About Freebear

what is freebear ?

① Conveying by means of balls

Roller conveyors can only move workpieces linearly, while freebears that use balls can move 360°.

Conveying by means of balls

② Low starting frictional resistance

By using freebears, the friction on the load changes from “sliding friction” to “rolling friction”, which can easily move the load. (Starting frictional resistance refers to the initial resistance when moving a heavy object from rest.)

Low starting frictional resistance

Freebear structure

① Upward and downward freebears

*Please consult us for your use in the oblique and horizontal directions.

Upward type

Upward type

Put the small balls in the ball seat,and then put a main ball on them to rotate.

Downward type

Downward typ

The downward ball seat is mounted inside, in which the small balls circulate.

[Press-molded products]

Press-molded products

The ball seat is press-molded.
⇒ made from sheet metals.

[Cutting-machined products]

Cutting-machined products

The ball seat is cutting-machined.
⇒ made by cutting round bars.

② Press-molded products, cutting-machined products

From the above, the wall thickness of R face of press-molded product is relatively thin, while that of cutting-machined product is relatively thick.
*The weight of a single load for press-molded products shall not exceed 500 kg.

What is the allowable load of freebear ?

What is the allowable load of freebear

It refers to the maximum load which can be applied to a freebear with the starting frictional resistance(μ) keeping 3/100 or less when using a SS400-equivalent rigid body (the surface in contact with the freebear is made of polished soft material) as the load.

*As shown in the figure on the right, uneven load may result from the shape of the load and other reasons. In this case,the load to be applied to each freebear must be less than the allowable load.

Please set the mounting pitch according to the weight and size of the load.

The height of the freebear has a tolerance, and the bolster where the freebear is mounted and the conveying surface are not completely flat. Therefore, the load cannot be uniformly applied to all freebears mounted, and there may be uneven load on certain part.In such case, if the load on the freebear exceeds the allowable load, it may have a adverse effect on the starting frictional resistance and the service life.
For this reason,
●Cutting-machined products = Allowable load × 2/3
●Press-molded products = Allowable load × 1/2

Please determine the mounting pitch based on the load above.However, for freebears with spring, the restriction above is void since the freebear with uneven load is pressed down, which making more freebears enter the contact state.

The material of the load shall also be considered.

Table I is the measured results of the “starting frictional resistance μ” to the allowable load of each freebear on our test machine. On the test machine, the surface in contact with the ball is made of polished quenched steel (SK3, HRc60 or above).

Table I

C-6H C-8H C-12H C-8Y C-12K
Test load
(allowable load)
50kg 80kg 200kg 30kg 60kg
Starting frictional
resistance(μ)
0.013 0.011 0.012 0.015 0.013

Besides, if the surface in contact with the balls is made of a different material, the starting frictional resistance measured may vary. From Table II, the starting frictional resistance (μ) of SS400 is more than twice of that of SK3; for the same SS material, the starting frictional resistance of mill scale material is more than that of polished one. Therefore, to reduce the force moving a heavy object, the bottom of the load shall be made of a hard, smooth material.

Table II

C-8H (Allowable load 80kg)

Material
SK3HRc60 or above Polished contact surface SS400 Polished contact surface SS400 Mill scale
80kg 0.92kg(μ=0.011) 2.02kg(μ=0.025) 2.22kg(μ=0.028)

As shown in Table III, when the surface in contact with the ball is made of wood, generally μ=0.09~0.1, which is about more than 3 times of that of SS400 mill scale material.Therefore, when conveying wood, the number of contacts shall be maximized to disperse the load. In addition, for easier conveying, please mount a steel plate onto the bottom of the load.

Table III

C-8Y (Allowable load 30kg)

Material Wood (pine)
30kg 2.7kg (μ=0.09)

C-12K (Allowable load 60kg)

Material Wood (pine)
60kg 5.4kg (μ=0.09)