US3411440A - Manually operated printing machine including toggle spring mechanism - Google Patents

Description

Nov. 19, 1968 M. R. JOHNSTON ETAL 3,411,440

MANUALLY OPERATED PRINTING MACHINE INCLUDING TOGGLE SPRING MECHANISM Filed March 10, 1967 4 Sheets-Sheet 1 F/G. I

IN VENTORS.

MERLE R. JOHNSTON RICHARD M. GILE THEIR ATTO NEYS 19, 1968 M. R. JOHNSTGN ETAL 3,

MANUALLY OPERATED PRINTING MACHINE INCLUDING TOGGLE SPRING MECHANISM Filed March 10, 1967 4 Sheets-Sheet 2 IN VE N TORS MERLE R. JOHNSTON BY RICHARD M. GILE V THE IR ATTOFi Y5 Nov. 19, 1968 M. R. JOHNSTON ETAL 3,411,440

MANUALLY OPERATED PRINTING MACHINE INCLUDING TOGGLE SPRING MECHANISM Filed March 10, 1967 4fsneets-shee1 s INVENTORS. MERLE R. JOHNSTON BY RICHARD M. GILE THEIR ATT /NEYS Nov. 19, 1968 M. R. JOHNSTON ETAL MANUALLY OPERATED PRINTING MACHINE INCLUDING TOGGLE SPRING MECHANISM Filed March 10, 1967 4 Sheets-Sheet 4 MERLE R. JOHNSTON 'RICHARD M. GILE THEIR ATTOQ EYS United States Patent 3,411,440 MANUALLY OPERATED PRINTING MACHINE IN- CLUDING TOGGLlE SPRING MECHANISM Merle R. Johnston, Taunton, and Richard M. Gile, Kingston, Mass., assignors to Dymo Industries, Inc., Emeryville, Calif., a corporation of California Filed Mar. 10, 1967, Ser. No. 622,292 7 Claims. (Cl. 191-123) ABSTRACT OF THE DISCLOSURE A manually operated stencil printing machine of the type in which a print roll is made to traverse a printforming stencil in order to transfer ink from the print roll through the stencil to a workpiece, the machine being actuated by at least one operator lever mounted for movement relative to the base of the machine between a rest position, a depressed position and an intermediate position, and including a toggle spring mechanism coupling the operator lever with the base such that the toggle spring mechanism resiliently urges the operator lever toward the depressed position when the operator lever is located between the intermediate position and the depressed position to assist in pressing the print roll against the stencil and the workpiece and resiliently urges the operator lever toward the rest position when the operator lever is located between the intermediate position and the rest position to assist in moving the print roll and the stencil away from the workpiece and in returning the operator lever to and retaining the operator lever at the rest position.

The present invention relates generally to printing machines and pertains more specifically to printing machines which operate by the transfer of ink to the surface of a workpiece through print-forming elements, such as stencils. In particular, the invention is concerned with manually operated stencil printing machines which are known as addressing machines and is directed to an improvement which will reduce the amount of manual force necessary to actuate such a machine.

A variety of addressing machines are commercially available for use in sequentially addressing a series of envelopes, cards, documents or other items. The convenience provided by such machines has established an increased demand for generally smaller, less expensive manual machines which are practical for use in various offices where the volume of work does not warrant the expense of larger, more expensive machines. It is important, however, that such less expensive manual machines maintain a high quality in the printed image obtained by their use and that the maintenance of such high quality not be attained at the expense of ease of manual operation.

It is therefore an important object of the invention to provide a practical manually operated addressing machine of the type wherein a printing means, such as a print roll, is made to traverse a print-forming element, such as a stencil, in order to transfer ink from the printing means through the element to the surface of a workpiece.

Another object of the invention is to provide an improved manually operated addressing machine of the type described wherein the manual force required to operate the machine is reduced to a minimum.

Still another object of the invention is to provide a manually operated addressing machine of relatively compact size and having relatively few component parts of generally simple configuration and construction.

