Rotary cutting unit for trimming sheet material

Abstract

A rotary cutting unit for trimming sheet material has a support plate for receiving the sheet material. The rotary cutting device comprises a guide bar with a knife carriage guided displaceably. A rotary knife is rotatably mounted on the knife carriage. The guide bar is guided in guidance devices between an initial raised position raised and a lowered clamping position. The guide bar includes a clamping surface for contact against sheet material. The guide bar has a force impinged upon it by a spring device, in the direction toward the initial position. An actuation device moves the guide bar out of the initial position into the clamping position. The guide bar is clamped in vertically movable fashion between the spring device and a further spring device. The second spring device has a spring action directed oppositely to the first.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further illustrated, with reference to an exemplifying embodiment, in the drawings, in which:

FIG. 1 is an oblique view from above of the rotary cutting device according to the present invention;

FIG. 2 is a vertical section through the right-hand end of the rotary cutting device according to FIG. 1, in an oblique view with the guide bar in the initial position;

FIG. 3 shows the rotary cutting device as depicted in FIG. 2 with the guide bar in the clamping position, with a thin sheet material;

FIG. 4 shows the rotary cutting device as depicted in FIGS. 2 and 3 with the guide bar in the clamping position, with a relatively thick sheet material;

FIG. 5 is a side view of the rotary cutting device according to FIGS. 1 to 4 with the guide bar in the initial position;

FIG. 6 is the side view according to FIG. 5 of the rotary cutting device with the guide bar in the clamping position, with a thin sheet material; and

FIG. 7 is the view according to FIGS. 5 and 6 of the rotary cutting device with the guide bar in the clamping position, with a relatively thick sheet material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Rotary cutting unit 1 depicted in FIG. 1 comprises a support plate 2 that has on the upper side a horizontal sheet support surface 3. Arranged in the region of a longitudinal side of support plate 2 is a rotary cutting device 4 that serves to trim sheet material 5 placed on sheet support surface 3.

Rotary cutting device 4 comprises a guide bar 6 extending parallel to the longitudinal side of support plate 2 and parallel to sheet support surface 3; wrapping around both sides of said bar from the top is a knife carriage 7 that is displaceable along guide bar 6.

Knife carriage 7 is divided into an internally located guidance part (which is therefore not visible here) that fits positively around guide bar 6, and an external knife part 8 that is movable out of the raised position shown, against the action of a spring that is not visible here, vertically downward into a cutting position. Knife carriage 7 has at the top, for handling thereof, a hand grip 9 that is intended as a hand support and with which knife carriage 7 can be displaced along guide bar 6 and simultaneously lowered downward. Knife part 8 has a rotary knife concealed by a knife cover 10, which knife protrudes at the bottom slightly beyond knife cover 10 and sits in freely rotatable fashion on a knife axis extending horizontally and transversely to the longitudinal axis of guide bar 6.

Guide bar 6 projects at both ends into guide blocks 11, 12, in which guide bar 6 is laterally guided and is at the same time vertically movable. Guide blocks 11, 12 are joined rigidly to support plate 2. Actuation members 13, 14 are guided, once again laterally and vertically movably, in guide blocks 11, 12. Said members grip the ends of guide bar 6 on the upper side, at the end face, and on both vertical sides. At the top, actuation members 13, 14 comprise flat actuation flanges 15, 16 with which pressure can be exerted manually in the direction of sheet support surface 3.

A respective latching member 17, 18 is arranged behind each actuation member 13, 14. Latching members 17, 18 are mounted in guide blocks 11, 12, horizontally displaceably parallel to guide bar 6. They can therefore each be displaced outward, out of the latched position shown, into an unlatched position.

FIGS. 2 to 4 indicate, on the basis of sectioned views limited to the right-hand portion, more detail as to the configuration and coaction of actuation members 13, 14 and latching members 17, 18. Rotary cutting unit 1 is embodied in mirror-image fashion at the left end, so that the statements below also apply analogously to the description of the left end of guide bar 6.

Actuation member 18 is partially visible in FIGS. 2 to 4, with actuation flange 16 at the top and latching element 20 shaped thereonto and fitting around the end face of guide bar 6. Latching element 20 comprises a wedge-shaped latching depression 21 that is closed off at the top by a latching flange 22. The latter coacts with a latching lug 23 that projects downward, from the part of latching member 18 that projects at the top, into the space enclosed by guide block 12. Acting on latching lug 23 is the spring element already discussed above, which impinges upon latching lug 23, and thus on latching member 18, in the direction toward the end face of guide bar 6 and toward actuation member 14.

