CA2273584A1 - Rotary trimmer with flexible blade guard - Google Patents

Abstract

An improved rotary trimmer having a blade guard is shown and described. The blade guard features a circular outer rim flexibly mounted on curved spokes to a central hub which is concentrically mounted along side a circular cutting blade for rotational motion.
The rim is positioned adjacent to and overlying the cutting edge of the blade and deflects elastically away from the blade edge when sheet material is engaged for cutting by the blade, the rim returning to a circular shape when the cut is completed.

Description

ROTARY TRIMMER WITH FLEBIBLE BLADE GOARD
Related Applications This application is based on and claims the benefit of prior filed co-pending provisional Application No. 60/087,081, filed May 28, 1998.
Field of the Invention This invention relates to an apparatus for cutting sheet material and more specifically to a paper trimmer having a rotary cutting blade with a flexible blade guard.
Background of the Invention Sheet cutting devices, such as manually operated paper cutters, find great utility in the home and office, providing a user with the ability to make precise, straight cuts on single or multiple sheets of paper. Two types of paper cutters, the guillotine type and the sliding-carriage type, are well known examples of paper cutters currently in widespread use.
Guillotine-type cutters typically have a heavy base with an extended surface area to provide support for the paper being cut. A blade assembly having an elongated cutting blade is mounted along one edge of the base. The blade is pivotally mounted to the base at one of its ends and has a handle at the opposite end. To operate this type of cutter, the blade is grasped at the handle and pivoted upwardly away from the base. Paper sheets are positioned on the base with the portion to be cut overhanging the edge beneath the blade. The blade is then pivoted downwardly by the handle, engaging and shearing the overhanging portion of the paper sheets.
While guillotine-type cutters are effective at cutting relatively large numbers of sheets at one time, the obvious safety hazard presented by a long exposed cutting blade pivotally moving through a large arc render this type of cutter dangerous to the user.
Careless use can result in serious injury or amputation of a finger. Furthermore, guillotine cutters tend to be relatively expensive, heavy and do not provide for ready changing or sharpening of the cutting blade when it becomes dull.
Sliding-carriage type cutters are also well known and typically comprise a base having an extended surface area for supporting the sheets to be cut. An elongated guide rail positioned along one edge of the base is pivotally mounted to the base at both its ends and is movable from a position overlying the support surface to a position spaced away from the support surface. A carriage is mounted on the rail. The carriage is slidable along the length of the rail and holds a cutting blade, which could be a straight edge or a rotary blade. The blade is mounted in the carriage with its cutting edge parallel to the guide rail. The cutting blade engages the support surface along a cut-line adjacent and parallel to the guide rail when the guide rail is in the overlying position.
The sliding-carriage type cutter is operated by pivoting the rail into the position spaced away from the support surface. The sheet material to be cut is then positioned on the support surface overlying the cut-line. The guide rail is pivoted into its overlying position, and the carriage is moved along the guide rail where the cutting blade engages the sheet material and severs it along the cut-line.
While the sliding carriage cutter marks a safety improvement over the guillotine type cutter, the cutting blade of the sliding carriage cutter still presents a hazard. The blade is exposed when the rail is in the position pivoted away from the base and can cause injury when the device is handled or the user accidently brushes against the blade. Furthermore, the blade can also cut the user if the carriage is inadvertently moved across a finger during the cutting process.
Clearly, there is the need for improvements to sheet cutters which eliminate the serious safety hazards presented by both the guillotine-type cutter and the sliding carriage cutter.
Summary of the Invention The invention provides a blade guard for use with a blade having a cutting edge for cutting sheet material. The invention comprises a support for mounting the blade with a portion of the cutting edge extending from the support. A rim is yieldably and resiliently mounted on the support adjacent to the cutting edge portion of the blade. The rim has a surface portion extending beyond the cutting edge portion, the rim resiliently yielding and exposing the cutting edge portion for cutting the sheet material when pressure is applied to the support forcing the surface portion of the rim to engage the sheet material.
Preferably, the blade is circular and has a l0 circumferentially arranged cutting edge. A circular rim is used in conjunction with a circular blade. The surface portion of the circular rim is arranged circumferentially of the rim and the rim is mounted coaxially with the blade so that the rim surface portion can be positioned adjacent to and extend beyond the cutting edge portion of the blade.
The rim is supported on a circular hub mounted coaxially with the rim on the support. Preferably, the hub is rotatably mounted on the support. A plurality of resiliently yieldable spokes are connected between the hub and the rim for mounting the rim on the hub.
While there are many possible configurations for the spokes, the preferred embodiment has three spokes substantially equidistantly spaced around the hub, the spokes extending from the hub to the rim in non-linear paths, for example, in curved paths.
It is convenient to form the hub, rim and spokes integrally from a plastic material having adequate flexibility and elasticity to withstand constant resilient yielding without permanently deforming or breaking. BAYBLEND T G5 WN is an example of a plastic material suitable for fabricating the hub, rim and spokes. The curvature of the spokes, the number of spokes, the material from which the spokes are made, as well as the cross-sectional properties of the spokes 5 all affect the relative flexibility of the rim.
The blade guard according to the invention is conveniently used with a sheet cutting device comprising a base having a surface for supporting the sheets to be cut. The surface has a first edge arranged along one side of the base along which an elongated rail is arranged above the surface. The rail is pivotally mounted at both ends to the base, enabling the rail to move from a first position overlying the surface to a second position away from the surface.
The blade support is movably mounted on the rail and can slide lengthwise along it. A handle is mounted on the blade support for manually applying a downward force to the blade support and for manually moving the blade support along said rail. The blade is preferably circular and rotatably mounted on the blade support, the blade having a cutting edge with a portion extending from the support.
The rim of the blade guard is yieldably and resiliently mounted on the support adjacent to the cutting edge portion of the blade. As described above, the rim has a surface portion extending beyond the cutting edge portion. The rim surface portion engages the sheet material supported on the surface beneath the rail. The rim resiliently yields to expose the cutting edge portion when the downward force is applied to the support. Yielding of the rim exposes the blade allowing it to cut the sheet material when the blade support is moved along the rail.
Brief Description of the Drawings Figure 1 is a top plan view of a rotary trimmer according to the present invention;
Figure 2 is a partial perspective view of the rotary trimmer shown in Figure 1 featuring an exploded view of the rail assembly and carriage assembly;
Figure 3 is an end view of the rail assembly and l0 carriage assembly taken along line 3-3 of Figure 2;
Figure 4 is a cross-sectional view on an enlarged scale of the carriage assembly taken along line 4-4 of Figure 1;
Figure 5 is a sectional view of the carriage assembly taken along line 5-5 of Figure 4;
Figure 6 is a sectional view on an enlarged scale of the carriage assembly taken along line 6-6 of Figure 5;
Figure 7 is a detailed plan view of a component of a blade guard according to the invention; and Figure 8 is a partial exploded view on an enlarged scale of components of the carriage assembly shown in Figure 2.

