Dot matrix print head carriage with swingable heat sink

A dot matrix print head has a heat sink substantially surrounding the head for dissipating heat therefrom. A print head carriage includes a pivot or bearing assembly on one side of the print head and includes a bail type clamp pivoted on the carriage on the other side of the print head. The arrangement allows the heat sink to swing from a covered print head operating position to an uncovered position for servicing or for removing the print head.

CROSS REFERENCE TO RELATED APPLICATION 
Application entitled "Dot Matrix Printer Carriage", Ser. No. 176,957, filed 
Apr. 4, 1988, invented by James R. Del Signore, Robert A. Brull, and Alan 
H. Walker, and assigned to NCR Corporation. 
BACKGROUND OF THE INVENTION 
In the field of printing, the most common type printer has been the printer 
which impacts against record media that is caused to be moved past a 
printing line or line of printing. As is well-known, the impact printing 
operation depends upon the movement of impact members, such as print 
hammers or wires or the like, which are typically moved by means of an 
electromechanical drive system and which system enables precise control of 
the impact members. 
In the field of dot matrix printers, it has been quite common to provide a 
print head which has included therein a plurality of print wire actuators 
or solenoids arranged or grouped in a manner to drive the respective print 
wires a very short, precise distance from a rest or non-printing position 
to an impact or printing position. The print wires are generally either 
secured to or engaged by the solenoid plunger or armature which is caused 
to be moved such precise distance when the solenoid coil is energized and 
wherein the plunger or armature normally operates against the action of a 
return spring. 
It has also been quite common to provide an arrangement or grouping of such 
solenoids in a circular configuration to take advantage of reduced space 
available in the manner of locating the print wires in that specific area 
between the solenoids and the front tip of the print head adjacent the 
record media. In this respect, the actuating ends of the print wires are 
positioned in accordance with the circular arrangement and the operating 
or working ends of the print wires are closely spaced in 
vertically-aligned manner adjacent the record media. The availability of 
narrow or compact actuators permits a narrower or smaller print head to be 
used and thereby reduces the width of the printer because of the reduced 
clearance at the ends of the print line. The print head can also be made 
shorter because the narrow actuators can be placed in side-by-side manner 
closer to the record media for a given amount of wire curvature. 
In the wire matrix printer which is utilized for receipt and journal 
printing operation, the print head structure may be a multiple element 
type and may be horizontally disposed with the wire elements aligned in a 
vertical line and supported on a print head carriage which is caused to be 
moved or driven in a horizontal direction for printing in line manner 
across the receipt or journal paper and wherein the drive elements or 
transducers may be positioned in a circular configuration with the 
respective wires leading to the front tip of the print head. In the wire 
matrix printer which is utilized for business forms or like record media 
printing operation, the print head may be oriented in a manner wherein the 
nose is pointed downward for printing on the form, slip or like media 
while the carriage and print head are moved above and across the form or 
media in the horizontal direction. 
In the dot matrix printer which includes a print head of the circular 
configuration and multiple element type, there is a requirement for 
movement of generated heat away from the print head. These print heads 
operate at high speed and at large loading in a compact environment so 
that such generated heat is disposed of through means of a heat sink. The 
heat sink surrounds at least a portion of the print head to transfer the 
heat to and through the heat sink by conduction and convection. 
Representative documentation in the field of dot matrix printer heads 
includes U.S. Pat. No. 4,134,695, issued to J. E. Randolph on Jan. 16, 
1979, which discloses a carriage for positioning a print mechanism with 
facility for retracting the print mechanism. 
U.S. Pat. No. 4,064,984, issued to T. H. Toeppen on Dec. 27, 1977, 
discloses a releasable device for fastening a print head and includes a 
manually-operated control lever which effects the opening and closing of a 
pair of locking levers by cam action in the form of journal bearings in 
the control lever. 
U.S. Pat. No. 4,229,114, issued to A. C. Van Horne on Oct. 21, 1980, 
discloses a mechanism for mounting a print head to the shuttle of a 
printer and is designed to facilitate easy removal and replacement of the 
print head. The shuttle includes two slots for receiving molded bosses of 
the print head. The shuttle also has two locking members which are spring 
loaded to secure the parts. 
