US2988129A

US2988129A - Machine and method for dielectrically embossing trim strip material

Info

Publication number: US2988129A
Authority: US
Inventors: Bruce E Kevelin; Ted A Redo; Willett Joseph Woodrow
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1958-03-05
Filing date: 1958-03-05
Publication date: 1961-06-13
Anticipated expiration: 1978-06-13
Also published as: DE1151921C2; DE1151921B

Description

June 13, 1961 B. E. KEVELIN ET AL 2,988,129

MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL Filed March 5, 1958 6 Sheets-Sheet 1 UPPER D/E' GEN. l

LVVENTORS Brace ere/m,

ATTORNEY June 13, 1961 B. E. KEVELIN ET AL 2,938,129

MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL 6 Sheets-Sheet 2 Filed March 5, 1958 .5... .vv o M (Q o 0 0 O O 0 0 0 L 5? 251. 5

June 13, 1961 B E. KEVELIN ETAL 2,988,129

MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL 6 Sheets-Sheet 3 Filed March 5, 1958 IVVE/VTORS J3 z zzce 6161 6/ 2; B) 790 6 380256;, /@'Q 7 Joseph ll/aad 'azz/ [/1 /e/% A 7'7'ORNEY June 13, 1961 E. KEVELIN ET AL 2,988,129

MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL Filed March 5, 1958 6 Sheets-Sheet 4 I g [N VEN T0 R5 June 13, 1961 B. E. KEVELIN ETAL MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL 6 Sheets-Sheet 5 Filed March 5, 1958 2 A TTORNEY June 13, 1961 B. E. KEVELIN ETAL MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL 6 Sheets-Sheet 6 Filed March 5, 1958 INVENTORS I Ezzzce d'z/eAw a C7, @6027, p); Zbadzozy w/ezz w 5 My u m M U flaw "m" fiw/ w rm 1.3 .U 1., M w n VI 2,988,129 Patented June 13, 1961 2,988,129 MACHINE AND METHOD FOR DIELECTRICALLY EMBOSSING TRIM STRIP MATERIAL Bruce E. Kevelin, Detroit, Ted A. Redo, Birmingham, and Joseph Woodrow Willett, Harper Woods, Mich, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 5, 1958, Ser. No. 719,438 11 Claims. (Cl. 154--1.6)

The present invention relates to a method and appara tus for joining decorative strips to a sheet material for use as interior trim in automotive vehicles. While the embellishment of such trim materials for automobile interiors represents an important application of the subject method and apparatus, it will be apparent that the invention has general utility wherever decorative trim materials are employed.

While it is generally old to emboss or bond one trim material upon another, no method or apparatus has been available whereby this may be done fast enough for use with products being made on assembly line basis. In the present invention a method and apparatus has been developed which permits such trim panels to be embellished with decorative strips at rates consistent with assembly line operation and at a cost not substantially greater than non-decorated trim panels previously used.

There is increasing demand to provide trim sheets or panels having decorative designs or highlighted materials formed thereon and further which decorated trim panels are capable of being fabricated into diiferent, including three dimensional shapes after the decoration or embellishment has taken place. These demands have not been satisfied by previously known methods of fabricating trim panels which most commonly have included embellishing a sheet or trim panel by securing a rigid trim or strip material thereto by means of a clip or other mechanical clamping devices. It is apparent that the use of such rigid trim strips considerably limits, both physically and economically, the extent to which such trim strips may be utilized. The present invention, on the other hand, represents a significant contribution in that it permits the use of flexible thermoplastic trim strip materials dielectrically bondable or embossable upon a sheet of similarly thermoplastic material in a way which permits the composite to be subsequently fabricated into innumerable forms. Thermoplastic materials refer to any heat softenable materials and are not limited to plastic substances.

The subject method and apparatus permits one or more trim strips to be fed along a die member where a finite length of such material is cut off and clamped to the die. Thereafter the sheet material to be decorated is brought into proximity with the strip material following which the trim strip and sheet material are dielectrically heated bonding or embossing the strips upon the sheet material.