Detailed Description of he Preferred Embodiment Figure 1 shows a manually-operated, sheet cutting device 10 for cutting paper. Cutting device 10 has a cutting board 12 having a generally planar support surface 13 for supporting the sheet material to be cut.
Surface 13 is flanked by one or more raised edge portions 11. For convenience, edge portions 11 display indicia and scales lla allowing the user to position the sheet material on surface 13 for precisely measured l0 cutting.
As best shown in Figure 2, the edge portions 11 are raised slightly above the planar support surface 13. Accordingly, the edge portions 11 of the cutting board proximate to the planar surface 13 provide two parallel vertical abutment surfaces 29. The abutment surfaces 29 are arranged perpendicularly to the line of travel of the cutting blade (described below) allowing the user to make a right angle cut when an edge of the sheet material to be cut is abutted against the abutment surface 29.
Figure 2 shows a rail assembly 14 comprising a pair of rail supports 16 and 18, rail pivot pins 15 and 17 and a rail 20. Rail 20 is supported at both ends on rail supports 16 and 18. The rail supports are pivotally attached to cutting board 12 at respective slots 19 and 21 by means of the pivot pins 15 and 17.
The pivot pins are coaxially arranged and define an axis of rotation for the rail assembly which allows pivotal movement of the rail assembly illustrated in Figure 3. Rail assembly 14 is movable between a first position overlying cutting board 12 (seen in solid line in Figure 3) to a second position away from the cutting board (seen in phantom line).
The rail assembly 14 is mounted on one side of the cutting board 12 with the rail 20 oriented lengthwise perpendicularly to the planes defined by the vertical abutments 29. Rail 20 defines the line of travel of the cutting blade and a perpendicular arrangement of the rail and the abutment surfaces ensures a right angle cut when surface 29 are used to orient the sheet.
As seen in Figure 2, the rail 20 includes a head 20A, a web 20B and a flange 20C. The rail 20 is suspended between the rail supports 16 and 18. In order to provide stability to the rail, the preferred embodiment of the rail supports include respective notches 16A, 18A and end and side grooves 16B, 18B.
The notches receive the web 20B, and the end and side grooves 16B, 18B receive the ends of flange 20C holding the rail firmly in place.
As further depicted in Figures 1 and 2, a carriage assembly 30 is slidably attached to the rail 20. The carriage assembly 30 comprises a housing 32, a rotary cutting blade 34, a blade support member 38 including a spindle 48 and an actuating means comprising a handle 40.
The rotary cutting blade 34 has a circumferentially extending cutting edge 34A and is mounted for rotary motion on the spindle 48. The cutting plane of blade 34 is oriented parallel to rail 20, which is perpendicular to the abutment surfaces 29.

