[0001] The present invention relates to a motor-driven compressor unit, particularly for
airtight compressors on fluid compressing or refrigerating machines, comprising: a
main part with at least a first and second cylindrical seat at right-angles to each
other; a piston with at least one hole in its side walls and which slides inside the
said first cylindrical seat; a crankshaft with a crank pin which rotates in the said
second cylindrical seat; a connecting rod for converting the circular movement created
by the crank pin into a back-and-forth movement of the said piston, the said connecting
rod having at least a first and second eye, the first for connecting the said connecting
rod to the said piston by means of at least one pin inserted inside the said hole
of the said piston and in the said first eye, and the second inserting the said connecting
rod inside the s&id crank pin.
[0002] One of the major problems involved in designing and manufacturing motor-driven compressor
units is to cvercome the difficulty of assembling the various parts on the refrigerating
fluid compression system, in particular the crankshaft, connecting rod and piston
assembly. A number of solutions to this problem are already known.
[0003] In one of these, the connecting rod has a side slot and eye for the crank with a
larger diameter than on the crank pin. For assembling the parts, the crankshaft is
first inserted into the main part on the compressor, followed by the connecting rod-
pin-piston group already assembled together.
[0004] The connecting rod is then turned round the pin and inserted, through the said slot,
into the crank pin. The difference between the diameters is then adjusted by means
of a bushing.
[0005] This solution, however, entails machining difficulties for making the slot and also
increases the number of component and moving parts involved.
[0006] In another solution, connection is made by assembling a ball joint between the connecting
rod and piston so that the crankshaft can be assembled first in the main part of the
compressor followed by the connecting rod-piston assembly. The connecting rod is then
lowered and inserted into the crank pin which has a smaller diameter than the eye
on the connecting rod. In this case too, a clearance bushing is assembled between
the connecting rod and crank pin. The difficulties involved in this solution are machining
the ball joint and accurate assembly of the bushing which again increases the number
of component and moving parts involved.
[0007] In yet another solution, the eye of the connecting rod on the crank side is made
very flat with s. short crank pin smaller in diameter than the eye. This is done so
that it cannot be inserted straight into the eye to which it must be connected using
a bushing. In this case the crankshaft is inserted first, followed by the piston-pin-connecting
rod assembly, the connecting rod being passed over the crank pin which is short enough
not to interfere with it. The drawbacks of this solution, however, are the critical
nature of the system which provides for only an indirect connection of the crank pin
to the eye of the connecting rod and the higher number of component parts involved.
[0008] Other solutions provide for assembling the crankshaft after the connecting rod-piston
assembly. The shaft is generally longer with a smaller diameter than the part inserted
into the main part on the compressor or the eccentric part of the crank so it can
be inserted into the main part through the eye on the connecting rod. In this case,
the flywheel is on the oppcsite side of the crankshaft as compared with the previous
solutions which means a second support is needed for the crankshaft. This is assembled
after the shaft thus resulting in greater friction, more machining and increased weight
of the overall mechanism.
[0009] Other solutions provide for a connecting rod in two parts so that it can be assembled
after inserting the piston into the cylinder and the two parts screwed together. Besides
the obvious difficulty of machining the connecting rod in two parts, this solution
also involves the problem of increased weight of the moving parts.
[0010] The aim of the present invention is therefore to overcome the above drawbacks by
providing a means of constructing a mctor-driven compressor unit which enables the
component parts of the refrigerating fluid compression system to be assembled quickly
and easily.
[0011] A further aim of the present invention is to overcome the difficulties involved in
machining the said component parts. A further aim is to reduce the weight and number
of the said component parts so as to reduce the friction and bending moments exerted
on the crankshaft.
