US2681684A - Apparatus for stitching the plies to form the carcass of large-size (e. g. truck andtractor-size) pneumatic tires - Google Patents

Description

June 22, 1954 (5|| ETTA ETAL 2,681,684

APPARATUS FOR STITCHING THE PLIES TO FORM THE CARCASS 0F LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES Filed Dec. 27. 1951 '7 Sheets Sheet l i' I s I1 enter;

June 22, 1954 D TT ETAL 2,681,684

APPARATUS FOR STITCH INC THE PLIES TO FORM THE CARCASS OF LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES W was June 22, 1954 D. GILETTA ETAL 2,681,684 APPARATUS FOR STITCHING THE PLIES TO FORM THE CARCASS OF LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES Filed Dec. 27, 1951 7 Sheets-Sheet 3 4 4a bvraM/a Pa 0 cream/'1 June 22, 1954 GlLETTA 2,681,684

APPARATUS FUR STITCHING'THE PLIES TO FORM THE CARCASS OF v LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES Filed Dec. 27, 1951 7 Sheets-Sheet 4 fornleys June 22, 1954 glLETTA ET AL 2,681,684

APPARATUS FOR STITCHING THE PLIES TO FORM THE CARCASS OF LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES Filed Dec. 27, 1951 '7Sheets-Sheet 5 a 40 IQIVTOA/IO P4 c c 1 72/4 ttorney June 22, 1954 D. GILETTA ET AL APPARATUS FOR STITCHING 2,681,684 THE PLIES TO FORM THE CARCASS OF LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIR Filed Dec. 27, 1951 ES 7 Sheets-Sheet 6 Foot 4/)" Switch Stop Over/cad W Over/cad BOO M Oven/cad 9/ 9O 1 n U e n tom '44 o 7474/ 704/10 Pace/"7a m/z June 22, 1954 GlLE-TTA ETAL 2,681,684

APPARATUS FOR STITCHING THE PLIES TO FORM THE CARCASS OF LARGE-SIZE (E.G. TRUCK AND TRACTOR-SIZE) PNEUMATIC TIRES Filed D80. 27, 1951 7 Sheets-Sheet '7 J sac/G F F/G/O.

Patented June 22 1954 UNITED STATES PATENT OFFIl'JE APPARATUS FOR STITCHING THE, PLIES TO FORM THE CARCASS OF LARGE SIZE (E. G. TRUCK AND TRACTOK- SIZE) PNEU MATIC TIRES,

Dario Giletta, Antonio Pacciarini, and Marcello Zuliani, Milan, Italy, assignors toPirelli Societa per Azioni, Milan, Italy, a limited liability com:-

pany of Italy Application December 2'7, 1951, Serial No. 263,664

Claims priority, applioationltaly July, 14, 1951 ous plies of rubber and rubberised fabric of which the carcass of the tyre is built up.

Carcasses for tyres are normally built bylaying various plies of cord fabric and of unvulcanised rubber onto a revolving buildin drum. The various plies must then be stitched, i. e. they must be compressed against the drum surface, in order to cause them to adhere to one another and to remove any air trapped between them.

In truck and tractor-sized tyre building equipment now in use, the stitching operations are performed by means of a pair of discs, which are moved symmetrically with one another from the centre of length of the building drum outwardly thereof and parallel to, the axis of the drum while this latter is rotated, and a second pair of discs which are moved around the cross-sectional contour of the ends of thedrum. Thus, to perform the stitching operations, two separate appliances are required, each of which is provided with a pair of discs, and which appliances are arranged one beneath the drum and the other on the side thereof Opposite, to the side at which the operator stands, the whole available space around the drum bein thereby taken up. The above mentioned appliances are hand-controlled and the arrangement of the controls is such that the operator has to leave his position and move to the side of the machine in order to accomplish the various stitching operations.

One object of the present invention is to provide a single appliance in which the whole sequence of the stitching operations is carried out by means of a single pair of discs, the appliance being fitted behind the building drum in order to leave the whole space therebelow available for the fitting of further tyre building appliances.

A furtherobject of the invention is to provide an appliance wherein all of the stitching operations are efiected mechanically and the com trols are all arranged within easy reach of the operator, who can therefore control all of the ap-, pliances from a fixed position relative to the machine.

