion of the piano wire as is shown in FIG. 17, by the edges of the slot 202, shown in FIG. 8a, the width of the slots 202 accommodating the lateral movement of the foot 198.

The jacks 180 and 208 stop up at their extreme position while the jack 246 continues to drive the rack 242 for rotating the chucks 158; and the second stage in the sequence of operation is reached when a switch-actuating dog 390 protruding laterally from the rack 242 engages an actuating lever 392 ofa position switch 394 shown in FIG. 14. Returning to FIG. 21, closing of the switch 394 will be seen to complete a circuit through a solenoid operated three-position valve 396 for energizing the jack 294 on the loop kinking arrangement 142 shown in FIGS. 14 and 16. This energization of the jack 294 causes the piano wire to be pulled up and tensioned and a hitch pin loop 370 kinlted in the wire while the formation of the coils 368 is completed. At the moment the kinking of loop 370 is completed, a forward end portion 398 of the rack 242 will engage an actuating lever 400 of a position switch 402 shown in FIG. 14. Returning to FIG. 21, closing of the switch 402 completes circuits to the valves 376, 378, 380 and 396 and to a solenoid operated three-position valve 404 associated with the jack 256. Completing of this latter circuit repositions the valve element in valves 376, 378, 380 and 396 whereby to reverse the jacks 180, 208, 246 and 294. At the same time, valve 404 is actuated to energize the jack 256 so that the ejector rods 248 will act to drive the tuning pins 162 out of the chucks 158, the cup supports 164 having previously been retracted, the reciprocable foot 198 being retracted, and the rotation of chucks 158 ceased.

Continuing now with reference to FIG. 12, a switch-actuating arm 406 is seen mounted to extend laterally of the yoke 262 for engaging a switch-actuating lever 408 of a position switch 410 when the ejector rods 248 have expelled the tuning pins 162 from the chucks 158. Returning to FIG. 21, closing of the switch 410 will be seen to complete a circuit to the valve 404 for reversing the jack 256 whereby to retract the ejector rod 248. Closing of the switch 410 also completes a circuit energizing the motor 132 for stepping the wire magazine unit 54 so as to present the next wire size for fabrication of the successive string assembly.

Advantageously, the switches 374, 394, 402 and 410 are of a type that, when closed mechanically, remain closed for a short period and then recondition themselves into the open position.

When a string assembly is completed and ejected from the winding arrangement 140, the tuning pins of the assembly are grasped and the loop 370 draped over a hitch pin 38 as is shown in FIG. 18. The tuning pins are then lightly set in the appropriate bushings 40 and tapped in with a steel mallet or like implement. A number of string assemblies are loosely installed in this manner; and at an appropriate time in the work cycle, the operator will pull the pneumatic hammer 326 toward the loosely set tuning pins and will fit the tool 342 to the pins successively, actuating the hammer 326 by depressing a trigger 412 shown in H6. 2. The hammer will deliver successive blows to the tuning pin until automatically deactivated by means of the rod 350 contacting the piano plate 30. Thereafter, the operator will draw some tension into the strings using a hand-wrench 414, as is suggested in FIG. 20 whereby to ready the strings for subsequent tuning.

The worker will continue to fabricate and install string assemblies in this manner until he has completed stringing that section of the piano plate which is assigned to him and which is appropriate to the wire length that can be accommodated by the loop kinking arrangements 142. Thereupon, the lever 79 will be actuated to raise the movable carriage 66, freeing the plate assembly 46 for rollable transport to a subsequent work station. The cycle will then be repeated.

The drawings and the foregoing descriptions are not intended to represent the only forms of the invention in regard to the details of its construction and manner of operation. Changes in form and in the proportion of parts, as well as the substitution of equivalents, are contemplated as circumstances may suggest or render expedient; and although specific terms have been employed, they are intended in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being delineated in the following claims.

We claim:

1. Apparatus for use in stringing pianos and like musical instruments, comprising: string forming means including winding means for coiling piano wire on tuning pins to produce string assemblies and including loop kinking means for permanently deforming a. midportion of the wire of a said string assembly into a hitch pin loop; work table means connected to said string forming means and including platen means for supporting a piano plate in fixed position during installation of said string assemblies; and pin driving means with said work table means for seating the pins of said string assemblies in a piano plate supported by said platen means.

