US3589557A

US3589557A - Slide dispenser

Info

Publication number: US3589557A
Application number: US813063A
Authority: US
Inventors: Leighton Clifford Johnson
Original assignee: Miles Laboratories Inc
Current assignee: Bayer Corp
Priority date: 1969-04-03
Filing date: 1969-04-03
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29

Abstract

Apparatus is provided for dispensing rectangular platelike objects, such as microscope slides, one at a time. This dispenser also provides means for producing desirable liquid smears on microscope slides. A supporting track is located along the top of the dispenser for supporting a slide having a blood drop, for example, on its lower face. A stored slide protrudes from a storage magazine and forms an acute angle with the plane of the supporting track. The leading edge of the protruding slide projects slightly above the plane of the supporting tract and is capable of being depressed so as to be in the same plane as the supporting tract. The slide having the blood drop is moved in one direction along the track in depressing engagement with the leading edge of the protruding slide until the blood drop on its under side contacts said protruding slide and forms a liquid capillary meniscus in the acute angular space between the two slides. The slide having the blood drop is then moved along the supporting track in the opposite direction to spread out the liquid along the lower surface of such slide and form a desired liquid smear.

Description

United States att Leighton Clifford Johnson Edwardsburg, Mich. 813,063

Apr. 3, 1969 June 29, 197 1 Miles Laboratories, lnc. Elkhart, 11nd.

lnventor Appl. No. Filed Patented Assignee SLIDE DISPENSER 7 Claims, 8 Drawing Figs.

U.S. C1

References Cited UNITED STATES PATENTS Neddo Knickerbocker 221/285 X 221/304X 221/279 X 221/303 X 221/199 221/279 Primary ExaminerSamuel F. Coleman Attorneys-Joseph C. Schwalbach, Michael A. Kondzella,

Louis E. Davidson and Harry T. Stephenson ABSTRACT: Apparatus is provided for dispensing rectangular platelike objects, such as microscope slides, one at a time. This dispenser also provides means for producing desirable liquid smears on microscope slides. A supporting track is located along the top of the dispenser for supporting a slide having a blood drop, for example, on its lower face. A stored slide protrudes from a storage magazine and forms an acute angle with the plane of the supporting track. The leading edge of the protruding slide projects slightly above the plane of the supporting tract and is capable of being depressed so as to be in the same plane as the supporting tract. The slide having the blood drop is moved in one direction along the track in depressing engagement with the leading edge of the protruding slide until the blood drop on its under side contacts said protruding slide and forms a liquid capillary meniscus in the acute angular space between the two slides. The slide having the blood drop is then moved along the supporting track in the opposite direction to spread out the liquid along the lower surface of such slide and form a desired liquid smear.

mm lit a PATENTEUJUNZQIQYI 3,589,557

sum 1 or 3 FIGURE I.

INVENTOR LEIGHTON CUF FORD JOHNSON ATTORNEY PATENTEDJUNZSlBH 3,589,557

sum 2 OF 3 INVEN TOR LEIGHTON CLIFFORD JOHNSON FIGURE 5. BY K 8 SM AT TORNEY PATENTEU JUN29 l9?! SHEET 3 BF 3 FIGURE 6.

FIGURE 7.

FIGURE 8 INVENTOR LEIGHTON CLIFFORD JOHNSON BY 5;, 1 sgw w q ATTORNEY FIGURE 4 SLIDE DISPENSER BACKGROUND AND PRIOR ART It is well known in the art that microscope slides should be as clean as possible, i.e., free of surface dirt and fingerprints, prior to use in the preparation of liquid smears, for example, for subsequent microscopic examination. Microscope glass slides are generally available in clean form in original packages, but they become dirty, especially with fingerprints, when they are removed from such packages and handled prior to microscopic examination. This is especially true when the glass slides are employed to prepare liquid smears, such as blood smears.

There have been various efforts in the prior art to provide mechanical dispensers for dispensing clean slides, but these efforts have not been commercially successful, especially for the dispensing of slides one at a time.

