Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A DEVICE FOR RELEASABLY SECURING A READ AND/OR WRITE HEAD
The invention relates to a device for releasably securing a read and/or write head
to other apparatus. The invention relates particularly, though not exclusively, to m~netic
read and write heads associated with card or ticket transport apparatus in a card or ticket
reading system.
The nature of ticket or card reading systems (for ex~mple in access control systems
having many parallel ch~nnPlc in particular) is such that during busy periods it is e.ssenti~l
that ch~nn~lc are not taken out of service for maintenance or repair. This results in queues
developing which may give rise to safety problems in the event of an evacuation, or
security problems associated with ticket theft or pick-pockets. In addition, repair personnel
10 may be unwilling to spend long periods of time in areas such as subway tnrnctil~.s because
of the threat of assault. Providing more çh~nnelc than are strictly neces.c~ry to allow for
breakdowns is an unpopular solution to this problem with the system operating authorities
who wish to purchase the miniml1m number of tllrnstil~s or access control barriers for a
given location to minimi7~ capital expenditure. To help reconcile these conflicting
15 rlPm~nrlc it is desirable to design ticket transport systems which can be m~int~in~d quickly
and easily in-situ without using special tools or relying on skilled maintenance personnel
who have to work for long periods at the card or ticket transport apparatus.
In card or ticket reading systems, read and/or write heads (generally optical ormagnetic) are usually ~tt~ch~d to a card or ticket transport apparatus adjacent a train of
20 rollers, wheels or belts which guide and drive the card or ticket through the apparatus and
past the heads in use. In such systems using m~gnPtic coding, it is important that the
magnetic head can be urged into contact with the card or ticket whilst it moves past. It
is important to be able to set the force urging 1he head into contact with the ticket
accurately to the minimum required to give reliable reading, thereby minimi7ing frictional
25 wear of the head and prolong its useful life. A furlher r~u-le~llent of card or ticket
~r reading systems is to limit movement of the read or write head in the direction of ticket
or card transport. In a m~gn~tic read/write system, if the ticket is m~gnPtic~lly coded
with a coding density of (for example) 75 bits per inch, a normal design toler~n~e for
lateral movement of the m~gnPtic head in the direction of ticket motion of 8% of the code
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pitch tr~n~l~tçs to a m~ximnm movement in this direction of a~proxi~ t~Ply plus or minus
25 microns.
In a known device disclosed in US 4,377,828, a fixed m~gnetic head housing is
coupled to an adjustable pressure pad which is used to bias the ticket towards a further
5 opposing read and/or write head. The size of the gap between the pad and the further head
is adjusted by means of a screw.
The present invention provides a device for releasably securing a read and/or write
head to a card or ticket transport system, the device compri.~ing a frame ~tt~ch~hlP to the
10 system, a carriage for the head, and mounting means for mounting the carriage on the
frame, at least one of the c~rri~ge and the frame being reciliPnt the mounting means
cnmpri.~ing a pair of rolling çkPm~nt bearings being loaded axially by the restoring force
of the resilient frame and/or carriage when the c~rri~g~p~ is mounted on the frame, the
carriage being moveable in a direction subst~nti~lly normal to a major surface of any card
15 or ticket in said card or ticket transport system in use.
This arrangement can provide a minimum and con~ tçnt re~ist~nce to movement
perpendicular to the direction of ticket or card transport to ensure that additional frictional
force components do not result in accelerated head wear. Manual setting of the bearing
load can be elimin~t~l using this arr~ngement Such manual load sefflng is a time20 consuming task which requires a technician with considerable practical experience.
The carriage and the frame are preferably a snap-fit. This can enable devices tobe re,pl~ced easily and quickly for m~intPn~nce or repair without the need for hand tools
or a particularly skilled technician working on the ticket transport equipment.
The device preferably further compricçs a m~gnPtic read or write head, a resilient
25 housing for the head and further mounting means for mounting the housing on the c~rri~ge,
the said head being pivotable about at least one axis substantially parallel to the said
direction of transport. This can enable the reading of and/or writing to tickets or cards
having a wide range of thicknPsses or to enable the m~gnPtic head to move in a direction
substantially normal to a major surface of the card or ticket to cope with warped or creased
30 cards or tickets or uneven surfaces whilst m~int~ining low friction movement and the
advantages of quick and easy ch~nging of a device for m~inten~n~e or repair or
repl~cemPnt.