A further object of the invention is to provide a manually operated addressing machine of the type described 3,411,440 Patented Nov. 19, 1968 ice which is capable of accommodating workpieces of varying thicknesses without the need for separate adjustment.

A still further object of the invention is to provide a manually operated addressing machine of the type described which will afford improved ink distribution, greater versatility, enhanced flexibility of operation, improved efiiciency and reliability, and which will reduce fatigue of the operator through reduction of the manual forces necessary to actuate the machine.

The above objects as well as further objects and advantages are attained in the invention which may be described briefly as an improvement in a manually operated printing machine of the type in which a printing means is pressed against a workpiece in response to manual pressure in order to transfer ink from the printing means to the workpiece, the improvement comprising, in combination, a base, operator means mounted for movement relative to the base between a rest position, a depressed position and an intermediate position between the rest and depressed positions, means for moving the printing means toward the workpiece in response to movement of the operator means from the rest position toward the intermediate position, for urging the printing means against the workpiece in response to movement of the operator means from the intermediate position toward the depressed position and for moving the printing means away from the workpiece in response to movement of the operator means from the intermediate position toward the rest position, and a toggle spring mechanism coupling the operator means and the base such that the toggle spring mechanism resiliently urges the operator means toward the depressed position when the operator means is located between the intermediate position and the depressed position to assist in pressing the printing means against the workpiece and resiliently urges the operator means toward the rest position when the operator means is located between the intermediate position and the rest position to assist in moving the printing means away from the workpiece and returning the operator means to and retaining the operator means at the rest position.

The invention will be more fully understood and further objects and advantages thereof will become apparent in the following detailed description of an embodiment of the invention illustrated in the accompanying drawing, in which:

FIGURE 1 is a front elevational view of a manually operated addressing machine constructed in accordance with the invention;

FIGURE 2 is a top plan view of the machine of FIG- URE 1 with portions removed to show the internal construction;

FIGURE 3 is a side elevational view of the machine with portions sectioned to illustrate details of construction;

FIGURE 4 is a cross-sectional view taken along line 4-4 of FIGURE 2;

FIGURES 5, 6 and 7 are fragmentary side elevational views of a portion of the machine illustrating the opera tion of the printing mechanism and toggle link mechanism of the machine.

Referring now to the drawing, a manually operated addressing machine is designated generally at 10 in FIGURES l, 2 and 3 and is shown to have a generally horizontal base 12 with depending feet 14 which enable machine 10 to be placed upon a table top or another stand for convenience of installation and use. A horizontally extending platen 16 is provided at the top surface of the base 12 for receiving any one of a variety of workpieces, such as envelopes, cards, documents or other items, which must be addressed. Located above the platen 16, and spaced vertically therefrom, is a track assembly 18 which is mounted for movement toward and away from the base in response to the movement of operator means, illustrated in the form of a print lever assembly 20 which includes an operator handle 22, in a manner which will be described hereinafter. The track assembly 18 carries first and second hoppers 24 and 26, respectively. A stack of print-forming elements shown in the form of stencils 28 is located in the first, or feeding hopper 24 such that the lowermost stencil may be withdrawn from the stack and carried along the track assembly by a pusher assembly 30 to a printing station at 32 for a printing operation and then beyond the printing station to the second, or receiving hopper 26. The pusher assembly 30 is operated manually by pushing finger 34 to the left or to the right, as viewed in FIGURE 1, to advance or retract the pusher assembly along the track assembly in a manner now known in the art. A printing mechanism 36 is also located above the platen at the printing station and is movable toward and away from the base, along with the track assembly, in response to the movement of the print lever assembly 20. Thus, in the illustrated adressing machine 10, each of the stencils 28 carries an address and when a stencil is positioned at the printing station and a workpiece 38 (see FIGURE 3) is properly located on the platen, a downward push on handle 22 will actuate the print lever assembly, the track assembly will be brought downwardly against the workpiece 38 and the printing mechanism will print the address upon the workpiece. A stop-plate 40 provides a convenient shoulder 42 against which the workpiece is placed for proper location at the printing station, the location of shoulder 42 being selectively adjustable forward or rearward by movement of lever 44.