Carriage assembly 30 forms a support for mounting the blade 34.
The housing 32 includes a front blade cover 32A
that is releasably attached to a rear blade cover 328 (described in detail below). A retainer plate 32C
having a finger 42 is located between the front and rear blade covers. As seen in Figures 2, 4 and 5, blade support member 38 is fitted to retainer plate 32C
and engages finger 42 with a bifurcated rear projection 39 which straddles the finger. Retainer plate 32C is mounted onto rear blade cover 32B by means of holes 46B
in the retainer plate engaging pins 46A extending from the rear blade cover 32B. Thus, the retainer plate retains the blade support member 38 to the rear blade cover 32B.
Figure 8 illustrates the attachment of front blade cover 32A to rear blade cover 32B. A pair of tabs 50A
project from the front blade cover 32A. The tabs have notches 50C and are designed to fit and interlock behind ears 50B recessed within the rear blade cover 32B. Ears 50B are arranged next to locking slats 50D
which project inwardly of the rear blade cover. To attach the cover portions, tabs 50A are aligned adjacent to ears 50B. Upon relative clockwise twisting movement of the two cover portions (as viewed from the front blade cover), tabs 50A engage ears 50B until notches 50C engage slats 50D on either side of the rear blade cover 32B, thereby locking the front blade cover 32A to the rear blade cover 32B.
In the preferred embodiment, the front blade cover 32A has a substantially circular shape which enshrouds the cutting blade 34. A flattened portion 32D of the front blade cover arranged along its lower part adjacent cutting board 12 allows a portion 35 of blade 34 to project from the carriage 30 as best seen in 5 Figure 5.
The front blade cover 32A also supports the blade 34 laterally and prevents all but circular motion of the blade as it cuts the sheet material. As seen in Figures 4 and 8, the front blade cover 32A has a 10 circular boss 70 which extends inwardly toward rear blade cover 32B and bears against the blade 34 to prevent it from wobbling, thereby insuring a clean, straight cut when the carriage is moved along the rail and the blade engages the sheet material to be cut.
If the blade is damaged or becomes dull, it can be replaced by twisting the front blade cover 32A
counterclockwise to disengage it from the rear blade cover 32B, removing the old blade 34 by sliding it off of the spindle 48, sliding a new blade onto the spindle 48 and locking the front blade cover 32A back on the rear blade cover 32B by twisting it clockwise.
The rear blade cover 32B has a rail-hugging raceway as shown in Figure 4 which slidably attaches the carriage assembly 30 to the rail 20. The raceway is formed by front and rear lips 68 and 66 respectively, which protrude from opposite sides of the rear blade cover 32B toward each other. Rear lip 66 is positioned between the head 20A and flange 20C, proximate the web 20B. Front lip 68 is similarly placed between head and flange on the opposite side of the rail. The head 20A and web 20B are thus sandwiched between lip 66 and lip 68 forming the raceway. The lips provide stability for the carriage assembly 30 and prevent all motion of the carriage except sliding motion lengthwise of the rail.
In the preferred embodiment, rail 20 is made of aluminum and the housing 32 is made of a polymeric material. In order to reduce the friction between the carriage assembly 30 and the rail 20 (as the carriage assembly is moved in a translational direction along the rail), a ball and spring arrangement, illustrated in Figure 6, is used. The rear blade cover 32B
includes a pair of wells 60 on its outer surface.
Guide springs 62 are placed in the bottom of each well 60 for urging a ball bearing 64 against the web 20B.
A ring 60A at the top of each well (or a slight deformation made at the top of each well 60 during the manufacturing process) secures the ball bearing 64 and guide spring 62 in each respective well to facilitate the attachment of the carriage assembly to the rail assembly 14. A portion of each ball bearing 64 protrudes above the well 60 and contacts the web 20B of the rail 20, thus, reducing friction between the carriage assembly 30 and the rail 20.
In the preferred embodiment, the actuating means (see Figures 1 and 2) consists of a semi-circular handle 40 attached to the blade support member 38.
Handle 40 allows an operator to manually move the carriage assembly 30 and rail assembly 14 between the positions illustrated in Figure 3. The shape of the handle also promotes the translational movement of the carriage along the rail. By pushing and pulling the handle 40, the carriage assembly 30 can readily be made to travel lengthwise along the rail assembly 14.
The positioning of the rail assembly along one side of the cutting board promotes access to the blade by an operator. As seen in Figure 3, the rail assembly 14 rotates away from the cutting board 12. The operator can easily twist off the front blade cover 32A
to access the underlying blade 34, if it needs to be replaced.
Referring to Figures 2 and 4, a self-healing sacrificial mat strip 71 is placed in a channel 72 of the cutting board 12 underlying the path of travel of the cutting blade 34. The mat strip prevents damage to the cutting board 12 during the cutting process. The strip 71 has a tacky or lightly glued side which secures the strip to the cutting board 12. The strip 71 is easily replaced if it is damaged or worn out.
Figure 2 shows an exploded view of the carriage assembly 30 with blade guard 100. Blade guard 100, as shown in detail in Figure 7, comprises a rim 102 supported on three curved flexible spokes 104 emanating from a central hub 106. Guard 100 is preferably made of a high quality plastic material having adequate flexibility and elasticity allowing rim 102 to repeatedly flex and deflect resiliently on the spokes 104 when a force is applied but to always return to a round shape concentric with cutting edge 34A of blade 34.
As best illustrated in Figure 8, blade guard 100 is rotatably mounted on housing cover 32A. Central hub 106 is sized to accept boss 70 which projects inwardly from housing cover 32A toward blade 34. The cross-sectional view shown in Figure 4 depicts boss 70 interfitting within hub 106 which allow the guard 100 to rotate freely about the same axis as the blade 34.
Figure 5 shows a side view of a section through housing 32 which illustrates the relationship between guard 100 and blade 34. A portion 35 of blade 34 extends from housing 32 and rim 102 overlies and extends beyond cutting edge 34A of this extended blade portion in adjacent relation. A portion of guard 100 is shown in phantom line to indicate that it is behind blade 34 when seen in this view.
In operation carriage assembly 30 is pivoted upwardly on rail 20 as seen in phantom line in Figure 3. This allows paper to be placed on support surface 13, a portion of the paper to be cut beneath rail assembly 14 and overlying mat 71.
With the housing pivoted upwardly blade 34 would otherwise be exposed and present a potential cutting hazard, however, blade guard 100 is in position on boss 70 with rim 102 adjacent to and extending beyond cutting edge 34A. Rim 102 effectively prevents accidental contact between the operator's fingers and blade 34, thereby preventing injury. If a finger does contact the guard with sufficient force to deflects it such that the finger contacts the blade, the contact force between the finger and the blade is spread out over the larger surface area of the rim thus the guard 100 continues to prevent the blade from injuring the operator.