It is also well known in the art that liquid smears, such as blood smears, on a microscope slide are generally prepared in the following manner. A drop of blood is applied to the upper surface of a first glass slide near one end of the slide. A second glass slide having a substantially straight leading edge is positioned over the first slide with the leading edge of its lower surface in contact with the blood drop and the upper surface of the first slide and with the plane of the lower surface of the second slide forming an acute angle with the plane of the upper surface of the first slide. The blood drop forms a liquid capillary meniscus in the acute angular space between the two slides. The second-slide is then moved along the first slide with the liquid-containing acute angular space in a trailing position. This forms a liquid smear along the upper surface of the first slide. This prior art manual procedure has the disadvantage that the production ofa high quality liquid smear is dependent upon the maintenance ofa proper liquid capillary meniscus in the acute angular space between the two slides during the formation of the liquid smear. In this manual operation the maintenance of the desired acute angle is dependent primarily on the dexterity of the person handling the slides. The uniformity of consecutive liquid smears made by the same operator is often of a low order and between liquid smears made by dif ferent operators can be even worse.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide improved apparatus for dispensing rectangular platelike objects, such as microscope slides.

It is another object of the present invention to provide apparatus for the production of consistent acceptable quality liquid smears on slides.

In accordance with the present invention, apparatus for storing and dispensing rectangular platelike objects, such as slides, having substantially flat upper and lower surfaces and substantially straight end edges is provided which comprises a magazine having a boxlike cavity capable of storing a plurality of such objects in stacked relation, means in said cavity bias ing the topmost object stacked therein to a predetermined position, said magazine also having an opening positioned to permit said topmost object to be withdrawn from said cavity by endwise movement, means for preventing more than said topmost object from being withdrawn from said cavity when said topmost object is withdrawn through said opening, supporting track means adjacent said opening adapted to receive and support one of said objects for longitudinal movement therealong, said track means and cavity being positioned such that one of said objects when placed flat against said track means has its lower surface engaged by an end edge portion of the topmost of any objects stacked in said cavity and forms an acute angle with the upper surface of said topmost object. The end edge portion of said topmost object normally projects slightly above the plane of said track means and is depressable against said biasing means unto said plane by slight downward pressure on said object on said track means.

When a slide having a drop of liquid depending from its lower surface is placed on said supporting track and is moved so that the liquid contacts the upper surface of the slide projecting from the magazine, a liquid capillary meniscus is formed in the acute angular space between the upper surface of the projecting slide and lower surface of the slide on said tract. Subsequent longitudinal movement of the slide on said track along and flat against said supporting track is effective to cause the liquid to be spread out over the lower surface of the supported slide and form a desired liquid smear thereon.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the assembled dispenser of the present invention shown containing slides to be dispensed;

FIG. 2 is a side view with a portion removed of the slide magazine unit removed from the assembly of FIG. 1;

FIG. 3 is a plan view of the magazine unit of FIG. 2;

FIG. 4 is an end view of the magazine unit taken along line 44 of FIG. 2;

FIG. 5 is an end view ofa portion of the magazine unit taken along line 55 of FIG. 2;

FIG. 6 is a partial crosssectional view taken along line 6-6 of FIG. 3 showing the relationship between two slides and a drop of liquid contained therebetween at the start of the preparation ofa liquid smear on one of the slides;

FIG. 7 is a similar view to FIG. 6 showing the partially formed liquid smear; and

FIG. 8 is a side view similar to FIG. 2 showing a portion of the magazine unit having a preferred apparatus configuration.

DESCRIPTION OF THE INVENTION Referring to FIG. 1, the dispenser of the present invention comprises a rectangular boxlike case 10, an attached base 12, and a magazine unit 14, shown in more detail in FIG. 2, which is removably positioned within case 10. Case 10 as shown has vertical sidewalls l6 and 18 and

vertical end walls

20 and 22. A notched portion 17 is cutout of the upper edge of sidewall 16 as shown in FIG. 1. A corresponding notched portion 19 is cut out of sidewall 18 directly opposite the notched portion 17. A slanted slot 21 is also cut through sidewall 16. Base 12 has spaced parallel

upstanding ribs

24 and 26 forming a channel 28 therebetween. Case 10 is positioned within channel 28 and is attached to the base 12 by suitable means. Base 12 also has

flange portions

30 and 32 extending laterally outwardly from

ribs

24 and 26 respectively.

Flange portions

30 and 32 terminate in

longitudinal rib members

34 and 36 respectively of T-shaped cross section.

