Overbed Table

Abstract

A table including a base carrying a vertical telescopic support for a horizontal, cantilevered, table surface. The telescopic support includes a locking mechanism for vertically positioning the table surface and includes friction means for automatically disengaging itself to permit upward movement without undesirable sound, and for positive reengagement upon downward movement. To permit such downward movement, a manual unlatch means is provided to override the positive engagement feature, and is operable only in an upward direction.

Description

BACKGROUND OF THE INVENTION

This invention relates to overbed tables of the type normally cantilevered over a bed or chair to support food or other materials consumed or utilized by hospital patients. More specially, this invention relates to a cantilevered table surface mounted on a movable base by a telescopic support or pedestal.

Tables of this general construction are well known in the art. For example, the following U.S. patents generally relate to such structure: U.S. Pat. Nos. 1,867,763; 2,171,653; 2,685,478; 3,064,934; 3,194,187; 3,380,405; and 3,504,643.

Since such tables are relatively heavy, and may additionally support substantial weight placed thereon, it is desirable to provide unimpeded upward movement of the table surface. Thus, where the table is cantilevered over a patient automatic unlocking and free upward movement will avoid injury to the patient if his bed is elevated. Too, a positive lock which precludes downward movement in the absence of positive manual support of the table weight is desirable. Additionally, vertical adjustment of the table should not cause undesirable sound due to the environment in which it is utilized.

SUMMARY OF THE INVENTION

This invention comprises an overbed table having a base carrying a telescopic support for a cantilevered table surface. The telescopic support includes two members capable of relative vertical movement to position the table surface. Between these members is a locking mechanism for fixing the vertical position of the table against downward movement while permitting relatively free movement in an upward direction. This locking mechanism includes a rack or notched element carried by one member of the telescopic support and a spring biased detent mechanism carried by the other member of the telescopic support. The detent mechanism includes a pawl or dog which is spring biased into engagement with the rack and friction elements continuously engaged with the rack to positively move the pawl away from the rack upon upward movement so as to prevent undesirable sound. Additionally, the spring bias in conjunction with the friction means urge the pawl into engagement with the rack upon the slightest unintentional, unsupported downward movement of the table surface. An unlatch lever is positioned so as to require manual support of the table to accomplish downward movement.

Accordingly, it is an object of the instant invention to provide a vertically adjustable overbed table which precludes undesirable sound through the use of an automatic unlatching mechanism upon upward movement of the table. Another object of the invention is to provide positive friction and spring biased locking action of a table upon the unintentional downward movement of the table so as to preclude the inadvertent dropping of the table against the patient or support. The invention also includes a unique detent mechanism which permits silent, one way movement of telescopic members while positively precluding telescopic movement of the members in the opposite direction. Finally, it is an object of the instant invention to provide a telescopic support pedestal for a table which accomplishes the above objects and is yet amendable to mass manufacture at a relatively low cost and in a simple and economical fashion.

DESCRIPTION OF THE DRAWINGS

The manner in which the objects of the invention are attained will be made clear by consideration of the following specification and claims when taken in conjunction with the drawings in which:

FIG. 1 is a perspective view of a perferred embodiment of my invention;

FIG. 2 is an exploded view in perspective of this embodiment;

FIG. 3 is a side elevation view of a portion of the preferred embodiment with interior portions being shown in phantom;

FIG. 4 is an exploded view in perspective of a preferred embodiment of the locking mechanism;

FIG. 5 is a sectional view of the preferred embodiment taken along the lines 5--5 of FIG. 3;

FIG. 6 is a side elevational view of a preferred embodiment of the detent mechanims of my invention as viewed along the lines 6--6 of FIG. 5;

FIG. 7 is a side elevational view (with portions broken away) of a preferred embodiment of the locking mechanism of my invention as viewed along the lines 7--7 of FIG. 5;

FIG. 8 is a side elevation view partially in section taken along the lines 8--8 of FIG. 5; and

FIG. 9 is a view similar to FIG. 8 depicting the locking mechanism in an unlocked position.

DETAIL DESCRIPTION

As shown in FIG. 1, the preferred embodiment of the overbed table comprises an H-shaped base section 10 having spaced apart end members 12 joined by an intermediate member 14 perpendicular thereto. These members may be formed of square tubing and joined in a convenient manner such as by welding. Castors 16 may be mounted on the extremities of the base members 12 to support the same above the floor in a portable manner.

Upstanding from one end of the base section 10 is a vertical telescopic support section 20 which carries a cantilevered table 110 parallel to the base section 10 so as to extend in the same direction from the telescopic support. Thus, the base section may be rolled underneath a bed or chair so that the table 110 is cantilevered over the patient therein.

