GB2142599A - Device for retensioning an endless delivery chain on the delivery of a printing press - Google Patents

Description

SPECIFICATION Device for retensioning an endless delivery chain on the delivery of a printing press The invention relates to a device for retensioning an endless delivery chain on the delivery of a printing press, with chain wheel bearings which are displaceable in the side walls of the printing press and to which pressure is applied in the chain tensioning direction, and with chain wheels axially supported in said chain wheel bearings.

The sheets are delivered constantly at the delivery of sheet-fed offset printing presses. The sheet carriers, e.g. delivery chains, which go round at identical speed serve to convey the products, e.g. printed sheets, from the loading point to an unloading point.

The conveying sequence is dependent on the conveying speed.

The efficiency of the conveyor is determined by the conveyed quantity per unit time. To guarantee a certain efficiency, the correct operation of the delivery chain drive is essential. This therefore involves a practical arrangement, careful mounting, proper lubrication and adjustment of the chain tension. As a result of the polygonal action of the chain wheels the distance between shafts changes periodically while the drive is in operation. To achieve optimum guidance of the sides of the chain, use is made of numerous auxiliary devices, such as support wheels or tensioning wheels of tensioning screws on the slack side. In addition to regulating the angle of contact, these devices are also intended to provide a support, particularly in the case of large distances between shafts, to prevent chain vibrations and to guarantee a certain means of adjustment, among other things after wear. The shaft wheels and chain wheels must be axially parallel and must run wobble-free, and the chains must not be tensioned too tightly.

The correct chain tension is very important for the safety and service life of the chains and chain guided as well as to reduce the noise of the chains. With the present-day types of tensioning devices, a mechanic needs a great amount of time to retension the gripper chains in the delivery of printing presses. By dismantling the chain guides it is then possible to messure the chain tension, e.g. with a spring balance.

Therefore the object of the invention is to develop a device with which any elongation occuring in operation in the delivery chain of a printing press can be compensated in simple manner in order to guarantee the safety, smoothness and service lift of the drive, and with which the chain tension required for trouble-free running of the chain cannot only be maintained constant, but can also - without using additional aids - be easily checked by the press operator, quickly retensioned and set to a precisely defined tension value.

The object of the invention is achieved in that the chain wheel bearings are elastically under pressure, are lockable in their respective positions and, when unlocked, are automatically adjustable as a function of increasing chain elongation. Such an arrange ment makes it possible for the press operator precisely to monitor the maintainance of the desired chain tensioning force and, if required, to readjust it in the shortest possible time whereby thanks to the simple manner of operation excluding any kind of measuring instrument, adjustment errors are more or less impossible.

A further independent solution according to the characterizing clause of Claim 2 provides that the chain wheel bearings are elastically under pressure, are guided with zero-play and are automatically and continuously adjustable while the chain is running as a function of increasing chain elongation. In addition to the aformentioned advantages, the pre cise guidance of the chain wheel bearings dispenses with the need for any locking means with the result that the tension of the chain is constantly guaranteed while the press is in operation and the delivery need not necessarily be stopped to regulate the chain tension.

In order to automate the hitherto manual displace ment of the chain wheel bearings in the chain tensioning direction and in order to preclude diffe rent tension in the two delivery chains caused by non-identical displacement of the chain wheel bearings, an advantageous embodiment of the invention provides that for the continuous application of pressure to each chain wheel bearing there is a tensioning element constantly producing a chain tensioning force and having an elastic pressure equalization storage element by means of which a defined chain tensioning force can be set and adjusted.

In a further development of the invention the bearing box is automatically adjustable by the pressure equalization storage element in the case of chain elongation, the distance between bearing and housing-rigid stop thus being variable, whereby to hold constant the pressure force of the pressure equalization storage element for producing a defined chain tension, the end face of the activating part can, by turning, be brought into alignment with an aligning edge of the support element. This simple method of operation with absolute alignment against an edge without the use of measuring scales helps to shorten the adjusting time and to rule out adjustment errors.

In a particularly practical form of the invention the pressure equalization storage element is in the form of a cup spring column with adjustable total spring travel. With decreasing chain tension the individual cup springs of the cup spring column are spread due to the adjustment of the bearing boxes, thereby increasing the total spring travel. This can be set again to its original value by means of the adjustable activating part, as a result of which its total spring force remains constant - neglecting any changes in the force characteristic of the cup spring column.

In a further preferred embodiment of the invention both chain wheels are mounted on a straightthrough shaft. In a practical further development of the invention the bearing boxes are provided with locking screws which are to be loosened prior to automatic adjustment by the tensioning element.

This simple design can be manufactured at low cost whereby the purely mechanical action of locking and unlocking the bearing boxes does not require any extra care and attention from the operator than during normal press operation with its attendant operational adjustments.