The removable magazine unit 14 is shown in detail in FIGS. 2, 3 and 4. Magazine unit 14 has parallel

rectangular sidewalls

38 and 40. Sidewall 38 has a rectangular opening 50 formed therein. At opposite side margins of said opening 50 parallel

transverse end walls

42 and 44 are bent inwardly from wall 38 toward sidewall 40 and are joined by welding, for example, to sidewall 40. Along the bottom margin of the opening 50 a transverse bottom plate 46 is bent inward from sidewall 38 toward sidewall 40 and is also attached by welding, for example, to sidewall 40. Bottom plate 46 is provided with an upstanding pin 52 as shown. An angled top plate member 48 has one leg thereof attached to the upper edge portion of end wall 44 and another leg thereof extending parallel to bottom plate 46 as shown. The planes of bottom plate 46 and top plate 48 are normal to the planes of the

end walls

42 and 44. A rectangular boxlike magazine cavity 51 is thus formed having

end walls

42 and 44, bottom plate 46, top plate 48, closed sidewall 40 and an open side 50 formed in sidewall 38. Apertures 53 and 55, as shown in FIG. 2, are formed in sidewall 40 near the two lower corners of cavity 51.

Cavity 51 is tilted with respect to magazine unit 14 so that

end walls

42 and 44 are from about 10 to about 20, preferably about 15, from the vertical, and parallel bottom and

top plates

46 and 48 are from about 10 to about 20, preferably about 15, from the horizontal. A channel-shaped pressure plate 57 having an elongated rectangular substantially flat upper surface portion 54 and depending

end flanges

56 and 58 is located in the cavity, Upper surface portion 54 is substantially parallel to bottom and

top plates

46 and 48 and

end flanges

56 and 58 are substantially parallel to end

walls

42 and 44. As shown in FIG. 5, the flange 58 has a hook portion 59 formed therein. Flange 56 has a similar hook portion. The pressure plate 57 is positioned in the cavity 51 in such manner that the the hook portions of the

end flanges

56 and 58 are adjacent to sidewall 40. The pressure plate 57 is capable of sliding movement within cavity 51 along and between the

end walls

42 and 44 thereof. Pressure plate portion 54 has a vertically depending pin 60 attached thereto.

A single leaf pleated compression spring 62 having an upper aperture 64 and a lower aperture 66 therein is placed in the cavity 51 between portion 54 ofthe pressure plate 57 and bottom plate 46 with the pin 60 of pressure plate portion 54 extending through upper aperture 64 and the pin 52 of bottom plate 46 extending through lower aperture 66. Compression spring 62 thus biases the pressure plate 57 upwardly toward the top plate 48. The cooperation between

pins

52 and 60 and

apertures

64 and 66 tends to keep the pressure plate 57 and compression spring 62 within the cavity 51.

A first supporting track member 68 is located along the top of magazine unit 14 and is attached thereto between

sidewalls

38 and 40 in a manner to be described hereinafter. Member 68 has a generally U-shaped transverse cross section with a flat bottom wall portion 70 and stepped

side portions

72 and 74 shown in FIGS. 1 and 3. The

side portions

72 and 74 are formed with elongated spaced parallel coplanar supporting track surfaces 76 and 78, respectively, elongated spaced parallel coplanar

top surface portions

80 and 82, respectively, and coplanar inclined top surface portions 92 and 94, respec tively. Member 68 has an outer end surface 84 and a narrower inner end surface 86. Inclined top surface portions 92 and 94 intersect the upper surface of bottom portion 70 at inner end surface 86. Coplanar supporting track surfaces 76 and 78 intersect inclined surface portions 92 and 94 along edges 96 and 98, respectively. Track member 68 also has parallel

side surface portions

100 and 102 and converging

side surface portions

104 and 106.

Side surface portions

100 and 102 extend in a longitudinal direction from outer end surface 84 for a distance equal to the longitudinal dimension of

top surface portions

80 and 82, and converging

side surface portions

104 and 106 extend longitudinally from the inner end surface 86 a distance equal to the longitudinal dimension of the inclined surface portions 92 and 94. Elongated longitudinal

parallel slots

88 and 90 extend inwardly along the

undersurface ofside portions

72 and 74 respectively as shown in FIG. 1.

