Pfaff 145 safety clutch understanding

[Brtz]

Can anyone could help me to understand how the safety clutch in pfaff works?

I described an issue in the file below.

Regards, Bert

HOW THE SAFETY CLUTCH WORKS IN PFAFFS.pdf

[Uwe]

The safety clutch on my Pfaff 545 works like this:

 

[Uwe]

I realized after making the previous video that I had used potentially confusing terminology. I made a second  "proper" video that uses the correct terminology for the parts involved. The black part is the "latch". 

 

Edited April 10, 2018 by Uwe

[Brtz]

It was very helpful, thank you Uwe!

It appeared that the regulating spring in the safety clutch of my machine was set to maximum force, so I couldn't release fearing not to damage it.

It works now the same way as on your great videos.

Btw - in the manual of the 1245 they call the latch - a 'pawl with a hook'

And I apologise for improper naming of the parts in my introducing pdf.

Best regards, Bert

[Northmount]

4 hours ago, Uwe said:

I realized after making the previous video that I had used potentially confusing terminology. I made a second  "proper" video that uses the correct terminology for the parts involved. The black part is the "latch".

Hi Uwe

Is the pin supporting the latch (or pawl) an eccentric?  Where there happens to be 2 lock screws, there isn't likely a flat on the pin so 2 screws to make sure the pin stays in position.  Just a guess, but you are the fellow to investigate ... and can avoid having to grind the latch if such is the case.  (I used to work on a lot of mechanical accounting machines in the ancient past.  There were many eccentrics to adjust!)

Tom

[Gregg From Keystone Sewing]

All I know is that the Pfaff safety clutch can be frustrating when it's not set correctly, to the point that I've seen many come in welded into one piece to make it a straight hook driving shaft.  Here are some more opinions of mine, please feel free to add on or comment, please.

My favorite type is the Adler type, also common on Seiko STH-8BL and Consew 206RB series as well.  Juki DNU-241HS comes to mind as well.  This is my favorite spring and ball clutch.  Very reliable, and adjustable with the single adjusting screw.

The second image has the Singer 211 type clutch.  This was the least common, and least popular clutch I've seen, and for good reason.  On paper, it looks pretty good.  Until you have to go and use it.  This is also a spring and ball type clutch, but the good stops there.  We have three springs, balls, adjusting and check screws.  Difficult to adjust correctly.  I was taught to do one lose, one medium, and one tight.  I don't know if this was the best way, at all.  The other complete downside to this is that the stitch length was incorporated into the safety clutch.  This eliminated the need for two confusing silver shinny buttons on the bed of the machine.  But now, worst of all, the clutch is incorporated into the stitch length.  It is not uncommon for an operator to disengage the clutch if you simply went too far either way adjusting the stitch length.  And imagine if the stitch length regulator is messed up and loose?  

Singer 111W155 type appears on many, many makes and models, so I don't even want to start.  This one works well, is reliable, and is nice in that the cog can spin free when the clutch is released and not engaged.  The only downside is that the counter hook spring (index #48) that is about the thickness of a paper clip, likes to fly off and disappear.  We then have to push, or hold the counter hook in place to rest the clutch. 

Again, these are just some opinions of mine, and I'm interested in what other may have to say.  

 

Edited April 13, 2018 by Gregg From Keystone Sewing

[wabbit]

Uwe - I saw your "Safety Clutch" video on U-Tube and besides being - as usually - awed  at the quality production and clarity, I immediately played with the one on my 545.  It was a little stiff and possibly set too firm, so I eased the spring tension.  I presume that if it disengages too easily I need to tighten it?

Erik

[Scoutmom103]

I'm using the numbers and names from Brtz's pdf 

 

Has anyone replaced the springs in the  hook/Pawl  #3 and or the button that the hook/pawl catches on when the hook jams and engages the safety clutch?    I have a 145 H3 and when I look at pin under the pawl that depress for the pawl to catch on the button, I don't see any portion of the spring like I do in Uwe's great video's above.

 

Also was wondering if the hook/pawl #3  when it is riding on the button (that engages when the hook trips the safety ) is supposed to still touch part of the small barrel #4  at times since it is an eccentric?   Mine does when the pawl is riding on the button, but if I hold the left axil #5 the entire safety clutch (parts 3, 3a, 2 & 1) spins separately.

[Scoutmom103]

8 hours ago, Scoutmom103 said:

I'm using the numbers and names from Brtz's pdf 

 

Has anyone replaced the springs in the  hook/Pawl  #3 and or the button that the hook/pawl catches on when the hook jams and engages the safety clutch?    I have a 145 H3 and when I look at pin under the pawl that depress for the pawl to catch on the button, I don't see any portion of the spring like I do in Uwe's great video's above.

 

Also was wondering if the hook/pawl #3  when it is riding on the button (that engages when the hook trips the safety ) is supposed to still touch part of the small barrel #4  at times since it is an eccentric?   Mine does when the pawl is riding on the button, but if I hold the left axil #5 the entire safety clutch (parts 3, 3a, 2 & 1) spins separately.

I forgot to ask, if you did replace the spring or springs did you have to take the clutch off the axil's or were you able to change out the springs with the clutch while it was still attached to the machine.   

[shoepatcher]

Do NOT have to take the safety clutch off the axils to change them. There are 2 springs.  Change one of them at a time and adjust the depth of the set screw that goes on top of the spring to set the spring tension.  They are sealed with a plastic material  on top of the Allen set when they are set at the factory.  If both springs have been adjusted, start with one.  back out old spring, insert new spring and screw Allen screw down about one third of  the threads in the hole.  Try it.  It may have to go in more or out more.  I had to trial and error it on the 1295 I was working on to get it about where it should be.  Turn Allen screw in to increase tension, out to decrease tension.

glenn

[Scoutmom103]

Thank you shoepatcher.  I'm heading Uwe's advice in one of his answer's to not take apart things if you don't have to, and to not turn screws if you don't know what they do.   I find the pfaff 145\545 parts manual hard to trace what goes where at times.   These beauties have a lot of parts and screw.