As best seen in FIGURES 2 and 3, the print lever assembly 20 includes an operator handle 22 fixed at one end thereof, which handle interconnects a pair of operator or print levers 46. Adjacent the other end of the print lever assembly, cam rollers 48 are journaled for rotation on a pin 50 which is fixed between a pair of relatively short arms 52 which are a part of the print levers 46, the cam rollers 48 resting upon the base 12 to provide a fulcrum for the print lever assembly. The printing mechanism 36 is carried at the forward end of a fulcrum bracket 54 which is pivotally mounted intermediate the ends thereof by means of another pin 56 fixed between a pair of pivot brackets 58 which are anchored to the base 12 by threaded fasteners 60 so that the printing mechanism is movable toward and away from the platen by rotation of the fulcrum bracket about the pivot provided by pin 56. Such rotation is etfected by downward and upward movement, respectively, of the handle 22 by virtue of still another pin 62 which is fixed between the print levers 46 at a point located a relatively short distance away from the cam rollers 48 and which passes through the fulcrum bracket 54 adjacent the rearward end thereof. The downward and upward movement of handle 22 and the accompanying movement of the entire print lever assembly 20 will move the cam rollers 48 rearward and forward along the base 12 between forward stops provided by the rearward portions of pivot brackets 58 (see FIGURE and rearward stops provided by pegs 64 (see FIGURES 2 and 7).

Turning now to FIGURES 4 through 7, the printing mechanism is seen to comprise printing means in the form of a print roll 66 journaled upon a shaft 68 fixed between a pair of pressure links 70 which are, in turn, pivotally mounted adjacent the forward end of the fulcrum bracket at 72. Shaft 68 is provided at each end thereof with a notch 74 (see FIGURE 4), each of which cooperatively engages a frame 76 fixed to the track assembly 18, thereby coupling the pivoted fulcrum bracket 54 with the track assembly 18, maintaining the print roll 66 against the track assembly and confining the movement of the shaft 68, the print roll 66 and the pressure 4 links between a first position located toward the rear of the track assembly (see FIGURE 6) and a second position located toward the front of the track assembly (see FIGURE 7). A pair of pressure springs 78 extend between each leg of the fulcrum bracket 54 at 80 and each pressure link 70 at 82 to bias the pressure links against the stops 84 on the fulcrum bracket, which stops positively define the first position of the pressure links and of the print roll 66. The track assembly 18 is also mounted for pivotal movement with respect to the base 12 by virtue of pivot arms 86 (see also FIGURE 2) which are hinged to the pin 56 that passes between pivot brackets 58.

Thus, upon the application of a downward force upon handle 22, the handle will move downwardly from the rest position illustrated in FIGURE 5 and the print lever assembly 20 will be pivoted about the fulcrum provided by cam rollers 48 which will begin travelling toward the rear of the base 12 and toward pegs 64 until the handle 22 and print lever assembly 20 reach an intermediate position as seen in FIGURE 6, wherein pin 62 is raised and fulcrum bracket 53 is pivoted about the pin '56 to lower the track assembly 18, and the associated print roll 66, against the workpiece 38 lying on the platen 16. Continued downward movement of the operating handle 22 toward the fully depressed position shown in FIGURE 7 will further raise pin 62 forcing the fulcrum bracket to rotate even further so that pressure links 70 are driven away from stops 84, against the biasing force of pressure springs 78, and print roll 66 travels forward along the track assembly from the first position to the second position to traverse the stencil 28 which is held in the track assembly and now lies against the workpiece. The traverse of the print roll thus prints an address upon the surface of the workpiece whereupon the handle, the print lever assembly, fulcrum bracket, track assembly and print roll are raised, and the workpiece removed from the machine.