A second supporting track member 108 is also located along the top ofmagazine unit 14 between

sidewalls

38 and 40 and is spaced from and aligned with the first supporting track member 68. Member 108 also has a generally U-shaped transverse cross section, as viewed in FIGS. 1, 3 and 4, with a flat bottom wall portion 110 and stepped

side portions

112 and 114. The

side portions

112 and 114 are formed with elongated spaced parallel coplanar supporting

track surfaces

116 and 118, respectively, and elongated spaced parallel coplanar

top surfaces

120 and 122, respectively. Elongated longitudinal

parallel slots

91 and 93 extend inwardly along the undersurface of

side portions

112 and 114 respectively as shown in FIGS. land 4. Member 108 has an outer end surface 124 and an inner end surface 126. A lower portion ofinner end surface 126 is cut away to form a flat inclined surface 127 which is disposed at an angle offrom about to about 20, preferably about from the supporting

track surfaces

116 and 118. This is shown in FIG. 2. Supporting track surfaces 116 and 118 are slightly widened near the inner end surface 126 by

divergent surfaces

128 and 130 which cut through

side portions

112 and 114 between

top surfaces

120 and 122 and track

surfaces

116 and 118. Track surfaces 76 and 78 of the first supporting tract member 68 are coplanar respectively with

track surfaces

116 and 118 of the second supporting track member 108.

The second supporting track member 108 is conveniently attached to magazine unit 14 in the following manner.

Indent portions

132 and 134 are partially cut out of

sidewalls

38 and 40 respectively and indented as shown in FIG. 4. Appropriate slots, such as slot 136, shown in FIG. 2, are formed in the

indent portions

132 and 134 to receive the opposite end portions ofa flat transversely extending bar 138 having a centrally located threaded aperture 141 formed therein. A screw 140 passing transversely through an appropriate passage in the bottom wall portion of member 108 may be threaded into the aperture 141 to secure member 108 in place. Alternatively, as shown in FIG. 4, screw can be ofa size to pass freely through the aperture 141 and be threaded into a nut 142 positioned below the bar 138. When supporting track member 108 is attached to magazine unit 14, sidewalls 38 and 40 extend into the elongated

longitudinal slots

93 and 91 respectively as shown in FIG. 4.

The first supporting tract member 68 can be attached to the magazine unit 14 in a similar manner. As shown in FIG. 2, with a portion of sidewall 38 removed, a screw 144 is threaded through a threaded aperture in bar 146 the ends of which respectively fit into appropriate slots such as slot 148 ofindent portion 150 of sidewall 40. The opposite end of bar 146 fits into a similar slot (not shown) in sidewall 38. When supporting track member 68 is attached to magazine unit 14, sidewalls 38 and 40 extend into the

elongated slots

90 and 88 respectively ofmember 68.

Supporting

track members

68 and 108 are longitudinally spaced from each other along the top of magazine unit 14 so as to form an opening 152 therebetween which communicates with cavity 51.

Abutment means consisting of a generally Vshaped member 154 of flat spring stock has an upturned abutment portion 158 which extends into opening 152 and terminates adjacent and parallel with the inner end surface 86 of member 68. Member 154 is located as shown in FIG. 2 with one leg thereof underlaying the bottom surface of member 68 and with supporting screw 144 passing through appropriate apertures in member 154. As shown in FIG. 2, a knurled nut 156 is threaded onto screw 144 and compressively engages the V- shaped portion of member 154. Rotational movement of nut 156 adjusts the vertical position of the abutment portion 158, the upper edge of which is preferably adjacent to and slightly below the plane of

coplanar surfaces

76, 78, 116 and 118 of

track members

68 and 108.

The improved dispenser apparatus of the present invention is filled with microscope slides in the following manner. Magazine unit 14 is removed vertically from case 10. Pressure plate 57 is depressed toward bottom plate 46 against the pressure of spring 62 until the hook portions 59 of the

flanges

56 and 58 engage in the

apertures

53 and 55 of sidewall 40 near the bottom of cavity 51. Engagement of the hook portions 59 in said apertures holds the pressure plate in the loading position. A box of clean microscope slides is opened and the clean slides, generally about 6065 slides, are placed into the cavity by stacking them on top of each other in face-to-face relation. During this stacking care should be taken to handle the slides on their edges only, thus minimizing the chances ofplacing fingerprints on the faces of the slides. When the cavity is fully loaded, the hook portions 59 of the pressure plate 57 are disengaged from

apertures

53 and 55 whereupon the compression spring 62 expands, forcing the pressure plate 57 against the slides and forcing the slides against the top plate 48 and against the inclined undersurface 127 of second track member 108. The uppermost slide in the magazine cavity then protrudes into opening 152 and can abut against the portion 158 of abutment member 154. The substantially straight end edge 164 ofthe uppermost slide 160 is then positioned slightly above the plane of

coplanar surfaces

76, 78, 116 and 118. Slide 160 now forms an acute angle of from about 10 to about 20, preferably about 15, with the plane of the above coplanar surfaces. The magazine unit 14 is then placed into case 10 as shown in FIG. 1.

