US3439901A - Method and apparatus for agitating material and in particular for tossing salads - Google Patents

Description

April 22, 1969 R p. McCULLQCl-l 3,439,901

, METHOD AND APPARATUS FOR AGITATING MATERIAL AND IN PARTICULAR FOR TOSSING SALADS Filed Feb. 6. 1968 Sheet FIGI INVENTOR ROBERT P. McCULLOCH April 22, 1969 R. P. MCCULLOCH 3,439,901

METHOD AND APPARATUS FOR AGITATING MATERIAL AND IN PARTICULAR FOR TOSSING SALADS Sheet Z of 2 Filed Feb. 6, 1968 United States Patent 3 439,901 METHOD AND APPARATUS FOR AGITATING MA- TERIAL AND IN PARTICULAR FOR TOSSING SALADS Robert P. McCulloch, 555 Perugia, Los Angeles, Calif. 90024 Filed Feb. 6, 1968, Ser. No. 703,285 Int. Cl. B01f 9/02 US. Cl. 259-89 11 Claims ABSTRACT OF THE DISCLOSURE An apparatus for imparting diverse motions to loose material. The apparatus includes a container adapted to receive and enclose the material. The container is supported for rotational motion thereof about two mutually perpendicular rotational axes by releasable support means. Drive means connected with the support means frictionally contacts the container to rotate the container simultaneously about the two rotational axes. In an additional aspect of the invention, stopping of movement of the container is arranged to occur only at times when the container is in a convenient orientation relative to the support means for removal of the contents.

A method aspect of the invention includes supporting a spherical container for universal rotation on a support. The method further includes driving the container by a wheel which has a point of peripheral contact With the container to apply multi-directional frictional turning force thereto. This drive technique imparts to the container one velocity component disposed in one plane passing diametrically of the receptacle and a second velocity component disposed in a plane perpendicular to the first plane.

BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for agitating loose materials and in particular, but not exclusively, for tossing salads.

In preparing salads, it is common to perform a saladtossing operation in which the various elements of the salad, lettuce, vegetables, dressing and the like, are given a thorough mixing to insure that the ingredients are uniformly distributed with the dressing evenly applied. The tossing operation is frequently performed manually, by shaking or stirring or the like, and may prove quite tiring and time consuming. It has therefore been previously proposed to provide apparatus for performing salad-tossing operations by machine suitable for domestic or commercial catering.

Prior mechanical salad tossers have sometimes included a receptacle into which the salad ingredients are placed and a housing for receiving and supporting the receptacle. The receptacle may be rotated about a single axis by a motor-driven drive wheel contained within the housing. Although prior salad tossers of this type have been in use, they may prove unsatisfactory in operation for a number of reasons.

For example, using a receptacle which is spun about a single axis, there is a tendency for the most mobile ingredients of the salad, notably the liquid dressing, to be moved in undue proportion by centrifugal force against the exterior of the receptacle, rather than being evenly distributed throughout the salad. Furthermore, the rotation about a single axis may result in the centrifugal force exerting a stabilizing action upon the ingredients as they rotate so that mixing may be impeded rather than elfectuated.

Another problem with prior salad tossers frequently occurs in connection with removal of the salad after toss- 3,439,901 Patented Apr. 22, 1969 ing. This problem may arise if the receptacle has a cover which moves through various inaccessible positions within the housing during motion of the receptacle, or through a downwardly facing position in which removal of the cover would result in spilling of the salad. To insure that the receptacle does not come to rest in one of these undesirable positions at the conclusion of tossing, it has often been necessary to monitor the position of the receptacle and to switch off the driving motor at the precise instant when the receptacle cover is in a suitable location. It would therefore be desirable to provide switching which could be operated at any time but which would insure that the receptacle would only come to rest positioned in a convenient orientation for removal of the salad.

SUMMARY OF INVENTION It is therefore a general object of the invention to provide a method and apparatus for agitating loose materials and in particular for tossing salads, intended to obviate or minimize problems of the type previously described.

It is a particular object of the invention to provide an agitating apparatus for material, in which diverse motions of the material occur in at least two directions simultaneously.

It is another object of the invention to provide an agitating apparatus of the power-driven type which may be switched off at any time and yet in which the apparatus will come to rest in a position suitable for convenient access to the contents.