[0012] With these aims in view, the present invention relates to a motor-driven compressor
unit, particularly for airtight compressors on fluid compressing or refrigerating
machines, comprising: a main part with at least a first and second cylindrical seat
at right-angles to each other; a piston with at least one hole in its side walls and
which slides inside the said first cylindrical seat; a crankshaft with a crank pin
which rotates in the said second cylindrical seat; a connecting rod for converting
the circular movement created by the crank pin into a back-and-forth movement of the
said piston, the said connecting rod having at least a first and second eye, the first
for connecting the said connecting rod to the said piston by means of at least one
pin inserted inside the said hole on the said piston end in the said first eye, and
the second for inserting the said connecting rod inside the said crank pin, characterised
by the fact that the said crank pin constitutes one of two ends of the said crankshaft,
that the said connecting rod is a single piece, that the said crank pin and the said
second eye are connected directly with no component parts inbetween, and that construction
means are provided for assembling the said connecting rod after inserting the said
crankshaft in the said second cylindrical seat without altering the axial position
of the said crankshaft after it has been inserted, and for connecting the said piston
to the said connecting rod by means of the said pin after assembling the connecting
rod in the crank pin.
[0013] The invention will now be described with reference to the attached diagrams in which:
- Fig. 1 shows an exploded cross section of a number of parts on a motor-driven compressor
unit showing one possible arrangement of the present invention;
- Fig. 2 shows the same section as in Fig. 1 after the parts are assembled;
- Fig. 3 shows a top view of how the present invention is arranged;
- Fig. 4 shows a cross section of the motor-driven compressor unit showing another
possible arrangement of the present invention;
- Figs 5-10 show a number of possible arrangements of particular parts of the present
invention.
[0014] Number 1 in Fig. 1 indicates the main part on the motor-driven compressor unit. This
comprises a cylindrical seat for piston 2 and a seat for crankshaft 3 which, in turn,
comprises crank pin 4. Connecting rod 5 between piston 2 and crankshaft 3 has one
eye (6) for accomodating crank pin 4 and another eye (7) for accomodating pin 8. The
latter also passes through holes 9 in piston 2 for connecting rod 5 and piston 2.
[0015] On the main part of motor-driven compressor 1 with the cylindrical seat for piston
2, there is an opening (10). When assembling the component parts, crankshaft 3 is
turned until crank pin 4 reaches the bottom dead centre as shown in the diagram. Connecting
rod 5 is then inserted horizontally, as shown in the diagram, through opening 10.
Piston 2 is then inserted into the cylindrical seat of main part 1, starting from
the position shown in the diagram, until holes 9 coincide with eye 7 of connecting
rod 5. At this point, pin 8 is assembled and secured using one of the techniques described
later on. Finally, cover 12, including valves not shown in the diagram, is fitted
to main part 1 using screws 11.
[0016] Fig. 2 shows the Fig. 1 parts after assembly using the same numbering system.
[0017] Fig. 3 shows a top view of the arrangement already described with the component parts
numbered in the same way as for Figs 1 and 2. Notice in particular the shape and position
of opening 10 for assembling connecting rod 5. Piston 2 inside main part 1 of the
motor-driven compressor is drawn with a dotted line.
[0018] The diagrams clearly show to what extent opening 10 simplifies assembly of the various
component parts involved.
[0019] There is no need to divide the connecting rod in two or assemble a bushing between
crank pin 4 and eye 6 on the connecting rod. What is more, the crankshaft may be as
short as possible with no need for a second support for the shaft on the crank pin
side. The number of component parts used and, consequently, also the weight of moving
parts is reduced to a minimum in that both the crankshaft and connecting rod may have
minimum diameters resulting in a big reduction in friction, machining and the bending
moments exerted on the crankshaft.
[0020] Fig. 4 shows another possible arrangement of the present invention. The component
parts and numbers are the same as in the previous diagrams so only the changes will
be described. In the Fig. 4 arrangement, piston 2 has been made longer to bring the
pin 8 seat area sufficiently clear of main part 1 (opening 10 is no longer needed)
so as to enable the parts to be assembled in the same way as previously, i.e.: first
crankshaft 3, then connecting rod 5, piston 2 from the main part (1) side, including
the valves not shown and, finally, pin 8.
