Inflation device

An inflation device according to the present invention includes a barrel, a piston at least partially disposed within the barrel, and a collar surrounding at least a portion of the barrel. The piston includes a threaded portion. The collar and the barrel are axially movable with respect to one another, with the barrel being biased towards an equilibrium position within the collar by a collar spring. A nut is disposed at least partially within the barrel, the nut including an interior threaded surface and an exterior camming surface. The nut is movable along an axis substantially transverse to the barrel axis, and is biased towards a collar camming surface by a nut spring. When the barrel is in the equilibrium position, the nut is in a locking position in which the interior threaded surface engages the threaded portion of the piston. This prevents free movement of the piston within the barrel. When the barrel is moved from the equilibrium position the collar camming surface deflects the nut so that the piston is freely movable within the barrel.

FIELD OF THE INVENTION 
The present invention relates to inflation devices, and in particular to 
inflation devices for use with inflatable members such as balloon 
catheters. 
BACKGROUND INFORMATION 
Balloon catheters are used for several medical procedures, including 
balloon angioplasty and stent delivery. The balloon may be inflated by an 
inflation device in the general form of a syringe assembly, and in general 
it is advantageous for the device to be capable of providing rapid 
inflation or deflation of the balloon while also providing fine adjustment 
of the balloon pressure. In addition, it is advantageous for the inflation 
device to maintain the balloon at a desired pressure without force being 
applied continuously by the operator. 
Several inflation devices of the syringe design have been proposed which 
enable the piston of the syringe to move with respect to the barrel in 
both a freely reciprocating mode and a threaded or locked mode, for 
example U.S. Pat. No. 5,137,514 to Ryan and U.S. Pat. No. 5,147,300 to 
Robinson et al. A device such as described in these patents includes a 
thread engagement mechanism that may lock the piston into a threaded mode. 
However, in each case the operator is required to either depress a trigger 
or move a control button before the thread engagement mechanism is 
released. 
SUMMARY OF THE INVENTION 
An inflation device according to the present invention includes a barrel, a 
piston at least partially disposed within the barrel, and a collar 
surrounding at least a portion of the barrel. The piston includes a 
threaded portion. The collar and the barrel are axially movable with 
respect to one another, with the barrel being biased towards an 
equilibrium position within the collar by a collar spring. A nut may be 
disposed at least partially within a recess of the barrel, the nut 
including an interior threaded surface and an exterior camming surface. 
The nut may be movable along an axis substantially transverse to the 
barrel axis, and is preferably biased towards a collar camming surface by 
a nut spring. When the barrel is in the equilibrium position, the interior 
threaded surface of the nut is in a locking position which prevents free 
movement of the piston within the barrel. When the barrel is moved from 
the equilibrium position the collar camming surface deflects the nut so 
that the piston is freely movable within the barrel.

DETAILED DESCRIPTION 
FIG. 1 illustrates an exemplary embodiment of an inflation device according 
to the present invention. The exemplary inflation device includes a barrel 
11 surrounded by a collar 13. A piston 15 acts in conjunction with barrel 
11 to form a syringe assembly, with a handle 23 being attached to a 
proximal end of piston 15, "proximal" generally designating the portion of 
the inflation device closer to operator (towards the right in FIGS. 2-4). 
Via mechanisms described below, barrel 11 is axially movable within collar 
13, but biased towards a central equilibrium position. When barrel 11 is 
in its equilibrium position, piston 15 is capable only of threadable 
movement within barrel 11. When barrel 11 is moved away from the 
equilibrium position, however, piston 15 is freely movable within barrel 
11. As will be described below, pulling or pushing on piston 15 tends to 
move barrel 11 away from its equilibrium position. Accordingly, if it is 
desired to quickly move piston 15 within barrel 11, piston 15 may simply 
be pushed or pulled in the desired direction and it will move freely in 
that direction. Once released, piston 15 will again be locked in place 
within barrel 15, capable only of threadable movement. 
Barrel 11 is preferably cylindrical in shape, the term "cylindrical" 
including configurations in which barrel 11 (or any other element) is 
substantially cylindrical in shape. A distal end of barrel 11 is 
constructed to connect to and be placed in fluid communication with an 
inflatable member, for example a balloon catheter (not shown). Any known 
or suitable connection may be utilized for this purpose. The proximal end 
of barrel 11 may be open to accommodate piston 15. Collar 13 is also 
preferably cylindrical in shape, and may include an arcuate opening 49 
that reveals the exterior surface of barrel 11. Opening 49, best shown in 
FIGS. 1 and 5, may then allow the operator to see graduated markings on 
the exterior surface of barrel 11. 
