Process for insert molding wet-shaving razor unit and unit made therefrom

Abstract: The present invention provides a wet-shaving razor unit with at least one exposed blade edge (E) for shaving which comprises a continuous thermoplastic body (9) to which the blade (B) is secured against movement and vibration during shaving. The body (9) includes skin-engaging portions which provide a constant shaving geometry over the length of said blade. A method of producing the razor unit is also provided in which the blade (B) is supported in a mould with the edge (E) surrounded by male mould members (M₁, M₂, M₃). The blade (B) is mechanically buttressed on both sides and thermoplastic material is injected into the mould to provide counterbalancing high pressure on both sides of the blade (B) during moulding to prevent deformation of the blade (B).

Description: The present invention relates to a process for insert moulding a wet-shaving razor unit and the unit made therefrom. In particular, it is concerned with manufacturing a shaving unit, such as a disposable razor or a cartridge, by moulding a thermoplastic material around the blade (or blades) so that the edge is protected during moulding and exposed for shaving in the final product. Injection of a thermoplastic material around prefixed plastic or non-plastic parts to provide a composite article having a desired geometry can be referred as to insert moulding. Currently, wet-shaving units, such as disposable razors and cartridges, form a substantial portion of the demand of wet-shaving market. With the exception of the blade or blades (and possibly a spacer) these units have been made out of thermoplastic material. The cap and blade support or seat components, depending upon the ultimate design, are moulded separately and then assembled. For example the "MicroTrac" disposable razor manufactured by Gillette holds a single unit blade seat, back and cap, with the cap including outwardly extending fingers. The blade subassembly, consisting of two blades and a spacer, is inserted between the moulded cap and seat with the finger-like projections extending from the top of the cap serving as leaf springs to retain the blade subassembly. This combination is then mated to a handle by press fitting into the blade subassembly. It is apparent that this process involves not only separate steps, but separate work stations requiring individual subassembly and ultimate assembly. Other assembly processes for shaving units utilize projections extending either from the cap or the seat, which mate with openings in the opposing part and position the blades and/or spacer. The handle is usually made separately from the seat portion. Again, separate assembly steps at separate locations are required to produce the disposable razor. A significant problem occasioned in the manufacture of wet-shaving units is the difficulty in establishing a reproducible shave geometry which provides optimum blade edge performance. Shave geometry relates to the spatial relationship, e.g. distance, angle(s), etc., of the surface(s) and blade edge(s) as they come into contact with the skin. Inherently, separate fabrication and assembly required to produce wet-shaving units detracts from the ability to precisely reproduce a selected shave geometry. Manufacturing such units also requires continuous vigilance to ensure quality control. Usually such vigilance translates into increased cost of production which results from additional labour. Furthermore, blade edge performance relates to the response of the blade edge to forces imparted to it during shaving. Undue or uncontrolled vibration of the blade as it is drawn across the skin, sometimes referred to as "chatter", has been blamed by some experts as detracting from the feel of the shave and causing injury to the user. Separate fabrication and assembly required in known methods of manufacturing wet-shaving units are inimical to reducing "chatter" during shaving. Even minor tolerances built into mating parts for assembly will contribute to "chatter". Consistently reproducible shave geometry has been improved to a certain extent by use of moulded plastic parts having consistent dimensions. Quality assurance, however, still requires constant monitoring of production to ensure fabrication and assembly of parts are consistent. Overall blade edge performance has not been significantly improved by mere use of moulded plastic parts. Presently, there are no known hard and fast technical theories with respect to blade edge performance, but certain design characteristics are believed to enhance performance of wet-shaving units. Constant shave geometry whereby the spatial relationship of the skin-engaging portions, the seat, the cap, and the blade, are maintained over the entire length of the blade is certainly very important. In most cases, the blade over which constant shave geometry need be maintained is in a flat configuration with the edge having the profile of a straight line, although some artisans also recommend that the blade have a crown in the central portion for optimum shave feel. More recently, the discovery by the owners of the present technology of a flexible wet-shaving unit which deflects in response to forces imparted during shaving has required that shave geometry be maintained over the length of a blade which experiences a changing profile. Regardless of the selected blade profile, it is substantially universally agreed that, in addition to maintenance of shave geometry, the blade edge should not be distorted from the edge profile, whether it is rigid or flexible. In the case of a flexible cartridge, although the entire cartridge body bends in response to forces during shaving (i.e. has a changing profile), the blade(s) should not deviate out of the fixed geometry of the shaving unit. Such blade distortion can easily result from several manufacturing difficulties. For example, care must be given to carefully matching mating parts during assembly of shaving units. Again, such care generally requires labour intensive quality assurance measures. Vibration of the blade results from several structural features. One kind of vibration can be described as a "clam-shelling" affect of