Working with relatively narrow, but aesthetically desirable, trim strips creates many problems particularly where it is desired to simultaneously work with a plurality of such strips and to dielectrically bond or emboss the same to a trim sheet at assembly line rates. It is the purpose of the present invention to provide an apparatus which is uniquely able to permit such embossment. Inasmuch as it is an object of the present invention to provide an apparatus capable of working with a plurality of these narrow trim strips and further in which it is desired to work with finite lengths of such materials, a unique feeding mechanism has been provided which is capable of grasping a plurality of such strips moving the same into position on a die member where the strips may be clamped and cut to the appropriate length prior to dielectric embossment and after which embossment the feeding mechanism may repeat the cycle.

The use of narrow trim strips creates a further problem of providing a suitable die member which is capable of maintaining the strips in the proper position preliminary to as well as during the bonding or embossing steps. The subject die is not only capable of guiding the trim strips, as proposed, but is also uniquely constructed in a manner permitting the guiding structure to be moved to a noninterfering position during the actual bonding or embossing step. It is still a further object to provide such a die mechanism which is uniquely constructed to permit an optimum electrical field to pass through the trim strip material to achieve proper dielectric bonding without the likelihood of arcing to which such narrow trim strips are otherwise highly susceptible.

Other objects and advantages of the present method and apparatus will be apparent from a perusal of the detailed description which follows.

In the drawings:

FIGURES 1-3 are diagrammatic showings of the subect apparatus;

FIGURE 4 shows a sheet having a decorative trim strip bonded thereto;

FIGURE 5 is a plan view of the subject apparatus;

FIGURES 6 and 7 are enlarged detail views of the carriage clamping head;

FIGURE 8 is an enlarged elevational view of the carrrage;

FIGURE 9 is a view along line 9-9 of FIGURE 8;

FIGURE 10 is a view along line 10*10 of FIGURE 9;

FIGURE 11 is a view along line 11-11 of FIGURE 8;

FIGURE 12 is a partial isometric view of the lower die;

FIGURES l3 and 14 are fragmentary sectional views showing upper and lower die coaction; and

FIGURE 15 is a fragmentary enlargement of the embossing blade.

Referring to FIGURES 1 through 3 of the drawings, a schematic representation of the subject apparatus is shown and includes a dielectric press 10 which includes a lower die member 12 and an upper die member 14. One of the die members is movable relative to the other in order that the dies may be positioned in proximate or embossing relation. For illustrative purposes, upper die 14 may be considered vertically movable with respect to lower die 12.

A high frequency generator is shown generally at 16 and is adapted to cause an alternating current to flow between the dies when dielectric heating is desired. The theory of dielectric heating and embossing is set forth in considerable detail in prior patents and other literature on subject. For present purposes, it should sufiice to note that when a high frequency alternating current is passed through a suitable thermoplastic material, molecular heating takes place which enables such material to be embossed or bonded to another similarly heated material. The dielectric press, per se, forms no part of the present invention.

Trackways 20 are formed on either side: of the lower or fixed die 12 and are adapted to support a carriage 22 for movement relative thereto. Carriage 22 includes a clamping head indicated generally at 24 adapted to clampingly engage a plurality of strips of thermoplastic material 26 wound respectively on spools 28. Spools 28 are rotatably mounted upon a support bracket 30. After the carriage head 24 has clampingly engaged the trim strips 26, infra, the carriage is adapted to be moved leftwardly in trackways 20 feeding out and positioning the strips within aligning and embossing grooves 32 in lower die member 12. After carriage 22 has moved a sufficient distance to lay trim strips 26 throughout the longitudinal length of the die grooves 32, clamping or tensioning arms 34 and 36 pivotally mounted at 38 and 49 upon die supporting structure 42 clamp the strips upon the die and simultaneously cut off the strips from both the rolls 28 and from the clamping head 24. Thereafter a sheet of thermoplastic material 44 is brought into an overlaying position with respect to said strips, as best seen in FIGURES 13-15, and die member 14 moved toward lower die 12 to clamp the assembly together. Thereafter the high frequency generator is energized dielectrically bonding strips to the sheet material. A pair of rubber pads 46 are disposed between sheet 44 and die 14 to prevent arcing during dielectric heating. After the dielectric embossment step the trim sheet or panel is removed from the die and the carriage member returned to its starting position where it is again prepared to clampingly engage the trim strips to repeat the c cle.

The various components of the subject apparatus will now be considered in greater detail.