It is a further object of the invention to provide a salad tosses capable of mixing the contents of a salad together in such a way as to produce particularly uniform distribution-of the ingredients of the salad.

It is yet another object of the invention to provide a power-driven salad tosser of reduced complexity suitable for large-scale production as a domestic or commercial culinary item.

In its broadest aspects the invention comprises an apparatus for imparting diverse motions to material contained within the apparatus, including container means adapted to receive and enclose the material. The container is releasably supported for rotational motion about at least two mutually perpendicular rotational axes by support means. Drive means connected with the support means contacts the container to rotate, the container simultaneously about the two mutually perpendicular rotational axes.

In more detail, the container means include a spherical receptacle defining an enclosed interior space, with the support means including a housing having underlying means in abutting contact with the underside of the receptacle supporting it for universal rotation relative to the housing. The drive means includes a drive wheel rotatably connected with the housing. The drive wheel has a point of peripheral contact with the receptacle to apply force thereto having one component acting in a first plane passing diametrically of the receptacle and a second component acting in a second plane perpendicular to the first plane.

A method aspect of the invention includes the steps of supporting a spherical receptacle for universal rotational motion and of applying a continuously acting, first force component to the exterior of the receptacle acting in a plane passing diametrically of the receptacle. At the same time, a second component of force is app-lied to the exterior of the receptacle acting in a second plane perpendicular to the first plane. The effect of the two force components is to rotate the receptacle simultaneously about two axes perpendicular to the first and second planes.

In more detail, the step of applying force components is performed utilizing a drive wheel frictionally contacting the exterior of the receptacle and at its point of contact therewith having one component of velocity lying in a first plane passing diametrically of the receptacle, and another component of velocity in another plane perpendicular to the first plane.

THE DRAWINGS One preferred embodiment of the invention is illustrated in the accompanying drawings in which,

FIGURE 1 is a side view of an apparatus constructed in accordance with a preferred embodiment of the invention;

FIGURE 2 is a top view of a supporting housing forming a part of the apparatus shown in FIGURE 1;

FIGURE 3 is a cross-sectional end view of the supporting housing shown in FIGURE 2 taken along the lines 3-3 therein, but with a removable receptacle forming a part of the present invention shown in position on the supporting housing;

FIGURE 4 is a cross-sectional side view of the supporting housing shown in FIGURE 2 taken along the lines 44 therein, but with the receptacle in position on the housing;

FIGURE 5 is a cross'sectional side view of the supporting housing shown in FIGURE 2 taken along the lines 55 therein, but with the receptacle shown in position in the housing;

FIGURE 6 is a simplified schematic view of an electric drive circuit forming a part of the apparatus shown in FIGURE 1;

FIGURE 7 is a cross-sectional side view of a portion of the removable receptacle shown in FIGURE 1; and

FIGURE 8 is a cross-sectional side view of a portion of a magnetic bowl support forming a part of the present invention.

DETAILED DESCRIPTION General summary Referring to FIGURE 1 of the drawings, one preferred embodiment of the invention there shown includes a spherical receptacle 2, suitable for receiving loose ma terial such as salad or the like, resting on an underlying support housing 4. The receptacle 2 includes an upper hemispherical cover 6 and a lower, hemispherical bowl 8, releasably secured together. To avoid difliculties of description arising from the symmetry of the apparatus, an arbitrary system of axes is defined as follows:

A longitudinal axis yy aligned with one horizontally disposed diameter of the spherical receptacle 2;

A transverse axis x-x (FIGURE 2) perpendicular to the longitudinal axis yy, aligned with another horizontal diameter of the recptacle 2; and

A vertical axis zz (FIGURE 1) aligned with a vertically disposed diameter of the receptacle 2, intersecting the longitudinal and transverse axes yy and xx respectively at a common point defining the center of the spherical receptacle 2.

The support housing 4 (FIGURES 2 and 3) includes an upright, generally frustoconical body 10 adapted to rest upon a flat surface such as a table or the like. The body 10 is provided with a downwardly dished upper surface 12 shaped as a portion of a sphere configured to be concentric with and of slightly greater diameter than the adjacent under side of the receptacle 2.