U.S. Pat. No. 4,239,402, issued to F. Jung et al. on Dec. 16, 1980, 
discloses a wire matrix print head configured for detachable mounting on a 
complementary shaped support and held thereto by a spring device which 
urges the complementary surfaces in secure contact with one another. 
U.S. Pat. No. 4,469,454, issued to G. J. Crean on Sept. 4, 1984, discloses 
a print wheel mounting arrangement for a print head and ribbon cartridge 
assembly that provides for tilting the assembly into a inoperative 
position with the ribbon cartridge in an extended tilted position for 
removal and replacement of the print wheel. 
U.S. Pat. No. 4,473,312, issued to E. Forschner on Sept. 25, 1984, 
discloses a fastening mechanism for removably fastening a print head 
housing and a carriage. A locking member on the carriage effects 
rotational and axial movement relative thereto and has abutment surfaces 
cooperating with cam surfaces on the housing to latch the housing and the 
carriage by action of a spring. 
U.S. Pat. No. 4,514,100, issued to R. E. La Spesa on Apr. 30, 1985, 
discloses apparatus for mounting a print head on a movable carriage and 
includes a projection on the carriage, an opening in the print head to 
receive the projection, a compression spring for maintaining the 
projection in the opening, and a movable cam surface in contact with the 
projection. 
And, U.S. Pat. No. 4,708,502, issued to K. Murakami on Nov. 24, 1987, 
discloses a mounting mechanism for releasably mounting a print head to a 
carriage which includes a pair of pivotable levers located on opposite 
sides of the print head. A spring biases the levers in a predetermined 
direction and the levers are pivotable between a print head secured 
position and a print head released position. 
SUMMARY OF THE INVENTION 
The present invention is directed to printers and more particularly to a 
dot matrix print head on a movable carriage. The carriage is of unitary 
construction and includes a plurality of bearings which ride along guide 
rails or shafts of the printer. The guide shafts are attached to side 
frames or plates of the printer and the carriage is moved by means of an 
electric motor in transverse direction. 
The dot matrix print head is supported on the carriage and includes a 
plurality of actuating coils for driving print wires in printing operation 
as the print head and carriage assembly is moved back and forth across the 
printer. 
A heat sink is swingably supported from the carriage in an arrangement 
wherein the heat sink is pivoted at one side and is latched at the other 
side. The heat sink substantially surrounds the print head to transfer 
heat from the print head to and through the heat sink by conduction and 
convection methods. 
A knife assembly is also provided and is supported on the top surface of 
the heat sink. The knife assembly includes a solenoid actuator that moves 
a circular knife from a cam into cutting position for severing record 
media such as receipt paper. The cutting action may involve either partial 
or full cutting of the paper as the carriage is moved across the printer. 
In view of the above discussion, a principal object of the present 
invention is to provide a dot matrix print head with heat transfer means. 
Another object of the present invention is to provide a dot matrix print 
head carrying a swingable heat sink thereon. 
An additional object of the present invention is to provide a print head 
assembly having heat transfer means and media cutting means. 
A further object of the present invention is to provide a dot matrix print 
head supported from a carriage with pivot means for enabling swingable 
movement of a heat sink and a knife assembly to permit access to the print 
head. 
Additional advantages and features of the present invention will become 
apparent and fully understood from a reading of the following description 
taken together with the annexed drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 illustrate a side elevational view and a front elevational 
view, respectively, of the print head assembly of the present invention. A 
pair of guide rails or shafts 20 and 22 carry a carriage 24 in transverse 
manner across a printer 26 of the type, as shown in FIG. 3. The printer 
includes a journal station 28, a receipt station 30, and a slip station 
32. The journal station 28 is positioned on the right hand side of the 
printer 26 and the receipt station 30 and the slip station 32 occupy the 
left hand side of the printer. A more detailed description of the printer 
26 is found in co-pending U.S. application Ser. No. 67,757, filed June 29, 
1987, now U.S. Pat. No. 4,780,007, issued Oct. 25, 1988, and assigned to 
the same assignee as the present application. 
