Knife locks part 3

In the third part of this series, we look at three very different knife locking mechanisms: Opinel's Virobloc, the Klecker Lock and the WE Slide Lock.

Since the 1950s, the larger Opinel knives have had a Virobloc lock. It is used on all models from No. 6
upwards. So the No. 8 (above) has a Virobloc, the No. 4 (below) does not.
Opinel's Virobloc seems like a simple lock: a handy ring at the front of the handle that can be turned to lock the blade. In reality there is a lot more to it than that. Moreover, the history of the Virobloc is not as simple as it seems.
According to the Opinel website, it is very clear. In 1955 Marcel Opinel invented the Virobloc: a rotating ring around a fixed bushing on the front of the handle. The bushing and the ring each have a narrow slot. If these are flush, the blade can be opened. If the ring is turned slightly, it blocks the movement of the unfolded blade and locks it in place. For decades, the Virobloc has been of Opinel's main features. It is used on all larger models (from No. 6 upwards).
However, it is a bit more complicated than that. The patent application for the original version of the Virobloc was filed on February 27, 1953 by Joseph Opinel's two sons, Marc and Léon. The patent was granted in France on March 3, 1954, under number 1.071.530.
Well, a year earlier, what does that matter? Well, it matters inasmuch as the patent is not about the way the blade is locked. It only describes an easier way to mass-produce this lock. The operation of the lock itself is assumed to be common knowledge.
Left: The drawings accompanying patent 1.071.530 from Marcel and LéonOpinel, granted on 3 March 1954. This patent is not
about the principleof the Virobloc, but only about the method of producing it.
Right: One of the heads of the blade axis can be seen here in the groove of the Virobloc ring.

According to the description of Marc and Léon Opinel, the locking mechanism until then consisted of three main parts: the ferrule, which was fixed to the handle with the axis of the blade, a fixed bushing on the ferrule and the rotating ring. In the Virobloc, there are only two parts: the ferrule and the ring, both of which are also easier to produce.
The ring has a pressed-in groove exactly where the heads of the blade axis protrude from the ferrule. These heads therefore act as guides and hold the ring in place. The advantages for production are obvious: the axis heads do not need to be ground off and the ring is simply pressed around the ferrule. The patent also shows a variant of this construction, in which the ring has no groove, but an elongated slot on either side for the axis heads.
In October 1969, the Établissements Joseph Opinel & Cie applied for a new patent. In the meantime it had apparently realised that the original patent from 1953 offered only limited protection. After all, it was not the construction of the lock that was at issue, but the method of production.
French patent 2.063.532, granted on 14 June 1971, describes no less than fifteen different ways in which the ferrule and the ring can be joined together, the rotating ring acting as a locking device. In the drawings, figures 2A to 2O each represent the ring, and figures 3A to 3O represent the ferrule.  
In almost all of these constructions, the heads of the blade axis are ground smooth. A cam on the fixed ferrule is used as a locking and guiding device for the ring. The heads of the axis are only used in Figures 5 and 6. It almost seems as if Opinel included this method of locking as an afterthought.

In 1969 Opinel applied for a patent on a large number of variations on the Virobloc. These are the drawings of the different versions.

Another patent is about the exterior of the Virobloc. In all previous constructions the ring is provided with some kind of bulge or opening. In patent 2,102,698, granted on 13 March 1972, the ring is completely smooth on the outside. It is guided by a ridge on the inside, directly opposite the opening for the blade. This cam falls into a horizontal slot in the ferrule. The ring can therefore still turn, and is also held in place by the cam.
Despite all these variations, the rotating ring has always been produced by Opinel in its original form. As far as is known, no more than a few prototypes have been made of any of the alternative constructions.

Different positions of the Virobloc.
Top left: The ring is positioned so that the blade may be opened.
Top right: The ring is turned and now blocks the blade so that it cannot be opened.
Bottom left: The ring is opened.
Bottom right: The ring is turned and now blocks the blade so that it cannot be closed.

