FR2609457A1 - METHOD AND DEVICE FOR CONSTANTLY MAINTAINING THE VALUE OF THE FRICTION COEFFICIENT ON THE SURFACE OF REACH OF A ROLLER - Google Patents

Abstract

THIS ROLLER INTENDED FOR A MOTORIZED ROLLER TRANSFER CONVEYOR SHOWS A PLURALITY OF LUBRICANT PRESSURE REDUCTION ZONES DISTRIBUTED ON OR IN THE WORKING SURFACE AND WHICH HAVE THE EFFECT OF INCREASING AND MAKING CONSTANT DRIVE POWER IN ROTATION WHICH IS TRANSMITTED FROM A MOTORIZED AXIS 12 TO ROLLER 30.

Description

The present invention relates to a roller

  belonging to a modern roller conveyor

  torized5 and it relates more particularly to the apparatus

  reil and the process implemented by a roller which pre-

  Feels a plurality of regions for reducing the pressure of the lubricant in or on the bearing surface,

  so as to obtain a constant transmission and reinforce

  creation of the rotary power of the motorized axis on the road

  the water. For certain automotive components, such as

  engine- gearboxes, we use transDor-

  tears d- ansfert motorized rollers to circulate

  ler i = Fa ces in manufacturing and assó-

  blace. The parts are mounted on pallets which are

  driven on the conveyor by driven rollers

  born by axes that rotate slowly but continuously-

  is lying. Rollers have an inner bearing surface

  lubricated, of the socket type, which is suitable for mounting

  ter on the axes. To propel the pallets, the motorized axes rotate the rollers by taking advantage of

  the friction between the axle and the bearing surface of the wheel

  the water. In certain positions of the transfer line, it is desirable to stop the pallets. At these points

  stop device, a stop mechanism retains physical-

  the pallet. The rollers located under the rear pallet

  also stop turning and slide on

  axes tournanps. This sliding is facilitated by the lubrication

  fiant inte; placed between the axis and the bearing surface of the roller.

  The driving force necessary to accelerate

  rer the pallets from the stop or to propel

  a palette by making him cross a small resistance

  this, such as a small drop, is determined by the coefficient of friction between the motorized axis and the interior bearing surface of the roller. In turn,

  the coefficient of friction is affected by the conditions

2,2609,457

  lubrication between the axis and the bearing surface of the roller. Lubrication mode

  desired for the motorized roller of the conveyor

  fert described above is thin-layer lubrication

you.

  However, under certain working conditions

  vail, an additional amount of lubricant from

  of the machining operation or the environment may pro-

  gressively enter the range slot. The lubricant

  additional fiant switches the lubrication mode

  from boundary layer mode to hydrodynamic mode. The lubrication

  hydrodynamic cation significantly reduces friction

  between the roller and the motorized axis. The strength of

  drag transmitted by the axes to the rollers is thus

  considerably reduced. The reduced driving force

  te which is transmitted by the rollers to the pallets causes the pallets to accelerate incorrectly and move irregularly. This is undesirable

  in automated manufacturing and assembly lines

sées.

  An object of the invention is to maintain at a ni-

  constant and acceptable calf the driving force which

  is transmitted from a motorized axis to a roller.

  Another goal is to maintain a coeffi-

  sufficiently high friction value

be the motorized axis and the roller.

  Another aim is to avoid an addi-

  tional lubricant contained in the reach slot

  of a roller does not cause an unwanted passage of the

  boundary layer lubrication to hydrodynamic lubrication

  mique. Another goal is to locally reduce the

  lubricant pressure on the bearing surface in pre-

  indicator of areas of decrease in lubricant pressure

  reliable, so as to maintain boundary layer lubrication on the bearing surface and to maintain this

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  way a high coefficient of friction between the motor axis

  laughed and rolled, which results in a transmission-

  constant rotary power of the motorized axis

  with the roller which turns in intermittent rotation.

  The aims and advantages of the present invention

  are achieved by providing a plurality of zones of re-

  decrease in lubrication pressure on the surface

range of an annular roller.

  An unexpected advantage of the present invention is the increase in the driving force.

  transmitted from the motorized axis to the roller under conditions

  operating comoort with the presence of an ex-

this lubrication.

  Other features and advantages of the

  vention will be better understood on reading the description

  tion which follows, from an exemplary embodiment and with reference to the accompanying drawings in which, Figure 1 is a view partly in section and in elevation of part of a transfer conveyor; Figure 2 is a front view of the roller;

  FIG. 3 is a side view in section of the wheel

  water according to the invention; Figure 4 is an enlargement of the encircled portion of the roller of Figure 3;

  FIG. 5 represents another form of embodiment.

sation of the invention.