To remove a slide from the dispenser the side surfaces 165 land 166 of the uppermost slide 160, as shown in FIG. 1, are

grasped between two fingers and said slide is pulled up and out. Notches 17 and 19 in

sidewalls

16 and 18 of case enable the side surfaces of the uppermost slide to be exposed for ease in removal. The reduced width of the inner end 86 of track member 68 also facilitates access to the slides. As long as the upper edge portion 158 of abutment member 154 is located along the leading end surface 163 of the slide 160 while it is stored in the magazine, it will abut against the next below slide 162 and prevent it from being removed during withdrawal of slide 160 from the dispenser. Abutment member 154 is adjusted by nut 156 to achieve this condition and such adjustment permits slides of various thicknesses to be used in the improved dispenser.

In FIG. 2, slide 160 is shown being withdrawn over the top of the abutment portion 158 of member 154 while the remaining slides are maintained within the magazine. This apparatus thus provides means for dispensing slides one at a time. Once slide 160 is completely removed, spring 62 will force the next slide 162 into the uppermost position for subsequent removal. This procedure is repeated every time a slide is withdrawn from the dispenser. The slanted slot 21 in sidewall 16 of case 10 exposes a portion of the interior of magazine 14 to view and allows one to determine how many slides are available for use before the magazine needs refilling.

This improved dispenser apparatus can be used to prepare uniformly desirable liquid smears on slides, and in such use, the

coplanar surfaces

76, 78, 116 and 118 of supporting

track members

68 and 108 provide a supporting track which engages longitudinal edge portions only of the lower surface of a slide placed therein. As shown in FIG. 6, a slide 168 having a liquid drop, such as a blood drop, applied to one surface thereof generally along the longitudinal centerline is placed on the above-described supporting track with the liquid-bearing surface thereof facing downwardly and with the liquid drop on the right hand side of the leading edge 164 of uppermost slide 160 stored in the magazine, as viewed in said FIG. The leading edge 164 of uppermost slide 160 is then in contact with lower surface 170 ofslide 168. Slide 168 is then moved to the left, as viewed in FIG. 6, until the depending liquid drop contacts slide 160 and forms a liquid capillary meniscus 172 in the acute angular space formed between the protruding slide 160 and the lower surface 1700f the supported slide 168. Slide 168 is then moved to the right, as shown in FIG. 7, with the simultaneous application of a light downward pressure sufficient to depress the leading edge 164 of the uppermost slide 160 into substantially the same plane as the supporting

surfaces

76, 78, 116 and 118. Such longitudinal movement of the slide 168 spreads out the liquid along lower surface 170 thereof and forms a desirable liquid smear 174. The slanted surfaces 128 and 130 of member 108 guide the slide 168 onto the supporting

track surfaces

116 and 118 during such slide movement. This apparatus is capable of producing uniformly acceptable liquid smears, because it provides a substantially constant angle between the lower surface of the supported slide and the upper surface of the coacting protruding slide. This substantially constant angle, which is predetermined to be from about 10 to about preferably about 15, has been found to be most satisfactory for the production of acceptable liquid smears.

Slide 168 is generally moved to the right, as viewed in FIG. 7, for a sufficient distance to enable all of the liquid contained in the acute angular space between

slides

168 and 160 to be spread along undersurface 170 of slide 168. In the event that all the liquid is not spread along slide 168, any liquid residue remaining on the upper surface of slide 160 will not interfere with subsequent use of slide 160 so long as it is withdrawn from the dispenser and its leading edge portion is not subsequently employed for the production of another liquid smear.

Once the liquid smear is applied to slide 168, it is then removed from the supporting track and dried. The configuration of the apparatus of the present invention also aids in drying of applied smears. To this end the slide 168 bearing the liquid smear can be leaned against a sidewall of the case 10 with its lower end portion rested against a longitudinal rib 34 of the base 12. This is shown in phantom in FIG. 1.

