GB2340790A

GB2340790A - Improvements relating to power saws

Info

Publication number: GB2340790A
Application number: GB9923248A
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: 2000-03-01
Anticipated expiration: 2016-05-31
Also published as: GB2313571B; GB9611339D0; GB2340790B; GB2313571A; GB9923248D0

Abstract

A power saw has a blade 20 reciprocated by arms 30,31 which oscillate about pivots points 40,41. The blade 20 is held between blade holders 10,12 which are formed to accept both pin-end and 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

A 2340790 1 1 _"ImDrovements relating to power saws" 2 3 This invention

relates to power saws which use straight 4 reciprocating blades, such as scroll saws.

G In a scroll saw, a replaceable straight blade is 7 tensioned between the ends of a pair of arms, and is 8 reciprocated by the arms in a vertical plane. The 9 blades must be replaced from time to time, either to replace a blade which has become blunt or to mount a 11 blade suited to a different type'of work.

12 13 Many existing types of blade holder require a 14 relatively time consuming and awkward operation to effect a blade change, typically requiring the use of 1G tools. Moreover, blades are conventionally available 17 with either plain ends or pin ends, and changing from 18 one type to the other requires modification of the 19 machine.

21 The present invention provides a power saw comprising 22 first and second spaced, generally parallel arms, a 23 blade releasably secured to the first and second arms 24 adjacent a first end of each arm for substantially linear reciprocating motion, the arms being pivotally 2 1 mounted to a frame intermediate their ends with the 2 second ends normally secured together, in use, to cause 3 tensioning of the blade; and the saw being provided 4 with blade release means acting on the second ends of the arms, the blade release means comprising a stop 6 arrangement preventing relative movement of the second 7 ends, and means for selectively moving the stop 8 arrangement to permit relative movement of said arms.

9 Said means preferably comprises a cam lever. A tension 11 spring is preferably provided to bias the second ends 12 together, and thus to tension a blade in the blade 13 holders.

14 The stop arrangement preferably comprises a rod secured 16 to said second end of each arm and having one end 17 pivoted to said cam lever, the cam lever bearing on a 18 pressure surface fixed in relation to a main frame of 19 the saw, and a fixed tubular member surrounding the rod and having an end acting as a stop for one of the arms.

21 22 An embodiment of the invention will now be described, 23 by way of example, with reference to the drawings, in 24 which:

26 Fig. 1 is an exploded perspective view of part of 27 a scroll saw; 28 Fig. 2 is a side view corresponding to Fig. 1; 29 Fig. 3 is a detail side view illustrating one use of the saw; 31 Fig. 4 is a plan view of part of Fig. 3; and 32 Fig. 5 is a detail side view, to an enlarged 33 scale, of another part of the saw.

34 Referring particularly to Figs. 1 and 2, a scroll saw 36 has arms 30 and 31which are pivoted at 40 and 41 in a 1 3 1 frame (part of the frame being seen at 42 in Fig. 5, 2 but the frame being omitted from the other views). The 3 outer ends of the arms 30, 31 carry a removable blade 4 20. The inner ends of the arms 30, 31 are driven by a known mechanism (not shown) to cause the blade 20 to 6 reciprocate and thus to cut a workpiece fed past it.

7 8 The arms 30, 31 at their outer ends carry blade holders 9 10 secured in place by pressure plates 32 and cap screws 15 engaging in screw-threaded bores in the arms 11 30, 31. As better seen in Figs. 3 and 4, each blade 12 holder 10 is formed with an axial slot 13 the sides of 13 which can be forced inwards by the action of a cap 14 screw 14 engaged with threads 141. The entry to the is slot 13 from the front is chamfered at 131. The blade 16 holders 10 are also formed to form a forward hook 17 shaped projection 16 partially defined by a transverse 18 semi-cylindrical groove 17.

19 The saw may be used with pin-ended blades as shown in 21 Figs. 1, 2 and 3. To mount a blade 20, the arms 30, 31 22 are manipulated (as will be described) to reduce the 23 spacing between the blade holders 10, transverse pins 24 21 in the ends of the blade 20 are engaged in the grooves 17, and the arms 30, 31 are then forced apart 26 to secure the blade 20 under tension.

27 28 The saw may also be used with plain-end blades. As 29 best seen in Fig. 4, a plain end blade 20 may be inserted in the slot 13 and secured in position by 31 tightening the screw 14.

32 33 Referring now particularly to Figs. 1, 2 and 5, the 34 means by which the blade holders may be brought together for blade changing and forced apart to tension 36 the blade for use will now be described.

4 1 The rear ends of the arms 30, 31 are biased together by 2 a tension coil spring 50. The arms 30, 31 are formed 3 with outwardly facing V notches 51 which are engaged by 4 apertured wedge members 52a, 52b received on a rod 53. 5 The lower wedge member 52b is secured to the rod 53 and 6 to the lower arm 31 by means of a nut 54 threaded on 7 the rod 53 and engaging a slotted clamp plate 55b 8 secured to the lower arm 31 by a fastener 56b. the 9 upper wedge member 52a is secured to the upper arm 30 10 by a similar clamp plate 55a and fastener 56a. 11 12 The upper end of the rod 53 is secured to a threaded 13 sleeve 63 to the top of which a lever 64 is pivotally 14 connected by a pin 65. The lever 64 has a cam surface 15 58 bearing on a thrust washer 59 seated on a spacer 60 16 on the frame 42 of the saw, the thrust washer 59 17 trapping a tube 62 which limits upward movement of the 18 upper wedge member 52a on the rod 53. 19 20 Thus, in normal use the spring 50 tensions the rear 21 ends of the arms 30, 31 together, which forces the 22 forward ends of the arms 30, 31 apart and applies 23 tension to the blade 20. When it is desired to change 24 the blade 20, the lever 56 is simply lifted by hand 25 through 900 (to the position shown in full line in Fig. 26 2) which increases the spacing between the wedge 1 members 52 allowing the front of the upper arm 30 to be 2 depressed by hand by the user to free the blade 20. 3 4 Modifications and improvements may be made to the 5 foregoing example within the scope of the present 6 invention. 7 8 6

Claims

1 CLAIMS

2 3 1. A power saw comprising first and second spaced, 4 generally parallel arms, a blade releasably secured to the first and second arms adjacent a first end of each 6 arm for substantially linear reciprocating motion, the 7 arms being pivotally mounted to a frame intermediate 8 their ends with the second ends normally secured 9 together, in use, to cause tensioning of the blade; and the saw being provided with blade release means acting 11 on the second ends of the arms, the blade release means 12 comprising a stop arrangement preventing relative 13 movement of the second ends, and means for selectively 14 moving the stop arrangement to permit relative movement of said arms.

16 17

2. A power saw according to claim 1, in which said 18 means for selectively moving the stop arrangement 19 comprises a cam lever.

21

3. A power saw according to claim 1 or claim 2, in 22 -which a tension spri ng is provided to bias the second 23 ends together, and thus to tension a blade in the blade 24 holders.

26

4. A power saw according to any preceding claim, in 27 which the stop arrangement comprises a rod secured to 28 said second end of each arm and having one end pivoted 29 to said cam lever, the cam lever bearing on a pressure surface fixed in relation to a main frame of the saw, 31 and a fixed tubular member surrounding the rod and 32 having an end acting as a stop for one of the arms.

33 34 36