Guide bar 6 is made up substantially of an aluminum profile. It comprises at the bottom a clamping strip 24, made of elastomeric plastic, that extends over the width of sheet support surface 3. The underside of clamping strip 24 forms a clamping surface 25.

Guide bar 6 is acted upon on the underside at each end, in the region of guide blocks 11, 12, by a respective compression spring 27. The two compression springs 27 are each braced against support plate 2 in a mirror-symmetrical arrangement.

A respective second compression spring 28 is arranged between the upper side of guide bar 6 and the underside of actuation flanges 15, 16. Guide bar 6 is therefore not joined rigidly at both ends to actuation members 13, 14, but instead is clamped in by compression springs 27, 28 acting respectively in opposite directions, and is therefore guided movably with respect to both support plate 2 and actuation members 13, 14.

Before a cutting operation, guide bar 6 is in a raised initial position. This is visible in FIGS. 2 and 5. In this starting position, clamping surface 25 is spaced well away from sheet support surface 3. In this initial location, guide bar 6 is braced at the ends on first compression springs 27. It is pushed by these springs 27 toward second compression springs 28, which in turn are braced against the undersides of actuation flanges 15, 16. Actuation members 13, 14 likewise assume an initial position in which they protrude upward beyond the surface of guide blocks 11, 12. Latching lugs 23 project into the respectively associated latching depressions 21 of latching elements 20.

When sheet material 5 is to be trimmed, it is placed onto sheet support surface 3 (as is shown in particular in FIG. 1) and is then slid through the gap between guide bar 6 and sheet support surface 3 until it protrudes on the other side, beyond the plane of the rotary knife, to the distance to which it is to be trimmed. Guide bar 6 is then pushed down in order to clamp sheet material 5 in linear fashion between clamping surface 25 and sheet support surface 3. This will be explained first with regard to trimming of a single sheet, with reference to FIGS. 3 and 6.

In order to lower guide bar 6, the two actuation members 13, 14 are pushed downward by impinging upon actuation flanges 15, 16. Because second compression springs 28 have a higher spring constant than first compression springs 27, this compresses first compression springs 27 for the most part, and second compression springs 28 only very slightly. This continues until clamping surface 25 comes into contact with sheet material 5. Because of the resistance, guide bar 6 cannot be moved farther, i.e. it has reached its clamping position. Latching members 17, 18, however, have not yet reached their final position, i.e. they are moved even farther downward against the resistance of second compression springs 28, until latching flanges 22 of latching depressions 21 end up underneath latching lugs 23. This produces a clearly audible click. Latching lugs 23 now block the ability of actuation members 13, 14 to move upward. The clamping force exerted by guide bar 6 on sheet material 5 is determined substantially by second compression springs 28. In order to distribute the pressure uniformly over the length of the guide bar, compression springs 28 are embodied identically and are arranged at identical distances from the center of guide bar 6. At the same time, second compression springs 28 press latching flanges 22 with their upper sides against the lower sides of latching lugs 23.

The clamping of a thicker sheet material stack 29, as shown in FIGS. 4 and 7, proceeds no differently in principle. The difference is that guide bar 6 comes into contact with sheet material stack 29 substantially earlier, and therefore assumes a clamping position that greater by an amount equal to the thickness of sheet material stack 29. This is shown by a comparison of FIGS. 3 and 6 on the one hand with FIGS. 4 and 7 on the other hand.

In order for actuation members 13, 14 to reach their above-described final position, they must be pushed down just as far as in the case of trimming a single sheet. Second compression springs 28, however, are compressed substantially more strongly, as is likewise shown by a comparison between FIGS. 3 and 6 on the one hand and 4 and 7 on the other hand. Also correspondingly higher is the clamping force exerted on sheet material stack 29 when latching members 17, 18 have reached the final position, depicted in FIGS. 4 and 7, in which latching flanges 22 abut at the bottom against latching lugs 23. In both cases, the surfaces of actuation flanges 15, 16 terminate flush with the upper sides of guide blocks 11, 12, i.e. actuation members 13, 14 have a defined final position, in contrast to the clamping position of guide bar 6, which depends on the thickness of sheet material 5.

For the cutting operation itself, after the clamping of sheet material 5 or sheet material stack 29, knife part 8 is pushed downward by manual impingement upon handle 9 so that the downwardly protruding rotary knife pushes into sheet material 5 or sheet material stack 29. The cutting operation is carried out by displacing knife carriage 7 along guide bar 6 over the entire width of sheet material 5 or sheet material stack 9.

