FIELD OF THE INVENTION

The present invention generally relates to devices used for printing and/or cutting sheet material articles, and specifically to vacuum beds or tables used to secure the articles while being printed on and/or cut.

BACKGROUND OF THE INVENTION

Vacuum beds are frequently used to hold sheet material articles such as, for example, fabrics, paper, films, and the like, so that they may be printed on and/or cut into shapes. The vacuum beds, which may be stationary or movable (for example, a conveyor) typically, comprise a flat surface (plate) with holes. A vacuum pump is communicated with the underside of the vacuum bed, being adapted to produce vacuum forces which are applied to the article through the holes in the plate. The vacuum forces, which create a suctioning action in the holes, draw the article against the flat surface, and in this manner, the article is held in place.

Vacuum beds are well known in the art- see e.g., U.S. patent No. 6,422,548. A problem frequently encountered when using vacuum beds is that a size of the article to be printed on and/or cut is smaller than a hole area of the plate, and not all holes are covered by the article. Suction of air through the uncovered holes causes reduction of the vacuum forces applied to the holes which are covered by the article, making the article less secure. One solution has been to manually cover the uncovered holes with a plastic tape material, but this solution has shown to be problematic as it may be a time consuming process. Another solution comprises means to adjust the hole area of the plate (vacuum zone) such as, for example, by using movable channels, gates, and the like, to reduce the length and/or width of the active vacuum zone. This solution has also shown to be problematic as frequently the adjustment is manually performed, which may also be relatively time consuming. Even if the adjustment is automatically performed, a problem may arise if the size of the article to be printed on and/or cut is varied frequently as the vacuum zone must be continuously adjusted according to the size of the article, which may also be a time consuming process.

It is therefore the prime object of the invention to overcome these and other drawbacks of the conventional vacuum beds.

It is a further object of the invention to provide a novel vacuum bed which does not require that the area of the vacuum zone be adjusted according to the size and shape of the article.

It is still a further object of the invention to provide for a vacuum bed wherein vacuum forces are applied only to holes in the plate which are actually covered by the article, thereby eliminating the need to adjust the vacuum zone according to the article.

SUMMARY OF THE INVENTION

Provided according to the invention is a vacuum bed for securing an article, the vacuum bed comprising a plate comprising, a plurality of holes adapted to have one or more holes covered by the article; a vacuum distribution element adapted to distribute vacuum forces to the plurality of holes; and a valve connecting each hole of the plurality of holes to the vacuum distribution element and adapted to regulate the vacuum forces in the hole. Regulating the vacuum forces in the hole comprises allowing the vacuum forces to act in the hole when covered by the article, and preventing the vacuum forces from acting in the hole when not covered by the article.

In some embodiments, each valve comprises a movable plug adapted to prevent transfer of vacuum forces through the valve. Further comprised in each valve is a spring adapted to push the movable plug and further adapted to be compressed by the movable plug. Additionally comprised in each valve are one or more slots adapted to transfer vacuum forces from a first side of the movable plug to an opposing second side of the movable plug.

In some embodiments, each valve comprises a spring disc adapted to prevent transfer of vacuum forces through the valve. Optionally, the spring disc comprises a circular shape. Optionally, the spring disc comprises a non-circular shape.

Further provided according to the invention is a method for securing an article to a vacuum bed, the method comprising covering one or more holes of a plurality of holes comprised in a plate with the article, distributing vacuum forces to the plurality of holes; and regulating the vacuum forces acting in each hole of the plurality of holes. Regulating the vacuum forces acting on each hole of the plurality of holes comprises allowing the vacuum forces to act in the hole when covered by the article, and preventing the vacuum forces from acting in holes not covered by the article.

In some embodiments, the method further comprises preventing transfer of vacuum forces through a valve. Further comprised is pushing a movable plug, and compressing the spring. Additionally comprised is transferring vacuum forces from a first side of the movable plug to an opposing second side of the movable plug.