  A typical motorized axle-roller sub-assembly

  a transfer conveyor is shown in the figure

  gure 1. The axis 12 revolves in a frame element 16 by means of the bearings 14. A bevel torque 18 and 20 transmits a constant rotary power to the axis, taking its movement on a power source, such as a motor, which is connected to a drive shaft

22.

  In the transfer transporter shown

  in Figure 1, two rollers 30 are mounted on the axis.

  A spacer 24 and two rings 26 position the wheels

  leaux on the axis. Other configurations are also

  possible. FIG. 2 shows a front view

  this from a roll. The roller is usually a cylin-

  are solid metal ring with a surface ex-

  and an interior surface. The exterior surface

  re 32 constitutes the contact surface of the roller, which

  is intended to carry a pallet such as that shown

  felt at 28 in FIG. 1. The interior surface 34

  forms a bearing surface to rest on axis 12.

  The bearing surface 34 is formed by a central bore

  roll tral and is usually concentric

  on the outer surface of the roller.

  The inner bearing surface 34 is dimen-

  such that there is a small slit

  of range between the motorized axis 12 and the bearing surface

  tee. A lubricant is provided in the bearing slot.

  In a preferred embodiment, the roller is made of a sintered material impregnated with lubricant. In

  alternatively, a lubricant can be introduced into the window.

  te of reach by other conventional means, for example by a wick or by a lubricant pump. Another known suitable means for introducing a lubricant into

  the opening slit consists in using a passage of ali-

  ment, such as a feed groove provided on the axis or on the bearing surface of the roller. A throat

  lubricant supply has large dimensions

  sions and is widely spaced on the surfaces of the axle or roller so as to ensure the best possible

power function.

  In normal operation, a roller has

  on a smooth bearing surface works as follows.

  The motorized axis 12 rotates continuously. A thin film of lubricant occupies the bearing gap between the axis and the bearing surface of the roller. The speed of

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  axis rotation, and other factors are

  that the effect of the lubricant occurs in the moCe

  boundary layer lubrication. The coefficient of friction

  between the axis and the bearing surface of the roller is high. This is well known from the Stribeck diagram which links the lubrication mode to the coefficient of friction for plain bearings. In this way,

  the axis forces the roller to rotate and propel tangent

  the pallet forward. The coefficient of friction in the boundary layer lubrication mode is high enough for the driving force

  transmitted by the axis to the roller can overcome the small

  resistance that a pallet may encounter on the transporter.

  In addition, in normal operation, the

  The lubrication in the roller bearing surface allows the roller to slide on the axis if the pallet encounters strong resistance, such as that of a stop mechanism. The lubrication that exists in the slot what

  range facilitates continued rotation of the axis

  torized with respect to the stopped roller.

  During the operation of the cat, an excess of lubricant can gradually penetrate into

  the range slot. This increased lubricity

  tion switches the lubrication effect from layer mode

  limit to hydrodynamic mode. The coefficient of friction

  between the axis and the roller decreases when the mode

  lubrication changes from thin-layer lubrication

  hydrodynamic lubrication. This is also

  indicated by the Stribeck diagram.

  In a hydrodynamic lubrication mode, the driving force transmitted by the axis to the roller is not large enough to overcome a small resistance. The rollers therefore begin to slide on the axes and the pallets contained in the conveyor are subject to describe erratic movements. In

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  in other words, when an excess of lubricant enters the bearing slot, the rollers tend to slide

  on the motorized axis instead of driving the pallets.

  The invention solves the problem cited above.

  Even in the presence of excess lubrication, the lubricant can be kept in the lubrication mode at

  boundary layer by dividing the bearing surface into cor-

  narrow gifts separated by narrow areas of reduced lubrication pressure. The hollowed out areas of

  pressure reduction let the lubricant pressure

  relying on excess escape and prevent the passage to hydrodynamic lubrication. In the preferred form of

  production of the roller 30A which is shown in the figure

  gure 3 and by an enlarged view on figure 4, gor-

  narrow or thin ages 36 with a sensitive orientation-

  circumferential provide local exhaust

  lubricant pressure. The gorges are preferably

  sufficiently narrow not to reduce noticeable-

  ment the range. The range cords included in-

  the gorges are also relatively narrow but they are preferably of a width equal to three to ten

  times the width of the grooves. This relationship seems important to

  aunt to provide an adequate reach area and a sufficient pressure reduction area to release the lubricant pressure. It is visible that

  these narrow grooves for reducing the lubricant pressure

  closely related, differ notably

  by their construction, their function and their effect, large grooves supplying lubricant

  widely spaced which have been described above.

