Sliding block with adjustable track positioning

A sliding block with adjustable track positioning comprising a prismatic body, in one face of which there is a longitudinal recess arranged to receive a rail by way of rolling elements positionable in respective tracks, the body being essentially of C-shaped cross-section consisting of a central part from which two flanges extend, wherein in at least one of the two flanges of the C-shaped cross-section there is provided a second longitudinal recess which divides it into separate portions connected together at the central part, the second recess containing elements for adjusting the distance between the two separate portions.

This invention relates to a sliding block with adjustable track 
positioning. 
Linear sliding guide units generally comprise two main constituent 
elements, namely an inner element and an outer element slidable relative 
to each other by way of rolling elements. The inner element is of 
prismatic shape whereas the outer element is of C-shape, the recess of 
which carries the inner element. The former is usually known as the rail 
while the latter is known as the sliding block. 
A required basic characteristic of the sliding block is that its rolling 
tracks for the rolling elements be of adjustable distance apart. This 
adjustment has two main purposes, namely to adapt the distance between the 
tracks to the type and size of the rolling element used, and to enable the 
user to directly adjust the loading or the slack. 
In this respect in sliding blocks formed by extrusion, as the distance 
between the tracks can vary within a range of a few tenths of a millimeter 
as allowable tolerance in accordance with the relevant standards, the 
exact distance must be able to be reset. In addition the user must be able 
to choose the most suitable slack or preload condition for his specific 
requirements. In known linear sliding units this is not always possible or 
is inherently difficult because of their structure. 
The object of the present invention is to provide a sliding block in which 
the distance apart of the rolling element tracks can be adjusted in order 
to be able to use the prechosen best operating condition. 
This object is attained according to the present invention by a sliding 
block with adjustable track positioning comprising a prismatic body, in 
one face of which there is a longitudinal recess arranged to receive a 
rail by way of rolling elements positionable in respective tracks, said 
body being essentially of C-shaped cross-section consisting of a central 
part from which two flanges extend, characterised in that in at least one 
of said flanges of said C-shaped cross-section there is provided a second 
longitudinal recess which divides it into separate portions connected 
together at said central part, said second recess containing elements for 
adjusting the distance between said two separate portions. 
The characteristics and advantages of a sliding block according to the 
present invention will be more apparent from the description given 
hereinafter by way of non-limiting example with reference to the 
accompanying schematic drawings, in which: 
FIG. 1 is a partly sectional elevation of a linear sliding unit using a 
sliding block with adjustable track positioning according to the present 
invention; 
FIG. 2 is a partly sectional top plan view of the sliding block shown in 
FIG. 1; 
FIGS. 3 and 4 are an elevation and a top plan view of a second embodiment 
of the sliding block according to the present invention; 
FIGS. 5 and 6 are an elevation and a top plan view of a third embodiment of 
the sliding block according to the present invention; 
FIGS. 7 and 8 are an elevation and a top plan view of a fourth embodiment 
of the sliding block according to the present invention; 
FIGS. 9 and 10 are an elevation and a bottom plan view of a fifth 
embodiment of the sliding block according to the present invention; 
FIGS. 11 and 12 are an elevation and a top plan view of a sixth embodiment 
of the sliding block according to the present invention.

With general reference to FIG. 1, this represents an elevational view of a 
linear sliding unit using a sliding block with adjustable track 
positioning according to the present invention. The figure shows 
specifically a sliding block, indicated overall by 11, within a recess 12 
of which there is located a rail 13. Both the sliding block 11 and the 
rail 13 are provided in facing surfaces with tracks 14 and 15 
respectively, for receiving rolling elements such as balls 16. Both the 
sliding block 11 with its recess 12 and the rail 13 extend in a direction 
which will be known as the longitudinal direction. Neither the rail 13 nor 
the balls 16 are represented in the subsequent exemplifying figures, for 
ease of description and comprehension. 
As stated, the sliding block 11 has a prismatic body, one face of which, 
for example the upper face, contains the recess 12 for receiving the rail 
13. The body is essentially of C-shaped cross-section and thus consists of 
a central part 17 from which there extent two flanges, which also lie in 
said longitudinal direction. According to the present invention, one of 
the two flanges is divided by a variously shaped second recess 18, also 
lying in the longitudinal direction, into two separate portions 19 and 20 
which are connected together in a region extending laterally from the 
central part 17. A recess 18 could also be provided in the other flange of 
the sliding block in like manner. 
