Mandrel clamping arrangement

Abstract

 A mandrel clamping arrangement is described comprising an actuation mechanism (4) coupled to a clamping assembly (9). The actuation mechanism (4) comprises a linearly actuable connection rod (8) coupled to a pivotally mounted cam actuator (12) which is angularly displaced by virtue of the linear motion of said connection rod (8). The actuation mechanism is coupled to the clamping assembly by means of interengaging teeth and toothed sprockets (22,24) or by means of a pin (54) disposed at the free end of the actuator which is received in a slot (58) in an eccentric component. In either case, the rotation of the actuator (12) in one direction causes rotation of a cam (28) in the alternate direction, said cam (28) having an arcuate surface through which a clamping force can be exerted on a mandrel (18) beneath said cam (28). Optionally, a clamping bar (30) biased against the cam (28) may also be provided so that the clamping force on the mandrel (18) is exerted by said bar (30). The cam arrangement (28) ensures uniform and precisely applied clamping force over the entire mandrel (18) length and does not require any particularly precisely machined components to achieve this end.

Description

[0001] This invention relates to a clamping arrangement for a mandrel, and more specifically to a clamping arrangement specifically adapted for use in machinery for the automated manufacture of tin boxes.

[0002] Automated tin box manufacture is accomplished by juxtaposing several different pieces of machinery and providing transfer means therebetween. Tin boxes can be manufactured in a vast number of different shapes and sizes and accordingly a single piece of machinery is required to be sufficiently versatile to enable manufacture of tin boxes in a large number of said shapes and sizes. It will be understood by those skilled in the art that the machinery used has a number of different components which can be exchanged to facilitate the manufacture of different boxes and currently the length of time taken to exchange all these various components to enable a particular set of machines to manufacture a different box shape can be up to an entire day. The invention hereinafter set forth, and also set forth in our co-pending applications have as their object the reduction of this time. Any reduction achievable in the "changeover" time is especially desirable when it is considered that tin box production rates using the machinery described hereinafter may reach 40 per minute.

[0003] Tin boxes can contain a wide variety of different goods, such as bottles, chocolates, biscuits, tea, coffee and the like. Manufacturers of such products commonly consider the containment of their product in tins because of the rigidity and durability which the sheet steel, from which such tins are commonly made, provides. Additionally, the containment of a product in a tin box may also suggest that the product therein is of a certain quality, especially as ornate and detailed print effects can be obtained on the surface of the metal plates from which the tin boxes are manufactured. Such effects cannot be achieved, or are achieved only to a much lesser degree by the containment of products in cardboard cartons or receptacles of plastics materials. A tin box in which such a product is contained has the further advantage of being reusable to contain other household items such as screws, nuts bolts, pencils and pens, etc. after the product originally contained therein has been consumed or otherwise utilised.

[0004] The various separate machines required in the manufacture of tin boxes are an "Automatic Curling Notching and Beading" machine, a "bodymaker", a "round and irregular seamer", and an "end feeder", each of which has a specific task to perform during the process of tin box manufacture. Each of these is now descirbed.

[0005] The first stage in the process of automated tin box manufacture is the profiling of a simple sheet steel, and generally rectangular, blank from which the walls of the tin box are ultimately constituted. The blank is fed through an "Automatic Notching, Curling and Beading" machine, referred to hereinafter as an ANCB machine. This machine consists of a plurality of consecutively driven rollers disposed both above and below the blank as it passes therebetween, each of said rollers performing a forming step on the blank. The particular profile of each blank as it exits the ANCB machine depends on the ultimate shape of the tin, but in general the blank is substantially flat with the exception of a hem provided parallel with one of the longer edges of the blank and proximate thereto, a bead is provided on one of said longer edges, a partial curl is provided around the alternate longer edge, and a pair of hooks oppositely disposed with respect to one another on the shorter edges. Additionally, the ANCB machine has cutting means which notch the corners of the blank to preclude any interference effects which may be caused by said corners either when the blank is profiled and provided with the flanges along its shorter edges, when it is formed into the cross-sectional shape of the tin box, or when wrapped around and attached to the base of said tin box.

[0006] The hem provides a surface behind which the beaded lip of a tin lid can engage to inhibit the removal of a lid separately formed and applied around the uppermost edge of the tin box, the bead is provided to hide the sharp longer edge of the blank which ultimately forms said uppermost edge of the tin box, the partial curl on the alternate longer edge of the blank is provided to facilitate the attachment of the blank, after same has been formed into the desired cross-sectional shape, to the base of the tin box, and the hooks provided along the shorter edges of the blank facilitate the connection of said edges to one another after the forming operation. In practice, the bodymaker may be responsible for the formation of the hooks on the shorter edges of the blank to facilitate connection of said edges to one another.