[0021] Figs 5 and 6 show a type of pin 8 that may be used with the present invention and
how it is fitted inside piston 2. Two slots (15) are milled on the . ends of pin 8
and two holes drilled in the piston so that pin 8 may be secured using one or two
pins (13). One of these may even be inserted in piston 2 before it is assembled in
its cylindrical seat.
[0022] Groove 16 and hole 17 are for lubricant.
[0023] Figs 7 and 8 show another possible type of pin 8 and how it is fitted inside piston
2. There is a blind hole (18) at each end so that pins 13 cannot go right through.
[0024] Fig. 9 shows another type of pin 8 with a groove (19) at each end for accomodating
spring plates 14 securing the pin 8 to piston 2. The -two grooves (19) are positioned
so that, when the pin is inserted into the piston, they correspond with the gaps between
the connecting rod and inside walls of the piston so that the spring plates can be
inserted straight into the grooves on the pin with no need for slots in the walls
of the piston.
[0025] Figs 10, 11 and 12 show other possible types of pins combining the features of the
previous ones with; groove 19 for spring plate 14 and blind hole 18 for pin 13 (Fig.
10); groove 19 and milled slot 15 for pin 13 (Fig. 11); blind hole 18 and milled slot
15 (Fig. 12).
[0026] The advantages of the present invention will be clear from the description given.
[0027] Firstly, the possibility of constructing a motor-driven compressor unit in such a
way that the parts comprising the refrigerating fluid compression system may be assembled
quickly and easily.
[0028] Secondly, the advantage of reducing the number of component parts and, consequently,
also the amount of machining involved.
[0029] Thirdly, the advantage of reducing the weight of moving parts and, consequently,
also friction, machining and the bending moments exerted on the crankshaft.
[0030] To those skilled in the art it will be clear that a number of changes can be made
to the device described without, however, departing from the scope of the present
invention.
1) Motor-driven compressor unit, particularly for airtight compressors on fluid compressing
or refrigerating machines, comprising: a main part (1) with at least a first and second
cylindrical seat at right-angles to each other; a piston (2) with at least one hole
(9) in its side walls and which slides inside the said first cylindrical seat; a crankshaft
(3) with a crank pin (4) which rotates in the said second cylindrical seat; a connecting
rod (5) for converting the circular movement created by the crank pin (4) into a back-and-forth
movement of the said piston (2), the said connecting rod (5) having at least a first
and second eye, (7, 6) the first for connecting the said connecting rod (5) to the
said piston (2) by means of at least one pin ( 8) inserted inside the said hole (9)
on the said piston (2) and in the said first eye (7), and the second (6) for inserting
the said connecting rod (5) inside the said crank pin (4), characterised by the fact
that the said crank pin (4) constitutes one of two ends of the said crankshaft (3),
that the said connecting rod (5) is a single piece, that the said crank pin (4) and
the said second eye (6) are connected directly with no component parts inbetween,
and that construction means are provided for assembling the said connecting rod (5)
after inserting the said crankshaft in the said second cylindrical seat without altering
the axial position of the said crankshaft (3) after it has been inserted, and for
connecting the said piston (2) to the said connecting rod (5) by means of the said
pin (8) after assembling the connecting rod (5) in the crank pin (4).
2) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said construction means comprise an opening (10) in the said main part (1) allowing
access'to the said first cylindrical seat, the said opening (10) being made on the
said main part (1) opposite the said second cylindrical seat, nearer the said crank
pin (4) and of such a size that the eye (7) of the said connecting rod (5) can pass
through it.
3) Motor-driven compressor unit according to Claim 2, characterised by the fact that
the said opening (10) .is semicircular in shape.
4) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said construction means provide for such a distance between the said first and
second cylindrical seats and such a length of the said piston (2) that, when the said
piston (2) reaches bottom dead centre, the said hole (9) in the side walls of the
piston (2) remains sufficiently clear of the said first cylindrical seat to allow
assembly of the said connecting rod (5) and piston (2) without altering the position
of the said crankshaft (3).
5) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has a slot (15) milled at each end and the said piston (2) two holes
drilled on the side facing the connecting rod (5) and that the said pin (8) is secured
to the said piston (2) by means of two pins (13) passed through the said holes and
slots (15).
6) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has a blind hole (18) at each end and the said piston (2) two holes
on the side facing the connecting rod (5) and that the said pin (8) is secured to
the said piston (2) by means of two pins (13) inserted into the said blind holes (18).
7) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has two grooves (19) positioned so that, when the said pin (8) is
inserted into the said piston (2), they correspond with the gaps between the said
connecting rod (5) and inside walls of the said piston (2) and that the said pin (8)
is secured to the said piston (2) by means of two spring plates (14) inserted straight
into the said grooves (19).
8) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has a blind hole (18) at one end and a milled slot (15) at the other,
that the piston (2) has two holes drilled on the side facing the connecting rod (5)
and that the said pin (8) is secured to the said piston (2) by means of two pins (13)
inserted through the said holes, one terminating inside the said blind hole (18) and
the other passing through the said slot (15) as well.
9) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has a blind hole (18) at one end and a groove (19) at the other positioned
so that, when the said pin (8) is inserted into the said piston (2), the said groove
(19) corresponds with the gaps between the said connecting rod (5) and inside walls
of the said piston (2) and that the said pin (8) is secured to the said piston (2)
by means of a pin (13) inserted into a hole in the piston and terminating in the said
blind hole (18) and a spring plate (14) inserted straight into the said groove (19).
10) Motor-driven compressor unit according to Claim 1, characterised by the fact that
the said pin (8) has a milled slot (15) at one end and a groove (19) at the other
positioned so that, when the pin (8) is inserted into the said piston (2), the said
groove (19) corresponds with the gaps between the said connecting rod (5) and inside
walls of the said piston (2) and that the said pin (8) is secured to the said piston
(2) by means of a pin (13) inserted through a hole in the piston (2) and the said
slot (15) and by means of a spring plate (14) inserted straight into the said groove
(19).
11) System for assembling a motor-driven compressor, particularly for airtight compressors
on fluid compressing or refrigerating machines comprising: a main part (1) with at
least a first and second cylindrical seat at right-angles to each other; a piston
(2) with at least one hole (9) in its side walls and which slides inside the said
first cylindrical seat; a crankshaft (3) with a crank pin (4) which rotates in the
said second cylindrical seat; a connecting rod (5) for converting the circular movement
created by the crank pin (4) into a back-and-forth movement of the said piston (2),
the said connecting rod (5) having at least a first and second eye (7, 6), the first
for connecting the said connecting rod (5) to the said piston (2) by means of at least
one pin (8) inserted inside the said hole (9) on the said piston (2) and in the said
first eye (7), and the second for inserting the said connecting rod (5) inside the
said crank pin (4), the said crank pin (4) constituting one of two ends of the said
crankshaft (3), the said connecting rod (5) being a single piece and the said crank
pin (4) and second eye (6) being connected directly with no component parts inbetween,
characterised by the following stages: insertion of the said crankshaft (3) into the
said main part (1) turning it to bring the said crank pin (4) to bottom dead centre
and without altering the axial position of the said crankshaft (3) further during
assembly; insertion of the said second eye (6) of the said connecting rod (5) straight
into the said crank pin (4); insertion of the said piston (2) into the said first
cylindrical seat until the said hole (9) on the said piston (2) mates with the said
first eye (7); insertion of the said pin (8) into the said hole (9) on the said piston
(2) and into the said first eye (7) to connect the said connecting rod (5) to the
said piston (2).
12) Assembly system as per Claim 11, characterised by the fact that, when the said
connecting rod (5) is inserted, the part comprising the said first eye (7) is passed
through an opening (10) in the said first cylindrical seat.
13) Motor-driven compressor unit as described and shown in the attached diagrams.