the subassembly components vibrating with respect to each other. Another vibration is that of the subassembly moving as a single component of the total razor unit. The cantilever configuration of the blade (and/or the blade subassembly) extending from its point of securement toward the unsupported edge contributes to this undesirable vibration. The inherent looseness of components in assembled wet-shaving units is yet another source of vibration. It is desirable, therefore, to minimize or eliminate one or more of the causes of vibration. Still another source of vibration is caused by the blade engaging hair growing out of the skin surface. Recovery time of the blade should be minimized. This quick recovery may be characterised as stiffness. In order to cure these problems, a disposable razor which could be assembled at a single work station having all the plastic parts assembled at one time or produced in a single cavity is desirable. The steps of subassembly, final assembly, as well as inspection, and conveying of the various components from location to location in and about the manufacturing area are thereby eliminated. Prior art patents have disclosed various attempts to accomplish this. British Patent 1,565,296 discloses making a unitary handle guard member and blade support and then attaching a z-shaped blade by upset rivets or the like to the support. US Patent 4,489,626 describes a razor manufacturing process in which a double edged strip of blade metal is parted along a center line and cropped to form two strips, each containing a series of spaced apart blades connected by webs to an elongate backing strip. The strip of razors must be modified before subjecting it to moulding thermoplastic material around the blades. Each modified strip, which then consists of a plurality of blades and a backing strip, is fed into a moulding machine in which either the shaving unit or blade-containing-component of a razor is moulded directly around each individual blade. The web is then parted to release the moulded razor, etc. from the backing strip. It is unclear from US 4,489,626 how the remaining razor components are manufactured. It is apparent, however, that the moulding process relies, in part, on the blade being supported by metal connecting elements, e.g. webs 18, 24, et al. US 4,489,626 therefore, requires the handling of an elongated metal strip, its control and insertion in either a multi-cavity mould or a single cavity mould, and in either case a sequential step of separating heads joined together in a single strip. Conveyance of a metal web of the type described is extremely difficult when it is necessary to protect a delicate cutting edge and even more so when two cutting edges must be protected. Moreover, a subsequent operation of separating the moulded razor heads from the continuous strip must be performed. Thus, the process of US 4,489,626 cannot be used to effect insert moulding of an independent single or twin blade unit while maintaining a desired blade geometry, especially in a high speed process which will accommodate unit production in conjunction with existing razor blade manufacturing lines. Moreover, the need to control the elongated metal strip in process of US 4,489,626 makes it unattractive for manufacturing, and it is not presently conceivable how the procedure of US 4,489,626 could be adapted to producing twin blade products. Other patents disclosing moulding a plastic razor head around a blade are US Patent 3,070,883; US Patent 2,789,246; and US Patent 3,703,765. US patent 5 053 178 describes the concept of forming a center mandrel of thermoplastic material and utilizing the combination of the blade and the center mandrel as a template-male mould member for subsequent moulding of a compatible cap and blade support. This was a first attempt to overcome the problems associated with blade unit assembly and resulting inconsistency in blade performance. Although the technology reported and claimed in this first predecessor application indeed improved the wet-shaving assembly product, there still existed a need to eliminate an additional process step and further stabilize blade contour and performance. EP-A-0 289 228 discloses a method of making a razor unit having a substantially continuous thermoplastic body extending on either side of a blade to support the blade. However, EP-A-0 289 228 does not propose a method of optimising supporting of the blade during shaving. US patent 5 104 605 is directed to a method which includes 1) supporting the blade within the mould on a forked member, 2) forming a unitary blade support and covering means, and 3) mating the unitary means with a handle. While each of the above disclosures sets forth related techniques and products therefrom which are directed toward reducing the steps required to manufacture high quality blade assemblies consistently at a commercially-acceptable production rate, they do not appear to have provided the ultimate guidelines for adapting current blade production technology to an efficient method for high volume manufacture of shave-assembly units. The present invention reduces the problems described above which are encountered in known procedures, and seeks to provide optimum production of consistently high quality blade assemblies. The present invention provides a method of making a wet-shaving razor unit, having at least one blade with an exposed cutting edge comprising supporting said blade within a mould for said razor unit and injecting a thermoplastic material into said mould whereby said razor unit is formed around said blade with said edge free from contact with said thermoplastic material characterised in that the blade is supported in the mould with the edge surrounded by mould members which are arranged to remain out of contact with said edge such that the blade is mechanically buttressed on the sides thereof, and wherein the method further comprises providing a thermoplastic delivery channel which runs along the length of said mould cavity with delivery ports extending to said cavity for fluid flow of thermoplastic material whereby thermoplastic material is delivered throughout said cavity substantially simultaneously to impinge on