The under side of the receptacle 2 is supported in spaced concentric relation above the dished surface 12 of the housing 4 by three wheels 14, 16 and 18 (FIGURE 2) connected to the under side of the dished portion 12 and extending upwardly through apertures therein into abutting contact with the receptacles. The wheels 14 and 16 are positioned on opposite transverse sides of the longitudinal axis yy and spaced in a forward direction of the transverse axis xx. The wheel 18 is positioned transversely intermediate the wheels 14 and 16 and is spaced rearwardly of the transverse axis xx, so that the three wheels 14-18 provide three-point support for the receptacle 2.

The wheel 18 is a freely rotatable, idler wheel but the wheels 14 and 16 are driven by power so that they cause the receptacle to rotate in the vertical plane about the axis x-x. Additionally, the wheel 14, being larger in diameter than wheel 16, has a higher peripheral speed at its point of contact with the receptacle 2 than does the wheel 16, and thus generates a turning force tending to rotate the receptacle 2 about the vertical axis zz as well.

It will be appreciated that in this manner a compound tumbling motion is imparted to the contents of the receptacle 2 so that the contents are constantly kept in a state of tumbling and mixing motion to insure the most efficient distribution of the dressing and other contents of the salad.

In an additional significant aspect of the invention, termination of movement of the receptacle is controlled by an OFF switch 20 which, after it has been actuated, permits motion of the receptacle 2 to continue until the cover 6 of the hemisphere reaches a centralized upright position above the bowl 8 at which time further movement is automatically terminated.

The receptacle drive Referring in more detail to FIGURE 3, the previously mentioned drive wheels 14 and 16 are supported at the opposed extremities of a horizontally disposed drive shaft 30 to which they are keyed. The idler wheel 18 (FIGURE 2) is supported by a horizontally disposed, transversely extending idler shaft 31 rotatably mounted in two lugs 32 depending from the under side of the dished portion 12. The drive shaft 30 is supported in parallel relation to the transverse axis xx spaced forwardly therefrom, by two lugs 33 formed integrally with the under side of the dished portion 12 of the support housing 4 and containing bearing members 34.

To drive the shaft 30, a gear wheel 36 keyed to the shaft 30 is meshingly engaged by a worm gear 38 provided at the free extremity of an output shaft 40 of a conventional electric motor 42 (FIGURE 5). The worm gear 38 is held in meshing engagement with the gear wheel 36 by a housing 44 which also extends about and supports the motor 42 and its output shaft 40. The housing 44 extends generally parallel to the longitudinal axis yy of the apparatus (FIGURE 2) and is supported at one longitudinal end by an elongate threaded connector 46 (FIG- URE 5) to the interior of the support housing 4 adjacent the side wall 10. At the other end, the housing 44 extends about and is supported by the previously mentioned drive shaft 30.

Power for the electric motor 42 is supplied by a storage battery 48 which may be recharged in a conventional manner from a domestic electric power source through terminals 50 (FIGURE 4) provided "for this purpose. Initiation of the operation of the motor 2 (FIGURE 6) is effected by closing an ON-OFF switch 52 which completes an electrical circuit from the battery 48 through a pair of spring terminals 24 (to be discussed in more detail hereinafter) to the motor 42. The ON-OFF switch 52 (FIGURE 5) is positioned on the side wall 10 of the housing 4 adjacent the previously mentioned OFF switch 20.

The wheels 14 and 16 are both formed of fairly hard rubber or the like having a high degree of frictional engagement with the receptacle 2, to insure that lost motion through slippage between the wheels and the receptacle is minimized. The wheels are additionally bevelled along their edges in contact with the receptacle to increase traction. It will be appreciated that the wheels 14 and 16 rotating in the same direction on the shaft 30 will rotate the receptacle 2 about the axis x-x.

Additionally (as previously mentioned), the peripheral speed of the wheels 14 and 16 at their respective points of contact with the receptacle 2 are diflerent. This is achieved by making the diameter of the wheel 14 larger than that of the wheel 16 so that its periphery has a higher speed. Because of the greater diameter of the wheel 14, it is necessary to position it a somewhat greater distance transversely on one side of the longitudinal axis 3 -3 of the receptacle than the transverse spacing of the smaller wheel 16 on the other side, to avoid canting over the receptacle 2.

The speed ditferences between the peripheral positions of the wheels 14 and 16 at the respective points at which they contact the under side of the receptacle 2 causes the receptacle to be rotated about the vertical axis zz as well.

