Multiple synchronized linear friction welding oscillators

A linear friction welding oscillator consists of a plurality of individual linear oscillators which are ganged together so as to operate in unison. The total force exerted by the composite oscillator is thus the sum of the output forces of the individual oscillators. The individual oscillators produce variable amplitude, linear reciprocation of an output ram by converting rotary motion into linear motion using conversion/coupling means such as a swash plate connected by a bending elements to drive a crank. Each of the individual oscillator cranks is rotatably engaged with the output ram so as to transmit to it axial, reciprocal movement due to the angular alignment of the swash plate axis with the ram. All of the individual oscillators are mounted in a common frame in which they can be swung in unison so as to vary and control their individual movements in synchronism.

The invention relates to friction welding oscillators. 
In particular, the invention concerns an arrangement in which several 
linear friction welding oscillators, for example, of the kind described in 
our earlier filed GB Patent Application No 9526038.6, and a subsequently 
filed European patent application claiming the priority thereof, may be 
ganged together. 
As discussed in the above mentioned earlier application, amongst others, 
linear friction welding is a technique of joining two components, or a 
component to a workpiece, by moving one component relative to the other in 
a linearly reciprocal movement while urging the interface surfaces 
together with a force to generate sufficient frictional heat to produce a 
weld. It will be appreciated from consideration of the factors governing 
the forces involved that the work required from a welding oscillator is 
dependent on a number of things including the area of the weld interface, 
the force applied during the frictional heating phase, and the coefficient 
of friction between the joint faces. Thus, an oscillator designed for the 
manufacture of a joint of one size may not be suitable for another joint, 
especially one of large size. The oscillator may possess either too much 
power, and thus be wasteful and too expensive to purchase and operate, or 
it may lack sufficient power to overcome the frictional forces tending to 
resist linear movement. Consequently, hitherto oscillators have been 
specifically designed for a particular application or the nearest suitable 
has been selected from the range of different power oscillators available. 
An objective of the present invention is to provide one standard 
oscillator, such as described in the above mentioned earlier applications 
and to provide, in addition, means for ganging together a plurality of 
such individual oscillators to provide a desired output power. 
Accordingly the invention provides a linear friction welding oscillator 
comprising an output ram mounted for linear reciprocal movement, a 
plurality of rotary prime movers which are ganged together in parallel by 
a like plurality of rotary to linear motion coupling means to drive the 
output ram, each of said coupling means being adapted to convert a rotary 
output of a prime mover into reciprocal linear movement whereby the total 
output force of the ram is the sum of the forces exerted by the individual 
prime movers. 
In a preferred form of the invention each of the prime movers is carried on 
a pivoted yoke whereby the amplitude of the reciprocal movement is 
determined by swinging of the yoke, and the yokes of the individual prime 
movers are ganged together for synchronous pivotal movement.

An individual linear friction welding oscillator of the kind referred to, 
in general, comprises input shaft rotatable about a first axis, an output 
shaft rotatable about a second axis, axis movement means adapted to move 
the angle of the input shaft relative to the axis of the output shaft, 
coupling means having an input component rotatable with the input shaft 
and spaced radially from the first axis, and an output component rotatable 
with the output shaft adapted to couple the input shaft with the output 
shaft for rotational movement thereby to drive the output shaft, the 
arrangement being such that when the first and second axes are aligned the 
input component rotates so as to have no axial movement in the direction 
of the second axis, but when the first axis is inclined with respect to 
the second axis the input component rotates so that as it rotates about 
the first axis it also reciprocates with respect to the second axis 
thereby causing the output shaft to reciprocate in the direction of the 
second axis. 
The individual oscillator apparatus of FIG. 1 comprises a prime mover 2 in 
the form of a rotary electric machine rigidly mounted on a frame or yoke 4 
which is pivoted at one end about a pivot axis 6. The rotary machine 2 has 
an output shaft 8 and is mounted on the yoke 4 so that its axis of 
rotation 10 intersects the pivot axis 6. The output shaft 8 drives a swash 
plate 12 through a shaft 14 and coupling 16. The shaft 14 is journalled in 
bearings 18a,18b which are securely mounted in a portion 20 of the frame 
4. The bearings 18a,18b and shaft 14 are also arranged co-axially with the 
motor shaft 8 and rotary axis 10. A flywheel may be provided on the output 
shaft 8 to increase the angular inertia of the machine, for example this 
flywheel may consist of a separate item or may be integral with a part of 
the coupling means 16. 
An output ram arrangement, generally indicated at 22, is mounted for linear 
reciprocation with respect to an earth or reference member 26. This 
arrangement includes a ram output member 28 slidably mounted in the earth 
reference member 26, and rotary to linear motion conversion means 25 which 
converts the motion of the swash plate 12 relative to the axis of 
reciprocation of ram 28 into linear reciprocal movement. In the 
arrangement of FIG. 1 ram 28 has a square cross-section which is slidably 
mounted by means of sliding pads 24a,24b within a square hole formed 
through the earth reference member 26. 
