US3674584A

US3674584A - Method and apparatus for positioning a continuous thread or cord on a support surface

Info

Publication number: US3674584A
Application number: US826889A
Authority: US
Inventors: Norman E Klein
Original assignee: Milliken Research Corp
Current assignee: Deering Milliken Research Corp; Milliken Research Corp
Priority date: 1969-05-22
Filing date: 1969-05-22
Publication date: 1972-07-04
Anticipated expiration: 1989-07-04
Also published as: ZA702659B; NL7007452A; NO141926C; AT305807B; DE2024607A1; LU60939A1; CH520563A; NO141926B; BE750741A; JPS5310113B1; ES379542A1; GB1317594A; FR2048666A5

Abstract

A method and apparatus for positioning a continuous length of thread or cord on a support surface in a desired pattern wherein the cord is positioned on the support surface with means including a cord guide mechanism moving relative to the support surface while applying rolling pressure against the cord to minimize movement of the cord on the surface due to tension forces acting on the cord and to prevent dislocation of the cord with respect to the support surface.

Description

July 4, 1972 E, KLE|N 3,674,584

METHOD AND APPARATUS FOR POSITIONING A CONTINUOUS THREAD OR CORD ON A SUPPORT SURFACE Filed May 22. 1969 5 Sheets-Sheet 1 INVENTOR.

NORMAN E. KLEIN By w ATTORN N. E. KLEIN 3,674,584 METHOD AND APPARATUS FOR POSITIONING A CONTINUOUS July 4, 1972 THREAD OR CORD ON A SUPPORT SURFACE 5 Sheets-Sheet 2 Filed May 22. 1969 INVENTOR.

NORMAN E. KLEIN ATTORNEY Juiy 4, 1972 N. E. KLEIN METHOD AND APPARATUS FOR POSITIO 3,674,584 NING A CONTINUOUS THREAD OR CORD ON A SUPPORT SURFACE 5 Sheets-Sheet 5 Filed May 22. 1969 INVENTOR. NORMAN EKLEIN ATTORNEY July 4, 1972 KLElN 3,674,584

METHOD AND APPARATUS FOR POSITIONING A CONTINUOUS THREAD OR CORD ON A SUPPORT SURFACE ruled May 22. 1969 5 Sheets-Sheet 4 II I 64 I.

e5 1 e2 56 5 H 55 l I V '11 \l INVENTOR.

I NORMAN E.KLE|N BY ATTORNEY July 4, 1972 N. E. KLEIN 3,674,584

METHOD AND APPARATUS FOR POSITIONING A CONTINUOUS THREAD OR CORD ON A SUPPORT SURFACE Filed May 22. 1969 5 Sheets-Sheet 5 if 897 $22M \5 I I). 90 F2 1! 85 89 7? 5i 3 83 76 r J J ,1 6 Q5 87 I 82 8 INVENTOR. NORMAN E.KLE|N BY 1 r ATTORNEY METHOD AND APPARATUS FOR POSITIONING A CONTINUOUS THREAD OR CORD ON A SUP- PORT SURFACE Norman E. Klein, Inman, S.C., assignor to Deering Milliken Research Corporation, Spartanburg, SC. Filed May 22, 1969, Ser. No. 826,889 Int. Cl. B291: 17/28 US. Cl. 156173 21 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for positioning a continuous length of thread or cord on a support surface in a desired pattern wherein the cord is positioned on the support surface with means including a cord guide mechanism moving relative to the support surface while applying rolling pressure against the cord to minimize movement of the cord on the surface due to tension forces acting on the cord and to prevent dislocation of the cord with respect to the support surface.

This invention relates to a method and apparatus for positioning continuous thread or cord on a support surface in a desired pattern, and more particularly to a method and apparatus of forming reinforcing belts for use in the fabrication of pneumatic tires.

It is known in the production of pneumatic tires, both of the radial and bias ply type constructions, to provide an annular reinforcing belt or breaker strip about the periphery of the tire between the tread and main body or carcass portion for better road stability and longer tread life for the tire. Such reinforcing belts are formed of relatively inextensible threads or cords coated with or embedded in a suitable insulating material such as rubber, plastic or other resinous material, which serves to prevent direct cord to cord contact while anchoring the cords in a desired pattern within the belt. The cords generally are disposed in a pattern in which portions thereof extend in opposite directions to each other and in directions biased with respect to the longitudinal axis of the belt. The fabricated belt is positioned on the periphery of a tire carcass, tread rubber stock applied thereover, and the assembly vulcanized in conventional manner to form an integral belted tire construction.