A practical version of the invention is characterized by the fact that each chain wheel is mounted separately on a short bearing pin. It may be advantageous for the bearing boxes to be disposed in the side walls with zero-play guidance. The precise - also lateral - guidance of the bearing boxes in the side walls counteracts a tipping of the chain wheels on the short bearing pins particularly in the case of high chain tensile force or chain tension, thereby providing the advantage that even while the chain is running chain elongation is automatically sufficiently catered for in order to guarantee safe, smooth operation.

Further features and details of the invention as well as resultant advantages will become apparent from Claims 4, 5 and 8 as well as from the following description of three specimen embodiments with reference to the drawings.

Figure 1 shows a diagrammatic representation of a chain tensioning device according to a first embodiment of the invention, partially cut, as a top view of a sheet delivery; Figure 2 shows a diagrammatic representation of a chain tensioning device according to a second embodiment of the invention, partially cut, as a top view of a sheet delivery; Figure 3 shows a detailed partially-cut section from Figure 1 with representation of a tensioning element for the delivery chain in the normal position; Figure 4 shows the same view as in Figure 3, but with the tensioning element in extremely retensioned position after chain elongation; Figure 5 shows a detailed partially-cut section from Figure 2 with representation of a tensioning element for the delivery chain in extremely reten sioned position after chain elongation; Figure 6 shows a partial section of a third embodi ment with representation of a chain wheel mounted on a short bearing pin and a bearing box guided with zero clearance.

In a first embodiment of the chain tensioning device according to Figure 1 the side walls 10 of a printing press are provided with longitudinal reces ses 9. Disposed in the recesses 9 are displaceable chain wheel bearings which are in the form of bearing boxes 7. Each bearing box 7 exhibits, in the direction of displacement, a longitudinal slit 16 through which project locking screws 11 which engage the side wall 10 and by means of which each bearing box 7 can be locked on its side wall 10.

Mounted in bearing holes 17 of the bearing boxes 7 are short bearing pins 13 on which a chain wheel 2 is rotatably mounted in front of each side wall 10.

Endless delivery chains 1 go round on the chain wheel 2. Transverse to the sheet conveying direction according to arrow 3, continuous gripper support bars 4 are mounted on the delivery chains 1, rotating with them, and provided with grippers 5 for gripping and transporting sheets 18.

As shown in Figures 3 and 4, for the elastic application of pressure to each bearing box 7, a tensioning element 8 is provided between each bearing box 7 and the end face of the recess 9 which serves as a housing-rigid stop 19. The tensioning element 8 consists of an adjustable activating part 12, an elastic pressure equalization storage element 14 disposed in the latter, as well as a support element 13 coming after the pressure equalization storage element 14. The activating part 12 is provided with an adjusting screw 21 which engages a female threat 20 leading to the bearing hole 17. The elastic pressure equalization storage element is in the form of a cup spring column 14, consisting of oppositely arranged cup springs. In the normal position with the tensioning element 8 in the starting condition, the cup spring column 14 is preloaded and is supported on the end face of the following support element 13. In turn, the latter is in contact with the housing-rigid stop 19 and is provided with an aligning edge 22 which cooperates with the end face 24 of the activating part 12.

The operating principle with the device of the first specimen embodiment and its mode of action are described in greater detail in the following.

In the normal position shown in Figure 3, the adjustable activating part 12 engages a recess 25 in the bearing box 7. This position is assumed by the tensioning element 8 as the starting position for a new delivery chain 1. With increasing operating time the chain tension in the delivery chains 1 decreases through chain elongation. When a certain chain elongation is exceeded, the safety smoothness and service life of the chain drive are no longer fully guaranteed. For this reason, the delivery chains must be retensioned.

For this purpose, the chain boxes 7 are unlocked from the side walls 10 by loosening the locking screws 11. Due to the preload of the cup spring column 14 the two bearing boxes 7 in their guides 9 are automatically displaced in the chain tensioning direction with the total force of the springs. The individual cup springs thereby relax, and the total spring travel increases whereby the total spring force decreases. With increasing chain elongation the chain tension is thus also reduced.

To preclude this completely undesirable sideeffect and to hold the chain tensioning force always constant, the total spring travel of the cup spring column 14 must be reset to its original value. Forthis purpose, the adjustable activating part 12 must be returned to its defined starting position which it assumed prior to the relaxation of the cup spring column 14 and the adjustment of the bearing box 7.

This is done by turning the activating part 12 toward the housing-rigid stop 19 until the end face 24 of the activating part 12 has been brought into alignment with the aligning edge 22 of the support element 13.