A further object is to provide an appliance wherein all of the stitching operations are performed by symmetrical movements on both sides of the drum simultaneously, thereby enabling the operator to control them by watching the carcass from one side thereof only.

The whole stitching process has been thoroughly analysed in order to establish exactly what motions are required from the discs during, the various manufacturing stages. As shown by Figure l of the accompanying drawings, the stitching process can be divided into two phases, as follows:

1st ph se.In this phase the discs, starting from the centre line (i. e. the transverse medial plane of the drum) at A'A, move parallel to the rotational axis of the drum until they reach the positions B and B, disposed symmetrically about the centre line. 2nd phasef-In this phase the discs perform the following movements:

(a) A rotation through 90 around the centres X and X (thus moving from B and B to C and C) (b) A rectilinearmotion normal to the axis of the building drum (fromC and. C" to D and D'.)

(c) A rotation through 45" around the centres Y and Y (from D and D to E and E) (d) A rectilinear motion parallel to the building drum axis (fromE and E to F and. F)

To perform thestitching operations as above described with only one pair of discs it isessen tial that the discs shall be bringable into contact with one another (position AA of Figure 1) and also that they shall be rotatable each around an imaginary vertical axis passin through the centre of curvature of the cross-sectional con tour of the radially outer shoulder of the drum at the corresponding end thereof This latter requirement tends, however, to be in conflict with the former one, for the mechanical devices that would be required in order to make possible such a rotation of the discs would need to be fitted bef neath the arms supporting the discs and in such positions they would interfere with each other when the discs were brought into contact with one another (position AA).

In a stitching apparatus in accordance with this invention, this problem has been solved by connecting the disc-supporting arms with two housings slidably fitted on a saddle, by means of a lever assembly formin a system of parallelogram linkages. The mechanical elements from which the arms derivetheir swivellin movement are fitted within th housing and the drive is transmitted to the arms by means of the lever assemblies, a detailed description of which will be given hereinafter.

Such an arrangement allows the driving elee ments for the discs to be conveniently spaced apart from one another, thereby enabling the arms to be drawn closer and closer together, un-

3 til the respective discs thereon are brought finally into contact with one another.

From the foregoin it will be understood that the invention may be said to relate to apparatus for stitching the plies of cord fabric and rubher to form the carcass of a large-size (e. g. truck or tractor-size) pneumatic tyre during fabrication thereof on a rotatable building drum, the plies to be stitched being wrapped around the drum and the stitching operation bein performed by means of freely rotatable discs which beer at the periphery thereof and with rolling contact upon the outermost ply on the drum as the latter with the plies in position thereon rotates, while being traversed across said outermost ply, so as to cause the plies to adhere to one another and at the same time to drive out any air that may be entrapped between them.

It will be seen that the invention is applicable to apparatus wherein the building drum has at each end thereof, in the axial section of the drum, a rounded shoulder tangential to the outer periphery of the drum and the end face thereof, around which shoulder the plies are laid during or prior to the stitching operation. With the invention the stitching operation is performed by two discs only, which are progressively traversable simultaneously and symmetrically with respectto the transverse medial plane of the drum, first lengthwise of the drum, parallel to the rotational axis thereof, from a starting position immediately adjacent said transverse medial plane to a position, in the case of each disc, coincident with the point of tangency of the rounded shoulder aforesaid with the outer periphery of the drum. In a second stage of the traverse movement the discs are traversed around said shoulder, performing in this second stage of traverse movement an arcuate movement about an imaginary axis passing through the centre of curvature of the shoulder (in the axial section of the drum). The discs are traversable in this second stage by a drive transmitted through a pair of lever assemblies which during the first stage of the traverse movement are movable bodily with the discs and without relative motion of the levers of the assemblies and during the second stage of the traverse movement are stationary and operative as the result of relative articulatory movement of the levers to rotate the discs about said imaginary axes.

As hereinafter described, the second stage of traverse movement of the discs is or may be followed by further stages, namely the stages hereinafter referred to as the third, fourth and fifth stages.

The features and also the principle and manner of operation of an apparatus in accordance with the present invention Will now be further described with reference to the drawings already referred to, which illustrate a preferred embodiment of the invention by Way of example.