In order to provide vertical adjustability to the table 110, the telescopic support section 20 comprises a lower U-shaped member 22 which is preferably welded to the base section 10 and an upper box-shaped member 30 which telescopes over the lower member 22. The upper portion of the lower member 22 may have a cut out section 24 in the rear plate thereof, such that antifriction means 26 in the form of ball bearing rollers mounted on a shaft may extend outwardly therefrom to engage the internal surfaces of the upper member 30. Additionally low fiction plastic buttons 28 may be placed on the side surfaces of the lower member 22 to facilitate telescopic movement. Finally, a U-shaped bracket 29 may be affixed to the interior surface of member 22 adjacent the top portion by bolts (not shown) for purposes subsequently explained.

As more thoroughly depicted in FIGS. 2 and 3, the upper member 30 is of rectangular shape to telescope over the lower member and is also provided with antifriction buttons 32 on its interior surface near the bottom. An operating handle 36 which permits downward telescopic movement is pivotally connected to the top of the member 30. It may comprise two extending arms or levers 40 which are pivotally connected at 42 to each side of the rectangular member 30 in any conventional manner, and are joined at their rearward extremity by cross piece 38 which may be manually moved upwardly to unlatch the locking mechanism subsequently explained. To protect the cross piece 38 from engagement with walls or furniture, it should not extend beyond the edges of surface of the table. Too, the handle is preferably formed or stamped from a single piece of steel. The arms 40 of the handle are interconnected by an elongated pin 44 which passes through apertures 46 in each side wall of member 30, the size of the aperture permitting sufficient vertical movement of pin 44 through an arc about pivot 42 to operate the locking mechanism subsequently explained.

Additionally, the upper member 30 carries a U-shaped bracket 48 having two upstanding arms attached to the interior surfaces of the member 30 with a horizontal cross member extending between the side walls thereof to support a spring cage subsequently described. Finally, an elongated guard of stainless stell or other material (not shown) may be attached to the side of the member 30 which is to be adjacent the bed.

With particular reference to FIG. 3, it will be seen that the upper member 30 telescopes downwardly over the lower member 22 with the antifriction means 26, 28 and 32 providing relatively friction free telescopic movement of the two members while simultaneously eliminating any substantial tolerance which might otherwise permit relative movement between these members in a horizontal direction.

With further reference to FIGS. 2 and 3, it will be seen that the lower and upper members 22 and 30 are interconnected by constant force spring unit 52. The purpose of the spring unit 52 is to exert a constant force upwardly upon the table member 110 so as to minimize the effort required to raise same. The spring unit may take the form of a pair of constant force springs 56 which are journaled between the side arms of the spring cage by pins 58. The extending ends 57 of the constant force springs 56 are bolted to a hook 60 which is engaged over a top edge of member 22, or as shown in FIG. 3, may be hooked over the top edge of a rack member 72 (subsequently explained) which is affixed to and closes the open side of the lower U-shaped member 22. Constant force springs commercially available have been found to be satisfactory for use in this environment. These springs when unwound tend to rewind themselves and exert a constant force upwardly. Preferably this force is not sufficient to overcome the pull of gravity on the upper portion of the table but rather falls short of that force by a small amount. To connect the spring cage 54 to the upper member 30, an elongated rod 62 extends upwardly and is bolted to the depending U-shaped bracket 48 as depicted in FIG. 3. A large flat member 64 may be welded to the top portion of the rod 62 so as to provide more stability to the spring cage and to limit downward movement of the table 110. With reference to FIG. 3, it will be seen that the left side of flat member 64 will interfere with and abut the top surface of U-shaped bracket 29 to limit downward travel of the table. Additionally, the spring cage 54 will strike the bottom of bracket 29 to limit upward telescopic movement of outer member 30 and table 110.

Also interconnecting the upper and lower members 22 and 30 is a locking mechanism 70 specifically depicted in FIGS. 4 through 9. This locking mechanism comprises a rack 72 having a flat surface with U-shaped arms 74 extending from each side thereof. On the flat surface of the rack 72 are notches 76 which may be engaged by a detent mechanism 80 subsequently explained. Although the rack 72 may be of unitary construction, as shown in FIG. 4, a more preferred form is disclosed in FIGS. 5, 8 and 9. In these figures rack 72 is formed of a thin stainless steel member and includes a U-shaped backing member 72A welded within lower member 22 to provide strength and to facilitate painting and assembly. Member 72A is provided with notches which mesh with the notches 76 of rack 72. After welding member 72A in place, the arms 74 or reverse bends of rack 72 may be wrapped around the edges of U-shaped lower member 22 and backing member 72A as shown in FIG. 5. Thus, rack member 72 also acts as a protective bumper when the table is moved against a bed or other furniture. Too, being unpainted and corrosion resistant, the detent mechanism does not deteriorate its surface.

