Abstract:
A quick release mechanism for a roller ( 6, 7 ) wherein the roller ( 6, 7 ) is mounted in a frame and rotationally driven (for example, a roller ( 6, 7 ) carrying a roll of stretch wrapping film ( 4 ) in a stretch wrapping head ( 1 )). The quick release mechanism includes a pair of stub axles ( 22, 43 ) which support either end of the roller ( 6, 7 ) in the frame. One of the stub axles ( 22 ) are fixed within the frame and driven by a motor ( 8 ). The connection between this driven stub axle ( 22 ) and the roller ( 6, 7 ) ensures that no relative rotational movement occurs. The other stub axle ( 43 ) is “lockable” in a hole in the frame but is removable therefrom. The connection between the removable stub axle ( 43 ) and the roller ( 6, 7 ) allows free relative rotational movement. Withdrawal of the removable stub axle ( 43 ) from the frame allows the roller ( 6, 7 ) to be disconnected from its connection with the driven stub axle ( 22 ) and removed from the frame. Refitting of the roller ( 6, 7 ) is simply a reversal of this process.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a system for fitting mounted rollers which allows for quick release/re-fitting of the rollers and more particularly though not solely to a quick release roller mechanism for use in a stretch head of a stretch film wrapping machine incorporating driven rollers. 
     2. Brief Description of the Prior Art 
     Apparatus which include rollers having an axis of rotation wherein the roller is supported at either end often require the roller to be removed for re-fitting or servicing and/or subsequent replacement. Some apparatus including rollers as described above include driving means for rotating the roller, complicating the removal and re-fitting process significantly. 
     An example of apparatus having driven rollers which are often required to be removed and re-fitted is a stretch wrapping head for a stretch wrapping film used in the packaging of products, often on pallets, wherein the stretch wrapping head is rotated about the goods on the pallet and moved in a vertical direction so that the goods on the pallet are held in position and protected from the environment by the stretched wrap. An example of such a stretch wrap head is disclosed in EP-B-747287 and an alternative apparatus which includes a similar type of stretch head is disclosed in EP-A-803437 in which the stretch wrap head is suspended from a rotating arm which rotates above the object to be wrapped. 
     The stretch heads disclosed in the above mentioned patent specifications both include two driven rollers, the surface speeds of which are not the same and through which a continuous length of plastics film is passed and stretched by the difference in speed between the surface of the rollers. EP-A-919467 discloses an improved stretch wrapping head which includes two parallel driven rollers but which also includes at one end of the rollers an opening to allow easier access to wind the film on the rollers prior to commencing operation. 
     In each of the above mentioned stretch wrap heads, replacement or removal of the rollers is time consuming and requires the use of tools. It would be an advantage if the rollers could be quickly and simply removed to allow for maintenance and or re-fitting. 
     Accordingly, it is an object of this invention to provide a quick release mechanism for a roller which at least goes some way towards overcoming the above disadvantages. 
     SUMMARY OF THE INVENTION 
     According to this invention, a quick release mechanism for a roller comprising: 
     frame means in which the roller is adapted to be mounted in use; 
     apertures in either end of the roller, the apertures aligned with the axis of rotation of the roller; and 
     stub axle means which connect either end of the roller to the frame means by passing through respective holes aligned in the frame means and into the respective roller apertures, the connection between the roller and each stub axle means allowing substantially free angular rotation of the roller relative to the frame means; 
     wherein one of the stub axle means is axially fixed in the frame means and driven rotationally and provided at or near its end with a non-circular cross-section, the cross-section of the roller aperture into which the driven stub axle means fits having a corresponding shape to allow the roller to be rotated by the driven stub axle means; and 
     wherein the other stub axle means is releasable from its connection with the roller aperture and its connection with the frame means solely by movement along the axis of rotation of the roller, away from the roller, the removable stub axle means having a cylindrical shaft which is adapted at one end to pass through the hole in the frame means and to fit within the aperture in the roller and provided at its opposite end with a knob to facilitate removal of the removable stub axle means from the roller aperture and frame means, the cylindrical shaft including at least two axially separated detents to allow the removable stub axle to be selectively positioned either engaged with the roller and frame means or disengaged from the roller but still engaged with the frame means to facilitate removal of the roller from the frame means. 
