GB2313571A

GB2313571A - Blade holding and tensioning

Info

Publication number: GB2313571A
Application number: GB9611339A
Authority: GB
Inventors: Ruey-Zon Chen
Original assignee: REXON Ltd
Current assignee: REXON Ltd
Priority date: 1996-05-31
Filing date: 1996-05-31
Publication date: 1997-12-03
Anticipated expiration: 2016-05-31
Also published as: GB2340790B; GB9923248D0; GB9611339D0; GB2340790A; GB2313571B

Abstract

A power scroll saw has a blade (20) held between blade holders (10,12) which are formed to accept both pin-end and plain-end blades by means of both pin 15 engaging formations and a slot 13 to clamp plain-end blades. The arms are biased apart by a spring (50) whose tension is controlled by a stop arrangement (52-63). A cam lever (58) cooperates with the stop arrangement (52-63) to provide quick release of the blade tension.

Description

"Improvements relatina to power saws" This invention relates to power saws which use straight reciprocating blades, such as scroll saws.

In a scroll saw, a replaceable straight blade is tensioned between the ends of a pair of arms, and is reciprocated by the arms in a vertical plane. The blades must be replaced from time to time, either to replace a blade which has become blunt or to mount a blade suited to a different type of work.

Many existing types of blade holder require a relatively time consuming and awkward operation to effect a blade change, typically requiring the use of tools. Moreover, blades are conventionally available with either plain ends or pin ends, and changing from one type to the other requires modification of the machine.

The present invention provides a power saw comprising a pair of spaced, generally parallel arms having a blade releasably secured to each arm adjacent a first end for substantially linear reciprocating motion, in which the blade is secured to each arm by a respective blade holder comprising a body having a first portion for attachment to the arm and a second portion formed with a slot aligned with the blade direction for receiving one end of the blade, the blade holder being provided with means for selectively forcing the sides of the slot together, and in which said second portion is also formed with a formation facing outwardly of the blade location and adapted to receive a pin of a pin-end blade, whereby the blade holder may be used with either a plain-end blade clamped in said slot or with a pinend blade located in said slot with its pin engaged in said formation.

The means for forcing the sides of the slot together may suitably be a screw engaging a threaded bore.

Said formation is preferably a part-cylindrical groove across an out face of said second portion.

The blade holder may conveniently be releasably secured to its arm by a threaded fastener.

In a particularly preferred form of the invention, the arms are pivotally mounted to a frame intermediate their ends with the second ends normally secured together, in use, to cause tensioning of the blade; and the saw is provided with blade release means acting on the second ends of the arms. The blade release means comprises a stop arrangement preventing relative movement of the second ends, and means for selectively moving the stop arrangement to permit relative movement of said arms. Said means preferably comprises a cam lever. A tension spring is preferably provided to bias the second ends together, and thus to tension a blade in the blade holders.

From another aspect, the invention provides a power saw comprising a pair of spaced, generally parallel arms having a blade releasably secured to each arm adjacent a first end for substantially linear reciprocating motion, the arms being pivotally mounted to a frame intermediate their ends with the second ends normally secured together, in use, to cause tensioning of the blade; and the saw being provided with blade release means acting on the second ends of the arms, the blade release means comprising a stop arrangement preventing relative movement of the second ends, and means for selectively moving the stop arrangement to permit relative movement of said arms.

Said means preferably comprises a cam lever.

A tension spring is preferably provided to bias the second ends together, and thus to tension a blade in the blade holders.

The stop arrangement preferably comprises a rod secured to said second end of each arm and having one end pivoted to said cam lever, the cam lever bearing on a pressure surface fixed in relation to a main frame of the saw, and a fixed tubular member surrounding the rod and having an end acting as a stop for one of the arms.

An embodiment of the invention will now be described, by way of example, with reference to the drawings, in which: Fig. 1 is an exploded perspective view of part of a scroll saw; Fig. 2 is a side view corresponding to Fig. 1; Fig. 3 is a detail side view illustrating one use of the saw; Fig. 4 is a plan view of part of Fig. 3; and Fig. 5 is a detail side view, to an enlarged scale, of another part of the saw.

Referring particularly to Figs. 1 and 2, a scroll saw has arms 30 and 31 which are pivoted at 40 and 41 in a frame (part of the frame being seen at 42 in Fig. 5, but the frame being omitted from the other views). The outer ends of the arms 30, 31 carry a removable blade 20. The inner ends of the arms 30, 31 are driven by a known mechanism (not shown) to cause the blade 20 to reciprocate and thus to cut a workpiece fed past it.

The arms 30, 31 at their outer ends carry blade holders 10 secured in place by pressure plates 32 and cap screws 15 engaging in screw-threaded bores in the arms 30, 31. As better seen in Figs. 3 and 4, each blade holder 10 is formed with an axial slot 13 the sides of which can be forced inwards by the action of a cap screw 14 engaged with threads 141. The entry to the slot 13 from the front is chamfered at 131. The blade holders 10 are also formed to form a forward hookshaped projection 16 partially defined by a transverse semi-cylindrical groove 17.