Reinforcing belts of the type described may be formed by various methods, several of which are disclosed in Us. Pats. Nos. 2,982,327 and 3,422,874. One particularly desirable method of forming such belts reduces the number of free ends of reinforcing cord in the belt and produces a splice-free belt construction. This method involves winding one or more continuous lengths of cord onto a rotating support surface such as a revolving drum, while employing reciprocating guide means to traverse the drum surface and lay the cord in a generally zigzag pattern thereon. Prior to application of the cord to the surface, the cord is coated or wrapped with a covering such as unvulcanized rubber, which is quite tacky or sticky and provides a pressure sensitive adhesive afiinity between the cord and support surface to permit it to be positioned on the drum surface in the desired pattern. A belt is formed by displacing the zigzag path around the periphery of the drum for a sufiicient number of drum revolutions to form the finished belt.

Although annular reinforcing belts formed by the abovedescribed method possess desirable structural qualities, several problems are presented in the production of belts in this manner. The tension created in the cord by its longitudinal movement from a supply source onto the supporting surface tends to displace the cord from the curvilinear path in which it is laid it it is not quickly and Patented July 4, 1972 firmly secured to the support surface at the initial contact point. This tendency is particularly pronounced at points where the direction of the cord path abruptly changes such as at the side edges of the belt when a zigzag pattern is employed. For this reason, existing apparatus for forming belts in the above manner generally utilizes cord guide mechanisms which lay the cord in a desired pattern on the support surface While pressing the cord against the surface to prevent its dislocation by the aforementioned tensional forces. However, due to the relatively soft, deformable nature of the insulating rubber coating on the cord and its relatively high coefficient of fric tion, it is difficult to maintain sufiicient pressure on the cord to insure its adhesion to the support surface without causing damage to the coating or causing dislocation of the cord path due to frictional engagement with the cord guide mechanism.

Attempts have been made to reduce friction between the moving cord guide mechanism and the cord by providing a freely rotatable element such as a pivotally mounted roller or caster wheel adjacent the contact point, which element is biased against the support surface by suitable means such as a spring, and presses the cord against the surface as it rolls thereover. Although guide means employing such rotatable elements generally are effective to secure the cord in the desired path when the cord is laid in a substantially straight line over the support surface, they are relatively ineffective at points of abrupt change in the direction of the cord path such as at an edge of a belt, because of the diificulty of quickly reorienting the pressing element for movement in a new cord path direction. In such instances, unless relatively complicated, heavy and expensive control means are employed to automatically reposition the rolling axis of the cord deposition elements for a new direction of movement, this element will cause an undesirable increase in the radius of the cord reversal at the edges and/or the deposition element will become canted and drags along the support surfaces, causing dislocation of the cord on the surface and damage to the deposited cord which now forms the belt.

The present invention provides a method and apparatus for positively positioning a continuous thread or cord on a support surface in a desired pattern which provides benefits and advantages not heretofore attainable. Furthermore, the invention provides a method and apparatus for adhesively securing a continuous length of thread or cord on a support surface in a desired pattern with accurate positioning of the cord on the support surface and without dislocation or damage to the cord due to external forces acting thereon. In addition, the apparatus provides smooth, uniform operation even at high speeds. Moreover, the cord guiding and positioning portion of the apparatus is relatively small in size and light in weight.

Other advantages and benefits of the present invention will become apparent from the following detailed discussion and the description of the drawings in which:

FIG. 1 is a diagrammatic presentation of apparatus employed in the production of reinforcing belts for pneumatic tires in which the novel features of the present invention are incorporated;

FIG. 2 is a diagrammatic presentation of the winding drum of the apparatus seen in FIG. 1 showing in more detail the associated components for positioning a continuous cord on the surface of the drum in a desired pattern;

FIG. 3 is an enlarged fragmentary right side elevation, with portions shown in section, of the traverse and cord guide mechanism for positioning cord on the surface of the drum as seen in FIG. 2;

FIG. 4 is a further enlarged fragmentary right side elevation, with portions shown in section, of the cord guide portion of the traverse and cord guide mechanism seen in FIG. 3, showing in greater detail its position with respect to the support surface of the drum during the winding operation; 7

FIG. is an enlarged top elevation of a cord pusher in the apparatus shown in FIG. 4;

FIGS. 6, 7, 8 and 9 are side elevations of the cord guide mechanism seem in FIG. 4, showing the different relative positions of the various components thereof during progressive stages of operation;

FIG. 10 is an enlarged fragmentary right side elevation of another guide and cutter mechanism for positioning cord on the surface of the drum;

FIG. 11 is a further enlarged bottom elevation of the cutter portion of the apparatus shown in FIG. 10; and FIG. 12 is a further enlarged top elevation of the thread guide portion of the apparatus shown in FIG. 10.

