The invention relates to a printing machine with a finger protector and, more particularly, a finger protector that is formed as a blast tube. 
Protective devices of this general type serve as protection for the hands in printing machines, and prevent the operator""s hand from being pulled in between two cylinders if the operator should carelessly reach too far into the cylinder nip during cleaning or maintenance work. 
German Patent 44 17 054, corresponding to U.S. Pat.  No.  5,537,922, describes, by way of example, a proofing device in the printing unit of a printing machine.  This multifunctional proofing device serves mainly as a guide element for printing plates and additionally as a finger protection and blasting device.  The blasting or blowing function makes it possible to supply drying air to the cylinder surface of a rubber blanket cylinder at the end of a washing operation.  The proofing device is arranged in a nip formed by a plate cylinder together with a rubber blanket cylinder, and therefore not in a nip formed by an impression cylinder together with an adjustable cylinder. 
The published German Patent Document DE 43 18 777 C2 describes a device for assisting the guidance of sheets.  As illustrated diagrammatically in this document, the blast tubes of this device do not extend over the entire cylinder width and have no finger protection function.  On the contrary, the object upon which this device is based is to build up an air cushion between a sheet and a rubber blanket cylinder, on a printing unit that is not involved with printing and that has a nip between the rubber blanket cylinder and an impression cylinder.  The device does not have an adjustable cylinder that is adjustable into a clearance position far removed from an impression cylinder.  The build up of the air cushion is, of course, only possible when the clearance between the rubber blanket cylinder and the sheet-guiding impression cylinder is 2 millimeters, as specified, which is thus a very small clearance. 
The published German Patent Document DE 690 22 419 T2, corresponding to U.S. Pat.  No.  4,934,305, corresponding to the published European Patent Document EP 0 477 283 B1 describes a retractable coating device with a rubber blanket cylinder.  The coating cylinder can be adjustable relative to an impression cylinder into an operating position for coating the printing-material sheet resting on the impression cylinder, into a cut-off position with a small clearance relative to the impression cylinder and into a position, designated as a second position, far removed from the impression cylinder and with good access to the coating cylinder for the purpose of maintenance or cleaning.  There is no finger protector in this coating device. 
The published German Patent Document DE 297 10252 U1 describes a guide arrangement for sheetlike printing material in a printing machine.  The guide arrangement includes a guide tube that is preceded by a pivotably mounted pneumatic system and, for example, a blast tube extending over the entire width of a sheet guide cylinder.  The guide plate can be coupled to a circuit-safeguarded protective device for protecting against hazardous locations in the region of the sheet guide cylinder.  The guide arrangement includes, in addition to the guide plate described hereinabove, a further guide plate that is mounted so as to be pivotably movable and that is sensor-safeguarded which serves as a switching protective device if a person enters the region formed by the sheet guide cylinder.  The two guide plates are assigned to sheet guide cylinders functioning as transfer drums between a printing unit and a varnishing unit.  The transfer drums are not mounted so as to be capable of being thrown off or disengaged from one another, but, as is known, are mounted fixed in position location in the machine frame. 
It is accordingly an object of the invention to provide a printing machine that is safeguarded against risks of injury, that can be operated in a maintenance-friendly manner and operates with a smear-free sheet run.  It is a further object of the invention to provide a method for operating a sheet-fed printing machine. 
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, in a printing machine, an improvement therein comprising a finger protector formed as a blast tube and arranged in a region of a wedgelike cylinder nip formed by an impression cylinder together with an adjustable cylinder, the adjustable cylinder being adjustable into a clearance position far removed from the impression cylinder. 
In accordance with another feature of the invention, a minimum circumferential clearance of the cylinders relative to one another, when the adjustable cylinder is located in the far-removed clearance position, is equal to at least several centimeters and, in particular, several decimeters. 
In accordance with a further feature of the invention, in a protective position protecting against entry into the cylinder nip, the finger protector is movably mounted and the position thereof is sensor-monitored. 
