How to Move It?

Somebody from the Bulgarian Women's Weightlifting Team can do this pretty easily. Some other choices might include a ball-screw mechanism, a chain drive around a pair of sprockets, or a water-based hydraulic system.

In food processing there's always the possibility of contamination from lubrication or hydraulics. Good design and maintenance minimises this. All food plants I've worked in any hydraulics would be below the product flow. All chains would be contained within splash proof guards. The list is endless, but it all comes down to understanding the circumstances.

The polite way to explain is; the forum rules CR4 FAQ prohibit the posting of links to our businesses, or posting personal email addresses. There is a 'private mail' (PM) system available via clicking on the ID of any member. It is not for spam, it's for private dialogue.

From me; Welcome and I hope you enjoy the experience

Thanks for the feed back.

I'll look into the sprocket chain and water based hydraulics.

G. Albert

I would favour a hydraulic lift for your application. Certainly you would place it so that the "oil end" is below the food products you are handling - but I would also use one of the totally inert food grade oils that are available for use in the system, so that any inadvertent leaks would have minimal impact on your process.

pour hot coffee on your lap, and you will be up in that weight up in 0.4 seconds!

Does it have to be powered...I mean, like a conveyor belt, and running eight hours a day, or can you have a person heave on a lever to lift the five gallon pail up to the shelf? If you are just doing one lift an hour, then a simple buggy jack would work fine.

I envision a tool which scoops up a wine carboy and lifts it up to the racking station. It would look much like a large bell crank.

There are a number of linkages which will provide an almost straight line movement or maybe you could get away with a curved path. These could be made of stainless steel including the pivots (easily cleaned).

The driver of this mechanism be it a LA or motor gearbox and could be attached to a shaft and thus sealed of from the food area.

LA's either electric, pneumatic or hydraulic are fine for lifting and could also be shielded with a stainless linear shaft sealed in nylon slides which could protrude into the food area.

Tony

How about a wheel with a pin & crank (see diagram).

You can adjust lever length and/or pin position to get required lift of 700mm. Adjust rotation speed with motor speed and or gearing to achieve 1 revolution of main wheel in 5.6 secs (i.e. down to up is half a revolution of 2.8 secs).

You could Start/Stop the lift manually, with limit switches on the wheel/lever arm, or by using some sort of synchronous motor to drive it. Possibilities are endless.

One BIG advantage is thas the start & stop velocities are slowed by the rotational axis of the wheel. This means your load will not jump up off the platform as it stops at its upper limit, as the vertical velocity approaches zero as the wheel pin comes to the top of the rotation.

Cheers

Tony

0.7 M in 2.8 sec.= 0.25 M/sec.;

for a ball lead screw of 1 mm pitch, it means a revolution of 250 x 60 = 15000 RPM, driven by a servomotor of 0.5 kw capacity,(using 2x∏xNxT/60).

May I, therefore, suggest your using a bellows covered ball lead screw and linear slide assembly to move (lift) your load of 20 Kg.f in 2.8 seconds. Please apply P.I.D. control in the servo motor amplifier circuit along with a parking brake in Normally "on" mode, to prevent back-slide and also for holding the precise position.

Please feel free to correct me and/or seek clarifications. Please do not employ water hydraulics!!

Where can you find a ball screw of 1mm pitch?

What is wrong with water hydraulics?

Try THK or Misumi (Japan/Korea). The suggestion for 1mm pitch was as a "worst case" example. If we opt for higher pitch values, RPM will come down favorably.

Hydraulics is "Messy" with even unacceptably wet floors. Jets of high pressure water from even less than pin hole leaks can harm or even kill people!!

Can anything beat the elegance of electric/electronics/mechatronics systems??

In the mechatronic system suggested, there is zero potential for contamination and has extreme MTBF enhancing reliability.

For 40 lb, a 1-inch diameter cylinder at 60 psi (a fairly typical water supply pressure) would give 47 lb of lift. The cylinder and a 3-way valve (or two simple valves) would be all that is needed, with no danger of high-pressure leaks.

We should not forget the power required to generate the "Pressure",isn't it??

We can make the mechatronic system even simpler by using a set of one timing belt and two pulleys (one at either end), substituting lead screw.A multicore cable lead is all that is required to power the stepper or servo motor.

I think the device you are looking for is called a crane. The load sits on a tray, to the four corners of which are attached cords. These cords are linked to a single cord, which may be wound onto a motorised drum. The upward and downward movement of the tray may be constrained by guide tracks, on which switches which limit the extent of the movement may be mounted.

A comparable device, using an enclosed cage to transport people as well as goods, is known as a lift or elevator.