both sides of the blade substantially simultaneously to provide counterbalancing high pressure thermoplastic material on both sides of the blade during moulding, so that the blade is maintained without deformation during high pressure moulding. In this way, the delicate edge provided on the razor blade is protected from damage during moulding. The present invention also provides a wet-shaving razor unit obtainable by the above method and comprising at least one blade with an exposed edge for shaving, and a substantially continuous thermoplastic body comprising skin-engaging portions, characterised in that the thermoplastic material is substantially equally distributed on both sides of the blade, such that said blade is secured substantially rigidly against movement and vibration during shaving and the skin-engaging portions provide a constant spatial relationship between said skin-engaging portions and said blade over the length of said blade as it comes into contact with the skin. The razor unit can also include a wet-shaving aid secured against removal to one of the skin-engaging portions, such shaving aid having a skin lubricant which is lubricious when wet. Polyethylene oxide is an example of a preferred shaving aid which provides a lubricant between the skin-engaging portion of the shaving unit and the skin. In order to provide the shaving aid described above, the shaving aid can be adhered to a skin-engaging portion or can be mechanically restrained against removal by stakes or tabs which are deformed to overlie the shaving aid and secure it against the skin-engaging portion. The shaving aid can also be incorporated into a skin-engaging portion of the wet-shaving unit. Preferably, the shaving aid is deposited in a cavity provided in the skin-engaging portion such as by sequentially moulding polyethylene oxide as a thermoplastic material into the cavity after formation of the shaving unit. It is important to the present invention that the razor blade itself be supported during moulding against deformation of the blade edge profile in the presence of extremely high pressure, even up to 20,000 psi (138000 KN/M 2 ) without deformation. In concept and practice, the blade must be arranged to eliminate any unbalanced force sufficient to shear the thin metal, e.g. approximately 0.004 inch (0.010 cm), or deform it. This has been achieved in the present invention by simultaneously providing mechanical buttressing such that the blade forms part of the male mould member against pressurized thermoplastic material, and equalizing the force of the pressurized material on both sides of the blade. Thus, the entire length and width of each blade is positioned to bear against the blade support mould member in such a way that either the mould itself is in direct contact with the blade surface or the pressurized thermoplastic material impinges on both sides of the blade substantially simultaneously to provide equal opposing force on the blade during moulding. In order to achieve the unique process and product resulting therefrom and protect the fragile blade edge, the present invention includes the concept of utilizing the blade itself as a valve in conjunction with the male mould member to protect the edge and direct the flow of thermoplastic material. In a twin blade system the male mould member includes additional finger mould elements which are interposed between the first and second blades. The second blade must be supported by the finger elements during moulding just as the first blade is supported. Thermoplastic material must also be permitted to be injected between the first and second blades in order to secure the twin blade product against profile distortion and unwanted vibrational frequency response during shaving. Preferably mould finger elements extend through the rear of the unit to permit flow-through rinse slots in the final product. Moreover, in order to enhance the exquisite control required for such detailed moulding, the present invention has provided for the use of the moulded plastic to serve as a guide for accurate removal of male mould members so that efficient manufacturing can be implemented. This feature provides positive control over high speed removal of male mould members while preserving both blade edge and shave geometry. Preferably the mould includes a continuous cavity to provide a handle of the wet-shaving unit as well as a connecting member to extend from the handle to the shaving head. In an alternative embodiment, the shaving unit can be a flexible shaving cartridge for fixing on a shaving handle. The same concept will apply except that the thermoplastic material will be formed with a series of discontinuities over the length of the blade so that the cartridge will bend to conform to contours on the face. In the case of providing a twin blade flexible shaving cartridge, other inventive concepts relating to accommodating parallel flexible blades apply to making the final product. For example, one end of each blade in the flexible twin blade cartridge can be made to be relatively free to move so that constant shave geometry is maintained over the entire length of the blade during flexing. Preferably, the opposite end of each blade is free to move. In one embodiment, this feature has been achieved by providing a slightly elongated opening through which one of two positioning pins is passed during moulding. Inasmuch as the distance from the blade edge to the center line of the positioning holes (and pins) is critical to preserve shave geometry during fabrication, the opening must be elongated only in the direction parallel to the blade edge. Furthermore, since the pressurised thermoplastic material must be quickly directed to both sides of the blade so as to impinge on the blade substantially simultaneously, the method of manufacturing also includes provision of a mould cavity channel which runs along the length of the mould cavity. Ports extend from the channel to selected openings in the cavity whereby thermoplastic material can be forced under pressure to the entire cavity substantially simultaneously. A further refinement includes the provision of a plastic step in the channel against which a male mould