In accordance with an added feature of the invention, the printing machine includes a sensor for monitoring the position of the finger protector, the sensor being responsive for stopping a drive for rotating the adjustable cylinder, when the finger protector is forced out of the protective position. 
In accordance with an additional feature of the invention, the sensor is formed as an electric motor. 
In accordance with yet another feature of the invention, the finger protector is forcible out of the protective position due to manual contact during cleaning of the adjustable cylinder. 
In accordance with yet a further feature of the invention, the finger protector and the blast tube forming the finger protector, respectively, are able to be acted upon by blowing air and are functionable as a sheet guide element when the adjustable cylinder is adjusted to the far-removed clearance position. 
In accordance with yet an added feature of the invention, the blast tube is connected to a compressed air source for supplying the blast tube with blast air having such a pressure level that jet pressure of blast air flowing out of blast orifices formed in the blast tube maintains a printing-material sheet, that is being transported past the finger protector by the impression cylinder, at a distance from the finger protector at least over most of the sheet length thereof. 
In accordance with yet an additional feature of the invention, the blast air orifices formed in the blast tube are oriented, in the angular position thereof, in a manner that, due to the jet direction of the blast air jets impinging on the printing-material sheet, the sheet that is transported past the finger protector by the impression cylinder is maintained at a distance from the finger protector at least over most of the sheet length thereof. 
In accordance with still another feature of the invention, the impression cylinder and the adjustable cylinder are components of a unit of the printing machine, the unit being arranged downline of at least one of a printing and a coating unit of the printing machine, as viewed in the sheet transport direction, and being capable of being placed selectively into an activated and into an inactivated state, the adjustable cylinder, in the inactivated state, being adjusted to the far-removed clearance position, and the blast tube, in the inactivated state, being acted upon by blast air. 
In accordance with still a further feature of the invention, the unit is one of a printing, a coating and a finishing unit, respectively. 
In accordance with still an added feature of the invention, the adjustable cylinder is adjustable into a throw-on position wherein it has operative contact with one of the impression cylinder and the printing-material sheet resting thereon, respectively, the adjustable cylinder being one of a cylinder for printing the printing-material sheet in the throw-on position, a cylinder for coating the printing-material sheet, and a cylinder for processing the printing-material sheet. 
In accordance with still an additional feature of the invention, the printing is with at least one of impressions and numberings, respectively, the coating is with varnish, and the processing is by at least one of perforating, scoring, embossing, cutting, punching, smoothening, calendering and dedusting, respectively. 
In accordance with a concomitant aspect of the invention, there is provided a method for operating a sheet-fed printing machine, which comprises disposing at least one of a printing unit and a coating unit, respectively, and a further unit inline with and downline of the latter; in one operating mode of the sheet-fed printing machine, respectively printing and coating a printing-material sheet in the at least one printing unit and coating unit, that is in an active state; and thereafter, in an in-line process, passing by the further unit, that is in an inactive state; by an impression cylinder of the further unit, transporting the printing-material sheet; adjusting an adjustable cylinder into a clearance position far removed from the impression cylinder of the further unit; and applying blast air to the finger protector of the further unit from smearing the, respectively, freshly printed and coated printing-material sheet transported past the finger protector. 
The printing machine with a finger protector constructed as a blast tube is distinguished in that the finger protector is arranged in the region of a wedgelike cylinder nip formed by an impression cylinder together with an adjustable cylinder, the adjustable cylinder being adjustable to a clearance position far removed from the impression cylinder. 
The finger protector reliably protects the operator from any injuries, for example, during the manual cleaning of the adjustable cylinder.  The adjustable cylinder is easily accessible in the far-removed clearance position for maintenance purposes, and, for example, a varnishing or printing form located on the adjustable cylinder can be exchanged, without any need for reaching deeply into the machine or similar difficulties.  Constructing the finger protector as a blast tube ensures a smear-free run of the printing-material sheet past the finger protector. 
An embodiment that advantageously develops the printing machine according to the invention is distinguished in that, with the adjustable cylinder located in the clearance position, a minimum circumferential clearance of the adjustable cylinder relative to the impression cylinder amounts to at least several centimeters and, in particular, several decimeters. 