Said second recess 18 contains elements for adjusting the distance between 
the two separate portions 19 and 20 and indicated overall by 21 in the 
various embodiments. It should be noted that in addition one of the two 
separate portions, in the illustrated example that indicated by 20 and 
facing the interior of the recess 12, has a smaller cross-sectional 
thickness than the other portion 19. 
In this respect, FIGS. 1 and 2 show a first embodiment in which the second 
recess 18, formed between the separate portions 19 and 20 of one of the 
two flanges, is of open L-shaped cross-section, ie with an obtuse angle 
between the two inner parts of the L and the lower end facing the first 
recess 12. The portion 20 extending from it is connected to the central 
part 17 of the sliding block by a reduced section 22 which enables the 
portion 20 to flex so that it can approach or withdraw from the other 
portion 19. This flexure therefore determines a decrease or increase in 
the distance between the track 14 provided in this first flange and the 
track 14' provided in the opposing second flange 23 located at the other 
end on a lateral extension of the central part 17 of the body of the 
sliding block 11. 
In the illustrated embodiment, the adjustment elements 21 consist of a 
shaft 24 arranged in the longitudinal direction and having an eccentric 
body inserted into a profiled housing 25 provided in facing surfaces of 
the two separate portions 19 and 20. The ends of the shaft are provided 
with seats 26 for hexagonal keys for its rotation. Along the body of the 
shaft 24 there are provided recesses 27 at which screws 28 are positioned. 
The screws 28 are arranged perpendicular to the shaft 24, ie in a 
transverse direction both to the flanges and to the recesses in the 
sliding block. The head of the screws 28 is housed free to rotate in a 
seat 29 in the first portion 19, the threaded other end being screwed into 
a corresponding threaded hole 30 provided in the second portion 20. 
In this embodiment the operation of the adjustment elements 21 is extremely 
simple in that by rotating the shaft 24, the portion 20 of the first 
flange of the sliding block 11 is caused to approach or withdraw from the 
second flange 23, so as to vary the distance between the tracks 14 and 
14'. Having made this adjustment the shaft can be locked in the chosen 
position by tightening the screws 28, which pass within the recesses 27 to 
lock it relative to the body of the sliding block. Moreover, the 
tightening of the screws 28, which pulls the separate portions 19 and 20 
of the first flange together, increases the distance between the tracks 14 
and 14', so reducing the preload on the sliding unit to hence create slack 
conditions. Finally the location of the screws 28, for example three in 
number and cooperating with the respective three cavities 27, prevents 
withdrawal of the eccentric shaft 24 from its housing 25, even if the 
portions 19 and 20 are not tightened together. 
Reference will now be made to the further embodiments of the sliding block 
according to the present invention, in which identical elements are 
indicated by the aforegoing reference numerals. 
FIGS. 3 and 4 show a second embodiment in which the shaft 24 is not 
provided, ie the second cavity 18 is empty. Screws 28' are provided, 
passing through in this case a threaded hole 29' in the portion 19 of the 
first flange. The second portion 20 of the first flange is without holes, 
the ends of the screws 28' acting against that inner surface thereof 
facing the first portion 19. Again in this case the screws 28' can be 
three in number. 
The operation of this second embodiment is even more simple in that the 
tracks 14 and 14', provided on the recess 12 of the sliding block, are 
made to approach or withdraw from each other by screwing the screws 28' 
inwards or outwards. This type of operation is possible again because of 
the presence of the reduced section 22 of the portion 20 of the first 
flange, which flexes to vary the distance between the tracks. With this 
movement the slack and preload of the sliding unit is increased and/or 
decreased by virtue of the flexure of the reduced section 22. It should 
also be noted that because of the pressing of the end of the screws 28' 
against the surface of the separate constituent portion 20 of the second 
recess, on slackening the screws 28' there is a spontaneous retraction of 
the portion 20 towards its rest condition by the effect of the elastic 
reaction of the reduced section 22. 
FIGS. 5 and 6 show a further embodiment of the sliding block according to 
the present invention in which the adjustment elements consist of a double 
wedge. 