During the above described traverse, the print roll 66 applies ink to the workpiece through the stencil 28 located at the printing station. The print roll itself is inked by contact with inking roll 86 which is also journaled between the pressure links 70 by virtue of shaft 88 and is urged into rolling contact with the print roll by springs 89. The inking roll is fabricated of an absorbent material, such as felt, so that it will carry sufiicient ink to assure that the print roll is adequately inked during successive operations of the machine 10 during an addressing run. In order to provide even spreading of the ink upon the surface of the print roll as well as automatic inking of print roll 66 for each addressing operation, means are provided for positively rotating inking roll 86 during the return movement of the pressure links from the second position to the first position after an addressmg operation and return of the operator handle to the starting position so that the print roll is evenly inked and ready for a subsequent addressing operation. These means include a ratchet wheel 90 fixed at one end of the inking roll mounting shaft 88 and a ratchet rack '92 pivotally mounted at 94 to a ratchet bracket 96 fixed to the base 12 by the threaded fasteners 60, the ratchet rack 92 being resiliently biased against the ratchet wheel 90 by a spring 98. The ratchet teeth are arranged so that upon traverse of the print roll from the rear toward the front of the track assembly, relative motion between the ratchet wheel and the ratchet rack is permitted without rotation of the wheel. However, upon release of operator handle 22 and return of the pressure links 70 to the first position against stops 84, the ratchet teeth will mesh and inking roll 86 will rotate and, in turn, rotate print roll 66 to evenly distribute ink upon the surface of the print roll.

The inking roll 86 is itself inked manually from time to time by the use of an ink supply assembly which includes a cylindrical ink reservoir 100 journaled upon an ink reservoir bracket 102 pivotally mounted upon the fulcrum bracket 54 at 72 and biased upwardly by spring 104 to ord narily maintain the ink reservoir out of contact with inking roll 86. As required, ink is passed from the reservoir to the inking roll by manually pivoting bracket 102 downwardly to bring reservoir 100 into contact with the inking roll 86 and then rotating the inking roll by turning knob 168 (see FIGURES 2 and 4), thereby causing rotation of the reservoir and allowing ink to pass through perforations 110 provided in the reservoir and become absorbed by the material of the inking roll, Perforations 110 are normally kept at an uppermost orientation to prevent ink from spilling out of the reservoir except as desired when the reservoir is in contact with the inking roll.

The entire printing mechanism is protectively encased by a cover 120 (see FIGURE 3) which is hinged to the rear of the base at 122 so that the cover may be lifted for ready access to the ink supply assembly.