2. Apparatus according to claim 1 wherein said work table means further includes antifriction conveyor means for transporting string plates to and from said platen means and lifter means for moving one of said conveyor means and said platen means into and out of engagement with a string plate at said work table means.

3. Apparatus according to claim 1 wherein said winding means includes'a pair of rotatable pin chucks, a rotatable cup support confronting each of said chucks for locating a tuning pin axially of the associated chuck, and coil guide means including a guide surface between each of said chucks and the associated cup support, said guide surface being disposed generally parallel with the axis between the chuck and the cup support and spaced apart therefrom to direct the piano wire into a cylindrical coil upon rotation of said chuck and the tuning pin held therein.

4. Apparatus according to claim 3 wherein said winding means further includes a reciprocable winding blade associated with each of said chucks and arranged to advance parallel with the axis between said chuck and its associated cup support upon rotation of said chuck whereby to cooperate in directing the piano wire into a cylindrical coil and drive means for said winding blades.

5. Apparatus according to claim 3 wherein said winding means further includes positioning means for advancing and retracting said cap supports relative to said chucks, ejector means including an ejector element reciprocally and coaxially disposed within each of said chucks, and drive means for ac- 11% tuating said ejector means to expel tuning pins from said chucks when said positioning means have retracted said cup supports.

6. Apparatus according to claim 3 wherein said guide surfaces have apertures opening toward said tuning pins to receive tip portions of the piano wire and form the same into hooks bent along the sides of the tuning pins.

7. Apparatus according to claim ll wherein said apparatus further com rises a rotary wire magazine having separate compartmen s for differen lengths of piano wire, a stationary selector plate including an aperture adapted to expose a single one of said compartments, and drive means for incrementally rotating said magazine.

8. Apparatus according to claim 7 wherein said compartments have open top ends, wherein said top ends are coplanar, and wherein said selector plate is spaced closer to the plane of said top ends than the smallest difference between the lengths of the piano wires whereby to prevent loading of wires of too great a length in said compartments.

9. Apparatus according to claim 7 wherein said winding means includes a pair of rotatable pin chucks, a rotatable cup support confronting each of said chucks for locating a tuning pin axially of the associated chuck, and coil guide means including aguide surface between each of said chucks and the associated cup support, said guide surface being disposed generally parallel with the axis between the chuck and the cup support and spaced apart therefrom to direct the piano wire into a cylindrical coil upon rotation of said chuck and the tun ing pin held therein.

10. Apparatus according to claim 1 wherein said loop kinking means includes track means mounted in alignment with said winding means, stretching means slidably disposed in said track means and having a holder element for retaining a midportion of the piano wire during loop kinking, and crimping means for kinking a loop into said wire when it is stretched.

11. Apparatus according to claim 10 wherein said crimping means includescam means on said track means and cooperating follower means on said stretching means for actuating said cam means when said wire isstretched.

12. Apparatus according to claim 11 wherein said cam means includes pivoted, opposed cam arms.

13. Apparatus according to claim 10 wherein said winding means includes a pair of rotatable pin chucks, a rotatable cup support confronting each of said chucks for locating a tuning pin axially of the associated chuck, and coil guide means including a guide surface between each of said chucks and the associated cup support, said guide surface being disposed generally parallel with the axis between the chuck and the cup support and spaced apart therefrom to direct the piano wire into a cylindrical coil upon rotation of said chuck and the taning pin held therein.

14. Apparatus according to claim 10 wherein said apparatus further comprises a rotary, wire magazine having separate compartments for different lengths of piano wire, a stationary selector plate including an aperture adapted to expose a single one of said compartments, and drive means for incrementally rotating said magazine.

15. Apparatus according to claim 1 wherein said pin driving means includes impact means, control means for said impact means including a switch, and position responsive means for sensing the depth that said tuning pins are seated in said piano plate by said impact means and for actuating said switch to deenergize said impact means when said tuning pins have been seated to a preselected depth.

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