BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of nestable, thin walled plastic containers of the disposable variety which incorporate stacking means in the sidewalls thereof to prevent jamming between adjacent telescopically arranged containers. 
     It is well known to incorporate a stacking ring structure in the side walls of such containers, as shown in U.S. Pat. Nos. 3,139,213 and 3,091,360 to overcome the tendency of telescopically nestable cups to jam when subjected to handling, axial impact, etc. These examples of prior art show a stacking ring with an internal shoulder and external shoulder interconnected by a back tapered support strut. Such a configuration adequately prevents jamming and provides a certain amount of resilience in the axial direction due to the back taper of the strut. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a thin walled, nestable cup with improved axial resiliency when arranged in a stack of telescoping like containers. 
     It is a further object of the present invention to provide a thin walled, nestable cup having a stacking ring configuration which permits the minimization of the thickness of the walls of the container while continuing to protect each container from impact damage when assembled in a telescopic stack arrangement. 
     These and other objects and advantages of the present invention are attained by the provision of a bulbous or blister-like protuberance on one of the co-acting shoulders in the stacking means. The bulbous or blister-like protuberance, being of a relatively large surface area, freely deflects axially upon axial shock or pressure. This, coupled with the natural resilience provided by the back taper in a stacking ring of the type described, should protect even very thin walled containers from axially directed impact damage. 
     It is contemplated that the basic aspects of this invention can be incorporated in a container wherein the stacking means is adjacent the bottom of the wall, as in U.S. Pat. No. 3,091,360, as well as adjacent the lip, for example, when the container is designed to accept a lid and wherein the stacking means incorporates a camming feature to facilitate the association of the lid to the container. 
     Other objects and advantages of the present invention will become apparent from the following description when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view in partial section of the inside of a first embodiment of nestable cup configured in accordance with the invention; 
     FIG. 2 is an enlarged fragmentary sectional view illustrating the stacking configuration of a plurality of cups of the FIG. 1 variety; 
     FIG. 3 is a front elevational view with the bottom region in section of an alternate form of nestable cup utilizing the invention; 
     FIG. 4 is an enlarged fragmentary sectional view illustrating the stacking between cups of the FIG. 3 variety and as taken along lines 4--4 of FIG. 3 of a bottommost cup in the stack; and 
     FIG. 5 is an enlarged fragmentary sectional view illustrating the stacking between cups of the FIG. 3 variety and as taken along lines 5--5 of FIG. 3 of a cup in the bottommost stacking relationship. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to FIGS. 1 and 2, there will be seen a plastic molded or thermoformed cup designated generally by the numeral 10. The cup, as shown in FIGS. 1 and 2, is typically utilized as a dairy or cottage cheese container, but the invention is not necessarily restricted to such a use. Such cups or containers are typically handled for filling by nestably stacking or associating a plurality of like containers and vending or separating the lowermost container from the other containers in the stack. Such containers typically are made of plastic and preferably of high-impact polystyrene. Basically, the container includes a bottom wall 12, upwardly and outwardly tapering side walls 14 joining a thickened rim portion 16 having a predetermined axial extent for a purpose to be described later herein. Container 10 will include a stacking ring structure 18 generally typical of prior art containers of this type. 
     Stacking ring structure 18 will be shown to include an externally projecting shoulder means 24 at the lowermost extremity of the stacking ring structure and an internally projecting shoulder means 26 at the upper extremity of the stacking ring structure. A slightly back tapered support strut 28 integrally connects the two shoulders. 
     In the embodiment shown in FIG. 1, the external shoulder 24 is essentially a peripherally extending, radial ledge extending in a plane generally perpendicular to the axis of the container and which terminates at a juncture line 25 between the ledge 24 and the back tapered support 28. The uppermost internally projecting shoulder 26 is shown to be tapered inwardly and downwardly defining an inner diameter which is less than the outer diameter of the external shoulder means. 