The rotary to linear motion conversion means 25 which converts the motion 
of the swash plate 12 relative to the axis of reciprocation of ram 28 into 
linear reciprocal movement comprises a crank 30 on which the ram 28 is 
journalled by means of bearings 32a,32b. The inner races of these bearings 
are securely fixed to the journal portion of crank 30 while the outer 
races are securely fixed in the interior of the cylinder that includes ram 
28. The bearings 32a,32b therefore retain freedom for the crank 30 to 
rotate relative to the ram 28 but restrain the two parts from relative 
axial movement so that an axial load is transmitted from the crank 30 to 
the ram 28. 
The crank 30 is further formed at one end, the end opposite the portion 
journalled to the ram 28, with an offset web 34 which is mounted 
concentrically with an annular balance weight 36. Preferably the crank 30 
is formed with a square cross-section on which the balance weight is 
slidably mounted, this is feasible since the crank and balance weight do 
not rotate relative one to the other but only reciprocate co-axially. 
Thus, the crank and the balance weight are mounted for co-rotation about 
axis 38 while being capable of relative axial movement, at least to a 
limited extent. 
The crank 34 and balance weight 36 are coupled respectively by means of 
flexible, inextensible ligaments or elements 40,42 to the swash plate 12 
at opposite ends of a swash plate diameter. The so-called ligaments or 
elements 40,42 in the particular embodiment comprise elongate steel 
bending elements which have flanged ends for attachment between the swash 
plate 12 and the crank offset 34 and balance weight 36. 
The prime mover 2 and the yoke 4 upon which it is carried are arranged so 
that the axis 6 of the yoke pivot also intersects the crank axis 38. The 
arrangement, therefore, is that the driving portion of the oscillator 
comprising the pivotable yoke 4 and parts mounted thereon is capable of 
being swung about the pivot axis 6 while crank 30 and balance weight 36 
are free to rotate and execute linear reciprocal motion, and ram member 28 
is free only to reciprocate in an axial direction. These different motions 
on opposite sides of pivot axis 6 are linked by means of the bending 
elements 40,42. 
In operation, the prime mover 2 is energised to rotate swash plate 12 about 
the rotary axis 10. Depending upon the angular orientation of motor axis 
10 relative to crank axis 38 the ram 22 will execute linear reciprocation 
with a variable amplitude. This amplitude may be controlled by pivoting 
the yoke 4 carrying the motor 2 and swash plate 12 about the pivot axis 6. 
Since the opposite ends of elements 40,42 are attached to crank offset 34 
and balance weight 36 respectively the motion of those components is a 
combination of rotation around axis 38 and axial reciprocation with 
respect thereto. The crank balance weight 36 is not connected to any 
portion of ram 22 but crank 30 is rotatably mounted by means of bearings 
32a,32b to ram output member 28. Therefore crank 30 is free to rotate 
relative to the ram output member 28 but the member, in turn, is 
restrained from rotation and is able only to reciprocate linearly in the 
axial direction of axis 38. 
When the yoke 4 is swung back so that motor axis 10 lies co-axially with 
crank axis 38 the motion of element mounting points on swash plate 12 is 
pure rotation and gives rise to no linear reciprocation of crank 30. 
Therefore, the amplitude of linear reciprocation can be controlled simply 
by pivotal alignment of motor frame 4. However, when the yoke 4 is pivoted 
about axis 6 by an angle o and the swash plate 12 no longer rotates about 
the ram reciprocation axis 38 and the attachment points of the elements 
40,42 to the swash plate begin to reciprocate with respect to the axis 28 
as they revolve around axis 10. 
Referring now to the welding oscillator arrangement illustrated in the 
third angle projection views of FIG. 2, 3 and 4, there are shown three 
individual oscillators of the kind shown in FIG. 1 ganged together to 
provide a composite oscillator possessing three times the power output. In 
respect of the components of the individual oscillators like parts carry 
like references. 
In this arrangement the earth reference member 26 is shown more fully as a 
mounting frame or box-like structure housing the composite arrangement of 
the three ganged oscillators 50, 52, 54. Individually each of the 
oscillators is of the kind illustrated in FIG. 1. 
The housing generally indicated by member 26 comprises a generally 
rectangular shaped structure consisting of a base side 56, two elongate 
sides 58 & 60 spaced apart by the width of the housing, a further side 62 
opposite the base 56 which is joined to the sides 58,60 by inclined edges 
64,66. The housing is enclosed by top and bottom plane members 68,70 
(FIGS. 3 & 4) the edges of which follow the outline of the sides 56-66. 
Contained within the housing 26 are the three individual oscillators 
50,52,54, a synchronising mechanism, and a composite output ram 72. 