Referring more specifically to the drawings, FIG. 1 shows apparatus for producing annular pneumatic tire reinforcing belts by a continuous cord winding process. As shown schematically, the apparatus broadly includes a cord supply source 12 such as a rotatable package of cord, a cord coating unit such as extruder device 14, and a belt-forming device 16. Continuous cord 18 composed of a relatively inextensible material conventionally employed as tire cord such as fiber glass, rayon, cotton, polyester, nylon, Wire or the like, in single or multistrand, twisted or untwisted form, is longitudinally directed by guides 20a and 20b from the supply source 12 to the extruder device 14 where the moving cord is coated in known manner with a protective coating such as unvulcanized, partially vulcanized or vulcanized rubber. The coated cord 22 with a tacky, pressure sensitive adhesive surface characteristic, is directed by guides 23a, 23b, 230 to the belt-forming device 16 where it is wound in a manner to be described, to form an annular reinforcing belt. A weighted movable pulley 24 is positioned in the cord path between the guides 23b, 23c and functions to vary the length of the cord path to compensate for slight variations between the delivery rate of the cord from the extruder device 14 and the take-up speed of the beltforming device 16.

As better seen in FIG. 2, the belt-forming device 16 usually includes a rotatable winding drum 26 having a generally cylindrical outer surface 27 for supportably receiving the cord, and means associated therewith for properly positioning the cord on the support surface 27 to form a desired pattern while pressing the cord with rolling pressure against the surface closely adjacent its first contact therewith to secure the cord to the support surface and to positively position the cord in the desired pattern. During the winding operation the belt may be formed by winding the cord in a desired pattern directly on the peripheral surface of the drum, or if desired, a substrate layer such as a band of unvulcanized, partially vulcanized or vulcanized rubber, may be placed on the drum to serve as the cord support surface and become a part of the final belt construction.

The cord positioning and pressing means 28 as shown in FIGS. 2 and 3 generally comprises a cord guide mechanism 30 mounted for reciprocating movement across the surface 27 of the winding drum 26 on an elongate support rod 31 and also includes drive means 32 for moving the guide mechanism 30 and support surface 27 of the drum relative to each other to position the cord 22 in a desired pattern thereon. As shown schematically in FIG. 2, the drive means 32 includes a motor 34 driven by a suitable power supply, not shown, which is drivingly connected by a belt and pulley arrangement 36 through a gear transmission 37 on rotatable shaft 38. Shaft 38, in turn, is directly connected to a barrel cam 40 and drivingly connected by a suitable gear train 42 to the drive shaft 44 of the winding drum 26 such that power from motor 34 simultaneously rotates the cam 40 and winding drum 26 during the winding operation. A cam follower 45 connected to the cord guide mechanism 30 via connector rod 33 engages a groove 40a in the surface of the cam 40.

The groove is configured so that during rotation of the winding drum 26, the guide mechanism 30 is reciprocated across the surface 27 of the drum transverse to its direction of rotation to lay the cord in a zigzag pattern thereon; The gears of gear train 42 are configured to displace the position of the cord pathon the drum surface during subsequent revolutions of the drum and produce a desired pattern to form the reinforcing belt. 2