The clearance between the cylinders may amount, for example, to at least 20 centimeters. 
A further embodiment is distinguished in that, in a protective position protecting against entry into the cylinder nip, the finger protector is movably mounted, and the position thereof is sensor-monitored. 
A further embodiment is distinguished in that the position of the finger protector is monitored by a sensor formed, in particular, as an electric switch which responds and stops a drive rotating the adjustable cylinder when the finger protector is forced out of the protective position, for example, due to manual contact when the adjustable cylinder is being cleaned. 
A further embodiment is distinguished in that the finger protector or the blast tube forming the latter can be acted upon by blast air, and functions as a sheet guide element when the adjustable cylinder is adjusted to the far-removed clearance position. 
A further embodiment is distinguished in that the blast tube is connected to a compressed air source and can be supplied by the latter with blast air having such a pressure level that the jet pressure of the blast air flowing out of blast orifices of the blast tube keeps a printing-material sheet, that is transported past the finger protector by the impression cylinder, at a distance from the finger protector at least over most of the sheet length. 
For example, as a result of the action of the blast air, a printing-material sheet is kept at a distance from the finger protector over the length of a freshly printed-on printed image facing the finger protector, and it is perfectly possible for a narrow nonprinted marginal strip usually present at the trailing edge of the printing-material sheet to abut against the finger protector, without causing any problems. 
A further embodiment is distinguished in that the blast air orifices of the blast tube are oriented, in the angular position thereof, in such a manner that, due to the jet direction of the blowing air jets impinging on the printing-material sheet, the sheet, that is transported past the finger protector by the impression cylinder, is kept at a distance from the finger protector at least over most of the sheet length. 
By rotation of the entire blast tube or by an individual setting of blast air nozzles of the blast tube, the orientation of the blast air orifices can be adapted to the printing-material sheet which, for example, is somewhat stiffer in one case and somewhat less stiff in another case.  The orientation of the blast air orifices may be such that a central jet of the respective blast-air orifice impinges on the printing-material sheet substantially perpendicularly or obliquely opposite to the sheet transport direction, i.e., at an acute angle to the printing-material surface. 
A further embodiment is distinguished in that the impression cylinder and the adjustable cylinder are components of a unit, in particular a printing, a coating or a finishing unit of the printing machine, the unit being arranged downline of at least one printing or one coating unit of the printing machine as viewed in the sheet transport direction, and being capable of being placed selectively into an activated and into an inactivated state, the adjustable cylinder, in the inactivated state, being adjusted to the far-removed clearance position, and the blast tube being acted upon by blast or blowing air. 
A further embodiment is distinguished in that the adjustable cylinder can be placed into a throw-on position having operative contact with the impression cylinder or with the printing-material sheet resting on the latter, and is a cylinder for printing, for coating or for processing the printing-material sheet in the throw-on position. 
For example, the adjustable cylinder may be a printing form cylinder for the printing of impressions or numberings, or an applicator cylinder for coating the printing-material sheet with a varnish, or a tool-fitted cylinder for perforating, scoring, embossing, cutting, punching, smoothing, calendering or dedusting the printing-material sheet. 
In the method according to the invention for operating a sheet-fed printing machine that is constructed, in particular, according to one of the embodiments described hereinabove and that comprises at least one printing unit or one coating unit and a further unit located inline with and downline of the latter, in one operating mode of the sheet-fed printing machine, a printing-material sheet is printed or coated in the printing unit or coating unit, active in this case, and subsequently, in the in-line process passes the further unit, inactive in this case, an impression cylinder of the further unit transporting the printing-material sheet, an adjustable cylinder being adjusted into a clearance position far removed from the impression cylinder of the further unit, and a finger protector of the further unit being protected, by being loaded with blast air, from smearing the freshly printed or coated printing-material sheet transported past the finger protector. 
Other features which are considered as characteristic for the invention are set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a printing machine with a finger protector, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: