IMPROVEMENTS RELATING TO TRANSFER MECHANISMS

Abstract: A transfer mechanism (56, 60), particularly for use as part of a punching device for punching a plurality of holes in a stack of paper sheets, has drive means (50) which operates to drive the punch assembly (32) into its advanced or its retracted position without significant overrun. A transfer mechanism (56, 60) is present between the drive means (50) and the punch assembly (30) which transmits drive to the punch assembly (30) only between the advanced and retracted positions.

Description: Title: Improvements Relating to Transfer Mechanisms Description of Invention This invention is concerned with transfer mechanisms which transmit drive from a drive means to an actuating member, for example, for devices for punching a plurality of holes in a stack of sheets, such as of paper. An example of a conventional transfer mechanism in such devices is a rack and pinion mechanism which includes a plurality of pinions, rotatable by a motor or other drive means, to move the actuating member between selected positions. A problem encountered with conventional transfer mechanisms is that the drive means may, particularly if a powerful motor is used, overrun, causing the actuating member to move beyond the position at which it should have stopped. The amount of overrun depends, among other factors, on the mass of the actuating member, the force generated by the drive means, and the resistance encountered by the actuating member in operation. Thus it is difficult to predict the amount that the actuating means will move and hence it is necessary either to employ position sensing means to determine the position of the actuating means at the end of its travel or to use a type of drive means, for example a stepper motor, which can be moved by a precise measured amount. Stepper motors, however, are relatively expensive and are unable to handle large, unpredictable loads. A further problem with conventional transfer mechanisms is that the amount of overrun of the actuating member must be accommodated in the design of its housing, causing the device to bulkier than would otherwise be necessary. A specific example of the problems that can arise in practise will now be described with reference to a conventional punching device, but it will be appreciated that similar problems arise with other mechanical devices. A conventional punching device for punching a plurality of holes in a stack of sheets such as of paper, comprises a housing defining an opening or slot into which one or more sheets of paper or the like material (hereinafter referred to as paper, for convenience) may be located preparatory to the performance of a punching operation, said opening or slot hereinafter being referred to as the punching slot. The slot is conventionally bounded by a guide plate and a base plate or die, each being provided with a plurality of aligned apertures. Mounted on the housing is a punch assembly comprising a plurality of punches guided for rectilinear movement between retracted and advanced positions. Drive means is provided, conveniently an electric motor, which is operative through the intermediary of a transfer mechanism, to move the punch assembly from its retracted to its advanced position, causing the punches to pass through the apertures in the guide plate, across the punching slot and through the sheets of paper therein, and into the apertures in the base plate. Such a device is hereinafter referred to as being of the kind specified. The punches may form part of a punch plate which is mounted for rectilinear sliding movement, and a conventional transfer mechanism comprises a rack and pinion device, including a plurality of pinions, rotatable by the motor, the rack formation being provided on the punch plate, whereby rotation of the pinions moves the punch plate between said retracted and advanced positions. A problem encountered with conventional punching devices of the kind specified is the force required to cause the punch members to pass through a stack of sheets located in the punching slot, particularly when it is desired to punch the maximum number of holes, conventionally twenty-one. Additionally, there is an increasing tendency for such devices to be utilised to maximum capacity, and for this reason, it has been standard practice as of late to utilise relatively powerful motors. This causes problems, as follows: a) It is necessary during operation of a punching device of the kind specified to terminate movement of the punch assembly when the punches have completed their punching operation. When the punches have completed passage through the stack of paper in the punching slot, resistence to movement suddenly decreases. Conventionally, sensing means is utilised to sense the arrival of the punch assembly in its advanced position, which may involve the direct positional sensing of the punch assembly, or the positional sensing of another element associated with movement of the punch assembly, and the sensing means operates to terminate operation of the drive motor. However, difficulty is caused by motor over-run, causing the punch assembly to move beyond its advanced position. This problem is, as will be appreciated, exacerbated by the reduction in resistence at the point at which the punches complete movement through the stack of sheets; and b) It is also required to terminate movement of the punch assembly when only a few sheets are presented for punching, and only