US2827840A - Step and repeat mechanism for photocopying machines - Google Patents

Description

March 25, 1958 w. H. KEMP 2,827,840

STEP AND REPEAT MECHANISM FOR PHOTO-CCPYING MACHINES Filed April 22, 1955 3 Sheets-Sheet l A 3!, P u E 1 1' l zr-y 7;; by/ I; 23-? [1 7 E i I d L o /I o 1 r 6 1 [i i 6 f f I? llll lllIlK/ 1 l Um mil/4mm W. H. KEMP March 25, 1958 STEP AND REPEAT MECHANISM FOR PHOTO-COPYING MACHINES Filed April 22, 1955 3 Sheets-Sheet 2 March 25, 1958 w. H. KEMP 2,327,340

STEP AND REPEAT MECHANISM FOR PHOTOCOPYING MACHINES Filed April 22, 1955 5 Sheets-Sheet 3 illnite ates Patent STEP AND REPEAT MECHANISM FOR PHOTO- COPYING MACHINES William Henry Kemp, Leeds, England, assignor to George Mann & tjompauy Limited, Leeds, England, a British company Application April 22, 1955, Serial No. 503,150 Claims priority, application Great Britain April 27, 1954 6 Claims. (Cl. 95-73) This invention relates to mechanical pressure-applying means applicable to step-and-repeat printing-down or photo-copying machines used in the printing trade, and wherein it is necessary to cause relative movement between a unit-transparency carrier and a support for photosensitive material, so as to bring the surfaces into contact with a controllable pressure. For convenience the term step-and-repeat machine is used hereafter to refer to the above type of machine.

Machines of the above character are used for multiplying photographic images by repeatedly copying a unittransparency onto a sheet of photographic film, a glass photographic plate, or onto a non-transparent material, such as zinc, coated with a photo-sensitive layer. It is essential that a perfect contact shall be made between the surfaces of the original transparency and the photo-sensitive material, and to effect this two systems are used on existing types of machines for applying pressure, i. e. vacuum or mechanical.

In the case of the vacuum system, even pressure of a predetermined number of pounds per square inch can be applied, regardless of the area of the unit, but this system has the disadvantage that unless the vacuum is kept to a very low degree, the photo-sensitive surface is marked by the edges of the unit and, in the case of glass plates, there is considerable risk of breakage.

In the known mechanical systems, the disadvantage commonly encountered is the difficulty of determining the exact amount of pressure which is applied per square inch of unit. In some existing machines no provision is made for control and the result depends entirely on the operators judgment. In other known forms, the pressure is controlled by an adjustable slipping clutch, but the control is not sufiiciently accurate except when heavy pressures are being applied. In other known forms, the support, e. g., a bed, carrying the photo-sensitive material, is raised against pressure springs acting on the upper surface of the unit-transparency carrier, suitable measuring equipment being provided to read the distance the negative carrier has been raised and thus the degree to which the superimposed springs have been compressed. This system has the disadvantage, firstly, that the pressure must be observed on the indicator each time contact is made and, secondly, that, if a considerable range of pressures is required, the total lift of the receptive surface must be considerable.

In order to obtain a consistent result and to eliminate all risk of damaging the receptive surface, the pressure applied must be proportional to the area of the material carrying the unit, e. g., if a pressure of one pound per square inch is required, a unit of 3" x 2" requires six pounds total pressure, whereas a unit of 15'' X 12" requires 180 pounds pressure.

The present invention has for its object to provide improved mechanical pressure-applying means for use with machines of the character referred to, in which accurate control of the pressure-applied through a relatively wide range of pressures is required. 7 v

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According to the present invention, mechanical means for applying pressure between two elements, as for ex erting contact pressure between surfaces of a transparency and a receptive surface carried by said respective elements, comprises a first movable member operable to apply pressure, a second movable member operatively connected to mechanism for effecting relative movement between said elements, and spring means arranged to transmit movement from said first movable member to said second movable member whereby said members move in unison until movement of said second movable member is arrested by contact between surfaces to be pressed together, whercafter pressure is applied through said spring means to exert pressure between said elements to a degree dependent on relative movement between said first and second movable members against said spring means. One of said elements may be fixed or held stationary and the other of said elements connected through said mechanism with said second movable member.

The degree of pressure exerted may be determined by indicator means associated, or connected for movement, with said first and second members and registering the pressure exerted through said spring means dependent on the amount of relative movement between the said first and second movable members. Adjustable stop means may be provided for limiting movement of said first movable member in a direction for applying pressure, whereby a predetermined degree of pressure may be applied on effecting movement of said first movable memher to the extent determined by said stop means. Means may be provided for retaining said first movable member in a pressure-applying position determined by said stop means.