Associated with the guide mechanism 30 is a roller 47 disposed across the cord path and in contact with the drum surface 27. The roller 47 is operatively connected to a support member 46 and attached thereto through arms 48 disposed on each end of the roller. Support 46 is pivotally mounted on shaft 49 and actuated, e.g., by .an

air cylinder 50 to urge roller 47 against support surface,

Guide mechanism 30 is .shown in greater detail in FIGS. 3 and 4 and includes a base member '51 which is mounted for reciprocation on rod 31 by way of bushing assembly 3 5. A cord guide tube 52- is aifixed'to base member 51 with its longitudinal opening. at an angle to the surface 27 of the drum 26. The outlet 53 of guide tube 52 is gen-. erally adjacent the nip of drum 26 and roller 47. Also attached to base member 51 is blade 54 with a cutting edge adjacent the guide tube 52. Associated with blade 54 is a guide member 55 with an opening 554: adjacent the blade 54. Member 55 is operatively connected with pull rod 56 and link member 57 which is pivoted on rod. 60. A spring 5 8 and adjustable stop 59 are disposed on pull rod 56. Also, as shown in FIG. 4, an eccentric roller 61 is positioned adjacent the path of the cord through the guide mechanism 30. A spring 62 is attached to winged tube 52 and to member 55. A cord pusher 63 is positioned in contact with the underside of the inverted U portion of winged guide tube 52 and is operatively connected to pull rod '56 through bracket 64-. A spring 65 is disposed between upstanding ears on cord pusher 63 and bracket 64.

.An alternate form of guide and cutter'mechanism for inclusion in the apparatus of the invention as shown in FIGS. l0, l1 and i2 is mounted for movement along elongate support rod 31. Guide plate member 71 mounted for reciprocation via bushing assembly 35 has

plates

72 and 73 attached thereto. In the space between

plates

72 and 73 are disposed freely rotatable spaced rollers 74.

Scissor blades

76 and 77 having. wings 76a and 77a are mounted for sliding movement in opening 78' of a support member 79 which has a tail portion 80.

Blades

76 and 77 are maintained in proper alignment by attachment to slide plate 82 by screw 83 and stud 84. Support member 79 has a pair of upstanding ears 85 near one end thereof and a second pair of ears 86 disposed intermediate of its length. Support 79 is pivotally mounted on frame member 87 which is aifixed to bushing assembly 35 which engages rod 31. The pivotal movement of support 79 is biased counterclockwise by a spring 8-8, one end of which is connected to the top of stud 84 and the other end to frame member 87. A cable 89 makes a two to three radian bend around pulley 90 and is attached also to the top of stud 84 to control the angular movement of plate 79 and the action of the

scissors

76 and 77.

In the operation of the apparatus shown in FIGS. 2-9 of the drawings, the winding drum 26 is continuously rotated to draw an endless length of coated cord 22 over the

guides

23a, 23b and 23c and through guide tube 52 and from the outlet 53 thereof into proper position on support surface 27. The guide mechanism 30 simultaneously is reciprocated across roller 47 and the surface 27 in a zigzag pattern. As the drum 26 draws the coated cord 22 onto its surface, freely rotating roller 4-7 which is biased against surface 27 of drum 26 presses the cord 22 with rolling pressure into secure engagement with the support surface 27. As shown in FIG. 3, the cord 22 preferably contacts roller 47 prior to the positioning on surface 27 of the drum. Alternatively, the cord may be drawn into the nip of drum 26 with roller 47 or the cord first may contact surface 27 and then roller 47. In any case, it is important that roller 47 press the cord 22 against the surface 27 with rolling pressure at the first contact of the cord on surface 27 or closely adjacent thereto, particularly at the points of cord path change at the edges of the belt. This is desirable so as to provide proper positioning of the cord on the support surface without dislocation or distortion as the guide mechanism 30 reciprocates across the surface to form the desired cord pattern.

It is important that the surface of roller 47 which is utilized to apply rolling pressure to positively position the cord on the support surface have low or minimal pressure sensitive adhesive afiinity for the coated cord and/or the support surface. Particularly useful as the roller surface are silicone rubbers.

After the drum has been rotated a sutficient number of revolutions to complete the formation of the desired belt, roller 47 and thread guide mechanism 30 are withdrawn from the support surface 27 to permit rapid removal of the finished belt from the drum 26. This may be accomplished by actuating cylinder '50 which rotates support member 46 about shaft 49 to withdraw guide mechanism 30 and roller 47. At the same time guide mechanism 30 separates from roller 47 by relative movement generated within the parallelogram configuration formed by shaft 49, pivot rod 60, support member 46 and link member 57 such that with counterclockwise movement about shaft 49, link member 57 rises in respect to support 46 which in turn tilts the right end of base member 51 downward and away from roller 47. Upon withdrawal of the guide mechanism 30 and roller 47, solenoid 67 is momentarily actuated causing pull rod 56 to retract member '55 drawing cord '22 into engagement with blade 54 so that the cutting edge of the blade severs the cord. This movement of member 55 is accomplished through pull rod 56 and link member '57 which pulls bracket 64 on link member 56 against the upturned portion of member 55 and urges the opening 55a thereof into contact with the cord and with blade 54. The movement of pull rod 56 during the cutting operation also causes cord pusher 63 to withdraw as shown in FIGS. 6 and 7. Eccentric roller 61 which engages the cord prevents reverse movement of the cord in the guide tube 52 during this operation.