a small resistence to movement of the punch assembly is encountered. According to this invention there is provided a transfer mechanism which in use provides a selective transmission of drive between a drive means and an actuating member between two selected positions only, and not beyond. The transfer mechanism may comprise two transfer members, a first member and a second member, in which the second member acts against the first member to move the actuating member between the selected positions only, and not beyond. Preferably, the first transfer member comprises at least two faces, and the second transfer member acts against the faces during operation of the drive means. Conveniently, the construction and arrangement is such that when the second transfer member acts against one of the faces, movement of the actuating member is produced, and when the second transfer member acts against the second of the faces no such movement is produced. Preferably, the first transfer member comprises four faces, two of which, being active, act to produce movement of the second transfer member and two of which, being passive, do not produce such movement. The second transfer member may be a driving member operative against the first transfer member to produce movement thereof or maybe a driven member, which is moved when engaged by the first transfer member. Thus, the second transfer member may be provided by the actuating member, or part thereof. Alternatively, the transfer mechanism make comprise a member comprising three faces which may be engaged directly or indirectly with a further transfer member, engagement by said further transfer member with a first face being operative to cause movement of the actuating member in a first direction, engagement thereby with a second face being operative to cause movement of the actuating member in a second direction, and traverse thereby of a third face being inoperative to cause movement of the actuating member. According to this invention there is also provided a transfer means operative to transmit drive from a drive means to an actuating member, said transfer means comprising a first transfer member forming part of or which is connected to said drive means, and a second transfer member which forms part of or is connected to said actuating member, characterised in that one of the said transfer members comprises a first face which on traverse thereby of the other member produces movement of the transfer member, and a second face which on traverse thereby of the other member does not produce movement of the actuating member. Preferably the transfer member comprises a third face, which on traverse thereby of the other member does not produce movement of the actuating member. Preferably the drive means is operative to produce movement of the transfer member along a predetermined path, such movement causing the said transfer member to traverse said faces. Conveniently the movement of the drive member is rotary movement, and preferably the third face extends when the actuating member is in one terminal position, circumferentially of the axis of rotation of the said transfer member. According to this invention there is also provided a punching device of the kind specified, characterised in that it includes a transfer mechanism of the kind set out above, the actuating member being provided by or being connected to the punching assembly of the device, the guide means operating to drive the punch assembly to an advanced position and no further. Thus, preferably operation of the drive means terminates at or shortly subsequent to the punch assembly moving into its advanced position, but the drive means is inoperative to effect movement of the punch assembly beyond its advanced position. According to this invention there is also provided a punching device of the kind specified, in which the drive means operates to drive the punch assembly to its advanced position and no further. Thus, conveniently, the advanced position is defined as the position in which some at least of the punches do not project beyond the base plate. Preferably operation of the drive means terminates at or shortly subsequent to the punch assembly moving into its advanced position, but the drive means is inoperative to effect movement of the punch assembly beyond its advanced position. It will be appreciated that whilst the advanced position may conveniently be the position of the punch assembly on completion of movement thereof into the punch apertures of the die plate, it may if desired be a defined position a short distance beyond said position. Additionally, retractive movement of the punch assembly from its advanced position towards its retracted position is effected against the force needed to withdraw the punches from the apertures which have been punched in the sheets of material, and on completion of such withdrawal, further retractive movement is undesired. Similarly, however, difficulty is encountered in minimising such movement of the punch assembly beyond its retracted position, caused by the drive motor over-run, and indeed it is preferable that retractive movement of the punch assembly terminates with some at least of the punches themselves within the apertures of the guide plates. Thus, according to this invention there is also provided a punching device of the kind specified, in which the drive means operates to withdraw the punch assembly from its advanced to its retracted position, and no