surface will bear to remove the finished thermoset product. The product, once set, can then be expulsed from the main mould cavity by a combination of process features. First of all, the entire moulded product along with the excess plastic can be held in place by the plastic step referred to above, while one member of the mould is removed. Then other mould members can be removed to provide clearance for expulsion of the product. Substantially simultaneously, the plastic set in the gates through which the material was introduced is severed. Finally, the product is pushed out of the main mould cavity by mechanical pusher elements without damage to the finished edge. This series of events can be provided synchronously to efficiently remove each product unit. As a result of the production method of this invention, a wet-shaving razor unit can be efficiently made by one-shot insert moulding in a continuous process. The resulting shaving unit has a blade or blades secured against vibration during shaving and aberrant frequency response is minimized. Furthermore, the inventive method allows the manufacturing of the shaving units to be integrated with existing razor blade production lines. Manufacturing processes to date include the use of singly or multiply supported blades in combination with moulding techniques and subsequent assembly techniques for providing the razor unit. The method disclosed herein, however, eliminates the need for moulding separate parts, and then assembling them to form a razor unit. In the "Microtrac" razor, where the cap, back and support structure are moulded as a single unit, the seat portion has a center support connected to the back position of the seat by as many as 13 transverse ribs, which serve as leaf springs in conjunction with the fingered cap. Because the blades are held by springs and lugs at either end the blades tend to "chatter", i.e. vibrate during shaving. Furthermore, the support bar in the "Microtrac" configuration as viewed from the front is ramped downward to aid in blade assembly insertion in the premoulded razor head. The bar only provides support at the apex of the ramp, which exacerbates this problem. The wet-shaving razor unit of the present invention, however, anchors the blade to continuous thermoplastic body by, among other things, the plastic flowing through blade holes, and the insert moulding scheme which integrates the blade into the male mould member itself. Consequently, the thermoplastic material injected into the razor-bearing mould, even up to pressures of 20,000 psi (138000 KN/M 2 ), is forced over and around the blade as if the blade were one with the mould. This results in a wet-shaving unit which has a smooth consistent edge profile and has minimal aberrant frequency response during shaving. One of the important factors in the present invention is the mechanical intimacy between the contacting surfaces of the blade and the plastic. If the blade and surrounding plastic are moulded and act as a single unit with no space between the surfaces, vibration resulting from similar razor construction having even minute spaces between the contacting surfaces is eliminated. The present invention provides this valuable blade-plastic intimacy. One important aspect of the invention is that the insert technique avails itself of the natural shrink occasioned by setting thermoplastic material. This provides a very tight package in the end product. Another deficiency in blade characteristic which can be alleviated is that of deviation of the blade edge out of its designed profile. This deficiency has been referred to herein as blade distortion. These deficiencies have been reduced in the present invention by providing a method and shaving unit product wherein the blade or blades are secured against any movement whatsoever during moulding and afterwards by stable continuous support. In order to achieve this, the inventors had, in the past, provided minimal amount of blade seat body in the final product, replacing blade seat body (i.e. plastic) during moulding with a supporting surface of the male mould member. It was reasoned that since the area and positioning of the support during moulding protects the blade from distortion, larger open areas in the blade seat as moulded are preferred. To that end, it was disclosed in a commonly-owned co-pending application that the area of male mould support surface be about equal to that of the blade seat, about equal meaning that the open area formed from the support surfaces be between 40 and 60 percent and preferably between 45 and 55 percent of the total blade surface area. This phenomenon has been found to be effective, and high quality wet-shaving products having excellent rigidity with virtually no vibration during use have been made. However, it has now been discovered that the required support required during the moulding process can be provided by means other than contact with the surface of the male mould member. In particular, it has been found that if high pressure thermoplastic material can be provided equally on both sides of the razor blade during the instantaneous moulding process, the blade will be adequately supported. That is to say that the blade itself will undergo no distortion whatsoever, and there will be even greater area of blade to plastic body securement to prevent distortion and vibration. Quite simply, the blade will be surrounded by a greater amount of continuous thermoplastic body on both sides. Moreover, the length of the blade extending forward from its point of securement is reduced so that any vibration resulting from forces against its edge are reduced. Reference is now made to the accompanying drawings in which:- Fig 1 is a front perspective view of the head of a single blade shaving unit according to the present invention; Fig 1A is a rear perspective view of the whole shaving unit of Fig 1; Fig 2 is a front perspective view of a shaving unit with twin blades according to the present invention; Fig 2A is an enlarged partial view of the encircled detail 2A shown in Fig 2; Fig 2B is an exploded perspective view of the segment shown at 2A depicted with the male mould member in spaced relationship thereto as it is