US 2689375 A
Description (OCR text may contain errors)
Sept. 21, 1954 R. H. HUGGER APPARATUS FOR CASTING SOLES 0N SHOES 4 Shee ts-Sheet 1 Filed 001;. 25, 1950 .AI'TO NEY 4 Sheets-Sheet 2 Sept. 21, 1954 R. H. HUGGER APPARATUS FOR CASTING SOLES 0N SHOES Filed Oct. 25, 1950 ATTORNEY Sept. 21, 1954 R. H. HUGGER 2,639,375
' APPARATUS FOR CASTING SOLES ON. SHOES Filed Oct. 25, 1950 4 Sheets-Sheet 3 ATTORNEY p 21, 1954 R. H. HUGGER 2,689,375
APPARATUS FOR CASTING SOLES ON SHOES Filed Oct. 25, 1950 4 Sheets-Sheet 4 ffl 74 a 4 2 J J23 k /V \\\\j)\\ i 77 7f .iQE-QZS 75 ATTORNEY Patented Sept. 21 1 954 APPARATUS FOR CASTING SOLES ON SHOES- Richard H. Hugger, Ridgewood, N. J assignor to United States Rubber Company, New York, N. Y.', a corporation of New Jersey Application October 25, 1950, Serial No. 192,0113
1 This invention relates to an improved. shoe, and the improved method and apparatus. for
casting a rubber composition outsole, with or without a foxing, directly onto the shoe from gelable latex composition contained. in an open mold cavity, and into which the bottom of. the shoe forming the outsole foundation is suspended from above in the open mold cavity.
Heretofore, rubber composition soles have been formed on the bottom of lasted shoe uppers by molding processes, in which the upper was sealed against the rigid rim of a metal mold by forcing the bottom of the upper in. contact with the rim. In such processes a closed mold was used to mold the charge ofrubber composition into a properly shaped shoe sole. Air was trapped inthe closed system and unless it was discharged prior to the vulcanization of the sole, which was carried out in the mold, the air caused voids or blisters to be formed. in the vulcanized sole. The
air was eliminated in some cases by molding the charge-under pressure. Due to variations in the bottom sealing surface of lasted shoe uppers, it was difficult to produce a good seal between. the upper and the mold rim, and when the" pressure on the mold charge was increased, the difliculty of producing a seal was also increased. In order to seal the mold cavity under high pressure, the shoe upper was sometimes cut as a result of its pressure against the mold rim.
The foregoing and other disadvantages of the processes are eliminated or reduced in accordance with the practice of the present invention by utilizing an open mold cavity containing a freely flowable charge of gelable latex and suspending the bottom of the shoe, or the outsole foundation in the liquid charge without closing the mold cavity. The liquid latex is poured into theopen mold cavity having its side walls, which form the outer edge of the outsole, extending upwardly. The outsole foundation is lowered into latex to the required depth. The displaced latex is forced upwardly, and the displaced air is free to flow through the open rim of the mold cavity.
The latex. gells very quickly and is thereby cast onto the outsole foundation of the shoe upper to form the outsole. A foxing integral with the outsole may be formed on the upper depending upon the distance the upper is lowered into the mold cavity. After the latex has gelled, the shoe is removed from the mold and the outsole is dried and vulcanized, which may occur simultaneously.
Other important characteristics of this invention are the novel last and mold, and the apparatus formanipulating the last and mold in carrying out. the process: for the. manufacture of the improved rubber soled shoe which is free from mold markings or cuts and isalso light. and durable, and less costly.
The invention is further described in reference to the accompanying: drawings,
Fig. 1 illustrates the conventional method of lasting a shoe upper over an insole to which an outsole isapplied. in accordance with thisinvention;
Fig. 2 is a perspective view of. the novel apparatus for casting a rubber composition sole onto the conventionally lasted shoe upper, which is being held above the casting position;
Fig. 3 is a side elevation. of the apparatus illustrated in Fig. 2,, but. showing some-of the parts in cross-section and with the shoe upper lowered into the gelable latex which is being cast onto the bottom of the upper, or outsole foundation;
Fig. 4 is a top plan view of a detail of the mechanism for adjusting the mold support in. a horizontal plane;
Fig. 5 is an elevationalview, partly in. section, of the adjusting mechanism shown in Fig. 4, taken on line. 5-5, and. looking. in the direction of the arrows;
Fig. 6 is atransverse cross-section through the toe portion of, the shoe andthe mold in the casting position shown in. Fig. 3, and, in which the last is shown in full frontelevation;
Fig. 7 is a. vertical longitudinal cross-section of, the elements shown in; Fig. 6, excepting the last is shown in side elevation;
Fig. 8 is a perspective view; partly in section, of the improved shoe: made inaccordance with this invention and by the. use of the apparatus illustrated in the. foregoing figures of the drawings;
Fig. 9 is a. longitudinalcross-section of a shoe and mold for making a modified: form of outsole, which is provided; with a raised heel; and
Fig. 10 is a side elevational view of the shoe made by means of the last and mold shown in Fig. 9.