  A helical groove similar to a screw thread and formed in the interior bearing surface of the roller, as shown in FIGS. 3 and

  4, represents the preferred embodiment for training

  Sea areas of reduction of lubricant pressure for the bearing surface of the roller. The groove has a bottom groove width of approximately 0.127 mm, a pitch

  of thread between 0.381 min and 1.27 mm, and a pro-

  net founder between 0.076 mm and 0.152 mm.

  The sides of the throat have an included angle of 60. A helical thread configuration is preferable because

its ease of machining.

  It was surprisingly found that by dividing the

  bearing surface in narrow cords framed by zo-

  lubricant pressure reduction, such as

  than circumferential grooves machined in the surface

  this range, we increased the driving force

  transmitted to the roller when an ex-

  this lubricant. For example, a roller 9 which has a smooth bearing surface, free from grooves, has been found to initially transmit a force of about

  11.34 kg to a pallet with a weight of 204.12 kg. When-

  an excess of lubricant was introduced into the slot

  range, the driving force fell to a value

their from 1.81 to 3.18 kg.

  In the above situation, when riding

  leaux having circumferential grooves machined in the bearing surface, as what is achieved by

  the present invention, a driving force was obtained

  from 12.70 to 13.61 kg. When an excess of lubricant

  was inserted into the seat slot, the roller ra-

  nuré provided a force of 11.34 to 13.61 kg, or

  roughly four times the driving force as the over-

  smooth bearing surface, not grooved, transmits in the presence

excess lubricant.

  Other configurations can be adopted for the lubricant pressure reduction areas and

  these configurations are considered to be within the domain

  born of the invention. Thin axial grooves formed on

  the lower surface of the roller would also allow

  if excess lubricant pressure to escape.

  Alternatively, as shown in Figure 5, we

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  may provide axial or circumferential grooves 38 on the axis 12A, facing the inner bearing surface of the roller. Of course, various modifications may be made by those skilled in the art to the device which

  has just been described only by way of non-binding example

  mitative without departing from the scope of the invention.

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Claims (8)

R E V E N D I C A T IONS   1 - Roller comprising an annular roller (30) which has an external working surface (32) and a lubricated internal bearing surface   (34); and characterized by means (36) which maintain-   have a high coefficient of friction and   acceptable on said interior bearing surface.   2 - Roller according to claim 1, character-   se in that the means of maintenance of the coefficient of   friction include a plurality of reduction zones   lubrication pressure (36) which are distributed   ties on said bearing surface (34).   3 - Roller according to claim 1, character-   se in that the means of maintenance of the coefficient of   friction include a plurality of circumferential grooves   narrow and closely spaced annuities (30) which   are formed in said bearing surface.   4 - Roller according to claim 1, character-   in that the means for maintaining the coefficient of friction comprise a narrow helical groove   (36) formed in said bearing surface.   - Roller according to claim 4, characterized in that the groove (36) has a groove bottom width of 0.127 mm, a helix pitch between   0.381 mm and 1.27 mm, a thread depth between-   be 0.076 mm and 0.152 mm, and flanks of the groove with an included angle of 60.   6 - Roller assembly comprising: a motor axis   sé; an annular roller (30) having a transverse surface   valiant exterior (32) and an interior bearing surface   lubricated lower (34) adapted to be mounted on said motorized axis, and characterized by means (36) which maintain lubrication in boundary layer mode   on said interior bearing surface.   7 - roller assembly according to claim 6, 0l 2609457   characterized in that the means of lubrication by   che boundary include a narrow helical groove   (36) formed on the bearing surface of the roller.   8 - Roller assembly according to claim 6, characterized in that the boundary layer lubrication means comprise a narrow helical groove (38) provided on the axis.   9 - Process for transmitting the driving force   nement by rotation of an axis in continuous rotation to an intermittently rotating roller having an inner bearing surface and mounted on the axis, characterized by the phases consisting in: lubricating the bearing surface of the roller; and maintain a coefficient of friction on the bearing surface of the roller of a high value and acceptable.   - Method according to claim 9, character-   laughed at the fact that the phase of maintaining a coef-   high friction ficient further includes the phase of reducing the pressure of the lubricant on the bearing surface.