     According to a second aspect of the present invention, a stretch wrapping head for a stretch wrapping machine is adapted to pre-stretch a plastics film through stretch rollers supported in a frame, the rollers held in the frame by a quick release mechanism according to the above paragraph. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A particular embodiment of the present invention will now be described with reference to the accompanying drawings in which; 
     FIG. 1 is a plan elevation of a stretch wrapping head according to a particular embodiment of the present invention; 
     FIG. 2 is a front elevation of the stretch wrapping head of FIG. 1; 
     FIG. 3 is a cross-sectional plan elevation through the stretch wrap head of FIGS. 1 and 2 along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a cross-sectional elevation along the line  4 — 4  of FIG. 3; 
     FIGS. 5A and 5B are cross-sectional end elevations through one of the rollers of the stretch wrapping head of FIG.  1  through the line  5 — 5  of FIG. 1 showing insertion and/or removal of the stub axle of the roller; 
     FIG. 6 is a front elevation of the shaft of the stub axle as shown in FIGS. 5A and 5B; 
     FIG. 7 is a front elevation of the driven stub axle shown in FIG. 4; 
     FIG. 8 is a cross-sectional view of the driven stub axle of FIG.  7  through the line  8 — 8 ; and 
     FIG. 9 is a cross-sectional view of the driven stub axle of FIG.  7  through the line  9 — 9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and in particular FIGS. 1 to  3 , a stretch wrapping head  1  is adapted for use in a stretch wrapping machine such as that disclosed in European patent number EP-B-747287 and comprises a base plate  2  (see FIG. 2) upon one end of which a lower bearing member  3  is mounted so as to rotatably support a substantially upstanding or vertically oriented wrapping film supply roll  4  from which a fresh supply of wrapping film  5  is able to be withdrawn in connection with the operation of a package, article, or pallet wrapping operation. The wrapping film  5  may comprise suitable plastics wrapping film which may be “pre-stretched” and which will subsequently “shrink back” towards its unstretched condition after it has been applied to a package, article or pallet. 
     The basic operation of stretch head  1  is substantially as described in the co-pending European patent application published as EP-A-919467, a summary of which follows. 
     The wrapping film  5  is fitted around first  6  and a second  7  tension rollers in a substantially reverse “S” shaped path and moves in the direction indicated by the arrows in FIG. 1. A motor  8  rotates a sprocket wheel  9  through a suitable gear box  10 . An endless sprocket chain  11  connects the gear box sprocket  9  around a series of other sprockets including a sprocket  14  which is connected by means which will be explained further below to the first tension roller  6  and a sprocket  13  which is connected (also by means which will be explained further below) to second tension roller  7 . The position of a further sprocket wheel  12  is adjustable in order to adjust the tension in the endless sprocket chain  11 . 
     It can be seen in FIG. 1 that the diameter of tension roller  6  is less than the diameter of tension roller  7 . Accordingly, if both the tension rollers  6  and  7  were rotated at the same speed, the tangential velocity of the film  5  at the surface of roller  6  would be lower than the tangential velocity of the film at the surface of roller  7  and therefore the film would be stretched between rollers  6  and  7  as it is passed through the stretch head. As the rotational speed of the rollers  6  and  7  is also dependent on the diameter of the sprocket wheels  13  and  14 , the difference in surface speed of the rollers (and hence the amount of stretch put into the film) is dependent on the roller and sprocket diameters. 
     It can also be seen in FIG. 1 that although one end of both of the tension rollers  6  and  7  are connected to the same planar part of the structure or frame of the stretch wrap head (that is, base plate  2 ) the opposite ends of the rollers (the ends shown in FIG. 1) are not directly connected together (one end of roller  6  is mounted in a plate  42  and one end of roller  7  is mounted in a separate plate  50 ) and therefore a space exists through which the film  5  may be fed in order to facilitate winding the film  5  through the stretch wrap head prior to continuous operation. 
     With reference now to FIGS. 4 and 7 to  9 , the connection between the base plate  2  and the driven end of rollers  6  and  7  will now be described with reference to the roller  6  (the driven connection with roller  7  is preferably identical to the connection with roller  6  and will not therefore be described in detail). In FIG. 4 it can be seen that the driven sprocket  14  (which is preferably provided in various alternative diameters, each having a different number of teeth thereby allowing an operator of the stretch wrap apparatus to vary the speed of the rollers by simply replacing gear wheel  14  while maintaining the speed of drive motor  8  constant) has a central hub  20  within which is housed the cylindrical end portion  21  of a driven fixed stub axle  22  (see FIG.  7 ). The hub  20  is keyed, having an axially extending slot  23  provided therealong. The cylindrical end portion  21  of fixed stub axle  22  is provided with a complementary slot  24  (seen in cross-section in FIG. 8) which in use is aligned with the slot  23  in the hub of gear wheel  14 , a fixing means  25  (such as a steel rod or ball bearing) being positioned within both of the slots to prevent relative rotational movement between the gear wheel and the fixed stub axle  22 . 