Piston 15 is partially disposed within barrel 11, and preferably includes a 
piston head 17, a shaft 21, and handle 23. Piston head 17 is designed to 
retain a fluid within the distal portion of barrel 11, and may include any 
configuration which forms a seal against the interior surface of barrel 
11. In the exemplary embodiment, piston head 17 includes a broad, conical 
distal end face and an o-ring 19, which is preferably disposed in an outer 
circumferential groove of piston head 17. Preferably o-ring 19 is 
compressible in order to maintain a resilient seal against the interior 
surface of barrel 11. 
In the illustrated embodiments of FIGS. 2 to 4, shaft 21 is supported 
within barrel 11 by an interior support structure 65 located in the 
proximal portion of barrel 11. In addition to stabilizing piston 15, 
support structure 65 may act as an abutment for piston head 17, preventing 
proximal movement of piston 15 beyond a desired point. Shaft 21 includes a 
threaded portion 22 that engages a threaded surface 33 of a nut 31, 
described in detail below. Because the inflation fluid used to inflate the 
inflatable member will often apply a force to piston 15 in the proximal 
direction, it is advantageous for the engagement between threaded portion 
22 and nut 31 to particularly resist proximal movement of piston 15. To 
this end, threaded portion 22 preferably includes an asymmetrical thread 
in which the distal face of each thread is disposed at a higher angle with 
respect to the piston axis than the proximal face of the thread. This 
thread configuration is illustrated in each of FIGS. 2 to 4. 
Handle 23 may be provided on the proximal end of shaft 21, if desired. 
Handle 23 may include any suitable formation, including a knob, a ring, or 
other graspable member capable of being manipulated by the operator. 
Preferably, however, handle 23 is a curved, elongated member disposed 
transverse to shaft 21, as illustrated in FIGS. 1 to 4. 
Axial movement of piston 15 may be regulated by nut 31, which may also be 
provided within barrel 11. Nut 31 is preferably movable along an axis 
which is substantially transverse to barrel 11 and shaft 21. In order to 
prevent axial movement of nut 31, nut 31 is preferably maintained within a 
recess 63 of barrel 11, although nut 31 may be maintained in axial 
position in any suitable manner. It should be understood that "recess" 
includes any formation that minimizes or prevents axial movement of nut 
31. Thus recess 63 may include, for example, one or more holes in barrel 
11, positive structure disposed on the interior surface of barrel 11, or 
one or more indentations on the interior surface of barrel 11. In the 
illustrated embodiments, recess 63 is formed within support structure 65 
and includes, for example, an opening shaped to support a nut spring 37. 
Nut 31 includes, for example, an interior threaded surface 33 that 
selectively engages threaded portion 22. In general, "nut" should be read 
to include any element which includes such a threaded surface. Preferably, 
nut 31 also includes an exterior camming surface 35, which is preferably 
located substantially opposite interior threaded surface 33 with respect 
to piston 15. Nut 31 may extend through an opening 61 in barrel 11 so that 
exterior camming surface 35 may contact a collar camming surface 39. 
Collar camming surface 39 is therefore preferably aligned with opening 61, 
so that the protruding exterior camming surface 35 contacts collar camming 
surface 39. Preferably exterior camming surface 35 is provided as a 
smooth, convex surface that allows exterior camming surface 35 to slide 
smoothly along collar camming surface 39. Any suitable shape of exterior 
camming surface may be utilized, however. In order to maintain contact 
between camming surfaces 35 and 39, a nut spring 37 is provided to bias 
nut 31 towards collar camming surface 39, "nut spring" including any 
spring, elastic member, or other element capable of biasing nut 31 towards 
collar camming surface 39. 
Collar camming surface 39 is preferably bi-directional, meaning that nut 31 
is biased downwardly by collar camming surface 39 (as viewed in FIGS. 2 to 
4) when nut 31 is moved either proximally or distally along collar camming 
surface 39. In particular, collar camming surface 39 is preferably a 
shallow, concave surface as shown in FIGS. 2 to 4. In addition, because 
the forces involved in pressurizing (inflating) the balloon and evacuating 
the balloon are different, collar camming surface 39 is preferably less 
inclined towards its proximal end than towards its distal end. This offers 
the operator greater mechanical advantage when evacuating the balloon. 
Alternatively, a shallow V-shaped or other suitably-shaped surface may be 
utilized. A bi-directional collar camming surface 39 need not be provided 
if free movement in only a single direction is desired. In that situation, 
a "uni-directional" camming surface may be provided. 