Carriage The carriage 22 is shown in greater detail in FIGURES 6 through 8 to which reference is now made. While the actual construction of the carriage may take any number of forms, a preferred embodiment utilizes a rod or tubular construction as shown. A pair of transverse rods 50 have rollers or wheels 52 formed respectively at the ends thereof and which rollers are disposed in trackways 20. Rods 50 are reinforced by rods 51 and 53. There appears to be no practical limit to the size of carriage 22 the dimensions of which will be determined in general by the width of the material to which the trim strips are to be embossed.

The size of clamping head 24 is also a variable depending on the number of trim strips with which it is desired to work. A single large clamping head might be used which was capable of pulling a large number of trim strips or as is the case with the apparatus illustrated, a plurality of such heads may be used, the precise number again being determined by the number of strips to be embossed. While the means for so doing is not shown, it is to be understood that the clamping heads may be adapted to be moved transversely of the carriage depending on the desired disposition of the strips on the sheet material. Clamping head 24 includes a supporting block 54 suitably mounted upon transverse rod 56. A rake-like member 56 is supported from the bottom of supporting block 54 and extends forwardly therefrom in the direction of the strip rolls 28. Member 56 has a downwardly offset portion 58 formed at one end thereof and which portion terminates in a plurality of forwardly extending fingers 60. A similar member 62 is pivotally supported by pin 64 on block 54 in vertically spaced relation to member 56. Block 54 is actually recessed at 66 permitting member 62 to rotate about its pivot. Member 62 also includes a downwardly extending portion 68 terminating in a horizontal lip 70. A plurality of members 72 corresponding in number to and aligned with fingers 60 of member 56 are dependingly supported from lip 70. Members 72 are formed of hardened steel preferably mounted to lip 70 upon suitable resilient pads 73 to cushion the engaging action between members 72 and fingers 60.

A U-shaped spring member 74 is disposed within the recessed portion 66 of block 54 so as to normally bias the pivoted member 62 in an upwardly or counterclockwise direction away from the fixed member 56. A lever 76 is pivotally supported in block 54 upon pin 78 above the pivoted member 62 and is adapted when rotated in a clockwise direction to its vertical position, as shown in FIGURE 8, the pivot cam against member 62 rotating the latter in a downwardly direction whereby the resilient members 72 engage fingers 60 of member 56.

Strip flow restrictor Referring momentarily to the trim strip feeding apparatus, it will be noted that the strip materials 26 from the various rolls 28 are fed through a strip flow-restrict ing device indicated generally at 80. The flow restrictor 80 includes a block member 82 having a plurality of openings 84 formed therethrough and corresponding in number to and axially aligned with die grooves 32. A vertically adjustable stud 86 is arranged to project toward each strip opening 84. A pad 88 which is noninjurious to strip 26 is mounted upon the lower end of stud 86 for relatively light frictional engagement with the strip providing a variable resistance to the flow of the strip material therethrough. The purpose of device 80 is to insure that the trim material will remain under tension as carriage 22 draws the same over the die 12. In this way the strip segments will be under tension when the clamping or tensioning bars 34 and 36 clamp the strips to the die. By maintaining strips 26 under tension it insures that there will be no wrinkling and further that there will be intimate engagement between the embossing dies and the material. It is apparent that the amount of tension on the trim strips may vary by adjusting the studs 86.

An L-shaped plate or lip 90 is clamped to flow restrictor block 82 for supporting the terminal ends of the trim strips whereby the latter may be presented to the clamping head 24 of carriage 22 in a substantially horizontal attitude.

The trim strip clamping operation is as follows: the clamp actuating arm '76 is pivoted to the dotted position shown in FIGURE 8 which permits the spring 74 to open members 56 and 62. Thereafter, carriage 22 is moved in the direction of the trim rolls 28 which ultimately results in the front wheels of the carriage dropping into a downwardly inclined portion 92 of the trackways 20. This permits the fixed clamping member 56 to pass underneath the strip supporting lip 96. The movement of the carriage is limited by stop members 94 formed of any suitable material such as hard rubber. In this position of the carriage the members 72 and fingers 60 are aligned on opposite sides of lip 99. Next, clamping lever 76 is rotated to its vertical position moving the resilient members 72 into engagement with strips 26 supported on lip 90. Carriage 22 now is moved to the left causing strips 26 to be clamped between fingers 6i) and resilient members 72. Continued leftward movement of the carriage feeds the respective strips through the corresponding embossing grooves 32 formed in die 12. The carriage continues to traverse the trackways 20 in a leftwardly direction until the rear wheels thereof engage stops 96 suitably longitudinally spaced from the die I2 to permit the embossing grooves to be completely overlaid with the strips 26.