positioned between the twin razors during moulding; Fig 2C is a partial plan view of the male mould member of Fig 2B; Fig 2D is a front elevation view of the section shown in Fig 2C; Fig 3 is a perspective view of a twin blade flexible razor unit of the present invention; Fig 3A is a front perspective view of a preferred embodiment of the twin flexible razor of the present invention; Fig 4 is a bottom perspective view of the shaving head portion of the razor unit of Fig 1; Fig 5 is an enlarged perspective partially broken away taken along line V - V of Fig 4; Fig 6 is an elevated sectional view of the blade supported in the mould for casting the thermoplastic razor unit of Fig 1; Fig 6A is an enlarged partial view of the encircled detail 6A shown in Fig 2; Fig 7 is a bottom perspective view of the twin razor unit of Fig 2; Fig 8 is a rear elevational view partially broken away along line VIII - VIII of the twin razor unit of Fig 2; Fig 9 is a sectional view of twin blades supported in the mould for casting the thermoplastic razor unit of Fig 2; Fig 9A is an enlarged partial view of the encircled detail 9A shown in Fig 9; Fig 10 is a bottom perspective view of the twin blade flexible razor unit of Fig 3; Fig 10A is a bottom perspective view of the twin flexible razor unit of Fig 3A; Fig 11 is an enlarged fragmentary perspective taken along the line XI - XI of Fig 10; Fig 12A is an exploded diagrammatic perspective view of the valving combination used to implement the present invention; Fig 12B is a representation of the valve mechanism provided by cooperation of the elements set forth in Figure 12A; Fig 12C shows the moulded product in elevated partial cross-section which results from the valve mechanism of 12A and 12B; Fig 13 depicts the portion of set plastic resulting from the access channel to the mould cavity and a portion of the male mould member used as a means of removal; Fig 13A shows the portion of a male mould member as it provides a removal means of the excess portion of a plastic shown in Fig 13; Fig 14A and 14B are diagrammatic representations depicting the mechanical requirements for the concept of the present invention; and Figures 15A and 15B shows the embodiments which include a shaving aid. Referring to Figures 1 and 1A, a single razor unit 10 is shown which was made by a single-shot moulding technique in accordance with the present invention. The head 12 has been moulded along with the handle as a single unitary piece which includes a cap 22 attached to a blade seat 15 by a continuous thermoplastic body which extends around the rear portion of the blade B to form back 9. The continuous thermoplastic body also includes connecting thermoplastic tabs extending through blade slots to join the cap 22 to the blade seat 15. Furthermore, plastic anchors have been injected into blade openings thereby anchoring the blade securely against both longitudinal and lateral movement. Referring to Figures 4 and 5 in conjunction with Figure 1, the blade support portion can be clearly seen as including a linearly extending rear bar 17 which forms the bottom of back 9 and is connected with a linearly extending support bar 18 by means of ribs 19. Progressing toward the front of the blade where the guard bar 21 is located, ribs 20 can be seen extending from bar 18 to the bottom of the guard bar 21. The back 9 of the razor head is a continuous body which extends from the blade seat 15 to the cap member 22. The cap 22 is formed with overbite securing fingers 23 and side members 24. Figure 6 is a sectional view of the blade supported in the mould for casting the thermoplastic razor unit of Figure 1. The area of the rear end of the blade which is secured by thermoplastic material is significant with respect to the entire width of the blade. Figure 6A is a detail of Figure 6 which shows how the moulding techniques of the invention simultaneously provides protection to the edge E and permits equivalent force to bear against opposite blade surfaces at all times. In particular, the mould includes male mould members M 1 , M 2 , and M 3 with cavities 9′, 18′, 21′ and 22′. The cavities are in fluid communication with each other, but the edge protection cavity E′ is not in fluid communication with any other cavity. Specifically with reference to Fig 6A it can be seen that cavity E′ ends by the joining J of male mould members M 1 and M 2 . Consequently, when the blade B is fixed in the mould, the blade itself acts as a valve to cut off flow of thermoplastic material to the edge area of the blade thereby protecting its exquisite finish during moulding. This is one of several key factors in achieving the very dependable high speed process and excellent product of the present invention. Consequently, the blade will be mechanically buttressed during the entire moulding process by the combination of male mould members and thermoplastic material under high pressure impinging on both surfaces of the blade substantially simultaneously during the moulding process. In Figure 7 the results of this technique can be seen. The combination of positioning anchors 13 and the use of the cap and cap fingers 22 extending in the direction of the blade edge beyond the cap seat, the blade within the head assembly is significantly rigidified. As a result of this invention, the blade B is highly secured against movement, and the shaving geometry is maintained to within a high degree of accuracy along the entire blade length. Applying the concept of the present invention to making razors has resulted in products which are quite superior in use, i.e. during shaving. Moreover, the moulding procedure herein can be easily integrated in a manufacturing configuration with well known razor blade production methods and machinery. Once established, the present invention provides a very inexpensive method for continuous manufacture of consistently high quality razor units. In the past it was found that in order to successfully mould a unitary cap and cover utilizing the blade as a portion of the male mould member, it was necessary to support the blade against the forces generated by inflowing thermoplastic material primarily by male support members. While this theory is true in and