The saw may be used with pin-ended blades as shown in Figs. 1, 2 and 3. To mount a blade 20, the arms 30, 31 are manipulated (as will be described) to reduce the spacing between the blade holders 10, transverse pins 21 in the ends of the blade 20 are engaged in the grooves 17, and the arms 30, 31 are then forced apart to secure the blade 20 under tension.

The saw may also be used with plain-end blades. As best seen in Fig. 4, a plain end blade 20 may be inserted in the slot 13 and secured in position by tightening the screw 14.

Referring now particularly to Figs. 1, 2 and 5, the means by which the blade holders may be brought together for blade changing and forced apart to tension the blade for use will now be described.

The rear ends of the arms 30, 31 are biased together by a tension coil spring 50. The arms 30, 31 are formed with outwardly facing V notches 51 which are engaged by apertured wedge members 52a, 52b received on a rod 53.

The lower wedge member 52b is secured to the rod 53 and to the lower arm 31 by means of a nut 54 threaded on the rod 53 and engaging a slotted clamp plate 55b secured to the lower arm 31 by a fastener 56b. the upper wedge member 52a is secured to the upper arm 30 by a similar clamp plate 55a and fastener 56a.

The upper end of the rod 53 is secured to a threaded sleeve 63 to the top of which a lever 64 is pivotally connected by a pin 65. The lever 64 has a cam surface 58 bearing on a thrust washer 59 seated on a spacer 60 on the frame 42 of the saw, the thrust washer 59 trapping a tube 62 which limits upward movement of the upper wedge member 52a on the rod 53.

Thus, in normal use the spring 50 tensions the rear ends of the arms 30, 31 together, which forces the forward ends of the arms 30, 31 apart and applies tension to the blade 20. When it is desired to change the blade 20, the lever 56 is simply lifted by hand through 900 (to the position shown in full line in Fig.

2) which increases the spacing between the wedge members 52 allowing the front of the upper arm 30 to be depressed by hand by the user to free the blade 20.

Modifications and improvements may be made to the foregoing example within the scope of the present invention.

Claims

1. A power saw comprising a pair of spaced, generally parallel arms having a blade releasably secured to each arm adjacent a first end for substantially linear reciprocating motion, in which the blade is secured to each arm by a respective blade holder comprising a body having a first portion for attachment to the arm and a second portion formed with a slot aligned with the blade direction for receiving one end of the blade, the blade holder being provided with means for selectively forcing the sides of the slot together, and in which said second portion is also formed with a formation facing outwardly of the blade location and adapted to receive a pin of a pin-end blade, whereby the blade holder may be used with either a plain-end blade clamped in said slot or with a pin-end blade located in said slot with its pin engaged in said formation.

2. A power saw according to claim 1, in which the means for forcing the sides of the slot together comprises a screw engaging a threaded bore.

3. A power saw according to claim 1 or claim 2, in which said formation is a part-cylindrical groove across an outer face of said second portion.

4. A power saw according to any preceding claim, in which the blade holder is releasably secured to its arm by a threaded fastener.

5. A power saw according to any preceding claim. in which the arms are pivotally mounted to a frame intermediate their ends with the second ends normally secured together, in use, to cause tensioning of the blade; and the saw is provided with blade release means acting on the second ends of the arms.

6. A power saw according to claim 5, in which the blade release means comprises a stop arrangement preventing relative movement of the second ends, and means for selectively moving the stop arrangement to permit relative movement of said arms.

7. A power saw according to claim 6, in which said means for selectively moving the stop arrangement comprises a cam lever.

8. A power saw according to any of claims 5 to 7, in which a tension spring is provided to bias the second ends together, and thus to tension a blade in the blade holders.

9. A power saw comprising a pair of spaced, generally parallel arms having a blade releasably secured to each arm adjacent a first end for substantially linear reciprocating motion, the arms being pivotally mounted to a frame intermediate their ends with the second ends normally secured together, in use, to cause tensioning of the blade; and the saw being provided with blade release means acting on the second ends of the arms, the blade release means comprising a stop arrangement preventing relative movement of the second ends, and means for selectively moving the stop arrangement to permit relative movement of said arms.

10. A power saw according to claim 9, in which said means for selectively moving the stop arrangement comprises a cam lever.

11. A power saw according to claim 10 or claim 11, in which a tension spring is provided to bias the second ends together, and thus to tension a blade in the blade holders.

12. A power saw according to any of claims 9 to 11, in which the stop arrangement comprises a rod secured to said second end of each arm and having one end pivoted to said cam lever, the cam lever bearing on a pressure surface fixed in relation to a main frame of the saw, and a fixed tubular member surrounding the rod and having an end acting as a stop for one of the arms.

13. A power saw substantially as herein described with reference to the drawings.