It is to be understood that the movement of lever 76 as well as carriage 22 itself may be accomplished either manually or automatically. To simplify the illustrated embodiment of the present invention the apparatus is shown as manually operable.

Tensioning and cutter devices With the carriage in the position as thus far described, trim strips 26 will have passed tensioning and cutter devices indicated generally at -98 and 100. The tensioning and cutter devices are mounted on the die supporting structure 42 proximate either end of die 12 and extend transversely thereof. Since they are identical, it will only be necessary to describe one set of the devices. Device 100 includes a fixed or female member Th2 mounted directly on the die supporting structure and arm 36 pivotally supported upon a bracket 104. When the die is being loaded with trim strips the pivoted arm 36 is adapted to be rotated to an upwardly position, shown in FIGURES l and 2 permitting traversal of the die by carriage 22. With the carriage in its leftmost position, however, arms 34 and 36 are pivoted toward the fixed supporting member 102 clamping the trim strips between itself and the supporting member. To provide clamping engagement between the members 36 and 102, they have been shown tapered in cross section, see FIGURE 10. It is also possible to utilize a square or rectangular cross section for members 36 and 102 if desired.

A cutter bar 106 is fixed to the pivoted arm 36 so that as the arm is rotated and has clamped the trim strips to the member 102, the final movement of the arm will cause the cutter bar to cut off the trim strips intermediate clamping head 24 and the flow-restricting device 80. A similar cutting device and operation obtains with respect to arm 34.

A pair of tensioning and cutter devices is normally provided for each cutting head, therefore, in the illustrative embodiment a pair of clamping and cutting devices 98' and 100' is provided for coaction with clamping head 24'. Since locking devices 98- 18 and 100100 are axially aligned, as shown in FIGURE 5, it is possible to use single tensioning arm locking members -108-110 at each end of die 12. As seen in FIGURE 9, locking member 108 includes an arm 112 pivotally mounted on stud 116. Arm 112 is resiliently urged in a clamping direction by a spring 114. Arm 112 is rotated to release clamping devices 100100'.

At this point the trim strips have been severed from the carriage 22 and the rolls 2 8 and are retained under tension within the die grooves 32 in condition for bonding and embossment to the appropriate thermoplastic sheet material 44.

Before proceeding further with a description of the apparatus it is well to consider the manner in which the sheet material 44 may be presented to the lower die member 12 and trim strips 26. As best seen in FIGURE 13, silicone rubber pads 46 are loosely disposed intermediate sheet 44 and the upper die 14 in order to prevent arcing between the die members and the thermoplastic materials involved. In this type of arrangement the trim strip material is embossed upon the sheet 44, see FIGURE 4, leaving the latter in a flexible condition to permit its being fabricated into any desired form.

Die construction A most important part of the subject apparatus is the lower die 12 and the manner in which the same is constructed. Referring particularly to FIGURES 12 through 15, it will be appreciated that the die is built up of a plurality of components. A plurality of aligned and transversely spaced embossing blades 116 are suitably fixed to supporting plate 42. The embossing dies are of L- shaped cross section to provide a rigid support. The embossing ends 129 of blades 1 16 are of an arcuate, al though optional, shape to provide the appropriate embossed contour of the trim strips 26 on sheet 44. In order that the trim strips be properly guided into superadjacent alignment with the embossing blade when the carriage device feeds the strips to the lower die, guide plates or guide members 122 are provided on either side of each blade. At least a portion of the guide plates is adapted to be vertically positioned above the embossing blades to an extent sufficient to cooperate with the blades to define therewith the die grooves 32 into which the trim strip is fed by the carriage mechanism.