Effective operation of machine requires that the track assembly be pressed against the workpiece with a force which will adequately clamp the workpiece in place upon the platen to preclude movement of the workpiece during traverse of the print roll and printing of the address. In addition, sufficient printing pressure must be established by the force of the print roll against the stencil and the stencil against the workpiece. These forces must originate in a manually applied force at the operator handle 22, and the operating components of the machine must be arranged so that the required manual force is held to a minimum, The above described arrangement allows a relatively long length between the operator handle 22 and the cam rollers 48, while arms 52 provide a relatively short length between cam rollers 48 and pin 62. Thus, a given downward force upon handle 22 results in a considerable upward force upon the fulcrum bracket at pin 62. In addition, the above arrangement permits a long print lever assembly without the assembly extending beyond the overall length of the machine 10, thereby permitting a compact machine. The upward force upon pin 62 results in a generally downward force upon the pressure links 70, which force is transmitted to the print roll 66. As best seen in FIGURES 5 and 6, the pressure links 70 are normally maintained at an angle to the track assembly 18 by virtue of the pressure springs 78 biasing the pressure links against stops 84, the angle being illustrated by the angle A lying between dashed line L, along which the downwardly directed force is transmitted, and dashed line N, the normal to the track assembly, The force along line L is therefore resolved into a first component directed downwardly along line N and a second component directed forward at a right angle to the first component. 1 Thus, the first component becomes the clamping and printing force while the second component becomes the force which effects traverse of the print roll across the stencil. Since it is important to maintain the magnitude of the force upon operator handle 22 at a minimum, it will be evident that the magnitude of the force required along line L should be maintained at the minimum which can be resolved into the magnitude neces sary for the two components set forth above. By carefully choosing the angle A, the relative magnitudes of the two components may be set so that neither component will become excessively large before the'other component reaches the necessary minimum magnitude. Thus, at the proper angle A, the downward component has the magnitude necessary to clamp the workpiece and effect a proper printing pressure when the forward component reaches the magnitude necessary to effect traverse of the print roll. Referring to FIGURES 5 through 7, since relatively little resistance is offered to the downward movement of track assembly 18 in FIGURE 5, very little downward force is required at operator handle 22 until the workpiece is being clamped between the track assembly and the platen 16, as shown in FIGURE 6. At this point, the magnitude of the operating force must be increased to increase the magnitude of the force F along line L and thus increase the magnitude of the first and second components P and T, respectively. The biasing force provided by pressure springs 78 is such that force F must become great enough to establish the proper component force P when the magnitude of component force T becomes great enough to overcome the biasing force and effect the traverse of the print roll from the first position (FIGURE 6) to the second position (FIGURE 7). If angle A were made larger, a greater force F would be necessary before the minimum force P could be attained and pressure springs 78 would be required to exert a greater biasing force to prevent traverse of the print roll before the essential force P could be established. If angle A were made smaller, the magnitude of component force P would become excessive before component force T became great enough to effect traverse and again force F would be greater, Hence, deviation from the optimum angle A will have the efiect of increasing the magnitude of the operating force necessary at operator handle 22 while careful choice of angle A will minimize the operating force. In choosing angle A, it must be noted that the angle between lines L and N increases as the print roll traverses from rear to front of the frame 76 and it is necessary to assure that the magnitude of component force P does not drop below that which will provide the minimum required clamping and printing pressure even though the angle changes. This can be accomplished either by making angle A initially small enough to assure that component force P will not drop below the required minimum as long as component force T is great enough for traverse, or by increasing the biasing force provided by pressure springs 78. Either measure would, of course necessitate an increase in the required operating force. The optimum angle A for machine 10 has been found to be in the order of magnitude of about 23. The angle is accurately determined by accurate positioning of the stops 84.