During this aligning operation, the adjusting screw 21 on the activating part 12 is screwed out of the female thread 20 of the chain box 7, thereby pushes the bearing box 7 forwards in the chain tensioning direction, thus increasing the chain tensioning force.

Thus, the cup spring column 14 is preloaded again.

The flush finishing of the end face 24 of the activating part 12 with the aligning edge 22 of the support element 13 is proof of constantly, accurately defined chain tension.

After tensioning, the bearing boxes 7 are locked again on the side walls 10 by means of the locking screws 11. The retensioning of the delivery chains 1 can be carried out with the printing press in operation while the chains are running; preferably, however, the printing press will be stopped briefly.

After repeated retensioning of the delivery chain 1, the bearing box 7 has been moved so far in the chain tensioning direction, and the activating part 12 has been turned against the housing-rigid stop 19 so often that the activating part 12 has left the recess 25 and the adjusting screw 21 is only a short way into the female thread 20 of the chain box 7. The tensioning element 8 is now in its end position and can no longer be readjusted, with the result that it is now necessary to replace the delivery chain 1 (Figure 4).

The second specimen embodiment shown in Figures 2 and 5 differs from the previously described first speciment embodiment in that both chain wheels 2 are mounted together on a straightthrough chain wheel shaft 15 extending overthe entire machine width and rotatably mounted in the bearing holes 17 of the bearing boxes 7. In addition, for being displaced in the recesses 9, the bearing boxes (7) are provided with zero-play guidance 26.

This dispenses with the locking and unlocking of the bearing boxes 7 and the locking screws 11 used in the first embodiment are not necessary.

The bearing boxes 7 of the third specimen embodiment according to Figure 6 are also equipped with this zero-play guidance 26. For this purpose, the bearing boxes 7 are of two-pa rt design whereby an accurate bearing shell 27 adapted to the width of the recess 9 and with a support collar in contact with the outer side wall 10 guarantees relatively zero-play displacement in the chain tensioning direction and a bearing cover 28 screwed to the bearing shell 26 on the inner side wall 10 by means of clamping screws 29 ensures the lateral zero-play guidance of the bearing boxes 7 in conjunction with the aforementioned support collar.

As in the first specimen embodiment, in the third specimen embodiment according to Figure 6 the short bearing pins 13 are fixed by means of taper pins 30 in the bearing holes 17 of the bearing boxes 7, and the bevel wheels 2 are rotatably disposed on the bearing pins 13 by means of ball bearings 31. To counter axial displacement of each chain wheel 2, either side of the ball bearing 31 are circlips 32 and a support ring 33 which is supported on the ball bearing 31 and which is screwed onto the chain wheel 2 at the front.

The zero-play guidance 26 of the second and third specimen embodiments permits the automatic compensation of chain elongation while the chain is running since the bearing boxes 7 are continuously adjusted in the chain tensioning direction by the application of pressure from the tensioning elements 8. This requires neither the switching off of the printing press northe loosening of locking screws. Of course, the zero-play guidance 26 of the bearing boxes 7 is not limited to the arrangement of a straight-through chain wheel shaft 15 (Figure 2), but is also possible if using two separate short bearing pins 13 (Figure 6) whereby, particularly if using the latter, the lateral zero-play guidance 26 of the bearing boxes 7 at the side walls 10 prevents the tipping inward of the bearing pins 13 - caused by the chain tensile force.

Thus, in these embodiments, there is no need for manual adjustment of the bearing boxes 7 as a result of automation so that only the originally set, defined chain tensioning force need be re-established by turning the adjustable activating part 12. Of course, the invention is not restricted to the three embodiments described in the specification and presented in the figures. On the contrary, numerous design modifications and further developments are likewise within the scope of the invention. Thus, for example, it is quite conceivable to make the pressure equalization storage element 14 pneumatic or hydraulic instead of spring-elastic, whereby, in this case, it is an obvious step - by means of constant pressure generation and monitoring - not only to fully automate the displacement of the chain tensioning boxes 7, but also the setting of a defined chain tensioning force. Likewise, it is conceivable to monitor the chain tensioning force directly by means of electronic measuring at the delivery chains and, for example, to readjust the tension by means of electric motor.