Shoe manufactured: in accordance with this invention are illustrated in Figs. 8 and 110, and theremaining figures ofth'e drawings illustrate the method and apparatus used in the manufacture of the shoes. Referring to Fig. 8, the shoe I5 has. the appearance of a conventional tennis shoe. It comprises-a canvas upper I6i having its bottom edge I! lasted a conventional manner over an. insole. Ill;v to which the lower edge. I1 is adhered. The bottom; of the upper I6 and the insole I8 forms an outsole foundation onto which I the outsole I9 is cast directly from a gelable latex. As illustrated herein the shoe is provided with a foxing 20, which is cast integrally with the outsole E9. The foxing is provided to protect the bottom of the upper 16 from wear, and to strengthen the union between the sole and the upper; however, the foxing 20 may be omitted if desired. In any event a very good bond is formed between the cast outsole l9 and the upper by the penetration of the liquid latex into the interstices of the upper prior to the gelling of the latex. The outsole foundation is made sufficiently rigid to resist the shrinkage of the deposited latex after being dried. For that pur pose the insole I8 is relatively stiff, and it is also provided with perforations 2| into which the latex flows and strengthens the bond between the outsole I9 and the shoe sole foundation. The perforationsjl also operate to prevent blisters, or air pockets from forming between the outsole and the insole. After the latex has been dried and vulcanized, it contains tension strains due to the shrinkage of the wet gelled rubber composition. In order to compensate for the shrinkage of the outsole l9 and foxing 2e, they are cast into a slightly different shape than the final desired shape of the shoe after vulcanization, and the induced tension strains in the dried and vulcanized outsole and foxing draws these members into the desired conventional shape.
The outsole as cast is provided with a convex tread surface for the purpose of relieving the subsequent shrinkage stresses to the extent required to prevent them from pulling the sole into an improper shape. As the convex surface shrinks, the stresses due to shrinkage are relieved by the curvature of the convex surface becoming, flatter and without any substantial change in the vertically projected area of the sole. In the casting operation the unconfined surface of liquid latex comes to a level around the edge of the upper and forms a straight foxing line, The foxing is thinner than the outsole, and a greater portion of its contractive force due to shrinkage is resisted by the upper material. However, the foxing shrinks to some extent and draws the toe portion of the shoe upwardly. The longitudinal curvature of the shoe sole tread, as cast, may be so controlled that the downward shrinkage pull of the tread surface and the upward shrinkage pull of the foxing results in providing the shoe sole, and the foxing to some extent, with an upward curvature at the toe which gives the shoe toe spring.
The outsole l9 may be cast with a substantially flat bottom as shown in Fig. 8, or it may be provided with a raised heel 22 as illustrated in Fig. 10. In either case the cast outsole may be provided with an upwardly curved toe portion 23, which provides the usual toe spring to the shoe.
The method of casting the sole l9 onto the bottom of the upper 16 is described inreference to the apparatus shown in Figs. 1 to '7. Referring to Fig. 1, the upper 16 may be lasted in a conventional manner, in which the insole I8 is placed upon the bottom of a last 24, and an assembled upper I6 is slipped over thev last. Its bottom edge I! is turned over and cemented to the bottom of the insole IS. The last 24 with the upper thereon is then removed from the stand 25 and aflixed to a jig 26 for manipulating the last so that it may be moved accurately downwardly into, and upwardly out of a mold cavity 2'! of a the mold cavity.
4 mold 28. For most efiicient operation of the process, the walls of the mold cavity are coated with a liquid, hereinafter referred to as a lubricant, and liquid gelable latex 29 is then poured The lubricant prevents into the mold cavity. the latex from sticking to the cavity, and acts as a wetting agent for the latex. A suitable mold lubricant for this purpose is the sodium salt of di-octyl ester of sulfo succinic acid, preferably mixed with gasoline in the proportion respectively of 100 to 315 parts by weight. Such lubricant also inhibits synaeresis of the latex which sometimes causes the fabric upper to be stained. One application of this lubricant is sufficient for four casting operations.