In order to further decrease the magnitude of the operating force which must be manually applied to operator handle 22 and thereby render machine It) more easily operated manually, the machine 10 is provided with a toggle spring mechanism which couples the print lever assembly 20 with the base 12 as seen in FIGURES 2 and 5 through 7. The toggle spring mechanism 130 includes a toggle link 132 pivotally mounted upon in 50 at journals 134 such that the uppermost end 136 of the toggle link may swing freely through an arc, the center of which lies along the axis of pin 50. A pair of helical toggle springs 140 extend between the uppermost end 136 of the toggle link 132 and an anchoring rod 142 which is fixed to an anchoring bracket 144 secured to the base 12 by means of machine screws 146. When the print lever assembly 20 is in the rest position, as seen in FIGURE 5, the toggle springs 140 are in tension and exert a force at the uppermost end 136 of the toggle link 132 which force is transmitted through the toggle link to the pin 50 urging the pin 50 to the right and tending to bias the print lever assembly toward the rest position and retain the print lever assembly in the rest position. In this position, pin 50 is received within a slot 148 in the anchoring bracket 144 and is located far enough to the right with respect to the anchoring rod 142 to assure that the force established by the toggle springs 140 will retain the print lever assembly in the uppermost rest position. The toggle link 132 rests against pin 62 at 150 so that pin 62 serves as a positive stop for the toggle link when the print lever assembly is in the rest position. As the handle 22 is depressed, the print lever assembly is urged toward an intermediate position, as seen in FIGURE 6, moving cam rollers 48 and pin 50 toward the rear of the machine or toward the left as seen in FIGURE 6. Such rearward movement of pin 50 will cause the toggle link 132 to pivot about pin 50 in a clockwise direction with a concomitant increase in the tension of the toggle springs 140 until the toggle spring mechanism is brought to the neutral position shown in FIGURE 6 wherein the force established by the tension in the toggle springs is aligned with a line 7 C passing through the pin 50 and the rod 142 and the force of the toggle springs will no longer tend to urge the print lever assembly toward the rest position. Upon further depression of the handle 22, the print lever assembly 20 will be moved from the intermediate position in FIGURE 6 toward the lowermost depressed position shown in FIGURE 7, the cam rollers 48 and pin 50 will be moved further toward the rear of the machine or toward the left as seen in FIGURES 6 and 7 and the toggle link 132 will rotate further in the clockwise direction such that as the print lever assembly moves through the intermediate position on its way toward the lowermost depressed position, the force exerted upon pin 50 and the print lever assembly 20 by the toggle springs 140 through the toggle link 132 will be reversed and will tend to urge the print lever assembly from the intermediate position toward the depressed position thereby reducing the manual force required at operator handle 22 to establish the necessary magnitude in force F, When the print lever assembly 20 is in its fully depressed position as seen in FIGURE 7, cam rollers 48 will abut pegs 64 and the toggle spring mechanism 130 will again come to rest by virtue of arm 152 of the toggle link 132 resting against pin 62. Upon return movement of the print lever assembly from the fully depressed position toward the rest position shown in FIGURE 5, the print lever assembly will again pass through the intermediate position shown in FIGURE 6 and the toggle spring mechanism will rotate in a counterclockwise direction to reverse the force established by the toggle springs so that the toggle springs will once again resiliently urge the print lever assembly 20 and operator handle 22 back toward the uppermost rest position from the intermediate position and will retain the print lever assembly in the uppermost rest position. Thus, the toggle spring mechanism 130 performs the dual function of returning the print lever assembly to the rest position and resiliently retaining the print lever assembly at that rest position and assisting in establishing the force necessary to actuate machine 10 through a printing opera tion to thereby reduce the magnitude of the manual force necessary to actuate machine 10 through a printing operation as described above.

In view of the above described operation, it is evident that the machine 10 will automatically compensate for workpiece of various thicknesses without requiring adjustment. The angle A remains very nearly constant regardless of the thickness of the workpiece at the printing station since the track assembly, the pressure links and the print roll are all coupled together for movement with the print lever assembly and fulcrum bracket. The required forces become established by the resistance to downward movement of the track assembly and this resistance can occur at various heights above the platen without adversely affecting the operation of the printing mechanism.

It will be apparent that the illustrated construction of machine 10 allows sease in the fabrication of the operating component parts in that the parts are simple in configuration and can be made of relatively light weight materials with inexpensive manufacturing techniques. For example, the various links and lever and bracket assemblies are most advantageously stamped from sheet metal.

It is to be understood that the above detailed description of an embodiment of the invention is provided by way of example only and is not intended to limit the invention. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a manually operated printing machine of the type in which a printing means is pressed against a workpiece in response to manual pressure in order to transfer ink from the printing means to the workpiece, the combination comprising:

a base;

operator means mounted for manual movement rela tive to said base between a rest position, a depressed position and an intermediate position between said rest and depressed position;

means for moving the printing means toward the workpiece in response to movement of the operator means from the rest position toward the intermediate position, for urging the printing means against the workpiece in response to movement of the operator means from the intermediate position towards the depressed position and for moving the printing means away from the workpiece in response to movement of the operator means from the intermediate position toward the rest position; and

a toggle spring mechanism coupling the operator means and the base such that said toggle spring mechanism resiliently urges the operator means toward the depressed position when the operator means is located between the intermediate position and the depressed position to assist in pressing the printing means against the workpiece and resiliently urges the operator means toward the rest position when the operator means is located between the intermediate position and the rest position to assist in moving the printing means away from the workpiece and in returning the operator means to and retaining the operator means at the rest position.