In an unbiased, equilibrium position, which may be defined as its "home 
position," barrel 11 is disposed axially within collar 13 so that exterior 
camming surface 35 may be at or near a center point of the valley of 
collar camming surface 39. This position is illustrated in FIG. 2. Barrel 
11 may be urged towards the equilibrium position by collar spring 41, 
which engages both barrel 11 and collar 13. In the illustrated 
embodiments, collar spring 41 is bordered by a plurality of abutments 43, 
which are disposed on the exterior surface of barrel 11 and the interior 
surface of collar 13. Abutments 43 may be radially spaced so that they do 
not interfere with one another as barrel 11 moves axially within collar 
13. When barrel 11 is in its equilibrium position, nut 31 is in a "locking 
position" in which interior threaded surface 33 engages threaded portion 
22 of shaft 21. When nut 31 is in the locking position, piston 15 is only 
capable of threadable movement within barrel 11. That is, piston 15 may be 
rotated, and rotation will produce fine axial movement. 
FIG. 3 illustrates an inflation device with barrel 11 away from its 
equilibrium position, which in this Figure has been achieved by drawing 
piston 15 proximally. Proximal movement of piston 15 with respect to the 
collar 13 initially will move barrel 11 and piston 15 proximally within 
collar 13 (because barrel 11 and piston 15 are initially locked by nut 
31). This proximal movement of barrel 11 and piston 15 causes nut 31 to 
travel along collar camming surface 39, biasing nut 31--and in particular 
interior threaded surface 33--downwardly (with respect to FIG. 3). 
Eventually, interior threaded surface 33 will no longer engage threaded 
portion 22, and piston 15 will become freely movable within barrel 11. It 
should be understood that "freely movable" merely designates a state in 
which piston 15 may move axially without being rotated, and includes 
movement in which piston 15 maintains some slight contact with interior 
threaded surface 33. 
When the desired position of piston 15 is reached, the operator can simply 
release piston 15 while holding collar 13, or simply release the entire 
inflation device, if desired. Collar spring 41 will then urge barrel 11 to 
its equilibrium position, which in turn will allow nut 31 to return to the 
locking position (as illustrated in FIG. 2). Piston 15 then will be 
axially locked within barrel 11, capable only of threadable movement. In 
this manner, when it is desired to quickly deflate an inflatable member, 
the operator may pull piston 15 proximally to draw piston 15 to a desired 
position within barrel 11. Once a desired pressure is reached, the 
operator can release piston 15 or release the device as a whole. Barrel 11 
will be urged to its equilibrium position by collar spring 41, and nut 31 
will enter the locking position, thereby limiting axial movement of piston 
15 to fine adjustment by the operator. 
FIG. 4 illustrates the same principle in reverse, for example when it is 
desired to quickly move piston 15 distally to inflate a balloon catheter. 
Moving piston 15 distally into barrel 11 (i.e., to the left in FIG. 4) 
causes barrel 11 to move distally within collar 13. This movement in turn 
causes nut 31 to travel along collar camming surface 39, biasing nut 31 
downwardly. Eventually, piston 15 becomes freely movable within barrel 11, 
and continues to move distally as long as it is pushed. When piston 15 is 
released, barrel 11 returns to the equilibrium position and nut 31 returns 
to the locking position, locking piston 15 in place. 
An inflation device according to the present invention is thus extremely 
simple and convenient to use, because operation of the device is 
effectively transparent to the operator. Piston 15 may be moved proximally 
or distally very rapidly simply by applying force in the desired direction 
of movement. Once the desired position is reached, piston 15 may be locked 
in place by releasing it. At the same time, fine adjustment of piston 15 
is achieved simply by rotating piston 15. Because the operator is not 
forced to actuate a separate trigger, button or switch, the operator is 
free to better concentrate on the task at hand. 
Tabs 51 and 53 provide an additional method of depressurizing a balloon or, 
if the balloon has been evacuated to a vacuum state, pressurizing the 
balloon (i.e. eliminating the vacuum). In operation, an inflatable member 
such as a balloon may be maintained at a high pressure for some time. 
Alternatively, a balloon may be deflated to a vacuum state at times. These 
states may be negated by simply squeezing tabs 51 and 53 together to bias 
barrel 11 within collar 13. This will move nut 31 away form its locking 
position, allowing piston 15 to freely move within barrel 11 to 
depressurize or pressurize the balloon (depending on its initial state). 
Tabs 51 and 53 may be squeezed together with only one hand, allowing 
depressurization or pressurization even when an operator's other hand is 
occupied. 