However, while the guide plates are necessary for properly positioning the trim strips with respect to the embossing blades, it is equally necessary that these plates be depressed or retracted so as not to interfere with the dielectric bonding and embossing step. To this end, guide plate supporting channels 124 are provided adjacent the embossing blades 116 and secured to support 42 through studs 118. In order that they may be retracted during the embossing step, however, the guide plates are mounted upon resilient pads or strips 126. Pads 126 may he formed of any suitable. resilient material such as rubber or di-isocyanate foam.

Earlier modifications of the die mechanism utilized guide plates formed of non-conductive substances such as wood which, however, proved to contribute to unsatisfactory embossment. The unsatisfactory embossment was traced to several factors all of which were eliminated by forming the guide plates of a metallic material and shaping the plates so as to provide the ridges or lips 128 at the outer edges thereof.

Previous to the present die construction, it was found that the field intensity was increased at the edges of the embossing blades and trim strips due to their sharp edges. The result was, of course, voltage concentrations and periodic discharges along these edges burning or scarring the thermoplastic materials. The field intensity concentration was also enhanced by the fact that non-conductive materials, e.g. wood guide plates, were disposed between the respective embossing blades causing all. stray flux lines to pass through the nearest conductor, in this instance, the embossing blades.

In the present modification, however, the metal guide plates 122 are maintained at the same potential through contact strips 130 as the embossing blades. Likewise, guide plate elevation is maintained substantially equal to that of the embossing end of the blades. The guide plate elevation actually refers to the ridges or lips 128 which, as seen in FIGURE 15, are flush with the embossing edge 120 when the plates are depressed during embossing. In this Way the electric field between die 14 and the embossing blade 116 is more uniformly distributed greatly reducing the field intensity at the edges of the trim strip and resulting in better overall embossment. This demonstrably better embossment is attributed, at least in part, to the fact that stray lines of flux tend to be collected by the guide plate lips 128 rather than by the embossing blade edges as in the past.

The embossing blade voltage is transmitted to each guide plate 122 through copper contact strip 130. Contact strip 130 is fixed at one end to supporting channel 124 through stud 118. The other end of the contact strip is fastened to the guide plate through a screw 132. The embossing blade voltage is thus transmitted through the short leg 134 of channel 124 which rests upon the horizontal leg 136 of the embossing blade.

It is apparent that various modifications may be made in the illustrated embodiment of the present invention within the scope of the appended claims.

We claim:

1. A dielectric bonding and embossing apparatus comprising relatively movable die members, means for passing a high frequency alternating current between said die members, an embossing blade formed on one of said die members, means for drawing a strip of thermoplastic trim material across said one die member in superadjacent alignment with said embossing blade, means for cutting and clamping a finite length of said strip in supported relation upon said blade, whereby the strip is positioned for bonding to a sheet of thermoplastic material, said one die member also including guide members for maintaining the strip in alignment with the embossing blade, and means for maintaining said blade and guide members at the same voltage.

2. A dielectric bonding and embossing apparatus as set forth in claim 1 in which means is provided for resiliently supporting said guide members upon the die member whereby the guide members are depressed to expose the embossing blade during the bonding operation.

3. A dielectric bonding and embossing apparatus as set forth in claim 1 in which the strip drawing means comprises a carriage movable relative to said dies, the carriage including a head having a device for clampingly engaging and retaining said strip whereby the strip is adapted to be drawn across the embossing blade as the carriage is moved relative to the dies.

4. A dielectric bonding and embossing apparatus comprising a pair of relatively movable die members, means for passing a high frequency alternating current between said die members, an embossing blade formed on one of said die members, means for drawing a strip of thermoplastic trim material across said embossing blade to longitudinally support said strip upon said blade, means for maintaining said strip under tension When being drawn across said embossing blade, guide members longitudinally coextensive with and abutting said embossing blades and vertically adjustable with respect thereto, means biasing the guide members in a vertically extended position whereby said guide members and said embossing blade coact to define a trim strip guiding groove, means for maintaining a finite length of said trim strip under tension within said groove such that said trim strip can be dielectrically heated and bonded to a sheet of thermoplastic material disposed between said strip and the other of said die members upon movement of said die members one toward the other, the movement of said die members being adapted to depress said guide members to eliminate the trim strip guiding groove.