Provided according to a still further aspect of the invention is a system for printing, and/or cutting, comprising a vacuum bed for securing an article comprising a plate comprising a plurality of holes adapted to have one or more holes covered by the article; a vacuum distribution element adapted to distribute vacuum forces to the plurality of holes; and a valve connecting each hole of the plurality of holes to the vacuum distribution element and adapted to regulate the vacuum forces in the hole; and a vacuum pump.

BRIEF DESCRIPTION OF THE DRAWINGS

These and additional constructional features and advantages of the invention will become more clearly understood in the light of the following description of several preferred embodiments thereof given by way of example only, with reference to the attached drawings, wherein -

Rg. 1 is a schematic block diagram of a system for printing and/or cutting a sheet material article, in accordance with a preferred embodiment of the invention; Fig. 2 is a schematic top view of the vacuum bed of Fig.l, in accordance with a preferred embodiment of the invention;

Fig. 3A is a schematic cross-sectional view A-A of the vacuum bed of Fig. 1, in accordance with a preferred embodiment of the invention; Fig. 3B is a schematic exploded view of a portion of the vacuum bed of

Fig. 1, in accordance with a preferred embodiment of the invention;

Fig. 4A is a schematic cross-sectional view B-B of the vacuum bed of Fig. 1 with an uncovered hole, in accordance with a preferred embodiment of the invention; Fig. 4B is a schematic cross-sectional view B-B of the vacuum bed of

Fig. 3A with a covered hole, in accordance with a preferred embodiment of the invention;

Fig. 5A is a schematic cross-sectional view A-A of the vacuum bed of Fig. 1, in accordance with another preferred embodiment of the invention; Fig. 5B is a schematic exploded view of a portion of the vacuum bed of

Fig. 1, in accordance with another preferred embodiment of the invention;

Fig. 6A is a schematic cross-sectional view B-B of the vacuum bed of Fig. 5A with an uncovered hole, in accordance with another embodiment of the invention; and Fig. 6B is a schematic cross-sectional view B-B of the vacuum bed of

Fig. 5A with a covered hole;

DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS In Hg. 1 is shown a schematic block diagram of a system 1 for printing and/or cutting a sheet material article (not shown), the system comprising a vacuum bed 10, a vacuum pump 11, and other system equipment 12 as may be required by the system to print on and/or cut the sheet material article. Vacuum bed 10 is adapted to hold the sheet material article tight during printing and/or cutting operations, by applying vacuum forces only in areas covered by the article, and by preventing the application of air suction in areas not covered by the article. The vacuum forces are created by vacuum pump 11 which may be of any conventional type. Vacuum bed 10 is shown in greater detail in Hg. 2 which is a schematic top view of the vacuum bed; in Hg. 3A which is a schematic cross- sectional view A-A of the vacuum bed; and in Rg. 3B which is a schematic exploded view of a portion of the vacuum bed.

Vacuum bed 10 comprises a flat surface such as plate 100 with holes 102 traversing through the plate, a vacuum distribution element including connection ports 105 for each hole 102, and valves 106 connecting each hole to a vacuum supply conduit 104.

Generally, the article which is to be printed on and/or cut is laid flat unto plate 100. Depending on the size and shape of the article, one or more holes 102 may be covered, and optionally, all the holes may be covered. Securing of the article to prevent movement is generally done by applying vacuum forces through (in) hole 102 such that a portion of the article covering the hole experiences a pulling action into the hole (suction). A combined pulling of all holes 102 holds the article in place. The vacuum forces reach holes 102 through valves generally designated 103, which are adapted to allow the vacuum forces to act in a hole 102 when it is covered by the portion of the article, and to prevents the vacuum forces from acting in a hole when it is not covered by a portion of the article all in a manner now to be explained in conjunction with Figs. 3B, 4A and 4B.

Valve 103 comprises a cylindrical valve chamber 106 having a bore 109 with axial, peripheral slots ill. Note that the length of the slots 111 (three in the example shown in Hg. 3B) is less than the depth of the bore 106. The bore 109 is extended by passage 110 connecting the valve 103 to the vacuum source.

