Latch for an ink cartridge

Apparatus for reciprocally moving one or more ink cartridges through the printing station of an ink jet printer. A carriage having at least one open top compartment equipped with a latching mechanism which is arranged to urge the front face of the ink cartridge into contact with the front wall of the compartment. The latching mechanism includes a frame that is pivotally supported in the rear wall of the compartment so that it can move between a rearwardly canted position into an upright vertical position. A biasing member is pivotally supported in the frame and contains a pair of spaced apart ramps. A spring rotates the biasing member within the frame so that the ramp rides in biasing contact with the back of an ink cartridge being inserted into the compartment as the frame is rotated from the canted position into the upright position.

BACKGROUND OF THE INVENTION
 This invention relates to apparatus for removably mounting one or more ink
 cartridges within a carriage for reciprocally moving the cartridge of a
 small ink jet printer through the printing station of a machine.
 In particular, this invention relates to a latching mechanism for removably
 securing one or more ink cartridges in the carriage of a small point of
 sale type printer. Many of the devices for securing an ink cartridge in a
 carriage involves lever and spring mechanisms that are relatively large
 and complex devices. As a consequence, these devices consume a good deal
 of valuable space and leave little room for the user to operate the
 mechanism during insertion and removal of the cartridge. It should be
 further noted that many of these prior art devices are arranged so that
 they bear directly upon the back wall of the cartridge when the cartridge
 is latched within the carrier. The cartridge is typically constructed of a
 thin material such as plastic and the holding force of the latching device
 can deform the cartridge forcing ink from the nozzles. This, in turn,
 produces unwanted dirt problems within the printer which, in extreme
 cases, requires the machine to be taken out of service for cleaning.
 By the same token, if the latching mechanism does not hold the cartridge
 securely within the carrier, there is a high probability that the
 electrical connector located upon the front face of the cartridge will not
 make positive contact with the input terminals located on the opposing
 front wall of the carrier. When this occurs, the printer will produce a
 faulty or unintelligible printout.
 As disclosed in U.S. Pat. No. 4,709,247, some latching devices require
 specially configured ink cartridges to insure proper engagement and
 operation of the latching mechanism. The cost of the ink cartridge is
 therefore substantially higher than the less complex cartridges presently
 in the market and therefore, reliability is generally lessened due to the
 close tolerances between parts.
 SUMMARY OF THE INVENTION
 It is therefore a primary object of this invention to improve apparatus for
 reciprocally moving one or more ink cartridges through the printing
 station of a small ink jet printer.
 It is a further object of the present invention to reduce the size of a
 carriage required to reciprocally move one or more ink cartridges through
 the printing station of a small ink jet printer.
 A still further object of the present invention is to provide for easy
 insertion and removal of an ink cartridge from an ink cartridge carrier.
 Another object of the present invention is to provide for more positive
 registration of an ink cartridge in an ink cartridge carriage.
 Yet another object of the present invention is to positively register an
 ink cartridge within a carriage without deforming the ink cartridge.
 These and other objects of the present invention are attained by apparatus
 for reciprocally moving one or more ink cartridges through the printing
 station of a small ink jet printer. The apparatus includes a carriage
 containing an open top compartment for removably containing an ink
 cartridge. The ink cartridge rests upon a raised pad mounted in the floor
 of the compartment and a latching mechanism urges the front wall of the
 cartridge into registration with the front wall of the compartment. The
 latching mechanism includes a frame that is rotatably supported in the
 rear wall of the compartment. A biasing member is pivotally supported in
 the frame and contains a pair of spaced apart ramps that are adapted to
 contact the back of an ink cartridge that is inserted into the compartment
 immediately behind the corner where the back wall of the cartridge joins
 the side walls. The ramps are contoured so that they ride in rolling
 contact against the back of the cartridge as the frame is raised from an
 initial rearwardly canted position to an upright vertical position. When
 the frame is placed in the upright position, the flat section on each ramp
 snaps over into vertical alignment with the back wall of the cartridge
 thereby urging the front of the cartridge into positive registration with
 the front wall of the compartment.