of itself, it has now been discovered that portions of the male mould support can be replaced by equal force of thermoplastic material on either side of the blade. This can be achieved by providing mould cavity on both sides of the blade combined with a delivery system whereby thermoplastic material under pressure is delivered substantially simultaneously to both sides of the blade. In Figure 4 it can be seen that a good deal of the mechanical support to the blade has been provided by thermoplastic material substantially equally distributed on both sides of the blade. The open areas of the ventral razor body illustrated in Figure 4 represent those portions of a blade which are in direct contact with the male mould member during moulding. Consequently, when using thin blade technology, the present invention permits significant reduction of the mass of the razor unit. In concept, the blade should experience forces during thermoplastic moulding diagrammatically represented in Figures 14A and 14B. The force vectors shown in this representation can be provided by male mould members and by thermoplastic material on either side of the blade substantially simultaneously injected thereabout by the injection moulding procedures of the present invention. Referring now to Figure 2, a twin razor unit 30 is shown in which the head portion 32 is injection moulded and has been subsequently attached to the handle portion 31. There are two blades a seat blade B 1 and a cap blade B 2 arranged in the shaving head 32 between the cap 34 and seat 35 in a constant shave geometry over the entire length of the twin blades. Referring to Figure 7 along with Figure 2, the seat 31 can be seen having a rear portion 36 connected to a middle bar 38 by ribs 37, and the guard bar 39 is connected to the middle bar 38 by ribs 40. Referring to Figure 8, an additional feature, which can be provided in accordance with the present invention, is a flow-through feature provided by rinse slots 42 extended from front to rear of the blades and exiting from the back 41 so that water and debris resulting from shaving can be rinsed therethrough. The principles and the concept of moulding set forth hereinabove with respect to the single blade system is equally applicable to the twin blade system. However, the mould configuration for the twin blade System is more intricate. In particular, a mould support must be provided between the blades during moulding preferably from front all the way to the rear male mould member so that the rinse slots are formed. The resulting structure also includes support fingers 47 (Fig 8) between the blades. As in single blade razor production, the concept for effecting an intricate twin blade shaving unit includes the use of male mould members and the delivery of high pressure thermoplastic material substantially simultaneously on both sides of the twin blade arrangement. Referring to Figure 9 and 9A, a side elevational section of the mould is shown with the twin blades included for injection moulding. It can be seen from this view that the edges E 1 and E 2 of the twin blades B 1 and B 2 are protected by male mould members M 1 ′, M 2 ′, M 3 ′ and M 4 which contact the blade somewhat removed from the edge and provide cavities E 1 ′ and E 2 ′ around the edges. The cavities E 1 ′ and E 2 ′ are closed at either end by the junction J 1 , between male mould members M 3 ′ and M 4 , and J 2 between male mould members M 1 and M 4 . The blades B 1 and B 2 themselves form valves which prevent the flow of thermoplastic material into the edge-protecting cavities. This concept is clearly illustrated in Figures 12A-C. Fig 12A is an exploded diagrammatic representation of the male mould member M 4 and a blade B 1 which provides a valve to prevent flow of thermoplastic material during moulding. Figure 12B is an elevated side sectional view of members M 1 ′ and M 4 in spaced relationship before moulding. Junction line J 2 is shown in phantom. Member M 4 is formed with a center tongue T against which one surface S T of each blade is intimately contacted during moulding. At each end on both sides of the mould member M 4 valve ramps VR are formed against which blade edge ramps ER bear during the moulding procedure. The mould member M 4 is sized and positioned so that the blades extend beyond the end of the member M 4 a distance D which sufficient to secure the ends of the blades in thermoplastic material P. (See Figure 12C). The member M 4 must be provided with exquisite detail since the dimensions are minute. For example, blades have a thickness on the order of only 0.004" (0.010 cm). Thus, the elevation H of the valve ramps VR is only about 0.002" (0.005 cm). Consequently, extreme care must be taken during moulding to protect the exquisitely detailed member M 4 . The present invention accommodates this design feature by providing a positive guidance for mould removal. Consequently, high speed manufacturing can be used to produce the units. Referring to Figures 2A-D, this unique feature can be seen. In Figure 2A a twin blade unit is shown in detail with a positive mould return step S between blade B 1 and B 2 . This positive return step feature permits the member M 4 to be removed quickly and efficiently without danger of damaging the exquisite detail of the member. In Figure 2B, the member M 4 is shown in an exploded view in spaced relationship to the completed shaving unit and in particular with respect to positive mould return step S. In this regard also refer to Figure 2C which is a plan view of member M 4 and Figure 2D which is a front elevational view of the member M 4 . As can be seen with reference to these figures, the positive mould return step S is provided by a guide channel G formed at the end of member M 4 . Thus, when the member M 4 is removed at high speed, there is absolutely no vibration since the set plastic material includes the guide step S in intimate surface-to-surface contact with the member M 4 throughout the removal stroke. Moreover, all vibration between the blades B 1 and B 2 is significantly reduced or totally eliminated. This feature enhances the ultimate product, since it protects the fragile edges of the twin blades in addition to protecting the mould member M 4 . In addition, it permits the expedient expulsion of the product from the main mould body. More specifically, once sufficient male mould members have been removed to provide clearance for expulsion of the product, mechanical pusher elements are used to engage the product and separate it from the main mould cavity. Once again as a result of the present insert moulding technique, this can be achieved without damage to the blade edge because of the clearance provided therefor. Thus, the pusher elements bear against the product surface without contacting the finished edge. Further with reference to Figures 2A-2D, it is noted that the tongue of the member M 4 has been provided with cut out sections O leaving inserts I which extend between the blades during moulding. As a consequence of the cut out portion O, thermoplastic material is permitted to flow between the twin blades and form support fingers, e.g. 47. (See Figure 8). One very important element of the present invention is to provide high pressure thermoplastic material substantially simultaneously to both sides of the blades as they are supported in the mould. To that end, it has been discovered that a thermoplastic delivery system can be arranged along the entire length of the blade with delivery ports conveniently placed for fluid communication between the delivery channel and the mould cavity. Referring to Figures 13 and 13A, an example of such a delivery system is depicted by showing the thermoplastic waste member 60 which results from the plastic which sets in the delivery system. Figure 13 is a perspective view of the waste material having introduction point 61 which is where thermoplastic material is introduced from a high pressure delivery means. The material then flows through a connecting conduit which results in the formation of neck 62. The pressurized thermoplastic material then flows into a delivery channel which results in bar 63 extending along the length of the wet shaving unit. Finally, the material is directed into delivery ports at selected areas along the length of the mould cavity. The setting of the thermoplastic material in these individual delivery ports result in fingers 64. After the thermoplastic material has become set, it must be removed from the finished shaving unit. Once again, in a high speed process, this can become problematic. However, the present inventors have discovered that the removal of the excess plastic resulting from the unique delivery system can be effected efficiently and at high speed by use of mechanical grabbing means in combination with a stabilizing male mould member. Referring to Figures 13 and 13A, such a member has been shown as mould wedge 65. Mould wedge 65 is interposed in the delivery channel (which forms in neck 62) thereby forming a stabilizing cavity 66 in the neck 62. After the thermoplastic material has set, a force F can be applied to the thermoplastic waste member 60, preferably along extension 68. This unique innovation provides for a quick and very effective waste-plastic removal technique which can be implemented at high speed without damage to the fragile wet shaving product. While the embodiments shown herein depict the technology relating to formation of the razor head, the entire razor unit including the handle could be moulded in one injection. Alternatively, the head could be moulded and then attached by methods known in the art. In any event, the blades are held substantially rigid against vibrational motion and they are formed without any distortion in the blade profile whatsoever. Referring now to Figure 3, Figure 10, and Figure 11, a twin flexible razor unit prepared in accordance with the present invention is depicted. The thermoplastic material provided in this embodiment is a solid substantially non-flexible material, which is inexpensive to acquire and easy to handle in moulding processes. The flexible characteristic is provided by discontinuities 91 and 92 along the length of the unit. Referring to the figures, a twin blade system having a blade B 3 and a blade B 4 is shown with a multifingered cap having overbite fingers 93 and side tabs 94. The seat of the head assembly in the drawings is shown having support planks 95 in conjunction with sinusoidal webs 96 which form living hinges on the bottom portion of the twin blade system. The planks 95 are also provided with elevated ribs 97 which support at each end thereof guard bar elements 98. Discontinuities 92 are provided in the cap member, and the guard bar is segmented or provided with discontinuities 91 so that the unit is flexible in response to forces imparted to it during shaving. The advantage of this construction is that easily moulded rigid thermoplastic material can be used to make a flexible shaving unit. Another preferred embodiment is again shown at Figure 3A and 10A wherein like members are provided with like numbers bearing a prime notation. This flexible shaving cartridge can be single shot moulded by use of a very intricate mould cavity utilizing the principles of alternating mechanical support by male mould member and mechanical support by thermoplastic material positioned on either side of the blades. Unique to the flexible cartridge shown in Figures 3, 10 and 11, is a flow through characteristic provided by the discontinuities in the back of the cartridge. Furthermore, the blades are supported and separated one from the other by means of support fingers that are positioned between the blades as a result of areas wherein there are no male mould support members. Referring to Figures 15A and 15B, the shaving aid feature of the invention is shown. This feature can be provided as spot cavities 102 (along either the guard elements or the cap elements) wherein shaving aid material 104, such as polyethylene oxide, polyurethane-polyvinylpyrrolidone interpolymer, etc, is deposited. Otherwise, shaving aid composition can be incorporated in the skin-engaging surfaces of the assembly or coated or adhered to such surfaces as, for example, a strip 106 shown in Figure 15A. In any case, the skilled artisan will be able to decide which skin-engaging surface(s) he or she wishes to use to deliver the shaving aid.