The carriage 24 is of unitary construction and includes a pair of spaced 
bearings 34 and 36 at the rear part of the carriage. The carriage 24 has a 
single bearing 38 of U-shaped construction at the front part. The details 
of the carriage 24 are more fully described in the co-pending U.S. 
application Ser. No. 176,957, filed Apr. 4, 1988, and assigned to the same 
assignee as the present application. 
A print head 40 of the dot matrix type in a circular configuration (FIG. 2) 
is mounted on the carriage 24. The print head includes a plurality of print 
wires (not shown) which are moved in back and forth manner by a plurality 
of actuating coils (also not shown) in printing operation. The print head 
operates in a compact environment and generates an amount of heat that 
must be transferred or transmitted away from the print head for efficient 
operation. 
The means for transferring or dissipating heat from the print head 40 is 
effected with and comprises a heat sink, generally at 42. The die cast 
aluminum heat sink 42 generally covers and surrounds the actuating or rear 
portion 44 of the print head 40. The heat sink 42 includes a top plate 
portion 46, a right hand plate portion 48, and a left hand plate portion 
50. The heat sink 42 is of unitary construction and includes ribs 52 on 
the exterior of plate portion 48 and ribs 54 on the exterior of plate 
portion 50. The heat sink 42 also includes ribs 56 formed in an arcuate 
arrangement which bridges the side plate portion 48 and the top plate 
portion 46. Ribs 58 are formed in an arcuate arrangement and bridge the 
side plate portion 50 and the top plate portion 46. The top plate portion 
46 extends to the right in FIG. 1 and covers the nose portion 60 of the 
print head 40. 
The heat sink 42 includes a pair of doglegs 62 and 64 at the right hand 
side thereof. A pivot pin 66 is secured to the doglegs to provide for 
swinging movement of the heat sink. The carriage 24 has a bearing 68 as an 
integral part at the right hand side thereof and of a length occupying the 
space between the doglegs 62 and 64. The bearing 68 and the pivot pin 66 
provide means for swinging the heat sink 42 from a position covering the 
print head 40 to a position wherein the print head is uncovered for the 
purpose of servicing the print head or for removal thereof. 
A latch or clamp 70 is provided at the left hand side of the heat sink 42 
to maintain the heat sink in position during printing operation. The 
carriage 24 has a pair of spaced bearings 72 as an integral part at the 
left hand side thereof, and the latch or clamp 70 is formed in wire bail 
manner and has ends 74 journaled in the bearings 72. The latch or clamp 70 
is formed with a curved portion 76 to fit over a ledge 78 of the heat sink 
42. The wire bail construction of the latch 70 provides for maintaining 
the heat sink 42 in a secure position by reason that as the heat sink is 
started to be raised by an operator or other person from the operational 
mode position, the latch exerts an increased force on the ledge 78 to 
retain the parts in position. 
An additional feature of the print head assembly is the provision of a 
knife mechanism 80 for use in receipt printing operation. The knife 
mechanism 80 includes a solenoid 82 coupled with a crank arm 84 that is 
journaled at pivot 86. A bifurcated arm 88, as an integral part of the 
crank arm 84, supports a knife blade 90 which is movable to a cutting 
position for severing the receipt paper. A detailed description of the 
knife mechanism is found in Shipos et al. Pat. No. 4,525,088. 
If the knife mechanism is not required in the printing operation, a 
modification of the print head assembly includes the carriage 24, the 
print head 40, and the heat sink 42. FIG. 3 illustrates the print head and 
the swingable heat sink but does not show the knife mechanism. 
It is thus seen that herein shown and described is a print head assembly 
that includes a swingable heat dissipating element. The mechanism and 
arrangement enable the accomplishment of the objects and advantages 
mentioned above, and while a preferred embodiment of the invention has 
been disclosed herein, variations thereof may occur to those skilled in 
the art. It is comtemplated that all such variations not departing from 
the spirit and scope of the invention hereof are to be construed in 
accordance with the following claims.