Movement of said first movable member may be effected by means of a pinion or toothed quadrant engaging a rack on or associated with said first movable memher, and said pinion or toothed quadrant may be operated by a lever carried by a member mounted on a shaft carrying said pinion or toothed quadrant. The member carrying the lever may be in the form of a disc, and a coaxial disc freely rotatable about the axis of the shaft may be operatively connected with the second movable member for movement therewith, said discs being provided with means, such as a pointer and scale, for indicating the degree of relative movement between said first and second movable members.

Counter-weight means are provided for the purpose of neutralizing the back pressure of the aforesaid spring means. For example, at least one counter-weight may be suspended by means of a flexible member, such as a chain, from a cam associated with the operating mechanism for the second movable member, said cam being shaped so that the torque exerted by the counter-weight means at any angular position of the cam is substantially equal to the force required to compress the spring means to an amount determined by the relative movement between said first and second movable members.

One of said elements, in the form of a table, may be supported by means of arms or bell-crank levers on parallel shafts, said second movable member being an arm fixed to one of said parallel shafts and said shafts being connected together as by lever and link means for movement in unison.

The invention is hereinafter described, by wayof example, with reference to the accompanying diagrammatic drawings, in which:

Fig. 1 is a diagrammatic elevation illustrating the invention in a simple form;

Fig. 2 is a front elevation of a practical embodiment of the invention, as applied to a step-andrepeat machine;

Fig. 3 is a part sectional plan view of the construction Patented Mat. 25, 1958 shown in Fig. 2, but with the table and unit-transparency carrier omitted; and

Fig. 4 is a section on the line lV-IV, Fig. 2.

In its application to a step-and-repeat machine as shown in Fig. 1 embodying a lifting table 1 providing a receptive surface supportand a unit-transparency carrier 2 which, in operation of the machine, is fixed or held stationary, the table 1 and carrier 2 constituting relatively movable elements, the mechanical pressure-applying means according to the invention broadly comprises a first movable member 3 operable to apply pressure, a second movable member 4 operatively connected to mechanism, such as bell-crank levers 5 pivoted at 6 and connected to the table 1 by links 7 for effecting lifting movement of the table and consequent relative movement between the elements 1, 2, and spring means 8 arranged between the members 3, 4 to transmit movement from the first movable member 3 to the second movable member 4 whereby said members move in unison until movement of the second movable member 4 is arrested by contact between opposed surfaces carried by the elements 1, 2 whereafter pressure is applied through said spring means 8 to exert pressure between said elements to a degree dependent on relative movement between the members 3, 4 against said spring means 8. Movement of said first movable member 3 may be effected by mechanism, such as a rack 9 on the member 3, a pinion 10 or toothed quadrant co-operating with the rack 9, and a manually operated lever 11 for effecting movement of the pinion 10 or toothed segment about its axis.

The degree of pressure exerted may be predetermined by means associated, or connected for movement, with the first and second members. For example, a pointer 12 on one member may co-operate with a scale 13 on the other member. Adjustable stop means 14 are provided for limiting movement of the first movable member 3 in a direction for applying pressure, whereby a predetermined degree of pressure may be applied for efiecting movement of said first movable member 3 to the extent determined by said stop means. It will be understood than on operating the hand lever 11, the pointer 12 does not move in relation to the scale 13 until movement of the member 4 is arrested by reason of contact between the surfaces carried by the elements 1, 2, while, on further movement of the lever 11, the pointer 12 moves in relation to the scale 13 to indicate the degree of pressure exerted through the spring means 8. By setting the adjustable stop 14 at a suitable position, any desired predetermined pressure may be applied by operating the lever 11 to move the first movable member 3 to the full extent permitted by the stop 14.

As the manual effort to operate lever 11 would be considerable, means are furnished to neutralize the back pressure of the spring 8. One convenient way is shown in the form of a second pinion 10a engaging the rack 9 and having a lever 10!) from which is suspended a weight 190.