In this case, at the upper end of the second recess 18 there are located 
two wedge elements 31 and 32, arranged facing each other along their 
inclined surfaces in profiled seats 33 provided in the facing surfaces of 
the two separate portions 19 and 20 of the first flange. Elements for the 
shifting and mutual axial positioning of the two wedges are provided at 
the opposing ends of the second recess 18. These elements consist of 
plates 34 fixed at their first end to the portion 19 of the body of the 
sliding block by screws 35. The screws 35 are positioned in relative blind 
threaded holes 36 with their axis substantially parallel to the axis of 
the second recess 18. The plates 34 extend towards the interior of the 
sliding block by projecting over the second recess 18. This projecting 
second end is provided with threaded through holes 37 with their axis 
parallel to that of the holes 36, and carrying further screws 38. At that 
end facing outwards from the sliding block the screws 38 are provided with 
a nut 39 positionable to abut against the outside of the plate 34, whereas 
at their other end they act against a respective end surface of the wedges 
31 and 52, causing them to interact. 
Consequently the distance between the tracks 14 and 14' of the sliding 
block is adjusted by operating the two screws 38, which then act on the 
two wedges 31 and 32. By screwing said screws 38 further in, the wedges 
become inserted into the second recess 18 to a greater extent, so moving 
the separate portion 20 towards the second flange 23 of the sliding block. 
In this manner the tracks 14 and 14' move closer together to result in a 
change in the slack and/or a greater preload. In contrast, if the screws 
38 are unscrewed, the wedging is released with consequent return of the 
portion 20 of the first flange to its rest position, with preload 
reduction and increased slack. FIGS. 7 and 8 show an embodiment in which 
the adjustment elements also consist in this case of a double wedge, but 
positioned in a simplified form. 
In this respect, the screws 35 are again inserted into blind threaded holes 
36 in the portion 19 of the first flange of the body of the sliding block. 
The heads of the screws 35 act directly on the free ends of the wedges 31 
and 32, which for example for better interaction can comprise recesses 40 
able to receive and better house the base of their head. 
Hence in this case the wedging or the disengagement between the facing 
surfaces of the two wedges 31 and 32 is achieved by simply turning the 
screws 35 so that the wedges cause the portion 20 either to flex or to 
return towards its rest position. FIGS. 9 and 10 show a further embodiment 
of the sliding block according to the present invention in which the 
adjustment elements are extremely simple and consist of a single wedge. 
In this respect a wedge 41 is located in the second recess 18, which in 
this embodiment is of a shape complementary to that of the wedge 41. A 
through hole 42 is provided in the central part 17 of the sliding block 
body below the first flange, in a position corresponding with the second 
recess 18, for a screw 43 which passes into a corresponding blind threaded 
hole 44 provided in the narrow end of the wedge 41. In this manner by 
operating the screw 43, or preferably two screws 43 as in the example, the 
wedge 41 is made to penetrate further into the relative recess 18. This 
wedging results in flexure of the portion 20 of the first flange with the 
tracks 14 and 14' coming closer together, and in adjustment of the slack 
and/or preload of the sliding unit. Finally in a further embodiment shown 
in FIGS. 11 and 12 the adjustment elements consist of a conical pin. 
In this respect, the portions 19 and 20 of the first flange carry, in 
facing surfaces, rounded seats 45 for receiving lateral portions of a 
conical pin 46. The conical pin 46 is for example of frusto-conical shape 
and comprises along its axis blind threaded holes 47 extending from its 
two opposite ends. A pair of screws 48 can be screwed into said holes 47 
to act against washers 49 located at opposite ends of the second recess 18 
in widened end portions 50 of greater diameter than the rounded seats 45. 
In this case by screwing one of the two screws 48 and unscrewing the other 
screw 48 the conical pin becomes wedged in to a greater or lesser extent. 
The portion 20 of the first flange flexes or returns to its original 
position to bring the tracks 14 and 14' for containing the rolling 
elements of the sliding unit closer together or further apart. The 
position of the tracks is hence again adjusted, with variation in the 
slack and in the preload conditions. 
FIG. 11 shows that the tracks 14 and 14' can be shaped to receive different 
rolling elements such as rollers 16' shown by continuous lines. The 
rollers arranged in a row can be positioned either simply one behind the 
other or mutually crossed in order to be able to support forces of 
different types. A sliding block and the relative rail according to the 
present invention can be constructed as an extrusion, in steel or in any 
other suitable material, and as stated can comprise one or two 
longitudinal recesses with relative adjustment elements. A sliding block 
with adjustable track positioning is hence provided according to the 
invention, which enables the slack and preload conditions of the sliding 
unit in which it is used to be varied by virtue of the particular form of 
the body of the sliding block and the use of suitable adjustment elements.