This detent mechanism 80 comprises a U-shaped housing 82 which is adapted to be welded or riveted to the lower portion of upper member 30. This U-shaped bracket has substantially horizontal slots 84 extending from the outer edges inwardly towards the back plate thereof, and is adapted to receive a cross shaft 86. Mounted between the extending arms of the bracket 82 and upon the shaft 86 are two antifriction wheels 88 which serve to additionally minimize the tolerance between the upper member 30 and lower member 22. A pawl or latch element 90 taking the form of a flat and having an aperture 92 therethrough is mounted on the center of the shaft 86 for limited pivotal movement. Preferably the plate has two edges (unnumbered) which intersect to form a right angle 93 to act as the detent portion cooperating with the notches 76 of the rack 72. This cooperation is more thoroughly depicted in FIG. 8 which illustrates the detent in a locking position with the major axis of the plate 90 (identified by line A--A) being at approximately a 45.degree. angle to the vertical. On this major axis and above the aperture 92 is a second aperture 91 to which is attached an operating link 101 used to cause pivotal movement of the pawl in a counterclockwise direction for disengaging the detent portion 93 from the notches 76. Finally, the pawl 90 is also provided with an indentation 94 which receives a portion of a spring means 96 for imposing a pivotal bias upon the pawl 90 as subsequently explained.

Mounted on shaft 86 adjacent each side of latch element 90 is a flat rubber washer or disc 95 having a sufficient diameter to frictionally engage rack 72 when the unit is assembled. Disposed against the outside surfaces of discs 95 are the coils of a double torsion spring 96. This torsion spring 96 has two extending arms 97 which are adapted to engage the back surface of the U-shaped bracket 82, and two other arms 98 extending at an angle to the arms 97, the latter being joined together by a bridge 99. Thus, with the bridge 99 engaging the indentation 94 of the latch element 90, and with the other arms 97 engaging the back surface of the U-shaped bracket 82, the pawl 90 is pivotally biased in a clockwise direction as viewed in FIGS. 8 and 9. Preferably, bridge 99 of the spring 96 spaces the coils close enough together to cause tight frictional engagement between discs 95 and latch element 90 such that rotational movement of these discs causes pivotal movement of the latch element.

With specific reference to FIG. 7, it should be noted that the notches 76 on the rack 72 have a width only slightly exceeding that of the pawl member 90. This permits substantially continuous frictional engagement between the discs 95 and the rack surface on either side of the notches during telescopic movement of member 30.

With continuing reference to FIGS. 8 and 9, it will be observed that if the upper member 30 with the detent mechanism attached thereto is elevated, the friction discs 95 will tend to rotate in a counterclockwise direction. In view of their frictional engagement with the pawl or latch element 90, such counterclockwise movement of the two discs 95 will also cause counterclockwise movement of the latch element 90 so as to disengage it from the notches 76 and hold the detent portion 93 away from the rack 72. Thus, vertical movement of the table 110 will hold the pawl 90 out of engagement with the notches 76 and such permits elevation of the overbed table without undesirable sound since there is little or no engagement between these parts. Obviously, if the notches 76 have a width exceeding that of pawl 90, maximum frictional contact of the discs 95 with the rack is not obtained and some clicking sound may result.

To lower the table, an operating handle 36 (previously mentioned) is utilized. As noted, this handle is pivoted at 42 on the upper member 30 and has a cross bar 44 joining the two extending arms or levers 40. From this crossbar 40 depends a bifurcated fork 100 to which is attached a linkage 101, preferably by a threaded connection. At the lower end of linkage 101 is formed a right angle 102 for engagement of the link with the upper aperture 91 of the pawl 90. The washers 95 may have a section cut away, as shown in FIG. 4, to facilitate such engagement. Thus, upward movement of the crosspiece or handle 38 causes the linkage 101 to rotate the pawl 90 about the shaft 86 and out of engagement with the notches 76. When the pawl 90 is so disengaged, the table may be lowered, but it should also be apparent that due to the continued frictional engagement between the friction discs 95 and the rack 72, such will aid the spring means 96 in locking the pawl if the operating handle 36 is released. It may be desirable to provide a one-way connection between the control rod of 101 and the bifurcated fork 100 such that the pawl 90 is free to rotate and unlatch from the notches 76 without raising or overcoming the weight of the lever 36.