The lasted shoe upper I6 is lowered into the latex 29 and suspended therein in spaced relation to the walls of the mold cavity, as shown in Fig. 3, to form a space between the lasted upper and the walls of the cavity for the gelable latex. Upon gelling, the latex is cast onto the bottom of the lasted upper which forms the outsole foundation. The volume of latex poured into the open mold cavity 21 is selected to produce an outsole of the desired thickness, and a foxing of the desired height when the bottom of the upper has been lowered to a certain level in the mold cavity 21 and preferably when the latex is forced to the level of the upper rim 3!! of the cavity, such rim preferably being located in a horizontal plane. As the bottom of the upper is lowered into the latex 29, it is displaced around the bottom of the upper, andthe air in the cavity is free to flow outwardly through the space between the rim 30 of the mold and the upper. The air that may be trapped between the surface of the latex and the bottom of the upper is permitted to pass out through the perforations 2| of the insole it. Such perforations are conical in shape. Their apexes 3i point upwardly, and form small openings through the top surface of the insole. The larger bases of the perforations 2| at the bottom surface of the insole I3 permits the entry of the liquid latex. The smaller openings at the top surface of the insole excludes the latex but permits the discharge of the trapped air. 7
The latex 29 is compounded with curing agents prior to adding the gelling agent, which latter is done immediately prior to pouring thelatex into A sufficient quantity of the gelling agent is added to cause the latex to gel quickly at a room temperature of about 70 F. After it has gelled, the lasted upper it with the gelled latex outsole i9 and foxing 2E3 adhered thereto are raised upwardly out of the mold cavity 2'5. Where the sidewalls 3! of the mold 28 overhang the mold cavity, they aremade of flexible elastic material having a relatively low modulus of elasticity, such as soft elastic rubber, so that the side walls may be spread outwardly by the gelled latex without injury to the foxing and outsole. The overhanging portions of the sidewalls 3i may result from their inward inclination to the top rim or from indentations formed therein to produce decorative surfaces on the sides of the outsole sole and foxing.
The last 24 is removed from the jig 2t, and it together with the lasted upper E5 and cast latex sole l9 thereon are passed through a vulcanizer, where the cast latex sole and foxing are simultaneously dried and vulcanized, preferably at a temperature of about 270 F. for minutes. During the drying and vulcanization of the cast latex sole and foxing, tension strains are set up in the sole and foxi-ng due to the tendency of the gelled rubber composition to shrink. After the vulcanizing operation, the shoe I is removed from the last 24, and the tension strains in the rubber composition causes a change in the shape of the sole and foxing. The change of shape is resisted by the stiifness of the outsole foundation including the bottom ofthe upper 16 and the insole I58, however, some change in shape takes place. i
This invention is notlimited toa definite compound of gelable latex, and maybe varied for special conditions and results desired. As a specific examplethe compound may-be composed of components A, B, C, and D; in which all parts are by Weight, and where:
A is a 68% ammonia preserved concentrated natural rubber latex deammoniated with formaldehyde, and restabilized by the addition of 0.1 part ammonia and .045 part potassium hydroxide per 100 parts dry weight of rubber latex.
B is a conventional curing paste containing:
1.0 part sulphur 5. parts zinc oxide 2;.. Parts ultra accelerators (composed of 1.2 parts zinc salt of 2-mercaptobenzothiazole and 1.3 parts zinc diethyldithiocarbamate) 0.51 part antioxidant 0.2 part, dispersing agent containing 6.1 parts Water.
C is water. D is a gelling agent per U. S. Patent 2,343,545, and containing:
1.0 part sodium silicofluoride 002 part sodium fluoride 0.02 part colloidal clay (bentonite) in 0.96 parts of water ball-milled together for 24 hours 6.5. parts Water added to the mixture of the preceding ingredients.
To produce the gelable latex the above components are mixed as follows:
147 parts of A is mixed with 15.3 parts of B and then 39.7 parts of C are stirred into the mixture of A and B. The mixture of A,.B and C is allowed to stand from 36 to 48 hours to deaerate and partially vulcanize the latex before adding the component D (the gelling agent). The partial vulcanization is carried to the extent of chemically combining 0.05 parts of the sulphur in the latex compound. The mixture of A, B and C' is mixed with the component D in the proportion of 150 grams of the mixture A, B and C to 5.8 cc. of component D.