[0007] The profiled blank is then fed from the ANCB machine into a bodymaker by suitable transport means which generally comprises a pair of reciprocating feed bars in conjunction with "disappearing guides" which simultaneously urge the profiled blank towards and over a forming mandrel and precisely align said blank thereon. The disappearing guides are rotated away from the blank when it is held in contact with the uppermost portion of the mandrel, which is generally of similar shape to the desired cross-sectional shape of the tin box to be manufactured, by a mandrel clamping arrangement. The removal of the disappearing guides (so-called because they "disappear" within the machine during the forming of the blank around the mandrel) allows a pair of forming wings pivotally connected together and disposed above the mandrel to rotate about their pivot and form said blank, which is at this stage still substantially planar, around the said mandrel. The forming operation performed by the wings also constrains the oppositely disposed hooks on the shorter edges of the blank to interlock on the underside of the mandrel whereupon a second forming tool, known as a hammer, compresses the metal of the blank in the interlocked region to form the vertical seam within the wall of the tin box. During all forming operations the blank is clamped against the upper surface of said mandrel by said mandrel clamping arrangement.

[0008] This invention is specifically concerned with the provision of a novel mandrel clamping arrangement.

[0009] The current clamping arrangement comprises a pair of interlocking bars having precision machined and corresponding saw-tooth formations on their interlocking faces, their alternate faces being substantially planar. The orientation of the saw-tooth formations is such that relative longitudinal movement of the bars separates them. The saw-tooth formations must be precisely machined to ensure that as one or other of the bars is urged longitudinally of the other, the separation is exactly uniform over the entire length of the bars. In such circumstances, the clamping pressure applied by the lower of the two bars on the blank against the upper surface of the mandrel is uniform and precisely applied along a line in the same plane as the axis of the mandrel and the said bars. When it is considered that the mandrel is usually curved downwardly and away from the line of contact of the blank therewith, the line of clamping action is critical because imprecise clamping of the blank could result in either slippage of the blank on the surface of the mandrel or in the blank being angled to the horizontal tangent with the uppermost region of said mandrel. .

[0010] The actuation of the abovedescribed clamping arrangement is typically effected in synchronisation with the actuation of the other parts of the machine, and moreover it is the uppermost bar which is longitudinally moved and urges the lower bar into contact with the blank to clamp same on the upper surface of the mandrel.

[0011] The fundamental disadvantage of this clamping arrangement is the cost of precisely machining the saw-tooth formations on the bars. Furthermore, the nature of the actuation mechanism and the connection of said bars within the bodymaking machinery is intricate and complex and the time taken to exchange all the various components is lengthy.

[0012] It is an object of the invention therefore to provide a clamping arrangement which is relatively simple to actuate and connect within a bodymaker, and which is capable of being used to clamp blanks of a wider range of shapes and sizes against a mandrel.

[0013] According to the invention there is provided a mandrel clamping arrangement comprising an actuation mechanism movable between a first position and a second position, and connected to a clamping assembly comprising clamp means disposed proximate the surface of a mandrel over which a blank of sheet material is to be formed, characterised in that said clamp means comprises a rotateable cam having an axis of rotation parallel to the axis of the mandrel, said cam being coupled to said actuation means which cause said cam to rotate exert a clamping force on a blank interposed between portions of the surfaces of said cam and said mandrel.

[0014] Preferably the cam exerts a force along a line parallel and in the same plane as the axes of rotation of said cam and said mandrel against a blank interposed between said cam and said mandrel.

[0015] Preferably the clamping assembly can be exchanged for an alternative clamping assembly by simply disconnecting same from said actuation mechanism and sliding said assembly along supports provided along the length of said assembly.

[0016] Preferably the clamping assembly is further provided with a clamp bar of substantially similar length to the axial length of the mandrel and having an upper and lower surface, said bar being urged towards the mandrel as the cam rotates and comes into contact with the upper or lower surface of said bar, the alternate surface exerting a uniform clamping force along the length of the bar on the mandrel and any blank interposed therebetween.

[0017] Preferably the clamp bar is resiliently biased within the clamping assembly, the cam acting against said bias such that the clamp bar retracts automatically when the cam is no longer in contact with said surface.

[0018] The use of a rotating cam significantly decreases the cost of the clamping arrangement, and increases the versatility thereof as the cam can be orientated to allow clamping of blanks of different shapes and sizes against the mandrel. Furthermore, the use of a simple cam arrangement and allows unprecedented speed of replacement of the clamping assembly as a unit.