A preferred form of the abutment means is shown in FIG. 8. A threaded shaft 49 is fixed to and projects generally normal to cavity end wall 42. A bowed spring member 47 having substantially flat opposite end portions 41 and 45 and a generally centrally located aperture 39 is positioned with said end portions in contact with the end wall 42' and the threaded shaft 49 extending through aperture 39. Lower end portion 45 of spring member 47 is attached to the end wall 42' near the lower end thereof by welding, for example. Upper end portion 41 of spring member 47 has an outer edge 35 positioned subjacent the plane of supporting track 78' of track member 68'. A knurled nut 33 is threaded onto shaft 49 and compressively engages spring member 47 as shown. As nut 33 is rotated in wardly along the shaft 49, it depresses spring member 47 and causes edge 35 to move upward as shown in FIG. 8. If nut 33 is rotated so that it moves outwardly along the shaft 49, it relaxes member 47 and allows edge 35 to move downward. This movement of outer edge 35 achieves the same function as similar movement of outer edge portion 158 of abutment member 154 described above.

What I claim is:

1. Apparatus for storing and dispensing rectangular platelike objects, such as slides, having substantially flat upper and lower surfaces and substantially straight end edges, which apparatus comprises a magazine having a boxlike cavity capable of storing a plurality of such objects in stacked relation, means in said cavity biasing the topmost object stacked therein to a predetermined position, said magazine also having an opening positioned to permit said topmost object to be withdrawn from said cavity by endwise movement, means for preventing more than said topmost object from being withdrawn from said cavity when said topmost object is withdrawn through said opening, supporting track means adjacent said opening adapted to receive and support one of said objects for longitudinal movement therealong, said track means and cavity being positioned such that one of said objects when placed flat against said track means has its lower surface engaged by an end edge portion of the topmost of any objects stacked in said cavity and forms an acute angle with the upper surface of said topmost object.

2. Apparatus according to claim 1 wherein said end edge portion of said topmost object normally projects slightly above the plane of said track means and is depressable against said biasing means into said plane by slight downward pressure on said object on said track means.

3. Apparatus according to claim 1 wherein the acute angle between the upper surface of the topmost object in the cavity and the lower surface of an object placed flat along said supporting track means is from about 10 to about 20.

4. Apparatus according to claim 3 wherein the acute angle is about 15.

5. Apparatus according to claim 1 wherein the means for preventing withdrawal of more than the topmost object from said cavity is adjustable to compensate for variations in object thickness.

6. Apparatus according to claim 1 wherein said cavity is defined by a bottom plate portion, a top plate portion, and two substantially parallel end wall portions which have planes which are substantially normal to the planes of the bottom and top plate portions, and said biasing means comprises a pressure plate having a substantially flat upper surface and which is capable of sliding movement along and between said end wall portions and a compression spring located between said bottom plate portion of said cavity and the pressure plate, the objects stored in said cavity being located between the substantially flat upper surface of the pressure plate and the top plate portion of the cavity, the pressure of said compression spring against the pressure plate being operable to force the there is releasable retention means for retaining the pressure plate in a position in which the compression spring is substantially fully compressed to thereby facilitate insertion ofobjects into said cavity

Claims

3. Apparatus according to claim 1 wherein the acute angle between the upper surface of the topmost object in the cavity and the lower surface of an object placed flat along said supporting track means is from about 10* to about 20*.

4. Apparatus according to claim 3 wherein the acute angle is about 15*.

6. Apparatus according to claim 1 wherein said cavity is defined by a bottom plate portion, a top plate portion, and two substantially parallel end wall portions which have planes which are substantially normal to the planes of the bottom and top plate portions, and said biasing means comprises a pressure plate having a substantially flat upper surface and which is capable of sliding movement along and between said end wall portions and a compression spring located between said bottom plate portion of said cavity and the pressure plate, the objects stored in said cavity being located between the substantially flat upper surface of the pressure plate and the top plate portion of the cavity, the pressure of said compression spring against the pressure plate being operable to force the topmost stored object against said top plate portion and position said end edge of said topmost stored object slightly above the plane of the supporting track means.

7. Apparatus according to claim 6 wherein the cavity has an open side for insertion of objects into said cavity and wherein there is releasable retention means for retaining the pressure plate in a position in which the compression spring is substantially fully compressed to thereby facilitate insertion of objects into said cavity.