The setting or gelling of the latex may be accomplished by the use of gelling agents other than sodium silicofluoride. For example, potassium silicofluoride, polyvinyl methyl ether and an acid, ammonium nitrate, etc., may be used. However, a temperature of 95 F. or higher is required to set or gel the latex, where potassium silicofiuoride is used.
The period of time required for the latex to gelor set may be decreased by increasing the proportion of the gelling agent or by increasing the temperature of the latex for any selected gelling agent; It is also contemplated that the setting time of the latex may be decreased for a given proportion of the gelling agentused in the latex by either heating the mold 28 or the lasted upper I6, or both to raise the temperature of the latex after it has been poured in the mold. It is preferable to heat the lasted upper either by heating the last 24' prior to lasting the upper 16 thereon, or by heating the last 24: after thelasting operation and immediately before lowering the upper into the latex, because the accelerated gelling action due to the supplied heat will not be effective until the lasted upper is placed in position in the mold cavity. By virtue of heating the lasted upper, the heating of the mold may be avoided, and the subsequent cooling of the mold prior to placing the gelable latex therein may also be avoided, The heating of the shoe upper has the further advantage of quickly gelling the latex so as to prevent the staining of a fabric shoe upper due to the capillary attraction of the fabric of the latex, which causes it to rise above the level of the sole or foxing.
It is also contemplatedthat the staining of the fabric by the travel of the latex above the level line may be prevented-by thinly coating the bottom of the lasted upper i6 and the bottom edge of the upper to the height of the top of the foxing line with a latex cement, which is compounded with wetting agents and commonlyused for adhering unvulcanized rubber parts to fabric. The cement is permitted to dry but not to be vulcanized prior to placing the bottom of the shoe upper in the mold cavity 21'. If the last is heated to accelerate the setting period of the latex in the mold cavity and a latex cement is also used, the latex cement should have a vulicanizing temperature above that to which the upper is heated.
The application of heat to the gelable latex in the mold has; the further advantage of permitting the gelling agent to be added to latex in bulk and held available for pouring into the mold as required. In such, case it is necessary to hold the gelable latex at a temperature below the active temperature of the gelling agent.
The use ofultra accelerators, in the latex compound has the advantage of reducing the com posite time for drying and vulcanizing thev rubber coagulum in the sole by permitting such processes to take place concurrently. Where accelerators, other than ultra accelerators, are used which are not effective at temperatures below 220 F the sole of rubber coagulum must besubstantially dried before the sole is vulcanized to avoid blistering. That practice requires a much longer time than when the processes are carried on concurrently. It has been. found. that with the use of ultra accelerators and radiant heat,
the sole of rubber coagulum. may be treated at temperatures higher than 220 F. to concurrently dry and vulcanize it. As a specific example, a rubber sole deposited from latex compounded in accordance with the preceding specific example was completely dried and vulcanized Within minutes in. an oven through which. air was circulated at 270 F. The thickness. of the dried sole was 0.120 to 0.125 inch. A longer time would be required for thicker soles.
In order to provide for the change-in shape of the outsole I9 due to shrinkage of the-rubber, the last 24 as shown in Figs. 6 and '7 is provided with a decidedly convex bottom 33, thatis, itsbottom surface is curved both transversely, and longitudinally from heel to toe- The mold 281 isprovided with a correspondingly shaped. bottom surface 34. The border of the convex. surface 33 of the last 24 lies in one. plane 35.. The borders of. the concave curvature of the bottom 34 of. the mold. 28, also lie in one plane, which. isparallel to the. plane 35 of thebordersof the curvature of the last 24. The. insole l8.is,p referably astedto the curvature 33 of the last 24', so that a uniform thickness of rubber will be deposited between the insole and the bottom 34 of the cavity 2'! to form the outsole 59. The foregoing construction causes the bottom surface of the outsole l9 to be cast with the convex curvature and of uniform thickness. When such curvature of the surface contracts after the shoe i is removed from the last, the convex surface decreases in area, and therefore flattens out and tries to assume a flat surface in response to the tension strains. The initial convexity given the outsole is sulficient to allow the shrinkage of the surface of the bottom of the outsole to take place to relieve some of the tension strains and to allow them to be balanced or come into equilibrium with the resistance of the outsole foundation when the shoe has obtained its proper final shape.
When the bottom surface of the outsole shrinks, its side edges contract and the sides of the foxing have a tendenc to lean away from the inside of the shoe. In order to allow for the change in the angle of the side edges of the sole and foxing, such side edges are initially formed at an inwardly inclined angle by undercutting the sides of the mold as shown in Fig. 3. It is desirable to taper the thickness of the foxing 2U upwardly from the outsole, and for that purpose the last 24 is provided with vertically extending sides 36, which project from the plane of the border of the convex surface 33 to a plane 31 as high as the level of the rim 39 of the mold 28.
