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 and a blade biasing member for retracting the cutting blade into a housing when the paper cutter is not in use.

Background of the Invention

Apparatus for cutting or trimming sheet material utilizing rotary or circular cutting blades are well known in the art. The earliest sheet cutting apparatus were found in industrial situations in which large rolls of sheet material needed to be cut. Rotary trimmers were adapted for office use but their basic design is similar to the large industrial cutters.

A rail for carrying a carriage that houses the circular blade is suspended over the sheet or sheets to be cut. The rail arrangement positions the cutting edge of the circular cutting blade perpendicular to the plane of the sheet. This promotes a fast, straight and clean cut of the sheet material.

A drawback of trimmers utilizing a circular cutting blade is that the blade is always exposed. Accordingly, there is a

significant chance of being cut by the razor-sharp cutting edge of the blade. With the advent of the home office, children have access to office products including rotary trimmers. Accordingly, the exposed blade design is of concern to many.

Another drawback of rotary blade paper trimmers is that the rail used to suspend the carriage assembly tends to interfere with the operator's line of sight, thereby blocking the operator's view of the sheets being cut.

summary of the Invention

The present invention relates to a blade biasing member for use in a rotary trimmer. A carriage assembly is usually suspended from a rail assembly. The carriage assembly, according to the present invention, includes a housing; a blade support movably connected to the housing; a circular cutting blade, having a circumferentially extending cutting edge that is mounted for rotary motion on the blade support, and a biasing member. The biasing member communicates with the blade support and the housing for biasing the blade from an operative position in which the cutting edge projects from the housing to an inoperative position in which the cutting edge is retracted into or covered by the housing when the rotary trimmer is not in use.

A manually activated actuating means connected to the blade support is used to overcome the bias of the biasing member and moves the blade from the inoperative position into the operative

position. Since the cutting edge of the circular cutting blade is not continuously exposed, the probability of being cut is reduced.

The rail assembly of the present invention is pivotally mounted on one side of the cutting board and the carriage assembly is suspended from the rail such that the blade is on the outer side of the circumferential arc travelled by the rail as it is pivoted. This provides the operator with a clear view of the blade at all times.

Brief Description of the Drawings

Figure 1 is a top plan view of a rotary trimmer constructed in accordance with the present invention;

Figure 2 is an exploded perspective view of the rail assembly and carriage assembly shown in Figure 1; Figure 3 is side view of the rail assembly and carriage assembly taken along line 3-3 of Figure 2;

Figure 4 is a sectional view of the carriage assembly taken along line 4-4 of Figure 1 with the blade in the inoperative position; Figure 5 is a sectional view of the carriage assembly, similar to the view of Figure 4, with the blade in the operative position;

Figure 6 is a sectional view of the carriage assembly taken along line 6-6 of Figure 4;

Figure 7 is a perspective view of the front and rear blade covers shown in Figure 2;

Figure 8 is a sectional view of the carriage assembly taken along line 8-8 of Figure 5; and Figure 9 is a sectional view of the raceway taken along line 9-9 of Figure 6 with certain parts removed for the sake of illustration.

Detailed Description of the Preferred Embodiment

Referring to the drawings, a sheet trimmer device in accordance with the present invention, intended for cutting paper sheets, is generally referred to as 10. A cutting board 12, as seen in Fig. 1, has a generally planar support surface 13 for supporting the sheet material to be cut and edge portions 11 displaying markings for measurements.

The planar support surface 13 is preferably at a lower elevation than the edge portions 11 of the cutting board 12. As shown in Figure 1, the edge portions 11 are raised slightly above the planar support surface 13. Accordingly, the edge portions 11 of the cutting board proximate the planar surface 13 provide two parallel vertical abutment surfaces 29 to which the sheet material is abutted. The vertical abutments 29 promote a square cut (i.e. , the edge of the sheet after it is cut is perpendicular to the two remaining sides that the cut intersects) .