Parts List 1 Chain 2 Chain wheel 3 Sheet conveying direction 4 Gripper support bar 5 Gripper 6 Bearing pin 7 Chain wheel bearing, bearing box 8 Tensioning element 9 Recess 10 Side wall 11 Locking screw 12 Activating part 13 Support element 14 Pressure equalization storage element, cup spring column 15 Chain wheel shaft 16 Longitudinal slit 17 Bearing hole 18 Sheet 19 Housing-rigid stop 20 Female thread 21 Adjusting screw 22 Aligning edge 23 24 End face 25 Recess 26 Zero-play guidance 27 Bearing shell 28 Bearing cover 29 Clamping screw 30 Taper pin 31 Ball bearing 32 Circlip 33 Support ring

Claims (17)

1. Device for retensioning an endless delivery chain on the delivery of a printing press, with chain wheel bearings which are displaceable in the side walls of the printing press and to which pressure is applied in the chain tensioning direction, and with chain wheels axially supported in said chain wheel bearings, wherein the chain wheel bearings (7) are elastically under pressure, are lockable in the respective positions (10) and, when unlocked, are automatically adjustable as a function of increasing chain elongation.

2. Device for retensioning an endless delivery chain on the delivery of a printing press, with chain wheel bearings which are displaceable in the side walls of the printing press and to which pressure is applied in the chain tensioning direction, and with chain wheels axially supported in said chain wheel bearings, wherein the chain wheel bearings (7) are elastically under pressure, are guided with zero play and are automatically and continuously adjustable while the chain is running as a function of increasing chain elongation.

3. Device according to Claim 2 or 2, wherein for the continuous application of pressure to each chain wheel bearing (7) there is a tensioning element (8) constantly producing a chain tensioning force and having an elastic pressure equalization storage element (14) by means of which a defined chain tensioning force can be set and adjusted.

4. Device according to any one or more of the preceding claims, wherein the chain wheel bearings are in the form of bearing boxes (7) whereby each tensioning element (8) is disposed between a housing-rigid stop (17) in the side wall (10) and the bearing box (7).

5. Device according to any one or more of the preceeding claims, wherein the tensioning element (8) consists of an adjustable activating part (12) connected to the bearing box (7), a pressure equalization storage element (14) disposed in said activat ing part, and a support element (13) coming after the pressure equalization storage element (14) and in contact with the housing-rigid stop (17).

6. Device according to any one or more of the preceeding claims, wherein the bearing box (7) is automatically adjustable by the pressure equalization storage element (14) in the case of chain elongation, the distance between bearing (7) and housing-rigid stop (17) thus being variable, whereby to hold constant the pressure force of the pressure equalization storage element (14) for producing a defined chain tension, the end face (20) of the activating part (12) can, by turning, be brought into alignment with an aligning edge (21) of the support element (13).

7. Device according to any one or more of the preceeding claims, wherein the pressure equalization storage element (14) is in the form of a cup spring column with adjustable total spring travel.

8. Device according to any one or more of the preceeding claims, wherein after chain elongation and adjustment of the bearing boxes (7), the total spring force of the cup spring column (14) can be set to the previously produced pressure by shortening the total spring travel by means of turning the activating part (12) against the housing-rigid stop (17).

9. Device according to any one or more of the preceeding claims, wherein both chain wheels (2) are mounted on a straight-through shaft (15).

10. Device according to any one or more of the preceeding claims, wherein each chain wheel (2) is mounted separately on a short bearing pin (6).

11. Device according to any one or more of the preceeding claims, wherein the bearing boxes (7) are provided with locking screws (11) which are to be loosened prior to automatic adjustment by the tensioning element (8).

12. Device according to any one or more ofthe preceeding claims, wherein the bearing boxes (7) are disposed in the side walls (10) with zero-play guidance (26).

13. A device for regulating the tension of system chains arranged at the discharge system end of printing machines, according to which the system chains run on chain wheels while the axle of the chain wheels is carried by rigidly securable chain bearing boxes which, on their part, are slideably arranged, in tensioning direction, in the lateral structure of the printing machine, wherein between a catch (10) rigidly fixed to the mount and the chain bearing box (7) a tensioning element (8) is provided which always acts with a clearly defined force, and the said tensioning element (8) is provided with a regulating part (12, 13), which is used to vary the distance between the chain bearing box (7) and the catch rigidly fixed to the mount (10), so that upon loosening specific fixing means (11) by turning the regulating part (12, 13) the pertinent tension force required of the system chain (1) can be adjusted.

14. A device for regulating the tension of system chains arranged at the discharge system end of printing machines according to claim 13, wherein a straining screw (12) is provided in the tensioning element (8) for exerting the tension force required and transferring it upon the system chain (1), the said straining screw acting upon a bolt (13) and an adjustable spring (14) in order to exert the tension force required in the direction of the slideable chain wheel axle (6).

15. A device for regulating the tension of system chains arranged at the discharge system end of printing machines according to claim 13 or 14, wherein a guiding system free from backlash has been provided for the tensioning element (8) to enable it to exert the tension force required and transfer it on the system chain (1).

16. Device according to claim 1, substantially as described with reference to any figure or figures of the accompanying drawings.

17. Device according to claim 13, substantially as described with reference to any figure or figures of the accompanying drawings.