Thus, it will be realized that the receptacle 2 is rotated about two mutually perpendicular axes simultaneously, the vertical axis z-z and the transverse axis xx. This imparts a very effective, compound tumbling motion in two directions to the contents to overcome any stabilizing effect of centrifugal force that might otherwise retard mixing. This compound motion is also particularly advantageous in salad tossing in preventing separation of the more mobile ingredients (such as the dressing) under centrifugal force, thereby insuring a more uniformly mixed salad in which the dressing is equally applied throughout.

This eifect of combined rotation about two perpendicular axes would persist even if the wheels 16 and 18 were removed and the device operated as a single drive-wheel system. However, it is important in such a circumstance to insure that the tangential direction of motion of the periphery of the wheel 14 at its point of contact with the receptacle should be oblique to the receptacle surface so as to have one component of velocity acting in a plane passing diametrically of the receptacle and another component of velocity acting in a second plane perpendlcular to the first. Only in this way will there be two mutually perpendicular axes of rotation for the receptacle, simultaneously. The present two-wheel drive system may in eifect be considered to be the equivalent of a one-wheel drive system in that the unbalanced forces exerted by the unequal diameter wheels may be equated with the effect of a single wheel suitably located.

The stopping system The previously mentioned OFF switch 20 includes a generally horizontal lever arm 60 extending along the longitudinal axis yy (FIGURE 4). The arm 60 is provided on its upper surface with a vertically extended female hinge member 62, at a point spaced from the forward end. The member 62 comprises two transversely spaced projections positioned on opposite sides of the previously mentioned idler wheel supporting bracket 32, and is rotatably supported by the lateral extremities of the idler wheel shaft 31.

At its forward end the lever 60 supports the previously mentioned spring or reed switch 24 and a magnet 64 (to be discussed). The various portions of the switch 20 are equally balanced about their point of pivotal connection to the idler wheel support shaft 31 so that the switch 20 may remain in stable equilibrium when moved to either of its ON and OFF positions. The lever 60 projects outwardly through a vertical opening 70 in the side wall of the support housing 4 and is limited in its downward motion by abutment with a closed lower extremity 72 of the slot 70. With the lever 21 resting against the closed extremity 72 in an OFF position, the magnet 64 is positioned in very close adjacency to the bottommost portion of the receptacle 2.

The previously mentioned switch 24 includes two spring or reed contacts 66 and 68 of material having magnetizable properties, such as spring steel. The contacts 66 and 68 are resiliently biased apart by their inherent springiness to an open position of the switch, but are held in contact in a closed position by the magnetic flux of the magnet 64 which is fixedly secured to the upper side of a housing 70 enclosing the switch 24. An element 72 of high magnetic permeability, such as soft iron, is set into the under side of the bowl portion 8 of the receptable 2. When the element 72 is immediately adjacent the magnet 64, it provides a preferred magnetic path for the lines of flux of the magnet 64 so that the external magnetic field of the magnet 64 is weakened to a suflicient extent to permit the contacts 66 and 68 of the switch 24 to open under their own resiliency.

In operation, the switch 20 is initially moved upwardly to an ON position away from the abutment 72 to move the magnet 64 away from the element 72, so that the weakening of the magnetic flux effected by the element 72 ceases. The magnet 64 then has sufficient strength to overcome the springiness of the contacts 66 and 68 to close the switch 24. Subsequent operation of the ON-OFF switch 52 to its ON position completes the power circuit to the motor 42 to commence receptacle rotation. When it is desired to stop the receptacle, the lever arm 60 of the switch 20 is moved down to the OFF position to place the magnet 64 closely adjacent to the exterior of the receptacle 2. As the receptacle 2 continues to rotate, the element 72 eventually moves to the bottom position, at which time it is in close adjacency with the magnet 64 with the result that the switch 24 opens in the manner described, thereby terminating further rotation of the receptacle. The magnetic attraction between the magnet 64 and the element 72 also provides a holding action tending to prevent overrun of the bowl due to momentum once rotation under power ceases, and additionally provides a centering force for holding the bowl 8 centered in the housing 4 when the receptacle contents are being filled or removed.

In this way, the receptacle may always be brought to rest in the same orientation without requiring visual observation to insure that the motor is turned off at the crucial moment when the cover 6 is uppermost.