An inflation device according to the present invention may be constructed 
using any suitable materials and construction processes. Preferably, 
barrel 11 is formed from glass or a clear plastic such as polycarbonate. 
Collar 13 is preferably formed of ABS (), while piston may be formed of 
polycarbonate. 
FIGS. 6-13 illustrate additional embodiments of an inflation device 
according to the present invention. In FIG. 6, for example, recess 63 and 
nut 31 are disposed at a slight "backward angle" with respect to piston 
15. In this orientation, back pressure from piston 15 will drive nut 31 
against angled recess 63, which will deflect nut 31 downwardly (as viewed 
in FIG. 6). This downward force may enhance, for example, the engagement 
of interior threaded surface 33 and threaded portion 22. Alternatively, 
recess 63 and nut 31 could be maintained at a slightly "forward angle," in 
which back pressure from the piston tends to decrease the engagement of 
interior threaded surface 33 and threaded portion 22. A forward angle 
arrangement is particularly advantageous, for example, in high-pressure 
applications in which friction between the threads makes disengagement 
difficult. 
FIGS. 7-13 illustrate several additional exemplary engagement mechanisms 
for controlling the engagement of nut 31 and piston 15. In each of these 
arrangements, engagement mechanism is coupled to barrel 11, collar 13, and 
piston 15. As with the mechanism described above, axial movement of barrel 
11 within collar 13 disengages the engagement mechanism to allow free 
movement of piston 15 within barrel 11. Likewise, when barrel 11 is in its 
equilibrium position, piston 15 is axially locked within barrel 11, 
capable only of threadable movement. As with the mechanism described 
above, barrel 11 may be biased to its equilibrium position. 
FIGS. 7 and 8 illustrate an engagement mechanism basically in the form of a 
lever. In particular, movement of exterior camming surface 35 along collar 
camming surface 39 causes nut 31 to rotate around a pin 71, disengaging 
nut 31 from piston 15. 
In other embodiments, there may be a direct linkage between nut 31 and 
collar 13. FIGS. 9 and 10, for example, illustrate engagement mechanisms 
in the form of a gear or rack and pinion arrangement. In FIG. 9, for 
example, rack 81 may be connected to collar 13, while gear 91 may be 
rotatably connected to barrel 11 through pivot 95. Link arm 97 is also 
connected to gear 91, for example at pivot 99. Rack teeth 83 cooperate 
with gear teeth 93 so that as barrel 11 is moved within collar 13, gear 91 
rotates, causing link arm 97 to draw interior threaded surface away from 
piston 15. FIG. 10 employs essentially the same arrangement, with the 
exception that link arm 97 is connected to gear 91 on the opposite side of 
pivot 95, and interior threaded surface 31 is on the opposite side of 
piston 15. In this configuration, movement of barrel 11 within collar 13 
causes link arm 97 to push (rather than pull) interior threaded surface 31 
away from piston 15. 
FIGS. 11 to 13 illustrate engagement mechanisms including linkage 
arrangements. In FIG. 11, for example, link member 103 is rotatably 
connected to collar 13 at pivot 105 and to barrel 11 at pivot 107. Pins 
111, which are disposed on nut 31, project through a slot in link member 
103 just below a slot contact surface 109. As barrel 11 is moved within 
collar 13, link member 103 rotates. Slot contact surface 109 contacts one 
of the pins 111, biasing nut 31 downwardly (as viewed in FIG. 11) so that 
interior threaded surface 33 disengages from piston 15. In FIG. 12, slot 
contact surfaces 109 are oriented in the opposite direction from those in 
FIG. 11, and interior threaded surface 33 is on the opposite side of 
piston 15. In this arrangement, movement of barrel 11 causes link member 
103 to pull (rather than push) interior threaded surface 31 away from 
piston 15. In the embodiment of FIG. 13, link member 103 is formed in an 
L-shape, the arms rotating around pivot 107 to move interior threaded 
surface 33 into and out of engagement with piston 15 as barrel 11 moves 
within collar 13. 
The device according to the present invention has been described with 
respect to several exemplary embodiments. It can be understood, however, 
that there are many other variations of the above-described embodiments 
which will be apparent to those skilled in the art, even where elements 
have not explicitly been designated as exemplary. For example, collar 
camming surface 39 could be a convex rather than concave surface, and 
interior threaded surface 33 could then be disposed on the same side of 
piston 15 as collar camming surface 39. In addition the inflation device 
may include additional features such as ridges 47 or a shoulder 55 to 
provide a secure grip for the operator. It is understood that these and 
other modifications are within the teaching of the present invention, 
which is to be limited only by the claims appended hereto.