In the drawings:

Figure 1 shows diagrammatically the diiferent positions to which the discs have to be brought during the course of the stitching operation;

Figure 2 is partly a side view and partly a crosssection of the complete stitching apparatus;

Figure 3 is a plan view partly in section of the complete apparatus;

Figure 4 is a plan view of one of the lever assemblies of the apparatus, showing the corresponding disc fitted thereon. In this figure the levers are shown in the positions they occupy when the disc is in the position in which its plane 4 is perpendicular to the axis of the building drum (positions A and A and B and B of Figure l) Figure 5 is a corresponding kinematic diagram of the same lever assembly, the levers being shown in the positions in which they appear in Figure 4;

Figure 6 is, also a kinematic diagram of the lever assembly of Figure 4, but showing the levers in the positions they occupy after a rotation of the disc through 45;

Figure '7 is a further plan view of the lever assembly of Figure 4, showing the levers in the positions they occupy after a rotation of the disc through (positions E and E, also F and F of Figure 1) and Figure 8 is a corresponding kinematic diagram of the same lever assembly, the levers being shown in the positions in which they appear in Figure 7.

Figure 9 is a wiring diagram of the electric control arrangement for controlling the apparatus, Whilst Figure 10 is a plan view of the apparatus showing the location of the limit switches used in the control arrangement.

Like reference characters are applied to like parts in the various figures.

Referring to Figures 2, 3 and 4, the machine comprises a fixed base i whereon a saddle 2 is guided for sliding movement along the base towards and away from the drum. This saddle is driven by a threaded spindle 3, engaging a nut 3a and driven by a motor unit d incorporating a speed reduction gear, through sprockets 5, 6 and. a chain 1. Two housings 8, 9, slidably guided on the saddle 2 and located symmetrically with respect to the centre line thereof and therefore to the transverse medial plane of the drum ll since this is disposed symmetrically with respect to the saddle, are driven by a screw Hl carrying two threads, one of left hand and the other of right hand, engaged respectively with a pair of nuts ll, l2, and the screw is driven by a second motor unit [3 incorporating a speed reduction gear through sprockets l4, l5 and a chain 16. The housings 8, 9, by sliding along the saddle 2, allow the first stage of the stitching process to be properly accomplished, said first stage involving traverse movement of the stitching discs from positions A and A to positions B and B (Figure 1). The two sets of mechanical elements associated respectively with the housings 8, 9 then swing the corresponding discs around their imaginary vertical axes in the manner previously described.

Since the two housings 8, 9 are identical, one only will be described in what follows, namely the housing 9, a cross-section of which is shown in Figure 2.

Within this housing is a cylindrical drum l'i' rotatable around its own axis and carrying on its periphery a worm wheel Hi. This worm wheel engages a worm l9 keyed onto a shaft 29 driven by a third motor unit 2| incorporating a speed reduction gear, through sprockets 22, 23 and a chain 24. Two pins 25, 26 project from opposite faces of the drum il. These pins are coaxial and their common axis is disposed eccentrically with respect to the axis of the drum ii. A lever 21 is keyed at one end thereof onto the pin 25. At the opposite end the lever carries a pin 28 whereon the adjacent (outer) end of one arm of a two-arm lever 29 is pivoted. Lever 29, which as shown (see Figures 4 and 7) is in part U- shaped, the U having a tail-like extension pro- 9 Two arms 35, 36 fastwith a cylindrical boss.

3-! are pivoted respectively on the pins 25, 26.

The arm is formed with an extension 38, one

end of which is pivotally mounted on a pin 39 carried on the lever 33. A pivot on the member 3| is rotatable in the cylindrical boss 31. An arm4'2 provided at one end thereof with a conical disc 43 is pivoted on a pin- 4| carried on the member 3 I. A piston is reciprocatable within a cylinder 44 formed integral with the arm 42 and. a piston rod 46 pivotally connected at one end thereof to the piston 45 is also pivotally connectedat the opposite end to the member 3i through a pivot pin 41 thereon.

The working of the apparatus in the two phases of the stitching process as referred to above can be readily appreciated from the preceding statemnts. The disc 43 (see Figures 1 and 2) has to move during the first phase from position A to position 33, the opposite disc moving symmetrically with it from position A to position B, By allowing compressed air to enter the cylinder 14, the disc 43'is forced against the building drum with a force that can be adjusted as necessary by Suitably proportioning the air pressure. Then, by starting the motor unit I3, the housings 8 and 9 are moved along the saddle by reason of rotation of the screw 10, with the result that the two discs are similarly moved along the drum, from said positions A and A to positions B and B As soon as the discs have attained the positions B and B, the motor unit 13 is stopped, being' so stopped automatically by means of an adjustable limit-switch.