Figs. 2, 3 and'4 illustrate a practical embodiment of the invention in its particular application to a machine of the character referred to. In these figures, the table 1, which is suitably guided for vertical movement in a frame 1a, is supported by pairs of links 7 pivotally attached to substantially horizontally extending arms 15 fixed to parallel shafts 16 mounted in fixed bearings 17. A unittransparency carrier 2 is located fixedly in the frame In above the table 1. The shafts 16 are linked together for movement in unison by means of downwardly extending arms 18 connected by a link 19. Gne shaft 16 also has fixed thereto a downwardly extending arm 26 which carries the second movable member 4, or itself constitutes said member. The member 4 on the arm 20 carries a rod 21 which extends beneath an operating shaft 22 and is supported in any suitable manner so that a rack 9 on the first movable member 3, in the form of a sleeve slidable on said rod 21, is maintained in engagement with a pinion or't'o'othe'd quadrant iii-carried by the shaft 22. A compression spring 8 is arranged between the members 3 and 4 so that on turning the toothed quadrant 10 in a clockwise direction indicated by arrow a, movement of the member- 3 to the left exerts pressure on the member through the spring 8. The operating shaft 22 is extended, as shown in Fig. 3, to project at one side of the machine frame or bed, and at its extremity is provided with a disc 23 which is keyed or otherwise fixed to the shaft 22 to rotate therewith. The disc 23 is provided on its outer face with lug means 24 for the pivotal mounting of the operating lever 11 which also is pivotally connected to a pin 25 extending through the disc 23 and influenced by a spring 26 to urge the lever 11 towards the face of the disc 23. At the inner side of the disc 23 a second disc 27 is mounted so as to be rotatable about the axis of the shaft 22, this disc being connected for movement with the second movable member 4 by means of a member 2% projecting from the inner face of the disc 27 and connected by means of a link 29 to an arm 30 fixed to, and projecting downwardly from, the shaft 16 carrying the arm 20. The discs 23 and 27 are provided at their periphery with co-operating pointer and scale means 12, 13 registering relative movement between the members 3 and 4 when the spring 8 is compressed incident to upward movement of the table 1 being arrested on contact being made etween the surfaces carried by the table It and the r2. A t the inner side of the second disc 27 a third d1sc 31 is mounted to be freely rotatable about the axis or the shaft 22, this disc 31 having means, such as a mole 32, for engagement by a member associated wit the disc 23 carrying the operating lever 11 and constituted by an extension 33 of the pin 25. At least part of the periphery of the disc 31 is provided with teeth 34 aoapted to be engaged by a correspondingly toothed releasably engageable stop member 35 which can be moved to a disengaged position against the action of a spring so by means of a hand lever 37. The stop member as shown is an ordinary bolt with a tooth machined on one end to engage with the teeth 34. The disc 27 is slotted circumferentially at 38 to accommodate a boss 39 projecting from the disc 23 and housing the pin 25 and spring 26. The disc 31 also is circumferentrally slotted at 40 to accommodate the member 23 extending from the disc 27. The disc 31 also may be circumferentiall y slotted to accommodate the extension of the pin 33, this slot terminating in a ramp (not shown) whereby the pm 25 may be pressed back against the spring 26 to allow it to pass into engagement with the hole 32 in the disc 31.

The range of movement of the operating lever 11 is approximately in the embodiment shown, and the circumferential slots in the discs 27 and 31 are of corresponding extent. 7

In operation, the machine may be set for the application of a predetermined degree of pressure in the following manner:

Materials corresponding in thickness to those to be used in the machine are positioned on the table 1 and carrier 2. The pin 25 having been previously engaged with the hole 32 in the disc 31, the operating lever H is moved in the clockwise direction so that, first of all, the pressure surfaces carried by the table 7. and carrier 2 are brought into contact, whereafter pressure is applied through the spring 8. When the desired degree of pressure is indicated by the pointer 12 on the scale 13, the stop member 35 is released to engage the teeth on the disc 31 which is thereby locked in a definite position corresponding to a certain degree of pressure. The op erating lever 11 is then pulled outwardly so as to disengage the pin 25 from the hole 32 and can then be returned in the anti-clockwise direction to the initial posi tion to lower the table 1. The machine is thus set for applying a predetermined pressure and for all subsequent operations with the same area of contact surface and the same thickness of materials, a constant pressure may be applied accurately by moving the operating lever 11 in the clockwise direction until the pin 25 engages the hole 32. The pin 25 and hole 32 also provide means for maintaining the predetermined degree of pressure while exposure is effected.

