US2480493A - Printing bed for screen-process printing machines - Google Patents

Description

1949- L. MARTIN 2, 0,493

PRINTING BED FOR SCREEN-PROCESS PRINTING MACHINES Filed March 23, 1948 Patented Aug. 30, 1949 OFFICE PRINTING BED FOR SCREEN-PROCESS PRINTING MACHINES Louis Martin, Brooklyn, N. Y.

Application March 23, 1948, Serial No. 16,576

This invention relates to printing by the screen process and more particularly to an improved printing bed forming a part of a screen-process printing machine.

In machines of the type contemplated by the invention, goods are printed by means of One or more screens beneath which the goods are intermittently moved while carried on a movable printing bed.

The object of the present invention is to improve the printing bed which carries the goods along beneath the screens, the bed of the invention being so constructed and operated as to insure accurate positioning of the goods successively beneath a plurality of screens so that accurate registration of successive printings may be obtained. More specific objects are to provide a bed so constructed as to eliminate any side or end play of the surface to be printed. Other objects will hereinafter appear.

11 Claims. (Cl. 101407) The invention will best be understood from I parts of a screen-process printing machine, shown more or less diagrammatically;

Fig. 2 is a detailed perspective view showing the novel printing bed, its driving means and portions of associated parts;

Fig. 3 is a side elevation taken on the line of Fig. 2;

Fig. 4 is a fragmentary detailed perspective View of one of the ribs which is used on the driving means; and

Fig. 5 is a fragmentary detail showing another form of protuberance which may be applied to the surface of the driving means.

Referring to Fig. l, the screen printing machine comprises a supporting framework III which may be formed of jointed pipe or the like upon which is supported a flat-topped table Ii. Mounted above the table is a screen supporting framework 82 in which are carried, by any suitable clamping means (not shown), one or more printing screens having rectangular frames Id.

The supporting framework 12 is adapted to be intermittently lifted upwardly away from the table II by means of cams [5 which engage lugs i6 attached to frame l2, the cams being driven by chains l8 driven from a suitable source of motive power Hi. The side of frame I 2 opposite the side which is lifted by the cams i5 is preferably hinged to the table I i. It will be understood that any movement of frame i2 is transmitted to the screen frames l4 through the means by which they are connected together.

Extending across the top of table II, longitudinally thereof, is an endless movable belt, generally indicated at 20, forming part of the printing bed. This belt moves on and is supported at its ends by rotatable members carried on the shafts 2| and 22. In the embodiment shown, the belt is transported by intermittent rotation of shaft 22 through the medium of suitable driving mechanism indicated at 24 and powered fromthe source l9 through a crank 25. It is unnecessary to describe this driving mechanism in detail but it should be understood that it brings about intermittent rotation of shaft 22 during the periods when the framework I2 is raised away from table H. Details of the driving mechanism are described in my copending application Ser. No. 701,927, filed October 8, 1946.

The lower reach of the belt 20 may be supported at each side by endless belts 26 supported on rollers 21 rotatably mounted on elements of the framework Ill. Belts 2B are of such Width that they contact only the ends of the slats 38 and not the blanket 46. hereinafter described.

The fabric to be printed is fed onto the belt 20 at the right-hand end from suitable feeding mechanism 30 and is taken off at the left-hand end onto take-up mechanism 3 I, the fabric being indicated at 32.

The particular structure of. the belt 20, which is a principal feature of the invention, will now be described. This belt comprises a pair of endless metal bands 34 which pass over pulleys 35 mounted on shaft 22 and similar pulleys mounted on shaft 2 l.- Preferably these pulleys have slightly cambered supporting surfaces to prevent any tendency to shift the bands laterallyt Extending transversely of the bands 34 and secured thereto as by rivets.36 are slats 38 preferably made of some light metal alloy such as duraluminum. These slats are uniformly dimensioned and evenly spaced on the bands 34 with their ends in alignment and parallel to the edges of the bands. The slats slide over the flat surface of table I l, which is preferably provided with a sheet metal covering, and is preferably relieved as shown at 3-9 to accommodate the bands. Fastened to the top of table II in abutting relation to the ends of the slats 38 are .guide strips 40 the vertical surfaces 4| of which have just suflicient clearance with the slats 38 to permit the free movement of the latter. Strips 40 may be adjustably mounted on the table top so that this clearance may be kept to a minimum. The materials of the slats and the strips is selected so that there will be a minimum of wear on either of these elements. It has been found that if the strips are made of glass with the surfaces ll polished, wear on the ends of the slats is practically eliminated and the strips, being harder than the slats. do not wear at all.