From this disclosure it should be apparent that the friction discs 95 will operate to positively disengage the pawl 90 from the notches 76 and preclude contact of this pawl from the rack 72 during upward vertical movement of the table 110 and upper member 30. Such precludes the emission of undesirable sound and is quite inexpensive in manufacture. Obviously, the friction elements 95 may take many forms and the pawl 90 could have several configurations. Too, if should be noted that one very advantageous feature of this invention is that these friction discs, acting in conjunction with the bias of spring 96, always insure positive engagement of the pawl 90 with the rack 72 upon downward movement of the table. Such requires that the user positively and continuously hold the operating handle 36 in an elevated position in order to lower the table. Consequently, in lowering the table, its weight must be partially supported by upward manual force against an inadvertent drop. Other modifications of this invention are apparent.

Claims

I claim:

1. In a hospital table having a base vertically supporting a first member with a second member telescopically mounted thereon and having a table cantilevered from said second member, the improvement comprising:

a. Surface means having spaced notches vertically carried by one of said members;

b. A detent mechanism carried by said other member and having a pawl means engageable with said notches for normally precluding downward telescopic movement of said second member and friction means continuously engaging said pawl means and said surface means for automatically disengaging the pawl means upon upward telescopic movement of said second member;

c. Mechanical unlatch means carried by the other member and attached to said pawl means for manually unlatching said detent mechanism for downward telescopic movement of second member.

2. An apparatus as recited in claim 1 in which said detent mechanism comprises:

a. A housing having an open area through which the pawl means extends for engagement with said notches; and

b. A shaft supported by said housing and pivotally mounting said pawl means.

3. An apparatus as recited in claim 2 in which said friction means comprises discs mounted on said shaft and having a flat surface engaging said pawl means and having a portion of its circumference engageable with said surface means.

4. An apparatus as recited in claim 3 in which said detent mechanism includes resilient means mounted on said shaft for biasing said pawl means towards said notches and for biasing said discs against said pawl means.

5. A locking assembly for telescopic members comprising:

a. A rack having teeth means carried by one of said telescopic members;

b. A detent mechanism carried by said other member and having a pawl for engaging the teeth means of said rack to lock same against telescopic movement in one direction and having friction means carried adjacent said pawl and engaging said rack for automatically disengaging said pawl to permit free movement in the other direction without undesirable sound; and

c. Mechanical means for unlatching said detent for movement in said one direction.

6. An apparatus as recited in claim 5 in which said detent mechanism comprises:

a. Pivotal means mounted on said other member for pivotally supporting said pawl;

b. Resilient means carried by said detent mechanism for biasing said pawl to an engaging position with said teeth means; and

c. Friction discs engaging said pawl and said rack for disengaging said pawl to permit movement without undesirable sound in the other direction.

7. An apparatus as recited in claim 5 in which said detent mechanism comprises:

a. A housing;

b. A shaft carried by said housing for pivotally supporting said pawl;

c. Friction means on said shaft frictionally engaging said rack and said pawl for pivotal movement therewith;

d. Spring means biasing said pawl outwardly, but permitting pivotal movement thereof in response to a rotational force directed against said friction means.

8. A hospital table comprising:

a. A base;

b. Lower and upper telescopic members vertically supported on said base;

c. A flat surface member carried by said upper member;

d. A rack and pivotal pawl for engaging same carried by said upper and lower telescopic members respectively, for locking the upper member against downward telescopic movement, and for permitting upward telescopic movement, said pawl carrying means continuously engaging said rack for causing automatic disengagement of said pawl upon upward telescopic movement;

e. Lever means carried by said upper member for pivotal movement in a vertical plane for disengaging said pawl for permitting downward telescopic movement of the upper member only upon upward vertical movement of said lever.

9. An apparatus as recited in claim 8 in which said means for causing automatic disengagement includes friction discs engaging said pivotal pawl and said lower member.

10. In a table having a base vertically supporting a first member with a second member telescopically mounted thereon and having a table cantilevered from said second member, the improvement comprising:

a. A detent mechanism carried by one of said members and having engagement means for normally engaging a surface of the other member for precluding downward telescopic movement of said second member;

b. Friction means carried adjacent said engagement means and coacting with a surface of the other member for automatically disengaging the engagement means upon upward telescopic movement of said second member; and

c. Unlatch means carried by one of said members and attached to said engagement means for unlatching said detent mechanism for downward telescopic movement of said second member.