Referring to Figs. 1, 2, 4 and 5, a self healing mat strip 70 is placed in a channel 72 of the cutting board 12 to prevent damage to the cutting board 12 during the cutting process. The strip 70 has a tacky or lightly glued side which secures the strip to the cutting board 12. The strip 70 is easily replaced if it is damaged or worn out.

Referring again to Fig. 2, a rail assembly 14 comprises a pair of rail supports 16, 18, rail pivot pins 15, 17 and a rail 20. The rail assembly 14 is mounted on one side of the cutting board 12 with the rail 20 perpendicular to the planes defined by the vertical abutments 29. Slots 19, 21 on the cutting board 12 are designed to accept the rail supports 16, 18. The rail supports are pivotally secured to the cutting board 12 with the rail pivot pins 15, 17.

The rail 20 includes a head 20A, a web 20B and a flange 20C. The rail 20 is suspended between the rail supports 16, 18. In order to provide stability, the preferred embodiment of the rail supports 16, 18 include 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.

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, a biasing member 36 and an actuating meanε 40. The rotary cutting blade 34 has a

circumferentially extending cutting edge 34A and is mounted for rotary motion on the blade support member 38. In the preferred embodiment, the circular cutting blade 34 is rotatably mounted on a spindle 48 which extends from the blade support member 38.

The housing 32 includes a rear blade cover 32A, a front blade cover 32B that is releasably attached to the rear blade cover 32A, and a slide member 32C located between the front blade cover 32A and the rear blade cover 32B. The slide member 32C is also releasably attached to the rear blade cover 32B.

Referring now to Figure 7, a pair of tabs 50A on the front blade cover 32A are designed to fit behind ears 50B of the rear blade cover 32B upon relative twisting movement of the two cover portions, for releasably securing the front blade cover to the rear blade cover. Tabs 50A are twisted until notches 50C engage slats 50D on either side of the rear blade cover 32B, thereby frictionally 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 with a flattened portion that allows it to glide on top of the sheets to be cut.

The front blade cover 32A also supports the blade by preventing all but circular motion of the blade 34. The front blade cover 32A has a circular boss 70 which bears against the blade 34 to prevent it from wobbling, thereby insuring a clean, straight 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.

Referring now to Figs. 2, 6 and 8, in the preferred embodiment, pins 46A on the rear blade cover 32B are designed to align with and frictionally engage pinholes 46B on each side of slide 32C, thereby releasably securing slide 32C to the rear blade cover 32B.

The rear blade cover 32B forms with the slide 32C a rail- hugging raceway as shown in Figs. 4 and 5. This rail-hugging raceway provides support and stability to the carriage assembly 30. The rear blade cover 32B is designed to accept approximately one-half of head 20A of the rail 20 and to engage one side of the web 20B. In a similar fashion, the slide 32C engages the remaining half of the head 20A and the opposite side of web 20B.

Rear lip 66 which protrudes from the rear blade cover 32B is positioned between the head 20A and flange 20C, proximate the web 20B. Front lip 68 which is attached to slider 32C is placed under the head 20A of rail 20. When slider 32C is attached to the rear blade cover 32B via pins 46A and pinholes 46B, the head 20A and web 20B are sandwiched between lip 66 and lip 68 forming

the raceway. This provides stability for the carriage assembly 30.

Referring now to Figs. 7 and 9, the raceway along rail 20 is shown. In the preferred embodiment, the rail is made of aluminum and the housing 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 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 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.

Referring again to Figs. 4-6 and 8, in the preferred embodiment, the biasing member 36 is a coil spring that communicates with the vertically movable blade support 38 and the stationary slide member 32C. The slide member includes a bias guide 42; the blade support 38 includes a bifurcated rear projection 39 having a bias guide slot 43 for accepting the bias

guide 42. The bias spring 36 is retained by the rear projection 39 and the bias guide 42 thereby limiting substantially all but compressive motion of the bias spring 36.