The first phase of the stitching process is now completed. Before turning, however, to describe the second phase, it will be convenient to describe the form and working of the lever assemblies and also the manner of operation of the elementsassociated with the housings 8 and 9 by which these assemblies and therefore the discs are driven.

As already stated, all motions of the discs are symmetrical and simultaneous. It will therefore be'sufiicient to consider the motion of one disc and correspondingly one lever assembly only.

Starting from position B (see Figure l), the disc 43has to rotate around the imaginary vertical axis passing through the centre of curvature Xof the cross-sectional contour of the radially outer shoulder of the drum at the corresponding end thereof as hereinbefore set forth. The rotation of the disc 43 is derived however from the rotation of the drum I! around its own axis, which axis does not pass through said centre of curvature X. As hereinbefore stated, therefore, theleve'r assembly by which the disc 43 is supported and through which it is driven, is designed to'transmit the drive from drum I! to disc 43 in such a manner as to allow the disc to rotate around the imaginary vertical axis passing through X.

Figure 4 shows the positions taken by the various parts of the lever assembly when the disc 43 has attained the position B. The levers are connected in such a manner as to form four parallelogram linkages (see Figures 5, 6 and 8), one of which has four real sides, another three real" sides and one imaginary side; and each 6. of the remaining two two real" sides and two imaginary. ones. These paralellograms can be identified in. Figures 5, 6 and 8 by means of the following" diagrams:

ParaZZeZogram 1 Zto 28: Imaginary side 34:, to 3,2 :1 Real side Z .to134: Imaginary side 28.130 32:. Real side Parallelogram 2 Z to 25: Real side 39 to'34: Real side Z to 34: Imaginary side 25 to 39: Real side Paralielogram 3 25- to 28: Real side 4! to 3.9-: Real side 25- to 40: Real side 28 to. 3! Real side Pm'allelogram 4 Z to 25: Real side X to 4G: Imaginary side Z to X: Imaginary side 25 to 49: Real side By the four parailelograms l, 2, 3, 4 a system isformed wherein, as in a pantograp-h, all pivots have to follow predetermined paths. The system also comprises two points, i. e. the centre Z of drum ll and the centre of the pivot on the housing 5%. When the drum ill rotates, all'of the levers are caused to travel along strictly ure-established paths.

In Figures 4 to 8 the disc 23 is shown in the position which, it would occupy if the building drum were not present; as is readily seen from Figures 5, 6 and 8, the disc 3, while remaining with its diametral plane always perpendicular to the surface of the building drum, rotates around a vertical axis passing through the axis X.

With the drum present, the periphery of the disc 43 cannot coincide with the axis X but instead lies on the outer surface of the plies, the arm 42 carrying the disc 43 being inclined at an appropriate angle. The disc 63 thus rotates bodily around the axis X with its diametral plane always perpendicular to the outer surface of the plies.

The stability of the system is positively ensured by the fact that the parallelograms l and 2 have two fixed points in common, viz. the fixed points Z and 34. Since the disc 43 has to accomplish a total rotation of these parallelogram-s will take'alternately a position wherein the angles between the levers are equal to zero, whi h position is obviously highly unstable. However, the apparatus has been designed in such a manner that, when one of the parallelograms is closed, the. other one is open and vice versa, the stability of the system being thereby positively ensured.

In fact, the angle formed between the pairs of sides 39 to 34, 34 to 32 and 25 to Z, Z to 28 is invariable, since the centres 34, 39, 32 and Z, 25, 28 are rigidly connected. As can be seen from Figures 4 and 7, the centres 34, 3t, 32 are carried on thelever 33, while the centres Z and 25 are carried on the drum ll, the centre 23 being carried on the lever 21 keyed to the pivot 25.

It follows, therefore, that if the parallelogram 2 is closed, as in the starting position (Figure 5), the parallelogram I must be open. Figure 6 shows an intermediate position of the parts of 7. the lever assembly, the disc 43 having been rotated through 45. In this position,the parallelogram is closed and the parallelogram 2 open.