2. The combination of claim 1 wherein:

said means for moving and urging the printing means includes a bracket mounted on said base for pivotal movement relative thereto;

said operator means includes an operator lever coupled with said bracket; and

said toggle spring mechanism includes a toggle link pivotally mounted to the operator lever at a point on the operator lever movable with respect to said base upon movement of the operator lever and at least one toggle spring coupling the toggle link and the base at a point fixed on said base and normally exerting a resilient biasing force through said toggle link to the operator lever at said point thereon to urge the operator means toward either the rest position or the depressed position, said point on the operator lever being movable with respect to said point fixed on the base such that the biasing force of said toggle spring against the operator lever is reversed as the operator lever is moved through said intermediate position.

3. The combination of claim 1 wherein the printing means is made to traverse a print-forming element in order to transfer ink from the printing means through the print-forming element to the workpiece, and wherein:

the base includes means for supporting the workpiece;

said machine includes means for holding a print-forming element against the workpiece supported on said base;

the means for moving the printing means include bracket means mounted upon the base for movement toward and away from the base in response to movement of the operator means from the rest position to the intermediate position and from the intermediate position to the rest position, respectively, link means pivotally mounted upon the bracket means for movement relative thereto between a first position and a second position in response to the movement of the operator means between the intermediate position and the depressed position and corresponding movement of the bracket means, the printing means being carried by the link means and capable of being urged against the print-forming element to press said element against the workpiece and movable across the print-forming element in response to movement of the link means from the first position to the second position, and means biasing the link means toward the first position with a force precluding pivotal movement of the link means and traverse of the printing means across the print-forming element until the printing means is urged against the printforming element and the element pressed against the workpiece with a predetermined force;

the link means making an angle with the print-forming element when at the first position such that the force exerted by the bracket means upon the link means is transmitted by the link means to printing means and resolved into a first component for urging the printing means against the print-forming element and pressing the print-forming element against the workpiece and a second component for effecting traverse of the printing means across the print-forming element, the magnitude of the angle being such that the magnitude of the first component will reach the required predetermined force when the magnitude of the second component reaches the force necessary to overcome the biasing force and effect said traverse; and

said toggle spring mechanism resiliently urging the operator means from the intermediate position toward the depressed position to reduce the magnitude of the manual force required upon the operator means for the establishment of the force exerted by the bracket means.

4. The combination of claim 3 wherein the printing means is a print roll and the print-forming element is a print-forming stencil and wherein:

the operator means includes at least one operator lever;

the machine includes a track for carrying the stencil,

said track being mounted for movement toward and away from the base in response to the movement of the operator lever for positioning the stencil in cooperative relationship with the workpiece;

the print roll is journaled upon the link means and is capable of being urged toward the stencil and the track to press the stencil against the workpiece and is movable across the stencil in response to the movement of the link means from the first position to the second position.

5. The combination of claim 4 wherein the bracket means includes a bracket pivotally mounted to said base intermediate the ends of the bracket, the link means includes a link mounted upon the bracket for pivotal movement adjacent one end of the bracket, and the operator lever is pivotally interconnected with the bracket at a point adjacent the other end thereof and includes an operator handle located a relatively long distance from said point and a fulcrum located a relatively short distance from said point whereby movement of the operator handle toward the base will move said point away from the base and said link toward the base to urge the print roll against the stencil and press the stencil and the track against the workpiece, and the toggle spring means includes a toggle link pivotally mounted to the operator lever at a point on the lever movable with respect to said base upon movement of the operator lever and at least one toggle spring coupling the toggle link and the base at a point fixed on said base and normally exerting a resilient biasing force through said toggle link to the operator lever at said point on the operator lever to urge the operator means toward either the rest position or the depressed position, said point on the operator lever being movable with respect to said point fixed on the base such that the biasing force of said toggle spring against the operator lever is reversed as the operator lever is moved through said intermediate position.