It is evident that the force required to operate the lever 11 will steadily increase as the spring 8 is compressed until, with large units and considerable pressures per square inch, a very large amount of force would be required to operate the lever 11. To overcome this disadvantage, counter-weight mechanism is provided in which the shaft 22 carrying the pinion or toothed segment It} is provided with a suitably shaped cam 41 from which a counter-weight 42, or weights, is or are suspended by means of a flexible element, such as a chain 43. It will be appreciated more than one cam, with associated weight, may be provided. The shape of the cam 41 is so calculated that the force applied by the counter-weight or Weights at any angular position of the cam is substantially equal to the force required to compress the spring 8 to an amount determined by the relative movement between the members 3 and 4. Thus, when the cam is in its upright position, as shown in Fig. 2, a negligible amount of torque is applied by the counter-weight 42 to the shaft 22 while, as the cam 41 moves in the clockwise direction, the torque exerted on the shaft 22 by the counter-weight 42 progressively increases. By this means, total pressures ranging from a few ounces to several hundred pounds can be applied with a minimum and equal amount of manual effort.

If desired, resilient loading may be incorporated in known manner in the unit-transparency carrier 2, or in the table 1, to allow for uneven thickness of material. Moreover, instead of the pre-setting scale being graduated in terms of pressure, the figure may be multiplied by a factor to give direct reading which corresponds to areas of unit-transparency.

It will be understood that the invention is not limited to the particular embodiments hereinbefore described. For example, the mechanism connecting the second movable member 4 to the table 1 may be of any other suitable form. Thus, instead of bell-crank lever arrangements and links, rack and pinion means may be employed. Furthermore, the spring means between the first and second movable members may be otherwise arranged, and any other suitable means may be provided for effecting movement of said first movable member. The indicating means also may be otherwise arranged and connected in any suitable manner for movement with the respective first and second movable members.

What I claim is:

1. A step-by-step mechanism for photo-copying machines having a fixed carrier member to which a transparency is secured and a movable support carrying a photo-sensitive material; mechanical means for moving said movable support adjacent said carrier member to exert contact pressure between said transparency and said photo-sensitive material comprising a main operating shaft, a pinion secured to said shaft, a first movable member having a rack engaging said pinion, a second movable member connected to said movable support to lift the same toward said fixed carrier, spring means between said first and second movable members so that when movement of said movable support is arrested by contact between adjacent surfaces of said movable support and said fixed carrier the degree of pressure exerted on said surfaces depends on the compression of said spring means, a first disc keyed to said shaft and carrying an operating lever, a second disc rotatable about the axis of said shaft and connected for movement with said second movable member, a third disc also rotatable about the axis of said shaft, means for selectively locking said third disc within a predetermined angular range of movement, and means carried by said first disc cooperating with the locking means on said third disc whereby angular movement of the operating lever is limited by the setting of said third disc to apply a predetermined pressure.

2. A step-by-step mechanism as defined in claim 1 including counterweight means to neutralize the back pressure of the spring.

3. A step-by-step mechanism as defined in claim 1 wherein said means for selectively locking said third disc comprises a spring-influenced member releasably engageable with peripheral teeth on said third disc.

4. A step-by-step mechanism as defined in claim 1 wherein said lever is pivotally connected to said disc keyed shaft, and a spring influenced member is connected to said lever for engaging locating means comprising an aperture in said third disc.

5. A step-by-step mechanism for photo-copying ma chines having a fixed carrier member to which a transparency is secured and a movable support carrying a photo-sensitive material; mechanical means for moving said movable support adjacent said carrier member to exert contact pressure between said transparency and said photosensitive material, said mechanical means comprising a first movable member; a second movable member connected to said movable support; spring means connecting said first movable member to said second movable member, said spring means being arranged so that said members move in unison until movement of said second movable member is arrested by contact between said fixed carrier and said movable support and upon further movement of said first movable member pressure is applied through said spring means to effect contact pressure between said carrier member and said movable support; counterweight means for neutralizing the back pressure of the spring comprising a cam associated with the operating mechanism for said second movable member, and a counterweight suspended by means of a flexible member from said cam, said cam being shaped so that the torque exerted by the counterweight at any angular position of the cam is substantially equal to the force required to compress the spring means to an amount determined by the relative movement between said first and second movable members; means for moving said first movable member; and adjustable stop means adapted to limit the pressure applying movement of said first movable member, whereby a predetermined degree of pressure may be applied on effecting movement of said first movable member to the extent determined by said stop means.

6. A step-by-step mechanism as defined in claim 5 and further including means for retaining said first movable member in a pressure-applying position determined by said stop means.

References Cited in the file of this patent UNITED STATES PATENTS 2,072 Church May 4, 1841 3,637 Jackson June 24, 1844 24,258 Bond May 31, 1859 1,015,167 Francis Jan. 16, 1912 2,124,954 Pirmov July 26, 1938 2,249,730 Gentry July 22, 1941

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