[0019] A specific embodiment of the invention is now described by way of example only and with reference to the accompanying diagram wherein:

[0020] Figure 1 shows a sectional view of the clamping arrangement according to the invention.

[0021] Figures 2A, 2B, 2C show respectively a sectional side view, and front elevations in retracted and extended positions of an alternative clamping arrangement according to the invention.

[0022] There is shown in Figure 1 a clamping mechanism 2 comprising an actuation mechanism 4 and a clamp assembly 6. The actuation mechanism 4 comprises an axially actuable connection rod 8 pivotally connected at 10 to a cam actuator 12 which is pivotally mounted at 14 to a brace 16 connected to a bodymaking machine (not shown) and disposed above a mandrel 18.

[0023] The cam actuator has an arcuate bulbous end 20 which is provided with gear teeth 22 which mesh with teeth 24 provided on the outer surface of a shaft 26 freely rotatably mounted within the clamping assembly 6. The axial dimension of the shaft 26 is relatively small when compared to the axial dimension of the mandrel 18, and indeed the shaft is disposed entirely behind the said mandrel. The shaft 26 may be replaced by a toothed sprocket.

[0024] A cam 28 is eccentrically mounted to said shaft or toothed gear 26 and is caused to rotate as the said shaft rotates by virtue of the meshing gear teeth provided thereon and on the cam actuator 12.

[0025] The clamping assembly 6 is further provided at its lower extremity with a clamping bar 30 which is suspended from said assembly by springs 32, 34 which depend at one end from removable spring supports 36, 38 within the assembly and are connected at their alternate end to clamp bar support rods two of which are shown at 40, 42. It is to be mentioned that the clamp bar is ideally supported by at least two pairs of springs disposed along the length of and within the assembly connected to at least two pairs of clamp bar support rods.

[0026] Forming wings 44, 46 shown in dotted line are pivotally connected together at a pivot 48 also shown in dotted line and are typically mechanically actuable between the position shown in the figure in which they surround the mandrel 18, and a retracted position in which the tips of the forming wings (not shown) are disposed above the uppermost surface of the mandrel 18 allowing for a blank of substantially planar sheet material which may be wider than the distance between said tips in their retracted position can be slid over the upper surface of said mandrel without interference therefrom. The formed blank is shown in dotted line in the figure at 50, but it is to be pointed out that in the arrangement shown in Figure 1, the clamping bar is in the retracted position as the cam 28 is not in contact with the uppermost surface of said clamping bar. It is more likely that at this stage in the forming operation, the clamping bar would be urged into contact with and exert a clamping force on the blank 50 against the mandrel 18.

[0027] The actuation of the clamping arrangement will now be described.

[0028] Once a profiled, but substantially flat blank is precisely positioned on the mandrel, the connection rod 8 is forced in a direction 9 and causes the cam actuator to rotate in a direction shown at 13. This in turn causes the shaft or toothed gear 26 and the cam 28 connected thereto to rotate in opposite direction to that shown at 13 and thus the bulbous end of the cam is urged into contact with the upper surface of clamp bar 30. Said clamp bar is urged away from the assembly 6 by the action of the cam and into clamping contact with the substantially flat blank thereon. The blank is thus clamped against the mandrel 18.

[0029] Thereafter, the forming wings are mechanically rotated about the pivot 48 and form the blank around the mandrel, ultimately coming to rest at the position shown in the figure. The blank 50 is then unclamped by the reverse actuation of the various components describe above, the wings are again retracted and the formed blank, in which the seam has been formed against the lowermost surface of the mandrel (not shown) by suitable means while the wings are disposed therearound, and the formed blank is shunted off the mandrel into the next machine where a base is attached to said blank.

[0030] Referring now to Figures 2A, 2B, 2C there is shown an alternate clamping arrangement 50. In the interests of clarity, only the salient components to the arrangement are shown, and reference numerals used in Figure 1 are used to identify like components in the Figures 2A, 2B, 2C. In the arrangement shown, the connection rod 8 is connected at 10 to the cam actuator 12 which as a result of horizontal actuation of said connection rod 8 is constrained to rotate about a pivot in a direction shown at 52 in Figures 2B, 2C.

[0031] The cam actuator is provided with a pin 54 at its remote end 56, said pin 54 being slidingly received in a slot 58 provided in a teardrop-shaped link component 60. The slot 58 is disposed collinearly with the single axis of symmetry of said link component 60, the length of the cam actuator between the remote end 56 and the pivot 14, the maximum extent of rotation of said cam actuator, and the length of the slot being designed such that a suitable angular displacement of the cam 28 is achieved. Ideally, the maximum angular displacement of the cam should be in the region of 37° to allow for a variety of different blank thicknesses to be secured by the said clamping arrangement to the mandrel.