Another modification, however, did go into production. In June 1971 Opinel applied for a patent on an improved locking ring. That patent was granted on January 2, 1973, under number 2.142.258. The invention consists of two small recesses in the underside of the ring, on either side of the slot for the blade. Thanks to these recesses, the locking ring can also be turned when the blade is closed. Thus, the knife can be locked both open and closed. By the way: although the patent drawings show two notches at the bottom of the ring, left and right, the actual knives have just one.

The drawings for patent 2,102,698 from 1972. Thanks to
a slight modification, the ring now locks both the opened
and closed blade.

With this last change, the Viroblock seemed to have found its final shape form. Since the early 1970s, the lock has been made unchanged. But in 2016 Opinel made another modification. The locking ring got a little cam on the inside, which falls into a horizontal slot in the ferrule, near the handle. This has two functions: the cam acts as an extra guide, and also limits the rotating movement of the locking ring.

In Denis Opinel's patent application, from March 2015, the ferrule has an additional cam (18) that falls
into a slot (17) in the ring. This construction is used on several Opinel models.
Denis Opinel, from 1998 onward the successor of his father Maurice, submitted a European patent application in March 2015 for this 'Virole de blocage améliorée', or improved locking ring. Whether the patent has now been granted is not clear. Why this modified construction? Perhaps it is simply a question of competition. Of all the connections between ferrule and locking ring that Opinel had already thought up, at least one is not in the 1971 patent: a double guide. In 2005 Bruno Sauzedde of the company Facosa S.A. from Thiers received patent 2.859.658, for a lock that is very similar to the Virobloc. Sauzedde's locking ring, however, has a double groove. The upper one rotates around the heads of the blade axis, the lower one around an extra notch on the ferrule.
Although Sauzedde's construction has never been made on a large scale, Opinel seems to want to take the sting out of it. Whether that is useful is another matter.
The 2005 patent from Bruno Sauzedde of Facosa S.A. This lock is very
similar to the Virobloc, but has a double groove on the inside.
Italian version
In 1985, Todesco Arduino & Ottorino S.n.C. got Italian patent 1187282 for an interesting variant of the Virobloc. In their version, the outer ring is firmly connected to the handle. It has a narrow sliding plate on the inside, with a notch protruding through an elongated slot in the ring. With this notch, the plate can be turned clockwise and counter clockwise, so it may or may not block the movement of the blade. This mechanism is currently used on the Old Bear series of knives made by the Italian manufacturer Antonini. The locking mechanism can be used both with the blade open and closed.
A close-up from the lock on Antonini’s Old Bear knives.
The Klecker Lock

And now for something completely different: the Klecker Lock. This was invented by Glenn Klecker, an American, former marine, engineer, knife maker and industrial designer. In November 2010 he applied for a patent in the United States, which was granted under number 8.443.521 on 21 May 2013.

One of the drawings accompanying Klecker's US Patent 8,443,521, issued on 21 May 2013.
The two arrows (52 and 53) show the essence of the mechanism.
Already in the year of the patent application, CRKT came up with the first knife of Klecker's design, the NIRK. With some refinements, that design evolved into the CRKT Graphite. Klecker uses his locking mechanism on a number of models from his own company, Klecker Knives, such as the Slice, Cordovan and Cordovan Lite. The lock has also been adopted by other knife makers, such as Brian Tighe's NIRK Tighe, also from CRKT. But what is it all about?

Two different versions of the Klecker Lock, on the original CRKT Klecker NIRK from 2010 (above), and
the NIRK Tighe 2.
According to the explanation in Klecker's patent, the initial idea was threefold. Firstly, he wanted to make a knife in which the handle and lock were made of just one component, a simple piece of sheet metal. The additional advantages of this construction were a much easier production and a greater strength.
CRKT's Klecker NIRK shows the basis design. The knife is almost identical to the patent drawings. The handle consists of a single piece of pressed and folded sheet metal. This fulfils the functions of the frame, the spring and the lock. Carefully thought-out recesses and slots in the handle ensure that the various parts of the handle can move slightly in relation to each other, just enough to lock the blade, or release it when the back is pressed down.