As cord pusher 63 is moved to its rearmost position, bias spring 65 keeps the tip of pusher 63 generally adjacent cord 22. Return movement of pull rod 56 and cord pusher 63 forces cord 22 in a forward direction through guide tube 52 to project from the outlet 53 so that cut end of the cord 22 contacts surface 27 to begin the formation of a new belt. As pull rod '56 advances, cord pusher 63 is rotated from engagement with the cord to again facilitate free movement of the cord 22 through the guide tube 52.

In the operation of the alternate cord guide and cutter mechanism shown in FIGS. 10, 11 and 12, the cord 22 moves between rollers 74 into contact with pressure roller 47 and advances thereon onto the surface 27 of drum 26. When the winding of a belt has been completed, the cord 22 is cut by the action of

scissor blades

76 and 77. FIGS. and 11 show the blades in an open position with little tension in cable 89. Cutting of the cord is achieved through a momentary pull on cable 89 which is produced by actuating solenoid 67 shown in FIG. 3 which in turn moves link member 57 in a counterclockwise direction to pull rod 56 which would be attached to cable 89 (not shown). The other end of cable 89 is attached to the top of stud 84. Since cable 89 is attached to stud 84 at a position above the pivot point of support member 79, a clockwise force is imparted to support member 79 so that the

scissor blades

76 and 77 move away from

plates

72 and 73. The extent of movement is limited by the contact of tail portion 80 of support member 79 which engages frame member 87. Further pull on cable 89 moves

open scissor blades

76 and 77 toward the cord 22. This movement of the blades causes wings 76a and 77a to contact ears imparting respectively clockwise and counterclockwise movements to the blades closing them on cord 22 outboard of rollers 74, servering the cord and leaving a projecting cord end. The completed belt then can be removed from the drum 26.

After the cord 22 is cut, reducing the tension on cable 89

causes blades

76 and 77 to slide backward away from the cord 22 through bias action of spring 88. This movement of

blades

76 and 77 with respect to opening 78 in member 79, forces wings 76a and 77a against ears 86 on support member 79. Contact of the wings with the ears 86 pivots the blades to an open position for the next cutting operation. The release of the tension of cable 89 pivots support member 79 back to a position as shown in FIG. 10 of the drawings. This moves the cut cord end into contact with roller 47 which now has returned to an operating position and the winding of a new belt can be started.

An advantage of the apparatus shown in the drawings is the capability of the guide mechanism and the pressure roller to maintain any desired relative position or pressure with respect to an increase in thickness of the support surface as the belt is formed. Thus, as a number of cord layers are wound on the support surface, the guide mechanism and the roller are displaced slightly from the drum while remaining in the desired angular position with respect to the drum.

The above description and drawings show that the present invention provides a novel method for positive- 1y positioning thread or cord on a support surface in a desired pattern. The invention also provides a method and apparatus for accurately positioning thread or cord on the surface without dislocation or damage to the cord due to the action of external forces. Moreover, the method and apparatus of the invention accomplishes these improved results with cord having a high pressure sensitive adhesive affinity for the support surface and for itself. In addition, the apparatus operates smoothly and efliciently even at high speeds and is light in weight and small in size.

It will be apparent that various modifications can be made in the above detailed procedures and apparatus within the scope of the present invention. For example, the arrangement of the various components and the specific design details may be changed provided the cord contacts the support surface adjacent the nip between the pressure roller and the support surface and provided the pressure roller applies rolling pressure to the cord at or closely adjacent to the point of contact. If desired, multiple cords and/or rollers may be used. Also, the roller may have surface variations such as increases or decreases in diameter along its length to provide' pressure differences and include axial or circumferential grooves or ribs, or be divided into a plurality of roller segments in adjacent or spaced relationship and similar modifications. Therefore, the invention is to be limited only by the following claims.