The traverse movement of the discs is performed in five successive stages. The first of these, namely from position A or A to position B or B (Figure 1), has already been described. The remaining four, namely the stages hereinbefore referred to as the second, third, fourth and fifth stages, will now be described as follows:

Second staye.-Rotation of disc through 90 around the centre X or X, from B or B to C or As previously stated, the disc 43 rotates around the axis X or X in consequence of the rotation of drum IT. This drum, in turn, derives its motion from worm l9 meshing with worm wheel H3 and keyed on shaft 20 driven by motor unit 2|. After a rotation through 90 has been accomplished by the disc, motor unit 2| is automatically stopped by an adjustable limit switch, with the result that the disc is thus stopped at position C or C (Figure 1).

Third stage.Rectilinear motion of disc along a path perpendicular to the drum axis, from positionC' or C to D or D.

The motion during this stage is produced as the result of movement of the saddle 2 along the guides on the base in the direction towards the rotational axis of the building drum. Motor unit i rotates the threaded spindle 3 and causes it to screw into the nut 3a. The entire unit comprising the saddle and the whole of the parts thereon is thereby moved towards the building drum. Upon the disc 43 reaching position D or D, motor unit 4 is automatically stopped, by the action of an adjustable limit switch as hereinafter more particularly described.

Fourth stage.Rotation of disc through 45 around centre Y or Y from D or D to E or E.

The motion of the saddle 2 by which the disc 43 was brought from position C or C to position D or D produced also a displacement of the axis X or X to the position Y or Y, due of course to the fact that said axis is in stationary relation to the saddle. The motion of the disc from position D or D to E or E is the result of rotation of the disc through 45 about the axis X or X now at position Y or Y, under drive from motor unit 2|, said rotation being accompanied by movement of the pivoted arm 42 carrying the disc about the axis of pivot 4| (Figure 2) in the direction towards the axis X or X now at position Y or Y, the disc moving, in consequence of said movement of the arm 4|, in its own plane and under thrust from the compressed air piston and cylinder device 44, which causes it at all times to maintain pressure contact with the plies of fabric on the drum, with the result that it follows faithfully the axial-section contour of the drum as it is traversed therealong from position A or A to position F or F.

Fifth stage.-Rectilinear motion of disc along a path parallel to the building drum axis, from position E or E to F or F.

The motion during this stage is derived from a combination of a further step of forward movement of the saddle 2 in the direction towards the rotational axis of the drum to a position in which the axis X or X is brought to a further displaced position YY or YY, with a further movement of the pivoted arm 42 about the axis 4| in the direction towards the axis X or X, i. e. as this undergoes its movement from position Y or Y to YY or YY, said further movement of the arm 42 being controlled by the axial-section contour of the building drum, with the result that the disc is caused to travel inwardly of'the drum and along a path parallel to the rotational axis thereof from position E or E. to position F or F as the saddle pursues its further step of movement in the direction towards the drum.

To control and to co-ordinate the motions of the various elements of the machine, by which the paths followed by the stitching discs are established in the manner above described, an electrical control and adjustment installation, provided with remote-control switches, is employed in the machine.

This installation includes the requisite motors and mechanical controls, as well as the corresponding wiring, as shown in Figures 9 and 10.

Referring to these figures, the saddle 2 is driven by the motor unit 4 (Figure 10), the operation of which is controlled by remote-control switches 9% for the forward stroke and 9| for the return stroke (Figure 9).

Limit switches 9B9, 902 mounted upon the base I, serve to adjust the limits of the forward stroke, while the return stroke limits are adjusted by means of other limit switches 9|0, 9 also mounted upon the base.

The two housings 8, 9 (Figure 10) are driven by the motor unit |3, under the control of remote-control switches Hi, 7| and their travel is controlled in the two directions by limit switches 2'80, H0.

The discs are driven by the motor unit 2| under the control of remote- control switches 80, 8|, while the angle of rotation of the discs (1. e. about the axes X, X) is controlled by limit switches 806, 8H1.