5. An apparatus as set forth in claim 4 in which the strip drawing means comp-rises, trackways disposed on opposite sides of the embossing blade supporting die, a carriage movably mounted upon said trackways, said carriage including a clamping device having a first element rigidly fixed to the carriage, a second element pivotally mounted relative to the first element, means controlling the pivotal movement of said second element, said tension maintaining means including a ledge member for supporting said strip proximate one end of the embossing blade supporting die, said trackways having depressed portions adjacent said ledge member, at least part of said carriage being movable into the depressed portions of said track- Ways permitting the first element of the clamping device to be disposed below and the second element above said ledge member to position said elements for clamping engagement with said strip.

6. A dielectric bonding and embossing apparatus comprising a pair of die members, means for passing a high frequency alternating current between said members, one of said die members including a blade having an outer embossing surface facing the other die member, metal members disposed on laterally opposite sides of said blade in abutting relationship therewith each having an outer elongated ridge portion coextensive with said blade and facing the other die member, said metal members being depressible with respect to said blade, and means for biasing said metal members into an extended position with respect to said blade whereby said metal members and said blade define a guide groove adapted to support a strip of thermoplastic material therewithin, one of said die members being movable toward the other to thereby depress said metal members and expose said strip of thermoplastic material for bonding to another body of thermoplastic material, the ridge portions of said metal members having a rounded contour to reduce voltage concentration at the edges of the embossing blade during said bonding.

7. A dielectric bonding and embossing apparatus com prising a pair of relatively movable die members, means for passing a high frequency alternating current between said die members, one of said die members including a blade having an outer embossing surface facing the other die member, guide members disposed on laterally opposite sides of said blade in abutting relationship therewith and having outer surfaces coextensive with said embossing blade and facing the other die member, said guide memhers being depressible with respect to said blade to a position wherein the outer surfaces of said guide members are generally flush with the embossing surface of said blade, and means for biasing said guide members into an extended position with respect to said blade whereby said guide members and blade define a guide groove adapted to support a body of dielectrically bondable material therewithin, the relative movement of said dies being adapted to depress said guide members during dielectric bonding.

8. A dielectric bonding and embossing apparatus comprising a pair of relatively movable die members, means for passing a high frequency alternating current between said die members, one of said die members including a blade having an outer embossing surface facing the other die member, metal members disposed on laterally opposite sides of said embossing blade in abutting relationship therewith each having an outer elongated raised edge surface adjacent said blade and facing the other die member, said metal members being depressible with respect to said blade to a position wherein the outer raised edge surfaces of said metal members are generally flush with the embossing surface of said blade, and means for biasing said metal members into an extended position with respect to said blade whereby said metal members and said blade define a guide groove adapted to support a body of thermoplastic material therewithin, the relative movement of said dies being adapted to depress said metal members to expose said body of material for bonding to another body of thermoplastic material.

9. An apparatus as set forth in claim 8 and including means for maintaining said blade and said metal members at the same potential with respect to the other die member.

10. Apparatus as set forth in claim 8 wherein each of the raised edge surfaces of said metal members is in the form of a ridge having a rounded contour so as to reduce the voltage concentration at the edges of the embossing blade during the dielectric bonding.

11. A dielectric bonding and embossing apparatus comprising a pair of relatively movable die member, means for passing a high frequency alternating current between said die members, one of said die members including a blade having an outer embossing surface of concave contour facing the other die member, metal plate members disposed on laterally opposite sides of said blade in abutting relationship therewith each having an outer convex rounded edge surface adjacent said blade and facing the other die member, said plate members being depressible with respect to said blade to a position wherein the edge surfaces of said plates are generally flush with the embossing surface of said blade, and resilient members under said plate members to bias said plate members into an extended position with respect to said blade whereby said plate members and blade define a guide groove adapted to support a body of thermoplastic material therewithin, the relative movement of said dies being adapted to depress said plate members to expose said body of thermoplastic material for bonding to another body of thermoplastic material.

References Cited in the file of this patent UNITED STATES PATENTS 492,116 Smith Feb. 21, 1893 945,249 Shields Jan. 4, 1910 2,371,847 Saunders Mar. 20, 1945 2,573,466 Lyijynen Oct. 30, 1951 2,758,631 Peterson Aug. 14, 1956 2,804,419 De Woskin Aug. 27, 1957 2,822,454 Rothstein Feb. 4, 1958