How does the blade interlock on Charge, Wave and Surge work? An explanation

[Dutch_Tooler]

Ever wondered why on the Charge, Wave and Surge (and possibly some other OHO tools) the plain and serrated-edge blades don't extend when the pliers head is extended? Some forum members apparently have.

This is a safety measure designed to prevent inadvertent opening of the blades when handling something with the pliers, It wouldn't do at all to have your fingers or pieces of palm skin caught between a cutting edge and the handles, and then apply pressure.

This thread is meant to provide a brief explanation of the technique used, supplemented by pictures I shall be posting in subsequent instalments.

For those that can't wait for pictures and my text, please see this link to the relevant US Patent.
In that patent, Figs. 1, 2 and 5-7 most clearly show what happens. Compare Figs. 6 and 7 for instance, where you see how the latch finger 182 moves to lock or unlock the blade, driven by a cam surface on cam 192 at the base of the plier head. Open the pliers and the latch finger moves to lock the blade, and (due to inherent spring power) vice versa as well.

By the way, this has implications for reassembly - make sure this takes place with the pliers in the closed position, otherwise the spring won't manage to correctly engage the sloped cam surface and end up on the latter's outer flat face (and either not work, or be bent out of plane, or both )

The relevant text of the patent is in the spoiler below.

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The knife blades 104 and 108 both define holes 180 extending through their blades to be engaged by a user's thumb or finger to push the blades open from their folded positions in the outer channels 92 and 96. An interlock catch in the form of a latch finger 182, however, extends into the hole 180 of respective blade 104 or 108, preventing the blade from being opened outwardly from its folded position whenever the base of the tool housed in the central channel 44 of the particular handle 32 or 34 is moved at least a predetermined distance away from its fully stowed position within the central channel of the handle. It will be understood that for outer blades that have no holes extending entirely through them as do the holes 180, a suitable blind hole or ledge could be provided to be engaged by the finger 182, or the finger 182 could be located so as to engage the back of a blade.

Referring again to FIGS. 6 and 7, a fork-like spring 184 is attached to the bottom 84 of the central channel 44 by the rivet 126. Instead of being a separate piece as shown in FIGS. 6 and 7, the spring 184 could be integrated with the spring 124 and the finger 152, as shown in FIG. 9B.

A first prong 186 of the spring 184 extends within the channel 44 alongside the side wall 82 and closely along the channel base 84. A second prong 188 of the spring 184 has a tapered outer end 190 and carries the interlock latch finger 182.

A cam 192 extends around part of the base portion 50 of the pliers jaw 38. The cam 192 has a flat side 194 facing toward and oriented generally parallel with the channel side wall 82. The opposite side of the cam 192 is sloped with respect to the flat side 194, with a generally helical surface 196 centered on the pivot pin 56. When the folding tool 30 is in its folded configuration as shown in FIGS. 2 and 6, the tapered outer end 190 of the second prong 188 of the latch spring 184 rests against the helical surface 196 at the narrowest portion of the cam 192, and the outermost portion of the interlock latch finger 182 does not extend substantially beyond the outer side of the channel side wall 80. That is, the latch finger 182 does not extend far enough into the outer channel 92 in which the knife blade 104 is located in its folded position to interfere with movement of the knife blade 104. Except for the engagement of the detent bump 172 in the dimple 174, the knife blade 104 is thus free to be moved from within the outer channel 92 to its extended position.

When the handle 32 is moved away from the folded configuration of the multipurpose tool 30, so that the base 50 of the pliers jaw is pivoted with respect to the handle 32 about the pivot pin 56 away from the position shown in FIG. 6 and toward the position shown in FIG. 7, the cam surface 196 moves with respect to the tapered outer end 190. As the tapered end 190 follows the cam surface 196, the second prong 188 of the forked spring 184 carries the latch finger 182 laterally outward away from the interior of the central channel 44, so that it extends into the interior of the hole 180 in the blade of the knife 104 as soon as the base 50 of the pliers jaw has moved more than a very few degrees away from its folded position within the handle 32.