A third limit switch 903, actuated by the rotational motion of the arms 42 about the axis X or X, serves to cause the saddle 2-after motor unit 4 has been stopped by the action of the corresponding limit switch 90|--to accomplish a further forward motion, controlled as regards extent by the limit switch 902, but only after-the arms have accomplished a pre-established rotation of 90. I

A special compounding switch C.8, having eight positions, enables the motor units 4 and 2| to be driven each of them separately and in either direction or in any of four combinations, namely (.1) both in coupled drive clockwise, (2) both in coupled drive anti-clockwise, (3) one clockwise and the other anti-clockwise in coupled drive, (4) the reverse of combination (3). In this way the rotation of the disc-carrying arms 42 about the axis X or X and the rectilinear motion of the saddle 2 can be effected either independently or contemporaneously.

The limit switch Hill is designed to prevent the arms from being rotated when the housings 8, 9 are not in their end-of-stroke positions. In efiect, it allows the transmission of the drive current to be applied to compounding switch C.8 only after it has been driven.

The electro-pneumatic valves for controlling the motion of the arms 42 are driven by the switch marked Foot Air Switch (see Figure 9) 9 After having thus described the component parts of the electrical installation, the operation of these parts whilethe various successive stages of traverse movement of the stitching discs are being performed will -now bedescribed as follows:

First stage of traverse movement By depressing the push button marked stitching the switch EVA is lifted and through two contacts EVA thereof (one of which is normally closed), the electro-pneumatic valves for the control of the air inlet and the air exhaust are actuated, thus controlling the piston and cylinder devices by means of which the discs 43 are forced against the building drum.

At the same time, theswitch ,EVA, by a third contact EVA, is also automatically closed and,

through the time-relay EVAT, the motor unit I3 is started. By the motor unit I3, the discs are moved from position A or A to position B or B, whereby the stitching operation in a direction parallel to the drum axis is accomplished, i. e. as regards the portion of the wrapping of plies on the drum extending axially thereof from the transverse medial plane of the drum to the positions B and B of traverse of the stitching discs permit the movementof thediscs in a direction i parallel to the axis of the building drum, there being during this stage of the transverse movement of the discs no air under pressure in the piston 45 of cylinder 44.

Second stage of traverse moement.-Rotation of discs through 90 around ares X and X The compounding switch 0.8 is moved to the left, thus closing thecontact through which current flows to remote-control switch 89 for the motor unit 25. By suitably adjusting the compounding switch, the discs oan be caused to accomplish the rotation required to pass from position B or B to position C or C".

Third stage of traverse movement.Rectilinear motion of discs in a direction perpendicular to drum axis The compounding switch 0.8 is moved downward, whereby current is caused to flow to remote-control switch at controlling the forward operation of motor unit 4. Saddle 2 moves forward in consequence toward the position determined by the limit switch 90l, thus displacing the discs from the position C or C to the position D or D.

Fourth stage of traverse movement-Rotation of discs through, 45 around ames X and X at positions Y and Y The compounding switch 0.8 is moved to the left whereby, as in the preceding stage of traverse movement, current is applied to remote-control switch at, with the result that motor unit 2| is started and the discs are rotated until attaining the end of their rotary (around axes X and X at positions Y and Y) motion as determined by thelimit switch 880. i

10 Fifth stage of traverse mooement.--Rectilinear motionof discs in a direction parallel to drum arts The compounding switch 0.8 is moved downward, diagonally to the left, and the foot air pedal then depressed. This results in the remotecontrol switch as of motor unit Al, and the electropneumatic valves for the drive of the piston by which the arms d2 are rotated about their pivotal axes ll, being simultaneously operated. The foregoing operation is made possible by the combination of two motions, already described (see fifth stage above). "The motion of the motor unit 4 is limited bythe limit switch 902.

The electrical installation also includes the push-buttons marked Forward and Reverse, to bring the saddle 2 to respectively the work and rest positions, and the push-buttons marked Open and Close for the control of the rectilinear movement of the housings and the parts carried thereon in a direction parallel to the drum axis during the idle motions.

The remainingpositions of the compounding switch (3.8 are allocated to the bringing of the discs and the housings back to their initial (start) positions.