The blade support 38 includes a pair of ears 44 that communicate with cut-outs 52 on slide 32C for aligning the blade support 38 - and ultimately the blade 34 - with the housing 32.

The cut-outs 52 permit the blade support 38 to move in the vertical direction but resist movement in other directions.

The cut-outs 52 of slide 32C in combination with ledges 31 of the rear blade cover 32B define the boundaries for vertical travel of the blade support 38. The ears 44 communicate with the slide 32C for stopping the downward movement of the blade support 38 as shown in Fig. 8. The ears 44 engage ledges 31, as seen in Fig. 7, for defining the ultimate upper boundary that the blade support can travel.

The bias member 36 directly biases the blade support 38 and the blade 34 in an inoperative position whereby the entire circumferential cutting edge 34A of the blade 34 is covered by the housing. As seen in Fig. 6, the blade support 38 is in its upper most position wherein the ears 44 have engaged ledges 31. In a preferred embodiment, the bias member 36 retracts the blade so that no portion of the blade 34 is exposed.

When the carriage assembly 30 is in its rest or inoperative position, as shown in Figs. 4 and 6, the blade 34 is fully

retracted into the housing 32. The actuating means 40 is used to manually overcome the bias of the biasing member 36. When an operator depresses the actuating means 40, the cutting blade 34 is moved in a substantially radial direction such that at least a portion of the cutting edge 34A of cutting blade 34 projects from the housing 32. (see Figs. 5 and 8) The position of the cutting edge 34A when it projects from the housing is defined as its operative position.

In a preferred embodiment, the actuating means 40 consists of a semi-circular handle attached to the blade support 38. This allows an operator to manually actuate the blade 34 by moving it into its operative position. The shape of the handle also promotes the translational movement of the carriage 30 along the rail 14. By pushing and pulling the actuating means 40, the carriage assembly 30 travels along the rail 14 in a longitudinal direction.

The positioning of the rail assembly along one side of the cutting board promotes access to the blade by an operator. As seen in Fig. 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. Furthermore, when the rail assembly 14 is lying flat over the sheets to be cut, the blade 34 will be clearly visible to the operator during the cutting procedure. This ensures that the operator can see the placement of the cut allowing adjustments to be made during the cutting procedure.

An actual cutting process will now be described. The rail assembly 14 is rotated away from the planar cutting surface of the cutting board 12 to its rest position as shown in Figure 3. The sheet or sheets of material to be cut are placed on the planar surface 13 of the cutting board 12, abutting either vertical surface 29. The rail assembly 14 is then rotated back over the cutting board 12 with the carriage assembly 30 positioned at either end.

The operator depresses the handle 40 of the carriage assembly, thereby moving the cutting edge 34A of blade 34 out from the housing and into the self healing mat 70. (See Figs. 5 and 8.) The handle 40 preferably has a semi-circular design with a portion sloping generally downwardly towards the rail 20 in order to facilitate the translational movement of the carriage assembly 30 along the rail 20. The large surface area of the handle 40 assists the operator in manually moving the carriage assembly back and forth along the rail 20.

When blade 34 is in its operative position, it engages the mat 70 and begins to turn as the carriage assembly is translationally moved along the rail 20. The blade 34 continues to turn as long as the downward force on the handle is greater than the bias provided by the bias member 36 and a longitudinal force substantially parallel to the rail is imparted to the carriage assembly. If either force is not preεent, the blade 34 will not turn.

As the blade 34 engages the sheets to be cut, it continues to turn traversing the entire width of the sheet. Although the blade is razor-sharp, it may not cut through a stack of sheetε during one pass. Accordingly, after the carriage assembly 30 has traversed the entire length of the rail 20, it may be necessary to retrace the path by pushing the carriage assembly 30 back across the rail and the sheets to complete the cutting process.

It should be noted that the operator has complete control of the force applied during the cutting process. That is, after the bias of the bias member 36 is overcome, the operator determines the pressure applied to the sheets during the cutting process.

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 present invention.