6. In a manually operated stencil printing machine of the type in which a print roll is made to traverse a printforming stencil in order to transfer ink from the print roll through the stencil to a workpiece, the combination comprising:

a base including a horizontally extending platen for supporting a workpiece at a printing station in the machine;

a print lever asesmbly including a fulcrum cooperatively engaging the base and an operator handle located vertically above the base and a relatively long distance from the fulcrum for vertical movement toward and away from the base to pivot the assembly about the fulcrum between an uppermost rest position, a lowermost depressed position and an intermediate position between the uppermost and lowermost positions;

a track assembly mounted on the base for pivotal movement above the base toward and away from the platen in response to actuation of the print lever assembly and including means for sequentially positioning each of a plurality of stencils at said printing station;

a generally horizontally extending fulcrum bracket mounted intermediate the ends thereof to the base and operably interconnected adjacent one end thereof with the print lever assembly at a relatively short distance from the fulcrum of said print lever assembly for pivotal movement vertically in response to actuation of the print lever assembly;

at least one pressure link pivotally mounted adjacent the other end of the fulcrum bracket for movement relative thereto between a first position and a second position in response to movement of the print lever assembly between the intermediate position and the depressed position and a corresponding movement of the fulcrum bracket;

a print roll journaled upon the pressure link above said printing station;

means maintaining the print roll in cooperative engagement with the track assembly such that the print roll will move generally horizontally across the track assembly and the stencil therein in response to movement of the print lever assembly from the intermediate position to the depressed position and in response to the corresponding movement of the pressure link from the first position to the second position;

spring means biasing the pressure link toward the first position with a force sufiicient to preclude pivotal movement of the pressure link and traverse of the print roll across the stencil until the track assembly is positioned upon the workpiece, the print roll is urged against the stencil and the stencil and track assembly are pressed against the workpiece with a predetermined force;

the pressure link making an angle with the generally horizontally oriented track assembly and the stencil therein when at the first position such that the force exerted by the fulcrum bracket upon the pressure link as a result of actuation of the print lever assembly from the intermediate position toward the depressed position is transmitted by the pressure link to the print roll and the track assembly and resolved into a vertical component for urging the print roll against the stencil and pressing the stencil and the track assembly against the workpiece and a horizontal component for effecting traverse of the print roll across the sencil, the magnitude of the angle being such that the magnitude of the vertical component will reach the required predetermined force when the magnitude of the horizontal component reaches the force necessary to overcome the biasing force and effect said traverse; and

a toggle spring mechanism coupling the print lever assembly and the base such that said toggle spring mechanism resiliently urges the print lever assembly toward the lowermost depressed position when the print lever assembly is located between the intermediate position and the depressed position to assist in the establishment of the force exerted by the fulcrum bracket upon the pressure link as a result of actuation of the print lever assembly from the intermediate position toward the depressed position to maintain the manual force required to move the print lever assembly to the depressed position at a minimum and resiliently urges the print lever assembly toward the uppermost rest position when the print lever assembly is located between the intermediate position and the rest position to assist in moving the print lever assembly, the track assembly and the print roll away from the workpiece and in returning the print lever assembly to and retaining the print lever assembly at a rest position.

7. The combination of claim 6 wherein the toggle spring mechanism includes:

a toggle link pivotally mounted to the print lever assembly at a point on the print lever assembly movable with respect to said base upon movement of the print lever assembly; and

at least one toggle spring coupling the toggle link and the base at a point fixed on said base and normally exerting a resilient biasing force through said toggle link to the print lever assembly at said point on the print lever assembly to urge the print lever assembly toward either the rest position or the depressed position, said point on the print lever assembly being movable with respect to said point fixed on the base such that the bias force of said toggle spring upon the print lever assembly is reversed as the print lever assembly is moved through said intermediate position.

References Cited UNITED STATES PATENTS 5/1956 Gruver et a1 101269 X 10/1959 Stielow 101-423 F. A. WINANS, Assistant Examiner.

Images