DETAILED DESCRIPTION OF THE INVENTION
 Referring initially to FIGS. 1-3, there is illustrated a relatively small
 point of sale ink jet printer capable of accepting a data input from a
 computer or the like and providing a printed receipt. This type of printer
 is typically employed in a cramped working environment and, through
 necessity, the size of the printer must be relatively compact.
 Accordingly, the available space within the unit is limited. The printer
 includes a housing generally referenced 10 that contains a base 11 upon
 which is hinged a front cover 12 and rear cover 13. The front cover 12,
 when raised as illustrated in FIG. 2, provides ready access to the ink
 cartridge carriage 15 that reciprocally moves one or more cartridges 16
 horizontally through a printing station 26. The rear cover, when raised as
 illustrated in FIG. 2, similarly provides ready access to a paper supply
 bin 19 that is adapted to hold a supply roll 20 of paper upon which
 receipt data is printed. The leading section 21 of the paper roll is fed
 over an idler roll 22 and beneath a drive roller 24 where it is engaged by
 a pair of pinch rolls 25 which holds the paper in friction driving contact
 against the drive roller. Under the influence of the drive roller, the
 paper is advanced through the printing station 26 and through an opening
 27 in the front cover into a read out station 28 (FIG. 1). The apparatus
 for driving the carriage and rotating the drive roller are well known in
 the art and will not be explained in greater detail herein.
 Turning now to FIGS. 4-8 there is further illustrated in greater detail
 carriage 15 which contains a pair of side-by-side compartments 30 and 31,
 each of which is adapted to hold an ink cartridge 16. In practice, each
 cartridge contains ink of different color than its neighbor so that the
 printer can produce a two color image in response to the input data
 provided by a control computer or microprocessor (not shown). The front
 wall 33 of each cartridge compartment contains a set of electrical input
 terminals 34 that are arranged to make contact with a terminal board 35
 contained on the front face 36 (FIG. 7) of the ink cartridge 16 when the
 cartridge is latched in place within the carriage as shown in FIG. 9.
 Input leads 38--38 are attached to the underside of the carriage and
 provide a data link between the input terminals and a computer 40 (FIG.
 1). Each cartridge contains a series of nozzles located in the front face
 of the cartridge that lay down an image pattern in response to the data
 input to the cartridge. Here again, the operation of the ink cartridge is
 well known in the art and need not be explained in any greater detail.
 Each cartridge is equipped with a pair of forwardly protruding lugs 43--43
 which, as will be explained in detail below, serve to help index and
 register the cartridge within the associated carriage compartment.
 The lugs are located at the side edges of the cartridge front wall so that
 each lug is supported by both the front wall and one side wall of the
 cartridge housing.
 The carriage 15 contains a horizontally disposed floor 44 upon which the
 two compartments 30 and 31 reside. Each compartment shares a common side
 wall 45 with its neighbor and an opposed side wall 47. The back of each
 compartment is closed by common elongated back wall 49. The side walls of
 the compartments are spaced apart to provide a close running fit with a
 cartridge that is slidably received within the compartment through the
 open top thereof.
 As best illustrated in FIG. 5, the carriage is arranged to ride upon a rail
 52 and is reciprocated through the printing station 26. As noted above, a
 paper substrate 21 is advanced through the printing station via the drive
 roller 24 where a two color image can be printed on the paper.
 A latching mechanism 55 is mounted on the rear wall of the carriage behind
 each compartment. The mechanism includes a frame 56 and a locking member
 57 that is pivotally mounted in the frame. The frame includes a hinge 58
 located in the lower part of its back wall 59 that is adapted to pivotally
 engage a horizontally disposed hinge pin 60 that is supported in assembly
 between end walls 47. The frame is permitted to rotate about a horizontal
 axis 66 upon the hinge pin between a rearwardly canted position as
 illustrated in FIG. 8 and a vertical or upright position as illustrated in
 FIG. 9. A plunger 62 is slidably mounted in the carriage within a bracket
 63 and is biased upwardly into contact with the hinge by spring 65 to
 apply a slight friction holding force on the frame whereby the frame will
 remain in whatever position it is placed.
 Two opposing bearing caps 70 are mounted in the side walls of the frame
 that are adapted to receive therein trunnions 71 that protrude from the
 side walls of the locking member 57. Accordingly, in assembly, the locking
 emmber can pivot within the frame about a horizontal axis 72 that is
 parallel with the pivot axis 66 of the frame. A pair of compression
 springs 73--73 are suppored withint the frame and act upon the back of the
 locking member to rotate the locking member in a counter clockwise
 direction. The counter clockwise movement of the locking member is
 arrested by a stop 74 located in the top of the frame.
 A pair of ramps 75--75 are supported in the lower section of the locking
 member and are adapted to ride in contact along the vertical edges 77
 (FIG. 6) of a cartridge rear wall as the cartridge is being loaded as
 shown in FIG. 8 into one of the carriage compartments. Each ramp includes
 an arcuate shaped lower section 78 which transitions into a flat
 vertically disposed upper section 79. To insert a cartridge into a
 compartment, the lugs situated in the front part of the cartridge are
 placed at an angle into locating holes 83 formed in the front wall of the
 carriage compartment and the back wall is brought into contact with the
 arcuate lower section of each ramp as shown in FIG. 8. The cartridge is
 then forced downwardly toward the floor of the carriage which causes the
 frame to rotate in a clockwise direction while at the same time rotating
 the locking member back within the frame against the biasing action of the
 spring. The cartridge continues down until the bottom wall comes to rest
 against a raised rib 85 situated on top of the compartment floor. At this
 time, the front wall of the cartridge is vertically aligned with the front
 wall of the compartment and the cartridge connectors are in registered
 contact with input terminals 34 mounted on the front wall of the
 compartment. As the ramps ride down the rear wall of the cartridge, each
 ramp crosses over the transition line between the two ramp sections and
 the upper planar section snaps over into flat contact against the rear
 wall of the cartridge, thus holding the cartridge securely against the
 front wall of the compartment. To remove the cartridge from the
 compartment, the back portion of the cartridge is simply grasped and then
 pivoted upwardly about its front edge. This, in turn, causes the latching
 mechanism to rotate rearwardly unlatching the cartridge.
 As shown in FIG. 6, the ink cartridges are typically fabricated of a thin
 walled plastic material. Placing pressure upon the center portion of any
 of the walls can cause the wall to deform and thus force ink from the
 nozzle ports. By arranging the ramps so that they ride in contact against
 the edge regions 77 of the back wall causes most of the spring force
 applied to the ramps to be resisted in compression by the two side walls
 of the cartridge thereby preventing the cartridge from deforming to a
 point where ink is forced from the nozzles.
 While the present invention has been particularly shown and described with
 reference to the preferred mode as illustrated in the drawing, it will be
 understood by one skilled in the art that various changes in detail may be
 effected therein without departing from the spirit and scope of the
 invention as defined by the claims.