     The central part of the fixed stub axle  22  includes a collar  26  which is mounted in a rolling bearing  27  which is itself fixed within a mounting plate  28  which is fixedly attached about an orifice in base plate  2  so that the end  29  of the fixed stub axle protrudes through the base plate  2 . 
     Roller  6  (which preferably is a rubberized roller having a thin layer of rubberized material around its outer surface to enable the plastics film to be gripped) is preferably a hollow metal cylinder having disc inserts fitted within either end, the disc inserts provided with apertures for mounting the rollers within the frame of the stretch wrap head. The disc insert  30  provided at the driven end of the roller  6  is provided with an aperture having first a square shape cross-section  31  and then a circular shaped cross-section  32  further into the roller. The end  29  of the fixed stub axle  22  has a circular cross-section which fits within aperture  32  of the end disc  30 , while a section  33  of the ends  29  of the fixed stub axle  22  has a square cross-section which fits within the square aperture  31  of the end disc  30  to ensure that there is no relative rotational movement between the fixed stub axle  22  and the roller  6 . It should be noted that the cross-section of section  33  could be any other appropriate non-circular shape. 
     From the above description it can be seen that rotation of gear wheel  14  will cause roller  6  to rotate at a speed set by the motor and the diameter of sprocket  14 . 
     The non-driven end of roller  6  (and also roller  7  which preferably has an identical connection mechanism although it should be noted that only one of rollers  6  or  7  could be fitted with the quick release mechanism herein described) is connected in the frame of the stretch wrap head as shown in FIGS. 5A,  5 B and  6 . The end of roller  6  is provided with a further disc insert  40  which is provided with a central aperture having mounted therein rolling bearing  41 . The part  42  of the frame adjacent the end of roller  6  is provided with a hole through which a removable stub axle  43  passes, the end  44  of the removable stub axle  43  being rounded in cross-section and being a good slide fit within the rolling bearing  41  to allow relative rotational movement between the roller  6  and removable stub axle  43 . The removable stub axle  43 , as seen in FIG. 6 comprises a cylindrical body portion  45  between narrowed neck sections  46  and  47 . 
     In order to prevent the removable stub axle  43  from moving axially once installed in the stretch wrap head, means are provided within the part  42  of the stretch wrap head frame to lock the removable stub axle in position. For example, a captive ball bearing  48  may be provided in the wall of the hole through which the removable stub axle must pass. The captive ball bearing may be biased (by a spring for example) towards a position protruding into the path of the removable stub axle while being capable of movement out of the stub axle&#39;s path. The two neck portions  46  and  47  of the shaft of the removable stub axle  43  form two “detents” into which the ball bearing  48  will protrude, holding the removable stub axle in position until a predetermined axial force is applied to the removable stub axle to force the ball bearing out of the neck portion  46  or  47  against the biasing spring force. The neck portion  46  is useful for holding the stub axle in position within the frame of the stretch wrapping machine (but out of its operatively engaged position) while allowing removal of the roller  6  and the neck portion  47  in use accommodates the ball bearing  48  while the roller is installed and operational. 
     It can be seen in FIGS. 5A and 5B, that the removable stub axle  43  includes an axial bore or shaft  49  within which is fixed rod  50  protruding from a knob or handle  51 . The rod  50  is secured within the axial bore  49  and to the knob or handle  51 , the knob  51  being of a convenient size for an operator to grip so that the removable stub axle  43  may be withdrawn or inserted into the frame of the stretch  20  wrapping machine and connected to or disconnected from the rolling bearing  41  in the roller  6  as desired. 
     In use, in order to remove a roller from the stretch wrapping head it is simply a matter of removing the removable stub axle  43  in a direction along the axis of rotation of the roller away from the roller (in order to remove the roller) or along the axis of rotation towards the roller (to install the roller). In the case of roller removal, once the removable stub axle  43  has been removed from the rolling bearing  41  and positioned as shown in FIG. 5A, it is simply a matter of lifting the other end of roller  6  off the fixed stub axle in order to remove the roller. Replacement or re-fitting of the roller is simply a matter of connecting the driven end of the roller to the fixed stub axle (ensuring that the section  31  of the end  29  of the stub axle is properly engaged with the correspondingly shaped aperture in the end disc  30 ) and then pushing the moveable stub axle further towards the roller so that the end  44  of the removable stub axle is engaged within the rolling bearing  41 . 
     Accordingly, at least in the preferred form of the present invention a simple, convenient and effective manual system for allowing removal and re-fitting of rollers, and in particular driven rollers, is provided which does away with the need for an operator to use hand or motorised tools and therefore allows much faster and easier removal or replacement of a roller.