A movable plug 107 is housed in the bore 109. The top of the plug 107 is slotted or otherwise deformed to form air passages 107A. The total height of the plug is jess than the length of slots 111. The movement of movable plug 107 inside bore 109 is regulated by a spring 108, the spring being adapted to compress when the movable plug is pushed towards the bottom of bore 109 (Hg. 4A) and seals off the communication with the vacuum system.

Spring 108 normally presses movable plug 107 towards hole 102 (Hg. 4B), allowing the vacuum forces to reach hole 102, namely to bypass around the movable plug 107 through slots 111.

When hole 102 is not covered (Hg. 4A), air enters the hole into the bore section 109B and a pressure differential is created between the top side of movable plug 107 and the bottom side thereof, namely atmospheric pressure acting of the top side while a vacuum (sub-pressure) created by the vacuum forces acts on the (projected) area of the bottom surface. This pressure differential causes the movable plug 107 to be pushed in a direction towards and through the passage 110 (spring 108 is compressed), sealing off the valve 103. However, once the hole 102 is covered, e.g. by a portion of sheet 13 to printed upon, the pressure on both sides of movable plug 107 is substantially equal (pressure differential is eliminated) and spring 108 pushes movable plug 107 against the perforated bottom of plate 100. In some embodiments the pushing action of spring 108 occurs as the spring returns to its natural state. Elimination of the pressure differential is achieved by allowing vacuum forces entering through the passage 110 into bore section 109A, to bypass movable plug 107 through slot 111 and reach hole 102, creating a pulling effect on article 13.

In another preferred embodiment, valve 103 may be replaced by a valve 156, as shown in Figs. 5A and 5B. Valve 156 comprises a spring disc 158 housed in a bore 159 within the valve, the spring disc adapted to prevent a transfer of vacuum forces from vacuum distribution system to hole 102 when the hole is uncovered. Spring disc 158 is further adapted to allow transfer of vacuum forces from vacuum distribution element 101 to hole 102 when the hole is covered. In some embodiments, spring disc 158 is adapted to be pushed towards the bottom of chamber 159 by the pressure differential created as a result of the air at atmospheric pressure entering through hole 102 (when the hole is not covered) and pushing on one side of the disc, and by the sub-pressure created by the vacuum forces acting on the other side of the disc. When pushed to the bottom of bore 159, passage 160, through which the vacuum forces enter valve 156 from conduit 105, is sealed by spring disc 158. Spring disc 158 is further adapted, by means of a spring-like action, to return to a natural, open state when there is no pressure differential between the two sides of the disc, the spring-like action pushing the spring disc away from the bottom of valve bore 159. In its natural state, spring disc 158 allows an opening for the vacuum forces entering passage 110 to enter into the bore 159 and reach hole 102. In some embodiments, spring disc 158 is attached inside valve 156 by means of a pin 158A inserted through an opening 158B in the spring disc. In some embodiments, spring disc 158 may comprise a circular shape. Optionally, spring disc 158 may comprise a non-circular shape.

Operation of vacuum bed 10 comprising valve 156 may be appreciated with reference to Figs. 6A and 6B, which show the position of spring disc 158 inside valve 156 when hole 102 is not covered by an article 13 (Hg. 6A), and when covered by article 13 (Hg. 6B), respectively. When hole 102 is not covered, air under atmospheric pressure enters the hole into chamber 109 and exerts a pushing force on spring disc 158 in a direction towards bore 160. The pressure differential due to the air on one side of spring disc 158 and to the vacuum forces in passage 160 causes spring disc 158 to pivot downwards, sealing off the passage. Air is then prevented from flowing into vacuum generating system. When hole 102 is covered, the pushing force of the air under atmospheric pressure is eliminated and spring disc 158 pivots to its natural state, away from passage 160. Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can effectuated without departing from the true spirit and scope of the invention as defined in and by the appendent claims.