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The further mounting means preferably comprises a pair of rolling element be~ringc
being loaded axially when the housing is mounted on the carnage. The housing andfurther mounting means are preferably a snap-fit.
The device advantageously includes biasing means being arranged such that the
~ .,
S carriage and/or ms~gnPtic head is biased towards any card or ticket present in the t~ansport
system in operation. This can result in more reproducible reading and writing to warped
or creased cards or tickets or to uneven surfaces. The biasing means can convelliently
compri.ces a resilient member provided between the carriage and the frame. The biasing
means is preferably constituted by a spring.
In a pr~rel,ed embo~liment~ the c.~rri~ge and/or head movement is limited by themounting means in the plane of the direction of transport of the card.
The c~ ge is preferably substantially rigid whilst the frame is rçcilient
Embodiments of the invention will now be described, by way of e.~mple only, withreference to the accompanying di~gr~mm~tic drawings, in which
Figure l shows a front and an end elevation of a device according to the invention,
Figure 2 shows a front and an end elevation of the m~gnPtic head and housing portion of
the device of Figure 1,
20 Figure 3 shows a front elevation of the carriage portion of the device of Figure 1,
Figure 4 shows a plan view of the carriage of Figure 3 without the mounting means, and
Figure 5 shows an oblique view of the c~rri~ge of Figure 3.
In these Figures, to avoid ambiguity corresponding component parts are given the25 same reference numerals in all the Figures.
In Figure 1, a device for relP~c~bly securing a m~gnPtic read and/or write head to
a card or ticket transport system is shown in a front elevation 18 and in an end elevation
19 looking along the direction of transport of the card or ticket. The device comprises a
30 resilient frame 1, a carriage 2 for the head 3, and mounting means (which cannot be seen
in this Figure, but are shown in Figure 3 as elP.mP.nt.C 4 and S) for mounting the carriage
on the frame. The mounting means 4 and 5 in the present eY~mrlP both comprice rolling
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element be~ringc - in the present example commercial quality steel ball be~ring~ being
loaded axially in operation by the restoring force of the resilient frame such that the
carriage is moveable about a first axis 6 (shown in Figure 3) ~bs~ lly parallel to the
direction of transport of any card or ticket in said ticket transport system in operation. The
S arrangement of the mounting means is such that the c~rri~ge is limited from being
pivotally moveable in the plane of the paper of the front elevation 18 of Figure 1, i.e. in
a plane s~lkst:~nti~lly parallel to the direction of transport. The figure also shows
electri~:llly conductive wire 23 and a connPctor 24 for connPcting the head to control
means (not shown).
The type of be~rin~.~ used in the device possess both radial and axial intPrn~l
clP~r~nces which are completely removed in the design of the bearing mountings by axially
loading the be~ring.c. The type of bearing chosen and the low axial loading provided
permits con.~ictPntly low rotational resistance to be obtained at the same time as removing
the clearances as noted above. This limits lateral movement of the magnetic head in the
15 direction of ticket travel to plus or minus 25 microns. The actual range of movement
pçrmittP~ and the amount of axial loading provided can be easily changed by ch~nging the
design (for ex~mrlP the m~tPri~l and/or the ~limen~ions) of the frame or of the carriage or
both. The figure of plus or minus 25 microns given for the present ex~mrlP is purely
illustrative and does not limit the scope of the invention. Smaller or larger distances may
20 be chosen.
In the example shown in Figure 1, the c~rri~ge is made of a rigid m~tPri~l such as
~lnminillm and the resilient frame is made from a thermoplastic m~tPri~l Although either
the frame or the carriage or both could be made from a resilient m~tçri~l such as a
thermoplastic to produce the restoring force to axially load the rolling çlPmPnt bearing
25 mount or mounts, for the most accurate and reproducible reading of m~gn~tically encoded
tickets the use of a rigid carriage and resilient frame is preferred. This minimi7es head
motion in the direction of transport of the ticket or card.