That which is claimed is:

1. A method for positioning at least one continuous length of cord on a substantially cylindrical support surface in a zigzag pattern with a plurality of repeating cycles per revolution of said support surface wherein the cord and support surface have a pressure sensitive adhesive affinity for each other comprising:

(a) passing the cord onto the support surface While 7 moving the cord and support surface relative to each other to position the cord in a zigzag pattern on the surface, and t (b) pressing the cord against the support surface with 4. A' method as defined in claim 1 wherein the cord is pressed against the-support surface with arolling surface acting substantially parallel'to the cord path and the support surface. 1

5; A method as defined in claim 1 wherein the support surface is an endless surface and the relative movement between the support surface and the cord'is effected by longitudinally moving the support surface past the d; I

6. A method as defined in claim 5 wherein the relative movement is further effected by moving. the cord trans-' versely to the face.

7. A method'as defined in claim 5 wherein'the endless surface is generally cylindrical and is rotated about its cylindrical axis to efifect longitudinal movement thereof. 8. A method as defined in claim 7 wherein the reladirection of movement of the support surtive movement is further effected by reciprocating the cord across the support surface during movement thereof to produce a zigzag cord pattern thereon.

9. Apparatus for positioning at least one continuous cord on a support surface in a zigzag pattern with a plurality of repeating cycles per revolution of said support surface comprising means defining a cord support surface, and means associated therewith a position a cord on the support surface to form a desired pattern including roller means extending across an entire width of said pattern to press the cord against the surface with rolling pressure at a position closely adjacent its first contact thereon to facilitate positive positioning of the cord path on the support surface and adhesion of the cord thereon.

10. Apparatus as defined in claim 9 wherein the cord positioning and pressing means includes (a) cord guide means having a cord outlet for directing cord onto the support surface,

(b) means supporting the guide means with itscord outlet positioned closely adjacent the support surface,

(c) means for moving the guide means and support surface relative to each other to position the cord in a desired path on the support surface, and

(d) roller means for applying pressure against the portion of the cord in contact with said support surface to facilitate prompt adhesion to and proper positioning of the cord on the support surface while permitting relatively unrestricted'fiow of the cord onto the support surface. a

'11'.'Apparatus as defined in claim 10 wherein the means defining the cord support surface comprises a generally cylindrical outer surface for "supporting said cord, and wherein the means for relatively moving the cord guide means and the support surface comprises means forrotating said cylindrical surface about its cylindrical axis while simultaneously reciprocating said cord guide means transversely to the direction of movement of the outer surface of said cylindrical surface to position cord in a zigzag pattern thereon.

12. Apparatus as defined in claim 10 wherein said roller means is disposed substantially transverselyto-the cord path.

13. Apparatus as defined in claim 10 wherein said roller means has a low pressure sensitive adhesive affinity for said cord and said support surface.

14. Apparatus as defined in claim 11 wherein said roller means is disposed substantially transversely t0 the cord path and across the support surface from one edge to the other. f

15. Apparatus as defined in claim 11 wherein said cord guide means is positioned to direct said cord first intocontact with said roller means and then into' contact with' said support surface. I

16. Apparatus as defined in claim 11 wherein said cord guide means is positioned to direct said cord into the nip between said rotatable cylindrical surface and said roller means.

17. Apparatus as defined in claim 10 wherein said roller means includes biasing means to urge said roller means toward said support surface.

-18. Apparatus as defined in claim 10 wherein said roller means includes means for moving said roller means away from said support surface.

19. Apparatus as :defined in claim 18 wherein cutting means is disposed adjacent said cord outlet.

20. Apparatus as defined in claim 19 wherein said cutting means includes a scissors means.

21. Apparatus as defined in claim 19 wherein said cord guide means includes means for advancing said cord into contact with said support surface.

References Cited UNITED STATES PATENTS R6.25,349 3/1963 Hanson 156-117 X 847,041 3/1907 Bayne et al. 156-397 1,460,949 7/1923 Currier 156-439 X 3,082,140 3/1963 VanZO 156-l17 X 3,458,146 7/1969 Warner 156-117 X 3,379,591 4/1968 Bradley 156-173 FOREIGN PATENTS 1,230,892 9/1960 France 156-397 STEPHEN C. BENTLEY, Primary Examiner U.S. Cl. XrR- 156-117, 397, 429