Secured to the upper surface of the slats, as shown in Fig. 2, is an endless blanket ,II which is preferably made of a solid resilient rubber composition which is adhesively secured to the slats 38 by any of the well known adhesives which are known to give a good bond to the material of which the slats are made.

The fabric to be printed is, as is customary in this art, adhesively secured to the surface of the blanket 44. Preferably this surface is rough as it has been found that the non-drying adhesive coating which is applied thereto has a superior degree of adhesion and can be coated with less likelihpod of air bubbles being formed therein if this surface is rough rather than smooth.

In order to transport the belt consisting of the bands 34, slats 38 and blanket 44, a driving drum is is mounted on shaft 22 between the pulleys 35. This drum may be formed of wood and is provided with evenly spaced, parallel, axial grooves 48. In these grooves at each end of the drum are mounted driving ribs 49 having the configuration shown in Fig. 4. The bottoms of these ribs are shaped to fit. the grooves 48 and their upper surfaces are curved as shown so as to be capable of entering the spaces 50 between the slats 38 and of contacting the opposed edges of adjacent slats when they are positioned tangentially of the drum 46. These ribs 49 may be fastened to the drum by means of screws 5| placed at intervals along their length in the manner shown in Fig. 4.

It is contemplated that instead of the ribs 49 the drum may be provided with rows of screws or nails having specially shaped heads and driven into the drum as shown in Fig. 5 wherein the drum is indicated at 46c and the nails or screws at 52. In this case, the drum surface may be smooth.

Either or both of the shafts 2| and 22 may be mounted in adjustable bearings, making possible perfect alignment of these shafts and the taking up of slack in the belt 20.

It will be evident from the foregoing description that the movable portion of the printing bed consists of a rigid, inelastic base structure which cannot warp, twist, shrink or swell and which is prevented from any lateral shifting by means of the guide strips 40. The driving means are such that the bed will be accurately and uniformly transported through the distances determined by the adjustment of the driving mechanism 24 without any possibility of longitudinal end play. It is thus possible to print on material adhered to the surface of blanket 44 with very great accuracy and with perfect registration of successive printings.

It is to be understood that the invention is not limited to the details of the embodiment herein disclosed for purposes of illustration but is to be construed broadly within the purview of the claims.

What is claimed is:

1. A printing bed for a screen-process printing machine comprising, a pair of parallel endless metal bands, pulleys supporting said bands at their looped ends, evenly spaced and uniformly dimensioned slats extending transversely of said bands and fastened thereto with their ends in alignment, a continuous blanket secured to the surface of said slats, a table having a flat surface positioned to support the upper reach of slats, guide means extending longitudinally of said table surface adapted to prevent lateral movement of said slats, and driving means coaxial with said pulleys at one end of the bands adapted to move said bands and the slats carried thereby along said table.

2. A printing bed according to claim 1 wherein said guide means consists of elements extending longitudinally of said table which have vertical surfaces adapted to engage the opposite ends of said slats.

3. A printing bed according to claim 1 wherein said blanket is adhesively secured to said slats.

4. A printing bed according to claim 3 wherein said slats are made of aluminum alloy and said blanket is made of a rubber compound.

5. A printing bed according to claim 4 wherein said blanket has a rough surface.

6. A printing bed according to claim 1 wherein said pulleys have cambered band-supporting surfaces.

7. A printing bed according to claim 1 wherein said driving means comprises a drum having axially aligned protuberances adapted to enter the spaces between said slats.

8. A printing bed according to claim 7 wherein said protuberances are of such size as to engage the opposite edges of two adjacent slats when they are positioned tangentially of said drum.

9. A printing bed according to claim 7 wherein said protuberances are in the form of ribs adapted to :sngage substantial extents of the edges of said sla 10. A printing bed according to claim 7 wherein said protuberances are in the form of separate slat-engaging teeth arranged on said drum in rows.

11. A movable endless printing bed for a screenprocess printing machine comprising, a pair of laterally spaced parallel endless metal bands, a pair of pulleys supporting said bands at each of their looped ends, an endless series of evenly spaced uniformly dimensioned slats extending transversely of said bands and fastened thereto with their ends in alignment, a continuous blanket adhered to the surface of said slats, a table having a flat surface positioned between the upper and lower reaches of said bands to support the slats on the upper reach, parallel guide strips on said table surface positioned to abut the opposite ends of said slats, and a driving member coaxial with one pair of said pulleys comprising a cylindrical drum having longitudinally aligned protuberances on its surface which are adapted to enter the spaces between said slats as they pass over said drum.

LOUIS MARTIN.-

No references cited.

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