In the ç~r~mlllP of Figure 1 the device includes a m~gnPtic read head 3 and further
mounting means (8, 9 shown in Figure 3) for mounting the said head on the c~rri~ge, the
30 said head being rotatable about a second axis 7 (shown in Figure 3) snhst~nti~lly parallel
to the first axis 6. The mounting means 8 and 9 are again axially loaded rolling el~mPnt
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bearings as described above. The device includes a housing 12 which carries the m~gnptic
head.
The housing 12 and the magnetic read head 3 are shown in greater detail in Figure
J 2. The housing has been de~ign~d to be resiliPnt and a snap-fit over the cylindrical outer
S race of the bearing such that during snap fitting the correct axial loading of the bearing is
~ tom~ti~lly obtained through the restoring force of the deforming housing. Figure 4
shows a view from below of the c~rri~e of Figure 3 with the rolling element be~rings 4,
5, 8 and 9 removed. The rolling ehPmPnt bearin~c are a push fit onto the pins 20 att~ched
to the c~rri~ge Each pin is provided with a shoulder 21 which engages with the inner
10 races of the corresponding bearing. When assembled the outer race of each bearing is
arranged to abut a shoulder provided on either the housing or the frame, thereby providing
the axial lo~rling The head and housing assembly can thus be easily removed for
replacement without the need for tools of any kind. The ~rr~n~ement also elimin~tes the
need for a skilled technician to set the loading force of the rolling element be~ring.~ using
15 for ex~mpl~ a screw thread.
The device of Figure 1 further includes biasing means 11 being arranged such that
the carriage and m~gnPtic head is biased towards any card or ticket present in the transport
system in operation. In the present example this biasing means compri.~çs a compression
spring sitl-~t~d between the frame and the carriage. However, other biasing means such
20 as a weight (the magnetic head plus the housing could be used as at least part of this
weight if the axes 6 and 7 are not in vertical ~lignme~t), or a resilient member such as a
rubber rod or a leaf or helical spring placed between the carriage and another body may
be used ~ltprn~tively or in addition. The oblique view of the carriage 2 shown in Figure
S illustrates the presence of a notch 14 which is used l;o locate one end of the spring or
25 resilient member in use.
The housing 12 need not substantially surround the m~gnPtic head, the housing
carries the head and enables the head to be easily mounted onto the c~rri~ge. M~gnPtic
heads each in a housing would typically be kept as integral replaceable units for use as
spare parts. M~gnPtic read heads and m~gnPtic write heads may be mounted in the system
30 using a device according to the invention. Heads which do not use magnetism to read or
write may be used as an ~lt~rn~tive falling within the scope of the present invention. For
ex~mple optical or electronic heads may be provided if desired.
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The present invention can provide accurately controllable limit~tion of the
movement of the head in a plane sllbst~nti~lly parallel to the direction of movement of the
card or ticket, whilst simultaneously providing a minimum and consistent rç~i~t~n~e to
movement orthogonal to the direction of ticket or card transport so that additional frictional
5 force components do not result in accelerated head wear. M~ny~l setting of the bearing
load is not nloctçss~ry using this arrangement. The device is simple to m~mlf~cture. The
axial loading is cle~i~ned to be achieved by the restoring force of the resilient components.
When the carriage and the frame and/or the c~rri~ge and the housing are a snap-fit, the
carriage unit and/or the housing and head unit can be replaced very easily and quickly for
10 m~intçn~n~e or repair without hand tools or a skilled terhnici~n working on the ticket
transport equipment. In practice, such devices are usually mounted on pivotable bodies
which are releasably secured to the ticket reading system such that they can be swung out
of the line of the card or ticket transport for access during m~inten~nce
In summary, a device for releasably securing a m~gnP.tir, electronic or optical read
15 and/or write head to a card or ticket transport system, compri~es a resilient frame (1), a
carriage (2) for the head, and mounting means (4, 5) for mounting the carriage on the
frame, the mounting means compri~ing a pair of rolling elP.ment bearing axially loaded by
the restoring force of the resilient frame. The c~rri~ge is pivotally moveable about a first
axis parallel to the direction of transport of any ticket and not pivotally moveable in the
20 direction of transport. The device may further comprise a m~gnetic head (3) in a resilient
housing (12) and biasing means (11), the head being pivotally moveable about a second
axis substantially parallel to the first axis. In operation, the biasing means biases the
magnetic head towards any card or ticket.
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