[0032] It will be seen from Figures 2B and 2C in particular that the rotary motion of the cam actuator causes concomitant rotation of the link component 60 in the reverse direction, and thus the cam 28 to which said link component is secured around a spindle provided at the end of the cam 28 by means of a screw clamp 64 disposed at the rear bulbous end of the link component 60. Similarly to the arrangement shown in Figure 1, the arrangement in Figures 2A, 2B, and 2C is also to be provided with a spring biased clamp bar which contacts the blank and transmits the clamping force applied by the cam therethrough to said blank disposed on the mandrel. It is also to be mentioned that cam 28 is approximately of the same length as the mandrel and that the cam is supported is teardrop-shaped link components at either end, although the said cam is only driven through connection rod 8 at one end. This ensures a uniform clamping force on the blank through the clamping bar over the entire length of the blank disposed on said mandrel.

[0033] Furthermore, those skilled in the art will appreciate that the particular orientation of the cam at the extremity of its angular displacement, which position the position shown in Figure 2C most closely approaches, need not necessarily be perpendicular, i.e. where the longest axis of symmetry of the cam is vertical. The provision of the clamping bar beneath the cam and the arcuate surface of the cam in tangential contact therewith ensures that the clamping force exerted by said cam is always exerted vertically downwardly, which is also the motion of said clamping bar clamping bar. The design of the various components can therefore be chosen simply to ensure that the extent of vertical displacement of the clamping bar is sufficient to accommodate a variety of different blank thickness between said clamping bar in its retracted position and the mandrel upper surface on which said blank is disposed.

Claims

1. A mandrel clamping arrangement comprising an actuation mechanism movable between a first position and a second position, and connected to a clamping assembly comprising clamp means disposed proximate the surface of a mandrel over which a blank of sheet material is to be formed, characterised in that said clamp means comprises a rotateable cam having an axis of rotation parallel to the axis of the mandrel, said cam being coupled to said actuation means which cause said cam to rotate and exert a clamping force on a blank interposed between portions of the surfaces of said cam and said mandrel.

2. An arrangement according to claim 1 wherein the cam exerts a force along a line parallel and in the same plane as the axes of rotation of said cam and said mandrel against a blank interposed between said cam and said mandrel.

3. An arrangement according to claim 1 wherein the clamping assembly can be exchanged for an alternative clamping assembly by simply disconnecting same from said actuation mechanism and sliding said assembly along supports provided along the length of said assembly.

4. An arrangement according to claim 1 wherein the cam is similar in length to the length of the mandrel on which it exerts a clamping force.

5. An arrangement according to claim 1 wherein the clamping assembly is further provided with a clamp bar of substantially similar length to the axial length of the mandrel and having an upper and lower surface, said cam having a contact surface in contact with one of the surfaces of said bar such that the rotation of said cam causes linear displacement of said bar towards the mandrel to achieve a clamping effect on a blank interposed between said clamp bar and said mandrel.

6. An arrangement according to claim 5 wherein the clamp bar is biased within the clamping assembly against the contact surface of the cam to ensure automatic retraction of said bar as the cam is rotated in an alternate direction reducing and ultimately removing the clamping force.

7. An arrangement according to claim 1 wherein the connection between the actuation mechanism and the clamping assembly is achieved by means of gear teeth interengaging with a sprocket.

8. An arrangement according to claim 7 wherein the teeth are provided on a pivotally mounted cam actuator, the angular displacement of which is effected by means of a linearly actuable connection rod, said teeth interengaging with the teeth of sprocket connected to the cam.

9. An arrangement according to claim 1 wherein the cam is provided with spindles both ends thereof, said spindles providing a means of support for said cam.

10. An arrangement according to claim 1 wherein the connection between the actuation mechanism and the clamping assembly is achieved by means of an eccentric component coupled to the said cam in which is provided a slot in which a pin, angular displacement of said pin in one direction causing angular displacement of the eccentric component and thus the cam in the alternate direction.

11. An arrangement according to claim 10 wherein the actuation mechanism comprises a linearly actuable connection rod coupled to a pivotally mounted cam actuator on one side of a pivot which is angularly displaced as a result of the linear actuation of said connection rod, said pin being provided on said cam actuator on the alternate side of said pivot and received in the slot of said eccentric component to cause angular displacement thereof.

Drawing