[Poncho65]

Great info DT I need to check but I don't know if my SS Wave has that safety feature I know the orange Wave does and I am not sure about the other Been meaning to check and see but I always forget to look at it

[Dutch_Tooler]

Here are some pics:

Left in the bottom of the handle: the two-prong spring, the right one of which carries a latch finger; right: the plier head base with cam surfaces that are designed to move the latch finger via the spring.




Pliers head partially inserted in the handle:




Pliers head entirely inserted in the handle, note the cam inserted between the two prongs of the spring:




Plier head retracted: latch finger retracted:




Plier head extended: latch finger extended:




On a partly reassembled Wave
Pliers folded: latch finger retracted and does not inhibit blade deployment




Pliers extended: latch finger extended and inhibits blade deployment




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[Mechanickal]

Are we allowed to reply again?

[Dutch_Tooler]

Yup. That request was a temporary measure whilst the captions were being added (goes much better on a full size keyboard ).

Thanks for your patience and feel free to fire away!

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[SteveC]

Great explanation and pictures DT !     

[Mechanickal]

Ok...
Just checking

[Mechanickal]

And great job

[Dutch_Tooler]

Thanks . Hope it helps to give an insight into a mostly hidden feature... and maybe give a pointer or two for addressing problems in that area.

By the way, the plier heads of the Rebar and ST300 also have the cam surfaces, but these don't serve any purpose on these tools - no corresponding latch mechanism, this is unnecessary as all the tools open the other way.

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[NKlamerus]

Better question is, how is everyone trimming them?

Every time I swap a rebar head into a wave or charge, it seems that the new head "activates" the lock enough when the handles are closed that I can't open the knife. 

I usually use a sandpaper wheel on a Dremel and barely knock the edge of the pin off.

[Dutch_Tooler]

Well, the cams are identical in size and position between Wave/Charge and Rebar heads, as far as I can judge. Maybe the springs get misaligned when you reassemble the tool?

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[gerleatherberman]

The best safety feature ever put into an MT. IMHO.
Only down side it when the tool gets some years on it, the two engagement tines on each handle stretch a bit and the blades develope drag on the mechanism lock pins.
A buddy of mine who has had the same wave for a decade was having that issue, but we filed the safety  lock pin down and it works flawlesspy now. The blade still locks as well. Only removed around 1/64" off the safety pin.

[Dutch_Tooler]

Yes, I can see where the tine might wear down with heavy use... just apply a corresponding amount of artificial wear on the latch finger

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[Poncho65]

Great pics DT Very detailed and helpful

[Dutch_Tooler]

Glad you like it . Found the locks on your silver Wave yet ?

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[surfdaworld]

Nice writeup!

I ran into an issue with a used Wave that I picked up on ebay where the blade interlock spring tines appeared to be bent/weakened, and would not retract the locking pin all the way resulting in a serrated blade that could not be opened with one hand.
I put a couple drops of penetrating oil on the tines and worked it in as well as I could---blade opens smoothly again with one hand!

[ThundahBeagle]

Thanks Dutch.

I had stumbled into learning this soon after receiving my old model surge, used this past summer. I was trying to replicate the advertising pics where everything is half open, and discovered I could not, unless starting the outside blades open first

[Syncop8r]

Great explanation and pics DT. 
I love threads like this.

[Dutch_Tooler]

I'll entertain proposals for other threads like this, as long as compatible with my tool collection*. I don't mind taking things apart for that if necessary, provided unscrewing is all I need to do (won't pop rivets for that).

*LM at present (all modded): Surge R, Wave R, ST 300 VX, Rebar VX 
LM unmodded: another Wave (NIB; planning to maybe give to oldest son depending where he ends up going for his doctorate. I may start a thread with some Qs on that), Squirt PS4
LM expected (no mods planned): ST 300 BO CC

I also have a few Swisstools and SAKs and a Böker Tech Tool, all of which I haven't considered modding (yet?).

[Syncop8r]

Anything with springs on them? I'm guessing the springs on a Skeletool work with a cam action as well (just in a different plane). 

[Dutch_Tooler]

Hmm yes, don't own any unfortunately...

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