DE102017218186A1 - belt conveyors - Google Patents

Abstract

A belt conveyor comprises a vacuum belt (2) for transporting articles in a transport direction, a belt guide (21) with a blown air system (16) for producing an air cushion for air bearing of the vacuum belt (2) and a first control circuit for controlling the air cushion.

Description

The present invention relates to a belt conveyor with a vacuum belt for transporting articles in a transport direction and with a belt guide with a blown air system for producing an air cushion for air storage of the vacuum belt.

In belt conveyors with vacuum belt, the articles are held by suction air which flows through a perforation in the vacuum belt.

It is known to minimize the friction between this and a tape guide by an air bearing of the vacuum band.

For example, in US 3,889,801 a belt conveyor with a belt guide is described, which has two rows of blown air holes for generating an air cushion under the vacuum belt.

In DE 10 2015 213 406 A1 a belt conveyor with a perforated vacuum belt is described. High velocity air creates an air bearing between the vacuum belt and a belt guide to reduce or eliminate friction therebetween. In order to store information relating to certain variable speeds for high speed air introducing and exporting devices, data storage devices are used. The variable speeds for the high-speed air circulating through the system may be e.g. B. according to a composition of articles which lie on the perforated vacuum belt.

The invention has for its object to provide a further belt conveyor.

This object is achieved by a belt conveyor with the features of claim 1. The belt conveyor according to the invention comprises a vacuum belt for transporting articles in a transport direction, a belt guide with a blown air system for producing an air cushion for air storage of the vacuum belt and a first control circuit for controlling the air cushion.

The belt conveyor according to the invention has a high reliability and is wear-resistant under all circumstances. The quality of the air storage is no longer affected by disturbances. The invention is particularly advantageous with belt conveyors having a long vacuum belt and a long belt guide to thereby transport the articles past a large number of processing stations. With a long vacuum belt and a long belt guide, the sliding surfaces are large and must be reckoned with high friction. In addition, the invention is advantageous for use in a printing press. In printing presses, the print quality depends on the synchronization of the vacuum belt. In the invention, a stable air bearing is ensured by the first control loop and thus problems caused by high friction and synchronization fluctuations are otherwise avoided. The high number of processing stations mentioned above may be formed in the printing machine by printing stations for different colors and by dryers.

Various developments of the belt conveyor according to the invention are possible.

In a development that is advantageous with regard to determining the sliding friction of the vacuum belt, the first control loop has a sensor for measuring a movement or loading of the belt guide. This sensor can be a force transducer.

In a development which is advantageous with regard to a connection of the blown air system to a central compressed air supply, a pressure control valve which controls the supply of blown air into the blown air system is controlled by the first control loop. It is advantageous that no additional compressed air source with variable overpressure is required for the belt conveyor and in the central compressed air supply, the pressure can be kept constant.

In an advantageous with regard to the prevention of mutual interference of blown air and speed controls development, a motor for driving the vacuum belt and a second control circuit for controlling the motor are available.

With regard to the measurement of the deflection of the tape guide as a measure of their load advantageous development, the tape guide is movably mounted in a movement storage. The movement bearing can allow a movement or movement component of the tape guide in the transport direction or parallel to it. For example, the movement bearing pivot lever for supporting the tape guide include, wherein the thus enabled pivotal movement of the tape guide has a parallel to the transport direction movement component. The motion bearing may include one or more return springs which return the strap guide against its deflection due to belt friction. For example, one or more coil springs can engage the tape guide or the pivoting levers. The motion bearing may include one or more guides for guiding the movement of the tape guide. For example, there may be a linear guide or the guides can be formed by the hinges of the aforementioned pivot lever. Advantageously, a variant in which the movement bearing leaf springs comprises. The leaf springs form in functional unit return springs and guides (especially: bending joints) for the tape guide.

In an advantageous with regard to the cooling of the vacuum belt development, the tape guide Blasluftnuten with vents. Through the vents overheating of the vacuum belt is avoided.

In a further development of the belt conveyor is part of a digital printing machine, the articles are printed sheets. Here, the vacuum belt can convey the sheets on a series of inkjet printheads, which print the transported sheets.

• 1 die Draufsicht auf ein Vakuumband und eine Bandführung eines Bandförderers,
• 2 den Querschnitt durch das Vakuumband und die Bandführung gemäß der Schnittlinie II-II in 1,
• 3 die Seitenansicht des kompletten Bandförderers einschließlich seiner Bandrollen, und
• 4 einen elektronischen Regelkreis zum Regeln eines Luftlagers für das Vakuumband.