further. Thus, conveniently, the retracted position is defined as the position in which some at least of the punches have not been withdrawn beyond the apertures of the guide plate. There will now be given detailed descriptions, to be read with reference to the accompanying drawings, of two punching devices which are preferred embodiments of this invention, having been selected for the purposes of illustrating the invention by way of example. In the accompanying drawings: FIGURES 1 to 5 show various stages in the operation of the punch assembly of the punching device which is the first embodiment of this invention; Figure 5a shows an alternative arrangement which may be utilised in the first embodiment; and FIGURES 6 to 10 show various stages in the operation of the punch assembly of the punching device which is the second embodiment of this invention. The device which is the first embodiment of this invention comprises a punch assembly 30 comprising a punch plate 32 mounted for rectilinear movement, comprising a plurality of individual punches 42. The punch assembly also comprises a base- or die-plate 44, provided with a plurality of punching apertures 46, and, spaced a short distance from the die plate 44, a stripper-plate 48 provided with aligned apertures 50. Defined between the guide plate 48 and the die plate 44 is a slot 52, referred to hereinafter as the punching slot, into which a stack of documentary material such as paper may be placed, preparatory to an edge punching operation. Details of the construction and operation of the device described thus far are conventional, and reference may be made for details omitted herefrom, to the specification of other of our patent applications, pending and granted, details of which may readily be obtained. The punching device comprises drive means 50, comprising a rotary electric motor 52, comprising an output drive spindle 54 (shown in dotted lines in Figure 1) driven through gearing (not shown). Operative between the drive spindle 54 and the punch assembly 30 is transfer mechanism comprising a first transfer member 56 in the form of an arm provided with a transverse roller 58 thereon, a second transfer member 60 secured to a drive pinion 62, the drive pinion 62 and transfer member 60 being rotatable about a common axis 64, teeth 66 of the drive pinion being engageable with slots 34 in the punch plate 32, said slots also forming part of the transfer mechanism of the punching device. The second transfer member 60 is provided with four drive faces 72, 74, 76 and 78, two of said drives faces 72 and 78 being passive, and two of said drive faces 74 and 76 being active. In particular, the drive face 72 defines an arc centered about the axis 55 of the drive spindle 54 when the punch plate 32 is in its retracted position (shown in Figure 1) whilst the drive face 78 defines an arc centered about the axis 55, when the punch plate 40 is in its advanced position, as shown in Figure 5. The drive faces 74 and 76 define a slot 80 within which the roller 58 may travel, said slot extending radially of the axis 64. The sequence of operation of the drive means of the punch assembly will now be described with reference to Figures 1 to 5 of the drawings. As has been said, Figure 1 illustrates the position of the integers with the punch plate 30 in its retracted position, ie. with the punches 32 having just been withdrawn from the apertures of the guide plate 52. A stack of paper or the like material is entered into the aperture 52, and a signal commencing operation of the device is initiated, such as the pressing of a start button (not shown). The motor is caused to operate, involving rotation of the spindle 54 in an anticlockwise direction about the axis 55, as shown in the drawing, causing the roller 58 to move along the first drive face 72 without initially producing any significant rotative movement of the drive pinion 62, and thus producing no significant movement of the punch plate 32. When the drive roller 58 passes into the slot 80, as shown in Figure 2 of the drawings, the roller 58 engages the drive face 74 producing anti-clockwise rotation of the pinion 62, and movement of the punch plate from its retracted position towards its advanced position. Such movement continues whilst the drive roller 58 initially travels into, and then from the slot 80, the midpoint in the movement of the punch plate being shown in Figure 3, and the punch plate being shown in its advanced position in Figure 4, defined by engagement of the roller 58 at the junction of the drive face 76 and the drive face 78. At this point, or indeed shortly before if desired, a sensing member may be energised to cause termination of operation of the drive motor 52, run down of the motor being operative to produce movement of the roller 58 along the drive face 78 without any significant movement of the punch plate 30 from its advanced position. Thus, the advanced position may be determined accurately, and indeed may if desired by determined as being that point in which all of the punches 42 have passed just beyond the apertures 46 of the die plate 44, as shown in Figures 4 and 5, without the need for any accommodation for the over-travel conventionally produced. On completion of cessation of movement of the drive motor 52, a reverse signal is applied to the motor, causing the drive spindle 54 to rotate in a clockwise direction from the position shown in Figure 5, the drive roller 58 initially travelling along the