What we claim as our invention and desire to secure by LettersPatent of the United States is:

1. In an apparatus for stitch ng the carcass plies of large-size pneumatic tires on a building drum which has at each end thereof, in the axial section of the drum, a rounded shoulder tangential to the outer periphery of the drum and the end face thereof, around which shoulder the plies are laid prior to stitching, two rotatable stitching discs, progressivetraversing means for traversing said discs in a direction parallel to the rotational axis of the drum simultaneously and symmetrically with respect'to the transverse medial plane of the drum, thelimits of movement of said traversing means correspondingto a starting position of the discs immediately adjacent said transverse medial plane and a finishing position of each disc coincident with the point at which said rounded shoulder commences, further traversing means for traversing said discs around said shoulder whflst said discs perform an arcuate movement about the center of curvature of the "and Without relative motion of the levers of the assemblies, and, during the second traverse move ment, being stationary and operative as the result of relative articulatory movement of the levers to rotate the discs about said center of curvature.

2. An apparatus as claimed in claim 1, wherein each disc is carried upon the free end of an arm pivotally mounted upon one of the levers of the corresponding lever assembly for swinging movement relatively thereto in directions towards and away from the surface of the drum, which arm is yieldingly urged in the direction towards the said surface by means adapted to apply pressure to the arm for the maintenance of the disc thereon inoperative rolling contact with the plies of fabric on the drum.

3, An apparatus as claimed in claim 1, comprising means for'moving said discs in a direction parallel to the endface of the drum, and towards the rotational axisthereof, the discs being moved prising a pair of worms, a pair of worm wheels each in engagement with one of said worms, a

saddle movable in a direction at right-angles to' the axis of the building drum, and a pair of housings, each supporting one of said worm wheels and .both mounted on said saddle for movement together with the respective lever assemblies along a path parallel to the rotational axis of the building drum, said lever assemblies being mounted upon the respective housings in driving connection with the worm wheels therein.

5. An apparatus as claimed in claim 1 comprising at least one limit switch for automatically stopping the operation of said first traversing means at said finishing position and at least one further limit switch for preventing the commencement of operation of said further traversing means before completion of the operation of said first traversing means.

6. an apparatus for stitching the plies of a tire casing after the plies have been applied to a rotatable tire-building drum having curved corners at each end of said drum, a base fixed relative to said drum, a saddle movable bodily towards and away from the axis of said drum, two housings movable on said saddle in a direction parallel to the axis of said drum, said housings being movable in opposite directions symmetrically with respect to a plane perpendicular to said axis and equidistant from each end of said drum, two rotatable members each mounted on one of said housings and rotatable about vertical axes perpendicular to the axes of said drum, two stitching members; two stitching member supporting arms for supporting said stitching members, so that they are adapted to be brought into contact with said plies at points lying in a horizontal plane passing through the rotational axis of said drum, two sets of parallelogram linkages each coupling one of said sup porting arms to one of said rotatable members for arcuate movement of the stitching member about the center of curvature of one of said 'curved corners, said linkages lying in a hori- 7 two corners of one parallelogram linkage of each set are also corners of at least one of the other parallelogram linkages of that set and the mem bers pivoted to said corners and converging to the same point form an invariable angle between them such that as, one linkage closes the other opens; i r a -8. An apparatus according'to claim '7, wherein said two corners are fixed relative to the housing on which the set of linkages is mounted.

9. An apparatus according to claim 6, wherein at least one lever forming'one member of one parallelogram linkage and which is attached to its corresponding rotatable member .is fixed to at least one corresponding lever spaced'apart vertically therefrom, whereby said sets of linkages are reinforced against bending moments result- 12 ing from the reaction of the thrust of said stitching members on the drum.

10. Anapparatus for stitching the carcass plies of large-size pneumatic tires during fabrication thereof, on a rotatable building drum having a curved shoulder at each end thereof, comprising a base having guides thereon, a horizontal saddle disposed parallel to the rotational axis of the drum and slidable perpendicularly thereto along said guides, an electric motor for traversing the saddle along the guides whereby the saddle can be advanced towards the drum axis or retracted therefrom, two housings slidably mounted on the saddle in positions disposed symmetrically on either side of the transverse medial plane of the drum, for traverse movement simultaneously and in opposite directions, also in a symmetrical manner with respect to said medial plane, along a path extending parallel to the drum axis, a second electric motor for traversing the housings along said path, each'of said housings carrying a worm wheel, a shaft mounted in said saddle, two worms mountedonijsaid shaft and each engaging one of said' 'worm wheels, a third electric motor for driving the shaft, two lever assemblies each forming a system of parallelogram linkages and each in driving connection with one of said worm wheels respectively, two stitching discs, two pivoted upwardly extending arms each carrying at one end thereof one of said stitching discs, each of said arms being coupled to one of said lever assemblies for bodily rotation of the associated disc around the center of curvature of the curved shoulder at the corresponding end of the building drum by movement of said lever assemblies, and means urging the periphery of each disc into contact with the plies on the building drum.