Generally the ram 72 corresponds to the ram 28 in FIG. 1 but here is to be 
driven by the three oscillators in parallel. 
The ram 72 comprises an output member 74 which protrudes through an 
aperture in the end wall 62 of the housing. The sides of the member 74 may 
be journalled in the end wall 62 by means of sliding bearings (not shown) 
which provide lateral location of the member 74, and assist in locating 
the ram 72. The output member 74 is joined to or formed integrally with a 
delta-shaped main portion 76 of the ram which is enclosed within the 
housing 26. This main ram portion 76 is also slidably supported in the 
housing by means of longitudinal extending keys 78,80 engaged in keyways 
82,84 formed in the top and bottom side walls 68,70 respectively. The 
keyways 82,84 are disposed in the longitudinal direction of side walls 
58,60, and perpendicular to the end walls 56,62 so that the ram is free to 
reciprocate the output member 74 in the longitudinal direction. 
The three oscillators 50,52,54 are mounted side by side and in parallel 
within the housing 26. They are coupled to drive the ram 76 in unison, the 
arrangement serving to synchronise the movement of the output members of 
the individual oscillators. As a result the total force exerted by the 
output member 74 is the sum of the output forces of the individual 
oscillators. Compared to the parts described and referenced in relation to 
the oscillators of FIG. 1 each of the output crank members 30 of the 
oscillators is engaged with the delta-shaped main portion of the ram 76. 
Along the base side of the ram 76 there are formed crank receiving pockets 
86,88,90 spaced apart at the same pitch as the oscillators 50,52,54 into 
which the cranks 30 are inserted. The cranks are engaged with the ram 76 
by means of axial force transmitting, rotary bearings located inside the 
pockets. Thus, in the same manner as a crank 30 is able to rotate relative 
to the ram 28 of an individual oscillator of FIG. 1 but simultaneously 
transmit axial reciprocal motion to it, so the corresponding rams of the 
three oscillators 50,52,54 are free to rotate relative to the ram 76 while 
simultaneously transmitting to it axial reciprocal movement. 
Also in common with the single oscillator of FIG. 1 each of the oscillators 
50,52,54 is pivotally mounted, so that as previously described the 
amplitude of the movement of each linear oscillator output member is 
variable between a maximum value and zero. The prime movers of the three 
oscillators are mounted in respective ones of three pivotable yokes 
92,94,96 which have parallel axes 98,100,102 spaced apart across the width 
of the housing 26. The distal ends of the pivoted yokes are coupled 
together by a synchronising drawbar 104 disposed laterally across the 
housing close to the end wall 56. The yokes 92,94,96 are pivotally coupled 
to the drawbar 104 at locations 106,108,110 respectively for synchronous 
pivotal movement. The drawbar 104 is preferably bifurcated, as shown in 
FIG. 4, so as to avoid any tendency to twist the yokes. One end of the 
drawbar 104 is connected to an actuating mechanism 112 located in a side 
wall 58 of the housing 26. The mechanism 112 basically consists of an 
hydraulically actuable cylinder and piston carried on the side wall of the 
housing with an actuator output member 114 extending through an aperture 
in the side wall 58 and coupled to the end of the drawbar 104. By 
positioning the drawbar substantially linearly in the direction of its own 
length all of the individual oscillators may be pivoted in unison. 
Thus, each individual linear oscillator is mounted for movement relative to 
a reference position, all of the oscillators are ganged together for 
synchronous movement. The amplitude of that movement is variable and 
controlled by operating the actuator mechanism 112. The drawbar 104 is 
moved laterally across the oscillator housing 26 causing the individual 
oscillators 50,52,54 to swing in unison about their respective pivots 
98,100,102. As in the case of the single oscillator varying the angular 
orientation of the individual oscillators in unison relative to a 
reference axis is used to control the stroke of the composite oscillator. 
It will be readily understood that various parts of the apparatus described 
above may be altered, varied and substituted while retaining the principle 
of operation and construction of the invention. For example: the prime 
movers mentioned above comprise rotary electric motors but other forms of 
motor could be substituted; the coupling means between the prime mover and 
the ram driving crank is illustrated as a swash plate with bending 
elements but a ball and socket arrangement as described in our co-pending 
application claiming priority from GB 9526038.6 could also be used; the 
amplitude control actuator is represented as an hydraulic cylinder and 
piston but could be substituted by, amongst other things, a rotary 
actuator. Other features of the embodiment such as the shape of the 
housing, the shape of the ram, and the design of the housing may be 
changed. The number of individual oscillators utilised, as already 
foreshadowed is chosen to fulfil the power requirement of the overall 
oscillator; also although these are shown mounted side by side so that all 
push and pull in unison it would be possible to mount the selected number 
of oscillator in some other configuration, in a delta or square 
arrangement, for instance.