The rim 102 is supported by the spokes 104 with sufficient stiffness to prevent the blade from making an unintentional cut, however, the spokes are also flexible enough to allow the rim to deflect radially away from the cutting edge to expose the blade for cutting when sufficient force or pressure is applied to handle 40.
Intentional cuts are made by rotating carriage assembly 30 into the position away from board 12, as seen in phantom line in Figure 3, and placing sheet material to be cut on surface 13 overlying mat strip 71. Carriage assembly 30 and rail assembly 14 are then rotated into position overlying board 12 as seen in solid line in Figure 3. With the carriage positioned as far to one end of the rail as possible, the rim 102 will rest on mat 71 with the exposed portion 35 of cutting edge 34A displaced slightly above the mat.
Force or pressure is manually applied to handle 40, forcing the blade downwardly and sliding carriage assembly 30 along rail 20. As rim 102 of the blade guard encounters sheet material to be cut the rim deflects on flexible spokes 104 into a non-circular shape, exposing the portion 35 of blade cutting edge 34A which engages and cuts the sheets on the cutting board. Blade guard 100 rotates as necessary with hub 106 turning on boss 70 to ensure smooth operation.
Once the cut has been completed and pressure on the handle released, rim 102 resiliently returns to its circular shape extending beyond edge 34A, again providing protection against inadvertent cuts.
Even though particular embodiments of the present invention have been illustrated and described herein, they are not intended to limit the invention. It is, therefore, to be understood that modification and variation of the embodiments described herein may be made without departing from the spirit or scope of the 5 present invention.