11. An apparatus as claimed in claim 10 wherein each lever assembly comprises four parallelogram linkages, two of which have two fixed pivots in common and the levers pivoted to said fixed pivots forming invariable angles between them, whereby when one ofthe said parallelogram linkages is open, the other, during rotation of the pivoted arms carrying the stitching discs, is closed, all the levers of the latter mentioned parallelogram linkage being in this condition thereof in line with one another. 7

12. An apparatus as claimed in claim 10 comprising electrical limit switches each connected in the circuit of one of said electric motors for interrupting the circuit thereof upon a predetermined movement of the members traversed by the motor, each limit switch being slidably mounted on guides for adjustment therealong by means of screw controls, whereby the operative strokes of the switches are selectively adjustable to accommodate a change of building drum for another of different size.

13. In an apparatus for stitching the plies of a tire casing after the plies have been applied to a rotatable tire-building drum having curved corners at each end of said drum, a base fixed relative to said drum, a saddle movable bodily towards and away from the axis of said drum, two housings movable on said saddle in a direction parallel to the axis of said drum, said housings being movable in opposite directions symmetrically with respect to a plane perpendicular to said axis and equidistant from each end of said drum, two rotatable members each mounted on one of said housings and rotatable about axes perpendicular to the'axis of said drum, two sets of parallelogram linkages each set operatively connected to one of said rotatable members, two

arms each pivoted at one end to one parallelogram linkage and carrying a stitching member at the other end, whereby each stitching member is rotatable bodily about the center of curvature of one of said curved corners by rotation of its associated rotatable member, and is movable towards and into contact with the other stitching member by the opposite symmetrical movement of said housings, and thrust means urging said stitching member into engagement with the plies on said building drum.

14. An apparatus according to claim 13, wherein two corners of one parallelogram linkage of each set are also corners of the other parallelogram linkage of that set, whereby one linkage closes as the other opens.

15. An apparatus according to claim 14, wherein said two corners are fixed relative to the housing on which the set of linkages is mounted.

16. An apparatus according to claim 13, wherein at least one lever forming one member of one parallelogram linkage and which is attached to its corresponding rotatable member is fixed to at least one corresponding lever spaced apart vertically therefrom, whereby said sets of linkages are reinforced against bending moments resulting from the reaction of the thrust of said stitching members on the drum.

17. An apparatus according to claim 13 wherein each set of parallelogram linkages comprises a lever which is at least in part U-shaped, and has pivot holes at each extremity of the U-shaped part, said pivot holes constituting corners of a parallelogram linkage, and two further levers are each pivoted to one of said pivot holes and form members of a further parallelogram linkage, one of said levers carrying a further pivot hole constituting a corner of the further parallelogram linkage, which hole, during movement of this last-mentioned lever, crosses the line joining the two pivot holes at the extremity of the U-shaped part.

18. In an apparatus for stitching the plies of two housings movable on said saddle in a direction parallel to the axis of said drum, said housings being movable in opposite directions symmetrically with respect to a plane perpendicular to said axis and equidistant from each end of said drum, two stitching members each mov; i able with one of said housings into engagement with each other and movable by said housings away from one another to effect stitching along the side of the drum, said stitching members also being movable towards or away from the axis of said drum by corresponding movement of said saddle; means for urging the periphery of said stitching members in a direction perpendicular to the surface of said drum and into engagement with the plies on said building drum, two rotatable members each mounted on one of said housings, two arms each supporting one of the stitching members, and rotated by said rotatable members, and two parallelogram linkages for transmitting the rotatable movement of said rotatable members to said supporting arms, and so arranged that said stitching members can come into contact with one another, said linkages each being coupled to one of said rotatable members for eifecting arcuate movement of a stitching member about the center of curvature of one of said curved corners whilst said stitching member is urged in a direction perpendicular to the tangent at the point of contact of the stitching member with the plies placed around the curved corner.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,521,143 Benson Sept. 5, 1950 2,529,739 Powers Nov. 14, 1950 2,537,649 Smith Jan, 9, 1951

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