After completion of the cutting operation, the now-trimmed sheet material 5 or sheet material stack 29 is still clamped between guide bar 6 and sheet material support 3. To release the clamping, latching members 17, 18 are displaced outward by the exertion of pressure in the direction away from guide bar 6, against the action of the latter's spring elements, until latching lugs 23 come out of engagement with latching flanges 22. Actuation members 13, 14 can now be moved upward back into their initial position (FIGS. 2 and 5), which results in relaxation of compression springs 27, 28. Compression springs 27 ensure that guide bar 6 is raised into the initial position according to FIGS. 2 and 5. Sheet material 5 or sheet material stack 29 is now free and can be removed.

Claims

1. A rotary cutting unit (1) for trimming sheet material (5, 29), having the following features: a) the rotary cutting unit (1) has a support plate (2) for receiving the sheet material (5, 29);b) a rotary cutting device (4) is joined to the support plate (2);c) the rotary cutting device (4) comprises a guide bar (6);d) a knife carriage (7) is guided on the guide bar (6), displaceably along the guide bar (6);e) a rotary knife is rotatably mounted on the knife carriage (7);f) the guide bar (6) is held at both ends in guidance devices (11, 12);g) the guide bar (6) is guided in the guidance devices (11, 12) movably between an initial position raised with respect to the support plate (3) and a clamping position lowered in the direction toward the support plate (3);h) the guide bar (6) comprises on the lower side a clamping surface (25) for contact against the sheet material (5, 29);i) the guide bar (6) has a force impinged upon it by a spring device (27), in the direction toward the initial position and as far thereas;j) an actuation device (13, 14) is present for moving the guide bar (6) out of the initial position into the clamping position;k) the actuation device (13, 14) is movable between a starting position in which the guide bar (6) is in the initial position, and a final position in which the guide bar (6) is in the clamping position;l) the actuation device (13, 14) comprises an immobilization device by means of which the actuation device (13, 14) is releasably immobilized in the final position, characterized by the following features:m) the guide bar (6) is clamped in vertically movable fashion between the (first) spring device (27) and a further (second) spring device (28);n) the second spring device (28) has a spring action directed oppositely to the first;o) the actuation device (13, 14) acts on the guide bar (6) by means of the second spring device (28).

2. The rotary cutting unit according to claim 1, wherein the actuation device has an actuation member only on a single guidance device, and the first spring device is arranged only on that guidance device; and the second spring device is effective in the direction toward the support plate in the region of both guidance devices, on the one hand between the actuation member and guide bar and on the other hand between the guidance device and guide bar, the second spring device pressing the guide bar in its initial position onto the support plate in the region of the guidance device not having an actuation device.

3. The rotary cutting unit according to claim 1, wherein the actuation device comprises actuation members (13, 14) on both guidance devices (11, 12), which each coact with an immobilization device

4. The rotary cutting unit according to claim 3, wherein the immobilization devices are embodied in such a way that they immobilize the actuation members (13, 14) in the final position at identical distances from the support plate (2).

5. The rotary cutting unit according to claim 3, wherein the rotary cutting device (4) is embodied in mirror-symmetrical fashion with respect to the center of the guide bar (6).

6. The rotary cutting unit according to claim 1, wherein the second spring device (28) comprises at least one spring member that is arranged in the region of the pertinent guidance device (11, 12).

7. The rotary cutting unit according to claim 1, wherein the first spring device (27) comprises at least one spring member in the respective guidance device (11, 12) equipped with an actuation device (13, 14).

8. The rotary cutting unit according to claim 6, wherein the spring members (27, 28) are embodied as helical springs.

9. The rotary cutting unit according to claim 6, wherein the spring members (27, 28) of the first and the second spring device are located opposite one another.

10. The rotary cutting unit according to claim 6, wherein the spring member or members (27) of the first spring device act(s) on the underside of the guide bar (6).

11. The rotary cutting unit according to claim 6, wherein the spring members (28) of the second spring device act on the upper side of the guide bar (6).

12. The rotary cutting unit according to claim 1, wherein the immobilization device(s) is/are embodied as (a) latching device(s) with which the respectively pertinent actuation device (13, 14) automatically latches in the final position.

13. The rotary cutting unit according to claim 12, wherein the latching device(s) each comprise(s) an operating member (17, 18) by whose actuation the latching device is disengageable.

14. The rotary cutting unit according to claim 1, wherein the actuation device comprises a pushbutton (15, 16) guided vertically in the guidance device (11, 12).

15. The rotary cutting unit according to claim 1, wherein the rotary knife is lowerable with respect to the guide bar (6), toward the support plate (2), against the action of a return spring.