Claims: A wet-shaving razor unit comprising: at least one blade with an exposed edge (E) for shaving, and a thermoplastic body (9) comprising skin-engaging portions, the thermoplastic body (9) being substantially continuous; characterised in that the thermoplastic material is substantially equally distributed on both sides of the blade, such that said blade (B) is secured substantially rigidly against movement and vibration during shaving and the skin-engaging portions provide a constant spatial relationship between said skin-engaging portions and said blade (B) over the length of said blade (B) as it comes into contact with the skin. A razor unit according to Claim 1 characterised in that it includes a razor handle. A razor unit according to Claim 1 or 2 characterised by further comprising a wet-shaving aid (104) secured against removal to one of said skin-engaging portions. A razor unit according to Claim 3 characterised in that said shaving aid (104) comprises a skin-lubricant which is lubricious when wet. A razor unit according to Claim 4 characterised in that said shaving aid (104) is polyethylene oxide. A razor unit according to any one of Claims 3 to 5 characterised in that said shaving aid (104) is secured to said skin-engaging portion by one of either adhesion, mechanical restraint of said aid, or deposition of said aid in said skin-engaging portion as a part thereof. A razor unit according to Claim 6 characterised in that said shaving aid (104) is polyethylene oxide sequentially moulded into a cavity provided in said skin-engaging portion. A razor unit according to any one of the preceding claims characterised in that two blades (B 1 ,B 2 ) are provided in spaced relationship for shaving hair from the skin. A razor unit according to Claim 8 characterised by further comprising at least one opening between said two blades (B 1 , B 2 ) for flow through of water and debris resulting from shaving. A razor unit according to any one of the preceding claims characterised in that said thermoplastic body (9) has discontinuities (91,92) along the length of said blade (B) whereby said razor and said skin-engaging portions are deflected to conform to the skin surface of the user. A razor unit according to any one of the preceding claims characterised in that said thermoplastic body (9) further includes living hinges (96) to facilitate deflection of said unit. A razor unit according to any one of the preceding Claims characterised in that one of said skin-engaging portions is provided with a trough during moulding and a shaving aid (104) in the form of a thermoplastic material is deposited in said trough subsequent to formation of said unit. A method of making a wet-shaving razor unit, having at least one blade (B) with an exposed cutting edge (E) comprising supporting said blade (B) within a mould for said razor unit and injecting a thermoplastic material into said mould whereby said razor unit is formed around said blade (B) with said edge (E) free from contact with said thermoplastic material characterised in that: the blade (B) is supported in the mould with the edge (E) surrounded by mould members (M 1 , M 2 , M 3 ) which are arranged to remain out of contact with said edge (E) such that the blade (B) is mechanically buttressed on the sides thereof; and wherein the method further comprises providing a thermoplastic delivery channel which runs along the length of said mould cavity with delivery ports extending to said cavity for fluid flow of thermoplastic material whereby thermoplastic material is delivered throughout said cavity substantially simultaneously to impinge on both sides of the blade (B) substantially simultaneously to provide counterbalancing high pressure thermoplastic material on both sides of the blade (B) during moulding, so that the blade (B) is maintained without deformation during high pressure moulding. A method according to Claim 13 characterised in that it further comprises providing a shaving-aid to said thermoplastic body (9) adjacent said blade (B). A method according to Claim 14 characterised in that said shaving aid is secured to said thermoplastic body (9) by one of either adhesion, mechanical blocking of said aid, incorporating said aid in said thermoplastic body (9) or deposition of said aid on a skin-engaging portion of said unit. A method according to Claim 15 characterised in that said mould provides a cavity in said skin-engaging portion of said unit adjacent said edge and a shaving aid in the form of a thermoplastic material is deposited in said cavity subsequent to formation of said unit. A method according to any one of the preceding claims 13 to 16 characterised by further comprising providing a spacer mould member (M 4 ) which holds a second blade (B 2 ) in spaced relationship to said blade (B 1 ) said spacer having openings (O) for flow-through of thermoplastic material whereby supports (47) separating said blades (B 1 , B 2 ) are formed in the resulting product. A method according to Claim 17 characterised in that said spacer mould member (M 4 ) includes cavities (E 1 ', E 2 ') which receive the edges (E 1 ,E 2 ) of said blade (B 1 ) and said second blade (B 2 ) so that the flow of thermoplastic material is prevented from contact with said blade edges (E 1 , E 2 ). A method according to any one of the preceding claims 13 to 18 characterised in that said mould members (M 1 , M 2 , M 3 , M 4 ) are provided with a guide channel (G) for flow of thermoplastic material, said channel (G) arranged to provide guide steps (S) in said thermoplastic material after thermoset for high speed removal of said mould members (M 1 , M 2 , M 3 , M 4 ) without damage to said blades (B 1 , B 2 and blade edges (E 1 , E 2 ). A method according to any one of the preceding claims 13 to 19 characterised by further comprising providing a wedge (65) in said delivery channel having a surface which bears against set thermoplastic material for stabilization of unwanted set thermoplastic after moulding to facilitate removal from the product.

Inventors: BUTLIN C EDWARD, BUTLIN EDWARD S, CONRAD WILLIAM T JR, BUTLIN, C. EDWARD, BUTLIN, EDWARD S., CONRAD, WILLIAM T., JR.
Applicants: WARNER LAMBERT CO, WARNER-LAMBERT COMPANY
Application year: 1991
Main classification: B26B21
IPC codes: B26B21, B29C45, B29C33, B29K105, B29L31