The jig 26 for manipulating the last 24 and the mold 28 is provided with an overhanging arm 38, to which the last is attached by means of a hand wheel 39. As shown in Fig. 3, the hand wheel 39 is affixed to a stem 40, which is rotatably mounted in the arm 38 and held against removal by a screw 4| which is threaded into the arm 38 and extends into a groove 42 in the stem of the hand wheel 39. The stem to is provided with a threaded end 43, which screws into a threaded bore in a cap 44 which is attached to the last 24 by the screws 45. Pins 45 secured in the arm 38 extend into bores in the top plate 44 of the last and locate the last in a fixed position in reference to the arm 38.
The arm 33 is carried by a vertically movable slide 46, which is slidably mounted on guide rods 4 The slide 45 is actuated by a screw 43 mounted on a block 49 and operated by hand wheel 59 mounted on the stem 5! of the screw. The block 49 is affixed to a shaft 52, and the previously described system which is carried thereby is pivoted in a fixed journal 53 into which the round ends 54' of the shaft 52 are mounted.
As shown in Fig. 3, an operating arm 54 is attached to the shaft 52 and is adapted to pivot the last 24 in a vertical plane about the axis of the shaft. A latch 55 is slidably mounted on the operating arm 54, and it is provided with a detent 56 which is adapted to engage notches 51 in a fixed are 53, which is secured to the frame 59 of the jig. Several of the notches 51 are provided for the purpose of holding the last 24 in any one of several elevated positions, which may be selected by operators of different heights. The latch 55 is spring-pressed by a spring 59 held under compression between the latch guide 60 and a pin 6! secured to the latch 55. A handle 62 is attached to the operating arm 54, and a handle 63 is attached to the latch 55. Both handles are placed adjacent to each other so that the latch detent 56 may be withdrawn from the notches 51 by the operators hand which grips the handle 62 to operate the arm 54. V
"The downward movement of the arm 54 is limited by an adjustable screw stop 64, which abuts against the stationary bed plate 65, of the jig 26. The stop 64 is threaded into a bracket 66 attached to the arm 54. The lower position of the arm 54 is adjustable to change the angularity of the plane 31 of the last 24 longitudinally, or in the heel to toe direction with respect to the plane of the mold rim 39. Such adjustment is made by the thumb nut 61 which is attached to the stem of the screw stop 64. The stop 64 is also provided with a lock nut 68 which locks it in any adjusted position.
The transverse angularity of the plane 31 of the last to the plane of the mold rim 30 is also adjustable by two set screws 69, one in each of the ears IE! on each side of the slide block 46. The overhanging last supporting arm 38 is pivotally attached to the block 46 on a stud H which passes through a downwardly extending projection I2 of the last supporting arm 38 and is secured in the slide block 46 below the laterally adjusted screws 69. The ends of the screws 69 operate upon the arm 38 and pivot it about the stud l l.
The mold 28 is supported on a plate l3 which is adapted to be leveled and to be moved in a horizontal plane for the purpose of leveling the mold 28 and adjusting its position in all directions in the horizontal plane in respect to the last 24. The plate 73 is leveled by three leveling screws 14 which are threaded into the plate. The ends of the screws project through the plate 13 and support it on the horizontal base plate 65.
- The plate 13 may be adjusted in all directions in the horizontal plane by three thumb nuts 15, which are secured to the stems of horizontally arranged screws 16 threaded into brackets H on the plate 33. The adjusting screws 16 are rotatably mounted in notches 78 in brackets 79, which are affixed to the base plate 65. The details of the mechanism for adjusting the plate 13 horizontally are shown in Figs. 4 and 5. The stem of each screw 76 is provided with flanges 8|, which straddle the bottom of the notch in the brackets 19 on the plate 95 in order to prevent the screws 76 from moving in an axial direction. The stem 84 of the screw 16 between the flanges BI is smaller in diameter than the length of the notch it? so as to permit the screw to move transversely, and the flanges 8| are beveled to permit them to wobble in the notch 18, and thereby permit the plate 73 to move in any direction within its plane, in response to the individual pressure of each screw without causing the stem 80 or the flanges 8| to bind in the notch 18.
The mold 28 is usually sufficiently heavy to prevent it from being lifted when the cast latex sole i9 is moved vertically upwardly out of the mold cavity 21, but in order to prevent the mold from creeping out of position, it is desirable to secure the mold in a well 82 in a rigid frame 83, which in turn is held in a fixed position on the plate 13. The frame 83 is clamped to the plate 13 by two long bars 84 on opposite sides of the frame and by two short bars 35 placed on the opposite ends of the frame. The bars 84 and 85 are adjustably secured to the plate by means of bolts 86 having T-shaped heads 81 slidably mounted in under cut slots 83 in the plate 13. The bolts 86 extend up through the bars 84 and 85 and are aflixecl in place by tightening the nuts 89 thereon.
In the operation of the jig 26, its operating handle 54 is held in its raised position as shown in Fig. 2 by the engagement of the detent 56 with one of the notches 51 of the fixed sector 58. The last 24 having an upper l6 lasted thereon, as described in reference to Fig. l, is attached to the overhanging arm 38 by clamping it thereto with the hand wheel 39. The mold supporting plate 13 is leveled by the screws 14, and when that is done the plane of the top rim 30 of the mold will be parallel with the top surface of the plate 13. The mold frame 83 is removed from the plate 13, and the lie operating arm 54 is lowered until the stop 64 carried thereby rests upon the bed plate 65. The bottom plane 35 of the last 24 as defined by the border of its convex curvature is positioned parallel with the top surface of the plate 13 by turning the thumb nut 61 on the vertically adjustable stop 64, and by turning the set screws 69 on the horizontal adjusting screws. The lasted shoe [6 is then raised to its elevated position. The frame 83 and the mold 28 carried thereby is placed on the supporting plate 13 underneath the elevated position of the lasted upper l6, and the bars 84 and 85 are released from the plate 13, so that the frame 83 and the mold 28 carried thereby may bemoved freely on the plate 13. A layer of material, such as cardboard, having a thickness of the outsole to be cast on the bottom of the lasted upper IE is placed in the mold cavity as a thickness gauge for the purpose of determining the thickness of the outsole. The jig arm 54 is then lowered, and the mold 28 is adjusted on the plate 13 so that the bottom of the upper I6 is positioned in the mold cavity 21, and the mold rim 30 is evenly spaced from the bottom side edges of the upper around the entire circumference. In such position the stop 64 should be resting upon the bed plate 65, and the bottom of the upper should be slightly spaced from the sole thickness gauge. The vertically adjusting hand wheel 50 is then turned so as to bring the bottom of the shoe upper into contact with the outsole thickness gauge. The securing bars 85 are brought up against the sides and ends of the mold frame 83, and the nuts 89 are turned downwardly on the studs 86 so as to secure the mold and the frame 83 in their located position. The jig arm 54 is then elevated, and the sole thickness gauge is removed from the bottom of the mold cavity 21. The jig is now in its adjusted position to begin the casting of integral outsoles and foxings onto the bottom of the lasted upper I6.
A predetermined quantity of gelable latex is then poured into the mold cavity 21 while the jig manipulating arm is in itsraised position as showninFig. 2. The operator then grasps the handles 52 and 63 of the arm 54 and lowers the bottomof the shoe upper l6 into the latex 29 until the. downward movement of the arm 54 is stopped by the screw stop 64 which strikes against the base plate 65. When this occurs the latex should be forced up to the level of the top rim 30 of the mold cavity, and it should flow in between the rim and the shoe upper around its entire circumference, provided the proper amount of latex has been poured into the mold cavity. The latex normally gels in about three minutes, and the shoe with the cast latex sole thereon may be removed therefrom by lifting the jig varm 54 to the position shown in Fig. 2. The last .24 and shoe I is then removed from the jig 26 by turning the hand wheel 39. The last 24 with the shoe I5 thereon is then passed through the vulcanizer for the proper period of time to compound described herein is 80 minutes.
, After the removal of the last 24 having the rubber sole cast thereon, another lasted upper is afiixed to the jig arm 38. Another batch of gelable latex is poured into the cavity, and the foregoing operations are repeated. It will be found however that there are slight variations in the size of the bottoms of the lasted uppers, and that although the same quantity of latex is poured into the mold cavity in every instance, the latex will not rise to the same level when the bottom of the shoe is lowered thereinto, and the rim of the mold will not be evenly spaced from the upper all around its circumference. Therefore in order to bring the level of the latex up to the level of the top of the mold cavity in every instance it is sometimes necessary to manipulate the hand wheel 50 to raise or lower the last 24, and it may also be necessary to manipulate the horizontal adjusting thumb nuts 15 to move the mold laterally on the base plate 65 to properly space the shoe upper evenly from the rim 30 of the mold cav t 1- The flexible mold '28 may be prepared from well known liquid cold setting materials. For example, a suitable and inexpensive .mold may be made from Penna-Flex Cold Molding Compound which is manufactured by the Perma- Flex Mold Company, 243 North Fifth Street, Columbus, Ohio. The foregoing particular cold molding compound is a polymercaptan. base synthetic rubber. The compound when poured into the mold is a mixture of a clear, colorless syrup of a polymercaptan monomer, a curing agent comprising a thin paste containing a lead compound, and a thin light colored paste, which acts as a catalyst to cause the setting when poured into the mold. The compound when set has the soft flexible elastic characteristics of rubber, which has a relatively low modulus of elasticity. In the preparation of the mold, a model of the sole, or the sole and foxing to be cast is made. This is conveniently done by lasting an upper on the special last 24 in the conventional manher as described in Fig. 1, and then building onto the upper an outsole and foxing having the shape and decorations of the shoe parts, as cast. A box is then made similar to the frame 83, ex-. cepting the depth of the well in the box is equal to the overall height of the mold to be cast from the molding compound. The last 24 with the model thereon :is placed in the jig 2d, and the plane 35 to the border of the bottom'curvature of the sole is leveled, or made parallel with the top surface of the leveled mold supporting plate 13 in the manner described ingreference to the leveling of the lasted shoe upper 16. The hand wheel of the jig 50 is turned ,so as to raise the bottom of the model above the top rim of the box when it is placed on the leveling plate 13.
be'fo-rmed. Marks are made on the sides of the model at the level of the latex to be cast on the upper to form the sole, or sole foxing. The jig arm 54 is then lowered until the stop 64 strikes the base plate .65, and the hand wheel 55) is then turned .down into the molding liquid in the box until the markings placed on the sides of the model come even with the surface of the liquid moldin compound. The model shoe is then left in that position -.until the molding compound firmy sets. It is desirable to so gauge the quantity of molding compound placed in the box that it rises slightly above the top edge. The excess of the set compound is trimmed off to form a smooth straight and level top rim on the cast mold. The model is then released from the jig 26 by the hand wheel 39, and the model, mold, and box are removed together from the plate '13. The mold is then removed from the box and stripped from the model. The resulting mold has the soft, flexible, elastic characteristics of rubber, which has a relatively low modulus of elasticity. W
Substantially, the preceding procedure is followed .in making the last and mold shown in Fig. 9 and in casting the rubber parts on the shoe with a heel shown in Fig. 10. As shown in Fig. 9 the last 90 is provided with a convex bottom 91 in the toe portion of the last, which extends from the breast 92 of the heel to the toe.
The border of this convex portion of the bottom lies in a plane 93, but the heel portion is provided with a flat surface 94 to receive an insert filler 95, which is placed on top of the insole 8S and affixed thereto.
The bottom of the mold cavity 91 forward of the breast of the heel is concave and conforms to the corresponding convex curvature of the last 90. The bottom. of the heel portion of the cavity 91 is depressed and has a concave curvature to cast a corresponding convex curvature on the shoe heel from the gelable latex 98, and thereby relieve shrinkage strains after vulcanization.
Having thus described my invention, what I claim and desire to protect by Letters Patent is:
1. An apparatus for casting a shoe sole onto a sole foundation formed on the bottom of a shoe upper, said apparatus comprising a mold having a sole forming cavity therein, said cavity having toe and heel portions, said toe portion having a concave bottom surface provided with a perimeter lying substantially in one plane, a last adapted to carry the shoe upper and sole foundation thereon, said last having a toe portion and a heel portion, said toe portion of said last being provided with a convex bottom surface conforming substantially to the bottom curvature of said concave bottom surface of said cavity, said convex surface of said last having a perimeter lying substantially in one plane, the entire bottom perimeter of said last being smaller than the top'rim of said cavity, and a support for said last adapted to suspend the sole foundation on said last within said mold cavity below the top rim of said mold cavity with said perimeters of said last and mold substantially parallel to each 1other when said last is in its sole casting posi ion.
7 2. An apparatus for'casting a shoe sole onto a sole foundation comprising a mold having a cavity adapted to remain open to the atmosphere while the sole is being cast onto the foundation, said mold cavity having an upwardly facing bottom and upwardly extending side walls, said bottom of said cavity having toe and heel portions, said toe portion having a concave bottom surface provided with a perimeter lying substantially in one plane, means for levelling saidperimeter, a last adapted to carry the shoe upper and sole foundation thereon, said last having toe and heel portions, said toe portion of said last having a convex bottom surface conforming substantially to the bottom curvature of said concave bottom surface of said cavity and 12 having a perimeter lying substantially in one plane, the entire bottom perimeter of said last being smaller than the top rim of said cavity, a movable support for said last adapted to suspend the sole foundation thereon within the mold cavity while the sole is being cast onto the sole foundation, and means for adjusting said last support to bring said perimeter of said convex surface of said last in parallelism with said perimeter of said concave surface of said mold cavity. V
3. An apparatus for casting a shoe sole onto a sole foundation comprising a mold having a cavity adapted to remain open to the atmosphere while the sole is being cast onto the foundation, said ,mold cavity having an upwardly facing bottom and upwardly extending side walls, said bottom of said cavity having a concave surface provided with a perimeter lying substantially in a horizontal plane, means for moving said mold in all directions in said plane and maintaining said mold in any position so moved, a last adapted to carry the shoe upper and sole foundation thereon, said last having a convex bottom surface conformin substantially to the bottom curvature of said concave bottom surface of said cavity and having a perimeter lying substantially in one plane, the entire bottom perimeter of said last being smaller than the top rim of said cavity, a support for said last, and means for lowering and raising said support to suspend the sole foundation on the last within and in spaced relation to the walls of the mold cavity with said perimeter of said concave and convex surfaces parallel to each other and to remove the sole foundation and sole cast thereon from said cavity.
4. [an apparatus for casting a shoe sole onto a sole foundation comprising a mold having a cavity adapted to remain open to the atmosphere while the sole is being cast onto the foundation, said mold cavity having an upwardly facing bottom and upwardly extending side walls, said bottom of said cavity having a concave surface provided With a perimeter lying substantially in a horizontal plane, a support for said mold, means for moving said mold in all directions in said plane and maintaining said mold in'any position so moved on said support, a last adapted to carry the shoe upper and sole foundation thereon, said last having a convex bottom surface conforming substantially to the bottom curvature of said COD. cave bottom surface of said cavity and having a perimeter lying substantially in one plane, the entire bottom perimeter of said last being smaller than the top rim of said cavity, a support for said last pivotally mounted on a horizontal axis on said mold support, an arm for pivoting said perimeter of said last downwardly into and upwardly from said mold cavity, and an adjustable stop for limiting the downward movement of said arm when said perimeter of said last reaches a horizontal position. 7
5. An apparatus for casting a shoe sole onto a sole foundation comprising a mold provided with an open mold cavity when the sole is being cast onto the sole foundation, said mold cavity having an upwardly facing bottom and flexible elastic side Walls having a relatively low modulus of elasticity, said side walls having portions overhanging said cavity, a last for carrying the sole foundation, and means for moving said last with the sole foundation thereon into and out of said mold cavity and supporting said sole foundation in said mold cavity in spaced relation to the bottom and side walls thereof when the sole is being cast onto the sole foundation.
6. An apparatus according to claim 1, in which said mold cavity has upwardly converging side walls of flexible elastic material having a relatively low modulus of elasticity.
7. An apparatus for casting an integral shoe sole and foxing onto a bottom of a shoe upper comprising a mold having a molding cavity therein, said cavity having a concave bottom surface which has a perimeter lying substantially in one plane and overhanging flexible elastic side walls having a relatively low modulus of elasticity extending upwardly from the plane of said perimeter to at least the height of the foxing to be formed in the shoe upper, a last having a convex bottom surface having a perimeter lying substantially in one plane and adapted to be arranged parallel to said perimeter of said concave surface of said cavity, said last being provided with vertical sides extending from the plane of the perimeter of said convex surface and adapted to extend within the top rim of said mold cavity, and a support for said last adapted to suspend the bottom perimeter of the last with the shoe upper thereon below said top rim of said cavity and in spaced relation to the Walls of the mold cavity to provide a space for the sole material between the bottom of the shoe upper and the walls of the mold cavity when the bottom of the shoe upper is in the casting position.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,660,441 Gurnee Feb. 28, 1928 1,763,653 Harvey et a1 June 17, 1930 1,994,278 Halsall et a1. Mar. 12, 1935 2,071,646 Melind Feb. 23, 1937 2,305,945 Williams et a1 Dec. 22, 1942 2,330,989 Nevills Oct. 5, 1943 2,406,359 Doherty Aug. 27, 1946 2,464,232 Hudson Mar. 15, 1949