Further developments will become apparent from the following description of a preferred embodiment and the accompanying drawings, in which:

• 1 the top view of a vacuum belt and a belt guide of a belt conveyor,
• 2 the cross section through the vacuum belt and the tape guide according to the section line II-II in 1 .
• 3 the side view of the complete belt conveyor including its tape rolls, and
• 4 an electronic control circuit for controlling an air bearing for the vacuum belt.

In the 1 to 3 is a belt conveyor 1 shown as part of a digital press 38 for example for inkjet printing is. The from the belt conveyor 1 funded article 3 are printed sheets. The belt conveyor 1 includes a perforated vacuum belt 2 on which the transported items 3 be held by suction. That's the article 3 holding vacuum acts through the perforation in the vacuum belt 2 , The vacuum belt 2 runs around a drive roller 4 and a pulley 5 around. An electric motor 6 drives over the drive roller 4 the vacuum belt 2 at. Between the drive roller 4 and the pulley 5 is a band guide 21 arranged, which is designed as a pneumatic box. The band guide 21 has a tape guide surface 24 , on the transport area of the vacuum belt 2 slides. The tape guide surface 24 is located on a cover plate 23 that with a base plate 22 is composed. In the tape guide surface 24 are Saugluftnuten 15 and blown air grooves 20 introduced alternately. The suction air grooves 15 and the blown air grooves 20 run in the transport direction T of the vacuum band 2 , The band guide 21 includes a suction air system 11 for applying the Saugluftnuten 15 with suction air S , The suction air system 11 is connected to a vacuum generator, which is not shown in the drawing. In addition, the tape guide includes 21 a blast air system 16 for applying the Blasluftnuten 20 with blowing air B , The blowing air system 16 is via a pressure control valve 26 connected to a compressed air generator, which is not shown in the drawing. The suction air system 11 is in the base plate 22 introduced and includes a central vacuum connection 12 and parallel connected suction air distribution lines 13 , The blowing air system 16 is also in the base plate 22 introduced and includes a compressed air connection 17 and a blast air manifold 18 between the suction air distribution pipes 13 lies. The suction air distribution pipes 13 and the blast air distribution line 18 run transversely to the transport direction T , At the interfaces of the suction air distribution lines 13 with the Saufluftnuten 15 there are entrance holes 14 in the cover plate 23 are introduced. Through the inlet holes enters the suction air S into the suction air system 11 one. The entrance holes 14 are each in a row along the suction air distribution lines 13 arranged and put between this and the Saugluftnuten 15 air-conducting connections ago. In every Saugluftnut 15 opens an entrance hole 14 each suction air distribution line 13 , At the interfaces of the blast air distribution line 18 with the blown air grooves 20 there are exit holes 19 in the cover plate 23 are introduced. Through the exit holes 19 enters the blowing air B from the blown air system 16 out. The exit holes 19 are like the entrance holes 14 Through holes. The exit holes 19 are in a row along the blast air distribution line 18 arranged and put between this and the Blasluftnuten 20 air-conducting connections ago. At the end of the blast air grooves 20 these each have a vent opening 25 on, for cooling the vacuum band 2 serves. The vent 25 can be in the wall or the bottom of the respective Blasluftnut 20 be introduced. Through the vents 25 is the blown air flow in the Blasluftnuten 20 elevated. The from the vacuum belt 2 heated blowing air B in the blast air grooves 20 flows through the vents 25 into the environment.

The vacuum belt has on his, the article 3 carrying outside a raster relief 7 that made of suckers 8th and a projecting bounding grid 9 consists of which the suckers 8th are each surrounded. The articles 3 lie on the boundary grid 9 and are held on it by the negative pressure in the suction cups 8th prevails. The suckers 8th are square and the raster relief has a grid width that is transverse to the transport direction T to be measured center distance of Saugluftnuten 15 equivalent. In every suckling cup 8th opens a central passage bore 10 which are in the bottom of the suction cup 8th is introduced. The passage holes 10 form rows that are directly above the Saugluftnuten 15 along this in the transport direction T run. About the passage holes 10 enters the suction air S from the suckers 8th in the Saugluftnuten 15 , The vacuum belt 2 is a metal band made of steel and the grid relief 7 is an etched structure. The blown air grooves 20 are closed areas on the inside of the vacuum belt 2 across from. The from the Blasluftnuten 20 exiting blowing air B forms between the vacuum belt 2 and the tape guide surface 24 a carrying air cushion or air cushion 35 (see. 4 ), which is an air bearing for the vacuum belt 2 forms. Through the air cushion 35 becomes the circulating vacuum belt 2 worn and its sliding friction with the tape guide surface 24 minimized or eliminated.