It may be noted in this connection that the compound motion imparted to the salad receptacle by the wheels 14 and 16, whereby the receptacle is rotated only about the transverse horizontal axis xx and the vertical diameter axis z-z, insures that the element 72 travels in a vertically disposed circular orbit lying in the same vertical plane as the magnet 64. Thus, on operation of the OFF switch 20 to the OFF position, the element 72 will move into adjacency with the magnet 64 within one revolution of the receptacle 2.

Other details The bowl 8 and cover '6 of the receptacle 2 are made from plastic material having qualities of wear resistance, good impact strength and attractive appearance and the housing 4 is made of similar material. FIGURE 7 shows the manner in which the cover 6 and the bowl 8 are releasably secured together to enclose the material to be agitated. Adjacent their edges, the walls of the cover and the bowl are thickened. In addition, the edge of the cover 6 is provided with a downwardly extending annular lip engaging a concentric, corresponding annular recess 82 in the thickened portion of the wall of the bowl 8 to provide an overlapping and self-centering closure for the receptacle halves.

The cover and bowl 6 and 8 are also provided with abutting, peripherally extending, radial shoulders 84 and 86 respectively. Inset into the wall of the cover 6 is an annular ring of material having magnetizable qualities, such as steel, intersecting the shoulder 84. Set into the wall of the bowl 8 of the receptacle is a plurality of peripherally spaced magnets intersecting the shoulder 86 and positioned in abutting contact with the ring 88 when cover and bowl are disposed in closed relation, to provide a magnetic securing action. The bowl halves 6 and 8 may be separated by pulling them apart with sufficient force to overcome the magnetic attraction between the magnet 90 and the ring 88.

After the receptacle 2 has been removed from its housing it may sometimes be desired to place the bowl 8 on a table to function as a salad bowl containing the salad. In order to permit the covered bowl 8 to rest on a flat surface, a detachable stand 100 (FIGURE 8) is provided. The detachable stand 100 comprises a plastic body '101 having a generally flat base 102 and containing a cup-like portion 103 on its upper surface enclosing a magnet 104. The magnet 104 is attached to the previously mentioned element 72 in the base of the bowl 8 to secure them together. The stand 100' permits the bowl 8 to be rested on the table without rolling over.

The bowl 8 is additionally provided on its inner surface with an integrally formed cup 108 for receiving the dressing so that a standard measure may be provided.

SUMMARY OF ADVANTAGES It will be seen that in following the method and apparatus of the present invention for agitating loose materials, such as salad tossing opeartions, considerable advantages are provided.

Particularly significant is the provision of a receptacle which is rotated about two mutually perpendicular axes simultaneously so as to provide continuous, compound agitation to the contents to avoid stabilization thereof under centrifugal force.

In this connection, the use of drive wheels of different diameter contacting the receptacle on the under side provides a simple drive system suitable for low-cost production.

Also of particular significance, is the provision of the magnetic OFF switch which permits the apparatus to be turned off at any time, yet insures that the salad receptacle bowl comes to rest in a convenient orientation for removal of the contents with the removable cover 6 uppermost.

Other advantages are provided by the magnetic connection between the cover and the bowl of the salad bowl receptacle, and by the detachable stand which permits the bowl of the receptacle to be rested upon a table or the like for dining purposes once the salad has been tossed.

Although this invention has been described with primary reference to a salad tossing, it will be appreciated that the method and apparatus described may be of use for many diverse applications requiring diverse tumbling motions to be imparted to loose material. For example, an apparaus of this nature may be used for tumbling lottery tickets, for mixing assorted collections of candies or for any other like purposes requiring even mixing of loose materials.

Although the invention is described with reference to a preferred embodiment, it will be apparent to those skilled in the art that additions, deletions, modifications, substitutions and other changes may be made which will fall within the purview of the appended claims I claim:

1. A method for agitating material contained within an enclosed hollow receptacle of spherical shape, the method comprising the steps of,

supporting the spherical receptacle for universal rotational motion of the receptacle;

applying a continuously acting first force component to the exterior of the spherical receptacle, the first force component acting a first plane passing diametrically of the spherical receptacle to rotate the receptacle about a first axis perpendicular to the first plane; and

applying a continuously acting second force component to the exterior of the spherical receptacle, the second force component acting in a plane perpendicular to the first plane to rotate the receptacle about a second axis perpendicular to the second plane.