The essence of the NIRK not only lies in the method of locking, but also in the fact that the handle consists
of only one piece of sheet metal.

The NIRK Tighe 2 has a handle made of  two separate halves.

The back of the handle is U-shaped and open along almost its entire length. At the front there is a bridge. This falls over a ridge on the blade when the knife is open, thus blocking its movement. When the back of the handle is pressed down, the bridge slightly moves upward and releases the blade. When the blade is closed, the same bridge falls over a ridge on the underside of the blade. As this is rounded, it only serves as a friction hinge. With a little pressure, the bridge slides over the ridge. With the help of the oval opening in the blade, the knife can be opened with one hand.
Three positions of the locking mechanism. From left to right:
- Top view of the opened blade. A ridge on the blade lies behind the handle's bridge and the blade is locked in place.
- Th knife partly closed. A second cam on the blade with a rounded front pushes the bridge upwards.
- The blade closed. The second cam now lies between the bridge and the front of the handle and acts as a friction hinge.

As a technical tour de force, the Klecker NIRK was very impressive, but as a knife it was perhaps a little too minimalist. Both Klecker himself and CRKT have dressed up the design a little more. Klecker has shortened the spring back of his own knives to about half the length of the handle. The metal of the handle on the Cordovan is still in one piece, but with inserts. In the CRKT NIRK Tighe 2, they have gone a little further. The essence of the lock has been retained, but the grip consists of two separate side plates, which are connected to each other by means of shafts and bolts. The simplicity of the original design is thus partly lost.
The WE Slide Lock
In 2018, the Chinese WE Knife Co. introduced the Double Helix. This is a knife with a new locking system. The Double Helix has layered handles, with a recess on both sides. In that recess runs a pin with end in a round eye. That eye is fixed to the handle with two torx screws. It is a piece of sculpture in titanium (except for the blade of S35VN, all parts are of 6AL4V titanium). But it is not just decoration. The pin and eye serve as the spring for the blade's locking mechanism, the Slide Lock.
The WE Knife Double Helix with Slide Lock. The thin pin with the eye on the back is one of the springs of the Slide Lock.
One of the handle springs removed. It is a piece of titanium art.

The Slide Lock ensures that the blade is locked both when opened and closed. This is achieved by means of a transverse axis with a screw head protruding from the handles on both sides. Internally, the shaft falls into opposing notches in the blade, so that it is locked both when open and when closed.
Yes, that looks suspiciously much like the lock designed by William H. McHenry and Jason L. Williams, better known as the Benchmade Axis Lock. Just like the SOG Arc Lock and Spyderco's Ball Bearing Lock, for that matter. But just like SOG and Spyderco, WE Knife has also managed to give it an original twist.
When the axis of the slide lock is pushed back, the curl of the spring is slightly compressed.

First, the fact that the blade is locked in both positions; in most cases, only the opened blade is locked. But much nicer, of course, is the construction of the springs, which push the axis of the lock forward. The eye at the back looks a bit like a watch spring, in this case with only one winding. That back end is what gave the knife its name: Double Helix. The word is usually used in the sense of screw or spiral, but in this case it stands more for a curl. The end of that curl is screwed to the handle. When the Slide Lock is pulled back, it also pushes the pin and the curl back a few millimetres, thereby compressing the curl a little and putting extra tension on it.
The Slide Lock is a daring construction. Not because of the transversely positioned axis – no problem with that. It is mainly the two springs that keep surprising you. They are each made from a single piece of titanium, most of it only 1 mm thick. Spectacular, but it looks fragile, and somewhere in the back of your mind is the thought: when will they break? But according to WE Knife, they won’t. And in the unlikely event that something does happen, the spring is easy to replace.

The knife from the right, folded.