drive face without producing any significant rotational movement of the pinion 62, until the roller 58 enters the slot 80, at which point continued rotation of the drive spindle 54 produces clockwise rotation of the pinion 62, producing in turn retractive movement of the punch plate 40. Retraction of the punch plate 40 continues until the roller 58 leaves the slot 80, this position, shown in Figure 2, defining the retracted position of the punch plate 40, allowing said retracted position to be defined by the point of which the last of the punches 42 passes into the apertures 50 of the guide plate 52. As with advancement of the punch plate, transfer of the roller 58 from the drive face 54 to the drive face 72 may cause activation of a sensing member which terminates operation of the drive motor 52, or indeed if desired such a termination may be effected momentarily prior to such transfer. In either event, over-run of the drive motor 52 causes movement of the roller 58 along the drive face 72 (see Figure 1) without producing any further significant movement of the punch plate itself. It will be appreciated that the faces 72, 74, 76 and 78 have been referred to as drive faces purely for convenience, although in fact only engagement by the roller 58 with the faces 74 and 76 produces movement of the actuating member, the faces 72 and 78 being thus to an extent passive. Nonetheless, close proximity between the roller 58 and the faces 72 and 78 is effective to resist any undesired movement of the actuating member, either from its retracted towards it advanced position, or from its advanced towards its retracted position, as the case may be. Alternatively, as is shown in Figure 5a, the faces 72 and 78 may be formed by a Y-shaped cam track, along which the roller 58 traverses during operation of the transfer means, thereby ensuring restraint to movement of the actuating member, when in one or other of its selected positions. Whilst the drive roller 58 is said to engage the passive drive faces 72 and 78, in fact they may traverse the passive faces 72 and 78 without any actual contact being required, for the performance of the operation in accordance with this invention. By the use of the invention above described, powerful motors may be utilised to drive the punch plate, enabling large stacks of documentary material to be punched simultaneously, without any problem caused by motor over-run. The punching device which is the second embodiment of this invention is similar in general construction and operation to the device which is the first embodiment, and will be described hereinafter only insofar as it differs from said first embodiment. In the second embodiment, a transfer member 130 is utilised, having curved drive faces 82, 84 engageable within a slot 90 provided in the punch plate 32. A motor 131 is utilised, which is operative to rotate the transfer member about an axis 132. In addition to the two drive faces 82, 84, the transfer member 130 comprises a third drive face 86, which has a radius of curvature centred on the axis 132 of rotation of the transfer member 130. Thus, during movement of the punch member 32 from its retracted to its advanced position (shown in the stage, Figure 6 to Figure 7) the leading edge 92 of the slot 90 is engaged by the first drive face 82. The fully advanced position of the drive plate is defined by the point at which the drive face 82 moves out of engagement with the slot 90, to be replaced by the third drive face 86, (Figure 7). Continued rotation of the transfer member 130 as may be caused by over-run of the motor 131, thus produces no significant further advancement of the punch plate 32. It will be appreciated that during such final anti-clockwise rotation of the transfer member 130, the drive face 84 of the transfer member does in fact move away from the trailing edge 94 of the slot 90. Thus on commencement of retractive movement of the punch member 32, initially relative movement occurs between the drive face 84 and the leading edge 92, whilst the drive face 84 approaches the trailing edge 94, further clockwise rotation of the transfer member 130 producing the desired retractive movement of the punch plate 32. Movement of the punch plate 32 into its fully retracted position, shown in Figure 9, is defined by the point at which the drive face 84 of the transfer member 130 moves out of engagement with the trailing edge of the slot 90, to be replaced by the third drive face 86, and as previously, continued rotation of the transfer member 130 produces no additional retractive movement of the punch plate 32. By the use of the invention above described, a convenient solution is found to the problem of motor overrun, and simultaneously allows the punching machine to be built to a compact design format. Naturally the skilled reader will appreciate that the transfer mechanism outlined above, could be used for a wide variety of applications. It could be used where a motor must be used for relatively precise positioning and where for cost or other reasons stepper motors are inappropriate. For example the transfer mechanism could be used in automated positioning for an assembly line, for a security locking system, for movement of machine tool elements such as presses, or for many other such applications. In the present specification "comprise" means "includes or consists of and "comprising" means "including or consisting of. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims: CLAIMS 1. A transfer mechanism which in use provides a selective transmission of drive from a drive means (50) to an actuating member (30) between two selected positions only, and not beyond. 2. A transfer mechanism according to Claim 1 comprising two transfer members (58,60), a first transfer member (56) being operative to act against the second member (60) to cause the second transfer member to move the actuating member (30) between the selected positions only and not beyond. 3. A transfer mechanism according to Claim 2 characterised in that the second transfer member (60) comprises at least two faces (72,74,76,78) and the first transfer member (58) traverses the faces during operation of the drive means. 4. A transfer mechanism according to Claim 3 characterised in that when the first transfer member (58) traverses one of the faces (74,76), movement of the actuating member (30) is produced, and when the first transfer member (58) traverses a second of the faces (72,78) , no such movement is produced. 5. A transfer mechanism according to Claim 3 or 4 characterised in that the second transfer member (60) comprises four faces (74,76), two of which are operative to produce movement of the first transfer member and two (72,78) of which are not operative to produce such movement. 6. A transfer mechanism according to any of Claims 3 to 5 characterised in that the first transfer member is a drive member operative to engage with the second transfer member to produce movement thereof. 7. A transfer mechanism according to a further transfer member, engagement by said further transfer member with a first face being operative to cause movement of the actuating member in a first direction, engagement thereby with a second face being operative to cause movement of the actuating member in a second direction, and traverse thereby of a third face being inoperative to cause movement of the actuating member. 8. A transfer mechanism according to Claim 7 characterised in that the second transfer member is provided by the actuating member (32). 9. A transfer mechanism according to Claim 1 comprising a transfer member comprising three faces which may be engaged directly or indirectly with a further transfer member, engagement by said transfer member with a first face being operative to cause movement of the actuating member in a first direction, engagement thereby with a second face being operative to cause movement of the actuating member in a second direction, and traverse thereby of a third face being inoperative to cause movement of the actuating member. 10. A transfer means operative to transmit drive from a drive means to an actuating member, said transfer means comprising a) a first transfer member (56,130) forming part of or is connected to said drive means; and b) a second transfer member (60,32) which forms part of or is connected to said actuating member (32), characterised in that one of the said transfer members (60,130) comprises a first face (74,76; 82,84), which on transverse thereby of the other member produces movement of the transfer member, and a second face (72,78; 86) which on traverse thereby of the other member does not produce movement of the actuating member. 11. A transfer means according to Claim 10 wherein the said transfer member comprises a third face, which on traverse thereby of the other transfer member does not produce movement of the actuating member. 12. A transfer means according to one of Claims 10 and 11 wherein the drive means is operative to produce movement of the said transfer member along a predetermined path, such movement causing the said transfer member to traverse said faces. 13. A transfer means according to Claim 12 wherein movement of said one drive member is rotary movement. 14. A transfer means according to Claim 13 wherein the third face extends when the actuating member is in one terminal position, circumferentially of the axis of rotation of the said transfer member. 15. A punching device of the kind specified characterised in that it includes a transfer mechanism according to any preceding claim, the actuating member being provided by or being connected to the punching assembly of the device, the drive means operating to drive the punch assembly to an advanced position and no further. 16. A punching device according to Claim 15 characterised in that the operation of the drive means terminates at or shortly subsequent to the punch assembly moving into its advanced position, but the drives means is inoperative to effect movement of the punch assembly beyond its advanced position. 16 17. A punching device of the kind specified characterised in that it includes a transfer mechanism according to any of Claims 1 to 14, the actuating member being connected to the punching assembly of the device, the drive means operating to withdraw the punch assembly to a retracted position, and no further. 18. A punching device according to Claim 17 characterised in that the operation of the drive means terminates at or shortly subsequent to the punch assembly moving into its advanced position, but the drive means is inoperative to effect movement of the punch assembly beyond its advanced position.

Inventors: BUMPSTEED AUSTIN, MEAD DAVID, SMITH IAN, BUMPSTEED, AUSTIN, MEAD, DAVID, SMITH, IAN
Applicants: ACCO EUROP PLC, BUMPSTEED AUSTIN, MEAD DAVID, SMITH IAN, ACCO EUROPE PLC, BUMPSTEED, AUSTIN, MEAD, DAVID, SMITH, IAN
Application year: 2001
Main classification: F16H25
IPC codes: B26D5, F16H25