2. A method as defined in claim 1 wherein the step of applying the force components includes,

mounting a rotating drive wheel in frictional contact with the under side of the receptacle,

positioning the drive wheel so that the drive wheel at a point of peripheral contact thereof with the receptacle includes,

a first component of velocity lying in a first plane passing diametrically of the receptacle through the point of contact with the drive wheel, and

a second component of velocity lying in a second plane perpendicular to the first plane.

3. An apparatus for agitating material container within the apparatus, said apparatus comprising,

container means adapted to receive and enclose the material,

support means releasably supporting said container means for rotational motion thereof about at least two mutually perpendicular, rotational axes, and

drive means connected with said support means and contacting said container means for rotating said container means simultaneously about said two rotational axes.

4. An apparatus as defined in claim 3 wherein said container means includes,

a spherical receptacle defining an enclosed interior space,

said support means further including,

a housing, and

underlying means connected with said housing in abuttlng contact with the under side of said receptacle for supporting said receptacle for universal rotational motion about the center thereof relative to said housing;

said drive means including,

at least one drive wheel rotatably connected with said housing, said drive wheel having a point of peripheral contact with said receptacle to apply first and second force components to said receptacle, said first force component acting in a first plane passing diametrically of said receptacle and said second force component acting in a second plane perpendicularly disposed to said first plane.

5. An apparatus as defined in claim 4 wherein said apparatus is intersected by a longitudinal axis aligned with one horizontally disposed diameter of said spherical receptacle,

a transverse axis perpendicular to said longitudinal axis aligned with another horizontally disposed diameter of said spherical receptacle, and

a vertical axis aligned with a vertical diameter of said spherical receptacle and having a common point of intersection with said longitudinal and said transverse axes,

said drive means further including,

at least one drive wheel connected with said housing for rotating motion about a horizontally disposed, transversely extending axis, said drive wheel having,

an upper peripheral portion frictionally and drivingly contacting said spherical receptacle on the under side thereof at a point spaced longitudinally from said transverse axis and transversely from said longitudinal axis.

6. An apparatus as defined in claim 5, further includa second drive wheel frictionally and drivingly contacting said spherical receptacle on the under side thereof at a point spaced transversely from said first drive wheel, said drive wheels at their respective points of contact with said spherical receptacle having differing peripheral speeds.

7. An apparatus as defined in claim 6, further wherein said drive wheels are spaced transversely on opposite sides of said longitudinal axis, said drive wheels further being of unequal diameter, and

a transversely extending drive shaft rotatably connected with said housing, said drive shaft at the opposed extremities thereof, being fixedly connected to said drive wheels.

8. An apparatus as defined in claim 7, further including,

an idler wheel rotatably connected with said housing and contacting said spherical receptacle on the under side thereof at a point spaced longitudinally on an opposite side of said transverse axis from said drive wheels and transversely generally intermediate therebetween.

9. An apparatus as defined in claim 4 wherein said container includes a predetermined reference point, said apparatus further including,

selectively operable actuator means operatively connected with said housing and with said drive means, said actuator means responsive to the position of said reference point relative to said housing to automatically terminate operation of said drive means upon movement of said reference point to a predetermined location relative to said housing.

10. An apparatus as defined in claim 9 wherein said actuator means includes,

a magnetically responsive switch unit resiliently biased to an open position, said switch operatively connected with said drive means for terminating operation theresof upon opening of said switch unit,

a magnet connected with said switch, said magnet positioned on said housing closely adjacent said receptacle, said magnet normally having suflicient magnetic strength to maintain said switch unit closed,

said receptacle further including,

an element of relatively high mganetic permeability fixedly secured to said receptacle at said reference point, said element upon movement into close juxtaposition with said magnet offering a preferred flux path for the flux of said magnet, weakening the extrenal field thereof to cause said resiliently biased switch unit to open.

11. An apparatus as defined in claim 4 wherein said spherical receptacle includes,

two hollow, mating hemispheres positioned in abutting edge-to-edge relation to said sphere, one of said hemispheres being a bowl and the other a cover;

cooperating magnetic elements positioned in the opposed edges of said hemispheres to maintain said hemispheres in closed relation but permitting separation of said hemispheres upon application of predetermined force thereto.

References Cited UNITED STATES PATENTS 2,597,291 5/1952 Clegg 25989 X 3,081,070 3/1963 Welsch 259-89 3,103,677 9/1963 Gallant 1521 3,365,739 1/1968 Olinghouse 15-21 ROBERT W. JENKINS, Primary Examiner.

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