The band guide 21 is in a movement storage 27 in the transport direction T movably mounted. The movement storage 27 includes leaf springs 28 , which together form a so-called parallel link. Covered by the visible in the drawing front parallel link is a rear parallel link, which is of the same design as the front parallel link.

A sensor 29 serves to measure the movement of the tape guide 21 in the transport direction T , The sensor 29 is a force transducer, especially a so-called load cell, and between the tape guide 21 and a frame arranged.

4 shows that the sensor 29 Part of a first control loop 30 is that to the air cushion 35 and thus the frictional force between the vacuum belt 2 and the band guide 21 to a constant setpoint - the desired frictional force 31 - serves. The first control loop 30 is a closed loop and electronic design. For determining a control deviation 32 becomes the present actual friction force 36 determines which is proportional to the signal of the sensor 29 is. A change in the actual friction force 36 leads to the control deviation 32 which is a regulator 33 so long in a change in the valve setting 34 of the pressure control valve 26 converts until the control deviation 32 disappeared and the target friction force 31 is reached. Through the first control loop 30 becomes the pressure of the blown air B reinforced when the friction between the vacuum belt 2 and the band guide 21 increases, and decreases as the friction decreases. The first control loop 30 is integrated in an electronic control device of the digital printing press. This includes a second control loop 37 to keep constant the rotational speed of the vacuum belt 2 , where the manipulated variable is the motor current of the motor 6 is. The second control circuit 37 is in 3 represented as a symbol.

Although it would be theoretically possible, instead of the sensor 29 measured force and deflection of the tape guide 21 the motor current of the motor 6 as a measured variable of the first control loop 30 however, this would not work in practice. Namely, the motor current changes required for speed correction would become the control of the air bag 35 to disturb. That is why there are two different control circuits 30 . 37 for the air cushion 35 and the belt speed is advantageous. This will cause a constant drive torque of the motor 6 guaranteed.

LIST OF REFERENCE NUMBERS

1

belt conveyors

2

vacuum belt

3

items

4

capstan

5

idler pulley

6

engine

7

raster relief

8th

suction cups

9

limiting grid

10

Passage bore

11

suction system

12

vacuum connection

13

Suction air manifold

14

inlet bore

15

Saugluftnut

16

Blow

17

Compressed air connection

18

Blowing air distribution line

19

outlet bore

20

Blasluftnut

21

tape guide

22

baseplate

23

cover plate

24

Tape guide surface

25

vent

26

Pressure control valve

27

moving storage

28

leaf spring

29

sensor

30

first control loop

31

Target frictional force

32

deviation

33

regulator

34

valve timing

35

air cushion

36

Actual friction force

37

second control loop

38

Digital press

B

blowing air

S

suction

T

transport direction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 3889801 [0004]
• DE 102015213406 A1 [0005]

Claims (10)

Belt conveyor (1), comprising a vacuum belt (2) for transporting articles (3) in a transport direction (T), - A tape guide (21) with a blown air system (16) for generating an air cushion (35) for air bearing of the vacuum belt (2), and - A first control loop (30) for controlling the air cushion (35). Belt conveyor to Claim 1 wherein the first control circuit (30) has a sensor (29) for measuring movement or loading of the tape guide (21). Belt conveyor to Claim 2 wherein the sensor (29) is a force transducer. Belt conveyor after one of the Claims 1 to 3 , wherein by the first control circuit (30), a pressure control valve (26) is controlled, which controls the supply of blowing air (B) in the blown air system (16). Belt conveyor after one of the Claims 1 to 4 , wherein a motor (6) for driving the vacuum belt (2) and a second control circuit (37) for controlling the motor (6) are present. Belt conveyor after one of the Claims 1 to 5 , wherein the tape guide (21) is movably mounted in a movement bearing (27). Belt conveyor to Claim 6 in that the movement bearing (27) allows a movement or movement component of the tape guide (21) in the transport direction (T) or parallel thereto. Belt conveyor to Claim 6 or 7 wherein the movement bearing (27) comprises leaf springs (28). Belt conveyor after one of the Claims 1 to 8th , wherein the tape guide (21) Blasluftnuten (20) with vents (25) has. Belt conveyor after one of the Claims 1 to 9 wherein the belt conveyor (1) is part of a digital printing machine (38), wherein the articles (3) are printed sheets.

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