     In operation, a series of telescopically associated containers 10 will be configured so that the external shoulder 24, and more precisely, the juncture 25, which creates a first co-acting surface, abuts a second co-acting surface on the uppermost internal shoulder 26 to prevent the containers from jamming. The predetermined axial extent of the rim 16 should be no greater than the axial extent of the stacking ring means so as to not prevent proper mating functions between first and second co-axial surfaces. 
     Attention is directed to the plurality of circumferentially spaced, generally bulbous or blister-like raised regions 30 superimposed over the inclined internal shoulder 26. These regions 30, forming a co-acting surface, are of sufficient surface to be relatively freely flexed downwardly when contacted by the edge 25, which is the first mentioned co-acting surface, as shown clearly in FIG. 2. This compression may result from shock or axial pressure applied to the stack and provides sufficient protection from damaging the walls or components of the cup under such shock. 
     Reference should also be made to the provision for interruptions 32 circumferentially spaced about the perimeter of the internal shoulder means 26. This provides for proper venting and ease of association of a lid to the container. Lids and containers of this general type are, of course, shown in U.S. Pat. No. 3,061,139, and a container of this type may be provided with an undercut means 34 to aid in the locking of the lid on the container without harming the stacking and resilient shock impact resisting feature of this invention. 
     Turning to FIGS. 3 through 5, a further embodiment of the basic invention will be shown wherein a thermoplastic cup, thin walled in nature, is described generally by the reference numeral 10a and like elements throughout the various views of the drawings are intended to designate similar elements or components with the addition of the suffix &#34;a&#34;. For example, upwardly and outwardly tapering side walls 14a emanate from a bottom wall 12a toward and merging with rim 16a in cup 10a. However, unlike the embodiment shown in FIG. 1, the embodiment shown in FIGS. 3 through 5 includes the stacking means 18a adjacent the bottom wall rather than adjacent the rim. It should also be noted that the outer peripheral region of the bottom wall creates the externally extending shoulder 24a for the stacking ring structure. The internal shoulder 26a is configured as a gradually undulating circumferentially extending ledge which, in effect, presents a series of bulbous or V-shaped protrusions 30a interconnected at lowermost surface regions 31a. These bulbous axial protrusions 30a function in a manner similar to the portions 30 in FIG. 1. The function and operation of these resilient, bulbous regions 30a as second surface means designed to co-act with a first surface means 24a is clearly shown in FIGS. 4 and 5. FIG. 4 shows a cross section of a lowermost cup in a stack of cups taken at the circumferential region of the lowermost surface regions 31a or the regions intermediate the bulbous regions 30a. 
     Likewise, the section shown in FIG. 5 shows the cross section taken at the circumferential region of highest point of the bulbous regions 30a. 
     Throughout this description it should be understood that the word &#34;bulbous&#34; is intended to cover any relatively large surface area of slight axial raised region of a shoulder having a well defined plane. For example, in FIG. 1 the well defined plane of the internal shoulder 26 is frusto-conical with a series of raised protuberances 30 formed over this plane. In the other embodiments, in FIGS. 3 through 5, the well defined plane is that on which the junction lines 31a lies and the generally wide angled, V-shaped bulges 30a are the resilient means to permit the thin walled cups to reduce the impact damage upon one another. In all embodiments, a highly resilient section is created capable of absorbing a wide range of axially directed shock forces without damage to the cups. It should also be understood that due to the thin-walled thermoplastic construction, both co-acting surfaces described herein will exhibit resilience, thus contributing to the overall effect of the invention. 
     Having described the invention, it is to be understood that changes can be made in the described embodiment by one skilled in the art within the spirit and broad scope of the invention as defined by the claims herein.
A thin walled nestable thermoplastic cup having stacking rings configured in the side walls to permit nonjamming, telescopic association of a series of like containers, the stacking rings incorporating bulbous shoulder means to enhance axial resilience in a stack of so nested cups.