Claims (16)

1. A blade guard for use with a blade having a cutting edge for cutting sheet material, said blade guard comprising:
a support for mounting said blade with a portion of said cutting edge extending from said support; and a rim yieldably and resiliently mounted on said support adjacent to said cutting edge portion, said rim having a surface portion extending beyond said cutting edge portion, said rim yielding and exposing said cutting edge portion for cutting said sheet material when pressure is applied to said support forcing said surface portion to engage said sheet material.

2. A blade guard according to Claim 1, wherein said blade is circular, said cutting edge being arranged circumferentially thereof, and said rim is circular, said surface portion being arranged circumferentially thereof, said rim being mounted coaxially with said blade.

3. A blade guard according to Claim 2, further comprising:
a circular hub mounted on said support coaxially with said rim; and a plurality of resiliently yieldable spokes connected between said hub and said rim for resiliently and yieldably mounting said rim on said hub.

4. A blade guard according to Claim 3, wherein said hub is rotatably mounted on said support.

5. A blade guard according to Claim 3, wherein said spokes extend from said hub to said rim in non-linear paths.

6. A blade guard according to Claim 3, comprising at least three said spokes, said spokes being substantially equidistantly spaced about said hub.

7. A blade guard according to Claim 3, wherein said hub, said rim and said spokes are integrally formed from a plastic material.

8. A sheet cutting device comprising:
a base having a surface for supporting said sheets to be cut, said surface having a first edge arranged along one side of said base;
an elongated rail arranged above said surface along said first edge, said rail being pivotally mounted at both ends to said base, said rail being movable from a first position overlying said surface to a second position away from said surface;
a blade support movably mounted on said rail for motion therealong;
a handle mounted on said blade support for manually applying a downward force to said blade support and for manually moving said blade support along said rail;
a blade mounted on said blade support, said blade having a cutting edge, a portion of said cutting edge extending from said support;

a rim yieldably and resiliently mounted on said support adjacent to said cutting edge portion, said rim having a surface portion extending beyond said cutting edge portion; and said rim surface portion engaging said sheet material supported on said surface beneath said rail, said rim resiliently yielding to expose said cutting edge portion when said downward force is applied to said support, said blade thereby being exposed and cutting said sheet material when said blade support is moved along said rail.

9. A sheet cutting device according to Claim 8, wherein said blade is circular and said cutting edge is disposed circumferentially of said blade.

10. A sheet cutting device according to Claim 9, wherein said rim is circular and mounted coaxially with said blade.

11. A sheet cutting device according to Claim 10, further comprising a hub mounted on said support coaxially with said rim, said hub having a plurality of resiliently flexible spokes connected between said hub and said rim for resiliently yieldably supporting said rim.

12. A sheet cutting device according to Claim 11, wherein said blade and said hub are rotatably mounted on said support.

13. A sheet cutting device according to Claim 11, wherein said spokes extend to said rim in non-linear paths.

14. A sheet cutting device according to Claim 13, wherein said paths are curved.

15. A sheet cutting device according to Claim 11, having at least three substantially equidistantly spaced spokes.

16. A sheet cutting device according to Claim 11, wherein said hub, spokes and rim are integrally formed from a plastic material.