You need simple 50 kg Chain Electric Hoist with hoisting speed of 15 m/min. You can get such hoist or may be near to your specs.

Normally my EE experience would call for a purely electronic (motor) solution. However, I've recently spent many months working in the beverage packaging industry and have learned that there are better solutions. I would agree that the pneumatic approach is best for cost, simplicity, maintenance, and sanitary reasons.

There have been a number mistakes I have seen engineers do is,

1.) Remember to take into account not only the mass of the product, but the machine also.

2.) ensure that the machine base/frame is stout enough to move this mass as well as stop without flexing.

Now, how.

without know the particulars, such as cycle times so I'm just throwing stuff out there.

a) Hydraulic or pneumatic ^{(more info needed)} cylinders should be able to do it, as well. http://www.smcusa.com/smc.aspx

b) rack and pinion attention to safe guarding is required. as well as other processes

c) Ball screws I would also favor http://www.nookindustries.com/

d) cabling and/or chain,

don't forget the completely unique amacoil thingy.

so I'm just throwing stuff out there. me too!

How could I have forgotten, We just installed a linmot on a packaging machine. it is cool.

Interesting--it looks as though linear motor tech is progressing to substantial forces/speeds. This makes me think of door actuators, for instance, to replace some of the clunky ones we now have on our freezer rooms.

I would use a system similar to that used with windscreen wiper motors, in fact you could adapt a truck unit. For most of the stroke, power is supplied by a wiper on a circular track with a break in it (the park postion). When you supply power momontarily, the wiper moves onto the track and the motion continues until the break in the track (you can have two, top and bottom of stroke). As I suggested previously this can be contained in a sealed box and drive a mechanism similar to 12.

If you put a counterbalance to offset the weight, you can use any of the systems mentioned. Sadly you never mentioned if the weight is removed for the downward stroke or not.....which would imply a 40 lb. downward thrust....still easily achieved.

I personally would use 2 lead-screws, each with at least two "starts" and some 3 amp stepper motors, linked by a chain to keep them sychronised....A PIC as a controller with a relatively simple program and a couple of Allegro chips to drive the motors.....highly accurate for both the top and the bottom.....as well as fast.

This has become more of a discussion than a serious attempt to answer, what is a very open question.

One thing that must be pointed out with pneumatics, is that even with pressure locked either side of the piston or it pushed against a solid stop, the positioning is only as accurate as the compressing of the air. It does have the advantage of a great speed differential.

Whilst a hydraulic system contains a virtually incompressible oil and the linear motor is self locking even with no power.

Tony

"This has become more of a discussion than a serious attempt to answer,"

that is because the OP has never been back... in which case, the cr4 crowd has shown more interested in the subject than the OP... We don't have further guidance from the OP, so who knows what might happen... I know I tend to be flippant when it does..

chris

First off, I'd like to thank EVERYONE who responded.

Secondly, there is a significant time difference between the majority of you and myself. Add to this that this is not for my primary job, which comes first. I have checked the thread and read the comments when time permitted.

I learned more about what to consider for each method mentioned in the original post and then some.

It is precisely this kind of information that is generated by so called open ended questions. These start discussions where the pros and cons are hashed out by the veterans who've used them. You obviously don't mind sharing that information, and now this dialogue is a matter of open record for anyone in the future to read and learn. This kind of information cannot be found in textbooks. For this, I am truly grateful to all of you.

As far as this thread turning into a discussion, oftentimes open ended questions spark discussions, more so in open societies where people are willing to share their opinion. This is quite unlike Asian societies, specifically a particular island nation which first sees the light of day (personal experience).

I mentioned pneumatics in the OP, but knew that that depended greatly on the air supply and unless a hard stop is employed at the top, the upper stop position could vary, which is undesirable.

For those who insist on more details, the mechanism lifts a motor/reducer which has a bank of vacuum suction cups attached to a bar. This picks a flattened cardboard box from a stack and moves it upwards so that it opens (with the aid of air jets) and into position for the bottom to be taped.

The servo/reducer is there in case the box needs to be rotated 180deg (I know, I know, train a monkey, it's easier in the long run, they work for peanuts and bananas) so that the correct side is taped.

The method chosen will be a servo/reducer combination driving a chain with a counterweight attached to the other end. Piecing several replies together generated this method. As mentioned in one reply, I do need to consider the frame further. The cycle time is 2.8sec.

As the stack decreases in height, the distance traveled will increase, unless the platform is spring loaded (like the plate stacks in a buffet line, if you ever saw them). Since there are three different carton sizes, and weights, I'm still debating that issue.

Again, thank you all for you assistance.

G. Albert

I guess this is what it's all about, isn't it? Problem Solving at it 's best" DJ